United States Patent: 8158029

As we've documented for you now to the point of tedium, Coal can be converted indirectly into liquid hydrocarbon fuels via the nearly-ancient Fischer-Tropsch process, wherein Coal is first partially oxidized, or incompletely combusted, "gasified', to produce a mixture of Carbon Monoxide and Hydrogen, "synthesis gas", or "syngas", which syngas is then passed over and through any one of a number of known catalysts and is thereby chemically condensed into liquid and/or gaseous hydrocarbons.

The Fischer-Tropsch Coal gasification-liquefaction process was developed before, and widely practiced among the Axis powers during, WWII, again as we've many times documented.

And, as seen in just two examples:

Texaco 1950 Coal + Steam = Hydrocarbon Syngas | Research & Development | News; concerning; "United States Patent 2,516,974 - Gasifying Carbonaceous Material;1950; Assignee: Texaco Development Corporation, NY; Abstract: The present invention relates to gasification of solid fuels and is more particularly concerned with the conversion of carbonaceous materials into a gaseous product of high heating value composed primarily of carbon monoxide and hydrogen ... . In accordance with the present invention a stream of combustible gases, predominantly hydrogen and carbon monoxide, is produced by the reaction of water vapor with carbon"; and:

Standard Oil Co-Gasifies Coal & Carbon-Recycling Biomass | Research & Development | News; concerning;"United States Patent 2,633,416 - Gasification of Carbonaceous Solids; 1953; Assignee: Standard Oil Development Company; Abstract: The present invention relates to the production of gases from non-gaseous carbonaceous materials and, more particularly, to the production of gas mixtures containing carbon monoxide and hydrogen ... from such solid carbonaceous materials as ... various coals (and) cellulosic materials';

such Coal-to-hydrocarbon conversion technologies were the subject of further development by the US petroleum industry in the years immediately subsequent to WWII, even to the incorporation of renewable, carbon-recycling products of photosynthesis, "cellulosic materials", with Coal, in the gasification process.

Although Fischer-Tropsch Coal conversion, or Coal conversion of any sort, didn't, aside from a few notable exceptions, as seen in:

Coal to Methanol - Eastman & Air Products | Research & Development | News; concerning: "Commercial-Scale Demonstration of a Liquid-Phase Methanol Process; Eastman Chemical Company; Kingsport,TN;  
Abstract: The Eastman Chemical Company operates a coal gasification complex in Kingsport. Tennessee. 
The primary output of this plant is carbonylation-derived acetic anhydride. The required methyl acetate is made from methanol and acetic acid. Methanol is currently produced from syngas (in a plant where) coal is gasified and the resulting synthesis gas purified to a high degree. This gas, which consists chiefly of carbon monoxide and hydrogen, is used to feed the chemical plants. Methanol is produced in one plant by the Lurgi low-pressure gas-phase process. The syngas needed for these plants is produced by two high-pressure gasifiers. High-sulfur coal is ground and fed to these gasifiers as a water slurry with pure oxygen"; and:

North Dakota Commercial Coal to Methane | Research & Development | News; concerning: "Practical Experience Gained During the First Twenty Years of Operation of the Great Plains Gasification Plant and Implications for Future Projects; United States Department of Energy; Office of Fossil Energy; April, 2006; Executive Summary: The Dakota Gasification Company’s (DGC) Great Plains Synfuels Plant (GPSP) in Beulah, North Dakota has operated successfully for 20 years as the only commercial coal-to-natural gas
facility in the United States";

take any real root in the United States, as we've seen in many reports, as, for instance, in:

US EPA Recommends Coal Liquefaction as a Clean Alternative | Research & Development | News; concerning:"Clean Alternative Fuels: Fischer-Tropsch; United States Environmental Protection Agency; Transportation and Air Quality Transportation and Regional Programs Division; EPA420-F-00-036; March 2002; A Success Story (!) For the past 50 years, Fischer-Tropsch fuels have powered all of South Africa’s vehicles, from buses to trucks to taxicabs.The fuel is primarily supplied by Sasol, a world leader in Fischer-Tropsch technologies.Sasol’s South African facility produces more than 150,000 barrels of high quality fuel from domestic low-grade coal daily";

the nation of South Africa, via South Africa Synthetic Oil Limited, Sasol, did adopt Fischer-Tropsch Coal conversion technology immediately after WWII, and incorporated it as a key component of their national industry and economy.

