Adapting the MgO-CO\u3csub\u3e2\u3c/sub\u3e working pair for thermochemical energy storage by doping with salts:effect of the (LIK)NO\u3csub\u3e3\u3c/sub\u3e content \u3csup\u3e†\u3c/sup\u3e

Abstract

\u3cp\u3eThe MgO-CO\u3csub\u3e2\u3c/sub\u3e working pair has been regarded as prospective for thermochemical energy storage (TCES) due to its relatively high heat storage capacity, low cost, and wide availability. This study is aimed at the optimization of the molar salt content, α, for the MgO modified with the eutectic mixture of LiNO\u3csub\u3e3\u3c/sub\u3e and KNO\u3csub\u3e3\u3c/sub\u3e (Li\u3csub\u3e0.42\u3c/sub\u3eK\u3csub\u3e0.58\u3c/sub\u3eNO\u3csub\u3e3\u3c/sub\u3e) which was earlier shown to provide high conversion, ∆x, in heat-storage/release processes at 300–400 \u3csup\u3e◦\u3c/sup\u3eC. The composites that have different salt content were prepared and carbonation kinetics was investigated under various conditions (carbonation temperature, T\u3csub\u3ecarb.\u3c/sub\u3e, is 290–360 \u3csup\u3e◦\u3c/sup\u3eC and CO\u3csub\u3e2\u3c/sub\u3e pressure, P(CO\u3csub\u3e2\u3c/sub\u3e), is 50–101 kPa). Significant accelerating effect was revealed at α ≥ 0.05, and the ∆x value was maximized at α = 0.10–0.20. The largest conversion of 0.70 was detected at α = 0.10 and T\u3csub\u3ecarb.\u3c/sub\u3e = 350 \u3csup\u3e◦\u3c/sup\u3eC that corresponds to the specific useful heat (Q\u3csub\u3ecomp.\u3c/sub\u3e) is 1.63 MJ/kg-composite. However, the salt content of 0.20 ensures the high conversion, ∆x = 0.63–0.67 and Q\u3csub\u3ecomp.\u3c/sub\u3e = 1.18–1.25 MJ/kg-composite in the whole temperature range between 290 and 350 \u3csup\u3e◦\u3c/sup\u3eC. The (LiK)NO\u3csub\u3e3\u3c/sub\u3e/MgO composite with an optimal salt content of 0.20 exhibits reasonable durability through cyclic experiment at 330 \u3csup\u3e◦\u3c/sup\u3eC, namely, the stabilized reacted conversion ∆x = 0.34 (Q\u3csub\u3ecomp.\u3c/sub\u3e = 0.64 MJ/kg-composite). The studied (Li\u3csub\u3e0.42\u3c/sub\u3eK\u3csub\u3e0.58\u3c/sub\u3e)NO\u3csub\u3e3\u3c/sub\u3e promoted MgO-CO\u3csub\u3e2\u3c/sub\u3e working pair has good potential as thermochemical storage material of middle temperature heat (300–400 \u3csup\u3e◦\u3c/sup\u3eC).\u3c/p\u3