United States Patent: 7655213

 

We've earlier reported on the Coal gasification and conversion technologies that have been developed by the well-known General Electric Corporation.

 

For instance, in: General Electric Converts China Coal | Research & Development; concerning: "GE Energy Licenses its Gasification Technology for Coal-to-Methanol Plant in China; GE's gasification technology has been licensed by 38 facilities in China, allowing chemicals manufacturers to use successfully a variety of relatively inexpensive local coals to create a wide variety of industrial chemicals and fuels"; we documented GE's participation in China's ambitious industrialization plans based on a variety of Coal conversion technologies, which include WVU's direct Coal liquefaction technology in addition to Coal gasification for "indirect" conversion.

Herein, we see that General Electric has addressed, in a productive way, issues related to the co-generation of some potential pollutants in such Coal gasification and indirect conversion processes.

 

And, in doing so, they confirm at least one fact we have, from other sources, already documented.

 

As in one passage excerpted from deep within the full Disclosure:

 

"carbon dioxide will participate in the (Coal) gasification reactions, resulting in increased yield ...";

 

it is seen that CO2 can act as an agent of Coal gasification, resulting in an increased production of reactive, and thus useful for hydrocarbon synthesis, Carbon Monoxide.

 

Comment follows more extended excerpts from General Electric's explanation of how to produce commercially-valuable elemental Sulfur as a by-product of Coal gasification and conversion processes:

 

"United States Patent 7,655,213 - Direct Oxidation of Sulfur with Carbon Dioxide Recycle

 

Date: February, 2010

 

Inventors: John Winter and Raymond Steele, CO and TX

 

Assignee: General Electric Company, NY

 

Abstract: A method for removing hydrogen sulfide to produce elemental sulfur from a synthesis gas feed stream containing hydrogen sulfide, carbon monoxide, hydrogen, carbon dioxide and water using direct oxidation of hydrogen sulfide by contacting a feed stream containing synthesis gas with oxygen in the presence of a catalyst comprised of metal oxides to convert a substantial fraction of the hydrogen sulfide present in the feed stream into sulfur and water, followed by cooling the reaction products to a temperature below the dew point temperature of the water and sulfur, separating the reaction products into two streams, with the first stream containing elemental sulfur and water in liquid form and the second stream containing unreacted components from the synthesis gas, hydrogen sulfide, carbon monoxide, hydrogen, carbon dioxide and water, and then recycling a portion of the unreacted components to the feed stream.

 

Claims: A method for removing hydrogen sulfide to produce elemental sulfur and water from a synthesis gas feed stream containing hydrogen sulfide and carbon dioxide, said method comprising the steps of: Contacting said synthesis gas feed stream with oxygen in the presence of a catalyst to convert a portion of said hydrogen sulfide through direct oxidation into elemental sulfur and water; cooling initial reaction products to a temperature below the dew point temperature of the elemental sulfur; separating said initial reaction products into a first stream containing elemental sulfur and water and second stream containing carbon dioxide and unreacted components remaining in said synthesis gas, and recycling a portion of said unreacted components and carbon dioxide to said synthesis gas feed stream.

(And) wherein said synthesis gas feed stream comprises one or more of hydrogen sulfide, carbon monoxide, hydrogen, carbon dioxide, water and carbonyl sulfide.

 

(And) wherein said second stream includes one or more of unreacted hydrogen sulfide, carbon monoxide, free hydrogen, carbon dioxide and water.

(And, the method) further comprising the step of feeding air to said synthesis gas feed stream prior to contacting said feed stream with said catalyst.

(And) wherein said step of contacting said synthesis gas feed stream with oxygen in the presence of a catalyst forms elemental sulfur and water without reducing free hydrogen and carbon monoxide present in said initial feed stream.

 

A method ... wherein said catalyst is capable of directly oxidizing hydrogen sulfide to sulfur and water.

