Indian Patents. 277904:"A SYSTEM AND METHOD FOR RECOVERY OF WATER, LATENT AND SENSIBLE HEAT IN QUENCHING PROCESS FOR MANUFACTURE OF WHITE CEMENT CLINKER"

Title of Invention	"A SYSTEM AND METHOD FOR RECOVERY OF WATER, LATENT AND SENSIBLE HEAT IN QUENCHING PROCESS FOR MANUFACTURE OF WHITE CEMENT CLINKER"
Abstract	The invention provides a process for manufacturing white cement which includes steps of recovering flue gases generated during the quenching and drying process, extracting heat from the recovered flue gases to obtain water condensate and to generate electrical energy.

Full Text	FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2006 COMPLETE SPECIFICATION (See section 10 and rule 13) A PROCESS FOR MANUFACTURING WHI TE CEMENT GRASIM INDUSTRIES LTD an Indian company of Birlagram, Nagda 456 331, Madhya Pradesh, India THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION FIELD OF INVENTION The present invention relates to manufacturing of white cement. The invention envisages recovery of heat and water from waste heat source generated in the production of white cement. BACKGROUND White ordinary Portland cement known is an important raw material used in the construction of a building. White cement with the exception of whiteness has the same properties as Gray ordinary Portland cement. It is as durable and strong as Gray ordinary Portland cement but has high degree of whiteness. Obtaining this color requires substantial modification to the method of manufacture, and because of this, it is somewhat more expensive than the gray product. White Portland cement is used in combination with inorganic pigments to produce brightly colored concretes and mortars. White Cement is used in decorative works and also wherever vibrant colors are desired. White Cement is used to fill up the gaps between marble and ceramic tiles for a smoother and more beautiful finish. The characteristic greenish-gray to brown color of ordinary Portland cement derives from a number of transitional elements in its chemical composition. These are, in descending order of coloring effect, chromium, manganese, iron, copper, vanadium, nickel and titanium. The amount of these in white cement is minimized as far as possible. Cr203 is kept below 0.003%, Mn203 is kept below 0.03%, and Fe203 is kept below 0.35% in the clinker. Portland cement is usually made from quarried raw materials, and these usually contain substantial amounts of Cr, Mn and Fe. For example, limestones used in cement manufacture usually contain 0.3-1% Fe203, whereas levels below 0.1% are sought in limestones for white cement manufacture. In general, the rotary kilns used to chemically combine the raw materials are operated at a higher peak temperature (1450-1500°C) than that required for gray clinker manufacture (1400-1450°C). This requires a higher fuel consumption (typically 20-50% more). The reason for this is the relatively small amount of liquid produced during sintering, because of the low iron-content of the mix. In cases where in the clinker Fe203 content is above 0.2% (which is almost always the case), the unique processes of "quenching" is also employed. In white clinker production, where the iron content is low, this is not an issue. Subsequently, to prevent the re-oxidation of the iron, "quenching" is performed. This consists of rapidly lowering the clinker temperature from 1200°C to below 600°C in a few seconds, as it leaves the kiln. This usually involves dropping it into cold water. This contributes to the relatively poor energy efficiency of the process, since the sensible heat of the clinker is not recycled as in normal clinker manufacture. The various raw materials required for the production of White Cement are: Limestone, Clay, Sand, Iron Ore, Nickel, Titanium, Chromium and Vanadium. The important Unit operations involved in the process of making white cement are as follows: 1. Crushing 2. Blending 3. Grinding 4. Pre heating and Burning 5. Quenching and drying 1. CRUSHING: Limestone sourced from mines is crushed in specific size (it is passed 100% through +50 mm sieve for vertical roller mil), in accordance with the grinding equipment requirement and conveyed through a belt conveyor to the stacker for homogenization. 2. BLENDING: Crushed limestone, clay, sand and other additives are blended. 