We enclose, with advance apologies for the length and breadth of this dispatch, a series of United States Patents so closely related that treating them separately would have confused the issue and done injustice to the technical concepts they embody.
In brief sum, we have many times made reference to the use of Hydrogen donor substances in Coal conversion processes.
For instance, without linking to any of our prior reports on the subject, we remind you that West Virginia University, as do others, posits that hydrogenated primary Coal, or well-known Coke Oven, tars be used to transfer Hydrogen to the Carbon in Coal in direct liquefaction processes.
Many indirect Coal conversion technologies, on the other hand, specify the use of Steam, H2O, in an initial Coal gasification, wherein the H2O will contribute both the Hydrogen, and some of the Oxygen, required to convert Coal into a blend of Carbon Monoxide and Hydrogen, a synthesis gas, or syngas, that can then be catalytically condensed into liquid hydrocarbons.
Carbon Dioxide, too, can be utilized in such Coal gasification, where it contributes both more Carbon and some more Oxygen.
One problem with those Coal gasification schemes is that both the H2O and the CO2 reduction reactions with the Coal, or, more accurately, with Carbon, since any number of organic and Carbon-recycling substances can be so treated, are highly endothermic.
They have to be driven by heat energy, which most often is posited to be obtained by a partial, exothermic, oxidation of the Coal.
That certainly is practical, since, again as we've reported, they have been making liquid fuels that way in South Africa for many decades; and, that is how both Germany and Japan helped to fuel their militaries during WWII.
However, such processes not only imply a certain inefficiency, since, in the partial oxidation, some of the Carbon is converted not only into the desired Carbon Monoxide, but, into less reactive Carbon Dioxide, as well; which, though it can be utilized, requires additional energy inputs for such utilization.
Furthermore, to restrict the formation of energy-wasting Nitrogen Oxide pollutants during such Coal gasification, there are technologies which employ purified Oxygen, as opposed to Air, to support the combined oxidation-reduction reactions between Coal, Steam and/or Carbon Dioxide, that have been developed.
Those work, and work well, but do entail the expense of separating and supplying pure Oxygen.
We must note that alternative plans have been developed for supplying the needed thermal energy to drive the reactions, in CO2-free ways, strategies which employ focused Solar energy or electrical resistance heating, for example, and those are certainly worthy of far more attention and development.
But, those alternatives could well find more efficient use within the overall context of the technologies we report herein, which, taken together, disclose a way in which the chemical interactions of some common elements and compounds can be combined and ordered in such a way, so as to reduce the total energy needed to transfer Oxygen to Carbon in order to make Carbon Monoxide, restricting the co-production of Carbon Dioxide while doing so, and, to concurrently generate at least some of the Hydrogen needed to formulate a complete hydrocarbon synthesis gas.
First, by way of introducing the topic, we do remind you of one earlier dispatch, from almost exactly two years ago, as accessible via:
Japan Uses Zinc to Liquefy Coal | Research & Development; which concerns: "Coal liquefaction by in-situ hydrogen generation.: Zinc-water-coal reaction;
Hokkaido University, Japan
; Abstract:
Liquefaction of coal was carried out in a zinc—water—solvent system to give a product with high concentration of pyridine and benzene solubles. In this system the metal reacts with water to produce the corresponding metal oxide and hydrogen. This hydrogen was used for in-situ hydrogenation of coal."
That Japanese direct Coal liquefaction technology utilizes a complete system to, in a liquid solvent, use the unique properties of the element Zinc to chemically leverage the transfer of Hydrogen from Water to Coal.
Our read of it is, though, that in handling the Coal conversion in such a way, the products evolved, although liquid hydrocarbons, were restricted in their type and range.
Herein, via the initial and following links in this dispatch, we learn that Phillips Petroleum, with the help of one or two others, developed a different, and perhaps more efficient and much more versatile, way of utilizing Zinc, as an Oxygen donor, in a process that first converts Coal into, primarily and mainly, Carbon Monoxide.
