What is steam boiler ? Classification and Advantages

 Steam Boiler

              Steam boiler is an equipment which generates steam by transferring heat produced by burning of fuel to water.

 Heat energy released by burning of fuel ( solid, liquid or gaseous ) is transferred to the water in the boiler drum ( shell ) .

 This converts water into steam at the required pressure and temperature.

Application of steam 

 Steam is generated by boilers may be used for the following purposes:

 

1) Power  generation

    Steam is used in a steam engine or turbine. Thus mechanical work or electric power may be obtained.

2) Heating

   Steam is used in winter air conditioning of residential and industrial buildings. It is also used to heat water for hot water supply.

3) Industrial process

     Steam is used for certain industrial processes such as sizing, bleaching etc. in textile industries. Steam is also used in sugar mills and chemical industries.

Classification of Boilers

   Steam boilers are classified according to the following criteria.

1) According to flow of water and hot gases

  a) Fire tube boilers     b) Water tube boilers

2) According to method of firing

  a) Internally fired boilers     b) Externally fired boilers

3) According to method of water circulation

 a) Natural circulation     b) Forced circulation

4) According to pressure developed 

 a) Low pressure boilers     b) High pressure boilers

5) According to nature of service

 a) Stationary boilers     b) Mobile boilers

6) According to position of boiler drum

 a) Horizontal boilers     b) Inclined boiler     c) Vertical boilers

7) According to number of drums

 a) Single drum boiler     b) Multi drum boiler

8) According to nature of draught 

 a) Natural draught boiler     b) Forced draught 

9) According to fuel used

 a) Coal  fired boilers     b) Oil fired boilers

High pressure boilers

    The recent practice is to use steam at higher pressure and temperature to improve the efficiency of the power plant.

 Modern high pressure boilers generate  the steam at very high pressure (as high as 200 bar and even above) example of high pressure boilers are lamont, Benson, Lo-effler, velox etc.

1) Forced circulation of water

2) parallel system of tubing instead of one continuous tube.

3) Improved method of heating. 

4) Improved method of fuel firing such as pulverised fuel firing

5) Compact and less floor space occupation

6) Highly economical.

Advantages of high pressure boilers

1) Scale formation is eliminated since water is circulated with high velocity through the tubes.

2) Tubes having light weight and better heating surface arrangement can be used.

3) Less space is required

4) Uniform heating of the parts reduces the danger of overheating and thermal stress problems.

5) Steam can be raised quickly to meet variable load requirements.

6) Rapid Start from cold is possible.

7) High pressure and high temperature steam can be obtained. This increases efficiency of the plant. 

Boiler Accessories

       Boiler Accessories are the devices which are used to the improve the performance of boiler plant.

1) Economiser

2) Air preheater

3) Superheater

4) Feed pump

5) Steam seperator

6) Steam trap