The boiler comprises a primary furnace in which the combustion reactions are initiated, a secondary furnace extended by a radiating tube in which the combustion reactions are terminated, a heating surface disposed around the radiating tube and means for causing the combustion gases issuing from the radiating tube to pass into the annular space between the radiating tube and the heating surface. The secondary combustion radiating tube comprises two coaxial chambers, the first chamber terminating in a convergent part which directs the combustion gases toward the second chamber and the second chamber being closed at its end and having at its entrance a diameter larger than the diameter of the end of the convergent part so as to define with the end of the convergent part an annular opening through which the combustion gases injected into the second chamber are discharged. Means are provided for circulating the gases thus discharged in the annular space between said heating surface and the second chamber.