Replacement of Steam Driven Mill Drives with Electric DC Motors

Background

Conventionally, steam turbines are used as the prime movers for the mills, in a sugar industry. These steam turbines are typically, single stage impulse type turbines having about 25 - 30% efficiency.

The recent installation of commercial cogeneration system, with provision for selling the excess power to the grid, has made the generation of excess power in a sugar mill, very attractive. One of the methods of increasing the cogeneration power in a sugar mill is to replace the smaller low efficiency mill turbines, with better efficiency drives, such as, DC motors or hydraulic drives.

The power turbines (multi-stage steam turbines) can operate at efficiencies of about 65 - 70%. Hence, the equivalent quantity of steam saved by the installation of DC motors or hydraulic drives can be passed through the power turbine, to generate additional power.

This replacement can aid in increase of net saleable power to the grid, resulting in additional revenue for the sugar plant. This case study highlights the details of one such project, implemented in a 5000 TCD sugar plant.

Previous Status

A 5000 TCD sugar mill had six numbers of 750 HP mill turbines and one number of 900 HP shredder turbine. The average steam consumption per mill (average load of 300 kW) was about 7.5 TPH steam @ 15 Ata. The steam driven mill drives had an efficiency of about 35%, in the case of single-stage turbine and about 50%, in the case of two stage turbines.

The plant team was planning to commission a commercial cogeneration plant. This offered an excellent opportunity for the plant team to replace the low efficiency steam turbine driven mills, with DC motors or hydraulic drives and maximise the cogeneration potential.

Energy saving project

The plant team contemplated the replacement of the steam driven mills with electric DC motors, along with the commissioning of the cogeneration plant.

Concept of the project

The conventional single stage impulse type steam turbines have very low efficiencies of 35%. Hence, the steam consumption per unit of power output is very high. A single high capacity steam turbine is more efficient as compared to multiple numbers of smaller capacity steam turbines. Hence, the steam can be passed through the larger capacity steam turbine to generate more saleable power.

The latest drives, such as, DC drives and hydraulic drives have very high efficiencies of 90%. The steam saved by the installation of DC drives, can be passed through the larger capacity power turbines of higher efficiency (about 65 - 70%), to generate additional saleable power.

Implementation methodology, problems faced and time frame

The steam turbine mill drives were replaced with DC drives, once the cogeneration plant was commissioned. The modifications carried were as follows:

Four numbers of 900 HP and two numbers of 750 HP DC motors were installed in place of the six numbers of 750 HP mill turbines

Two numbers of 1100 kW AC motors were installed for the fibrizer, in place of the single 900 HP shredder turbine

There were no major problems faced during the implementation of this project. The implementation of the project was completed in 24 months.

Benefits achieved

The comparative analysis of the operational parameters before and after the modification is as follows:

The equivalent power saved (850 kW/mill) by the implementation of this project, could be exported to the grid, to realize maximum savings.

Financial analysis

The annual energy saving achieved was Rs.62.37 million. This required an investment of Rs.42.00 million, which had an attractive simple payback period of 9 months.

Installation of 30 MW Commercial Co-generation Plant

Background

The Indian sugar industry by its inherent nature can generate surplus power, in contrast to the other industries, which are only consumers of energy. This is mainly possible because of the 30 % fibre content in the sugar cane used by the sugar mills. This fibre, referred to as bagasse, has good fuel value and is used for generation of the energy required, for the operation of the sugar mill.

The bagasse is fired in the boiler, for producing steam at high pressures, which is extracted through various back-pressure turbines and used in the process. This simultaneous generation of steam and power, commonly referred to as Co-generation. Conventionally, the cogeneration system was designed to cater to the in-house requirements of the sugar mill only. The excess bagasse generated, was sold to the outside market.

In the recent years, with the increasing power Demand-Supply gap, the generation of power from the excess bagasse, has been found to be attractive. This also offers an excellent opportunity for the sugar mills to generate additional revenue. Co-generation option has been adopted in many of the sugar mills, with substantial additional revenue for the mills. This also contributes to serve the national cause in a small way, by bridging the Demand - Supply gap.

This case study describes the installation of a commercial co-generation plant in a 5000 TCD mill.

Previous status

A 5000 TCD sugar mill in Tamilnadu operating for about 200 days in a year had the following equipment:

Boilers - 2 numbers of 18 TPH, 12 ATA

2 numbers of 29 TPH, 15 ATA

1 number of 50 TPH, 15 ATA

Turbines - 1 number 2.5 MW

1 number 2.0 MW

1 number 1.5 MW

Mill drives - 6 numbers 750 BHP steam turbines

1 number 900 BHP shredder turbine

The plant had an average steam consumption of 52%. The power requirement of the plant during the sugar-season was met by the internal generation and during the nonseason from the grid.

Energy saving project

The plant went in for a commercial co-generation plant. The old boilers and turbine were replaced with high pressure boilers and a single high capacity turbine. The new turbine installed was an extraction-cum condensing turbine.

A provision was also made, for exporting (transmitting) the excess power generated, to the state grid. The mill steam turbines were replaced with DC drives. The details of the new boilers, turbines and the steam distribution are as indicated below:

Boilers - 2 numbers of 70 TPH, 67 ATA

Multi-fuel fired boilers

Turbines - 1 number of 30 MW turbo-alternator set

(Extraction-cum-condensing type)

Mill drives - 4 numbers of 900 HP DC motors for mills

2 numbers of 750 HP DC motors for mills

2 numbers of 1100 kW AC motors for fibrizer

Implementation methodology, problems faced and time frame

Two high capacity, high-pressure boilers and a 30 MW turbine was installed in place of the old boilers and smaller turbine. While selecting the turbo-generator, it was decided to have the provision for operation of the co-generation plant, during the off-season also. This could be achieved, by utilising the surplus bagasse generated during the season, as well as by purchasing surplus bagasse, from other sugar mills and biomass fuels, such as, groundnut shell, paddy husk, cane trash etc.

The shortfall of bagasse during the off-season was a problem initially. The purchase of biomass fuels from the nearby areas and the use of lignite solved this problem. The entire project was completed and commissioned in 30 months time.

Benefits

The installation of high-pressure boilers and high-pressure turbo-generators has enhanced the power generation from 9 MW to 23 MW. Thus, surplus power of 14 MW is available for exporting to the grid.

