Tests were made to evaluate the effectiveness of six selected solid sorbent materials in removing sulfur dioxide (SO2) from coal combustion gases in a chain grate-fired furnace. Effects of additive feed rate, particle size, and injection temperature were studied. Calcination and calcium oxide utilization were determined. The sorbents used in this investigation were an aragonite, a calcite, two types of dolomite, and a chalk. Red mud, the dried tailings from the namufacture of alumina from bauxite, was also tested. Sulfur dioxide removal ranged from 6 to 65 per cent depending upon operating conditions. Sorbents compared on a per-unit-weight-of-raw-stone basis show that the calcites and aragonite removed greater amounts of SO2 than the dolomites. Sorbent 1683, an aragonite, was the most effective of all materials tested when injected into the gas stream. However, it was relatively ineffective when mixed with the coal prior to combustion. It was found that SO2 removal increases with increasing sorbent feed rates. (Author)