Over the past several years, we've many times referenced and documented the development of an extraordinary body of Carbon conversion technology by New York's former Texaco, Incorporated, before they, and their familiar and famous red star, in 2001, got homogenized into the more ambiguous, regimental red and blue blazes of Chevron.
Our most recent report concerning Texaco and their Carbon conversion expertise is accessible via:
Texaco Prepares Coal for Gasification and Conversion | Research & Development.
And, note that we do prefer to think of Texaco's extensive portfolio of fuel conversion technology more in terms of "Carbon conversion" than of just "Coal conversion", since they did focus a great deal of attention on developing ways to utilize and convert a wide variety of Carbon resources, in addition to Coal, into more desirable hydrocarbons.
An example of our reportage concerning those efforts can be seen via:
Texaco Makes Methane from Coal & "Stuff" | Research & Development; which concerns itself with how Coal and other Carbon resources can be converted, via an initial gasification, primarily into Methane, and includes separate reportage of several United States Patents issued to Texaco, including:
"United States Patent 3,671,209 - Garbage Disposal Process; 1972; Texaco Development Corporation;
Abstract: Garbage and other inorganic and organic solid waste matter ... are converted into a stream of synthesis gas ... . The invention relates to a novel process for disposing of garbage without polluting the nation's environment while producing synthesis gas and valuable by-products"; and:
"United States Patent 3,888,043 - Production of Methane; 1975; Texaco Incorporated; Abstract: Continuous process for the production of a gaseous stream comprising at least 90 mole % of methane (dry basis) from a sulfur containing hydrocarbonaceous fuel without polluting the environment ... . The process ... wherein said hydrocarbonaceous fuel is pump-able slurry of solid carbonaceous fuels selected from the group consisting of coal (and) concentrated sewer sludge in a vaporizable carrier such as water".
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We find such technologies especially intriguing since, due to current economies of scale, reduction of them to commercial industrial practice would require that they be found primarily on the use of Coal as the base raw material; but, such use of Coal would then enable, through Texaco's inclusive Carbon conversion technologies, the utilization, the "recycling", of other, renewable and sustainable Carbon resources that might otherwise be considered and treated as wastes, and which would entail some expense for disposal.
We insist that such avoided, perhaps mandated, costs of disposal must be included in any calculation of the true product cost for hydrocarbons made by the conversion of Coal along with any co-fed organic wastes.
Again, Texaco's developed and formalized body of knowledge concerning such Carbon conversion technologies is nearly vast, and doing real justice to their exposition would require a textbook so thick that all but the most obsessive students of Carbon conversion art would be discouraged from cracking it open in the first place.
But, herein, we present a selection of US Patents that chronicle Texaco's ongoing, almost step-wise and methodical, improvement of that technology, as their work continued in the decades following issuance of
United States Patents "3,671,209" and "3,888,043", just prior to Texaco's acquisition by Chevron.
Comment, and additional links, including a few that should help to expand your understanding of the great environmental good that Texaco's Coal-based Carbon conversion technologies would bring to us, follows abbreviated excerpts from the initial link in this dispatch to:
"United States Patent 4,983,296 - Partial Oxidation of Sewage Sludge
Date: January, 1991
Inventors: Matthew McMahon, et. al., NY
Assignee: Texaco Inc., NY
Abstract: Municipal sanitary sewage sludge is disposed of by an improved partial oxidation process without polluting the environment. Aqueous slurries of sewage sludge are upgraded by hydrothermal treatment, preferably while being sheared, concentrated, and then mixed with a supplemental fuel, preferably coal.
(Keep the final word of that statement in mind throughout your reading of this dispatch. Texaco does try to obfuscate the fact in their later embodiments of this technology, for recycling and converting into products of high value what is otherwise just noxious waste; but, there is only one thing that makes it work: Coal.)
A pumpable aqueous slurry of sewage sludge-coal ... is ... produced having a greater total solids and heat content (HHV) as well as containing an increased amount of sewage sludge for reacting with oxygen containing gas in a free-flow partial oxidation gas generator. Hot quench water or steam produced by cooling the hot raw effluent stream of synthesis gas, reducing gas or fuel gas from the gasifier may provide heat for the hydrothermal step.
(And, thus, as in many similar technologies, the potential exists for the recycling of heat energy, with resultant economies.)
