As we've previously explained and documented, indirect processes for the conversion of Coal, into more versatile hydrocarbons, entail an initial gasification of the Coal, which forms the Hydrogen-Carbon Monoxide mixture known as synthesis gas, or "syngas"; which gas mixture is then catalytically condensed, via a number of processes that are well-known and well-established in the petroleum industry, and made thereby to form gaseous and liquid hydrocarbons.
Such gasification of Coal is actually a controlled oxidation process; a limited "burning" of it, with a reduced amount of Oxygen, so that the more reactive Carbon Monoxide is formed preferentially to Carbon Dioxide.
Again as we've documented, Steam, H2O, can be added to the mix of gases supplied to support such partial Coal combustion, in order to supply, through breakdown in reactions with the hot Carbon, supplemental Hydrogen for the syngas mixture.
More sophisticated Coal hydro-gasification processes utilize purified Oxygen, instead of Air, to support the partial combustion, so as to minimize loss of the available Hydrogen through reactions with the Nitrogen that would be present in Air, which reactions result in the formation of Ammonia, NH4.
The separation of purified Oxygen from the atmosphere, however, on the large scale required for such operations, is expensive; and, it thus adds significantly to the cost of producing hydrocarbons from Coal through such gasification processes.
The large-scale Coal conversion industry being established in China, again as we've previously documented, is, and intends, to address those issues by simply recovering the NH4 that is co-produced from lower-cost, air-based Coal gasification processes, and then utilizing it in the production of fertilizer.
There are however, it seems, other options.
Such co-produced Ammonia can be captured from the synthesis gas stream, and recycled back into the synthesis gas generator, where it can replace some of the otherwise needed Steam as a donor of Hydrogen to the Coal hydro-gasification process.
Comment follows excerpts from:
"United States Patent 4,693,883 - Ammonia Utilization Process
Date: September, 1987
Inventor: Donald Fleming, Illinois
Assignee: Institute of Gas Technology, Chicago
Abstract: An ammonia utilization process substantially eliminates by-product ammonia gas produced during hydrogen forming gasification processes by recycling sour water stripper off-gas comprising ammonia to a hydrogen forming gasifier wherein by-product ammonia gas is converted to desired hydrogen product gas and nitrogen.
Claims: In a process for gasification of organic carbonaceous materials in a hydrogen forming gasifier, the improvement comprising: separating ammonia from product gas of said gasifier by dissolving in an aqueous liquid forming sour water; separating said sour water from said gasifier product gas; separating gaseous ammonia from said sour water; and recycling said gaseous ammonia to said hydrogen forming gasifier operated under organic carbonaceous material gasifying conditions forming a substantial amount of hydrogen and nitrogen from said ammonia.
(And) wherein said organic carbonaceous (is) coal.
A process for ammonia utilization from organic carbonaceous material hydrogasification product gas from a hydrogen forming gasifier (which comprises) producing ammonia containing sour water by cooling and scrubbing said gasifier product gas with an aqueous liquid; separating gaseous ammonia from said sour water; and recycling said gaseous ammonia to said hydrogen forming gasifier operated under organic carbonaceous material gasifying conditions forming a substantial amount of hydrogen and nitrogen from said ammonia.
Background and Field: This invention relates to an ammonia utilization process which substantially reduces by-product ammonia gas present in product gas from gasification of organic carbonaceous materials and concomitantly enhances the hydrogen content of the product gas by recycling sour water stripper off-gas comprising substantial quantities of ammonia gas to the primary hydrogen forming carbonaceous material gasifier wherein the ammonia is converted to nitrogen and hydrogen.
Summary: According to the process of the present invention, sour water stripper off-gas is recycled to the primary hydrogen forming carbonaceous material gasifier, wherein it is converted to nitrogen and hydrogen, thereby enhancing the hydrogen content of the product gas.
This process provides effective utilization of ammonia in an energy conversion process with recovery of hydrogen values. The process is energy efficient and may be conveniently adapted for use in various types of existing energy conversion systems."
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Of course, when you see "energy conversion process", involving "organic carbonaceous materials", as phrased so discretely above, read it all as "coal conversion".
The gist of it is:
We can hydro-gasify Coal, to make a fully-hydrogenated synthesis gas, by using inexpensive Air, mixed with a little Steam, as the primary agent of Coal gasification. Ammonia, NH4, will be co-generated in such a process. But, we can capture that NH4 and recycle it back into the initial Coal hydro-gasification process.
There, it will contribute it's Hydrogen content to the Carbon hydrogenation reaction, and thereby reduce some of the requirements for Steam, and it's attendant costs.
Nitrogen, and likely some oxides of Nitrogen, would be the by-products. And, although Nitrogen itself is already the primary constituent of our atmosphere, and is thus unobjectionable, the various oxides of Nitrogen are pollutants that should, and could, be dealt with.
As we can learn in:
processes exist, and have been successfully installed in Japan, which can efficiently and concurrently "remove about 70%" of the Nitrogen oxides "and 90%" of Sulfur oxides "from flue gases".
In those processes, by the way, the Sulfur is recovered as a marketable product, with a return, albeit, perhaps, a small one, that helps to offset some of the cost.
And, against those total costs, we yet again submit, must be weighed the total loss to our national wealth, caused by continuing to allow ourselves to be extorted for the supply of our liquid hydrocarbon fuel needs by often-unfriendly foreign OPEC nations; with the concurrent loss of jobs, and of opportunity, in the USA.