DZL type boiler is a horizontal three return fire and water tube type wood fired industrial boiler. There are two fire tubes in the boiler barrel , with both sides light pipe water-wall tubes; the chain grate which can feed coal by stocker/ and is equipped with drums, induced draft fan realize mechanical ventilation. Fuel from coal scuttle fell to grate stoker, along with the chamber into after burning, smoke after the upper chamber after arch, the smoke pass through behind of combustor, through up the combustor into the first tube bundle then get front smoke box ,then through the front smoke box into the second tube bundle then get to back smoke box , finally through the induced draft fan smoke the introduction into the flue, dust catcher and the chimney, the last row to the atmosphere