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Chapter - 5

Case Studies in Cement Industries

5.1.0 Introduction: This chapter is fully devoted to industrial sector – Cement Industry. Cement industries covered in this chapter are large scale and medium scale industries. Small scale industries - mini cement plants have been considered separately. This chapter is further sub divided into three parts: Part – I Overview of cement production Part – II Implementation of lean philosophy in cement plant Part –III Energy Conservation through Design Modifications and Technical Advancement 5.2.0 Overview of Cement Production: Seven cement industries were visited and the over view of the production process along with the flow process charts for these industries is discussed in the following write up 5.2.1 Ambuja Cement Plant of Ambuja Cements Ltd., Ambujanagar:

i) Cement Manufacturing Process Description: The manufacturing process of cement in Ambuja is based on dry process. Process flow diagram is attached as figure 5.2. Selection of dry process is based on the fact that dry process consumes less thermal energy and minimizes pollution. Cement is manufactured in four stages: Quarrying and crushing, Grinding and blending of raw materials, Clinker production and finished grinding. Cement production is initiated with extraction and is composed of combination of limestone, clay and siliceous materials. The raw materials are transported to crushing plant/stockyard. The preparation of raw materials for Kiln (a large horizontal/rotating furnace) involved drying, proportioning, grinding and blending of various raw materials. The raw materials fed into kiln as dry powder. The raw materials are made dry in unit called Pre-heater by kiln flue gases to conserve heat energy. These grounded, blended and dried materials are fed to the kiln and contents are transported to the combustion zone of the kiln. The retention time in the kiln is 25 to 30 minutes with heating temperature of about 1300 - 1400° C. The bituminous coal is the fuel used for pyro-processing. Coal is required to be crushed and pulverized for efficient use. The product from the kiln consists of dark hard nodules called Clinker. The nodules are cooled in Clinker cooler prior to storage and further processing. Clinker is ground in a cement mill with adequate amount of gypsum and fly ash. The addition of which retards the settling time of cement. Finally, the product is packed in bags and bulk transport.

ii) Operation during cement manufacturing: a) Mining: In this operation, limestone is mined and then transported to the Crusher/ stack yard. b) Crushing, Stacking & Reclaiming: Limestone is stored in stack yard directly or crushed in Crusher into small size granules, then it is stacked in piles and the reclaimed for proper blending. c) Grinding: In this, the crushed raw material is ground (Limestone and other additives). d) Blending: In this operation, the ground raw materials are homogenously and proportionately blended. e) Pyro-processing: In this operation, the blended raw materials are pre-calcinated in Pre-heater. The calcinations is done in horizontal rotating kiln at 1300-1400° C temperatures. The actual chemical reaction takes place in kiln. In burning zone of kiln thermo-chemical reactions takes place and all the oxides are converted into the minerals in the form of clinker. The chemical constituents of the Clinker are follows. f) Clinker Cooling: In this operation hot clinker is cooled by grate coolers. The dust is collected by ESP and recycled to the process. In this operation there is no chemical reaction. Retention time is about 25-30 minutes.

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g) Pre-clinker Grinding: In this operation Clinker Grinding takes place through roller press. h) Clinker Grinding In this operation final grinding of Clinker takes place, Gypsum and fly ash are mixed to make Cement of different grades, which are stored in silos. i) Packing & Transportation: In this operation automatic Rotary Packers pack cements stored in silos in bags. j) Coal Storage and Grinding: In this operation Coal is fed in Coal mill hopper and further it is pulverized in Coal mill, which is used in clinkerisation.

iii) Mass Balance Diagram for the Manufacturing of Cement (For 1 Ton):

Fine Coal 0.119 MT

Limestone, 1.247 MT

Marl, 0.128 MT Clinker, 0.9098

MT

Sandstone, 0.050 MT

Laterite, 0.001 MT

Clinker, 0.9098 MT

Gypsum, 0.059 MT,

Fly ash, 0.102 MT

Cement Packing &

Dispatch 1 MT

Figure 5.1 Mass Balance Diagram for the Manufacturing of Cement (For 1 Ton)

CEMENT KILN

LOI of Raw Material-35%

(approx)

LOI of Coal=80% (approx)

CEMENT MILL

(LOI of Raw Material 5%)

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Figure 5.2 Flow Chart for Ambuja Cement Plant

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5.2.2 GajAmbuja Cement Plant Of Ambuja Cements Ltd., Ambujanagar:

i) Cement Manufacturing Process Description: The manufacturing process of cement in GajAmbuja is based on dry process. Manufacturing process flow diagram is as per figure 5.3. Selection of dry process is based on the fact that dry process consumes less thermal energy and minimizes pollution. Cement is manufactured in four stages: Quarrying and crushing, Grinding and blending of raw materials, Clinker production and finished grinding. Cement production is initiated with extraction and is composed of combination of limestone, clay and silicaceous materials. The raw materials are transported to crushing plant/stockyard. The preparation of raw materials for Kiln (a large horizontal/rotating furnace) involved drying, proportioning, grinding and blending of various raw materials. The raw materials fed into kiln as dry powder. The raw materials are made dry in unit called Pre-heater by kiln flue gases to conserve heat energy. These grounded, blended and dried materials are fed to the kiln and contents are transported to the combustion zone of the kiln. The retention time in the kiln is 25 to 30 minutes with heating temperature of about 13000C – 1400º C. The bituminous coal is the fuel used for pyro-processing. Coal is required to be crushed and pulverized for efficient use. The product from the kiln consists of dark hard nodules called Clinker. The nodules are cooled in Clinker cooler prior to storage and further processing. Clinker is ground in a cement mill with adequate amount of gypsum and fly ash. The addition of which retards the settling time of cement. Finally, the product is packed in bags and bulk transport.

ii) Operation during Cement Manufacturing: a) Mining: In this operation, limestone is mined and then transported to the Crusher/ stack yard.

b) Crushing, Stacking & Reclaiming: Limestone is stored in stack yard directly or crushed in Crusher into small size granules, then it is stacked in piles and the reclaimed for proper blending.

c) Grinding: In this, the crushed raw material is ground (Limestone and other additives).

d) Blending: In this operation, the ground raw materials are homogenously and proportionately blended.

e) Pyro-processing: In this operation, the blended raw materials are pre-calcinated in Pre-heater. The calcinations is done in horizontal rotating kiln at 1300-1400° C temperatures. The actual chemical reaction takes place in kiln. In burning zone of kiln thermo-chemical reactions takes place and all the oxides are converted into the minerals in the form of clinker. The chemical constituents of the Clinker are follows.

f) Clinker Cooling: In this operation hot clinker is cooled by grate coolers. The dust is collected by ESP and recycled to the process. In this operation there is no chemical reaction. Retention time is about 25-30 minutes.

g) Pre-clinker Grinding: In this operation Clinker Grinding takes place through roller press.

h) Clinker Grinding: In this operation final grinding of Clinker takes place, Gypsum and fly ash are mixed to make Cement of different grades, which are stored in silos.

i) Packing & Transportation: In this operation automatic Rotary Packers pack cements stored in silos in bags.

j) Coal Storage and Grinding: In this operation Coal is fed in Coal mill hopper and further it is pulverized in Coal mill, which is used in clinkerisation.

iii) Mass Balance Diagram for the Manufacturing of CEMENT (For 1 Ton)

Mass Balance Diagram for the Manufacturing of CEMENT (For 1 Ton) is same as for Ambuja cement plant as per figure 5.1.

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Figure 5.3 Flow Chart for GajAmbuja Cement Plant

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5.2.3 Sanghi Industries Limited, Sanghipuram Clinkerization & Cement Plant:

i) Brief Clinker Manufacturing Process Description: Cement Clinkerization process essentially consists of: - a) Mining: The lime stone excavation will be done by Surface Miners and loaded into dumpers and transported to lime stone crusher where it is sized and conveyed to stacker and reclaimer. The other raw materials such as Pozzlona Clay, Leterite, Silica Sand and bauxite are available around the plant site. Lignite will be purchased from GMDC Panandhro and Gypsum from local resources. b) Crushing & Stacking: There are two identical crusher supplied by L & T for crushing lignite and additives of 300 TPH. Separate stock yard and reclaimer for each i.e. lime stone lignite/coal and additives have been provided for holding 40000 x 2 MT lime stone, 5000 x 4 MT of lignite, 10000 MT silica and 4000 MT of bauxite respectively. c) Raw Material Grinding: A VRM for raw meal grinding is supplied by FKCP LM 59.480 Capacity 670 MT/Hr. with FMR. The preheater exit gas is used for drying of the raw meal upto 1-% moisture content. The VRM equipped with 8 cyclones followed by a Bag House (common for VRM & Kiln) for efficient raw meal/ dust collection. The product from VRM is transported to CF Silo having capacity to store 40000 MT and has continuous blending and extracting facility ensuring consistent quality of raw meal to be fed to the pyro system. d) Pyroprocessing: It consists of Kiln with 3 streams 6 stage pre-heater with in line and separate line calciner. The capacity of kiln is 10500 TPD with a size of 5.6 dia x 84 M length. For efficient cooling and heat recuperation CIS - CFG cooler is being used. Alkali bypass systems have been provided for controlling the quality of clinker and minimize operational problems. e) Lignite Grinding: Two-lignite mill VRM LM 26.30 D with a capacity of 37.5 MT/ Hr. has been provided. The entire lignite circuit has been provided with inertisation system and explosion vents to ensure safety against fire hazards. For Hot Gases to mill a pre-lignite ESP has been provided which separates dust from kiln PH Gases and sends clean gases to lignite mills. Process flow chart is enclosed. Please refer Annexure-I. ii) Chemical Reactions Involved In Formation of Clinker: The clinker is made up of four constituents which are as under : 1) Tricalcium Silicate (C3S) 3CaO + SiO2 2) Bicalcium Silicate (C2S) 2CaO + SiO2 3) Tricalcium Aluminate (C3A) 3CaO + Al2O3 4) Tetracalcium Alumino Ferrate (C4AF) 4CaO + Al2O3+Fe2O3 The sequence of the Chemical Reactions can be summerised as follows:

Sr. No. Temperature Chemical Reaction

I Below 800 OC Decomposition of limestone of CaO.Al2O3 begins

II 900 – 1100 OC

1) Decomposition of calcium carbonate is complete.

2) Formation & decomposition of Gehlenite (2CaO+ Al2O3+SiO2)

3) Formation of C3A, C4AF starts.

III 1000-1200 OC Formation of C2S, C3A & C4AF is nearly complete.

IV 1200-1300 OC Liquid formation starts

V 1200-1450 OC Assimilation of CaO through solid-liquid reactions & formation of C3S

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iii) Brief Cement Manufacturing Process Description:

a) Semi Finish Grinding System Single Compartment Type Mill Capacity : 180 TPH At 3200 Blain (Sq.m/Size)

Mill Size : 4.2 Dia X 11.00 Long

Mill Drive : 2700 Kw

Speed Of Mill : 15.819 Rpm

b) Hydraulic Roller Press Size of roller 2.08 Meter dia x 8500 width

Material carried out into sepax separator & worse material to HRC Cement Silo

Fuller – IBAU Designed Single & Four Compartment Silo

Capacity of Silo : 20,000 Tons each

c) Cement Grinding: Cement grinding is done by Ball Mill. But prior to that 95% Clinker and 5% Gypsum are reground in high pressure Roll Crusher. The crushed product from high pressure Roll Crusher is fed to high efficiency sepax separator. The separator has three outputs. The coarse grits are taken to Ball Mill for finer grinding. Fine product from separator are collected and dedusted in Bag House. The cement mill discharge which contains fine and coarse particles is taken to sepax separator by air slide and elevator. In the separator it is classified and fine products are taken to the Bag House. The mill gases are vented and dedusted through electrostatic precipitator. The cement product from ESP is sent to the separator. Finally the cement is taken from the Bag House and lifted to cement silos by bucket elevators.

d) Packing Plant: The Packing unit shall consist of 5 Nos. of 8 spout rotary packer with 10 Nos. Truck loader is used for packing and dispatch of cement in 50 Kg bags. Provision for Bulk Cement dispatch, jumbo bags loading and clinker dispatch will be provided. As 85% of production is dispatched through sea transport, cement bags, Bulk clinker and Bulk Cement are transported by conveyor to the ship loading bay for loading into the ships.

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Figure 5.4 Flow Chart for Clinkerization & Cement Plant, Sanghi Industries Limited, Sanghipuram

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5.2.4 Gujarat Sidhee Cement Ltd., Ta: Sutrapada, Dist. Junagadh: i) Cement Manufacturing Process Description: The process of clinker production at Gujarat Sidhee cement limited, Sidheegram can be briefly described as follows:

The relevant manufacturing process diagram is similar to figure 5.5 for Saurashtra Cement

a) Mining: The mining of the limestone is done by MineCAD – Computer aided mining development from the very rich captive mines which has storage of limestone to sustain the plant for over 30 years. In these captive mines, almost all the grades of limestone is available and a very little quantity of additive is to be obtained from outside. We have also switched over surface mining technology, which is most modern and eco-friendly.

b) Crushing, Stacking & Reclaiming: The mined limestone is hauled through Dumpers to a rotary hammer – impact type crusher which crushes the limestone to a size of 80% upto 75 mm size. Additive material is added to the crushed limestone through an additive hopper which bypasses the crusher. The material is passed on to the stacker via belt conveyors, which spreads the material in longitudinal layers. The stacked material is reclaimed by the reclaimer which reclaims it by cutting transversely the longitudinal stacked layers ensuring perfect blending and homogenizing. c) Raw Mill Grinding: The reclaimed material is fed to the Raw Mill along with the additive materials through belt conveyors and box feeder. The desired material is drawn from the box feeders and is fed to the vertical roller mill. The vertical mill consists of a rotating table upon which 3 rotating rollers are hydraulically pressed. The material is dried, ground and transported by the hot kiln exit gases. The size of the pulverized material is controlled by a static separator which separates the over sized grits and sends it back on the table for further grinding. The pulverized material is transported to the C. F. Silo via energy efficient bucket elevators. d) Storage & Blending ( Capacity 20,000 MT ): The pulverized material is stored and blended in the controlled flow silo. The blending action is achieved by extracting the material from the 7 outlets at a different rate. The extracted material is conveyed to a weighing bin where it is further blended. The operation of extraction is controlled by a PLC. The blended material is fed to the pre-heater for pre-heating via bucket elevator. e) Preheating, Clinkerisation and Cooling: The kiln feed from the silo, is fed into both the strings of pre-heaters. Approximately 40% of the feed is given to the preheater string where it is preheated by the hot kiln exit gases and gets Calcined upto 60% approximately. The balance 60% feed is fed to the calciner string where coal is fired in the calciner and the 60% Calcined feed from the preheater string is also added to the calciner. Here, about 90% calcinations are achieved. This 90% Calcined feed is transferred to the kiln for the remaining 10% calcinations and sintering where the flux materials and silica melt to react with lime to form four clinker phases. This is achieved by firing coal in the rotary kiln. Kiln presently operating @ 4000 TPD. The clinker coming out of the rotary kiln is at a temperature of 1300 – 1400° C and hence cooling of the same is required. This is achieved by pumping atmospheric air in the reciprocating grate cooler by 8 centrifugal fans. The clinker gets cooled and the air gets heated up and the excess air is vented out at a lower temperature. The recuperation of the heat in the cooler is in the range of 68– 74%. f) Clinker Storage & Transport: The clinker which is cooled to < 150° C is stored in a silo which has capacity of 40,000 MT. The clinker is transported to the silo by deep bucket conveyors. The silo for clinker is a salient feature of the plant as the clinker does not get weathered. Another silo of 2000 MT Capacity is provided to store specified products / non confirming products. The clinker from the clinker silo is transported to the clinker hoppers of the cement mills for grinding. g) Cement Mills: The clinker is ground along with gypsum in the highly efficient mills. The cement mills are two compartment tube mills. In the first compartment, the grinding is done by impact with balls and in the second compartment, it is done by surface grinding with small grinding media cylinders called cylpebs. The mill is swept with air which transports the material through the mill. The cement is pumped to the cement silos with the help of air lifts. There are four silos for cements of 5000 MT capacity each for storing different grades of cement.