Comment, and additional links and excerpts, follow excerpts from the initial link in this dispatch to:
"United States Patent 4,070,160 - Gasification Process with Zinc Condensation on the Carbon Source
Date: January, 1978
Inventor: John Cottle, OK
Assignee: Phillips Petroleum Company, Bartlesville
Abstract: In a process for gasifying solid carbon sources such as coal utilizing zinc oxide as the oxygen donor, the carbon source is first contacted in a preheat zone with product gas; any zinc in this product gas is condensed on the carbon source; the preheated carbon source and zinc are then exposed to steam whereby the zinc is oxidized to zinc oxide; the mixture of zinc oxide and carbon source finally is reacted at elevated temperature conditions to form a gas comprising carbon monoxide and zinc.
Claims: In a process for gasifying a solid carbon source wherein said solid carbon source is contacted wit zinc oxide at a temperature of 900 to 1650 C to form a carbon monoxide and zinc-comprising gas and wherein said zinc is separated from said gas, oxidized and recycled into contact with the carbon source and wherein a carbon monoxide-comprising gas is recovered as a product of the process.
Description and Background: The present invention relates to the production of carbon monoxide. More specifically, the present invention relates to the gasification of such carbon sources as coal.
Various carbon sources have been reported to be convertible to gases such as hydrocarbons by first converting these carbon sources to a carbon monoxide comprising gas.
There is a general need for further improvements of this basic process, particularly since economical reasons constitute a dominating factor for success or failure of any gasification process. The recovery of zinc and the most complete use of the heat developed in the process thus are of utmost importance.
It is thus one object of this invention to provide a new process for the gasification of such materials as coal.
Another object of this invention is to provide a gasification process utilizing zinc oxide as the oxygen donor wherein the zinc is completely recovered.
A further object of this invention is an energy efficient gasification process.
The present invention resides in a process for gasifying carbon sources utilizing zinc oxide as the oxygen donor in which process the carbon source is contacted in a preheating step with at least a portion of the gas produced in the gasification zone. The carbon source is thereby preheated and any zinc present in this portion of the gas is condensed on the carbon source. The carbon source together with zinc is exposed to steam for oxidizing the zinc to zinc oxide thus forming a mixture of the carbon source with zinc oxide. In the final gasification step the carbon source and zinc oxide are reacted to form a gas comprising carbon monoxide and zinc."
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Make note of the immediately foregoing, especially wherein they inform that the: "carbon source together with zinc is exposed to steam for oxidizing the zinc to zinc oxide thus forming a mixture of the carbon source with zinc oxide".
Something else, quite important, is, aside from the "zinc oxide", synergistically being formed when the "zinc is exposed to steam".
And, we'll eventually get to that; but, following, we see that Phillips, almost concurrently with the above invention, was working on further refinements of the process, as disclosed by:
"United States Patent: 4073630 - Production of Carbon Monoxide
Date: February, 1978
Inventor: Merritt V. Delano, OK
Assignee: Phillips Petroleum Company, Bartlesville
Abstract: In a system wherein carbon monoxide is produced from a carbon source by contacting the carbon source with solid zinc oxide in a primary reaction zone, zinc values which are entrained in the ash byproduct are recovered, reconverted to zinc oxide and reused for production of additional carbon monoxide in a secondary reaction zone wherefrom the zinc is recovered, reconverted to zinc oxide and thereafter reused in the primary reaction zone.
Claims: A process for the production of carbon monoxide which comprises:
a. reacting a first quantity of a solid carbon source in a first reaction zone with zinc oxide at a temperature of 910. to 1540 C. to produce a first volume of gas consisting essentially of zinc and carbon monoxide and a solids byproduct consisting essentially of ash having zinc values entrained therein,
b. separating zinc from said first volume of gas and recovering a carbon monoxide-containing gas as a product of the process,
c. passing said solids byproduct from said first reaction zone to an oxidation zone wherein said zinc values in said solids byproduct are oxidized to zinc oxide, thereby forming a solid mixture consisting essentially of ash and zinc oxide,
d. reacting said solid mixture in a second reaction zone at a temperature of 910. to 1540 C. with a second quantity of a carbon source to produce a second volume of gas consisting essentially of zinc and carbon monoxide and withdrawing solids containing ash which is essentially free of zinc from the second reaction zone, and thereafter
e. separating zinc from said second volume of gas and recovering a carbon monoxide-containing gas as a product of the process, and oxidizing the separated zinc to form zinc oxide which thereafter is recycled to said first reaction zone.
Description and Summary: This invention relates broadly to the gasification of carbon sources. In one of its more specific aspects, this invention relates to the production of carbon monoxide.
