CuO supported on olivine as an oxygen carrier in chemical looping processes with pine sawdust used as fuel

Abstract

Chemical looping is a promising low-cost technology for CO2 capture with a low energy penalty. In this study, CuO supported on olivine (CuO/olivine) was investigated as an oxygen carrier (OC) in chemical looping combustion (CLC) and in chemical looping with oxygen uncoupling (CLOU). The reactivity and oxygen uncoupling behavior were evaluated by thermogravimetric analysis (TGA). CLC and CLOU experiments using pine sawdust (PS) as fuel were conducted in a fluidized-bed reactor. The CLC cyclic performance and the oxygen release and uptake behaviors of CuO/olivine were explored. In CLC experiments, both carbon conversion (χc) and carbon capture efficiency (ηc) increased with increasing temperature and with increases in OC-to-fuel ratio (Φ); the maximum value of χc and ηc—96.81% and 95.54%, respectively—were achieved at 900°C with Φ=1.50. In CLC cyclic tests, the CuO/olivine displayed stable reactivity, and the values of χc and ηc were 94.64% and 92.59% at the 20th cycle, respectively. In the CLOU tests, oxygen transport capacity (Ro) of 3.55% was obtained via TGA. Complete conversion of pine PS and ηc=99.29% were also achieved at 950°C in a fluidized bed reactor. MgCu2O4 was found in the fresh CuO/olivine sample and it disappeared immediately during the first redox cycle; most of CuO accumulated on the olivine surface and then gradually spread and covered the olivine upon additional cycles. After 20 CLC cycles. CuO content of the CuO/olivine OC decreased slightly from 38.81% to 35.22%; a crushing strength of 4.8N was maintained, and no significant agglomeration was observed. The CuO/olivine has an excellent cyclic performance and it can be used as a good OC candidate in chemical looping processes.