Combustion system with partial recirculation of exhaust gases and feed mechanism therefor

A combustion system comprising a generally rectangular combustion chamber having side walls, front and back end walls, a bottom wall and a top wall, a fire tube boiler horizontally disposed in the top portion of said combustion chamber and which has its rear end wall spaced forwardly from said back wall, so as to define a rear combustion chamber portion disposed rearwardly of said boiler and in communication with the fire tube inlets opening at said rear end wall of of said boiler, a flue duct in communication with the fire tube outlets opening at the front end wall of said boiler, said boiler combustion chamber having a major portion located underneath said boiler, a particulate fuel feed conduit passing through a wall of said combustion chamber and having an inner straight portion exposed within said combustion chamber major portion and having a discharge end located underneath said boiler forwardly of said rear combustion chamber portion and intermediate said boiler and said bottom wall, said inner straight portion being directed upwardly forwardly towards said front wall and said boiler, means to feed primary air and means to throw particulate fuel into said combustion chamber major portion through said feed circuit, means to mix secondary air with the exhaust gases in said flue duct, means to separate suspended particles in the mixture of secondary air and exhaust gases in said flue duct, means to recirculate the separated particles and a portion of said mixture back into the combustion chamber, said last-named means including several inlets in said bottom wall of said combustion chamber, and means to discharge the remaining portion of said mixture into the atmosphere, said remaining portion being substantially free of suspended particles.