Experimental study on sawdust gasification in a spout-fluid bed reactor

Abstract

This paper summarizes the experimental results of sawdust gasification in a spout–fluid bed reactor. Three scenarios were investigated in this study. In the base case scenario, a total of 15 experiments consisting of three different flow rates (55, 65 and 75 m3 h− 1) of primary air of each of having five equivalence ratios (ER) (0.35, 0.3, 0.25, 0.2 and 0.15) were conducted. The influence of secondary air in the freeboard and the effect of the recirculation of carryover captured by the cyclone to the reactor's freeboard at an ER of 0.25 were investigated in two other scenarios. Higher heating values of 3.02 and 5.15 MJ Nm− 3 were obtained with the ER values of 0.35 and 0.15, respectively, in the base case. However, opposite trend was observed for the tar content in the producer gas. At ER of 0.35, a value of 2.35 g Nm− 3 was found compared with 8.4 g Nm− 3 at ER of 0.15. The tar content in the producer gas was reduced from 5.63 to 1.53 g Nm− 3 when secondary air was supplied in the freeboard due to an increase in temperature. The gasification efficiency was increased from 24.96% at the base case to 36.22% with the recirculation of carryover. Higher heating value of producer gas was found to be 4.2–4.4 MJ Nm− 3 in this case. The second law analysis of this process estimated the average exergy efficiency as 35.92% at ER of 0.35 and it increased with increasing ER. The recirculation of carryover not only increased the carbon conversion efficiency but also the exergy efficiency. Copyright © 2010 John Wiley & Sons, Ltd.