We've touched once or twice, in the long course of our reportage, on the now almost-fabled Athabasca Tar Sands, up in Canada, and the plans for their use as a source of liquid hydrocarbon fuels.
The "bitumen" recovered from the environmentally-devastating tar sand mining practices employed by the Canadians, in the remote northern Alberta and Saskatchewan lands bordering the fragile Arctic tundra - in addition to having to be transported distances that are difficult for Americans to fully fathom, likely by pipelines, that, in current published plans, would make the Alaska Oil Pipeline look like an inoffensive garden hose carefully strung through a flower bed - also have to undergo absolutely rigorous processing to make them suitable for use as liquid petroleum replacements.
Much of the above is true, as well, of the less-well-known tar sand deposits in Venezuela.
And the two deposits, taken together, according to Athabasca Tar Sands, wherein the Alberta Energy and Utilities Board states that, although "the Athabasca tar sands is the largest oil deposit in the world", the Venezuelan Orinoco tar sands are of comparable size; and, the two, taken together, account for two thirds "of the world's total oil deposits".
However, the rigorous refining required by tar sand bitumen - think of it as "immature" Coal - includes hydrogenation processes that employ, as in some more "conventional" petroleum refineries utilizing "heavy" crude, the direct, catalyzed application of pressurized, and expensive, pure Hydrogen.
In that respect, the bitumen processing is somewhat similar to that which might be needed by raw Coal liquids generated by some less-sophisticated indirect Coal conversion technologies that don't use hydrogenating Steam in their initial steps of gasification; and, to some direct Coal conversion technologies wherein the Coal liquefaction solvent is hydrogenated prior to Coal dissolution.
In any case, tar sand bitumen does require intensive processing; and, interestingly, and, somewhat ironically, as detailed herein, Coal, or, more accurately, Coal wastes - power plant fly ash and high-ash Coal fines - can facilitate the refining of that tar sand bitumen.
Comment, and additional link, follows excerpts from:
"United States Patent 4,299,685 - Hydrocracking of Heavy Oils-Fly Ash Slurries
Date: November, 1981
Inventor: Chandra Khulbe, et. al., Canada
Abstract: An improved process is described for the hydrocracking of heavy hydrocarbon oil, such as oils extracted from tar sands. The charge oil in the presence of an excess of hydrogen is passed through a tubular hydrocracking zone, and the effluent emerging from the top of the zone is separated into a gaseous stream containing a wide boiling range material and a liquid stream containing heavy hydrocarbons. According to the novel feature, the charge stock is in the form of a slurry of heavy hydrocarbon oil and finely divided fly ash or high ash coal fines. The presence of this ash in the charge stock serves to greatly reduce coke precursors and thereby prevent the formation of carbonaceous deposits in the reaction zone.
Claims: A process for hydrocracking a heavy hydrocarbon oil ... which comprises: passing a slurry of said heavy hydrocarbon oil and finely divided fly ash or high ash coal fines in the presence of 500-50,000 scf of hydrogen per barrel of said hydrocarbon oil through a confined hydrocracking zone.
Description: This invention relates to the treatment of hydrocarbon oils and, more particularly, to the hydrocracking of heavy hydrocarbon oils to produce improved products of lower boiling range.
Hydrocracking processes for the conversion of heavy hydrocarbon oils to light and intermediate naphthas of good quality for reforming feed stocks, fuel oil and gas oil are well known. These heavy hydrocarbon oils can be such materials as petroleum crude oil, atmospheric tar bottoms products, vacuum tar bottoms products, heavy cycle oils, shale oils,coal derived liquids, crude oil residuum, topped crude oils and the heavy bituminous oils extracted from oil sands.
The heavy hydrocarbon oils of the above type tend to contain nitrogenous and sulphurous compounds in exceedingly large quantities. In addition, such heavy hydrocarbon fractions frequently contain excessive quantities of organo-metallic contaminants which tend to be detrimental to various catalytic processes that may subsequently be carried out, such as hydrofining. Of the metallic contaminants, those containing nickel and vanadium are most common, although other metals are often present. These metallic contaminants, as well as others, are usually present within the bituminous material as organo-metallic compounds of relatively high molecular weight. A considerable quantity of the organo-metallic complexes are linked with asphaltenic material and contain sulphur. Of course, in catalytic hydrocracking procedures, the presence of large quantities of asphaltenic material and organic-metallic compounds interferes considerably with the activity of the catalyst with respect to the destructive removal of nitrogenous, sulphurous and oxygenated compounds. A typical Athabasca bitumen may contain 53.76% material boiling above 524.degrees C., 4.74 % sulphur, 0.59 % nitrogen, 162 ppm vanadium and 72 ppm nickel.