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h) Packing Plant: The packing is done by automatic rotary packers which have a capacity of 90TPH each. There are total 5 Nos. of packers. The packed bags are directly loaded into the trucks by belt conveyors. Bulk loading system is also available for cement loading in bowsers. i) Raw Coal & Fine Coal Plant: Raw coal is also stacked and reclaimed by a stacker and reclaimer hence ensuring a perfectly blended raw coal. This is a unique feature of the plant. The raw coal is pulverized in a vertical roller mill which is similar to that for the lime stone. The ground coal is fired to kiln & calciner through screw pumps. The coal mix is ground to 4 % residue on 90 micron sieve to ensure complete combustion. j) Control System: The plant is centrally controlled except for crusher, stacker, and the packing plant. The control is achieved by DCS and colour videography system. The kiln cooler operation is controlled by automatic system Called Fuzzy logic. The plant has commissioned most modern DCS Control, which in turn will improve overall efficiencies. DCS Control is supplied by M/s. Opto Intulation USA through M/s. Ramco System, Chennai.

k) Quality Control: The quality control is achieved with the help of a X – Ray Analyzer which gives accurate and fast results. However, a fully equipped chemical and physical laboratory is also available. Total compliance for BIS norm is ensured by Quality and Production Department. l) Quality Management: The organization was certified for ISO 9002 Quality Management System by TUV, Germany in March 1995. The company has been certified for ISO 9001:2000 in July 2001. The company is also accredited with ISO:14001, both by M/s. RW TUV Germany. k) Pollution Control Equipments: The plant employs the latest state of art pollution control equipments like ESPs, Bag Filters and Chemjets. The old generation pulse energized ESP has been modified to the latest generation ESP. The controllers for the transformers have been changed and a variable inductance is provided. The company has already replaced & Commissioned Gas cooling system supplied by M/s. Caldyan, Germany with more advanced system from Chemstols Samil. ii) Chemical Reactions Involved In Formation of Clinker:

The clinker is made up of four constituents which are as under : 1) Tricalcium Silicate (C3S) 3CaO + SiO2 2) Bicalcium Silicate (C2S) 2CaO + SiO2 3) Tricalcium Aluminate (C3A) 3CaO + Al2O3 4) Tetracalcium Alumino Ferrate (C4AF) 4CaO + Al2O3+Fe2O3 The sequence of the Chemical Reactions can be summerised as follows :

Sr. No. Temperature Chemical Reaction

I Below 800 OC Decomposition of limestone of CaO.Al2O3 begins

II 900 – 1100 OC

1) Decomposition of calcium carbonate is complete.

2) Formation & decomposition of Gehlenite (2CaO+ Al2O3+SiO2)

3) Formation of C3A, C4AF starts.

III 1000-1200 OC Formation of C2S, C3A & C4AF is nearly complete.

IV 1200-1300 OC Liquid formation starts

V 1200-1450 OC Assimilation of CaO through solid-liquid reactions & formation of C3S

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iii) General Mass Balance In Respect Of Input of Kg/Kg Raw Materials:

a) Clinker: 31 % Loss on Ignition

Lime Stone 0.982

Marl 0.421

Additives 0.04945

b) OPC Cement:

Gypsum 0.0515

Clinker 0.9485

c) PPC Cement:

Gypsum 0.0515

Clinker 0.7674

Fly Ash 0.1811

1 kg OPC Cement

Yield : 100 %

1 kg PPC Cement

Yield : 100 %

1 Kg Clinker

Yield : 69 %

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5.2.5 Saurashtra Cement Ltd, Ta: Ranavav, Dist. Porbandar: i) Cement Manufacturing Process Description (Dry Process): The process of clinker production at Saurashtra Cement Limited, can be briefly described as follows and the relevant manufacturing process flow diagram is given in figure 5.5.

a) Mining of Raw Material: Mining of major raw materials like limestone and marl are done by open cast mining. Surface miners are used for the mining of limestone from various benches. Heavy earth moving equipments like dumpers are used for the transportation of these limestone boulders to crusher. The crushed limestone and marl are taken to dumpers with the help of excavators etc. For maximum output from the given mine, mining planning is done which may be long term or short term mine planning

b) Crushing of Lime Stone: The crushers are selected depending on the hardness of raw material. In SCL impact crusher is used. The material is crushed upto the size of 75/25 mm depending upon in which mill either VRM or ball mill the material is to be fed for grinding. The crushed material is stacked in the form of stock piles and reclaimed to minimize variation in Raw Mill feed.

c) Raw Meal Grinding: The grinding of raw material is done either in Vertical Roller Mill or Ball Mill. Now a days a VRM is more preferable where hot gas from Kiln Exit Gases are taken for simultaneous drying and grinding of raw material. From Ball Mill or VRM, the fine particles named “Raw Meal” having the size of 20+/-4 retention on 90 micron sieve are output of mill. The prepared Raw Meal is stored in Silo after blending.

d) Pyro processing: Then comes the clinkerization or pyroprocessing of raw material which is done in preheater, precalciner and kiln. The blended material from blending silos are fed into the preheater, where they are preheated releasing the free moisture, combined moisture etc. Then they are Calcined at precalcinator releasing CO2 from CaCO3. After calcinations, it goes to kiln where the actual phase formation through the liquid formation takes place. These phases are C3S, C2S, C3A and C4AF. These are the main ingredient of cement, on which the entire cement characteristics depends.

e) Clinker Cooling: After the process of clinkerization, clinker of nodules shaped are formed and they are required to be cooled quickly for their easy and immediate handling, better quality and grindability, heat recuperation from these hot clinker etc. For this purpose clinker coolers of various designs are used like grate cooler, satellite cooler, rotary cooler etc. Cooled clinker is stored in yard using handling equipments like drag chain, deep pan conveyor etc.

f) Clinker Grinding: Then these clinker is ground in bal mill with 4-5% addition of gypsum to retard the settling time of clinker. With this the fine Magic Powder cement is formed.

g) Cement Packing & Dispatch: The fine powder of cement are ground and kept in cement silos. From these silos the cement is conveyed to packers from where they get dispatched through trucks, wagon in bulk or in bags.

i) Cement Manufacturing Process Description (Semi Dry Process): Limestone & clay / marl are crushed either separately in desired percentage and fed to the ball mill hopper. The material is ground and conveyed to homogenizing silos. The mix is thoroughly homogenized and fed to the storage silo where the same is fed to the nodulizer. The nodules are made of raw mix with the help of 10 to 11% of water and nodules are fed to the lepole grate for partial calcinations and to the kiln for complete calcinations and sintering. Clinker is made and cooled in cooler. The cold clinker is conveyed through the drag chain and stored in yard. The clinker along with the gypsum in desired ratio is ground in ball mill (closed circuit) to make cement and conveyed to the silo through bucket elevator and air slides. Process flow diagram is as per figure 5.5

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ii) Chemical Reactions Involved In Formation of Clinker:

The clinker is made up of four constituents which are as under : 1) Tricalcium Silicate (C3S) 3CaO + SiO2

2) Bicalcium Silicate (C2S) 2CaO + SiO2

3) Tricalcium Aluminate (C3A) 3CaO + Al2O3

4) Tetracalcium Alumino Ferrate (C4AF) 4CaO + Al2O3+Fe2O3 The sequence of the Chemical Reactions can be summarized as follows :

Sr. No. Temperature Chemical Reaction

I Below 800 OC Decomposition of limestone of CaO.Al2O3 begins

II 900 – 1100 OC

1) Decomposition of calcium carbonate is complete.

2) Formation & decomposition of Gehlenite (2CaO+ Al2O3+SiO2)

3) Formation of C3A, C4AF starts.

III 1000-1200 OC Formation of C2S, C3A & C4AF is nearly complete.

IV 1200-1300 OC Liquid formation starts

V 1200-1450 OC Assimilation of CaO through solid-liquid reactions & formation of C3S

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Figure 5.5 Flow Chart for Saurashtra Cement Ltd.

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5.2.6 Digvijay Cement Co. Ltd., Jamnagar: i) Cement Manufacturing Process Description (Dry Process): Limestone from various mines, which are mostly in the form of boulders, are brought by trucks or railway wagons to the factory premises and unloaded into the hoppers of the crusher. These materials are crushed to the size in the range of 25-100 mm and conveyed to raw material yard through belt conveyors.

Crushed limestone, which is piled in the yard by stacker are reclaimed and conveyed to the grinding mill hoppers, where the same are mixed with other additives/corrective materials in specified proportion and weighed quantities are allowed to go in the inlet of vertical raw grinding mill through belt conveyors. This is a closed vertical mill. Hot process air is also supplied to the mill for materials to dry and convey ground raw meal powder to the blending silo (C.F.silo). Raw meal is homogenized in the silo and stored. Ground raw meal is further extracted from C.F.silo, weighed and fed to the pre-heater cyclones. Pulverized coal firing is done in the kiln as well as in the calciner vessels of the pre-heater cyclones through which raw meal powder have fed. Raw meal comes in contact with hot gases in various stages of cyclones and kiln producing hot clinker at final stage. Hot clinkers are cooled in grate cooler and are either conveyed to clinker yard or conveyed directly to the hoppers of the cement mills. Gypsum is added in fixed proportion with the clinker and fed to the cement mill and transported pneumatically or mechanically to the cement storage silos. As and when required, the stored cement are extracted from the cement silos and packed in 50.kg bags by packing machines.

ii) Cement Manufacturing Process Description (Wet Process): Limestone from various mines, which are mostly in the form of boulders, are brought by trucks or railway wagons to the factory premises and unloaded into the hoppers of the crusher. These materials are crushed to the size in the range of 25-100mm and conveyed to raw material yard through belt conveyors.

Crushed limestone and other additives / corrective materials in specified proportion are fed into the ball mill with huge quantity of water to grind the raw material in form of slurry.

Moisture in slurry is kept between 30 to 35 %. Raw material slurry are taken to the silo for correction and homogenization and then discharged and stored in air agitated slurry basins.

The required quantity of slurry are extracted from the basin, measured and then fed to the long rotary kiln where pulverized coal firing is done from either end.

As materials (slurry) moves to discharge end of the kiln it comes in contact with hot gases and finally clinker is cooled by air in the cooler. Cooler hot gases are utilized in coal firing and drying system to save and utilize waste heat. Clinker is finally transported to clinker yard or directly to cement mill hoppers. Gypsum is added in fixed proportion with the clinker and fed to the cement mill and transported pneumatically or mechanically to the cement storage silos. As and when required, the stored cement are extracted from the cement silos and packed in 50 kg bags by packing machines loaded to trucks and wagons.

iii) Chemical Reaction:

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Figure 5.6 Flow Chart for Digvijay Cement

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5.2.7 Gujarat Anjan Cement Ltd., Seagram, Village: Vayor, Kutch: i) Cement Manufacturing Process Description:

a) Mining: The cement manufacturing process starts from the mining of limestone, which is the main raw material for making cement. Limestone is collected by Surface Miner by loader loaded on to dumpers, which transport the material and unload into hoppers of the limestone. .

b) Stacking & Reclaiming Of Limestone: From Limestone hopper material is discharge the material onto a belt conveyor, which takes it to the stacker. The material is stacked in longitudinal stockpiles. Limestone is extracted transversely from the stockpiles by the reclaimers and conveyed to the Raw Mill hoppers for grinding of raw meal.

c) Crushing Stacking & Reclaiming of Coal: The process of making cement clinker requires heat. Lignite is used as the fuel for providing heat. Raw Coal received from the collieries is stored in a coal yard. Raw Coal is dropped on a belt conveyor from a hopper and is taken to and crushed in a crusher. Crushed coal discharged from the Coal Crusher is stored in a stockpile from where it is reclaimed by a reclaimer and taken to the coal mill hoppers for grinding of fine coal.

d) Raw Meal Drying/Grinding & Homogenisation: Reclaimed limestone along with some laterite stored in their respective hoppers is fed to the Raw Mill for fine grinding. The hot gasses coming from the clinkerisation section are used in the raw mill for drying and transport of the ground raw meal to the Electrostatic Precipitator / Bag House, where it is collected and then stored and homogenized in the concrete silo. Raw Meal extracted from the silo (now called Kiln feed) is fed to the top of the Preheater for Pyroprocessing.

e) Clinkerisation: Cement Clinker is made by Pyroprocessing of Kiln feed in the preheater and the rotary kiln. Fine coal is fired as fuel to provide the necessary heat in the kiln and the Precalciner located at the bottom of the 5/6 stage preheater. Hot clinker discharged from the Kiln drops on the grate cooler and gets cooled. The cooler discharges the clinker onto the pan / bucket conveyor and it is transported to the clinker stockpiles / silos. The clinker is taken from the stockpile / silo to the ball mill hoppers for cement grinding.

f) Cement Grinding & Storage: Clinker and Gypsum (for OPC) and also Pozzolana (for PPC) are extracted from their respective hoppers and fed to the Cement Mills. These Ball Mills grind the feed to a fine powder and the Mill discharge is fed to an elevator, which takes the material to a separator, which separates fine product and the coarse. The latter is sent to the mill inlet for regrinding and the fine product is stored in concrete silos.

g) Packing: Cement extracted from silos is conveyed to the automatic electronic packers where it is packed in 50 Kgs. Polythene bags and dispatched in trucks

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Figure 5.7 Flow Chart for Gujarat Anjan Cement

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5.3.0 Implementation of Lean Philosophy in Cement Plant: Implementation of lean helps many organisations to improve their productivity and efficiency; on the other hand numerous organisations have failed to benefit from lean philosophy. The case of not achieving the expected results of implementing lean is not because of limitation of lean to specific organisations type; however the misconception of the lean philosophy is amongst the main failure’s factors. The lean thinking was originated in the automobile manufacturing sector and it widely spreads within the discrete industries; however the today’s challenge is to implement the lean philosophy within continuous manufacturing industries and different organizations regardless to the type, size, or mission of the applicant organisation. This has motivated this research to propose a standard generic transition steps which can be adopted by different organisations in order to become lean. The cement industry is ideal example of the continuous industry sector and it will be used to demonstrate that the lean philosophy is applicable to all different organization types. There are numerous challenges facing the cement industry in today’s competitive environments; one of the major challenges is the capability of the cement industry to adopt and introduce the improvement approaches and techniques by which the overall enhancement can be achieved. The problem is that the cement industry is under pressure to reduce the downtime, cycle time, inventories and batch sizes. The cement industry is characterised by intensive energy and raw materials, large Work-In-Progress inventories, high breakdown levels, and the need to increase the productivity in order to meet high demands. The situation of not achieving the expectation of high machine utilisation and production rates, low breakdown rates, and trouble free operation processes within the cement production line has motivated the undertaken research to design an integrated framework by which the cement production line will be improved and enhanced. The need for improving the efficiency of the cement production line is widely acknowledged in order to reduce the downtime rates, and satisfy high levels of market demand where the demand for cement is mostly second substance behind water. In response to this respect this thesis has investigated and addressed the implementation of the lean philosophy within the cement industry. The main contribution of this study is to convey the message to the decision makers that the lean philosophy is the proposed solution by which the continuous industry and different organisation types can be improved through eliminating or minimising wastes and non-value added activities within the production line. The developed transition steps have ability to: • Understand the cement manufacturing process in order to identify value added and non-value added activities within production line through applying the process mapping technique. • Determine and examine the interrelationships between the variables through developing of Cause-Effect matrix. • Quantify the benefits obtained from the changing process within the cement production line through employing of the experimental design technique where novel approach has been developed by integrating the simulation modeling technique with Taguchi Orthogonal Array. This research has led to observation that the cement industry can benefit from implementing lean philosophy once the organisation mission, aims, and objectives are clarified and communicated through all the organisation levels. Furthermore barriers and obstacles should be removed through changing the organisational culture, and empowering the people to be involved in identifying and problem solving process. 5.3.1 Lean Manufacturing Principles: The principles of lean manufacturing can be classified into five basic principles which are: i) Customer Value: The production process should be defined and analysed with respect to customer values and satisfactions; the customer can be internal or external. Customer value can be defined as how the customer predicts and perceives the product or service that offered by the organisation. Whilst, customer satisfaction means how the customer utilises and benefits from these products and services. Analysing value is the starting point for any production process. The production activities need to be created in such a way to eliminate and minimise the wastes and non-value added activities. ii) Value Stream: Value Stream illustrates the flow of material and information within the production system. The first step of this principle is creating of current state map (the currently way is used to provide service or product) and compare it with the future state map (the future operating way after improvement). Value Stream mapping tool is used in analysing and highlighting all non value added activities such as delay, excess stock, work in progress, moving, sorting, and long lead times. iii) Flow Process: Adoption of continuous flow principle will eliminate all types of wastes and obstacles that interrupt flow of the material or process. The continuous flow approach reduces the lead-time, processing time, and overall production costs. Availability of materials, tools, operators, and machines are essential factors for successful flow continuously system.

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iv) Pull System: In Pull system customer demand controls and governs the flow of production through the production line. (Lee and Lee5)This principle aims to eliminate overproduction, handling, and produce to stock situations. Scheduling process in pull system is based on actual consumption and demand rather than theoretical forecasted scheduling process which associated with push system. In other words, pull system means only to produce the right requested quantities of the right quality in the right time. Kanban: it is a tool to achieve the pull principle. Kanban is a singling system to pull materials or product through the production line. This tool aims to provide the material or product when they are requested by next workstation or the customer. It aims at achieving Just-In-Time manufacturing system. v) Perfection: Since the customer values have been defined, non-value added activities were eliminated, and philosophy of continuous process and pull system are adopted through correct implementation of the above principles. It is time to implement the fifth lean principle which aims at continually improvement. Elimination of all wastes will result in enhancing of the overall performance, and reducing the cycle time and production costs. 5.3.2 Wastes in Lean Manufacturing: Lean manufacturing is a process management philosophy. Lean production system aims to produce products or services through using the minimum levels of everything such as minimum capital investment, minimum human efforts, and minimum wastes. The key element of the lean strategy is to develop learning system that has the ability to identify and distinguish between the value added activities and wastes. Lean philosophy aims at enhancing the flow- rate of materials by eliminating or minimising the nonvalue added activities which can be listed as:

• Overproduction: It is a process of producing goods either more than the needed quantity or before the requested time. An extra inventory and raw materials, unnecessary work, and unbalanced material flow are accounted as a key symptom of overproduction waste.