3. RAW MATERIAL GRINDING: Blended raw materials (Lime stone + Clay) are fed to a grinding mill through hoppers and weigh feeders to get a desired proportion of each material. Ground material is collected in a blending silo for storage and homogenization. The fineness of the ground material may vary from 6.0% to 11% as per the acceptance of the burning equipment specifications. 4. PREHEATING AND BURNING: Homogenized material from the blending silo is extracted from below and fed at the top of the preheater. The preheater section consists of a series of cyclones with a Pre-calcinator and flow of the material and gas in the pre heater is counter current. Fuel is fired in the pre-calcinator to provide heat for preheating and de-carbonation. Before entering in the kiln for burning, 70 to 85% of the de-carbonation is completed. Fuel is fired in the kiln and pre-calcinator for preheating, de-carbonation and burning of the material. Normally oil is used as a fuel in white cement process, alternate fuels, like petroleum coke, rubber, agro waste, can also be used in white cement process due to high cost of oil. In the kiln sintering zone, fully calcined material is burned at 1500-1600 °C resulting in formation of clinker granules with all the essential constituents likeC3S, C2SandC3A. 5. QUENCHING AND DRYING: The ciinker formed in the kiln is then discharged in a Quencher or Decoloriser for water quenching. Quenching is carried in a reducing atmosphere. In grey cement clinker is cooled by air while in white cement clinker is cooled in water in the absence of air. 6. CEMENT GRINDING :- The clinker is next ground to cement (perhaps after a drying stage). Here Calcium sulfate is added to the control set, in the form of a high-purity grade of gypsum or anhydrite.Ceramic grinding media is preferred in the case of white cement grinding in place of high chrome grinding media for avoiding the detonation of cement whiteness. In the white cement process cement plants the quantity of heat lost from preheater exist gases ranges from 180 to 250 kCal/ kg clinker at a o temperature range of 300 to 400 C. In addition, 80 to 350kCal/ kg clinker o heat is lost at a temperature range of 200 to 300 C from exist gases of cooler-(decoloriser /dryer) Figure 1 illustrates a flow diagram of a conventional white cement manufacturing process. The raw material (typically limestone along with other materials) is fed in to the crusher/ stacker and reclaimer for crushing. The raw material from crusher enters the raw mill for fine crushing and drying and finally enters in to a kiln for heating. The clinker from the exit of the kiln is quenched with the help of water in a cooler (decoloriser /dryer) and finally enters the cement grinding station. In the conventional white cement manufacturing process the exhaust gases at raw mill, kiln and cooler (decoloriser/ dryer) are discharged in to atmosphere through Electrostatic precipitators (ESP) /Bag House. Figure 2 illustrates a white cement manufacturing plant at operating condition. In conventional white cement manufacturing process the white clinker formed from a kiln is discharged to a decoloriser or quencher for water quenching. The white clinker is cooled in a decoloriser with the help of water in the absence of air to avoid deterioration in whiteness. The temperature of the clinker at the discharge of the kiln is around 1200-1400°c. The temperature of the clinker at the discharge of dryer after quenching process is around 150-200°C. During the quenching process there is formation of super heated steam along with other gases and clinker dust. This steam with dust laden gases (55% steam + 45% air) is taken to an ESP/Bag House through cyclones and then discharged into the atmosphere. The kiln exhaust gases at 150 to 250°C are discharged into atmosphere through ESPs/ Bag House. Although there has been several reported studies for recovery of waste heat from the Preheater and cooler area in grey cement, there has been no work done to recovery of waste heat from coolers (the decoloriser and the dryer) which are unique to white cement. The exhaust gases at the coolers stage is at low temperature and laden with steam and heavy dust. This waste heat can be effectively utilized for electric power generation. Besides mitigating the problem of power shortage, this method of heat recovery for power generation will also help in energy conservation as well as reducing green house gas emissions. Therefore, there is felt a need for a system and method to extract the energy content and water content that is being wasted and to effectively generate power from the waste heat source in a white cement manufacturing plant. OBJECT OF THE INVENTION The main object of the present invention is to develop a process for manufacturing white cement whereby the heat generated during the process is extracted and utilized for generating electric energy and water. