United States Patent: 6216612
That the Ash resulting from our essential use of Coal in the generation of truly economical electric power is a valuable raw material resource; one which can be profitably consumed in, and enable, the manufacture of high-performance Portland-type Cement (PC) and Portland-type Cement Concrete (PCC), should, by now, be incontrovertible to all but the deliberately-dense, or willfully-disbelieving, among our readers.
Herein, we document a little more detail concerning just how sophisticated the understanding that Coal Ash is such a valuable raw material resource, and how it can be better harvested and utilized, has, in certain circles, become.
First, we remind you of one earlier report:
West Virginia Coal Association | Coal Ash Concrete More Durable, Resists Chemical Attack | Research & Development; concerning, in part:
"United States Patent 6,802,898 - Preparing Fly Ash for High Compressive Strength Concrete; 2004; 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 ... which can achieve greater compressive strength than (those) containing only concrete ... . Fly ash characterized (in that) greater than about 90% of the particles have a diameter (as specified, and) which is prepared by grinding unfractionated fly ash".
The point of the above being that, for certain concrete applications where "greater compressive strength than" what is most often referred to as "ordinary" PCC is desired; that is, where it's desired that the Fly Ash act as a "pozzolanic", reactive additive rather than just as a fine aggregate or just a substitute for sand, then the Fly Ash particles added to the Concrete mix should be, for the most part, smaller, within a size range that has been, as indicated by the New Jersey Institute of Technology, pretty well established.
However, as seen herein, some among the power generation industry have found a way to, as they collect their Coal Ash for market, separate it according to size, so that a pozzolanic Fly Ash that doesn't have to be ground to size, at some expenditure of time and energy. The end result being a value-added, and perhaps more profitable, Fly Ash product.
As seen in our excerpts from the initial link in this dispatch to:
"United States Patent 6,216,612 - Ultra Fine Fly Ash and a System for Collecting the Same
(Ultra fine fly ash and a system for collecting the same - American Electric Power Service Corporation)
Date: April, 2001
Inventors: John D. Hume, et. al., Ohio
Assignee: American Electric Power Service Corporation, Columbus
(We're assuming that the named Assignee is a company familiar to most of our readers, almost certainly to those readers associated with the eastern United States Coal industry. They have done some very good work in the development of techniques for the productive utilization of Coal Ash, among their many achievements; and, as will become clear in future reports, American Electric Power Service Corporation (AEPSC) is an operating unit of American Electric Power Company, Inc (AEP).
If you are unfamiliar with AEP, their web site is accessible via:
AEP; through which you can access subsidiary links to: AEP Ohio; AEP Texas; Appalachian Power; Indiana Michigan Power; and: Kentucky Power.)
Abstract: A system for collecting ultra fine fly ash from a dry fly ash removal system includes providing a bagfilter transport conduit for each bagfilter of the system. A vacuum shutoff valve is positioned in each bagfilter transport conduit. The bagfilter transport conduit is selectively connected to an educator that is, in turn, selectively connected to a blower. The blower creates a vacuum flow in the transport conduit that draws the ultra fine fly ash from the bagfilter and deposits the ultra fine fly ash in a collection bin. This system allows a dry fly ash removal system to segregate fly ash by size and separately collect the ultra fine fly ash from the larger fly ash particles. The ultra fine fly ash has been found to be commercially valuable as a concrete admixture filler in various applications.
(Now, the intricacies Coal-fired power plant operations are as rich and as complex as those of a Coal mine. What AEP are making reference to in the Abstract, and in the full Disclosure, are the functions of a Bag House filtration system; a large enclosed unit filled with big cloth or fabric "tubes", through and around which exhaust gasses flow, and which fabric tubes filter out fine Coal Ash that hasn't settled back into the furnace as "bottom" Ash, or otherwise precipitated out of the exhaust stream along the way. And, Bag Houses are not peculiar to Coal-fired power plants, as other industries where fine particulate matter is produced are also in some cases compelled to use them. More can be learned via:
What is a Baghouse; "The Baghouse is a generic name for Air Pollution Control Equipment (APC) that is designed around the use of engineered fabric filter tubes, envelopes or cartridges in the dust capturing, separation or filtering process.")
