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ContentsACKNOWLEDGEMENT....................................................................................................................3
Authors..........................................................................................................................................3
DEDICATED TO..........................................................................................................................4
Our................................................................................................................................................4
Parents,.......................................................................................................................................4
Respected Teachers................................................................................................................4
&.....................................................................................................................................................4
INTRODUCTION..............................................................................................................................6
INRODUCTION................................................................................................................................7
Cement...........................................................................................................................................7
History........................................................................................................................................7
Development of strong concretes..................................................................................................9
Types of modern cement..............................................................................................................11
Hydraulic Cements.................................................................................................................11
Portland Cement.......................................................................................................................12
Portland Cement Blends.......................................................................................................12
Portland Blast Furnace Cement................................................................................................12
Portland Fly Ash Cement..........................................................................................................13
Portland Pozzolan Cement........................................................................................................13
Masonry Cements.....................................................................................................................13
Expansive Cements...................................................................................................................14
Non-Portland Hydraulic Cements............................................................................................14
Pozzolan-Lime Cements............................................................................................................14
Calcium Aluminate Cements.....................................................................................................15
Calcium Sulfoaluminate Cements.............................................................................................15
Natural Cements.......................................................................................................................15
Geopolymer Cements...............................................................................................................16
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Environmental Impacts..........................................................................................................16
Chemical Composition of Portland Cement..................................................................................17
Properties of Major Constituents of Portland Cement...............................................................18
Minor Constituents.......................................................................................................................19
Gypsum (CaSO4.2H2O)...............................................................................................................19
Free Lime (CaO)........................................................................................................................19
Magnesia (MgO).......................................................................................................................20
Titanium Oxide (TiO2)................................................................................................................20
Phosphorus Pentoxide (P2O5)....................................................................................................20
Raw Materials...........................................................................................................................21
1-Lime Stone.............................................................................................................................21
2-Clay........................................................................................................................................21
Capacity Selection in Pakistan......................................................................................................22
Sector Overview.......................................................................................................................22
CEMENT INDUSTRY IN PAKISTAN..................................................................................................23
Pakistan Cement Market..............................................................................................................24
1-North.....................................................................................................................................24
2-South.....................................................................................................................................24
Cement Industry Growth..............................................................................................................26
Conversion................................................................................................................................27
Looking Into the Future................................................................................................................29
List of Cement Industries in Pakistan............................................................................................31
SURVEY OF SOME CEMENT INDUSTRIES IN PAKISTAN..................................................................32
SURVEY OF SOME CEMENT INDUSTRIES IN PAKISTAN................................................................33
1-Mapple Leaf Cement.............................................................................................................33
2-D.G Khan Cement Company Limited.....................................................................................33
3-Lucky Cement Limited...........................................................................................................33
4-Kohat Cement Company Limited...........................................................................................33
5-Pakistan Cement Company Limited.......................................................................................34
6-Fauji Cement Company Limited.............................................................................................34
Manufacturing Methods and Process Selection...........................................................................38
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A-Wet Process..........................................................................................................................38
B-Dry Process............................................................................................................................38
Dry Process Versus Wet Process...................................................................................................39
Choice Of Process.....................................................................................................................40
MATERIAL BALANCE.....................................................................................................................41
MATERIAL BALANCE.....................................................................................................................42
QUALITY CONTROL FORMULAE...................................................................................................43
1. Silica Ratio:........................................................................................................................43
2. Lime Saturation Factor......................................................................................................43
3. Hydraulic Ratio.................................................................................................................43
4. Alumina Ratio:..................................................................................................................44
5. Burn Ability Index..............................................................................................................44
RAW MIX PREPARATION...........................................................................................................45
DRY RAW MIX COMPOSITION...................................................................................................47
RAW MATERIAL REQUIRED.......................................................................................................49
CLINKER COMPOSITION...............................................................................................................52
ENERGY BALANCE.........................................................................................................................53
ENERGY BALANCE.........................................................................................................................54
Input Heat Calculations.............................................................................................................54
Heat Input by Consumption of Fuel......................................................................................54
Heat Input As Sensible Heat In Fuel..........................................................................................54
2-Sensible Heat In Kiln Feed.....................................................................................................55
a-Dry Feed Required To Produced One Ton Clinker..............................................................55
b-Feed Water Present In Kiln Feed...........................................................................................55
3-Secondary Air Sensible Heat..................................................................................................56
Basis: 1 Ton of Coal.....................................................................................................................56
5. Primary Air Sensible Heat........................................................................................................58
Output Heat Calculation...............................................................................................................59
1) Heat of Reaction..................................................................................................................59
2) Heat Losses with Kiln Exit Gases...............................................................................................60
a. Exit gas from coal burning:-.................................................................................................60
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B-Exit Gas From Kiln Feed.........................................................................................................61
c. Exit Gas Analysis (Excess Air).................................................................................................63
3. Heat Loss Due To Mixture in Raw Mix.....................................................................................64
4-Heat In Clinker At Kiln Discharge...............................................................................................65
Heat Loss Radiation And Convection............................................................................................65
Heat Balance Sheet.......................................................................................................................66
EQUIPMENT DESIGN.....................................................................................................................67
EQUIPMENT DESIGN.....................................................................................................................68
Kiln Design................................................................................................................................68
Calculation For The Diameter Of The Rotary Kiln..................................................................68
Calculation Of The Length Of The Rotary Kiln...........................................................................70
Basis: 6700 ton/day clinker..................................................................................................70
Kiln Slope..................................................................................................................................71
Degree Of The Kiln Filling..........................................................................................................71
Kiln filling degree fluctuates within the limits of about 5 – 17%. Independent from the kiln’s diameter............................................................................................................................71
Revolution Of The Rotary Kiln...................................................................................................72
Thermal Load Of The Cross – Section Of The Burning Zone..........................................................72
Residence Time.........................................................................................................................72
Thermal Expansion Of The Rotary Kiln......................................................................................73
a) Linear Expansion...................................................................................................................73
b) Expansion along Diameter....................................................................................................74
c) Expansion Along circumference............................................................................................74
Vertical Load Of Kiln.....................................................................................................................75
Horse Power Requirement Of The Rotary Kiln..............................................................................77
a-Load horse power..................................................................................................................77
Friction horse power.................................................................................................................77
CRUSHER.......................................................................................................................................79
PRINCIPLE OF CRUSHING..........................................................................................................79
Selection of Crushing Machinery..............................................................................................80
Selected Crusher Type..............................................................................................................80
Primary Crushing......................................................................................................................82
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Jaw Crusher:.............................................................................................................................82
Overload Safety Device.............................................................................................................83
Speed Of Rotation.....................................................................................................................84
Calculation Of Speed Of Rotation.............................................................................................84
Capacity Of Jaw Crusher...........................................................................................................85
By LEWENSON..........................................................................................................................86
Drive Power For Jaw Crusher........................................................................................................87
Designing Of Raw Material Crusher.............................................................................................88
Motor For Feed Driving.............................................................................................................88
Crusher For Lime Stone Crushing..............................................................................................88
Motor For Driving Crusher........................................................................................................89
Motor For Driving Feeding Rolls...............................................................................................89
Belt Conveyor...........................................................................................................................89
Motor For Driving Belt..............................................................................................................89
Crusher Capacity.......................................................................................................................89
Crusher Capacity Required.......................................................................................................90
Crusher Hopper Capacity..........................................................................................................90
Feeder Capacity for Crusher.....................................................................................................90
Transportation from Crusher....................................................................................................91
Maximum Capacity of Dumpers...............................................................................................91
VERTICAL ROLLER MILL.................................................................................................................93
Grinding Action Developed In The Roller Mill...............................................................................94
Draw In Action Of The Grinding Element......................................................................................95
Grinding Bed Formation...............................................................................................................96
BALL MILL...................................................................................................................................111
The Critical Speed...................................................................................................................111
Dia Of The Ball Mill.................................................................................................................111
According to Tavrov’s formula................................................................................................111
Dynamic Angle Of Repose Of Grinding Balls...........................................................................113
Distribution Of Grinding Media In The Mill Cross Section.......................................................113
Degree Of The Ball Charge......................................................................................................113
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Total Grinding Ball Charge......................................................................................................113
Grinding Ball Charge And Clinker Load...................................................................................114
According to Mardulier...........................................................................................................114
Ball Mill Power Demand.........................................................................................................114
Empirical formula for Ball Mill Power.....................................................................................114
Blanc’s formula.......................................................................................................................114
Bond’s Equation......................................................................................................................115
Apply Bond’s Equation............................................................................................................115
Site Selection..............................................................................................................................116
Site Selection..............................................................................................................................117
Raw Materials Availability.......................................................................................................117
Market....................................................................................................................................117
Energy Availability..................................................................................................................117
Climate....................................................................................................................................118
Transportation Facilities.........................................................................................................118
Water Supply..........................................................................................................................118
Waste Disposal.......................................................................................................................118
Labor Availability....................................................................................................................119
Taxation And Legal Restrictions..............................................................................................119
Site Characteristics.................................................................................................................119
Flood And Fire protection.......................................................................................................120
Community Factors.................................................................................................................120
PLANT SAFETY.............................................................................................................................121
PLANT SAFETY.............................................................................................................................122
OPERATIONAL SAFETY AND PRECAUTIONS............................................................................122
COST ESTIMAION........................................................................................................................124
COST ESTIMAION........................................................................................................................125
COST OF PRODUCTION...........................................................................................................125
Material..............................................................................................................................125
Labor.......................................................................................................................................125
Fuel.........................................................................................................................................126
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Power.....................................................................................................................................126
Other Supplies:.......................................................................................................................127
Overhead Charges..................................................................................................................127
COST ESTIMATION OF PROJECT..................................................................................................128
PURCHASE EQUIPMENT COST....................................................................................................128
Purchased Equipment Cost.....................................................................................................128
PURCHASED EQUIPMENT COST..............................................................................................129
Purchased Equipment Cost.................................................................................................129
Total Direct Cost.........................................................................................................................130
Total Direct Cost = 9.075x109 Rs.....................130
Indirect cost................................................................................................................................131
Total Indirect Cost = 3.713x109 Rs................................................131
Total Capital Investment =Fixed Capital Investment + Working Capital Investment...........................................................................................................132
Cost of Production......................................................................................................................132
Fixed Cost...................................................................................................................................133
Market Price...............................................................................................................................133
Pay out Period of the Plant.........................................................................................................134
Instrumentation & Process Control............................................................................................135
Instrumentation And Process Control........................................................................................136
OBJECTIVES:............................................................................................................................136
Safe Plant Operations:............................................................................................................136
Production Rate:.....................................................................................................................136
Product Quality:......................................................................................................................136
Cost:........................................................................................................................................136
Hardware Elements Of Control System:.....................................................................................137
Process:..................................................................................................................................137
Measuring Elements:..............................................................................................................137
Transducers:...........................................................................................................................137
Transmission Lines:.................................................................................................................137
Controller:...............................................................................................................................137
Final Control Element:............................................................................................................138
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Recorder:................................................................................................................................138
General Control Systems:...........................................................................................................138
Open Loop System:.................................................................................................................138
Closed Loop System:...............................................................................................................138
Feed back Control System:.....................................................................................................139
Forward Control System:........................................................................................................139
Combined Control System:.....................................................................................................139
Cascade Control System:........................................................................................................139
Modes Of Control:......................................................................................................................140
Proportional Control:..............................................................................................................140
Proportional Derivative Control:.............................................................................................140
Proportional Integral Control:.................................................................................................141
Proportional Integral Derivative Control:..........................................................................141
Typical Control System...............................................................................................................141
Recommended Thermocouple...................................................................................................142
For Kiln Process.......................................................................................................................142
Type – R..................................................................................................................................142
Temperature Indicator Controller:.........................................................................................142
Level Controller:.....................................................................................................................142
Pressure Controller:................................................................................................................142
Flow Controller:......................................................................................................................143
Alarm & Safety Tips:...............................................................................................................143
Interlocks:...............................................................................................................................143
THE LETTER CODES FOR INSTRUMENT SYSTEM.....................................................................144
NOTE:......................................................................................................................................145
ENVIROMENTAL PROTECTION & ENERGY UTILIZATION.........................................146
ENVIROMENTAL PROTECTION AND ENERGY UTILIZATION.......................................................147
ENVIROMENTAL PROTECTION IN THE CEMENT INDUSTRY.....................................................147
COST OF ENVIRONMENTAL PROTECTION...............................................................................148
ENVIROMENTAL PROTECTION AS A PROBLEM OF PLANT LOCATION:....................................148
IMPACT OF ENVIRONMENTAL STANDARDS ON ENERGY CONSIDERATION:.....................149
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TECHNICAL AND MANAGERIAL IMPEDEMENTS FOR IMPROVING ENERGY EFFICIENCY.........150
FUTURE TREND IN ENERGY EFFICINCY AND SUGGESTIONS OF STRATEGIES...........................151
MODREN FOUR STAGE SUSPENTION PREHEATER KILN..........................................................152
EFFICIENT USE OF CEMENT IN CONCRETE..............................................................................153
SUGGESTIONS.............................................................................................................................154
INDUSTRIAL LEVEL..................................................................................................................154
NATIONAL LEVEL.....................................................................................................................155
Bibliography................................................................................................................................165
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A PROJECT DESIGN REPORT ONPRODUCTION OF ORDINARY PORTLAND
CEMENT
Submitted to:BAHAUDDIN ZAKARIYA UNIVERISTY, MULTAN
In Partial Fulfillments of the Requirements for the Degree ofB.Sc. Chemical Engineering
Session: 2004-2008
Submitted by: Adnan Waheed 2K4-CHE-157
Supervised by:
Engr.Tariq MalikEngr. Najaf Ali Awan
INSTITUTE OF ENGINEERING & TECHNOLOGICAL TRAININGNFC IET MULTAN
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ACKNOWLEDGEMENT In the name of ALLAH, the all Corroborate Possessor of Majesty and
Splendor, the Omnipresent, The whole benevolent and ever merciful. Who’s
generosity and magnificence able us to complete to make this humble
contribution to already existing ocean of knowledge.
All praises to his last messenger Hazrat Muhammad (Peace Be Upon
Him) who is a source of guidance and knowledge for humanity as a whole is an
ever inspiring for all the learned personals by the order of ALLAH almighty.
In presenting this design report of production of Ordinary Portland Cement
6700 MTPD,we express our heart felt thanks to our project advisor, Engr. Tariq Malik and Engr. Najaf Ali Awan for his guidance, valuable suggestions and
constructive criticism in preparation of this design report.
We are grateful to our director Dr. M. Afzal Haque for providing us all the
facilities and encouragement regarding this project.
Our acknowledgment is also due to our Head of Chemical Engineering
Department Syed Nasir Abbas Abdi, for all his full moral support as well as his
helpful suggestions whenever needed.
The authors also express their appreciation to Cement Research Institute & Development Center and D.G.Khan Cement Company Limited for
helping us in taking difficult data and values of this project faced by us time to
time.
Authors
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12
DEDICATED TOOur
Parents,Respected Teachers
&Sincere Friends
13
INTRODUCTION
INRODUCTION
Cement “Portland cement is the product obtained by finely
pulverizing clinker produced by calcining to incipient fusion and intimate
and properly proportioned mixture of agrillaceous and calcareous
materials.”
14
In the most general sense of the word, cement is a binder, a substance
which sets and hardens independently, and can bind other materials
together. The name "cement" goes back to the Romans who used the term
"opus caementitium" to describe masonry which resembled concrete and
was made from crushed rock with burnt lime as binder. The volcanic ash
and pulverized brick additives which were added to the burnt lime to obtain
a hydraulic binder were later referred to as, cimentum, cäment and
cement. Cements used in construction are characterized as hydraulic or
non-hydraulic.
The most important use of cement is the production of mortar and concrete
- the bonding of natural or artificial aggregates to form a strong building
material which is durable in the face of normal environmental effects.
History The earliest construction cements are as old as construction,
and were non-hydraulic. Wherever primitive mud bricks were used, they
were bedded together with a thin layer of clay slurry. Mud-based materials
were also used for rendering on the walls of timber or "wattle and daub"
structures. Lime was probably used for the first time as an additive in these
renders, and for stabilizing mud floors. A "daub" consisting of mud, cow
dung and lime produces a tough and water-proof coating, due to
coagulation, by the lime, of proteins in the cow dung. This simple system
was common in Europe until quite recent times. With the advent of fired
bricks, and their use in larger structures, various cultures started to
experiment with higher-strength mortars based on bitumen (in
Mesopotamia), gypsum (in Egypt) and lime (in many parts of the world).
It is uncertain where it was first discovered that a combination of hydrated
non-hydraulic lime and a pozzolan produces a hydraulic mixture, but
15
concrete made from such mixtures was first used on a large scale by the
Romans. They used both natural pozzolans (trass or pumice) and artificial
pozzolans (ground brick or pottery) in these concretes. Many excellent
examples of structures made from these concretes are still standing,
notably the huge monolithic dome of the Pantheon in Rome. The use of
structural concrete disappeared in medieval Europe, although weak
pozzolanic concretes continued to be used as a core fill in stone walls and
columns.
Modern hydraulic cements began to be developed from the start of the
Industrial Revolution (around 1700), driven by three main needs:
Hydraulic renders for finishing brick buildings in wet climates
Hydraulic mortars for masonry construction of harbor works etc, in contact
with sea water.
Development of strong concretes In Britain particularly, good quality building stone became ever more
expensive during a period of rapid growth, and it became a common
practice to construct prestige buildings from the new industrial bricks, and
to finish them with a stucco to imitate stone. Hydraulic limes were favored
for this, but the need for a fast set time encouraged the development of
new cements. Most famous among these was Parker's "Roman cement".
This was developed by James Parker in the 1780s, and finally patented in
16
1796. It was, in fact, nothing like any material used by the Romans, but
was”Natural cement" made by burning septaria - nodules that are found in
certain clay deposits, and that contain both clay minerals and calcium
carbonate. The burnt nodules were ground to a fine powder. This product,
made into a mortar with sand, set in 5-15 minutes. The success of "Roman
Cement" led other manufacturers to develop rival products by burning
artificial mixtures of clay and chalk.
John Smeaton made an important contribution to the development of
cements when he was planning the construction of the third Eddystone
Lighthouse (1755-59) in the English Channel. He needed a hydraulic
mortar that would set and develop some strength in the twelve hour period
between successive high tides. He performed an exhaustive market
research on the available hydraulic limes, visiting their production sites,
and noted that the "hydraulicity" of the lime was directly related to the clay
content of the limestone from which it was made. Smeaton was a civil
engineer by profession, and took the idea no further. Apparently unaware
of Smeaton's work, the same principle was identified by Louis Vicat in the
first decade of the nineteenth century. Vicat went on to devise a method of
combining chalk and clay into an intimate mixture, and, burning this,
produced”artificial cement" in 1817. James Frost, working in Britain,
produced what he called "British cement" in a similar manner around the
same time, but did not obtain a patent until 1822. In 1824, Joseph Aspdin
patented a similar material, which he called Portland cement, because the
render made from it was in color similar to the prestigious Portland stone.
