nfl final report
TRANSCRIPT
INTRODUCTION
The rise in fertilizers consumption in India has been quite phenomenal
during past two and half decades. To meet the rise in consumption of fertilizers
creation of additional capacity was also planned. The change in the world wide
energy concept and rise in the oil prices in 1973 forced India to increase its
nitrogenous production by adopting new and sophisticated technology which
could use cheaper sources of raw material.
The NFL (public undertaking) was conceived to plan and implement two
modern large capacity single steam nitrogenous fertilizers plant in the
predominant fertilizer consuming oil to coup with the increasing demands of
fertilizers.
The industry was formed and registered on 23rd August 1974 to setup two
nitrogenous fertilizers plants each with capacity 5-11 lakh tones per annum of
idea at Panipat and Bathinda.
Bathinda was basically selected as one of the site of fuel oil based plant
from the consumption point of view since Punjab is mainly agriculture based
state and Bathinda was the best choice for it.
“Feed in” at Bathinda was achieved on 7th Dec. 1978. Bathinda project
produced ammonia successfully on May 28,1979 and urea on June 2, 1979.
NFL was incorporated on Aug 23, 1974 in order to implement this project
contract were entered into with M/s “TOYO ENGINEERING CORPORATION” a
well-known Japanese Engg. Company and Engg. India Ltd. (EIL), a public sector
and Engg. Organization. This contract becomes effective on Sept. 26, 1974 with
a guaranteed “feed in” on the Bathinda fertilizers project to implement with in 36
months from the zero date. Later on with the need of electric power NFL estd. Its
own powerhouse known as CPP (Captive power plant) with two turbines of 15
MW each.
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SALIENT FEATURES OF PLANT
PLANT RATED CAPACITY
UNIT UREA(Tonnes/annum)
NITROGEN(Tonnes/annum)
Nangal (PB) 318160 231340
Panipat (HR) 511500 235290
Bathinda (PB) 511500 235290
Vijaypur (MP) 1452000 667920
Total 2793160 1369840
PRODUCTS OF
National Fertilizers is producing “Kisan Khad, Kisan Urea & Ankur” on
commercial scale. NFL is marketing a number of industrial products produced as
by-products in its plants.
Fertilizer Products
1. Kisan Khad
Moisture by wt. 1.0% (max)
Total ammonical nitrogen by wt. 25% (min)
Ammonia nitrogen by wt. 12.5% (min)
Calcium nitrate by wt. 0.5% (max)
Particle size passes through 4mm 1.s sieve by wt. 80% (min)
Retained on 1mm 1.5 sieves below 1mm 1.s sieve 10% (max)
2. Kisan Urea
Moisture by wt. 1.0% (max)
Total nitrogen on dry basis 46% (min)
biuret by wt. 1.5% (min)
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Particle size pass 2.8mm by wt. 1.s sieve 80% (min)
Retained on 1mm sieves 80% (min)
Industrial Products
1. Anhydrous ammonia (NH3)
Ammonia by wt. 99.5% (min)
Water by wt. 0.5% (max)
Air content by wt. 0.02% (max)
2. Methanol (CH3OH)
Methanol by wt. 99.85% (min)
Density at 200C 0.793 Kg
3. Sulphur (S)
sulphur purity 99.5% (min)
4. Nitric Acid (HNO3)
Nitric acid by wt. 53%
5. Ammonium Nitrate (NH4NO3)
Purity by vol. 99% (min)
6. Nitrogen (N2)
Purity by vol. 99.99% (min)
7. Oxygen (O2)
Purity by vol. 98.0% (max)
Inert by vol. 2.0% (max)
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Moisture nil
Carbon nil
8. Carbon Dioxide (CO2)
Carbon dioxide by vol. On dry basis 98.0% (min)
Inert gases by vol. 2% (max)
Methanol by wt. As H2S 1ppm 500ppm (max)
9. Carbon (c) from slurry
Carbon on dry basis by wt. 98%
10. Sodium Nitrate
Ash etc. 2%
Purity by wt. 98% (min)
NaNO3 by wt. 0.50% (max)
FeNO3 by wt. 0.003% (max)
Water by wt. 1.0% (max)
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IMPLEMENTATION OF BATHINDA UNIT
To take up this challenging job for completion of this unit within a limited
period of 36 months from zero date 26 sep,1974 contracts were signed with
Toyo Engineering Corporation Limited well known Japanese and Indian
Consultancy Companies respectively.
Project cost
The approval project cost of Bathinda Unit is Rs 240.47 Crores with a
foreign exchange component which was mainly met from Japanese Yen
Credit; however, certain special equipment requirement from others was met
out of the free foreign exchange and Dutch credit.
REQUIREMENT OF RAW MATERIAL AND INPUTS
Fuel Oil/LHLS 850 MTonne/day
Coal 1680 MTonne/day
Water 13 MGD
Power 28 MW
BENEFITS
This project has not only helped in increasing the country’s food output but
has also given direct employment to 6000 persons. Till March 99 this unit has
produced more than 8 million tons of food grains. The farmers of Punjab,
Haryana and Rajasthan have been the largest beneficiaries of this project. Both
central and state governments have been benefited by way of exercise duties
and other local taxes on various raw material and end products. Apart from plant
level staff, there is employment potential for entrepreneurs to set up ancillary
industries based on requirement of this plant such as polythene-lined jute bags,
alum, stitching thread etc. while by-product sulphur produced is already being
sold to outside parties. There is scope for marketing other by-products like
carbon and industrial gases e.g. Oxygen, Nitrogen, Carbon dioxide etc.
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PRODUCTION PROCESS:
Ammonia is produced by the partial oxidation of heavy oil. Raw synthesis
gas is produced in the Gasification section by the partial oxidation of the
heavy oil. The raw synthesis gas produced in the Gasification section is
further purified in Desulphurised, CO-Shift Conversion and Decabonation
sections. After final purification in the nitrogen wash unit, it is compressed
to about 220 ATM pressure and is converted to ammonia using a special
synthesis catalyst. In order to manufacture Urea, the following procedure is
used. In Titanium Lined reactor, ammonia and carbon dioxide are mixed at
about 240 atmospheric pressure. The carbon dioxide used in the process
is obtained from ammonia plant. After decomposition and recovery steps,
to ensure maximum product yield, the urea solution obtained is
Concentrated, Crystallized, Centrifuged, dried and conveyed to the top of
the prilling tower where it is melted in the melter and sprayed through the
acoustic granulators to produce urea prills. By decomposition, uncoverted
carbonate solution is decomposition to recover ammonia, which along with
the carbonate solution is recycled back to the urea reactor.
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MAJOR AWARDS AND RECOGNITION
National Safety Award from the ministry of Labour, Government of India
for meritorious performance in industrial safety during 1989.
Merit certificate from National Productivity Council (NPC) for performance
improvement during 1991-92.
Received during year 1994-95 “Prime Minister’s Shram Award and
Vishwakarma Rashtriya Puruskar” under various suggestion schemes. It
also received “Punjab Safety Krit Shiromany Award and Krit Veer Awards”
from the state Government. It also received “Udyog Excellence Gold
Medal & Citation” from Industrial Economic Forum, New Delhi.
It also won “Jawaharlal Nehru Memorial National Award” constituted by
the International Greenland Society, Hyderabad for Pollution Control &
Energy Conservation.
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Three prizes were awarded by “Punjab Industrial Safety Council” it won
prizes in lower Accident Frequency Rate.
Maximum Reduction in accident Frequently Frequency Rate.
Longest Accident Free period.
An ISO-9002 & ISO-14001certified unit.
An OHSAS-18001 certified unit.
BRIEF WORKING OF PLANTS
BATHINDA FERTILIZER PLANT PROCESS
Bathinda Fertilizer Plant may be divided in four groups.
Offsite and Utilities Plants
Steam Generation And Material Handling Plant
Ammonia Plant
Urea and Bagging Plant
OFFSITES AND UTILITIES GROUP OF PLANTS comprised of “Raw
Water Filtration Plant, DM Water Plant”, “Instrument Air Compressor House”,
Cooling Tower”, “Sulphur Recovery Plant” & “Effluent Treatment Plant”.
Raw water plant is designed to treat 2400 M3/hr. of raw water into potable
water and thus its effective distribution to Township and NFL Plant. Thus to
avoid surface corrosion due to different minerals water is further
demineralised and finally polished in DM Plant before finally feeding it to
boilers. It consists of Cation Units Degasser Towers Anion Units and Mixed
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bed units no. H2 Instrument Air Compressor House supplies instrument air
and service air compressors and two service air compressor one in each as
standby. The cooling towers systems provided in NFL, Bathinda are closed
recirculating system supplying cooled water to various consumption points in
plants. Sulphur Recovery Plant has helps in production of additional by
product, sulphur in the plant. It is based on the process of recovery of
elemental sulphur from Hydrogen Sulphide gas. Effluent treatment plant
serves a major role in decreasing the extent of pollutants in the waste outlets
and also in the recovery of fuel oil from the oily effluents.
STEAM GENERATION PLANT
Steam generation plant produces and supplies steam at 100kg/cm2pressure and
4800C temperature to ammonia plant
Introduction
Steam has many qualities. It is easily distributed. It is used for power process
and heating. It is taste less and odorless steam for use in industry is
generated in boilers. Modern all welded packaged and water tube boiler is
very economical and popular as such units are compact mounted on a
common base fitted with mounting and fittings. Machine fuel fire devices and
equipments and auxiliaries accessories, automatic control for fuel burning
pressure and feed variations and thus have immersed as modern industrial
steam generators for the new order of over industrialization in our country and
world over.
The boilers are generally to fire conventional fuels such as coal, oil, natural or
waste gas at NFL Bathinda the steam is generated for dual purposes.
1. For running prime mover.
2. To exchange heat in the processes.
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There are 3 boilers supplied and erected by BHEL. Each boiler is designed to
produce steam at the rate of 150Tonne/Hr. Normally operation of two boilers
should be sufficient to meet the above mentioned objectives, but the third
boiler has to run simultaneously due to increase in steam load consumption
by main consumers.
The boilers are type of BU40. Coal is major source of heat, but oil spot is also
given to produce the steam of desired temperature and pressure. The plant is
designed for heat efficiency of 86.44% as per British standard of 1974. Coal is
used as fuel. Coal comes from coal handling plant through conveyor belt. In
the coal handling plant crushers are provided for crushing the coal into small
pieces. After the crushers a heavy electromagnet is also installed for
preventing the iron particles. Coal comes into bunkers and from the bunkers,
coal is sent to the grinding mill in a limited quantity.
Grinding mill coal is grind and converted into powder form. This powder form
of coal is sent into the boiler corners through a pump. This pump sucks the
coal from grinding mill and outlet of the pump is connected to a pipe and this
pipe is further branched into four pipes. These four pipes are connected to
four corners of the boiler. Initially coal cannot burn separately; therefore, oil
fuel LSHS/LDO is mixed with coal and sent into furnace and coal starts
burning. Initially burning temperature is necessary to maintain 1000C. After
burning this fuel and coal, the flue gases flow surrounding the water tubes
that are filled with water, due to these flue gases, steam is produced
WHY STEAM IS REQUIRED
Major consumption of steam is in ammonia plant and roughly 6.5 to 7 Te of
steam is required for producing one Te of ammonia, this steam is used:
a) for driving the turbo compressors
b) as process steam for various reactions
c) for heating purpose
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The designing and introduction of high pressure turbines and compressors
has revolutionized the industry especially the fertilizer industry. Single stream
high capacity plants of 2200Te/day urea and 1350Te /day. Ammonia have come
up which was not feasible a few decades back. The turbines used to run these
compressors are driven by high pressure and high temperature steam. If we add
the output power of various turbines run by steam, it comes around 50MW in
other words we are saving 50 MW of electricity.