(And) wherein said catalyst comprises one or more carbon based catalysts (with) Nb, Ti, Fe, Co or Ni (and) further comprises one or more catalyst promoters consisting essentially of the oxides of V, Cr, Mn, Fe, Co, Ni, Cu and Mo.

 

A method ... wherein between about 50% to about 93% by weight of said hydrogen sulfide present in said synthesis gas feed is converted to sulfur and water.

 

Description and Background: The use of high-sulfur content coal presents significant pollution concerns because the gasification process produces a raw fuel gas comprised of carbon monoxide, hydrogen, and lesser quantities of carbon dioxide (CO2), methane and gaseous sulfur compounds, principally hydrogen sulfide (H2S) and carbonyl sulfide (COS). ... From an environmental standpoint, it is important to remove such components from any emissions, particularly the sulfur compounds.

 

Higher processing efficiencies can be realized ... provided that waste components such as hydrogen sulfide are first removed.

 

The present invention relates to a method and system for removing hydrogen sulfide to produce elemental sulfur and water from a synthesis gas feed stream containing hydrogen sulfide and carbon dioxide. In one exemplary embodiment, the method comprises the steps of contacting the synthesis gas feed stream with oxygen in the presence of a catalyst to convert a portion of the hydrogen sulfide into elemental sulfur and water; cooling the initial reaction products to a temperature below the dew point temperature of the elemental sulfur; separating the initial reaction products into a first stream containing elemental sulfur and water, and a second stream containing carbon dioxide and unreacted components in the synthesis gas; and recycling a portion of the unreacted components and carbon dioxide back to the synthesis gas feed stream.

 

Nominally, the synthesis gas feed stream comprises hydrogen sulfide, carbon monoxide, hydrogen, carbon dioxide, water and carbonyl sulfide and the second stream includes unreacted hydrogen sulfide, carbon monoxide, free hydrogen, carbon dioxide and water. As described herein, the step of contacting the synthesis gas feed stream with oxygen in the presence of the catalyst forms elemental sulfur and water without significant reduction in free hydrogen and carbon monoxide present in the initial feed stream.

 

The present method for treating synthesis gas and/or gas streams containing hydrocarbon fuel components and unwanted sulfur compounds uses direct oxidation of hydrogen sulfide, with an appropriate catalyst to form elemental sulfur. Air, substantially pure oxygen or sulfur dioxide may serve as the oxidant. The oxidation reaction is selective for sulfur compounds and results in elemental sulfur that is removed from the synthesis gas stream. After a significant portion of the sulfur compounds have been converted to sulfur and removed from the synthesis gas in the direct oxidation unit, the synthesis gas is fed to a conventional acid gas removal unit, in which all or part or the carbon dioxide is thereby removed.

Because the acid gas removal units (amine or physical solvent) are more selective for sulfur compounds than carbon dioxide, any residual sulfur compounds will be removed with the carbon dioxide.

 

The carbon dioxide, together with the unconverted sulfur compounds from the direct oxidation process, is recycled to the gasifier.

 

The carbon dioxide will participate in the gasification reactions, resulting in increased yield and/or changes in the distribution of the synthesis gas components."

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Left unsaid, and unappreciated, are the potentials, since "carbon dioxide will participate in the (Coal) gasification reactions", thus "resulting in increased yield" of desired products, for actually importing Carbon Dioxide, generated from other sources, into the process, to enable even more of an "increased yield".

 

Also left unsaid by General Electric is precisely what their thus-desulfurized Coal-derived synthesis gas is to be used for.

 

We think, though, in our separate reference link above to the article: "GE Energy Licenses its Gasification Technology for Coal-to-Methanol Plant in China"; we can safely make some assumptions.

 

In light of those safe assumptions, by way of closing, we remind you of another United States Patent we have many times made reference to:

 

"United States Patent: 4035430 - Conversion of Methanol to Gasoline; 1977; Assignee: Mobil Oil Corporation, NY; Abstract: The conversion of methanol to gasoline."


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