BURN COAL ON FUEL BEDS IN SMALL INDUSTRIAL BOILERS.

Fuel beds provide the most economical method for burning coal in almost all industrial boilers rated less than about 200,000 lb/hr of steam. In fuel-bed firing, coal is pushed, dropped or thrown onto a grate by a mechanical device called a stoker. Stokers can be divided into two general classes, depending on the direction from which raw coal reaches the fuel bed: overfeeds, in which the fuel comes from above; and underfeeds, in which it comes from below. The overfeed group includes spreader and mass-burning stokers. The latter, sometimes called crossfeed stokers, are more commonly referred to by specific design: chain-grate, traveling-grate or water-cooled vibrating-grate. Types of underfeed stokers are single-retort and multiple-retort.