Coal-burning boiler

The utility model discloses a coal-burning boiler, which relates to the improvement technique of the boiler, comprising a furnace chamber, a fire grate arranged in the furnace chamber and a heat exchange portion. The upper part of the fire grate is provided with the heat exchange portion, and the heat exchange portion comprises a casing, a heat-exchanging water pipe; the casing is provided with a front and a back side walls and a top part, and the coal-burning boiler can be formed by the casing, an outer water sleeve and a furnace which are arranged in turn from inner to outer. The furnace and the outer water sleeve compose the water communication, the heat-exchanging water pipe is arranged transversely, and both ends of the heat-exchanging water pipe are arranged at the front and the back side walls of the casing and are communicated with the water communication at the front and the back walls of the casing. The bottom of the heat-exchanging water pipe is corresponding to the fire grate, the heat-exchanging water pipe can be arranged in the layered shape, and an upper and a lower furnace arches are arranged on the heat-exchanging water pipe. The contacting section of one end of the lower furnace arch and the back side wall is provided with a lower cleaning door, and gaps can be retained between the other end of the lower furnace arch and the front side wall. The upper furnace arch is arranged on the heat-exchanging water pipe at the upper part of the lower furnace arch. One end of the upper furnace arch is contacted with the front side wall, the gaps can be retained between the other end of the upper furnace arch and the back side wall, and the corresponding point of the upper furnace arch and the back side wall is provided with an upper cleaning door. The utility model has the advantages of high thermal efficiency and good cleaning effect.