| Calcium silicate hydrates are effective alkaline sorbents for the removal of acid gases from humid flue gas streams. This work investigated the formation of calcium silicates from recycled consumer glass and iron blast furnace slag. The reaction between these high surface area solids and SO 2 in a humid gas stream was also studied.; The formation of high surface area solids was found to be highly dependent on both the pH and calcium concentration of the slurry. Even with a high concentration of lime intrinsic in slag, excess additional lime was required to maintain a sufficient pH. Gypsum was shown to be an effective additive for maintaining a high calcium concentration at 92°C. Increasing the temperature to 120°C, increased the surface area formation at short times, but produced a more crystalline product, with lower surface area at longer times. Neither agitation nor solids/water loading had any effect on the preparation of sorbents up to 80 m2/g. Above this surface area, only agitation had a clearly positive effect. The addition of CaCl2 maintained a higher calcium concentration and high rate of surface area formation at 92°C, however the solids were less reactive with SO2 than comparable solids prepared with gypsum. It is believed that the high chloride concentration may have resulted in a different solid phase that was visible on SEM but not with X-ray.; The SO2 reactivity of high surface area glass sorbents was a strong function of the relative humidity of the gas, with temperature held constant. Sorbent surface area was also very important to the rate of SO 2 removal and maximum solids conversion. However, while surface area was necessary for high SO2 reactivity, it was not sufficient, as seen with sorbents prepared with chloride.; An empirical model for the SO2/glass sorbent system showed that for a baghouse filter cycle time of one hour at 58% relative humidity, a stoichiometric ratio of 1.0 will achieve 62% removal from a 1000 ppm SO 2 gas stream. Increasing the stoichiometry to 2.0 increased the removal efficiency to 94%. |
