Method and system for SO2 and SO3 control by dry sorbent/reagent injection and wet scrubbing

摘要

A method and system for removing SO₃ and SO₂ from a flue gas produced by the burning of a fossil fuel. Particulates are removed from the flue gas to produce partially cleaned flue gas. A sufficient amount of calcium-based, sodium based or magnesium-based dry sorbent, preferably having a particle size larger than 1.0-2.0 microns, is injected into the flue gas to react with and remove substantially all of the SO₃ from the partially cleaned flue gas to produce a substantially SO₃-free flue gas containing reacted and unreacted dry sorbent. The substantially SO₃-free flue gas is conveyed to wet scrubber means for removing SO₂ to produce cleaned flue gas. In a first embodiment, sufficient dry sorbent is provided to remove desired amounts of SO₃ and SO₂. In a second embodiment, a make-up reagent provided to the wet scrubber means wets the dry sorbent, removes both the reacted and unreacted dry sorbent from the substantially SO₃-free flue gas, and makes the unreacted dry sorbent available as a reagent for SO₂ removal, the make-up reagent and the unreacted dry sorbent reacting with and removing the SO₂ from the substantially SO₃-free flue gas to produce cleaned flue gas.