We submit herein exposition of even more technology, developed by the petroleum industry, for converting solid Carbon into the raw materials from which liquid hydrocarbon fuels can be synthesized.
Of most interest to us in this example, though, are the sources of that Carbon, which, in this case, are specified to include the still-carbonaceous residues resulting from various types of Coal processing intended to produce liquid hydrocarbon fuels, or, at least, a crude liquid Coal product that is compatible with conventional petroleum refinery raw material streams.
We have previously touched only sporadically and briefly on "Solvent Refined Coal", or "SRC", processes, even though the US Government at one time had sponsored multiple pilot plant demonstrations of the technology in several places around the nation.
In brief, raw Coal is treated, or "extracted", with one sort of liquid solvent or another, derived either from petroleum or from Coal itself, and soluble hydrocarbons are "leached" from the Coal by the solvent, which is then sent on for further refining and processing.
The solvent extraction leaves behind a residue, which, depending upon the grade of Coal initially processed, could be relatively pure Carbon. And, in fact, one of the primary target products of some SRC projects was the production of a refined Coke for steel making and other purposes, while the liquid "extract" was, most often, simply consigned for use, without further refining aside from filtration, as a crude form of boiler fuel.
Again, the USDOE once paid for the operation of multiple SRC facilities around the country, including, as we've reported, at Wilsonville, Alabama, and Fort Lewis, Washington.
Another SRC plant, closer to home, was installed near Allentown, Pennsylvania; and, was operated by a consortium of companies, apparently led by the Pennsylvania-based Air Products and Chemicals Company and organized as the "International Coal Refining Company", as seen, for just one example, in our previous report of:
USDOE Funds Pennsylvania Coal Liquefaction | Research & Development; concerning: "United States Patent 4,510,040 - Coal Liquefaction Process; 1985; Assignee: International Coal Refining Company; Abstract: This invention relates to an improved process for the production of liquid carbonaceous fuels and solvents from carbonaceous solid fuels, especially coal. The claimed improved process includes the hydrocracking of the light SRC mixed with a suitable hydrocracker solvent. The recycle of the resulting hydrocracked product, after separation and distillation, is used to produce a solvent for the hydrocracking of the light solvent refined coal. The Government of the United States of America has rights in this invention pursuant to Contract No. DE-AC05-780R03054 (as modified), awarded by the U.S. Department of Energy. This invention relates to the process for the liquefaction of carbonaceous solid fuels, particularly coals with respect to enhanced production of liquid carbonaceous fuels and solvents."
Again, there were a multiplicity of such Government-sponsored projects and processes, and we have yet to find a full and concise compilation, comparison and analysis of them by our USDOE.
However, although the "International Coal Refining" process, as above, could lead to a fairly complete dissolution, and/or refining, of the available Carbon in the raw Coal, most did not; and, technologies were developed by various parties directed toward the further conversion of residual Carbon in the solid solvent extraction residues, as seen, for example, in:
Consol Hydrogasifies CoalTL Residues | Research & Development; concerning: "United States Patent 4,248,605 - Gasification of Coal Liquefaction Residues; 1981; Conoco, Inc., CT; Abstract: A method for gasifying the bottoms fraction from a coal liquefaction process"; and, in:
Exxon Recycles CoalTL Residue | Research & Development; which makes report of: "United States Patent 4,060,478 - Coal Liquefaction Bottoms Conversion; Exxon Research and Engineering Company, NJ; Abstract: Heavy bottoms produced by the liquefaction of coal or similar carbonaceous solids are converted into more valuable products by adding an alkaline earth metal compound to the bottoms (and) pyrolyzing the bottoms ... to produce gases, hydrocarbon liquids and coke or char containing added alkaline earth metal constituents; and thereafter gasifying the char with steam".
Much of the above is true, as well, of processes intended not to directly liquefy Coal, or to extract hydrocarbon values from it with solvent, but, to, initially, at least partially gasify it, in order to extract both volatile hydrocarbons and synthesis gas blends of Carbon Monoxide and Hydrogen.
