United States Patent: 4597776

We have, in a few earlier reports, documented the somewhat unlikely development of various Coal conversion processes by the California-based high-technology company, Rockwell, whom we had always thought of as being primarily a Department of Defense aerospace contractor.

Those reports included: USA's Rockwell Liquefies Coal | Research & Development | News; and:

Rockwell International & Hydropyrolysis of Coal - 1978 | Research & Development | News.

Herein, we see that at least some of Rockwell's Coal conversion research, like much of what else they do, was, in fact, paid for by the US Government; i.e., by us.

 

And, that work culminated in a confirmation of at least two facts we have earlier reported, which are:

Steam can be utilized to effect the complete hydrogenation of Coal's carbon content. No external supply of elemental, and more expensive, Hydrogen, is needed; and:

Coal can be efficiently gasified with Steam and made thereby to form Methane gas.

That point has implications we again belabor, following excerpts from the initial link to:

"United States Patent 4,597,776 - Hydropyrolysis Process

 

Date: July, 1986

 

Inventors: Alan Ullman, et. al., California

 

Assignee: Rockwell International Corporation, El Segundo

 

Abstract: An improved process for producing a methane-enriched gas wherein a hydrogen-deficient carbonaceous material is treated with a hydrogen-containing pyrolysis gas at an elevated temperature and pressure to produce a product gas mixture including methane, carbon monoxide and hydrogen. The improvement comprises passing the product gas mixture sequentially through a water-gas shift reaction zone and a gas separation zone to provide separate gas streams of methane and of a recycle gas comprising hydrogen, carbon monoxide and methane for recycle to the process. A controlled amount of steam also is provided which when combined with the recycle gas provides a pyrolysis gas for treatment of additional hydrogen-deficient carbonaceous material. The amount of steam used and the conditions within the water-gas shift reaction zone and gas separation zone are controlled to obtain a steady-state composition of pyrolysis gas which will comprise hydrogen as the principal constituent and a minor amount of carbon monoxide, steam and methane so that no external source of hydrogen is needed to supply the hydrogen requirements of the process. In accordance with a particularly preferred embodiment, conditions are controlled such that there also is produced a significant quantity of benzene as a valuable coproduct.

The Government has rights in this invention pursuant to Contract (or Grant) No. DE-AT21-78ET10328 awarded by the U.S. Department of Energy.

Claims:  A process for producing methane by reacting a hydrogen-deficient carbonaceous material with a hydrogen-containing pyrolysis gas having a composition selected and controlled so that no external source of hydrogen is needed to provide the hydrogen requirements for the overall process.

(And) wherein the ...  the composition of the pyrolysis gas is controlled to comprise from about 1 to 10% carbon monoxide, 3 to 20% methane, 60 to 30% steam, and 40 to 90% hydrogen.

(And) wherein the mole ratio of the hydrogen present in said pyrolysis gas to the carbon content of said hydrogen-deficient carbonaceous material is within the range of about 1:1 to 5:1.

(Which range, we submit, would encompass that required for the catalytic synthesis of just about any hydrocarbon, liquid or gaseous, that one's heart might desire.)

A process for producing methane and benzene by reacting a hydrogen-deficient carbonaceous material with a hydrogen-containing pyrolysis gas having a composition selected and controlled so that no external source of hydrogen is needed to provide the hydrogen requirements for the overall process, which comprises the sequential steps of: introducing said pyrolysis gas consisting essentially of from about 1 to 10% carbon monoxide, 3 to 20% methane, 6 to 30% steam and a balance of hydrogen, at an elevated temperature and pressure, and said carbonaceous material into a single pyrolysis zone of an entrained flow reactor to react said hydrogen-deficient carbonaceous material with said pyrolysis gas at a (specified) temperature (and) at a (range of specified pressure) and for a time of from about 2 to 10 seconds, to form a product gas mixture including methane, benzene, carbon monoxide and a reduced hydrogen content relative to that in said pyrolysis gas ... .

(And) reacting a part of the carbon monoxide in said product gas mixture with a first controlled amount of steam in a water-gas shift reaction zone ...  sufficient to produce hydrogen in an amount substantially equal to the hydrogen consumed in the overall process;

(And) withdrawing from said water-gas shift reaction zone a shifted gas mixture containing additional hydrogen and introducing said shifted gas mixture into a gas separation zone (and) separating the shifted gas mixture in said gas separation zone into a product comprising methane and benzene, and a recycle gas comprising hydrogen, carbon monoxide and methane;

(And) introducing said recycle gas, a controlled amount of an oxygen-containing gas and a second controlled amount of steam into a gas treatment zone for partial oxidation of the recycle gas to produce said pyrolysis gas having said elevated temperature for introduction into said entrained flow reactor; and controlling (the)steps ... to obtain, under steady-state conditions, a composition of the pyrolysis gas mixture (such) that no external source of hydrogen is needed to provide the hydrogen requirements for the overall process.

Background and Description: The present invention relates to a process for preparing a high-Btu content gas by the reaction of a hydrogen-containing pyrolysis gas with a hydrogen-deficient carbonaceous material at an elevated temperature and pressure. It particularly relates to such a process wherein the pyrolysis gas comprises hydrogen as the principal constituent and the balance consists essentially of carbon monoxide, steam and methane such that substantially no additional external source of hydrogen is required for the process.

