JIS COLLEGE OF ENGINEERING

A descriptive view on thermal power plant “bokaro”

Prepared by : ANIS HAIDERDepartment of Mechanical engineering

Reg no. 141230120023Roll no.140307132

4th year- 7th semester

Introduction

Bokaro Thermal Power Station (BTPS ) is located at Bokaro district in Jharkhand 44 km from the bokaro steel city and is about 55 km from Dhanbad city. The nearest railway station is Bokaro Thermal. The power plant is one of the coal based power plants of DVC. Bokaro Thermal Power Station has an installed capacity of 630 MW. The First unit was commissioned in March 1986. The station is located on the banks of the Konar River near Bokaro Thermal Power Station. Entire power generated by the plant is supplied to DVC network.

INTRODUCTION OF THERMAL POWER PLANT Thermal power generation plant or thermal power station is the most

conventional source of electric power. Thermal power plant is also referred as coal thermal power plant and steam turbine power plant.

In coal thermal power plant, the steam is produced in high pressure in the steam boiler due to burning of fuel (pulverized coal) in boiler furnaces.

This supper heated steam then enters into the turbine and rotates the turbine blades.

In turbine this steam force rotates the turbine blades that means here in the turbine the stored potential energy of the high pressured steam is converted into mechanical energy.

1. Coal handling plant 2. Water Treatment Plant3. Boiler4. Steam Turbine5. Economizer 6.Turbine7. Generator 8. Super heater 9.Condenser10. Ash handling plant 11. Electrostatic Precipitator 12.Cooling Tower13. Chimney

Main Parts of Bokaro Thermal Power Station

COAL HANDLING PLANT(CHP) In a coal based thermal

power plant, the initial process in the power generation is “Coal Handling”.

The huge amount of coal is usually supplied through railways. A railway siding line is taken into the power station and the coal is delivered in the storage yard.

The coal is unloaded from the point of delivery by means of wagon tippler.

Conveyors convey coal from one point to another with the help of Belts, Pulleys and idlers. Conveyor belts are made of Polyester or Nylon.

Action of coal as a fuel:- There are mainly three classifications of coal: Anthracite, Bituminous and

Lignite. Lignite has the lowest grade of coal whereas anthracite is the highest one. Power plants generally use steam coal which is a grade between anthracite and bituminous.

Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverized coal combustion systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature

The hot gases and heat energy produced converts water – in tubes lining the boiler – into steam. The steam drives turbines which results in the generation of electricity

Water treatment plant Raw water which is taken from intake contains a lot of impurities in

the form of dissolves gases and other micro-organic component, however the water used in the power plant must be free from all types of impurities so water get treated before it used in plants. For which water is first deaerated and then by the help of a separator the micro-organic components and the other heavy impurities settled down at a section of the tank and then blown off

DM (Demineralised Water) Plant

Demineralized water also known as Deionized water, water that has had its mineral ions removed. Mineral ions such as cations of sodium, calcium, iron, copper, etc. and anions such as chloride, sulphate, nitrate, etc. are common ions present in water. Deionization is a physical process which uses specially-manufactured ion exchange resins which provides ion exchange site for the replacement of the mineral salts in water with water forming H+ and OH- ions. Because the majority of water impurities are dissolved salts, deionization produces a high purity water that is generally similar to distilled water, and this process is quick and without scale build up. PRINCIPLE: Raw water is passed via two small polystyrene bead filled (ion exchange resins) beds. While the cations get exchanged with hydrogen ions in first bed, the anions are exchanged with hydroxyl ions, in the second one.

 

Boiler and accessories

A boiler is usually a closed vessels type device used to create steam by applying heat energy to water. Boiler is generally of two types water tube boiler and fire tube boiler depending upon the requirement it often used. Coal is burned inside the combustion chamber of boiler.the products of combustion are nothing but gases. these gases which are at high temperature vaporize the water inside the boiler to steam.

Ash handling plant A large quantity of ash is, produced in steam power

plants using coal.

Ash produced in about 10 to 20% of the total coal burnt in the furnace.

A modern 2000MW plant produces about 5000 tons of ash daily.

Fly ash is collected with an electrostatic precipitator(ESP).

The stations use some conveyor arrangement to carry ash to dump sites directly or for carrying and loading it to trucks and wagons which transport it to the site of disposal

Accessories of a boiler Economizer :- An economizer is a device used to heat feed water by utilizing the heat in the exhaust flue gases before leaving through the chimney. Economizer improves the economy of the steam boilerAir preheater :-An air preheater (APH) absorbs waste heat from flue gas and transfers this heat to incoming cold air. APHs are typically used in Fired Heaters, Reformers, Process Furnaces, Boilers and other similar equipment to achieve high levels of thermal efficiencySuper heater :-A superheater is a device used to convert saturated steam or wet steam into superheated steam or dry steam. Super heaters are used in steam engines or in processes, such as steam reforming.

Re heater:- it is a type of super heater which is used to reheat the low pressure steam.

Stem turbine About 86% of all electric generation in the world is by use of steam turbines.In a thermal power plant generally 3 turbines are used to increase the efficiency.High Pressure Turbine(HPT):- The Superheated steam is directly fed to this turbine to rotate it.Intermediate Pressure Turbine(IPT):- The output from the HPT is reheated in a reheater and used to rotate IPT.Low Pressure Turbine(LPT):- The exhausted steam from IPT is directly fed to rotate the shaft of LPT.All the turbines are connect to a single shaft which is connected to the generator.

Cross section view of turbines

GeneratorConverts mechanical energy into electrical energy. Turbine is coupled with the Turbo-generator that normally spins at 3000 rpm in countries with 50 Hz supply frequency

The generated voltage is stepped up in Generator Transformer and the power is evacuated through transmission line feeders.

condenserTheses condensers are heat exchangers which covert steam from its gaseous to its liquid state, also known as phase transition.

It creates a very low pressure at the exhaust of turbine, this helps in converting heat energy of steam into mechanical energy in the prime mover.

The condensed steam can be used as feed water to the boiler.

Cooling towerRemove heat from the water discharged from the condenser so that the water can be re circulated and reused.

Air can be circulated in the cooling towers through natural draft and mechanical draft.In BTPS each unit has one cooling tower

consisting of 10 independent cells, each with its own induced draft fan, water supply & distribution grid.

An eight blade constant speed fan revolving at 114 rpm discharges warm saturated air through a kinetic energy recovery stake from each cell.

Electro static precipitator The principal components of an ESP are 2 sets of

electrodes insulated from each other.

First set of rows are electrically grounded vertical plates called collecting electrodes while the second set consists of wires called discharge electrodes.

The negatively charged fly ash particles are driven towards the collecting plate and the positive ions travel to the negatively charged wire electrodes.

Collected particulate matter is removed from the collecting plates by a mechanical hammer scrapping system

Chimney

A chimney may be considered as a cylindrical hollow tower made of bricks or steel. In BTPS the chimneys of eight units are made of bricks.

Chimneys are used to release the exhaust gases (coming from the furnace of the boiler) high up in the atmosphere. So, the height of the chimneys are made high.