In our factory where heavy fuel oil is used as feed stock, requirement of
steam is very high i.e. 7 Ton per tonne of ammonia as compared to plants using
natural gas or naphtha as feed where steam requirement is 3Te per ton of
ammonia. It shows the importance of steam and steam generation plant.
Moreover steady pressure and temperature is very essential for the life and
efficiency of these turbines. Hence role of SGP is very important
Steam in SGP is generated by three number VU-40 type boilers
supplied .by M/S BHARAT HEAVY ELECTRICALS LTD. These are in operation
from 1977 and each boiler can generate up to 150Te of steam per hour. These
are water tube boilers which mean the water used for steam formation is inside
the tubes and the heating material that is coal or oil is burnt in the outer furnace.
Roughly speaking about 750KCal of heat required to generate one ton of steam
at the present efficiency of these boilers. This heat is mainly supplied by
pulverized coal. Heavy fuel oil is used for initial start –up and continuous support
to coal burners and light diesel oil is also used for initial start-up.
FIRING SYSTEM:-
Pulverized coal is the coal grinded to easily combustible and economically
viable level so that it burns completely with in the available time inside the
furnace .BOWL MILLS are used for grinding the coal. Coal received from
material handling plant is stored in coal bunker and is fed to the bowl mill through
a coal feeder. Hot air is also supplied in the mill for heating the coal and
conveying it to the furnace through a fan called EXHAUSTER FAN which takes
suction from the mill and maintains it under negative pressure. Oversize and
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ungrindable material like stones are thrown out by the mill. Coal and air mixture
called pulverized fuel from the exhauster is supplied to COAL BURNER. Coal
burners are arranged tangentially on all the four corners of the rectangular
furnace at three elevation levels. Thus there are 12 coal burners. In between
these three elevations OIL BURNERS AND START UP BURNERS or IGNITERS
are arranged at two elevations. Thus there are 8 oil burners and 8 igniters. As
coal requires some minimum temperature for ignition, igniters use LIGHT
DIESEL OIL (LDO) and can be lighted by remote control. Oil burners use heavy
fuel oil (LSHS).
The FURNACE is a cubical suspended enclosure with water tubes forming
its four walls. The furnace is designed with sufficient volume to provide for
complete and efficient combustion at all loads without flame impingent by the
reaction of carbon present in coal and oxygen present in air to form carbon-
dioxide.
C + O2 → CO2 + Heat
These gases called FLUE GASES heat up the water in tubes to form steam.
As the FLUE GASES rise up, their heat is utilized in various ways as shall be
discussed later. The furnace is maintained at a negative pressure of 5 mm water.
WATER AND STEAM SYSTEM
The steam generated should be free from all impurities like minerals,
silica, oxygen, iron etc, for the safety of and efficiency of steam turbines and
boilers. For this purpose RAW WATER is physically and chemically treated and
finally supplied to SGP from ammonia plant. This water is called BOILER FEED
WATER. Feed water is further heated to around 2400C by the flue gases and
taken to STEAM DRUM. Steam drum acts as storage tank and also separates
water from the steam at 3150C and 106kg/cm2 pressure water then enters MUD
DRUM through BANK TUBES heated by flue gases. This drum helps to maintain
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circulation of water. Water from mud drum enters the RING HEADER formed at
the bottom of outside the furnace and rises by gravity through water wall tubes
on all the four sides, takes heat from furnace and enters steam drum as a
mixture of steam and water. Water is separated here and steam at about 3150C
is taken through two SUPER HEATERS called PLATEN SUPER HEATER AND
FINAL SUPER HEATER heated by flue gases to attain final temperature of
steam around 4900C. The outlet temperature from these super heaters is
controlled by adding boiler feed water.
FLUE GAS SYSTEM
The products of combustion in the furnace consist of carbon-di-oxide,
nitrogen, ash, oxygen and sulphur-di-oxide. After leaving the furnace the heat
Of these gases called FLUE GASES, is utilized at various levels.
First the steam from steam drum is heated in two super heaters to get the
required temperatures of 4950C and then feed water in BANK TUBES is also
heated and the gases leave bank tubes at around 4970C next the heat is utilized
to heat feed water in the ECONOMIZER and gases are cooled down to 3200C.
These gases are further cooled down to 1500C in ROTARY AIR HEATER where
the air is required for combustion and conveying the coal is heated up.
Temperature is not reduced further because at lower temperature oxides of
sulphur present in flue gases are converted to ACID which damages the down
stream equipments. These gases then pass through ELECTRO STATIC
PRECIPITATOR (ESP) where ash is removed. From ESP these gases pass on
to INDUCED DRAFT FAN which maintains draft in the furnace and finally the
gases are let off to the atmosphere through a chimney about 80mtr high.
POLLUTION AND THEIR DISPOSAL
Along with optimum utilization of company’s resources to achieve
maximum profitability, our unit has always performed its duty to keep the
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environment clean. We have installed latest available pollution control
instruments and equipments. The chief pollutants generated in SGP are ASH
and SULPHUR –DI-OXIDE. Their separation and disposal are discussed in brief.
ASH:
Ash is the incombustible material contained in raw coal which has about 40%
ash. It also consists of heavy metals like vanadium and nickel. If inhaled it can be
harmful to human beings.
After combustion of coal, ash remains as such. About 20% ash of total ash
generated consist of higher wt. particles which fall down to BOTTOM ASH
HOPPER provided at the bottom of the furnace. Ash slurry is formed here due to
water level maintained in the bottom ash hopper. This is taken out by water
ejector once in eight hours and sent for disposal in lagoons.
FLY ASH:
Fly ash is the ash containing light particles. It forms the major portion that
is 80% of the ash generated. It is carried away from the furnace along with the
flue gases. The ash particles are removed from the gases in electro-static
precipitators as shown in block diagram after air-pre heaters.
ELECTRO-STATIC PRECIPITATORS:
The electro-static precipitators’ forces to separate out dust particles from
the flue gas. High voltage is applied between electrodes arranged in rows
alternately. Due to high voltage gas particles are ionized. Most of the ions are
negatively charged. They stick to dust particles and carry them to positively
charged electrodes which are in the form of a rectangular plate. Thus dust
particles stick to those plates. These plates are rapped periodically to dislodge
the deposited dust which is collected in the hopper below.
Ash is ejected from these hoppers by water jet and it forms ash slurry. Fly
ash slurry and bottom ash slurry are mixed together and sent to ash slurry
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disposal ponds outside the factory where the slurry settles down and overflowing
clear water is recycled back to the system.
SULPHUR-DI-OXIDE:
Sulphur-di-oxide is formed due the presence of sulphur in coal which
varies from 0.1% to 0.5%. For safe disposal of SO2 minimum chimney height has
been recommended by pollution boards, depending upon the quantity of sulphur-
di-oxide generated per hour. In our case it comes out to be around 75 mts. taking
maximum amount of SO2 generated. Chimney height of SGP boiler is 80mtrs.
Suitable instrumentation has been provided for monitoring all the
parameters and important analyzers and cutouts of a part or even complete
boiler has been provided in case of emergency.
MAIN EQUIPMENT
Economizer
The main function of Economizer is to preheat the boiler water before it is
introduced into the steam drum. It recovers some of the heat from the flue
gases leaking out of the boiler. The economizer is located in the second pass
of the boiler above the air heater. Each section is composed of number of
parallel tubes circuit which is arranged in the horizontal rows. All tubes circuit
originated from inlet header and discharge at outlet header.
Feed water is supplied to inlet water header via free of stop and check valves.
The feed water flow is upward through the economizer that is in counter flow
to the hot flue gases. Any chance of steam generation within the economizer
is eliminated by the upward water flow that is led to the drum via the
economizer outlet link.
Super-heater
The main function of the super-heater is to superheat the steam. Super
heater is located at the outlet of the furnace.
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Operation
Before lighting off the unit, open wide inlet and outlet header drains, vents
links drains and main steam line drains. Close all the drains prior to lighting
off when the headers and links appear free of water drain that senses as a
starting drain header drain and is kept open after the unit is on line.
Desuper-heater
Mainly the function of desuper heater is to reduce the temperature of the
steam. Desuper heater are provided in super heater connecting links to
permit reduction of steam temp. When necessary and to maintain the
temperature at design values within the limits of the nozzle capacity.
Reduction in the steam temperature is accomplished by injecting spray water
into the path of the steam; the spray water source is the boiler feed water
system. It is essential that the spray water should be chemically pure and free
of suspended and dissolved solids. Containing only approved volatile organic
treatment materials in order to prevent the chemical deposition in the super
heater.
Drum
It is necessary to separate the saturated steam from the steam water
mixture for circulation type boiler. This performance is achieved by steam
separators arranged in the drum.
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CAPTIVE POWER PLANT
Since inception, Bathinda unit was drawing power from PSEB. Electricity is the
main driving force after steam, being used for moving auxiliary equipments. The
unit requires about 27MW’s of power per hour when running at full load.
NEED FOR CPP
It was thought to install a captive power plant in which electric power for
our requirement shall be generated in a COAL FIRED BOILER. The benefits
envisaged were:
1. Any disturbance in the PSEB grid used to trip the whole plant. Lot of
money was lost due to this as each re-startup costs around 40 to 50 lakhs
rupees. Moreover, frequent trippings had an ill effect on machines and
equipments extending the re-startup period.
2. Three boilers of 150Te/hr steam capacity were initially installed in SGP
to keep 25 boilers running and one stand by as designed steam requirement was
less than 300Te/hr. but in actual operation steam requirement was more and all
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three boilers had to be run and there was no breathing time for their
maintenance. As new boiler was to be installed for CPP, its capacity was so
designed that it could export around 60Te of steam for process requirement so
that only 2 boilers of SGP would be run keeping the 3rd as stand by.
With these points in mind CPP was installed. The functioning of CPP can
be sub-divided into parts:
1. BOILER AND ITS AUXILIARIES: for generation of high pressure
superheated steam.
2. TURBO-GENERATOR AND ITS AUXILIARIES: to generate power, using
steam from the boiler.
Operation of CPP is based upon microprocessor based computerized
instrumentation which allows automatic operation, start up, shut down of the
whole or the part of the plant.
BOILER
Boiler has been supplied by M/S MITSUI ENGINEERING AND SHIP
BUILDING CO. OF JAPAN. It has a capacity to produce maximum 230Te/he of
steam at 105KG/cm2 pressure and 4950C temp. 150Te/hr steam is used for
power generation if both generators are running at 15MWH each. Around 60Te
steam per hr is drawn for process use and joins with the SGP steam header.
The basic principle of this boiler is the same as discussed earlier for SGP
boiler that is formation of steam by heating boiler feed water inside furnace fired
by coal and heavy oil, utilization of heat of the gases and venting these gases at
a safe height. Main differences between the two boilers are:
1. SGP boiler is tangentially fired where as CPP boiler is front fired with 6
coal burners and 6 oil gun fixed inside the coal housing.
2. SGP boiler can be loaded upto 30% load with oil firing only whereas CPP
boiler can be fully loaded with oil alone.
3. Height of combustible zone in CPP boiler is more and it has residence
time of 1.5 sec where SGP boiler has 1.0 sec.
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4. Mills used for pulverizations of coal in SGP are negative pressure bowl
mills whereas in CPP ball tube mill are used which are positive pressure
mills.
5. Due to more residence time and better pulverization the efficiency of CPP
boiler is about 4% higher.
6. Boiler feed water required for steam generation can be fully generated in
CPP itself.
