MECHANICAL THEORY

Layout of Steam Power Plant, Simple Cross Tube Vertical Boiler-In detailed

The layout of Steam Power Plant-Construction, Working, Advantages, and Disadvantages with Diagram: The steam power plant is also called a Thermal Power plant. The steam power plant is an important source for producing electricity. The major source of electricity to our homes is through the thermal power plant. In this article, we will discuss the construction, working, components, advantages, and disadvantages of the steam power plant along with the diagram.

Layout of steam power plant
Layout of steam power plant

Layout of Steam Power Plant-Construction:

The layout of the steam power plant consists of the following parts. They are

  1. Coal and Ash Handling Unit
  2. Boiler
  3. Superheater
  4. Steam Turbine
  5. Generator
  6. Condenser
  7. Economizer
  8. Feed Pump
  9. Cooling Tower
  10. Chimney

Working of Steam Power Plant:

The layout of Steam Power Plant will be discussed by means of 3 circuits. They are

  1. Furnace Circuit
  2. Steam Circuit
  3. Cooling Water circuit

The explanation of these circuits is as follows.

1.Furnace Circuit:

Before feeding to the furnace, the coal is to be converted into the pulverized form and after combustion, the ash is to be collected into the Ash Pit (Ash handling unit).

2.Steam Circuit:

The water present in the boiler is heated up by means of a furnace and as the density of steam is less than the density of water, the steam will deposit on the surface of the water.

The steam is taken from the boiler and is superheated so that, the steam present should be free from the water molecules. Thus the superheated steam strikes the turbine blades with a high speed which makes the turbine to rotate.

A generator is attached to the rotor of the turbine and as the turbine rotates, it also rotates with the speed of the turbine. The generator converts one form of energy to another i.e. mechanical energy of the turbine into electrical energy.

After striking the turbine, the steam enters into the condenser where it gets condensed with the help of cold water from the cooling tower.

The condensed water(also known as condensate) along with the feedwater, enters into the economizer. The duty of the economizer is to extract a part of the heat from the condensate by adding the feed water to increase the feedwater temperature before supplying it to the boiler. 

This feedwater is sent to the boiler by means of a feed pump.

3.Cooling Water Circuit:

The water that is used to condense the steam in the condenser was supplied from the cooling tower. The hot steam cannot be released directly into the atmosphere from the chimneys and by doing so, the hot steam will affect the atmosphere.

For this reason, the hot steam along with water particles was released from the larger heights in the cooling tower, so that the water will fall down and the air particles will escape into the atmosphere.

After burning of the coal, it is transported to ash handling plant and finally to the ash storage.

In this way, the feed water rotates throughout the circuit with few loses of water and the power is generated from the steam which is used to drive the turbines.

This is the detailed explanation for the Layout of Steam Power plant. Now, let’s discuss the simple cross tube boiler with its parts and working so that we can understand easily how a steam power plant runs.

Read: Classification of IC Engine, Basic Engine Components, and Nomenclature of IC Engines


Simple Cross Tube Vertical Boiler:

The components of the simple cross tube boiler are as follows.

  • Cylindrical shell
  • Cross tubes
  • Grate
  • Firebox
  • Ashpit
  • Fire hole
  • Handhole
  • Manhole
  • Steam stop valve
  • Chimney
  • Uptake
  • Safety Valve
  • Pressure Guage
simple cross tube vertical boiler
simple cross tube vertical boiler

Working of Simple Cross Tube Vertical Boiler:

  • It consists of a cylindrical firebox placed at the bottom is a fire Grate which is surrounded by a cylindrical shell. The fuel is to be placed on the Grate and for combustion of fuel, the spark(fire) is given through the Fire hole.
  • To improve the circulation of water and to increase the heating surface, the firebox is fitted with one or more no. of cross tubes.
  • These cross tubes are riveted to the Firebox and these tubes are slightly inclined to ensure efficient circulation of water.
  • These cross tubes are cleaned from the hand hole which is placed at the end of each tube.
  • For inspection and cleaning of the boiler, Manhole is provided.
  • A chimney is placed at the top of Uptake, which passes from the crown of the shell.
  • Water is to be placed in the shell and when the fuel burns on the grate, the hot gases travel towards the chimney and heat the water in the shell and cross tubes.
  • The steam that is generated due to the flue gases will be deposited on the top of the water which is considered to be as steam space. The steam is then collected from the Steam stop valve and is used to drive the turbines for the generation of electricity.
  • The flue gases will be passed out from the chimney which is placed on the Uptake.
  • The ash from the burnt fuel is collected in the Ashpit.

Note:

  • The evaporative capacity of conventional cross tube boiler ranges from 50kg to 100 kg of steam/hr.
  • Pressure varies from 2 bar to 10 bar.
  • Total heating surface area is 8 to 10 times the Grate area.
  • The size of the cross tube vertical boiler ranges from 0.6m Dia *1.2m height and as small as 2m Dia *4m height.
  • The efficiency under normal factory conditions is about 50%.

This is the working of a simple cross tube boiler in a detailed way.

Types of Boiler:

1.Water Tube Boiler

Ex: Babcock and Wilcox Boiler

2.Fire Tube Boiler

Ex: Cochran Boiler

 

 

 

 

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