FIELD OF INVENTION
The present invention relates to an improved system for efficient power generation using hot exhaust gases of low temperature from waste heat recovery unit. The system captures waste heat of low temperature to improve efficiency of waste heat recovery unit for power generation.
BACKGROUND/ PRIOR ART OF THE INVENTION
In pyroprocessing of cement manufacturing, waste heat flares from exhaust gas at the end of preheater and cooler. At the preheater end, temp range of waste heat is 300-320°C during normal operation while at the cooler end after electrostatic precipitator temp range is 100-120°C. Waste heat of medium (120-650°C) and high (>650°C) temperature is feasible to use for the generation of electricity via different capturing processes whereas waste heat of low temperature range (0-120°C) is not feasible to use for electricity generation.
Flue gas from the top of the Pre-heater to the Waste Heat Recovery Boiler (WHRB), enters the Electrostatic precipitator (ESP). Similarly near Air Quenching Cooler (AQC), part of flue gases from the mid of the Air Quenching . Cooler (AQC) to the Waste Heat Recovery Boiler (WHRB) enters to the Electrostatic precipitator (ESP) Fan inlet and then Chimney. In the existing arrangement, the balance air quantity from clinker cooler after meeting the secondary & tertiary air requirement, is routed through the Air Quenching Cooler (AQC) boiler, cooler Electrostatic precipitator (ESP) fan & vented through stack.
Presently, about 2.72 Kg air/Kg clinker is supplied in the clinker cooler of which around 1.63 Kg air/Kg clinker is routed through AQC/cooler exhaust and balance air quantity is utilised as secondary & tertiary air. Air temperature at the exit of Air Quenching Cooler (AQC) boiler is about 100-120°C. Further, this air is treated in cooler Electrostatic precipitator (ESP) and vented through cooler vent stack.

Pre-Heater Boiler: The flue gas, at 300°C, from the top of the Preheater enters into boiler. The temperature of the flow gas from boiler is ~157°C, which is used for drying of raw material in Raw Mill.
When the boiler is shut down, the flue gas enters the G.C.T., wherein after G.C.T. the same circuit is followed.
Air Quench Cooler Boiler: The flue gas, at 400°C, from the mid tap of the Air Quenching Cooler (A.Q.C) enters into boiler, the temperature of the flue gas from boiler is 100-120°C, which is flared in atmosphere through existing E.S.P. fan. In this process, load on cooler Electrostatic precipitator (E.S.P) is lower side. The balance in draft is maintained by control dampers in Air Quenching Cooler (A.Q.C). Waste Heat Recovery Boiler (WHRB) and Electrostatic precipitator (E.S.P) inlet duct. When the boiler is shut down, the flue gas enters the Electrostatic precipitator (E.S.P) and after Electrostatic precipitator (E.S.P) the same circuit is followed.
The disadvantage associated with the above is that, the heat dissipated at the end of the system goes waste as gas vented out through stack. Hence, the system is required to be provided with an arrangement for further utilization of the waste heat so as to make the system efficient.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an improved system for efficient power generation using hot exhaust gases of low temperature from waste heat recovery unit which overcomes disadvantage(s) associated with the prior art.
Further object of the present invention is to provide an improved system for efficient power generation using hot exhaust gases of low temperature from waste heat recovery unit which is efficient and simple in construction.

STATEMENT OF INVENTION
According to this invention, there is an improved system for efficient power generation using hot exhaust gases of low temperature from waste heat recovery unit comprising of a preheater, flue gases from which is directed to gas condensing Tower (GCT) and Electrostatic precipitator (ESP), waste heat recovery boiler (WHRB) and also to clinker cooler provided in connection with air quenching cooler (AQC), in which the clinker cooler is supplied with ambient air and air quenching cooler (AQC) is connected to Electrostatic precipitator (ESP) and exhaust fan, wherein recycled air from the exhaust fan is supplied to a plurality of high efficiency fans through an arrangement of duct and booster fan.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows: pyroprocessing of cement manufacturing.
Fig. 1A shows: line diagram of the prior art.
Fig. 2 shows: present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
Reference may be made to fig. 1 and 1A, wherein flue gas from top of the pre¬heater is directed to gas condensing tower (GCT) and electrostatic precipitator (ESP) and also to waste heat recovery Boiler (WHRB) as shown. However, there may be provision of pre-heater fan and raw material grinding system between the gas condensing tower (GCT) and electrostatic precipitator (ESP) along with Damper positioned before said waste heat recovery Boiler (WHRB), gas condensing tower (GCT) and preheater fan.