• Transportation: any unnecessary transfer or movements of components or materials is defined as transporting waste.

• Waiting: Delay time occurs whenever time is not used efficiently. Waiting waste can be determined as the period of time when neither movement nor add value activity has been applied to the component or materials resulting in high levels of inventories and Work In progress between workstations.

• Inventory: Inventory waste is resulted from accumulating unnecessary quantities of raw materials and Work In Progress to comply just in case logic. Work In Progress (WIP) can be defined as unfinished product, which is stocked between different production stages and workstations. According to lean philosophy principles; WIP is symptoms of hidden problems within the imperfect system. High levels of WIP should be eliminated or minimised. Unnecessary inventory tends to raise production costs because it requires additional handling and space, and masks the real roots of problems components, work-in-progress and finished product not being processed.

• Motion: It is any unnecessary activities (motions) that the operator engages in for handling or monitoring actions. These activities include bending, stretching picking-up, and moving. Unnecessary motion is classified as kind of waste because it influences quality and productivity.

• Over-Processing: High rates of overproduction, defects items, or excess inventory will result in redundancy operations such as: reprocessing, recirculation, storage and handling

• Defects: Process of inspection, rework, or repair of services and products called waste of correction process. Waste of defects can be described by high levels of rework and scrap, and increase level of rejected and returned products. Correction wastes occur because of: poor product design, lack of process and quality control, unreliable equipments and unskilled operators, and unbalanced inventory levels. Total Productivity Maintenance (TPM) is one of methods by which defects and scrap wastes can be eliminated.

5.3.3 Implementation of Lean: The lean implementation process can be divided into three main stages such as: i) Preparation Stage: It is a fundamental starting stage of any successful process of lean implementation. Preparation stage means identifying and determining of missions, aims, objectives and area or activities that need to be improved. Recognising the need to change within the organisation, finding the change agent, and establishing the improvement team are accounted as the main steps of the preparation stage. ii) Design Stage: Process mapping of system’s current state is the first step of this stage in order to study and examine all activities and areas within the organisation. Visual stream mapping highlights all non-value added activities and

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wastes. In addition it analyses the system in order to determine all possible opportunities for future improvement. Planning the change becomes the final step of the design stage, where the detailed implementation plan need to be prepared and fully described in order to achieve the future vision of the organisation. iii) Implementation Stage: A specific area or part of value stream should be chosen to be as a pilot project in order to implement lean. The selected part or activity has to be important to the organisation giving immediate positive feedback. The positive feedback will be used to obtain the required support from decision makers and employees in order to expand lean philosophy through the whole system. The new system state should be evaluated and validated in order to identify all possible opportunities for future improvement. 5.3.4 Experimental Design: The main aim of the current research is to develop a proposed standard method by which the lean manufacturing can be implemented successfully within the cement production line. The work here aims to convey massage to decision makers that the cement industry can benefit from implementing lean manufacturing. In order to attain these aims, some objectives should be achieved first. These objectives can be listed as: a) Collect and verify the required data that needed to build-up a simulation model representing cement factory. The simulation model will give a visual image of the cement production line, highlight the value and non value activities, and help in decision making process which improves the line efficiency. b) Identify variables and factors, which one has a great influence or effect on the efficiency of the production line. c) An attempt to improve and enhance the performance parameters through eliminating or reducing wastes within the cement production line. d) In order to achieve a & b, it is very important to identify cement production line performance parameters which yield an immediate positive feedback e) Uses the Taguchi array to help in improvement of the cement industry efficiency. The undertaken research consists of six steps as: i) Data collection: The primary task is to identify the required data that can help in understanding the process. Once the right sources and accuracy levels of the data have been determined; identifying the method by which the required data will be collected becomes the next task. This exploratory undertaken research implements mixed method of both quantitative and qualitative data by identifying different factors that are associated or play an important role in the effectiveness of the cement production line (Bond et al2). Visits were arranged for data collection of the cement production line process. Interviews were made with production line operators, coaches and production manager of both of factors. The obtained data were used to develop the simulation modeling elements and validate the obtained results. The following data is required in order to determine different properties associated with every working area. a) Cycle time of each working area, b) Capacity for each buffer or storage area, c) Batch size or number of repetitions/ month for each working area d) The actual operating time for each working area e) % rework at every working area f) % scrap associated with each working area g) Number of breakdowns per month h) Mean Time To Repair (MTTR) for each working area, i.e. the time period which has been taken for the working area to be stopped i) Mean Time To Failure (MTTF) for each working area, i.e. the frequency of stoppages of the equipment or breakdowns causing production stop. ii) Developing of Simulation model: The main purpose of developing the model is to understand the process. Simul8 package is selected as an experimental testing tool for converting the cement production line into a simulation model. The main purpose of developing the model is to be able to highlight the value and non value activities that may occur within the cement production line and hence affect the efficiency (Tsai6). The model will include the following working areas: a) Raw milling working area, which includes raw materials store, mill feed building, raw milling workstation, and raw meal silo. b) Thermo-chemical working area, which includes the kiln system and clinker storage area c) Cement grinding working area, which includes finish grinding workstation, packing house, and cement silos. The simulation model is based on the following:

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• Run time: The simulation model will run for 43200 minutes (which equivalents to one month). • Shift: The plant works on non-stop base, i.e. 24 hours per day. • Results collection period: The results will be collected after 43200 minutes, which equivalents to one

month. • Schedule maintenance: The factory is planned to schedule maintenance stoppage for six weeks per

year, i.e. the Actual Available Time for the three working areas is 46 weeks per a year. • Types of products: No variety of products, i.e. only one type of Portland is produced.

iii) Identification of the interrelationships between the different variables: The research has identified several variables and factors, which control and govern the cement production line As there was a need to investigate the interrelationship between these factors, Cause-Effect matrix was used to determine the interconnections and relationships between the variables i.e. non-relations, indirect-relations, and direct-relations as identified in tables 5.1 to 5.3 The main technique which used to determine the variables is Brainstorming technique: It is a process of to identify problems, different factors that influence the efficiency of the cement production line, and it determines the measurement method of the process. In order to achieve the aim of the brainstorming sessions, preparation stage has been made by connecting the production people in the both sites informing them about the topic (identifying the main variables that associated within each working area, the interrelationships, and effects of the variables on the process performance. During the brainstorming sessions many creative ideas have been generated, and finally list of the most effective variables, the interrelationships, and their effects has been agreed through evaluation process of the all ideas. iv) Developing a Connectivity Matrix to Minimise the Number of Variables: It was difficult to carry out experiments including all variables that influence the performance of each process within the cement production line. Therefore, a connectivity matrix was developed in order to identify the most critical and influential variables which will be used in the different simulation model experiments i.e. the Taguchi Orthogonal Array. Only the variables that have the highest score of direct- relationships will be presented in the Orthogonal Array for each working area, see Tables 5.4-5.6. v) Using Taguchi Orthogonal Array: L27 was selected to be the orthogonal array for this research. L27 is suitable for range of (32 - 313) cases (Antony and Antony1). Tables 5.4-5.6 show the Orthogonal Array for the cement production line.

109

Ra

w M

illin

g

Pro

cess

V

ari

ab

les

Air

Flo

w R

ate

(cm

³/m

in)

Tem

p (

Cº)

Pre

ssu

re (

Psi

)

Mat

eria

l G

rin

da

bili

ty

Mat

eria

l m

ois

ture

(%

of

we

igh

t)

Mat

eria

l Bed

D

ep

th (

cm)

Pa

rtic

les

Siz

e

Pro

du

ct

Fin

en

ess

(c

m³/

gr)

Re

circ

ula

tion

R

ate

(%

of

feed

mat

eri

als

)

Ro

ller

Nu

mb

er

Ro

ller

Ra

diu

s (c

m)

Mill

Tab

le

Dia

met

er

(cm

)

Se

par

ato

r S

pee

d (

rpm

)

Air Flow rate (cm³/min) x Temperature (Cº) x Pressure (Psi) x Material Grindability x Material moisture (% of weight) x Material Bed Depth (cm) x Particles Size x Product Fineness (cm³/gr) x Recirculation Rate (% of feed materials)

x Roller Number x Roller Radius (cm) x Mill Table Diameter (cm) x separator Speed (rpm) x Table 5.1 Raw Milling Process Cause and Effect Matrix,

110

Th

erm

o-

Ch

emic

al

Pro

cess

V

ari

ab

le

Pri

ma

ry A

ir

Flo

w R

ate

(c

m³/

min

)

Se

con

dar

y A

ir

Flo

w R

ate

(c

m³/

min

)

Fre

sh A

ir

Flo

w R

ate

(c

m³/

min

)

Tem

pe

ratu

re

(C°)

Fla

me

C

har

acte

rist

ics

Pre

ssu

re (

psi

)

Vo

latil

e

Co

nce

ntr

atio

n

Mat

eria

l B

urn

abili

ty

Mat

eria

l Flo

w

Ra

te

(cm

³/m

in)

Scr

ap R

ate

(%)

Kiln

Sp

eed

(r

pm

)

Re

sid

en

ce

Tim

e in

Kiln

(m

in)

Co

ole

r sp

eed

(r

pm

)

Cyc

lon

es

Nu

mb

er

Primary Air Flow Rate (cm³/min) x Secondary Air Flow Rate (cm³/min) x Fresh Air Flow Rate (cm³/min) x Temperature (C°) x Flame Characteristics x Pressure (Psi) x Volatile Concentration x Material Burnability x Material Flow rate (cm³/min) x Scrap Rate (%) x kiln Speed (rpm) x Residence Time in Kiln (min) x Cooler speed (rpm) x Cyclones Number x Table 5.2 Thermo-chemical Process Cause and Effect Matrix,

111

Fin

ish

G

rin

din

g

Pro

cess

V

ari

able

s

Air

Flo

w

Ra

te

(cm

³/m

in)

Tem

pe

ratu

re

Cº

Pre

ssu

re

(Psi

)

Clin

ker

Fe

ed

Ra

te (

%o

f m

ill v

olu

me)

Clin

ker

Gri

nd

abili

ty

Clin

ker

No

du

les

Siz

e

Pro

du

ct

Fin

en

ess

(c

m³/

gr)

Re

circ

ula

tion

Rat

e (%

of

feed

m

ate

ria

ls)

Se

par

ato

r S

pee

d (

rpm

)

Mill

% B

all

Ch

arg

ing

Mill

Le

ng

th

Dia

met

er

Ra

tio (

L/D

)

Mill

sp

eed

(r

pm

)

Se

par

ato

r S

pee

d (

rpm

)

Air Flow Rate (cm³/min) x Temperature (Cº) x Pressure (Psi) x Clinker Feed Rate (%of Mill Volume) x Clinker Grindability x Clinker Nodules Size x Product Fineness (cm³/gr) x Recirculation Rate (% of feed materials) x separator Speed (rpm) x Mill% Ball Charging x Mill Length, x Diameter Ratio (L/D) x Mill speed (rpm x Table 5.3 Finish Grinding Process Cause and Effect Matrix

112

A

ir f

low

Rat

e (c

³m/m

in)

Rec

ircu

latio

n

Rat

e (%

wei

gh

t)

Mat

eria

l M

ois

ture

Mat

eria

l Gri

nd

-ab

ility

Mat

eria

l Bed

D

epth

(cm

)

Pro

du

ct F

inen

ess

(cm

³/g

r)

Sep

arat

or

Sp

eed

(r

pm

)

7100 0.15 12 Easy 4 3900 60 7100 0.15 12 Easy 5 3950 65 7100 0.15 12 Easy 6 4000 75 7100 0.2 16 Normal 4 3900 60 7100 0.2 16 Normal 5 3950 65 7100 0.2 16 Normal 6 4000 75 7100 0.25 20 Hard 4 3900 60 7100 0.25 20 Hard 5 3950 65 7100 0.25 20 Hard 6 4000 75 7200 0.15 16 Hard 4 3950 75 7200 0.15 16 Hard 5 4000 60 7200 0.15 16 Hard 6 3900 65 7200 0.2 20 Easy 4 3950 75 7200 0.2 20 Easy 5 4000 60 7200 0.2 20 Easy 6 3900 65 7200 0.25 12 Normal 4 3950 75 7200 0.25 12 Normal 5 4000 60 7200 0.25 12 Normal 6 3900 65 7300 0.15 20 Normal 4 4000 65 7300 0.15 20 Normal 5 3900 75 7300 0.15 20 Normal 6 3950 60 7300 0.2 12 hard 4 4000 65 7300 0.2 12 hard 5 3900 75 7300 0.2 12 hard 6 3950 60 7300 0.25 16 Easy 4 4000 65 7300 0.25 16 Easy 5 3900 75 7300 0.25 16 Easy 6 3950 60

Table 5.4 L27A-Raw Milling Process

Air

flo

w

Rat

e

(cm

³/m

in)

Tem

per

atu

re

(cº)

Fla

me

Ch

arac

teri

stic

s

Vo

latil

e C

on

cen

trat

ion

Mat

eria

l B

urn

-ab

ility

Res

iden

ce

Tim

e in

th

e ki

ln (

min

/ton)

Co

ole

r S

pee

d

(sp

m

50 200 Poor Low Easy 0.4 10 50 200 Poor Low Medium 0.5 11 50 200 Poor Low Difficult 0.6 12 50 940 Accepted Medium Easy 0.4 10 50 940 Accepted Medium Medium 0.5 11 50 940 Accepted Medium Difficult 0.6 12 50 1450 Optimum High Easy 0.4 10 50 1450 Optimum High Medium 0.5 11 50 1450 Optimum High Difficult 0.6 12 145 200 Accepted High Easy 0.4 12 145 200 Accepted High Medium 0.5 10 145 200 Accepted High Difficult 0.6 11 145 940 Optimum Low Easy 0.4 12 145 940 Optimum Low Medium 0.5 10 145 940 Optimum Low Difficult 0.6 11

113

145 1450 Poor Medium Easy 0.4 12 145 1450 Poor Medium Medium 0.5 10 145 1450 Poor Medium Difficult 0.6 11 215 200 Optimum Medium Easy 0.4 11 215 200 Optimum Medium Medium 0.5 12 215 200 Optimum Medium Difficult 0.6 10 215 940 Poor High Easy 0.4 11 215 940 Poor High Medium 0.5 12 215 940 Poor High Difficult 0.6 10 215 1450 Accepted Low Easy 0.4 11 215 1450 Accepted Low Medium 0.5 12 215 1450 Accepted Low Difficult 0.6 10

Table 5.5 L27A-Thermo-Chemical Process

Clin

ker

Gri

nd

-ab

ility

Clin

ker

Fee

d

Rat

e (%

of

Mill

V

olu

me)

Pro

du

ct

Fin

enes

s (C

m²/

g)

Mill

%

Bal

l C

har

gin

g

Mill

(L

/D)

Mill

sp

eed

%o

f cr

itica

l sp

eed

Sep

arat

or

spee

d (r

pm

Easy 20 3000 25 2 70 60 Easy 20 3000 25 3 80 70 Easy 20 3000 25 4 85 80 Easy 25 3500 30 2 70 60 Easy 25 3500 30 3 80 70 Easy 25 3500 30 4 85 80 Easy 30 4000 35 2 70 60 Easy 30 4000 35 3 80 70 Easy 30 4000 35 4 85 80 Normal 20 3500 35 2 80 80 Normal 20 3500 35 3 85 60 Normal 20 3500 35 4 70 70 Normal 25 4000 25 2 80 80 Normal 25 4000 25 3 85 60 Normal 25 4000 25 4 70 70 Normal 30 3000 30 2 80 80 Normal 30 3000 30 3 85 60 Normal 30 3000 30 4 70 70 Hard 20 4000 30 2 85 70 Hard 20 4000 30 3 70 80 Hard 20 4000 30 4 80 60 Hard 25 3000 35 2 85 70 Hard 25 3000 35 3 70 80 Hard 25 3000 35 4 80 60 Hard 30 3500 25 2 85 70 Hard 30 3500 25 3 70 80 Hard 30 3500 25 4 80 60

Table 5.6 L27A-Finish Grinding Process. vi) Performance Measurements Identification: Performance measurement is a tool which can inform whether the system in right path to achieve the objectives or not. Three parameters have been chosen to be the performance measures for the cement industry; these parameters are: a) Cycle Times: Any reduction of the cycle time contributes to improve the frame overall by increasing customer satisfaction, reducing production costs, and providing key competitive advantages (Browning3). The reduction of the cycle time can be obtained by eliminating or minimising all kinds of wastes and non-value added activities within the given system.

