|Shell Oil Coal Conversion Residues to Construction Aggregates|
|Sunday - July 29, 2012|
United States Patent: 4917732
We have a number of times documented, that, in addition to being able to convert the solid byproducts arising from our essential use of Coal in the generation of genuinely economical electric power into additives or substitutes for Portland Cement and Portland Cement Concrete, as seen, for one example, in:
Pittsburgh Converts Coal Ash and Flue Gas into Cement | Research & Development; concerning: "United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste; 1998; Assignee: Dravo Lime Company, Pittsburgh; Abstract: Cement is produced (from) a moist mixture of a flue gas desulfurization process waste product (and) aluminum, iron, silica and carbon ... wherein said source of aluminum and iron comprises fly ash";
we can also convert our Coal Ash into structural aggregates: replacements, in essence, for the sand and gravel which are ordinarily added to Concrete mixtures to enhance both handling characteristics and the final strength of the cured composite.
Examples of our reportage on that issue can be accessed, for two examples, via:
Consol Converts Coal Ash to Concrete Aggregate | Research & Development; concerning: "United States Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates; 1994; Assignee: Consolidation Coal Company, Pittsburgh; Abstract: A process for making high-strength aggregates including hydrating calcium oxide containing coal combustion ash ... . Method of producing high-strength aggregates from calcium oxide (CaO) containing coal combustion ash"; and:
West Virginia Coal Association | Wyoming Converts Coal Ash to Construction Aggregates | Research & Development; concerning: "United States Patent 6,334,895 - Producing Manufactured Materials from Coal Combustion Ash; 2002; Assignee: The University of Wyoming Research Corporation, Laramie; Abstract: This invention discloses a system for cold bond processing of combustion ash which enhances various characteristics of the resulting cured consolidated combustion ash materials. Specifically, the invention relates to processing techniques which enhances both density and strength of the of the consolidated combustion ash materials. The invention also relates to processing techniques which control various chemical reactions which assure that certain types of minerals are formed in the proper amounts which results in a cured consolidated combustion ash material which has greater dimensional stability and enhanced resistance to degradation. Embodiments for both normal weight and light weight combustion ash aggregates are disclosed which meet various ASTM and AASHTO specifications".
And, since the inorganic mineral residues left behind by our conversion of Coal into more versatile liquid and gaseous hydrocarbons will be, in essence, composed of the same compounds as Coal Fly Ash, it would stand to reason such Coal conversion residua could be utilized just like Coal power plant Fly Ash.
Indeed, as seen in:
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 by feeding residue solids containing carbonaceous material and ash constituents obtained from converting a carbonaceous feed material into liquids and/or gases into a cement-making zone and burning the carbon in the residue solids to supply at least a portion of the energy required to convert the solids into cement";
someone at least moderately credible in terms of mineral science and technology says that they can be.
And, herein, we see that another moderately-credible practitioner of chemical technologies says, that, in terms of synthesizing construction aggregates, as with Fly Ash in the above-cited processes of "United States Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates" and "United States Patent 6,334,895 - Producing Manufactured Materials from Coal Combustion Ash", the solid residua resulting from our conversion of Coal into hydrocarbon liquids and gases can be so utilized, as well.
Comment follows, and is inserted within, excerpts from the initial link in this dispatch to:
"United States Patent 4,917,732 - Flyash Treatment
(Should the initial link fail, try: Flyash treatment - Shell Oil Company.)
Date: April, 1990
Inventor: Daniel Baker, Texas
Assignee: Shell Oil Company, Houston
Abstract: A process for production of a flyash-slag composite is described in which, in one embodiment, slag particles are tumbled with an aqueous suspension of finely divided clay, flyash and a cementitious material are added, and the mixture is tumbled to produce the desired composite.
Claims: A process for producing a flyash-slag composite comprising discrete particles of slag dispersed in a solid mixture comprising
(a) tumbling slag particles with an aqueous suspension of finely divided clay, under conditions effective to provide aggregation, the ratio of slag to said clay, by weight, being from about 15 parts to about 40 parts slag per part of clay, and forming a mixture comprising aggregates of slag and clay in said suspension;
(b) adding flyash derived from the gasification of coal to said mixture while tumbling said mixture under said conditions, said flyash particles being added in a ratio of from about one part to about 5 parts flyash per part of slag, by weight, and forming a flyash-aggregate mixture;
(c) adding a finely divided cementitious material to said flyash-aggregate mixture while tumbling said flyash aggregate mixture, the ratio of cementitious material to flyash being from about 0.1 part to about 0.3 part cementitious material per part of flyash, by weight, and producing a flyash composite, the amount of water present in the suspension or added during tumbling, by weight, being sufficient to produce a ratio of water to the total solids tumbled of from about 0.1 to about 0.5.
