Overfeed Stoker Boilers

Overfeed Stoker Boilers. Coal combusted in overfeed stoker boilers is fed from above onto a traveling or chain grate, and bums on the fuel bed as it progresses through the furnace. Ash falls into a pit at the rear of the stoker.6 The same TDF issues apply as were mentioned under spreader stoker boilers. 

In stoker boilers, fuel is either dropped or rammed onto a grate. Stoker boilers are identified by the type of feed mechanism and the type of grate. Feed may be by spreader, overfeed, or underfeed. Grates may be travelling, reciprocating, chain, or dump type. 

The most common type of boiler configuration to bum hog-fuel is the spreader stoker type, although some overfeed stokers also exist. Spreader stoker boilers can bum fuel with high moisture content, are relatively easy to operate, and have relatively high thermal efficiency. Overfeed stoked boilers have lower particulate emissions relative to spreader stoker boilers because less combustion occurs in suspension.13... 

Solid fuels that have not been pulverized require a stoker to introduce the fuel into the boiler furnace at a controlled rate. There are two broad classes of stoker (overfeed and underfeed) and often several types within each class. 

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