114

b) Equipment Utilization: Machine utilisation can be defined as the amount of time which is spent on productive activities versus the available time for the machine to perform a work. Therefore, eliminate or minimise system wastes is essential element in order to increase the equipments utilisation (Jambekar4). The equipment utilisation is given as:

% Utilization = timeAvailable

time Unused- timeAvailable× 100%.

Available time= Monthly Available Time(MAT)=43200 min Unused Time = PMT = BT PMT= Planned maintenance time -minutes BT = Breakdown time -minutes Therefore the percentage of machine utilisation can be determined as:

% Machine Utilization =MAT

BT)(PMT - MAT +× 100%.

c) Throughput rate per a working area: WIP levels can be measured either in units of jobs or time. Therefore, the throughput is calculated as:

TH =CT

BT- SRTton

Where TH= Throughput (ton) SRT=Scheduled Running Time(min) BT=Breakdown Time(min) CT=Cycle time (min/ton) The above equations (1 and 2) will be used to determine and calculate the values of the machine utilisation and throughput as it can be seen in tables 5.10-5.18. These parameters are chosen because any improvement and enhancement within these three parameters give an immediate positive feedback which is easily to be recognised and reflected on the whole process aspects. Reduction of the cycle time and improvement of the throughput and machine utilization can be translated into increased customer satisfaction and the overall performance. vii) Experimental Results Results of the research Steps: A) Data collection. The collected data has been utilised to develop the simulation model of the cement factory and to validate the obtained results. a) Raw Milling Process:

• The designed production rate = 250 tons/hr • Actual available time - = 90% of total monthly time • Scheduled Running Time = 80 % of actual available time

=0.8*38880 = 31104 min/month • Designed cycle time =0.5 min/ton • % rework (% recalculated) = 15-25% of raw feed • % scrape =0 • Inventory and WIP capacities = 80000 and 20000 tons • Number of breakdowns =480 -1800 min per month

Mean Time to Repair (MTTR) the breakdowns = 12 – 300 min • Mean Time To Failure (MTTF) = 4850- 7608 min

b) Thermo-Chemical Process: • The designed production rate = 41 tons/hr • Scheduled Running Time = 90% of total monthly time • =0.9*38880 = 34992 min/month • designed cycle time =1.4 min/ton • % rework (% recalculated) = 0 % of raw feed • % scrape = 0.5%, • Clinker store capacity = 100000 tons • Mean Time To Repair (MTTR) the breakdowns = 300 – 480 min • number of breakdowns = 1800 – 3840 min per month

115

• Mean Time To Failure (MTTF) = 3867 – 5496 min c) Finish Grinding Process:

• The designed production rate= 133 tons/hr • Scheduled Running Time = 70% of total monthly time • =0.7*38880 = 27216 min/month • designed cycle time = 0.5 min/ton • % rework = 0 % • Cement silos capacity = 400000 tons • Mean Time To Repair the breakdowns (MTTR) 400- 600 min/month • number of breakdowns = 6-9 times per month = 4088- 5400 min/month • Mean Time To Failure (MTTF) =2405 – 3826 min/month

B) Developing of Simulation Model: Most modern cement factories adopt the dry cement production system; therefore the dry production system is the core of this research. The elements modeling of the cement factory consists of three main working areas such as: a) Dry Milling Working Area: The dry working area is composed of:

• Mill feed building where the raw materials are blended forming a homogeneous raw meal before conveying to the vertical roller

• mill, • Vertical roller mill; the raw meal will be milled under the revolving rollers pulverising forces, • Separator; the fine particles are separated using the separator which located at the top of the mill unit,

and • Product collector; the fine powder of the raw materials are swept up to the product collector using high

stream of air. b) Thermo-Chemical Working Area: The dry thermo-chemical working area consists of:

• Preheater tower, where process of heat transfer between the feed meal and the kiln exhausted gases takes place. The purpose of this process is to preheat the fed meal and partially hydro-carbonate the fed meal before reaching the kiln,

• Precalciner, where the fed meal is completely decarbonised, • The kiln; the final structure of clinker nodules are formed when the fed meal reached the peak

temperature at the burning zone, and • Cooler; high stream of fresh air is supplied aiming at cooling down the clinker which is discharged

from the kiln lower end. c) Finish Grinding Working Area: As it was demonstrated in (2.1.5) the finish grinding working area consists of:

• Feed system is composed of bins, weight-feeders, and belt conveyors. The purpose of the feed system is to provide the right quantity of the clinker to the ball mill unit,

• Ball mill; the cement powder will be obtained from the collision between the clinker nodules and the steel balls in the horizontal cylindrical drum,

• Elevator; bucket elevator is used to convey the mill discharge to the separator, and • Separator; 3rd generation of the high efficiency separator is used to convey the fine cement powder to

the electro-filter precipitator, then to the cement silos, refer to figure (2.5). C) Identifying Interrelationships Between Variables: Subsequent to the determination of variables and factors that control each process within the cement production line; all interrelationships types between these variables were identified using the cause and effect matrix Tables 5.7-5.9 illustrate the interrelationships between the identified variables. For example; D1 = direct interrelationship, D0 = indirect interrelationship, and I = absence of any interrelationships between the variables.

116

Raw

Mill

ing

Pro

cess

V

aria

bles

Air

Flo

w R

ate

(c

m³/

min

)

Te

mp

era

ture

(C

º)

Pre

ssu

re (

Psi

)

Ma

teri

al

Gri

nd

ab

ility

Ma

teri

al M

ois

ture

(%

of

we

igh

t

Ma

teri

al B

ed

Dep

th (

cm)

Par

ticle

s S

ize

Pro

du

ct F

inen

ess

(cm

³/g

r)

Rec

ircu

latio

n

Rat

e (

% o

f fe

ed

mat

eria

ls)

Ro

ller

Nu

mb

er

Ro

ller

Ra

diu

s (c

m)

Mill

Tab

le

Dia

met

er (

cm)

Sep

ara

tor

Sp

eed

(r

pm

)

Air Flow Rate (cm³/min) x D1 D1 I D1 D1 D0 D1 D1 I I I D1

Temperature (Cº)

D1 x I D1 D1 I I I I I I I I

Pressure (Psi)

D1 I x I I D1 I I I I I I D0

Material Grindability

I D1 I x D1 D1 D1 D1 D1 I I I I

Material Moisture (% of weight)

D1 D1 I D1 x D1 I I I I I D0 I

Material Bed Depth (cm)

D1 I D1 D1 D1 x D0 I I I I I D1

Particles Size

D0 I I D1 I D0 x D0 D0 I I I D0

Product Fineness (cm³/gr)

D1 I I D1 I D0 D0 x D1 I I I D1

Recirculation Rate (% of feed materials)

D1 I I D1 I I D0 D1 x I I I D1

Roller Number

I I I I I I I I I x D1 D1 I

Roller Radius (cm)

I I I I I I I I I D1 x D1 I

Mill Table Diameter (cm)

I I I I I D0 I I I D1 D1 x I

separator Speed (rpm)

D1 I D0 I I D1 D0 D1 D1 I I I x Table 5.7 Raw Milling Process Cause and Effect Matrix

117

The

rmo-

Che

mic

al

Pro

cess

V

aria

bles

Pri

ma

ry A

ir

Flo

w R

ate

(cm

³/m

in)

Sec

on

da

ry A

ir

Flo

w R

ate

(cm

³/m

in)

Fre

sh A

ir F

low

R

ate

(cm

³/m

in)

Te

mp

erat

ure

(C

°)

Fla

me

C

har

acte

rist

ics

Pre

ssu

re (

psi

)

Vo

latil

e C

on

cen

tra

tion

Ma

teri

al

Bu

rnab

ility

Ma

teri

al F

low

R

ate

(cm

³/m

in)

Scr

ap

Rat

e (%

)

kiln

Sp

eed

(r

pm

)

Res

iden

ce

Tim

e in

Kiln

(m

in)

Co

ole

r S

pee

d

(rp

m)

Cyc

lon

es

Nu

mb

er

Primary Air Flow Rate (cm³/min) x D0 D0 D1 D1 D0 D1 D1 D0 D0 I D1 I I

Secondary Air Flow Rate (cm³/min)

D0 x D0 D1 D0 D0 D1 D1 D0 D0 I I D1 D0

Fresh Air Flow Rate (cm³/min)

D0 D0 x D1 D0 I I I I D0 I I D1 I

Temperature (C°) D1 D1 D1 x D1 I D1 D1 I D0 I D1 D1 D0

Flame Characteristics

D1 D0 D0 D1 x I D1 I D0 D1 I D1 D1 D0

Pressure (psi) D0 D0 I I I x I I D1 I I I I D1

Volatile Concentration

D1 D1 I D1 D1 I x I D0 D0 I D1 D1 I

Material Burnability D1 D1 I D1 I I I x D1 I I D1 I I

Material Flow Rate (cm³/min)

D0 D0 I I D0 D1 D0 D1 x D0 D0 D1 D0 D1

Scrap Rate (%) D0 D0 D0 D0 D1 I D0 I D0 x I I D0 I

kiln Speed (rpm) I I I I I I I I D0 I x D1 D0 I

Residence Time in Kiln (min)

D1 I I D1 D1 I D1 D1 D1 I D1 x D0 I

Cooler Speed (rpm) I D1 D1 D1 D1 I D1 I D0 D0 D0 D0 x I

Cyclones Number I D0 I D0 D0 D1 I I D1 I I I I x Table 5.8 Thermo-Chemical Process Cause and Effect Matrix

118

Fin

ish

Grin

ding

P

roce

ss

Var

iabl

es

Air

Flo

w R

ate

(c

m³/

min

)

Tem

pe

ratu

re

(Cº)

Pre

ssu

re (

Psi

)

Clin

ker

Fee

d R

ate

(%o

f m

ill v

olu

me)

Clin

ker

Gri

nd

abili

ty

Clin

ker

No

du

les

Siz

e

Pro

du

ct F

ine

nes

s (c

m³/

gr)

Rec

ircu

latio

n

Rat

e (

% o

f fe

ed

mat

eri

als

)

Sep

arat

or

Sp

eed

(r

pm

)

Mill

% B

all

Ch

arg

ing

Mill

Len

gh

t, D

iam

ete

r R

atio

(L

/D)

Mill

Sp

eed

(rp

m)

Air Flow Rate (cm³/min) x D1 D0 D0 I I I D0 D1 I I I

Temperature (Cº) D1 x I I I I I I I I I I

Pressure (Psi) D0 I x D1 I I I I I I I I

Clinker Feed Rate (%of mill volume)

D0 I D1 x D0 D0 D0 D0 D0 D1 D1 D1

Clinker Grindability I I I D0 x D0 D1 D0 D0 D1 I D1

Clinker Nodules Size I I I D0 D0 x D0 I I I I I

Product Fineness (cm³/gr)

I I I D0 D1 D0 x D1 D1 I I I

Recirculation Rate (% of feed materials)

D0 I I D0 D0 I D1 x D1 I I I

Separator Speed (rpm)

D1 I I D0 D0 I D1 D1 x I I I

Mill% Ball Charging

I I I D1 D1 I I I I x D1 D1

Mill Length, Diameter Ratio (L/D)

I I I D1 I I I I I D1 x D1

Mill Speed (rpm) I I I D0 D1 I I I I D1 D1 x Table 5.9 Finish Grinding Process Cause and Effect Matrix,

119

D) Develop A Connectivity Matrix: In order to minimise the variables list into manageable number; connectivity matrixes have been developed for each process. Only the direct relationships will be presented within the connectivity matrixes, tables 5.10-5.12.

Raw

Mill

ing

Pro

cess

V

aria

bles

Air

Flo

w

Rat

e (c

m³/

min

)

Tem

pera

ture

(C

º)

Pre

ssur

e (P

si)

Mat

eria

l G

rinda

bilit

y M

ater

ial

Moi

stur

e (%

of w

eigh

t)

Mat

eria

l B

ed D

epth

(c

m)

Par

ticle

s S

ize

Pro

duct

F

inen

ess

(cm

³/gr

) R

ecirc

ulat

ion

Rat

e (%

of

feed

m

ater

ials

)

Rol

ler

Num

ber

Rol

ler

Rad

ius

(cm

)

Mill

Tab

le

Dia

met

er

(cm

)

sepa

rato

r S

peed

(rp

m)

Air Flow Rate (cm³/min) x D1 D1 D1 D1 D1 D1 D1 7

Temperature (Cº) D1 x D1 D1 3

Pressure (Psi) D1 x D1 2

Material Grindability D1 x D1 D1 D1 D1 D1 6

Material Moisture (% of weight)

D1 D1 D1 x D1 4

Material Bed Depth (cm)

D1 D1 D1 D1 x D1 5

Particles Size D1 x 1

Product Fineness (cm³/gr)

D1 D1 x D1 D1 4

Recirculation Rate (% of feed materials)

D1 D1 D1 x D1 4

Roller Number x D1 D1 2

Roller Radius (cm) D1 x D1 2

Mill Table Diameter (cm)

D1 D1 x 2

Separator Speed (rpm) D1 D1 D1 D1 x 4

7 3 2 6 4 5 1 4 4 2 2 2 4 Table 5.10 Raw Milling Process Connectivity Matrix

120

The

rmo-

chem

ical

P

roce

ss

Var

iabl

es

Prim

ary

Air

Flo

w R

ate

(cm

³/m

in)

Sec

onda

ry A

ir F

low

Rat

e (c

m³/

min

)

Fre

sh A

ir F

low

Rat

e (c

m³/

min

)

Tem

pera

ture

(C

°)

Fla

me

Cha

ract

eris

tics

Pre

ssur

e (p

si)

Vol

atile

C

once

ntra

tion

Mat

eria

l B

urn-

abili

ty

Mat

eria

l Flo

w

Rat

e (c

m³/

min

)

Scr

ap R

ate

(%)

kiln

Spe

ed

(rpm

)

Res

iden

ce

Tim

e in

K

iln (

min

) C

oole

r S

peed

(r

pm)

Cyc

lone

s N

umbe

r

Primary Air Flow Rate (cm³/min) x D1 D1 D1 D1 D1 5

Secondary Air Flow Rate (cm³/min)

x D1 D1 D1 D1 4

Fresh Air Flow Rate (cm³/min)

x D1 D1 2

Temperature (C°) D1 D1 D1 x D1 D1 D1 D1 D1 8

Flame Characteristics

D1 D1 x D1 D1 D1 D1 6

Pressure (psi) x D1 D1 2

Volatile Concentration

D1 D1 D1 D1 x D1 D1 6

Material Burnability

D1 D1 D1 x D1 D1 5

Material Flow Rate (cm³/min)

D1 D1 x D1 D1 4

Scrap Rate (%) D1 x 1

kiln Speed (rpm) x D1 1

Residence Time in Kiln (min)

D1 D1 D1 D1 D1 D1 D1 x 7

Cooler Speed (rpm) D1 D1 D1 D1 D1 x 5

Cyclones Number D1 D1 x 2

5 4 2 8 6 2 6 5 4 1 1 7 5 2 Table 5.11 Thermo-Chemical Process Connectivity Matrix

121

Fin

ish

Grin

ding

P

roce

ss

Var

iabl

es

Air

Flo

w R

ate

(cm

³/m

n)

Tem

pera

ture

(C

º)

Pre

ssur

e (P

si)

Clin

ker

Fee

d R

ate

(%of

mill

vo

lum

e)

Clin

ker

Grin

dabl

ty

Pro

duct

Fin

enes

s (c

m³/

gr)

Rec

ircul

aton

R

ate

(% o

f fee

d m

ater

als)

S

epar

ator

Spe

ed

(rpm

) M

ill%

Bal

l C

harg

ing

Mill

Len

ght,

Dia

met

er R

atio

(L

/D)

Mill

spe

ed (

rpm

)

Air Flow Rate (cm³/mn) x D1 D1 2

Temperature (Cº) D1 x 1

Pressure (Psi) x D1 1

Clinker Feed Rate (%of mill volume)

D1 x D1 D1 3

Clinker Grindabilty x D1 D1 D1 3

Product Fineness (cm³/gr)

D1 x D1 D1 3

Recirculation Rate (% of feed materials)

D1 x D1 2

Separator Speed (rpm)

D1 D1 D1 x 3

Mill% Ball Charging D1 D1 x D1 D1 4

Mill Length, Diameter Ratio (L/D)

D1 D1 x D1 3

Mill speed (rpm) D1 D1 D1 x 3

2 1 1 3 3 3 2 3 4 3 3 Table 5.12: Finish Grinding Process Connectivity Matrix

- 122 -

Tables 5.13-5.15 illustrate the variables and their levels which are associated with each process. Raw milling Process Factors

Level1 Level2 Level3

Air Flow Rate 7100 7200 7300 Recirculation Rate % of feeding rate

15 20 25

Material Moisture % of weight

12 16 20

Material Grindability Easy Normal Hard Material Bed Depth (cm) 4 5 6 Product Fineness 3900 3950 4000 Separator Speed (rpm) 60 65 75 Table 5.13 Raw Milling Process Variable Levels Thermochemical Process Factors

Level1 Level2 Level3

Air Flow Rate

50 130 210

Temperature 200 800 1400 Flame Characteristics

poor

accepted optimum

Material Burnability easy

normal difficult

Volatile Concentration

Low

Medium High

Residence Time in the kiln (min/ton)

0.4 0.6 0.8

Cooler Speed (spm) 10 11 12 Table 5.14 Thermo-Chemical Process Variable Levels Finish Grinding Process Factors

Level1 Level2 Level3

Clinker Grindability easy

normal difficult

Clinker Feed Rate %of Mill volume

20 25 30

Air flow Rate (m3/h) 70 105 140 Mill% Ball Charging 25 30 35 Recirculation Rate% of feed rate

Low Medium High

Product Fineness Cm²/g) 3900 3950 4000 Separator speed (rpm) 60 70 80 Table 5.15 Finish Grinding Process Variable Levels E) Results of Taguchi Orthogonal Array: Initially tables 5.16-5.18 demonstrate the theoretical values of the throughput and %machine utilisation for the three processes within the cement production line. The throughput and %machine utilisation are calculated using the equations (1 and 2).

