We submit to you herein just more evidence of the fact that our unjustly maligned Coal Ash can serve admirably, and be profitably employed, as a substitute raw material in the manufacture of kiln-fired ceramics, with the understanding that regular old "bricks", coarse as they might appear, do qualify as ceramics.
That fact was confirmed not all that long ago by our United States Navy, as seen in our report of:
West Virginia Coal Association | US Navy Makes Ceramics from Coal Ash | Research & Development; concerning: "United States Patent 5,521,132
- Ash-based Ceramic Materials; 1996; Assignee: The USA as Represented by the Secretary of the Navy; Abstract: A ceramic material made from raw coal fly ash".
But, as we saw in:
West Virginia Coal Association | 1936 Ceramics "New Market" for Coal Ash | Research & Development; concerning:"United States Patent 2,055,706 - Method of Making Ceramic Products;1936; Assignee: Chicago District Electric Generating Corporation; This invention relates to an improved method of making fired ceramic bodies by the addition thereto in the unfired state of fly ash resulting from the combustion (in) steam power generating stations (of) pulverized coal ... . Fly ash ... is usable in the medium and lower grade classes of ceramic products, among which may be mentioned all types of earthenware, stoneware, sanitary ware (subsequently glazed), drain and sewer pipe, terra-cotta and common building, face and paving bricks";
the fact that Coal Ash can serve so well as a raw material in the making of, perhaps especially, "medium and lower grade classes of ceramic products", such as, and again perhaps especially, "bricks", has actually been known for quite a long time.
And, as can be deduced from 2004 data supplied by the United States Geologic Survey, via the link:
http://minerals.usgs.gov/
about 12 to 13 million tons of bricks are produced annually in the US, so the potential market for Coal Ash in such applications, though not nearly as large as the one that exists for the use of Coal Ash in the making of Portland-type Cement and Portland-type Cement Concrete, is still quite significant.
And, herein we learn that the art of using Coal Ash to make kiln-fired bricks continued to evolve throughout the last century, subsequent to issuance of the above-cited "United States Patent 2,055,706 - Method of Making Ceramic Products".
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 2,576, 565 - Ceramic Product and Method of Making the Same
Date: November, 1951
Inventor: Charles Raymond Brown, PA
Assignee: G. and W.H. Corson, Inc., PA
(Should you have interest, at the time this patent was issued, as a number of web-based references inform, the Corson company, which produced limestone, burnt lime, and cement and mortar products was more than a century old. In the early 1970's, it became a subsidiary of another company called I.U. International Corporation, which either changed it's name, was acquired or ceased operations in 1982.)
The present invention relates to a ceramic product and to the body from which it may be produced and, more particularly, it relates to a ceramic product comprising the waste ash material obtained from coal burning industrial power and other plants, and to the method of producing same.
The product of the present invention, as will hereinafter appear, possesses properties at least equivalent to those of conventional clay or shale ceramic products and, therefore, may be used as a substitute therefor; for example, the product of the present invention may in the form of a brick, a tile or a pipe.
In the preparation of ceramic products, it is customary to use as a raw material source various forms of clay, shale, and the like. These products are to be found in nature in various deposits and are always associated with considerable quantities of water, both in the free and combined state. These materials when properly processed can be formed into desired shapes, and the intermediate product thus produced is placed in kilns where the material is subjected to various stages of drying, smoking, firing and vitrification to produce a hard, dense, homogenous structure, largely continuous or isotropic in character.
(The "isotropic" just means it has the same grain or pore or particle sizes distributed evenly throughout the mass of the thing. It is consistent.)
One object of the present invention is to provide a ceramic product of advantageous properties, making it especially suitable for use as a structural material.
Another object is to provide a ceramic product which, because of its properties, is available for use for the various purposes where conventional clay or shale ceramic products are now used, including the use of the product in the form of a brick, a tile, a sewer pipe, and the like.
A further object of the present invention is to provide a ceramic product by the utilization of waste material produced by the burning of coal in power and industrial plants.
Still another object of the invention is to produce a ceramic body from a new source of material, utilizing manufacturing methods similar to those employed for the conventional type of ceramic material, but which body, during its production into ceramic product, is characterized by low shrinkage during the drying and firing cycles, by reduced firing time, and by an increased available vitrification range.
(As is made more clear in the full Disclosure, in confirmation of other, similar processes we've documented for you, the use of Coal Ash offers certain advantages in terms of molding and some economies in energy consumption to produce the final, fired product.)
Still another object of the present invention is to provide a fired or vitrified ceramic body which, although not produced from the usual materials, possesses the red color characteristic of conventional brick ... .
Power plants and the like which consume large quantities of coal ... produce correspondingly large quantities of two types of waste ... fly ash and slag.
In accordance with the present invention, the fly ash is present in the ceramic product as the continuous glasseous phase or matrix, and coal ash slag comprises the refractory particles ... .
By the invention, a vitrified ceramic product is provided in which refractory particles are bound in a continuous matrix consisting primarily of thermally merged fly ash, that is to say the glasseous phase or matrix in the vitrified product comprises ... preferably at least about 90% fly ash.
The product of the present invention can replace the standard clay or shale ceramic bodies in the various fields where such products are now used. For example, the color, density, porosity, durability, texture, compressive strength, and modulus of rupture of the product of the invention will, in general, be in the range of the corresponding properties of the clay or shale type ceramic products.
The product of the invention may, therefore, be considered as a substitute or imitation clay or shale ceramic product.
In accordance with the process of the present invention, a moldable mass is prepared by mixing the fly ash containing composition with water ...; the moldable mass is then formed into the desired shape; and the shaped product is dried and oxidized and vitrified.
