http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/14_3_CHICAGO_09-70_0045.pdf
We have lately been reporting on the broad utility of Methane, i.e.: how it can be directly converted into liquid hydrocarbon fuels; how it can be reacted, or "tri-reformed", with Carbon Dioxide to synthesize higher hydrocarbons; and, how it can enhance the productivity of indirect Coal conversion technologies, to create improved synthesis gas suitable for catalysis into liquid hydrocarbons.
Herein, a report of research, financed by the US Government's Office of Coal Research, we believe to have been published in 1970, confirms that the versatile Methane can itself, as we have earlier documented, be manufactured via the steam gasification of Coal.
Comment follows extended excerpts from:
"HYDROGEN: A KEY TO THE ECONOMICS OF PIPELINE GAS FROM COAL
C. L. Tsaros; Institute of Gas Technology; Chicago, Illinois 60616
The objective in manufacturing supplemental pipeline gas is to produce high-heating-value gas that is completely interchangeable with natural gas -essentially methane. Large amounts of low-heating-value constituents like hydrogen or carbon monoxide or inert diluents like carbon dioxide or nitrogen cannot be tolerated.
The basic problem in making methane from coal is to raise the H2/C ratio. A typical bituminous coal may contain 75% carbon and 5% hydrogen, a ratio of 0.4:1; the same ratio for methane is 2:1. To achieve this ratio it is necessary to either add hydrogen or reject carbon. The most efficient way is to add hydrogen. The hydrogen in the coal can supply about 25-30% of the required hydrogen, but the bulk must come by the decomposition of water, the only economical source of the huge quantities needed for supplemental gas.
There are two basic methods for adding hydrogen to coal: In the first, or indirect, method, coal reacts with steam to form synthesis gas -mainly hydrogen and carbon monoxide.
This reaction is highly endothermic and requires combustion of carbon with oxygen, or some other heat source. The CO and H2 then react catalytically to form methane:
Prior to methanation, part of the CO is made to react with more water to increase the H2/C0 ratio.
In the second, or direct, method, methane is formed directly by the destructive hydrogenation of coal ... .
The indirect method is inherently less efficient because in the process water is decomposed ... . (And a) portion of the hydrogen product is then converted back to water ... .
The major effort at IGT has been in hydrogasification, now called the HYGAS Process ... .
Process economic studies have been carried out in conjunction with the development program at IGT for pipeline gas from coal. A number of different process designs have been prepared in which the price of gas was reduced ... . The most important effects on the cost of product gas have resulted from the way hydrogen is generated or utilized in the hydrogasifier; hydrogen has been the key factor in reducing the price of gas.
The original studies cover a period of about 10 years and have somewhat different process and cost bases. In this paper the results of seven different pipeline gas plant economic evaluations are compared.
1. Synthesis-gas methanation
2. Hydrogasification of coal by a hydrogen/char ratio of 300% of stoichiometric
3. Partial hydrogasification with 50% of the stoichiometric hydrogen rate
4. Hydrogasification with steam-hydrogen mixtures
5. Hydrogen by the steam-iron process
6. Hydrogen from synthesis gas generated by electrothermal gasification
7. Hydrogasification with synthesis gas
The data presented in this paper have all been derived from ... earlier studies ... .
Indirect Methanation-Synthesis-Gas Methanation
The first process, methanation of synthesis gas generated by Texaco steam-oxygen suspension gasification of coal,' is ... is expensive because of the high oxygen requirement and the low thermal efficiency.
Direct Hydrogenation
The rest of the studies are based on the direct hydrogenation of coal char to methane ... . They represent a historical and process economic study of major steps in hydrogen usage that have occurred in the development of the HYGAS Process.
Use of Excess Hydrogen
The first economic evaluation for hydrogasification was based on pilot plant data in which a large excess of hydrogen -300% of the stoichiometric hydrogen/char ratio-is fed to the hydrogasifier in a fluidized-bed reactor. Nearly complete gasification is achieved. A separate coal stream flows to the gasifier where synthesis gas for hydrogen production is generated. ... More hydrogen and other volatile matter is lost in the low-temperature carbonization, requiring more net hydrogen input.
With excess hydrogen, the hydrogasifier effluent contains CH2/H2 in a 0.32: 1 ratio, which is upgraded to a ratio of 8.7:1 by low-temperature separation.