- 123 -

Air

flow

Rat

e (c

m³/

min

) R

ecirc

ulat

ion

Rat

e (%

F

eed

mea

l) M

ater

ial M

oist

ure

(%

wei

ght)

Mat

eria

l Grin

dabi

lity

Mat

eria

l Bed

Dep

th (

cm)

Pro

duct

Fin

enes

s (c

m³/

gr)

Sep

arat

or S

peed

(rp

m)

Cyc

le T

ime

(min

/ton)

B

reak

dow

n T

ime

(min

) T

heor

etic

al T

hrou

ghpu

t (t

on)

The

oret

ical

% M

achi

ne

Util

isat

ion

7100 0.15 12 Easy 4 3900 60 0.2 480 153120 71 7100 0.15 12 Easy 5 3950 65 0.2 480 153120 71 7100 0.15 12 Easy 6 4000 75 0.2 1140 149820 69 7100 0.2 16 Normal 4 3900 60 0.2 1140 149820 69 7100 0.2 16 Normal 5 3950 65 0.5 1140 59928 69 7100 0.2 16 Normal 6 4000 75 0.8 1140 37455 69 7100 0.25 20 Hard 4 3900 60 0.8 1800 36630 68 7100 0.25 20 Hard 5 3950 65 0.8 1800 36630 68 7100 0.25 20 Hard 6 4000 75 0.8 1800 36630 68 7200 0.15 16 Hard 4 3950 75 0.5 1140 59928 69 7200 0.15 16 Hard 5 4000 60 0.8 1140 37455 69 7200 0.15 16 Hard 6 3900 65 0.8 1140 37455 69 7200 0.2 20 Easy 4 3950 75 0.5 1800 58608 68 7200 0.2 20 Easy 5 4000 60 0.8 1140 37455 69 7200 0.2 20 Easy 6 3900 65 0.8 1140 37455 69 7200 0.25 12 Normal 4 3950 75 0.8 1800 36630 68 7200 0.25 12 Normal 5 4000 60 0.8 1800 36630 68 7200 0.25 12 Normal 6 3900 65 0.8 1140 37455 69 7300 0.15 20 Normal 4 4000 65 0.8 1800 36630 68 7300 0.15 20 Normal 5 3900 75 0.8 1800 36630 68 7300 0.15 20 Normal 6 3950 60 0.8 1140 37455 69 7300 0.2 12 hard 4 4000 65 0.8 1800 36630 68 7300 0.2 12 hard 5 3900 75 0.8 1800 36630 68 7300 0.2 12 hard 6 3950 60 0.8 1800 36630 68 7300 0.25 16 Easy 4 4000 65 0.5 1140 59928 69 7300 0.25 16 Easy 5 3900 75 0.5 1140 59928 69 7300 0.25 16 Easy 6 3950 60 0.5 1140 59928 69 Table 5.16 Raw Milling Process Theoretical Throughput and %Machine Utilization

Air

flow

Rat

e (c

m³/

min

) T

empe

ratu

re (

cº)

Fla

me

Cha

ract

eris

tics

Vol

atile

Con

cent

ratio

n

Mat

eria

l B

urna

bilit

y R

esid

ence

Tim

e in

the

kiln

(m

in/to

n)

Coo

ler

Spe

ed (

spm

) C

ycle

Tim

e (m

in/to

n)

Bre

akdo

wn

Tim

e (m

in)

The

oret

ical

Thr

ough

put

(ton

) T

heor

etic

al %

Mac

hine

U

tilis

atio

n

50 200 Poor Low Easy 0.4 10 1.8 2820 17873 74 50 200 Poor Low Medium 0.5 11 1.8 2820 17873 74 50 200 Poor Low Difficult 0.6 12 1.8 3840 17307 72 50 940 Accepted Medium Easy 0.4 10 1.6 2820 20108 74 50 940 Accepted Medium Medium 0.5 11 1.6 2820 20108 74 50 940 Accepted Medium Difficult 0.6 12 1.8 2820 17873 74 50 1450 Optimum High Easy 0.4 10 1.6 1800 20745 77 50 1450 Optimum High Medium 0.5 11 1.6 1800 20745 77

- 124 -

50 1450 Optimum High Difficult 0.6 12 1.8 2820 17873 74 145 200 Accepted High Easy 0.4 12 1.8 1800 18440 77 145 200 Accepted High Medium 0.5 10 1.8 1800 18440 77 145 200 Accepted High Difficult 0.6 11 1.8 2820 17873 74 145 940 Optimum Low Easy 0.4 12 1.4 1800 23709 77 145 940 Optimum Low Medium 0.5 10 1.4 1800 23709 77 145 940 Optimum Low Difficult 0.6 11 1.6 1800 20745 77 145 1450 Poor Medium Easy 0.4 12 1.8 2820 17873 74 145 1450 Poor Medium Medium 0.5 10 1.8 2820 17873 74 145 1450 Poor Medium Difficult 0.6 11 1.8 3840 17307 72 215 200 Optimum Medium Easy 0.4 11 1.4 2820 22980 74 215 200 Optimum Medium Medium 0.5 12 1.6 1800 20745 77 215 200 Optimum Medium Difficult 0.6 10 1.8 2820 17873 74 215 940 Poor High Easy 0.4 11 1.8 3840 17307 72 215 940 Poor High Medium 0.5 12 1.8 3840 17307 72 215 940 Poor High Difficult 0.6 10 1.8 3840 17307 72 215 1450 Accepted Low Easy 0.4 11 1.4 1800 23709 77 215 1450 Accepted Low Medium 0.5 12 1.4 1800 23709 77 215 1450 Accepted Low Difficult 0.6 10 1.4 1800 23709 77 Table 5.17 Thermo-Chemical Process Theoretical Throughput and %Machine Utilization

Clin

ker

Grin

dabi

lity

Clin

ker

Fee

d R

ate

(%of

m

ill V

olum

e)

Pro

duct

Fin

enes

s (C

m²/

g)

Mill

% B

all C

harg

ing

Mill

(L/

D)

Rat

io

Mill

spe

ed (

% o

f crit

ical

sp

eed)

Sep

arat

or s

peed

(rp

m)

Cyc

le T

ime

(min

/ton)

B

reak

dow

n T

ime

(min

) T

heor

etic

al T

hrou

ghpu

t (t

on)

The

oret

ical

%M

achi

ne

Util

isat

ion

Easy 20 3000 25 2 70 60 0.5 4088 46076 53 Easy 20 3000 25 3 80 70 0.5 4088 46076 53 Easy 20 3000 25 4 85 80 0.5 4744 44764 52 Easy 25 3500 30 2 70 60 0.5 4088 46076 53 Easy 25 3500 30 3 80 70 0.7 4744 31974 52 Easy 25 3500 30 4 85 80 0.7 4744 31974 52 Easy 30 4000 35 2 70 60 0.7 4088 32911 53 Easy 30 4000 35 3 80 70 0.7 4744 31974 52 Easy 30 4000 35 4 85 80 0.7 4744 31974 52 Normal 20 3500 35 2 80 80 0.7 4088 32911 53 Normal 20 3500 35 3 85 60 0.7 4088 32911 53 Normal 20 3500 35 4 70 70 0.7 4744 31974 52 Normal 25 4000 25 2 80 80 0.7 4744 31974 52 Normal 25 4000 25 3 85 60 0.7 5400 31037 50 Normal 25 4000 25 4 70 70 0.9 5400 24140 50 Normal 30 3000 30 2 80 80 0.7 4744 31974 52 Normal 30 3000 30 3 85 60 0.7 4744 31974 52 Normal 30 3000 30 4 70 70 0.7 4744 31974 52 Hard 20 4000 30 2 85 70 0.7 5400 31037 50 Hard 20 4000 30 3 70 80 0.9 5400 24140 50 Hard 20 4000 30 4 80 60 0.9 5400 24140 50 Hard 25 3000 35 2 85 70 0.7 4744 31974 52 Hard 25 3000 35 3 70 80 0.7 4744 31974 52 Hard 25 3000 35 4 80 60 0.9 5400 24140 50 Hard 30 3500 25 2 85 70 0.7 5400 31037 50 Hard 30 3500 25 3 70 80 0.9 5400 24140 50 Hard 30 3500 25 4 80 60 0.9 5400 24140 50 Table 5.18 Finish Grinding Process Theoretical Throughput and %Machine Utilisation

- 125 -

F) Performance Measurements: In order to identify and examine the effect of the variables on the performance parameters (cycle time, equipment utilisation, and throughput) for each process, the experiments listed in tables 5.19 - 5.21 were carried out. As it has been mentioned that the only variables carrying high scores within each connectivity matrix will be presented in the Orthogonal Arrays; for example air flow rate, temperature, material grindability, material moisture, material bed depth, product fineness, recirculation rate, and separator speed are accounted as the most effective variables within the raw milling process and they will be included in the raw milling Orthogonal Array.

Air

flow

Rat

e (c

m³/

min

) R

ecirc

ulat

ion

Rat

e (%

F

eed

Mea

l)

Mat

eria

l Moi

stur

e (%

wei

ght)

M

ater

ial G

rinda

bilit

y M

ater

ial B

ed D

epth

(cm

) P

rodu

ct

Fin

enes

s (c

m³/

gr)

Sep

arat

or S

peed

(rp

m)

%W

aitin

g be

fore

WIP

m

inim

ise

%B

lock

ing

befo

re W

IP

min

imis

e %

Wor

king

bef

ore

WIP

m

inim

ise

Cyc

le T

ime

(Min

/ton)

B

efor

e W

IP

min

imis

e B

reak

dow

n T

ime

(m

in)

befo

re W

IP m

inim

ise

Thr

ough

put (

ton)

bef

ore

WIP

min

imis

e

%M

achi

ne U

tilis

atio

n be

fore

WIP

min

imis

e

7100 0.15 12 Easy 4 3900 60 22 11 67 0.27 135 114700 67 7100 0.15 12 Easy 5 3950 65 21 11 68 0.25 127 121957 68 7100 0.15 12 Easy 6 4000 75 32 14 54 0.26 258 119558 54 7100 0.2 16 Normal 4 3900 60 36 12 52 0.27 266 115932 52 7100 0.2 16 Normal 5 3950 65 37 11 52 0.53 266 57966 52 7100 0.2 16 Normal 6 4000 75 28 12 60 0.82 274 37506 61 7100 0.25 20 Hard 4 3900 60 40 16 44 0.88 438 35007 45 7100 0.25 20 Hard 5 3950 65 40 15 45 0.95 447 32135 46 7100 0.25 20 Hard 6 4000 75 37 15 48 0.92 429 33415 49 7200 0.15 16 Hard 4 3950 75 28 13 59 0.57 246 53948 59 7200 0.15 16 Hard 5 4000 60 29 12 59 0.4 246 77145 59 7200 0.15 16 Hard 6 3900 65 37 13 50 0.82 252 37809 50 7200 0.2 20 Easy 4 3950 75 37 16 47 0.58 405 52929 48 7200 0.2 20 Easy 5 4000 60 36 16 48 0.88 274 34955 48 7200 0.2 20 Easy 6 3900 65 38 12 50 0.92 286 33571 50 7200 0.25 12 Normal 4 3950 75 40 15 45 0.94 438 32763 46 7200 0.25 12 Normal 5 4000 60 47 16 37 0.92 445 33398 38 7200 0.25 12 Normal 6 3900 65 40 15 45 0.94 294 32707 45 7300 0.15 20 Normal 4 4000 65 41 15 44 0.86 399 35787 45 7300 0.15 20 Normal 5 3900 75 40 16 44 0.85 393 36301 45 7300 0.15 20 Normal 6 3950 60 29 12 59 0.85 264 36197 60 7300 0.2 12 hard 4 4000 65 38 15 47 0.89 417 34326 48 7300 0.2 12 hard 5 3900 75 38 16 46 0.91 423 33864 47 7300 0.2 12 hard 6 3950 60 32 16 52 0.93 435 32977 53 7300 0.25 16 Easy 4 4000 65 35 14 51 0.61 286 50356 51 7300 0.25 16 Easy 5 3900 75 26 15 59 0.59 274 52432 60 7300 0.25 16 Easy 6 3950 60 24 18 58 0.30 282 102060 59 Table 5.19 Raw Milling Process OA Before Reducing WIP

- 126 -

Air

flow

Rat

e (c

m³/

min

) T

empe

ratu

re (

Cº)

F

lam

e C

hara

cter

istic

s V

olat

ile C

once

ntra

tion

Mat

eria

l Bur

nabi

lity

Res

iden

ce T

ime

in th

e ki

ln (

min

/ton)

C

oole

r S

peed

(rp

m)

%W

aitin

g be

fore

WIP

m

inim

ise

%B

lock

ing

befo

re W

IP

min

imis

e %

Wor

king

bef

ore

WIP

m

inim

ise

Cyc

le T

ime

(min

/ton)

be

fore

W

IP

Bre

akdo

wn

Tim

e (m

in)

befo

re W

IP m

inim

ise

Thr

ough

put (

ton)

B

efor

e W

IP m

inim

ise

% M

achi

ne U

tilis

atio

n be

fore

WIP

min

imis

e

50 200 Poor Low Easy 0.4 10 30 14 56 2.3 449 15019 56 50 200 Poor Low Medium 0.5 11 29 14 57 2.4 488 14377 57 50 200 Poor Low Difficult 0.6 12 35 15 50 2.5 619 13749 50 50 940 Accepted Medium Easy 0.4 10 32 13 55 2.1 460 16444 55 50 940 Accepted Medium Medium 0.5 11 33 14 54 2 472 17260 54 50 940 Accepted Medium Difficult 0.6 12 28 11 60 2.4 476 14382 60 50 1450 Optimum High Easy 0.4 10 23 9 68 2.1 339 16501 68 50 1450 Optimum High Medium 0.5 11 20 9 70 2.2 342 15750 70 50 1450 Optimum High Difficult 0.6 12 10 14 67 2.6 449 13286 67 145 200 Accepted High Easy 0.4 12 28 11 60 2.6 348 13325 60 145 200 Accepted High Medium 0.5 10 34 12 54 2.4 336 14440 54 145 200 Accepted High Difficult 0.6 11 29 14 57 2.4 433 14400 57 145 940 Optimum Low Easy 0.4 12 35 15 50 1.9 327 18245 50 145 940 Optimum Low Medium 0.5 10 37 15 48 1.9 324 18246 48 145 940 Optimum Low Difficult 0.6 11 36 12 51 2.2 333 15754 51 145 1450 Poor Medium Easy 0.4 12 28 13 59 2.3 456 15016 59 145 1450 Poor Medium Medium 0.5 10 27 14 59 2.6 460 13282 59 145 1450 Poor Medium Difficult 0.6 11 37 15 48 2.6 566 13241 48 230 200 Optimum Medium Easy 0.4 11 39 15 46 1.9 321 18248 46 230 200 Optimum Medium Medium 0.5 12 38 15 47 2 324 17334 47 230 200 Optimum Medium Difficult 0.6 10 27 14 59 2.2 437 15707 59 230 940 Poor High Easy 0.4 11 34 14 51 2.1 547 16402 51 230 940 Poor High Medium 0.5 12 33 14 53 2.2 552 15683 53 230 940 Poor High Difficult 0.6 10 35 15 50 2.3 542 14978 50 230 1450 Accepted Low Easy 0.4 11 35 15 50 1.7 327 20391 50 230 1450 Accepted Low Medium 0.5 12 36 13 51 1.9 330 18243 51 230 1450 Accepted Low Difficult 0.6 10 33 14 53 1.9 333 18242 53

