Working Process of Thermal Power Plant

 A Thermal power plant is a power plant where steam is used to drive a steam turbine. This turbine is connected to an electrical generator. After this, the water is condensed, and may be used again. This is known as the Rankine cycle. There are different procedures that can be used to heat the water; this gives different types of thermal power plants:

Components of a Thermal Power Plant:

1. Cooling tower:

A cooling tower is a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature.

2. Cooling water pump:

Water cooling is a method of heat removal from components and industrial equipment. As opposed to air cooling, water is used as the heat conductor. Water cooling is commonly used for cooling automobile internal combustion engines and large industrial facilities such as steam electric power plants, hydroelectric generators, petroleum refineries and chemical plants.[1]Other uses include cooling the barrels of machine guns, cooling of lubricant oil in pumps; for cooling purposes in heat ex-changers; cooling products from tanks or columns, and recently, cooling of various major components inside high-end-personal computers. The main mechanism for water cooling is convective heat transfer

3. transmission line (3-phase):

Electric power transmission is the bulk transfer of electrical energy, from generating power plants to electrical substations located near demand centers. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. Transmission lines, when interconnected with each other, become transmission networks. The combined transmission and distribution network is known as the “power grid” in North America, or just “the grid”. In the United Kingdom, the network is known as the “National Grid”.

4. Step-up transformer (3-phase):

A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.these are of many types as following:1.step-up 2.step-down

5. Electrical generator (3-phase):

A Electrical generator,  is a solid state device that converts heat (temperature differences) directly into electrical energy through a phenomenon called the Seebeck effect (a form of thermal electric effect). electrical generators function like heat engines, but are less bulky and have no moving parts. However, TEGs are typically more expensive and less efficient.[1]

Thermal electric generators could be used in power plants in order to convert waste heat into additional electrical power and in automobiles as automotive thermal electric generators (ATGs) to increase fuel efficiency. Another application is radio-isotope thermoelectric generators which are used in space probes, which has the same mechanism but use radioisotopes to generate the required heat difference

6. Low pressure steam turbine:

A steam turbine is a device which extracts thermal energy  from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Sir Charles Parsons in 1884.it is mostly used in thermal power plant, Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 90% of all electricity generation in the United States (1996) is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process

7. Condensate pump:

Condensate pumps as used in hydronic systems are usually electrically powered centrifugal pumps. As used in homes and individual heat exchangers, they are often small and rated at a fraction of a horsepower, but in commercial applications they range in size up to many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. Large industrial pumps may also serve as the feedwater pump for returning the condensate under pressure to a boiler.

Applications:

Condensate pumps may be used to pump the condensate produced from latent water vapor in any of the following gas mixtures:

  • Conditioned (cooled or heated) building air
  • Refrigerated air in cooling and freezing systems
  • Steam in heat exchangers and radiators
  • The exhaust stream of very-high-efficiency furnaces

Condensate recovery systems help reduce three tangible costs of producing steam:

  • Fuel/energy costs
  • Boiler water make-up and sewage treatment
  • Boiler water chemical treatment

8. Surface condenser:

A surface condenser is a commonly used term for a water-cooled shell and tube heat ex-changer installed on the exhaust steam from a steam turbine in thermal power stations. These condensers are heat ex-changers which convert steam from its gaseous to its liquid state at a pressure below atmospheric pressure. Where cooling water is in short supply, an air-cooled condenser is often used. An air-cooled condenser is however, significantly more expensive and cannot achieve as low a steam turbine exhaust pressure (and temperature) as a water-cooled surface condenser.

Surface condensers are also used in applications and industries other than the condensing of steam turbine exhaust in power plants

9. Intermediate pressure steam turbine:

In Intermediate pressure steam turbine the working process of high pressure and the low pressure steam of the thermal power plant and the working carried out in the intermediate pressure of steam turbine is same as the steam turbine

10. Steam Control valve:

In the Steam control valves the flow of steam from the turbines from one phase of intermediate to the another phase the overflow take place in the steam turbine then the working of thermal power plant leads to explosive of high pressured steam which is unbearable.

11. High pressure steam turbine:

In High pressure steam turbine  working process of high pressure  of the thermal power plant and the efficiency carried out in the intermediate pressure of steam turbine is leads to the overflow of steam pressure

12. Deaerator:

A deaerator is a device that is widely used for the removal of oxygen and other dissolved gases from the feedwater to steam-generating boilers. In particular, dissolved oxygen in boiler feedwaters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). Dissolved carbon dioxide combines with water to form carbonic acid that causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less as well as essentially eliminating carbon dioxide

13. Feedwater heater:

A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system.This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduced back into the steam cycle.

In a steam power plant (usually modeled as a modified Rankine cycle), feedwater heaters allow the feedwater to be brought up to the saturation temperature very gradually. This minimizes the inevitable irreversibilities associated with heat transfer to the working fluid (water). See the article on the Second Law of Thermodynamics for a further discussion of such irreversibilities

14. Boiler steam drum:

A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam at the top end of the water tubes. The drum stores the steam generated in the water tubes and acts as a phase-separator for the steam/water mixture. The difference in densities between hot and cold water helps in the accumulation of the “hotter”-water/and saturated-steam into the steam-drum

15. Super heater:

A super heater is a device used to convert saturated steam or wet steam into dry steam used in steam engines or in processes, such as steam reforming. There are three types of superheaters namely: radiant, convection, and separately fired. A super heater can vary in size from a few tens of feet to several hundred feet (a few metres to some hundred metres)

16. Forced draught (draft) fan:

A blower (fan) that creates a positive pressure, forcing air into a combustion chamber.

17. Reheater:

1. Cookery to heat or be heated again: to reheat yesterday’s soup.
2. Aeronautics  to add fuel to the exhaust gases of an aircraft jet engine)to produce additional heat and thrust
3. Aeronautics another name  for after burning

18. Combustion air intake:

Combustion  or burning is a high-temperature exothermic redox chemical reaction between a fuel and anoxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion in a fire produces a flame, and the heat produced can make combustion self-sustaining. Combustion is often a complicated sequence of elementary radical reactions. Solid fuels, such as wood, first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that light in the form of either glowing or a flame is produced. A simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction commonly used to fuel rocket engines. This reaction releases 242 kJ/mol of enthalpy (heat).

2H 2(g) + O2(g) → 2H2O(g)

19. Induced draught (draft) fan:

A mechanical draft produced by suction stream jets or fans at the point where air or gases leave a unit.

Main Disadvantage of Fossil Fuel Thermal Power Plant[change | change source]

Fossil fueled thermal power plants produce a large part of man-made CO2 emissions to the atmosphere, and efforts to reduce these are varied and widespread.

  1. It occupies lot of space and release gases.
  • Geothermic power plant
  • thermal energy from the oceans
  • solar power
  • nuclear power plant
  • coal and other fossil fuels,

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Chinna

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