A part of the steam generated is exported for process use in ammonia plant and
rest is utilized for power generation in turbo generators as described below:
Description
MITSUI RILEY TYPE BOILER
Maximum evaporation 2,30,000kg/hr
Design process for boiler 124kg/cm2G
Steam temp at outlet 4950C
Heating surface 1250M2
FUEL COAL SYSTEM
The purpose of fuel coal system is to pulverize coal to dry coal and to
convey the pulverized coal from ball tube mill to burners by primary air for coal
firing.
Fuel coal system consists of three systems:
1. coal supply system.
2. primary air system.
3. seal air system.
Coal supply system
Primary air system
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Coal bunkers
Coal feeders
Crushers dryers
Ball tube mill
The primary air system performs two functions. It provides the proper
amount of air required to convey the pulverized coal to the burners and the heat
necessary to dry coal so it can be pulverized and burned efficiently. The details
of primary air fan are:-
Make MEIDEN
Degree of protection IP 55
No of poles 4
Frequency 50Hz
RPM 1475
Power factor 0.89
Insulation class F
Rated power 195kW
Type of construction IEC-34
Normal temp rise limit 700C
Seal air system
The seal air is distributed to the components by the sealing of the mill
system by the sealing air fan. The sealing air fan takes suction from silencer and
discharges it to a common header. The controller for each mill system provides a
constant differential pressure to protect against coal leaking into the bearings and
seals. This system should be in service before being placed in operation.
Crusher dryer system
Crusher-dryer performs the CRUSHING function. Metered coal from the
feeders blends with a properly heated amount of air from the primary air fan and
enter the crusher dryer. The non clogging pre crushing flash dryer operates
continuously at constant speed. Rotating hammers drive the incoming coal
against a breaker plate and adjustable crusher block, increasing the surface area
of the coal and mixing it with the incoming preheated air.
BALL TUBE MILL
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Grinding the coal to the proper fineness is done by ball tube mill. The
crushed coal and air mixture from the crusher dryers enter the mill through the
mill inlet boxes on both ends of the mill. The mill barrel rotating at constant
speed,contains thousands of kilograms of various sizes of hardened steel balls
which cascade down upon the entering coal and pulverize it to talcum powder
consistency. The heated primary air, entering with coal,not only completes the
drying process, but now conveys the coal dust from the mill through the mill
output boxes to the classifiers on both ends of the mill. The specifications of the
balll tube mill are as:-
Make MEIDEN
Degree of protection IP 55
Insulation class F
No of poles 4
Voltage 3300V
Frequency 50Hz
Current 98A
Power factor 0.89
Type of construction IEC-34
Power rating 445kW
Connection Y
Temp. risk limit normal 700C
RPM 1430
The pulverized coal from the BTM is fed to the boilers with the help of
primary air fans. The coal is burnt in the boiler to generate steam to move the
turbines. The forced and induced draft fans are used to assist in the combustion
of fuel and steam production. These two major types of fans supporting the units
operation.
FORCED DRAFT FAN
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The forced draft fans supply the proper amount of secondary air required
to support the combustion of the fuel delivered to the boiler. The details of the FD
fan are:
Make MEIDEN
Rating continuous
Insulation class F
Rated power 320kW
Voltage 3300V
Power factor 0.85
Current 71A
RPM 980
Poles 6
Connection Y
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INDUCED DRAFT FAN
The induced draft fans control the furnace draft by drawing the gases of
combustion through the boiler, regenerative air heaters, delivering them to the
stack. Thus the FD fan provides combustion air for the furnace while the ID fan
removes flue gases from furnace through chimney. The details of the ID fan are:
Make MEIDEN
Rating continuous
Insulation class F
Rated power 295kW
Voltage 3300V
Power factor 0.83
Current 67.5A
RPM 735
Poles 8
Connection Y
POWER GENERATION
There are two 15MW turbine generator sets to generate power at 11kV
which is fed into 132kV bus of PSEB and again distribution network.
TURBINE
The turbine used is supplied by M/S SGP of AUSTRIA. It is condensing cum
extraction turbine designed as single casing reaction turbine with single control
stage and high pressure (HP), mild pressure (MP) and low pressure (LP) reaction
parts.
The turbine is fed with high pressure steam at 100kg from boiler and flows
through various control valves for normal and emergency operation. It gets high
velocity through the nozzle group and then passes over the impellers fixed on to
the rotor and fixed diffusers thus rotating the turbine. The enthalpy of steam is
utilized in steps. Steam is also extrated from various stages. HP1 at 10.4kg/cm2,
HP2 at 8.1kg/cm2, feed water bleed at 4.3kg/cm2 and LP bleed at 0.9kg/cm2.
Page No. 23 of 75
The exhaust steam from the turbine is condensed in a condenser
maintained under vaccum to extract maximum steam enthalpy. The output of the
turbine depends on flow of steam and heat difference that is on condition of
steam at the main steam valve and the pressure at the turbine outlet or
condenser pressure. The turbine is connected to the generator through speed
reducing gears.
The exhaust steam is condensed in a condenser using cooling water. The
resulting condensate can be fed back to LP heater but is normally sent to the
polishing water plant.
As shall be clear from the attached block diagram various bleeds from the
turbine are utilized for heating purpose. HP1 and HP2 are used for heating boiler
feed water in HP1 and HP2 heaters. Feed water bleeds is used for heating the
feed water tank and LP bleed is used for heating the polish water make up to the
feed water tank.
A lubrication system is also there to lubricate the various bearings of the
turbine, gears and generator. Normally the oil pump driven by the turbine shaft
supplies oil but auxiliary motor driven pumps are used for start up and during
shutdown. A turning gear has been provided for slow cooling of turbine rotor.
Latest instrumentation has been used in this plant. Bailey’s net work-90
microprocessor based instrumentation system is being used. The NETWORK 90
SYSTEM is a distributed process control system. Using a series of integrated
control nodes. The network 90 system allows controlling process variables like
flow, pressure and temperature according to a control configuration. There is
operator interface unit (OIU) like a TV screen on which various parameters can
be displayed and controlled. It allows fully automatic start-up/shut-down of boiler,
turbine and other auxiliaries.
Description:-
Make Simmering Graz Panker, Austria
Type Multifunction (28 stages)
Capacity 65 T/H at 15 MW
Page No. 24 of 75
RPM 6789 at 50 Hz
Critical speed 3200-3600 RPM
GENERATORS
CPP is having two number turbo generators of capacity 15MW each. The
generators are type SAT three phase, 50Hz, 11kV, 984amps, at 0.8 power factor
rating supplied by M/S JEUMONT SCHNEIDER OF FRANCE. These are totally
enclosed self ventilated type with two lateral airs to water coolers for cooling. The
alternators are able to bear 10% overload for one hr with an increase in temp. of
100C while maintaining the voltage as near as possible to the rated one. The
excitation is compound and brushless with exciter rotor and Rectifier Bridge
mounted on the extended main shaft on non driving end. The excitation is
controlled automatically with automatic voltage regulator and a PLC controller. All
protection relays installed for protection of generator are solid state having high
accuracy, quick response and low power consumption.
Under normal running conditions of the plant and healthiness of the PSEB
grid, we generally run in synchronism with the grid merely drawing the power
corresponding to minimum charges to be paid to state electricity board. In case
of any disturbance in the grid measured by higher low frequency, high rate of
change of frequency, low voltage etc. our system gets isolated from the grid
automatically. With both generators running, we are able to feed power to the
whole plant, thus production is not affected. In case only one TG is in line and
grid cuts off, urea plant is cut off automatically to balance the load with one
generator. As soon as the grid becomes stable, the generators are again
synchronized with it.
Page No. 25 of 75
SYNCHRONOUS GENERATOR [3 Phase] [T.G’s]
Description:-
Make- SAT,(JEUMONT SCHNEIDER)-FRANCE
Degree of protection IP (54)
Type of excitation Brush less
Insulation class Rotor-FStator-F
Temperature rise Rotor-800C B CLASSStator-700C
Output Voltage 11,000V ± 5%
Frequency 50Hz
Current 984 A
Speed 3000 RPM, Permissible-3500 RPM
Excitation Voltage 163V
Excitation current 580 A
Power factor 0.8
Duty Continuous
Noise level at 186mt. 85dB ± 3dB
Total weight 45Tonnes
Capacity 15 MW, 12.75 MVA at 0.8p.f (Lag)
Page No. 26 of 75
Connection Star-Delta
Max. Inlet temperature Air 500CWater 360C
EXCITATION CHARACTERISTICS At no load I = 276A V = 55V At MRC I = 580A V =163VAt 125% of MRC I = 672A V = 189V
REACTANCES Synchronous Xd 133% Transient Xd’ 18.2% Subtransient Xd” 12.1%
TIME CONSTANT 4.5 secs
EFFICIENCY AT 0.8 PF At 100% load 97.53%At 75% load 97.25%At 50% load 96.49%
EFFICIENCY AT UNIT PF At 100% load 98.03% At 75% load 97.06%At 50% load 96.82%
Page No. 27 of 75
AMMONIA PLANT
TECHNICAL DATA
1. Liquid Boiler Feed Water
2. Pumping Temp. 131°C
3. No. of Stages 6
4. Impeller Type Closed
5. Dia 420mm
6. Wearing dia 224mm
7. Clearance 0.38mm
8. Brg. Radial Journal
9. Thrust Bearing Kingsbury Type
10. Lube oil Turbine Oil 90 forced
11. Coupling Gear type
12. Rotation CW (when viewed from coupling
end)
13. Capacity (Nor.) 382m3/hr
Page No. 28 of 75
14. Capacity (Des.) 473m3/hr
15. Suction Pr. 3 Kg /Cm2
16. Discharge Pr. 138.0 Kg /Cm2
17. Total Head 1477.5m
18. RPM 3230
19. Power 2310 kW
20. Des. Eff. 76.8%
21. Min. Cont. Flow 100m3/hr.
22. Cooling Water 33°C
TURBINE DATA
1. Rated Output 2541
2. RPM 5366
3. Inlet Steam Pr. 39.6 Kg/cm²
4. Inlet Steam Temp. 370˚C
5. Exhaust Pr. 0.126 Kg/cm²
Page No. 29 of 75
The ammonia plant of NFL Bathinda is based on the partial oxidation of
fuel oil. The plant went into commercial production in august, 1979 and has been
built by M/S TOYO ENGINEERING CORPORATION as the main engineering
contractor.
The ammonia plant has the following processing units:-
Sl no. Unit/section Supplier Features
1. Air separation unit M/S HITACHI
JAPAN
Mol. Sieve and
activated
alumina gel bed
for CO2&
moisture
removal, cold
recovery from
the products in
plate and fin type
heaty
exchangers and
conventional
double column
for distillation.
2. Gasification M/S TEC under
process licence
from M/S SHELL
INTERNATIONAL
3 refractory
gasifiers of
series 700.
3. Rectisol (de-
sulfurisation)
M/S TEC under
process licence
from M/S LURGI
Selective
absorption of H2S
and CO2by low
temperature
methanol
4. Rectisol(decarbonation M/S TEC under Total regenration
Page No. 30 of 75
) process licence
from M/S LURGI
of partial steam
only.
5. CO shift M/S TEC Double bed high
temperature CO
shift converter.
6. Absorption refrigeration M/S BORSIG Part of heat duty
is supplied by the
converted gas
from shift
convertor.
7. Nitrogen wash unit M/S HITACHI Mol.sieve
adsorbers for
removal of
methanol and
CO2
8. Ammonia synthesis M/S TEC under
process licence
from M/S
HALDOR
TOPSOE
Topsoe S-100
radial flow
basket, waste
haet recovery of
the converter exit
gases in BFW
economizers.
