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

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.