We've touched several times on the utilization, after some initial processing, of Coal combustion Ash as an aggregate, both for use as loose or compacted fill in general construction and as a component of structural materials, most especially concerning it's use as a substitute for at least some of the sand and gravel in concrete.
Fly Ash that has been cleaned of residual Carbon and crushed or sieved to size can, as we've documented, be added to cement, in place of at least some of the more typical sand, and even in place of some of the cement itself, as one component of concrete, a technique which, as seen in our report of:
Coal Ash Can Reduce Construction Costs | Research & Development; concerning: "United States Patent 5,624,491 - Compressive Strength of Concrete and Mortar Containing Fly Ash; 1997; Assignee: New Jersey Institute of Technology; The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. (Such) concrete and mortar containing about 15% to 25% fly ash as a replacement for cement ... can ... significantly reduce construction costs";
can lead to greater economies in concrete construction, aside from avoiding disposal costs for the Ash.
And, as seen in our report of:
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 for a sufficient period of time to convert a high percentage of the calcium oxide to calcium hydroxide prior to forming the aggregates and curing the aggregates in high humidity. The moisture of the hydrated material is monitored to vary the hydration moisture to the desired set point. Further, the process involves producing high-strength aggregates from calcium hydroxide containing FGD ashes such as generated from duct sorbent injection and spray dryer processes";
our Coal Fly Ash can even be combined with Flue Gas Desulfurization (FGD) wastes to make a larger-size and higher-strength aggregate, a replacement for crushed rock and gravel, for use in structural concrete.
We'll have more to offer on Consol's Fly Ash utilization technologies in future reports.
However, herein, we treat a related technology developed by a scientist working at the University of Wyoming, a technology similar to the above Consol invention, but one that it is centered on transforming Coal Ash into a, perhaps, lower-strength construction aggregate: an aggregate which still meets accepted standards for specific applications, but, which can be produced from Coal combustion wastes in a more economical, lower-energy process.
The technology is concerned not, as is the Consol process, with making a construction aggregate from Coal Ash that is noted for "high-strength", for use in higher-performance needs applications, but, one that meets appropriate specifications for specific end uses in what are, perhaps, larger-volume and general-usage applications for aggregate that would otherwise consume crushed stone, or similar material.
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 6,334,895 - Producing Manufactured Materials from Coal Combustion Ash
Date: January, 2002
Inventor: Alan Bland, Wyoming
Assignee: The University of Wyoming Research Corporation, Laramie
(Recall that we have previously cited the University of Wyoming, and their notable contributions to Coal utilization technology, as, for one example, in our report of:
Wyoming 1970 Coal + H20 = Hydrocarbons | Research & Development; concerning: "United States Patent 3,505,204 - Direct Conversion of Carbonaceous Material to Hydrocarbons; 1970; The University of Wyoming, Laramie; Coal (is) converted directly to hydrocarbons ... by reacting (it) with steam (and, the) condensed hydrocarbon liquid (generated by the process) may be further refined according to conventional refinery procedures to yield gasoline and diesel fuels".)
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.
(AASHTO - AASHTO Home - Organization; "AASHTO (American Association of State Highway and Transportation Officials) is a nonprofit, nonpartisan association representing highway and transportation departments in the 50 states, the District of Columbia, and Puerto Rico. AASHTO is an international leader in setting technical standards for all phases of highway system development. Standards are issued for design, construction of highways and bridges, materials, and many other technical are (and) is guided by a Board of Directors made up of the chief transportation officers from the 50 states, the District of Columbia, and Puerto Rico. AASHTO's policy development, standards setting, and technical activities are the product of volunteer state department of transportation personnel who work through the AASHTO committee structure. The committees collaborate throughout the year and ... address virtually every element of planning, designing, constructing, and maintaining transportation services.")
Claims: A combustion ash composition, comprising: an amount of combustion ash having a weight; and an amount of water mixed with said combustion ash, wherein said amount of water has a weight of about 10% to about 40% relative to said combustion ash; and, a reduced average pore volume achieved when said combustion ash and said water are mixed, wherein said reduced average pore volume comprises about 15% to about 40% of said combustion ash composition volume.
A composition made from combustion ash ... wherein said combustion ash is selected from the group consisting of fluidized bed combustion ash, pressurized fluidized bed combustion ash, Class C ash, off specification Class C ash, Class F (ash), off specification Class F ash, Spray drier ash, sorbent injection ashes, and incinerator ash.
A combustion ash composition ... further comprising a strength additive, wherein said combustion ash comprises Class F, and wherein said strength additive is selected from the group consisting of Portland Cement, Class C ash, lime, and self cementing ash.
(Note, as explained, for one instance, in our earlier report of:
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;
Abstract: A cement composition comprising a high calcium-content fly ash and calcium sulfate, and mortar and concrete compositions containing the cement. A combustion ash composition ... comprising a strength additive (and) said strength additive is ... Class C ash ... and self cementing ash";
some Coal Ash has cementitious properties of it's own, and, thus, without much, if any, processing, can, as "self cementing ash", substitute directly for some of the Portland cement.)
A combustion ash composition, comprising: an amount of combustion ash; an amount of water combined with said combustion ash, wherein said amount of water has a weight of about 10% to about 40% relative to said combustion ash.
