FORM - 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
"COMPLETE SPECIFICATION"
(See Section 10; Rule 13)
"A SYSTEM FOR ENHANCEMENT IN OUTPUT OF WASTE HEAT RECOVERY SYSTEM OF THE CEMENT PRODUCTION PROCESS BY RECIRCULATING CLINKER COOLER
VENT AIR"
TRANSPARENT ENERGY SYSTEMS PRIVATE LIMITED AN INDIAN NATIONAL "PUSHPA HEIGHTS", 1ST FLOOR, BIBWEWADI CORNER, PUNE-SATARA ROAD, PUNE-411 037, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION:-
The present invention relates to the process of enhancement in output of waste heat recovery system and overall energy efficiency of the cement production process in cement industry by virtue of recirculation of clinker cooler vent air. More particularly, the present invention relates to the process of recirculation of clinker cooler vent air to enhance the recovery of waste heat in the waste heat recovery system to in turn enhance power generation.
PRIOR ART:-
The conventional cement manufacturing process consists of three major steps all of which are energy intensive viz. preheating of limestone, clinkerisation, and clinker cooling. In the process of clinker cooling ambient air is supplied by forced draft fans to cool the hot cement clinker from about 1300°C at which it leaves the kiln to less than 100°C. The process takes place in equipment named clinker cooler of which Rotary Cooler, Cross Flow Grate Type Cooler and Planetary Cooler are some of the prevailing. In all these designs, the heat is exchanged with the supplied ambient air and the hot air generated during the process of cooling of clinker is utilized in several ways as following,
1. Secondary air of highest temperature range between 1000 to 1300°C is supplied to Rotary Kiln as preheated combustion air
2. Tertiary Air of relatively lower temperature in the range between 800 to 1000°C is supplied to raw feed preheater tower of cement plant.

3. The mid-tap air of further lower temperature in the range between 350 to 500°C is supplied to waste heat recovery system to drive steam rankine cycled based power plant or organic rankine cycle based power plant.
4. Further the remaining air from clinker cooler is vented out at temperature of about 150°C. The cooled mid tap air at the outlet of waste heat recovery system of temperature about 85-130°C is mixed with the clinker cooler vent air of 120 - 160°C. The mixed stream of temperature about 110 - 130°C is passed through particulate separation equipment such as electrostatic precipitator or bag filter where in temperature of the vent air drops to about 80 to 120°C. These gases are exhausted to atmosphere through chimney.
LIMITATIONS OF PRIOR ART:-
As described in the prior art, the heat from exhaust gases at 80 to 120°C is wasted to atmosphere as they are exhausted through chimney.
The mid-tap air supplied to waste heat recovery system is at relatively lower temperature of350 to 500°C lowering the overall efficiency of the cement making process.
OBJECT OF THE PRESENT INVENTION:-
Object of present invention aims at process of enhancement in output of waste heat recovery system and overall energy efficiency of the cement production

process in cement industry by virtue of recirculation of clinker cooler mid tap and/or vent air.
It is also object of present invention to eliminate limitations or drawbacks of the prior art.
SUMMARY OF THE INVENTION:-
According to the present invention, the vent gases of temperature about 80 to 120°C at outlet of particulate separation equipment (ESP / Bag Filter) are recirculated back in to the clinker cooler. These gases are supplied to cooler with the help of forced draft fan installed at outlet of particulate separation equipment. This hot air shall be distributed in various zones of clinker cooler using the forced draft fans of clinker cooler. As described in prior art, the conventional clinker cooler is supplied with ambient air of temperature about 30 to 45°C. By virtue of the present invention, the clinker cooler shall operate on cooling air of temperature 80 to 100°C. Due to which, the temperature of mid tap air shall rise by about 25to70°C. As a result of increase in the temperature and the heat content of the mid-tap air, more heat shall be recovered in the waste heat recovery system operating of mid-tap air thereby increasing the power generation.
STATEMENT OF INVENTION:-
A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air comprising of

clinker cooler; said clinker cooler having inlet to receive hot clinker from cilin and outlet to discharge the cooled clinker; said clinker cooler is provided with atleast three sets of blower fans (4). (5) and (6) below the said clinker cooler for supplying air for cooling the clinker; the said set of blower fans (4) and (6) supply ambient air and the set of blower fans (5) supplies the recirculated air from the outlet of biower fan (16) with the help of blower fan (21); the blower fan (16) is provided at outlet of particulate separation equipment (14).
BRIEF DESCRIPTION OF THE DRAWINGS:-
Fig. 1 is a schematic representation of the process for enhancement in output of waste heat recovery systemand overall energy efficiency of the cement production process as described in this invention.
DETAILED DESCRIPTION OF THE INVENTION:-
The invention will now be described with reference to the drawing of the accompanying specification.
Referring to Fig 1, from kiln '1'hot clinker '2' at temperature of around 1300°C enters clinker cooler '3' where it is to be cooled. Multiple fans are used to supply cooling air to the clinker cooler '3'. These fans could be split into three subsystems. The first set of fans '4' supplies ambient air'8'to the first section of the clinker cooler. Part of the air supplied by set '4'after cooling the clinker and at highest temperature between 1000 and 1300°C, called secondary air '6', is supplied to kiln. The remaining part of the air supplied by set '4' at 800-1000°C, called as tertiary air '9', is supplied to raw feed preheater tower of cement plant.