Claims: A process for the partial oxidation of sewage sludge (by) heating a concentrated aqueous slurry of sewage sludge obtained from sewage and ... mixing the pumpable aqueous slurry of sewage sludge produced ... with a supplemental solid fuel comprising particles of coal (and) reacting said pumpable aqueous sewage sludge-coal (slurry) in the reaction zone of a partial oxidation gas generator at (specified conditions of temperature and pressure) in the presence of a free-oxygen containing gas, thereby producing a hot raw effluent stream of synthesis gas."
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We'll abbreviate our excerpts there, since we have a lot of ground to cover. But, for the negativists and sticklers in our crowd, since we closed with the words "synthesis gas", we refer you to:
Syngas as fuel - What is syngas - Synthesis gas: "Syngas is the direct end-product of the gasification process (and is) suited for use in producing transportation fuels and other chemical products. As its unabbreviated name implies, Synthesis gas is mainly used as an intermediary building block for the final production (synthesis) of various fuels such as synthetic natural gas, methanol and ... synthesized gasoline and diesel fuel".
That said, Texaco's commendable Carbon conversion efforts were obviously a priority within their organization, since a different core team of Texaco scientists, not that long after issuance of the above United States Patent 4,983,296, were rewarded with:
"United States Patent: 5188739 - Disposal of Sewage Sludge
Date: February, 1993
Inventors: Motasimur Khan, et. al., NY
Assignee: Texaco Inc., NY
Abstract: A process for disposing of sanitary sewage sludge by producing a pumpable slurry of sewage sludge and solid carbonaceous fuel e.g. coal, ... rubber. The slurry is burned as a fuel in a partial oxidation gas generator, furnace, or boiler. In the process, an aqueous slurry of sewage sludge is concentrated by removing water by means of a conventional belt filter press or presses. The dewatered slurry of sewage sludge is hydrothermally treated and cooled and depressurized. The viscosity of the slurry of sewage sludge is reduced to less than about 2000 centipoise by shearing. The sheared sewage sludge is then ground together with a solid carbonaceous fuel to produce a pumpable slurry which is burned with a free-oxygen containing gas in a partial oxidation gasifier, furnace, boiler, or incinerator to produce a hot raw effluent gas stream. In a preferred embodiment, the effluent gas stream is cleaned and purified and non-contaminating ash and slag are separated. By this process, noxious sewage sludge may be disposed of without contaminating the environment. By-product synthesis gas, reducing gas, or fuel gas may be produced.
(Note: The full Disclosure is of extraordinary length, and proposes, through it's many Claims, multiple fuel uses for the Sludge-Coal slurry. We abbreviate our excerpts in the extreme to focus on the potentials of most current interest to us. The other fuel potentials, however, especially given the Carbon-recycling and Coal-conserving nature of the technology, are very worthy of further consideration.)
Claims: (Grinding) together the sheared sewage sludge (as described) with a solid carbonaceous fuel in a grinding means thereby producing a pumpable slurry of sewage sludge and solid carbonaceous fuel having a solids content in the range of about 45 to 70 weight %, a weight ratio in the range of about 3-7 parts by weight of sewage sludge to 3-7 parts by weight of solid carbonaceous fuel and a viscosity of less than about 2000 centipoise when measured at about 180 F; and:
introducing said pumpable slurry of sewage sludge and solid carbonaceous fuel ... into the reaction zone of a partial oxidation gas generator by way of one passage of a multi-passage burner while simultaneously passing through at least one other passage of said burner a stream of free-oxygen containing gas; and:
reacting said materials in said partial oxidation reaction zone ... at a temperature in the range of about 1800F to 3500F and at a pressure in the range of about 1-300 atmospheres to produce a hot raw effluent gas stream comprising at least one of the following: synthesis gas, reducing gas and fuel gas."
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We'll be abbreviating our excerpts from additional references even further, and we wanted to interrupt here to point out a few things.
First, should it not occur to anyone, the "sewage sludge" that seems the focus of these Texaco technologies, as it can be co-processed with Coal, is a relatively minor resource.
Think about it: Do any of you, as individuals, generate enough "sludge", on any given day, to, even if it were all converted into gasoline, get you back and forth to your nearest grocery store, so that you could get the raw materials you need to begin producing more sludge?
