In a brief series of recent reports, we've begun to document the use of various metal oxides as Oxygen donors in Coal gasification processes.
The use of such "Oxygen donors" to effect the partial oxidation of Coal, or, as we will demonstrate in other reports to follow, any Carbon source, is a far more effective way to accomplish the gasification since it enables the attainment of several important goals.
First, the use of specific metal oxides as Oxygen donors for the gasification of Coal, relative to the use of plain air, eliminates the wasteful and polluting co-production of Nitrogen Oxides.
Second, regarding that same issue, it is far less expensive to generate/regenerate Oxygen donor metal oxides than it is to physically separate Oxygen from air, and to then use that purified Oxygen in the Coal gasification process, to the same end of preventing such co-production of Nitrogen Oxides.
Third, metal oxides can ration and restrict the supply of Oxygen to the Coal oxidation reaction, thus leading to the generation of a far greater percentage of the desired Carbon Monoxide in the product gas, relative to the less-reactive and thus less-desirable Carbon Dioxide.
Fourth, and importantly, the metal oxide is chemically reduced to it's base, elemental metal, or a lower oxide of that metal, when it donates Oxygen to the restricted Carbon oxidation reaction. And, in some cases, the Oxygen donor can be regenerated by reacting the reduced metal with plain old Water, or Steam, which leads both to the metal oxide being reformed and to the co-production of Hydrogen, from the H2O, which Hydrogen can be added to the product Carbon Monoxide, thereby to form a blend of synthesis gas then suitable for catalyzed chemical condensation, as via the Fischer-Tropsch process for just one well-known example, into liquid hydrocarbons.
Much of that was explained in our recent post, as accessible via:
Oklahoma Oxygen Donor Coal Gasification | Research & Development; concerning, in part:
"United States Patent 4,073,630 - Production of Carbon Monoxide; 1978; Phillips Petroleum Company; Abstract: In a system wherein carbon monoxide is produced from a carbon source by contacting the carbon source with solid zinc oxide in a primary reaction zone, zinc values which are entrained in the ash byproduct are recovered, reconverted to zinc oxide and reused for production of additional carbon monoxide"; and:
"United States Patent 4,496,370 - Zinc Oxide-Char Gasification Process; 1985; Phillips Petroleum Company; Abstract: In the gasification of char with zinc oxide, the improvement which comprises reacting the off-gas stream of gaseous zinc and carbon monoxide with steam at elevated temperatures in a second reactor means thereby oxidizing the zinc to zinc oxide and yielding a second gaseous stream containing carbon monoxide and hydrogen."
And, such technology actually flowered out of previous work accomplished in the decade immediately following WWII, as we documented, for just one instance, in our report of:
Consol 1953 Coal to Hydrogen & Methane with No CO2 | Research & Development; concerning: "United States Patent 2,654,661 - Gasification of Carbonaceous Solid Fuels; 1953; Assignee: Consolidation Coal Company, Pittsburgh; Abstract: This invention relates to the gasification of carbonaceous solid fuels, and particularly to the production of hydrogen or high B.t.u. gas from such fuels. (A) process for the gasification of carbonaceous solid fuels by reaction between steam and solid fuels in the presence of calcium oxide is (elsewhere) described. A gaseous product is obtained which contains methane and hydrogen in varying relative proportions depending upon the particular temperature and pressure conditions (and) the gaseous products are substantially free of carbon dioxide".
The above Consol process was really only the start of their work with Oxygen donors, such as "calcium oxide", and, it was actually founded on similar Coal conversion science established in the late 1940's by components of our domestic petroleum industry.
We'll be documenting more on all of that in future reports. But, herein, we submit, again from Pittsburgh, PA, evidence of perhaps the original and seminal work on the Oxygen donor gasification of Coal, which work led to a process specifically designed to produce, from Coal, a blend of Carbon Monoxide and Hydrogen that was essentially free of Carbon Dioxide and Nitrogen.
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 1,484,225 - Method of Producing Gas
Date: February, 1924
Inventor: Carl Lundin, Pittsburgh, PA
(We have been unable to determine with certainty the corporate, government or academic affiliation, if any, of the named inventor. We rely herein solely on our own US Government patent examiners' expert verification of the facts.)
The invention relates to a method for producing gas.
It relates particularly to a method for producing an artificial gas high in carbon monoxide and hydrogen.
The usual fuel or producer gas contains a relatively high percentage of non-combustible elements which reduce the heat efficiency of the gas. The non-combustible component of these gases is mostly made up of nitrogen which is present in the gas, due to the fact that the oxygen required for the gasification of the coal is taken from the atmosphere.
It is important that a simple, efficient method for producing gas be devised in which gas produced is substantially free from nitrogen and high in desirable combustible elements.
In order to be commercially successful this process must require a minimum amount of heat and must be simple so that a complicated apparatus is not required for carrying it out.
