Kinetic study on desulfurization of limestone modified by wood vinegar

Abstract：The sulfation reaction process and kinetics of limestone modified by wood vinegar, a kind of waste liquid, were analyzed by thermogravimetie analysis method and grain reaction model. The results show that the desulfurization performance of limestone can be effectively improved after being modified by wood vinegar in the whole temperature range ( 850-1 000 ℃ ). The phase composition analysis measured by XRD of limestone modified by wood vinegar shows that the major composition in the sample is hydration calcium acetate. The thermal decomposition of modified limestone shows the characteristic of multi-stage. The structure of thermal decomposition product of modified lime- stone, measured by scanning electron microscope and nitrogen adsorption method, is much looser than that of original limestone ,which is conducive to the sulfation reaction. The rate constant of the surface reaction (k) of modified lime- stone is slightly smaller than original limestone' s, but there is huge gap between the effective diffusivity of reactant in the product layer ( Ds ) of these two samples. The enhancement of sulfation is more pronounced once the product layer has been formed and consequently the promoting effect becomes greater once the sulfation reaction becomes diffusion controlled.