A Kinetic Model of CO2 Absorption in Molten CaO-CaF2-CaCl2 (Supporting Information)

Post-combustion CO2 capture is a promising method for removing CO2 from processes where emissions cannot be mitigated by renewable energy input and where the chemical reactions required for production emit CO2, e.g. calcination of calcium carbonate (CaCO3) for cement production. One promising capture method is carbon capture in molten salts (CCMS). CCMS is a thermal swing gas-liquid process that utilizes CaO carbonation to absorb CO2. The molten salt used in this work is 15 wt% CaO in eutectic CaCl2-CaF2 (86.2 : 13.8 wt%). The CaCl2-CaF2-CaO system has been found to have high cyclic absorption capacity (0.6 g CO2/g CaO), though reaction kinetics has yet to be studied. By utilizing a novel experimental setup, data is collected, and a kinetic model is developed, which can be used in a techno-economic evaluation. The model proposes a simplified description of the CaCl2-CaF2-CaO system, with the assumption that the reaction is a first order elementary reaction where CaO and CO2 react to form CaCO3 without any solubility of CO2 in the molten salt. CO2 concentration, temperature, wt% CaO and surface area of molten salt are parameters in the proposed kinetic model. The result is a kinetic model that accurately fits the experimental data with an R2 value above 0.98. It has been found that increasing the CO2 concentration and decreasing the temperature yield a higher CaO to CaCO3 equilibrium conversion.

后燃式二氧化碳捕获是一种极具潜力的方法，适用于无法通过可再生能源输入来减轻排放以及生产过程中所需的化学反应会排放二氧化碳的工艺中，例如水泥生产中碳酸钙（CaCO3）的煅烧。其中一种有前景的捕获方法是熔盐碳捕集（CCMS）。CCMS是一种热循环气体-液体过程，利用CaO碳化来吸收二氧化碳。本研究中使用的熔盐为15 wt% CaO的共晶CaCl2-CaF2（86.2 : 13.8 wt%）。研究发现，CaCl2-CaF2-CaO系统具有高循环吸收能力（0.6 g CO2/g CaO），尽管反应动力学尚未进行研究。通过利用新颖的实验装置，收集数据并开发动力学模型，该模型可用于技术经济评估。该模型对CaCl2-CaF2-CaO系统进行了简化的描述，假设反应为一阶基元反应，其中CaO和CO2反应生成CaCO3，而熔盐中不存在CO2的溶解。CO2浓度、温度、CaO质量百分比和熔盐表面积是所提出的动力学模型中的参数。结果是一个动力学模型，其R2值高于0.98，能够准确拟合实验数据。研究发现，增加CO2浓度和降低温度可以提高CaO与CaCO3的平衡转化率。