Manufacture of gas mixtures containing carbon monoxide and hydrogen
We've presented several reports concerning technology for the gasification of Coal, wherein an Oxygen donor substance, rather than plain Air or purified Oxygen, is utilized to effect the partial oxidation of the Carbon contained in the Coal.
The supply of Oxygen, through a donor substance, is restricted, and, thus, reactive and desired Carbon Monoxide is generated preferentially to the less reactive Carbon Dioxide.
Further, no, or far fewer, undesirable oxides of Nitrogen are formed in such processes.
The essence of the thing is that an atom of hot Carbon is hungry enough for Oxygen that it is able to "steal" an atom of Oxygen from some specific "oxide" compounds.
That is the substance, in fact, of several Carbon Dioxide recycling technologies we've made report of, including, most recently:
Bayer Improves Coal + CO2 = Carbon Monoxide | Research & Development; concerning: "United States Patent 7,473,286 - Carbon Monoxide Generator; 2009; Bayer Material Science, AG, Germany; The present invention relates to a novel generator for the reaction of carbon-containing raw materials and also to an improved process for the production of carbon monoxide gas (CO gas) having a high degree of purity using such a generator. Carbon monoxide gas is ... produced ... by means of a continuous process in which carbon-containing raw materials are reacted with oxygen and carbon dioxide";
wherein just enough Oxygen is supplied to Coal to support an exothermic reaction that generates sufficient heat to drive the reaction between the Carbon Dioxide that is produced, and some additional Carbon Dioxide, and the thus-heated Carbon, to form Carbon Monoxide.
However, as attractive as such technologies might sound, they do require that the Coal, or Carbon, be heated to a fairly high temperature before the individual Carbon atoms are made reactive enough to wrest an Oxygen atom from the Carbon Dioxide.
As an alternative, technologies were developed quite a long time ago wherein certain metal oxides could be made to serve as Oxygen donors for Coal, in reactions where the Coal requires being heated to a far lesser degree for the hot Carbon to be able to wrest an atom of Oxygen from the metal oxide.
Consolidation Coal Company, Consol, recognized those potentials early on, as seen in:
Consol 1953 Coal to Hydrogen & Methane with No CO2 | Research & Development; wherein multiple Coal conversion technologies developed by Consol's award-winning scientist, Everett Gorin, are presented, including: "United States Patent 2,654,661 - Gasification of Carbonaceous Solid Fuels; 1953; Consolidation Coal Company", which, in the course of it's Disclosure the specific gasification technology, makes reference to: "a process for the gasification of carbonaceous solid fuels by reaction between steam and solid fuels in the presence of calcium oxide".
And, Consol, even after being assimilated by Conoco, went on to further develop such technology, for rather intriguing uses, over coming decades, as we reported in:
Consol Hydrogasifies CoalTL Residues | Research & Development; concerning: "United States Patent 4,248,605 - Gasification of Coal Liquefaction Residues; 1981; Conoco, Inc.; Abstract: A method for gasifying the bottoms fraction from a coal liquefaction process by mixing the bottoms fraction with at least one finely-divided calcium compound selected from the group consisting of calcium oxide, calcium carbonate and calcium hydroxide ... in an amount sufficient to produce agglomerate particles upon mixing with the bottoms fraction and thereafter gasifying the resulting agglomerate particles by reacting the agglomerate particles with steam in a fluidized bed";
and, wherein it was seen that a group of several Calcium-based Oxygen donors could be made to support the Steam-gasification of still-carbonaceous residues that result from an initial process of direct Coal liquefaction which utilizes a Hydrogen-donor Coal solvent.
An interesting, and valuable, feature of utilizing certain metal oxides as Oxygen donors for Coal gasification is that, when those metals have relinquished their Oxygen in the gasification process, they can be regenerated into Oxygen donors by reacting them with Steam, H2O, in a process that generates, along with the restored Oxygen donor, molecular Hydrogen.
Such potentials are described, for one instance, in our report of:
Japan, Switzerland and Indiana Oxygen Donor Coal Gasification | Research & Development; concerning: "Coal Gasification Using the ZnO/Zn Redox System; Energy & Fuels; 1996; Tokyo Institute of Technology, Japan; Laboratory for Energy and Process Technology, Paul Scherrer Institute, Switzerland; (and,) Mechanical Engineering Department, Valparaiso University, Indiana; A two-step thermochemical process ... for converting coal to high-quality synthesis gas. In the first, high temperature, endothermic step, coal is reacted with zinc oxide to form metallic zinc and an H2-CO gas mixture. In the second, low temperature, exothermic step, zinc is used for splitting water and producing hydrogen and zinc oxide."
