THERMAL POWER PLANT

THERMAL POWER PLANT

Thermal power plants are one of the main sources of electricity in both industrialized and developing countries. These plants have drawn flak on consumption of non-renewable sources of energy at a rapid rate and also since they release huge amounts of greenhouse gases into the atmosphere. The anti-greenhouse gas activists are calling for thermal power to be replaced by other cleaner sources of energy.

 

EXPLANATION:

Functioning of thermal power plant:

In a thermal power plant, one of coal, oil or natural gas is used to heat the boiler to convert the water into steam. The steam is used to turn a turbine, which is connected to a generator. When the turbine turns, electricity is generated and given as output by the generator, which is then supplied to the consumers through high-voltage power lines.

Detailed process of power generation in a thermal power plant:

1)   Water intake:

Firstly, water is taken into the boiler through a water source. If water is available in a plenty in the region, then the source is an open pond or river. If water is scarce, then it is recycled and the same water is used over and over again.

2)     Boiler heating:

 The boiler is heated with the help of oil, coal or natural gas. A furnace is used to heat the fuel and supply the heat produced to the boiler. The increase in temperature helps in the transformation of water into steam.

3)     Steam Turbine:

 The steam generated in the boiler is sent through a steam turbine. The turbine has blades that rotate when high velocity steam flows across them. This rotation of turbine blades is used to generate electricity.

4)     Generator:

A generator is connected to the steam turbine. When the turbine rotates, the generator produces electricity which is then passed on to the power distribution systems.

5)     Special mountings:

There is some other equipment like the economizer and air pre-heater. An economizer uses the heat from the exhaust gases to heat the feed water. An air pre-heater heats the air sent into the combustion chamber to improve the efficiency of the combustion process.

6)     Ash collection system:

 There is a separate residue and ash collection system in place to collect all the waste materials from the combustion process and to prevent them from escaping into the atmosphere.

Apart from this, there are various other monitoring systems and instruments in place to keep track of the functioning of all the devices. This prevents any hazards from taking place in the plant.

WORKING CYCLE:

               Coal & Ash Cycle

                  Steam& feed water cycle

                  Air & Flue gases cycle

                  Cooling water cycle

                  Electricity generation

Coal and ash cycle:

Coal arrives at storage yard and after necessary handling it passes on to the furnace through fuel feeding system. In case of pulversing system, coal is pulverised and then goes to the fuel burners. Ash resulting from combustion of coal gets collected at the ash pit and is removed to ash storage yard by ash handling equipment.

Air and gas cycle:

Air is taken in from atmosphere through forced draught or induced draught fans and passes to the furnace through air preheater, where it has been heated of the flue gases which pass to chimney via preheater. The hot gases of combustion first flow through boiler tubes, and superheater tubes in furnace then through economiser and then finally through air preheater and then discharges through chimey to the atmosphere.

Feed water and steam cycle:

The condensate leaving the condensor is first heated in a closed water heaters, the bleeded steam from the turbine is used to heat the feed water in the heaters.

In boiler drum and tubes, water circulates due to natural circulation. Wet steam from drum further is heated up in superheater.Steam then expands in turbine and produces power. From there it is exhausted in to condensor. The condensate is collected in hot well. Then it goes to feed water heaters, economiser and to the boiler. Make up water is added in the condensor after purification.

Cooling water cycle:

The condensor requires cooling water to condense the exhaust steam. The water is cooled in cooling tower or in cooling ponds and resued again and again. Some make up cooling water is added in the circuit.

ADVANTAGES: 

1. They can be located very conviniently near the load centres.

2. Does not require shielding like required in nuclear power plants.

3.Unlike nuclear power plants whose power production method is difficult, for thermal             power plants it is easy if compared.

4. Transmission costs are reduced as they can be set up near the industry.
5. The portion of steam generated can be used as process steam in differentindustries.
6. Steam engines and turbines can work under 25% of overload capacity.
7. Able to respond changing loads without difficulty.

DISADVANTAGES:

1. Large amounts of water are required.
2. Great difficulties experienced in coal handling and disposal of ash.
3. Takes long time to be erected and put into action.
4. Maintenance and operating costs are high.
5. With increase in pressure and temperature, the cost of plant increases.
6. Troubles from smoke and heat from the plant.

