Incorporation of CaO in inert solid matrix by spray drying sol mixture of precursors

Abstract

Sol mixing of one soluble precursor with one insoluble precursor has been investigated to incorporate CaO in an inert solid matrix to obtain superior CaO-based sorbents for CO₂ capture. However the generally used drying method in oven is a slow and high energy-consuming heating process. In this study, we investigated the application of spray-drying technique, which is a quick drying and energy saved method, to synthesize a series of CaO-based sorbents with sol mixture of calcium and inert support precursors. FSEM-EDS mapping has shown that CaO grains can be homogeneously dispersed in the inert solid support. Four synthetic CaO-based sorbents were prepared and tested under the same conditions of both pure N₂ and CO₂-rich calcination atmospheres and the associated surface area, morphology and grain size were also examined. Under the pure N₂ calcination atmosphere, all the synthetic sorbents show a much higher CO₂ capture performance than natural sorbent limestone, particularly CaO incorporated in Ca₁₂Al₁₄O₃₃ exhibiting the conversion twice as high as that of limestone at the 13^th cycle. However, under a CO₂-rich calcination atmosphere, quicker degradation of the capture capacity was observed for these sorbents. The decay is also associated with severer sintering due to the presence of CO₂, which could be proved by the larger grain size of CaO as well as smaller specific surface area of the sorbents after cycles. Nevertheless, the synthetic sorbents still perform better than natural limestone due to the presence of inert support matrix.