MXPA00003028A - Manufacture of ceramic tiles from industrial waste - Google Patents

Abstract

The present invention relates to a process of forming ceramic tiles having the appearance of tiles produced from clays. The process includes melting a material to form a glass melt, treating the glass melt to produce a solid glass product, grinding the solid glass product to produce glass particles having a particle size of less than 200 microns, mixing the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99 wt.%glass particles and 45-1 wt.%first additive, forming the glass powder mixture into tiles by dry pressing, where the tiles have a primary crystalline phase selected from the group consisting of nepheline, diopside, anorthite, wollastonite, melilite, merwinite, spinel, akermanite, gehlenite, crystalline phases based on iron substitutions in the crystalline phase, and mixtures thereof. The process includes a devitrifying step where the solid glass product is devitrified prior to the grinding step or the glass particles in the tile are devitrified after the forming step.

Description

MANUFACTURE OF CERAMIC SLABS FROM INDUSTRIAL WASTE FIELD OF THE INVENTION This invention relates to the manufacture of ceramic slabs that include a high percentage of recycled glass incorporated in the slab.

BACKGROUND OF THE INVENTION Industrial wastes such as boiler ash dust, crusher waste ash, sewage sludge ash, municipal solid waste incinerator ash, crucible coatings or containers worn from the reduction of aluminum, and kiln dust from electric arc, represent a larger portion of all solid waste that is placed in landfills in the United States and is therefore becoming a major environmental problem. These solid wastes may contain heavy metal contaminants that require adequate disposal methods to prevent leaching of metal contaminants.

