WO1994014714A1

WO1994014714A1 - Method of making foamed glass articles

Info

Publication number: WO1994014714A1
Application number: PCT/US1993/012466
Authority: WO
Inventors: Harold B. Mackenzie; Henry C. Oat; Carl Frahme
Original assignee: New Life Foundation
Priority date: 1992-12-22
Filing date: 1993-12-22
Publication date: 1994-07-07
Also published as: AU5957594A

Abstract

Foamed glass articles are produced from a mixture of pulverized glass particles, foaming agent, binder, and water, wherein the glass articles are dried to remove excess moisture and are further heated to cause the foaming agent to emit a foaming gas, thereby causing foaming of the glass articles. The foamed glass articles are annealed in a controlled cooling fashion to avoid thermal stress, cracking and embrittling. A production line comprising a mixer (20), pelletizing means (30), pellet feed means (40), a feeder (45), and a kiln assembly (10) made up of a drying area (60), a foaming area (70), and a cooling area (80) containing three cooling stages (90, 100, 110) are utilized to produce the foamed glass articles. The foamed glass articles may be used as artificial pumice stones in the stone-washed garment industry and are useful also in the construction industries.

Description

METHOD OF MAKING FOAMED GLASS ARTICLES ************************

Field of the Invention

This invention relates to foamed glass articles. More specifically, this invention relates to methods of producing foamed glass articles of particular size ranges with a specialized foaming and cooling process, for the particular industrial process of stone washing of garments.

Background of the invention

Glass is a common man-made substance with well known properties and many uses. It also constitutes a significant portion of the waste generated in our highly industrialized, consumer society. Much of this waste glass is container glass which can be reused to produce the same types of articles which it originally formed, or other articles, but the number of container glass plants presently in existence is limited.

Additionally, before actual recycling of waste glass into the glass container industry can be accomplished, other steps must be taken with the waste glass to prepare it for recycling such as sorting the glass for quality and color. These additional steps add to the expense of recycling and further complicate virtually all recycling procedures which must deal with large volumes of waste glass for processing.

Further, glass contain manufacturing plants are widely separated, and many areas generating large volumes of waste glass are far from such a plant. Also, the re-use of glass cullet in the making of new glass is limited, and across the United States large volumes of waste glass are accumulating for which there is no market. Much recycled glass is still going to landfills, and many recycling-minded communities have ceased collecting glass for recycling for lack of market. Thus it has been desirable in the art to develop economical, marketable by-products of waste glass which can be manufactured by efficient and cost effective processes. One such by-product is "foamed glass" which is well known in the art. See, e . g . , U.S. Patent No. 3,874,861, Kurz, the teachings of which are specifically incorporated herein by reference.

Foamed glass may be made into many different shapes and sizes for different purposes such as insulating panels for the construction industry. See, e.g., U.S. Patent No. 3,207,588, Slayter et al., the teachings of which are specifically incorporated herein by reference.

Natural pumice is a kind of volcanic glass that contains minute cavities which are produced by the expulsion of water vapors at high temperatures created as lava comes to the earth's surface. Natural pumice is used for a number of purposes. One important use has been in the garment industry for treating cloth, such as denim, in the stone-washing process. The stone-washing process with natural pumice mildly abrades cloth, including denim, to produce a faded and worn look which is in popular fashion today, and to soften the fabric of the garments.

There is a great deal of pumice in the United States, and it occurs near many geological formations of volcanic origins. However, much domestic pumice is not satisfactory for fabric-washing use, since it is generally either too soft or too hard and abrasive, or too heavy in contaminants, etc. , so a large amount of pumice used for stone-washing of garments is imported from abroad, from as far away as Greece, Turkey and Ecuador.

Unfortunately, the application of natural pumice has several problems which make it difficult to justify its continued use in the multi-billion dollar stone-washed garment industry. First, natural pumice must be obtained in very large quantities to satisfy the needs of the stone-washing fabric industry. This entails strip-mining of vast areas of pristine land preserves which are home to endangered indigenous plants and wildlife, and which often have particular beauty and environmental and historical importance. In the United States, the Jemez mountain areas of New Mexico are subject to such strip-mining with its attendant devastating environmental consequences. Various environmentally active groups have taken considerable umbrage at these effects of pumice strip-mining and have attempted to impeded mining of natural pumice through boycott, and regulatory and legal means.

