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THERMAL POWER STATIONS�

FACULTY- ER. GOSTA PANDA

SEMESTER- 6TH, MECHANICAL

SUBJECT- POWER STATION ENGINEERING

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CONTENTS

  • INTRODUCTION
  • WORKING PRINCIPLE
  • GENERAL LAYOUT OF THERMAL POWER PLANT
  • MAIN EQUIPMENTS
  • WASTE GENERATED AND THEIR CONTROL
  • ADVANTAGES AND DISADVANTAGES

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INTRODUCTION

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  • A Thermal Power Plant converts the heat energy of coal into electrical energy. Coal is burnt in a boiler which converts water into steam. The expansion of steam in turbine produces mechanical power which drives the alternator coupled to the turbine.Thermal Power Plants contribute maximum to the generation of Power for any country.�
  • Thermal Power Plants constitute 75.43% of the total installed captive and non-captive power generation in India.�
  • In thermal generating stations coal, oil, natural gas etc. are employed as primary sources of energy.

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WORKING PRINCIPLE

  • Firstly the water is taken into the boiler from a water source. The boiler is heated with the help of coal.
  • The increase in temperature helps in the transformation of water into steam. 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.
  • A generator is connected to the steam turbine. 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.

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GENERAL LAYOUT OF THERMAL POWER PLANT

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MAIN EQUIPMENTS

  • Coal handling plant
  • Pulverizing plant
  • Boiler
  • Turbine
  • Condenser
  • Cooling towers and ponds
  • Feed water heater
  • Economizer
  • Air preheater

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COAL HANDLING PLANT

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  • Coal is transported to power station by rail or road and stored in coal storage plant and then pulverized.
  • The function of coal handling plant is automatic feeding of coal to the boiler furnace.
  • A thermal power plant burns enormous amounts of coal.
  • A 200MW plant may require around 2000 tons of coal daily.

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PULVERIZING PLANT

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  • In modern thermal power plant, coal is pulverized i.e. ground to dust like size and carried to the furnace in a stream of hot air. Pulverizing is a means of exposing a large surface area to the action of oxygen and consequently helping combustion.
  • Pulverizing process consists 3 stages classified as:
  • Feeding
  • Drying
  • Grinding

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BOILER

The function of boiler is to generate steam at desired pressure and temperature by transferring heat produced by burning of fuel in a furnace to change water into steam.

TURBINE

In thermal power plants generally 3 turbines are used to increases the efficiency.

  • High pressure turbine
  • Intermediate pressure turbine
  • Low pressure turbine

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CONDENSER

The surface condenser is a shell and tube heat exchanger where cooling water flows through tubes and exhaust steam fed into the shell surrounds the tubes. as a result, steam condense outside the tubes.

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COOLING TOWERS AND PONDS

  • A condenser needs huge quantity of water to condense the steam.
  • Most plants use cooled cooling system where warm water coming from condenser is cooled and reused.
  • Cooling tower is a steel or concrete hyperbolic structure with the height of 150m.

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FEED WATER HEATER

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  • Feed water heating improves overall plant efficiency.

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  • Thermal stresses due to cold water entering the boiler drum are avoided.

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  • Quality of steam produced by the boiler is increased.

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ECONOMIZER

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  • Flue gases coming out of the boiler carry lot of heat. An economizer extracts a part of this heat from flue gases and uses it for heating feed water.

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  • Saving coal consumption and higher boiler efficiency.

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AIR PREHEATER

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  • The function of air preheaters is to preheat the air before entering to the furnace by utilizing some of the energy left in the flue gases before exhausting them to the atmosphere.

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  • After flue gases leave economizer, some further heat can be extracted from them and used to heat incoming heat. Cooling of flue gases by 20 degree centigrade increases the plant efficiency by 1%.

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WASTE GENERATED AND THEIR CONTROL

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  • ASH HANDLING PLANT

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  • WATER HANDLING PLANT

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ASH HANDLING PLANT

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  • The ash from the boiler is collected in two forms-

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  • Bottom ash(slurry): It's a waste which is dumped into ash pond.

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  • Fly ash: Fly ash is separated from flue gases in esp.

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WATER HANDLING PLANT

Water in a Power Plant is used for:-

  • Production of Steam- for rotating turbine.
  • Cooling Purpose- For cooling of various equipment .
  • Water is recycled and used for various purpose:

Raw Water For Cooling Purposes Steam Condenser Raw Water

  • About 4 cubic meter water is lost/day/mw.

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ADVANTAGES:

  • The fuel used is quite cheap.
  • Less initial cost as compare to other generating stations.
  • It can be installed at any place irrespective of the existence of coal. The coal can be transported to the site of plant by rail or roads.

DISADVANTAGES:

  • It pollutes the atmosphere due to producing large amount of smoke and fumes.
  • Higher maintenance cost and operational cost.
  • Huge requirement of water.

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Thank you