Abstract: It is known to remove sulfur dioxide from gas streams, particularly waste or flue gases, by contact with aqueous scrubbing solutions containing a metal salt, such as ferric sulfate, in which the valence of the metal is reduced by the sulfur dioxide. It is also known that such scrubbing solutions can be regenerated by oxidizing the reduced metal salt, such as ferrous sulfate, back to the higher valence for further use in removing sulfur dioxide. According to the invention, the regeneration of the scrubbing solution is advantageously effected by electrolytic or anodic oxidation, rather than air oxidation, of the reduced metal salt, since anodic oxidation is not adversely affected by the increase in sulfuric acid content of the scrubbing solution which results from the conversion of the sulfur dioxide absorbed in the scrubbing solution.

Abstract: In a "first" scrubbing operation, the sulfur dioxide containing flue gas is scrubbed with an aqueous solution containing ferric sulfate and aluminum sulfate. The ferric sulfate oxidizes the sulfur dioxide to sulfuric acid, which dissolves in the solution, and is reduced to ferrous sulfate. In a subsequent "second" scrubbing operation, the solution, now containing ferrous sulfate, aluminum sulfate, and sulfuric acid, is scrubbed with air. This regenerates, or re-oxidizes the ferrous sulfate to ferric sulfate. The presence of aluminum sulfate accelerates the rate of regeneration. The regenerated solution is then returned to its function in a "first" scrubbing operation, and the indicated cycle of "first" and "second" scrubbing operations are repeated.

Abstract: In a "first" scrubbing operation, the sulfur dioxide containing flue gas is scrubbed with an aqueous solution containing ferric sulfate and aluminum sulfate. The ferric sulfate oxidizes the sulfur dioxide to sulfuric acid, which dissolves in the solution, and is reduced to ferrous sulfate. In a subsequent "second" scrubbing operation, the solution, now containing ferrous sulfate, aluminum sulfate, and sulfuric acid, is scrubbed with air. This regenerates, or re-oxidizes the ferrous sulfate to ferric sulfate. The presence of aluminum sulfate accelerates the rate of regeneration. The regenerated solution is then returned to its function in a "first" scrubbing operation, and the indicated cycle of "first" and "second" scrubbing operations are repeated.

Abstract: The sulfur dioxide containing flue gases are passed through a gas scrubber containing an aqueous solution of a metal salt which can be reduced by sulfur dioxide from a high valence state to a lower valence state. This oxidizes the sulfur dioxide to either sulfur trioxide or sulfuric acid which dissolves in the solution. The sulfur compound containing solution is removed from the first gas scrubber and placed in a regeneration gas scrubber through which air is passed. The oxygen in the air oxidizes the reduced metal salt and thereby regenerates the solution to its original composition. The regenerated solution is then recycled to the first gas scrubber where further removal of sulfur dioxide from the flue gas occurs.