Further, natural pumice has other qualities which can cause problems for stone-washing usage: (1) it can differ widely in quality from mine to mine and within the same mine, as to hardness, composition analysis and impurities; and (2) impurities are almost always present to some degree, and can often be present in amounts sufficient to cause process damage. This is particularly true with iron, often present in large amounts, which can cause rust spots on garments during stone washing.

Finally, the use of natural pumice in the stone- washing process produces a significant amount of industrial waste sludge which must be removed and disposed of by landfilling. As natural pumice stone washes garments, the abrading effect of the stones on the garments causes the stones to wear away by attrition, thereby producing a muddy sludge substance in the stone-washing machines which process the stone- washed garments. This muddy sludge is difficult to handle, has no commercial use, and must be disposed of in a landfill. The costs of disposing this industrial waste is significant, which further adds to the overall cost of using natural pumice in the stone washing process.

Foamed glass articles should also have controllable sizes and shapes and utilize commonly available waste glass to improve the economic, environmental, and production results of stone-washing. Such results have not heretofore been achieved in the art. Summary of the Invention The foregoing objects are achieved, and problems solved, by methods of producing foamed glass articles from glass particles in accordance with the present invention. The methods preferably comprise the steps of finely pulverizing the glass particles and thoroughly mixing with the pulverized glass particles an amount of foaming agent, binder and water, to produce a glass particle mixture. The glass particle mixture is formed into glass articles of the desired size and shape and heated to a first elevated temperature and for a time to substantially remove moisture from the glass articles, thereby preventing the formation and emittance of steam during heating and foaming of the glass articles. The glass articles are further heated to a second elevated temperature and for a time to cause substantially all of the foaming agent to emit foaming gas emissions. The heated glass articles are cooled to produce the foamed glass articles and in a manner to reduce thermal stress and prevent thermal shock to the glass articles. This stress and shock can cause either collapse of many of the porous air cell structures inside of the glass articles, or cracks on the outside thereof, either of which would destroy the integrity and usefulness of the glass articles for stone-washing purposes.

In a further preferred embodiment, a kiln assembly comprising a kiln is provided for producing foamed glass articles in accordance with the present invention. The kiln assembly preferably comprises a pellet feeder means disposed at the entrance of the kiln for feeding kiln trays containing glass articles to be foamed, drying means disposed at an exit of the pellet tray feeder means which may be a drying area in front of a front portion of the kiln for removing moisture from the glass articles, and a heating area disposed at an exit of the drying means for heating the glass articles to a foaming temperature to produce the foamed glass articles.

In certain embodiments of the present invention, the drying means may be separate from the kiln, and the dried glass articles are conveyed from the drying means to the kiln by suitable conveyor means. The methods of producing foamed glass articles and kilns provided in accordance with the present invention allow for the production of foamed glass that is stable, robust, and useful in many different applications. The foamed glass article, provided in accordance with the present invention, may be used in various industries, including the construction industry for fireproof insulation, wall board, fireproof decorative panels and room dividers, fire doors, composition roof deck material, and roofing tiles. It also has an important use in the stone washing garment industry as artificial pumice, and in other industries which require foamed glass articles of predetermined sizes and shapes that can be mass produced and consistently obtained.

The present invention will be better understood by referring to the following detailed description of preferred embodiments in conjunction with the drawing.

Brief Description of the Drawing Figure 1 is a schematic diagram of a process line including a pair of kilns to produce foamed glass articles in accordance with the present invention.

Detailed Description of Preferred Embodiments In accordance with the present invention, foamed glass articles are produced in a predetermined size and shape. Foamed glass articles described herein are more robust than foamed glass particles according to the prior art, largely due to the controlled cooling process that is employed when foamed glass articles are produced in accordance with the present invention. It has been found that in the absence of such a controlled cooling process, the resultant foamed glass articles are brittle and imperfect. Furthermore, they are subject to greater attrition than foamed glass articles provided in accordance with the present invention. "Attrition" refers to the wearing down of the article, and is a function of the length of time that a foamed glass article or natural pumice stone may be used in the stone-washed garment industry before it is worn down to sludge or to the point where it is no longer usable and must be discarded. In a preferred method of producing individual foamed glass articles, the glass articles are produced from an appropriate mixture comprising pulverized glass particles, foaming agent, binder and water. These materials are mixed in the desired proportions, and the resulting glass particle mixture is formed to create glass articles of the desired size and shape. The term "foaming agent", as used herein, refers to any material or compound which evolves gas when heated to an elevated temperature and which causes the glass articles to foam. Preferably, the gas evolved by the foaming agent is generally non-toxic and non-flammable, for example, carbon dioxide (C0₂) . Materials which are particularly suitable for use as the foaming agent are carbonates, including calcium carbonate (CaC0₃) . However, it will be recognized by those skilled in the art that other foaming agents will also be suitable.