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a process for manufacturing white cement which includes the steps of: • forming cement clinker and feeding the cement clinker at 1100 C to 1400°C to a quencher in which the clinker is decolorized by quenching falling clinker with water spray in the absence of air; • recovering superheated steam laden gases produced in the quencher and dryer; • leading the quenched clinker to a dryer; • using the recovered steam laden gases in the dryer to dry the clinker ; • recovering flue gases at a temperature of 160 C -220 C from the dryer after they have extracted moisture from the clinker; • extracting specific and sensible & latent heat from the flue gases via a heat exchanger; • separating the dust particles from the flue gases either before or after heat extraction; • condensing the moisture in the flue gases to obtain water; and • using the water for the water spray in the quencher or in the process. Typically, the quenched clinker contains moisture in the range of 10 to 15%. The flue gases recovered from dryer contains 40 to 50 % moisture. The dust particles are separated by passing the flue gases through a cyclone and a filter bag. Typically, the dust content in the flue gases is reduced to less than 5mg/m3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention envisages a system and method to reduce the energy and water that is being wasted and to effectively generate power from a waste heat source in a white cement manufacturing plant. There are several ways to extract waste heat from process stream e.g, Waste heat recovery boilers, recuplators, Heat disc etc. In the white cement Industry waste heat source temperature are at lower ranges but have high heat content because it contains low temperature steam with good amount of latent heat, this needs a special thermodynamic cycle for extraction of heat and collection of condensate from the cooler exhaust gases. A Thermodynamic cycle such as the Rankine cycle converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 80% of electric power used throughout the world including virtually all solar thermal, biomass, coal and nuclear power plants. The Kalina cycle is a thermodynamic cycle for converting thermal energy to mechanical power, optimized for use with thermal sources which are at a relatively low temperature compared to the heat sink (or ambient) temperature. The cycle uses a working fluid with at least two components (typically water and ammonia) and a ratio between those components is varied in different parts of the system to increase thermodynamic reversibility and therefore increase overall thermodynamic efficiency. Thermodynamic cycles for waste heat recovery are commonly designed on the Rankine cycle which has been modified using binary fluid of ammonia and water as the working fluid in place of only water for improving the overall efficiency of conventional systems. This modified system is called 'Kalina Cycle'. In this system efficiency gain of upto 50% for low temperature heat sources (200-280 Deg C) and upto 20% for higher temperature heat sources have been observed as compared to conventional Rankine cycle based power plants. Figure 3 illustrates a flow diagram of a white cement manufacturing process in accordance with the present invention. In modified cement manufacturing process the latent and sensible heat in exhaust gases and steam from the exit of cooler (decoloriser/dryer) is recovered along with the recovery of condensate (water). The exhaust gases from the raw mill and kiln are discharged in to atmosphere through ESP/Bag House. Following Raw material are used to make white cement: - 1. Lime Stone -High Carbonate & Low Iron. 2. Clay - High Alumina and Low Iron 3. Oil/Pet Coke/Rubber 4. Gypsum / Salenite The cement clinker is formed by using the above raw materials and following the general method as described earlier. The clinker at a temperature range of 1100 °C to 1400 °C is fed to decolourizer/quencher and is quenched by spraying water on the falling clinker. The water is sprayed