As we have previously, though sporadically, documented over the course of our reportage, a number of different elements, all metals of one sort or another, and compounds of those metals, can serve as catalysts in processes wherein Coal is converted, directly or indirectly, into gaseous and liquid hydrocarbons.
In fact, in more-recently developed indirect Coal conversion technologies, wherein Coal is first gasified, that is, converted into a blend of Hydrogen and Carbon Monoxide synthesis gas, and, which "syngas" is then chemically condensed, as via the Fischer-Tropsch synthesis, into hydrocarbons, it's been demonstrated that catalysts can serve in at least two processes within such systems.
Not only can they promote, obviously, the formation of hydrocarbons from the synthesis gas; but, catalysts can also be utilized to promote the Coal gasification itself, and the initial syngas-forming reactions between Coal and the agents used for gasification; which agents can include, as seen for just one example in:
Conoco 2011 Coal + CO2 + H2O + O2 = Syngas | Research & Development; concerning: "United States Patent 7,959,829 - Gasification System and Process; 2011; Assignee: ConocoPhillips Company; Abstract: A system and process for gasifying carbonaceous feedstock with staged slurry addition in order to prevent the formation of tar that causes deposition problems. Dry solid carbonaceous material is partially combusted, then pyrolyzed along with a first slurry stream comprising carbonaceous material in two separate reactor sections, thereby producing mixture products comprising synthesis gas. Claims: A process for gasification of a carbonaceous material, comprising the steps of: introducing a dry feedstock comprising recycled char and a solid stream comprising particulate carbonaceous material into a reactor lower section and partially combusting therein with a gas stream comprising an oxygen supply selected from a group consisting of oxygen-containing gas, steam, and mixtures thereof, thereby evolving heat and forming products comprising synthesis gas and ... passing said synthesis gas from said reactor lower section upward into a reactor upper section and pyrolysing therein with a first slurry stream comprising a slurry of particulate carbonaceous material in a liquid carrier ,,, wherein said carrier liquid is selected from group consisting of water, liquid Carbon Dioxide, (or) mixtures thereof";
not only "water", H2O, but, as well, as reclaimed and recycled from whatever source, "Carbon Dioxide".
Since raw materials, i.e., Coal, CO2, H2O and O2, are constantly flowing into such a gasification process, and, the product hydrocarbon synthesis gas is constantly flowing out, but, with a solid residue comprised primarily of the inorganic mineral content of the Coal, but with some residual Carbon, left behind, it is inevitable that some, maybe most, of any catalyst used to promote the gasification reactions will get "bound" into that mineral residue, which itself must be removed from the gasification chamber to prevent accumulations of it that might impede the gasification process.
Consequently, to improve the economics of such indirect Coal conversion systems, some effort has been put into the development of technologies that recover the material used to catalyze the initial Coal gasification, so that it can be reused to catalyze the gasification of even more Coal.
One example of our reportage concerning that issue is accessible via:
Exxon Recovers and Recycles Coal Conversion Catalyst | Research & Development; concerning: "United States Patent 4,157,246 - Hydrothermal Alkali Metal Catalyst Recovery Process; 1979; Assignee: Exxon Research and Engineering Company; Abstract: In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles primarily in the form of water soluble alkali metal formates by treating the particles with a calcium or magnesium-containing compound in the presence of water ... and in the presence of added carbon monoxide. During the treating process the water insoluble alkali metal compounds comprising the insoluble alkali metal residues are converted into water soluble alkali metal formates. The resultant aqueous solution containing water soluble alkali metal formates is then separated from the treated particles and any insoluble materials formed during the treatment process, and recycled to the gasification process where the alkali metal formates serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary. (The) process of the invention provides an alkali metal recovery system which makes it possible to recover alkali metal constituents from alkali metal residues produced during catalytic gasification ... and at the same time enables inexpensive alkali metal sulfates to be used as a source of makeup alkali metal compounds thereby lowering the overall cost of the conversion process. The government of the United States of America has rights in this invention pursuant to Contract No. E(49-18)-2369 awarded by the U.S. Energy Research and Development Administration";
wherein it's demonstrated that our own US Government not only acknowledges the fact that Coal can be efficiently converted into liquid and gaseous hydrocarbons; but, at one time, liked those processes so much that it was willing to pay to have them made even more efficient.
