Chemical looping combustion of lignite using iron ore: C-gas products (CO2, CO, CH4) and NOx emissions

Abstract

This work investigates the feasibility of lignite in chemical looping combustion (CLC) with an iron ore oxygen carrier. In this paper, C-gas products (CO2, CO, CH4) and NOx emission from the CLC process of lignite based on bubbling fluidized bed were studied. The effects of different atmospheres—Ar, 80%Ar–20%CO2, or 80%Ar–20%H2O—on the distribution of C-gas products and NOx emission were investigated. The important characteristic parameters of CLC, including carbon conversion degree, carbon capture ratio, CO2 capture ratio and NOx generation ratio, were obtained. Compared with pure Ar atmosphere, both 20%CO2 and 20%H2O atmospheres promote the gasification of char in the fuel reactor stage. In addition, the carbon conversion degree, carbon capture ratio, and the CO2 capture ratio are increased to 80%, 95% and 60%, respectively. In these 3 atm, the NOx generation in the fuel reactor stage was dominated by NO. Compared with the Ar atmosphere, the 20%CO2 atmosphere causes a close NOx generation ratio, while the 20%H2O atmosphere has a NOx generation ratio of 13.79%. Compared with the lignite combustion under two O2 concentrations (18% and 45%), NOx emission in CLC is reduced by 12% and 50%, respectively.