Catalytic Radiant Tube For Industrial Process Heating Applications

This paper describes research on an innovative industrial process heating concept using catalytic radiant tubes. The gas-fired radiant tube concept employs a combustion catalyst applied to the inside surface of a ceramic tube. A preheated, combustible mixture of gas and air passing through the tube burns catalytically on the tube surface. Some of the heat generated conducts through the wall and is transmitted by radiation from the outside surface to the heat sink. Advantages over existing gasfired radiant tubes include more uniform tube heating and low NOx emissions. During this project, silicon carbide tubes were catalyzed with platinum and metal oxide catalysts and operated in a laboratory combustion test apparatus. The results were encouraging. A tube temperature of 11000C was achie~ed, and heat flux (47.3 to 94.6 kW/m ) was comparable to that of electric elements. NOx concentration was negligible. The tube material did not experience thermal shock. Catalyst stability was the limiting factor. Future work will concentrate on developing a better catalyst and catalyst coating method which will then lead to stable combustion operation. Following the identification of a reliable catalyst, a prototype furnace using the radiant catalytic tubes will be built and tested. When commercialized, this concept could be used in place of the currently popular electric resistance elements.