Increasing the rate of reaction in reducing calcium sulfate to calcium sulfide

Claim 2

A process according to claim 1 in which the accelerator agent used is a gaseous sulfur compound selected from class consisting of hydrogen sulfide, carbonyl sulfide, carbon disulfide, and sulfur dioxide.

Claim 3

A process for producing calcium sulfide from a calcium-sulfate-containing material, such as, gypsum, anhydrite, phosphogypsum, or the like which comprises introducing a charge of comminuted, dehydrated calcium sulfate produced from aid calcium-sulfate-containing material into a reaction vessel maintained at a temperature of 1,300* to 1,900* F. with a gaseous reductant wherein the reductant consists essentially of hydrogen, carbon monoxide and mixtures thereof, said gaseous reductant being further characterized in that it is obtained from a first source whereby said gaseous reductant contains substantially less than 0.1 percent by volume of compounds containing one sulfur atom per molecule and substantially less than 0.05 percent by volume of compounds containing two sulfur atoms per molecule, supplying to said reaction, from an external second source, an accelerator agent selected from the group consisting of compounds which will provide in said reaction vessel a sulfur compound selected from the group consisting of sulfur vapor, sulfur dioxide and gaseous sulfide in an amount sufficient to provide a concentration of at least from 0.1 to 10 percent by volume in the gaseous reductant in the case of sulfur compounds Ontaining only one sulfur atom and at least from 0.05 to 5 percent by volume in the gaseous reductant in the case of sulfur compounds containing two sulfur atoms per molecule.

Claim 4

A process according to claim 4 in which the accelerating agent is a gaseous sulfide.

Claim 5

A process according to claim 5 in which the gaseous reductant introduced into the reactor vessel contains 0.15 to 3 percent of the accelerator agent.

Claim 6

A process according to claim 5 in which the reaction vessel is maintained at a temperature in the neighborhood of 1,500* F.

Claim 7

A process according to claim 7 in which the accelerating agent is hydrogen sulfide, and the amount of hydrogen sulfide is about 1 percent of the gaseous reductant introduced into the reactor vessel.

Claim 8

A process according to claim 1 in which the reaction temperature is within the range of 1,400* to 1,700* F.

Claim 9

A process according to claim 4 in which the temperature is within the range of 1,400* to 1,700* F.

Claim 10

A process for producing calcium sulfide from gypsum, or the like, which comprises comminuting the gypsum, passing a charge of said comminuted gypsum the particles of which are within the range of minus 10 mesh and 65 mesh through a heating zone to dehydrate the gypsum and forming particles of calcium sulfate, passing the dehydrated, comminuted calcium sulfate through a reaction vessel maintained at a temperature of 1,300* to 1,900* F., providing a stream of gaseous reductant wherein the reductant consists essentially of hydrogen, carbon monoxide and mixtures thereof, said gaseous reductant being further characterized in that it is obtained from a first source whereby said gaseous reductant contains substantially less than 0.1 percent by volume of compounds containing one sulfur atom per molecule and substantially less than 0.05 percent by volume of compounds containing two sulfur atoms per molecule, adding to said stream of gaseous reductant, from an external second source, an accelerator agent selected from the group consisting of compounds which will provide in said reaction vessel a sulfur compound selected from the group consisting of sulfur vapor, sulfur dioxide and gaseous sulfide in an amount sufficient to provide a concentration of at least from 0.1 to 10 percent by volume in the gaseous reductant in the case of sulfur compounds containing only one sulfur atom per molecule and at least from 0.05 to 5 percent by volume in the gaseous reductant in the case of sulfur compounds containing two sulfur atoms per molecule, passing said gas stream through and in intimate contact with the particles of calcium sulfate in said vessel to reduce the calcium sulfate to calcium sulfide and forming a stream of carbon dioxide and water vapor as gaseous products of the reaction.

Claim 11

The process of claim 11 further including the step of passing said stream containing the carbon dioxide through a carbonation unit together with the calcium sulfide produced in the reactor vessel under conditions which convert the calcium sulfide to hydrogen sulfide and to calcium carbonate, passing a part of the hydrogen sulfide thus provided into the stream of hydrogen and carbon monoxide introduced into said reactor vessel to provide the hydrogen sulfide added as accelerator agent to said stream as aforesaid and converting the remainder of the hydrogen sulfide stream from said carbonation unit to elemental sulfur.

Claim 12

A process according to claim 12 in which the reactor vessel is maintained at a temperature in the neighborhood of 1,500* F.

Claim 13

A process according to claim 13 in which the stream of reductant consists essentially of hydrogen and carbon monoxide and is produced by reforming natural gas.

Claim 14

A process according to claim 14 in which the comminuted gypsum prior to introduction into the reactor vessel is heated to a temperature of 600* to 800* F.

Claim 15

A process according to claim 12 in which the temperature is within the range of 1,400* to 1,700* F.