Partial Hydrogasification With Less Than Stoichiometric Hydrogen
Further development of hydrogasification showed that it is advantageous to hydrogasify only the more reactive fractions of the coal and to use the less reactive residual char for hydrogen manufacture. By the use of a moving bed, a solids down-flow-gas upflow reactor, and a hydrogen/char ratio only 50% of the stoichiometric, a high-Btu gas is produced in the hydrogasifier.
A lower temperature and a reduced hydrogen/char feed ratio result in a high-Btu gas, eliminating the need for low-temperature separation. Partial conversion of the char reduces the net hydrogen input because more coal must pass through the reactor, yielding more volatile matter. ... the investment is reduced 15% and the efficiency is raised to 60%. .
... for pipeline gas by partial hydrogasification with spent hydrogasifier char as the basis for hydrogen manufacture. Steam is needed ... (and) alternative methods employ air, oxygen, or electricity as a
basic input.
Hydrogasification With Steam-Hydrogen Mixture: An important process and economic development was the successful use of steam in the hydrogasifier.
Steam decomposition generates hydrogen in situ, thus reducing the size of the hydrogen section and lowering the price of gas.
The economic effect of introducing steam into the hydrogasifier ... : Investment is lowered by 25%. In both cases hydrogen is derived from synthesis gas made by Texaco-type steam-oxygen gasification of spent char. When part of the hydrogen is made in the hydrogasifier ... net hydrogen is reduced by 30%.
The expense of using oxygen to make hydrogen has stimulated interest in alternative methods. The continuous steam-iron process ... offers potential for significant cost reduction.
Spent hydrogasifier char reacts with steam and air to make a producer gas ... . Power for air compression and other plant requirements is provided by an expansion turbine powered by spent ... gas. Savings in investment contribute most to the ... reduction in gas price ... . The hydrogen rate is the same, but the costs of hydrogen and onsite power generation are greatly reduced.
Hydrogen by the Electrothermal Process
Another alternative to steam-oxygen gasification is the electrothermal process ... . Here resistance heating of a fluidized bed of char operating at 1800 - 1900F supplies the heat for the steam-carbon reaction, and the steam serves both as a reactant and a fluidizing medium. Compression of high-purity oxygen is eliminated, and the reducing gas is not diluted by CO2 from combustion. ... There is enough spent char to supply needed electricity by either a magnetohydrodynamic or a conventional steam turbine system. Such a system would be adjacent to and integrated with the pipeline gas plant and could benefit from the use of hot char transferred directly as fuel to a fluidized boiler.
Hydrogasification With Synthesis Gas
Feeding raw, hot synthesis gas instead of hydrogen can substantially reduce the price of pipeline gas. We have shown the economic effect as applied to the electrothermal process. The synthesis gas is essentially CO and H2. As H2 is consumed in the hydrogasifier, CO reacts with the steam present to from more H2.
Because of the lower hydrogen partial pressure, a larger reactor column is needed, but its cost is largely balanced by the elimination of the hydrogen preheat system necessary when cold hydrogen is used. Major cost reductions are in the elimination of the CO shift and purification sections needed to make high-purity hydrogen and in savings in offsite equipment.
Important process changes have occurred in the development of the HYGAS Process, resulting in much improved economics.
The basic IGT scheme as presently conceived consists of three stages of coal conversion:
1) a low-temperature first hydrogenation stage, either free fall or upflow, for conversion of the volatile matter;
2) a fluidized-bed second hydrogenation stage where steam and synthesis gas ... produce methane
3)a third- stage fluidized-bed gasifier ... where spent char is converted to synthesis gas containing
methane by electricity and/or oxygen.
The work reported herein is under the cosponsorship of the American Gas Association and the U.S. Department of the Interior, Office of Coal Research. "
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So, in 1970, our US Government, via the US Department of the Interior's Office of Coal Research, financed research and development that defined, in some considerable detail, the best, most economical method for synthesizing Methane from Coal.
We remind you: Once we have the Methane, from Coal, we can, as per US Patented technology developed by ARCO, and others, convert that Methane in liquid hydrocarbons; or, we can "tri-reform" that Methane with Carbon Dioxide, using technology described most thoroughly by Penn State University, into useful hydrocarbons; or, we can use that Methane to enhance the productivity of some indirect processes of Coal conversion to produce liquid hydrocarbons.
Nearly half a century ago, we US taxpayers financed the apparently successful development of technology to convert our abundant Coal into the such seemingly valuable and versatile Methane.