A cadmium-magnesium looping for stable thermochemical energy storage and CO2 capture at intermediate temperatures

Abstract

Thermochemical energy storage (TCES) based on the carbonation/decarbonation cycle of metal oxide/carbonate is an attractive technology to address the intermittent problems of renewable energy and to recover industrial waste heat. The alkali metal salt-promoted MgO-based sorbent materials are promising for TCES at intermediate temperatures but suffer from severe thermal instability owing to the high decarbonation temperature of MgCO3 in pure CO2. In this study, we for the first time reported a novel Cd-Mg looping whereby CdO and MgCO3 with the aid of molten NaNO3 can be rapidly and reversibly converted into CdMg(CO3)2 through carbonation/partial decarbonation, which enabled a low working temperature and thus enhanced the stability of the NaNO3-promoted Cd-Mg containing materials. The effect of Cd/Mg atomic ratio on the property, activity and stability of the materials was systematically studied; moreover, the carbonation/decarbonation mechanism was carefully explored. The promising candidate containing equimolar amounts of Cd and Mg can not only perform stable intermediate-temperature TCES in 100 cycles, but also convert the low-concentration waste CO2 in integrated gasification combined cycle power plants into pure CO2. These findings offer new opportunities for TCES and CO2 capture at intermediate temperatures.