Grate firing

Grate firing is a type of industrial 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
 * 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.