The second set of fans '5' also supplies ambient air '8' in the conventional process in prior art while in this invention it partially or completely utilizes the recirculated air '20',The air supplied by set '5' after cooling the clinker, called mid tap air '10' is either supplied to heat recovery system '12' or cooled by some other means like evaporative cooling. Control system 7'at the inlet side of each fan in the set '5' controls the proportion of recirculated air and ambient air according to the temperature of mid tap air '10'. In the conventional process without recirculation of vent air, the mid tap air '5'is available at 350-500°C. With recirculation of vent air as described in this invention, the temperature of mid tap air increases by 25-70°C. The higher the temperature of mid taps air, higher is the heat content. Therefore more heat recovery is possible inwaste heat recovery system resulting in enhanced power output. The set of fans '6'supplies the ambient air to the last part of the clinker cooler. After cooling the clinker this part of cooling air at 120-160°C, vent air'11' passes to electrostatic precipitator '14'. Part of the heat in mid tap air '10'is recovered in the heat recovery system for generation of hot water, steam, or hot thermic fluid etc. After heat recovery the cooled mid tap air '13'at 85-130°C is mixed with vent air '11' and the mixed stream at 110-130°C passed through electrostatic precipitator '14'or other equipment to separate particulates in the gases. At the outlet of the electrostatic precipitator, the cleaned vent air '15'is available at 80-120°C. In the conventional process of prior art the cleaned vent air '15' is discharged to atmosphere by fan '16'through chimney '18'. In the present invention part '20 of the cleaned vent air is recirculated by fan '21'and supplied to second set of fans '5'for clinker cooling while only the remaining part '19' is

discharged through chimney '18'. Depending on the proportion, as decided in control system '7' of recirculated air and ambient air mixed by set '5'of fans, the temperature of mid tap air '10' varies. Following table gives comparison of different cases for various proportions of recirculated air and the corresponding enhancement in heat recovery.
A partial air diverter at chimney inlet provide dampers to vary the quantity of air to be diverted the control system of third sets of inlet fans. The said control system and partial air diverter are controlled by a PLC system in synchronized manner to maintain various set value of temperature here in described.

Parameter Case 1 Case 2 Case 3 Case 4 Case 5
Recirculation of clean vent air (fraction of total clean vent air available) 0%
(conventional
process) 25% 50% 75% 100%
Ambient Air Temperature
(°C) 30 30 30 30 30
Recirculated Clean Vent Air Temperature (°C) NA 90 90 90 90
Temperature of mixed cooling air available (°C) 30 45 60 75 90
Temperature of mid tap air (°C) 400 414 428 442 456
Optimum Pressure of Heat Recovery Steam Generator (bar g) 17 21 23 23 23
Superheated steam temperature (°C) 360 360 360 360 360

Steam generation (kg/ton gas) 85.5 89.6 95.3 102.1 108.8
Isentropic efficiency of steam turbine 75% 75% 75% 75% 75%
Gross power generation (kWh/ton gas) 15.6 16.8 18.1 19.4 20.7
Higher temperature of mid tap air also allows heat recovery at higher temperature and/or pressure in the heat recovery system. The pressure of heat recovery steam generation is selected so as to maximize the power generation under various operating conditions. As seen from the table, with recirculation of clean vent air as described in the present invention the gross power output of the waste heat recovery system can increase by up to 33%.
The clinker is cooled from about 1300°C to about 100°C in the clinker cooler. In the middle section of the cooler from where the mid tap air is supplied to heat recovery system, the clinker is typically at above 450°C. Due to recirculation of clean vent air, as shown in the table, the cooling air temperature increases only up to about 90°C. Thus sufficient temperature difference is still available for cooling the clinker to required temperature.
The present invention can be implemented in the existing clinker cooler after suitable modifications like changing the volumetric flow rate of cooling fans for supply of recirculation air of higher temperature. The present invention can be implemented in the green field cement plants as well.
In the foregoing specification, the invention has been described for a specific configuration for enhancement of output of waste heat recovery system and