Likely not. And, except for larger cities and their immediate environs, where modern sewer systems have been installed and consolidated, the collection and subsequent transport of enough sludge to a Coal-based conversion facility to be meaningful might not be a money-making proposition on a straightforward basis.
However, what these technologies speak to in the larger scheme of things, as Texaco does specify once or twice throughout all of it, is the co-conversion, with Coal, of "bio-solids", which generic label can apply not only to Sewage Sludge, but to a lot of other, renewable and Carbon-recycling, resources, as well.
And, in addition to Carbon recycling, there are even other potentials. As we emphasize following citations of:
United States Patent: 5188740 - Pumpable Fuel Slurry of Sewage Sludge and ... Solid Carbonaceous Fuel
Date: February, 1993
Inventor: Motasimur Khan, NY
Assignee: Texaco Inc., NY
Abstract: A process for disposing of sanitary sewage sludge by producing a pumpable slurry of sewage sludge and low grade solid carbonaceous fuel and burning said slurry as fuel in a partial oxidation gas generator, furnace, or boiler. The aqueous slurry of sewage sludge is concentrated (and, then mixed with) particles of low grade solid carbonaceous fuel e.g. lignitic coal, peat, wood and cellulose-containing materials are mixed with the slurry of sewage sludge.
(Note the increased potentials for Carbon recycling, since "wood and cellulose-containing materials" can be added to the blend of Sewer Sludge and Coal. It is those potentials, in part, that make, we think, the collection and transport, within reason, of Sludge to a Coal conversion facility worth considering.)
The dewatered slurry of sewage sludge and low grade solid carbonaceous fuel is (further) treated (and, then)
burned with a free-oxygen containing gas in a partial oxidation gasifier ... to produce a hot raw effluent gas stream. In a preferred embodiment, the effluent gas stream is cleaned and purified and non-contaminating ash and slag are separated. By this process, noxious sewage sludge may be disposed of without contaminating the environment. By-product synthesis gas, reducing gas, or fuel gas may be produced."
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Note mention, again, of by-product "non-contaminating ash and slag" being "separated"; a fact we address again a little further on.
And, just a few months later, even additional refinements in the art were confirmed as viable by our United States Government, as documented by:
"United States Patent: 5211723 - Process for Reacting Pumpable High Solids Sewage Sludge Slurry
Date: May, 1993
Inventor: Motasimir Khan, NY
Assignee: Texaco, Inc., NY
Abstract: This invention relates to a novel pumpable sewage sludge fuel and process for burning it. An aqueous slurry of sewage sludge is dewatered and dried to a solids content in the range of about 50 to 99 weight % in a drying zone in the absence of free-oxygen containing gas but while in contact with a gaseous material selected from the group consisting of N2, CO2, H2, CO, and mixtures thereof.
(We won't insert another link, but, we assure you: the gaseous blend of "N2, CO2, H2, CO, and mixtures thereof", which is used to pre-treat the Sludge, is precisely what would be produced by a Coal gasifier utilizing inexpensive Air to effect the partial oxidation of the Coal, and any other organic compounds blended with it. This is an example of internal energy recycling, with further implications for economy.)
The dried sewage sludge is mixed with a supplementary fuel from the group consisting of solid carbonaceous fuel, liquid hydrocarbonaceous fuel, mixtures thereof, and optionally with water to produce a pumpable slurry fuel feedstream having a solids content in the range of about 50 to 65 weight.% and a higher heating value of at least about 6,000 Btu/lb. The slurry fuel feedstream may be burned in a partial oxidation gasifier ... ."
(Again, we shouldn't have any trouble figuring out what they mean by "solid carbonaceous fuel". Furthermore, since they specify a "liquid hydrocarbonaceous fuel" as one component of the slurry, keep in mind that our above-cited earlier report:
Texaco Prepares Coal for Gasification and Conversion | Research & Development; which contains separate information concerning: "United States Patent 4,623,359 - Aqueous Slurries of Carbonaceous Fuel; 1986; Assignee: Texaco, Inc.; Abstract: Aqueous slurries of solid carbonaceous fuel that include a ... coal derived creosote oil"; and, for anpother. a for reducing the viscosity and increasing the solids content of the aqueous slurry";
and, others, such as:
Texaco 1954 Coal + Coal Oil + H2O = Syngas | Research & Development; concerning: "United States Patent 2,669,509 - Gasifying Carbonaceous Solids; 1954; Assignee: Texaco Development Corporation; Abstract: This invention relates to a process for the gasification of ... coal ...for the synthesis of hydrocarbons via the Fischer-Tropsch synthesis";
clearly identify perfectly acceptable "liquid hydrocarbonaceous fuel"s to be such materials as "coal derived creosote oil" and other primary Coal tars that can be condensed from Coke oven gases.)