The compressor house of ammonia plant has the follwing major equipments:-
Sl no. Section Supplier Features
1. Air compressor M/S MITSUI,
JAPAN
1,40,000NM3/hr
capacity 15.45
MW turbine
2. Nitrogen
compressor
-do- 30,000 NM3/hr
capacity 6.9 MW
Page No. 31 of 75
turbine
3. Oxygen
compressor
Compr.-DEMAG
Turbine-AEG
24,970 NM3/hr
capacity 6.59MW
turbine
4. Synthesis
compressor
BHEL Hyderabad 1,10,000 NM3/hr
for 1st ,2nd and 3rd
stages recycle
stage 15.983MW
turbine
5. Refrigeration
compressor
-do- 41,330 NM3/hr
capacity 2.8MW
turbine
Against the rated capacity of 900Te/day, plant has produced a record
production of 1011Te and has been constantly running above 105% for the past
few years.
The basic chemistry for production of ammonia is based on the
HABERS’S BOSCH PROCESS for ammonia synthesis. The reactants in the
ammonia plant are nitrogen and hydrogen. Nitrogen is obtained from its
abundant source i.e. atmosphere and hydrogen is obtained from fuel oil which is
hydrocarbon with C/H ratio of approximately 8.
As will be evident from above, the constituents in the synthesis gas other
than nitrogen and hydrogen does not play any part in the ammonia synthesis
reaction, rather they exercise undesirable effects like exerting their own partial
pressure, poisoning the catalysts etc.as such, the ammonia plant process is laid
down such that the undesirable constituents in the raw gas are removed in the
process of purification before the synthesis gas mixture, containing hydrogen and
nitrogen in the ratio of 3:1 at the required pressure is sent to ammonia synthesis
converter for synthesis reaction.
Page No. 32 of 75
The plant has been provided with a fail safety system to take care of all
eventualities. The periodical review of the safety system is also done and
incorporations whenever necessary are done.
The plant is also equipped with a flare system with 80M height flare stack
provide with pilot and main burners capable of burning around 90,000 NM3/hr
of process gas at a time and also mol. Seal to prevent flow of gas into the flare
gas system. The pilot burner is of automatic ignition system.
The harmless gases like CO2 and nitrogen are vented through a cold flare
outlet also at 80M height. The flare system has been designed so that the toxic
gases are burnt so that their combustion products are not harmful to the
environment.
Adequate measures have been taken to contain the air and water
pollutants with in the MINAS standard. As in this process of ammonia
manufacturing, the gases,CO and H2S are extremely toxic. Monitors have been
provided in the control room with sensors installed at sensitive locations of plant
for continuous monitoring of the environment.
BRIEF DESCRIPTION OF VARIOUS PROCESS UNITS IS GIVEN
HEREUNDER:-
The plant has been supplied as a package unit by M/S HITACHI and was
plagued with constraints during the initial years of operation. These constraints
have now been overcome by:
1. Interconnecting the screw refrigeration compressor with the main
refrigeration compressor of the synthesis section.
2. Changing the material of construction of the air precooolers at the
upstream of the chilling unit from C.S. tubes to S.S. tubes.
3. Increasing the packed volume of mol. Sieve in the ASU dryers.
4. Modifying the air drier post filtration system of air before entering
the cold box.
Air separation unit provides nitrogen while section nos. 2 to 7 is for generation
and purification of hydrogen. Eighth one is for synthesis of ammonia.
Page No. 33 of 75
Page No. 34 of 75
1. AIR SEPARATION UNIT
Supplier of air to ASU is air compressor. It draws 1, 40,000 NM3/hr of air
from atmosphere, compress it around 7.0kgf/cm2 pressure and sends the
compressed air to ASU air compressor is a multi-stage axial flow compressor
supplied by M/S MITSUI,JAPAN coupled with a steam turbine of 15,455KW
rated output supplied by M/S MITSUI BROWN BOVERI, JAPAN. It consumes a
maximum of 60Te/hr of steam. Capacity of the air compressor can be varied with
the movement of blades fitted into the stators of LPC and HPC casings. For
running plant at higher loads extra quantity of air is required. To augment this
shortfall, a small centrifugal compressor has been installed. It supplies around
4500 NM3/hr of air and is fitted with an electrical motor of 650KW rated output.
Air separation unit is having the capacity to supply maximum 25,920 NM3/hr
oxygen (minimum 98% purity) and 30,000 NM3/hr of nitrogen (minimum 99.99%
pure oxygen content less than 8ppm).
Feed air is first cooled in an ammonia chiller equipped with a screw
compressor (GB-5: with a refrigeration capacity of 825 refrigeration ton) and then
atmospheric moisture and carbon dioxide are removed from the air in air dryers,
filled with alumina gel and molecular sieves. This purified air is further cooled up
to its liquification temperature with cold outgoing product streams in the multi
path main air heat exchanger.
The cooled air gets partially liquefied. This liquid air is distilled in specially
designed two columns, lower column and upper column and a main condenser
which acts as condenser for lower column and reboiler for upper column.
In the distillation column liquid air is separated into pure oxygen and
nitrogen streams. The cold streams (along with impure and high pr. N2 streams)
are used to cool and liquefy the incoming air and subsequently oxygen is sent to
gasification section and nitrogen wash unit and for stripping in rectisol section.
To avoid cold loss from the equipments or pipings, operating at very low
temperatures, these equipments have been installed in a box known as cold box
and this box has been filled with PERLITE insulation.
Page No. 35 of 75
Since all the cold loss can be recovered from the outgoing streams, some
cold loss occurs which is compensated by expansion turbines provided inside the
cold box. The expansion turbines generate cold by expanding air from 7kg/cm2 to
0.7kg/cm2.
Liquid oxygen and liquid nitrogen are also drawn for selling as by product.
Refrigeration capacity of the screw compressor GB-5 provided for chilling air
prior to adsorption of CO2 and moisture is 825 refrigeration ton.
2. GASIFICATION SECTION
The hydrogen generation takes place in gasification section. This section
is provided with three nos 700 series gasifiers supplied by M/S SHELL
GASIFICATION. 700 series signifies the generation capacity of a gasifier i.e.
700×1000 NM3 of gas per day.
Fuel oil at a pressure of 130kg/cm2 and a temp of 2300C is partially
oxidized in the gasifiers with oxygen and 64kg/cm2 steam. As the reactions
involved are highly exothermic the inside temp of the gasifiers are maintained at
13600C with the help of steam and endothermic reaction. The gaseous mixture
formed by the partial oxidation of fuel oil leaves the gasifier at 13600C. The
operating pressure for gasifier is 55kg/cm2.
The waste heat of the gas is recovered in a boiler where 100kg/cm2 steam
is generated and in turn gas is cooled to 3180C from 13600C. Further the temp
of these gases is brought down to 2000C in the economizer by preheating the
boiler feed water. Residual carbon is formed during the gasification of oil is
separated in the form of carbon slurry in quench pipes and carbon separator,
with help of quench water. Gases leaving the carbon separators of all the three
streams are mixed together and further cooled in BFW preheater and scrubbed
with water or removal of the remaining content of carbon in the carbon scrubber.
It is necessary to remove the carbon completely from the gas otherwise it will
choke the down stream equipments in rectisol desulphurization section. The raw
gas contains mainly CO and H2 while other constituents like H2S, methane are
also present.
Page No. 36 of 75
Oxygen is fed to the gasifier in a controlled quantity which is lower than that
required for total oxidation, with the intention of partially oxidizing the
hydrocarbon content of the fuel oil, and this result in the formation of 48% of
carbon mono-oxide in raw gas. This CO content is then reacted with steam in CO
shift section to form further quantity of hydrogen and hence the name of the
process i.e. “PARTIAL OXIDATION OF FUEL OIL”.
100kg/cm2 saturated steam is superheated to 4800C from 3140C in the
steam super heater with the help of tail gas combustion (obtained from nitrogen
wash unit) and is then mixed with main steam header coming from auxiliary
reboilers. In order to have flame stability in the super heater, oil support is also
provided.
3. RECTISOL-1(DESULPHURIZATION)
The feed stock contains around 2.5%sulphur and this leads to the
formation of hydrogen sulphide in the gasifiers. This impurity of H2S has to be
removed from the gaseous mixture as sulphur is a serious poison for the
catalysts used in CO shift and synthesis section. Rectisol desulphurization
section is employed for the purpose of removal of H2S by absorption in low
temperature methanol.
The gaseous mixture coming from gasification section is first cooled to
220C in ammonia chiller and with cold desulphurized gas in exchangers. It is then
fed to a tall tower called H2S absorber, equipped with valve type trays. Cold
methanol at a temperature of -310C is fed at the top of the tower. As the gas
moves up and cold methanol flows downward, these have intimate contact with
Each other on the trays. Here the H2 in the gas is absorbed by methanol and
desulphurized gas leaves at the top of the tower. The operating pressure of the
tower is 46.1kg/cm2.
H2S loaded methanol withdrawn from the bottom of H2S absorber is
flashed to 12 kg/cm2.,0.5 kg/cm2.and then heated to 880C. Regenerated methanol
is subsequently cooled and recycled back to H2S absorber, one of the gases
generated during regeneration process of methanol in hot regenerator is known
Page No. 37 of 75
as clause gas and is rich in H2S content. It is sent to sulphur recovery plant,
where sulphur is produced from this gas as a by product.
4. CO SHIFT CONVERSION SECTION
Desulphurised gas coming from rectisol-1 is led to this section. In this
section CO in the gases reacts with steam as per following CO SHIFT reaction
CO + H2S CO2 + H2 + Heat
34.7TE/hr of 64 kg/cm2. steam is added form outside sources. Though the
actual steam consumed in CO shift reaction is only 37Te/hr but due to kinetics of
the reaction involved steam to gas ratio has to be maintained at 1.5 and for this,
large amount of steam will be required. But this demand of excess steam is met
by humidification of the gas. For this purpose gas is contacted with hot process
condensate, saturating the gas with water vapours and after the CO shift reaction
excess water is removed from the gas by dehumidification process.
Heat of the gas shifted is utilsed in the reboiler of absorption refrigeration
unit and subsequently 3 kg/cm2. Steam is generated. Gas is sent to
rectisol(decarbonation) after cooling to 450C. Gas leaving CO shift section
contain 3.5% CO.
5. RECTISOL-2(DECARBONATION)
This section is employed for the removal of CO2 content of the gas. Here
again methanol is used for absorption of CO2 though at a relatively colder
temperature than those in rectisol(desulphurization).
Similar to desulphurization process, CO shifted gas is first cooled with cold
CO2, synthesis gas from nitrogen wash unit washing column outlet and ammonia
chiller, then fed at the bottom of CO2 absorber, which is a tall tower equipped
with valve type trays. Methanol at temperature of -580C and -700C is charged at
the top and middle of the tower respectively. With the intimate contact of gas and
Page No. 38 of 75
liquid methanol on trays, CO2 is absorbed by methanol and operating pressure of
this tower is 39.5 kg/cm2.
CO2 loaded with methanol is withdrawn from the bottom of the tower and is
flashed to 0.8 kg/cm2 and (-) 0.4 kg/cm2 pressure and then stripped with nitrogen
for regeneration. A blower is used for generating vaccum for the 2nd stage
regeneration of the methanol. Generated CO2 from the flash and vaccum
sections of the tower is sent to the urea plant.
6. ABSORPTION REFRIGERATION UNIT
For cooling rectisol(desulphurization) and rectisol(decarbonation)
incoming gas streams and circulating methanol streams, ammonia chillers are
employed in which cooling is done by evaporating liquid ammonia. These chillers
are linked with absorption refrigeration unit (ARU).