All the above products could not compete with lime/pozzolan concretes
because of fast-setting (giving insufficient time for placement) and low
early strengths (requiring a delay of many weeks before formwork could be
removed). Hydraulic limes, "natural" cements and "artificial" cements all
17
rely upon their belite content for strength development. Belite develops
strength slowly. Because they were burned at temperatures below 1250°C,
they contained no alite, which is responsible for early strength in modern
cements. The first cement to consistently contain alite was that made by
Joseph Aspdin's son William in the early 1840s. This was what we call
today "modern" Portland cement. Because of the air of mystery with which
William Aspdin surrounded his product, others (e.g. Vicat and I C Johnson)
have claimed precedence in this invention, but recent analysis of both his
concrete and raw cement have shown that William Aspdin's product made
at North fleet, Kent was a true alite-based cement. However, Aspdin's
methods were "rule-of-thumb": Vicat is responsible for establishing the
chemical basis of these cements, and Johnson established the importance
of sintering the mix in the kiln.
William Aspdin's innovation was counter-intuitive for manufacturers of
"artificial cements", because they required more lime in the mix (a problem
for his father), they required a much higher kiln temperature (and therefore
more fuel) and because the resulting clinker was very hard and rapidly
wore down the millstones which were the only available grinding
technology of the time. Manufacturing costs were therefore considerably
higher, but the product set reasonably slowly and developed strength
quickly, thus opening up a market for use in concrete. The use of concrete
in construction grew rapidly from 1850 onwards, and was soon the
dominant use for cements. Thus Portland cement began its predominant
role.
18
Types of modern cementHydraulic Cements Hydraulic cements are materials which set and harden after
combining with water, as a result of chemical reactions with the mixing
water and, after hardening, retain strength and stability even under water.
The key requirement for this is that the hydrates formed on immediate
reaction with water are essentially insoluble in water. Most construction
cements today are hydraulic, and most of these are based upon Portland cement, which is made primarily from limestone, certain clay minerals, and
gypsum, in a high temperature process that drives off carbon dioxide and
chemically combines the primary ingredients into new compounds. Non-
hydraulic cements include such materials as (non-hydraulic) lime and
gypsum plasters, which must be kept dry in order to gain strength, and
oxychloride cements which have liquid components. Lime mortars, for
example, "set" only by drying out, and gain strength only very slowly by
absorption of carbon dioxide from the atmosphere to re-form calcium
carbonate.
Setting and hardening of hydraulic cements is caused by the formation of
water-containing compounds, forming as a result of reactions between
cement components and water. The reaction and the reaction products are
referred to as hydration and hydrates or hydrate phases, respectively. As a
result of the immediately starting reactions, a stiffening can be observed
which is very small in the beginning, but which increases with time. After
reaching a certain level, this point in time is referred to as the start of
setting. The consecutive further consolidation is called setting, after which
the phase of hardening begins. The compressive strength of the material
then grows steadily, over a period which ranges from a few days in the
19
case of "ultra-rapid-hardening" cements, to several years in the case of
ordinary cements.
Portland CementPortland cement is the most common type of cement in general
usage, as it is a basic ingredient of concrete, mortar and most non-
speciality grout. The most common use for Portland cement is in the
production of concrete. Concrete is a composite material consisting of
aggregate (gravel and sand), cement, and water. As a construction
material, concrete can be cast in almost any shape desired, and once
hardened, can become a structural (load bearing) element.
Portland Cement BlendsThese are often available as inter-ground mixtures from cement
manufacturers, but similar formulations are often also mixed from the
ground components at the concrete mixer.
Portland Blast Furnace Cement It contains up to 70% ground granulated blast furnace slag, with the
rest Portland clinker and a little gypsum. All compositions produce high
ultimate strength, but as slag content is increased, early strength is
reduced, while sulfate resistance increases and heat evolution diminishes.
Used as an economic alternative to Portland sulfate-resisting and low-heat
cements.
Portland Fly Ash Cement It contains up to 30% fly ash. The fly ash is pozzolanic, so that
ultimate strength is maintained. Because fly ash addition allows a lower
20
concrete water content, early strength can also be maintained. Where
good quality cheap fly ash is available, this can be an economic alternative
to ordinary Portland cement.
Portland Pozzolan Cement It includes fly ash cement, since fly ash is a pozzolan, but also
includes cements made from other natural or artificial pozzolans. In
countries where volcanic ashes are available (e.g. Italy, Chile, Mexico, and
the Philippines) these cements are often the most common form in use.
Portland Silica Fume cement
Addition of silica fume can yield exceptionally high strengths, and cements
containing 5-20% silica fume are occasionally produced. However, silica
fume is more usually added to Portland cement at the concrete mixer.
Masonry Cements These are used for preparing bricklaying mortars and stuccos, and
must not be used in concrete. They are usually complex proprietary
formulations containing Portland clinker and a number of other ingredients
that may include limestone, hydrated lime, air entertainers, retarders, water
proofers and colouring agents. They are formulated to yield workable
mortars that allow rapid and consistent masonry work. Subtle variations of
Masonry cement in the US are Plastic Cements and Stucco Cements.
These are designed to produce controlled bond with masonry blocks.
Expansive Cements These contain, in addition to Portland clinker, expansive clinkers
(usually sulfoaluminate clinkers), and are designed to offset the effects of
21
drying shrinkage that is normally encountered with hydraulic cements. This
allows large floor slabs (up to 60 m square) to be prepared without
contraction joints.
Non-Portland Hydraulic CementsPozzolan-Lime Cements
Mixtures of ground pozzolan and lime are the cements used by the
Romans, and are to be found in Roman structures still standing (e.g. the
Pantheon in Rome). They develop strength slowly, but their ultimate
strength can be very high. The hydration products that produce strength
are essentially the same as those produced by Portland cement. Slag-lime
cements
Ground granulated blast furnace slag is not hydraulic on its own, but is
“activated” by addition of alkalis, most economically using lime. They are
similar to pozzolan lime cements in their properties. Only granulated slag
(i.e. water-quenched, glassy slag) is effective as a cement component.
Super sulfated cements
These contain about 80% ground granulated blast furnace slag, 15%
gypsum or anhydrite and a little Portland clinker or lime as an activator.
They produce strength by formation of ettringite, with strength growth
similar to a slow Portland cement. They exhibit good resistance to
aggressive agents, including sulfate.
Calcium Aluminate Cements These are hydraulic cements made primarily from limestone and
bauxite. The active ingredients are monocalcium aluminate CaAl2O4 (CA in
22
Cement chemist notation) and Mayenite Ca12Al14O33 (C12A7 in CCN).
Strength forms by hydration to calcium aluminate hydrates. They are well-
adapted for use in refractory (high-temperature resistant) concretes, e.g.
for furnace linings.
Calcium Sulfoaluminate Cements These are made from clinkers that include ye’elimite (Ca4 (AlO2)6SO4
or C4A3 in Cement chemist’s notation) as a primary phase. They are used
in expansive cements, in ultra-high early strength cements, and in "low-
energy" cements. Hydration produces ettringite, and specialized physical
properties (such as expansion or rapid reaction) are obtained by
adjustment of the availability of calcium and sulfate ions. Their use as a
low-energy alternative to Portland cement has been pioneered in China,
where several million tonnes per year are produced. Energy requirements
are lower because of the lower kiln temperatures required for reaction and
the lower amount of limestone (which must be endothermically
decarbonated) in the mix. In addition, the lower limestone content and
lower fuel consumption leads to a CO2 emission around half that
associated with Portland clinker. However, SO2 emissions are usually
significantly higher.
Natural Cements These correspond to certain cements of the pre-Portland era,
produced by burning argillaceous limestone at moderate temperatures.
The level of clay components in the limestone (around 30-35%) is such
that large amounts of belite (the low-early strength, high-late strength
mineral in Portland cement) are formed without the formation of excessive
23
amounts free lime. As with any natural material, such cements have very
variable properties.
Geopolymer Cements These are made from mixtures of water-soluble alkali silicates and
aluminosilicate mineral powders such as metakaolin.
Environmental ImpactsCement manufacture causes environmental impacts at all stages of
the process. These include emissions of airborne pollution in the form of
dust, gases, noise and vibration when operating machinery and during
blasting in quarries, consumption of large quantities of fuel during
manufacture, release of CO2 from the raw materials during manufacture,
and damage to countryside from quarrying. Equipment to reduce dust
emissions during quarrying and manufacture of cement is widely used, and
equipment to trap and separate exhaust gases are coming into increased
use. Environmental protection also includes the re-integration of quarries
into the countryside after they have been closed down by returning them to
nature or re-cultivating them.
Cement manufacture can also provide environmental benefits by using
wastes from certain other industries, including slag from steel manufacture,
fly ash from coal burning, silica fume from silicon and ferrosilicon
manufacturing, and sometimes recycled concrete from demolition of older
structures.
Chemical Composition of Portland CementPortland cement consists of mainly lime (CaO), silica (SiO2), alumina
(Al2O3), and iron oxide (Fe2O3). The combined content of the four oxides is
approximately 90% of the cement weight and they are generally referred as the
24
‘major oxide’. The remaining 10% consists of magnesia (MgO), alkali oxides
(Na2O and K2O), Titania (TiO2), phosphorus pentaxide (P2O5), and gypsum (A few
percent of gypsum is added during grinding to regulate the setting time of the cement).
These are referred to as ‘minor constituents’. An idea of the composition of present-day,
Portland cement can be obtained from the approximate limits in the following table.
OXIDE
CaO
SiO2
Al2O3
Fe2O3
MgO
Na2O + K2O
TiO2
P2O5
SO3
COMPOSITION (WT %)
60-67
17-25
3-8
0.5-6.0
0.1-5.5
0.5-1.3
0.1-0.4
0.1-0.2
1-3
Properties of Major Constituents of Portland Cement Compound Alite Belite --------
Celite
Chemical Tricalcium silicate Dicalcium silicate Tricalcium aluminate
tetracalcium
Formulae 3CaO.SiO2 (C3S) 2 CaO.SiO2. (C2S) 3CaO.Al2O3(C3A)
aluminoferrite
25
55% 10-19% 5-12%
4CaO.Fe2O3.Al2O3
2-8%
Rate of Rapid (hours) Slow (days) Instantaneous very
rapid
Hydration
(minutes)
Strength Rapid (days) Slow (weeks) Very rapid very
rapid
Development (one day) (one
day)
Ultimate high probably high Low Low
Strength
Heat of Medium: Low: very high:
Medium:
Hydration 500 j/g 250 j/g 850j/g 420
j/g
Remarks Characteristic unstable in water, imparts
to the
Constituent of Portland sensitive to sulphate cement
its
Cements attack
characteristic
Color Grey
Minor Constituents
Gypsum (CaSO4.2H2O)Gypsum is added during grinding of the clinker in order to regulate
the setting time of the cement. There is an optimum gypsum content which
imparts to the cement maximum strength and minimum shrinkage, and this
optimum depends on the alkali oxides and C3A contents of the cement and
on its fineness.
26
On the other hand, the gypsum content must be limited because an excess
may cause cracking and deterioration in the set cement. This adverse
effect is due to the formation of ettringite (C3A.3CaSO4.31H2O) resulting
from reaction between gypsum and C3A.
Free Lime (CaO)The presence of free (uncombined) lime in the cement may occur
when the raw materials used in the manufacturing process contain more
lime than can combined with the acidic oxides SiO2, Al2O3, and Fe2O3.
Alternatively, free lime may occur when the amount of lime in the raw
materials is not excessive, but when its reaction with the oxides is not
complete after the clinkering process due to coarse raw meal and low heat
input.
Magnesia (MgO)The raw material for the cement usually contains a certain amount of
MgCO3 which on burning dissociates to magnesium oxide and carbon
dioxide. The magnesia does not combine with the major oxides. Some of it
is taken up in solid solution in the clinker material, and the remainder
crystallizes as periclase (MgO).
Alkali Oxides (K2O, Na2O)
27
The alkali oxides are introduced into the cement through the raw
materials and their content varies from 0.5% to 1.3%. On burning, the
alkali oxides combine, usually, with sulfur trioxide (SO3) giving a solid
solution of sodium potassium sulfate which tends to have the approximate
composition 3K2SO4. Na2SO4.
Titanium Oxide (TiO2)Titania (TiO2) occurs in the cement to a small extent and its content
varies from 0.1% to 0.4%. The titamia is introduced onto the cement
through the clay of the shale used in its manufacture.
Phosphorus Pentoxide (P2O5)The (P2O5) is usually introduced into the cement through the
limestone used in its manufacture. Its presence slower the cement
hardening because it breaks down the C3S to C2S, which contains the
(P2O5) in solid solution and CaO.
Raw MaterialsTwo types of raw materials are necessary for the production of
Portland cement, one rich in calcium such as limestone, and one rich in
silica such as clay.
1-Lime StoneCalcium carbonate (CaCO3) is wide spread in nature. Calcium
carbonate of all geological formations qualifies for the production of
28
Portland cement. The purest grades of lime stone are calspar (calcite) and
aragonite. Calcite crystallizes hexagonally and aragonite is rhombic. The
specific gravity of calcite is 2.7 and of aragonite are 2.95. The hardness of
lime stone depends on its geological age. The hardness of limestone is
between 1.8 and 3.0 of the Moh’s scale of hardness. Only the purest
varieties of lime are white.
Lime stone usually contains admixtures of clay substance, iron and
aluminum compounds, which influence its colour. In cement raw material
the lime component is generally represented up to an amount of 74-80%.
2-ClayClay is another raw material for cement manufacturing. Clay is
formed by the weathering of alkali and alkaline earth containing aluminum
silicates and of their chemical conversion products, mainly feldspar and
mica. The main component of clay is formed by hydrous aluminum
silicates.
Iron hydroxide is the principal colouring agent in clays; also organic
matter may give the clay with different colors. Clays with no impurities are
white. In addition to natural raw material some plants use slag and
precipitated carbonated obtained as by product from ammonium sulfate
industry Sand, waste bauxite and iron ore is some time used in small
amount to adjust the composition of the mixture.
Gypsum is added to regulate the setting time of the cement.
Capacity Selection in Pakistan
29
Sector OverviewThere are 29 cement production units in the country. Upto May
2007, the total installed cement production capacity is 36.841 million tones.
By the end of June 2011, the installed cement capacity will touch to the
level of 49.597 million tones.
Due to political instability and lack of allocation of funds for public
sector development program, cement industry of Pakistan was in the
recession phase had registered an average growth rate of 2.96% for the
period from 1990 to 2002. For the period from 2003 to 2007 cement
industry of Pakistan had registered an average growth rate of 20%. The
boost in cement sector is because of the rising construction activity in the
country, reconstruction activity in Afghanistan and increasing development
expenditure by the government. Construction of dames and export of
cement in the future will also increase the demand of Cement in Pakistan.
So to meet the future demand of the cement in Pakistan 6700 ton per day capacity (the minimum feasible) plant should be designed.
CEMENT INDUSTRY IN PAKISTAN
The Cement industry of Pakistan plays a vital role in the socio
economic development of the country. The development of cement
sector has made rapid strides, both in public and private sectors
during the last two decades. At the time of independence there were
only four units in the county having the capacity of 470,000 tons per
annum. These units were located at Karachi, Rohr, Wan, and Dandot.
30
The country at present has almost attained self-sufficiency in the
supply of cement with very little imports whatsoever during the last
few years.
But now, it has exceeded 36.841 million tones per anima as a
result of establishment of new manufacturing facilities and expansion
by the exiting units. Privatization and effective price decontrol in
1991-92 hearted a new era in which the industry has research a level
where surplus production after meeting local demand is expected in
2006.
The competitive environment, in the cement sector contributes
to the common benefits of the industry and the end users. Infect, the
framework of mixed economy is today truly evidence in cement sector
leading to the maximization of social and economic advantages.
The cement industry in Pakistan faces two serious threats:
closure of units based on the wet process. And the poor cash flow
rendering the units in capable of debts servicing due to the increasing
cast of electricity and furnace oil.
Pakistan has remained a net importer of the cement but due to the
privatization of the units operating under state control and
subsequent expansion programs by the new owners supported by
financial institution has pushed the industry to a point where the
country is bound to reach an oversupply situation. However, the
recent increase in the energy cast provides opportunity sustain the
situation for a relatively longer period. It would be possible because
31
the expansion by the existing units and establishment of new units
are being delayed.
Pakistan Cement MarketPakistan’s cement market is divided into two distinct regions.
1-North
2-South
1-NorthThe northern region comprises the entire province of Punjab, NWFP, Azad
Kashmir and upper parts of Balochistan, whereas the southern region
comprises the entire province of Sindh and some parts of Balochistan.
2-SouthTraditionally, the southern region has always been surplus in cement
production but with the establishment of more plants in the northern parts
of the country the regions has become almost sufficient in the supply of
cement.
Demand Vs SupplyThe demand supply gap which for the decade was in favour of
manufactures is now set to switch the other way with supply outpacing
demand by the end of 2006. Historically the demand has grown at an
average rate of 22.74% in the northern region while 22.65% in the
Southern region. There is much pessimism about the industry, future due
to the tremendous increase in supply expected by the end of next year.
32
The way new plants are being established and existing plants are
undertaking expansion, the demand supply equation is creating surpluses.
However, it has been observed that actual progress is slower than planned
to avoid a possible glut situation. This will effectively narrow down the gap
between demand and supply and thereby, ease the pressure on prices.
Factors that can possible change the surplus position into the near
equilibrium between the demand and supply are:
1. Formation of manufacturer’s cartel to avoid price decline.
2. Delay in implementation of planned additions and expansions.
3. Efforts to export cement.
4. Increase in demand if construction of some of the mega-sized
infrastructure project starts.
More CompetitionAs the cement market is moving from virtual “sellers” market to an
oversupply situation, it is expected that when prices stagnate and
profitability becomes a function of volume and economics of scale, location
advantages and proximity to markets will become extremely important
factors.
At present the freight charges are a massive 20% of the retail prices. The
plants located very close to each other and tapping the same market will
have to expand their markets, which will increase their freight expenses.
33
Dandot, pioneer, Mapple Leaf and Gharibwal are all located with in a
radious of 100 kilometers and are selling bulk of their production in the
same areas and will this face serious competition from each other.