During the oxidation, any carbon in the fly ash is burned out and the iron in the fly ash is converted to the ferric state.
It is an important feature of the invention that the fly ash body can be formed in the conventional type of machinery into ceramic shapes of sufficient green strength to be handled in the drier and of a sufficient dry strength to be handled satisfactorily in a kiln.
For example, a body may be prepared which can be formed in a dry press, or may be extruded in a conventional brick forming machine or may be molded in any other conventional manner ... .
(It) is an important feature ... that the shaped products do not shrink appreciably during the firing, and this substantial lack of shrinkage is to be contrasted to the relatively large amount of shrinkage obtained when clay or shale products are vitrified.
(The) linear shrinkage factor will generally be only a few tenths of a per cent and will not usually be greater than 1 percent.
(The full Disclosure then goes on at considerable length discussing an issue we thought to be primarily a more modern problem caused in part by mandated pollution controls that impacted the efficiency of Coal combustion, i.e.: residual Carbon in the Coal Ash. But, it seems, as indicated herein, to have been a problem in the utilization of Coal Ash, for quite some time. In the process of our subject, "United States Patent 2,576, 565 - Ceramic Product and Method of Making the Same", as indicated by the above claims, "any carbon in the fly ash is burned out" through a prescribed staging of the temperature in the kiln; that is, the temperature is raised by degrees. And, although that would seem to slow the process of firing, Coal Ash doesn't require as much residence time at the full vitrification temperature as do the clay or shale conventionally used; so it evens out in such a way that the Coal Ash still has the advantage in terms of energy efficiency. In particularly low-quality ash, however, with might be excessive carbon content, a separate calcining, or re-burning of the ash is suggested. Such a calcining which would be more akin to the "Carbon Burn-out" process touched on briefly in our report of:
West Virginia Coal Association | Virginia Converts Coal Ash to Cash | Research & Development; concerning, in part, the article: "South Carolina Electric and Gas Successful Application of Carbon Burn-Out (CBO) at the Wateree Station; 1999 International Ash Utilization Symposium; Center for Applied Energy Research, University of Kentucky; CBO combusts residual carbon in fly-ash, producing a very consistent, low-carbon, high-quality pozzolan".
Since there are other ways to render residual carbon inactive in Fly Ash intended for use in concrete, we haven't yet treated the "Carbon Burn-Out" technology to any real extent in the course of our reportage. We will eventually get around to doing so; but, the point herein is that "Carbon Burn-Out" of the Coal Ash can be integrated rather seamlessly into the brick-making process, without any real disruptions of genuinely separate steps.)
Large variations in the silica, alumina. and iron content (of the ash) have very little effect on the product and, therefore, the composition of the fly ash (except as to the carbon content) and of the slag does not play any significant role in the manufacture of the product. This means that fly ash and coal-ash slag from any available source may be used in the production of the invention.
(The above might or might not be, strictly speaking, accurate. The inventor was, at the time this work was accomplished, almost without doubt referring only to eastern US bituminous and anthracite Coals. Lignite, from western states and the lower reaches of the Mississippi valley, were almost certainly not considered; and, their inorganic ash contents, especially in terms of Calcium, would differ considerably from typical Appalachian Coal. That caveat might be trivial, but we do want to avoid any blatant inaccuracies.)
(The) products of the present invention possess a reddish coloration characteristic of conventional brick products and the more slag present, the redder will be the fired ceramic product. When a ceramic product is made of fly ash and only a small amount of slag, the final product will be a yellowish red and the red coloration increases as the proportion of slag is increased ... .
Claims: A ceramic article having a reddish coloration and possessing properties making it available for uses where clay and shale ceramic products are employed comprising, in the form of a shaped, dense, ceramic structure, refractory particles comprising coal-ash slag particles bound by interfacial fusion to and in a continuous matrix consisting of at least 80% of thermally merged fly ash, any remainder of said matrix being material fusible with said fly as and forming therewith said continuous matrix, and said coal-ash slag being present in an amount between about 5% and about 80% based on the weight of the coal-ash slag and fly ash present in the product, substantially all of the iron in said fly ash being present in the ferric state.
A ceramic article having a reddish coloration and possessing properties making it available for uses where clay and shale ceramic products are employed ... ."
---------------------------
Inventor Brown does explain in some detail how various blends of Coal Ash, with varying Iron contents, can be manipulated so as to yield fired bricks of varying reddish hues; bricks perfectly acceptable as substitutes for conventional clay bricks, or any other fired-clay ceramic construction product, such as fired clay pipe, in any sort of construction application.
As we've previously indicated, if we were to exploit the full market potential for utilizing our Coal Ash in the making of Portland-type Cement and Portland-type Cement Concrete, it's unlikely there would be any Coal Ash left over anywhere for anyone to be concerned about it's "disposal".
However, if there were some still lying about somewhere looking for a job, replacing Clay and Shale in the making of fired bricks, and related ceramic construction products, could be a good one to put Coal Ash to work in. It would conserve energy, conserve natural mineral resources, and, conceivably, result in a better product, since, as explained thoroughly in the full Disclosure, Coal Ash ceramics shrink much less when they're fired than do ceramic bodies molded of Clay and Shale.
In any case, it is demonstrated herein yet again:
The solid residua resulting from our economically essential use of Coal in the generation of abundant and truly affordable electric power comprise a valuable raw material resource. Coal Ash can be consumed and utilized in the economical manufacture of, in essence, red bricks.
And, speaking of red bricks, it's far past time someone hauled all of our Coal Country press folks off to a Coal Ash red brick school house somewhere, ain't it?
We've come to the conclusion here that they're all in rather desperate need of a little remedial education.