Further, as in our report of:

South Africa Presents Coal Gasification and Liquefaction | Research & Development | News; concerning; "Sasol: Reaching New Frontiers; Coal Gasification and Liquefaction- SA Experiences and Opportunities;

Setobane Mangena (PhD) Sasol Technology (Pty) Ltd; 4th EU -South Africa Clean Coal Working Group Meeting; 06 November 2012; The Sasol Coal to Liquids (CTL) Process: The Sasol-Fixed Bed Dry Bottom (Sasol(r) -FBDBTM) Gasification Technology & Development";

they continue to develop, refine and promote the concept and technology for converting Coal into clean liuid hydrocarbon fuels through initial gasification and the subsequent Fischer-Tropsch synthesis.

Herein, we just wanted to document and illustrate Sasol's ongoing development and improvement of Coal gasification technologies, specifically with respect to their above-mentioned "Fixed Bed Dry Bottom" Coal gasification process, the most recent evolution of which we believe to be embodied in the subject of this dispatch, as seen in excerpts from the initial link above to:

"United States Patent 8,158,029 - Method for the Production of Synthesis Gas and of Operating a Fixed Bed Dry Bottom Gasifier

Patent US8158029 - Method for the production of synthesis gas and of operating a fixed bed dry ... - Google Patents

Method for the production of synthesis gas and of operating a fixed bed dry bottom gasifier - Sasol Technology (Proprietary) L

April 17, 2012

Werner Siegfried Ernst, South Africa

Assignee: Sasol Technology Ltd., Johannesburg

Abstract: A method for the production of synthesis gas includes humidifying an oxygen-containing stream by contacting the oxygen-containing stream with a hot aqueous liquid to produce a humidified oxygen-containing stream, and feeding the humidified oxygen-containing stream into a gasifier in which a carbonaceous material is being gasified, thereby to produce synthesis gas.

(What much of this is really all about is getting more H2O into the stream of gas with which the Coal, and/or other "carbonaceous material", is being gasified, so as to increase the proportion of Hydrogen, H2, in the product syngas.) 

Claims: A method for the production of synthesis gas, the method including producing an oxygen-containing stream in an air separation unit; humidifying the oxygen-containing stream by contacting the oxygen-containing stream with a hot aqueous liquid to produce a humidified oxygen-containing stream; said humidifying of the oxygen-containing stream including heating the oxygen-containing stream by directly contacting the oxygen-containing stream with the hot aqueous liquid; and feeding the humidified heated oxygen-containing stream into a low temperature non-slagging gasifier in which a carbonaceous material is being gasified, thereby to produce synthesis gas, the gasifier forming part of a complex for Fischer-Tropsch hydrocarbon synthesis and which produces reaction water, with the oxygen-containing stream being contacted with said reaction water, and in which the reaction water includes oxygenated hydrocarbons, with at least some of these oxygenated hydrocarbons being taken up by the oxygen-containing stream during humidification. 

The method ... in which the humidified oxygen-containing stream being fed into the gasifier is at a temperature of at least 160 C (and) in which the humidified oxygen-containing stream being fed into the gasifier has a water concentration of between 40% and 90% by volume (and) in which the oxygen-containing stream is humidified in more than one humidification stage. 

The method ... in which the oxygen-containing stream is contacted with water used as cooling water (and) in which the oxygen-containing stream is contacted with water used as cooling water to cool a compressed gaseous stream in the air separation unit producing the oxygen-containing stream (and/or) in which the oxygen-containing stream is contacted with water used to cool reaction product from a hydrocarbon synthesis stage (and/or) in which the water is reaction water. 

(The "reaction water" would, as well, already be hot, as it is co-produced with hydrocarbons in the Fisher-Tropsch synthesis stage. Note as well all the potentials for recycling and energy economies through the use of water preheated through use as a cooling agent during various stages of the total process.) 

The method ... which includes operating a boiler stage and in which the oxygen-containing stream is contacted with boiler blow-down water (and) in which the flow rate of boiler blow-down water is increased above what is strictly required for boiler operation, and in which boiler stage feed water is preheated in indirect heat exchange with one or more hot process streams. 

The method ... which includes feeding steam to the gasifier as a gasification agent, the steam and the humidified oxygen-containing streams being combined before being fed to the gasifier. 

The method ... in which the gasifier is a fixed bed dry bottom gasifier, with the humidified oxygen-containing stream, steam and solid carbonaceous material being fed into said gasifier so that the carbonaceous material is gasified in the presence of oxygen and steam to produce synthesis gas and ash, the method including removing the synthesis gas and ash from the gasifier.

(Since the process includes "removing ... ash from the gasifier", we'll take the opportunity to remind you, that, as seen for one example in:

Standard Oil Converts Coal Conversion Residues into Cement | Research & Development | News; concerning: "United States Patent 4,174,974 - Process for Converting Coal Ash Slag into Portland Cement; 1979; Assignee: Standard Oil Company of Indiana, Chicago; Abstract: Disclosed is a manufacturing process for converting coal ash slag from a slagging coal gasifier into a marketable cement product having the characteristics and qualities of portland cement";

such Coal gasifier Ash can be treated as a byproduct of some commercial value.)

