Overview of Thermal Power Plants

India’s first thermal power plant was built in 1920 and was named Hussain Sagar thermal power station. 

Thermal power plants use the heat energy obtained from the combustion of solid fuels like coal to convert water into steam at high pressure and temperature. It then utilises this steam to rotate turbine blades connected to a generator. The generator converts the kinetic energy of the turbine into electric energy. It is based on the Rankine Cycle.

The outline of a thermal power plant is critical for its proper operation and maintenance. Selection of locations, cost calculation, and choosing the boiler, turbine, electrical generator, and cooling system are all part of a standard design.

This article will discuss thermal power plants, including their components such as the boiler and turbine. It will also talk about the types of thermal power plants in Kerala.

Fuel Application

Thermal power plants use coal to heat the water and produce steam. This steam rotates the steam turbine, which drives the electrical generator. After it passes through the turbine, the steam condenses in a condenser, and it is recycled where it is heated.

A -4450-5500 kcal/kg calorific value rotates the steam turbine and drives the electrical generator.

Boiler

A boiler is a closed vessel that converts water into steam under pressure.

1. Fire-tube boiler: The combustion product passes through tubes surrounded by water in this type of boiler.
2. Water-tube boiler: In this form of a boiler, hot gases flow outside the tube while water flows inside the tube.

The boilers in these plants are of the hanging type with natural circulation and are tangentially fired. Oil burners and coal burners provide for initial startup and flame stabilisation. The chemical energy in the fuel turns into thermal energy in the furnace, which is the essential portion of the boiler.

A pressure vessel is a boiler drum. Its job is to remove water and steam from the gaseous mixture produced by the furnace walls. The drum comprises two sections of carbon steel plates with thicknesses ranging from 133 to 135 m. The boiler drum is 53 metres above the ground. The drum gets its feed water from a well.

• Draught Fans

A fan is a volumetric equipment that, like pumps, transports large amounts of air or gas from one location to another. It does so by providing the fluid with the energy it needs to move in a controlled manner, overcoming resistance to flow.

• Primary Air Fan (P.A. Fan)

The pulverised coal is directly supplied from coal mills to the burners at the four corners of the furnace through a coal pipe, using hot air from the P.A. Fan. The P.A. fan segregates the fuel particles to directly come in contact with the air, resulting in efficient combustion of fuel particles.

• Forced Draught Fan (F.D. Fan)

The combustion process in the furnace can only occur under a constant airflow. As a result, the F.D. fan draws air from the atmosphere at room temperature and offers extra draught. Its rotational speed ranges from 600 to 1500 RPM.

• Induced Draft Fan

The Induced draft fan creates negative air pressure in a system and identifies the combustion process used in larger boilers.

• Economiser

The flue gases that exit the boiler carry significant heat. An economiser uses a portion of the heat extracted from the flue gases to heat the feedwater before reaching the steam drum. The use of an economiser reduces fuel consumption and improves boiler efficiency, although it requires additional expenditure. 

Between the two headers are a significant number of tiny diameter thin-walled tubes. Water enters the tube through the opposite end. Outside the tube, flue gases flow.

• Air Pre-Heaters

Air pre-heaters heat the entering air for combustion and recover heat from flue gases that exit the economiser. The efficiency of a plant increases by 1% when flue gases are cooled by 20%. Some regions use a regenerative sort of heater.

They employ a corrugated steel plate cylindrical rotor. A drum split into two compartments houses the rotor: air (primary air from the P.A. fan and secondary air from the F.D. fan with positive pressure) and flue gases (from the economiser with negative pressure). 

The rotor is mounted on an electrical shaft that rotates at 2 to 4 revolutions per minute.

• Superheater

The steam that contains more heat than saturated steam at the same pressure is superheated. A superheater is a device that eliminates the final trace of moisture from saturated steam exiting the boiler tubes while also raising the temperature above saturation.

Turbine

The turbine uses a heat source to heat the water extremely at high temperatures to convert it to steam. The working material’s dynamic action transfers the potential or kinetic energy of the working substance into mechanical power.

We can divide steam turbines into three categories:

1. Turbine with High Pressure (H.P. Turbine)
2. Turbine with Intermediate Pressure (I.P. Turbine)
3. Turbine with Low Pressure

Turbine Auxiliaries: Bearing Gear/ Turning Gear, Jack Oil Pumps, Gland Sealing, Generator, Turbo Generator

System of Cooling 

For generator cooling, a hydrogen cooling system is used. It uses hydrogen as a cooling medium because of its excellent cooling characteristics and low density. 

Hydrogen has a thermal conductivity of 7.3 times that of air. It has a more significant transmission coefficient as well. It has a 75 per cent higher capacity to transfer heat through forced convection than air.

Plant for water treatment

Controlling corrosion and steam quality are the main issues in high-pressure boilers. Internal corrosion may cost a power plant billions of rupees to fix if contaminants in the steam create deposits on turbine blades and nozzles.

Demineralised Plant (D.M. Plant)

Water is supplied from all of these dissolved minerals into this plant process. It uses a chemical method to separate the dissolved salt in raw water. Two streams with activated carbon filters, mild acid, cation exchange, and mixed bed exchanger make up this plant.

As we all know, the river serves as the Thermal Power Plant’s raw water intake.

P.A.C. (Poly ammonium chloride) and Chlorine Strong Acid Cation Unit- Cationic resin R-SO3H are the coagulants utilised in Thermal Power Plants.

C.W. Plant

It is a pump building for circulating water to condense steam for the condenser.

Filter Water B.C.W. Pump House

Efficiency

The combustion process converts the fuel’s potential or chemical energy into heat. The following components make up plant efficiency:

1. Cycle efficiency
2. Turbo-generator efficiency
3. Boiler efficiency
4. Auxiliary Power efficiency

Types of Thermal Power Plants in Kerala

There are only three thermal power stations in Kerala. Among these, the Brahmapuram and Kozhikode thermal power plants are diesel-based. 

The Kayamkulam power plant is the most prestigious of all the power plants in Kerala. This power plant has three units, and the total installed capacity is 350 MW. Former Prime Minister Atal Bihari Vajpayee inaugurated it in 1999. 

The Brahmapuram diesel-based thermal power plant is the biggest thermal power plant in Kerala.

Conclusion

It is necessary to reduce energy consumption globally to solve environmental and energy problems, such as global warming. Most of all, it is required for developing countries to take energy-saving measures where the economy and population present considerable growth. 

Thermal power plants were an energy-saving technology developed in Japan. Today, the energy efficiency of Japanese power companies has attained the highest level in the world.