(Darn - sounds a lot like Coal, don't it? We're left to wonder why everyone's so fired up about climbing into their dog sleds and going all the way up to the Arctic tundra to get it, when, without environmental devastation, or frostbite, we can pipe a big bunch of very similar stuff up the conveniently-located mine shafts in West Virginia, Pennsylvania, and the rest of US Coal Country.)
As the reserves of conventional crude oils decline, these heavy oils must be upgraded to meet the demands. In this upgrading, the heavier material is converted to lighter fractions and most of the sulphur, nitrogen and metals must be removed. This can be done either by a coking process, such as delayed or fluidized coking, or by a hydrogen addition process, such as thermal or catalytic hydrocracking.
Recent work has been done on an alternate processing route involving hydrogen addition at high pressures and temperatures and this has been found to be quite promising. In this process, hydrogen and heavy oil are pumped upwardly through an empty tubular reaction in the absence of any catalyst. It has been found that the high molecular weight compounds hydrogenate and/or hydrocrack into lower boiling ranges.
Simultaneous desulphurization, demetalization and denitrogenation reactions take place.
In thermal hydrocracking, the major problem is coke or solid deposition in the reactor, especially when operating at relatively low pressures, and this can result in costly shut-downs. Deposits form at the top of the reactor where the partial pressure of hydrogen and the ash content are at the lowest. Higher pressures reduce reactor fouling (but) plant operations at high pressures involve higher capital and operating costs.
It has been well established that mineral matter present in the feed stock plays an important role in coke deposition. (It has been shown) that feed stock containing high mineral content ... had less tendency to form coke in the reactor than feed containing low mineral matter.
Other studies have shown that a high mineral content ... suppressed coke deposition in the reactor and general reaction fouling.
It has also previously been shown that coke deposition in the reactor can be suppressed by recirculating a portion of heavy ends to the lower portion of the reaction zone (and, this) indicated the possibility of continuously adding and withdrawing a coke carrier in the reactor. The addition of coke carriers (or) "getters" (has been suggested) such as sand, quartz, alumina, magnesia, zircon, beryl or bauxite. These "getters" could be regenerated after use by heating the fouled carrier with oxygen and steam ... (and being made thereby) to yield regeneration-product-gases containing a substantial amount of hydrogen.
(It has been) observed that coal particles were able to accumulate metals and any coke formed during the hydrocracking process.
It is the object of the present invention to overcome the problem of deposits forming in the reactor during the hydrocracking process, while minimizing the costs of overcoming these problems.
In accordance with the present invention, there is described a process for hydrocracking a heavy hydrocarbon oil ... which comprises: passing a slurry of said heavy hydrocarbon oil and finely divided fly ash or high ash coal fines in the presence of ... hydrogen ... through a confined hydrocracking zone ... .
(And) removing from said hydrocracking zone a mixed effluent containing a gaseous phase comprising hydrogen and vaporous hydrocarbons and ... a liquid stream containing heavy hydrocarbons.
This process substantially prevents the formation of carbonaceous deposits in the reaction zone.
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The full Disclosure rambles on to some, even more lengthy, extent, explaining how Coal wastes can be employed to make the crude tar sand bitumen into something more useable.
Note, again, that the bitumen will require free Hydrogen in it's processing.
Of perhaps more interest, though, is the fact that it isn't just Coal wastes that make processing of the tar sand possible; but, it might well also be Coal liquefaction technology.
We have previously documented, though almost as an aside, that Coal plant fly ash can be used to facilitate some processes that convert Coal into more versatile hydrocarbons.
The synthetic zeolite minerals that are abundant in Coal plant fly ash, especially, seem to work a good effect in those transmutations. And, we remind you of ExxonMobil's "MTG"(r), methanol-to-gasoline, process, wherein the Methanol is posited to be made from Coal; and, wherein a zeolite often designated as ZSM-5 is specified as the catalyst, or the catalyst carrier, for some of the needed reactions.
But, in any case, returning to the point, or points:
They are, in Canada and Venezuela, enthusiastically processing a very crude carbonaceous mineral deposit, similar in many respects to Coal, into liquid hydrocarbons.
Further, in Canada at least, they are using Coal wastes to accomplish the refining of that crude material into those liquid hydrocarbons.
Too bad we haven't yet been able to build a similar amount of enthusiasm in US Coal Country for the similar treatment of Coal itself.