Description: This invention relates to a method for the production of synthesis gas, and to a method of operating a fixed bed dry bottom gasifier. 

There are various gasification technologies available to gasify a carbonaceous material, such as coal, to produce synthesis gas. With suitable coal used for fixed bed dry bottom gasification technology, less oxygen and coal are required for the production of a particular effective amount of synthesis gas than with high temperature gasification technologies, especially for coal containing a lot of inorganic matter and inherent moisture. (Effective synthesis gas is defined as that part of a synthesis gas that can potentially be converted into hydrocarbon product given the chosen product slate and conversion technology). However, the use of steam as gasification or moderating agent is higher when fixed bed dry bottom gasification technology is employed compared to other gasification technologies. If the coal required for steam production is included, the benefit provided by fixed bed dry bottom gasification technology of using less coal, compared to alternative high temperature gasification technologies, to produce an effective amount of syngas, is reduced or nullified. 

According to one aspect of the invention, there is provided a method for the production of synthesis gas, the method including: humidifying an oxygen-containing stream by contacting the oxygen-containing stream with a hot aqueous liquid to produce a humidified oxygen-containing stream; and feeding the humidified oxygen-containing stream into a gasifier in which a carbonaceous material is being gasified, thereby to produce synthesis gas. 

The term "gasifier" in this specification is used in the conventional sense, i.e. an apparatus for converting a hydrocarbonaceous feedstock that is predominantly solid (e.g. coal) or liquid into synthesis gas, as opposed to "reformer" which is an apparatus for the conversion of a predominantly gaseous hydrocarbonaceous feedstock to synthesis gas. 

In a preferred embodiment of the invention, the gasifier is a low temperature non-slagging gasifier, such as a low temperature fixed bed dry bottom gasifier (also known as a dry ash moving bed gasifier), e.g. a low temperature Sasol-Lurgi (trade name) fixed bed gasifier. 

In addition, certain types and/or applications of entrained flow gasifiers (i.e. high temperature slagging gasifiers), fixed bed slagging gasifiers, transported bed gasifiers, or fluidised bed gasifiers employ steam as a feedstock, albeit in lower amounts than what is used in low temperature non-slagging gasifiers. Such steam may for example be used as a moderator to protect burners of the gasifiers having burners, or to adjust the H2/CO ratio of synthesis gas produced by a gasifier. Thus, in different embodiments of the invention, the gasifier may be an entrained flow gasifier, or a fixed bed slagging gasifier, or a transported bed gasifier, or a fluidised bed gasifier. 

The method may include producing the oxygen-containing stream in an air separation unit (ASU), preferably a cryogenic ASU.

The gasifier may form part of a complex for hydrocarbon synthesis and which produces reaction water. In one or in a second humidification stage, the oxygen-containing stream may be contacted with said reaction water. 

Typically, the reaction water includes oxygenated hydrocarbons such as alcohols, ketones, aldehydes and acids. At least some of these oxygenated hydrocarbons may be taken up by the oxygen-containing stream during humidification.

(We won't track down the prior references, but, alcohols co-produced in the Fischer-Tropsch hydrocarbon synthesis, "oxygenated hydrocarbons", are typically, as above, specified to be recycled to the Coal gasification stage, a practice which would likely enrich the Hydrogen content, relative to Carbon Oxides, of the resulting synthesis gas.)

When the hot aqueous liquid is reaction water, the water is typically used for humidification on a once through basis, whereafter the reaction water may be routed to a water treatment plant or facility. Advantageously, at least some of these oxygenated hydrocarbons may thus be added in this fashion to the gasifier and less has to be treated or removed. 

In one, or as an alternative embodiment of the second humidification stage, the oxygen-containing stream may be contacted with water used to cool reaction product from a hydrocarbon synthesis stage. This water may be reaction water. The reaction product may be gaseous product at least a portion of which is condensed in order to separate components thereof, e.g. reaction water and heavy hydrocarbons. Instead, the reaction product may be a liquid product, e.g. wax, which is cooled before further processing or use. 

Typically, the gasifier will form part of a larger complex using or producing the synthesis gas.

The oxygen-containing stream may be contacted with the hot aqueous liquid in any suitable conventional gas liquid contacting device, e.g. a packed column or tower (and, the) method typically includes feeding steam to the gasifier as a gasification agent. The steam and humidified oxygen-containing streams may be combined before being fed to the gasifier. 

