Abstract: A bio-mass burner construction for alternate fuels at temperatures from about 1,800 degrees F. to about 2,800 degrees F. to replace oil and gas burners. The burner utilizes a first burning chamber having a falling fuel, entrained bed zone positioned above a traveling grate having a porous metallic woven belt. Primary air is directed through the porous belt to establish an oxygen-starved first burning chamber. A second burning chamber in fluid communication with the first burning chamber, but having a restricted diameter, effectively provides a hot air gas nozzle. The second burning chamber receives a superheated secondary air source from cored apertures in interfitting refractory block members which provide a refractory lining for a portion of the first burning chamber and receive heat from the first burning chamber to heat the secondary air.