The term "binder", as used herein, refers to any material or compound which causes the pulverized glass and water mixture to stick or bind together when forming the glass articles. Preferably, the binder comprises ball clays, bentonite clays, and/or sodium silicate. However, it will be recognized by those skilled in the art that other binders will also be suitable.

In yet further preferred embodiments, the glass mixtures are formed into shaped pellets before foaming occurs. Preferably, pellets may be produced by one of four methods disclosed herein; (1) cut out, (2) mold; (3) die pressing; and (4) briquetting of the pulverized glass mixture. The "cut out" method is described generally by its name, and involves cutting out pellets of the desired shape and size. The mold method involves paper molds which are used to hold the mixture in a predetermined shape until the heated glass particles are heated to a temperature and for a time such that they become self- adhering and stick together to hold the desired shape, after which the paper molds burn off. Suitable paper molds include paper cups, for example, DIXIE^® cups. The pressing method involves the use of a die with opposing plungers to create individual pellets. The briquetting method is very similar to methods used to produce charcoal briquettes, as substantially shown in U.S. Patent No. 5,049,333, Wolfe et al., the teachings of which are specifically incorporated herein by reference.

The desired pellets are produced according to any one of the above four methods, as determined largely by the particular application of the pellets and according to the preference of the end-user.

Irrespective of the peUetizing method used, the glass articles are then preferably subjected to a foaming process in a kiln. The glass articles to be foamed are preferably placed on kiln trays which are placed on a roller conveyor which moves the articles at a constant rate throughout the kiln to be dried, foamed and cooled. During this process in the kiln, two important heating areas exist. In the first such area, the glass articles are preferably heated to a first elevated temperature and for a time to dry the articles and to substantially eliminate moisture from the glass articles. This elimination of moisture prevents the formation of steam during elevated heating and foaming steps which might prevent the foamed glass article from forming correctly. In preferred embodiments, the glass articles on the trays are dried in the kiln by heating them to a temperature of about 350°F, and holding them there for about 15 to about 30 minutes.

In certain applications, it may be desirable to place glass articles first in a drying means which is separate from the kiln to partially dry them before placing them in the kiln. This separate drying process is especially preferred where the moisture content of the glass articles is high. Nevertheless, the kiln preferably comprises a specific drying area as part of its total heating means.

After the glass articles are substantially completely dried in the drying area, further heating is then preferably applied in a second heating area. The second heating area involves elevating the temperature to which the glass articles are exposed until the foaming temperature is attained. Preferably, the second heating area involves heating the glass articles for about one to about two hours or longer until the foaming temperature is reached. In preferred embodiments, the glass articles are heated to about 1570°F. The elevated temperatures in the second heating area cause the foaming agent, for example, CaC0₃, to decompose and release C0₂ as the foaming gas. It is contemplated that the foaming gas is generally trapped within the glass articles and produces the foaming effect. The foamed glass articles are then preferably held at the foaming heating temperature and in the second heating area for a short period, and preferably from about 15 to 30 minutes. In preferred embodiments of the present invention, the foamed glass articles are cooled. Preferably, the cooling process is conducted in three kiln cooling areas: (1) a first cooling area wherein the foamed glass articles are preferably cooled as rapidly as possible from the foaming temperature, for example, about 1570°F, to an upper critical temperature, for example, about 1000°F; (2) a second cooling area wherein the foamed glass articles are cooled from about the upper critical temperature to a lower critical temperature, for example, about 500°F, in a controlled, slow cooling fashion over a period of about one hour; and (3) a third cooling area wherein the foamed glass articles are preferably cooled as fast as possible to a temperature of less than the lower critical temperature.

All of the cooling steps described above are preferably regulated carefully in order to produce ideal foamed glass articles.

