United States Patent: 5160539
We have by now made a number of reports documenting the value of Coal Ash as a "pozzolan", an additive for Portland Cement that serves to enhance the properties of Mortar and Concrete made with that Cement.
As we've also documented, various pollution control measures can negatively impact the combustion of Coal in power generator furnaces, often resulting in a certain amount of Carbon being left unburned in the Ash.
Such unburned Carbon, if present in the Ash in too high a quantity, has a negative impact on the performance and physical properties of Concrete made with that Ash, primarily through interference with the function of "air entrainment" agents blended into the Concrete mix, additives which enable the incorporation of microscopic bubbles of air in the Concrete and thus impart greater resistance to freeze-thaw damage.
As seen in our report of:
West Virginia Coal Association | US EPA Approves Coal Fly Ash Carbon Burn Out | Research & Development;
the United States Environmental Protection Agency made an official statement of approval for a process known as "Carbon Burn Out", a process which removes, through oxidation, the residual Carbon in Coal Ash, while also generating some additional heat energy which can be cycled for use back to the power plant.
That EPA approval, by the way, was issued for one specific application of the technology, as more fully reported in:
West Virginia Coal Association | Virginia Converts Coal Ash to Cash | Research & Development; "Dominion Recycling Center Turns Ash to Cash; The Virginia Pilot; November, 2006; Dominion Virginia Power says the new, domed structure next to its Chesapeake power station will make money, create jobs and help the environment. (It) is an ash recycling center (that) bakes black, carbon-laden fly ash into a kinder, gentler and paler byproduct that can be sold and made into concrete, roof tiling and construction blocks, among other alternative uses".
Herein, we submit the United States Patent disclosing what we believe to be the specific "Carbon Burn Out" Coal Fly Ash beneficiation technology approved of by the EPA, for use by Dominion Virginia Power, in those earlier reports.
There are a few other Coal Ash beneficiation processes, conceptually related, "out there", and, we will likely address them, and their variations, as we go along. But, following, with information concerning another closely-related technology appended, are excerpts from the initial link in this dispatch, describing:
"United States Patent 5,160,539 - Fly Ash Beneficiation by Carbon Burnout
Date: November, 1992
Inventor: Joseph Cochran, FL
Assignee: Progress Materials, Inc., FL
Abstract: This invention relates to an apparatus, method and product wherein fine particles of fly ash containing carbon are oxidized in a dry, bubbling fluid bed of previously introduced fine particles of the same fly ash so that the subsequently removed particles have reduced carbon content and are useful as pozzolan, suitable for use, without further processing, to replace a portion of the cement in concrete. The preferred conditions are a temperature of about 1300 to 1800F, air velocity of between at least about 0.5, but not more than about 3 ft./sec., residence time of at least about 2 minutes but up to 100 minutes, volume ratio of air to fly ash of between about 1,000 and 1500, and an excess of oxygen between about 5% and 15%.
Claims: The method of reducing carbon content of fine particles of fly ash containing carbon, comprising
a) introducing said fly ash fine particles containing carbon to a dry bubbling fluid bed consisting essentially of said particles, and
b) oxidizing said carbon in the fly ash particles by intimately mixing said particles with air in said bed at a temperature of between about 1300 and about 1800F,
by introducing ambient air to said bed at a volume ratio of between about 1000 to about 1500, air to fly ash, at a velocity of between at least about 0.5, but less than about 3.0 ft./sec.,
and said particles having a residence time in said bed of at least about 2 minutes, but up to about 100 minutes,
c) then removing said fly ash particles from said bed,
wherein said particles have had the carbon content reduced by said oxidation, so that said removed fly ash particles are enhanced pozzolan suitable for use, without further processing, to replace a portion of the cement in concrete."
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We leave our excerpts deliberately brief, since we have some more ground to cover; and, we wanted to point out one very important fact:
Before the so "enhanced" Fly Ash is sent on "for use ... to replace a portion of the cement in concrete", they can undergo some "further", and valuable, "processing". As seen in our report:
West Virginia Coal Association | Efficient and More Economical Mercury Capture | Research & Development; concerning: "US Patent Application 20080314242 - Mercury Removal Systems Using Beneficiated Fly Ash; 2008; Inventor: Joseph Cochran, Frank Kirkconnell, Vincent Giampa; Assignee: Progress Materials Incorporated, FL";
it's disclosed how - - before the Fly Ash that has been "beneficiated" by the "Carbon Burnout" process described herein is used "to replace a portion of the cement in concrete" - - a portion of the beneficiated Ash, perhaps along with some special sorbents, can first be used to extract Mercury from Coal power plant flue gas; with the then Mercury-containing Ash being ultimately forever sequestered in the final "concrete" product.