The following operating parameters were achieved:

Typical (average) crushing rate = 5003 TCD

Typical power generation

During season = 5,18,321 units/day

During off-season = 2,49,929 units/day

Typical power exported to grid

During season = 3,18,892 units/day

(13.29 MW/day)

During off-season = 1,97,625 units/day

(8.23 MW/day)

Typical no. of days of operation = 219 days (season)

= 52 (off-season)

The summary of the benefits achieved (expressed as value addition per ton of bagasse fired) is as follows:

Financial analysis

The annual monetary benefits achieved are Rs.204.13 million (based on cost of power sold to the grid @ Rs.2.548/unit, sugar season of 219 days and off-season of 52 days). This required an investment of Rs.820.6 million. The investment had an attractive simple payback period of 48 months.

Note :

Critical factors affecting power generation

The efficient operation of a co-generation system depends on various factors. This has a direct bearing on the loss in power generation and the power exported to the grid. Some of these critical factors affecting the power generation (quantified as loss in generation per day) are as follows:

1% drop in bagasse % in cane : 18300 units

1% increase in moisture content of bagasse : 6800 - 10200 units

1% increase in process steam consumption : 4200 units

1% drop in crushing rate : 5000 - 7400 units

1 hour downtime : 20600 units

Drop in 1 ton of cane availability : 60 units

The above figures are based on the following operational parameters:

Crushing rate : 5000 TCD

Steam . bagasse ratio : 1 : 2.2

NCV of bagasse (50% moisture) : 1804 kCal/kg

Bagasse content, in % cane : 27%

How is fertilizer made?

Background

Fertilizer is a substance added to soil to improve plants' growth and yield. First used by ancient farmers, fertilizer technology developed significantly as the chemical needs of growing plants were discovered. Modern synthetic fertilizers are composed mainly of nitrogen, phosphorous, and potassium compounds with secondary nutrients added. The use of synthetic fertilizers has significantly improved the quality and quantity of the food available today, although their long-term use is debated by environmentalists.

Like all living organisms, plants are made up of cells. Within these cells occur numerous metabolic chemical reactions that are responsible for growth and reproduction. Since plants do not eat food like animals, they depend on nutrients in the soil to provide the basic chemicals for these metabolic reactions. The supply of these components in soil is limited, however, and as plants are harvested, it dwindles, causing a reduction in the quality and yield of plants.

Fertilizers replace the chemical components that are taken from the soil by growing plants. However, they are also designed to improve the growing potential of soil, and fertilizers can create a better growing environment than natural soil. They can also be tailored to suit the type of crop that is being grown. Typically, fertilizers are composed of nitrogen, phosphorus, and potassium compounds. They also contain trace elements that improve the growth of plants.

The primary components in fertilizers are nutrients which are vital for plant growth. Plants use nitrogen in the synthesis of proteins, nucleic acids, and hormones. When plants are nitrogen deficient, they are marked by reduced growth and yellowing of leaves. Plants also need phosphorus, a component of nucleic acids, phospholipids, and several proteins. It is also necessary to provide the energy to drive metabolic chemical reactions. Without enough phosphorus, plant growth is reduced. Potassium is another major substance that plants get from the soil. It is used in protein synthesis and other key plant processes. Yellowing, spots of dead tissue, and weak stems and roots are all indicative of plants that lack enough potassium.

Calcium, magnesium, and sulfur are also important materials in plant growth. They are only included in fertilizers in small amounts, however, since most soils naturally contain enough of these components. Other materials are needed in relatively small amounts for plant growth. These micronutrients include iron, chlorine, copper, manganese, zinc, molybdenum, and boron, which primarily function as cofactors in enzymatic reactions. While they may be present in small amounts, these compounds are no less important to growth, and without them plants can die.

Many different substances are used to provide the essential nutrients needed for an effective fertilizer. These compounds can be mined or isolated from naturally occurring sources. Examples include sodium nitrate, seaweed, bones, guano, potash, and phosphate rock. Compounds can also be chemically synthesized from basic raw materials. These would include such things as ammonia, urea, nitric acid, and ammonium phosphate. Since these compounds exist in a number of physical states, fertilizers can be sold as solids, liquids, or slurries.

History

The process of adding substances to soil to improve its growing capacity was developed in the early days of agriculture. Ancient farmers knew that the first yields on a plot of land were much better than those of subsequent years. This caused them to move to new, uncultivated areas, which again showed the same pattern of reduced yields over time. Eventually it was discovered that plant growth on a plot of land could be improved by spreading animal manure throughout the soil.

Over time, fertilizer technology became more refined. New substances that improved the growth of plants were discovered. The Egyptians are known to have added ashes from burned weeds to soil. Ancient Greek and Roman writings indicate that various animal excrements were used, depending on the type of soil or plant grown. It was also known by this time that growing leguminous plants on plots prior to growing wheat was beneficial. Other types of materials added include sea-shells, clay, vegetable waste, waste from different manufacturing processes, and other assorted trash.

Organized research into fertilizer technology began in the early seventeenth century. Early scientists such as Francis Bacon and Johann Glauber describe the beneficial effects of the addition of saltpeter to soil. Glauber developed the first complete mineral fertilizer, which was a mixture of saltpeter, lime, phosphoric acid, nitrogen, and potash. As scientific chemical theories developed, the chemical needs of plants were discovered, which led to improved fertilizer compositions. Organic chemist Justus von Liebig demonstrated that plants need mineral elements such as nitrogen and phosphorous in order to grow. The chemical fertilizer industry could be said to have its beginnings with a patent issued to Sir John Lawes, which outlined a method for producing a form of phosphate that was an effective fertilizer. The synthetic fertilizer industry experienced significant growth after the First World War, when facilities that had produced ammonia and synthetic nitrates for explosives were converted to the production of nitrogen-based fertilizers.

Raw Materials

The fertilizers outlined here are compound fertilizers composed of primary fertilizers and secondary nutrients. These represent only one type of fertilizer, and other single nutrient types are also made. The raw materials, in solid form, can be supplied to fertilizer manufacturers in bulk quantities of thousands of tons, drum quantities, or in metal drums and bag containers.

Primary fertilizers include substances derived from nitrogen, phosphorus, and potassium. Various raw materials are used to produce these compounds. When ammonia is used as the nitrogen source in a fertilizer, one method of synthetic production requires the use of natural gas and air. The phosphorus component is made using sulfur, coal, and phosphate rock. The potassium source comes from potassium chloride, a primary component of potash.