through nozzles in controlled manner for sudden cooling of clinker from 1250-1350° C to 200-250° Deg C, this process is carried out in the quencher under suction (in absence of air). Quenching of hot clinker results in formation of super saturated steam along some non-condensable gases. Quenched clinker containing moisture around (10-15%) is fed to dryer where super saturated steam formed during quenching is used for drying of quenched clinker. Retention time of clinker in dryer is 15-20 min. The gases at the exhaust of the dryer contain 45% moisture, 55% non condensable gases. The gases as generated above are passed through a heat exchanger to extract sensible and latent heat form the exhaust gases, leaving behind hot condensate (water). The condensed water is used for quenching purpose again. A heat exchanger is part of special thermodynamic cycle which converts the heat extracted to electrical energy. In one embodiment of the present invention, the gases as generated above are passed through a cyclone for removing clinker dust before passing through a heat exchanger. After passing through cyclone, dust content in the gas stream is in range of 25-35 gms/m3 (160-220° C). A bag filter is further installed at the exhaust of the dryer to reduce dust content in the exhaust gases to less than 5mg/m3. The thermal energy available at the decoloriser fan exit is about 15-17 MW and thermal energy available at the dryer fan exit is about 11-13 MW per hour for an 1800tpd production. With the present invention of extracting latent and sensible heat from the decolorizer/ dryer gases, a large amount of condensate in form of water is recovered (about 30000 -38000 kl/hr) and about 1-5MW of electrical energy can be recovered. Extracted clinker from storage is mixed along with dry Selenite and Gypsum cement setting time retarder, and is fed to the ball mill in a controlled way through weigh feeders and conveyor belts. Roller press or vertical roller mill can also be used for white cement grinding for cost economy. Ceramic grinding media is preferred in case of white cement grinding for avoiding the detonation of cement whiteness. TECHNICAL ADVANTAGES A system and method for recovery of water, latent and sensible heat in quenching process for manufacture of white cement clinker as described in the present invention has several technical advantages including but not limited to the realization of: • a method for recovery of water from waste heat source in a white cement manufacturing plant; a method of generating electricity from waste heat source in a white cement manufacturing plant; and • a method for recovery of thermal energy from waste heat source particularly during quenching and reusing during drying process . While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. We claim: 1. A process for manufacturing white cement which includes the steps of: • forming cement clinker and feeding the cement clinker at 1100°C to 1400°C to a quencher in which the clinker is decolorized by quenching falling clinker with water spray in the absence of air; • recovering superheated steam laden gases produced in the decolorizer; • leading the quenched clinker to dryer; • using the recovered steam laden gases in the dryer to dry the clinker ; • recovering flue gases at a temperature of 160 C -220 C from the dryer after they have extracted moisture from the clinker; • extracting specific, sensible & latent heat from the flue gases via a heat exchanger; • separating the dust particles from the flue gases either before or after heat extraction; • condensing the moisture in the flue gases to obtain water; and • using the water for the water spray in the quenching/ other process . 2. The process as claimed in claim 1, wherein the cement clinker is fed at the temperature range of 1250°C to 1350 °C to the decolourizer. 3. The process as claimed in claim 1, wherein the quenched clinker contains moisture in the range of 10 to 15%. 4. The process as claimed in claim 1, wherein the flue gases recovered from dryer contains 40 to 50 % moisture. 5. The process as claimed in claim 1, wherein the dust particles are separated are separated before heat extraction. 6. The process as claimed in claim 1, wherein the dust particles are separated by passing the flue gases through a cyclone and a filter bag. 7. The process as claimed in claim 5, wherein the dust content in the flue gases is reduced to less than 5mg/m3

