Furnace with integrated heat recovery utilizing radiative recuperator for preheating combustion reactants using heat from flue gas

A furnace utilizing recuperative heat exchange for preheating a combustion reactant with waste heat energy from flue gas, comprising:

• a combustion chamber including a combustion space enclosed by a furnace wall in which a fuel and an oxidant are combusted to heat solid and/or molten glass or glass-making materials or solid and/or molten metal and thereby producing flue gas;
• one or more burners mounted in the furnace wall adapted and configured to inject preheated fuel and/or preheated oxidant into the combustion chamber interior for combustion therein;
• a duct extending along an axis and having a first end receiving at least a portion of the flue gas produced in the combustion chamber and a second opposed end discharging the received flue gas;
• one or more insulating walls extending parallel to the duct axis and adjacently to an outer surface of the duct;
• the one or more insulating walls being comprised of an insulating material, a non-reactive gas space being defined between an outer surface of the duct and an inner surface of the insulating wall;
• and
• one or more metallic pipes extending through the non-reactive gas space, the one or more metallic pipes receiving the combustion oxidant or the combustion fuel and discharging the combustion oxidant or the combustion fuel after being preheated, wherein one or more portions of the duct is comprised of a material having a thermal conductivity of greater than 1 W/(m·K), wherein:
• each of the one or more metallic pipes are gas-tight;
• gaps exist in between the portion or portions with a thermal conductivity of more than 1 W/(m*K) and each of the one or more metallic pipes;
• gaps exist between each of the one or more metallic pipes;
• and
• gaps exist between each of the one or more metallic pipes and the one or more insulating walls,
• wherein the non-reactive gas space freely communicates with ambient air.