In this section ammonia vapours are absorbed in lean ammonia solution.
Rich ammonia solution thus formed is raised to a pressure of around 15.5 kg/cm2
and pure ammonia vapours and lean ammonia solution are separated in a
distillation tower. High pressure ammonia vapours are condensed with cooling
water and liquid ammonia thus formed is sent to ammonia chillers. Lean
ammonia solution formed is reused for absorbing low pressure ammonia vapours
coming chillers. Refrigeration capacity of ARU IS 1600 refrigeration ton.
7. NITROGEN WASH UNIT
Decarbonated gas coming to rectisol-2 at 39.5 kg/cm2 and 550C contains
5.21%CO ,0.50% CH4 , in addition to 93.62% of hydrogen and 0.67% of
N2+Ar.CO and CH4 are undesirable constituents in synthesis section,wher these
will act as catalyst poison and inert respectively. Hence these are removed from
the gaseous mixture in NWU. Hydrogen boils at a considerably lower
temperature than all other impurities i.e. CO and CH4 present in the
decarbonated gas. This difference in boiling points allows removing these
impurities by fractional condensation. Boiling points of hydrogen, nitrogen,
carbon-mono-oxide and methane at atmospheric pressure are -249.40C,
Page No. 39 of 75
-195.80C, -191.50C and -161.50C respectively. Nitrogen wash unit has been
supplied by M/S HITACHI ,JAPAN as a package unit.
Decarbonated gas coming form rectisol-2 unit at -550C contains a
maximum of 10ppm of methanol. These constituents are removed completely by
passing the gas through molecular sieve adsorber beds. There are three
adsorber beds filled with 5A type 7.0Te (for each adsorber) molecular sieves.
These adsorbers operate on a ten hour cycle. One adsorber remains in line and
other two undergo regeneration with 6 kg/cm2, N2 obtained from ASU. Nitrogen
wash unit operation takes place at very low temperatures, of the order of -1950C.
Hence the equipments,down stream of adsorbers, are installed in cold box filled
with perlite.
After CO2 and methanol removal, in adsorbers, the gases enter the cold
box. Here the gas is first cooled to -1900C by outgoing washed gas in raw gas
exchangers. It is then fed to the bottom of washing column in which liquid
nitrogen at a temperature of -1950C is charged from the top of the tower. This
tower consists of sieve trays and on these undesired components i.e. CO and
CH4 are carried along by the downward flow of liquid nitrogen.
Purified gas, slightly rich in nitrogen, leaves at the top of the tower. After
frigony recovery of the gases in exchangers of rectisol section, where the
incoming gases to CO2 absorber are cooled, and this gas goes to synthesis
compressor suction as make up gas for synthesis section. Tail liquid formed at
the bottom of the column is flashed to 0.6-0.8 kg/cm2 pressure and the tail gas is
burned in steam superheater,as it has high calorific value.
Cold requirement of NWU is fulfilled by sending a partially cooled nitrogen
stream to ASU for liquification and super cooling. In the course of operation of
adsorbers, due to attrition, fine dust of molecular sieve is formed. During the
earlier operation of the plant up to 1983-84, thus dust used to get deposited on
the heat transfer area of the heat exchangers causing higher cold loss which
used to result in stoppage of plant for back blowing of the equipment for dust
removal leading to production losses. To overcome this problem 2MOTT filters
Page No. 40 of 75
consisting of sintered iron candles with pore size of 5 microns were installed.
With this modification, problems sue to dust has been overcome.
Nitrogen to NWU is supplied by nitrogen compressor. It takes suction
nitrogen from air separation unit; it compresses it to 45 kg/cm2 and feeds to
NWU. It is a centrifugal type compressor having two casings i.e. high pressure
casing and low pressure casing. Each casing is having two compression stages.
Compressor is coupled with a steam turbine, supplied by M/S MITSUI,JAPAN.
The turbine is single cylinder, impulse reaction type extraction condensing type
turbine with rated output as 6890KW and requires a maximum of 83Te/hr of 100
kg/cm2 superheated steam. For normal operation it supplies 5659KW of power
with a steam draw of 75Te/hr. out of this 54Te/hr of steam at pressure of 64
kg/cm2 is drawn as extraction steam which is used in gasification and CO shift
sections.
8. SYNTHESIS SECTION
Make up gas coming from NWU is compressed to around 220 kg/cm2
pressure by synthesis compressor. Up to three stages of the compressor make
up gas is compressed; while at the suction of fourth stage know as recycle stage.
It is mixed with recycle gas coming from synthesis section. The compressor of
BHEL make and the turbine is of SIEMENS. The compressor is of multistage
vertically split casing type and consists of three barrels. Steam turbine of
synthesis compressor is an extraction condensing type with rated output of
15983KW. It requires 181Te/he of 100 kg/cm2 superheated steam at 4800C out of
this 145Te/hr at 40 kg/cm2 is drawn as extraction.
The compressed make up gas along with recycle gas is fed to the
ammonia converter after preheating with outgoing gases. Ammonia converter is
S-100 type radial flow converter supplied by M/S HALDOR TOPSOE. It consists
of two beds charged with reduced iron oxide catalyst. The operating temperature
for the converter is in the range of 3750C to 5000C. Nitrogen and hydrogen react
with each other in the presence of the catalyst as per following reaction.
Page No. 41 of 75
N2 + 3H2 2NH3 + Heat (26000Kcal)
Ammonia produced from the above reaction along with unreacted gasses
leave the converter at around 3170C. It is cooled in BFW economizer to 1690C,
then synthesis hot gas-gas exchanger up to 710C, in synthesis water cooler up to
400C ,synthesis cold gas-gas exchanger up to 330C and then finally to 100C in an
ammonia chiller. At this temperature product ammonia gets liquefied and is
separated in a separator. Separator gases are sent to the synthesis compressor
at recycle stage suction. The cooling system of NH3 chiller is equipped with
refrigeration compressor and capacity of this system is 2676 refrigeration ton.
The product ammonia thus formed at a rate of 37.5Te/hr is either sent to urea
plant or for storage.
9. BFW/STEAM SYSTEMS
a.) STEAM SYSTEMS
Fuel oil partial oxidation based ammonia plant is major consumer of
steam. It requires around 7Te of steam per ton ammonia. Around 310-320Te/hr
of 100 kg/cm2 superheated steam at 4800C is supplied by auxiliary boilers and
another 82Te of 100 kg/cm2 saturated steam is generated in waste heat boilers in
gasification section. This steam after super heating to 4800C in steam
superheater is mixed with the main steam coming from boilers. There are total
six steam headers.
b.) BFW SYSTEMS
Polish water at a rate of around 425Te/hr is supplied from
demineralising plant. After thermal dearation with steam, hydrazine is added as
oxygen scavenger. Further ammonia is dosed to raise its pH to 9.0. then this
boiler feed water is pumped to auxiliary boilers and waste heat boilers by BFW
PUMPS, which raises its production to around 131 kg/cm2. There are two steam
driven pumps and one electric driven available for this purpose, all supplied by
M/S EBARA,JAPAN.
Page No. 42 of 75
POWER DISTRIBUTION IN AMMONIA PLANT
Two feeders from MRS incomer A and incomer B feed the 11kV bus at
ammonia control panels for 11kV are provided by L&T. each panel is provided
with circuit breaker of 630A, 300MVA which are activated by the relay in case of
fault. Panels 1-5 and 12-17 are fed to 415V panel through 11kV/415V, 2MVA
transformer and panels 6 and 11 feed the 3.3kV panel through transformer of
rating 11/3.3kV, 10MVA. Bus coupling is provided between buses A&B from
ammonia there are two feeders to coal handling (1.6MVA), boilers (2MVA), and
D.M plant (2MVA). If one of the feeders fails or there is any abnormality then the
total load is transferred on the other feeder by using bus coupler. The 11kV
supply is then further stepped down to 3.3kV and 415V using step down
transformers, 3.3kV is used for H.T. motors and 415V is used for L.T. motors.
This plant also has the facility of battery room.
Page No. 43 of 75
Page No. 44 of 75
UREA PLANT
Urea plant has a rated capacity of 1550Te/day of prilled urea produced in
a single stream plant employing MITSUI TOATSU TOTAL RECYCLE C
IMPROVED PROCESS.
Features of the plant are as under:-
Sl no. Features MTC-C-IMPROVED
1. Type of process Conventional
2. Molecular ratio
NH3 : CO2
H2O : CO2
4:1
0.544:1
3. Conversion percentage 70%
4. Reactor conditions
Pressure kg/cm2
Temperature 0C
250
200
5. Reactor lining Titanium
6. Reactor features Hollow
7. Excess NH3 recycle As liquid NH3
8. Decomposition stages 1st: 17.5kg/cm2
2nd : 2.5 kg/cm2 ( 5% CO2
fed to 2nd decomposer)
3rd: 0.3 kg/cm2
9. Heat recovery in
carbonate condenser
For supplying heat to
crystallization to urea
slurry and heating hot
water.
10. Sp. Cons.
Te NH3/Te urea
Te CO2/Te urea
Power /Te urea KWH
Steam /Te urea
0.58
0.76
86.4
1.24
Page No. 45 of 75
11. No. of conc. Stages One
12. Type of prilling tower Induced draft
13. Approx. prilling height 40M
14. Salient features a.) power saving as
5% CO2 is fed to
LD
b.) P.T. height is less
cause of cooler at
bottom.
c.) Low biuret
d.) Because of Ti
lining in reactor
corrosion rate is
less and thinner
liner.
e.) Water recycle is
less due to
counter current
flow of liquid and
vapour in
decomposers.
The plant is divided into four sections:
1. Synthesis section.
2. Decomposition section.
3. Crystallization and prilling.
4. Recovery.
The brief description of various sections is given as under:
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SYNTHESIS SECTION
In MITSUI TOATSU TOTAL RECYCLE C IMPROVED PROCESS liquid
ammonia is recycled since it is easier to handle but require equipments like
rectification column storage tanks etc. and higher capacity liquid ammonia
pumps.
Recycling of carbamate requires higher capacity carbamate pumps.
CO2 is received from ammonia plant at a pressure of 0.2 kg/cm2 and 200C and is
compressed in a centrifugal booster compresser,UGB-101 to 32 kg/cm2 in 3
stage unit. The compressor supplied by M/S BHEL has a normal capacity of
25256NM3/hr and has 2 barrels 2 M.C.L. 805 and MCL 455. The drive of the
compressor is an extraction and condensing type by steam turbine supplied by
M/S BHEL. The turbine is driven by 40K super heated steam and has a rated
output of 5792KW.
UREA SYNTHESIS
2NH3 + CO2 NH2CONH4, H = -37.64Kcals 1
NH2CONH4 NH2CONH2+ H2O, H = 6.32Kcals 2
Where as reaction 1 is an exothermic and rapidly goes to completion of 2
and is endothermic and is always incomplete. The overall reaction is exothermic
and hence heat has to be removed continuously for the equilibrium reaction to
proceed. The conversion of ammonium carbamate to urea depends upon:
1. Reaction temperature.
2. Mol. Ration of NH3/CO2, H2O/CO2 of the feed reactants.
3. Residence time.
The conversion increases with the increase in temperature, NH3/CO2 ratio and
residence time and decreases with H2O/CO2 ratio since the presence of water
tends to shift reaction 2 in the backward direction. The pressure employed
depends on the reaction temperature and has to be kept higher than the
dissociation pressure of ammonium carbamate at that temperature. Further since
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the dehydration of ammonium carbamate to urea takes place in liquid phase
only. The pressure employed must also be higher than the vapour pressure of
ammonium carbamate which is rather high.