Claims: A process for burning sanitary sewage sludge comprising: mixing (up to) 7 parts by weight ... dried sewage sludge ... with about (up) to 7 parts by weight of at least one supplementary fuel from the group consisting of solid carbonaceous fuel, liquid hydrocarbonaceous fuel, mixtures thereof, and with or without water to produce a pumpable slurry fuel ... burning said pumpable slurry ... in a partial oxidation gasifier (as specified) to produce an effluent gas stream of synthesis gas.
In a preferred embodiment to avoid contaminating the environment, the effluent gas stream is cleaned and purified and non-contaminating fly-ash and slag are separated from the stream of gases."
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Note, first, the above mention of "non-contaminating fly ash and slag", which Texaco specifies as being produced as a by-product, and which we will address just a little further on.
And, further note that the whole process is conducted "to produce ... synthesis gas", which can then, of course, be catalytically condensed by a number of long-known technologies, such as the venerable and almost generic Fischer-Tropsch synthesis, and be converted thereby into liquid hydrocarbons.
In any case, Texaco's commendable efforts to improve the conversion of a potentially hazardous waste into something now almost desperately needed were detailed and thorough, and they were simultaneously awarded:
"United States Patent: 5211724 - Partial Oxidation of Sewage Sludge
Date: May, 1993
Inventors: Motasimir Khan, et. al., NY
Assignee: Texaco, Inc., NY
Abstract: An improved process for the low-cost disposal of noxious sewage sludge in a safe way without polluting the environment.
In the process, sewage sludge ... is concentrated (and) mixed with a supplemental fuel e.g., liquid hydrocarbonaceous and/or solid carbonaceous fuel to produce a pumpable fuel slurry ... . The fuel slurry may be reacted by partial oxidation in a conventional gasifier to produce synthesis gas and/or fuel gas.
The thermal energy in hot byproduct steam and flue gas streams are used to heat the dewatered sewage sludge
(Note, as in other Coal gasification and conversion technologies we have documented for you, the above potentials for economy by the internal recycling and use of heat generated by some process steps.)
Summary: Sanitary sewage sludge is disposed of by the process of the subject invention without polluting the nation's environment. In this process, highly dewatered sewage sludge is produced by pressing and is then heat treated, flash evaporated, mixed with supplemental fuel, and reacted in a partial oxidation gas generator along with free-oxygen containing gas and a temperature moderator. A hot raw effluent gas stream comprising at least one of the following is produced: synthesis gas, reducing gas and fuel gas.
Noxious sewage sludge is safely disposed of by the subject process without polluting the nation's environment. In addition, at least one useful nonpolluting gas from the group consisting of: synthesis gas, reducing gas and fuel gas is produced along with by-product steam and hot water. Non-contaminating ash and slag are separated from the gas stream. The ash and slag may be used for road bed fill and for making cement blocks."
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Concerning the use of "ash" resulting from the use or conversion of any Carbon resource, especially in the making of "cement blocks", please see:
Exxon Converts Coal Conversion Residues to Cement | Research & Development; concerning: "United States Patent 4,260,421 - Cement Production from Coal Conversion Residues; 1981; Assignee: Exxon Research and Engineering Company; Abstract: Cement is produced (from) residue solids ... and ash constituents obtained from converting a carbonaceous feed material into liquids and/or gases".
We'll have a little more to offer on that in reports to follow, but, shortly after the above US Patent was issued, our earlier-cited team of Texaco scientists returned to the scene with:
"United States Patent: 5230211 - Partial Oxidation of Sewage Sludge
Date: July, 1993
Inventors: Matthew McMahon, et. al., NY, TX and CA
Assignee: Texaco Incorporated, NY
Abstract: An improved process for the low-cost disposal of noxious municipal sewage sludge in a safe way without polluting the environment. In the process, a portion of a stream of dewatered sewage sludge having a solids content in the range of about 17 to 40 weight percent is dried to produce dried sewage sludge having a solids content in the range of about 75 to 99 weight percent. The dried sewage sludge is ground to a small particle size. A pumpable aqueous feed slurry having a solids content in the range of about 45 to 70 weight percent is produced comprising (a) solid carbonaceous fuel, (b) ground dried sewage sludge, and (c) sheared and/or unsheared dewatered sewage sludge.