Cement Industry Growth With the resurgence in demand, improvement at retention
level, coal conversion and debt restructuring, cement industry has entered
the era of improving profitability. With growth of the economy being linked
to infrastructure development, special emphasis was being paid to the
construction sector. The prospects of economic growth and construction
sector are being linked to each other.
Presently, a number of factors are attributed to this tremendous growth
represented by various indicators. Cement exports, mainly to Afghanistan
doubled during the three quarter period of the current years, Attaining a
level of 0.78 millions tones, but that accounts of only 8% of the total
production.
For a third world country like Pakistan in the process of development,
cement is very a very important commodity. The number of cement plants
and their production volume gives an indication of the stage of the
development in the country.
The cement industry in Pakistan, with a fixed investment of over 79 billion
rupees has started recovering at an increased pace after waging a long
struggle to survive. Domestic demand for cement, which was 66% of
capacity last year, was expected to reach over 92-95% by the end of
current financial year. But it surpassed the expectations and is already
34
utilizing 92-95% capacity due to unprecedented increase in demand of
cement. These phenomena generated optimism about the future prospects
of the cement industry in the country.
The government plays a vital role in the development of infra structure, it is
important for steering the economy towards accelerated growth. The
economy is now poised to take off, in the backdrop of all the positive
indicators. The government is also trying its utmost to bring local and
foreign investment in the different sectors of the economy. In order to
attract new investment for industrialization, substantial fiscal incentives
have been offered by the government to improve infra structure, which
would be huge quantities of cement.
ConversionConversion from furnace oil plants to coal firing system has already
taken place in majority of the cement processing units, which have started
getting high benefits, but they are also reluctant to pass on the benefits to
the consumer on the pretext that the industry has suffered great losses in
the past due to the high prices of furnace oil hence unless the losses of the
past are recovered they are not in the position to pass on the benefits of
end users. On the contrary, the experience shows that when ever the
prices of oil were increased the traditional cast was always passed on to
the consumers.
The conversion of furnace oil plants to coal fired the production cost of the
company resulting in the improved bottom-line. It is reported that the
domestic coal is not a very high quality how ever the processing and
35
blending the local coal with the imported one can produce required heating
content that is much cast –effective than the furnace oil.
End users would also be given their due share in the larger interest of the
economy, because reduction in price means increase in economic activity.
The cement industry has benefited a lot by shifting towards dry process.
Installation of electrostatic precipitators and preheaters, automation of
processes and installation of online analyzer which has resulted in
environmentally better and energy efficient industries. The production of
cement is high-energy intensive process. The cement manufacturers that
have utilized 100% of their installed production capacity are busy in the
rebottling process to further enhance their capacities. They require
upgrading of certain portions their production process to increase their
capacity. This might add one million in cement production capacity of the
country it would however come under pressure by 2007 planned additional
capacity would be operational.
However cement demand from PSDP is directly linked to actual
government spending on mega projects where the work on mega projects
where the work on mega projects remains slow and the government
however has not made any announcement regarding the construction of
any mega dam project.
Looking Into the Future
The radical change in the fuel system that from furnace oil to coal
and the increase in demand for cement has lifted the spirits of the industry
36
in fact in a sense plays the role of a mother industry if all the development
of infrastructure base of the country is taken into account. The increase in
consumption also pushes the economic activity. Besides encouraging
increase in cement consumption through positive policies and use the
cement in large public sector projects, this strong industrial sector
deserves incentives through considerable relaxation in the government
levies to make it competitive in the export market.
Besides current export trend to Afghanistan which has injected a
new life in our sick cement industry, there were ample scope of export in
the countries like Bangladesh where annual demand for cement is
estimated 5 million tons a year, Sri Lanka 3 million tons, Singapore 5
million tons, Egypt 4 million tons, Myanmar 1million tons, Vietnam 1 million
tons, Malaysia 2 million tons and Nepal 0.5 million tons All these countries
are not the producers of cement and meet their cement needs through
imports.
Another factor to keep this sector vibrant is to use cement in the
construction of huge national project of Gawader port in Balochistan,
Karachi-Makran coastal highways. The use of cement in huge network of
irrigation canals and new projects contributing in bridging the gap bet
demand and supply in cement network.
The cement outlook for cement industry looks positive. The capacity
utilization in the current year has improved due to increase in demand. The
earning of cement sector will show further growth in the fourth quarter
ending June, 30 owing to better retention prices, improved volume and
stable to declining production cost.
37
List of Cement Industries in Pakistan
1-D.G Khan Cement Company Limited2-Dandot Cement Company Limited
38
3-Gharibwal Cement Limited4-Javedan Cement Company Limited5-Mustehkam Cement Limited6-National Cement Industries Limited7-Pioneer Cement Limited8-Thatta Cement Company Limited9-Zeelpak Cement Industries10-State Cement Corporation of Pakistan Limited11-Bestway Cement Limited12-Cherat Cement Company Limited13-Dadabhoy Cement Industries14-Essa Cement Industries15-Fecto Cement Limited16-Galadari Cement (Gulf) Limited17-Haryana Asbestos Cement Industries Limited18-Anwarzaib White Cement Limited19-Associated Cement Rohri Limited20-Nizampur Cement Plant 21-Pakistan Slag Cement Industries Limited22-Sakhi Cement Limited23-White Cement Industries Limited24-Mapple Leaf Cement25-Askari Cement Limited26-Lucky Cement 27-Kohat Cement Company Limited28-Pakistan Cement Company Plant29-Fauji Cement Company Plant
39
SURVEY OF SOME CEMENT
INDUSTRIES IN PAKISTAN
40
SURVEY OF SOME CEMENT INDUSTRIES IN PAKISTAN
The cement industries in Pakistan are:-
1-Mapple Leaf Cement 2-D.G Khan Cement3-Lucky Cement4-Kohat Cement Company Limited5-Pakistan Cement Company Plant 6-Fauji Cement Company Plant
1-Mapple Leaf CementPlant Capacity: 6,700 + 5,000 (TPD) plantPlant Location: Located in Daudkhel District Mianwali at Northern PakistanProducts: Ordinary Portland Cement White Cement Sulfate Resisting Cement Low Alkali Oil Well Cement
2-D.G Khan Cement Company LimitedPlant Capacity: 6,700(TPD) plantPlant Location: Located In Dera Ghazi Kahar, District Punjab, Pakistan Products: Ordinary Portland Cement Sulfate Resisting Cement
3-Lucky Cement LimitedPlant Capacity: 4,200(TPD) plantPlant Location: Located In Mian Indus Highway, Pezu District Lucky Marwat, N.W.F.P Products: Ordinary Portland Cement Sulfate Resisting Cement Slag Cement
4-Kohat Cement Company LimitedPlant Capacity: 6,700(TPD) plant
41
Plant Location: Located at Kohat, Pakistan Products: White Cement (Kohat Super White) Grey Cement
5-Pakistan Cement Company Limited
Plant Capacity: 6,000(TPD) plantPlant Location: Located at Kalar Kahar, District Chakwal, Punjab, Pakistan Products: Ordinary Portland Cement Sulfate Resisting Cement
6-Fauji Cement Company Limited
Plant Capacity: 7,200(TPD) plantPlant Location: Located at Jhang Bahtar, Tehsil Fateh Jhang, District Attock, Punjab, Pakistan Products: Ordinary Portland Cement
42
Cement:- The product obtaining by calcining the intimate and proper proportionate mixture of argillaceous and calcareous material to produce clinker and then adding gypsum to it.
Raw Materials
1-CalcareousA-LimestoneB-Chalk
2-AgrillaceousA-ClayB-ShaleC-SlateD-Gypsum
Manufacturing Process:- There are two (2) processes for manufacturing of cement.
1-Dry Process2-Wet Process
Manufacturing Steps:-
1-Crushing & grinding of raw material2-Storage of raw material3-Correction Vats4-Kiln Feeder5-Rotary Kiln6-Collection of Clinker7-Grinding Of Clinker with gypsum8-Packing & Storage
43
44
45
Manufacturing Methods and Process Selection
Two fundamental methods are known for the preparation of the feed for
rotary kilns:
a. The Wet Process; slurry with a water content of approximately 18 – 45%
is prepared in wash mills or by wet grinding.
b. The Dry Process, where the dry state of the raw material components is
exploited to prepare the raw mix.
A-Wet Process1. The long wet process rotary kiln with internal heat exchangers such as
chains, segments of other arrangements.
2. The short wet process rotary kiln without internal installation, working in
conjunction with a heat exchanger for partial drying of the slurry. These
heat exchangers are known under the terms “slurry dryers”,
“concentrator”, “calcinatory”.
3. The medium long wet process rotary kiln with preliminary mechanical
dewatering of the slurry by suction or pressure filters. For disintegration
and final drying of the filter cake fed into the rotary kiln with a moisture
content of 15 – 20%, the kiln is furnished with a short chain section.
4. The short wet process rotary kiln without internal installation with
mechanical preliminary dewatering of the slurry. The resulting filter cake is
then processed to nodules. These are fed into a preheater , or to a heat
exchanger grate.
B-Dry Process1. The long dry process rotary kiln without internal installation.
46
2. The long dry process rotary kiln with internal heat exchangers, such as
chains, refractory bridges, etc.
3. The short dry process rotary kiln working in conjunction with preheaters,
such as suspension preheaters.
4. The dry process rotary kiln with waste boiler.
Dry Process Versus Wet Process The basic advantage of the dry production method over the wet
process is the lower specific heat consumption for clinker burning.
When deciding which production method to select for a new project, it
should be realized that there is no general valid rule, because of the
absence of a uniform method for a comparable appraisal of the
effectiveness of both production methods, and consequently the
impossibility of proving unequivocally the superiority of one over the
other method.
For this purpose, Expert developed a formula which tells in what case
the wet or dry process can be economically applied. However, the
factors used in this formula are based on charge prices of the
socialistic planned economy, and are therefore not applicable in the
domain of the competitive economy.
Previously, clinker produced by the wet method was considered to be
of higher quality and uniformity, because of the better homogenization
of the raw components in the state of slurry. Now, highly sophisticated
pneumatic homogenizing machinery and methods for dry raw mix,
allow the preparation of the raw mix with the same degree of uniformity
as raw mix prepared by the wet method. There is no difference in the
quality of the clinker.
Proportioning of dry raw material components to the required
composition is much easier than proportioning of moist, wet or plastic
raw material component. It is known that grinding of slurry requires a
lower grinding cost. When grinding the same material to the same
47
fineness, dry grinding requires approximately 30% more energy than
wet grinding. However, this advantage is neutralized by the fact that
the dry grinding wear rate of mill liners and grinding media is only 30 –
40 % of the wet grinding wear rate. Thus the higher wet grinding wear
rate offsets the cost of higher energy consumption of dry grinding of
the raw mix.
A wet process cement plant requires about 20% more silo volume for
slurry storage, compared to the raw mix silo volume of a dry process
cement plant with equal capacity.
A conventional heat consumption figure for the wet production process
is 860,000 Btu/bbl of clinker, whereas the heat consumption figure for
the dry process suspension pre heater kiln is roughly 529,000 Btu/bbl;
the difference is 331,000 Btu/bbl in favor of the dry process. For
example, using an average price of $ 0.35 per million Btu (1000 cf of
natural gas), and an assumed plant capacity of 3,850,000 bbl/year, we
get $ 447,000 saving per year on fuel.
The volume of kiln exit gases per bbl of clinker in the dry production
process is 529 cf natural gas X 12 = 6348 scf combustion gases plus
1815 scf carbon dioxide form raw mix, thus a total of 8163 scf/bbl.
The gas volume for the wet process is 860 cf gas X 12 = 10,320 scf
combustion gases, plus 1815 scf carbon dioxide, plus 323 lb water X
20 =6460 scf water vapor from slurry . The total volume of kiln exit
gases for the wet process is 18,595 scf, thus 18,595 – 8163 = 10,432
scf/bbl of clinker more than at the dry process.
48
Choice Of Process As a result of above discussion, the Dry Process is selected for the
manufacturing of Portland cement.
MATERIAL BALANCE
49
MATERIAL BALANCE
ANALYSIS OF LIMESTONE, CLAY AND CLINKER
Component
C1
Limestone
(Wt.% )
C2
Clay
(Wt. %)
C3
Clinker
(Wt. %)
SiO2 1.29 48.72 20.89
Al2O3 0.32 12.03 5.378
Fe2O3 0.10 2.60 3.53
CaO 53.53 7.95 62.64
SO3 0.02 0.02 0.04
MgO 0.70 2.93 2.5
Na2O 0.81 0.74 0.48
Cl2 0.003 0.005 -
K2O 0.04 2.14 0.85
Insoluble
residue - - 1.7
LOI 43.18 22.86 -
50
QUALITY CONTROL FORMULAE1. Silica Ratio:As SR = [SiO2]/ (Al2O3 + Fe2O3)By putting values, we get
SR = 20.89/[5.378 +3.53]
SR = 2.34
Range = 1.9 - 3.2 (In Range)
2. Lime Saturation FactorAs LSF = CaO / [2.8SiO2 + 1.65 AI2O3 + 0.35.Fe203]
By putting values, we get
= 62.64/ [(2.8 x20.89) + (1.65 x5.378) + (0.35 x3.53)]
= 62.64/68.60
=0.91
Range = 0.5 - 1.3 (In Range)
51
3. Hydraulic Ratio HR = CaO/ [SiO2 + Al2O3 + Fe2O3]
By putting value, we get
HR = 62.64 / [20.89+ 5.378 +3.53]
= 2.1
Range = 1.7-2.3 (In Range)
4. Alumina Ratio:AR = Al2O3 / Fe2O3
By putting values, we get
AR = 5.378/3.53
= 1.52
Range = 1.5-2.5 (In Range)
From these formulae it has been proved that the cement obtained
from this clinker has well and quality control is maintained.
5. Burn Ability IndexBI = C3S/ [C4AF + C3A]Where
C3S = 4.07 Hca - (7.6HSi + 6.72 HAl + 1.43HFe + 2.85 HMg)
And
52
HSi, HAl, HFe and HMg are compositions of SiO2, Al2O3, Fe2O3 and MgO
in clinker.
Putting the values, we get
= (4.07 x62.64) – {(7.6 x 20.89) + (6.72 x5.378) + (1.43 x 3.53) + (2.85 x
2.5)}
=47.87
C4AF = 3.04 HFe
C4AF = 3.04 x 3.53 = 10.73
C3A = 2.65 HAl - 1.69 HFe
C3A = 2.65 x 5.378 - 1.69 x 3.53
C3A = 8.29
Putting all these values in Eq.1, we get
BI = 47.87/[10.73 + 8.29]
BI = 2.52
RAW MIX PREPARATION
Hydraulic Modulus
HM = C/[S + A + F]
53
HM = Cm/[Sm + Am + Fm] (For raw mix)
According to this method of calculations:
Cm = [XC1 + C2] / [X + 1]
Sm = [XS1 + S2] / [X+1]
Am = [XA1 +A2] / [X+1]
Fm = [XF1 + F2] / [X+1]
Where 'X' is parts of limestone in raw mix
C1 = Composition of CaO in limestone
C2 = Composition of CaO in clay
S1, A1, F1 = Composition of SiO2, Al2O3 & Fe2O3 in limestone
S2, A2, F2 = Composition of SiO2, Al2O3 & Fe2O3 in Clay
Putting these values of Cm, Sm, Am & Fm in above formula we get
HM = (XC1+ C2)/ (X+1)___________________ [{(XS1+S2)/(X+1)}+{(XA1+A2)/(X+1)}+{(XF1+F2)/(X+1)}]
By solving and rearranging, we get
X = HM (S2+A2+F2)-C2
C1-HM (S1+A1+F1)
Assume HM = 2.1
Putting the values we get
X= 2.1 (48.718+12.03+2.6)-7.95
53.53-2.1(1.29+0.32+0.1)
X = 2.5
54
If HM Value of clinker is 2.1, we have to mix 2.5 parts of lime stone
and one part of clay.
Thus raw mix consists of
R1 = [2.5 /3.5]x 100 = 71.43%
R2 = [1/3.5] x100 = 28.57%
Where
R1 =composition of limestone in raw mix
R2 =Composition of clay in raw mix
DRY RAW MIX COMPOSITION
SiO2 =SiO2 X R1 +SiO2 x R2
=1.29 x 0.7143 +48.718 x 0.2857
=14.84 %
AI2O3 =Al2O3X R1 + Al2O3x R2
= [0.32 x 0.7143] + [12.03x 0.2857]
=3.66%
F e2O3 = Fe2O3 x R1 + Fe2O3 x R2
= [0.1 x 0.7143] + [2.6x 0.2857]
= 0.814%
CaO = CaO x R1 +. CaO x R2
=[53.53 x 0.7143] + [7.95x 0..2857]
= 40.51%
MgO = MgO X R1 + MgO x R2
55
= [0.7 x 0.7143] + [0.93x.2857]
=1.34%
Na2O = Na2O X R1 + Na2O x R2
= [0.81x 0.7143] + [0.74x 0.2857]
= 0.79 %
K2O = K2OX R1 + K2O x R2
= [0.04 x 0.7143] + [2.14 x 0.2857]
=0.64%
SO3 = SO3 X R1 + SO3 X R2
= [0.02 x 0.7143] + [0.02 x .2857]
= 0.02%
Cl= Cl X R1 + Cl X R2
= [0.003 x 0.7143] + [0.005 x 0.2857]
= 0.00357%
LOl =LOI x R1 + LOI x R2
= [43.18 x 0.7143] + [22.86 x 0.2857]
=37.37%
So Dry Raw Mix Composition
SiO2 14.8 4%.
