Functions of Condenser, Cooling Tower, Superheaters and Economizer/ Advantages of Water Tube Boiler
Q. State the function of cooling tower and condenser in thermal power station.
Function of condenser : The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. It provides lowest economic heat rejection temperature for steam. It is used to introduce make-up water.
Function of cooling tower : The function of cooling tower is to reduce temperature of water coming from the condenser.
Q. Draw a neat labelled sketch of water tube boiler and also state its two advantages over fire tube boiler.
Sketch of water tube boiler :
Advantages of water tube boiler over fire tube boiler :
- Steam at high pressure and high temperature is generated.
- Rate of steam generation per hour is more.
- Steaming time is very less.
- The output of the boiler is high.
- High efficiency.
- Better control on temperature of steam.
- Respond quickly to change in steam demand.
- Its weight is less.
- Suitable for large capacity thermal power plant.
Q.Write the purpose of coal and ash handling unit. Also write different activities that are carried out in this unit.
Fuel i.e. coal, from the storage is fed to the boiler through feeding device, which consists of conveyor belt, crushing mill etc. and is called as coal handling unit. Ash produced as a result of combustion of coal collects at the back of the boiler and is removed to ash storage through ash handling equipment. Activities in coal handling unit :
- Delivery of coal.
- Unloading of coal.
- Preparation of coal before feeding to the combustion chamber.
- Transfer : It is the process of carrying the coal from unloading point to the storage site from where it is discharged to the firing equipment.
- Outdoor storage (Dead storage).
- Indoor (Live) storage.
- Inplant handling.
- Coal weighing.
- Furnace firing.
Activities in ash handling unit :
- Bottom ash handling
- Coarse ash (economizer ash) handling
- Air preheater ash handling
- Fly ash handling
- Ash slurry disposal.
Q. State the function of superheater and economizer.
Function of superheater : The steam produced in the boiler is impure i.e. it contains some moisture in it. Hence, before supplying wet steam to the turbine, it is passed through superheater, where it is dried and superheated by the flue gases. Superheater Increases the overall efficiency of the plant.
Function of economizer : It extracts the heat from the flue gases and utilizes this heat to raise the temperature of the feed water to the boiler, so that efficiency of the overall system is increased.