Unless Coal gasification is undertaken in a specially-designed process that utilizes various gases, or other compounds such as Oxygen donors, to promote the gasification, only already-existing hydrocarbons in the Coal and a limited amount of Carbon Monoxide-Hydrogen synthesis gas will be produced from it, leaving behind a still-carbonaceous residue.
Such Carbon remaining from a partial gasification of Coal can, as well, be further processed and recovered by various methods, as seen, for example, in our reports of:
Texaco Recycles Coal Conversion Residues | Research & Development; concerning: "United States Patent 2,980,521 - Carbon Separation Process; 1961; Assignee: Texaco, Inc.; Abstract: This invention relates to a process for the production of synthesis gas from carbonaceous fuels. More especially, the invention is concerned with improvements in a method for the separation and recovery of free carbon particles from a carbon-water slurry formed in a synthesis gas generation process";
wherein Carbon particles not initially reacted are recovered and returned to the gasification process; and:
Pittsburgh USBM Converts CoalTL Residue - in 1953 | Research & Development; concerning: "United States Patent 2,634,286 - Production of Hydrocarbon Synthesis Gas from Coal; 1953; Abstract: The invention herein described and claimed may be manufactured and used by and for the Government of the United States of America for governmental purposes without the payment of royalties. This invention relates to the production of synthesis gas and more particularly to the production of a low-sulfur content mixture of carbon monoxide and hydrogen by gasifying the finely-divided low-sulfur content char obtained as a by-product of the direct hydrogenation of coal";
wherein residual carbonaceous "char", resulting from any Coal hydrogenation process, can be hydro-gasified into a blend of Carbon Monoxide and Hydrogen hydrocarbon syngas.
And, herein, we find that Mobil Oil applied themselves to developing a process very similar to that disclosed above by Consol/Conoco, Texaco and the USBM, in which process any Carbon left behind by an initial solvent extraction of Coal could then be gasified, and converted into a synthesis gas blend of Carbon Monoxide and Hydrogen, suitable for further catalytic processing to form liquid hydrocarbons.
As seen, with comment inserted and appended, in our excerpts from the initial link in this dispatch to:
"United States Patent 4,583,993 - Carbon Monoxide and Hydrogen from Carbonaceous Material
Date: April, 1986
Inventor: Nai Chen, NJ
Assignee: Mobil Oil Corporation, NY
Abstract: Hydrogen and carbon monoxide are produced from coal, char or other carbonaceous material in a processing combination comprising a catalytic CO generator employing as reactant materials, fluid carbon material and CO2 product of the reaction of steam with CO to produce hydrogen and CO2. CO2 produced in the process is relied upon as the primary endothermic heat source in the fluid CO generator.
Claims: A method for producing separate streams of hydrogen and carbon monoxide of relatively high purity from a char like product selected from the group consisting of coal, char product of coal solvation (and) char product of coal volatilization ... comprises ... passing a char product ... comprising carbonaceous material and metal deposits ... to a fluidized char particle carbon monoxide generation zone in admixture with preheated carbon dioxide wherein the primary source of endothermic reaction heat to form CO is supplied by said fluid char particles and said preheated carbon dioxide;
(Note, that, as in:
Germany 98% Pure Carbon Monoxide from Coal, CO2 and O2 | Research & Development; concerning: "Carbon Monoxide from Coke, Carbon Dioxide and Oxygen; Hydrocarbon Process(US); 1986; Lurgi GmbH, Frankfurt (Germany); Depending on the quality of the feedstocks the produced gas shows a CO concentration of 97 to 98.5% by volume";
using Carbon Dioxide as one of the agents for Carbon gasification can result in the production of very pure Carbon Monoxide.)
(and) separating a product of said CO generation zone into a carbon monoxide rich stream and an unreacted carbon dioxide rich stream;
recovering a portion of the carbon monoxide thus produced as a product of the process;
passing another separated portion of said produced carbon monoxide in admixture with steam to catalytic water gas shift reaction zone maintained under conditions to produce hydrogen and carbon dioxide;
(We've previously reported on the use of the "water gas shift reaction", wherein Carbon Monoxide can be reacted with Water to produce Hydrogen and Carbon Dioxide. More about it can be learned via:
Water gas shift reaction - Wikipedia, the free encyclopedia: "The water-gas shift reaction (WGS) is a chemical reaction in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen";
and, we have additional reports concerning it's potentials for application and use in various Carbon conversion technologies underway.)