The aqueous feed slurry is gasified in a free-flow partial oxidation gas generator.
Synthesis gas, reducing gas or fuel gas is produced
Ash and slag are separated from the gas stream and safely disposed.
Waste heat produced in the process may be used to dry the sewage sludge.
Claims: A process for the partial oxidation of sewage sludge and the production of clean synthesis gas, fuel gas, and electrical power without polluting the nation's atmosphere ... .
Background and Field: This invention relates to a partial oxidation process for disposing of biological sewage sludge without polluting the nation's environment.
With landfills closing, ocean dumping being curtailed, and high-technology incinerators becoming unpopular in many areas, communities are finding that it is getting increasingly more difficult and expensive to dispose of their sewage sludge. The term "raw municipal sewage" as used herein may be broadly defined as "water-carried wastes", particularly from municipal sanitary sewage lines containing body wastes (excreta), household wastes, community waste such as street washings, etc., and some industrial wastes.
The solids in sewage are mostly animal or vegetable substances, "organic matter," i.e. fats, carbohydrates, and proteins. Some mineral or inorganic constituents present include sand and clay, as well as the common mineral salts found in the water supply
Sewage sludge is obtained from raw sewage and may contain a number of pathogens known to be health hazards to humans. Almost any type of organism can be found in sewage including bacteria, protozoa, spores and cysts.
(The heat of Coal gasification will safely dispose of those nasty bugs, it should go without saying)
Sanitary sewage sludge is disposed of by the process of the subject invention without polluting the nation's environment. In this process, dried ground sewage sludge ... is mixed with dewatered sewage sludge ... and a solid carbonaceous fuel selected from the group consisting of coal ... to produce a pumpable aqueous slurry comprising sewage sludge and solid carbonaceous fuel.
The aqueous slurry of sewage sludge and solid carbonaceous fuel is reacted with a free oxygen-containing gas by partial oxidation in a free-flow non-catalytic gas generator. Noxious sewage sludge is safely disposed of by the subject process without polluting the nation's environment. In addition, useful nonpolluting synthesis gas, reducing gas, or fuel gas is produced along with by-product steam and hot water."
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Coal, thus, enables the recycling of a "noxious", and otherwise hazardous Carbon resource in the production of a "synthesis gas" which would be suitable for catalytic condensation into hydrocarbon fuels.
Moreover, as in Texaco's "United States Patent 5,188,740", far above in this dispatch, the Carbon-recycling potentials are extended even further by the admission that, in addition to Sewage Sludge, "wood and cellulose-containing" materials can be blended into the slurry with Coal, and gasified along with the Coal and the Sewage Sludge to form a hydrocarbon "synthesis gas".
And, since, as seen in:
Texaco 1951 Coal + CO2 + H2O + O2 = Syngas | Research & Development; concerning: "United States Patent 2,558,746 - Carbon Monoxide and Other Gases from Carbonaceous Materials; 1951; Assignee: The Texas Company, NYC; This invention relates to a process and apparatus for the generation of gases comprising carbon monoxide from carbonaceous materials. In one of its more specific aspects it relates to a process and apparatus for the generation of a mixture of carbon monoxide and hydrogen, suitable as a feed for the synthesis of hydrocarbons, from powdered coal (wherein) carbon dioxide, ... in contact with hot carbon, in turn, reacts with the carbon to produce carbon monoxide";
Carbon Dioxide can be converted into the valuable Carbon Monoxide in such Coal and organic waste gasification reactions and processes, the true potentials for Carbon Dioxide and hazardous waste recycling, in the manufacture of hydrocarbon fuels, through the fuller utilization of our abundant Coal, as in these Texaco Coal gasification technologies, could well lead not only to a greater economic prosperity for the United States of America, but a prosperity that entails as intrinsic elements a cleaner environment and a measure of sustainability.
And, all of that starts with only one thing: Coal.