Claims: A method for collecting ultra fine ash from a dry fly ash removal system having an inlet that directs a fly ash-laden transport air stream into a coarse separator where a portion of the fly ash is removed from the transport air stream and a bagfilter in fluid communication with the outlet of the coarse separator where the ultra fine fly ash is removed from the transport air stream; the method comprising the steps of:
(a) providing a transport conduit connected to the bagfilter;
(b) removing the ultra fine fly ash from the bagfilter by exposing the bagfilter to a removal flow by educing a vacuum flow by providing an eductor in selective communication with the bagfilter and directing a transport flow through the eductor to create a vacuum flow in communication with the bagfilter; and
(c) storing the ultra fine fly ash removed from the bagfilter separate from the fly ash removed by the coarse separator.
The method ... further comprising the step of temporarily storing the ultra fine fly ash in a storage silo after it is removed from the bagfilter.
The method ... further comprising the step of moving the ultra fine fly ash from the storage silo to a transport vehicle.
A method for collecting ultra fine fly ash comprising the steps of:
(a) directing a fly ash-laden transport air stream into a separator;
(b) removing a portion of the fly ash from the transport air stream in the separator;
(c) directing the transport air stream with the remaining fly ash into a bagfilter;
(d) removing the ultra fine fly ash from the bagfilter by exposing the bagfilter to a removal flow; and
(e) storing the ultra fine fly ash separately from the fly ash removed by the separator.
The method ... further comprising the step of temporarily storing the ultra fine fly ash in a storage silo after it is removed from the bagfilter (and) of moving the ultra fine fly ash from the storage silo to a transport vehicle.
Background and Field: This invention generally relates to the control of emissions from combustion processes such as coal-fired processes or other combustion processes that produce large quantities of solid fly ash particles. More particularly, the present invention relates to a system and method for segregating the separated fly ash particles based on particle size and collecting the segregated particles into individual storage containers. Specifically, the present invention relates to a separation system that allows ultra fine fly ash to be separately collected from a dry fly ash removal system by providing a dedicated removal system for removing fly ash particles only from the last separation device of the system.
The combustion of coal and other similar fuels produces molten inorganic matter that is carried away in the exhaust gas stream as the fuel burns. The molten inorganic matter cools as the exhaust stream flows away from the combustion and coalesces into spherical or ellipsoidal ceramic particles in the general range of 0.01 to 500 microns in diameter. These combustion by-product particles are known in the art as fly ash.
Fly ash must be removed from combustion exhaust streams before the streams are exhausted to the atmosphere because of environmental concerns. Numerous methods and systems for removing fly ash are known in the art that effectively remove the fly ash from an exhaust stream. One problem common to all of these methods and systems is the cost of disposing of the collected fly ash. Although some of the fly ash may be sold for various commercial purposes such as for fillers, most fly ash must be landfilled at the expense of the company creating the fly ash. It is thus desired in the art to increase the quantity of commercially-valuable fly ash and consequently decrease the amount of fly ash that must be landfilled.
As is known in the art, bagfilter(s) may often use a collection of fabric filters, similar to common household vacuum cleaners, but at a much larger scale, to entrap air-borne particulate matter onto a filter surface, allowing the largely particulate-free air to continue through the filter surface. During operation of bagfilter, particulate matter builds up on the surface of the filter. This buildup is commonly known as the bag's cake. Cakes are frequently allowed to build up to thicknesses of approximately 0.25 inch or somewhat more between intervals of cleaning. Bags in operational bagfilters are cleaned of cake buildup at periodic intervals that are determined by variables of operation and engineering design. The cleaning process often involves blowing air backwards through the bag filters, shaking the bags, or banging the tops of the bags, all of which cause a substantial portion of the filter cake to drop off the bags.
It has been discovered as part of the present invention that the fly ash collected in bagfilters (as specified) is commercially valuable and that it is desirable to separately collect this fly ash. It has been found that the fly ash collected in bagfilters comprises a plurality of particles with 90% of the particles having a diameter of less than 10 microns. It is known in the art that fly ash particles having diameters predominantly smaller than 25 microns are known as fine fly ash. U.S. Pat. No. 4,294,750 discloses the benefits of fine fly ash particles. The present invention refers to fly ash particles that are predominantly smaller than 10 microns in diameter as ultra fine fly ash. It is thus desired in the art to provide a system for collecting the fly ash."