In still further preferred embodiments of methods of producing foamed glass pellets in accordance with the present invention, glass particles are first pulverized. The glass particles can comprise many types of waste glass including, for example, clear or mixed-color container glass, window glass, plate glass, as well as new glass. Preferably, the glass particles are pulverized to obtain substantially fine mesh particles, for example, about 300 mesh.

The fine-mesh pulverized glass particles are then mixed with a sufficient amount of binder, foaming agent and water to form the glass articles. In accordance with preferred embodiments of the present invention, the foaming agent comprises carbonate, for example, calcium carbonate (CaC0) , which decomposes into calcium oxide (CaO) , and carbon dioxide (C0₂) . Applicants have found that a preferred composition comprises about 85% pulverized glass, about 15% foaming agent, plus about 6% binder of that total weight. This mixture is preferably moistened with water to about 6% of the total weight of the mixture, depending on the pellet-forming method and the type and amount of binder used, plus about 5% sodium silicate solution if the mold method of forming pellets is used. After preparing the mixture of glass particles, binder, foaming agent and water, the glass articles may be produced according to any one of the four different peUetizing methods discussed above. This enables the selection of a desired size and shape for the resultant foamed glass articles. In a further preferred embodiment, the pulverized glass mixture described above is pressed with a die to form glass articles in a desired shape. A preferred shape obtained is a cylinder which can have a size of between about 1" to about 1-1/2" in diameter, and between about 1-1/2" to about 2-1/2" in length. After foaming, the glass articles can increase substantially in size due to the foaming action.

A further preferred method of peUetizing the pulverized glass mixture is the briquetting method described in U.S. Patent No. 5,049,333, wherein the glass articles are formed in a method analogous to that of producing charcoal briquettes from a pulverized charcoal mixture. These glass articles may also be sized to about 1" to about 1-1/2" in width, and between about 1-1/2" to, about 2-1/2" in ength. Due to the foaming effect, these articles generally increase in size to about 2" in width and about 3" in length.

A third preferred method of peUetizing is the mold method, in which paper molds of a predetermined size and shape are filled with the preferred mixture of pulverized glass, foaming agent, binder and water, plus sodium silicate solution. The filled paper molds are vibrated to expel air, and are then dried, heated and cooled as described above. A fourth preferred method of forming pellets is the cut-out method, in which the glass particle mixture is formed into thick slabs, somewhat analogous to thick "pie crust dough." The cutters cut out pellets of the desired size and shape, which are then expelled by air onto stainless steel trays for heating as described above. The surplus cuttings of the "dough slab" are then returned to mixing to be formed into new "dough slabs." After the glass articles are formed and produced by any of the above four methods, they are preferably fed into a kiln for firing, to produce the final foamed articles.

Referring to the drawing, wherein like numerals refer to like elements, Figure 1 is a schematic representation of a process line according to preferred embodiments of the present invention. A pair of kilns, shown generally at 10, is shown for use in producing foamed glass articles in accordance with the present invention. For volume and efficiency in manufacturing, multiple kilns may be used.

The production line shown in Figure 1 preferably comprises a mixer 20 which produces the mixture of pulverized glass, binder, foaming agent and water. PeUetizing means 30 for producing the prefoamed glass pellets is provided and utilizes one or more of the preferred peUetizing methods described hereinbefore. Pellet feeding means 40 is further preferably provided at the entrance of kilns 10 for loading the kiln trays with the pre-foamed pellets. The pellets may be fed from pellet feeding means 40 through oscillating tray feeder means 45 onto stainless steel trays for transporting the pellets into and through the kilns.

Multiple oscillating tray feeder means 45 may be used, or other types of feeders known to those skilled in the art, to load the pellets on to the trays. The feeder means 45 feeds the glass articles at a uniform rate onto stainless steel trays traveling through the kilns 10. From the feeder means 45, the glass articles preferably enter the drying means 50 of the kiln 10. The drying means 50, which is preferably disposed at the exit of the feeder means 45, removes moisture from the glass articles. The glass articles are then conveyed through the kiln 10 to the drying area 60 for final removal of moisture. The temperature in the drying area 60 rises to about 350°F and the glass articles remain heated in the drying area 60 for about 15 minutes to about 30 minutes. Preferably, the glass articles are heated in the drying area 60 for about 20 minutes. While in the drying area 60, the glass articles become substantially completely devoid of all moisture.

