Supercritical water gasification of glucose in fluidized bed reactor: A numerical study

Abstract

Supercritical water fluidized bed (SCWFB) is a new reactor concept for gasification of biomass and coal in supercritical water. In this paper, physical fields, residence time and gas yield in a SCWFB reactor were investigated numerically based on the Eulerian two-fluid method with the kinetic theory of granular flow. A three-step reaction model including steam reforming, water-gas shift and methanation was used to describe the supercritical water gasification of glucose. Distributions of velocity and temperature were obtained, and the results show that the mixing of preheated water and cold glucose solution at the bottom in the bed leads to a region with low solid volume fraction and local swirl flow. In the freeboard, most of reactants flow near the wall and with a velocity much higher than the superficial velocity. The reaction rates and conversion ratio of glucose at different regions in the reactor were also obtained. Distribution of residence time was found to be non-uniform, and its effect on glucose gasification was analyzed. In addition, the effects of operation condition and reactor structure on gas yield and residence time were studied to explore best operation rules for increasing gas yield. The results from this work may be of interest to operators attempting to obtain more information in the reactor and provide instruction for the design of SCWFB reactor.