改性白云石制备CO_2吸收剂的活化条件优化

Optimization of the activation conditions of modified dolomites for preparing CO_2 absorbents

为了确定利用NaNO_3改性白云石制备CO_2吸收剂MgO-CaCO_3的制备工艺,本文利用热重分析仪研究了活化条件对钙镁复盐吸收剂活化程度及活化后所得吸收剂吸收性能的影响.研究结果表明活化温度越高、活化时间越长、活化气氛用空气代替N_2时,NaNO_3改性白云石制备的钙镁复盐在活化过程中的失重量越大.然而活化后所得吸收剂的CO_2吸收性能并不与样品在活化过程中的失重量成正比.结合钙镁复盐MgCO_3-CaCO_3的分解反应机制和熔融的NaNO_3通过离子液体通道促进离子扩散机制,分析了活化条件对吸收剂吸收性能的影响机理.样品活化过程过于剧烈会增大CaCO_3晶粒和MgO晶粒之间的间距,减弱CaCO_3对MgO基吸收剂CO_2吸收能力的促进作用,得到在高温条件下基本无CO_2吸收能力的独立的MgO吸收剂.

To further clarify the preparation techniques of the CO_2 absorbent of MgO-CaCO_3 using NaNO_3 modified dolomites, the effects of activation conditions on the activation degree of the calcium and magnesium double salts and on the CO_2 absorption ability of the activated absorbents were investigated using the thermogravimetric analysis. The results indicated that the weight loss of the prepared calcium and magnesium double salts was bigger during the activation, when the activation temperature was higher, the activation time was longer, and the activation atmosphere was air instead of N_2. However, the CO_2 absorption ability of the activated absorbent was not proportional to its weight loss during the activation. The affecting mechanism of the activation conditions on the CO_2 absorption ability of the activated absorbent was analyzed combined the decomposition mechanism of MgCO_3-Ca CO_3 double salts, and the promoting mechanism of molten Na NO_3 on the diffusion of ions by providing ionic liquid channel. The too intense activation process would result in a long distance between the CaCO_3 grains and the MgO grains, and weaken the promoting effect of CaCO_3 on the CO_2 absorption ability of MgO-based absorbent, and then obtain the separate MgO absorbent with almost no CO_2 absorbent ability under high temperature.