United States Patent Application: 0120216715
We've documented many times that Coal Ash can be added to Portland-type Cement, PC, as a reactive substitute for some of the sand and gravel aggregate traditionally used, with the result being Portland-type Cement Concrete, PCC, that is both stronger and more resistant to chemical attack and deterioration than conventional PCC.
As seen, for one example, in our report of:
West Virginia Coal Association | Coal Ash Concrete More Durable, Resists Chemical Attack | Research & Development; concerning: "United States Patent 5,772,752 - Sulfate and Acid Resistant Concrete and Mortar; 1998; Assignee: New Jersey Institute of Technology; Abstract: The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction and other applications, which hardenable mixtures demonstrate significant levels of acid and sulfate resistance".
That, of course, is in addition to the use of Coal Ash in the making of "PC" itself, as seen in:
West Virginia Coal Association | 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 by forming a moist mixture of a flue gas desulfurization process waste product containing 80-95 percent by weight calcium sulfite hemihydrate and 5-20 percent by weight calcium sulfate hemihydrate, aluminum, iron, silica and carbon (and) wherein said source of aluminum and iron comprises fly ash".
As we've discussed in a number of reports, some mandated pollution controls, using technologies like that seen in our report of:
West Virginia Coal Association | Efficient and More Economical Mercury Capture | Research & Development; concerning, in part: "United States Patent Application 20080314242 - Mercury Removal Systems Using Beneficiated Fly Ash; 2008; Assignee: Progress Materials Incorporated, FL";
result in the production of Coal Ash that is contaminated with both a high level of unburned Carbon and a certain amount of pollutants, relatively minute amounts of heavy metals, in part, entrained in and attached to the Ash.
In our report of:
West Virginia Coal Association | Hawaii Says No Mercury Leaches from Ash Concrete | Research & Development; concerning: "'Risk Evaluation of Leachable Mercury From Concrete Products Made With Fly Ash'; AES Hawaii, Inc., and URS Corporation; 2007; The study demonstrated that, even in cases where mercury in the raw fly ash exceeded the SWMP limit ... no detectable mercury is leachable from the final concrete products containing such fly ash";
we documented that Coal Ash used in such pollution control technologies, wherein stuff like Mercury is absorbed out of flue gas and onto the Ash, can still be used as an admixture for Portland-type Cement Concrete, since the heavy metals simply don't leach out of such compositions.
However, as we've documented and discussed, the chemical absorbents used for such things as Mercury control, and the unburned Carbon content of the resulting Ash, which is high because such absorbent compositions often include activated Carbon and because other pollution controls often result in incomplete combustion of the Coal, can interfere with the action of Air Entrainment Additives blended into concrete mixes to improve some physical properties of the cured Concrete, most especially resistance to the effects of freeze-thaw cycles.
As we've seen in:
West Virginia Coal Association | South Carolina Prepares Coal Ash for use in Concrete | Research & Development; concerning: "United States Patent 8,234,986 - Method and Apparatus for Turbulent Combustion of Fly Ash; 2012; Assignee: The Sefa Group, Inc., Lexington, SC; A method for reducing the carbon content of small particulate combustion products said small particulate combustion products consisting essentially of fly ash or fly ash with chemical residue and/or contaminants ... . It would be desirable to beneficially alter the characteristics of coal fly ash, especially the fly ashes that have been negatively affected by (described) pollution control methods. (One) major issue affecting the utilization and value of fly ash - the air-entraining characteristics of the fly ash - is also related to the impact of fly ash on concrete durability. Particularly, one aspect of concrete durability, namely, freeze-thaw durability, may be negatively impacted by the presence of fly ash, especially by the presence of unburned carbon that remains in fly ash ... . There are several processes in commercial use that aim to significantly reduce the (unburned carbon) of ... fly ashes--to a level below 3% by weight ... . A feature of the present disclosure is to provide a method and apparatus to thermally treat and, thereby, beneficially alter certain characteristics of low-Btu value fine particulate matter, especially coal fly ash ... . This process is designed to expose fly ash to high temperatures in order to effect certain physical and/or chemical changes which will increase the pozzolanic reactivity and/or the amount of reactive glass surface area, improve the air-entraining characteristics by decreasing the level of activated carbon, and reduce the presence of chemical residuals deposited in and/or on the fly ash during flue gas treatment";there are "thermal" Ash treatments available, often referred to as "Carbon Burn-Out", which can rid the Ash of unburned Carbon; but, such treatment can also re-volatilize and release pollutants, like Mercury or other heavy metals, which might be absorbed onto the surface of the Ash through the use of Ash-based flue gas scrubbing systems.
