United States Patent: 4230556
We recently made a report labeled "Self-powered Coal Liquefaction", which details United States Patent 4,227,991, officially entitled "Coal Liquefaction Process with a Plurality of Feed Coals", which was awarded to Pittsburgh's Gulf Oil Corporation in 1980.
Almost immediately thereafter, Gulf, and it's same team of scientists, including one from Gulf's P&M Mining subsidiary, received another US Patent for closely-related and supplemental Coal conversion technology; the disclosure of which reveals more details of how Coal gasification and Coal liquefaction processes can be combined, to convert Coal into a variety of more versatile fuels in an energy-efficient and thorough way.
We find the example presented herein quite interesting, because it is yet more confirmation that the Hydrogen needed to hydrogenate, into more versatile hydrocarbons, the primarily Carbon content of the raw Coal feed, can be efficiently generated as an integrated procedure within the total Coal conversion system.
Not only that, but, yet again, it is herein demonstrated that all, or nearly all, of the energy needed to convert Coal into hydrocarbon liquids and gases can be generated as a function of the system's operation. Little or no energy input from external sources would be required.
Summary comment follows extended excerpts from:
"United States Patent 4,230,556 - Integrated Coal Liquefaction-Gasification Process
Date: October, 1980
Inventors: Norman Carr, PA, and Bruce Schmid, CO
Assignee: Gulf Oil Corporation, Pittsburgh
Abstract: In a coal liquefaction process the yield of liquid coal is increased with a concomitant decrease in the yield of normally solid dissolved coal by recycle of a product slurry containing mineral residue. In an integrated coal liquefaction-gasification process employing product slurry recycle wherein the net yield of normally solid dissolved coal from the liquefaction zone comprises the entire hydrocarbonaceous feed to the gasification zone, a moderate net yield of normally solid dissolved coal is conducive to an optimized efficiency for the integrated process. However, it is frequently difficult to perform the process at slurry recycle rates which are sufficiently low to be economically practicable because of a pumpability constraint on the solids level in the feed coal mixing vessel. In the present process, mechanical operability is improved and enhanced conversion of normally solid dissolved coal is achieved by passing a portion of the liquefaction zone product slurry through a hydroclone with the hydroclone overflow stream constituting a second recycle slurry. Deployment of the second recycle slurry accomplishes selective recycle of relatively small particles of mineral residue and tends to reduce the yield of normally solid dissolved coal without resorting to excessive recycle rates, contributing to optimized efficiency for the integrated process.
Claims: An integrated coal liquefaction-gasification process wherein the net production of normally solid dissolved coal containing mineral residue from the liquefaction zone comprises the hydrocarbonaceous feed for the gasification zone; said process comprising passing mineral-containing feed coal, hydrogen, recycle dissolved liquid solvent, recycle normally solid dissolved coal and recycle mineral residue to a coal liquefaction zone which does not contain a fixed bed of added catalyst to dissolve hydrocarbonaceous material and to produce a mixture comprising hydrocarbon gases, dissolved liquid, normally solid dissolved coal and suspended mineral residue; passing a liquefaction zone effluent stream through a vapor-liquid separator means to remove overhead hydrogen, hydrocarbon gases and naphtha from a residue slurry comprising liquid coal and normally solid dissolved coal with suspended mineral residue; recycling to said liquefaction zone a first portion of said residue slurry; passing a second portion of said residue slurry to product separation means including vacuum distillation means; passing a third portion of said residue slurry through hydroclone means; recovering from said hydroclone means an overhead slurry comprising liquid coal and normally solid dissolved coal containing particles of suspended mineral residue having a smaller median diameter as compared to the median diameter of the particles in said first portion of residue slurry; recycling said overflow slurry to said liquefaction zone to reduce the median diameter of the particles recycled to said liquefaction zone; recovering from said hydroclone means an underflow slurry comprising liquid coal and normally solid dissolved coal containing particles of suspended mineral residue having a larger median diameter than the median diameter of the particles in said first portion of residue slurry; passing said underflow slurry to said product separation means; separating liquid coal in said vacuum distillation means in said product separation means from a gasifier slurry comprising normally solid dissolved coal and mineral residue; passing said gasifier slurry to the gasification zone for conversion to hydrogen; and passing said hydrogen to the coal liquefaction zone.
Description: The present invention relates to an improved process for the solvent liquefaction of coals such as bituminous or subbmituminous coals or lignites.
While the most desirable products from a coal solvent liquefaction process are coal liquids and hydrocarbon gases, such processes normally tend to also produce high yields of normally solid dissolved coal. Normally solid dissolved coal is economically less valuable than liquid coal and hydrocarbon gases because of its solid state and its generally higher content of sulfur and other impurities. In addition, because normally solid dissolved coal is recovered from the liquefaction zone in slurry with suspended mineral residue it must be processed in a solids-liquid separation step, such as filtration or settling. Since the suspended mineral residue particles are very small, the solids-liquid separation step is difficult to perform and has a considerable adverse effect upon the economics of the liquefaction operation.
A coal solvent liquefaction process can advantageously avoid a solids-liquid separation step by vacuum distilling the liquefaction zone product to prepare a liquefaction zone product slurry comprising normally solid dissolved coal and mineral residue and passing this slurry to a gasifier for conversion of its hydrocarbonaceous content to hydrogen and to syngas fuel for use in the process. The product slurry comprises all the normally solid dissolved coal produced in the liquefaction zone and is advantageously substantially free of liquid coal and hydrocarbon gases because liquid coal and hydrocarbon gases produced in the liquefaction zone constitute high quality fuels without further processing. This slurry can comprise substantially the entire hydrocarbonaceous feed for a gasification zone integrated with the liquefaction zone and essentially no other hydrocarbonaceous feed is required by the gasification zone."
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A close reading of the full Patent again confirms, and reveals, several important facts: One is that "no other hydrocarbonaceous feed" but that derived from Coal, "is required by the gasification zone" to ensure generation of needed Hydrogen. Moreover, some of the "syngas" can be employed as "fuel for use in the process".
Further, the procedure entails thorough carbon conversion by "employing product slurry recycle", wherein carbonaceous residues are further treated for the recovery of carbon values. That represents an advance over other Coal conversion technologies we've reported, such as in the FMC Corporation's New Jersey operations, where CoalTL residues, from a primary Coal conversion process, were shipped to another facility, in Spain, for further extraction and hydrocarbon conversion.
Gulf's Coal conversion technology seems complete and energy-efficient. And, as we implied in the case of the Exxon-Mobil merger, and as we will further document, Gulf's development of such viable methods of synthesizing liquid and gaseous hydrocarbon fuels from Coal might have inspired major shifts and realignments within the community of oil-producing corporations.