Effect of distribution patterns of refractory overlayers on cyclic high temperature CO2 capture using waste oyster shell
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Abstract
Waste oyster shell powder has been applied in cyclic high temperature CO2 capture, but the sintering effect during calcium looping (carbonation/calcination) significantly shortens the life span of the adsorbents. The association of waste oyster shell with refractory materials, such as zirconium oxide has been evaluated, using either furnace treatment or atmospheric pressure plasma treatment to improve the thermal stability. It was noted that samples with 5 wt% of ZrO2, by either furnace treatment or plasma treatment, exhibited the highest CO2 capture capacity (∼360 mol-CO2 per mol-CaO in 20 calcium looping cycles). The plasma treatment was found to quite effectively enhance the thermal stability when more ZrO2 was added; however, evaporation–condensation reactions during plasma treatment led to evenly distributed CaZrO3 particles, which hindered the access of CO2 to CaO, and therefore reduced the overall CO2 capture capacity. In contrast, furnace treatment leads to most of the ZrO2 functioning as wedges to mitigate the sintering effect, which essentially exposes more CaO for CO2 access and accounts for its high overall CO2 capture capacity. Accordingly, the distribution patterns of refractory overlayers on waste oyster shell play an important role in cyclic high temperature CO2 capture.
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