SITE SELECTION PARAMETERS:

1) Availability of water

Thermal power plant uses water as working fluid which is repeatedly evaporated and condensed. There is always some water loss and make up water is always required. Water is used in large volumes in a steam power plant for following purposes.

· In boiler to raise the steam

· For cooling purposes such as in condensers

· As a carrying medium such as in disposal of ash

· For drinking purpose.

Thus for a 250MW power station, cooling water required may be 62X106 litres per hour and make up water required may be something 1 million litre per hour. So while selecting a site for the thermal power plant, water is the most important factor.

2) Land:

Considerable area is required for a power station. For a 2000MW plant, the land requirement may be of order of 250 to 300 acres.The cost of land should be reasonable. Staff colony, coal storage, ash disposal requires appropriate amount of land. If the site is far away from a big city then entirely new facilities such as marketing, dairies, etc will have to be provided for the staff.
The distribution of land can be
Building=10%
Coal storage= 33%
Cooling towers= 27%
Switch yard=7%
Other areas= 23%
Hence land is also an important factor for site selection of thermal power station.

3) Availability of raw material:

 Modern steam power stations using coal and oil as fuel require large quantity of it per annum. A plant consumes a large quantity of coal so it should be located as near as possible to the coal fields to save the transportation charges. Besides transportation charges a plant located away from the coal fields may face some problems like, there may be failure of transportation system, strike at the mines, etc.

STATUS OF THERMAL POWER PLANT:

for status of international status use below link :
http://en.wikipedia.org/wiki/List_of_coal_power_stations
 FOR INDIA:

STATE                                           NAME OF POWER STATION                 CAPACITY (MW)

1. ANDHRA PRADESH                    Kothagndam                                                  240

2  ASSAM                                         Gauhati                                                            40

3  BIHAR                                          Barauni                                                          150

                                                          Bokaro                                                           225

                                                          Patratu                                                           400

4 DELHI                                           Rajghat                                                           200

                                                          Indraprashstha                                             350

                                                          Badarpur                                                       300

5 GUJARAT                                       Dhuvaran                                                      530

                                                          Ukai                                                                240

6 HARAYANA                                   Faridabad                                                      200

                                                          Panipat                                                           220

7 MADHYA PRADESH                     Kobra                                                             420

                                                          Satpura                                                          300

8 MAHARASHRTRA                        Nagpur (koradi)                                           480

                                                          Nashik                                                            280

                                                          Paras                                                              90

9 ORISSA                                          Talcher                                                           254

10  TAMILNADU                              Neyvelli                                                          600

                                                          Eunose                                                           450

11  UTTARPRADESH                       Harduaganj                                                   540

                                                          Obra                                                               550

12  WEST BENGAL                          Samtaldih                                                      480

          Chandrapur                                                   420

                              

CWIT, PUNE

MECHANICAL DEPARTMENT

Subject: POWER PLANT ENGINEERING

For such reasons a considerable amount of coal (at least 15 days supply) must be stored at all power station. It will be convinient to locate the power station to the nearest railway station if the coal fields are far away from the power station.

In case it is not possible to locate the power station near railway station, at least arrangement should be made for a railway siding to the power plant so that the coal wagon can be shunted from station to the site of power plant.

4)Topography

The civil engineering work involved in erecting the plant should be minimum. This involves levelling of the site, foundation work, etc. Site subsoil should not require filling or blasting. Also soil should not contain mineral deposits.

5) Expansion

The site should allow for economical extension due to growth of load. It means

while selecting land some land should be aquired for future expansion of plant.

6) Pollution

Site selected should not creat any sort of nuisance to the neighboring areas due

to emission of smoke, noise , pollutants, water vapour, etc.

7) Ash disposal

Ash is the main waste product of steam power plant.If the site is near the coalmine, then it can be dumped into the disused mines. Or the site may be near a river, a sea or lake into which the ash can be dumped.Some sites acquire waste land for ash disposal.

8) Town planning.

Since the workers have to remain in the plant for non-stop working of thermal power plant, facility for them and their family to live near the plant should be done

CONCLUSION:

After studying thermal power plant we conclude that thermal power plant is easy way to produce electricity. Row material of the Thermal power plant  is COAL & it is easily available. But Thermal power plant is more dangerous for environment.

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