Secondary nutrients are added to some fertilizers to help make them more effective. Calcium is obtained from limestone, which contains calcium carbonate, calcium sulphate, and calcium magnesium carbonate. The magnesium source in fertilizers is derived from dolomite. Sulfur is another material that is mined and added to fertilizers. Other mined materials include iron from ferrous sulfate, copper, and molybdenum from molybdenum oxide.

The Manufacturing Process

The various steps involved in the manufacture of finished fertilizer products, from raw materials through intermediate products, are shown in Figure 1.

Fully integrated factories have been designed to produce compound fertilizers. Depending on the actual composition of the end product, the production process will differ from manufacturer to manufacturer.

Nitrogen fertilizer component

Ammonia is one nitrogen fertilizer component that can be synthesized from in-expensive raw materials. Since nitrogen makes up a significant portion of the earth's atmosphere, a process was developed to produce ammonia from air. In this process, natural gas and steam are pumped into a large vessel. Next, air is pumped into the system, and oxygen is removed by the burning of natural gas and steam. This leaves primarily nitrogen, hydrogen, and carbon dioxide. The carbon dioxide is removed and ammonia is produced by introducing an electric current into the system. Catalysts such as magnetite (Fe3O4) have been used to improve the speed and efficiency of ammonia synthesis. Any impurities are removed from the ammonia, and it is stored in tanks until it is further processed.

While ammonia itself is sometimes used as a fertilizer, it is often converted to other substances for ease of handling. Nitric acid is produced by first mixing ammonia and air in a tank. In the presence of a catalyst, a reaction occurs which converts the ammonia to nitric oxide. The nitric oxide is further reacted in the presence of water to produce nitric acid.

Nitric acid and ammonia are used to make ammonium nitrate. This material is a good fertilizer component because it has a high concentration of nitrogen. The two materials are mixed together in a tank and a neutralization reaction occurs, producing ammonium nitrate. This material can then be stored until it is ready to be granulated and blended with the other fertilizer components.

Phosphorous fertilizer component

To isolate phosphorus from phosphate rock, it is treated with sulfuric acid, producing phosphoric acid. Some of this material is reacted further with sulfuric acid and nitric acid to produce a triple superphosphate, an excellent source of phosphorous in solid form.

Some of the phosphoric acid is also reacted with ammonia in a separate tank. This reaction results in ammonium phosphate, another good primary fertilizer.

Potassium fertilizer component

Potassium chloride is typically supplied to fertilizer manufacturers in bulk. The manufacturer converts it into a more usable form by granulating it. This makes it easier to mix with other fertilizer components in the next step.

Granulating and blending

To produce fertilizer in the most usable form, each of the different compounds, ammonium nitrate, potassium chloride, ammonium phosphate, and triple superphosphate are granulated and blended together. One method of granulation involves putting the solid materials into a rotating drum which has an inclined axis. As the drum rotates, pieces of the solid fertilizer take on small spherical shapes. They are passed through a screen that separates out adequately sized particles. A coating of inert dust is then applied to the particles, keeping each one discrete and inhibiting moisture retention. Finally, the particles are dried, completing the granulation process.

The different types of particles are blended together in appropriate proportions to produce a composite fertilizer. The blending is done in a large mixing drum that rotates a specific number of turns to produce the best mixture possible. After mixing, the fertilizer is emptied onto a conveyor belt, which transports it to the bagging machine.

Bagging

Fertilizers are typically supplied to farmers in large bags. To fill these bags the fertilizer is first delivered into a large hopper. An appropriate amount is released from the hopper into a bag that is held open by a clamping device. The bag is on a vibrating surface, which allows better packing. When filling is complete, the bag is transported upright to a machine that seals it closed. The bag is then conveyored to a palletizer, which stacks multiple bags, readying them for shipment to distributors and eventually to farmers.

Quality Control

To ensure the quality of the fertilizer that is produced, manufacturers monitor the product at each stage of production. The raw materials and the finished products are all subjected to a battery of physical and chemical tests to show that they meet the specifications previously developed. Some of the characteristics that are tested include pH, appearance, density, and melting point. Since fertilizer production is governmentally regulated, composition analysis tests are run on samples to determine total nitrogen content, phosphate content, and other elements affecting the chemical composition. Various other tests are also performed, depending on the specific nature of the fertilizer composition.

Byproducts/Waste

A relatively small amount of the nitrogen contained in fertilizers applied to the soil is actually assimilated into the plants. Much is washed into surrounding bodies of water or filters into the groundwater. This has added significant amounts of nitrates to the water that is consumed by the public. Some medical studies have suggested that certain disorders of the urinary and kidney systems are a result of excessive nitrates in drinking water. It is also thought that this is particularly harmful for babies and could even be potentially carcinogenic.

The nitrates that are contained in fertilizers are not thought to be harmful in themselves. However, certain bacteria in the soil convert nitrates into nitrite ions. Research has shown that when nitrite ions are ingested, they can get into the bloodstream. There, they bond with hemoglobin, a protein that is responsible for storing oxygen. When a nitrite ion binds with hemoglobin, it loses its ability to store oxygen, resulting in serious health problems.

Nitrosamines are another potential byproduct of the nitrates in fertilizer. They are the result of a natural chemical reaction of nitrates. Nitrosamines have been shown to cause tumors in laboratory animals, feeding the fear that the same could happen in humans. There has, however, been no study that shows a link between fertilizer use and human tumors.

The Future

Fertilizer research is currently focusing on reducing the harmful environmental impacts of fertilizer use and finding new, less expensive sources of fertilizers. Such things that are being investigated to make fertilizers more environmentally friendly are improved methods of application, supplying fertilizer in a form which is less susceptible to runoff, and making more concentrated mixtures. New sources of fertilizers are also being investigated. It has been found that sewage sludge contains many of the nutrients that are needed for a good fertilizer. Unfortunately, it also contains certain substances such as lead, cadmium, and mercury in concentrations which would be harmful to plants. Efforts are underway to remove the unwanted elements, making this material a viable fertilizer. Another source that is being developed is manures. The first fertilizers were manures, however, they are not utilized on a large scale because their handling has proven too expensive. When technology improves and costs are reduced, this material will be a viable new fertilizer.

Sugar Manufacturing Operations

2.1 Cane handling
2.2 Milling
2.3 Clarification/evaporation
2.4 The pan stage
2.5 The fugal stage
2.6 Final sugar
2.7 Energy supply systems
2.8 Associated operations

A sugar mill is a large factory used to produce raw sugar and other products from sugar cane. Mills are made up of a range of industrial plant such as boilers, storage and processing vessels, crushing and hammer mills and a large range of maintenance equipment. Mills operate in two distinct modes, crushing and non-crushing, both of which introduce a range of specific and general hazards to employers, workers and others. In essence, a sugar mill can be broken into the following processes (see Figure 2 for a diagram that shows the sugar milling process).