The conversion of solid carbon sources to carbon monoxide has been under development for many years. Such processes are of great interest since they generally have the capability of providing an environmentally clean process for carbon utilization, of producing a high heating value gas which can substitute for natural gas, and of producing a low heating value gas suitable for use as synthesis gas for subsequent conversion to hydrocarbons or chemicals ... .
However, many of such processes introduce air into the reactor, which is generally undesirable since large volumes of nitrogen must be handled in the process. These nitrogen gases have no function in a coal gasification process and add to the process costs as well as to the equipment size. To avoid the use of air, a system has been proposed wherein zinc oxide is used as the oxygen source."
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Note that, in the above reference to "undesirable ... nitrogen gases", they are indicating one reason why, in this more advanced process, they are recovering the Zinc, during and after two gasification procedures, of the Coal and the initial Coal gasification residues, and reconverting it to Zinc Oxide in a separate reaction zone.
And, we submit, that, in such a separate Zinc-Zinc Oxide reaction, as seen in:
http://www.nrel.gov/hydrogen/
we can make more of the needed Zinc Oxide using refined Zinc from another source in the above USDOE technology, which, as indicated, uses renewable Solar heat as the driving force for the needed reactions.
A close read of the full Disclosure does though reveal that, in the initial Phillips process of
"United States Patent 4,070,160 - Gasification Process with Zinc Condensation on the Carbon Source", a very similar type of reaction is incorporated, using recovered and recycled excess process heat to drive it.
However, and perhaps more importantly, the above National Laboratory "ZnO/Zn Water-splitting" process could, instead and as well, using Solar energy, provide a rather inexhaustible supply of molecular Hydrogen, for, if needed, addition to the Carbon Monoxide generated so efficiently from Coal via the Phillips-specified processes of reacting Zinc Oxide with Coal, in order to, as Phillips themselves further specify, make the resulting "synthesis gas" even better-suited "for subsequent conversion to hydrocarbons".
And, Phillips actually combined all of those concepts, finally, in a later, comprehensive Coal technology that takes advantage of just about everything specified above, except Solar energy, as seen in:
"United States Patent: 4496370 - Zinc Oxide-Char Gasification Process
Date: January, 1985
Inventor: William Billings, OK
Assignee: Phillips Petroleum Company, Bartlesville
Abstract: In the gasification of char with zinc oxide, the improvement which comprises reacting the off-gas stream of gaseous zinc and carbon monoxide with steam at elevated temperatures in a second reactor means thereby oxidizing the zinc to zinc oxide and yielding a second gaseous stream containing carbon monoxide and hydrogen. This improved process avoids having to condense and revaporize the zinc, heretofore an economic barrier to the development of the zinc oxide char processes.
(And, the Zinc is re-oxidized in the second reaction chamber through reactions with the Steam, which, as in the USDOE and University of Colorado report we cited above, results in the production of Hydrogen, thus providing, in this process of USP 4,496,370, integrated processes of both restoring the Oxygen donor, Zinc Oxide, and of producing Hydrogen, so that a complete hydrocarbon synthesis gas can be formulated.)
Claims: A process for the gasification of solid carbon-containing materials which comprises: heating under reaction conditions said carbon-containing material as finely divided carbon-containing particles with finely divided particulate zinc oxide, thereby producing a first hot gaseous stream comprising zinc vapor, carbon monoxide, and traces of carbon dioxide (and) contacting said first hot gaseous stream with ... steam in a separate zone ..., thereby converting said zinc to solid zinc oxide, and producing a second hot gas stream comprising carbon monoxide, hydrogen, methane, water, and carbon dioxide, separating said solid zinc oxide from the second hot gas stream, (and) recycling said zinc oxide to said (initial gasification reaction).
(And, a) process for controlling the ratio of CO:H2 in a produced gas stream (as described).
Description and Background: The invention relates to the gasification of source carbonaceous materials such as coal, char, or coke.
In the gasification of solid carbonaceous source material such as coal, char, and coke, a metal oxide particularly such as zinc oxide, is employed to provide the necessary oxygen.