High ratio of NH3/CO2 increases conversion and helps to minimize
corrosion. As this ratio increases the load on recovery section increases since
excess NH3 over stoichiometric requirement has to be recovered and recycled
back to reactor. This excess ammonia can either be recycled as liquid NH3 or
carbamate. In each case it becomes necessary to inject CO2 into carbamate
condensers.
The compressed CO2 is washed with water in a packed bed tower called
methanol absorber for removal of entrained methanol in CO2 which is normally
100ppm. The washed CO2 is further compressed to a pressure of 260kg/cm2 in a
two stage compressor, UGB-102 supplied by M/S KOBE STEEL, JAPAN. This
reciprocating compressor has a normal capacity of 26260NM3/hr and is driven by
a 2.2MW synchronous motor. Anti corrosion air at the rate of 120NM3/hr is fed to
CO2 at the suction of centrifugal CO2 booster compressor.
Liquid ammonia at 110C and 18kg/cm2 pressure is received in the
ammonia reservoir, UFA-401 from the Horton sphere. Ammonia booster pump
UGA-404A&B boost the pressure of the feed ammonia to 24kg/cm2 and feeds at
the suction of plunger type ammonia feed pumps UGA-101A-D. the ammonia
feed pumps are of URACA MAKE driven by 3.3kV/450KW and have capacity of
53.2M3/hr, 178RPM and 89% efficiency. The ammonia preheater UEA-101 and
102. The preheated ammonia at 85.30C is fed to the urea reactor at bottom.
The recycled carbamate solution of CO2 concentration, 7.5 lit per 25ml, at
1050C and 260kg/cm2 pressure is delivered to the urea reactor at bottom by
recycle carbamate solution pumps UGA-102A&B. these pumps are centrifugal
type and are driven by back pressure steam turbine, supplied by M/S
EBARA,JAPAN and have a capacity of 81M3/hr.
The three feeds i.e. CO2 liquid ammonia and recycled pump solution are
fed to a Ti lining multi layer urea reactor. The reactor is a 12 layered C.S vessel
with Ti liner thickness of 5mm, 4mm and 3mm for the 1/6th, 1/6th and 2/3rd of total
Page No. 48 of 75
height of the reactor from bottom. The reactor top temperature is maintained at
2000C maximum. The effluents from urea reactor from top are let down to
17.5kg/cm2 pressure through a pressure control valve PCV-101 and fed to the
high pressure decomposer at 1240C.
DECOMPOSITION SECTION
MITSUI TOATSU TOTAL RECYCLE C IMPROVED PROCESS is a
conventional process.
The decomposition reaction
NH4COONH2 2NH3 + CO2
Is favored by lower pressure of system or by low partial pressure of one of the
reaction products i.e. NH3 and CO2. Conventional process means the process
where the decomposition is affected by lowering in pressure in successive stages
followed by indirect heating whereas the processes where decomposition takes
place by lowering the partial pressure of either NH3 or CO2 followed by indirect
heating are called STRIPPING PROCESSES.
The reactor effluents at 17.5kg/cm2 and 1240C enters the part of high
pressure decomposer U-DA-201 having sieve trays at upper and falling film
heater at lower section. The flashed gases go up and liquid flows down through
sieve trays. On trays the high temperature gas from reboiler,U-EA-201 and falling
film heater contacts with the liquid flowing down. The sensible heat of gas and
heat of condensation of water vapour are used to evaporate the excess ammonia
and to decompose the carbamate.
This helps in minimizing water evaporation and thus reducing water
recycle to reactor. The reboiler further heats the liquid by 12kg/cm2 steam to
release excess ammonia and carbamate gases. The temperature at middle is
maintained at 1510C by a temperature control valve TCV-201. The temperature
at bottom is maintained at 1650C through TCV-202. The falling film heater is used
to minimize residence time in order to reduce biuret formation and hydrolysis of
urea.
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Anti corrosive air is fed to high pressure decomposer and reboiler through
air compressor UGB-201@ 2500ppm as air. Overhead gases from HD are
absorbed in HAC(high pressure absorber cooler). The bottom liquid flows to L.D.
(low pressure decomposer) at 2.5K, 1450C,upper part, having 4 sieve trays. A
similar phenomenon occurs in the low pressure decomposer. The reboiler U-EA-
202 provides heat using 7kg/cm2 steam for decomposition and hot stream from
H.D heats up the solution from L.D in an exchanger before entering the upper
part. The temperature is maintained at 1300C at middle by TCV-203. Small
amount of CO2 is fed below packed bed for improved stripping of decomposed
gases. The overhead gases from low pressure decomposer are absorbed in low
pressure absorber U-EA-402. Bottom liquid flows to 3rd stage of decomposer
called gas separator U-DA-203. The upper part of gas separator operates at
1060C, 0.3K and lower part with packed bed operates at 1000C and atmospheric
pressure. The sensible heat of solution from low pressure decomposer is enough
for evaporating the overhead gases. In the lower part, air containing trace
amounts of NH3 and CO2, is blown under the packed bed, by off gas recycle
blower UGB-401. The urea solution is concentrated to 70-75% and sent to
crystallization section.
CRYSTALLIZATION AND PRILLING SECTION
The urea solution obtained from the last decomposition stage i.e. gas
separator contains 25% H2O since every mole of urea one mole of H2O is
formed. Urea has to be concentrated to 99.5% before prilling.
MTC-C-IMPROVED PROCESS employs crystallization-remelt prilling
route and uses spray nozzles for prilling. The prilling tower is of induced raft type.
The solution from gas separator enters lower part of crystallizer, U-FA-
201. The upper part is vaccum concentrator with two stage ejectors and
barometric condenser.
In vaccum concentrator. Operating at 75mm of Hg and 600C, water is
evaporated and supersaturated urea solution comes down through barometric
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low into the crystallizer, where urea crystals grow. The heat required for water
evaporation comes from:
1. Sensible held of feed urea solution.
2. The heat of urea crystallization.
3. Heat recovered by urea slurry circulated through high pressure absorber.
The crystallizer is operated at 600C and atmospheric pressure, so the slurry
leaving the bottom contains 30-35% urea crystal by weight.
Hot water from hot water pump is used in jackets of crystallizer and pipe to
avoid crystal build up on vessels walls which may cause choking otherwise.
The urea slurry is pumped from crystallizer bottom to centrifuges U-CF-
201A-E (1000RPM, 43Te/hr of slurry) maintaining minimum recirculation to
crystallizer to prevent choking of lines.
Biuret remains with mother liquor, which after separation from urea
crystals in the centrifuges is recycled back to the system. Because of excess
ammonia in reactor biuret, thus recycled is converted back to urea.
NH2CONHCONH2 +NH3 2NH2CONH2
Urea crystals separated from slurry with 2-4% moisture are discharged to
fluididsing dryer UFF-301 at 1100C. The mother liquor flows down to mother
liquor tank, provided with steam coils. Mother liquor is pumped back to
crystallizer via LCV-207. a part of mother liquor going to low pressure absorber
has been cutoff and instead dust chamber overflow solution has been lined up.
Air is blown from blower U-GB-301(82360NM3/hr) and heated to 1000C in
air heater. This hot air droes the crystals to 0.1% to 0.3% moisture content. Dried
crystals are conveyed by a pneumatic duct to cyclones at the prilling tower top.
The collected crystals are melted in melter (1370C) and urea melt is sprayed
through 12 nos. acoustic granulators. Prills are cooled in fluidizing bed called
CFD,installed at the prilling tower bottom. Air/cyclone scrubbed for urea dust
separators. Air containing urea dust from P.T column is scrubbed with water and
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passed through 144 sets of poly urethane filters before exhaust to atmosphere to
reduce air pollution.
RECOVERY SECTION
The gases from gas separator are condensed in off gas condenser UEA-
406 to 620C and enter the bottom of off gas absorber DA-402(OGA). Condensed
liquid flows down to off gas absorber tank UFA-203. After cooling to 360C, liquid
is sent to top portion of OGA as absorbent. OGA bottom fluid is recycled as
absorbent at OGA middle position (2nd bed).
Air from top of OGA is blown to gas separator by GB-401 blower. The
gases from low pressure decomposer are absorbed in low pressure absorber
(EA-402) bubbling a sparger. Dust chamber over flow solution (10-15% urea) is
used as absorbent. Low pressure absorber temperature is controlled at 450C and
CO2 concentration 2.2 lit/2.5ml.
Solution from LA is pumped by GA-402A/B to high pressure absorber (DA-
401) middle through mixing cooler where liquid ammonia is mixed and serves as
medium in the absorber.
The gases from HD top are bubbled through a sparger in high pressure
absorber cooler EA-401, where 65% of CO2 is absorbed. Remaining gases from
HAC go to HA and are cooled down to 800C max. in middle cooler at the bottom
of HA 35% of CO2 is absorbed in packed bed by a mixture of lean carbamate
from low pressure absorber through FCV-401 and liquid ammonia from GA-
404A/B( temp. max 600C) through FCV-402. the scrubbed gas then passes
through five nos. of condensers(EA-404A-E) and purge condenser EA-403.
Liquid ammonia flows down to ammonia reservoir FA-401. Non-condensable
gases flow to ammonia recovery absorber. Recovery loop pressure is controlled
by PCV-405 at top of EA-405 lV. Cold steam condensate is fed for absorption.
Aqueous ammonia is with drawn from recovery absorber bottom by GA-405A/B.
Page No. 52 of 75
WATER AND AIR POLLUTION
AIR POLLUTION
The sources of air pollution in urea plant is the air from prilling tower which
in the process of cooling of molten urea being sprayed from the top of the prilling
tower gets entrained with urea dust. In order to contain the urea dust emissions
in the exit air, the air is scrubbed with water and subsequently passes through
144 poly urethane filters before being discharged to atmosphere. The normal
emission level in the exit air is 30-40mg/NM3 against the prescribed norms of
50mg/NM3.
LIQUID POLLUTANTS
The sources of liquid pollutants in urea plant are:-
1. dust chamber over-flow solution
The over-flow from dust chamber is being completely utilized after
introduction of innovative operational practice mentioned above.
2. Dilute urea solution during start-up and shut-down of plant
To take care of the dilute urea solution during start-up and shut-down of
the plant 3 SS tanks of 100M3 and 200M3 capacity have been provided.
Three tanks are equipped with steam coils for concentration of the urea
solution. The solution, thus stored, is reprocessed after the plant condition
is normalized.
3. C.F.D washing
The frequency of CFD washing is 11/2 months during summer months
and three months during winter months. The washed water from CFD
containing urea is stored in a pacca pit of 250M3 capacity. This pit has
been provided with a pump and the stored solution is reprocessed during
normal operation of the plant.
4. leaks from pumps and effluents generated during flushing of strainers
The pollutants generated are diverted to a effluent pit.
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The effluent is subsequently sent to the bio urea hydrolyser in the effluent
treatment plant for hydrolysis of the urea.
HYDROLYSIS OF UREA
In aqueous solution urea is sufficiently stable up to 800C. Above that
temperature , it changes into ammonium isocyonote and subsequently into
ammonium carbonate.
CO (NH2)2 = NH4NCO
NH4NCO + 2H2O = (NH4)2CO3
Which changes into ammonium hydro-carbonate and this ultimately dissociates
into ammonia and carbon-di-oxide.
(NH4)2CO3 = NH4HCO3 + NH3
NH4HCO2 = CO2 + H2O + NH3
The overall hydrolysis reaction is shown by equation:
(NH4)2CO3 + H2O 2NH3 + CO2
Page No. 54 of 75
POWER SOURCES AND FEEDERS
It was the final stage of the whole plant where urea is actually produced.
