On the high performance of a core-shell structured CaO-CuO/MgO@Al2O3 material in calcium looping integrated with chemical looping combustion (CaL-CLC)

Abstract

Calcium looping (CaL) is extensively used in post-combustion capture of CO2 and sorption-enhanced steam methane reforming because of its advantages of low cost and theoretically high CO2-capture capacity. Despite this, unstable reactivity of sorbent (CaO) and significant heat requirement for CaCO3 calcination were always encountered in CaL. To address the aforementioned issues, a core-shell structured CaO-CuO/MgO@Al2O3 sorbent (CCMA for short) was synthesized via the self-assembly template synthesis (SATS) method, and systematically investigated in terms of carbonation, calcination-reduction and oxidation cycles. In comparison to wet-mixing CaO-CuO material (CC), MgO-supported CaO-CuO (CCM) and Al2O3-supported CaO-CuO (CCA), the CCMA performed the highest CO2 uptake capacity, which was quite stable at around 0.08 [g CO2∙(g material)−1] in the 30 cyclic tests. In calcination-reduction stage, CaO in CCMA can be fully recovered by the decomposition of CaCO3, meanwhile the corresponding heat requirement can be compensated by the exothermic reaction between CuO and CH4, i.e., thermal neutrality can be achieved by using CCMA. The Cu in reduced CCMA can be subsequently oxidized back to CuO in the oxidation stage with a conversion of 97–98%, which is much higher than CC, CCM and CCA. After cycles, no serious sintering was observed for the CCMA and the measured crushing strength (1.4 N) was sufficient for fluidization, which, in combination with its high reactivity, makes this material very promising for CaL-CLC process.