We at least believe that to be the case. We suppose that if any Coal Country journalists really do have the convictions of their oft-editorialized love of the Coal industry, then they could resolve any questions about it by simply calling Progress Materials and asking. We just don't have a budget here for long-distance calls.
And, again, the above would apply only to Coal Ash being used as a "pozzolan" additive in, or direct replacement for, some of the Portland Cement in Concrete; not Ash that would be directed, as we have documented to be perfectly feasible, into the Cement-making process itself, as a replacement for some of the traditional mineral raw materials, where the high heat of calcination would revolatize the Mercury.
We believe it important to keep making that distinction, even though, as we have documented and as we will further document, Cement-making plants are having to install their own Mercury controls, so it likely wouldn't be an issue. The Mercury would simply be collected at one, central location: the Cement plant. And, if a Cement plant were using beneficiated Fly Ash as an additive for their Concrete mix, then they would have some on hand which they, too, could utilize in the process of "US Patent Application 20080314242" to remove the Mercury from their kiln's off-gas, and, then, dump that Ash into their Concrete mix to replace a portion of the Cement.
It all sounds kind of win-win to us.
But, another issue that needed resolving, apparently, is that, since there remains unburned Carbon, i.e., Coal, in Coal Ash nowadays, there will, as well, in Ash resulting from the use of high-Sulfur Coal, remain some un-oxidized Sulfur. And, as seen following, Progress Materials has that issue covered, as well:
"United States Patent Application: 0070193476 - Fly Ash Beneficiation with Sulfur Removal
Date: August, 2007
Inventors: Joseph Cochran and Frank Kirkconnell, Florida
Assignee: Progress Materials Incorporated, St. Petersburg
Abstract: A system and method for beneficiation of fly ash particles which at least partially reduces sulfur emissions includes at least one mixing reactor with a chamber and at least one exhaust, at least one fly ash source connected to provide fly ash particles to the chamber, at least one sorbent source, and at least one fluid supply system. The sorbent source provides at least one type of sorbent particles to be mixed with the fly ash particles to reduce sulfur emissions. A mass of the fly ash particles in the chamber is greater than a mass of the sorbent particles in the chamber. The fluid supply system provides at least one fluid to the chamber during a beneficiation of at least a portion of the fly ash particles in the chamber.
Claims: A system for beneficiation of fly ash particles which at least partially reduces sulfur emissions, the system comprising: at least one mixing reactor with a chamber and at least one exhaust; at least one fly ash source connected to provide fly ash particles to the chamber; at least one sorbent source that provides at least one type of sorbent particles to be mixed with the fly ash particles to reduce sulfur emissions, wherein a mass of the fly ash particles in the chamber is greater than a mass of the sorbent particles in the chamber; and at least one fluid supply system which provides at least one fluid to the chamber during a beneficiation of at least a portion of the fly ash particles in the chamber.
The system ... wherein an operating temperature of a fluid bed of the fly ash particles with the sorbent particles in the chamber is at or below about 1375F.
The system ... wherein sulfur emissions in the exhaust are reduced by at least about 50% (or) are substantially eliminated.
The system ... wherein the sorbent particles comprise at least one of calcium carbonate, magnesium carbonate, an oxide of calcium and an oxide of magnesium.
(By the above, they are simply specifying plain old ground Limestone, i.e., "calcium carbonate, magnesium carbonate" and/or your basic components of Portland Cement, i.e., "an oxide of calcium and an oxide of magnesium". It ain't really rocket science, folks.)
A method for beneficiation of fly ash particles which at least partially reduces sulfur emissions, the method comprising: beneficiating fly ash particles which results in an exhausting one or more gases; and adding at least one type of sorbent particles to the fly ash particles, wherein at least a portion of the sorbent particles interact with at least a portion of the fly ash particles and exhaust gases to at least partially reduce sulfur emissions in the one or more exhausted gases, wherein a mass of the fly ash particles during the beneficiating is greater than a mass of the sorbent particles.
Background and Field: This invention generally relates to systems and methods for processing fly ash particles and, more particularly, to a systems for beneficiation of fly ash particles which at least partially reduce sulfur emissions and methods thereof.