Consequently, as seen in:
West Virginia Coal Association | EPA-Sponsored Fly Ash Concrete Sequesters Flue Gas Mercury | Research & Development; concerning: "United States Patent Application 20030206843 - Methods and Compositions to Sequester Combustion-Gas Mercury in Fly Ash and Concrete; 2003; The United States Government may own certain rights to present invention pursuant to U.S. Environmental Protection Agency Contract No. 68-D-01-075 and National Science Foundation Award No. DMI-0232735, to Sorbent Technologies Corporation. Abstract: A method for removing mercury from a combustion gas in an exhaust gas system has the steps of providing a mercury sorbent; injecting the mercury sorbent into a stream of the mercury-containing combustion gas to enable mercury to adsorb onto the sorbent; and collecting and removing the sorbent from the combustion gas stream. The mercury sorbent is prepared by treating a carbonaceous substrate with an ozone-containing gas to increase the ability of the substrate to adsorb mercury. Concrete compositions with fly ash containing the mercury sorbents will have reduced interference with air-entraining-admixtures";
chemical additives have been developed which can de-activate the Carbon in the Coal Ash, making such high-carbon Ash compatible with Concrete Air Entrainment Additives, but without freeing the Mercury or other heavy metals which might be absorbed onto the Ash; thus enabling the permanent "sequestration" of entrained pollutants, like Mercury, in any Concrete which might be made from that Ash.
And, such technology, which preserves the Concrete value of Coal Ash that has been used for Mercury control, while enabling the permanent sequestration of Mercury in the resulting Concrete, is disclosed by the two United States Patent Applications, from what should be a very intriguing source, we bring to your attention herein.
First, as seen in excerpts from the initial link in this dispatch, we have:
"United States Patent Application 20120216715 - Treatment of Fly Ash for Use in Concrete
Patent US20120216715 - Treatment of fly ash for use in concrete - Google Patents
TREATMENT OF FLY ASH FOR USE IN CONCRETE - Boxley, Chett
Date: August, 2012
Inventors: Chett Boxley, et. al., Utah and Massachusetts
(As we've noted previously, the more publicly-accessible early versions of published US Patent Applications often do not identify the professional affiliation of the inventor, or, the eventual Assignee of rights to any Patent issuing from the Application. But, as seen in:
http://www.ceramatec.com/
Boxley's employer, and the likely assignee of rights to any Patent arising from our subject herein is likely to be the Salt Lake City, Utah, company, "Ceramatec", about whom we've previously reported, as, for only one perhaps interesting example, seen in:
West Virginia Coal Association | Utah 2011 CO2 + H2O = Hydrocarbon Syngas | Research & Development; concerning: "United States Patent 8,075,746 - Electrochemical Cell for Production of Synthesis Gas Using Atmospheric Air and Water; 2011; Assignee: Ceramatec, Inc.; Abstract: A method is provided for synthesizing synthesis gas from carbon dioxide obtained from atmospheric air or other available carbon dioxide source and water using a sodium-conducting electrochemical cell. Synthesis gas is also produced by the coelectrolysis of carbon dioxide and steam in a solid oxide fuel cell or solid oxide electrolytic cell.The synthesis gas produced may then be further processed and eventuallyconverted into a liquid fuel suitable for transportation or other applications".)Abstract: A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 40%, and in some cases less than 20%, of the foam index of the untreated fly ash. An optional alkaline activator may be mixed with the fly ash and SDA to facilitate the geopolymerization reaction. The alkaline activator may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.
(We've documented "geopolymers" previously. In essence, they take advantage of the fact that a few inorganic elements, like the Silicon in Coal Ash, especially, are capable, like Carbon, of forming large and complex molecules; in essence, inorganic polymers. More can be learned via:
Geopolymer - Wikipedia, the free encyclopedia; "Geopolymers are new materials for fire- and heat-resistant coatings and adhesives, ... and new cements for concrete. Raw materials used in the synthesis of silicon-based polymers are mainly rock-forming minerals of geological origin, hence the name: 'geopolymer'".)
Government Interests: This invention was made in part with government support under grant number DE-FG02-05ER84197 awarded by the United States Department of Energy. The Government has certain rights in the invention.
