THERMAL POWER PLANT

A thermal power plant is a power plant in which the prime mover is stream. Water is heated, turns into steam and spins a turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle.

A coal-fired thermal power station.

1. Cooling tower. 2. Cooling water pump. 3. Transmission line (3-phase). 4. Unit transformer (3-phase). 5. Electric generator (3-phase). 6. Low pressure turbine. 7. Condensate extraction pump. 8. Condenser. 9. Intermediate pressure turbine. 10. Steam governor valve. 11. High pressure turbine. 12. Deaerator. 13. Feed heater. 14. Coal conveyor. 15. Coal hopper. 16. Pulverised fuel mill. 17. Boiler drum. 18. Ash hopper. 19. Superheater. 20. Forced draught fan. 21. Reheater. 22. Air intake. 23. Economiser. 24. Air preheater. 25. Precipitator. 26. Induced draught fan. 27. Chimney Stack.

WORKING SYSTEM

Coal is conveyed (14) from an external stack and ground to a very fine powder by large metal spheres in the pulverised fuel mill (16). There it is mixed with preheated air (24) driven by the forced draught fan (20). The hot air-fuel mixture is forced at high pressure into the boiler where it rapidly ignites. Water of a high purity flows vertically up the tube-lined walls of the boiler, where it turns into steam, and is passed to the boiler drum, where steam is separated from any remaining water. The steam passes through a manifold in the roof of the drum into the pendant superheater (19) where its temperature and pressure increase rapidly to around 200 bar and 570°C, sufficient to make the tube walls glow a dull red. The steam is piped to the high pressure turbine (11), the first of a three-stage turbine process. A steam governor valve (10) allows for both manual control of the turbine and automatic set-point following. The steam is exhausted from the high pressure turbine, and reduced in both pressure and temperature, is returned to the boiler reheater (21). The reheated steam is then passed to the intermediate pressure turbine (9), and from there passed directly to the low pressure turbine set (6). The exiting steam, now a little above its boiling point, is brought into thermal contact with cold water (pumped in from the cooling tower) in the condensor (8), where it condenses rapidly back into water, creating near vacuum-like conditions inside the condensor chest. The condensed water is then passed by a feed pump (7) through a deaerator (12), and pre-warmed, first in a feed heater (13) powered by steam drawn from the high pressure set, and then in the economiser (23), before being returned to the boiler drum. The cooling water from the condensor is sprayed inside a cooling tower (1), creating a highly visible plume of water vapor, before being pumped back to the condensor (8) in cooling water cycle.The three turbine sets are sometimes coupled on the same shaft as the three-phase electrical generator (5) which generates an intermediate level voltage (typically 20-25 kV). This is stepped up by the unit transformer (4) to a voltage more suitable for transmission (typically 250-500 kV) and is sent out onto the three-phase transmission system (3).Exhaust gas from the boiler is drawn by the induced draft fan (26) through an electrostatic precipitator (25) and is then vented through the chimney stack (27).

COAL FEEDING SYSTEM

Coal is conveyed through rail wagon from out side of plant and through conveyor system collected in hopper and ground to a very fine powder by large metal spheres in the pulverised fuel mill.

Conveyor Coal Hopper

Pulverised Mill

Wagon Tippler

COAL FEEDING SYSTEM

Then it is mixed with preheated air driven by the forced draught fan. The hot air-fuel mixture is forced at high pressure into the boiler.

Air Pre-heater Forced Draft Fan

Wagon Tippler 1 & 2

Wagon Tippler 3 & 4Sloping Conveyor Tunnel

TP-3

Conveyor 3A/3B

CHP Retaining Wall

Overview of Under construction BOP- Coal Feeding System

Crusher House

TP-4

TP-5

Conveyor 4A/4B

Conveyor 5A/5B

Stacker Reclaimer

Coal Stock Yard

Overview of Under construction BOP- Coal Feeding System

BOILER

A boiler or steam generator is a device used to create steam by applying heat energy to water.

The steam generator or boiler is an integral component of a steam engine when considered as a prime mover; The boiler is a furnace on a side. Its walls are made of a web of high pressure steel tubes.Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput and is typically driven by pumps. As the water in the boiler circulates it absorbs heat and changes into steam at 700 °F (371 °C) and 3,200 psi . It is separated from the water inside a drum at the top of the furnace.

Overview of Under construction Boiler System

ASH HANDLING SYSTEM

At the bottom of the furnace, there is a hopper for collection of bottom ash. This hopper is always filled with water to quench the ash and clinkers falling down from the furnace. Some arrangement is included to crush the clinkers and for conveying the crushed clinkers and bottom ash to a storage site.

SUPER HEATER

In a power plant, after the steam is conditioned by the drying equipment inside the steam drum, it is piped from the upper drum area into tubes inside an area of the furnace known as the super heater, which has an elaborate set up of tubing where the steam vapor picks up more energy from hot flue gases outside the tubing and its temperature is now superheated above the saturation temperature. The superheated steam is then piped through the main steam lines to the valves before the high pressure turbine.

Superheated steam is steam at a temperature higher than water's boiling point. If saturated stream is heated at constant pressure, it increases toward 100% Dry Saturated Steam. Continued heat input will then generate superheated steam. This will occur if saturated steam contacts a surface with a higher temperature. The steam is then described as superheated by the number of degrees it has been heated above saturation temperature

STEAM TURBINE

The hot reheat steam is conducted to the intermediate pressure turbine where it falls in both temperature and pressure and exits directly to the long-bladed low pressure turbines and finally exits to the condense

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion.The steam turbine is a form of heat engine that derives much of its improvement in thermodynamics efficiency through the use of multiple stages in the expansion of the steam.

