An Investigation on Sulfation Mechanisms of Ca-based Sorbent Modified by Sodium Salt

This paper discusses the calcination and sulfation characteristics of a limestone modfied by Na2CO3, in order to find the causes of enhanced sulfation capacity of the modfied sorbent. It is shown by the experiments that the decomposition rate of modified limestone is quicker than for the original sample, and the CaO formed by the modified limestone (abbreviated as M-CaO) has higher calcium conversion in sulfation than that formed by the original sample (abbreviated as N-CaO). Although the sulfur capture capability of M-CaO is in excess of that of N-CaO, pore structure measurements showed that specific surface area and porosity of the former are less than that of the latter Therefore, the M-CaO sulfation phenomena cannot be explained based only on the pore structure. The crystal structure parameters of CaO were measured and require further investigation. According to solid-state ions diflusion theory, a new sulfation mechanism is proposed. More lattice defects are formed in M-CaO, which reduces the resistance of ion diffusion in the product layer and increases the calcium conversion.