Grate firing

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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[edit]

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[edit]

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[edit]