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Chapter: Mechanical and Electrical - Power Plant Engineering - Steam Power Plants

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Important Questions and Answers: Steam Power Plants

Mechanical and Electrical - Power Plant Engineering - Steam Power Plants

STEAM POWER PLANT

 

1. Write about out plant handling?

 

Out plant handling includes the handling of coalmine to the thermal power plant. These handlings are outside the plant in the following ways.

 

·        Transportation by sea (or) river

 

·        Transportation by rail

 

·        Transportation by road

 

·        Transportation of coal by pipeline.

 

2. Write about inplant handling of-coal?

 

In order to handle large quantity of coal inside the plant, some mechanical handling systems are provided f6r smooth, easy and better controlled operation. The inplant coal handling is divided, into following categories.

 

·        Coal unloading

 

·        Coal preparation

 

·        Coal transfer

 

·        Coal storage

 

3. Why the preparation of coal is necessary?

 

The coal from coal nines cannot be directly fed into the furnace. Proper preparation of coal should be done before feeding the coal to the furnace. In the coal preparation, the coal passes through the different equipments like 1. Crushers 2.Sizers 3.Driers and Magnetic Separators.

 

4. Name the different types of coal transforming equipments?

 

1.  Belt conveyors 2. Screw conveyors 3. Bucket elevators 4. Grab bucket elevators 5. Skip hoists 6. Flight conveyors. The coal transfer starts by carrying of coal from-unloading point to the storage site.

 

5. Write the classification of Mechanical Stokers?

 

1.  Travelling grate stoker 2.  Chain grate stoker

 

3.  Spreader stoker    4.  Vibrating grate Stoker

 

5.  Underfeed stoker.

 

6. Define draught, what is the use of draught in thermal power plants?

 

Draught is defined as a small pressure difference required between the fuel bed (furnace) and outside air to maintain constant flow of air and to discharge the gases through chimney to the atmosphere. Draught can be obtained by chimney, fan, steam jet (or) -air jet (or) combination of these. The uses are

 

·        To supply required quantity of air to the furnace for combustion of fuel.

 

·        To draw the combustion products through the system.

 

·        To remove burnt products from the system

 

 

7. Why the balanced draught system is preferred than other system?

 

 

 

In the induced draught system, when the furnace is opened for firing, the cold air enters the furnace and dilate the combustion. In the forced draught system, when the furnace is opened for firing, the high pressure air will try to blow out suddenly and furnace may stop. Hence the furnace cannot be opened for firing (q) inspection in both, systems. Balanced draught, which is a combination of induced and forced draught, is used to overcome the above stated difficulties.

 

8. Define forced draft and induced draft cooling towers

 

If the fan is located at the bottom of the tower and air is blown by the fan up through the descending water it is called as forced draft cooling towers. If the fan is located at the top of the tower

and air enters through the louvers located on the tower’s side and drawn up and discharge through the

 

fan casing, it is called as induced draft.

 

9. What is the working principle of Cooling Towers?

 

The hot water is sprayed from the top of the tower, while the air is made to flow from the bottom of the tower to the top. This air cools the hot water in the cooling tower. Air vaporises a small percentage of water, there by cooling the remaining water. The air absorbs the heat and leaves at the top of the tower and cooled water leaves at the bottom and recirculated to the condenser.

 

10. How the atmospheric (or) natural draught cooling towers- are classified?

 

In atmospheric (or) natural cooling towers, the natural air provides the required Cooling without the use of fans. This is classified into three types.

 

1. Natural draft spray filled towers

 

2. Natural draft packed type towers.'

 

3. Hyperbolic cooling towers

 

11. How mechanical draft cooling towers are classified?

 

Mechanical draft cooling tower is classified into three types

 

1. Forced draft tower.

 

2. Induced draft counter flow tower

 

3. Induced draft cross flow tower.

 

 

12.        Write the classification of Ash handling system?

 

1.     Hydraulic system,

 

2.     Pneumatic system

 

3.     Mechanical system

 

 

13.        What are the Ash discharge equipments?

 

1.     Rail road cars

 

2.     Motors truck

 

3.     Barge

 

 

13.        List the different types of components (or) systems used in steam (or) thermal power plant?

 

1. Coal handling system.

2. 2. Ash handling system.

 

3. Boiler 4. Prime mover

 

5. Draught system.

 

a.Induced Draught

 b. Forced Draught

14. What are the merits of thermal power plants?

 

Merits (Advantages) of Thermal Power Plant:

 

1. The unit capacity of thermal power plant is more. The cost of unitdecreaseswith the increase in unit capacity

 

2. Life of the plant is more (25-30 years) as compared to diesel plant(2-5 years)

 

3. Repair and maintenance cost is low when compared with diesel plant

 

4. Initial cost of the plant is lessthan nuclearplants

 

5. Suitable for varying load conditions.

 

15.        What are the Demerits of thermal power plants? Demerits of thermal Power Plants:

 

1. Thermal plant are less efficient than diesel plants

 

2. Starting up the plant and briningintoservice takes more time

 

3. Cooling water required is more

4. Space required is more.

 

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