Fly ash particles are a byproduct of coal fired power plants. These particles constitute about 10% of the total weight of the coal burned and, if not beneficially used, can be a substantial disposal problem.
The largest volume and highest value use of fly ash particles is as an admixture in Portland cement concrete.
For use in concrete, the fly ash particles must meet stringent chemical and physical specifications, such as ASTM C-618. Often, the fly ash particles have a carbon content which precludes this beneficial use of the fly ash particles.
To utilize these fly ash particles, methods and apparatuses which use combustion processes to beneficiate fly ash particles by reducing the carbon content have been developed, such as those disclosed in U.S. Pat. Nos. 5,160,539 and 5,399,194, which are each herein incorporated by reference in their entirety. The beneficiated fly ash particles can be used to replace a portion of the cement in concrete, instead of requiring disposal in landfills.
(Concerning the above references, US Patent 5,160,539 is the initial subject of this dispatch, and:
"United States Patent: 5399194 - Method of Fly Ash Beneficiation; Inventors: Joseph Cochran, et. al., Assignee: Electric Power Research Institute, CA; Abstract: A method for beneficiating particles of fly ash containing carbon which includes the following steps. The particles of fly ash are introduced into a dry bubbling fluid bed and air is supplied thereto. The fluid bed is operated at a temperature ranging from approximately 800 to 1300F during which the air intimately mixes with the particles of fly ash and oxidizes the carbon therein. The beneficiated particles of fly ash are then removed from the fluid bed. The carbon reduction in the particles of fly ash permits these particles to be used as pozzolan to replace a portion of the cement in concrete. An apparatus is provided for performing the method of the invention";
is one closely-similar developed by Progress Materials, it seems, under contract to the "Electric Power Research Institute", out in California.)
Unfortunately, when the fly ash is beneficiated, gaseous compounds formed from sulfur in the fly ash are emitted into the environment in the exhaust gases. As environmental emission standards continue to be raised, new techniques for controlling sulfur emissions are required.
The basic chemical reactions that allow use of limestone (CaCO3) to capture gaseous sulfur compounds resulting from combustion processes are well known. For example, limestone mixed with water is sprayed into boiler exhaust gases to capture sulfur in many power plants in devices known as Flue Gas Desulfurization units (FGD) or more simply as wet scrubbers.
(Note, that, 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";
the product of such "Flue Gas Desulfurization units", can, as well, be used and consumed, along with Coal Fly Ash, in the making of Cement.)
Summary: The present invention provides a number of advantages including providing an effective system and method for beneficiation of fly ash particles which at least partially reduces sulfur emissions. More specifically, the present invention is able to reduce sulfur emissions during the beneficiation of fly ash particles ... in temperature ranges optimal for fly ash beneficiation, at efficiencies far higher than previously believed possible. One factor which enables sulfur reduction at this lower temperature range is the use of limestone particles having a range of sizes which are substantially the same size or smaller than a range of sizes for the fly ash particles. Additionally, through the use of pulverized limestone the present invention increases the quantity of the beneficiated ash product. Further, the present invention does not harm the resulting commercial quality of the beneficiated ash product because the small mass of pulverized limestone does not cause the beneficiated fly ash product to exceed the chemical limitations of specifications, such as ASTM C-618."
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We summarize by suggesting that the entire, combined system represented by our primary subjects, "United States Patent 5,160,539 - Fly Ash Beneficiation by Carbon Burnout" and "United States Patent Application 0070193476 - Fly Ash Beneficiation with Sulfur Removal", would result in a Coal Fly Ash product with greatly-enhanced properties for use in making Portland Cement Concrete; a Concrete that would, as well, be enhanced, in terms of it's properties, by being made in part of the beneficiated Coal Ash.
The upshot is, that, we don't really have a Coal Ash problem in US Coal Country, but an opportunity.
An opportunity, that, as we understand it, Progress Materials and one or two others are helping some folks in some parts of the country take advantage of.
The "problem" is really one of education and enterprise.
If we were somehow able to get ourselves educated about the practical, commercial opportunities herein indicated for Coal Ash, and somehow get motivated enough to undertake the enterprise of collecting our Ash, cleaning it up a bit, and marketing it, we just might be able to establish a new profit, and employment, center for United States Coal Country.
And, maybe, get the EPA off our backs a bit.
But, it does take education and motivation. Is there anyone out there listening who's willing and able to help out with that a little?
