Investigations of Zhundong Coal with Removing Water-Soluble Sodium in Chemical Looping Combustion

Abstract

Zhundong (ZD) coal is one significant fuel source in China but contains a lot of sodium, limiting its utilization. In this work, the effects of sodium in ZD coal were investigated on coal conversion and NO x emissions with a batch fluidized bed reactor in chemical looping. Here, ZD coal was processed by the water-washing method to remove water-soluble sodium in ZD coal. During the traditional combustion process, water-soluble sodium had negative effects on coal conversion and NO generation. When chemical looping was applied to ZD coal combustion, the NO emission was restrained largely and mainly from pyrolysis. In addition, the gasification agent facilitated NO generation, and CO2 had a stronger effect on chemical looping. The NO generation was ascribed to the oxidization of the oxygen carrier and increased with the increase of the oxygen carrier in reactivity. Besides, water-soluble sodium promoted NO generation but restrained coal conversion in chemical looping. Furthermore, the NO generation rate was also affected by the reaction temperature, and an increasing reaction temperature promoted NO generation, especially using hematite as the oxygen carrier.