Al2O3 3.66%
Fe2O3 0.814%
CaO 40.51%
MgO 1.34%
56
Na2O 0.79%
K2O 0.64%
SO3 0.02 %
Cl 0.00357
LOI 37.37%
Total 99.99
RAW MATERIAL REQUIRED
BASIS: 6700 TPD clinker (Dry basis)Raw mixture required for 1 ton= 100/ (100-LOI)
= 100/ (100-37.37)
= 1.597 ton/day
Raw mix required for 6700 TPD
=1.597 x 6700
=10699.99 tons/day
Dust factor =1.005
Raw mix required for 6700 T/day
=10699.9x 1.005
=10753.4 TPD
Moisture in raw material = 0.5%
57
Lime Stone =[10753.4/0.995]x 0.7143
=7719.7 TPD
Clay =[10753.4/0.995] x 0.2857
=3087.7 TPD
For 6700 tons/day manufacture of cement, we requireLimestone =7719.7 TPDClay =3087.7 TPD
SiO2 = SiO2 raw mix x 6700
1-[LOI/100]
=0.1484/[1-0.3737] x 6700
=1587.54 TPD
Al2O3 = Al2O3 raw mix x 6700
1-[LOI/100]
=0.0366/[1-0.3737] x 6700
=391.62 TPD
Fe2O3 = Fe2O3 raw mix x 6700
1-[LOI/100]
= 0.00814 / [1-0.3737] x 6700
58
= 87.09 TPD
CaO = CaO raw mix x 6700
1-[LOI/100]
=0.4051/[1-0.3737] x 6700
=4334.66 TPD
MgO = MgO raw mix x 6700
1-[LOI/100]
= 0.0134/[1-0.3737] x 6700
= 143.38TPD
SO3 = S03 raw mix. x 6700
1-[LOI/100]
= 0.0002/[1-0.3737] x 6700
=2.14 TPD
Na2O = Na2O raw mix x 6700
1-[LOI/100]
=0.0079/[1-0.3737] x 6700
=84.53 TPD
K2O = K2O raw mix x 6700
1 - [LOl/ 100]
= 0.0064/[1-0.3737] x 6700
= 68.48 TPD
Cl = Cl raw mix x 6700
1 - [LOl/ 100]
=0.000036/[1-0.3737] x 6700
= 0.385 TPD
59
CLINKER COMPOSITION
SiO2 1587.54tons/day
Al2O3 391.67tons/day
Fe2O3 87.09 tons/day
CaO 4334.67 tons/day
MgO 143.38 tons/day
SO3 2.14 tons /day
Na2O 54.53 tons/day
K2O 68.48 tons/day
Cl 0.385 tons/day
Total 6699.9tons/day
60
ENERGY BALANCE
61
ENERGY BALANCEThe energy balance is carried out on the pre calciner kiln system.
During the balance many assumed values may appear as due to
unavailability of data.
Input Heat Calculations
Heat Input by Consumption of FuelBy the calculations it was found that the coal required to produced 1ton of
Clinker = 0.120 ton.
Calorific value of Coal =6700, 000 kcal/ ton
Heat input through the combustion of fuel
=0.12 x 6700,000
=804,000 kcal/ton of clinker
For 6700 ton clinker = 804,000 x 6700
=5.41 x 109 kcal/6700 ton clinker
About 60% fuel is burning in calciner and about 40% burning is carried out at kiln.
62
Heat Input As Sensible Heat In FuelMass of coal =0.12 ton/ton of clinker
Mean specific heat capacity of coal = 225 kcal / ton.oC
Temperature of coal at inlet =100oC
Reference temperature =25 oC
Heat input = m Cp ∆t
= 0.12 x 225 x (100 – 25)
=2025 kcal/ ton clinker
For 6700 ton of clinker =1.355 x 107 kcal/6700 ton
clinker
2-Sensible Heat In Kiln Feed
a-Dry Feed Required To Produced One Ton Clinker= 1/[1 – (LOI/100)]
=1/[1 – 0.3737]
= 1.597 ton /ton of clinker
Temperature of feed at pre heater entrances = 60 oC
Specific heat of dry feed = 236 kcal/ton. oC
Reference temperature = 25 oC
Heat input as sensible heat = m Cp ∆t
= 1.597 x 236 x (60 – 25)
=13191kcal/ton of clinker.
b-Feed Water Present In Kiln Feed = 0.5% (water in kiln feed for dry
Process should be less than 1%)
Temperature of feed = 60 oC
63
Reference temperature = 25 oC
Specific heat of water = 1000 kcal/ton oC
Sensible heat due to water in kiln feed = (0.5/100) x1.597x100x (60-25)
= 279 kcal/ton of clinker
Total sensible heat in kiln feed = 13191+279
= 13470 kcal/ton of clinker
For 6700 ton of clinker =9.03x107 kcal/6700 ton of clinker
3-Secondary Air Sensible Heat
Coal required = 0.12 ton
Coal used for burning has following analysis
Ultimate Analysis
C = 86.70%
H = 2.2%
O = 2.9%
N2 = 0.8%
S = 0.5%
Ash = 6.9%
Combustion of fuel gives following reaction
C + O2 CO2
H2 + ½ O2 H2O
S + O2 SO2
64
N2 + 2O2 2NO2
Basis: 1 Ton of Coal Theoretical Air Required
According to the above four reaction, oxygen required for combustion
= 2.312 + 0.176 + 0.0183 + 0.01
= 2.5163 ton of O2
O2 present already in coal = 0.029 ton
So net O2 required = 2.5163 – 0.029
=2.4873 ton of O2
Air required 23 ton O2 present in = 100 ton of Air
1 ton O2 present in = 100/23 ton Air
2.4873 ton O2 present in = 100 x 2.4873/ 23
= 10.81 ton of Air /ton of coal
One ton clinker required coal = 0.12 ton
So Air required to produced one ton clinker = 10.81 x 0.12
= 1.297 ton Air /ton of clinker
For 6700 ton clinker = 1.297 x 6700
= 8689.9 ton Air /6700 ton clinker
Excess Air depends upon type of fuel and burner,
Assume excess air used = 12%
Total Air required = 1.12 x 1.297
= 1.452 ton Air/ ton clinker
About 60% of this Air required for combustion is fed as secondary Air
So mass of secondary Air =1.452 x 0.6
=0.872 ton Air /ton clinker
Temperature of secondary Air = 900oC
Reference temperature = 25oC
Specific heat of secondary Air = 279.9 kcal/ton.oC
65
Heat input in secondary Air = m Cp ∆t
= 0.872 x 279.9 x (900 – 25)
= 213461.8 kcal/ton clinker
For 6700 ton of clinker = 213461.8 x 6700
= 1.43 x 109 kcal/6700 ton clinker
5. Primary Air Sensible Heat
About 40% of total air is fed as primary Air, primary air required for combustion
= 1.452 x 0.4
= 0.581 ton Air /ton clinker
Temperature of primary Air = 25oC
Specific heat of primary Air = 239 kcal/ton.oC
Heat input as sensible heat = m Cp ∆t
=0.581 x 239 x (25 – 25)
= 0 kcal/ton clinker
66
Output Heat Calculation1) Heat of ReactionThe raw mix yield the following analysis of clinker
Component percentage (%)
SiO2 20.89
Al2O3 5.378
Fe2O3 3.53
CaO 62.64
MgO 2.5
Na2O 0.48
SO3 0.04
K2O 0.85
I.R 1.5
67
During the clinker formation exothermic and endothermic reaction takes place,
the heat evolved can be calculated as
Heat of Reaction = 4.11%Al2O3 + 6.48%MgO + 7.646%CaO –
. 5.11%SiO2 – 0.59%Fe2O3
= 4.11 x 5.378 + 6.48 x 2.5 + 7.64 x 62.64 – 5.11 x
. 20.89 – 0.59 x 3.53
= 0.59 x 3.53
= 408.04 kcal/kg clinker
= 408040kal/ton clinker
For 6700 ton clinker = 2.734 x 109 kcal/6700 ton clinker
2) Heat Losses with Kiln Exit Gases
a. Exit gas from coal burning:-
As the composition of coal is
Ultimate Analysis
C = 86.70%
H = 2.2%
O = 2.9%
N2 = 0.8%
S = 0.5%
Ash = 6.9%
Combustion of fuel gives following reaction
68
C + O2 CO2
H2 + ½ O2 H2O
S + O2 SO2
N2 + 2O2 2NO2
Air required to produced 1 ton clinker = 10.814 x 0.12
= 1.297 ton/ton clinker
N2 in Air = 1.297 x 0.77
= 0.9987 ton N2/ton clinker
CO2 in exit gases = 44 x 0.897/12
= 3.179 ton CO2 / ton of coal
CO2 formed for 1 ton of clinker = 3.179 x 0.12
= 0.381 ton CO2 /ton clinker
H2O in exit gases = 18 x 0.022/2
= 0.198 ton H2O /ton coal
For 1 ton clinker = 0.198 x 0.12
= 0.237 ton H2O/ton clinker
SO2 in exit gases = 64 x 0.005/32
= 0.01 SO2 /ton of coal
SO2 for 1 ton clinker = 0.01 x 0.12
=1.2 x 10-3 ton SO2 /ton clinker
NO2 in exit gases = 60 x0.008/28
= 0.0171 ton NO2 /ton coal
NO2 for 1 ton clinker = 0.0171 x 0.12
= 2.05 x 10-3 ton NO2/ton clinker
Total exit due to fuel burning = 0.381 + 0.237 + 1.2 x 10-3 + 2.05 x 10-3
= 0.4079 ton gas/ton clinker
69
B-Exit Gas From Kiln Feed
Kiln feed required = 1.597 ton feed / ton clinker
Composition of feed
Component Percentage (%)
SiO2 14.84
Al2O3 3.66
Fe2O3 0.814
CaO 40.51
MgO 1.34
LOI 37.37
CaCO3 CaO + CO2
MgCO3 MgO + CO2
56 ton CaO required = 100 ton CaCO3
0.4051 ton CaO required = 100 x 0.4051/56
= 0.724 ton CaCO3/ton feed
For 1 ton clinker = 0.724 x 1.597
= 1.156 ton CaCO3 /ton clinker
40 ton MgO required = 84 ton MgCO3
0.0134 ton MgO required = 84 x 0.0134/40
= 0.02814 ton MgCO3/ton feed
For 1 ton clinker = 0.02814 x 1.597
= 0.045 ton MgCO3 /ton clinker
CO2 evolved due to CaCO3
70
= 44 x 1.156/100
= 0.51 ton CO2 / ton clinker
CO2 evolved due to MgCO3 = 44 x 0.045/84
= 0.024 ton CO2 /ton clinker
Total CO2 due to kiln feed = 0.51 + 0.024
= 0.534 ton CO2/ton clinker
H2O (free) evaporated in kiln feed = 0.5 x 1.597/100
= 0.008 ton H2O/ton clinker
H2O Combined evaporated = (0.02/1.597) x (0.00075%SiO2) +
(0.0035%Al2O3)
= (0.02/1.597) x (0.00075 x 14.84) +
(0.0035 x 3.66)
=0.014 ton water/ ton clinker
Total water due to feed in exit gases = 0.008 + 0.014
= 0.022 ton water/ton clinker
c. Exit Gas Analysis (Excess Air) Excess Air = 12%
Weight of Excess Air = %age excess air x air used for
Combustion
= 0.12 x 1.297
=0.1556 ton Air / ton clinker
N2 in excess air = 0.1556 x 0.77
= 0.1198 ton N2/ton clinker
O2 in excess air = 0.1556 x 0.23
= 0.0358 ton O2/ton clinker
Weight of gases in exit gases as follows
71
N2 = 0.9987 + 0.12 = 1.118 ton /ton clinker
CO2 = 0.381 + 0.534 = 0.915 ton /ton clinker
O2 = 0.358 ton /ton clinker
H2O = 0.0237 + 0.02 = 0.0437 ton /ton clinker
SO2 = 1.2 x 10-3 ton /ton clinker
NO2 = 0.002052 ton /ton clinker
Exit gas temperature is 300oC. Its specific heat is given as
CO2 = 259.9 kcal /ton.oC
H2O = 489.9 kcal /ton.oC
N2 = 259.9 kcal /ton.oC
SO2 = 179.9 kcal /ton.oC
O2 = 239.9 kcal /ton.oC
NO2 = 249.5 kcal /ton.oC
T1 = 25oC
T2 = 300 oC
Heat loss due to
CO2 = m Cp ∆t
= 0.915 x 259.9 x (300 – 25)
= 65379.3 kcal/ton clinker
H2O = m Cp ∆t
= 0.449 x 489.98(300-25)
= 5887.37 kcal/ton clinker
N2 = m Cp ∆t
= 1.118 x 259.9 x (300-25)
= 79906.25 kcal/ton clinker
O2 = m Cp ∆t
= 0.0358 x 239.9 x (300-25)
= 2361.81kcal/ton clinker
SO2 = m Cp ∆t
=1.20 x 179.9 x (300-25)
72
= 59.37kcal/ton clinker
NO2 = m Cp ∆t
= 0.002055 x 249.9 x (300-25)
= 141.22 kcal/ton clinker
Therefore total heat output due to exit gas =1543735.02 kcal/ton clinker
For 6700 ton clinker =153735.02 x 6700
=1.03x109kcal/6700 ton clinker
3. Heat Loss Due To Mixture in Raw Mix Moisture in raw mix = 0.5%
Raw mix required = 1.597 ton/ton clinker
Specific heat of water =1000 kcal/tonoC
Latent heat of vaporization =510 kcal/ton
Temp. Of kiln feed =60oC
Heat loss due to moisture = m Cp ∆t+mλ
= (0.5/100) x 1000 x (100-25)
+ (0.5/100) x 1.597 x 510
= 7.984+4.072
= 12.056 kcal/ton clinker
For 6700 ton =12.056 x 6700
=80775.2 kcal/6700ton clinker
=8.07x104 kcal/6700ton clinker
4-Heat In Clinker At Kiln Discharge
Reference temperature T1=25oC
Temp. of clinker at outlet of kiln T2=1300 oC
Specific heat of clinker at 1300oC = 270 kcal/tonoC
Heat loss Due to Clinker Discharge = m Cp ∆t
= 1 x 270 x (1300-25)
= 344250 kcal/ton clinker
73
For 6700 ton =344250 x 6700
= 2.306x109 kcal/6700 ton clinker
Heat Loss Radiation And Convection
Heat loss by convection and radiation from whole the system is given as;
= 90.149 kcal/kg clinker
= 90149 kcal/ton clinker
For 6700 ton = 90149 x 6700
= 6.04x 108 kcal/6700 ton clinker
Heat Balance Sheet
Heat Input Kcal/6700 ton clinker
Heat Input by Consumption of Fuel 5.41x109
Heat Input As sensible Heat in Fuel 1.355x107
Sensible Heat in Kiln Feed 9.03x107
Primary Air Sensible Heat 1.43x109
Secondary Air Sensible Heat 0.0
Total 6.94 x 109
74
Heat Output Kcal/6700 ton clinker Heat of reaction 2.734 x 109
Heat losses with kiln exit gases 1.3 x 109
Heat losses due to moisture in raw mixture 8.07 x 104
Heat in clinker at kiln discharge 2.306 x 109
Heat losses by radiation and convection 6.04 x 108
Total 6.94 x 109
75
EQUIPMENT DESIGN
76
EQUIPMENT DESIGNKiln Design
Calculation For The Diameter Of The Rotary Kiln
Basis 6700 ton/day clinker
Martin’s formula considering thermodynamic condition in the rotary kiln:
This formula reads
Q = 2.826D2 . V/Vg
Notation:
Q = Kiln capacity, t/h
D = Kiln diameter on bricks, m
V = Gas velocity in the gas discharge end, m/s
Vg = Specific gas volume, m3/kg clinker
Since the kiln capacity formulas take into consideration only a
fraction of the factors influencing the kiln’s capacity, they have merely
limited application.
Applying martin’s formula to dry kiln of a capacity of 125 t/h (3000
t/day) with the kiln diameter 4.15m on the bricks, we get following results.
125 = 2.826(4.15)2 V/Vg
V/Vg = 2.568
Keeping the same value of V/Vg, for a dry process cement kiln of
capacity 279.167 t/h (6700 t/day), the diameter of the kiln will be as
follows;
77
279.167 = 2.826D2 (2.568)
D2 = 38.47
D2 = 6.2m
Similarly the outlet diameter of the kiln will be given as:
125 = 2.826 (3.75)2 V/Vg
V/Vg = 125/[2.826(3.75)2 ]
V/Vg = 3.145
Where 3.75m is the on brick dia of a 125t/h capacity dry process kiln.
The same ratio of V/Vg for a 279.167t/h (6700 ton/day) capacity kiln.
Replacing values in martin’s formula:
279.167 = 2.826 D2 (3.145)
D2 = 31.41
D = 5.6 m
78
Calculation Of The Length Of The Rotary Kiln
Basis: 6700 ton/day clinkerThe length of the rotary kiln can be calculated by the formula:
Q = D.L [45 + K {(D/L) – 0.02}]
1000 [1 + (W – 40)(1.6/100)]
The above formula is simplified for dry process when water contents will be
zero.
Q = D.L [45 + K {(D/L) – 0.02}]
Notation;
Q = Rotary Kiln capacity/h
D = Mean Kiln dia on brick, m
L = length of the kiln, m
K = characteristic index of kiln, t/h.m2
Data
Q = 279.167 t/h
D = 5.902 m
K = 3064 t/h.m2
The length can be calculated as follows;
279.167 = 5.902 x L [45 + 3064{(5.902/L) – 0.02}]
L = 64.75 m
79
Kiln SlopeNo generally valid rule exists for the proper slopes of rotary kiln.
Rotary kilns show slopes from 2 to 6%. Lower kiln slopes require higher
number of revolutions. This has the benefit of better mixing of the kiln feed,
together with a more intensive heat exchange. Lower slopes also permit
higher degrees kiln filling or kiln load.
The following kiln slopes were found by Bohman to the correct.
5% slope for kiln with dia upto 9’2”
4% slope for kiln with dia from 9’10” to 11’2”
3% slope for kiln with dia above 11’2”
As until now, this recommendation is proved good, since most of the
rotary kilns with dia above 11’2”, show slopes of about 2 – 3.5% on the
basis of the result of Bohman the slope assigned to the kiln is 3%.
Degree Of The Kiln Filling The feed form a segment of the rotary kiln’s cross-
section. The area ratio of this segment to the area of the kiln’s cross-section
expressed in percent is called kiln’s degree or percent of filling.
Kiln filling degree fluctuates within the limits of about 5 – 17%. Independent from the kiln’s diameter.
Selecting degree of kiln filling 15%.
From the graph of %age filling and centric angle the following results were
obtained for kiln.
Kiln load = 15%
Centric angle ά = 108o
80
Revolution Of The Rotary Kiln Form the graph between kiln dia and revolutions in the case of
circumferential speed of 14.7 in/sec, kiln revolutions were calculated to be
1.8rpm.
Thermal Load Of The Cross – Section Of The Burning Zone The quantity of heat which glows during one hour through 1 m2 of the
cross –section of the kiln’s burning zone. Formulae read:
Qp = 1.4 x 106 x D (kcal/m2.h)
Qp = 1.4 x 106 x (5.902)
Qp = 8.26 x 106 kcal/m2.h
Residence Time Formula for calculating residence time of the rotary kiln is:
Residence time = t = 1.77 x L x 6.325 x F
P x D x N
Notation:
t = Residence time, min
L = Length of rotary kiln, m
D = Diameter of rotary kiln, m
P = Slope of the kiln degree
N = Number of revolutions per min
F = Factor = 1
Replacing values, we get
t = 1.77 x 64.75 x 6.325 x 1
1.717 x 5.902 x 1.8
t = 39.74 min
By using proper kiln slope and varying the number of revolutions, can control the
residence time (t).