2.1 Cane handling

Cane handling describes the methods used to move cane billets into the milling section of the process. Billets are transported and stored using items such as:

1. cane railway bins
2. road transport systems (such as multi-lifts and semi trailers)
3. in field transporters.

The cane billets are then transferred into the milling system by:

1. trans-loaders (such as from road to rail)
2. tipplers (tipping cane bins into carriers)
3. direct tip into the carrier (by infield transporters and road transport).

Rail transfer methods use large hydraulic systems to push or pull rakes of bins into the tippler which tips them onto a ‘carrier’ (a moving floor conveyor). Most mills have storage yards for excess bins. Tipplers are a rotary device which hold the rail bin in place and turn it 180 degrees to empty its contents into the main conveyor (carrier).

2.2 Milling

The milling process involves the initial breakdown of cane into its primary fibres by a large hammer mill (shredder). Shredders consist of a number of large hammers (usually around 12 kg in weight) attached to a rotor by swing rods which are then driven at around 1200 revolutions per minute (rpm) by mechanical means (either by steam turbine or electric motor). The billets are shredded by smashing them between the hammers and the grid bar (a hard set of plates on one side of the shredder) breaking them into individual strands of fibre. This fibre is then processed through a series of crushing mills to extract juice. Mill rollers exert huge forces on the shredded cane which is fed through them via a vertical chute. The pressure between the rollers is large enough to break down the cell structure of the fibres so that the sucrose can be extracted within the juice. Juice contains a large amount of water which is removed or reduced in subsequent processes. The remaining fibre is then burned in a boiler to produce steam which drives most mill processes in a typical factory.

Extraction of as much of the sucrose as possible is a key element in milling. Mills use a number of methods to aid sugar extraction which include the application of hot water (around 95ْ C) to the fibre within the mill set, a series of crushing mill sets (the milling train) and reapplication of mixed juice and water (maceration) throughout the milling process.

2.3 Clarification/evaporation

The clarification/evaporation stage executes a number of functions such as:

• mixed juice incubation
• adjusting PH by addition of lime
• heating
• addition of flocculant (a product which assists contaminants to subside)
• addition of anti-scale chemicals
• removal of mud and heavy contaminants
• reduction of water levels in the juice.

Heating is completed using shell and tube heaters that are normally either cylindrical units with multiple passes for juice in tubes surrounded by steam (allowing thermal transfer between the two products) or multi-path plate and frame commercial units that are smaller than conventional heaters and are constructed from pressed SS sheets separated by gasket material.

Lime and flocculant are usually added to the juice as a slurry. A subsider then removes heavy contaminants from the juice. Subsiding, the process of allowing heavy materials to sink or fall to the bottom, usually removes the majority of dirt and the chemical mud formed from the reaction between the phosphate in the juice and the added lime from juice. The mud is then spread across a moving filter (a rotary drum filter) and ‘washed’ to leech out any remaining sucrose before removal from the factory. Mill mud is a nutrient rich product which is normally returned to the field.

The effet stage consists of a number of evaporators (large kettles) in series that boil the juice to reduce the water content. Effets are constructed in a particular pattern using multiple effet evaporation. Vapour produced from each vessel is used to boil the juice in the subsequent vessel at a lower pressure making maximum use of the energy initially put into the first vessel as low pressure steam. The latter effets in the set are operated at a vacuum in order to reduce the boiling point. The final product from the effet stage is usually known as ’liquor’ or ‘syrup’ and is a dark gold coloured liquid.

Dependent on juice properties heating surfaces within the effets and contact heaters are prone to contaminant build up (scale) which reduces heating efficiencies and after a period needs to be removed. Most factories use a chemical process to remove scale build up, normally by boiling caustic soda in the vessels or other chemical means such as sulphamic acid or rarely EDTA. On some occasions manual cleaning is required and is completed by blasting with high pressure water or mechanical brushing.

2.4 The pan stage

The pan stage is a similar process to the effets in that a pan boils off additional water. The main function of the pan stage is to produce sugar crystal from the liquor. In order to increase the speed of this process the pan stage operates in a manner which utilises ’seed crystal’ and a combination of products with varying levels of sugar content to produce a range of crystal sizes and hence qualities. The pan stage has many storage tanks such as receivers (tanks which receive product from the pans), crystallisers (a series of tanks and stirrers which cool the product from the pan stage resulting in additional crystal growth before fugaling) and large transfer pipes and valves.

2.5 The fugal stage

A fugal is a large electric centrifuge which spins up to 1200 revolutions per minute (rpm) dependent on its function and stage of operation (while filling batch fugals only turn at around 50 rpm). There are two types of centrifuge in use within sugar mills, high grade centrifuges (usually batch, but sometimes continuous) and low grade centrifuges which are continuous. Continuous fugals maintain a constant flow of product through them while batch fugals fill, operate and then discharge the final product. The fugal stage removes the remaining liquid product which surrounds the crystal, washes the crystal and delivers it into the final sugar system through a series of conveyors and a drier. The material removed during the centrifuge process is known as molasses and has a range of uses including sale as stock feed, fermentation for distillery production and as a component of cattle licks.

2.6 Final sugar

Finally, the sugar crystal is dried and moved to large storage bins awaiting transport to sugar terminals or other areas (such as refineries). Driers are large cylinders which are fluted and rotate to pass the crystal through at an even rate whilst dry air is applied via ducted fans or large air conditioners. Moisture levels and sucrose purity are important measures for sugar quality. Storage bins hold large amounts of raw sugar and the conveyor system supplying them can be directed into different bins dependent on the product type. Low moisture levels in final sugar product and atmospheric conditions can create a risk of sugar dust explosion. Sugar dust explosions are rare, however, they have caused significant damage and loss of life in sugar mills overseas.

2.7 Energy supply systems

Mills are usually powered by steam and subsidised by electrical devices, however in recent years a number of factories are moving to predominantly electric powered equipment. A standard sugar mill will still include equipment such as suspension or multiple fuel boilers, steam turbines, electrical generators and all of the associated distribution equipment for electric and steam power. A range of equipment is associated with steam and electric energy including transformers, high and low voltage distribution systems, protection devices such as circuit breakers, steam relief valves, expansion joints and water traps.

Mills also have extensive air distribution systems supplying general and instrument air.

