United States Patent: 4318797

 

As we've documented in a number of reports, South Africa Synthetic Oil Limited, "Sasol", or, as variously reported in other sources, from the Afrikaans: "Suid Afrikaanse Steenkool en Olie, Ltd.", has been converting Coal into liquid hydrocarbon fuels, and supplying thus a large percentage of the gasoline and diesel used by South Africa's motoring public, and their military, for many decades.

According to the article accessible via:

Sasol | Company Structure Information from ICIS; wherein we're told, that:

"Sasol is a diversified petrochemical company with production facilities in South Africa and several other countries worldwide. It produces more than 200 fuel and chemical products that are exported to 90 countries around the world. Its principal feedstocks are obtained from coal which the company converts into value-added hydrocarbons through Fischer-Tropsch process technologies .... (and, their) history ... dates back to 1927 when a white paper was tabled in parliament to investigate the establishment of an oil-from-coal industry in South Africa. (The) the company was eventually formed in 1950";

they have been at it for better than half a century.

But, even though they have that long history of successfully converting Coal into liquid motor fuels on a commercial basis, they continue to improve their processes and technologies for doing so, as we've documented, for just two examples, in:

South Africa seeks US Coal-to-Jet Fuel Patent | Research & Development; concerning: "United States Patent Application 20100264061A1 - Synthetic Aviation Fuel; 2010; Sasol Technology Ltd., Johannesburg; Abstract: The invention relates to a Fischer-Tropsch derived aviation fuel, which fuel is used either as a fuel on its own or as a component in an aviation fuel blend ... . Distillate fuel derived from the Fischer-Tropsch (FT) process is highly paraffinic and has excellent burning properties and very low sulfur. The FT process is used industrially to convert synthesis gas, which may be derived from coal ... into hydrocarbons"; and:

Sasol Improves Coal Syngas Hydrogenation | Research & Development; concerning: "United States Patent Application 20090261296  -  Method for the Production of Synthesis Gas; 2009; Assignee: Sasol Technology Limited, Johannesburg; Abstract: A method for the production of synthesis gas includes humidifying an oxygen-containing stream by contacting the oxygen-containing stream with a hot aqueous liquid to produce a humidified oxygen-containing stream, and feeding the humidified oxygen-containing stream into a gasifier in which a carbonaceous material is being gasified, thereby to produce synthesis gas."

And, they weren't idle in the intervening six decades. They did, in fact, work on the continuous improvement of the processes they had in hand in 1927, and put into commercial practice all the way back in 1950, for converting Coal into liquid hydrocarbon motor vehicle fuels.

Among our reports attesting to that fact, we remind you specifically of one we made last December:

South Africa 100% Coal Conversion | Research & Development; which concerns: "United States Patent 4,251,346 - Process for Coal Liquefaction; 1981; Assignee: SASOL One, Proprietary, Limited, Orange Free State; Abstract: The invention provides a process for the liquefaction of coal. The comminuted coal is slurried in a solvent or pasting oil and digested ... . The solvent or pasting oil is obtained wholly or mostly by recycling from the distilled fractionation of the reaction products. ... The process can be controlled so that the coal is converted virtually completely into distillable products, more particularly predominantly in the crude diesel fuel range."

We make note of "US Patent 4,251,346", as above, since that invention is cited, specifically, as the technical basis for the two related Sasol refinements on Coal liquefaction processes and apparatus we address herein.

First, with additional links and comment inserted and appended, we present excerpts from the initial link in this dispatch to:

"United States Patent 4,318,797 - Process for Converting Coal into Liquid Products

Date: March, 1982

Inventors: Berend Jager, et. al., South Africa

Assignee: Sasol One Proprietary, Sasolburg

Abstract: The invention provides a process and an apparatus for hydrogenative liquefaction of coal to produce high yields of gasoline fraction and optional yields of diesel and residue fraction, all of superior quality. The coal is slurried and digested in two separate and distinct streams. The pasting oil of the first stream is heavy residue fraction derived to a substantial extend from the second stream, mixed with light oil derived partly or wholly from the first stream. The pasting oil of the second stream is middle oil derived from the fractionated discharge of the first stream, any shortfall being made up from the discharge of the second stream. A high degree of flexibility is possible by varying the ratio of coal fed to the respective streams between 3:1 and 1:3, and individual manipulation of the process parameters within each stream in respect of pressure, temperature, catalyst, residence time, pasting oil composition and coal quality.