Claims: A geopolymerized fly ash generated by a method comprising ...:
- obtaining a quantity of fly ash that contains between 0.1 and 50% carbon, by weight, based upon foam index testing; and mixing the fly ash with a sufficient quantity of spray dryer ash and water to initiate a geopolymerization reaction and form a geopolymerized fly ash, wherein the spray dryer ash contains an unreacted flue gas desulfurization sorbent, wherein the geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing.
The geopolymerized fly ash ... wherein the flue gas desulfurization sorbent is selected from the group consisting of sodium sesquicarbonate, hydrated lime, and sodium carbonate (and) further comprising the step of mixing an alkaline activator with the fly ash and spray dryer ash.
(Concerning "spray dryer ash", and what that might be about, for a pretty good, albeit commercial, introduction, see:
http://www.babcock.com/
installations now have more than 28 years of operating history".
The term "spray dryer ash" could be taken to mean a number of things, actually, including, even, flue gas gypsum, about which we've many times reported. We'll try to sort it out a bit in future reports.)
The geopolymerized fly ash ... wherein the alkaline activator is selected from the group consisting of a metal carbonate, a metal silicate, a metal aluminate, a metal sulfate, a metal hydroxide, and mixtures thereof.
The geopolymerized fly ash ... wherein the ratio of spray dryer ash to fly ash is between 1:5 and 5:1.
The geopolymerized fly ash ... further comprising the step of granulating the geopolymerized fly ash (and) wherein the geopolymerized fly ash is granulated by spray drying (and) wherein the geopolymerized fly ash is heated to a temperature between 20 and 250 C.
The geopolymerized fly ash ... wherein the geopolymerized fly ash is granulated by crushing (and) has a mean particle size between 0.1 and 1000 microns.
The geopolymerized fly ash ... further comprising the step of adding the geopolymerized fly ash in wet form directly to a concrete mixture (and) wherein the geopolymerized fly ash has a foam index less than 20% of the foam index of the untreated fly ash.
The geopolymerized fly ash ... further comprising the step of mixing the granulated and geopolymerized fly ash with a second quantity of spray dryer ash and water sufficient to initiate a second geopolymerization reaction and form a second geopolymerized fly ash.
The geopolymerized fly ash ... wherein the alkaline activator comprises a metal carbonate, alone or in combination with a metal hydroxide.
A geopolymerized fly ash generated by a method comprising the steps of: obtaining a quantity of fly ash that contains unwanted metals or heavy metals; and mixing the fly ash with a sufficient quantity of spray dryer ash and water to initiate a geopolymerization reaction and form a geopolymerized fly ash, wherein the spray dryer ash contains an unreacted flue gas desulfurization sorbent selected from sodium sesquicarbonate, hydrated lime, and sodium carbonate, wherein the unwanted metals or heavy metals are entrapped within the geopolymerized fly ash to inhibit leaching into the environment.
Background and Field: This invention relates to a process for treating fly ash to render it highly usable as a concrete additive. The invention further relates to treated fly ash, to concrete mixtures containing treated fly ash, and to treated fly ash that entraps unwanted metals or heavy metals.
Coal combustion exhaust gases sometimes contain contaminants, such as heavy metals, that must be removed to meet environmental standards. This is often accomplished using activated carbon or other similar sorbents. The activated carbon is usually collected by electrostatic precipitators or filter bags together with the fly ash. Hence, the collected fly ash may be combined with carbon and adsorbed heavy metals. The carbon content may range up to 50% by weight, or more. Because bark ash has a high carbon content, fly ash that contains some bark ash may have a high carbon content.
Air entraining agents can be costly. Fly ash is often added to concrete compositions because it is less expensive than the Portland cement it replaces. However, if the addition of fly ash to concrete compositions requires significantly increased amounts of AEAs, then there may be little or no cost savings gained by adding fly ash to the concrete composition. It would be an improvement in the art to provide a process for treating fly ash so that it substantially reduces the amount of AEA added to the concrete composition compared to untreated fly ash.
Concrete manufacturers and concrete users in the construction industry require concrete to have consistent, predictable properties. Fly ash carbon content can vary widely depending upon the power plant configuration, boiler type, coal type, etc. Differences in fly ash can affect the amount of AEA that must be added to produce the desired concrete properties. It would be an advancement in the art to provide a process for treating fly ash that substantially reduces the affect of varying fly ash carbon content. Such a process is provided herein.