2.8 Associated operations

A range of facilities associated with sugar production are located on site including:

• laboratory and associated processes
• packaging lines
• engineering workshops covering areas such as rolling stock repair, general engineering and fabrication, and electrical
• administration areas
• molasses storage and distribution systems
• water supply and effluent systems
• mud, ash, bagasse and other by-product handling and storage.

Figure 2 The sugar milling process

1. Cane marshalling yard
2. Cane receival
3. Weight bridge tippler and empty bin return system
4. Shredder
5. Milling train
6. Juice heater
7. Evaporator station
8. Filtration
9. Crystallisation and separation
10. Bulk sugar handling
11. Bagasse storage bin
12. Boiler station

How Paper is Made

A schematic of the papermaking process is shown below. In this case, a chemical pulping process is depicted. However, if the digester, blow pit, and washer were replaced with a mechanical refiner, the drawing would also describe a mechanical pulp and paper mill. (Move your mouse across the drawings below to learn more about the processes shown.)

Note that once the wood has been converted to pulp, the pulp is beaten (more on this in a moment), refined in a Jordan refiner, and then sent to a large machine where a slurry of fiber is metered onto a moving wire. In this machine, called a Fourdrinier, a slurry that is 99% water by weight flows from the head box onto the wire, after which suction boxes pull water rapidly away. The result is a fiber mat that is then pressed, dried, coated and/or sized, re-pressed, and cut into desired sizes of paper.

A Fourdrinier unit is pictured here. A slurry of fiber is being metered onto the moving wire at the far right in this picture, with movement of the wire toward the left. The drier units can be seen at the far end of the production line. (Photo courtesy: American Forest and Paper Association)

The beating and refining processes are very important in the papermaking process. An examination of beating, in particular, provides several insights as to some of the technology involved.

This is a photo of softwood that has been chemically pulped. Note that the fibers are straight, smooth, and largely undamaged.

For the most part, however, smooth surfaces and rounded, undamaged fiber are not what is needed in making a quality sheet of paper. Fibers must be flattened to increase the contact area (and thus the bond potential) between them.
Flattened fibers can be readily seen in this highly magnified photo of the surface of paper. (Photo by John Crist and Ron Teclaw)
Moreover, by unraveling microfibrils from the cell walls, surface area (and thus hydrogen bonding potential) can be greatly increased as illustrated by this photo of mechanically produced fiber. (Photo: John Crist and Ron Teclaw)
The way that fibers are flattened, and subjected to a mechanical rubbing action that unravels microfibrils, is through the use of a beater. A simple beater (a Hollander beater) is shown here. A slurry of fiber goes around and around in the tub, each time passing between a fixed bedplate and the ribs of a rotating beater wheel. The opening between the bedplate and wheel is set to about the width of a single wood fiber, meaning that fibers are pounded and deformed with each pass. (Image adapted from TAPPI)

The longer fibers remain in the beater, the more beat-up they become, and the more the surface area of the fiber is increased.

Cement Process

Raw Materials The main raw materials used in the cement manufacturing process are limestone, sand, shale, clay, and iron ore. The main material, limestone, is usually mined on site while the other minor materials may be mined either on site or in nearby quarries. Another source of raw materials is industrial by-products. The use of by-product materials to replace natural raw materials is a key element in achieving sustainable development. Raw Material Preparation Mining of limestone requires the use of drilling and blasting techniques. The blasting techniques use the latest technology to insure vibration, dust, and noise emissions are kept at a minimum. Blasting produces materials in a wide range of sizes from approximately 1.5 meters in diameter to small particles less than a few millimeters in diameter. Material is loaded at the blasting face into trucks for transportation to the crushing plant. Through a series of crushers and screens, the limestone is reduced to a size less than 100 mm and stored until required. Depending on size, the minor materials (sand, shale, clay, and iron ore) may or may not be crushed before being stored in separate areas until required. Raw Grinding In the wet process, each raw material is proportioned to meet a desired chemical composition and fed to a rotating ball mill with water. The raw materials are ground to a size where the majority of the materials are less than 75 microns. Materials exiting the mill are called "slurry" and have flowability characteristics. This slurry is pumped to blending tanks and homogenized to insure the chemical composition of the slurry is correct. Following the homogenization process, the slurry is stored in tanks until required. In the dry process, each raw material is proportioned to meet a desired chemical composition and fed to either a rotating ball mill or vertical roller mill. The raw materials are dried with waste process gases and ground to a size where the majority of the materials are less than 75 microns. The dry materials exiting either type of mill are called "kiln feed". The kiln feed is pneumatically blended to insure the chemical composition of the kiln feed is well homogenized and then stored in silos until required. Pyroprocessing Whether the process is wet or dry, the same chemical reactions take place. Basic chemical reactions are: evaporating all moisture, calcining the limestone to produce free calcium oxide, and reacting the calcium oxide with the minor materials (sand, shale, clay, and iron). This results in a final black, nodular product known as "clinker" which has the desired hydraulic properties. In the wet process, the slurry is fed to a rotary kiln, which can be from 3.0 m to 5.0 m in diameter and from 120.0 m to 165.0 m in length. The rotary kiln is made of steel and lined with special refractory materials to protect it from the high process temperatures. Process temperatures can reach as high as 1450oC during the clinker making process. In the dry process, kiln feed is fed to a preheater tower, which can be as high as 150.0 meters. Material from the preheater tower is discharged to a rotary kiln with can have the same diameter as a wet process kiln but the length is much shorter at approximately 45.0 m. The preheater tower and rotary kiln are made of steel and lined with special refractory materials to protect it from the high process temperatures. Regardless of the process, the rotary kiln is fired with an intense flame, produced by burning coal, coke, oil, gas or waste fuels. Preheater towers can be equipped with firing as well. The rotary kiln discharges the red-hot clinker under the intense flame into a clinker cooler. The clinker cooler recovers heat from the clinker and returns the heat to the pyroprocessing system thus reducing fuel consumption and improving energy efficiency. Clinker leaving the clinker cooler is at a temperature conducive to being handled on standard conveying equipment. Finish Grinding and Distribution The black, nodular clinker is stored on site in silos or clinker domes until needed for cement production. Clinker, gypsum, and other process additions are ground together in ball mills to form the final cement products. Fineness of the final products, amount of gypsum added, and the amount of process additions added are all varied to develop a desired performance in each of the final cement products. Each cement product is stored in an individual bulk silo until needed by the customer. Bulk cement can be distributed in bulk by truck, rail, or water depending on the customer's needs. Cement can also be packaged with or without color addition and distributed by truck or rail.

