Thermal Power Station

In thermal power station the heat energy of coal is converted into mechanical energy and then this mechanical energy is converted into electrical energy.It is also known as Steam Power Station. Boiler is the heart of thermal power station. The main equipment of thermal power station is boiler and it has three main inputs namely: coal (fuel of thermal power station), air (for combustion of coal) and water for producing steam.
This topic will cover:-

Thermal Power Station

• Selection criteria of site for thermal power station
• Coal Handling Plant
• Working
• Condenser 
• Cooling Tower
• Ash Handling Plant

Selection criteria of site for thermal power station:- 

While installing the thermal  power station this point should be taken in consideration.

1. Availability of Coal :The power station should be installed near coal mines. Coal is the primary requirement of thermal power station for the generation of electricity. A thermal power station of 400 MW capacity requires 5000 to 6000 tons of coal per day. Nearer to coal mines reduces the transportation cost. 
2. Space requirement :Quite large space is required by the thermal power station up to 3 to 5 acres per MW for installing equipment, machinery, coal storage, ash disposal, staff colony etc. And the land available for power plant must be available at low cost also it should have sufficient bearing capacity for holding the heavy equipment's, to withstand the load of machinery.  
3. Availability of water :Water is the secondary requirement of thermal power station. In thermal power station water is required for many purpose. But the two main purposes are, firstly for conversion into steam for steam turbine and secondly for condenser. It is also required for drinking purpose for staff colony. Therefore the plant should be located near the resources of water such as rivers, ponds, lake, canal, etc.
4. Ash disposal facilities:20 to 40% of ash is produced of total weight of coal i.e. 1500 to 2000 tons per day. So it becomes a problem for handling ash. It becomes a more serious problem as it comes out in the hot condition and is highly corrosive. Therefore, large space is required for the disposal of large quantity of coal. Nowadays the ash from the power plants is used for many industrial process such as for making bricks, cement and more. Therefore disposal problem does not arise.
5. Transportation facilities:We can say this point is not very important and also important. Because every power plant is built near coal, water resources. Power plants should have the transportation facility such as road and rail for transportation of materials and machinery. ( But nowadays the materials and machinery are built on site.)  
6. Away from populated area:Due to burning of huge amount of coal thermal power plant produces smoke and fumes.This pollutes the environment. Hence plant should be located at considerable distance from populated area.
7. Near to load center:This is a common point for all the power station. Power station should be located near to load center to minimize the transmission cost of electrical energy. 

Coal Handling Plant: 

Coal Handling Plant

As huge amount of coal is required for the generation of electricity; it is required to store coal in storage plant. Storage of coal avoids the shortage in case of failure of failure of transportation and other abnormal conditions.

Working :

Working is same. Firstly, in the boiler the coal is burnt and heat is utilized to convert the water into steam. Flue gases after the combustion of coal are released to atmosphere through chimney. Flue gases are passed through the super heater, economizer and air preheater before releasing to atmosphere.

Working Thermal Power Plant

• Superheater: The steam produced in the boiler is impure. That means it contains some impurities in it such as moisture. Hence wet steam is passed through superheater to dry and superheat. Superheater also helps to increase the efficiency of the plant.     
• Economizer: The heat lost in the process is recovered in economizer to heat the feed water.
• Air preheater: In economizer the heat lost is not entirely recovered. Therefore air preheater is employed to recover some of heat in the flue gases. This helps to increase the steam capacity per square meter of the boiler.
• Steam Turbine: The superheated steam obtained from the superheater is fed to the low pressure steam turbine. The steam expands in the high pressure turbine. Therefore steam attains higher velocity. The potential energy of steam is converted into kinetic energy due to pressure and internal energy.
• Alternator: The mechanical/kinetic energy obtained from steam turbine is converted into electrical energy.

Condenser:

Condenser

The cooling water is generally passes through number of closed tubes and steam surrounds the tube called condenser. Non mixing type of condenser is generally used universally.

Cooling System:

Natural Draft Cooling Tower

1. Cooling Tower:- In cooling tower the amount of water which is large is divided in smaller quantities practically of the size of drops.These water droplets fall from a height of 8 to 10 meters to the bottom of cooling tower. The splitting of water helps to cool water quickly. The water from the base of cooling tower is pumped back to the condenser and same cycle is repeated.There are two types of cooling tower: a) Natural Draft Cooling b) Forced draft cooling
2. Spray Pond:- In this system water is circulated in closed loop and is used again and again. The water is cooled by both convection and evaporation.

Ash Handling Plant:

Ash Handling Plant

The ash storage plant is located 15 KM away from the power station. In ash handling plant the ash is removed from the coal and then delivered to the ash storage plant. Also ash is distributed to industries for various purposes such as for making bricks and cement.

In this way electricity is generated in Thermal Power Station.