Catalytic Radiant Tube. Phase 2. Proof of Concept. Phase 3. Catalyst and Tube Evaluation. Final Report February 1, 1986-April 30, 1988

摘要

Phase 2, Proof of Concept, covered testing of both ceramic and metal tubes with either oxide or precious metal catalysts applied to the interior tube wall. Premixed natural gas and air was reacted at the catalyzed wall and the energy produced by combustion conducted through the tube wall and was transmitted primarily by radiation to the load. Exterior tube wall temperatures of 2000 F were achieved and NOx emissions were less than 5 ppmv. A major problem, however, was catalyst durability. The best results were obtained with a 3/4 inch OD x 1/2 inch ID x 12 inch L silicon carbide tube with a platinum catalyst. The tube remained radiant less than 10 hours during continuous operation. Based on the results of Phase 2 testing, Phase 3 work was directed toward improving radiant tube longevity. Research was specifically focused on the washcoat (catalyst support) in an effort to improve catalyst life and therefore extend radiant tube life. A zirconia washcoat was developed which has excellent stability and surface area retention at temperatures encountered in catalytic radiant tubes (1600-2200 F). The washcoat was used as a support for a platinum catalyst on both metal and ceramic tubes. Catalytic radiant tube life was significantly extended from 10 hours to nearly 1000 hours using the zirconia washcoat.