Table 5.20 Thermo-Chemical Process OA Before Reducing WIP

Clin

ker

Grin

dabi

lity

Clin

ker

Fee

d R

ate

(%of

M

ill V

olum

e)

Pro

duct

Fin

enes

s (C

m²/

g)

Mill

% B

all

Cha

rgin

g M

ill (

L/D

) M

ill s

peed

(%

of

criti

cal s

peed

) S

epar

ator

spe

ed

(rpm

) %

Wai

ting

befo

re

WIP

min

imis

e %

Blo

ckin

g be

fore

WIP

m

inim

ise

%W

orki

ng B

efor

e W

IP

min

imis

e C

ycle

Tim

e (m

in/to

n)

befo

re

WIP

min

imis

e B

reak

dow

n T

ime

Bef

ore

WIP

min

imis

e T

hrou

ghpu

t (to

n)

Bef

ore

WIP

m

inim

ise

%M

achi

ne U

tilis

atio

n be

fore

WIP

min

imis

e

Easy 20 3000 25 2 70 60 19 12 69 0.65 460 41025 69 Easy 20 3000 25 3 80 70 22 9 69 0.63 464 42321 69 Easy 20 3000 25 4 85 80 24 9 67 0.65 595 40817 67 Easy 25 3500 30 2 70 60 23 9 68 0.64 472 41647 68 Easy 25 3500 30 3 80 70 23 11 66 0.92 610 28822 66 Easy 25 3500 30 4 85 80 23 11 66 0.95 625 27896 66 Easy 30 4000 35 2 70 60 23 9 68 0.93 492 28639 68 Easy 30 4000 35 3 80 70 21 12 67 0.92 605 28827 67 Easy 30 4000 35 4 85 80 25 12 63 0.97 640 27305 63 Normal 20 3500 35 2 80 80 23 11 66 0.95 500 28027 66 Normal 20 3500 35 3 85 60 22 10 68 0.94 496 28330 68

- 127 -

Normal 20 3500 35 4 70 70 22 11 67 0.95 630 27891 67 Normal 25 4000 25 2 80 80 21 11 68 1 655 26471 68 Normal 25 4000 25 3 85 60 29 14 57 1 810 26316 57 Normal 25 4000 25 4 70 70 32 14 53 1.28 792 20573 53 Normal 30 3000 30 2 80 80 25 11 64 0.97 645 27300 64 Normal 30 3000 30 3 85 60 24 11 65 0.95 625 27896 65 Normal 30 3000 30 4 70 70 38 16 45 1 665 26461 45 Hard 20 4000 30 2 85 70 41 15 43 1 792 26334 43 Hard 20 4000 30 3 70 80 40 15 44 1.4 870 18754 44 Hard 20 4000 30 4 80 60 36 14 50 1.4 858 18763 50 Hard 25 3000 35 2 85 70 38 13 49 1 665 26461 49 Hard 25 3000 35 3 70 80 41 14 45 1 680 26446 45 Hard 25 3000 35 4 80 60 34 13 53 1.4 864 18759 53 Hard 30 3500 25 2 85 70 39 13 48 1 798 26328 48 Hard 30 3500 25 3 70 80 47 14 39 1.4 870 18754 39 Hard 30 3500 25 4 80 60 46 13 41 1.4 858 18763 41

Table 5.21 Finish Grinding Process OA Before Reducing WIP. Many problems and root causes of performance insufficiencies can be shrouded and buried behind the WIP high levels. Therefore; the priority of implementing Lean within the cement industry is to eliminate or minimise the WIP and inventories levels. In addition; one of the research objectives is to determine and examine effects of WIP minimisation on the performance parameters. One of the main reasons of high WIP levels is the non-optimised batch size. Therefore, all workstations capacities have been reduced by10% in order to minimise the WIP levels. Tables 5.22- 5.24 illustrate the effects of WIP reduction on the system performance parameters.

Air

flow

Rat

e (c

m³/

min

) R

ecirc

ulat

ion

Rat

e (%

Fee

d m

eal)

Mat

eria

l Moi

stur

e (%

wei

ght)

M

ater

ial

grin

dabi

lity

Mat

eria

l B

ed D

epth

(cm

) P

rodu

ct F

inen

ess

(cm

³/gr

) S

epar

ator

Spe

ed (

rpm

) %

Wai

ting

afte

r W

IP m

inim

ise

%B

lock

ing

afte

r W

IP m

inim

ise

%W

orki

ng a

fter

WIP

min

imis

e

Cyc

le T

ime

min

/ton)

af

ter

WIP

min

mis

e

Bre

akdo

wn

Tim

e (m

in)

afte

r W

IP m

inm

ise

Thr

ough

put (

ton)

afte

r W

IP m

inim

ise

%M

achi

ne u

tiliz

atio

n af

ter

WIP

min

imis

e

7100 0.15 12 Easy 4 3900 60 18 8 74 0.12 132 258100 74 7100 0.15 12 Easy 5 3950 65 17 8 75 0.16 125 188896 75 7100 0.15 12 Easy 6 4000 75 24 14 62 0.11 256 285630 62 7100 0.2 16 Normal 4 3900 60 27 12 61 0.12 262 265879 61 7100 0.2 16 Normal 5 3950 65 24 16 60 0.38 263 80736 60 7100 0.2 16 Normal 6 4000 75 15 18 67 0.67 271 45882 67 7100 0.25 20 Hard 4 3900 60 31 18 51 0.63 435 48992 51 7100 0.25 20 Hard 5 3950 65 30 17 53 0.77 444 39612 53 7100 0.25 20 Hard 6 4000 75 27 16 57 0.77 427 39944 57 7200 0.15 16 Hard 4 3950 75 21 13 66 0.22 243 139014 66 7200 0.15 16 Hard 5 4000 60 22 12 66 0.25 241 123452 66 7200 0.15 16 Hard 6 3900 65 23 14 63 0.64 250 48513 63 7200 0.2 20 Easy 4 3950 75 28 17 55 0.43 401 71402 55 7200 0.2 20 Easy 5 4000 60 32 11 57 0.70 270 43923 57 7200 0.2 20 Easy 6 3900 65 27 14 59 0.74 283 41763 59 7200 0.25 12 Normal 4 3950 75 31 17 52 0.76 433 40570 52 7200 0.25 12 Normal 5 4000 60 37 14 49 0.77 438 39930 49 7200 0.25 12 Normal 6 3900 65 25 22 53 0.69 387 44389 53 7300 0.15 20 Normal 4 4000 65 29 19 50 0.68 395 45294 50 7300 0.15 20 Normal 5 3900 75 28 20 52 0.70 289 44274 52 7300 0.15 20 Normal 6 3950 60 18 13 69 0.67 261 45897 69 7300 0.2 12 hard 4 4000 65 32 13 55 0.74 410 41255 55 7300 0.2 12 hard 5 3900 75 29 17 54 0.66 419 46776 54 7300 0.2 12 hard 6 3950 60 32 16 52 0.78 431 39324 52

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7300 0.25 16 Easy 4 4000 65 26 15 59 0.46 282 66714 59 7300 0.25 16 Easy 5 3900 75 28 16 56 0.41 271 75571 56 7300 0.25 16 Easy 6 3950 60 28 14 58 0.15 279 202796 58

Table 5.22 Raw Milling Process OA After Reducing WIP

Air

flow

Rat

e (c

m³/

min

) T

empe

ratu

re (

Cº)

F

lam

e C

hara

cter

istic

s V

olat

ile C

once

ntra

tion

Mat

eria

l Bur

nabi

lity

Res

iden

ce T

ime

in th

e ki

ln (

min

/ton)

C

oole

r S

peed

(sp

m)

%W

aitin

g af

ter

WIP

m

inim

ise

%B

lock

ing

afte

r W

IP

min

imis

e %

Wor

king

afte

r W

IP

min

imis

e

Cyc

le T

ime

(min

/ton)

af

ter

WIP

min

mis

e

Bre

akdo

wn

Tim

e af

ter

WIP

min

mis

e

Thr

ough

put (

ton)

afte

r W

IP m

inim

ise

%M

achi

ne U

tilis

atio

n af

ter

WIP

min

imis

e

50 200 Poor Low Easy 0.4 10 25 13 62 2.1 404 16470 62 50 200 Poor Low Medium 0.5 11 23 14 63 1.6 463 21581 63 50 200 Poor Low Difficult 0.6 12 28 13 59 2.3 594 14956 59 50 940 Accepted Medium Easy 0.4 10 27 12 61 1.9 415 18198 61 50 940 Accepted Medium Medium 0.5 11 24 16 60 1.8 427 19203 60 50 940 Accepted Medium Difficult 0.6 12 15 18 67 2.2 451 15700 67 50 1450 Optimum High Easy 0.4 10 10 15 75 1.9 294 18262 75 50 1450 Optimum High Medium 0.5 11 13 9 78 1.4 297 24782 78 50 1450 Optimum High Difficult 0.6 12 11 15 74 2.2 404 15722 74 145 200 Accepted High Easy 0.4 12 20 13 67 2.4 313 14450 67 145 200 Accepted High Medium 0.5 10 22 18 60 1.7 291 20412 60 145 200 Accepted High Difficult 0.6 11 23 14 63 2.3 398 15041 63 145 940 Optimum Low Easy 0.4 12 28 17 55 1.7 292 20412 55 145 940 Optimum Low Medium 0.5 10 25 22 53 1.1 299 31539 53 145 940 Optimum Low Difficult 0.6 11 27 16 57 1.9 298 18260 57 145 1450 Poor Medium Easy 0.4 12 25 15 65 2.1 411 16467 65 145 1450 Poor Medium Medium 0.5 10 18 16 66 1.8 425 19204 66 145 1450 Poor Medium Difficult 0.6 11 25 22 53 2.4 521 14363 53 230 200 Optimum Medium Easy 0.4 11 29 19 51 1.8 286 19281 51 230 200 Optimum Medium Medium 0.5 12 28 20 52 1.8 269 19291 52 230 200 Optimum Medium Difficult 0.6 10 19 15 66 1.4 392 24714 66 230 940 Poor High Easy 0.4 11 27 16 57 1.9 492 18158 57 230 940 Poor High Medium 0.5 12 25 14 59 2 517 17238 59 230 940 Poor High Difficult 0.6 10 31 13 55 2.1 487 16431 55 230 1450 Accepted Low Easy 0.4 11 30 16 55 0.9 272 38578 55 230 1450 Accepted Low Medium 0.5 12 25 18 57 1.1 275 31561 57 230 1450 Accepted Low Difficult 0.6 10 26 15 59 1.7 298 20408 59

Table 5.23 Thermo-Chemical Process OA After Reducing WIP

Clin

ker

Grin

d-ab

ility

C

linke

r F

eed

Rat

e (%

of

Mill

Vol

ume)

P

rodu

ct F

inen

ess

C

m²/

g)

Mill

% B

all C

harg

ing

Mill

(L/

D)

Rat

io

Mill

spe

ed (

% o

f crit

ical

sp

eed)

S

epar

ator

spe

ed (

rpm

) %

Wai

ting

afte

r W

IP

min

imis

e %

Blo

ckin

g af

ter

WIP

m

inim

ise

%W

orki

ng a

fter

WIP

m

inim

ise

Cyc

le T

ime

(min

/ton)

af

ter

WIP

B

reak

dow

n T

ime

(min

) af

ter

WIP

min

mis

e

Thr

ough

put (

ton)

afte

r

WIP

min

mis

e

%M

achi

ne U

tilis

atio

n af

ter

WIP

min

imis

e

Easy 20 3000 25 2 70 60 14 8 78 0.29 435 92038 78 Easy 20 3000 25 3 80 70 16 7 77 0.51 409 52386 77 Easy 20 3000 25 4 85 80 17 9 74 0.48 540 55388 74 Easy 25 3500 30 2 70 60 16 8 76 0.49 417 54508 76 Easy 25 3500 30 3 80 70 16 11 73 0.8 585 33176 73 Easy 25 3500 30 4 85 80 16 11 73 0.8 570 33195 73

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Easy 30 4000 35 2 70 60 17 7 76 0.76 437 35117 76 Easy 30 4000 35 3 80 70 16 7 75 0.8 530 33245 75 Easy 30 4000 35 4 85 80 17 8 72 0.72 585 36863 72 Normal 20 3500 35 2 80 80 16 11 73 0.8 445 33351 73 Normal 20 3500 35 3 85 60 15 8 76 0.82 421 32567 76 Normal 20 3500 35 4 70 70 16 9 74 0.83 595 31965 74 Normal 25 4000 25 2 80 80 17 8 75 0.65 630 40763 75 Normal 25 4000 25 3 85 60 34 11 55 0.85 755 31025 55 Normal 25 4000 25 4 70 70 29 19 52 1.18 717 22381 52 Normal 30 3000 30 2 80 80 18 11 71 0.63 590 42121 71 Normal 30 3000 30 3 85 60 17 11 72 0.83 570 31995 72 Normal 30 3000 30 4 70 70 21 11 68 0.66 630 40145 68 Hard 20 4000 30 2 85 70 31 16 53 0.82 717 32206 53 Hard 20 4000 30 3 70 80 32 17 51 1.3 785 20262 51 Hard 20 4000 30 4 80 60 28 20 52 1 833 26293 52 Hard 25 3000 35 2 85 70 32 13 55 0.83 610 31947 55 Hard 25 3000 35 3 70 80 29 17 54 0.68 635 38957 54 Hard 25 3000 35 4 80 60 31 16 53 1.25 839 21030 53 Hard 30 3500 25 2 85 70 26 15 59 0.81 763 32547 59 Hard 30 3500 25 3 70 80 31 16 53 1.29 845 20373 53 Hard 30 3500 25 4 80 60 29 14 57 1.23 823 21385 57 Table 5.24 Finish Grinding Process OA After Reducing WIP 5.3.5 SWOT Analysis of the Cement Industry: The findings and desiccations in the preceding section have revealed that there are strengths, weaknesses, opportunities, and threats associated with the cement industry. In this section a SWOT analysis will be employed in order to identify the current state of the cement industry and highlight the need to change. Strength:

• Availability of cheap raw materials. • Availability of cheap fuels and energy in some of developing countries as India. • Need of the cement and absence of substitutes materials to replace the cement.

Weaknesses: • High rates of unexpected breakdown and maintenance costs. • Un-standard operating process. • Transportation and freight costs. • Organisational culture.

Opportunities: • Increase the domestic demands, and potential to export the cement. • Technological changes

Threats: • Unstable and sudden changes in political rules and regulations. • Economical changes and competition environments.

The SWOT analysis emphasises that the cement industry has the features to be successful industry, and there are number of changing-forces which drive the decision maker to think about applying and implementing lean philosophy; these forces are: a) Fuel and energy prices: the significant global increases of fuel and energy costs has heavily impacted the cement industry, b) Market pressure: the undue pressure to keep prices lower than the competitors. Furthermore the high market demands put the cement industry under pressure to simultaneously reduce cycle time and downtimes, and increase utilisation and throughput of the equipments. Based on the findings that the cement industry might be far away from implementing lean thinking approaches because awareness lacking about adoption of lean philosophy. Therefore it is essentially necessary to eliminate and minimize all kinds of non valued added activities within the cement industry in order to achieve customer satisfaction, product costs reduction, and overall performance improvement. i) Barriers to Implement Lean Within Cement Industr y: On one hand the cement industry is motivated to be lean in order to increase the productivity and enhance the overall performance. On the other hand, there are numerous of roadblocks and barriers which may prevent the implementation of lean within the cement industry such as:

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a) Competition and Motivation Environment: • Political rules and regulations: The cement industry is protected by the government in some developing

countries. For example many of cement factors in the developing countries are part of a large corporation firms or involved with government bodies and feel no need for any changing program (Al-Khalifa et al, 2000).

• Absence of customer voice and competition: No customer pressure drives or enforces the cement industry to initiate any improvement process. For example most of the Indian cement industry stockpiles are traded and consumed within the domestic market where customers buy what found not what they expect (Al-Khalifa et al, 2000). Furthermore absence or low competition levels because of high market restrictions. This leads to misconception of no need to implement any kind of improvement strategies.

b) Organisational Culture: Substantial changes in the organisational culture are required for most organisations that seek to be a learning organisation. Cultural barriers can be grouped into three categories such as:

• Employees participation obstacles: People will be reluctant to involve in any improvement process because of lack of knowledge, skills, and adequate training programs. Existing of missconcepts of the lean philosophy especially in the third world organisations where the lean is viewed as a collection of tools which can be used to solve the temporary problems instead of new way of thinking.

• Management obstacles: There are limitations of the management body within the cement industry towards the implementation of any improvement techniques. Furthermore the study has identified number of problems, attitudes, and issues that hamper any changing process. For example the absence of communications, management commitments, and unclear strategy towards continuous improvement are among the main factors that halt any changing process.

