Coal plants without scrubbers account for a majority of SO
SO 2 is formed during the combustion of coal. The amount of SO 2 produced depends on the sulfur content of the coal burned in a boiler. FGD scrubbers remove the SO 2 from a boiler's postcombustion exhaust (flue gas) by passing it through an alkaline solution. This process is also effective in removing acid gases, such as hydrochloric acid.