81
Thermal Expansion Of The Rotary Kiln
a) Linear ExpansionWhen in operation, length and circumference of the rotary kiln are larger
than in the inactive state. These circumferences must be taken into
consideration, so that the riding rings can always rest entirely on the roller and
that the seals on both ends of the kiln will not be impaired.
The linear expansion in the rotary kiln’s length is given as:
A1 = α [{(t1 + t2)/2} – t] L1
A2 = α [{(t1 + t2)/2} – t] L2
Notation:
α = Linear expansion index for steel, = 0.000012
t1 = Highest temperature on the kiln’s circumference
= 350oC
t2 = temperature on the kiln’s ends, 155oC and 60oC respectively
L1&L2 = Length from the highest temperature point to both kiln ends
L1 = 10.79 m = 10790mm
L2 = 53.96 m = 53960mm
T = Ambient Temperature = 25oC
Then the linear expansion is given as:
A1 = 0.000012[{(350+155)/2} – 25] 10790
= 29.456 mm
A2 = 0.000012[{(350+60)/2} – 25] 53960
= 116.55mm
Total expansion = 29.45 + 116.55
= 146.01mm
Linear expansion, expressed in percent = 146.01 x 100/64750
= 0.225%
82
b) Expansion along DiameterThe formula is given as:
= α (300 – t) D
= 0.000012(300 – 25)6200
= 20.46mm
c) Expansion Along circumference From previous case it is clear that the kiln’s dia on heating will be 6220.46mm.
Some result can be obtained after considering the expansion in the
circumference.
Expansion = α (300 – t) U
U = π D
= 3.1415 x 6200
= 19477.87 mm
Expansion = 0.000012 (300 – 25) x 19477.87
= 64.28 mm
Expansion Along total circumference = 19477.87 + 64.28
= 19542.45mm
Kiln’s dia in hot state = 19542.45/ π
= 6220.45mm
83
Vertical Load Of Kiln
The vertical load of kiln is due to the
a) Mass of kiln shell
b) Mass of kiln lining
a) Mass of kiln shell
D = Dia of kiln shell (without lining) = 6.2m
L = Length of kiln shell = 64.75m
Thickness of kiln sheet = 0.02m
Area = (D22 – D1
2) π
Area = (6.242 – 6.22) x 3.1415
Area = 1.56 m2
Density of steel (at 200oC) = 7830kg/m3
Volume of kiln shell = Area x length
= 1.56 x 64.75
= 101.01 m3
Mass of kiln shell = volume x density
= 101.01 x 7830
= 790908.3 kg
b) Mass of kiln lining
Dia of kiln with lining = 5.78m
Dia of kiln without lining = 6.2m
Length of kiln = 64.75m
84
Cross sectional area of lining = (6.22 – 5.782) x 3.1415
= 15.8m2
Length of calcining zone = 64.75 x 0.4 = 25.9m
= 25900mm
Length of burning zone = 64.75 x 0.35 = 22.66m .
=22660mm
Length of cooling zone = 64.75 x 0.25 = 16.19 m .
16190mm
Mass of lining in calcining zone (fire bricks) = 25.9 x 15.8 x 2100
= 859362kg
Mass of lining in burning zone = 22.66 x 15.8 x 2550
= 912971.4 kg
Mass of lining in cooling zone = 16.19 x 15.8 x 2900
= 741825.8kg
Total Mass of lining = 859362 + 912971.4 + 741825.8 =2514159.2kg
Density of fire bricks
Having basic material chansotte = 2100kg/m3
Density of high Alumina bricks
Having basic material bauxite = 2550 kg/m3
Having basic material dolomite = 2900 kg/m3
Total vertical load of kiln = Mass of kiln shell + Total mass
of lining
= 790908.3 + 2514159.2
= 3305067.5kg
85
Horse Power Requirement Of The Rotary Kiln
Horse power requirement can be calculated by the following
formula:
a-Load horse power It is calculated by formula:
Hp = (D x Sin θ)3 x N x L x K
Notation
D = Inside kiln dia (ft)
Sin θ = Factor calculated by % of kiln load
N = RPM of kiln
L = Length of kiln (ft)
K = 0.00076 for dry process.
Data
D = 20.33 ft
Kiln load = 15 %
Sin θ = 0.82 ( from the graph)
N = 1.8 RPM
L = 212.38 ft
Hp = (20.33 x 0.82)3 x 1.8 x 212.38 x 0.00076
= 1346 hp
Friction horse power Formula for friction horse power is given as:
86
Hp = W x bd x td x N x F x 0.0000092
rd
Notation
W = Total vertical load on all roller shaft bearing (lb)
bd = Roller shaft bearing dia, inch
rd = Roller dia, inch
td = Riding tyre dia. inch
N = RPM of kiln
F = Co-efficient of friction of roller bearing, 0.018 for oil
Lubricated bearing.
Hp = 7286351.8 x 16 x 174 x 1.8 x 0.018 x 0.0000092
42
= 143.96 hp
Total horse power required = Load horse power + friction horse power
= 1346 + 143.96
= 1489.96 hp
= 1111.9 KW
87
CRUSHER
PRINCIPLE OF CRUSHINGThe raw materials are quarried in lumps up to 1-2 m and must be reduced
to less than 0.2 mm. This reduction is carried out in two stages, crushing down to
25 mm because the mill is designed for a feed of that maximum size and
subsequent grinding. Raw materials occur in widely varying forms and a large
range of crusher types is available. Combination, i.e. the process of fragmenting
materials, can be effected according to three different principles.
Impact: (Hammer, crusher, drier-crusher)
Compression: (Jaw crusher, cone crusher)
Shearing: (roll-jaw crusher, roller crusher)
The relationship between feed size and exit size of the material is termed as
the reduction factor. Crushers with high reduction factors like hammer crushers
can crush to the required size in one stage. The material is delivered from the
quarry usually by dampers, and tipped into the reinforced inlet chute whose
bottom a lamellate conveyor is feeding the crusher.
88
The remaining crusher types are used for very hard and abrasive respectively
soft and sticky materials. They all have low reduction factors and in the cement
factory they are normally operated in multi-stage crushing.
After the first stage, the fine fraction of pre-crushed material is removed on a
vibrating screen and added to the coarse fraction which is finish crushed in a
smaller secondary cone crusher.
Selection of Crushing Machinery The table should be guidance to the selection of crushers for cement
raw materials.
Material Crusher usedLimestone, hard., abrasive Cone crusher
Jaw crusher
sandstone, hard and massive Cone Crusher
Selected Crusher Type
1. Jaw Crusher2. Blake Jaw crusher3. Hammer crusher
The hammer crushers without inlet grate are basically secondary
crushers, but their robust and sturdy design makes them well-suited for primary
crushing for materials which have been quarried by ripping or similar fragmenting
methods as well as for gypsum and raw coal. They can also handle materials
containing some degree of moisture.
89
Hammer crushers without inlet grate are available with rotational speeds
suitable for primary as well as secondary crushing, and can be tailored to suit
individual raw materials. The slot widths in the outlet grates may be adapted to
the operational conditions in question.
Hammer crushers without inlet grate are available with one or two sets of
rotors. The rotor shafts are fitted with hammer discs on which the hammers are
pivotally mounted.
The rotor shafts run in sturdy oil bath-lubricated roller bearings and are
supported on the crusher casing of heavy cast steel and welded up sections
bolted together. The casing is fined with replaceable wear plates.
The double hammer crusher has a heavy anvil with replaceable crushing
plates which are adjustable in relation to the hammers to compensate for wear.
The double hammer crusher has a heavy anvil with replaceable crushing jaws
and outlet grate, both of which can be adjusted to compensate for wear.
The single hammer crusher has an outlet grate with replaceable grate
bars and an adjustable crushing plate.
90
Hammer crushers without inlet grate are designated EUI (single without
inlet grate) and DUI (double without inlet grate), followed by two digits specifying
the diameter across the hammers and the width of the rotor unit.
Primary Crushing For outlet slots 34 ≥50 mm, base calculations on 1.2 x rated output
for the motor size stated.
For outlet slots 34 ≥75 mm, base calculations on 1.4 x rated output
for the motor size stated.
For outlet slots 34 ≥1000mm, base calculations on 1.6 x rated
output for the motor size stated.
For secondary crushing, outlet slots larger than 34 mm are used only in
exceptional cases.
Jaw Crusher:
In the cement industry the jaw crusher is in general use; this is due to its
relatively simple design and also to the circumstance that this is manufactured in
large units. The jaw crusher serves mainly as a primary crusher. The size
reduction of the crusher feed is performed between two crusher jaws; one of
them is stationary, and the other is moved by toggle pressure. The jaws are lined
with ribbed liners, consisting of chill cost or quenched steel. The crusher frame
consists of cast steel; frames of large units consist of 4 to 6 assembled sectional
steel frame plates.
To crush hard, semi-hard and brittle rocks, ribbed liners are used. The
included angle of the ribs amounts to 90-100°. For crushing of coarser and
considerably harder rocks, the ribs should be corrugated; here the rib angle
should be 100-110°. For large and very hard rocks, liners with more widely
91
spaced ribs are used. The most effective ratio between the rib width and its
height is expressed as:
t ~ 2 /3hDepending on the size of the crusher feed, the width of the ribs in Jaw
crushers employed as primary crushers 2 to 6 inches. Jaw crushers employed
as secondary crushers have ribs with a width of 0.4-1.6 inches. The width of the
crushers discharge opening is being measured from the fop of the rib of one liner
to the opposite notching of the other liner; it is the distance between the planes.
When working very hard materials, the ribs generate lateral forces which have a
negative influence on the swing Jaw shaft, in such cases even jaw liners are
preferred.
For the pre crushing of limestone, so called super elevated ribs are
successfully employed. Every third or fourth rib has a greater height than the
normal liner ribbing. Formation of lamella or needle-shaped pieces in the crushed
material is hereby prevented. The greater wear shows at the lower part of the
fixed jaw plate; next the lower part of the swing jaw plate. The constructional
design of the jaw liners makes it possible to turn over a worn jaw liner 180°, so
that the worn sides come upwards, this makes it possible to extend the life time
of the jaw liners. The liners consist of austenitic manganese steel with a Mn
content of 12-14%. The life time of the liners amounts to 800-1000 working
hours, depending upon the hardness of the crushed material.
Overload Safety DeviceIf unbreakable objects such as tramp iron, digger teeth etc, enter the
crusher, they can cause considerable damage to the crushing elements. To
prevent this, toggle plates which shatter, when tramp iron causes an overload
were developed as safety devices for protecting the crusher from serious
damage. Two different modifications of safety toggle plates with predetermined
cracking lines. After cracking, the toggle plates have to be replaced; this usually
results in an extended interruption of production time.
92
To avoid this, a hydraulic overload safety device has been developed;
because of it un-crushable objects can automatically be removed from the
crushing space without any interruption of operation. With this construction the
stationary jaw is designed as a swing jaw, capable of giving way and having its
fulcrum at the upper end. The lower end is supported on three hydraulic cylinders
the pistons of which are in the front end position when the swing jaw is closed.
In case an un-crushable object enters the space between the crushing
jaws, the resulting over-pressure in the hydraulic system opens the jaw and the
foreign materials falls out of the crushing space. Subsequently, the hydraulic
cylinders move the swing jaw back to the normal operating position. During this
procedure the feeding of the material to be crushed is automatically interrupted,
whereas the crusher drive runs continuously. The increase in investment cost for
the hydraulic protection device is approximately 25% of the crusher price.
Speed Of Rotation
In addition to its size, the through put capacity of a jaw crusher is also
determined by the number of revolutions. However, the speed of rotation should
not be excessive, since practical experience has proved that an increase in
speed beyond a certain limit does not yield an increase in capacity. The
backward and forward motion of the swing jaw must be regulated so as to give
the crushed material enough time to leave the discharge opening of the crusher.
The formula derived for the speed of rotation of the jaw is
n = √(tgα)/S
n = Number of revolutions/min
S = Way length of the swing jaw
α = Angle of the crusher jaw, degree
93
Calculation Of Speed Of Rotation
Feed opening = 47 x 36 inches
Jaw crusher angle = α = 22°
Way length of swing jaw = S = 4.5 cm
n = √(tgα)/S
= tan√(22/45)
However, regarding the friction between the crusher feed and crusher jaw
the upper limit of the jaw crusher recommended is 170 RPM.
Capacity Of Jaw Crusher
According to LEWENSON
Q = 150 n.b.s.d.µ.r
Where,
Q = crushed capacity, ton/hr
B = Width of the Jaw, centimeter
d = mean size of the crushed material
n = RPM of drive shaft
Loading factor of crushed material depending upon its physical property.
µ = about 0.25 to 0.5
r = specific gravity of crushed feed (Ton/m3)
94
RPM of Drive shaft = 220 RPM
Width of the swing Jaw = 1.20 m
Amplitude of swing jaw = S = 4.5 centimeters
Mean size of crushed material = 0.17 meter
Specific gravity of limestone =2.7 ton/m3 (Perry)
µ = 0.3 (By literature for limestone)
By LEWENSON
Q = 150 x 170 x 1.20 x0.045 x 0.17 x 0.3 x 2.7
Q =190 Ton/hr.
By TAGGART
Q=0.093 b.d.
Where,
Q = crushed capacity, ton/hr
b= Width of the Jaw, centimeter
d = size of the crushed material
b=120 cm
d=17 cm
95
SO,Q = 0.093 x 120 x 17
Q = 190 Ton/hr.
Drive Power For Jaw Crusher
According to Viand's formula
N=0.0155 b.D
Where,
N=Jaw Crusher motor size
b=Width of swing jaw, cm
D=Maximum dimension of crusher feed, cm
According to Lewenson's formula
N = [n.b (D2-d2)]/0.34Where,
N = Motor size of jaw crusher
n = RPM of the main drive shaft
b= Width of the swing jaw, meter
D = Mean dimension of crusher feed
So,Width of Jaw = b = 1.2 meter
RPM of main shaft = n = 170 RPM
Dimension of crushed feed = D = 0.5 meter.
Dimension of crushed feed = 0.17 meter
According to Viand's formula
96
N = 0.0255 x 120 x 50
N=153 HP
According to Lewenson's formula
N = 170 x 1.2 [(0.5) 2 - (0.17) 2 ]
0.34
N = 132 HP
Safety factor = 10~15%
Actual Motor HP = 132(1.15)
=152 HP
Designing Of Raw Material CrusherHeavy Duty Feeder For Limestone Feeding
SIZE : 2200*10000mm
WIDTH : 2200mm
DISTANCE OF CENTER : 100000mm
Motor For Feed Driving
POWER: 55Kw
ROTATING SPEED: 980rpm
Crusher For Lime Stone Crushing
97
INPUT SIZE: 2400*2500mm
ROTATING SPEED: 375rpm
CAPACITY: 650 T/Hr
Motor For Driving CrusherPOWER: 1000Kw
VOLTAGE: 6000V
Motor For Driving Feeding Rolls
POWER: 45KW
VOLTAGE: 380V
ROTATING SPEED: 740rpm
Belt Conveyor
CAPACITY: 650T/Hr
BELT SPEED: 106 m/s
Motor For Driving Belt
POWER: 18.5KW
Crusher Capacity
Qdk = Kiln Capacity = 6700 TPD
BDls = Bulk density of limestone = 1.4 tons/m3
98
K1 = Factor for converting clinker = k1 = 1.8
Cl = Total lime stone component = 85 %
Tcrw = No. of days Crusher runs = 6 days/week
Thd = No of hours Crusher runs in a day = 12 hours/day
Ht = Hopper to hold material equivalent to Crusher = 20 min
RMw = Raw material req. per week = Qdk*K1*7
= 6700* 1.8*7
= 84420 tons/week
LSw = Lime stone req. per week = Cl*RMw/100
= 85*84420/100
= 71757 tons/week
Crusher Capacity Required Qcr = Lsw / Tcrw * Thd
= 71757/(6*12)
= 996.62tons/hr
Crusher Hopper Capacity
Hv = (Qcr * Ht) / (BDls * 60)
= (996.62*20) / (1.4*60)
= 237.29 m3
Feeder Capacity for Crusher
As
Qcr = 996.62 tons/hr
99
k2 = 1.2 (Over capacity factor)
Qcrf = Qcr * k2
= 1195.94 tons / hr
Transportation from Crusher
Q tcro = 1.5 * Qcr
= 1494.93 tons / hr
Maximum Capacity of Dumpers
Vd = Hv / Nd
= 237.29/2
= 118.64 m3
100
Where
Nd = No of Dumpers = 2
Hv = Hopper capacity = 237.29 m3
101
Size & DimensionSetting
dimensions, inches
Size of the feed opening 47 x 35
Max. feed size 23
Width of discharge opening 6-8
Drive shaft RPM 170
Drive motor HP 152
Throughput capacity t/hr 190
Fly Wheel diameter 82
Width of fly Wheel 21
Weight of crusher, Ton 68
Width, inches 148
Height 89
Length 177
VERTICAL ROLLER MILL
102
The vertical mill is the most common type of mill for grinding of raw materials. Due to excellent grinding efficiency combined with a high production capacity as well as a high drying capacity, this type of mill has replaced the ball mill now a day. Rollers mills have a lower energy consumption than ball mills, and require less space per unit and capacity at substantial lower investment cost. Roller mills are developed to work as air swept grinding mills. The working Principe of vertical roller mills is based on two to four grinding rollers with shaft carried on hinged arms and riding on a horizontal grinding table or grinding bowl.
A common characteristic of all the roller mill is that size reduction is effected by rollers or grinding table traveling over a circular bed of material and that the material, after passing under the rollers, is subjected to a preliminary classifying action by a stream of air sweeping through the mill. Depending on the air flow velocity, a certain proportion of the pulverized material is thus carried into a classifier (Air separator ) which normally forms an integral feature of the upper part of the casing of the mill. Oversize particles rejected by the classifier fall back into the grinding chamber, while the fines are swept with the air out of the mill and are collected in a filter or a set of cyclones. As the pneumatic conveying of the material in the mil to the separator requires considerable air flow rate, and as the material leaving the grinding bed and carried up into the classifier comes into intimate contact with air, roller mills are especially suitable for drying of moist feed materials in combination with grinding. This is particularly advantageous because these mills can accept large quantities of hot air or gas at relatively low temperature. The roller mills employed in cement industry have grinding elements of various shapes. Thus, in some mills there are cylindrical rollers, in other the rollers are of truncated conical shape or have flat lateral rollers and a convex circumferential surface. The force that keeps the rollers pressed in contact with the bed of material on the grinding path may be centrifugal force, spring pressure, tension action etc.
Design Features.
The material is comminuted by the grinding element rolling on a circular bed of feed material. The larger pieces of material are crushed by the rollers while the smaller one are reduced by the rubbing action. The pulverized material spilling over the edge of grinding table is entrained by the high velocity stream of air, so that the smaller particles are swept upward into the classifier, and the coarser one fall back on the roller path.