The Carbon Monoxide and the Hydrogen produced by such an integrated procedure can then, of course, be subjected to catalytic processing, a version of which is described succinctly in:
Fischer–Tropsch process - Wikipedia, the free encyclopedia; which states that the "Fischer–Tropsch Synthesis is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid
hydrocarbons";
and be chemically condensed into a wide variety of both liquid and gaseous hydrocarbons.
Herein, we learn that a very major component of the United States Petroleum industry, more than half a century ago, brought all of those concepts together in a coordinated technical process for the conversion of both our abundant Coal, and a variety of Carbon-recycling renewable resources, into a synthesis gas blend of Hydrogen and Carbon Monoxide well-suited for catalytic chemical condensation into hydrocarbon fuels.
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 2,592,377 - Manufacture of ... Carbon Monoxide and Hydrogen
Date: April, 1952
Inventors: Frank Barr and Homer Martin, NJ
Assignee: Standard Oil Development Company, DE
Abstract: The present invention relates to the manufacture of gas mixtures containing carbon monoxide and hydrogen from ... carbonaceous materials such as coal (and) cellulosic materials ... and more particularly to the manufacture of such gas mixture as are suitable for the catalytic synthesis of hydrocarbons.
It has long been known that non-volatile carbonaceous materials such as coal ... may be converted into water gas by a high temperature reaction with steam. The process yields mixtures of CO and H2 in varying proportions depending mainly on the conversion temperatures and the feed ratio of steam.
The flexibility of the process may be illustrated by a series of possible chemical reactions:
C + 2H2O = 2H2 + CO2
C + H2O = H2 + CO
C + CO2 = 2CO
(The) water gas process permits the production of gas mixtures of varying composition ... .
Furthermore, the process as such is extremely well suited ... for the production of feed gases for hydrogenation process and particularly for the catalytic synthesis of hydrocarbons ... .
However, the technical utilization of the water gas process, particularly for hydrogenation processes and the production of synthesis feed gas, has been appreciably impeded by difficulties encountered in heat supply and continuous operation as well as in the substantial removal of sulfur compounds from the gas ... .
It is ... the principal object of our invention to provide an improved process for the production of gas mixtures containing carbon monoxide and hydrogen from non-volatile carbonaceous materials.
Another object ... is to provide improved means for converting carbonaceous materials into gas mixtures suitable for the catalytic synthesis of hydrocarbons ... .
A more specific object ... is to provide improved means for supply heat to a water gas generator using a carbonaceous charge in the form of a dense fluidized mass of finely divided solids.
In accordance with the present invention the gasification of solid carbonaceous materials with steam is carried out in the presence of metal oxides supplying the heat required.
(Note, that, not only are the "metal oxides" serving as Oxygen transfer agents, they are also serving as agents for the transfer of heat, so that heat-producing oxidation reactions, with their consequent production of some Carbon Dioxide, do not have to take place in the synthesis gas generator.)
(The) metal oxide is intimately contacted with, and gives off its oxygen to, the fluidized solid carbonaceous charge of the gas generator.
The resulting combustion ... may generate at least a substantial portion of the heat required by the water gas reaction.
In addition, the metal oxide is reduced so that it may be reoxidized in an exothermic reaction to produce heat required by the gasification reaction.
(Note that it might not be necessary to supply much, if any, additional heat energy from external sources to drive all of these combined reactions forward. That is especially so when it is considered that the final, Fischer-Tropsch synthesis for which the product gases are destined is itself exothermic, and could provide even additional heat energy for transfer into the Coal hydro-gasification process.)
(After it has donated it's Oxygen) reduced metal oxide is ... circulated to a separate oxidation zone to be regenerated by oxidation with air at temperatures within the range of about 1400 to 2500 F. Regenerated (particles of) metal oxide (are) returned to the gas generation zone substantially at the temperature of the oxidation zone thus supply sensible heat ... to the gas generation zone in addition to heat which may be generated by partial combustion within the gas generation zone.
(With all of those heat sources, and heat recovery/utilization potentials, it seems unlikely that any heat energy, at all, would really have to be supplied from outside the system.)
In accordance with our invention the necessity of low carbon concentration in a heater is obviated and the water gas generator may be operated at highest carbon concentrations and rates of reaction.
