Grate firing
Grate firing was the first combustion system used for solid fuels. It now is used mainly for burning waste and biomass, but also for smaller coal furnaces.
- Capacities 0.3 to 175 MWth in industry and CHP
- Fuel fired per grate area 1-2 MW/m2, maximum grate area 100 m2
- Grates are typical only suitable for coarse particles, for fine particles a spreader is required, increases max. capacity
- Primary air through the grate (also used for cooling) and secondary air
Types
travelling grate in an old steam boiler
- Travelling grate
- A moving grate which is covered with a fuel layer, 10-30 cm. Power control by means of varying the grate velocity
- Reciprocating grate
- For ash-rich, low calorific fuels like municipal waste, arrangement of stationary and moving grates -> conveying and mixing (forward-moving type or reverse-action grate)
- Vibrating grate
- Water cooled membrane wall, with holes for air. For burning coal or wood.
Grate area
The grate area is the area of the grate (length x width). The larger the grate area, the more fuel can be burned per hour. The amount of fuel burned also depends on the fuel or bed movement velocity.
See also
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