Full Text

FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
A PROCESS FOR MANUFACTURING WHI TE CEMENT
GRASIM INDUSTRIES LTD
an Indian company of Birlagram, Nagda 456 331, Madhya Pradesh, India
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION

FIELD OF INVENTION
The present invention relates to manufacturing of white cement. The invention envisages recovery of heat and water from waste heat source generated in the production of white cement.
BACKGROUND
White ordinary Portland cement known is an important raw material used in the construction of a building. White cement with the exception of whiteness has the same properties as Gray ordinary Portland cement. It is as durable and strong as Gray ordinary Portland cement but has high degree of whiteness. Obtaining this color requires substantial modification to the method of manufacture, and because of this, it is somewhat more expensive than the gray product.
White Portland cement is used in combination with inorganic pigments to produce brightly colored concretes and mortars. White Cement is used in decorative works and also wherever vibrant colors are desired. White Cement is used to fill up the gaps between marble and ceramic tiles for a smoother and more beautiful finish.
The characteristic greenish-gray to brown color of ordinary Portland cement derives from a number of transitional elements in its chemical composition. These are, in descending order of coloring effect, chromium, manganese, iron, copper, vanadium, nickel and titanium. The amount of these in white

cement is minimized as far as possible. Cr203 is kept below 0.003%, Mn203 is kept below 0.03%, and Fe203 is kept below 0.35% in the clinker.
Portland cement is usually made from quarried raw materials, and these usually contain substantial amounts of Cr, Mn and Fe. For example, limestones used in cement manufacture usually contain 0.3-1% Fe203, whereas levels below 0.1% are sought in limestones for white cement manufacture.
In general, the rotary kilns used to chemically combine the raw materials are operated at a higher peak temperature (1450-1500°C) than that required for gray clinker manufacture (1400-1450°C). This requires a higher fuel consumption (typically 20-50% more). The reason for this is the relatively small amount of liquid produced during sintering, because of the low iron-content of the mix.
In cases where in the clinker Fe203 content is above 0.2% (which is almost always the case), the unique processes of "quenching" is also employed. In white clinker production, where the iron content is low, this is not an issue. Subsequently, to prevent the re-oxidation of the iron, "quenching" is performed. This consists of rapidly lowering the clinker temperature from 1200°C to below 600°C in a few seconds, as it leaves the kiln. This usually involves dropping it into cold water. This contributes to the relatively poor energy efficiency of the process, since the sensible heat of the clinker is not recycled as in normal clinker manufacture.
The various raw materials required for the production of White Cement are:

Limestone, Clay, Sand, Iron Ore, Nickel, Titanium, Chromium and Vanadium.
The important Unit operations involved in the process of making white cement are as follows:
1. Crushing
2. Blending
3. Grinding
4. Pre heating and Burning
5. Quenching and drying
1. CRUSHING:
Limestone sourced from mines is crushed in specific size (it is passed 100% through +50 mm sieve for vertical roller mil), in accordance with the grinding equipment requirement and conveyed through a belt conveyor to the stacker for homogenization.
2. BLENDING:
Crushed limestone, clay, sand and other additives are blended.
3. RAW MATERIAL GRINDING:
Blended raw materials (Lime stone + Clay) are fed to a grinding mill through hoppers and weigh feeders to get a desired proportion of each material. Ground material is collected in a blending silo for storage and homogenization. The fineness of the ground material may vary from 6.0% to 11% as per the acceptance of the burning equipment specifications.

4. PREHEATING AND BURNING:
Homogenized material from the blending silo is extracted from below and fed at the top of the preheater. The preheater section consists of a series of cyclones with a Pre-calcinator and flow of the material and gas in the pre heater is counter current. Fuel is fired in the pre-calcinator to provide heat for preheating and de-carbonation. Before entering in the kiln for burning, 70 to 85% of the de-carbonation is completed.

Fuel is fired in the kiln and pre-calcinator for preheating, de-carbonation and burning of the material. Normally oil is used as a fuel in white cement process, alternate fuels, like petroleum coke, rubber, agro waste, can also be used in white cement process due to high cost of oil.
In the kiln sintering zone, fully calcined material is burned at 1500-1600 °C resulting in formation of clinker granules with all the essential constituents likeC3S, C2SandC3A.
5. QUENCHING AND DRYING:
The ciinker formed in the kiln is then discharged in a Quencher or Decoloriser for water quenching. Quenching is carried in a reducing atmosphere. In grey cement clinker is cooled by air while in white cement clinker is cooled in water in the absence of air.
6. CEMENT GRINDING :-
The clinker is next ground to cement (perhaps after a drying stage). Here

