Syngas production from cellulose solid waste by enhanced chemical looping gasification using Ca-Fe bimetallic oxygen carrier with porous structure

Abstract

Chemical looping gasification (CLG) is a promising and innovative technology used to produce synthesis gases without the preparation of gasifying agents, which exhibits advantages in synthesis gas heating value, tar inhibition and production cost Metal Oxide as oxygen carrier (OC) transfers the oxygen and heat in CLG process to avoid product syngas to be mixed with nitrogen, which decides the efficiency and feasibility of CLG system. Ca-Fe bimetallic OCs are considered as the potential available OC for its excellent selectivity on CO and H2 and char conversion activity. However, the low activity presents great challenges in further application for Ca-Fe OCs. To improve the performance of OCs, Ca-Fe OC with porous structure were prepared with simple method and investigated in a fixed bed with cellulose as fuel combined with various analytical methods. The results reveal that the pore area and pore volume increased significantly with increasing sol pH. The OCs with pH adjustment improved the syngas yield by over 28% and the carbon conversion efficiency by over 10%. Using the sample with pH = 6 as OC, from 800 °C to 950 °C, the carbon conversion efficiency increased more than 25%, and O/B = 0.5 and S/B = 1.2 should be the most property conditions for cellulose CLG. After 10 redox cycles, the performance of OCs with pH adjustment was better than that without adjustment in steam atmosphere. The improvement of OCs might be due to the higher pore surface area increasing the efficiency of steam reforming and the inner redox cycle of OCs. Therefore, Ca-Fe bimetallic OCs with large surface areas could potentially be used as good candidate oxygen carriers for CLG of cellulose solid waste.