• Resistance to change: it is one of the most significant barriers to change within the cement industry where the people tend to continue operating as they have in past. In addition case of skepticism about any new ideas is typical attitude within the cement industry. Changing process is not easy task and it needs significant efforts for Generating and increasing of the lean awareness through the whole organisation levels in order to achieve the commitment and supports from the management, and people involvement. It includes motivation of the people and providing the right training and education programs:

5.3.6 Discussion of the Research Results: The proposed steps have started with process mapping of the cement industry in order to achieve a fully understanding of the cement production line, and to track unsought processes. The process mapping of the cement production line has identified some non-value added activities such as large batch sizes and high levels of WIP and inventories. Table 5.25 illustrates the wastes and non-value added activities which are associated with the cement industry. Lean Wastes The Cement production line wastes Overproduction Overproduction within the cement manufacturing process results in very high levels of

WIP between sub-processes. Waiting Different batch sizes are associated with the cement production line create waiting wastes

which affect flow of materials. Furthermore the unplanned maintenance can be one of the main sources of waiting waste within the cement industry.

Motion The workers travel long destinations between different workstations. Transportation Materials need to be transported for a long journey starting form quarry site to the cement

silos. In addition the layout of the cement factory may cause transportation wastes. Inventory Cement industry is one of the industries with largest inventories and WIP. Un-

standardisation and batch size verities can be among the causes of excessive inventories situation.

Over processing Unnecessary long time is spent for milling the hard and large particles.

Defects High levels of recirculation (rework) are associated with the both raw milling and finish grinding processes.

Table 5.25 Wastes Within the Cement Production. The interrelationships between these variables were investigated and examined aiming to determine the most effective variables through applying Cause and Effect matrix. Tables (5.4-5.6) have illustrated all the types of the interdependently relationships between different variables that associated with each process. These interrelationships can be classified into three main categories such as: direct interrelationships, where situation of direct effects are existing between particular variables. For example there is direct relationship between the air flow rate and pressure inside the vertical roller mill in the raw milling process. Furthermore table (5.4) shows

- 131 -

the indirect relationship between pressure inside the vertical roller mill and the separator speed. The indirect interrelationship is resulted from the direct relationship between the both pressure and separator speed with the air flow rate. The results show that the values of cycle time, waiting and blocking percentages, and breakdown time within the raw milling process are proportional to:

• The increasing in the values of the air flow and recirculation rates. • Percentages of moistures within raw materials. • Grand-ability levels of raw materials. In order to simplify the research task the number of the variables

needed to be minimised into manageable list through applying the connectivity matrix for each process and the only variables with high score of direct interrelationships will be represented within the Orthogonal Arrays, i.e. the orthogonal array was chosen based on the outcomes of the Cause Effect and connectivity matrices, see tables (5.7-5.9).

A successful lean journey should identify the most important performance measures which ensure immediate feedback and visible results. According to 5.3.4 i) that the cycle time, throughput, and machine utilisation have been chosen as the key performance parameters in order to identify positive feedbacks (improvement) within the cement production line, see tables (5.13- 5.18). The research here has proposed a design of improvement exercise method which combines the simulation modeling technique with proper Taguchi Orthogonal Array in order to examine the obtained results from the experiments. The simulation will run with a specific number of experiments according to the chosen array which will be updated at the end of each run. The Taguchi orthogonal array has been used to collect the results according to different scenarios in order to determine the effects and influences of the variables on the response variables (performance parameters). Tables (5.13-5.18) demonstrate the Orthogonal Arrays which illustrate the different scenarios where the selected variables can have an effect on the selected performance measurements. The undertaken research has proven the vital impacts of variables and factors on the performance parameters. For example high throughput in the raw milling process will be obtained at low air flow and material recirculation rates, and low levels of moisture in combination of easy to grind properties. Furthermore the throughput and machine utilization within the finish grinding process will be improved when appropriate flow rate of easy to grind clinker is fed into the tube grinding machine which has the right percentage of ball charges in order to produce cement with medium product fineness. The insufficient flow rate of hard grindability clinker, high product fineness, and incorrect ball charging percentage are the main causes of the high levels of waiting and blocking percentages, and long cycle and breaking times within the finish grinding process.

Figure 5.8 Throughput Before and After WIP Reduction

Figure 5.9: %Machine Utilisation Before and After WIP Reduction.

- 132 -

Figure 5.10 Cycle Time Before and After WIP Reduction.

Figure 5.11 Breakdown Times Before And After WIP Reduction. The WIP reduction has a great effect on the production line efficiency. Figures (5.8-5.11) illustrate comparison picture of variables and factors values before and after reducing the WIP within the raw milling process in order to demonstrate the enhancement that obtained within the raw milling process after reducing the WIP level. The throughput and machine utilisation are improved in combination with reduction of the cycle time, and breakdown time as a result of WIP reduction The research has used the cement industry which is accounted as the typical representative of the continuous process industry where the mass production system is adopted using inflexible and expensive machines to produce, transport, and accumulate tens of thousands of materials within each working area. The research has contributed to the body of the knowledge by studying and identifying the non-value added activities and attempted to implement lean within the cement industry. The cement industry is ideal example of the continuous process manufacturing; however the research has studied the cement industry through dividing the cement production line into three main processes such as raw milling process, thermo-chemical process, and finish grinding process. The research has handled each process as discrete or single process aiming to identify the interrelationships between the variables that associated with each process, and to determine the effects of these variables on the chosen performance parameters for each process. The research has highlighted some of the barriers that may cause the gap between the desired and the actual results, and prevent the cement industry from achieving any improvement. Based on the research findings the misconception and absence of open communication and commitments are among the most effective roadblocks within the cement industry. Furthermore the research has contributed to the knowledge through proposing standard steps which can be used as road map for implementing the lean philosophy within continuous industries and other organisations. The proposed transition steps are simple, direct, and understandable by the all people at the different organisation levels. The proposed transition steps have the answer to the possible questions and requests of the decision makers within the cement industry or other organisations. The proposed transition steps can be summarised as:

• Achieving a fully understanding of the system through applying of the process mapping technique. • Identifying the main variables and factors that control the system. • Identifying different types of interrelationships between the variables and their effects on the

performance parameters. • Validating the obtained results. The main novelty of the proposed steps was the combination of the

simulation model with the Taguchi Orthogonal Array aiming to improve the cement production line’s efficiency. The cement industry has all the features to be very thriving sector through adopting lean thinking. The successful implementation of the lean strategy ensures the achievement of the maximum efficiency in combination of simultaneous reduction of lead time and production costs within the cement production line.

The successful lean implementation will be achieved when: • The right training and education program is provided to the people aiming to misconceptions about the

lean philosophy. • The right support and commitments of the management are obtained.

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• The right motivation system is established 5.4.0 Energy Conservation through Design Modifications and Technical Advancement: The production of cement is an energy-intensive process. Increasing energy prices are driving up costs and decreasing their value added. Successful, cost-effective investment into energy efficiency technologies and practices meet the challenge of maintaining the output of a high quality product despite reduced production costs. This is especially important, as energy-efficient technologies often include “additional” benefits, such as increasing the productivity of the company. 5.4.1 Process Description: The cement plant processes in India generally falls in to three major categories, namely:

• Dry process • Wet process and • Semi-dry process.

Out of the above, 93% of the total kiln capacity comprised of dry process, 5% wet process and 2% semi-dry process. The various stages involved in the cement production as shown in Figure-1 are discussed below: i) Mining Limestone, the key raw material for cement production, is mined in the quarries through compressed air drilling followed by blasting with explosives. The mined limestone is transported via dumpers to the plant ii) Limestone Crushing & Raw Meal Preparation The mined limestone is fed into a crusher to reduce the size of the stone and then is stockpiled. The crushed limestone and other ingredients bauxite and ferrite are stored in feed hoppers from where they are fed into the raw mill in the required proportions for grinding into raw meal. The ground raw meal is stored in silos c) Coal Milling Coal from a stockyard is first crushed in a hammer crusher and then fed into the coal mill where it is pulverized. Hot air generated in a coal-fired furnace is used to dry the pulverized coal in the mill. The pulverized coal goes to the kiln and precalciner where it is used as fuel. Any coal particles are collected in a bag filter through a grit separator d) Pyro processing The raw meal is fed through a 4-stage preheater and cyclones into the top of a rotary kiln. Pulverized coal is fired from the bottom of the kiln so that the raw meal gets hotter and hotter as it passes down the kiln. Once the raw meal reaches the bottom of the kiln it has turned into clinker e) Clinker Cooler The hot clinker is cooled in a planetary cooler consisting of 10 circular ducts. Ambient air is supplied through these circular ducts and gets heated when it gets in contact with the hot clinker. This heated air is used as secondary air for combustion in the kiln (saving energy to heat up the kiln). The cooled clinker is transported to the clinker stock yard f) Cement Grinding The cooled clinker from the clinker storage yard is fed into a cement ball mill along with gypsum to produce cement. The produced cement is then collected in bag filters and taken to cement silos. Finally cement is packaged for sale 5.4.2 Energy Efficiency Technologies and Measures for the Cement Industry: Table 5.26 gives the comparison of Average and Best Practice Energy Consumption Values for Indian Cement Plants with the world best practices. Opportunities exist within cement plants to improve energy efficiency while maintaining or enhancing productivity. Improving energy efficiency at a cement plant should be approached from several directions

Process

Unit India Average

World Best Practice

Raw Materials Preparation

Coal mill kWh/t clinker 8 2.4

Crushing kWh/t clinker 2 1.0

Raw mill kWh/t clinker 28 27

Clinker Production

Kiln & cooler Kcal/kg of clinker 770 680

Kiln & cooler kWh/t clinker 28 22

Finish Grinding

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Cement mill kWh/t cement 30 25

Miscellaneous

Utilities: mining & transportation

kWh/t clinker 1.6 1.5

Utilities: packing house kWh/t cement 1.9 1.5

Utilities: misc kWh/t cement 2.0 1.5

Total Electric kWh/t cement 95 77

Source: Cement Manufacturer’s Association, 2003; Worrell, 2004

Table 5.26 Average and Best Practice Energy Consumption Values for Indian Cement Plants

First, plants use energy for equipment such as motors, pumps, and compressors. These important components require regular maintenance, good operation and replacement, when necessary. Thus, a critical element of plant energy management involves the efficient control of crosscutting equipment that powers the production process of a plant. A second and equally important area is the proper and efficient operation of the process. Process optimization and ensuring the most efficient technology is in place is a key to realizing energy savings in a plant’s operation. Finally, throughout a plant, there are many processes simultaneously. Fine-tuning their efficiency is necessary to ensure energy savings are realized. Several technologies and measures exist that can reduce the energy intensity (i.e. the electricity or fuel consumption per unit of output) of the various process stages of cement production.

5.4.3 Measures to Reduce the Energy Intensity at Various Stages in Cement Production: i) Raw Materials Preparation

• Efficient transport systems • Raw meal blending systems • High-efficiency roller mills • High-efficiency classifiers • Fuel Preparation: Roller mill

ii) Clinker Production • Energy management and process control • Seal replacement • Kiln combustion system improvements • Kiln shell heat loss reduction • Use of waste fuels • Conversion to modern grate cooler • Refractories • Heat recovery for power generation • Low pressure drop cyclones for suspension pre-heaters • Optimize grate coolers • Addition of pre-calciner to pre-heater kiln • Long dry kiln conversion to multi-stage pre-heater kiln • Long dry kiln conversion to multi-stage pre-heater, precalciner kiln • Efficient kiln drives • Oxygen enrichment

iii) Finish Grinding • Energy management and process control • Improved grinding media (ball mills) • High-pressure roller press • High efficiency classifiers

iv) General Measures • Preventative maintenance (insulation, compressed air system, maintenance) • High efficiency motors • Efficient fans with variable speed drives • Optimization of compressed air systems • Efficient lighting

v) Product & Feedstock Changes • Blended Cements • Limestone cement • Low Alkali cement • Use of steel slag in kiln

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• Reducing fineness of cement for selected uses Not all measures listed will apply to all plants. Applicability will depend on the current and future situation in individual plants. For example, expansion and large capital projects are likely to be implemented only if the company has about 50 years of remaining limestone reserves onsite. Plants that have a shorter remaining supply are unlikely to implement large capital projects, and would rather focus on minor upgrades and energy management measures While a number of cement plants in India approach world best practice levels in terms of energy efficiency, average Indian cement plants are relatively inefficient Table 5.26 provides average energy consumption values by process for Indian cement plants. In almost all cases, the average energy consumption value is significantly higher than the best practice value, indicating a strong potential for energy efficiency improvement in many plants.

5.4.4 Energy Conservation Measures (ECM) via Design: Following Cement Plants have been considered for implementation of Total Energy Management (TEM). Detailing has been already done w.r.t. process plant diagram consisting of different equipments wherein thermal engineering aspects have been considered in section 5.2.0

• Ambuja Cement Plant of Ambuja Cements Ltd., Ambujanagar • Gajambuja Cement Plant of Ambuja Cements Ltd., Ambujanagar • Sanghi Industries Limited, Sanghipuram Clinkerization & Cement Plant • Gujarat Sidhee Cement Ltd., Ta: Sutrapada, Dist. Junagadh • Saurashtra Cement Ltd, Ta: Ranavav, Dist. Porbandar • Digvijay Cement Co. Ltd., Jamnagar • Gujarat Anjan Cement Ltd., Seagram, Village: Vayor, Kutch

5.4.5 Generalized Overview of Energy Conservation Measures in Visited Plants: A generalized overview of the various energy conservation measures considered in above plants has been discussed in the case study. The main modifications are as listed below.

• Coal Mill /Modification of the furnace grate bars to25 mm from existing 50 mm • Coal Mill: Electrical power saving by increasing coal mill drying chamber lifters height and angle • Improved Drying of Coal through Insulation and Additional Hot Air Duct from the Coal Mill Furnace • Increase of Inlet Duct Diameter of Circulating Air Fan to Reduce Flow Velocity and Pressure Drop • Prevention of False Air Entry across Coal Mill Circuit • Reduction of Velocity in Coal Mill Outlet Duct • Reduction of Motor Size in Limestone Primary Crusher • Reduction of Speed of Circulating Air Fan in the Coal Mill through Replacement of AC Motor with

DC Motor i) Coal Mill /Modification of the furnace grate bars to25 mm from existing 50 mm: It was observed that large lumps of coal were burnt on the furnace grate bars that were 50 mm apart from each other. This resulted in coal particles falling through the grate into the ash pit before they were completely burnt and therefore lower temperatures of the hot air sent to the coal mill (making the drying of coal in the coal mill less effective). Options to resolve this included reducing the size of coal lumps fed into the furnace, reducing the distance between the furnace grate bars to 25 mm, and training of operators on coal feeding and combustion management of the furnace. Annual coal savings were 50 tons worth Rs 2.25 lacs with an immediate payback period because no financial investment was necessary. Greenhouse gas emission reductions were 77 tons of CO2 per year. a) Observations: Coal is burnt in a furnace to provide hot air to the coal mill to dry coal prior to grinding (the drier the coal, the more efficient the grinding process). Three observations were made:

• A large amount of unburnt / semi-burnt coal particles in the ash pit at the bottom of the furnace • A large amount of coal particles dropping through the grate bars into the ash pit • The temperature of the hot air sent to the coal mill was measured to be 200 0C which is relatively low • Upon investigation this had two causes: • Large coal lumps were fed into the furnace, resulting in high amounts of access air because the coal

could not be burnt effectively and therefore insufficiently hot air was sent to the coal mill • The distance between the grate bars was large: 50 mm, resulting in coal particles falling through the

grate into the ash pit below before the coal was burnt completely b) Options: Three options were implemented:

• The coal size fed into the furnace was reduced • The space between the grate bars in the furnace was reduced to 25 mm (see picture below)

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• Operators were trained in proper coal feeding and combustion practices c) Results: Through the implementation of the three options, the overall combustion efficiency was improved resulting in an increase of the furnace outlet temperature (i.e. the temperature of the outgoing flue gases) from an average of 200°C to 240°C. This resulted in improved drying of coal in the coal mill (or less coal was needed in the furnace to achieve the same drying result). The financial benefits are as follows: Financial benefits:

• Investment: none • Annual cost savings: Rs.2.25 lakh (50 tons coal /year * Rs.4500/T Coal) • Payback period: Immediate

ii) Electrical Power Saving By Increasing Coal Mill Drying Chamber Lifters Height and Angle: a) Observations: As part of the existing design to facilitate drying of coal in the mill-drying chamber, they are provided with lifters, especially during the four rainy months (coal mill used for grinding the coal). These lifters are fixed angle plates welded to the inside surface of the mill drying chamber and arranged along a fixed portion of the length which would lift the coal from the bottom and drop them as a falling spray when they reach the top during the mill rotation. These lifters were increased in height, angle and number to ensure carrying of larger quantity of coal. The increase in angle ensured that the spraying of coal is from the top most point of the rotating mill. This resulted in faster drying and better performance of the coal mill. And thus, the annual energy savings (four months aggregate) is 20, 003 kWh/year with an annual GHG reduction of 17.8 tons of CO2//year. The investment was negligible and the entire modification was done with in house resources There were initial reservations from the production department during implementation of this measure, as they feared increase in dead load (total weight of the coal mill would be increased because you are adding more lifters) and large down-time and production loss. Gradually, however, the entire production and the Team ensured successful implementation. It was a big boon for the operations department, who always found it a challenge to keep pace with kiln coal demand during the troublesome rainy months. b) Results Financial benefits

• Investment: none • Annual cost savings : Rs. 97000 ( Rs.4.86/kWh X 20,003 kWh) • Payback period: immediate

iii) Improved Drying of Coal through Insulation and Additional Hot Air Duct from the Coal Mill Furnace: It was observed that grinding efficiency reduces with the increase in wetness thus affecting the flow of the coal. In addition, the coal mill performance is affected due to ingression of cold air. Options to resolve included the provision of additional hot flue gas duct to help dry coal while falling from the table feeder into the mill. It also helps create a higher pressure zone, as well as in reducing the opening at the table feeder, both of which help to minimize cold false air ingress into the coal mill, resulting in reduced fuel consumption in the kiln. Besides the above, the hot gas duct from the furnace to the coal mill was insulated by sheets of mineral wool leading to better coal furnace operation and reduction in furnace fuel consumption. This measure has resulted in 214 X 106 k Cal/year savings equivalent to 48 tons of coal annually worth Rs. 2,14,650. The entire modification was engineered with in-house resources and capabilities with no additional investment. a) Observations Hot combustion air from the coal-fired furnace was supplied to the coal mill for drying the coal prior to grinding, which resulted in severe problem with the flow of the coal due to the wetness, especially during the rainy season. The coal mill performance was affected due to the cold air ingress occurring from the openings near the table feeder into the coal feed chute. The following observations were made:

• High Heat loss from bare duct carrying hot gases • Frequent choking of coal mill inlet at table feeder due to wetness • Cold air ingress into the coal mill through large gaps.

