Selective sulfidation and desulfidation
Various embodiments utilize selective sulfidation and/or desulfidation for such things as ore and concentrate cracking, metal separation, compound production, and recycling. Selective sulfidation can be used to selectively convert an oxide or other material in a feedstock to a sulfide or other sulfur-containing material, and selective desulfidation can be used to selectively convert a sulfide or other sulfur-containing material in a feedstock to an oxide or other material. In some cases, the material produced by such selective sulfidation/desulfidation of the feedstock can itself be novel and/or commercially valuable, while in other cases, such selective sulfidation/desulfidation can be followed by one or more processes to extract, isolate, or concentrate the converted material.
1. A process for selective sulfidation of a target metal compound of a feedstock material within a reactor, the target metal compound consisting of a metal oxide, oxysulfide, carbonate, sulfate, or sulfide, the process comprising:
introducing a flow of sulfur-containing gas into the reactor through a gas inlet of the reactor; and
passing the flow of sulfur-containing gas through the feedstock material within the reactor while controlling a roasting atmosphere in the reactor about the feedstock material including at least a process temperature and a ratio of sulfur to sulfur dioxide chosen for selective sulfidation of the target component to produce a selectively sulfidized compound including a sulfate, oxysulfide, or sulfide of the target metal, the ratio of sulfur to sulfur dioxide being maintained above a predetermined critical ratio for such selective sulfidation of the target metal compound.
2. A process according to claim 1 , wherein the selective sulfidation is run as a continuous or semi-continuous process.
3. A process according to claim 1 , wherein the selective sulfidation includes high temperature selective sulfidation of an individual metal oxide, sulfate, carbonate, oxysulfide, or sulfide from a mixture of highly chemically-similar metal compounds in the feedstock material.
4. A process according to claim 1 , wherein controlling the roasting atmosphere further includes implementation of a carbothermically-driven sulfur reflux system by back-reacting product sulfur dioxide to control sulfide product selectivity and valency.
5. A process according to claim 4 , wherein implementing the carbothermically-driven sulfur reflux system comprises:
introducing a carbon species into the reactor during selective sulfidation to remove sulfur dioxide from the reactor and reflux it back into sulfur while producing carbon monoxide or carbon dioxide.
6. A process according to claim 1 , wherein the selective sulfidation includes at least one of:
crystallization of the target metal compound from a mixed amorphous or semi-amorphous metal compound; or
spontaneous separation of the selectively sulfidized compound upon sulfidation from a mixed metal compound due to differences in phase stability of the selectively sulfidized compound compared to the original target metal compound.
7. A process according to claim 1 , further comprising:
extracting the selectively sulfidized compound from the feedstock material.
8. A process according to claim 1 , further comprising:
using at least the selectively sulfidized compound in a subsequent molten sulfide electrolysis process.
9. A process according to claim 8 , wherein the selectively sulfidized compound includes at least one of barium sulfide or a rare earth sulfide.
10. A process according to claim 1 , wherein controlling the roasting atmosphere further includes controlling a ratio of carbon monoxide to carbon dioxide within the reactor to stabilize or react the target metal compound.
11. A process according to claim 1 , wherein controlling the roasting atmosphere further includes controlling porosity change of the feedstock material within the reactor to stabilize or react the target metal compound.
12. A process according to claim 1 , further comprising:
pre-treating the feedstock material prior to introducing the feedstock material into the reactor including at least one of calcination, dehalogenation, dephosphorization, or sulfidative sintering.
13. A system for selective sulfidation of a target metal compound of a feedstock material, the system comprising:
a reactor comprising a gas inlet and a receptacle for receiving a feedstock material containing a target metal compound consisting of a metal oxide, oxysulfide, carbonate, sulfate, or sulfide;
a source of sulfur-containing gas; and
a process controller configured to control introduction of a flow of sulfur-containing gas from the source of sulfur-containing gas into the reactor through the gas inlet of the reactor and passing of the flow of sulfur-containing gas through the feedstock material within the reactor while controlling a roasting atmosphere in the reactor about the feedstock material including at least a process temperature and a ratio of sulfur to sulfur dioxide chosen for selective sulfidation of the target component to produce a selectively sulfidized compound including a sulfate, oxysulfide, or sulfide of the target metal, the ratio of sulfur to sulfur dioxide being maintained above a predetermined critical ratio for such selective sulfidation of the target metal compound.
14. A system according to claim 13 , wherein the reactor is configured to run selective sulfidation as a continuous or semi-continuous process.
15. A system according to claim 13 , wherein the selective sulfidation includes high temperature selective sulfidation of an individual metal oxide, sulfate, carbonate, oxysulfide, or sulfide from a mixture of highly chemically-similar metal compounds in the feedstock material.
16. A system according to claim 13 , wherein controlling the roasting atmosphere further includes implementation of a carbothermically-driven sulfur reflux system that back-reacts product sulfur dioxide to control sulfide product selectivity and valency.
17. A system according to claim 16 , further comprising:
a carbon source that introduces a carbon species into the reactor during selective sulfidation to remove sulfur dioxide from the reactor and reflux it back into sulfur while producing carbon monoxide or carbon dioxide.
18. A system according to claim 13 , wherein the selective sulfidation includes at least one of:
crystallization of the target metal compound from a mixed amorphous or semi-amorphous metal compound; or
spontaneous separation of the selectively sulfidized compound upon sulfidation from a mixed metal compound due to differences in phase stability of the selectively sulfidized compound compared to the original target metal compound.
19. A system according to claim 13 , wherein controlling the roasting atmosphere further includes controlling a ratio of carbon monoxide to carbon dioxide within the reactor to stabilize or react the target metal compound.
20. A system according to claim 13 , wherein controlling the roasting atmosphere further includes controlling porosity change of the feedstock material within the reactor to stabilize or react the target metal compound.