Grate firing
# 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 $MW/m^2,$ maximum grate area 100 $m^2$
* 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.