REF .: 119088 heavy within the aqueous supplies. This has focused attention on the landfill reduction and regulations that prevent leachable toxic materials from being deposited in landfill fields. Therefore, substantial efforts have been made to develop the uses for these solid waste materials as safe recycled products. The traditional method of slab manufacturing involves the mixing of clays and other materials in a powder batch that can be shaped by dry pressing on a slab, drying, glazing, and baking to produce a final product. Typically, clays, minerals and other additives are mixed in a ball mill with water. Ball milling provides a method to reduce particle size and intimately mix raw materials. The process of grinding with balls results in a suspension of raw materials in water. The suspension of the ball mill is spray dried to remove the water, and to produce a granular material that provides a feed material to the slab presses. The granular material from the spray dryer consists of agglomerates of raw material particles. The agglomerates typically form a free-flowing powder that is easy to transport, which does not form cakes, and evenly fills the dies used to press the slabs. The slabs are pressed to form them, using a hydraulic press. Pressed slabs are dried to remove water that may be present after pressing. The dry slabs are then glazed to provide a smooth, durable and aesthetically pleasing finish. The slabs are then typically lit in a tunnel kiln. During the baking process, clays and other compounds react to fuse in a solid ceramic material. The current cooking or baking technology allows the baking cycle in traditional slab production to be less than one hour. The shorter baking times of traditional clay bodies are limited by the organic material present in the clay. A composition with high carbon content in the clay can lead to "black core" in the final slab product. The black core occurs when the center of the slab body gets a dark color due to the effects of reducing the incompletely oxidized carbon. This effect is undesirable in the production of slabs. The raw materials combined to produce a slab body perform different roles in achieving the properties of the final product. The fluxes soften and form a liquid that dissolves and binds the particles together. The fluxes used in the slab industry include feldspars and glass frits. The plasticizers and binders join the slab together before the slab is baked. The plasticizers and binders include clays with fine particle sizes such as ball clays and organic binders. 'Body fillers provide the structure of the slab body. Typically, these materials do not deform significantly during the baking process. Body fillers include quartz, flint, anorthite, raw clays (kaolin), and molochita "calcined clay". One method of using recycled glass involves the incorporation of waste or pieces of waste glass from vessels into ceramic slab bodies. The broken glass waste from containers has a soda-limestone-silicate composition (approximately 14% by weight of Na20, 10% by weight of CaO, and 76% of Si02). The waste of broken glass is crushed into a fine powder, mixed with other materials such as clay, silica, or talc, pressed into a slab shape, glazed, and baked to give a final product. During the firing or firing process, the glass melts and forms a viscous liquid that dissolves the other materials in the batch and leads to a high densification ratio of the slab body. In this way, due to the low temperature of softening of the waste or broken pieces of broken glasses of containers (approximately 700 ° C), the use of broken glass waste from containers is limited to the role of a flux in the body of the slab. Consequently, this method is not satisfactory, because the addition of recycled glass to the batch is limited to less than 40% by weight. British Patents Nos. 1,163,873, 1,167,812, 1,195,931 and French Patent No. 1,557,957 to Bondarev et al. Describe a process for vitrifying various industrial waste materials, in a glass, forming the molten glass into sheets, and then heat treating the glass to form a devitrified product. U.S. Patent No. 5,250,474 to Siebers discloses a method for producing hexagonal cordierite from sintered glass. The method includes melting a glass powder, quenching the melt to form a piece of glass, grinding the slice, pressing the particles into a shaped article, and sintering it to form a devitrified product. U.S. Patent No. 3,942,966 to Kroyer et al. Relates to a method for the preparation of a ceramic material comprising particles of a devitrified glass and a silicate binder. The method includes the formation of a mixture of crystallizable glass frit particles and a silicate binder and, optionally, waste glass. The mixture is heated to melt and de-vitrify the glass, followed by cooling the mixture, forming a plate, and firing the plate to produce construction elements, such as bricks. The crystallizable glass frit used in the mixture is prepared by melting the initial materials, preferably having the following composition: more than 60% by weight of SiO2; more than 20% by weight of CaO + MgO; less than 5% by weight of A1203; less than 5% by weight of K20 + Na20; less than 1% by weight of Fe203; and less than 1% by weight of S. The melt is then quenched and crushed to less than 2 mm. British Patent No. 986,289 relates to a material produced by the devitrification of a glass made from a metallurgical slag. The material, which may be a floor slab, is produced by the steps of preparing a melt consisting essentially of 45 to 65% by weight of SiO2, 15 to 45% by weight of SaO, 5 to 30% by weight of A120, and up to 10% by weight of MgO, and the thermal treatment of the melt to cause devitrification. A nucleating agent may be added to the melt to cause devitrification of the composition during this heat treatment. The heat treatment is comprised of either heating or cooling the melt to cause devitrification. Although these methods have been found to be useful in the conversion of waste products to a useful form as a final product, they do not sufficiently oxidize the organic material and metal contaminants in the waste material to produce a quality ceramic product. uniform. In addition, these procedures are not adequate to use high percentages of recycled waste as a raw material in the process. In addition, none of these procedures produces a high value final product with significant demand in the market. As a result, the economic justification for the capital and operational costs of implementing such procedures for the disposal of industrial waste tends to be problematic. The present invention is directed to overcome these deficiencies.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process of forming ceramic slabs that have the appearance of slabs produced from clays. The process includes the melting of a material to form a glass melt, the treatment of the glass melt to produce a solid glass product, the grinding of the solid glass product to produce glass particles having a particle size of less than 200. micrometers, the mixing of the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99% by weight of glass particles and 45-1% by weight of a first additive, the formation of the mixture of glass powder in slabs by pressing by drying, where the slabs have a primary crystalline phase selected from the group consisting of nepheline, diopside, anorthite, wollastonite, melilite, erwinite, spinel, ermanite, gelenite, crystalline phases based on iron substitutions in the crystalline phase, and mixtures thereof. The process includes the step of devitrification where the solid glass product is devitrified before the milling step or the glass particles in the slab are devitrified after the forming step. Yet another aspect of the invention is a ceramic slab having a composition of 35 to 60% by weight of SiO2; from 3 to 25% by weight of A1203, from 0 to 25% by weight of CaO, from 0 to 20% by weight of MgO, from 0.5 to 15% by weight of Fe203; from 0 to 15% by weight of Na20, from 0 to 5% by weight of K20, from 15 to 30% by weight of CaO + MgO, from 0 to 15% by weight of Na20 + K20 and from 0 to 5% by weight weight of other oxides. The method of the present invention provides the use of waste or recycled glass as a material to be incorporated with other materials to produce a high-value, low-cost, high-quality final product. In addition, the very low carbon content in the recycled glass allows high baking rates to be utilized with the slab bodies without the appearance of "black core", which is commonly found with ceramic bodies made from raw materials standards In addition, the method of the present invention allows the use of high percentages of recycled glass as a raw material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow diagram of the process of the present invention.