CONDENSER

Condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it.

The exiting steam from steam turbine, now a little above its boiling point, is brought into thermal contact with cold water (pumped in from the cooling tower) in the condenser. where it condenses rapidly back into water, creating near vacuum-like conditions inside the condenser chest.

Water Cooled Condenser

Air Cooled Condenser

COOLING TOWER

Natural Draft Cooling Tower

Induced Draft Cooling Tower

Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers either use the evaporation of water to remove process heat and cool the working fluid or in the case of closed circuit dry cooling towers rely solely on air to cool the working fluid.

NDCT

Overview of Under construction NDCT

DE AREATOR

De Areator

The condensed water is then passed by a feed pump through a deaerater.

A deaerator is a device that is widely used for the removal of air and other dissolved gases from the feed water to steam-generating boiler.

ECONOMISER

Economiser

Pre-warmed water first enter in a feed heater powered by steam drawn from the high pressure set, and then in the economiser

Economizer are mechanical devices intended to reduce energy consumption, or to perform another useful function like preheating a fluid.

Economizer is a flue gas to water heat exchanger. Usually it is located below the LPSH in the boiler and above Air pre heater. Outside surface of the economizer tubes are heated by flue gases leaving the superheater and reheater which subsequently transfer heat to feed water flowing inside the tubes.

Advantages of Economizer include1) Fuel economy: – used to save fuel and increase overall efficiency of boiler plant.2) Reducing size of boiler: – as the feed water is preheated in the economizer and enter boiler tube at elevated temperature. The heat transfer area required for evaporation reduced considerably.

Electrostatic Precipitator

Exhaust gas from the boiler is drawn by the induced draft fan through an electrostatic precipitator

Electrostatic precipitators are mandatory installation in modern power plants to control stack emission. Each boiler has electrostatic precipitators which contain high voltage electrodes, these attract the pulverized fuel ash (PFA) from the flue gases. At regular intervals the electrodes are rapped with motor-driven hammers and the PFA falls into hoppers below.

Electrostatic precipitator is a collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.

Under Errection : Electrostatic Precipitator

CHIMNEY

Exhaust gas from electrostatic precipitator vented through the chimney tack.

A chimney is a structure for venting hot gases or smoke from a boiler, furnace or fireplace to the outside atmosphere.

A chimney is a vertical structure for venting hot flue gases or smoke from a boiler to the outside atmosphere by means of the stack effect. The space inside a chimney is called aflue. The height of chimneys plays a role in their ability to transfer flue gases using stack effect. The dispersion of pollutants at higher altitude helps to ease down its influence on surroundings and reduces their concentrations in compliance with regulatory limits.

AUXILIARY SYSTEMS

Boiler make-up water treatment plant and storage

Fuel Oil System

Generator Cooling

Other Structure

BOILER MAKE-UP WATER TREATMENT PLANT & STORAGE

Boiler make-up water treatment plant and storageSince there is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blowdown and leakages have to be made up to maintain a desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. Impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water, and that is done by a water demineralising treatment plant

FUEL OIL SYSTEM

An auxiliary oil system pump is used to supply oil at the start-up of the steam turbine generator. It supplies the hydraulic oil system required for steam turbine's main inlet steam stop valve, the governing control valves, the bearing and seal oil systems, the relevant hydraulic relays and other mechanisms.

Light oil used as the fuel for igniters. Light oil is also required for warming up oil guns to start the boiler from cold conditions.

TURBO GENERATOR

Turbo Generator - Generator consisting of a steam turbine coupled to an electric generator for the production of electric power. They are usually preferred, since they offer much better fuel efficiency and are also more reliable, but on the other hand they are much heavier and need more space.

GENERATOR COOLING

Hydrogen gas is used for generator cooling. So supply of pure hydrogen is essential for generator filling and maintaining of hydrogen gas pressure inside the generator casing.

Hydrogen Plant

Direct current passes through caustic potash and DM water for hydrogen gas production .

OTHER STRUCTURE – AERATOR & CLARIFLOCCULATOR

Aeration is the process of bringing water and air into close contact in order to remove dissolved gases, such as carbon dioxide, and to oxidize dissolved metals such as iron. It can also be used to remove volatile organic chemicals (VOC) in the water.

As lot of water used in thermal plant for various purpose. Structure to clear it from undesirable gases & dirt are required. Raw water generally supplied from pond are first pass through aerators which remove gases by mixing water with air.

OTHER STRUCTURE – AERATOR & CLARIFLOCCULATOR

Aeration is the process of bringing water and air into close contact in order to remove dissolved gases, such as carbon dioxide, and to oxidize dissolved metals such as iron. It can also be used to remove volatile organic chemicals (VOC) in the water.

Raw Water Pump House

Raw Water Reservoir

Chemical House

Pipe Rack PR-32

Cascade Aerator

Sludge Pit HRSCC -

1B

Back Wash Pit

HRSCC – 1A

Rapid Gravity Sand Filter Filter Water Tank & Pump

House

Overview of Under construction BOP- Raw Water System

DM Plant

DM Tanks

Neutralization Pit

DM Regeneration Area

Overview of Under construction BOP- De-mineralization System