Further, as indicated in fig. 1A, flue gases from mid of the cooler goes to air quenching cooler (AQC), from which it is directed to the electrostatic precipitator (ESP) fan inlet and subsequently through chimney.
In the currently known arrangement (fig. 1), the balance air quantity from clinker cooler after meeting the secondary and tertiary air requirement, is routed through the to air quenching cooler (AQC) boiler, cooler electrostatic precipitator (ESP), cooler electrostatic precipitator (ESP) fan and finally vented through stack.
Further, plurality of fans provided below the cooler are supplied with ambient air.
Now, reference may be made to fig. 2 showing improved system of the instant invention. The recycled air from the exhaust fan is supplied to a plurality of specially designed fans. The supply of recycled air is through a duct provided with a booster fan in series.
The fans are compartible with high temperature of recycled air at required volume and pressure.
The remaining fans are the fans provided in the existing known system, which are as usual supplied with ambient air.
Waste gases of temp 100-120°C is re-circulated from cooler Electrostatic precipitator (ESP) fan outlet to clinker cooler through cooler fans at 1st & 2nd compartment of the cooler to maximize the heat gain. To re-circulate the hot air from cooler Electrostatic precipitator (ESP) fan exit to clinker cooler fans, a booster fan and a new duct arrangement are installed suitably. Also, air to cooler fans is at higher temperature compared to previously used ambient air. These fans are partly replaced with suitably designed high efficiency fans.
Since, the recycled hot air is dust laden, it is routed through the existing cooler electrostatic precipitator (ESP). Alternatively, a new dust separation system like

separation cyclone is provided in the duct between cooler vent stack & cooler fans intake.
While utilizing the hot recirculating air in cooler to achieve the benefits of increased secondary & tertiary air and hot air to air quenching cooler (AQC), the clinker cooler grates speed ratio is optimized further in phased manner during kiln operation.
The above mentioned system is connected to steam turbine with air cooled condenser for generation of steam used to generate electricity.
The provision of specially designed fans along with the supply of recycled air through booster fan makes the system of the instant invention effective and efficient.
ADVANTAGEOUS FEATURES
 Gain in secondary 8B tertiary air temperature by about 10-20°C.
 Gain in air quenching cooler (AQC) boiler inlet temperature by 40°C.
FEATURES OF THE INVENTION
 New duct between cooler electrostatic precipitator (ESP) fan exit and booster fan.
 The old cooler electrostatic precipitator (ESP) fan is used as a booster fan.
 A new duct between booster fan exit to new cooler fans.
 Installation of additional new clinker cooler fans.
 Installation of damper along with actuators, pressure 8B temperature transmitter.

 Thermal insulation of the existing cooler electrostatic precipitator (ESP), cooler electrostatic precipitator (ESP) fan, booster fan, ducts & new cooler fans.
 Modification in the operational logics & interlocks in PLC.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM:
1. An improved system for efficient power generation using hot exhaust
gases of low temperature from waste heat recovery unit comprising of a
preheater, flue gases from which is directed to gas condensing Tower
(GCT) and Electrostatic precipitator (ESP), waste heat recovery boiler
(WHRB) and also to clinker cooler provided in connection with air
quenching cooler (AQC), in which the clinker cooler is supplied with
ambient air and air quenching cooler (AQC) is connected to Electrostatic
precipitator (ESP) and exhaust fan, wherein
recycled air from the exhaust fan is supplied to a plurality of high efficiency fans through an arrangement of duct and booster fan.
2. An improved system for efficient power generation as claimed in claim 1, wherein the arrangement comprising of a duct provided with a booster fan in series.
3. An improved system for efficient power generation as claimed in claim 1 or 2, wherein the high efficiency fans are compatible with high temperature of recycled air at required volume and pressure.
4. An improved system for efficient power generation as claimed in any of the preceding claims, wherein a dust separation system such as separation cyclone is provided in the duct between cooler vent stack and cooler fans intake.

5. An improved system for efficient power generation as claimed in any of the preceding claims, wherein the hot recirculating air in cooler is used to achieve benefits of increased secondary and tertiary air and hot air to air quenching cooler (AQC) boiler, in which the clinker cooler grates speed ratio is optimized further in phased manner during kiln operation.
6. An improved system for efficient power generation as claimed in any of the preceding claims, is associated with the features/advantageous features such as herein described.
7. An improved system for efficient power generation using hot exhaust gases of low temperature from waste heat recovery unit substantially as herein described with reference to the accompanying drawings.