In certain embodiments of the present invention, the moisture content of the glass articles may be high. In such cases, it is contemplated that a separate drying means 50 to dry the glass articles, which is separate from the kiln 10, may be used. Such a separate drying means 50 advantageously minimizes kiln investment and operating expense. However, even in such a case, the drying area 60 in the kiln is desirable, since the pellets are raised to the drying temperature in any case, in passing from ambient temperature to the foaming area 70, as discussed more fully hereinafter. After passing through the drying area 60, the glass articles are transported further into the kiln at steadily increasing temperatures until they reach the foaming temperature area 70. In the foaming area 70, the glass articles are heated to a first elevated temperature and for a time to cause the foaming agent to evolve gas, thereby producing foamed glass articles. In accordance with preferred embodiments of the present invention, the glass articles are heated in the foaming area 70 to a temperature of about 1570°F for about 15 to about 30 minutes. Preferably, the glass articles are heated at the foaming temperature for about 20 minutes.

After heating the glass articles to the foaming temperature and holding them at that temperature for a desired time in the foaming area 70, the foamed glass articles are preferably removed from the foaming area 70 and cooled to ambient temperature in a controlled manner in the cooling area 80 of the kiln, in three cooling areas or stages as follows: (1) Much of the cooling may be accomplished at a relatively rapid rate by injection of ambient air in a first rapid cooling area 90 to cool the foamed articles to an upper critical temperature of about 1000°F;

(2) Additional cooling is achieved in a slow cooling area 100 wherein the slower cooling rate of the foamed articles importantly affects the properties of the final product. Cooling of the foamed articles in the cooling area 100 is preferably sufficiently slow to allow for proper annealing of the foamed glass articles. This "slow cooling area" 100 is characterized by the temperature boundaries described earlier as the upper critical temperature and the lower critical temperature. The upper critical temperature is preferably about 1000°F, and the lower critical temperature is preferably about 500°F;

(3) The foamed glass articles are then preferably cooled rapidly in the third cooling area 110 wherein the foamed glass articles are cooled to a temperature between the lower critical temperature and the ambient temperature surrounding the kiln 10.

It has been found that the foamed glass articles can be cooled very rapidly by injection of large amounts of ambient air, from the foaming temperature of about 1570° to the upper critical temperature of about 1000°F; from the upper critical temperature of about 1000°F to a lower critical temperature of about 500°F; and from the lower critical temperature of about 500° F to about ambient temperature, without causing thermal deterioration or destruction of the integrity of the pellets.

When the cooling process is completed, the foamed glass articles are taken out of the kilns 10 by the roller conveyor means 120 to a storage facility or to shipping. The resulting foamed glass articles will have different dimensions depending on the dimensions of the glass articles before foaming, and will have varying shapes according to the desired application. The foamed glass articles are generally larger than the glass articles before foaming and have good abrasive qualities. In accordance with preferred embodiments, the foamed glass articles can be sized between a smaller size about the size of a golf ball and a larger size about the size of a baseball. Generally, the foamed glass articles of the present invention are about 1 to about 1-1/2 inches in diameter and about 2 to about 4 inches in length. It is contemplated, however, that the foamed glass articles can be produced in any size desired. Applicants have found that the foamed glass articles produced according to the methods of the present invention possess various desirable characteristics. For example, the foamed glass articles of the present invention are annealed and are generally lacking in brittleness, stresses, and fractures. Accordingly, the foamed glass articles are substantially durable, and can be used repeatedly for various applications, including stone-washing of garments.

The following prophetic examples are useful to understand the characteristics of foamed glass articles provided in accordance with the present invention and the methods of making the same:

EXAMPLE 1

A mixture of 85% finely pulverized glass and 15% pulverized CaC0₃, about 300 mesh, is prepared. Based upon the total weight of this mixture, about 6% by weight bentonite clay binder and about 6% by weight water is added. Glass articles are made by pressing the mixture with a die to create a cylinder. A preferred dimension of these glass articles is about 1" to about 1-1/2" in diameter, to about 1-1/2" to 2-1/2" in length.

The articles are then placed in a kiln having a drying area as described above. Once in the kiln drying area, the temperature rises gradually to about 350°F, and the articles are held at this temperature for about 20 minutes. After the pellets have been thus dried, they are conveyed through increasing heat to the kiln foaming area. The foaming area is heated to a temperature of about 1570°F where the glass articles remain for about 20 minutes. During this time, substantially all of the foaming agent decomposes to produce gas and thereby produces the foamed glass article.

