Using both bench-scale and pilot-scale systems, direct furnace injection of calcium-based sorbents was investigated for SO/sub 2/ control and both catalytic and noncatalytic techniques were evaluated for NO/sub x/ control. Furnace injection tests focused on the injection of high-calcium pressure-hydrated lime (PHL) at flue gas temperatures ranging from 1500/sup 0/ to 2800/sup 0/F. Particulate was collected in one of two baghouses, one operated at temperatures ranging from 800/sup 0/ to 1000/sup 0/F, the other ranging from 145/sup 0/F to 300/sup 0/F, or an electrostatic precipitator (ESP) operated at conventional temperatures (approx.300/sup 0/F). Sulfur dioxide reduction as high as 80% was observed for high-calcium PHL injected at a Ca/SO/sub 2/ mole ratio of 2.0 with essentially all of the SO/sub 2/ capture occurring in the flue gas at temperatures above 1400/sup 0/F. Residence time and the temperature regime (1400/sup 0/ to 2200/sup 0/F) experienced by the sorbent in the flue gas stream appear to be the critical parameters controlling SO/sub 2/ reduction and sorbent utilization. Furnace sorbent injection was observed to have a minimal impact on ash fouling. Further pilot-scale tests have shown that furnace injection of high-calcium PHL results in 65% to 70% SO/sub 2/ capture if the baghouse is operated near approx.160/sup 0/F. Catalytic reduction of NO/sub x/ using throwaway catalysts collected in a high-temperature baghouse was investigated. Reductions of up to 29% were achieved with a lignite fly ash containing about 8% Fe/sub 2/O/sub 3/, and up to 65% reduction using a synthetic mordenite. Simultaneous SO/sub x/NO/sub x/ control was demonstrated using direct furnace injection of pressure-hydrated lime and a selective catalytic reduction (SCR) reactor. Eight percent SO/sub 2/ and NO/sub x/ reduction was achieved at a Ca/SO/sub 2/ mole ratio of 2.0 and a NH/sub 3//NO mole ratio of 1.0 while operating the baghouse at a temperature of 980/sup 0/F to remove particulate upstream of the SCR reactor.