Cu-Mn oxygen carrier with improved mechanical resistance: Analyzing performance under CLC and CLOU environments
Iñaki Adánez-Rubio, Amanda Nilsson, M.T. Izquierdo, Teresa Mendiara, Alberto Abad, Juan Adánez
Abstract
Chemical Looping Combustion process allows combustion of gaseous, liquid or solid fuels with CO2 capture. The oxygen necessary for combustion can be supplied using lattice oxygen (CLC) or oxygen uncoupling (CLOU) mechanisms. The present work studies the effects of kaolin addition on CuMn oxygen carrier behavior for CLC and CLOU processes. CuMn oxygen carrier was prepared by granulation with a composition: 27.2 wt% CuO, 52.8 wt% Mn3O4 and 20 wt% kaolin. Oxygen release rates and fluidization behavior were analyzed by TGA and batch fluidized bed reactor. The oxygen carrier was studied for CH4 and synthetic biogas combustion in a 500 Wth CLC continuous unit for 50 h of combustion at temperatures up to 930 °C. No agglomeration problems were observed. Results found during biogas combustion were similar to methane combustion. The addition of 20 wt% kaolin changed the mixed oxide chemical composition generating Cu1.2Mn1.8O4 and improved significantly the oxygen carrier mechanical resistance, increasing the extrapolated lifetime to 19,000 h, 3.6 times over the value found for any Cu based oxygen carrier in CLC. However, the oxygen carrier reactivity had an important decrease with respect to a similar oxygen carrier without kaolin addition, whose fraction in oxygen carrier must be optimized.