As soon as the foaming is complete, the foamed glass articles continue to travel through the kiln into the cooling areas. Rapid cooling of the foamed glass articles occurs from the foaming temperature until the glass articles reach the upper critical cooling temperature, about 1000°F. The foamed glass articles are cooled slowly between the upper critical cooling temperature and the lower critical cooling temperature, about 500°F. Finally, the foamed glass articles are cooled rapidly again from the lower critical cooling temperature to ambient temperature in a second rapid cooling zone. The foamed glass articles are then sent out of the kiln, and can have dimensions of from about 1-1/2" in diameter up to about 4" in length, or any other size desired. EXAMPLE 2

A mixture of 85% finely pulverized glass and 15% pulverized calcium carbonate, about 300 mesh, is prepared. Based on the total weight of this mixture, about 6% by weight bentonite clay binder and about 6% by weight water is added. This mixture is formed into briquettes resembling charcoal briquettes, which generally have dimensions of about 1-1/8" in width by about 1-7/8" in length. The briquettes are sent through a drying means and through a kiln substantially as described in Example 1 above. The resulting foamed glass articles can have dimensions of about 1-3/4" in width by about 2-1/2" in length, or any other size desired. EXAMPLE 3

A mixture of 85% finely pulverized glass, and 15% calcium carbonate, about 300 mesh, is prepared. Based upon the total weight of this mixture, about 6% by weight of clay binder, about 6% by weight water, and about 5% by weight liquid sodium silicate is added.

Paper molds are filled with the above mixture. The filled paper molds are placed on stainless steel kiln trays and vibrated vigorously for a few minutes. Due to the presence of sodium silicate in the mixture, the mixture becomes thixotropic, and air in the mixture in the molds is removed. This importantly prevents undesirable air voids in the final glass articles. The loaded kiln trays are then be sent to the drying area of the kiln, and on through the kiln as described above.

Foamed glass articles and methods of producing foamed glass articles provided in accordance with the present invention achieve superior quality artificial pumice stones compared to natural pumice stones, and are particularly useful for use in the stone-washed garment industry since they have many advantages over natural pumice. The residue produced by the wearing away of foamed glass stones is of substantially higher quality than the sludge produced in connection with natural pumice. Pumice sludge is useless and must be disposed of in a landfill at substantial cost to the user. Foamed glass residue, on the other hand, is virtually 100% glass, and a substantial amount of this glass can be re-used in the manufacture of other foamed glass pellets, and for other foamed glass uses, such as in the construction industry.

Foamed glass pellets described herein can be made almost totally from mixed color waste glass cullet, for which in most parts of the country there is little or no market. Thus, the methods disclosed and claimed herein make a major contribution towards recycling efforts and to the environmental improvement of the nation. The use of foamed glass pellets will substantially completely eliminate the need of strip-mining of natural pumice deposits such as those in the Jemez mountains of New Mexico, which have great environmental, historic, and natural beauty significance. It also appears that it may be possible to produce foamed glass pellets at less expense than the cost of producing pumice stones from natural pumice, which includes mining, crushing, screening, and very large transportation costs. This may result in economies to the stone-washing companies and lower prices for consumers.

There have thus been described certain preferred embodiments of foamed glass articles and methods of making the same provided in accordance with the present invention. While preferred embodiments have been described and disclosed, it will be recognized by those with skill in the art that modifications are within the true spirit and scope of the invention. The appended claims are intended to cover all such modifications.

Claims

CLAIMSWhat is claimed is:

1. A method of producing foamed glass articles comprising the steps of: (a) pulverizing glass particles and mixing with the pulverized glass particles an amount of foaming agent, binder and water to produce a glass particle mixture;

(b) forming the glass particle mixture into glass articles; (c) heating the glass articles to a first elevated temperature and for a time to substantially remove moisture from the glass articles and to prevent the formation and emittance of steam during heating and foaming of the glass articles;

(d) further heating the glass articles to a second elevated temperature and for a time to cause substantially all of the foaming agent to emit a foaming gas emission; and

(e) cooling the glass articles to produce foamed glass articles.

2. The method according to claim 1 comprising mixing the glass particles with a binder selected from the group consisting of ball clays, bentonite clays, and sodium silicate.

