DZL Series boiler is single drum, horizontal, three-pass, package, and water tube, fire-tube boiler. On both sides of the boiler chamber, there are bare-tube water-cooled wall, top ends of which are connected to the upper drums, and lower ends are linked with the headers respectively, and forming the combustion chamber with the front and the rear walls. Two bundles of gas tubes are set in the drum. The burned gas from the boiler chamber flows off longitudinally in the gas tubes, then is induced into the cast-iron economizer laid at the end of the boiler, finally is discharged into the chimney via the dust extractor. The lower part of the boiler is the burning device that is equipped with the light-type chain grate stoker, the coal supply machine, the ash extractor, the dust collector and the electric control box. It realizes the mechanization of coal supply and ash discharging and the automatic control of feed water.