A flyash-slag composite comprising discrete particles of slag dispersed in a solid mixture formed by tumbling, under aggregation conditions, slag, and aqueous suspension of a finely divided clay, flyash derived from the gasification of coal, and a cementitious material, the slag being present in an amount of from about fifteen percent to about forty percent, the flyash being present in an amount of from about fifty percent to about seventy-five percent, the clay being present in an amount of from one-half of one percent to about one percent, and the cementitious material being present in an amount of from about ten percent to about thirty percent, all by weight, based on the finished dry weight of the composite.
The process ... wherein the clay is bentonite clay.
(To be clear, Shell are talking about the mineral residua left by the preparation of a synthesis gas from Coal, as in our report of:
West Virginia Coal Association | Shell Oil Maximizes Carbon Use in Coal Gasification | Research & Development; concerning: "US Patent 4,969,931 - Process for the Preparation of Synthesis Gas; 1990; Assignee: Shell Oil Company; Abstract: A process for the preparation of synthesis gas by the partial combustion of an ash-containing fuel with an oxygen-containing gas is described, ... wherein the fuel is coal or lignite. In the gasification of an ash-containing fuel, synthesis gas is prepared by partially combusting the fuel with an oxygen-containing gas. The fuel used for this purpose can be coal, but lignite, peat, (and) wood ... are also suitable";
which synthesis gas is presumably intended for use in a process like that disclosed in our report of:
Shell Oil Coal to Gasoline with By-Product Isobutane | Research & Development; concerning: "United States Patent 4,218,388 - Preparing Hydrocarbons from Gasification of Coal; 1980; Assignee: Shell Oil Company;
Abstract: Synthesis gas is converted into gasoline by contacting the gas with a crystalline aluminosilicate zeolite catalyst".)
Background: Partial combustion or gasification of coalinvolves reacting the coal at elevated temperatures and possibly elevated pressures with a limited volume of oxygen, the reaction preferably being carried out in the presence of additional agents such as steam, carbon dioxide, or various other materials. Gasification of coal produces a gas, known as synthesis gas, that contains mostly carbon monoxide and hydrogen. Also produced are various liquid and solid materials, such as small particles of ash and carbon commonly known as flyash. This flyash, because it is derived from a "reducing " atmosphere, tends to be different in composition and properties from flyash normally associated with combustion boilers where a fully oxidizing atmosphere is utilized. For example, the flyash from processes for partial combustion of coal may contain elemental iron, sulfides, and deposited carbon, components not normally associated with boiler flyash. In general, the flyash entrained with the gas in partial combustion processes is usually removed from the raw synthesis gas by a combination of cyclones or separators, or a water scrubbing system employing washer coolers, venturi scrubbers, or filters or electrostatic precipitators, or combinations of these systems.
In at least one process for the gasification of coal to produce synthesis gas, significant quantities of unreacted impurity matter, variously referred to as char and/or slag, are also produced during combustion or oxidation in the gasification zone. This matter generally segregates in the bottom of the gasification zone, normally in a water bath. Upon separation of the char and/or slag (collectively referred to herein as slag) from the gasification zone, a further solids issue exists, since these materials have undesirable properties which limit options for their utilization or disposal.
The invention addresses the problem of flyash and slag treatment, accomplishing the treatment and providing a novel composition having properties indicating utilities of greater value than mere landfill.
(Please note, that, as in the above implied definitions, and, as in the Claims: "A process for producing a flyash-slag composite comprising discrete particles of slag dispersed in a solid mixture comprising:
(a) tumbling slag particles (and) (b) adding flyash derived from the gasification of coal", the required "slag" herein, in addition to the "flyash", is derived from the gasification of the Coal.)
