Cyclic reactivity of the sol–gel and graphite impregnation-derived Cu-based oxygen carriers for chemical looping with oxygen uncoupling

Abstract

Chemical looping with oxygen uncoupling (CLOU) is a promising technology to be used in combination with the oxy-fuel combustion/gasification processes for carbon capture and sequestration in that it reduces the energy penalty for O2 generation; hence, much attention has been focused on the production of proper oxygen carriers. In this work, four oxygen carrier candidates for CLOU made of 90% CuO and 10% ZrO2 or Y2O3 are first prepared with the sol–gel and graphite impregnation methods. The reduction reactivity of the prepared oxygen carriers is investigated at 900, 950, and 1000 °C in the CO2 atmosphere, and the redox stability is evaluated through ten sequential cycles using the thermogravimetric analyzer. It is found that the Avrami–Erofeev random nucleation and subsequence growth model (A2) describes the reduction process very well. CuO/ZrO2 prepared by the graphite impregnation performs better reactivity and stability than the others. The agglomeration and sintering of the oxygen carriers at high temperatures are found to be the main cause of the low reactivity over the repeated cycles.