Herein, we submit a sequence of documents which, taken in total, might represent a productive route for the utilization of a pollutant that can be created during the Steam-gasification of Coal, itself undertaken to generate a synthesis gas suitable for subsequent catalytic processing into hydrocarbons.
First, we remind you of: FMC Corporation Recovers Sulfur from Coal Syngas | Research & Development; which makes report of a technique for the extraction of Sulfur from a process for the:"gasification of carbonaceous solids (i.e., Coal) with steam to give product gas containing carbon monoxide and hydrogen" suitable for catalytic condensation into various hydrocarbons, and wherein the Coal gasification can result in the co-production of Sulfur Oxides.
In that technique, such objectionable Sulfur Oxides can be extracted from the raw hydrocarbon synthesis gas and then reprocessed within the system to yield Hydrogen Sulfide, which can, then, as specified, be conveyed to a "Klaus"-type processor for the recovery of commercially-valuable elemental Sulfur.
There might, it seems, be even better ways to go about utilizing the Hydrogen Sulfide generated in such a Sulfur Oxide control process, at a Coal conversion facility or anywhere else where Sulfur Oxides might arise from an industrial process, such an oil refinery or a natural gas processing plant.
In: Exxon Improves Coal Liquefaction with Hydrogen Sulfide | Research & Development; for instance, wherein is reported: "United States Patent 4,094,765 - Coal Liquefaction Process;1978; Assignee: Exxon, NJ; Abstract: A coal liquefaction chargestock is first treated with a hydrogen sulfide-containing gas and thereafter subjected to coal liquefaction conditions"; we're taught that such Hydrogen Sulfide can be used to improve the hydrogenation and conversion of Coal into liquid hydrocarbons.
But, as an alternative, according to some scientists at the University of Central Florida, environmental energy, i.e., sunlight, can be engaged to, instead, transform such by-product Hydrogen Sulfide into both elemental Sulfur and elemental Hydrogen.
And, that has implications we will emphasize, following our excerpts from the initial link in this dispatch, with links to other references further illustrating the potentials also appended:
"United States Patent 6,572,829 - Photocatalytic Process for Decomposing Hydrogen Sulfide
Date: June, 2003
Inventors: Clovis Linkhouse and Nazim Muradov, FL
Assignee: University of Central Florida, Orlando
Abstract: System for separating hydrogen and sulfur from hydrogen sulfide (H2S) gas produced from oil and gas waste streams. Hydrogen sulfide (H2S) gas is passed into a scrubber and filtration unit where it encounters polysufide solution. Elemental sulfur is freed and filtered through a porous media and continues to a stripper where excess H2S is removed. The excess H2S returns to the scrubber and filtration unit, while the sulfide solution passes into a photoreactor. The sulfide solution inside the photoreactor is oxidatively converted to elemental sulfur and complexed with excess sulfide ion to make polysulfide ion, while water is reduced to hydrogen. Hydrogen percolates out of the photoreactor, while the polysulfide solution is fed back to the scrubber where the system starts over.
Claims: A system for recovering sulfur from hydrogen sulfide (H2S) waste streams using a photochemical process with semiconductor particulates, comprising: means for producing hydrogen sulfide gas; means for mixing the hydrogen sulfide gas with a polysulfide solution to form a mixture solution; means for filtering the mixture solution to produce a sulfide solution; ... and a photoreactor for receiving the sulfide solution, the photoreactor having semiconductor particulates and a light source and configured to separate the sulfide solution into hydrogen gas and elemental sulfur.
The system for recovering sulfur ..., wherein the means for producing hydrogen sulfide gas is chosen from at least one of: an oil refinery, a gas refinery, a hydrodesulfurization plant, and a sour natural gas well.
(There you go - - maybe we can help out the producers of Marcellus Shale gas, as well)
The system for recovering sulfur ... wherein the photoreactor includes: a photocatalyst composed of Cadmium Sulfide (CdS) (and/or) Zinc Sulfide (ZnS) .
(Other "photocatalyst"s are suggested, as well; none of them too exotic or too expensive.)
Description and Background: This invention relates to sulfur recovery from oil and gas refinery waste streams, and in particular to a method and apparatus for sulfur recovery from oil and gas refinery waste streams using semiconductor particulates, where hydrogen sulfide (H2S) having been absorbed into an alkaline solution is decomposed in a photochemical scheme to yield both sulfur and hydrogen which can be later sold or used internally at a refinery.
(Again, note: All of this is being established for the conventional Oil and Gas industry, which does have a Sulfur problem, not much openly-discussed, and, a need for Hydrogen, to hydrogenate less-than-ideal natural petroleum and petroleum-like materials, such as "heavy" crude oil and Tar Sand bitumen.)
Oil refineries typically pump crude oil from the ground which contains unusable organic sulfur, the latter of which must be separated from the crude oil in order to allow the oil to become a useful product. Typically, the pumped crude oil is treated with hydrogen and a catalyst under a high temperature which decomposes the organic sulfur in the crude oil and releases the sulfur in the form of hydrogen sulfide (H2S) gas. The problem is what do the refineries do with the H2S gas, which is a noxious poisonous gas that cannot be released into the atmosphere.
Recent environmental regulations generally require oil and gas refineries to develop waste minimization technologies for the treatment of sulfur-containing compounds, such as hydrogen sulfide (H2S) within their facilities. Current technology typically requires a solvent absorption and stripping process to separate the acid gases, a Claus type reactor to perform a partial oxidation of the sulfide to make elemental sulfur ... .
Currently refineries must now go out and buy or make hydrogen to perform hydrodesulfurization. Afterwards, the resultant H2S must then be decomposed at the plant.