Installation of High Efficiency Dynamic Separator for Raw Mill

Background

The Raw Mill is one of the important equipment in the Cement industry used for grinding Limestone into fine raw meal powder. The older plants had Ball Mills for this operation.

Consequently the energy efficient Vertical Roller Mills ( VRM ) came into being. The VRMs have comparatively 30 – 35 % lower energy consumption than the Ball Mills. In the older Cement plants the VRMs had a simple static separator installed for separation of the coarse and fine material. The separator was an integral part of the VRM.

In the conventional separators, the ground material is lifted to the separator by high velocity hot air at the louvres. The separator separates the coarse and fine particles and fine particles are carried away by the airflow to the dust collectors. The coarse material subsides through the raising freshly ground material. This creates additional pressure drop in the VRM and also leads to increased circulation inside the Mill. The particle size distribution is also wider with both very fine and coarse particles present.

The latest trend has been to install cage type high efficiency separator. In these separators, the material enters radially through a cage type separator. The coarse material after separation is collected in a cone just below the separator and is dropped on to the grinding table through a gravity air lock. In this manner the contact between the freshly ground material and the coarse is avoided. The advantages of these separators are as below.

Closer particle size distribution

Less pressure drop across the VRM

Higher output at the same fineness as before or finer product at the same output rate

Previous status

In a million tonne dry process pre-calciner plant, a Vertical Roller Mill ( VRM ) was being used for grinding raw meal. The VRM had a conventional static separator.

Energy saving project

The existing static separator was replaced with a new cage type dynamic high efficiency separator.

Implementation methodology & time frame

The new separator could not be accommodated in the Mill body. So the Mill casings were modified to accommodate the new separator. Hence, to save on time the drawings were prepared and the new separator assembled outside and kept ready for installation.

With all these preparations, the actual installation needed only 21 days of Mill stoppage.

Benefits of the project

There was an increase in the output of the Mill , finer product and reduction in the specific power consumption of the Mill. Additionally, the Mill vibration also got reduced resulting in trouble free operation. The comparison of the conditions and the power consumption before and after installation of the dynamic high efficiency separator are as below:

Parameter	Before Implementation	After Implementation
Feed Rate	200 TPH	225 TPH
Raw Meal Residue
• 90 Microns	18 – 18.5 %	17 – 18 %

• 212 Microns	2.2 – 2.5 %	2.0 – 2.2 %
Mill DP	500 – 520 mmWg	480 – 500 mmWg
Mill Vibration	1.6	0.75
Power Consumption	24.5 units / ton	22.0 units / ton

The power saving amounted to 2.5 units / ton of Raw meal or 3.0 units / ton of Cement which annually amounted to 18 lakh units / year.

Financial analysis

This amounted to an annual monetary saving (@ Rs 3.0 /unit) of Rs 54.0 lakhs. The investment made was around Rs 60 lakhs. The simple payback period for this project was 13 months.

Benefits of high efficiency separator

Closer particle size distribution

Low pressure drop across VRM

Higher output at same fineness (or) same output with finer product.

Cost benefit analysis

Annual Savings - Rs. 54.0 lakhs

Investment - Rs. 60.0 lakhs

Simple payback - 13 months

TECHNOLOGICAL ADVANCEMENTS IN INDIAN CEMENT INDUSTRY

The Indian cement industry is the second largest producer in the world comprising of 130 large cement plants and 206 operating mini cement plants consisting 13 rotary kiln plants and 193 VSK plants. The installed capacity and production during the year 2006-07 are expected to be 180 mn.t and 162 mn.t respectively.

Modernization and technology up-gradation is a continuous process for any growing industry and is equally true for the cement industry. The Indian cement industry today is by and large comparable to the best in the world in respect of quality standards, fuel & power consumption, environmental norms, use of latest technology and capacity. The productivity parameters are now nearing the theoretical bests and alternate means, like alternate fuels and raw materials have to be found to ensure further improvement in productivity and reduce production costs.

Cement industry being energy intensive, the energy conservation and alternate cheaper, renewable and environmentally friendly sources of energy have assumed greater importance for improving productivity. The major challenges confronting the industry today are raging insecurity in indigenous fuel availability, perennial constraints like higher ash content, erratic variations in quality of indigenous coal and inconsistent power supply with unpredicted power cuts. Keeping these challenges in view, the efforts by the industry towards energy conservation and finding alternate cheaper, renewable and environmentally friendly sources of energy are given utmost importance.

Review of Technological Status

Process Profile

The Cement Industry today comprises mostly of Dry Suspension Preheater and Dry-Precalciner plants and a few old wet process and semi-dry process plants. Till late 70’s the Cement Industry had a major share of production through the inefficient wet process technology. The scenario changed to more efficient large size dry process technology since early eighties. In the year 1950, there were, only 33 kilns out of which 32 were based on wet process and only one based on semi-dry process. Today, there are 162 kilns in operation out of which 128 are based on dry process, 26 on wet process and 8 on semi-dry process.

Changing Process Profile of Indian Cement Industry

Item	1950	1960	1970	1983	1995	2001	2006
Wet Process Number of Kilns	32	70	93	95	61	32	26
Capacity (TPD)	9151	25011	38441	39641	25746	13910	11420
% of Total	97.3	94.4	69.5	41.1	12	5	3
Dry Process Number of Kilns		1	18	50	97	117	128
Capacity (TPD)		300	11865	51265	188435	282486	375968
% of Total		1.1	21.5	53.2	86	93	96
Semi-Dry Process Number of Kilns	1	3	8	9	8	8	8
Capacity (TPD)	250	1200	5000	5500	5244	5260	4195
% of Total	2.7	4.5	9	5.7	2	2	1
Total Kilns	33	74	119	154	166	157	162
Capacity (TPD)	9401	26511	55306	96406	219425	310706	391583
Average Kiln Capacity (TPD)	285	358	465	626	1322	1921	2417

Kiln Capacity and Size

The economic unit capacity for cement plants in India till early sixties was about 300 TPD. In mid sixties this was standardized at around 600 TPD for both wet and dry process plants. About a decade later, i.e. from mid seventies, the new plants installed were of 1200 TPD capacity. The advent of precalciner technology in mid eighties provided an opportunity to the industry to modernize and increase the capacity of existing dry process plants, to convert plants from wet to dry process as well as to set up large capacity plants incorporating the latest technological advancements. This led to installation of single line kilns of 3000 TPD (1 MTPA) capacity and more. The present trend indicates the preference of still larger kilns of about 6000 TPD capacity and above. Already there are nine kilns of 8000 tpd capacity in operation and three kilns of capacity 10000 – 12000 TPD are under installation. The green-field plants being installed now are based on most advanced and the best available technology.