Claims: Process for converting a liquefiable coal directly into predominantly liquid products suitable for making hydrocarbon fuel.

Process ... wherein hydrogen used in digesting the coal is produced by reforming of gaseous products of the digestion.

(Our take on the full Disclosure is that all, or at least most, of any Hydrogen which might be required can be produced as a "side" product within the total system, by Steam-reforming any hydrocarbon gases that might be driven off from the Coal slurried in the "pasting oil", which "oil" is also derived as a by-product of the total Coal liquefaction process.)

Background and Summary: A process ... now granted under U.S. Pat. No. 4,251,346 and corresponding patents and patent applications in other countries, which are not to be considered as prior publications, but which by reference thereto are to be considered as part of the present disclosure. As described in those earlier applications, there exists a long and technologically important history of prior art which accordingly need not be repeated here.

Preferred embodiments of the present invention are directed to process configurations capable of converting substantially all the liquefiable coal components to distillate products, whilst being capable optionally to be so modified that part of a distillation residue formed in the process is not recycled but withdrawn as a valuable byproduct having surprisingly superior characteristics as a raw material for making premium electrode coke.

(Thus, like our previously-reported process of "United.States Patent Number 4,251,346", fully 100% of the Carbon in the Coal can be transformed into liquid hydrocarbons. Only "optionally", for reasons that will be explained further on, can some of the product be directed into a pure, solid Carbon.)

Whilst a preferred embodiment contemplates that all or substantially all the light oil fractionated from the digested slurry ... is recycled to the pasting stage ..., the process can be so conducted that the light oil produced ... exceeds the amount recycled to the pasting oil for the first stream ... and that the excess is withdrawn as a product."

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So, the "pasting oil" in which the Coal is initially blended, or "slurried", prior to treatment is, indeed, a product of the Coal liquefaction itself. And, enough of it is made so that some of it can still be diverted into the production of hydrocarbon liquids.

In any case, Jager and his Sasol colleagues continued their efforts, and were, in the following year, acknowledged for having improved the equipment needed for carrying out the process of "United States Patent 4,318,797", as seen in:

"United States Patent: 4394215 - Apparatus for Converting Coal into Liquid Products

Date: July 19, 1983

Inventors: Berend Jager, et. al., South Africa

Assignee: Sasol One, Sasolburg, SA

Abstract: The invention provides a process and an apparatus for hydrogenative liquefaction of coal to produce high yields of gasoline fraction and optional yields of diesel and residue fraction, all of superior quality. The coal is slurried and digested in two separate and distinct streams. The pasting oil of the first stream is heavy residue fraction derived to a substantial extent from the second stream, preferably mixed with light oil derived partly or wholly from the first stream. The pasting oil of the second stream is middle oil derived from the fractionated discharge of the first stream, any shortfall being made up from the discharge of the second stream. A high degree of flexibility is possible by varying the ratio of coal fed to the respective streams between 3:1 and 1:3, and individual manipulation of the process parameters within each stream in respect of pressure, temperature, catalyst, residence time, pasting oil composition and coal quality.

Claims: An apparatus for carrying out a coal liquefaction process comprising in parallel separate and distinct first and second coal digestion reactors for digesting particulate coal in a pasting oil under pressure (and)wherein the first and second reactors and the first and second coal slurrying means are constructed and arranged for coal feed rates to the respective reactors in a dry mass ratio ranging from 3:1 to 1:3. 

Apparatus ... comprising discharge means for discharging as a product middle oil derived from the discharge of the second reactor.

Background and Summary: The present invention relates to a process for converting coal directly into predominantly liquid products suitable for making hydrocarbon fuel ... .