I have discovered in the zinc oxide/char gasification process wherein zinc oxide and a carbon source are contacted in a reactor at elevated temperatures to produce a gaseous product stream of zinc vapor and carbon monoxide, surprisingly that I can react this stream as gases with steam at elevated temperatures in a second reactor means to yield a final gaseous product containing carbon monoxide, hydrogen, methane, water, and carbon dioxide, and importantly reoxidized zinc oxide
According to the process of my invention, I take the off-gas stream from the zinc-char gasification stage and react it directly at elevated temperatures with steam, thereby oxidizing the zinc to zinc oxide for recycle to the gasification step, and producing off-gases suitable for use as a medium Btu gas stream. Alternatively, the gas stream from the steam-oxidation step can be further separated to recover desirable components thereof.
The solid carbon or carbonaceous sources employed in my process are those carbonaceous materials characterized as solid at temperatures of about 20 C. Non-limiting examples of suitable carbon sources include coal, coke, char, tar sand, peat, oil shale, lignite, rubber scrap, and so forth.
The process of my invention is effective to gasify and convert to valuable fuel gas, primarily carbon monoxide, solid carbon sources or solid residues from other gasification or liquefaction processes such as those resulting from treating coal (such as) coal pyrolysis processes of various types.
(As above, we have herein yet another process which can productively utilize any still-carbonaceous residues resulting from another type of Coal conversion process.)
(Zinc) in the vapor state can be oxidized with steam at a rate much faster than the oxidation of carbon monoxide. The result is that the gaseous zinc becomes solid zinc oxide which is easily separated, without appreciable loss of CO to CO2. The product gas is largely hydrogen and carbon monoxide, with traces of methane, water, and carbon dioxide.
(One) disadvantage of my process is that the steam oxidation of zinc is less exothermic than air oxidation by, according to my calculations, roughly about 35 percent. Nevertheless, my process is much more efficient than prior art processes, by not having to firstly cool and condense the zinc vapor to molten zinc for separation, and then reheat and revaporize for oxidation with air. By my process, the costly and technically troublesome step of cooling the gasification stream is eliminated, and since in accordance with my process zinc oxide is produced by steam oxidation, the energy intensive step of vaporizing the liquid zinc to gas also is eliminated. Also, by my process, hydrogen can be produced as a major product or can be produced in combination with carbon monoxide ... ., by simple adjustment of CO:Zn ratios and/or by adjustment of steam-oxidation temperatures.
The mol ratio of hydrogen:carbon monoxide can vary considerably, such as about 1:99 to 99:1 as may be desired. The ratio can be varied ... by varying the Zn:steam ratios and the steam oxidation reaction temperature."
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First of all, we note that relatively minor amounts of "methane, water, and carbon dioxide" are generated as co-products, and, we submit, that particular blend of gases could be recovered from the primarily Hydrogen and Carbon Monoxide product, the ratios of which gases can, obviously as above, be controlled to provide whatever final product mix might be desired, and, then, be themselves reacted in a process such as that in:
Standard Oil 1950 CO2 + CH4 + H2O = Syngas | Research & Development; concerning: "United States Patent 2,522, 468 - Production of Synthesis Gas; 1950; Assignee: Standard Oil Development Company;
Abstract: (The) production of a mixture of carbon monoxide and hydrogen suitably proportioned for use as a feed-gas in the synthesis of hydrocarbons (by) charging a mixture of methane, steam and carbon dioxide to a reforming zone containing (a specified) catalyst (under specified conditions) ... and recovering from said zone, a product gas containing ... carbon monoxide and hydrogen. It is a matter of record and commercial practice, particularly in countries foreign to the United States, to prepare hydrocarbons, including those boiling in the gasoline and gas oil range, by reacting a mixture of carbon monoxide and hydrogen";
and be made thereby to form an additional gas mixture, like that obtained from Coal gasified with Zinc Oxide, in conjunction with the Steam-recycling of spent Zinc, by the Phillips Petroleum processes reported herein.
Further, again note that, in addition to Coal, various Carbon-recycling wastes, such as "rubber scrap" can be utilized, as well, with advantages that should be obvious, especially since our subject Phillips Petroleum technologies are economical processes for gasifying Coal with, in the first place, very minimal co-production of Carbon Dioxide.
And all of it goes, as Phillips specifies in their full Disclosure, above, of "United States Patent 4,073,630", to the production of a "synthesis gas" particularly well-suited "for subsequent conversion to hydrocarbons or chemicals".