Abstract: Flue gas containing sulfur dioxide is purified (and the sulfur content thereof is recovered in elemental form) by scrubbing the gas with aqueous sodium aluminate-sodium hydroxide solution thereby forming an underflow suspension consisting essentially of sodium and aluminum sulfites and sulfates and fly ash; oxidizing the sulfites to sulfates; evaporating the free water present; reducing the resulting apparently dry mixture of sodium and aluminum sulfates by the action of reactive hydrogen and a carbonaceous reducing agent thereby forming a solid mixture of a sodium oxide and sodium aluminate and a gaseous mixture comprising sulfur dioxide, sulfur, and hydrogen sulfide; condensing said sulfur; and inter-reacting said sulfur dioxide and hydrogen sulfide to provide elemental sulfur. The solid mixture is dissolved in water to regenerate the scrubbing solution, which is then recycled. The solution is filtered at any convenient point to remove fly ash and any other solids present.

Abstract: Flue gas having a content of sulfur dioxide is passed upwardly through a scrubbing tower against a descending flow of recycled aqueous sodium aluminate-sodium hydroxide liquor. The sulfur dioxide in the gas is converted to sodium and aluminum sulfates and sulfites and the liquor removes any fly ash present in the gas. Underflow is continuously discharged from the tower and is sent to an evaporator for removal of excess water. Make-up solutions of sodium sulfate and aluminum sulfate are added, as necessary. Carbonaceous reducing agent is added to the discharge from the evaporator. The mixture is continuously fed into a reducing furnace where the sulfates and sulfites are reduced to sulfides. The product of the furnace (molten sodium and aluminum sulfides) is charged into a continuous hydrolyzer. Hydrogen sulfide is evolved and collected, and, if desired, its sulfur content is converted to elementary sulfur. The underflow from the hydrolyzer is filtered.

Abstract: Flue gas containing sulfur dioxide is purified (and the sulfur content thereof is recovered in elemental form) by scrubbing the gas with aqueous sodium aluminate-sodium hydroxide solution thereby forming an underflow suspension consisting essentially of sodium and aluminum sulfites and sulfates and fly ash; oxidizing the sulfites to sulfates; evaporating the free water present; reducing the resulting apparently dry mixture of sodium and aluminum sulfates by the action of reactive hydrogen and a carbonaceous reducing agent thereby forming a solid mixture of a sodium oxide and sodium aluminate and a gaseous mixture comprising sulfur dioxide, sulfur, and hydrogen sulfide; condensing said sulfur; and inter-reacting said sulfur dioxide and hydrogen sulfide to provide elemental sulfur. The solid mixture is dissolved in water to regenerate the scrubbing solution, which is then recycled. The solution is filtered at any convenient point to remove fly ash and any other solids present.

Abstract: Flue gas having a content of sulfur dioxide is passed upwardly through a scrubbing tower against a descending flow of recycled aqueous sodium aluminate-sodium hydroxide liquor. The sulfur dioxide in the gas is converted to sodium and aluminum sulfates and sulfites and the liquor removes any fly ash present in the gas. Underflow is continuously discharged from the tower and is sent to an evaporator for removal of excess water. Make-up solutions of sodium hydroxide, sodium sulfate and aluminum sulfate are added, as necessary. Carbonaceous reducing agent is added to the discharge from the evaporator. The mixture is continuously fed into a reducing furnace where the sulfates and sulfites are reduced to sulfides. The product of the furnace (molten sodium and aluminum sulfides) is charged into a continuous hydrolyzer. Hydrogen sulfide is evolved and collected, and, if desired, its sulfur content is converted to elementary sulfur. The underflow from the hydrolyzer is filtered.

Abstract: Flue gas having a content of sulfur dioxide is passed upwardly through a scrubbing tower against a descending flow of recycled aqueous sodium aluminate-sodium hydroxide liquor. The sulfur dioxide in the gas is converted to sodium and aluminum sulfates and sulfites and the liquor removes any fly ash present in the gas. Underflow is continuously discharged from the tower and is sent to an evaporator for removal of excess water. Make-up solutions of sodiuum hydroxide, sodium sulfate and aluminum sulfate are added, as necessary. Carbonaceous reducing agent is added to the discharge from the evaporator. The mixture is continuously fed into a reducing furnace where the sulfates and sulfites are reduced to sulfides. The product of the furnace (molten sodium and aluminum sulfides) is charged into a continuous hydrolyzer. Hydrogen sulfide is evolved and collected, and, if desired, its sulfur content is converted to elementary sulfur. The underflow from the hydrolyzer is filtered.