-------------------------
The full Disclosure is of actually quite some considerable length and detail; and, describes the intricacies of bag house operation, so that the "commercially valuable" "fine fly ash particles" can be better collected.
In addition to the need for quality pozzolans as an admixture for Cement, AEP does reference "U.S. Pat. No. 4,294,750" as further explanation as to why one might want to go to the bother:
"United States Patent: 4294750 - Pyroplastoid Particles, Composition and Method of Production
(Pyroplastoid particles, composition and method of production - Penn Virginia Corporation)
Date: October, 1981
Inventors: Richard Klingaman and Leo Ehrenreich, PA and NY
Assignee: Penn Virginia Corporation, Philadelphia
(Penn Virginia Corp. - About PVA - PVA at a Glance; Penn Virginia - Wikipedia, the free encyclopedia; "Penn Virginia are three interrelated ... companies that trade separately on the NYSE. Penn Virginia Corporation owns natural gas and oil and has large ownership interest in Penn Virginia GP Holdings, L.P. (and) Penn Virginia Resources (who control) coal and pipeline operations.")
Abstract: Particulate material, composites containing said material, and a method of making said particulate material. The material is composed of at least about 85% (number basis) of regular, well-defined ellipsoidal particles having a size less than about 25 microns, at least 90% and 50% by weight of the particles being less than about 15 and 10 microns in size respectively, a surface area of about 0.75 to about 2.5 square meters per gram and a specific gravity of about 2 to 3. The composites contain this particulate material and up to about 99% of one or more polymeric media. The particulate material is produced by subjecting a diverse mixture of flyash particles to dry air classification in an air classifier controlled to recover particulate particles as described above.
Claims: A composite comprising from about 15 to 99% by volume of one or more polymeric media and about one to about 85% of particulate material composed of particles (as described).
The composite ... wherein said polymeric media is a thermoplastic polymer.
Background: When finely divided coal is burned in suspension in a boiler, as in a coal-fired electric power generating plant, combustion converts ash and magnetite components of the coal into "flyash" particles. These depart the combustion chamber suspended in the gaseous and vaporous products of combustion. This suspension is then passed through an appropriate device, such as an electrostatic precipitator, to separate the particulate matter from the gases and vapors, thereby reducing the concentration of solid pollutants discharged into the atmosphere through the plant smoke-stack.
However, "flyash" is not a precise term of definition. For instance, the materials described as "flyash" can vary widely from plant to plant, depending upon a variety of factors including composition of the coal, furnace and separator design and combustion conditions. Moreover, the "flyash" being collected at a given plant at a given instant includes particles of widely varying particle size, density, shape, porosity, internal structure, surface chemistry and other properties. Accordingly, prior literature references setting forth specific particle sizes, densities, chemical analyses and the like for a given flyash generally constitute average or approximate values for a multitude of particles in a sample, in which many of the particles differ widely from the average values. Thus, "flyash" may be aptly described as a composition of diverse particled, which varies from plant to plant. Hereinafter, the unmodified term "flyash" refers to this varying, diverse material.
The abundance and low cost of flyash has created interest in finding uses for it. Early attempts at utilization involved the use of flyash itself. Thereafter, more and more effort focused on isolating specific fractions of the flyash and preparing specially modified forms thereof, such fractions or modifications being chosen based upon what was thought most advantageous for the contemplated end use.
(Some) researchers who have given detailed consideration to synthetic resin/flyash interrelationships have attributed superiority to flyash or flyash fractions characterized by abundant quantities of hollow particles. Contrary to the expectations produced by these teachings, we have discovered a material which has excellent utility in synthetic resin composites, and which does not involve a requirement for an abundant content of hollow particles.
(The Disclosure devotes some considerable and interesting length to documenting prior art uses for Fly Ash; and, takes pains to make clear, as above, that this invention does not concern itself with "hollow particles", that is, "cenospheres".
See:
West Virginia Coal Association | Wisconsin Recovers "Cenospheres" from Coal Fly Ash | Research & Development; concerning: "United States Patent 8,074,804 - Separation of Cenospheres from Fly Ash; 2011; Assignee: Wisconsin Electric Power Company".)
