Fluidization Behavior of Binary Mixtures of Coal in a Top-Fed Bubbling Fluidized Bed Gasifier

Abstract

Bubbling Fluidized Bed Gasifier (BFBG) technology is an efficient and economical way of producing syngas from various feedstocks, such as coal, biomass, and municipal waste. However, the prediction of the gasification process inside the BFBG is quite complex due to many factors, including multiphase flow hydrodynamics. This study analyzed the hydrodynamics of a bench-scale top-fed bubbling fluidized bed coal gasifier with sand or glass beads used as bed materials at different bed aspect ratios. Two separate test rigs were built with the same dimensions for cold flow (without reaction) and hot flow (with reaction) studies, respectively. The cold flow test rig was used to investigate the hydrodynamics of BFBG fluidization. Bed pressure drop, minimum fluidization velocity, and mixing were analyzed in the test room conditions. Following that, gasification tests were carried out in the hot flow BFBG test rig with a novel feeding system using the optimum hydrodynamical parameters determined from cold flow analyses. Results showed that syngas was successfully produced at an adequate composition. This study contributes to a better understanding of the fluidization hydrodynamics of the binary coal and bed material mixtures in a top-fed BFBG for a more optimum gasification process and easier operation of the BFBG.