Grinding Action Developed In The Roller Mill.
This is the preliminary classifying effect, as distinct from the final separation accomplished in the internal classifier in the upper part of the casing. Because of the shorter residence time of the feed material in the grinding chamber, the bed of material is kept substantially free from fine particles which do not require further grinding, unnecessarily load the mill and tend to form undesirable agglomerations. The important basic conditions for effective grinding in a roller mill are that the grinding element develops a good draw in action and
adequate pressure and that a stable bed of material is formed.
Draw In Action Of The Grinding Element.
103
The particles of feed materials are gripped between the roller and
grinding table. The larger which project above the other and are first subjected to
the grinding action, are broken down.
Compaction Of The Bed Of Material.104
In roller mills, the maximum feed particle size of between 1/20 and 1/ 15 of the roller diameter are permissible. If the material coarser than this is fed to the mill, then there is a danger that the coarser particle will not be drawn in under the rollers but will simply displaced be i.e. pushed in front of the rollers. Furthermore, with in the permissible maximum particle size limit, the draw in action is governed by the granulometric composition and coefficient of friction of the feed material. Thus the bed of material should possess adequate stability so as not to be displaced by the rollers. Also, in order that the rollers do indeed roll on the material and not merely slide along, a sufficiently large frictional force must be developed between their circumference and the material. It may occur when the mill is operating in steady state conditions, the granulometric composition of the feed material changes drastically, due to segregation on emptying the feed hopper, so that the mill temporally receives only feed material. This way adversely affect the stability of the bed, part of the material is displaced, the depth of the bed is, therefore, reduced and the pressure on the rollers to be unchanged. The specific pressure exerted on the material is increased. It may thus happen that the rollers punch through; the bed is displaced, causing mill vibration. As the condition of the feed material is liable to vary with regard to it grind ability, composition granulometric, and moisture content, mill should be designed keeping in view to achieve adequate draw in capacity of the rollers that will deal effectively with any variation likely to occur in the mill feed material. Measures required to achieve adequate draw in capacity of the rollers includes, providing the rollers and roller path with raised ridges and utilizing the joints of renewable segments on these components to provide positive grip.
Grinding Bed Formation.
The grinding process that the material undergoes between the rollers and the roller path on the grinding table comprises the following actions.
Drawn - In Of The material.
In conjunction with the reduction in size there occurs intensive spatial re- arrangement of the individual particles under crushing load. The compressive and shearing forces associated with crushing load have a further size reducing effect, mainly by attrition which indeed the key factor in achieving fine pulverization in a roller mill. The final size reduction is achieved substantially by rubbing together of the material particles subjected to compression and shear while undergoing rearrangement of their position in the bed. To accomplish this requires the fulfillment of several conditions.- Sufficiently high specific grinding pressure - Sufficiently large number of points and area of contact of the particle in relation to one another.- Sufficient large number of movement of the particles in relation to one another.These conditions are directly interrelated, if the bed of material increases in depth, the specific pressure exerted on the material, for a given pressure applied by the rollers, becomes less, if the depth of the bed decreases, the specific pressure increases, but the scope for relative movement of the particles is restricted and number of their points and areas of contact is reduced. Hence every bed of material in a roller mill must be a compromise between the specific grinding pressure that pulverize the material and the bed depth needed for achieving the product fineness required. In most cases, if the mill is fed with material which is uniform in its granulometric composition and size reduction properties and which develop sufficient friction, a stable bed of more or lessConstant depth is formed on the grinding table. With difficult materials there is a scope for modifying and controlling the depth of the bed by dam rings. If the materials are too dry and has a high contents of fine particles, stabilization of the bed may be achieved by moistening it. For grinding of soft materials such as marl, the addition of high grade hard limestone is required primarily for correction of the deficient chemical composition of the raw material, improves the performance of roller mills in term of throughput and of operational behavior. To achieve such improvement, the limestone should be as coarse as possible within the bed consisting largely of softer and finer particles. Particles including a very high proportion of recycled classifier rejects that have already been crushed, the coarse limestone particles act as individual “Hard spot" that offer high resistance to the rollers and cause them to lift slightly. The rollers with their mechanical or hydro pneumatic spring action then fall back onto the bed and performCorrespondingly more size reduction on the finer particles they then encounter. Moreover, these hard spot promote more intensive spatial re - arrangement of the particle of material in the bed and thus help to loosen it up, which likewise makes for more effective fine pulverization.
105
Grinding Speed
106
The grinding speed is determined by the dimensions of the grinding table and the magnitude of the centrifugal force needed for transporting the material. Apart from minor differences bound up with individual design feature of the various mills, the grinding speed is much the same in all the usual roller mills for any given grinding ring diameter.There is a characteristic value k which expresses the time of action of the grinding pressure (contact force per effective unit area) and provide a criterion for comparing roller mills differing in design:
k = Z PV W
kgsec
m2
z = number of rollers p = total contact force (kg )v = angular velocity. Rolling circle radius (m / secW = effective width of rollers ( m ).
The effective width of conically tapered rollers can be taken as 100% of the actual width of the contact surface, while for rollers with convex surface about 60% may be adopted. For convex surface roller, a more precise value can be found by examining the extent of wear on the rolling surface.
In Roller Mills size reduction take place by two mechanism : by crushing and by direct attrition on heavy bed of material. The particles of feed materials are gripped between the rollers and the grinding rings. The larger ones, which project above the other and are the first to be subjected to the crushing action, are broken. In conjunction with the reduction in size there occurs intensive spatial rearrangement of the individual particles under crushing load. The compressive and shearing forces associated with this have a further size reducing effect, mainly by attrition, which is indeed a key factor in achieving fine pulverization in a roller mill which in turn is a function of angle of friction between material and and the metal of grinding element. The limiting value of specific friction coefficient ( ) is constant for a given material. It is found that the larger the diameter of the grinding element, the larger the feed size it can be accepted. Contact area is proportional to Wd, where W is the roller width and d is the roller diameter.
107
Contact Area.
KW net( )
The theoretical power consumption of a vertical roller mill is expressed by the formula
N =
Where
KT A Z V
A = roller projected area m^2KT = specific grinding pressure kNz = number of rollers v = grinding track speed m/ secN = Mill power intake Kw
Capacity Of Roller Mill.
Rollers Projected Area
A = DR WR
DR = Roller diameter (m).WR = Roller width (m)
For Attox Mill The Flowing Applies
KTN
DR W
DRKT : typically 500 ~ 700
DR 0.6 Do Do
0.2 Do (m)
n =
108
W =
DM 0.8 Do Do
56
Do
Where
Do = Table diameter (m).
The following formulae apply for roller mills :
F = FR FH KN
where
F = Grinding force (kN).FR = Roller grinding force (kN).FH = hydraulic grinding force ( kN)Mr = Roller assembly weight one roller ( kg )
But kN FR = MR
9.811000
The grinding force consists of
109
Phyd Dcyl2 DPiston
2
4
100
FH =kN( )
And
The specific grinding pressure will then be
KTFA
kN
m2
KT DR WT =
Where
T = Roller pressure per roller (kN)KT = specific roller pressure (kN)DR = Roller diameter ( m )W = Roller width ( m)
110
DMn60
V =
V = velocity at mean diameter of track (DM) m/ sec DM = Mean diameter of track ( m).n = Table speed ( rpm)
The power absorption of each roller is the tangential load on the table * T times the velocity at the mean diameter of the grinding track. Expressed by the specific rollerpressure KT
N = z T V = z KT DR W DM n60
N = 0.844 KT D2.5Which inserted in the above equation gives This reveals that the capacity of vertical mill, by direct upscaling, grows with the dimension in
power 2.5. The capacity factor here 0.844 varies by different mills designs between 0.4- 1.0 .Most vertical mills for coal and cement raw meal are operated with a specific roller pressure KT between 400 and 800 kN/m^2.The coefficient of rolling friction is about 1/3 of the gripping angle. The gripping angle increases with the grinding bed thickness upto a certain critical value, depending on the material and to a lesser degree on the surface of the rooler. The friction coefficient therefore, also grows with the grinding bed thickness upto a certain limit, which with smooth roller is usually in the range as follows :
Friction coefficient
Cement raw material 0.09 +/ - 0.02Coal 0.10 +/ - 0.02Cement 0.06 +/ - 0.01
The specific power consumption N/P and thereby the mill capacity P, depends not only on the grindability of the material and the required fineness, but also on the efficiency of the classifier, the air flow and other operational parameter. Typical value for cement raw materials are in the range 5 ~ 8 kwh / ton.
Material Movement On The Table.
In vertical mills the grinding table not only functions as a grinding member but also as a spreader dishes that distributes and transport the fresh material to the rollers. The speed of the table is so high that the centrifugal force exceeds the materials' friction against the table. The material particles are therefore in constant sliding motion toward the peripheryof the table. For identical centrifugal field, the table rpm must be inversely proportional to the square root of the table diameter.
For optimum operation table speed should be at such a value, which will give low mill vibration and maximum capacity at minimum power consumption. Table speed is determined by its diameter and by the magnitude of centrifugal force required for transporting the material.Its value is same for all type of roller mills.
111
56 Do56
The high value gives a proportionally high production, also much higher vibration in case of hard materials. The shape of material layer and the movement of the particle are determined by the table profile, the table speed, the return of the material and friction against the table.
Roller mill production rate depends upon gas flow through the mill. Constant quantity of air flow is essential for stable mill operation. Mill output and gas flow can be approximated by a straight line exponential function.
Mill output =
Where V is the gas flow and a and b are the empical constant.Minimum specific air flow is needed to maintain the rate of production in roller mill to carry the feed through the mill, classifier, and dust collector. The mill fan capacity is kept at higher rate than the specified volume of gases to cope with changes in gas temperature in the mill circuit and possible false air supply. An average of 10 % is taken for false air. Normally 2.3 kg gases per kg of clinker are required for vertical mill to grind raw mix. Normally 1.8 to 2.00 kg preheater gases per kg of clinker are available, hence it is possible to use entire preheater gas in the roller mill.At the nozzle ring, a gas velocity of around 80 to 90 m/sec is maintained. Nozzles are normally inclined at 45 degree to the grinding table which gives cyclonic effect to the material leaving the grinding table and coarse particles are thrown against the wall. Following gas velocities are maintained inside the mill above the rollers.
Gas Flow Through The Mill.
a Vb
MPS And Polysius Make Roller Mills
For proper operation of air classifier, a gas velocity of 3.2 m / sec should be maitained at the rotor of the classifier and 10 m / sec at the mill exit
112
1.5 Do
Loeshche And Atox Make Roller Mills
2.5 Do
Where Do is the table diameter.
Mill Differential Pressure Adjustment.Mill differential pressure has a strong influence on mill capacity. Mill differential pressure is effected by grinding table speed. As table speed increases, more and more material is thrown on the table in the form to rain down evenly over the table area and the differential pressure increases which is an indicator for the mill loading and is always used for controlling the mill feed rate. Increase in product fineness also results in decrease in differential pressure. Mill differential pressure is controlled by feed rate to the mill and hydraulic pressure on rollers. Generally differential pressure in the mill in mm H2O is given by :
350 Dop =
Where Do is the outer diameter of the grinding table in meter. Differential pressure is limited by ability of the system fan to provide the static pressure.
Mill exit temperature is very important for proper mill operation. Changes in mill temperature is caused by variation in moisture content of the feed. Mill temperature is controlled by regulating hot gases flow into the mill. Changing mill exit temperature cause change in gas volume, hencechange in gas velocity inside the mill. Continuously varying mill conditions upset the internal balance of circulating load and destroyed the stability of the material bed .It has been found that fluctuating mill exit temperature results in reducing the mill capacities as much as by 50%.Generally mill exit temperature are maintained in raw mill at 85 to 95 oC and 80 to 85 oC in coal mill subject to the % of volatile matter. High mill temperature cause damage to seals, journals and bearings.
Mill Exit Temperature.
113
All vertical mills operate with some slippage or speed difference between the surface of the roller and the grinding table. The slippage generates shear forces that contributes to the grinding and prevent agglomerates. The maximum slippage at the sides of the rollers 9 and 44% of the roller speed. The slippage causes no extra wear. Practically it appears that slippage has very little influence on the roller wear rate. Experience shows that the wear primarily where the pressure is highest which is close to the rolling point a little outside the middle of rollers. This is due to compression which generates a far largerShear than the slippage.
Slippage And Wear In Vertical Roller Mill.
114
The clinker cooling process greatly influences the mineralogical composition as
well as the structure of the clinker. Besides this the grind ability and quality of the
cement is also affected by the rate of cooling. Clinker cooling is very essential because
of the following reasons,
1. Mechanical transportation of hot clinker to storage point is difficult to convey.
2. Hot clinker has negative effect on the grinding process.
3 Reclaiming of useful heat energy from hot clinker is about 200 kcal/kg clinker is an
important factor for lowering production cost.
4. Proper and effective cooling improves the quality of cement.
Selection Criteria Of Clinker Cooler The following requirement should be considered in choosing the
appropriate type of cooler
Obtaining good quality clinker by optimum cooling rate.
Final cooling of the clinker to the lowest possible temperature.
Maximum thermal efficiency.
Best adaptation to the burning system preceding the cooler.
Least possible pollution impact on the environment.
Low susceptibility to faults i.e. minimum down time.
Low capital cost.
Low power consumption.
Low wear and maintenance cost.
Favourable heat balance with a high degree of recuperation to obtain secondary
air temperature as stable and high as possible to achieve overall kiln operating
stability and good fuel efficiency.
Cooler exit air temperature should be as low as possible and volume as small as
possible to assure a minimal amount of heat wasted to atmosphere.
CLINKER COOLING
The sizes of cooler are normally designed on the basis of the the following
operating
parameters.
Grates specific loading 30 ~ 40 tpd per cubic meter of grates at nominal kiln
output.
clinker temperature cooler inlet 1350 ~ 1450, 0C
cooler outlet 65 ~ 100, oC
The cooling air required to reclaimed heat and obtained the desired temperature of
the clinker is 3 ~ 3.5 kg air/ kg clinker.
About 1.00 ~ 1.2 of the cooling air is used as secondary and tertiary air in the kiln
and precalciner and the rest of this air vented or utilized for drying in coal mill.
The cooler capacity and size is normally designed keeping in view the normal kiln
output and expected maximum kiln production per day.
G =
115
Cooler Selection Criteria On The Basis Of Cooler Size
1. Weight of clinker in the cooler,
G=A*h*ρG= weight of clinker in cooler (Kg)
A= area of the grates grate surface (m2) = 52.8
h= clinker bed depth (m ) = 0.500m
ρ = clinker density (kg/m3 ) = 1350 kg/ m3
Cooler Performance Calculation
A h
52.8 0.500 1350 3.564 104 kg
116
35.64 tons
The clinker retention time in the cooler can be calculated on
theoretical basis for the purpose of selection. The bed depth is directly
proportional to the grate speed. If the area of the cooler, the bed depth under
normal operating condition for a given kiln out put rate and density of clinker
are known, then the clinker retention time can be calculated by the equation:
T =( A*h* ρ) * 60/Gt
Area of grate surface = A = 48.6 m2
Clinker bed depth = h = 0.660m
Density of clinker = ρ = 1350kg/m3
T = ( 52.8 * 0.5 * 1350 * 60)/100000
= 21.4 min.
Clinker Residence Time In Cooler
V = 21.4 x 100000/(60 x 1350)
V = 26.42m3
=279166.167x 0.347
=96870.8 m3/hr
117
Volume Of The Clinker Residing In The Cooler At Any Time
V = T*Gt/ (60* ρ )
Gt = Grate Speed
One of the most commonly used way of designating the efficiency
of cooler is by using the heat recuperation efficiency. The heat
recuperation efficiency expresses the ratio of the heat contained in the hot
clinker to the cooler that is returned to the preprocess in the form of
secondary and tertiary air
Secondary and tertiary air required for heat saving kilns per kg of
clinker at the rate of 0.85 ~ 0.95 NM^3/kg of clinker. herefore, secondary
air required per kg of clinker is assumed in the range of 0.347 to 0.373
NM^3 as well as he tertiary air 0.569 ~ 0.587Nm^3
Kiln production per day= 6700 tons
6700 x 1000/24 = 279166.67 kg/hr.
Secondary Air Required Per hr
Density of ir at NTP = Do = 1.21 kg/m3
=11213.67/279166.67
Q = mCp(T2-T1)
=0.419*0.239*(825-25)
=80.12 kcal/kgxcl
118
Volume of secondary air at NTP = 96870.8Nm3
Mass of secondary air at NTP = m = Do* Vo
=1.21*96870.8
=117213.67 Kg
Kg Of Secondary Air Required Per Kg Of Clinker
=0.419
Heat Contents In Secondary Air
=163870.83m3/kg cl
Do=1.2m3/kg
=196644.99/279166.67
=0.704kcal/kg cl
=0.419*0.235*(975-25)
119
Tertiary Air Requirement
Kiln output rate = 279166.167kgs/hr
Tertiary air required per kg of clinker = 0.587 Nm3
Therefore tertiary air required per hr = 279166.167*0.587
Vo=163870.83m3
DomVo
Vo
M =163870.83*1.2
=196644.99 kg
Kg Of Tertiary Air Required Per Kg Of Clinker =
Heat Contents From Tertiary Air =
=93.54kcal/kg cl
Do= 1.21m3/kg
Vo= 279167x1.363
=380504.621m3
Mass = 380504.621*1.21
= 460410.59kgs
120
kgs of tertiary air required per hour = 117213.67kg
kgs of tertiary air required per hour =196644.99 kg
killn out put rate=279.167ton/hr
=279.167*1000
=2.79x105 kg/hrVent Air At Cooler Outlet
vent air at cooler outlet is exhausted at the rate of 1.363 ~ 1.4 Nm3 per kg of
clinker.
r
Kg of excess air per kg of of clinker in cooler
=460410.59/279167
=1.65 kg of excess air/kg of clinker
BALL MILL
The Critical Speed
The critical speed of a ball mill is that speed of rotation at which the
centrifugal power neutralizes the force of gravity which influences the grinding
balls; the grinding ball do not fall and therefore, perform grinding work.
Critical speed = n = 76.6/√3.6
Dia Of The Ball Mill
Basis capacity = 6700 ton/day
According to Tavrov’s formula
Q = q× (a×b×c)/1000×6.7×v×√D.√GN
121
Where
V = Volume = Π/4*d2 * L
Q = Mill capacity
q = Specific mill capacity = 40kg\kwh
a = Grinding index = 0.7143 ×1.2+0.2857 ×1.4 = 1.26
b = Correction index for fine grinding = 0.82
c = Correction type for mill type =0.9
N = No. of revolutions 1/4*d2
Putting all above parameter in eq.
