General Block Diagram of Topping Cycle
Topping Cycle :
- Topping cycle is that cycle in which fuel supplied is first used to produce power, and then it is used to generate thermal or heat energy i.e. heat energy is the byproduct of this cycle.
- The heat energy available from this code is used for heating of various processes or it is used to meet the requirement of heat for different purposes.
- In most of the systems of topping cycle co-generation is widely used, and it is the most popular method of co-generation.
- Figure A represents a simple typical example of topping cycle co-generation system of thermal power generation plant.
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| Figure A |
(A) Gas Turbine Topping System :
- A natural gas turbine drives a generator. The exhaust gas from the turbine goes to a heat recovery boiler, where the heat available in the exhaust gas is utilized to produce steam.
- The steam from heat recovery boiler is further utilized as process steam and then as process heat
- A typical gas turbine topping co-generation system is represented in Figure B.
(B) Steam Turbine Topping System :
- In this type of topping co-generation system, the fuel, which may be in the form of coal, oil, wood etc. is burnt to produce high pressure steam which is passed through a steam turbine.
- The low pressure steam obtained from the exhaust of turbine can be utilized for other purposes such as heating of any other products of industry, houses or it may also be used in generating plant for heating of feed water.
- Also the flue gases going to the chimney from boiler may be utilized in economizer to heat feed water to boiler itself.
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| Figure B |