Summary: The present invention is a composite of a polymeric material and particulate material derived from flyash and having the shape, size, specific surface area, and density as described ... .
The particulate material is composed substantially of particles having a well-defined regular ellipsoidal shape, e.g. spherical. However, contrary to what has been emphasized in the art heretofore, hollowness is not an essential feature, and in preferred embodiments disclosed hereinafter the material is composed substantially of non-hollow particles.
The invention also includes composites, as above defined, containing, by volume, about 15 to about 99 percent of one or more polymeric media and about one to about 85 percent of the above-described particulate material. The composites consist essentially of the media and particulate material, which includes, for example, the alternative of replacing up to about three quarters of the above-described particulate material, on a volume basis, with filler(s) or extender(s) of larger particle size(s) up to about 100 microns to provide multi-modal packing. Preferably the volume percentages of media and particles are about 50 to about 95 and about 5 to about 50 respectively.
As indicated above, the particulate material of the present invention may be used in composites with organic or inorganic binders. However, it is preferred that more than half, and preferably substantially the entire weight of components which bind the particulate material in the composites is organic binder material. Normally, the filled synthetic polymer composites contemplated by the present invention will be solid compositions of matter comprising the solid particulate material of the present invention embedded in any polymer material including natural or synthetic; rubbery elastomeric or resinous, thermosetting or thermoplastic and porous or non-porous polymeric media. In general, the particulate material of the present invention will find its greatest utility in non-porous composites wherein the polymeric media is present as a substantially continuous phase in which the solid particulate material is embedded as discrete particles.
Examples of thermosetting polymeric media suitable for the present invention include epoxy resins formed from mixtures of epichlorohydrin and bisphenol, phenolic resins formed from formaldehyde and phenol, unsaturated polyesters formed from mixtures of polyfunctional alcohols and polyfunctional acids, amino resins, alkyd resins, urethanes, silicones, cross-linked polyethylene and the like.
Examples of thermoplastic polymeric media which can be used in the invention are polyamides, polyesters, polyester amides, polyolefines, high-pressure and low-pressure polyethylenes, polypropylenes, polyvinyl chlorides, polyvinylidene chlorides, polychlorofluoroethylenes, polytetrafluoroethylenes, polystyrenes, cellulose acetobutyrates, polyacetals, polycarbonates and others, including copolymers of the foregoing.
With the filler of the present invention has been used successfully with a variety of thermosetting materials, it exhibits an unexpected advantage in respect to bonding directly to thermoplastic polymers. Various explanations can be given for the bonding of these particulate materials to thermosetting resins or rubbers during the curing, vulcanization and/or cross linking of the latter. However, the explanation for the tenacious bonding of the fillers to thermoplastic resins is not fully understood at present.
Best results have been attained when incorporating the particulate material in nylon."
------------------------
Nylon - Wikipedia, the free encyclopedia; "Nylon is a generic designation for a family of synthetic polymers known generically as polyamides";
and, that is a big, big market; especially when you consider that up "to about 85%" of an article molded from Nylon, or other "polyamides", can consist of the specific-size Coal Ash particles described herein.
AEP does suggest specifically such application for the Fly Ash particles collected by the process of their "United States Patent 6,216,612 - Ultra Fine Fly Ash and a System for Collecting the Same", which would be in addition to that seemingly called for in our above citation of "US Patent 6,802,898 - Preparing Fly Ash for High Compressive Strength Concrete; New Jersey Institute of Technology".
But, that, of course, leaves the bulk of Ash to be dealt with and otherwise utilized, which, as seen, for two examples, in:
West Virginia Coal Association | Fly Ash and Desulfurization Waste Make "Premium" Cement | Research & Development; and:
West Virginia Coal Association | Pittsburgh Converts Coal Ash and Flue Gas into Cement | Research & Development;
is something we could and should look at as more of an additional economic opportunity for Coal Country, rather than as a problem.
In any case, yet again, we see that the solid byproducts arising from our essential use of Coal in the generation of truly economical electric power are a valuable raw material resource.
It's far past time we, all of us - the Coal Industry, the Coal Country press, and the Coal Country political leadership - started thinking of them, and publicly talking about them, that way.
