The characteristics of a novel after-burner used for metal-supported planar SOFC system

Abstract

A novel after-burner used for the heat-up and normal operating conditions of metal-supported planar solid oxide fuel cell (SOFC) system, is designed and experimentally studied in this paper. The burner construction and the calculation of maximum burner power are showed in detail. Meanwhile, its static characteristics are researched through the influence of excess air ratio (ER), air velocity, inlet air temperature and fuel utilization rate (Uf); its transient characteristics are researched through the processes of burner start-up, burner operating state switch and stack start-up. Results suggest that the best ER value gets larger with the increased burner power. The air velocity is better controlled within 3 m·s-1 to prevent the influence of lifted flame. High inlet air temperature can extend lean combustion range and reduce incomplete combustion products, but large ER mutation should still be avoided. In case of anode off gas combusting with cathode off gas, there are nearly zero emissions. Meanwhile, the flue gas temperature decreases to about 760 °C because of enlarged heat loss, but it is minimally influenced by Uf. Under static condition, the optimal point with both controlled temperature and lowest emissions can be obtained in wide range, and the after-burner can well adapt to various operating states of the stack. Under transient condition, the after-burner has good response performance with much shorter time in burner start-up and burner operating state switch than conventional porous media ones. It can start up the stack in 1715 seconds.