We've made previous reports on the use of Coal Ash both as a property-enhancing and cost-reducing inorganic "filler" for some types of plastic, as seen in:
Carbon Dioxide + Coal Fly Ash = Synthetic Lumber | Research & Development; concerning, in part: "United States Patent Application 20080029925 - Filled Polymer Composite and Synthetic Building Material; 2008; Abstract: The invention relates to composite compositions having a matrix of polymer networks and dispersed phases of particulate or fibrous materials. The matrix is filled with a particulate phase, which can be selected from one or more of a variety of components, such as fly ash particles";
and, as a property-enhancing "pozzolan" component of Portland-type cement and concrete, as seen in:
Federal Highway Administration Recommends Fly Ash Concrete | Research & Development; concerning the FHWA's "Infrastructure Materials Group: Fly Ash"; and their explanation that the use of Coal Ash particles "in concrete improves its workability, reduces segregation, bleeding, heat evolution and permeability, inhibits alkali-aggregate reaction, and enhances sulfate resistance".
All of that is pretty much what a pozzolan is supposed to do for cement and concrete; and, the function of Coal Ash as a pozzolan is even better explained by former US Department of Interior scientist, Ed Dunstan, in our report of:
Coal Fly Ash Makes Concrete "Green" | Research & Development; which contains the details of Dunstan's recent presentation to the 2011 World of Coal Ash Conference, held last year in Denver: "How Does Pozzolanic Reaction Make Concrete 'Green'?"
Herein, we learn that both of those commercial applications for our solid Coal Utilization Byproducts have been examined more closely by the University of Kentucky; who have consequently devised a process which facilitates the processing of Coal Ash, to make it better suited for use in both the plastics filler and the concrete pozzolan applications.
Comment follows, and is inserted within, excerpts from the initial link in this dispatch to:
"United States Patent 6,533,848 - High Quality Polymer Filler and Super-Pozzolan from Fly Ash
Date: March, 2003
Inventors: Thomas Robi and John Groppo, Kentucky
Assignee: The University of Kentucky, Lexington
Abstract: A novel method for producing fly ash material with a range of particle sizes (as specified) is provided utilizing superplasticizers. The method produces fly ash material suitable for use as filler material in the plastics industry and super pozzolan for the concrete industry.
(As noted above. concerning the Federal Highways Administration and their recommendations for the use of Coal Ash, a "pozzolan" can improve many of concrete's properties. As we will further document in some reports to follow, a "super pozzolan" does that really, really well; and, the term "super pozzolan" is a product description actually used in the concrete industry. - JtM)
Claims: A method of providing fly ash with a mean particle size in the range (specified) comprising: slurrying fly ash with water in the presence of a superplasticizer; bringing said slurry to a pH of 7.5-10.5; and elutriating the resulting slurry in a column/hydraulic classifier.
(In the above, "elutriating" just means that they separate the particles according to size and weight by washing them with, basically, water. And, yeah, we had to look it up.)
The method ... wherein said superplasticizer is selected from a group consisting of sulphonated naphthalene-formaldehyde condensate, sulphonated melamine-formaldehyde condensate, polycarboxylates and any mixture thereof.
(Note: Concerning the above "superplastcizer", "naphthalene-formaldehyde condensate", "napththalene" is a primary and well-known Coke oven tar, or oil, derived from Coal; and, as reported by our USDOE's National Energy Technology Laboratories, via:
NETL: Gasifipedia; "Coal to Derivative Chemicals: Primary chemicals produced directly from synthesis gas (syngas), i.e., carbon monoxide (CO), hydrogen (H2) and methanol (MeOH) can be used as intermediates to manufacture a variety of derivative chemicals such as ... formaldehyde";
we can make the formaldehyde from Coal, as well.)
The method ...including subjecting said slurry to hydraulic classification prior to addition of said superplasticizer (and) subjecting said slurry to froth flotation prior to addition of said superplasticizer.
The method ... including operating said column/hydraulic classifier under laminar flow conditions.
Background and Field: The present invention relates to a method for producing a filler material suitable for use in the plastics and concrete industries from fly ash. More specifically, this invention relates to a method for reducing particle flocculation, thereby allowing production of a fly ash-based filler material containing a narrow range of particle sizes.
Plastics have become the dominant material of our age, replacing wood, metal and ceramics. Plastic products almost never contain the pure polymer but are compounded materials containing plasticizers, antioxidants, biocides, UV blockers, fire and smoke retardants, coloring agents (stains and pigments) and mineral fillers.
Substances previously used as mineral fillers include naturally occurring or precipitated calcium carbonate (CaCO3, ... ground glass, talc and fly ash. The total usage and value of fillers is difficult to estimate as much of the production of fillers and additives is tightly controlled. However, filler production is in the range of millions of tons with monetary value in the billions of dollars.
Mineral fillers have two major functions in the plastics industry.
First, they may be utilized as material extenders to displace the resin or polymer and reduce the overall cost of the product.
Second, they may be used as material modifiers to change the physical characteristics of the final product. Thermoplastic polymers filled with rigid inorganic particles display higher values of Young's modulus, better thermal stability and lower wear under friction than unfilled polymers. However, certain prior art mineral fillers may also greatly reduce the polymer tensile strength, disadvantageously contributing to embrittlement.