overall energy efficiency of the cement production process in cement industry by recirculation of clean vent air as cooling air for clinker cooler. It is evident that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention. Accordingly the specifications are to be regarded as illustrative rather than restrictive. Therefore, the invention is not restricted to the embodiments described and illustrated here and also covers all modifications which may fall within the scope of claims. The possible modifications are including but not limited to
1. Changes in the specific temperatures of clinker, ambient air, secondary air, tertiary air, mid tap air, and/or vent air.
2. Various ways of recovering heat from the mid tap air including hot water generation, saturated or superheated steam generation, thermic fluid heating
3. Various ways of generating power by heat recovery including steam rankine cycle, organic rankine cycle, kalina cycle.
4. Various temperature and pressure for heat recovery system
5. Recirculation of vent air before or after particulate separation electrostatic precipitator, bag filter, or any other equipment.
6. Recirculation of vent air by various number and configuration of fans
7. Partial or complete recirculation with or without provision for mixing recirculation air and ambient air

ADVANTAGES OF PRESENT INVENTION:-
1. The present invention shall improve heat utilization in cement plant therefore bring down cost of energy required for manufacturing cement
2. The present invention shall improve power generation from waste heat recovery based power plant due to recirculation of clean vent air
WORKING OF SYSTEM FOR CEMENT PRODUCTION PROCESS WITH ENHANCEMENT IN OUTPUT OF WASTE HEAT RECOVERY:-
a. Partially or completely recirculating the vent air from clinker cooler
as cooling air for clinker cooler
b. The remaining vent air is discharged to atmosphere
c. Mixing the circulated vent air with ambient air and the mixture is
supplied as cooling air to the clinker cooler
d. Cooling the clinker by exchanging heat with said mixture of air
e. Recovering the heat from the mid tap air by heat recovery boiler
f. Mixing the mid tap air after heat recovery with vent air of clinker
cooler
g. The vent air is cleaned by separating particles by electrostatic
precipitator, bag filter etc.
h. The air is cleaned by separating particles by electrostatic precipitator, bag filter etc before discharging to atmosphere

i. The hot water generator or pressurized hot water generator is used instead of heat recovery boiler
j. The thermal oil heater is used instead of heat recovery boiler
k. The steam turbine, generator and condenser to convert thermal energy of steam into mechanical or electrical energy
I. The organic rankine cycle based power plant to convert thermal energy of steam into mechanical or electrical energy
m. Partially or completely or partially recirculating the mid tap air from clinker cooler after heat recovery in heat recovery system as cooling air for clinker cooler
n. The remaining mid tap air is discharged to atmosphere
o. Cooling the clinker by said recirculated mid tap air
p. Recovering the heat from the mid tap air by heat recovery boiler
q. The hot water generator is used instead of heat recovery boiler
r. The thermic fluid heater is used instead of heat recovery boiler
s. The steam turbine, generator and condenser to convert thermal energy of steam into mechanical or electrical energy
t. organic rankine cycle based power plant to convert thermal energy of steam into mechanical or electrical energy

WE CLAIM:-
1. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air comprising of clinker cooler; said clinker cooler having inlet to receive hot clinker from clin and outlet to discharge the cooled clinker; said clinker cooler is provided with atleast three sets of blower fans (4). (5) and (6) below the said clinker cooler for supplying air for cooling the clinker; the said set of blower fans (4) and (6) supply ambient air and the set of blower fans (5) supplies the recirculated air from the outlet of blower fan (16) with the help of blower fan (21); the blower fan (16) is provided at outlet of particulate separation equipment (14).
2. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air as claimed in claim 1 wherein the said second set of fan (5) may supply 100 %recirculated air.
3. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air as claimed in claim 1&2 above wherein the said set of fan (5) may supply partially recirculated air mixed with ambient air (8) using the control system (7) provided at inlet of the said set of blower fans (5).
4. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent airas claimed in claims 1 to 3 wherein the part of air (19) at outlet of blower fan (16) remaining after recirculation effected through blower fan (21) is discharged to atmosphere through chimney (18).
5. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air as claimed in claim 1 to 4 above wherein the said set of air inlets are on the

lower side and the said set of outlets are at upper side of the said clinker cooler to allow cooling air to pass through the hot clinker for effective heat transfer.
6. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent airas claimed in claims 1 to 5 wherein the said waste heat recovery system is a steam generator / boiler / thermal oil heater / hot water generator / pressurized hot water generator.
7. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent airas claimed in claims 1 to 6 wherein the said outlet of the said waste heat recovery system is provided with electrostatic precipitator or bag filter or any particulate separation equipment capable of separating air and particles.
8. A System for enhancement in output of waste heat recovery system of the cement production process by recirculating clinker cooler vent air as claimed in claims 1 to 7 wherein the said control of third sets of inlet and chimney partial air diverter provided with PLC operated dampers in synchronized manner to maintain operating various set temperature of system as herein described.