Dry Scrubbing Systems Research Articles

SO2 in Aluminum Reduction-Cell Dry Scrubbing Systems

Samples of six smelter-grade aluminas with different surface areas from 41 to 85 m2/g were equilibrated with 500 ppm SO2 in dry air at 80°C. The amount of adsorbed SO2, as S, tends to increase with surface area, being in the range 0.40–0.70 wt.%. The presence of up to 2% water vapor in the gas did not affect the amount of SO2 adsorbed. The addition of 500 ppm HF to the gas prevented SO2 adsorption, and SO2 previously adsorbed on the alumina could be desorbed by passing HF. Tests run on a full-scale plant dry scrubber tend to confirm laboratory results in that the alumina saturates with SO2 at rather low concentrations of S, and the adsorbed S can be displaced by fluoride. Comparison heating tests on alumina saturated with SO2 in the laboratory and plant scrubber catch samples suggest the presence of other forms of sulfur. Further heating tests suggest that carbon is involved in removing sulfur from the catch, probably by reducing sulfates. The implications of the work on scrubber and cell operations are discussed.