Moreover, the metal oxide may act simultaneously as a cracking catalyst for organic sulfur compounds, thus simplifying the desulfurization of the product gas.
(Note: The proper Oxygen donor can not only convey restricted amounts of Oxygen into the Carbon gasification reaction, it can also supply much of the heat needed to drive that reaction and serve to catalyze the reactions that remove Sulfur from the resulting hydrocarbon synthesis gas.)
(And) any methane formed by cracking of the carbonaceous feed is more easily reformed in the presence of metals such as iron, nickel, etc.
(As we've documented in many previous reports, Methane is often a co-product, with Hydrogen and Carbon Monoxide, of Coal hydrogasification processes directed primarily to the production of synthesis gas blends. Herein, the metal which conveys Oxygen into the restricted Coal oxidation and gasification reaction also serves to help break any co-produced Methane apart into more Carbon Monoxide and Hydrogen.
We remind you, however, that we might wish instead to recover any co-produced Methane for use in a separate synthesis gas generation process, such as described, for just one example, in our report of:
1939 CO2 + CH4 = Hydrocarbons | Research & Development; concerning: "US Patent 2,180,672 - Process for Converting Gaseous Hydrocarbons; 1939; Phillips Petroleum; This invention relates to processes for the conversion of normally gaseous hydrocarbons into organic products of higher molecular weight and more specifically to the conversion of methane and ... oxides of carbon into ... hydrocarbons suitable for motor fuel ... (by reacting) gaseous hydrocarbons of lower molecular weight ... with oxides of carbon ... (via a process wherein) carbon dioxide ... may be mixed directly with the gaseous hydrocarbons ... predominating in methane";
wherein the by-product Methane can be reacted with Carbon Dioxide, reclaimed from whatever source, with both being converted through such reactions into even more of the Carbon Monoxide and Hydrogen syngas blends which are the products of our subject herein, "United States Patent 2,592,377".)
The metal oxides which may be used in the present process are quite generally such oxides as have such an affinity for oxygen at the temperatures of our process (and, typical) of these are cupric oxide, ferric oxide and vanadium pentoxide.
(We don't know about the "vanadium", but, it shouldn't be too hard to scrape together a little copper or iron for the "cupric oxide" and "ferric oxide".)
Suitable also are mixtures of these ... with carrier materials such as ... alumina.
Claims: The process of producing carbon monoxide and hydrogen which comprises passing steam upwardly through a dense fluidized bed of finely divided carbonaceous solids ... maintained ... in the presence of ... a metal oxide (and) withdrawing a gas containing carbon monoxide and hydrogen upwardly.
The process ... wherein tail gas from a hydrocarbon synthesis reaction is recycled to (that) bed.
(In other words, we can pass the Carbon Monoxide-Hydrogen synthesis gas made by our subject process of "United States Patent 2,592,377 - Manufacture of ... Carbon Monoxide and Hydrogen", through a "hydrocarbon synthesis" reactor, such as, we suggest, a Fischer-Tropsch converter, and, after condensing all of the liquid hydrocarbon fuels we can out of that synthesis gas, we can send the exhaust gas from the Fischer-Tropsch, or similar, reactor back, to be combined with the Coal and the Steam and the metal oxide Oxygen donor in the original gasification chamber, where it will be reprocessed into even more Carbon Monoxide and Hydrogen.)
The process ... wherein at least a portion of .. heat is supplied as exothermic heat (of) oxidation ... .
The process ... wherein at least a portion of ... heat is supplied as sensible heat of said reoxidized metal oxide highly heated ... by ... reoxidation reaction."
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And, there you have it:
Using common and inexpensive metal oxides, we can, in a combined process that also utilizes Steam to provide needed Hydrogen, convert, on a very nearly Nitrogen Oxide- and CO2-free basis, our abundant Coal and any Carbon Dioxide-recycling, botanically-derived "cellulosic materials" we want to toss into the mix, into a blend of Carbon Monoxide and Hydrogen "suitable for the catalytic synthesis of hydrocarbons", in a process that requires the input, from outside the reaction system itself, of little or no additional energy.
We gotta ask:
Just how danged good and thorough does the technology for converting our abundant Coal, and for recycling our renewable Carbon resources, in "the catalytic synthesis of hydrocarbons", have to get, before we, much less than actually doing it, just start making public exposition, and start conducting public discussion, of it?