(and) separating a hydrogen rich stream from a carbon dioxide rich stream produced in said shift reaction zone (and) recycling carbon dioxide product of said shift reaction zone admixed with CO2 separated from the CO product of said CO generator zone through indirect heating zones to heat the mixed CO2 stream to an elevated temperature before passing said fluid char particles to the CO generation zone;
(Any Carbon Dioxide incidentally generated within the process, as in the water gas shift Hydrogen generation step, is recycled back into the initial gasification stage, for reaction with more hot Carbon and conversion, as in the above-cited Lurgi GmbH process, into more Carbon Monoxide.)
(and) separating unreacted fluid char particles from said CO generation zone; and passing the separated fluid char particles to a heating zone to maintain the heat of said particles at elevated temperature.
The method ... wherein the char product passed to said CO generation zone comprises fluidizable particles of coke at an elevated temperature obtained from either one or both of a fluid coking operation or a fluid coke partial burning operation.
The method ... wherein the reaction of carbon dioxide with carbonaceous material is accomplished (by) adding oxygen to the reaction.
(Again as in the above-cited Lurgi GmbH process, a little Oxygen must be added to support the CO2-Char reaction. And, as seen in:
Japan Hydrogen from Water and Sunlight | Research & Development; concerning: "United States Patent 7,909,979 - Water Photolysis System and Process; 2011; Panasonic Corporation; Abstract: The present invention provides a water photolysis system ... (wherein) vapor generated from the water ... is decomposed into hydrogen and oxygen by ... photocatalyst particles, which are excited by sunlight";
we have some efficient and economical methods available to us for generating the needed Oxygen, using technology that would, by harnessing freely-available environmental energy, also generate Hydrogen, which could be used to enrich the "Carbon Monoxide and Hydrogen" blend of synthesis gas, made, via our subject process of Mobil's United States Patent 4,583,993, by gasifying Coal conversion residues with Steam, Carbon Dioxide and Oxygen.)
Background: The conversion of coal to gaseous products of low and higher heating value has been pursued by many technologists over the years. However, coal, because of contaminating metal components, sulfur and nitrogen in the gaseous conversion products, has been regarded by many as a dirty fuel. Removal of sulfur and nitrogen from product gases is costly for which there has yet been no satisfactory economic solution. The conversion of coal has pursued three basic routes involving the production of low BTU heating value gas, medium or high BTU heating value gas; the thermal production of oil from coal which is then treated with hydrogen to remove sulfur from the oil and improve the oil quality; and thirdly, the solvation of coal with the filtering out of ash and pyretic sulfur.
The present invention is concerned with producing a clean gas composition of hydrogen and carbon monoxide from coal which is free of sulfur and nitrogen. A further object of this invention is to produce separate streams of hydrogen and carbon monoxide which can be blended to form any desired ratio thereof for syngas conversion with a Fischer-Tropsch synthesis containing catalysts.
Summary: The present invention contemplates an integrated operation comprising one or more steps including solubilizing coal, fluidized coal volatilization, fluid coking, conversion of coke obtained from one or more or a combination of the above to CO and the generation of CO2 employed in said CO generator by use of the well known water gas shift reaction.
Hydrogen produced in the process may be used in part to hydrogenate a coal solubilizing liquid passed to the coal solubilizing step.
(In the above, they posit utilizing the Hydrogen generated in this process to hydrogenate a Coal liquefaction solvent, for use in a Coal hydrogenation process that co-produces, in addition to liquid hydrocarbons, the "char" gasified in their process of our subject, "United States Patent 4,583,993".)
The integrated operation is particularly desirable in utilizing metal contaminated carbonaceous materials which are products of one or more of the herein described operations involving coal ... .
