Understanding the Sulfation Pattern of CaO-Based Sorbents in a Novel Process for Sequential CO2 and SO2 Capture
2016
He, Donglin | Shao, Yan | Qin, Changlei | Pu, Ge | Ran, Jingyu | Zhang, Li
The CaO-based sorbent is considered to be a potential candidate for high-temperature CO₂ capture. However, its application is limited by the loss in CO₂ sorption activity with increasing number of calcium looping (CaL) cycles, which leads to vast spent sorbents with a potential for pollution. To solve the problem, the optimized utilization of CaO-based sorbents through a novel process to achieve sequential CO₂ capture and SO₂ retention is studied in the work, and the sulfation pattern of spent CaO coming from CaL process under different variables is investigated. It is observed that spent CaO-based sorbents experiencing dozens of carbonation/calcination cycles under severe CaL conditions have even a better capacity for SO₂ capture than the fresh CaO. By use of a combination of testing approaches, the phenomenon is revealed to be related to the variation of the sulfation pattern of CaL-spent CaO, and pores with a diameter of approximately 60–100 nm in the material are thought to be the key factor determining the capacity of spent sorbents for SO₂ retention. On the basis of the results, a novel sulfation model is proposed to understand the reaction behavior of the highly cycled CaO in SO₂ capturing. Moreover, it is found that sulfation mode of CaL-spent CaO is sensitive to the variation of calcination in CaL process and particle size of the CaO-based sorbents.
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