Calcium sulfate is added to the control set, in the form of a high-purity grade of gypsum or anhydrite.Ceramic grinding media is preferred in the case of white cement grinding in place of high chrome grinding media for avoiding the detonation of cement whiteness.
In the white cement process cement plants the quantity of heat lost from preheater exist gases ranges from 180 to 250 kCal/ kg clinker at a
o
temperature range of 300 to 400 C. In addition, 80 to 350kCal/ kg clinker
o
heat is lost at a temperature range of 200 to 300 C from exist gases of cooler-(decoloriser /dryer)
Figure 1 illustrates a flow diagram of a conventional white cement manufacturing process. The raw material (typically limestone along with other materials) is fed in to the crusher/ stacker and reclaimer for crushing. The raw material from crusher enters the raw mill for fine crushing and drying and finally enters in to a kiln for heating. The clinker from the exit of the kiln is quenched with the help of water in a cooler (decoloriser /dryer) and finally enters the cement grinding station. In the conventional white cement manufacturing process the exhaust gases at raw mill, kiln and cooler (decoloriser/ dryer) are discharged in to atmosphere through Electrostatic precipitators (ESP) /Bag House.
Figure 2 illustrates a white cement manufacturing plant at operating condition. In conventional white cement manufacturing process the white clinker formed from a kiln is discharged to a decoloriser or quencher for water quenching. The white clinker is cooled in a decoloriser with the help

of water in the absence of air to avoid deterioration in whiteness. The temperature of the clinker at the discharge of the kiln is around 1200-1400°c. The temperature of the clinker at the discharge of dryer after quenching process is around 150-200°C. During the quenching process there is formation of super heated steam along with other gases and clinker dust. This steam with dust laden gases (55% steam + 45% air) is taken to an ESP/Bag House through cyclones and then discharged into the atmosphere. The kiln exhaust gases at 150 to 250°C are discharged into atmosphere through ESPs/ Bag House.
Although there has been several reported studies for recovery of waste heat from the Preheater and cooler area in grey cement, there has been no work done to recovery of waste heat from coolers (the decoloriser and the dryer) which are unique to white cement. The exhaust gases at the coolers stage is at low temperature and laden with steam and heavy dust.
This waste heat can be effectively utilized for electric power generation. Besides mitigating the problem of power shortage, this method of heat recovery for power generation will also help in energy conservation as well as reducing green house gas emissions.
Therefore, there is felt a need for a system and method to extract the energy content and water content that is being wasted and to effectively generate power from the waste heat source in a white cement manufacturing plant.
OBJECT OF THE INVENTION

The main object of the present invention is to develop a process for manufacturing white cement whereby the heat generated during the process is extracted and utilized for generating electric energy and water.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a process for manufacturing white cement which includes the steps of:
• forming cement clinker and feeding the cement clinker at 1100 C to 1400°C to a quencher in which the clinker is decolorized by quenching falling clinker with water spray in the absence of air;
• recovering superheated steam laden gases produced in the quencher and dryer;
• leading the quenched clinker to a dryer;
• using the recovered steam laden gases in the dryer to dry the clinker ;
• recovering flue gases at a temperature of 160 C -220 C from the dryer after they have extracted moisture from the clinker;
• extracting specific and sensible & latent heat from the flue gases via a heat exchanger;
• separating the dust particles from the flue gases either before or after heat extraction;
• condensing the moisture in the flue gases to obtain water; and
• using the water for the water spray in the quencher or in the process.
Typically, the quenched clinker contains moisture in the range of 10 to 15%. The flue gases recovered from dryer contains 40 to 50 % moisture.