Coke and char products of these operations are laden with metals selected from the group consisting of iron, nickel, vanadium and copper. The metals, iron and nickel, are particularly desirable for promoting the reactions herein particularly desired. Thus the build-up of metals, iron and nickel, on the coke particles circulated from the fluid coker to the CO generator and back to the fluid coker is not an undesirable expedient on the overall combination.
(In plain English: The build-up of Iron Group metals naturally found in Coal is a good thing.)
The present invention particularly contemplates processing char or coke residue particles obtained as herein defined by contacting the coke particles with CO2 in the presence of a reducing catalyst to produce a (CO) carbon monoxide rich gaseous product stream. In this CO producing operation, a fluid coke particle system is preferably employed for effecting the desired highly endothermic reaction in the presence of (CO2) carbon dioxide heated to an elevated temperature as herein described. The primary source of CO2 used in the combination operation of this invention is that recovered from a shift reactor system comprising the reaction of carbon monoxide (CO) with water (steam).
(The "primary source" of Carbon Dioxide for this Carbon Monoxide production system is that regenerated within the system when some of the product Carbon Monoxide is reacted with Steam to generate Hydrogen. Secondary sources of CO2 might, thus, be required, and, that, especially so if we were to supplement the Hydrogen required to add to the product Carbon Monoxide, in amounts required for Mobil's specified "Fischer-Tropsch synthesis" of hydrocarbons, via a technology such as that explained in our report of:
Consol 1953 Coal to Hydrogen & Methane with No CO2 | Research & Development; concerning: "United States Patent 2,654,661 - Gasification of Carbonaceous Solid Fuels; 1953; Consolidation Coal Company, Pittsburgh; Abstract: This invention relates to the gasification of carbonaceous solid fuels, and particularly to the production of hydrogen or high B.t.u. gas from such fuels.A gaseous product is obtained which contains methane and hydrogen in varying relative proportions depending upon the particular temperature and pressure conditions. In accordance with my invention, a two-vessel system is employed to convert carbonaceous solid fuels to a gas containing primarily methane and/or hydrogen as desired";
which is such a productive process for the Steam-gasification of Coal that it can generate extra Hydrogen, as a by-product, along with, primarily, Methane.)
The reaction of coke, char or carbon particles with carbon dioxide in the presence of a catalyst promoter to produce carbon monoxide is highly endothermic ... . The heat of reaction may be supplied in part by effecting a partial oxidation with oxygen as opposed to air within the fluid reactor operation. It is believed by some experts in the art that surface oxidation of the coke contributes measurably to the operation. Relatively pure oxygen is preferred for this purpose so that the product gas comprising carbon monoxide and carbon dioxide will not be contaminated with nitrogen as would occur should one use air as the oxygen source.
(As we've previously discussed; and, which preferred Oxygen could be generated, as in our above-cited process of "United States Patent 7,909,979 - Water Photolysis System", as a byproduct of using environmental energy to pry some extra needed Hydrogen out of H2O.)
The present invention contemplates the blending of the hydrogen and CO produced in the operation and the conversion of the blend to methanol and thence to an olefinic or aromatic product. It also contemplates the conversion of the blend as by Fischer-Tropsch synthesis to produce hydrocarbon products in single or multiple stage operation."
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And, the statement immediately above summarizes the true purpose of our subject process of Mobil Oil's "United States Patent 4,583,993", which is:
To make blend of "hydrogen and CO" via the "conversion of coke obtained from" an initial process for "solubilizing coal" done to obtain hydrocarbon liquids, and, which "hydrogen and CO" are then themselves suitable, as Mobil herein specifies, for the "Fischer-Tropsch synthesis" of even more hydrocarbons.
And, to again emphasize the point:
Not only is this particular process essentially CO2-free, since all of the Carbon Dioxide it generates internally is recycled back to the Carbon Monoxide generator; but, it might also allow for the importation and conversion of even more CO2 from an external source, through reactions with a "char product of coal solvation" that, in the first place, was conducted to synthesize hydrocarbons, all to form a blend of Carbon Monoxide and Hydrogen synthesis gas, which is itself compositionally well-suited for "conversion .. to methanol and thence to an olefinic or aromatic product".