An investigation on mechanisms of modified limestone sulfation
调质碳酸钙硫化机理的实验研究

The sulfation characters of limestone modified by Na\-2CO\-3 solution were investigated in this laboratory. The modified limestone decomposed more quickly than nonmodified limestone. It is shown that modified CaO the Ca conversion in modified CaO is nigher than in nonmodified CaO when sulfation reaction completed. It is also found that influence of CO\-2 concentration on sulfation character of modified CaO is more violently than of nonmodified CaO. Although the surfur capture capability of modified CaO is well excess that of nonmodified CaO, the microstructure measurement shows that specific surface area and porosity of the former are less than that of the latter. A new sulfation mechanism is proposed that the sulfation reaction of modified CaO is divided into two steps,i.e. at initial stage the chemical reaction between CaO and SO\-2 is rate\|limiting step and as reaction continue the rate\|limiting step changs to solid\|state diffusion through product layer. The crystal structure of CaO was measured by X\|ray diffraction(XRD) analysis.The parameters, such as crystallite size, lattice distortion degree,\% et al.\% are base of this mechanism. Fractal theory has been applied to the pore structure of CaO, it is found that a certain CaO the sulfation impact getting worse with fractal dimension decreasing.