Energy Citations Database (ECD) - - Document #125377

In many previous reports, we've documented that Coal can be converted into a synthesis gas, or "syngas", consisting primarily of Carbon Monoxide and Hydrogen, and well-suited for catalytic condensation into liquid and gaseous hydrocarbons, through gasification with both Oxygen and Steam, H2O; which H2O supplies the necessary Hydrogen.

 

 

Such "hydro-gasification" of Sulfur-bearing Coal also leads to the formation of Hydrogen Sulfide, H2S, in and of itself an unpleasant thing to have floating freely about.

However, we've also documented, as, for just two examples, in:

Exxon Methane and Hydrogen from H2S and Carbon Monoxide | Research & Development; concerning:

"United States Patent 4,517,171 - Synthesis of H2 and CH4 from H2S and CO; 1985; Assignee: Exxon Research and Engineering Company; Abstract: Hydrogen and methane are synthesized from a gaseous feed comprising a mixture of H2S and CO"; and:

Florida Hydrogen and Sulfur from H2S | Research & Development; which concerns the: "United States Patent 6,572,829 - Photocatalytic Process for Decomposing Hydrogen Sulfide; 2003; Assignee: University of Central Florida; Abstract: System for separating hydrogen and sulfur from hydrogen sulfide (H2S) gas produced from oil and gas waste streams";

that, H2S can be recovered, from whatever gas streams it might be found in, and profitably utilized for the recovery of both it's Sulfur and it's Hydrogen.

Herein, we submit a report made by Georgia Tech University to the Morgantown, WV, office of the USDOE, relating how Hydrogen Sulfide can, in a single step utilizing one integrated processing unit, be extracted out of a synthesis gas stream produced from Coal, and economically "split" into Hydrogen and elemental Sulfur.

Comment follows excerpts from the initial and following links in this dispatch to:

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"Title: Electrochemical Polishing of Hydrogen Sulfide from Coal Synthesis Gas

Advanced coal-fired power systems `95 review meeting, Morgantown, WV; June,1995

Published: November, 1995; System Entry Date: November, 2009

OSTI ID: 125377; Report Number: DOE/PC/94207--96/C0547; USDOE Contract: FG22-94PC94207

Authors: E.F. Gleason and J. Winnick

Research Organization: Georgia Tech Research Institute, Atlanta

Abstract: An advanced process has been developed for the separation of H2S from coal gasification product streams through an electrochemical membrane.

H2S is removed from the syngas by reduction to the sulfide ion and Hydrogen at the cathode. The sulfide ion migrates to the anode through a molten salt electrolyte suspended in an inert ceramic matrix. Once at the anode it is oxidized to elemental sulfur and swept away for condensation in an inert gas stream.

The syngas is enriched with the H2.

(As we've earlier documented from other sources, Hydrogen Sulfide can be made to yield Hydrogen for the further hydrogenation of Coal-derived synthesis gas.)

Order-of-magnitude reductions in H2S have been repeatedly recorded (100 ppm to 10 ppm H2S) on a single pass through the cell. This process allows removal of H2S without cooling the gas stream and with negligible pressure loss through the separator. Since there are no absorbents used, there is no absorption/regeneration step as with conventional technology. Elemental sulfur is produced as a by-product directly, so there is no need for a Claus process for sulfur recovery. This makes the process economically attractive since it is much less equipment intensive than conventional technology.

Conclusions: Selective removal of H2S has been demonstrated for polishing application to a coal
synthesis gas (100 ppm H2S) and for a purification application to coal synthesis gas (10 ppm H2S).

The economic study ... shows that the proposed technology is economically favorable as a method
of coal gas sweetening."

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Anyone care for some sweet "coal gas"? Some Coal gasoline really would be sweet, wouldn't it?

But, truth to tell, our USDOE didn't engage, publicly at least, in this bit of "coal gas sweetening" for the purposes of making synthetic liquid fuels.

Though not reflected in our excerpts, this work was performed entirely for the purposes of making synthesis gas, derived from Coal, less polluting when burned in a power plant; or, used in a "Molten Carbonate Fuel Cell", whatever that irrelevant bit of futuristic exotica might be.

Coal burns just fine, as is, in power plants; and, need be, we can scrub the Sulfur from the exhaust gases, as some already are, and sometimes sending it along to, as above, "a Claus process for sulfur recovery".

But, this Georgia Tech technology is "economically attractive since it is much less equipment intensive than conventional technology', i,e., a separate Claus plant.

What this actually is, though they are loathe for whatever suspect reasons to tell us, is a way to remove Sulfur from hydrocarbon synthesis gas, as an integral step in the syngas production process, before that syngas is passed over an Iron, Nickel or Cobalt catalyst, all of which are very sensitive to Sulfur poisoning, for Fischer-Tropsch, and related, condensation into low-Sulfur hydrocarbon liquids and gases.

The elemental Sulfur has established commercial uses and value; and, as a by-product, such Sulfur production would serve to offset some of the costs of liquid hydrocarbons produced from the Coal syngas.

Further, the Hydrogen recovered herein from the Hydrogen Sulfide could not only be used, as indicated in: "syngas is enriched with the H2", to improve the syngas going into the Fischer-Tropsch reactor, it would also serve nicely in a relatively standard, Petroleum refinery-type "hydro-treater", or "hydro-cracker", to further refine and hydrogenate, and to increase the utility and value of, the Coal-based liquid hydrocarbons issuing from that Fischer-Tropsch reactor.


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