279.167 =40× (1.26×0.82×0.9)/1000×6.7×п/4×D2L√D√(D2L/(1/4)D2L)
D2.5L = 713.98
Since for Ball mill
L/D = 2
Let
L/D = 2.8 (length to dia ratio)
D2.5L = 713.98
D =4.87 meter
Dia of ball mill =4.87 meter
Length of ball mill = 4.87×2.8 =13.64m
Therefore, critical speed =76.6/√4.87 =34.71RPM
Working speed is 65.90% of critical speed
So,
122
N =32/√D
=32/√4.87
= 14.47 RPM
Critical speed = 34.71 RPM
Working speed = 14.47 RPM
Optimum speed is one half or one third of critical speed.
Dynamic Angle Of Repose Of Grinding BallsTheoretical calculation shows that the maximum kinetic energy of the fall balls is
at a dynamic angle of repose equal to 35˚ 20’. Some time its value is 54˚40’.
Distribution Of Grinding Media In The Mill Cross SectionSince angle of repose =35˚20’
It means 35% of total ball is lifted and 63% of the total grinding ball falls.
Degree Of The Ball Charge For steel ball = 28-45%
For sylphs = 25-33%
Total Grinding Ball Charge
According to stierninG = 4000 D2L
Where
123
G = total weight of ball charge in kg.
D = inner dia of mill in meter = 4.87m
L = useful mill length =13.64m
G = [4000(4.87)2 ×13.364] /2
= 649843.06kg
=649.84 ton
Grinding Ball Charge And Clinker Load
According to MardulierSteel ball charge/clinker charge =8.1 to10.1
Steel ball charge = 45% of total ball
So,
weight of ball charge = 649.84×0.45
= 292.43ton
Therefore, clinker charge =292.43/10 = 29.24 ton
Ball Mill Power Demand
Empirical formula for Ball Mill Power
P = 12.5×G
G = 649.84 Ton
124
P = 12.5×649.84
= 8123 Hp
Blanc’s formula
P = C.G√D
C = index relating to grinding ball and mil charge (From grinding index,Peery)
C = 7.00
G = 649.84 Ton
D = 4.87 m
P = 7.0 × 649.84 ×√4.87
P = 10038.5 Hp
Bond’s Equation
W = [10w√P]-[10w√F]
Basis capacity = 6700 Ton/day
Gypsum = 352 ton/day
Clinker = 6700 Ton/day
Standard size of clinker 80% passing 9/16 inch F = 14300microns
Standard size of cement
80% passing through 37 microns
Work index for clinker
13.49×1.3 = 17.53
(1.3 is dry grinding factor)
125
Apply Bond’s Equation
W = 10×17.53 - 10×17.53
√37 √14300
= 28.83 – 1.46 = 27.7 kwh/ton
= 27.37×1.113 = 30.46 kwh/ton
1.113 = cement fine product fraction
Cement production =293.833ton/hr
= 293.833×30.46
=8950.15 × 1.341
Power = 11993.2 hp
126
Site Selection
Site Selection
Raw Materials Availability The source of raw material is one of the most
important factors influencing the selection of a plant site. This is partially true if
large volumes of raw material are consumed, because location near the source
of raw material permits considerable reduction in transportation and storage
charges, attention should be given to the purchased price of the raw materials,
distance from the source of supply, freight or transportation expenses, availability
and reliability of supply, purity of the raw material and storage requirement.
127
Market The location of markets or intermediate distribution center affects the cost
of product distribution and the time of shipping. Proximity to the major markets is
an important consideration in the selection of a plant site, because the buyer
usually finds it advantageous to purchase from nearby source. Note that markets
are needed for by-product as well as for major final products.
Energy Availability Power and steam requirements are high in most industrial
plants, and fuel is ordinarily required to supply these utilities. Consequently,
power and fuel can be combined as one major factor in the choice of a plant site.
Electrolytic processes require a cheap source of electricity. If the plant requires
large quantities of coal or oil, location near a source of fuel supply may be
essential for economics operation.
Climate If the plant is located in a cold climate, cost may be
increased by the necessity for construction of protective shelters around
the process equipment, and special cooling towers or air conditioning
equipment may be required if the prevailing temperature are high.
Transportation Facilities Water, railroads, and highways are the common means
of transportation used by major industrial concerns. The kind and amount of
products and raw material determine the most suitable types of transportation
facilities. In any case, care attention should be given to local freight rates and
128
existing railroad lines. The proximate to railroad center and the possibility of
canal, river, lake, or ocean must be considered.
Water Supply The process industries use large quantities of water for cooling,
washing, steam generation, and as raw material in plants, therefore, must be
located where dependable supply of water is available. A large river or lake is
preferable, although deep well or artesian wells may be satisfactory if the amount
of water required is not too great.
Waste Disposal In recent years, many legal restrictions have been placed on the
methods for disposing of waste materials from the process industries. The site
selected for a plant should have adequate capacity and facilities for correct waste
disposal. Even though given areas have minimal restrictions on pollution, it
should not be assumed that this condition will continue to exits.
Labor Availability The type and supply of labor available in the
vicinity of a proposed plant site must be examined. Consideration should be
given to prevailing pay scales, restrictions on number of hours worked per week,
competing industries that can cause dissatisfaction or high turnover rates among
the workers, and variation in the skill and productivity of the worker.
Taxation And Legal Restrictions State and local tax rates on property income,
unemployment insurance and similar items vary from location to another.
129
Similarly, local regulations on zoning, building codes and transportation facilities
can have major influence on the final choice of a plant site.
Site Characteristics Characteristics of the land at a proposed plant site should be
examined carefully. The topography of the tract of land and the soil structure
must be considered, since either or both may have a pronounced effect on
construction costs. The cost of the land is important as well as local building
costs and living conditions. Future changes may make it desirable or necessary
to expand the plant facilities.
Flood And Fire protection Many industrial plants are located along rivers or near
large bodies of water, and there are risks of flood or hurricane damage. Before a
plant site is chosen, the regional history of natural events of this type should be
examined and consequences of such occurrences considered. Protection from
losses by fire is another important factor in selecting the plant location. In case of
a major fire, assistances from outside fire departments should be available. Fire
hazards in the adjacent areas of plant site must be overlooked.
130
Community FactorsThe characters and facilities of a community can have quite an effect on
the location of the plant. If a certain number of facilities for satisfactory living of
plant personals do not exist, it often becomes a burden for the plant to subsidize
such facilities. Cultural facilities of the community are important to sound growth.
Mosques, libraries, schools, civil theatres etc do much to make a community
progressive. Recreation activities deserve special considerations.
131
PLANT SAFETY
PLANT SAFETY
OPERATIONAL SAFETY AND PRECAUTIONS The ultimate goal of safety and fire protection is
the complete protection of personnel injury, loss of life and destruction of
property as a result of accidents, fires, explosion or other hazardous situation.
The process industries introduce a wide range of hazards as a result of presence
of sizeable quantities of flammable and sometimes unstable materials,
132
Frequently at high temperature, which promote
ignition or decomposition with high pressure the potential energy release is
increased in the presence of structural failure, explosion, detonation, or violent
exothermic reaction.
In order to safeguard against accidents due
mechanical failure under severing operating condition, the equipment should be
designed to meet the specifications and need of recommended authorities. For
example, the design and construction of pressure vessels and storage tanks
should follow A.P.I or A.S.M.E. codes, and they should be tested two or more at
the design pressure.
Beside consideration of safety in the design of
equipment, it is essential to select adequate instrument and control for safe
operation. Safety beside other factor acts as a guide-line in the design of control
system.
Clear and effective operating procedures play an
important role in safe operation of chemical plant. The equipment manufacturers
normally provide operating instructions. But, in the plant where hundreds of small
units are held it is necessary to lay down standard operating procedure (S.O.P)
to ensure safe start up, operation and shut down.
Accident on plant often results during handling and storage of hazardous
material. Injury to plant personnel may also result due to the toxicity of chemical
being handled. It is therefore necessary to have a full understanding of chemical
and physical properties of the materials being handled.
1. Delayed symptoms accruing within 48 hours after breathing light nitrous
oxide fumes. This form of poisoning occurs most frequently in industry.
2. Mild immediate effects from which recovery is apparently complete after
which pneumonia eventually follows:-
In type case of `NO` poisoning, the sequences of events may be:
i) A few breaths of apparently harmless gas.
ii) Only slight discomfort with the worker continuing his job.
133
iii) 5-8 hours after exposure, the victim’s lips and ears become
cyanotic.
3. Increasing difficulty in breathing follows, accompanied by chocking,
dizziness and irregular respiration. Severe untreated cases frequently
terminated fatally from excessive pulmonary congestion or suffocation.
Remedial measures to be taken as soon as possible after an indication
that poisoning has occurred are:
i) Patient should be moved to uncontaminated atmosphere and no
physically excretion permitted. But result should be enforced.
ii) Patient should breathe 100% Oxygen for 30 minutes every 6
hour. If after this time breathing is normal O2 inhalation may be
discontinued.
iii) During period of O2 inhalation patient should exhale against a
positive pressure of about 4 cm water unless there is indication
or history of cardiovascular failure. This is intended to prevent
the development of pulmonary.
134
COST ESTIMAION
135
COST ESTIMAION
COST OF PRODUCTION
MaterialThe cost of raw materials differs with in wide limits between one plant and
another. Factors affecting it are royalties payable, the nature and accessibility of
the deposit, its hardness the amount of overburden the depth available and are
proximity to the works. A hard stone which requires drilling and its blasting before
it can be handled will necessarily cost more per ton than soft material which can
be dug direct with a digger. Again, as the removal of overburden is and
unremunerative operation it adds to the cost in proportion to its depth. if there is
little material available above water level we may be necessary to go lower, in
which the case of cost continued pumping is incurred except in the case of clay
or soft chalk, which can be dug below water. If the quarry is reasonably close to
the works it may be found convenient to erect the crushing or washing plant in
the quarry, and when the wet process is adopted the slurry can be conveniently
pumped to the works. On the other hand, it may be necessary to load the
material into trucks or vessels and convey them for long distance.
Labor Unless labor is exceptionally is cheap, hand labour must be replaced by
machinery in every department, and an output of two tons or more per day for
every man employed on manufacturing operation may be looked for in modern
plant. This takes no account of men employed on repair work or on packing ang
shipping, and is of course only an approximate guide. It varies with the
arrangement and equipment of the factory, and especially in cases where raw
material or power may be purchased.
136
Fuel
The type of coal is to be used is usually settled by considerations of
price, the particularly applies to the coal used for burning where something like
one quarter of the work cost of manufacturing. Cement is incurred. Some coals
are so high in ash content, or otherwise unsuitable, that they are not satisfactory
no matter how they cheap may be. In England bituminous coals of fair quality are
so readily obtainable that price becomes the final arbiter, and this in turn is
affected by the relative positions of cement works and collieries and the means
and cost of transport. In the best modern practice not more than 5 cwt. Of coal of
12,600 B.T.U's per lb. are used for burning a ton of cement on the wet process,
and approximately 1 cwt. less per tons on the dry process. Oil is not used in
British works as its cost is high in comparison with coal.
Power
Coal for power is usually of a more specialized character, depending
upon the type of power plant, and as the tonnage required is so much smaller
than that used in burning the higher cost of the selected quality is not of such
serious import. If waste heat boilers are installed and power is obtained from the
kiln gases, than the quantity of power coal required is further reduced. When
electric power coal required is obtain from the kiln gases, and then the quantity of
power coal required is further reduced. Where electric power is purchased its
cost is usually on a sliding scale subject to coal prices and other factors.
Agreements for such supplies customarily contain provisions for peak and
minimum loads and in designing a new plant a careful balancing of units should
be made in order to secure a constant load factor.
137
Other Supplies:
Gypsum, stores, lubrication oils etc. are usually purchased and costs can
be calculated fairly accurately as a rule about 5% of raw gypsum stone is
likely to be used. Some cements works have contracts under which their
requirements of lubricants are supplied at a fixed price per ton of cement
produced. Haulage and transportation again are much influenced by the
location of the works in relation to material deposits and market. Machinery
repairs and replacement are usually a heavy item, and the saving which
can be affected under this head in designing a new plant is often
considerable. The item, of course, tends to rise in every plant as time
passes, and cement works machinery, notwithstanding its robust
construction, has a relatively short life.
Overhead Charges
The cost of administration and management is usually the inverse ratio to the
output, the larger the plant the less the cost per ton under this head. Rates and
taxes, and insurance may amount to as much as 6 to 8 %of the manufacturing
cost. Allowances of depreciation and obsolescence of plant and machinery
should be at least 5% of their first cost and may well be 10% in some cases if a
sound and conservative financial policy is purchased. Charges for raw materials
depletion and reserves will depend upon very variable factor, and must be
determined separately in each case.
138
COST ESTIMATION OF PROJECT Before an industrial plant can be put into operation, a large amount of
money must be supplied to purchase and install the necessary machinery and
equipment, land and service facilities must be obtained and plant must be
created complete with all piping, controls and services. In addition it is necessary
to have money available for the payment of expenses involved in the plant
operation.
PURCHASE EQUIPMENT COST On way of estimating the equipment cost is by the use cost indexes.
Because prices change considerably with time, due to change in equipment cost,
other specifically to labor construction material or other specialized fields. A cost
index is merely a number for given year showing the cost at that time when the
past value is known. The equitant cost at the present time will be:
Purchased Equipment Cost = Original cost x (Index value at present time index) x (Capacity of present plant ) 0.6
(Value at time original cost is obtained)(Capacity of original plant)0.6
The value of Marshal and Steven installed equipment index process for
process industry, with base year 2005=1152, and in 2008 it is 1200.
On the other hand, to estimate the cost of equipment when no cost data are
available for particular size or operational capacity involved the Logarithmic
relationship known as "Six-tenth-factor rule" is quite effective. According to this
rule, if cost of the given unit at capacity is known, the cost of similar unit with x
time the capacity of the first is approximately (X)0.6 time the cost of the initial unit.
139
PURCHASED EQUIPMENT COST
Purchased equipment cost can calculate by capacity ratio method or what is
known as “Six-tenth-factor rule”.
From a working industry purchased equipment cost for
Purchased equipment cost for 2500 ton per day on dry basis =1.57x109 Rs.
For 6700 ton per day capacity of same plant
Purchased Equipment Cost E = Original cost x (Index value at present time index) x (Capacity of present plant ) 0.6
(Value at time original cost is obtained)(Capacity of original plant)0.6
E = 1.57x10)9x (1200/1152) x (6700/2500)0.6
E =2.95x109 Rs.
140
Total Direct Cost Purchased equipment cost = 2.95x109 Rs.
Purchased equipment installed = 39% E
= 2.95 x 109 x 0.39
= 1.15x109 Rs.
Instrumentation installed = 26% E
= 2.95 x 109 x 0.26
= 7.6x108 Rs.
Conveyor Belt installed =31% E
= 2.95 x 109 x 0.31
= 9.14x108 Rs.
Electrical (installed) = 10 %
= 2.95 x 109 x 0.1
= 2.95x108 Rs.
Building (included services) = 29% E
= 2.95 x 109 x 0.29
= 8.55x108 Rs.
Land = 6% E
= 2.95 x 109 x 0.6E
= 1.77x108 Rs.
Yard improvement = 12% E
= 2.95 x 109 x 0.12
= 3.54x108 Rs.
Service facilities = 55% E
= 2.95 x 109 x 0.55
= 1.62x109 Rs.
Total Direct Cost = 9.075x109 Rs.
141
Indirect cost
Engineering and supervision = 32% E
=2.95 x109 x 0.32
= 9.44x108 Rs.
Construction Expenses = 34% E
=2.95x109 x 0.34
= 1.00x109 Rs.
Legal expenses = 4% E
= 2.95x109 x 0.04
= 1.18x108 Rs.
Contractor fee = 19% E
= 2.95x109 x 0.19
= 5.61x109 Rs.
Contingency = 37% E
= 2.95x109 x 0.37
= 1.09x109 Rs.
Total Indirect Cost = 3.713x109 Rs.
Fixed Capital Investment = 9.075x109 + 3.713x109 Rs.
= 12.788x109 Rs.
142
Working Capital Investment = 15% ( Fixed Capital Investment)
= 0.15x12.788x109
= 1.92x109 Rs.
Total Capital Investment =Fixed Capital Investment + Working Capital Investment
=12.788x109 + 1.92x109
Total Capital Investment = 14.69x109 Rs.
Cost of Production
Variable Cost Rs. /Ton Rs. /Bag
1. Raw and Packing Material 326.93 16.352. Fuel and power 1432.03 71.603. Stores and Spares 154.74 7.74 (Including Repair & Maintenance)
Subtotal 1913.70 95.69
Fixed Cost1. Salaries & Wages 156.67 7.832. Depreciation 206.65 10.333. Admin & Selling Expenses 97.19 4.864. Financial Expenses 378.69 18.935. Misc.Expenses 93.05 4.65
143
Sub Total 932.25 46.61Total Cost of Production 2,845.95 142.30(Variable Cost + Fixed Cost)
Market Price
Cost of production 2,845.95 142.30 Excise Duty 750.00 37.50 Sales Tax @ 15% 539.39 29.97Average Freight & Un-loading 600.00 30.00 Dealers Commission 140.0 7.0Manufactures profit @ 10% on Equity 497.54 24.88
Market Price (Total) 5,372.89 268.64
Pay out Period of the Plant
Pay out period = total capital investment Annual profit + annual depreciation
Total Cement produced per day = 6700(clinker) + 352 (gypsum 5% )
= 7052 ton/day
144
Annual Profit = 497.54 x 7052 x 300
= Rs. 1052595624
Annual Depreciation = 206.65 x 7052 x 300
= Rs. 437188740
Total Capital Investment = Rs. 14.69 x 109
Pay out Period = 14.69 x 109
1052595624 + 437188740
= 9.86 years
145
Instrumentation & Process Control
Instrumentation And Process Control
No plant can be operated unless it is adequately instrumented. The
monitoring of flow .pressure, temperature and level is necessary in almost every
process in ordered that the plant operator can see that all parts of plant are
functioning as required. Additionally it may be necessary to record and display
may other quantities which are more specific to the particular process in
question. For example, the composition of process stream, the heat radiation
produce or humidity of the gas stream.
146
OBJECTIVES: The primary objective of the designer then specifying
instrumentation and control scheme are;
Safe Plant Operations: To keep the process variables within known safe operating limit
To detect dangerous situations as they develop and to provide alarms and
automatic shutdown system
.
Production Rate: To achieve the design product output.
Product Quality: To maintain the product composition within the specified quality standards.
Cost: To operate at the lowest production cost.
