Chain-grate boiler

The utility model relates to a chain-grate boiler which comprises a boiler body, an induced draft fan, a circulating fan, a primary fan and an air supply bin. Primary air drawn out of natural air is supplied into the air supply bin through the primary fan, coal is promoted to be dried, combusted and burnt out, circulating smoke drawn out of total smoke behind the induced draft fan is supplied into combustion air supply bin bodies in the air supply bin through the circulating fan, and generation of NOx is restrained. Furthermore, the circulating smoke drawn out of the total smoke behind the induced draft fan is partially supplied into a rear arch air distribution opening through the circulating fan, smoke and gas mixing in a hearth is enhanced, combustion of fuel is promoted, and the combustion efficiency of the chain-grate boiler is improved.