The invention relates to design of solid fuel boilers for heating domestic and industrial utilities adapted to utilize carbon-containing wastes. The technical inventive task is aimed at enhancing operation indices due to improvement of fuel combustion efficiency. The assigned task is characterized in that a heating boiler comprises a fire chamber, in the combustion chamber of which there are arranged an afterburner in the form of horizontally-disposed cylindrical pipe with a blanked-off end and holes on its surface and an ashpit connected to a source of forced oxidant supply, a heat exchanger and a smoke removal chimney communicated therebetween by gas pipes. The afterburner chamber is made with longitudinal inclined ribs on the lateral surface and holes therebetween and has a reaction chamber in the form of a cylinder with holes on the side surface arranged coaxially therein and with an annular gap connected to the channel of the forced oxidant supply, wherein the reaction chamber is connected to the heat exchanger via a catalyst mounted at its free end. Guiding cylindrical pipes of the afterburner chamber and the reaction chamber are designed as ovals, the big axes of which are perpendicular to the base of the combustion chamber.