And, at the same time the Coal conversion-related process of "US Patent 4,157,246 - Hydrothermal Alkali Metal Catalyst Recovery Process" was, with US Government support, being developed by Exxon, we see herein that Exxon were motivated enough by the economic potentials for converting Coal into hydrocarbons that they were using their own money, as well, to develop Coal gasification catalyst recycling technology.
As seen, with comment appended, in excerpts from the initial link in this dispatch to:
"United States Patent 4,159,195 - Hydrothermal Alkali Metal Recovery Process
Date: June, 1979
Inventor: LeRoy Clavenna, TX
Assignee: Exxon Research and Engineering Company, NJ
Abstract: In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles by treating them with a calcium or magnesium-containing compound in the presence of water. The treating process is carried out under conditions such that the calcium or magnesium-containing compound reacts with water insoluble constituents of the alkali metal residues such as alkali metal aluminosilicates to produce an aqueous solution containing water soluble alkali metal constituents. The aqueous solution is recycled to the gasification process where the alkali metal constituents serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. The process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary.
Claims: In a process for the conversion of a solid carbonaceous feed material in the presence of an alkali metal-containing catalyst into liquids and/or gases wherein char particles containing carbonaceous material, ash and alkali metal residues are produced, the improvement which comprises: treating said char particles containing said carbonaceous material, ash and alkali metal residues with a calcium or magnesium-containing compound in the presence of liquid water under conditions such that said calcium or magnesium-containing compound reacts with water-insoluble compounds in said alkali metal residues to produce an aqueous solution containing water soluble alkali metal constituents; and:
using said alkali metal constituents from said aqueous solution in said conversion process as at least a portion of the alkali metal constituents comprising said alkali metal-containing catalyst.
A process ... wherein said conversion process comprises gasification.
A process ... wherein said conversion process comprises liquefaction.
A process ... wherein said carbonaceous feed material comprises coal.
Background and Description: This invention relates to the conversion of coal and similar carbonaceous solids in the presence of alkali metal-containing catalysts and is particularly concerned with the recovery of alkali metal constituents from spent solids produced during coal gasification and similar operations and their reuse as constituents of the alkali metal-containing catalysts.
Potassium carbonate, cesium carbonate and other alkali metal compounds have been recognized as useful catalysts for the gasification of coal and similar carbonaceous solids. The use of such compounds in coal liquefaction, coal carbonization, coal combustion and related processes has also been proposed. To secure the higher reaction rates made possible by the presence of the alkali metal compounds it has been suggested that bituminous coal, subbituminous coal, lignite, organic wastes and similar carbonaceous materials be mixed or impregnated with potassium, cesium, sodium or lithium compounds, alone or in combination with other metallic constituents, before such materials are reacted with steam ... or other agents at elevated temperatures to produce gaseous and/or liquid effluents. Studies have shown that a wide variety of different alkali metal compositions can be used for this purpose, including both organic and inorganic salts, oxides, hydroxides and the like.
Coal gasification processes and similar operations carried out in the presence of alkali metal compounds at high temperatures generally result in the formation of chars and alkali metal residues. The chars normally include unconverted carbonaceous constituents of the coal or other feed material and various inorganic constituents generally referred to as ash. It is generally advisable to withdraw a portion of the char from the reaction zone during gasification and similar operations in order to eliminate the ash and keep it from building up within the reaction zone or other vessels in the system. Elutriation methods and other techniques for separating char particles of relatively high ash content and returning particles of relatively low ash content to the reaction zone in order to improve the utilization of carbon in such processes have been suggested.
(Concerning the final statement, above, see, for one example among others, our report of:
Texaco Recycles Coal Conversion Residues | Research & Development; concerning: "United States Patent 2,980,521 - Carbon Separation Process; 1961; Texaco, Inc.; Abstract: This invention relates to a process for the production of synthesis gas from carbonaceous fuels. More especially, the invention is concerned with improvements in a method for the separation and recovery of free carbon particles from a carbon-water slurry formed in a synthesis gas generation process.)
