Study on Gas Diffusion Characteristics Inside Shell-type Sorbents

Gas diffusion characteristics inside shell-type sorbents were investigated in some aspects,such as microstructural feature,gas diffusion mechanism and diffusion coefficient,which were compared with that of the limestone.Scanning electron microscope(SEM)photos indicate that the shells' microstructure is more beneficial to SO2 and other reaction gases diffusing inside them than the limestone.The research results on gas diffusion mechanism show that gas diffusion mode of the raw shells is transition diffusion,those of the calcined and sulfated shells are both molecular diffusion mainly,and those of the raw,calcined and sulfated limestones are all Knudsen diffusion.The effective diffusion coefficients of the shells are all in the same order of magnitude approximately,which are bigger 2 or 3 orders of magnitude than those of the limestone respectively.In conclusion,gas diffusion characteristics of the shell are similar,and they are better than that of the limestone.The conclusion derived from a thermogravimetric experiment is that the relation between desulfurization performance and gas diffusion characteristic is very close.