Characteristics and Air Distribution of Staged Combustion on Chain Grates

A chain grate uses staged combustion to raise combustion efficiency and reduce pollutant emissions. The fuel completes preheating, drying, ignition, combustion and burnout in stages on the grate, and air is distributed according to the need of each stage.

Staged combustion

Fuel enters at the front of the grate and moves gradually backwards, passing in turn through preheating, drying, ignition, combustion and burnout. Staged combustion lets the fuel burn more fully, reduces unburned losses and raises boiler thermal efficiency.

Air distribution

Staged combustion on a chain grate usually follows the strategy of “less air at the front and rear, more air in the middle”. At the front and rear the fuel is in preheating and burnout and needs less oxygen, so the air volume can be reduced; in the middle the fuel is igniting and burning and needs the most oxygen, so the air volume is increased. This adjusts air supply to the combustion process, avoids unnecessary oxygen waste and heat loss, and full combustion also reduces the formation of carbon monoxide, nitrogen oxides and other harmful substances.

Operating adjustment

In practice the air distribution should be adjusted flexibly to the fuel characteristics and boiler operating conditions. Only when staged combustion and air distribution work together can the boiler keep stable combustion and good thermal efficiency.