Process for making a gas from solid fuels and burning the gas in a close coupled combustor to produce clean heat

A process for providing clean combustion of solid fuels comprising a means of delivering a relatively small quantity of primary air to the bottom of a quantity of solid fuel ignited at the top, said combustion forming a flaming pyrolysis zone producing charcoal and combustibly gas and moving slowly down through the solid fuel convering all of it to gas and charcoal at a constant rate, and a regulated quantity of secondary air then mixing with the gases to produce substantially complete combustion of the gases which produce clean hot combustion gases which are used for process heat, space heating or cooking.