Semi-continuous Operation of Chemical Looping Combustion of Coal Using a Low-Cost Composite Oxygen Carrier

Abstract

To reach the carbon peak by 2030 and achieve carbon neutrality by 2060, the implementation of low-carbon combustion approaches for fossil fuels (especially coal, a high-carbon fuel) is urgent in China. Chemical looping combustion (CLC) has been considered as one of the most promising technologies for low-carbon, efficient, and clean utilization of coal. However, a low-cost and high-performance oxygen carrier (OC) holds the bottleneck that constrains the industrial application of coal-fueled CLC. In this paper, a low-cost composite OC named Cu13.0Red87.0@C (with the mixing mass ratio of copper ore to red mud being 13.0:87.0, except for a 20 wt % cement bonder) was first prepared by the hydroforming method and then systematically evaluated by designing CLC tests in a semi-continuous fluidized bed using lignite as fuel. The results showed that this composite OC exhibited superior combustion performance in comparison to pure red mud. Moreover, it was found that increasing the temperature could significantly improve the average carbon capture efficiency but had a relatively small positive effect on the average CO2 yield. Additionally, with the elevation of the oxygen/fuel ratio, the resulting average carbon capture efficiency and average CO2 yield both tended to increase. Generally, the semi-continuous unit can simulate the continuously operated fuel reactor with an adjustable bed inventory and solid circulation rate, and it is easy to attain smooth operation of ca. 30 min, achieving both carbon capture efficiency and a CO2 yield of ca. 90%.