The dust particles are separated by passing the flue gases through a cyclone and a filter bag.
Typically, the dust content in the flue gases is reduced to less than 5mg/m3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention envisages a system and method to reduce the energy and water that is being wasted and to effectively generate power from a waste heat source in a white cement manufacturing plant.
There are several ways to extract waste heat from process stream e.g, Waste heat recovery boilers, recuplators, Heat disc etc. In the white cement Industry waste heat source temperature are at lower ranges but have high heat content because it contains low temperature steam with good amount of latent heat, this needs a special thermodynamic cycle for extraction of heat and collection of condensate from the cooler exhaust gases.
A Thermodynamic cycle such as the Rankine cycle converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 80% of electric power used throughout the world including virtually all solar thermal, biomass, coal and nuclear power plants.

The Kalina cycle is a thermodynamic cycle for converting thermal energy to mechanical power, optimized for use with thermal sources which are at a relatively low temperature compared to the heat sink (or ambient) temperature. The cycle uses a working fluid with at least two components (typically water and ammonia) and a ratio between those components is varied in different parts of the system to increase thermodynamic reversibility and therefore increase overall thermodynamic efficiency.
Thermodynamic cycles for waste heat recovery are commonly designed on the Rankine cycle which has been modified using binary fluid of ammonia and water as the working fluid in place of only water for improving the overall efficiency of conventional systems. This modified system is called 'Kalina Cycle'. In this system efficiency gain of upto 50% for low temperature heat sources (200-280 Deg C) and upto 20% for higher temperature heat sources have been observed as compared to conventional Rankine cycle based power plants.
Figure 3 illustrates a flow diagram of a white cement manufacturing process in accordance with the present invention. In modified cement manufacturing process the latent and sensible heat in exhaust gases and steam from the exit of cooler (decoloriser/dryer) is recovered along with the recovery of condensate (water). The exhaust gases from the raw mill and kiln are discharged in to atmosphere through ESP/Bag House.
Following Raw material are used to make white cement: -
1. Lime Stone -High Carbonate & Low Iron.
2. Clay - High Alumina and Low Iron

3. Oil/Pet Coke/Rubber
4. Gypsum / Salenite
The cement clinker is formed by using the above raw materials and following the general method as described earlier. The clinker at a temperature range of 1100 °C to 1400 °C is fed to decolourizer/quencher and is quenched by spraying water on the falling clinker. The water is sprayed through nozzles in controlled manner for sudden cooling of clinker from 1250-1350° C to 200-250° Deg C, this process is carried out in the quencher under suction (in absence of air). Quenching of hot clinker results in formation of super saturated steam along some non-condensable gases.
Quenched clinker containing moisture around (10-15%) is fed to dryer where super saturated steam formed during quenching is used for drying of quenched clinker. Retention time of clinker in dryer is 15-20 min. The gases at the exhaust of the dryer contain 45% moisture, 55% non condensable
gases.
The gases as generated above are passed through a heat exchanger to extract sensible and latent heat form the exhaust gases, leaving behind hot condensate (water). The condensed water is used for quenching purpose again. A heat exchanger is part of special thermodynamic cycle which converts the heat extracted to electrical energy.
In one embodiment of the present invention, the gases as generated above are passed through a cyclone for removing clinker dust before passing through a heat exchanger. After passing through cyclone, dust content in the gas stream is in range of 25-35 gms/m3 (160-220° C). A bag filter is further

