United States Patent: 3971636

 

Herein, we again cite the Coal conversion expertise of Pittsburgh's former Gulf Oil Corporation.

In this case, they combined a couple of Coal gasification techniques to improve the production of Carbon Monoxide and Hydrogen, i.e., hydrocarbon synthesis gas, from Coal; and, they did so in a way which illustrates, in confirmation of some of our previous reports, that Carbon Dioxide can be utilized, and recycled, in Coal gasification processes.

By way of introduction, note that they are, herein, first deliberately making Carbon Dioxide, from Coal, for further chemical reduction, with more hot Coal, into Carbon Monoxide.

That fact, and others, have implications we attempt to highlight, in comment following excerpts from:

 

"United States Patent 3,971,636 - Condensate Scrubbing of Coal Gasifier Product

 

Date: July, 1976

 

Inventor: Charles Matthews, PA

 

Assignee: Gulf Oil Corporation, Pittsburgh

 

Abstract: A process for gasifying coal to produce carbon monoxide and hydrogen in which a first stream of coal is burned without bed formation in a combustion zone in the presence of water under oxidation conditions to produce gases containing carbon dioxide and steam. A second stream of coal is maintained as a fluid bed in a separate gasifier zone by upflowing carbon dioxide and steam from the combustion zone while being gasified under reducing conditions to produce carbon monoxide and hydrogen. The water vapor in the gasifier product stream is condensed and the condensate is used to scrub char and pollutants from the same gasifier product stream to form a slurry which is utilized as fuel in the combustion zone.

Claims: A process for gasifying feed ash-containing solid carbonaceous particulates comprising passing a first feed stream comprising a water slurry of carbonaceous particulates ... and oxygen-containing gas to a combustion zone to provide heat and reactants for said process, passing a second feed stream of carbonaceous particulates to a fluidized bed gasifier zone disposed upon grate means with said second feed stream entering said gasifier zone above said grate means, maintaining said combustion zone under exothermic oxidation reaction conditions ... to produce hot combustion gases and steam and ... passing said hot combustion gases and steam upwardly from said combustion zone through said grate means into said fluidized gasifier zone to form a fluidized bed of said second feed stream particulates ...; injecting at least one coolant selected from the group consisting of water and steam into said hot combustion gases between said combustion zone and said grate means (and, via specified reaction conditions, causing) carbon dioxide and water vapor (to) react with carbon to produce carbon monoxide and hydrogen ... .

(And) wherein said feed solid carbonaceous particulates comprise at least one member selected from the group consisting of coal and coke.

Water is consumed within the process by the chemical reaction: C + H2O = CO + H2, and is thereby converted to the desired gaseous product.

A high degree of process heat economy is achieved by virtually complete gasification of the carbonaceous portion of the feed.

In accordance with the present invention, coal is converted to carbon monoxide and hydrogen by a process which exhibits a minimum potential for polluting.

(Coal combustion) generates heat to support the endothermic gasification reactions in the gasifier and heat to vaporize and superheat water for reaction in the gasifier.

Gaseous impurities, having a potential for pollution, which are generated within the process are treated within the process and converted into acceptable forms for sale or disposal, or the impurities are destroyed within the process. For example, sulfur compounds entering the process are converted to hydrogen sulfide directly, or to sulfur dioxide and then to hydrogen sulfide; the hydrogen sulfide is recovered by known processes; and the recovered hydrogen sulfide is converted to elemental sulfur for sale or storage by use of known processes. Nitrogen compounds entering the process are converted mainly into ammonia, or to nitrogen gas, or to nitrogen oxides and then to ammonia or nitrogen gas; the ammonia is recovered and purified by known processes for sale. Gas streams before venting are first water scrubbed within the process to remove all dust and particulate contaminants.

The gaseous product may be utilized as a moderate Btu-content fuel; as a reducing gas for metallurgical or chemical purposes; and as an intermediate for conversion to hydrogen for use in  ... coal conversion plants for manufacture of coal liquids or high Btu-content gas."

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In sum, a "water slurry" of Coal particles is first combusted "to provide heat and reactants", i.e,, "carbon dioxide and water vapor",  which are then passed into a "gasifier zone" which contains "a second feed stream" of particulate Coal, and wherein "carbon dioxide and water vapor ... react with carbon (Coal) to produce carbon monoxide and hydrogen".

And, such "carbon monoxide and hydrogen" constitutes, we submit, an ideal mixture for Fischer-Tropsch, or other catalytic, condensation into hydrocarbon "liquids".

But, Gulf notes, almost as an aside, deep within the full Disclosure, that the "carbon dioxide and water vapor" could be obtained from other sources, instead of deliberately burning additional Coal just for that purpose.

Couldn't, thus, Carbon Dioxide reclaimed, for instance, from a Coal-fired power plant's exhaust be combined with Steam generated by, again  for instance, solar heat or hydroelectricity, and, the two then passed into a "gasifier" charged with Coal, therein to "react with carbon" and "to produce" as above, "carbon monoxide and hydrogen"?

Either way: In Gulf Oil's technology, as herein, Coal and Steam are converted into a hydrocarbon synthesis gas; and, even if no extra Carbon Dioxide is imported into, and consumed within, such a process, no Carbon Dioxide generated by the process itself is left un-reacted; and, thus, no Carbon Dioxide needs to be emitted.


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