Sulfur recovery process

Claim 2

A process for the gaseous reduction of calcium sulfate comprising the steps of heating the sulfate to reaction temperature by transferring heat from hot gaseous products of a subsequent reaction of the sulfate with reducing gases before the sulfate enters the reaction zone, reacting the sulfate with reducing gases containing hydrogen and carbon monoxide at a temperature with the approximate range of 2,000* F. to 2,5000* F. to produce calcium sulfide, calcium oxide, and substantial quantities of sulfur dioxide. thereby converting from about five percent to about 95 percent of the sulfur to sulfur dioxide, and recovering the products.

Claim 3

A process for the gaseous reduction of calcium sulfate comprising the steps of heating the sulfate to reaction temperature by transferring heat from hot gaseous products of a subsequent reaction of the sulfate with reducing gases before the sulfate enters the reaction zone, the sulfate is reacted at a temperature within the approximate range of a 2,000* F. to 2, 500* F. with reducing gases containing hydrogen and carbon monoxide in a molar ratio which converts approximately one-third of the sulfate sulfur to sulfur dioxide, and concurrently converting the remaining two-thirds of the sulfate to calcium sulfide.

Claim 4

Process of claim 4, wherein the calcium sulfide is reacted with carbon dioxide and water to form hydrogen sulfide, and the sulfur dioxide and hydrogen sulfide are combined to form elemental sulfur.

Claim 5

A process for recovering elemental sulfur from gypsum which comprises a. crushing and screening the gypsum to a uniform particle size, b. dehydrating the gypsum to drive off its water of crystallization, c. heating the calcium sulfate up to reaction temperatures by exchanging heat with the hot gaseous products of the subsequent reaction, occurring in step (d) d. contacting the calcium sulfate with a stream of reducing gases comprising hydrogen and carbon monoxide in approximately equal quantities at a temperature within the approximate range of 2,000* F. to 2,5000* F. to convert one-third of the sulfur in the metal sulfate to sulfur dioxide, e. collecting the sulfur dioxide produced during the reduction reaction. f. converting the calcium sulfide to hydrogen sulfide, and g. combining the sulfur dioxide and hydrogen sulfide streams to produce elemental sulfur.

Claim 6

The process of claim 6, wherein less than one-third of the sulfur contained in the metal sulfate is converted to sulfur dioxide and a portion of the hydrogen sulfide is converted to sulfur dioxide to control the ratio of hydrogen sulfide-to-sulfur dioxide ratio at 2-to-1 for the production of elemental sulfur.

Claim 7

The process of claim 4, wherein the calcium sulfide is reacted with carbon dioxide and water to form hydrogen sulfide, and wherein all or part of the sulfur dioxide is converted to sulfuric acid and the hydrogen sulfide is converted to elemental sulfur or sulfuric acid.

Claim 8

The process of claim 8, wherein carbon dioxide from flue gases or an outside source is added as needed to provide sufficient carbon dioxide to convert all of the calcium to calcium carbonate.