Solid fuel furnace

A solid fuel furnace for heating a recirculating heat medium and comprising:

• a combustion chamber having an inlet and an outlet, fuel support means located between the inlet and the outlet for supporting a supply of particulate fuel for combustion thereof,
• the combustion chamber inlet being located above the support means for receiving a supply of fuel and a supply of air to be delivered to the fuel support means from fuel delivery means and air supply means respectively, the combustion chamber being defined in part by walls which converge downwardly from the inlet towards the fuel support means, said convergement walls constituting means effective to throttle said air supply as it passes through or over said fuel,
• a combustion products suspension and separation chamber for separating heated combustion gases from combustion products, and for retaining said combustion products in suspension sufficiently long to permit continued combustion thereof, the combustion products suspension and separation chamber having an inlet connected to the outlet of the combustion chamber and an outlet for permitting the passage of heated combustion gases and incompletely combusted products therethrough;
• downwardly extending passage means having an inlet connected to the outlet of the combustion products suspension and separation chamber, and an outlet connected to a main expansion chamber, said passage means having a smaller cross-section in the direction of heated combustion gas from the said combustion products suspension and separation chamber, and said smaller cross-section constituting means effective to throttle and accelerate said heated combustion gases and incompletely combusted products into said main expansion chamber,
• said main expansion chamber being of substantially greater volume than said passage means to cause said heated combustion gases and incompletely combusted products to slow down sufficiently such that said incompletely combusted products are separated by gravity from said heated combustion gases,
• means for collecting said incompletely combusted products,
• heat exchange means having an inlet for receiving the heated combustion gases from the outlet of the main expansion chamber, and said heat exchange means transferring heat from the combustion gases to the recirculating heat medium, the heat exchange means having an outlet for venting said combustion gases to atmosphere after transferring heat to the recirculating heat medium.