Summary: This invention includes a process for treating fly ash to render it highly usable as a concrete additive. The invention also includes treated fly ash, concrete mixtures containing the treated fly ash, and to treated fly ash that entraps unwanted metals or heavy metals. As used herein, the term concrete refers to a material made by mixing a cementing material, such as Portland cement, an aggregate, such as sand and/or gravel, and sufficient water to cause the cement to set and bind the mixture. Under the foregoing definition, mortar, which comprises a cementing material, sand, and water, may be considered a type of concrete.
In one embodiment of the process of treating fly ash for use as a concrete additive within the scope of the invention, a quantity of fly ash is obtained that contains carbon. The fly ash will typically be considered unusable for concrete based upon foam index testing. Foam index testing, described in greater detail below, is a measure of how much air entraining agent (AEA) must be added to a concrete mixture to be effective. A low foam index test measurement means less AEA must be added to the concrete mixture to produce the desired air entraining effect.
The fly ash is mixed with a quantity of spray dryer ash (SDA) and water to initiate a geopolymerization reaction and form a geopolymerized fly ash. As used herein, the terms mix and mixing are intended to include processes that combine, blend, or contact the fly ash, SDA, and water in a manner that initiates or facilitates the geopolymerization reaction. The geopolymerized fly ash may be added directly to concrete mixtures in a wet or dry form. Upon mixing fly ash with a quantity of SDA and water, the homogeneous mixture may be directly added to a concrete mixture. Alternatively, geopolymerized fly ash may be granulated or powderized and added to concrete mixtures at a later time. A geopolymer encapsulation layer remains around the offending carbon in the fly ash. The encapsulation layer prevents the absorption of the AEA. The resulting geopolymerized and pulverized fly ash is considered, at a minimum, usable fly ash for concrete according to foam index testing. The invention includes geopolymerized fly ash prepared according to the foregoing process and to concrete mixtures comprising the geopolymerized fly ash.
Spray dryer ash (SDA) is produced as a byproduct of a dry sorbent injection flue gas desulfurization (FGD) system. "
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The above is accompanied by what is referred to as a "divisional application" of the disclosed process, as seen in:
"United States Patent Application: 0120216716 - Treatment of Fly Ash for Use in Concrete
August, 2012
Inventors: Chett Boxley, et. al., Utah and Massachusetts
Abstract: A process for treating fly ash to render it highly usable as a concrete additive. A quantity of fly ash is obtained that contains carbon and which is considered unusable fly ash for concrete based upon foam index testing. The fly ash is mixed with an activator solution sufficient to initiate a geopolymerization reaction and for a geopolymerized fly ash. The geopolymerized fly ash is granulated. The geopolymerized fly ash is considered usable fly ash for concrete according to foam index testing. The geopolymerized fly ash may have a foam index less than 35% of the foam index of the untreated fly ash, and in some cases less than 10% of the foam index of the untreated fly ash. The activator solution may contain an alkali metal hydroxide, carbonate, silicate, aluminate, or mixtures thereof.
Government Interests: This invention was made with government support under Contract No. DE-FG02-05ER84197 awarded by the U.S. Department of Energy. The government has certain rights in the invention."
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The above actually seems more of a detail supplement to "US Patent Application 20120216715 - Treatment of Fly Ash for Use in Concrete" than a disclosure of new and different, albeit related, technology. Secondary patent record sites don't make copies of it available, and differences in specifics seem minor.
For instance, you will find in the full Disclosure of "United States Patent Application 0120216716" entries like:
"It has been found that the process of treating fly ash may be repeated one or more times to further lower the foam index test results. In other words, geopolymerized fly ash may be treated again with an activator solution to lower the foam index even more. In some cases, the foam index may be lowered to less than 1% of the foam index of the untreated fly ash".
And, it all serves to emphasize the main point herein:
Using only inexpensive, non-toxic chemicals, and without the capital expense or pollutant re-emission hazards of a "Carbon Burn-Out"-type process, high-Carbon Coal Ash, which has been used to scrub pollutants from flue gas, can be processed so as to be useable as a fine, reactive, property-enhancing aggregate for Portland-type Cement Concrete; in which Concrete any and all of the pollutants collected by and adhered to the Coal Ash will be completely and permanently "sequestered".