Plants with a total capacity of two million tonne and above at a single location, numbering 25, are having a total capacity of 65.6 MTPA accounting for 41% of installed capacity of large plants, whereas plants with a capacity between 1 to 2 million tonnes, numbering 48 are having a total capacity of 68.4 MTPA, accounting for 43% of installed capacity. Balance 57 plants are of capacity less than 1 MTPA, having a total capacity of 25.8 MTPA, accounting for 16% of total installed capacity of large cement plants.

Average annual installed capacity per plant in India is about 1.2 MTPA as against more than 2.1 MTPA in Japan. This is due to blend of small and large plants coming up at various stages and still operating in India as against smaller plants having been decommissioned in Japan.

Present Status of Technology

A comparison of the status of the modernization in equipment and also the technologies absorbed or implemented by the Indian cement industry alongwith status of Global Technology is as under :

Present Status of Technology

	Low Technology Plants	Modern Plants	Global Technology
Mining & Material Handling	Conventional	Computer aided	Computer aided
Crushing	Two stage	Single stage	In-pit crushing & conveying
Conveying of Limestone	Dumpers/Ropeway/ Tippers	Belt conveyors	Pipe conveyors, Belt conveyors
Grinding	Ball Mills with / without conventional classifier	VRM’s Roll Presses with dynamic classifier	VRM’s, Roll Presses, Horo Mills with dynamic classifier
Pyro Processing	Wet Semi Dry Dry - 4 stage preheater - Conventional cooler - Single channel burner	Dry - 5/6 stage preheater - High Efficiency Cooler - Multi Channel Burner	Dry - 6 stage preheater - High Efficiency Cooler - Multi Channel Burner - Co-processing of WDF - Co-generation of power - Low NOx/SO2 emission technologies
Blending & Storage	Batch-Blending Silos	Continuous Blending silos	- Continuous Blending - Multi-Chamber Silos - Dome silos
Packing & Despatch	Bag	- Bag - Bulk	- Bulk - Palletizing & Shrink Wrapping
Process Control	Relay Logic / Hard Wired / PLC	- DDC - Fuzzy Logic expert system	- DDC - Neurofuzzy expert system
Plant Size, TPD	300-1800	3000-6000	6000-12000

The directions in which the modernization activities are proceeding are as illustrated below :

Mining

For rational exploitation of the raw material source, a systematic mine plan is developed by cement plants. Computer-aided techniques for raw material deposit assessment to arrive at proper extraction sequence of mining blocks, keeping in view the blending operational requirements, are envisaged and put to use in number of units.

Crushing

Mobile crushers have come in use in some of the newer plants, keeping in view the split location of limestone deposits and long conveying distances. The mobile crushing plant is stationed at the mine itself and raw material is crushed at the recovery site.

Grinding

Vertical Roller Mills (VRM) have given the real breakthrough in the area of grinding. The VRM draws 20-30 % less electrical energy as compared to the corresponding ball mill system, apart from its ability to give much higher drying capacity. These mills can accept larger feed size and hence mostly be used with single stage crushing. VRMs are now being used in clinker and slag grinding and also as pre-grinder to existing grinding installations.

Another breakthrough that has come with the application of high pressure grinding rolls (HPGR) has been widely adopted in Indian cement industry. The HPGR is being used as pre-grinder for upgrading the existing ball mill systems. Different modes of operating HPGR in open circuit, pretreatment with circulation, pretreatment with de-agglomeration and recirculation and closed circuit are in operation. Such installations could achieve an increase in capacity upto 200% and savings in power consumption to the extent of 30 to 40% as compared to ball mills.

High efficiency separators are now widely used for better classification of product and help in increasing the mill capacity besides reducing the specific power consumption. The new classifier designs include two stage separation integrating primary and secondary separation. High efficiency separators are also used now with VRM’s for further improvement in their performance.

A new mill system called Horizontal roller mill has been developed which is capable of producing uniform raw meal and have advantages in processing raw materials containing higher percentage of quartz.

Pyro-processing

The introduction of precalciner technology has increased the production from the kiln by 2.0 to 2.5 times and enabled utilization of high ash coals with lower calorific value, as well as various agricultural and industrial combustible wastes. Systems have been developed to use fuels like lignite and petcoke and various alternate fuels.

The advantages of economy of scale are fully exploited by the cement industry through the precalciner technology. Many single kilns capable of producing more than 6000 tpd capacity have already been installed and are operating with state-of-the-art technology and kiln capacities in the range of 10000-12000 tpd are under installation.

Many cement plants have some excess capacity at both upstream and downstream, which could be utilized economically if the kiln output can be increased at modest costs. Traditionally, the kilns have been designed with specific volumetric loading of 1.5 to 2.2 tpd/m³ for SP kilns and 3.0 to 4.0 tpd/m³ for precalciner kilns. The corresponding thermal loads in burning zone for such kilns have remained between 3.5 to 4.5 x 10⁶ Kcal/m²/hr. Many cement plants have gradually increased the specific volumetric loading upto 7-7.5 tpd/m³, ensuring much higher than originally designed output.

The introduction of high efficiency and low pressure-drop-cyclones have led to conversion of conventional 4-stage cyclone preheaters to 5-stage and even 6-stage cyclone preheaters with improved thermal efficiency.

The latest development like controlled flow grate clinker cooler system and cross bar cooler ensure better clinker distribution, increase in cooler heat recuperation efficiency, decrease in clinker exit temperature and reduced maintenance costs.

The limitations of the conventional straight pipe burner have been overcome by use of highly flexible multi-channel burner. The multi-channel burner enables easy and sensitive flame shape adjustments as well as gives rise to better entrainment of secondary air.

High Alumina refractory bricks which were mostly used in pre-heating / precalcining zone in the past, are now replaced by light weight high strength insulating bricks. The Aluminum-Zirconium-Silicate bricks with coating repellent properties are also in use now in transition zones. With the new improved refractory bricks it is possible to increase the refractory lining life and reduce the radiation losses in the kiln. Greater use of monolithic refractories in preheater, precalcinator, cooler, kiln outlet zone etc. is in practice now.