The single line diagram is quite similar to that of ammonia plant. There are three
feeders to DM plant of 2MVA and 10MVA. Two 11kV feeders are coming from
MRS to this plant namely incomer-A and incomer-B. These feeders comprises of
bus of 11kV at urea plant. Further there are transformer which steps down the
voltage i.e. 10MVA and 1.6MVA. There are two 10MVA and four 1.6MVA
transformers. One feeder at 11kV from urea directly feeds the 11kV synchronous
motor. The stepped down voltage i.e. 3.3kV and 415V is further fed to HT and LT
motors. Further new buses are made at 415V and is fed to motor control
center(MCC). Bus coupling is also provided in between the two feeders at the
bus so that in case there is nay fault on one feeder the total load will
automatically shifts to other feeder.
EQUIPMENT DETAILS
There are about 150 small and big motors in urea plant and about 40
motors in bagging plant. Some important motors are:
11kV-2200kW synchronous motor for UGB102
3.3kV-600kW induction motor for UGB302
3.3kV-450kW motor for UGA101
415V-110kW induction motor for UGB301
415V-60kW induction motor for UGD304
415V induction motor for PJD107
Total connected motor load for urea plant is about 8MW and normal
running load is about 5.5MW for bagging plant, connected motor load is about
200KW and running load is 140KW.
Power supply system
We receive two 132kV feeders from PSEB and two 132kV feeders from CPP in
MRS where after stepping down to 11kV through transformer, this supply is
distributed to various plants.
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In urea plant, two feeders of 11kV supply are received from MRS in urea
substation at 11kV panel designated and UNB205. This is further stepped down
to 3.3kV & 415V through transformer. There are two nos. 11kV/3.3kV 10MVA
transformer and four nos. 11kV/415V 1.6MVA transformers. Power supply to
O&U plant is fed from 11kV bus. Supply to UGB102 motor is also given from this
bus.
For 3.3kV supply system, output of 10MVA transformer is terminated at
3.3kV panel designated as UNB301. It also has two sections A&B. normally;
similar feeders are divided into two groups and fed from alternative sections. It is
being done to have availability of partial equipments in case of limitation to some
sections.3.3kV motors connected to both the sections are as under:
3.3kV SECTION ‘A’ 3.3Kv SECTION ‘B’
UGA302 UGB303
UGA101A& B UGA101C& D
CGA302A CGA302B
IGB101A MGA101A
CGA101D CGA101F& G
CGA201A& B CGA201C& D
CGA301A CGA301B
Similarly, for 415V system, there are 4nos. transformers feeding 2 nos.
415V panels designated as UNB401 &UNB402. Both these panels are also
having two sections A& B. there is one more panel namely UNB403. This panel
has two power supply source, one from UNB402B and other from emergency
diesel generating set installed near instrument air compressor house. In case of
normal power failure to this panel, emergency power panel is made available to
this panel within 40 secs and all the sequence of power to this panel is
automatic. One more panel namely UNB404 has recently has been introduced in
the system. Power to this panel is coming from MRS through an old construction
power sub-station. All the welding outlets, cranes etc are connected to the panel.
An additional source is also connected to this panel from UNB401 a section for
reliable power availability during shutdown.
Page No. 56 of 75
Besides above power supply system, we are also having one 110V DC
supply system backed by battery bank. This power is used for protection system
of electrical equipments and instrumentation.
SYNCHRONOUS MOTOR
Description
Output 2200kW
Speed 333.3RPM
Poles 18, excited field voltage- 55V
Voltage 11kV, excited field voltage-13A
Power factor 0.8
Current 153A
Motor field volts 220V, motor field current-152A
Armature insulation class motor-B,exciter-B
Field insulation class motor-B, exciter-B
Space heater 2.5kW, 240V
Make TOKYO SHIBAURA ELECTRICAL CO LTD
Purpose For CO2 compressor
Synchronous motor is not self starting. The current in a synchronous
motor is approximately in phase opposition in phase to the EMF generated
current, remains high for longer period to avoid the tripping of motor circuit. The
effect of armature reaction is to increase the flux in leading half of each pole. The
flux is distorted in the direction of rotation and the lines of flux in the gap are
skewed in such a direction as to exert a clockwise torque on the rotor. Since the
resultant magnetic flux due to stator current rotates at synchronous speed, the
rotor must also rotate at the same speed. As in case of induction motor if load is
increased, speed slows down but in case of synchronous motor if there is
increased in load then there is no change in speed. But in case of synchronous
motor if there is increase in load the there is no change in speed. But in case the
RPM decreases, the motor will stop running even a point difference in RPM
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causes the motor to stop running. Varying the field current can control power
factor of synchronous motor.
STARTING OF SYNCHRONOUS MOTOR
When the rotor of three phase synchronous motor is stationary, the
rotating magnetic field due to stator currents produces an alternating torque on
the rotor i.e at once instant the rotor is moved clockwise and other counter
clockwise. Since a net torque is zero, a synchronous motor is not self starting.
The method to bring the motor up to synchronism is as follows:-
By damping grid in pole shoes:- these grid consist of copper bars short
circuited at each end. The rotating magnetic flux induces current in these grids
and the machine accelerates. During the starting period the rotor field winding is
usually closed through the armature of exciter, normally a DC shunt generator
carried on the extension of the shaft and current in the stator is limited to
permissible value. When the machine has reached nearly full speed, the rated
voltage is applied to stator winding and the exciter voltage will have built up
sufficiently to magnetize the rotor poles. The resultant magnetic flux due to stator
current is then moving past the rotor poles at a slow speed and produces a slow
frequency alternating torque superimposed upon that exerted by the damping
grids. Consequently the rotor is accelerated at one instant and retarded at other
and the fluctuation of speed is sufficient to bring the rotor up to synchronous
speed. Once this speed has been attained the rotor can run in synchronism.
Page No. 58 of 75
SYNCHRONOUS MOTOR SELECTION CRITERIA
We are having 2200kW, 11kV synchronous motor for running CO2
compressor UNB102. Why this motor was selected? Why we have not gone for
an induction motor or steam turbine? Some of the reasons are:-
1. Low speed reciprocating compressor
CO2 compressor popularly known as KOBE compressor is a low
speed reciprocating compressor. We need very constant speed for this
compressor. Normal induction motor has effect of voltage, frequency &
mechanical loading on its speed due to said reasons, so this synchronous
motor is selected.
2. Power factor improvement
In electrical AC system, voltage and current are concurrent. They
always deviate with each other by some angle when drawn vertically.
Cosine of this angle is known as power factor. Low power factor has some
disadvantages; it affects the efficiency of generating station. Large
electrical equipment such as transformers, motors are inductive in nature
and they result in low pf of the system. Resistive loads have limiting pf.
Capacitive loads are used to improve pf, which takes care of the motor of
the loads. If we would have used an induction motor of 200kW, then
capacitor requirement to improve the pf must have increased
considerably. To overcome that problem, synchronous motor has been
used, which maintains its own pf along with improving the pf of the
system.
3. Protection of motors
All the equipments are provided with sufficient & efficient protection
system. For HV motors, sophisticated relays such as CIM relays,CAU
relays etc are provided which monitor the current drawn by the motors
while running and isolate the individual feeder in case the current exceeds
Page No. 59 of 75
the present values. There is one more relay called 86-P, which must be pf
of your interest. Normally when any HV motor is started, 86-P relay is to
be got reset. This relay monitors various parameters that are to be fulfilled
before the main equipment is started. These parameters are lube oil
pressure, seal oil pressure, value positions, dampers position etc. in case
the requisite parameters are not fulfilled , the 86-P relay will get reset
hence the equipment cannot be started. For LV motors, protection is fuses
and thermal overload relay fuses & relay are selected in accordance with
size of motor, starting and running conditions for monitoring of process
parameters, one interlock contact is given in the starting circuit of the
motor, which restricts the starting of the equipment if the parameter is not
met. There are some other interlock also depending upon the service of
equipment such as conveyors etc thermal overload relay is bimetallic
conductor exceeds the limits bimetallic conductor expands in uneven
fashion and actuate the trip system, tripping the motor. Fuses are provided
as back up protection and for severe faults.
Advantages of synchronous motor
1. The ease with which the pf can be controlled. An overexcited synchronous
motor having a leading pf can be operated in parallel with induction motors
having lagging pf thereby improving the power factor of the supply.
2. The speed is constant and independent of the load this is mainly used
when the motor is required to derive another alternator to generate a
supply of different frequency.
Disadvantage of synchronous motor
1. Cost per kW is higher then induction.
2. DC supply is necessary for rotor excitation. Small DC shunt generator
carried on the extension of the shaft usually provides this.
Page No. 60 of 75
Page No. 61 of 75
BAGGING PLANT
The bagging plant can be divided into two main sections:
1. Storage system
2. Reclamation system
Under storage system, 3 conveyors come namely; PJD-101, PJD-102, PJD-
103 is the overhead conveyor inside silo. One tripper is provided over PJD-103
which can be placed at any convenient position depending upon the requirement.
By means of the tripper, the material can be poured over any vibrofeeder
desired. Tripper is designated as PJD-104.
The reclaimation system comprises of six electromagnet vibrofeeders,seven
no. of belts conveyors namely PJD’S 106,107,109,109A,110,111,111A,one
electromagnet (PJD-108),six no. of weighing machines,stiching machines
&loading platform namely;A-1,A-2,B-1,B-2,C-1 and C-2. In addition to these,
there are 3 bunkers/platform, one empty bag storage and one filled bags storage.
By operating flap gate no.102, the material can be directly fed to PJD-107 without
taking it to silo.
The plant has a capacity to load 2250Te/Day of packed material either in road
wagons or road trucks or in both. The loading platforms can accommodate six
trucks at a time or three BCN type wagons or 6CRT type wagons.
The weighing machines are microprocessor based and have speed of 12 to
14 bags per minute. The machines run with an accuracy of ± 50 grams. The
system of counter checking of weight of filled bags is rigorously followed to
ensure correct weightment.
The plant is provided with a central control room from where the system is
started or stopped. The two systems of storage and reclaimation are separately
provided with safety interlocks to trip the belts in case one belt in the link trips.
The urea silo is designed to accommodate 30 days production. For reclaiming
urea from silo, front end pay loaders are used.
Page No. 62 of 75
The plant is also provided with empty bags storage and overhead E.O.T
crane for shifting the bags from the storage to the loading platform.
The filled bags storage is provided for stacking the filled urea bags.
Both jute and HDPE bags are used for filling of product urea. The stitching
thread used is normally of cotton unbleached and at times poly. Thread is also
used.
The consumption of bags is approximately 104 lacks per annum and pf
thread 41600KMs.
Normally four operators, one heavy equipment operator, 6 stichers, 6 fillers
and 24 loaders besides sealman and weight checking staff are deployed every
shift. The shift engineer coordinates with the operational activities of the plant
and also coordinates with the transportation section for the movement of finished
goals.
The spitted urea or the urea from the ruptured bags is recycled back to the
system by 2 buckets elevators, which transport the material from the loading
platform to the conveyor PJD-109.
Normally locomotive is used for shunting of rail wagons. However, a winch is
also provided to take care of exigencies when the locomotive is not available.
Page No. 63 of 75
OFFSITES AND UTILITIES PLANTS
The 0&U group of plants consist of the following sections : -
i) Raw Water Plant.
ii) D.M. Water Plant.
iii) Instrument .Air Compressor House.
iv) Cooling Tower.
v) Sulphur Recovery Plant.
vi) Effluent Treatment Plant & Steam Generation Plant.