As the world supply of petroleum decreases, the average sulfur content of crude oil has begun to rise. In recent years the average oil refinery has gone from being a net producer to a net consumer of H2. The oil producers would thus be interested in any process that increases the amount of H2 available in-house.
Summary: A primary objective of the present invention is to provide a method of recovering sulfur from oil and gas refinery waste streams using semiconductor particulates, where hydrogen sulfide (H2S) having been absorbed into an alkaline solution is decomposed in a photochemical process to yield both sulfur and hydrogen.
The secondary objective of the present invention is to decompose noxious poisonous gas such as hydrogen sulfide into separate amounts of hydrogen and sulfur using light and a photocatalyst.
A third objective is to recoup the H2 contained in H2S and return it to the hydrodesulfurization plant for reuse in oil refinery applications.
The energy to drive the reaction can either come from the sun or an artificial light source."
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So, in sum, it is possible to, by using light energy, transform Hydrogen Sulfide, which, as in the FMC process, above, can be made from Sulfur Oxides that might arise from Coal gasification, into elemental Sulfur and elemental Hydrogen.
The Hydrogen is then available for use "in oil refinery applications".
We'll address an even better use for it later on. But, first, here is yet another United States Patent, also assigned to the University of Central Florida, for what appears to be an even improved version of the technology disclosed by USP 6,572,829:
"United States Patent: 7220391 - UV Photochemical ... Decomposition of Hydrogen Sulfide
Date: May, 2007
Inventors: Cunping Wang and Clovis Linkhouse, FL
Assignee: University of Central Florida Research Foundation, Orlando
Abstract: Methods and systems for separating hydrogen and sulfur from hydrogen sulfide (H2S) gas. Hydrogen sulfide(H2S) gas is passed into a scrubber and filtration unit with polysulfide solution. Interaction frees elemental sulfur which is filtered, excess continues to a stripper unit where the excess H2S is removed. The excess H2S returns to the scrubber and filtration unit, while the sulfide solution passes into a photoreactor containing a photocatalyst and a light source. The sulfide solution is oxidatively converted to elemental sulfur and complexed with excess sulfide ion to make polysulfide ion, while water is reduced to hydrogen. Hydrogen is released, while the polysulfide solution is fed back to the scrubber unit where the system operation repeats.
In a second embodiment, the photocatalyst is eliminated, and the hydrogen sulfide solution is directly illuminated with ultraviolet radiation with a light source such as a low pressure mercury lamp ... .
(Note, again: Natural sunlight, often in short supply in US Coal Country, isn't really needed.)
Claims: A method of recovering sulfur from hydrogen sulfide (H2S) waste streams using a photochemical process in a closed cycle system without photocatalysts ... .
The method of recovering sulfur (which) further includes: producing the hydrogen sulfide from a source chosen from at least one of: an oil refinery, a gas refinery, a hydrodesulfurization plant, a sour natural gas well, a sewage treatment plant, and a kraft process paper mill.
(Coal facilities, it seems, don't really rank that high in the roster of Sulfur offenders. Who knew?)
(A) method of recovering sulfur (which) further includes: applying the light from a low pressure mercury lamp.
A method of decomposing hydrogen sulfide(H2S) to sulfur(S) and hydrogen(H2)."
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So, using what could be environmental and renewable Solar light energy, or, perhaps, "the light from a low pressure mercury lamp" powered by a dedicated Hydro or Wind electricity generator, we can convert Hydrogen Sulfide, as we can make from any Sulfur Oxides that might arise from an indirect process of Coal conversion, as in the FMC Corporation technology noted above, or from any Sulfur Oxides in the exhaust of a Coal-fired power plant, into commercially-valuable by-product Sulfur, and, elemental Hydrogen.
Now, since we don't, as seen, for just one example out of now many, in:
Exxon 1981 Coal to "High-Quality Liquids" and Methane | Research & Development; concerning: "United States Patent 4,292,048 - Coal Devolatilization and Steam Gasification Process; 1981; Assignee: Exxon Research & Engineering Company, NJ; Abstract: Hydrocarbon liquids and a methane-containing gas are produced from carbonaceous feed solids";
really need any elemental Hydrogen to fully hydrogenate the carbon content of Coal, in order to synthesize hydrocarbons, since we can accomplish the hydrogenation of Coal by gasifying it with Steam, there might be better uses for that Hydrogen, as for instance, in the recycling of Carbon Dioxide via the 1912 Nobel-winning Sabatier process, which, as explained in:
CO2 Solution Wins Nobel Prize - in 1912 | Research & Development; enables a catalytic reaction to occur between Hydrogen and Carbon Dioxide, obtained from whatever handy source, with the product of that reaction being Methane gas.
And, Methane - as valuable as it, in and of itself, might be - has some intriguing potentials. As seen, for just one example, again out of now many, in:
Standard Oil 1944 CO2 + CH4 + H20 = Aviation Fuel | Research & Development | News; Methane can be reacted with Carbon Dioxide, recovered from whatever abundant source, perhaps a Corn Ethanol fermentation and distillation facility, and both of them converted through such a reaction into high-performance liquid hydrocarbon fuels.
Thus, one potential pollutant that can arise from our use of Coal, Hydrogen Sulfide, can be utilized to manufacture one commercially-valuable product, elemental Sulfur, which has industrial markets already in need of it; and, another, Hydrogen, which, via the Sabatier reaction with Carbon Dioxide, to form Methane, and, the subsequent reforming of that Methane with even more Carbon Dioxide, to make such useful things as "Aviation Fuel", can enable the commercially-valuable,