Enhancement of SO₂ sorption on lime by structure modifiers

The presence of certain inert compounds in lime can improve the rate and the final limiting conversion significantly during the lime SO₂ reaction. This physical effect is primarily due to modification of porosity. In particular, the enhancement appears to he due to increase in macro‐porosity and macro‐pore diffusivity; this in turn increases the sulfation rate and decreases pore plugging. In certain lime application processes, these compounds (structure modifiers) can be added to lime as beneficial additives to promote the reaction. Experimental data on the effect of kaolin, silica and bauxite as structure modifiers are presented. A theoretical model is developed which explains the observed effects both qualitatively and quantitatively.