Important Questions and Answers: Power Plants and Boilers

INTRODUCTION OF POWER PLANTS AND BOILERS

1. Name the four major circuits in steam power plant.

·        Coal and ash circuit

·        Air and flue gas circuit

·        Feed water and steam circuit

·        Cooling water circuit

2. What is the use of surge tank?

The surge tank is used to provide better regulation of water pressure in the system. The surge tank controls the water when the load on the turbine decreases and supplies water when the load on the turbine increases. Thus, surge tank controls the pressure variations resulting from the rapid changes in water flow in penstock and hence prevents water hammer.

3. Explain about penstock?

The pipe between surge tank and prime mover is known as penstock. It is designed to withstand high pressure. It is made up of reinforced concrete. In very cold areas, the penstock is buried to prevent ice formation and to reduce the expansion joints.

4. What are the types of power plants?

1. Thermal Power Plant

2. Diesel Power Plant

3.       Nuclear Power Plant     

4. Hydel Power Plant

5.       Steam Power Plant       

6. Gas Power Plant

7.M.H.D. Power Plant

5. What consists of lubrication system in diesel engine power plant?

The lubrication system consists of oil pumps, oil tanks, filters, coolers and connecting pipes. The purpose of the lubrication is to reduce the friction of moving parts and also pipes to reduce the wear and tear of moving parts.

6. What is the purpose of intercooler in gas turbine power plant?

Since the power required to compress the air is less in isothermal process it is required to maintain the, temperature of air constant as far as possible. Hence the air leaving the L.P. compressor is cooled by intercooler and then passed to the H.P compressor.

15. What is the purpose of Draught?

(i)  To supply required amount of air to the furnace for the combustion of fuel. The amount of fuel can be burnt per square foot of grate depends upon the quantity of air circulated through fuel bed.

(ii) To remove the gaseous products of combustion.

8. Write about Benson boiler? State some important advantages of Benson boiler?

Benson boiler is the high pressure, vertical fire tube boiler. This boiler has no drum and is ~designed to operate at critical pressure of 225 bar. Benson boiler has no drum. So the total weight of the Benson boiler is reduced by-20%, when compared to other boilers.

o  The erection of Benson boiler is easier and quicker.

9. Define load curve?

·        Load curve is a graphical representation between load in kW and time in hours. It. shows variati6n of load at the power station. The area under the load curve -represents the energy generated in a particular period.

10.            Explain Reheat cycle?

If the dryness fraction of steam leaving the turbine is less than 0.88, then, corrosion and erosion of turbine blades occur. To avoid this situation, reheat is used. In the reheat cycle, the expansion of steam takes place in one (or) more-turbines. Steam is expanded in the HP turbine first, and then it is reheated. The reheated steam is again expanded in. the LP turbine.

11.            What are the important advantages of Re-heating?

·        Due to reheating, network done increases

·        Heat supply increases

·        Thermal efficiency increases

Due to reheating, the turbine exit dryness fraction increases so moisture decreases - so blade erosion becomes minimum - so life of the turbine will be increased.

12. Define bleeding in steam power plant?

Assume I kg of steam is expanded in the turbine. Before complete amount of steam -is expanded, some amount of steam (m kg) is -extracted ' Extracting the steam in the turbine before exhaust is called bleeding. This bled steam is used to heat the feed water.

13. Explain the term Regeneration & advantages of Regeneration cycle?

Regeneration means heating the feed water by steam taken from the turbine. The steam is exhausted (bled) from the turbine at several locations before exhaust and is supplied to regenerator (feed water heater) to heat the feed water.

Advantages of Regeneration cycle

·        Heat supplied to boiler becomes reduced

·        Thermal efficiency is increased since the average temperature of heat addition to the cycle is increased.

·        Due to bleeding in the turbine, erosion of turbine due to moisture is reduced.

14..         Define the term waste heat recovery?

Waste heat is the heat which is not at all used and exhausted out as a waste product. Waste heat is normally available from the industry in the form of process steam and water at high temperature. Also, the waste heat is discharged with the exhaust gases in so many industries. This heat can be recovered for useful purpose. This process is known-as waste heat recovery.

15. What are the waste materials, which can be used for fuel for power generation?

·        Municipal waste

·        Industrial waste

·        Paper waste

·        Rubber waste.