Summary: Accordingly, the invention relates, in one embodiment, to a process whereby both flyash and slag are combined in a novel fashion to produce a composite which may be used in road construction. More particularly, the invention relates, in one scheme, to a process in which slag particles are tumbled with an aqueous suspension of finely divided clay ... . Flyash is added to the mixture while tumbling the mixture (and, a) cementitious material is then added to the flyash aggregate mixture while tumbling the flyash-aggregate mixture ... . In an alternate embodiment, the cementitious material may be added to the mixture along with or simultaneously with the flyash.
(As far as the "cementitious material" is concerned, we suggest that such as produced via the process disclosed in:
West Virginia Coal Association | US Government Coal Ash Cement Stronger than Portland Cement | Research & Development; concerning: "United States Patent 4,256,504 - Fly Ash-based Cement; 1981; Assignee: The United States of America (as represented by the Secretary of the Interior); Abstract: A cement composition comprising a high calcium-content fly ash and calcium sulfate";
might be appropriate.)
In another embodiment, the invention relates to a particulate flyash-slag composite comprising discrete particles of slag dispersed in a solid mixture formed by tumbling, under aggregation conditions, slag, and aqueous suspension of a finely divided clay, flyash, and a cementitious material, the slag being present in an amount of from about 15 percent to about 40 percent, the flyash being present in an amount of from about 50 percent to about 75 percent, the clay being present in an amount of from about 0.5 percent to about 1 percent, and the cementitious material being present in an amount of from about 10 percent to about 30 percent, all by weight, based on the finished dry weight of the composite."
And, the "composite" is actually an aggregate which can be utilized in place of mined gravel and stone in the formulation of structural concrete. We'll presume that, as in other of our reports, which we won't cite since more, similar, are forthcoming, the Coal Ash and Slag "composite" can be sized by either a preliminary "pelletizing" or subsequent crushing, as described in our report of:
West Virginia Coal Association | Massachusetts Fly Ash Cement & Fly Ash Concrete Aggregate | Research & Development; concerning, in part: "United States Patent 4,336,069 - High Strength Aggregate for Concrete; 1982; Abstract: Concretes containing a hydratable cementitious binder such as Portland cement are described. The high strength aggregate material is produced from hydrated cementitious compositions which contain relatively low proportions of Portland cement and relatively high proportions of a select fly ash component. The hydrated aggregate product may then be reduced in size (e.g. by crushing) and screened prior to combination with the cementitious binder to produce concrete compositions".
This is, in fact, a technology complementary to those which disclose similar and related processes for the use of solid Coal-use residua that result from the combustion of Coal in the generation of truly economical electrical power, the only difference really being that the source of the Coal Ash and Slag is the gasification of Coal for the generation of, via an intermediate synthesis gas, liquid and gaseous hydrocarbons.
Nonetheless, we would imagine such Coal conversion residua to fall under the auspices of proposed legislation, such as:
West Virginia Coal Association | WV Senators Rockefeller and Manchin Support Coal Ash Reuse | Research & Development; concerning: "S1751; Coal Residuals Reuse and Management Act; (Sponsors: Jay Rockefeller, Joe Manchin, et. al.); Summary: 10/20/2011--Introduced.Coal Residuals Reuse and Management Act - Amends the Solid Waste Disposal Act to authorize states to implement coal combustion residuals permit programs. Requires each state governor to notify the Administrator of the Environmental Protection Agency (EPA) within six months about whether such state will implement such a program. Prohibits this Act from being construed to alter the EPA's regulatory determination, entitled "Notice of Regulatory Determination on Wastes from the Combustion of Fossil Fuels," that "the fossil fuel combustion wastes addressed in that determination do not warrant regulation under such Act";
which would prevent them from being regulated as some sort of "hazardous" waste by the US EPA, which regulation, if not forestalled, would, in turn, critically impair our ability to use such Coal conversion residua for such practical, and environmentally beneficial, applications as that described by our subject herein, "United States Patent 4,917,732 - Flyash Treatment", wherein, again, the "Flyash" is that which results from the "gasification of coal ... in the presence of additional agents such as steam (and) carbon dioxide", a process which "produces a gas, known as synthesis gas", suitable, as in our above citation of Shell Oil Company's own "United States Patent 4,218,388 - Preparing Hydrocarbons from Gasification of Coal; 1980; Assignee: Shell Oil Company; Abstract: Synthesis gas is converted into gasoline", for catalytic condensation into, well, Gasoline.