Method for removing acid gases from flue gas

A method is provided for removing contaminants, such as sulfur trioxide, sulfur dioxide and hydrogen halides, out of a gas, such as an exhaust gas from a coal or oil fired burner, by injecting a bisulfite containing solution into the gas so that the bisulfite reacts with the sulfur trioxide and/or hydrogen halides in the gas to produce salts and sulfur dioxide, or by injecting a sulfite containing solution into the gas so that the sulfite reacts the sulfur dioxide in the gas to produce bisulfite and this bisulfite reacts with the sulfur trioxide and/or hydrogen halides to result in the formation of salts and sulfur dioxide. The sulfur dioxide in the gas can be washed out of the gas in a downstream wet scrubber. By removing the sulfur trioxide and/or hydrogen halides out of the gas, corrosion of the gas scrubbing apparatus can be reduced.