(The full discussion of Claims goes on to explain how the density of the cured product can be controlled to a certain extent by the addition of other chemicals and compounds to the mix, which, as desired, can fill available pore space with crystallized minerals or Carbon Dioxide. The CO2 is generated through chemical reactions in the mix, and, though the CO2 would be forever "sequestered" in the final cement product, it is not added from outside the process itself.)
A combustion ash composition ... wherein said amount of water (utilized) is selected from the group of waste waters consisting of ... coal pile runoff (and) industrial waste waters ... .
(The potential thus exists to "sequester" other pollutants in this Coal Ash utilization process.)
A combustion ash composition ... wherein said cured combustion ash composition meets ASTM specifications for normal weight aggregate for road base (and, a) combustion ash composition ... wherein said cured combustion ash composition meets ASTM specifications for light weight aggregate for concrete.
(So, this final product can be designed to serve both as a loose, but compacted, "road base" and as an aggregate in concrete. The "ASTM", by the way, is the American Society for Testing and Materials, another respected and universally accepted technical standards-setting organization.)
The invention discloses basic ideas and concepts ... relating to cured consolidation materials from cold bonding processes (and) provides apparatus and methods for the processing, consolidation and curing of combustion ash to form novel materials, as well as, for the improvement of various characteristics relating to cured combustion ash materials processed by existing technology.
(The full Claims and Description sections provide quite a lot of enlightening detail concerning how evolved and advanced the science and technology for utilizing Coal combustion waste surprisingly is. The University of Wyoming's discussion is thoroughly documented; and, you can check their references out for yourself; or, be patient, and you will certainly be getting fuller expositions of many of them, eventually, from us.)
Summary: Accordingly, it is the broad object of the present invention to provide a system for the production of cured consolidated combustion ash materials from cold bonding processes having novel or enhanced characteristics. One specific goal in this respect is to provide both methods and apparatus for a combustion ash cold bonding process to produce standardized normal weight aggregate for use in road base; for use in concrete having structural, masonry and insulation applications, and for use in light weight aggregate applications.
A second broad objective of the invention is to provide technology which may improve previously disclosed or presently used processes for cold bonding combustion ash. Such technology, may improve the products of existing technologies so as to be more readily accepted in existing markets, or may allow the improved products to be introduced into new markets, or simply make the existing technologies more economical.
A specific objective of the invention is to control the amount of expansion of combustion ashes which contain high levels of oxide when the combustion ash is combined with water. Controlling the molar volume expansion of oxides may decrease the linear expansion and improve the unconfined compressive strength of cured consolidated combustion ash materials. For certain applications, the hydrated combustion ash material may be intentionally designed to expand to fill a specific volume.
Another specific objective of the invention is to control the potential for the formation of minerals, such as enttringite and gypsum, in cured consolidated combustion ash materials. Controlling the potential for formation of such minerals and in turn the amount of deposition of such minerals in the pore volume of consolidated or cured combustion ash materials may allow manufacturers to predetermine and select certain attributes of the cured consolidated combustion ash material to meet certain specifications, or the requirements of various markets.
Another specific objective of the invention is to assess and control the manner of combining various types combustion ash with water and other additives. By controlling the manner of combining the combustion ash with water, various characteristics of the cured consolidated combustion ash product may be adjusted. A significant goal in this respect is to broaden the achievable range for some characteristics. Specifically this may allow for cured consolidated combustion ash materials having increased density and unconfined compressive strength, as well as decreased linear expansion.
Similarly, another goal is to allow for the use of a wider variety of combustion ashes in the production normal weight and lightweight aggregates.
Another specific objective of the invention is to increase the strength of cured consolidated combustion ash material so as to compensate for the decrease in strength attributed to the incorporation of light weight filler materials. .
Yet another objective of the invention is to disclose apparatus and methods which allow for the use of or improvement in the processing of a wide variety of combustion ashes, examples include, fly ash which resulting from the combustion of fossil fuels which is entrained in flue gases and is then collected; bottom ash resulting from the combustion of fossil fuels that does not become entrained in the flue gases and is removed from the bottom of the combustor; bed ash resulting from the combustion of FBC, CFBC, or PFBC combustion of fossil fuel; Class C ash resulting from the combustion of low ranked coals, such as lignites and subbituminous coals; Class F ash resulting from the combustion of bituminous and anthracite coal ... .
Still another objective of the invention is to make use of a variety of waste waters such as coal pile runoff produced by rain percolating through or running off coal piles which are required to be treated before discharge; cooling tower blowdown produced at power plants as a result of being associated with cooling towers and which must be treated prior to discharge."
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And, believe it or not, there is still quite a lot more to it.
In sum, though, it all reflects that a great deal of knowledge exists, at the University of Wyoming and elsewhere, which makes possible the practical and, in the case of our subject herein, "United States Patent 6,334,895 - Producing Manufactured Materials from Coal Combustion Ash", efficient conversion of Coal Ash into commodity products; products with desirable physical performance and economic characteristics, for specific, and high volume, construction applications.
As with the very real potentials that exist for converting our abundant Coal into anything we now allow ourselves to be extorted by OPEC for the supply of, and for recycling our unjustly-maligned Carbon Dioxide into a range of hydrocarbon chemicals, we, those of us resident in United States Coal Country, need to wise up to the fact that a wealth of opportunity surrounds us, opportunity that, as in the case herein of Coal Ash, lies, almost literally, at our feet.