(i) RAW WATER FILTERATION PLANT
This water treatment plant has a design capacity to treat 2400 NM3/hr of raw
water into portable occasional over lead of 20%. The plant consists essentially of
flash Mixers Clarifloculators, rapid gravity filters and a chemical House
comprising of Alum tanks, lime tanks and a chlorine room etc.
The raw water from the pumping main is received by the inlet of the RCC Ventury
flume. In the ventury flume the calculated amount of alum solution is closed for
mixing with the raw water. The chemically treated water then flows to
clarifloculators. The pludge thus formed after chemical treatment settles down in
the clarifloculator where from it is expelled out while the clear water overflows to
the launder leading to filter beds. The filter water is disinfected with the addition
of chlorine and then collected in filter eater sump.
(ii). D.M. WATER PLANT
D.M. water plant was supplied by M/s Ion Exchange (India) Ltd. It consists of
cation units, Degasser Towers, An-ion units. Mixed bed units No.l&2. Filtered
water coming from raw water filtration plant is received in filter water reservoir.
From reservoir filter water passes through a strongly acidic cat-ion exchange
resin where cat-ions like Ca, Ng & Na are removed, the water passes through
degasser tower where dissolved, Ce2 is removed. Then water passes through
Anion exchange resin and Anion like CI, S, Se4 and silica, are removed in this
Page No. 64 of 75
unit. Free from cations and anions water passes through mixed bed unit No.l,
where further removal of cations and anions takes place. Then treated water
coming out from MB, unit goes to DM water tank.
Return condensate from Ammonia and Urea Plants is collected in D.M. water
tank after treatment in cat-ion unit No.2. Then D.M. water is pumped from DM
water tank to mixed bed No.2(MB) for further polishing and collected in polish
water tank, which is supplied to boilers through Ammonia Plant.
(iii) INSTRUMENT AIR COMPRESSORS HOUSE
The purpose of this section is to supply instrument air and service air to all the
plants. The instrument air compressor house consists of three instrument air
compressors and one service air compressor. One is kept in line generally.
The compressed air from instrument air compressors at 9.3 kg/cm2 absolute
pressure passes through two sets of dryer, which is filled with silica-gel for
removal of moisture. Air coming out from dryer is sent to instrument air feeder
for supplying to different plants through instrument air receiver in order to
drive various valves and instruments.
(iv) COOLING TOWERS
The cooling water system provided in NFL, Bathinda is closed re-circulating
system supplying cooling water to various consumers in the plant. The system
mainly consists of cooling towers, cooling water re-circulation pumps, supply &
return headers and cooling water treatment facility.
There are three cooling water systems : -
1) C.W. system supplies cooling water to Ammonia Plant.
2) Urea Plant and Boilers, Instrument -Air Compressor, Caustic dissolving
facilities & Sulphur Recover Plant.
3) C.W. system supplies cooling water to Crystallization section of Urea Plant.
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(v) SULPHUR RECOVERY PLANT
The separation of sulphur by catalytic reactions is as follows:-
H2S + 3/2 O2 SO2 + H2O
H2S + 1/2 O2 S+ H2O
2H2S+ SO2 2H2O + 3S
The capacity of the plant:
Generation steam : 26.5 T/day
Export steam : 6.4 T/Hr.
Plant performance : 85%
PROCESS OF SULPHUR RECOVERY:
The Acid gas from Rectisol Section of Ammonia Plant is composed of 47.5%
H2S, 50.3% C02 and a little COS & CO and flows to this unit, 70% of feed gas is
introduced into Acid gas exchanger where 1/3 of total H2S is burnt to S02 with air
supplied through furnace air blower. The S02 reacts with H2S and forms
elemental sulphur. I he sulfur is thus condensed at 191 deg.C and separated in
sulphur storage tank. The gas stripped off the above sulphur is mixed with the
remaining 30% of feed acid gas and bypass from acid gas exchanger in such a
way that the temp. of mixed gas is controlled at 215 deg.C and proportion of H2S,
S02 in this gas is over 2:1 ratio. This gas reacts over the first catalyst bed of
reactor to form elemental sulphur. This gas is cooled to 177 deg.C in acid gas
exchanger and stripped off and so condenses sulphur in the sulphur storage
tank. The remaining H2S & S02 react again to form elemental sulphur.
D.M. WATER PLANT
Water in its natural form contains no. of dissolved salts such as sulphates,
chlorides and nitrates of calcium magnesium and sodium. If water is used as
such in the boilers for raising steam, these salts will form scale on the tubes,
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which in addition to heat losses lead to many other many problems. Hence,
removal of these salts from the water becomes quite essential. Ion exchange
resign are used for this purpose of salt removal.
The de mineralizing water plant of NFL Bathinda was supplied by M/s ION
exchange (India) ltd Delhi.
It consisted of three units each of cation, anion, mixed bed, four secondary mixed
bed and three units of condensate cation. At the time of setting up of a captive
power plant, another stream to augment the existing capacity of polish water
generation was by M\s BPMEL. It consisted of one unit each of cation, anion,
primary mixed bed, two secondary mixed bed and two condensate cations.
Filtered water is received from raw water filtration plant into two filtered water
reservoir feed water pumps discharge water from these reservoir tom cation units.
These are total five feed pumps each having a capacity 0f 130m3/hr and four cation
units. Three of these are charged with 13125L of cation resin and fourth unit is
having 11900 0f resins. Cation like Na+, Ca++, and Mg++ present in the water are
removed in the cation unit once exhausted, these units are regenerated with the
counter current flow of dilute sulphuric acid.
The present day resins are made of cross linked polystyrene and cross linking is
done by di vinyl benzene.Cation resins are made of sulphonated polystyrene
SO3H can be represented by as RH.anionic resin is similarly made but is
chloromethylated and then is animated. The final product is quaternary
ammonium compound a strong base and is represented by ROH.
CATION UNIT:
In the cation unit’s free H+ ion of the resin is replaced by Ca and Mg or Na ions
as per the following reactions.
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RH + NaCl---------------RNa+ HCl
2RH + MgSO4--------------------- R2Mg + H2SO4
2RH + Ca (HCO3)2---------------------------R2Ca +2CO2 + 2H20
Natural salts are converted into respective mineral acid and alkaline salt
split into carbon dioxide. The outlet water has low pH.
DEGASSER:
From the cation units water move to the degasser. Here the free CO2 content of
the water is splitted off with the help of air by passing the water over by the
rasching ring packed bed. Water from the degasser is received into three Nos.
degasser water sump each of having a capacity 40m3 from these sump
degassed water pumps discharge water into the anion units. There are total five
Nos of pumps each having a capacity of 150M3/ hr.
ANION UNITS:
Anionic impurities of water beside CO2 and silica are removed in the anionic unit.
There are total four No of anionic units. Two anionic units having a capacity
7920L of resin while the two are 5965 and 8400L of resin. Anion present in the
water gets removed as per the following reactions.
2ROH + H2SO4---------------- R2SO4 + 2 H2O
ROH + HCl------------------------ RCl + H2O
MIXED BED UNITS (PRIMARY):
Certain amount of sodium and silica ions gets slipped from cation and anion
units. Very large volume of resin is required to check these leakages. Hence
these ions are removed in mixed bed units. It consists of bed of mixed cation and
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anion resins. This water is stored in DM water tank there are two DM water tanks
each having a capacity 1400L. Each of cation and anion resin is charged in three
mixed bed units while in fourth unit the quantity is 1880L.
CONDENSATE CATION UNITS:
Steam condensate is received from ammonia plant. It contains ionic and colloidal
iron. Colloidal iron is removed in colloidal filters while ionic iron is removed in
condensate cation units. Condensate coming from ammonia plant is first cooled
to 45 C in a condensate cooler. There are total five condensate units. Three units
are charged with 1810L of resin while two are charged with 4200L of resin. After
polishing the condensate it is stored in DM water tanks.
SECONDARY MIXED BED UNITS:
DM water from DM water tank is pumped to secondary mixed bed units with the
help of DM water pumps. Final traces of impurities are removed again with the
help of mixed bed cation and anion resins. After passing through the bed polish
water of the following specifications is obtained.
pH 7+0.2
Conductivity 0.2 micro mhos/cm
Total iron as Fe 0.015 mg/l
Silica 0.015 mg/l
Hardness NIL
Polish water thus obtained is stored in polish water tanks. There are two polish
water tanks each having a capacity of 1500M3. it is pumped to ammonia pant and
captive power plant with the help of five nos. of polish water pumps each having
a capacity of 220M3/hr.
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FINAL DISPOSAL AREA
This area is used for receiving, storing and finally disposing off the treated
water from ETP and storm water. This area is having five ponds. Their capacities
and services for which these are used are given below.
Sl no. Name Capacity Service
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1. Pond no 1 25,000 Ash pond
overflow & off
grade effluent
2. Pond no 2 25,000 -do-
3. Pond no 3 26,000 Treated water
4. Pond no 4 48,000 Storm water
5. Pond no 5 60,000
Treated water meeting the MINAS standard is received in pond no 3 and 5 from
final effluent pump discharge located in EFFLUENT TREATMENT PLANT.
If this water is not conforming to MINAS standard, then provision is to
receive it in pond no no. 1& 2. Storm water from the factory is received in pond
no.4 and stagnant water area. It is then pumped from this place to pond no. 1&2
with the help of four vertical pumps. Effluent from ponds no 1&2 is pumped to
factory for deashing in SGP and CPP. Three pumps each with a capacity of
500m3/hr, have been provided for this purpose.
Treated water received in pond no. 3 and 5 is supplied for irrigation in fields and
township. Provision is also being made to use this water as fire water and for
kitchen garden in township. Two pumps each with a capacity of 275M3/hr has
been provided for this purpose.
WATER BALANCE ACROSS FINAL DISPOSAL AREA
WATER IN WATER OUT
Sl no Source Qty M3 Sl no Supplied to Qty M3
1 From ETP 230 1. For
deashing in
350
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SGP
2. Ash ponds 388 2. For
deashing in
CPP
139
3. For
irrigation in
township
73
4. For fire
header
changing
and for use
in
township.
56
Total 618 618
SAFETY
Safety & fire Department manned by qualified personnel in various disciplines
has been provided in the Factory. High quality safety equipments are made
available to the employees free of cost. In order to make workers safety
conscious, regular publicity and frequent training programmes are arranged.
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As this plant containing chemicals therefore it is dangerous while working in
factory.
As protecting from these gasses these are prepares and kept in spheres, still
there is chance of leakage of gasses; gasses like Ammonia, CO are very
dangerous to the human life. As some gases smell less they can be detected.
For this reason windsocks have been installed at several places on Plant/building
tops to see the direction of wind. In case of any toxic gas / vapours in to
atmosphere, it is preferable to run in a direction at right angle of wind. They have
a separate department known as 'Safety Department' that gave the knowledge
about these things. Fire station also comes under this section. They placed fire
detectors at different places. Some secret automatic systems are also there for
security purposes.
“Safety Comes In Cans”
I CAN, YOU CAN, WE CAN
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HOW WINTER PROJECT IS USEFUL
Industrial training is very useful for an engineer. It gives an overall idea
about the company’s production problems one has to face in realizing companies
goals, when he is in the field. Winter Project done under IFFCO fetched me much
of the practical knowledge. I was at least aware of many factors that play crucial
role in an Manager’s life while working with in an industry. Training made me
understand the rudiments of an manager.
At IFFCO I came in contact with workers and officers of various cadres. I
found both of them to be well versed in their fields.
Exposure to industry makes an MANAGER grasp the subject in a better
way since confidence plays an important role in it and it is some thing which can
be gained only by practical training.
Having came in contact of IFFCO AONLA, its glories, its triumphs, its
success due to its toiled, zeal and zest employees. I am fully inspired to work
hard with dedication and my uttermost sincerity.
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