installed at the exhaust of the dryer to reduce dust content in the exhaust gases to less than 5mg/m3.
The thermal energy available at the decoloriser fan exit is about 15-17 MW and thermal energy available at the dryer fan exit is about 11-13 MW per hour for an 1800tpd production. With the present invention of extracting latent and sensible heat from the decolorizer/ dryer gases, a large amount of condensate in form of water is recovered (about 30000 -38000 kl/hr) and about 1-5MW of electrical energy can be recovered.
Extracted clinker from storage is mixed along with dry Selenite and Gypsum cement setting time retarder, and is fed to the ball mill in a controlled way through weigh feeders and conveyor belts. Roller press or vertical roller mill can also be used for white cement grinding for cost economy. Ceramic grinding media is preferred in case of white cement grinding for avoiding the detonation of cement whiteness.
TECHNICAL ADVANTAGES
A system and method for recovery of water, latent and sensible heat in quenching process for manufacture of white cement clinker as described in the present invention has several technical advantages including but not limited to the realization of:
• a method for recovery of water from waste heat source in a white
cement manufacturing plant; a method of generating electricity from waste heat source in a white cement manufacturing plant; and

• a method for recovery of thermal energy from waste heat source particularly during quenching and reusing during drying process .
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. A process for manufacturing white cement which includes the steps of:
• forming cement clinker and feeding the cement clinker at 1100°C to 1400°C to a quencher in which the clinker is decolorized by quenching falling clinker with water spray in the absence of air;
• recovering superheated steam laden gases produced in the decolorizer;
• leading the quenched clinker to dryer;
• using the recovered steam laden gases in the dryer to dry the clinker ;
• recovering flue gases at a temperature of 160 C -220 C from the dryer after they have extracted moisture from the clinker;
• extracting specific, sensible & latent heat from the flue gases via a heat exchanger;
• separating the dust particles from the flue gases either before or after heat extraction;
• condensing the moisture in the flue gases to obtain water; and
• using the water for the water spray in the quenching/ other process .
2. The process as claimed in claim 1, wherein the cement clinker is fed at
the temperature range of 1250°C to 1350 °C to the decolourizer.
3. The process as claimed in claim 1, wherein the quenched clinker contains moisture in the range of 10 to 15%.
4. The process as claimed in claim 1, wherein the flue gases recovered from dryer contains 40 to 50 % moisture.

5. The process as claimed in claim 1, wherein the dust particles are separated are separated before heat extraction.
6. The process as claimed in claim 1, wherein the dust particles are separated by passing the flue gases through a cyclone and a filter bag.
7. The process as claimed in claim 5, wherein the dust content in the flue
gases is reduced to less than 5mg/m3

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Patent Number

277904

Indian Patent Application Number

2286/MUM/2009

PG Journal Number

51/2016

Publication Date

09-Dec-2016

Grant Date

05-Dec-2016

Date of Filing

01-Oct-2009

Name of Patentee

ULTRA TECH CEMENT LIMITED

Applicant Address

AHURA CENTRE,B-WING, 2ND FLOOR, MAHAKALI CAVES ROAD, ANDHERI(E), MUMBAI-400 093, MAHARASHTRA, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	KAPOOR H. R.	GRASIM INDUSTRIES LTD, BUNGALOW NO.EX-02, P.O. RAJSHREE NAGAR, VIL. KHARIA KHANGAR, TEH. BHOPALGARH, DIST. JODHPUR-342606.
2	VYAS INDER RAJ	GRASIM INDUSTRIES LTD, BUNGALOW NO.EX-02, P.O. RAJSHREE NAGAR, VIL. KHARIA KHANGAR, TEH. BHOPALGARH, DIST. JODHPUR-342606.
3	CHHAPERWAL SUNIL	GRASIM INDUSTRIES LTD, BUNGALOW NO.EX-02, P.O. RAJSHREE NAGAR, VIL. KHARIA KHANGAR, TEH. BHOPALGARH, DIST. JODHPUR-342606.
4	TREHAN SANJEEV	GRASIM INDUSTRIES LTD, BUNGALOW NO.EX-02, P.O. RAJSHREE NAGAR, VIL. KHARIA KHANGAR, TEH. BHOPALGARH, DIST. JODHPUR-342606.
5	P.M.V SUBBA RAO	VAISHALI APARTMENT, IIT CAMPUS, HAUZ KHAS, NEW DELHI.

PCT International Classification Number

C04B7/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA