United States Patent: 7666505
We've made a number of reports over the past few years concerning the use of Coal Ash in the manufacture of various building and construction products - - in addition to and separate from those reports affirming and documenting the great current and potential value of consuming solid Coal Utilization Byproducts in the making of Cement and Concrete - - as, for example, in:
West Virginia Coal Association | Coal Fly Ash Makes Wallboard Stronger | Research & Development; concerning: "United States Patent 4,403,006 - Sag-resistant Gypsum Board Containing Fly Ash; 1983;
United States Gypsum Company; Abstract: A gypsum board consisting essentially of a monolithic cellular core of set gypsum and a fiberous cover sheet encasement provided with improved properties by the gypsum core having incorporated therein coal fly ash in an amount of about 1-20% by weight of stucco in the gypsum slurry used in forming the board and method of producing the board are disclosed"; and:
West Virginia Coal Association | Coal Fly Ash Roof Shingles Better, Cheaper | Research & Development; concerning: "United States Patent 6,695,902 - Asphalt Composites Including Fly Ash Fillers or Filler Blends; 2004; Boral Material Technologies; Abstract: The present invention is a fly ash filler or filler blend having a particle size distribution with at least three modes that when combined with asphalt produces asphalt composites such as roofing shingles with improved mechanical properties at a lower cost than asphalt shingles produced using conventional calcium carbonate fillers".
And, there is one unique component of some Coal Ash that can convey some especially desirable properties to the products in which it is utilized; and which has gained special notice and attention, as seen in our report of
West Virginia Coal Association | Georgia Tech Recycles Coal Utilization Byproducts | Research & Development; concerning: "United States Patent 8,057,594 - High Strength Pozzolan Foam Materials and Methods of Making Same; 2011; Georgia Tech Research Corporation; Abstract: The various embodiments of the present invention relate generally to high strength foam materials and methods of making the same. More particularly, various embodiments of the present invention relate to high strength foam materials comprising pozzolans, such as cenospheres derived from fly ash. One component of fly ash is cenospheres, which are spherical inorganic hollow microparticles comprising the lightest component of fly ash. Cenospheres typically comprise approximately 1%-2% of fly ash and can be recovered or "harvested" from fly ash. There is currently a great demand for strong and lightweight materials that are easily and economically manufactured. Such materials have long been sought by the construction and automotive industries to increase the strength, durability, and resilience of structures while reducing the weight of the structure. In an embodiment of the present invention, an aluminosilicous material can comprise a plurality of cenospheres. The pozzolan of the pozzolan foam material can comprise about 50% to about 90% of the foam material. A pozzolan foam material can further comprise one or more of gravel, sand, soil, stone, pigment, calcined soil, Portland cement, limestone, gypsum, concrete, mortar, and grout. In an embodiment of the present invention, the plurality of cenospheres can comprise about 50% to about 90% of the foam material. In an embodiment of the present invention, a method of making a pozzolan foam material can further comprise prior to step curing the mixture to form a pozzolan foam material, forming the mixture into an article, wherein the ... article can comprise a building element".
Such Coal Ash "Cenospheres", even though, generally speaking, hollow and light in weight, are still made of the same stuff as Coal Ash, and can thus act as a "pozzolan" in Cement and Concrete mixtures; that is, they can react with the free lime in Cement in a way which forms a stronger chemical binder.
So valuable and useful are Cenospheres that, even though they might "typically comprise", as above, only "1%-2% of fly ash", effort has been made to develop processes by which they can be more efficiently recovered from the bulk of the Ash, as seen, for one example, in:
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; Wisconsin Electric Power Company; Abstract: Methods for increasing the amount of cenospheres in a fly ash sample are disclosed. The cenospheres are obtained in a dry state by using air as the "fluid" media for separation. In one version, the invention is a two step process, that is, screen by size followed by density separation such as in a fluidizing vertical column by density. In another version of the invention, the separation by density is followed by screening by size. Additional cycles can improve purity as defined by concentration of cenospheres".
However, rather obviously it would seem, even though we apparently have, according to outcries from alarmed environmentalists, too much Coal Ash, at a typical yield of only "1%-2%" it might be tough to gather enough Cenospheres to make collecting, marketing and distributing them worth the effort.
But, herein, we learn that a major international producer and distributor of building products, in order to make certain that we have enough Coal Ash Cenospheres, has devised a way to synthesize them - out of plain old, run-of-the-mill Coal Ash.
As seen in excerpts from the initial link in this dispatch to:
"US Patent 7.666.505 - Synthetic Microspheres Comprising Aluminosilicate and Methods of Making Same
Synthetic microspheres comprising aluminosilicate and methods of making same - James Hardie Technology Limited
Date: February, 2010
Inventors: Amlan Datta, et. al., Australia and California
Assignee: James Hardie Technology Limited, Ireland
("James Hardie" might be unfamiliar to many of our readers. But, they are, in fact, a large international manufacturer and distributor of building products, started in Australia, strangely enough, back in the late 1800's; with a subsequent headquarters move to the Netherlands, and, then, Ireland. They do have facilities, and employees, in the United States - - along with something of an unfortunate history related to their use of asbestos in various types of fiber-reinforced construction materials.
With apologies for what might seem a lengthy digression, more can be learned via:
James Hardie: Company Information | Residential Siding from James Hardie; "A publicly-owned company, James Hardie Industries Ltd, was listed on the Australian Stock Exchange in 1951. In the following years, the company built up a diverse portfolio of building and industrial products businesses. In the mid 1980s, James Hardie pioneered the development of fiber-cement technology, and began designing and manufacturing a wide range of fiber-cement building products that made use of the benefits that came from the product´s durability, versatility and strength. Using the technical and manufacturing expertise it developed in Australia, James Hardie Inc. expanded its operations to become a world-leading, specialized, high-technology manufacturer of a wide range of fiber-cement building materials. Today, James Hardie Inc. is purely a fiber-cement business. It operates in markets around the world, with manufacturing operations in the United States, Australia, New Zealand and the Philippines. The businesses employ over 2,500 people who generate revenue of more than $1.5 billion a year"; and:
James Hardie - Wikipedia, the free encyclopedia; "For much of the twentieth century, James Hardie was the dominant manufacturer in Australia of asbestos cement sheet and other related building products which used asbestos as a reinforcing material. As concern grew about the serious adverse health effects of asbestos, in the mid 1980s James Hardie pioneered the development of asbestos-free fibre cement technology, and began designing and manufacturing a wide range of fibre cement building products that made use of the acknowledged durability, versatility and relative strength of fibre cement, without the dangers associated with asbestos. In December 2001, the company shareholders unanimously voted to restructure and relocate the company in the Netherlands as a parent company. This was part of a strategy to separate the company from the stigma of its asbestos liabilities. On 19 February 2010, James Hardie moved its corporate domicile from The Netherlands to Ireland, in a transaction designed to transform James Hardie Industries NV into an Irish Societas Europea company, and James Hardie Industries NV became James Hardie Industries SE. The final stage of the move was completed on 17 June 2010".
We included the above information since we will be returning to additional James Hardie Coal Ash utilization technologies in the future; and, we wanted to get their background established.)
Abstract: A synthetic microsphere having a low alkali metal oxide content and methods of forming the microsphere and its components are provided. The synthetic microsphere is substantially chemically inert and thus a suitable replacement for natural cenospheres, particularly in caustic environments such as cementitious mixtures. The synthetic microsphere can be made from an agglomerate precursor that includes an aluminosilicate material, such as fly ash, a blowing agent such as sugar, carbon black, and silicon carbide, and a binding agent. The synthetic microsphere is produced when the precursor is fired at a pre-determined temperature profile so as to form either solid or hollow synthetic microspheres depending on the processing conditions and/or components used.
Claims: A synthetic microsphere, comprising: a synthetic, substantially spherical wall comprising an aluminosilicate material; wherein the microsphere has a particle diameter of greater than about 30 microns, wherein the microsphere comprises 12.8 weight % to 40 weight % aluminum oxide, 5.2 weight. % to 30 weight % calcium oxide, and greater than 4 weight % to less than about 10 weight % sodium oxide, wherein the microsphere has a total alkali metal oxide content of less than about 10 weight %, based on the weight of the microsphere, and wherein the microsphere has a void volume of between about 30% and 95% based on the total volume of the microsphere.
The synthetic microsphere ... wherein the substantially spherical wall defines at least one inner void, wherein the at least one inner void is synthetically formed by a pre-determined amount of a blowing agent.
The synthetic microsphere ... wherein the blowing agent is selected from the group consisting of powdered coal, carbon black, graphite, carbonaceous polymeric organics, oils, sugar, starch, polymeric organic oils, polyvinyl alcohol, carbonates, carbides, sulfates, sulfides, nitrides, nitrates, glycol, glycerine, and combinations thereof.
(Pretty much anything that will burn, vaporize or off-gas with the application of heat, in other words.)
The synthetic microsphere ... wherein the at least one inner void has a volume of between about 30-95% of the aggregate volume of the microsphere.
The synthetic microsphere ... wherein the synthetic substantially spherical wall further comprises a binding agent (and) wherein the binding agent is selected from ... ultra fine fly ash, Class C fly ash, Class F fly ash, (etc.), and combinations thereof.
The synthetic microsphere ... wherein the microsphere is formulated to be substantially chemically inert in a caustic environment having a pH of about 12-14.
(The above is to admit of the use of these microspheres in hydrated Portland-type Cement, which is very basic; that is, it has a high Ph, to the point where it can be caustic.)
The synthetic microsphere ... further comprising a wall thickness of between about 1 to 100 microns (and) the average particle diameter of the microsphere is between about 30 and 1000 microns (and) wherein the aluminosilicate material is derived from fly ash.
The synthetic microspheres ... wherein each synthetic microsphere has a substantially spherical outer wall defining a synthetically formed, substantially enclosed cavity therein.
Background and Description: Embodiments of this invention generally relate to synthetic microspheres and processes for manufacturing the microspheres. These embodiments have been developed primarily to provide a cost-effective alternative to commercially available cenospheres.
Cenospheres are spherical inorganic hollow microparticles found in fly ash, which is typically produced as a by-product in coal-fired power stations.
Cenospheres typically make up around 1%-2% of the fly ash and can be recovered or "harvested" from fly ash. These harvested cenospheres are widely available commercially. The composition, form, size, shape and density of cenospheres provide particular benefits in the formulation and manufacture of many low-density products.
One of the characterizing features of cenospheres is their exceptionally high chemical durability. This exceptionally high chemical durability is understood to be largely due to the very low content of alkali metal oxides, particularly sodium oxide, in their composition. Accordingly, low-density composites produced from harvested cenospheres usually have the desirable properties of high strength to weigh ratio and chemical inertness. Chemical inertness is especially important in Portland cement applications, where relative chemical inertness plays an important role in achieving highly durable cementitious products.
Thus, harvested cenospheres have proven to be especially useful in building products and in general applications where they may come into contact with corrosive environments where high chemical durability is desirable.
Despite the known utility of harvested cenospheres, their widespread use has been limited to a large extent by their cost and availability. The recovery of cenospheres in large quantities from fly ash is a labor intensive and expensive process.
It may also be possible to alter combustion conditions in power stations to increase the yield of cenospheres in fly ash (but, it) is not economically viable to increase the yield of cenosphere production at the expense of coal-burning efficiency.
(There) is a need for low-cost synthetic microspheres with properties similar to those of natural microspheres harvested from fly ash. There is also a need for synthetic microspheres with acceptable chemical durability suitable for incorporation into fiber cement compositions. To this end, there is a particular need for a low-cost, high yield process of producing synthetic microspheres from commonly available raw materials. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
Summary: Although the term "microsphere" is used throughout the specification, it will be appreciated that this term is intended to include any substantially spherical microparticle, including microparticles that are not true geometric spheres.
As used herein, the term "primary component" means that this component is the major constituent of the agglomerate precursor, in the sense that the amount of primary component exceeds the amount of any other individual constituent.
Preferably, the synthetic microsphere comprises a pre-determined amount of at least one aluminosilicate material and at least one pre-selected chemical. In some embodiments, the at least one pre-selected chemical acts as a binding agent.
In certain preferred embodiments, the substantially spherical wall defines at least one inner void, wherein the at least one inner void is synthetically formed by a pre-determined amount of at least one blowing agent and preferably has a volume of between about 30-95% of the aggregate volume of the microsphere. The at least one blowing agent can be selected from the group consisting of powdered coal ... .
Moreover, the synthetic, substantially spherical wall of the microsphere preferably has a make-up comprising an aluminosilicate material and the binding agent ... selected from ... ultra fine fly ash, Class C fly ash, Class F fly ash, colloidal silica, inorganic silicate cements, organic polymers, and combinations thereof.
In one embodiment, the pre-selected formulation comprises about 30 to 80 weight % SiO2, about 2 to 45 weight % Al2O3 ... (and, in) certain embodiments, the aluminosilicate material is derived from fly ash and is preferably calcined.
(The) preferred embodiments of the present invention provide a plurality of synthetic microspheres (that) are formulated from aluminosilicate particles (in) a pre-selected size range (as specified; and, wherein) the primary component comprises fly ash and the blowing agent is ... powdered coal ... .
From the foregoing, it will be appreciated that certain aspects of the preferred embodiments provide a synthetic microsphere that is substantially chemically inert and can be used as a substitute for natural harvested cenospheres.
(The) preferred embodiments of the present invention provide a chemically durable, synthetic microsphere having properties and characteristics similar to natural cenospheres harvested from fly ash. The preferred embodiments also provide a method for manufacturing the microspheres, including raw material composition and processing, and uses for the microspheres in various applications, including fiber cement products.
The synthetic microspheres ... comprise an aluminosilicate material. Aluminosilicates are inexpensive and widely available throughout the world, for example from ... waste by-products, particularly bottom ash and fly ash.
It is particularly advantageous that the synthetic microspheres can be prepared from fly ash.
(The) synthetic microspheres ... can be formed by first combining the primary component with a binding agent and a blowing agent so as to form an agglomerate precursor (as described) ... .
Synthetic microspheres according to the present invention may be used as fillers in composite materials, where they impart properties of cost reduction, weight reduction, improved processing, performance enhancement, improved machinability and/or improved workability. More specifically, the synthetic microspheres may be used as fillers in polymers (including thermoset, thermoplastic, and inorganic geopolymers), inorganic cementitious materials (including material comprising Portland cement, lime cement, alumina-based cements, plaster, phosphate-based cements, magnesia-based cements and other hydraulically settable binders), concrete systems (including precise concrete structures, tilt up concrete panels, columns, suspended concrete structures etc.), putties (e.g. for void filling and patching applications), wood composites (including particleboards, fibreboards, wood/polymer composites and other composite wood structures), clays, and ceramics. One particularly preferred use of the microspheres according to the present invention is in fiber cement building products."
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Our presentation herein is already overlong; but, it seems important to emphasize a few facts, which we will be returning to with more detail in future reports.
First, we'll attempt to address the market potential for Cenospheres and Microspheres, as derived herein from Coal Ash, in future reports. There are a number of companies which have been established for their collection, preparation and marketing; and, China and India promote them as export commodities; although, at this time, we have so far been unable to quantify actual volumes which are used or could be used.
Quite a few products, like some artificial stone countertops, incorporate them to take advantage of their weight-saving characteristics.
But, we've previously documented the value of using Coal Ash in the above James Hardie-enumerated applications; as, for one instance, in:
West Virginia Coal Association | Texas Converts Coal Ash to Cash | Research & Development; concerning, in part: "United States Patent 6,916,863 - Filler Comprising Fly Ash for Use in Polymer Composites; 2005; Boral Material Technologies; Abstract: The present invention is a fly ash filler or filler blend having a particle size distribution with at least three modes that can be combined with a polymer at higher filler loadings to produce a filled polymer for polymer composites that, in many cases, can produce improved mechanical properties for the polymer composites over polymer composites using conventional fillers".
And, it is significant that the technology disclosed herein is one which enables the production of relatively low density particulates, from Coal Ash, that, while still possessing the chemical characteristics which enable those particles to serve as fillers and aggregates, for both Portland Cement-type concrete and various plastics that enhance the properties of the resulting composite materials, also reduce the density, and the unit weight, of those composite materials.
All of which has implications, based on the final uses to which those composites are put, for improved performance in terms of, among other things, construction efficiency, thermal insulation and fuel economy; and, thus, for the relatively economical production on an industrial, commercial basis of what could be seen as a profitable, value-added product, "Cenospheres", as found naturally in Coal Ash; and, "Microspheres", as, according to James Hardie herein, through disclosure of their "US Patent 7.666.505 - Synthetic Microspheres Comprising Aluminosilicate and Methods of Making Same", synthesized from Coal Ash.
