United States Patent: 3726784
This Esso Coal conversion patent, as linked above, is, for us, very technically dense. They have a lot going on in here.
We'll try to sort it out a bit, following the excerpts, but, look sharp and you'll see that they're liquefying Coal using a Coal-derived liquid as the solvent, and, at the same time, recovering Hydrogen-rich off-gasses to use in the hydrogenation, the hydrotreating, of the resulting Coal liquids.
Comment follows:
"United States Patent 3,726,784 - Integrated Coal Liquefaction and Hydrotreating Process
Date: April, 1973
Inventor: Juan Correa, et al., NJ
Assignee: Esso Research and Engineering Company, NJ
Abstract: A hydrotreated liquid product from coal is obtained by a process in which liquefaction and hydrotreating zones are operated at essentially the same moderate pressures (1000-2000 psig). Without prior cooling, all the overhead vapor from the liquefaction reactor is admixed with a portion of a light liquid fraction (700.degree. F.) recovered from the liquefaction liquid product, giving a hydrotreating feed having a temperature within a predetermined range. The remaining portion of the light liquid fraction of the liquefaction product is fed to the hydrotreating zone at quench points in the hydrotreating zone downstream from the point of introduction for the admixture, thus utilizing the heats of reaction in the hydrotreating zone to heat the remaining liquid portions (which provide quench to the hydrotreating zone).
Claims: A process for producing hydrotreated liquid product from coal, which comprises:
Subjecting a slurry of coal particles in a hydrogen-donor solvent to coal liquefaction in the presence of hydrogen for a sufficient period of time and at a sufficient temperature to form a liquid product and a vaporous product; admixing all of said vaporous product with a portion of said liquid product, without prior cooling of said vaporous product, to obtain an admixture having a temperature within a predetermined range;
introducing said admixture into a hydrogenation zone having essentially the same pressure as said liquefaction zone; introducing a second portion of said liquid product into said hydrogenation zone at a location downstream from the point of introduction of said admixture where the temperature of said hydrogenation zone exceeds said predetermined range by a specified minimum, the quantity and temperature of said second portion being correlated with the temperature at said location as as to cool the hydrogenation zone downstream of said location to a temperature within a predetermined range; and
recovering a hydrotreated liquid product from said hydrogenation zone.
A process for producing a hydrogenated liquid product from coal, which comprises:
In a coal liquefaction zone, liquefying coal slurried in a hydrogen-donor solvent in admixture with from about 1 to about 6 weight percent hydrogen, under liquefaction conditions, to produce a vaporous product, containing from about 1 to about 12 weight percent hydrogen, and a liquid product, including a fraction boiling within the range from about 300 F to about 700 F.
A process for producing a hydrogenated liquid product from coal, which comprises:
In a coal liquefaction zone, liquefying coal slurried in a hydrogen-donor solvent in admixture from about 1 to about 6 weight percent hydrogen, under liquefaction conditions including a pressure within the range from about 1000 psig to about 2000 psig, a temperature within the range from about 750 F to about 850 F, and a liquid residence time of from about 5 to about 60 minutes, to produce a vaporous product containing from about 1 to about 12 weight percent hydrogen, and a liquid product including a fraction boiling within the range from about 300 F. to about 700 F; removing said vaporous product and said liquid product separately from said liquefaction zone ... .
In this invention, all of an overhead vaporous product obtained from a coal liquefaction zone is admixed, without prior cooling, with a portion of a liquid product recovered from the liquefaction zone, thereby heating that portion of the liquid product to a temperature within a predetermined range desired for hydrotreatment of the liquid product. Preferably, hydrogen treat gas, for hydrotreatment of the liquid product, is also heated by admixing it with the vaporous overhead and the light liquid portion, without prior cooling of the vaporous product. The resultant admixture is introduced into a hydrotreating zone having essentially the same pressure as the liquefaction zone. The remaining portion of the liquid product is fed into the hydrotreating zone at a location downstream from the point of introduction for the admixture where the temperature of the hydrotreating zone exceeds the predetermined hydrotreatment temperature by a specified amount, the quantity and temperature of the remaining portion being correlated with the temperature at the location where it is introduced so as to cool the hydrotreating zone downstream from that location to a temperature within the predetermined range for hydrotreatment. The heats of reaction in the hydrotreating zone thus serve to heat the remaining portion of the liquefaction liquid product and such portions conversely provide a liquid quench for the hydrotreating zone. The hydrotreated liquid product is recovered from the effluent of the hydrotreating zone, a hydrogen treat gas preferably also being recovered from the effluent and recycled to admix with the feed to the inlet of the hydrotreating zone, as above described. In the present context, hydrotreating refers to all catalytic hydrofining and hydrogenation reactions conducted at essentially non-cracking temperatures and productive of exothermic heats of reaction.
In accordance with this invention, a liquid product boiling above about 200 F (at atmospheric pressure) and a vaporous product are produced in a coal liquefaction zone. The vaporous product includes hydrogen gas in concentrations of from about 0.5 to about 12 weight percent, preferably from about 1 to about 4 weight percent thereof. To produce the liquid product and vaporous product, a coal liquefaction zone is charged with coal particles ... slurried, at a solvent-to-coal ratio of from about 0.8:1 to about 2:1, in a coal-derived hydrocarbonaceous solvent nominally boiling within the range from about 300 F to about 900 F The coal feedstock is a solid particulate coal such as a bituminous coal, subbituminous coal, lignite, brown coal, or a mixture thereof."
----------
As our limited capacities allow us to understand it, Exxon developed, as herein, a process where off-gasses, a "vaporous product obtained from a coal liquefaction zone", with or without the subsequent addition of other, unspecified "hydrogen treat gas", which could, we submit as conjecture, be Methane obtained via the Sabatier conversion of Carbon Dioxide, are blended into "a portion of a liquid product", and, the resultant hydrogenated material is then combined with the "remaining portion of the liquid product" in a "hydrotreating zone", where the final hydrogenated Coal liquid is produced.
Note, that, as we have from other sources reported, some segments of some Coal conversion processes are exothermic, as in "productive of exothermic heats of reaction", and such internally-generated heat energy could be harnessed and recycled to help drive other parts of the reaction sequence, with resulting economy.
In any case, we herein again have irrefutable and detailed document evidence that the petroleum industry, and our own US Government, knew, more than three decades ago, that highly-developed technologies existed and were available which would enable us to convert our abundant domestic Coal into the liquid hydrocarbon fuels that, even in 1973, we were already getting pinched for.