Hardware Elements Of Control System:
Process: “Material together with equipment, the physical and chemical
operation that occurs” is called process.
Measuring Elements: The instruments used to measure the process variables such as;
Pressure
Temperature.
Flow rate.
147
Level.
Transducers:It converts the unstandard signals (sensor signal) into standard signals (control
signals).
Transmission Lines: These are used to carry the signals from measuring device to controller.
Standard electronic signal 4-20 mA.
Standard pneumatic signal 3-15psig.
Controller: It generate the error by comparing process signal with set point and
sending theses signals to final control elements.
Final Control Element: It receives the signal from the controller and by some predetermines
relationships changes the energy input to the process.
Recorder: It is used to give the visual demonstration about the behavior of the
process.
General Control Systems:Following are the important general control systems.
Open and close loop system.
Feedback control system.
148
Forward control system.
Combined control system.
Cascade control system.
Open Loop System: Control system in which information about the
controlled variable is not used to adjust any of the system inputs to compensate
for variation in the process variables. These terms is used to indicate
uncontrolled process dynamic.
Closed Loop System: The control system in which the controlled
variable is measured and the result of this measurement is used to
manipulate one of the process variable.
Feed back Control System: In a close loop control system
information about controlled variable is feed back as the basis for the controlled
of the process variable .for automatic control ,a measuring device is used as the
signal. The signal is feed to a controller, which compare it with a preset desired
value or set point, if a difference exists the controller send a signal to final control
element.
Forward Control System: Process disturbances are measured and
compensate without waiting for a change in a controlled variable, to indicate a
disturbance has occurred. It is also useful when a final controlled variable cannot
be measured.
149
Combined Control System: Forward feed control system can
rarely fulfill the entire control requirement so that feed control is normally used in
combination with forward feed control system .such arrangement reduces
accuracy and amount of process knowledge ,detailed requirement for
specification of transfer function.
Cascade Control System: It is often used for minimizing disturbance
entering in a slow process. it also speed up the response of the control system
by reducing time constant relating the manipulated variable process output.
Instead of adjusting the final control element such as control valve, the output of
primarily controller is made the set point of secondary controller.
Modes Of Control:The various type of control are called “mode” and they determine the type of
response obtained. in other words these describes the action of the controller
that is the relationship of output signal to the input or error signal .it must be
noted that it is the error that actuates the controller. The four basic modes of
controls are;
Proportional control
Proportional derivative control
Proportional integral control
Proportional integral derivative control.
150
Proportional Control: The output of proportional controller is fixed
multiple of the measured error, that is, proportional controller is simply a
multiplier. In this control system the controller variable is measure and signal is
compared with a set point. The difference is the error
() Manipulated variable derives the final control element.
Which is amplified Kc times by proportional gain. The output of proportional
controller,
This controller is used when precise control is necessary. Offset and oscillatory
response is tolerated. A special type of proportional control is on off control. it is
simplest and most common mode of control such as thermostat used in space
heating and refrigeration.
Proportional Derivative Control: In this kind of control,
offset remains but response to any change becomes smooth i.e. problem of
oscillatory response can be overcome by use of this type of controller.
Proportional Integral Control: The output of Proportional integral control
consists of two parts, the first proportional to the error and second proportional to
the integral of the error. Even small errors can eventually provide enough
controller output to force the error to zero. This controller removes the offset but
response of the system to a change may not be smooth.
Proportional Integral Derivative Control: Three modes of
controller combine an action of Proportional, integral and derivative
elements into a single events. proportional elements give faster transient
151
response but more oscillatory, integral element eliminates steady state
offset and derivative elements allows higher proportional gain. This kind of
controller is used to give very precise control and it is most expensive of
all.
Typical Control SystemA collective general description of the instruments used will be given which may
be conveniently divided into following groups.
Temperature recorder
Temperature indictor controller
Level controller
Pressure controller
Flow controller
Temperature recorder
The thermo couples are the most common Temperature measuring devices,
particularly in industry. Since mercury may react with chemicals to form explosive
components, the use of mercury filled pressure spring thermometer is avoided.
These are used to measure Temperature of the stream entering the units.
Recommended Thermocouple
For Kiln Process
Type – R- positive wire is PT 87-RH13
- negative wire is platinum
- milli volts (minimum to maximum) per oC = 0.00645 – 0.0118
- Temperature Range -18 to 1704oC
- Good at high temperatures, poor below 538oC
-
152
Temperature Indicator Controller: The normal method of
controlling a heat exchanger is to measure the exit temperature of the fluid
being processed and to adjust the input of the cooling or heating medium
to control the desired temperature. Therefore temperature recorder
controllers are installed to control the heat exchanger.
Level Controller: In any equipment where interface exits between two
phases (e.g. liquid, vapor) some, means of equipments as is usually done
for the automatic control of the flow from the equipment.
Pressure Controller: Pressure control will be necessary for most system
handling vapor or gas. The method of control will depend on the nature of
process.
Flow Controller: Flow control is usually associated with inventory control
in a storage tank or other equipment. There must be a reservoir to take up the
changes in the flow rate. To provide flow control on a compressor or pump
running at fixed speed and supply a near constant volume output, by pass control
would be used.
Alarm & Safety Tips: Alarms are used to alert the operators of serious
and potentially hazardous, deviations in process conditions .key instrument are
fitted with switches and relays to operate audible and visual alarms on the control
153
panels. Where delay or lack of response by the operator is likely to lead rapid
development of a hazardous situation. The instruments would be fitted with a trip
system to take action automatically to alert the operators, such as shutting down
pumps, closing valves, operating emergency system.
The basic components of an automatic trip system are;
A sensor to monitor the control variable and provide an output signal when
present value is exceeded.
A link to transfer the signal to the actuator usually consisting of the system
of pneumatic or electric relays.
An actuator to carry out the required action, close or open the valve,
switch off motor.
Interlocks: Where it is necessary to follow a fixed sequence of operations,
interlocks are included to prevent operators departing from the required
sequence. They may be incorporate in the control system design as pneumatic
or electric relay or may be mechanical interlocks. Various propriety special
interlocks and key system are available.
THE LETTER CODES FOR INSTRUMENT SYSTEM
Property measured
First lette
Indicating only
Recording only
Controlling only
Indicating and
Recording and
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r controlling
controlling
Flow rate F FI FR FC FIC FRC
Level L LI LR LC LIC LRC
Pressure P PI PR PC PIC PRC
Temperature
T TI TR TC TIC TRC
Radiation R RI RR RC RIC RRC
Weight W TI WR WC WIC WRC
Quality analysis
Q WI QR QC QIC QRC
NOTE: The letter A can be added to indicate the alarm, with H and L
placed next to the instrument circle to indicate high or low.
D is used to show difference or differential, PD for pressure differential.
F as the second letter indicates ratios e.g. FFC = flow ration controller.
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The first letter indicate the property measured e.g. F = flow subsequent letter
indicate the function e.g. I = indicating.
RC = recorder controller.
The suffixes E and A can be added to indicate the emergency action and / or
alarm functions. The instrument connecting lines should be drawn in manner to
distinguish them from the main process lines. Dotted or crosshatched lines
normally used.
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ENVIROMENTAL PROTECTION &
ENERGY UTILIZATION
ENVIROMENTAL PROTECTION AND ENERGY UTILIZATION
ENVIROMENTAL PROTECTION IN THE CEMENT INDUSTRY
The cement industry’s duties in the relation to the environment come price
mainly the following form of population:
1. Prevention of air population;
2. Noise abatement;
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3. Prevention of vibration;
4. Protection of landscape and watercourses.
Environmental protection has for many decades been par and parcel of the
entrepreneurial problems of our industry. it is gratifying to note that cement
manufacturing to note that cement manufacturing activities are not among those
industries that more particularly come in for criticism in the public debate on
population prevention. I can furthermore be noted that the cement industry has
recognized and accepted the principle of causer responsibility before it became a
subject of conservationist discussion.
Expert understanding of this comprehensive statutory requirement and their
implementation calls more and more for not only the technical knowledge of the
cement engineer, but also for substantial legal knowledge. The professional
image of cement and process engineer will therefore have to undergo an
evolution towards the training of environmental engineering legal experts.
The consequences of this mass of legislation as a cause of cost and as
a deterrent to investment are something that may also appropriately be
mentioned at this point.
COST OF ENVIRONMENTAL PROTECTION
In terms of amount spent by industry as a whole upon environmental
protection, the rock product industry and thus the cement industry occupies a
leading position.
As revealed by the latest survey conducted by the institute of expenditure on
environmental protective measures in the rock products industry in the years
1971-1975 amounted to 105 of the overall capital expenditure. The order of
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magnitude of the operating cost in respect to environmental protection can at
present only be estimated within approximate ranges
All public discussions on the burden that that can be imposed on the
economy in fulfillment of environmental protection requirements should be on
based on considerations of effect upon return on investment.
ENVIROMENTAL PROTECTION AS A PROBLEM OF PLANT LOCATION: In the past, the prerequisite condition for establishing
new cement plant sites or for the expansion or reestablishment of existing plants
consisted in satisfactory coming to terms with the conventional planning factors
such as raw material availability technical infrastructure, marketing possibilities
and earning power.
In recent years, however new planning criteria such as regional
development, zonal economic planning, anti pollution planning, scheme for built-
up-areas, land scope preservation and nature reserves, to mention just a few
have emerged as important factors in deciding where to locate a cement work.
The latitude and scope available for varying the sitting of the work are further
narrowed down sometime to point of impracticability, by the imperative need to
remain close to the source of raw material. A further difficulty is that the forward
planning of public authorities more particularly the municipalities seldom
extended for more than ten years ahead. Whereas planner concerned with
industrial raw material supplies have to think in term of 30-50 years in assessing
the development potential of site if a dependable decision as to plant location is
to be made.
In addition to this uncertainty of planning there accrued changes, relatively
short notice, in the requirement imposed by the environmental protection
regulations. The statutory requirement on completion of the official approval and
licensing procedure are often found to change in relation to these, which existed
at the start of planning of an industrial project, has become an entrepreneurial
risk.
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The minimum distance of industrial and commercial installations from
residential areas, which in instances have to be compiled with also, increase the
area of land required for quarries and cement works. Thus the total area required
for quarry and works site is increased almost fourfold.
IMPACT OF ENVIRONMENTAL STANDARDS ON ENERGY CONSIDERATION: The cement industry in Pakistan has been
observing environmental standards for the fall out of dust from Raw Dry grinding,
cement grinding, packing, by controlling emission of dust by bag filters and
electrostatic precipitator. The clinker dust in air is collected in multi cyclones
before discharge. We need a constant check and efficient use of this equipment
and may also go in for improved equipments where necessary. But we are not
controlling fall out of dust from the flue gases of existing to two stage suspension
preheat kiln in due course of time and will have to install electrostatic
precipitators in such units. In these kiln where conversion would not be possible,
we would have to go for dust collection equipment for flue gases. The other
aspects of environmental standards are the following;
1-Noise abatement
2-Prevention of vibration
3-Prevention of land scope and water courses
These aspect have not been received much attention in Pakistan as mostly
the factories were as, with the tremendous growth in cities residential areas have
stretched to cement factories in some cases. We will have to take cognizance of
these facts ultimately for the existing factories and for planning the new sites for
cement factories.
Sound insolating buildings may be necessary in some cases and ventilation
through silencers coupled with cooling the building may be required, in future.
The energy requirement will increase in future for observing environmental
standards.
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TECHNICAL AND MANAGERIAL IMPEDEMENTS FOR IMPROVING ENERGY EFFICIENCY
The great demand of cement in country is keeping the industry in working on
top speed and improvement in energy efficiency us not receiving the attention as
it should as it would entail more stoppage for modification and conversion which
cannot be afforded at present. But this to some extent, is compensated by high
capacity utilization about 90% and keeping the imports of cement to minimum
possible. The new projects however being planned on energy efficient modern
processes.
The government and industry relationship is quite good there is a barrier in
improving energy efficiency. As a matter of fact, the government is keeping
abreast of energy consumption and requirement of the industry. There is
incentive to employees on production basis, which also help in energy efficiency
indirectly.
The most important impediment in energy efficiency improvement is in training
and technical assistance. The cement technology like other technologies is
developing fast and it will be difficult to have improvement in energy efficiency
without imparting good training and giving assistance to developing countries for
operating modern energy saving cement plants efficiently. The training and
assistance to developing countries for operating modern energy saving cement
efficiently. The training and assistance should be in operation, maintenance and
instrumentation so that the developing countries are able to keep the automatic
control system in every good condition. The training in the latest energy efficient
plants should not be less than the six months in any field It will be of interest to
note that when cement factories were being established in fifties and sixties, the
training period of personnel varied from six months to a year. Such training
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should be given to middle management technical personnel ant technical
assistants in the form of experts should also be provided
.
FUTURE TREND IN ENERGY EFFICINCY AND SUGGESTIONS OF STRATEGIES
1. The pattern of consumption of energy in cement industry is;
75% to 95% energy as fuel for drying and calcining process and 10-25% for
generating electrical power consumed. There has been much improvement in
efficient use of fuel energy during the last 25 years; the modern dry process
suspension preheated kiln with calcinatory has improved the efficiency of energy
utilization from (28 to 50%) of the theoretical requirement. The improvement in
utilization of electrical energy about 75% is in the raw meal and cement grinding
processes, where the utilization of energy efficiency has not exceeded 20% The
useful utilization is not in size reduction and greater part of energy emission is
lost in the form of friction, heat and noise emission.
The only useful utilization of fuel energy in cement industry is for calcining
and for drying the raw materials and slurry. We should therefore go in for dry
process as for as possible and wet grinding is necessary; we should filter the
slurry to a reasonable moisture, for drying by the hot gases from two stage
preheated kiln.
The losses of fuel energy on other side are;
Losses through flue gases.
Losses through cooler, sealing rings.
Losses through radiation.
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MODREN FOUR STAGE SUSPENTION PREHEATER KILN
The present day suspension pre heater-calcinator kiln utilizes the energy
in the flue gases and hot gases from cooler for drying the raw material and
source of air to calciner. The improvement of pre calcination process in
suspension-preheated kiln has increased the calcinations. From 40-90% in the
suspension preheated by secondary firing from a pre calcining furnace installed
between the preheated and kiln inlet. This increase the kiln output capacity for
the same kiln volume and vice versa. This kiln capacity may be increased by
70% the thermal load in the kiln is reduced which increases the refectory life kiln
availability.
EFFICIENT USE OF CEMENT IN CONCRETE
The structural use of cement is governed by various codes where the use
of cement is properly controlled, in relationship to quality, quantity of cement,
aggregates and environmental conditions. Presently mixes are specially
designed according to strength, which they give on maturity and this varies from
aggregates to aggregate.
The codes are fairly broad based and for larger works these can be further
refined where the quality control could be employed. However in smaller jobs
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where the quality control cannot be established properly, some extra use of
cement is unavoidable. In this respect the design parameters and limitations laid
in various codes, need proper implementation.
The efficient use of cement can further be ensured by maximum utilization
of pre casting and pre stressing techniques which;
1. Reduces the consumption of cement as well as steel, which is also a
sources and imported item in many developing countries.
2. Produces high strength concrete under factory-controlled conditions,
which is more economical to use as against lower strength concrete for
and equal load carrying capacity.
The administrative authorities need to carry out following action;
Report maximum to design-cum-construction bid which will arouse,
encourage and will reward maximum techniques that will save cement
and overall cost.
Standardize a few say one or more dozens precast and prestressed
concrete members at the National level so that standard shuttering could
be used and production cost reduced on account of greater repetitive
use shuttering.
Private industrialists be encouraged to set up plants for manufacture of
hallow pre stressed concrete planks by extrusion methods and
manufacture of Light Weight Aggregates which go a long way in
economizing construction and improving insulations an energy
economizing step.
Considerable cement can be saved from non-use as cement plasters
can be replaced by gypsum /lime plaster inside the buildings. Similarly
for masonry work can be done in lime or in mud.
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SUGGESTIONS
INDUSTRIAL LEVEL1. All new plants should be based on latest energy efficient cement
technologies proved beyond doubt.
All plants where possible should be based on dry process 4 stage
suspension preheated kiln preferably with pre calciner. As these are very
modern, highly sophisticated plants, we should get technical assistance
for one year in the form of expert for operation, maintenance
instrumentation and control equipment, after commercial production. A
large number of middle management technical officers are trained in
foreign countries on such plants in these fields.
2. The wet plant may be converted to semi wet-wet or dry process plant in
due course of time but should be planned in advance.
3. The insolating firebricks should be tried where possible.
4. The moisture should be kept at minimum.
5. Belt conveyor possible may substitute the transportation by dumper.
6. The site should be chosen where homogeneous materials are available
and an economic raw mix with reference to burn ability can be designed.
7. We should try to reduce losses through cooler and sealing rings and
modify it where necessary.
8. The power factor the ratio of working power in KW or KVA in delivered
power may appear directly or indirectly on utility bills. It may be retained as
an option on the part the utility. Most operation can and should work within
the range of 90-95%. Working below 85% range contributes to poor
energy affiance.
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NATIONAL LEVEL1. The government should encourage establishment of only latest energy
efficient plant of cement technologies proved beyond doubt.
2. The government may provide direct incentive to cement industry, that
those factories which improve fuel consumption per ton of clinker on
yearly basis, from their most efficient fuel consumption recorded so far,
for each type of product, by allowing the savings so accrued to be tax
free. The new plant who improves upon their guaranties of fuel
consumption will also be considered similarly.
3. We should promote generation of power on coal near their deposits near
the investment in coal machinery for power generation may be much
lesser as compared to cement industry so that natural gas is available to
cement and other industries.
4. In case it is not possible those cement factories are nearer to coal
deposits should use coal but the Government as a policy matter should
help them to have better profitability than the cement factories fired with
natural gas, as an incentive.
REGIONAL LEVEL
1. The technical assistance in the form of technical experts and training to
middle management technical personnel is provided by the developed
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countries in the region for operation maintenance, instruments and control
of modern cement plants.
2. The development work in cement technology in the region should be
made available to regional countries.
3. Regional financing agencies should help in modernization and balancing
as well as new projects preferably with untied loans.
Bibliography
Perry & Green Perry’s Chemical Engineering Hand Book Peter Timmerhaus & Ronald E. West Plant Design and Economics
for Chemical Engineers Welter H. Duda Cement Data Book D.Q. Kern Process Heat Transfer George T. Austin Shreve’s Chemical Process Industries
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Abdul Majid Hand Book For Cement Engineers McCabe Smith Herriot Unit Operation of Chemical Engineering Coulson and Richardson’s Chemical Engineering
In addition we are also thankful to various industries for their co-operation & co ordination with us in a friendly manner to accomplish this project.
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