It has been known for hundreds of years that a combustible gas could be produced from coal by simply heating the coal in a closed vessel.

(Finally, immediately above, they get around to identifying, specifically, just what a "hydrogen-deficient carbonaceous material" might be. Coal really is what this is all about.)

In the latter part of the 1800's, the water-gas process was developed in which steam was reacted with hot coal to produce large quantities of a combustible gas. The ... technology was inefficient by today's standards. Nonetheless, it accounted for over half of the manufactured gas production in the United States (until) as late as the middle 1900's.

Manufactured gas was gradually replaced by natural gas as new reserves were developed and pipelines constructed for its distribution.

In recent years worldwide concern has arisen over the rapid increase in petroleum and natural gas consumption, and the realization that the world's supplies of petroleum and natural gas are limited.

Accordingly, considerable effort is being expended to develop alternate sources of energy. One such alternate energy source is synthetic petroleum and synthetic (or substitute) natural gas (SNG) produced by the conversion of coal.

The advantages of converting coal to a substitute natural gas (essentially methane) are that the United States has enormous established reserves of coal that can readily be mined, the distribution and end use apparatus for the gas are presently in existence and SNG is a relatively clean burning fuel.

Several coal gasifier systems have been demonstrated on a commercial scale. The most widely known of these is the Lurgi system which is in commercial operation in South Africa. Also in use are the Winkler and Koppers-Totzek systems. All of these systems gasify coal with a mixture of steam and oxygen. A disadvantage of these systems is that a substantial amount of the coal is consumed in generating the heat required for the steam to react with the coal. In addition, the temperatures required for a rapid reaction and significant conversion of the coal are relatively high and do not favor methane formation. Thus, the gaseous products produced must be further processed if the desired product is methane.

(Note that "the Lurgi system which is in commercial operation in South Africa", is in "commercial operation" there to manufacture a synthesis gas, from Coal, which South Africa Synthetic Oil Limited, Sasol, then catalytically condenses into Diesel fuel, Jet fuel and Gasoline.)

It also has been proposed to react coal with hydrogen at elevated temperatures to produce a substantially high yield of methane directly. This approach, however, requires a separate reactor for the production of the large amounts of hydrogen consumed in the process, which adds considerably to the complexity of the process and the expense of the methane produced. Thus, various processes have been proposed to obviate some of these disadvantages and provide a means for the production of methane from coal which is both economical and energy efficient.

(One) process for the production of substitute natural gas from coal utilizing catalytic gasification is described by J. E. Gallagher, Jr. and H. A. Marshall of Exxon Research and Engineering Company in "Production of SNG from Illinois Coal Via Catalytic Gasification," AICHE Symposium on Reaction Engineering in Processing Solid Fossil Fuels, November 1978, Miami Beach, Fla. In the disclosed process, dried coal is coated with potassium hydroxide catalyst. The coated coal is then reacted in a fluidized bed with a preheated mixture of steam, recycle hydrogen and carbon monoxide to produce a product gas substantially free of any heavy hydrocarbons. Any acid gases present in the product gas are removed, and the remaining gas, consisting essentially of only hydrogen, carbon monoxide and methane, is sent to a cryogenic distillation system. The methane is separated, and the CO and H2 are mixed with gasification steam and recycled to the gasifier. In the presence of the catalyst, the carbon monoxide and hydrogen react to produce methane and generate heat in a sufficient quantity to substantially offset the concurrent endothermic reaction between the steam and coal.

The principal disadvantage of this process is that it requires a catalyst and a separate catalyst recovery system.

In spite of the intensive research being done in the area of coal gasification there still exists a need for further improvement in processes for the gasification of coal to produce methane.

Summary: The present invention provides an improvement in a process wherein a hydrogen-deficient carbonaceous material is treated in a reaction zone with a hydrogen-containing pyrolysis gas at an elevated temperature and pressure to produce a product gas mixture including methane, carbon monoxide and hydrogen.

In accordance with the present invention, the requirement for an external source of hydrogen for use in such a process is eliminated."

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We'll close our over-long excerpts right there, since the point is made, i,e.:

We can fully hydrogenate Coal, to make gaseous and liquid hydrocarbons, using Steam as the source of Hydrogen. And, thus, need for "an external source of hydrogen for use in such a process is eliminated".

First, note that Benzene seems to be the one by-product of Rockwell's efficient system. Without citing references, we remind you that Benzene is one of the liquid hydrocarbon components of the "BTX",  Benzene -Toluene-Xylene, blend which modern petroleum refineries use to compound Gasoline.

Methane, however, is the main product. And, we remind you, that, as in, for just one example, our report:

Texas CO2 + Methane = Methanol + Gasoline | Research & Development | News;

Methane can be reacted, "reformed", with Carbon Dioxide, reclaimed from whatever source, and made thereby to form valuable liquid hydrocarbons; including, as in that report, Methanol and Gasoline.

Furthermore, Methane, as herein manufactured so efficiently from Coal, can, all by itself, as seen in:

Pittsburgh DOE Methane to Gasoline | Research & Development | News; be directly, and efficiently, catalytically condensed into a full range of higher, liquid, hydrocarbons.

And, as Rockwell specifies, with official US Government affirmation of the fact, all we need to start out with are "steam and coal".


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