Preparation of calcium silicate absorbent from iron blast furnace slag

Calcium silicate hydrate (CSH) solids were prepared from hydrated lime and iron blast furnace slag in an aqueous agitated slurry at 92 degrees C, Whil e it was hoped a minimal lime/slag ratio could be used to create near-amorp hous CSH, the surface area of the product improved by increasing the lime/s lag weight ratio to 2. The addition of gypsum to the lime/slag system drama tically improved the formation of surface area, creating solids with 139 m( 2)/g after 30 hr of reaction when only a minimal amount of lime was present . The SO2 reactivity of solids prepared with gypsum greatly exceeded that o f hydrated lime, achieving greater than 70-80% conversion of the alkalinity after 1 hr of reaction with SO2. The use of CaCl2 as an additive to the li me/slag system, in lieu of gypsum, also produced high-surface-area solids, 115 m(2)/g after 21 fir of reaction. However, the SO2 reactivity of these s orbents was relatively low given the high surface area. This emphasized tha t the correlation between surface area and SO2 reactivity was highly depend ent on the solid phase, which was subsequently dependent on slurry composit ion.