The hydrocarbon synthesis may be Fischer-Tropsch synthesis.

The synthesis gas removed from the gasification stage ...  is typically subjected to cooling and various cleaning stages, e.g. a sulphur removal stage (not shown), before being fed into the Fischer-Tropsch hydrocarbon synthesis stage for Fischer-Tropsch hydrocarbon synthesis. 

The Fischer-Tropsch hydrocarbon synthesis  ... is a conventional three-phase low temperature catalytic Fischer-Tropsch hydrocarbon synthesis stage, operating at a temperature of about 240 C ... . Liquid hydrocarbon product is produced in the Fischer-Tropsch hydrocarbon synthesis stage ... . The Fischer-Tropsch hydrocarbon synthesis stage also produces gaseous products which are removed ... and (further processed).

The Applicant believes that the invention, as illustrated, results in improved efficiency in the manufacturing of synthesis gas, particularly when a low temperature non-slagging gasifier, such as a low temperature fixed bed dry bottom gasifier is used to gasify coal.

Less high pressure steam is required as feed to the gasifier, as a portion of the gasification agent steam requirement is supplied together with the humidified oxygen. This will typically result in a reduction in coal usage.

The method of the invention, when used in a process to produce hydrocarbons, as illustrated, thus has the potential to increase overall carbon efficiency and to reduce plant CO2 emissions. This is important, as the CO2 emissions which are least capture ready on a large coal to liquids plant are from the coal powered steam plant. Reducing these emissions are thus of particular value in meeting reduced CO2 emission specifications. 

The invention makes it possible to increase the amount of steam obtained from current coal-based hydrocarbon synthesis plants (e.g. coal to liquids or CTL plants) without the addition of boilers to generate steam from low level heat. For new plants, the capacity of coal-fired boilers can be decreased, resulting in less CO2 production and thus a more competitive gasification footprint. The advantages will be lower capital cost and a reduced environmental footprint for coal-based hydrocarbon synthesis plants, especially so when fixed bed dry bottom (e.g. Sasol-Lurgi gasification) is employed.".

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We know our excerpts have been overlong, and that even though we resisted the urge to include links to some of the schematics available in the full patent document, as accessible via auxiliary links on the official US Patent and Trademark Office web site, which demonstrate more clearly how both energy and Coal can be conserved, and both the co-production of Carbon Dioxide and the consumption of water drawn from natural reservoirs reduced, in a process, that, through an initial gasification, converts Coal into liquid hydrocarbon fuels and chemicals via the Fischer-Tropsch technology.

And, we'll also note, that, as seen in our report of:

South Africa Co-produces Power and Hydrocarbons from Coal | Research & Development | News; concerning: "United States Patent 8,247,462 - Co-production of Power and Hydrocarbons; 2012; Assignee: Sasol Technology Limited, South Africa; Abstract: A process for co-producing power and hydrocarbons includes in a wet gasification stage, gasifying coal to produce a combustion gas at elevated pressure comprising at least H2 and CO; enriching a first portion of the combustion gas with H2 to produce an H2-enriched gas; and generating power from a second portion of the combustion gas. In a dry gasification stage, coal is gasified to produce a synthesis gas precursor at elevated pressure comprising at least H2 and CO. At least a portion of the H2-enriched gas is mixed with the synthesis gas precursor to provide a synthesis gas for hydrocarbon synthesis, with hydrocarbons being synthesized from the synthesis gas";

Sasol has increased the intrinsic value of such optimized Coal-to-hydrocarbon processes even further, by demonstrating how waste heat generated during the Coal gasification and hydrocarbon synthesis steps of the overall process, and some, a portion, of the synthesis gas when used as fuel, can be utilized to generate steam not just for use in reacting with Coal during the gasification phase, but, for generating by-product electrical power, perhaps especially on an as-needed basis, as well.

The takeaway from all of this should be that the available technology which would enable us to start converting our abundant domestic United States Coal into liquid hydrocarbon fuels, into anything we now squander our national wealth to buy from the often unfriendly nations of OPEC, has become very sophisticated, very efficient.

That technology is being practiced on a significant industrial and commercial basis in at least one other modern, mainstream nation with a globally-significant economy and population.

But, for whatever suspect reasons, information concerning those facts isn't being openly and broadly disseminated among the US public, most especially among that US public resident in US Coal Country.

And, it's far past time enough of us who actually do care about the future, and about the actual people, of this nation, enough of us who care, perhaps most especially, about the Truth, found some way to get together, and to start asking questions about it all in one, unified, and much louder, voice; a voice too loud to be, as it has been - - by our Coal Country public press at least - - so far ignored.


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