Correct Answer - Option 4 : Cyclone burner
Pulverised Coal Burners:
- Burners are devices that allow uniform mixing of fuel with air hence lead to efficient and complete combustion.
- The burner receives the fuel along with the primary air in a central passage, while the secondary air is supplied around the passage.
- A good design of the burner is essential to achieve complete combustion of the fuel.
Thus a good burner should meet a number of design requirements. The important requirements of an efficient pulverised coal burner are as follows:
- It should mix the fuel and primary air thoroughly and inject the mixture into the furnace.
- It should create proper· turbulence for air-fuel mixing and maintain a stable combustion.
- It should be able to control the flame shape and flame travel by varying the amount of secondary air.
- Coal-air mixture should move away from the burner at a rate equal to the flame travel so as to avoid flash back.
- It should be projected properly to avoid overheating, wear and internal fires.
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Types of burners:
There are four types of burners used for the pulverized fuel burning.
1) Long-Flame or U-Flame or Stream lined burner
2) Short Flame or Turbulent Burner
3) Tangential Burners
4) Cyclone Burner
With reference to steam power plant, cyclone burner is used because of the following advantages.
- Since it uses crushed coal, it saves the cost of pulverization.
- All the incombustible is retained in cyclone burner, and hence the boiler fouling problems are reduced.
- It requires less excess air, as it uses forced draught
- Slag-recovery is around 80% and dust passing to the stack is about 10%. Thus simple equipment can be used for dust removal.
- Fly ash problem is reduced to a great extent.
- Low grade fuels can be used.
Disadvantages of cyclone burner:
- It requires high pressure draught and consumes higher power
- It produces more oxides of nitrogen, which creates atmospheric pollution
