Performance improvement of chemical looping combustion with coal by optimizing operational strategies in a 3 kWth interconnected fluidized bed

Chemical looping combustion (CLC) for industrial-scale applications is hindered by challenges of inefficient fuel conversion, auto-thermal operation, and complex system operation. To improve the CLC performance under low temperature, operational strategies were optimized in a 3 kW(th) CLC plant with the design criterion of a simplified circulation mechanism. The gas conversion efficiency was enhanced by employing internal distributors in a multistage fuel reactor (FR). The CO2 capture and carbon conversion efficiencies were improved by each of the following: optimizing the FR fluidization flow, utilizing staged fluidization, and optimizing the steam coal (S/C) ratio. The potential of each of the abovementioned operational strategies was evaluated by analyzing the axial distribution of the gas concentration in the FR. The staged fluidization was the most effective method among the three operational strategies. It could increase the particle residence time, FR bed inventory, and cyclone efficiency. The CO2 capture efficiency increased from 57.8% to 80.3%, the carbon conversion efficiency increased from 81% to 96%, and the OC lifetime was improved from 300 h to 342 h. The OC attrition behaviors were also evaluated under different operational conditions. The FR internals had a limited effect on the OC lifetime; however, increasing the inlet velocity of the cyclone would aggravate the OC abrasion.