3. The method according to claim 1 comprising mixing the glass particles with a foaming agent comprising CaC0₃.

4. The method according to claim 1 wherein step (b) comprises pressing the glass particle mixture with a die to form glass articles substantially in the shape of cylinders.

5. The method according to claim 4 comprising forming the glass articles substantially in the shape of cylinders having a diameter of about 1 to about 1-1/2 inches and a length of about 2 to about 4 inches.

6. The method according to claim 1 wherein step (b) comprises forming the glass articles into briquettes.

7. The method according to claim 1 wherein step (b) comprises placing the glass particle mixture in paper molds to maintain the mixture in a predetermined shape until the mixture becomes substantially self-adhering.

8. The method according to claim 1 wherein step (b) comprises cutting out the glass articles with a cutting means and expelling the glass articles from the cutter means by air.

9. The method according to claim 1 wherein step (c) comprises heating the glass articles to about 350°F for a time to substantially remove the moisture from the glass articles.

10. The method according claim 9, wherein step (c) comprises heating the glass articles to about 350°F for about 15 minutes to about 30 minutes.

11. The method according to Claim 10, wherein step (c) comprises heating the glass articles to about 350°F for about 20 minutes.

12. The method according to claim 1 wherein step (d) comprises heating the glass articles to a temperature of about

1650°F.

13. The method according to claim 11 wherein step (d) comprises heating the glass articles to about 1570°F for about 15 minutes to about 30 minutes.

14. The method according to claim 13 wherein step (d) comprises heating the glass articles to about 1570°F for about 20 minutes.

15. The method according to claim 1 wherein the cooling step (e) comprises the steps of:

(i) cooling rapidly the glass articles from the foaming temperature to a first cooled temperature; (ii) cooling slowly the glass articles from about the first cooled temperature to a second cooled temperature;

(iii) cooling rapidly the glass articles from about the second cooled temperature to a third cooled temperature.

16. The method according to claim 15 wherein step (i) comprises cooling the glass article from about the foaming temperature to about an upper critical temperature.

17. The method according to claim 16, wherein step (ii) comprises cooling the glass article from about the upper critical temperature to about a lower critical temperature.

18. The method according to claim 17 wherein step (iii) comprises cooling the glass articles from about the lower critical temperature to about ambient temperature.

19. The method according to claim 18 wherein the upper critical temperature is about 1000°F.

20. The method according to claim 19, wherein the lower critical temperature is about 500°F.

21. A kiln assembly comprising a kiln for producing foamed glass articles comprising: (a) pellet tray feeder means disposed at an entrance of the kiln for feeding kiln trays containing glass articles to be foamed;

(b) drying means disposed at an exit of the pellet tray feeder means and in front of a front portion of the kiln for removing moisture from the glass articles; and (c) heating means disposed at an exit of the drying means for heating the glass articles to a foaming temperature to produce the foamed glass articles.

22. The kiln assembly according to claim 21 wherein the heating means comprises a plurality of heating areas having different temperatures, the heating areas being adapted to heat the glass articles to a temperature to cause the glass articles to become foamed glass articles.

23. The kiln assembly according to claim 22 wherein the heating means further comprises a controlled cooling means for cooling the foamed glass articles in a controlled manner.

24. The kiln assembly according to claim 23 wherein the cooling means comprises:

(a) a first cooling area which is adapted to cool rapidly the foamed glass article from about the foaming temperature to about an upper critical temperature;

(b) a second cooling area which is adapted to cool slowly the foamed glass articles from about the upper critical temperature to about a lower critical temperature; and (c) a third cooling area which is adapted to cool rapidly the foamed glass articles from about the lower critical temperature to about ambient temperature.

25. The kiln assembly according to claim 24 wherein the upper Critical temperature is about 1000°F.

26. The kiln assembly according to claim 25 wherein the lower critical temperature is about 500°F.

27. The kiln assembly according to claim 21 wherein the kiln further comprises a drying area which is separate from the drying means for final removal of moisture from^" the glass articles.

28. A foamed glass article being produced from a glass article comprising a mixture of pulverized glass particles, foaming agent, binder and water, wherein the glass article is heated and dried to remove excess moisture and further heated to cause the foaming agent to emit a foaming gas, thereby foaming the glass article which is then cooled.