Biomass heat exchanger furnace

Claim 1

A heat exchanger furnace comprising a first upright cylindrical housing; a second upright cylindrical housing disposed within said first housing and defining a combustion chamber having an inlet for fuel and an outlet for combustion gases generated within said combustion chamber; a plenum chamber formed between said first and second housings and having a top and a bottom; a first manifold having plural compartments and disposed adjacent the top of said plenum chamber and said second housing and having a first compartment thereof communicating with said outlet; a second manifold having plural compartments and disposed adjacent the bottom of said plenum chamber and said second housing; an inlet formed in said first housing and communicating with said plenum chamber for admitting a gaseous fluid; an outlet formed in said first housing and communicating with said plenum chamber and spaced substantially from said inlet for the gaseous fluid; means for circulating the gaseous fluid through said plenum chamber; means defining at least four sets of passageways for the combustion gases disposed within said plenum chamber and interconnecting corresponding compartments within said first and second manifolds for four successive passages of the combustion gases between said manifolds through said plenum chamber whereby the combustion gases flow successively between the corresponding compartments of said first and second manifolds and are in heat exchange relation with the gaseous fluid circulating through said plenum chamber; vent means formed in said first housing and in communication with said passageways whereby the combustion gases are discharged from the furnace subsequent to having successively flowed through the corresponding compartments of said manifolds and said passageways; and means for causing said combustion gases to flow through said manifolds, conduits and vent means.