A system for removal of SO2 from pollution sources by injecting calcined limestone into the exhaust gas system. In a wet scrubber (the most common type), the absorbent, a mixture of water and limestone, is sprayed inside a treatment area onto the flue gas, which rises from the bottom of the absorber area. Most of the SO2 in the gas is absorbed by the droplets of absorbent, and is oxidized into calcium sulfate and calcium sulfite compounds. The used absorbent (waste sludge) is disposed of as solid waste or is sold as a gypsum product. The cleaned flue gas (possibly reheated to avoid corrosive condensation) is released to the atmosphere.