As per some of our earlier reports, the inventor named in this US Patent, Ernest (variously: Ernst) Donath, was a key scientist in Germany's extensive Coal liquefaction industry during WWII.
All indications are that he was established in a remote US Virgin Island exile subsequent to the War, where, for some decades, he continued to develop and refine Coal conversion technologies, the rights to all of which, it seems, were automatically assigned to the Government of the United States, as represented by the Secretary of the Interior.
Keep in mind that, prior to creation of the US Department of Energy, the US Bureau of Mines was a component of the Interior Department.
In any case, Donath's Coal conversion achievements in this instance, as documented by the Patent Office, are of some special interest since they are derivative of two-stage Coal gasification technology first developed by the Pittsburgh, PA, outpost of the USBM, as illustrated by this advance excerpt from the main body of the Disclosure:
"The two-stage gasification process described above was developed at Bituminous Coal Research, Inc., at Pittsburgh, Pennsylvania (BCR). The process is described in a publication of the Department of Interior, Office of Coal Research (OCR), dated 1965 and entitled "Gas Generator-Research and Development Survey and Evaluation.""
So, the Coal conversion technology refined herein by this former Axis scientist was, in part, founded on USBM research and development seemingly first accomplished in Pittsburgh, PA.  
Provocative trivia aside, what interests us most in this patented technology is the fact, again confirmed herein by the US Government, that Steam can be utilized to hydrogenate Coal, providing the needed Hydrogen so that Coal's content of Carbon can be transformed into Hydrocarbons.
Comment follows excerpts from:
"United States Patent 3,844,733 - Two-Stage Downflow Gasification of Coal
Date: October, 1974
Inventor: Ernest E. Donath, US Virgin Islands
Assignee: The United States of America
Abstract: A process for the two-stage downflow gasification of coal to produce a methane rich fuel gas. In a first stage, partially gasified char recycled from a second stage is reacted with super-heated steam and oxygen to produce a first stage synthesis gas. In the second stage, the first stage synthesis gas is mixed and reacted with coal and steam to produce partially gasified char and a hydrogen-rich product gas containing methane. Pressures in the first and second stages are maintained at at least 50 atmospheres. Slag formed in the first stage reaction is maintained in the molten state at temperatures in excess of 2, F. Gases, excess char and slag flow into the second stage in which coal, synthesis gas and steam react whereby the slag is cooled and solidified before it contacts the walls of the reactor in the second stage. After removal and separation of the partially gasified char and product gas from the second stage, the char is recycled to the first stage and the product gas is purified and methanated. The solidified slag is collected in the second stage and is thereafter elutriated with steam and quenched before disposal.
Summary: This invention resides in a process for the production of a methane-rich fuel gas by a two-stage gasification of coal in a process providing for downward flow of the reactants and products in the process. In a first gasification stage, downwardly flowing, partially gasified recycle char is reacted with steam and oxygen, at a pressure of at least 50 atmospheres and preferably above 70 atmospheres, to produce a first stage synthesis gas containing hydrogen and oxides of carbon and a slag maintained in the molten state by the high reaction temperature maintained in the first stage. In a second stage, downwardly flowing first stage synthesis gas, partially gasified char and molten slag from the first stage are mixed and reacted with downwardly flowing coal and steam introduced into the second stage to produce a second stage product gas containing hydrogen, oxides of carbon and methane, partially gasified char and slag solidified at the reaction temperature maintained in the second stage. The second stage product gas is separated and treated to remove the carbon oxides and other impurities and is ultimately methanated to produce a methane-rich fuel gas. The char is separated and recycled to the first gasification stage. Solidified slag is collected at the bottom of the second stage for removal and disposal from the system. The residence time of partially gasified char in the first stage and the residence time of coal in the second stage are adjusted and maintained at the conditions of temperature and pressure prevailing in each stage respectively, to assure rapid reaction and heating of the coal at a temperature above its range of plasticity and to assure rapid gasification of the char at a temperature above the ash melting point.

Maintenance of downward flow of the reactants and products in both reaction stages and the rapid mixing and cooling of char and molten slag with coal in the second stage provide rapid solidification of the slag and prevents accumulation of molten slag on the reactor walls in the second stage while providing for efficient transfer of heat from the molten slag to the reacting coal, complete carbon utilization, more effective separation of the slag quenching process from the high temperature first stage reaction, and the recovery of partially gasified char from the elutriated solidified slag."
Note that, although high temperatures and pressures are required, there is recovery and utilization of heat derived from the process, as indicated in the passage regarding "transfer of heat from the molten slag to the reacting coal" immediately above. 
Moreover, in this process to manufacture a "methane-rich" gas from "coal and steam", "complete carbon utilization" is realized.
And, keep in mind that there could be an even more "complete carbon utilization", if the "methane-rich" gas produced, via Donath's technology, from Coal and Steam, were then employed in a "tri-reforming" reaction, as explained, for instance, by Chunsan Song at Penn State University, as we have in other reports documented, to react with reclaimed Carbon Dioxide and thereby synthesize even more, higher, hydrocarbons.
Methane, as we have documented, even from the US EPA, can also be directly converted into liquid hydrocarbon fuels.
In any case, as we have been reporting:
Coal can be hydrogenated, to synthesize hydrocarbons, by relatively straightforward reactions with Steam.

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