Preferred embodiments of the present invention are directed to process configurations capable of converting substantially all the liquefiable coal components to distillate products, whilst being capable optionally to be so modified that part of a distillation residue formed in the process is not recycled but withdrawn as a valuable byproduct having surprisingly superior characteristics as a raw material for making premium electrode coke.

(We must interrupt to note that the process can again be "optionally ... modified", if desired, to produce the "electrode coke" raw material. If that is a profitable option, fine. But, as in the precedent technology of "United States Patent 4,251,346 - Process for Coal Liquefaction", cited above, and, as in Jager's own "United States Patent 4,318,797", we can, if preferable, just go ahead and convert all of the available Carbon "virtually completely into ... crude diesel fuel".)

(The)present invention sets itself the difficult task of providing further improvements or advantageous modifications in a number of respects and in particular when not only high total yields of liquid in the liquid fuel range are desired, but where it is desired that a substantial proportion of that liquid fuel, say in excess of 40%, preferably 50% or more should be gasoline which should preferably be of a quality useful without expensive refining. The present invention can also be used to introduce a novel measure of flexibility in the ratios of liquid fuels in the diesel and gasoline boiling ranges respectively and in addition still provides the valuable facility for producing a high grade raw material for making premium electrode coke of a quality not only equal to, but often superior to that which is conventionally manufactured from scarce petroleum based raw materials.

(Note that this process will produce Gasoline from Coal that can be used, as is, for vehicle fuel without "expensive" further "refining". Such adjustment, to produce more of an already-refined Gasoline product, is, as we read it, what leads to the co-production of a highly-refined solid Carbon. Otherwise, if more of the production is turned to Diesel, with less Gasoline, less of the solid Carbon will be co-produced.)

Where different qualities of coal are readily available, it is possible in a manner which will be readily understood to manipulate the yields of products in the individual streams and their qualities to some extent by using such different qualities in the different streams of the process. In this regard it is pointed out that as in the case of the process according to U.S. Pat. No. 4,251,346, a wide variety of coals can be used, ranging from peat through brown coal to all kinds of liquefiable black coal (i.e., bituminous.)

For example, where in a given area both brown coal and liquefiable black coal are available, it may be advantageous to feed black coal to one stream and brown coal to the other stream. Different grades of coal for use in the different streams may also be derived from a single coal deposit, e.g. by selective mining or by sorting processes or by subjecting such coal to different degrees of coal washing. 

The flexibility of the process allows for individual adjustment of the process conditions in each stream in respect of temperature, pressure, residence time and catalyst considerations, whether different coals are used in the feed streams or not, to optimise and/or control and/or adjust the required product distillation."

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By which, we think they actually mean "product distribution".

And, we note, that, if we would rather make more gasoline and less Diesel, we don't necessarily have to find a large-scale commercial market for "electrode coke".

If we don't, for some reason, want to just dump that Coke back into the feed hopper with the raw Coal, since it all is, after all, Carbon, then, we could, as in:

Exxon 1997 Coal Liquefaction Residue Steam-Gasification | Research & Development; concerning: "United States Patent 4,060,478 - Coal Liquefaction Bottoms Conversion by Gasification; 1977; Exxon Research and Engineering Company; Abstract: Heavy bottoms produced by the liquefaction of coal ... are converted into more valuable products by ... (after initially producing) gases, hydrocarbon liquids and ...char, thereafter gasifying the char with steam;

just as Exxon proposes doing with a somewhat similar-sounding carbonaceous residue arising from a somewhat similar-sounding Coal liquefaction process, simply gasify the residue with Steam, and thereby generate both a blend of Carbon Monoxide and Hydrogen synthesis gas, suitable for catalytic condensation into more liquid hydrocarbons, and, it seems, according to the full Disclosure of the Exxon patent, enough extra Hydrogen to feed back into a process such as that disclosed above by Sasol's "United States Patent 4,318,797 - Process for Converting Coal into Liquid Products", which converts "coal directly into ... liquid products suitable for making hydrocarbon fuel" and "wherein hydrogen (is) used in digesting the coal".


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