One of the objects of the present invention is to provide an improved process for producing a fuel gas which is substantially free from nitrogen, has a high percentage of combustible elements, and one in which the heat generated in the production of the gas is utilized for carrying out the process itself.
A further object is to provide an improved process for producing a gas high in carbon monoxide and hydrogen and substantially free from nitrogen by distilling carbonaceous material, out of contact with air, and furnishing oxygen to the gases produced by means of a metallic oxide, the heat of the combustion caused by uniting of the oxygen of the metallic oxide with the gases produced from the coal furnishing heat for carrying out the process.
(As we've documented in many previous reports, the reaction comprising the partial oxidation of Coal is exothermic, as is, by the way, the Fischer-Tropsch catalytic condensation of the product gases into hydrocarbons. As we will further document in coming reports, heat energy from them both can be utilized to help drive other, endothermic reactions such as, as will be seen following, the reduction of Carbon Dioxide, a little of which might be produced by the process of our subject, "United States Patent 1,484,225", with hot Carbon to produce more Carbon Monoxide.)
Generally stated the process consists in the destructive distillation of a carbonaceous material, such as coal, to produce carbon monoxide (CO), hydrogen (H2), and other gases, the percentage of each depending on the quality of the carbonaceous material used; the passing of these gases into contact with a metallic oxide, such as magnetic oxide of iron (Fe3O4) to change the carbon monoxide to carbon dioxide (CO2), thereby producing heat for carrying out the entire process; and the subsequent passing of the carbon dioxide over heated carbonaceous material to again change it to carbon monoxide; air being excluded from the entire process to exclude the non-combustible gases of the atmosphere, such as nitrogen, from the gas.
(The Disclosure then goes on at significant length to explain the apparatus for conducting the specified syngas generation process, with numerous references made to schematics which accompany the full document and which are available via the enclosed link.)
When the gas producing process is first started it is necessary to heat the retorts by some suitable means such as by initially burning a part of the coal in the retorts, but, after the process has been started, it is no longer necessary to do so, the heat of the process itself being utilized for this purpose.
The coal retorts and also other principal elements of the system are provided with heat insulating linings which prevent material loss of heat by radiation, and provided with fire brick or other refractory material arranged to absorb the heat of the hot gases flowing there through and transfer the same to the coal.
The flow of gases from the coal retorts to the combustion chambers causes the hot gases comprising CO2, hydrogen ... and other gases to be forced through the second set of coal retorts where the carbon dioxide (CO2) is converted into carbon monoxide (CO) when it comes into contact with the heated carbon or coal.
The gases, which have passed through the second set of coal retorts, consist principally of carbon monoxide, hydrogen, and a small amount of other gases ... .
(There is, thus, no Carbon Dioxide remaining, either to dispose of or otherwise deal with.)
Claims: The method of producing gases rich in carbon monoxide and hydrogen but substantially free of nitrogen, which consists in distilling carbonaceous material without exposing the same to air (and) passing the resulting gases into contact with a metallic oxide to furnish oxygen to the gases and produce heat (and) repassing the hot oxidized gases into contact with the carbonaceous material to furnish carbon to the gases, and passing the free metal resulting from the oxidation of the gases into heat exchanging relation with the carbonaceous material used in the process to warm (it) and utilize the heat of the metal."
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The full disclosure is more than a little unclear about just exactly how much Hydrogen will be available in the resulting Syngas, seeming to rely on the inherent moisture content of the Coal to provide enough of it through the decomposition of that moisture.
If not, then we suggest the process could be modified a bit, to allow for regeneration of the Iron oxide, or other, "metallic oxide", not through contact with "air", but, with Steam; where, as in:
Consol 1969 Hydrogen for Coal Liquefaction | Research & Development; concerning: "United States Patent 3,442,619 - Production of Hydrogen via the Steam-Iron Process; 1969; Assignee: Consolidation Coal Company; Abstract: An improved process for making hydrogen by the steam-iron reaction ... . This invention relates to the production of hydrogen and steam-hydrogen mixtures for use in synthesis processes. In the process of this invention, hydrogen is produced by oxidation of reduced iron solids by steam";
not only would the Iron Oxide required by our subject process herein, of "US Patent 1,484,225 - Method of Producing Gas", to convert Coal into a hydrocarbon synthesis gas essentially free of both Nitrogen and Carbon Dioxide, be regenerated, but, additional Hydrogen would be produced as well, which could be added to the nearly-pure product "artificial gas high in carbon monoxide and hydrogen", in order to, if needed, adjust its composition so that it would be even more suitable for catalytic, Fischer-Tropsch or other, chemical condensation into specifically-targeted hydrocarbon gases and liquids, including Methane, Methanol, Diesel, and the various components of Gasoline blending stock.