Conventional analog instrumentation is gradually being replaced with digital instrumentation. The large mimic diagrams used of late are being replaced by cathode ray tube (CRT) display. Motor control by relay sequence is being changed to programmable logic controllers. Analog PID controllers are being replaced with multi-loop digital controllers. Due to the advent of microprocessors, a variety of advanced control concepts like adaptive control, self-tuning control, feed forward control, etc. have been introduced in the Indian cement industry.

As a corollary to automation, quality is also maintained by continuous monitoring of the raw mix composition with the help of X-ray analyzer and automatic proportioning of raw mix components. New type of on-line bulk material analyzers have also been developed based on Prompt-Gamma-ray Neutron Activation Analysis (PGNAA) for giving maximum control over raw mix. The analyzer quickly and reliably analyses the entire flow-on-line providing real time results. The latest trends in on-line quality control include computers and industrial robots for complete elemental analysis by X-ray fluorescence, on-line free lime detection and particle size analysis by latest instrumental methods and x-ray diffraction techniques respectively.

It is also important to phase out the manual sampling systems especially so when the super high capacity plants are being installed. Auto sampler technology should be dovetailed into the plants for ensuring disciplined sampling and control.

Upgradation of Technology of Low Technology Cement Plants

The technological spectrum in the industry is very wide. At one end of the spectrum are the old wet process plants, while at the other end, are the new state-of-the-art technology plants presently being built by the Industry. In between these two extremes, are the large number of dry process plants built during the period 1965-90. These plants could not fully modernize or upgrade side by side with advent of newer technologies and had thus remained at intermediate technology level. Also, the level of technology is not same at all the plants built during the same period.

Majority of the cement plants in the country in the capacity range of 0.4 to 1.0 MTPA were set up more than 15-20 years ago i.e. before 1990’s. They were based on state-of-art technology at that time. Since then, numerous developments have taken place in the cement manufacturing technology.

Though some of the old plants have been modernized to a limited extent by retrofitting the new technologies, substantial scope still exists for adopting the state-of-art technologies and bringing the old plants at par with world-class plants in terms of productivity, energy efficiency and environment friendliness, leading to cost competitiveness.

Moreover, the emission norms are likely to become more stringent in future and at the same time, the cement plants will be required to utilize waste derived raw materials and fuels to a large extent. The modifications of old plants to comply with these future requirements will also become inevitable. Therefore, there is a need to carry out a comprehensive assessment of all the earlier generation plants in the country to identify the extent of modernization required to improve their all round efficiency and enable them to meet the future criteria of viability, competitiveness and compliance with regard to energy consumption enabling them to comply with the provision of the Energy Conservation Act 2001.

Perceived Benefits of Technology Upgradation

It is envisaged that the technology upgradation measures for the Pre-1990 era cement plants would result in :

Increase in capacity : 25-30 MTPA

Reduction in thermal energy consumption : 15-20 kcal/kg clinker

Reduction in electrical energy consumption : 5-10 units/t

Reduction in cost of production of cement : 5-10% because of above initiatives

Reduction in energy costs through co-processing : 10–15%

Reduction in the CO₂ emissions : 20%

(through blended cements & energy conservation)

Future Modernization Needs of the Indian Cement Industry

Although the industry has largely set up plants with energy efficient equipment, there are still some areas for further improvements like:

Appropriate pre-blending facilities for raw materials

Fully automatic process control and monitoring facilities including auto samplers and controls.

Appropriate co-processing technologies for use of hazardous and non hazardous wastes

Interactive standard software expert packages for process and operation control with technical consultancy back-up

Energy efficient equipment for auxiliary/minor operations

Mechanized cement loading operations, palletization/shrink wrapping

Bulk loading and transportation, pneumatic cement transport

Low NO_x/SO₂ combustion systems and precalciners

Standards for making composite cement so that all the flyash and other industrial wastes viz. slag are fully used.

Co-generation of power through cost-effective waste heat recovery system (only one demonstration unit in operation)

Horizontal roller mills (Horo Mills) for raw material and cement grinding

Advanced computerized kiln control system based on artificial intelligence

Fuel Requirements and Alternate Sources of Energy

Fuel

Coal continues to be the main fuel for the Indian cement industry and will remain so in the near future as well. The industry is mainly using coal from various coalfields in the country. It is also procuring coal through open market and direct imports. Lignite from deposits in Gujarat and Rajasthan is also being used by cement plants. Pet coke has also been successfully utilized by some cement plants, mainly in Gujarat, Rajasthan and MP, thereby substituting main fossil and conventional fuel coal upto 100% in some plants. In the recent past, waste derived fuels including hazardous combustible wastes have also been tried due to economic pressures in cement manufacturing process owing to tough competition in domestic and global markets as well as ecological reasons on account of waste disposal and co-processing in cement rotary kilns being most effective mode of waste treatment.

Use of Industrial Wastes

i) Cement plants in India utilized about 19% of flyash generated by power plants and 100% of granulated slag generated by steel plants (year 2005-06), as compared to almost 100% flyash and 84% of granulated slag in the Japanese cement industry.

ii) Recycling of Industrial wastes in manufacture of cement is highest in Japan followed by India.

Use of Alternate Fuels

i) Use of hazardous and refuse derived combustibles and Municipal Solid Waste (MSW) as fuel is common in countries like Canada, EU, Japan and Korea, but regulations do not yet permit in India.

ii) CPCB is actively engaged in plant level trials in respect of wastes viz. used tyres, refinery sludge, paint sludge, Effluent Treatment Plant (ETP) sludge and Toluene Di-Isocyanite (TDI) tar waste from petroleum industries and in formulation of guidelines for use of these wastes as fuel by cement industry.

Energy Management

The industry’s average consumption in 2005-06 was 725 kcal/kg clinker thermal energy and 82 kWh/t cement electrical energy. It is expected that the industry’s average thermal energy consumption by the end of Year 2011-12 will come down to about 710 kcal/kg clinker and the average electrical energy consumption will come down to 78 kWh/t cement.

The best thermal and electrical energy consumption presently achieved in India is 667 kcal/kg clinker and 68 kWh/t cement which are comparable to the best figures of 650 kcal/kg clinker and 65 kWh/t cement in a developed country like Japan.

The improvements in energy performance of cement plants in the recent past have been possible largely due to :

Retrofitting and adoption of energy efficient equipment

Better operational control and Optimization

Upgradation of process control and instrumentation facilities

Better monitoring and Management Information System

Active participation of employees and their continued exposure in energy conservation efforts etc.