In gasification and other processes referred to above that utilize alkali metal-containing catalysts, the cost of the alkali metal constituents is a significant factor in determining the overall cost of the process. In order to maintain catalyst cost at reasonable levels, it is essential that the alkali metal constituents be recovered and reused. There have been proposals for the recovery of alkali metal constituents by leaching as they are withdrawn from the reaction zone with char during operations of the type referred to above. Studies indicate that these constituents are generally present in part as carbonates and other water soluble compounds which can be recovered by water washing. Experience has shown that only a portion of the potassium carbonate or other alkali metal constituents is normally recovered and that substantial quantities of makeup alkali metal compounds are therefore required. This adds appreciably to the cost of such operations.
Summary: The present invention provides an improved process for the recovery of alkali metal constituents from char particles produced during coal gasification and other conversion processes carried out in the presence of an alkali metal-containing catalyst. In accordance with the invention it has now been found that increased amounts of alkali metal constituents can be effectively recovered from particles containing alkali metal residues produced during coal gasification and related high temperature conversion processes by treating the particles with a calcium or magnesium-containing compound in the presence of water under conditions such that the calcium or magnesium-containing compound reacts with water insoluble compounds, such as alkali metal aluminosilicates, in the alkali metal residues to produce water insoluble precipitates and an aqueous solution containing water soluble alkali metal constituents. These alkali metal constituents are then used in the conversion process as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. Preferably, such use is achieved by recycling the aqueous solution directly to the conversion process.
(Thus, the water, H2O, in the "aqueous solution" can donate it's Hydrogen to the syngas production.)
The invention is based in part upon studies of the reactions that catalysts containing alkali metal constituents undergo during coal gasification and similar operations. Coal and other carbonaceous solids used in such operations normally contain mineral constituents that are converted to ash during the gasification process. Although the composition of ash varies, the principal constituents, expressed as oxides, are generally silica, alumina and ferric oxide. The alumina is usually present in the ash in the form of aluminosilicates. Studies have indicated that at least a portion of the alkali metal compounds, such as potassium carbonate, that are used as gasification catalyst constituents react with the aluminosilicates and other ash constituents to form alkali metal residues containing water soluble alkali metal compounds such as carbonates, sulfates, and the like, and water insoluble, catalytically inactive materials such as alkali metal aluminosilicates. Unless the alkali metal constituents in the insoluble alkali metal residues can be recovered, they are lost from the process and must be replaced by makeup alkali metal compounds.
The process of this invention allows recovery of these alkali metal constituents and thereby decreases the costs incurred by utilizing large amounts of makeup alkali metal compounds. As a result the invention makes possible substantial savings in gasification and other conversion operations carried out in the presence of alkali metal-containing catalysts and permits the generation of product gases and/or liquids at significantly lower cost than would otherwise be the case."
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We close our over-long excerpts there to emphasize the final point made:
This technology, as developed by Exxon, enables the conversion of "bituminous coal" and Carbon-recycling "organic wastes", as they specify, into hydrocarbon "liquids and/or gases"; and, contributes to "the generation of" such Coal-, and other, renewable, Carbon sourced-, "gases and/or liquids at significantly lower cost".
Our ongoing questions, as always, are:
Just how much "lower" does the "cost" of producing liquid hydrocarbon fuels from our domestically-mined Coal and our domestically-grown "organic wastes" have to get, before it makes more sense than continuing to pour our national wealth into the royal treasuries of the OPEC sheikdoms?
Just how big do the "substantial savings", in converting Coal and renewable "wastes", into hydrocarbon fuels have to get, before we can start to realize other savings, such as in our Defense budget, by cutting back on Persian Gulf patrols and OPEC-inspired wars?
And, finally, just how big, and how complete, does the body of technical knowledge growing out of the fact that our abundant Coal, and our CO2-recycling "wastes", can be converted, through an initial gasification, into a complete range of needed hydrocarbons, have to get, before someone, somewhere, takes notice of the elephant squatting smack dab in the middle of our Coal Country living room floor - hiding, apparently, under a discrete doily crocheted by Big Oil - and calls everyone else's attention to it?