Two options were implemented: Option 1: Provision of additional hot flue gas duct from the coal fired furnace to dry coal while falling on to the table feeder. Implementing the above options with Coal throughput at 7 Tons/hr and with the provision of the additional Hot Air Duct resulted in moisture percentage reduction by 0.2%, with total moisture reduction (7 Tons Coal/hr X (0.2/100)) at 14 kg/hr thus resulting in thermal energy saving (avoiding heat drawn from kiln for coal drying (14 kg/hr X 620 kCal/kg)) of 8680 k Cal/hr. Financial Benefits Option 1

• Investment: Nil • Annual energy savings at end use: 34.72 X 106 kCal (= 4000 hrs/yr X 8680 kCal/hr)

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• Annual coal savings : 7.7 tons (= 34.72 X 106/4500 kCal/kg ) • Annual cost savings : Rs.34,650 (7.7 tons X Rs.4500/Ton of Coal)

Option 2: The hot gas duct from the furnace to the coal mill was insulated leading to better coal furnace operation and reduction in furnace fuel consumption The various parameters involved with the insulation of Hot Air Duct before and after the options used are given the following table 5.27

Parameter Before After Clinker Production rate 440 tons/day 450 tons/day Exposed surface area of hot duct (from furnace top to coal mill inlet)

21.03 m2 23.81 m2

Average exposed bare surface temperature

219°C 123°C

Ambient Temperature 30°C 30°C Radiation loss 1.37 kCal/kg Clinker 0.50 kCal/kg Clinker Convection loss 0.63 kCal/kg Clinker 0.31 kCal/kg Clinker Total loss (Radiation + Convection) 2 kCal/kg Clinker 0.81 kCal/kg Clinker

Table 5.27 Finish Grinding Process OA After Reducing WIP Financial benefits Option 2

• Annual cost savings : Rs. 1,80,000 (40 tons of Coal X Rs.4500/ton of Coal) b) Financial benefits Option 2 Total savings due to provision of additional hot air duct (option 1) and main duct insulation (option 2)

• Investment: none • Annual coal savings : 47.684 tons of coal • Annual cost savings : Rs.2,14,650 • Payback period: Immediate

iv) Increase of Inlet Duct Diameter of Circulating Air Fan to Reduce Flow Velocity and Pressure Drop: The coal is milled to a fine powder (45 mesh) and is conveyed to the storage hopper pneumatically by air being sucked through the circulating air fan. Towards this the fan consumes power which is dependant on quantity of material to be conveyed flow and the pressure drops it has to encounter in this process. The duct diameter from dust collector outlet to CA fan inlet was increased from 500 to 600mm, thereby decreasing the pressure drop and in turn achieving power saving. This resulted in a reduction in power consumption by CA fan to the tune of 0.2 kW totaling 744 kWH per year. a) Financial Benefits

• Investment: none • Annual cost savings : Rs. 3,616 = 744 kWh X Rs.4.86/kWh • Payback period: immediate

v) Prevention of False Air Entry across Coal Mill Circuit: The coal mill circulating air fan (CM-CA) serves the all important function of ensuring drawl of hot gas from the coal fired furnace through the mill, via the bag filter dust collection system and then venting the dust free air into the atmosphere. Since the entire system is under suction, any stray cold air ingress is detrimental to the CM performance as The temperature is reduced because of mixing with cold air and the suction capacity of the fan to draw hot gas is compromised (to the extent of stray cold ingress air quantity) resulting in throughput drop of coal mill. Air in leak points were identified between the coal mill (CM) outlet and circulating air (CA) fan inlet portion of the ducting system. A differential O2 analysis along this portion gave an indication of air inleaks (i.e increasing O2 profile) of 4%. Identified air leak points were plugged and the measurement of per cent O2 at the fan (CM-CA) inlet reduced to a value of 2 %. This resulted in reduction of 10-10.5 per cent (by calculation) cold air inleaks equivalent to 1290 m3/min. a) Financial Benefits

• Investment: none • Annual cost savings : Rs. 37, 616 = 7740 kWh X Rs.4.86/kWh • Payback period: Immediate

vi) Reduction of Velocity in Coal Mill Outlet Duct: In this option implemented by the plant, the coal is milled to a fine powder (200 mesh) and is conveyed to the storage hopper pneumatically by air from the circulating air fan. Towards this the fan consumes power which is dependant on quantity of coal to be conveyed and the pressure drops it has to overcome in the process of conveying from mill outlet to the hopper. It is known that higher velocities (acceptable up to 18 m/s to 20 m/s) and smaller duct cross sectional areas result in high-pressure developed by the fan and thereby higher power consumption. The existing fan speed was reduced from 875 to 750 resulting in drop in conveying air velocity in the outlet duct from 24 to 20 m/s. This manifested as reduction in power consumption in the CA fan to the tune

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of 8 kW (28 kW to 20 kW). Speed reduction was affected by replacing the existing AC drive with a DC drive available in the stores. a) Observations: Prior to modification the CA fan was supplying ‘conveying air’ at an air velocity in the mill outlet duct of 24 m/s. The drive motor was an AC induction squirrel cage motor operating at a speed of 1440 rpm and delivered at a speed of 875 rpm at the fan shaft through a pulley arrangement. The power being consumed by the motor was 28 kW. Before Modification: Velocity of conveying air in discharge duct of mill (875 rpm) = 24 m/s Corresponding power consumption by the fan drive = 28 kW After Modification: Velocity of conveying air in discharge duct of mill (750 rpm) = 20 m/s Corresponding power consumption by the fan drive = 20 kW b) Financial Benefits

• Investment: none • Annual cost savings : Rs.15,5,520 (= 32000 kWh X Rs.4.86/kWh) • Payback period: immediate

vii) Reduction of Motor Size in Limestone Primary Crusher: Limestone arrives from the mine quarry by dumpers in the form of blocks and boulders of around 300 mm size. These are subjected to primary size reduction by a primary crusher (hammer) operating at a capacity of 50-60 TPH (rated 100 TPH). The specified input size to crusher is 300 mm. The Limestone Primary Crusher main motor of 220 kW was replaced by another motor of 165 kW in order to reduce the power consumption. This measure resulted in an annual monetary benefit of Rs1,35,205 and the investment of Rs. 100,000 was recovered in less than a year. a) Observations: Reduction of Limestone Crusher motor power consumption by operating with a smaller sized motor. Before Modification

• Lime stone Primary Crusher Main Motor Capacity: 220 kW • Corresponding power consumption by the Crusher drive : 118 kW

After Modification • Lime stone Primary Crusher Main Motor Capacity: 165 kW

b) Financial Benefits • Investment: Rs. 100,000 • Annual cost savings : Rs. 1,35,205 = 27820 kWh X Rs.4.86/kWh • Payback period: less than one year

viii) Reduction of Speed of Circulating Air Fan in the Coal Mill through Replacement of AC Motor with DC Motor: It was observed that the coal mill Circulating Air (CA) fan evacuates gases from the coal mill dust collector bag filter exit and discharges clean air into the atmosphere. The coal mill CA fan before modification was driven by an AC induction motor and air flow being higher than required, had to be adjusted as per process requirement, using inefficient damper control. The fan drive was replaced with a direct current (DC) motor, which enabled speed reduction with ease to match actual flow requirement without using damper to throttle fan airflow. (The use of VSD was not considered taking into account the cost economics involved since the motor under consideration was of a low capacity 28 kW, also the O&M of VSD would be very high in comparison to DC motor) This measure resulted in reduced power consumption by the coal mill CA fan motor to the tune of 5 kW totaling 18600 kWh per year worth Rs. 77,796 annually. The associated annual GHG reduction was of the order of 17 tons. The investment towards the purchase and installation of a new DC drive motor for the coal mill CA fan amounting to Rs. 77,780 was paid back in about 13 months. The capital was drawn from the unit’s own funds. a) Observations: The coal mill CA fan before modification was driven by an AC induction motor and air flow being higher than required, had to be adjusted as per process requirement, using inefficient damper control. The following observations were made:

• Coal mill exhaust fan suction damper was always kept closed (more than 60 %) • Speed of the motor was always constant

Options: The need for throttling Coal Mill CA fan flow to match process requirements (by damper) was eliminated by replacing the existing Coal mill CA fan AC drive motor, by a new DC drive motor and operated at reduced rpm and full flow. b) Financial Benefits

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• Investment: Rs. 77780 • Annual cost savings : Rs. 71,796 = 18600 kWh X Rs. 4.86/kWh • Payback period:13 months

5.5.0 Conclusions: This chapter is fully devoted to industrial sector Cement Industry wherein large scale and medium scale cement industries have been covered. This chapter is further sub divided into three parts: Part – I Overview of cement production Part – II Implementation of lean philosophy in cement plant Part –III Energy Conservation through Design Modifications and Technical Advancement 5.5.1 Overview of Cement Production: Plant visits were carried out for studying overall process of manufacturing and the Energy Conservation Measures (ECM) via design have been considered for various equipments involved in these following cement plants:

1. Ambuja Cement Plant of Ambuja Cements Ltd., Ambujanagar 2. Gajambuja Cement Plant of Ambuja Cements Ltd., Ambujanagar 3. Sanghi Industries Limited, Clinkerization & Cement Plant , Sanghipuram 4. Gujarat Sidhee Cement Ltd., Ta: Sutrapada, Dist. Junagadh 5. Saurashtra Cement Ltd, Ta: Ranavav, Dist. Porbandar 6. Digvijay Cement Co. Ltd., Jamnagar 7. Gujarat Anjan Cement Ltd., Seagram, Village: Vayor, Kutch

A generalized overview of the various energy conservation measures considered in above plants has been discussed in the case studies undertaken. 5.5.2 Implementation of Lean Philosophy in Cement Plant: Implementation of lean helps many industries to improve their productivity and efficiency. The today’s challenge is to implement the lean philosophy within continuous manufacturing industries. The cement industry is ideal example of the continuous industry sector and this research study has demonstrated that the lean philosophy is applicable to even continuous manufacturing industries. The main contribution of this study is to convey the message to the decision makers that the lean philosophy is the proposed solution by which the continuous industry and different organization types can be improved through eliminating or minimizing wastes and non-value added activities within the production line. Thus undertaken research consisted of six steps as

• Data collection. • Developing of Simulation model. • Identification of the interrelationships between the different variables. • Developing a connectivity matrix to minimize the number of variables. • Using Taguchi Orthogonal Array. • Performance measurements identification.

The developed transition steps have ability to: • Understand the cement manufacturing process in order to identify value added and non-value added

activities within production line through applying the process mapping technique. • Determine and examine the interrelationships between the variables through developing of Cause-

Effect matrix. • Quantify the benefits obtained from the changing process within the cement production line through

employing of the experimental design technique where novel approach has been developed by integrating the simulation modeling technique with Taguchi Orthogonal Array.

This research has led to observation that the cement industry can benefit from implementing lean philosophy once the organization mission, aims, and objectives are clarified and communicated through all the organization levels. Furthermore barriers and obstacles should be removed through changing the organizational culture, and empowering the people to be involved in identifying and problem solving process. It has been concluded that the cement industry is characterised by high levels of WIP and inventories. Many problems and root causes of performance insufficiencies can be shrouded and buried behind the WIP high levels. Therefore; the priority of implementing Lean within the cement industry is to eliminate or minimise the WIP and inventories levels. In addition; one of the research objectives is to determine and examine effects of WIP minimization on the performance parameters. One of the main reasons of high WIP levels is the non-optimised batch size. Hence all workstations capacities were reduced by10% in order to minimise the WIP levels. Experimental results illustrate the effects of WIP reduction on the system performance parameters have been tabulated.

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The SWOT analysis carried out emphasizes that the cement industry has the features to be successful industry, and there are number of changing-forces which drive the decision maker to think about applying and implementing lean philosophy; these forces are:

• Fuel and energy prices: the significant global increases of fuel and energy costs has heavily impacted the cement industry,

• Market pressure: the undue pressure to keep prices lower than the competitors. Furthermore the high market demands put the cement industry under pressure to simultaneously reduce cycle time and downtimes, and increase utilisation and throughput of the equipments. Based on the findings that the cement industry might be far away from implementing lean thinking approaches because awareness lacking about adoption of lean philosophy. Therefore it is essentially necessary to eliminate and minimize all kinds of non valued added activities within the cement industry in order to achieve customer satisfaction, product costs reduction, and overall performance improvement. The main novelty of the proposed steps was the combination of the simulation model with the Taguchi Orthogonal Array aiming to improve the cement production line’s efficiency. The cement industry has all the features to be very thriving sector through adopting lean thinking. The successful implementation of the lean strategy ensures the achievement of the maximum efficiency in combination of simultaneous reduction of lead time and production costs within the cement production line. The successful lean implementation will be achieved when:

• The right training and education program is provided to the people aiming to misconceptions about the lean philosophy.

• The right support and commitments of the management are obtained. • The right motivation system is established

5.5.3 Energy Conservation through Design Modifications and Technical Advancement: The production of cement is an energy-intensive process. Increasing energy prices are driving up costs and decreasing the value added. Successful, cost-effective investment into energy efficient technologies and practices meet the challenge of maintaining the output of a high quality product despite reduced production costs. This is especially important, as energy-efficient technologies often include “additional” benefits, such as increasing the productivity of the company. As can be seen from Table 5.26 opportunities exist within cement plants to improve energy efficiency while maintaining or enhancing productivity. Improving energy efficiency at a cement plant should be approached from several directions First, plants use energy for equipment such as motors, pumps, and compressors. These important components require regular maintenance, good operation and replacement, when necessary. Thus, a critical element of plant energy management involves the efficient control of crosscutting equipment that powers the production process of a plant. A second and equally important area is the proper and efficient operation of the process. Process optimization and ensuring the most efficient technology is in place is a key to realizing energy savings in a plant’s operation. Finally, throughout a plant, there are many processes simultaneously. Fine-tuning their efficiency is necessary to ensure energy savings are realized. Several technologies and measures exist that can reduce the energy intensity (i.e. the electricity or fuel consumption per unit of output) of the various process stages of cement production. Not all measures listed will apply to all plants. Applicability will depend on the current and future situation in individual plants. For example, expansion and large capital projects are likely to be implemented only if the company has about 50 years of remaining limestone reserves onsite. Plants that have a shorter remaining supply are unlikely to implement large capital projects, and would rather focus on minor upgrades and energy management measures In almost all cases, the average energy consumption value is significantly higher than the best practice value, indicating a strong potential for energy efficiency improvement in many plants. The main modifications are as listed below.

• Coal Mill /Modification of the furnace grate bars to25 mm from existing 50 mm • Coal Mill: Electrical power saving by increasing coal mill drying chamber lifters height and angle • Improved Drying of Coal through Insulation and Additional Hot Air Duct from the Coal Mill Furnace • Increase of Inlet Duct Diameter of Circulating Air Fan to Reduce Flow Velocity and Pressure Drop • Prevention of False Air Entry across Coal Mill Circuit • Reduction of Velocity in Coal Mill Outlet Duct • Reduction of Motor Size in Limestone Primary Crusher • Reduction of Speed of Circulating Air Fan in the Coal Mill through Replacement of AC Motor with

DC Motor