Production of H2 S from SO2 obtained from flue gas

Claim 1

The regenerable process for the removal, and its subsequent recovery as hydrogen sulfide, of the bulk of the sulfur dioxide contained in a flue gas, said process comprising the steps of: (a) contacting said flue gas with an aqueous, alkaline, sodium-carbonate containing reaction medium essentially saturated with sodium sulfite to react the bulk of the sulfur dioxide and a portion of the oxygen with the carbonate values to form a slurry of sodium sulfite and sodium sulfate dispersed in the reaction medium, the sodium and alkalinity being supplied to said reaction medium by the addition of recycled solid sodium carbonate from step (g); (b) separating sodium sulfite and sodium sulfate crystals from the reaction medium; (c) reducing the separated sodium sulfite and sodium sulfate crystals to solid sodium sulfide; (d) forming an intimate blend consisting essentially of said solid sodium sulfide and the separated solid sodium bicarbonate of step (i); (e) heating said blend in the substantial absence of air to a temperature sufficient to remove any water present in said blend and to react the sodium bicarbonate with the sodium sulfide in the blend to form gaseous hydrogen sulfide and dry, solid, anhydrous sodium carbonate; (f) recovering the gaseous hydrogen sulfide; (g) recycling at least part of the sodium carbonate formed in step (e) to step (a); (h) adding the remainder of the sodium carbonate formed in step (e) to a sodium bicarbonate saturated solution and carbonating with carbon dioxide to form a slurry composed of solid particles of sodium bicarbonate dispersed in said solution, and; (i) separating particles of sodium bicarbonate from the slurry formed in step (h) and recycling said separated solid particles of sodium bicarbonate to step (d).