Design issues for membrane-based, gas phase microchemical systems

The use of finite element simulations to characterize the operating behavio r of a microchemical reactor and enhance its design is described. Important design issues for a microreactor, specifically heat and mass transfer, are explored with the design of a micro-flow sensor and the redesign of the re actor heater. The impact of the design choices for a flow sensor is quantit atively evaluated and an optimal design is proposed. This design was fabric ated and testing confirmed the simulation work. The reaction channel heater was redesigned to improve thermal uniformity in the reaction zone. Simulat ions showed that before ignition significant non-uniformity still existed, but this was dramatically reduced after ignition. The use of previously rep orted kinetic models for ammonia oxidation in microreactor simulations is a lso discussed. It was found that kinetic models evaluated in conventional r eactor experiments are inadequate for use in microreactor simulations becau se of the lower operating temperature and broader range of temperatures of the microreactor. (C) 2000 Elsevier Science Ltd. All rights reserved.