Solid Fuel Firing
The solid fuels like coal, coke etc. are burned by following methods :
1. Hand firing system :
Though the hand firing system is simple and suitable for small power plants but it cannot be used for high capacity power plants since it is difficult to achieve the uniform combustion and it gives low combustion efficiency. In this grate is used to support the fuel and the openings are provided for air to enter on to the grate for combustion of fuel.
2 . Stoker firing :
A stoker is a power operated fuel feeding mechanism and grate. With stoker firing, it allows to burn large quantities of fuel, with case in controlling the combustion with higher combustion efficiency, less labour of handling ash and they are self cleansing. The only problem is that stokers are costly and they have high maintenance and repair cost resulted from high furnace temperatures.
Advantages of Stoker Firing :
- Ease of control of combustion.
- High combustion efficiency.
- Cheaper grade of fuel can be used.
- Progressive and gradual distillation of volatile matter.
- Smokeless combustion.
- Less labour is needed therefore labour (fireman) cost is reduced.
- System is reliable.
Disadvantages of Stoker Firing :
- Capital cost is high.
- There is a loss of coal through the grates.
- Steam demand due to load fluctuations on plant cannot be met efficiently.
- It has complicated construction and arrangement.
- There is excessive wear of moving parts due to abrasive action of coal.