Addition of other prior art fillers such as calcite or talc to plastics causes problems in the compounding step by entraining air. Also, these materials greatly increase the viscosity of the melt, making injection molding more difficult. The shape and texture of the siliceous glassy portion of fly ash provide certain superior and desirable attributes as a mineral filler for, e.g., plastics. The smooth round surface of fly ash reduces both air entrainment and melt viscosity compared to other fillers. Lower melt viscosity also improves the dispersion of the filler in the melt. The roundness of the fly ash particle further results in reduced abrasiveness compared to materials such as ground glass or wollastinite.
Accordingly, fly ash has been used as a filler at low loadings (1% to 2%) since the 1950's to improve the stiffness of some plastic. However, certain disadvantageous properties of fly ash have limited its widespread usage. Untreated fly ash contains a broad range of particle sizes and, compared to more commonly used fillers, is very coarse.
The presence of significant amounts of coarse material greatly contributes to the loss of strength of the filled polymer. Also, untreated fly ash contains carbon char particles and "magnetite" particles (a highly substituted iron-rich spinel) which are undesirable as they adversely affect color, increase the bulk density and may cause problems with polymer crystallization.
Beneficiation of fly ash is required in order to produce a quality mineral filler. Contaminants must be removed, and the finest particle sizes separated efficiently. It is known in the art to accomplish such beneficiation of fly ash for use as, e.g., an admix in concrete, by such means as hydraulic classification and flotation separation.
(But), there is need in the art for a method of treatment of fly ash for removal of contaminants and efficient separation of the finest particle sizes to result in a suitable filler material for, e.g., plastic polymers, concrete, and cement. To have practical economic value, the recovery efficiency of the small particles (i.e. yield) must be relatively high. The end product must also have a very small median particle size with a narrow size range distribution, with minimal contamination by larger particle sizes. Finally, the technology must operate at reasonable feed pulp density to generate product at a reasonable rate to allow the use of generally available conventional equipment.
Summary: In accordance with the purposes of the present invention as described herein, a process for producing fly ash filler material with a (specified) uniform mean particle size ... is provided. The fly ash provided by the method of this invention is suitable as a filler material for, e.g., plastic polymers, mortar, and concrete.
In one aspect, the method of the present invention comprises the step of slurrying fly ash in water in the presence of a superplasticizer, followed by elutriating the resulting slurry by any suitable means such as an elutriation column or a hydraulic classifier.
(The "hydraulic classifier" is actually a fairly standard type of industrial equipment used in a variety of industries. And, if you're interested in what they are and how they work, more can be learned via:
http://www.mineraltech.com/MODSIM/ModsimTraining/Module2/TechnicalNotes3.pdf.)
The superplasticizer of choice may be added to the slurry at a concentration of from about 1.0 g/kg of fly ash to about 8.0 g/kg of fly ash. In a preferred embodiment of the present invention, the superplasticizer is added to the slurry to near saturation, but preferably maintained below the saturation point.
(The "1.0 g/kg" means you only need about one tenth of one percent of it, relative to the Coal Ash itself, to make this work. The cost, thus, would be rather minimal. That, aside from the fact that some of the "superplastcizer" could probably be reclaimed from the Ash and reused after the classification. - JtM
In one preferred embodiment of this invention, the method is conducted utilizing fresh fly ash at a pH range of from about 8.0 to about 9.5. In a particularly preferred embodiment, the method is conducted utilizing fresh fly ash at a pH range of from about 8.0 to about 8.9. In another preferred embodiment, the method is conducted on stored fly ash at a pH range of from about 9.5 to about 10.5. The method of this invention provides for adjusting the pH of the fly ash/water slurry to a desired range.
In still another aspect of this invention, a composition for use in mortar and concrete is provided wherein fly ash filler material (super pozzolan) having a (specified) mean particle size ... is added in a sufficient amount to replace 20-30% of the added cement.
In yet still another aspect of this invention, a plastic polymer composition is provided wherein 20-30% of any suitable plastic polymer is replaced by fly ash filler".
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So, in other words, we can displace nearly a third of some more expensive materials with, otherwise unwanted, Coal power plant Fly Ash; a practice which actually improves the physical properties of the products to which the Fly Ash is added.
Thus, by using Coal Ash as a filler, we can make those products, concrete and some plastics, better, while, at the same time, reducing their cost of manufacture.
And, the University of Kentucky has provided us with a method herein, via their process of "United States Patent 6,533,848 - High Quality Polymer Filler and Super-Pozzolan from Fly Ash", whereby we can harvest our Coal Ash and make it suitable and available for sale into those concrete and plastics industries; a method that utilizes essentially off-the-shelf industrial equipment and widely-available commodity chemicals, some of which can be made from Coal.
We have, thus, everything we need to establish another profitable industry of some appreciable size in United States Coal Country; and, everything we need to avoid and prevent regulation of our Coal Ash as some sort of hazardous waste we must, somehow, at great expense to our Coal utilization industries and their customers, find some way satisfactory to the EPA, and others, to dispose of.
The only thing we lack, it seems, is the Coal Country people motivated enough to, first, get the information out there; and, second, motivated enough to get off their cans and git 'er done.