Figure 2 is a perspective view of an apparatus useful for carrying out the process of the present invention.

Figure 3 is a side cross-sectional view of the apparatus of Figure 2.

Figure 4 is a top cross-sectional view of the apparatus of Figure 3, taken along line 4-4.

Figure 5 is a temperature profile used for devitrification in the glass process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for forming ceramic slabs that have the appearance of slabs produced from clays. The process includes the melting of a material to form a glass melt, the treatment of glass melt to produce a solid glass product, the grinding of the solid glass product to produce glass particles having a particle size of less than 200 micrometers, the mixing of the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99% by weight of glass particles and 45-1% by weight of a first additive, the formation of the mixture of glass powder in slabs by dry pressing, where the slabs have a primary crystalline phase selected from the group consisting of nepheline, diopside, anorthite, wollastonite, melilite, merwinite, spinel, akermanite, gelenite, crystalline phases in iron substitutions in the crystalline phase, and mixtures thereof. The process includes the step of devitrification where the solid glass product is devitrified before the milling step or the glass particles in the slab are devitrified after the forming step. Typically, the chemical composition of the raw materials used to produce slabs by the processes of the prior art consists mainly of oxides and hydroxides of metals, Si, Al, Ca, and Mg, which react during the cooking process to produce the body of final ceramic. To reduce the industrial waste materials generated by the society that have high concentrations of these oxides, it is highly desirable to replace these traditional raw materials with industrial waste. Waste materials, however, need to be selected to adequately fill the required roles of the raw material that is replaced. The method of the present invention allows the use of recycled glass compositions which may comprise the majority of a slab composition. The method for incorporating these high amounts of recycled glass as a feedstock involves the engineering design of a recycled glass composition from. industrial waste. By selecting the optimum composition of the recycled glass, the recycled glass no longer fulfills the role of a flux in the slab body, but is selected to act as a filler for the slab body. The composition of the recycled glass is critical, because the glasses are thermodynamically unstable with respect to the crystalline forms of the oxides below the melting temperature of the crystalline phase.

By heating a glass according to the specific cycle of thermal treatment, the oxides that make up the glass can be converted to crystalline phases. The materials produced in this way are referred to as glass ceramics. The crystallization rate and the crystalline phases obtained are dependent on the composition of the glass and the heat treatment cycle. The physical properties of the glass material change with the transition from a glass to a crystal. As an example, the melting temperature of the crystalline phases is greater than the softening temperature of the glass. The method of the present invention allows devitrification of the glass at one of two points in the process. The glass is devitrified either before or after the glass (and other materials) are formed in the slab and cooked. By devitrifying the glass prior to formation in the body of the slab, the softening / melting temperature of the material is increased above the cooking or firing temperature of the ceramic body. Alternatively, if the glass is mixed with other materials and formed in the slab body without prior devitrification, during the firing process, the small glass particles will soften slightly and de-vitrify to form a crystalline material. The melting temperature of the devitrified glass in both cases is such that the body of the slab is not deformed during the cooking process. In addition to producing a product that is suitable for use as a body filler in the manufacture of slabs, the initial process of vitrification during oxidation stabilizes hazardous metals and destroys the organic materials that may be present in these waste streams. The selected glasses can be prepared from industrial waste and / or from commercially exploited raw materials. The general composition range of the industrial waste useful in the present invention is given in Table 1: Table 1 Other oxides include copper, manganese, chromium, nickel, zinc, arsenic, lead, gold, silver, sulfur, and mixtures thereof. In addition, industrial waste can include carbon and metallic contaminants. A variety of industrial waste suitable for producing a recycled glass composition comprises most of the material in a traditional slab process by dry pressing. By using these industrial wastes, ceramic slab bodies with up to 98% by weight of recycled glass can be obtained in the body of the slab. The types of industrial waste useful as a feedstock for the present invention include, for example, ash dust from boilers of facilities ignited by mineral coal, ash from municipal waste incinerators, coatings from spent vessels or pots, from the aluminum reduction, metal plating wastes, electric arc furnace dust, smelting sands, drainage slag ash, and cement kiln dusts. The composition of the coating of spent pots or containers, typical is given in table 2.

Table 2 Composition of crucible coating, worn, typical Constituent Concentration range (ppm Arsenic .001-26 Bario < .09-200 Cadmium .01-4.9 Chrome < .01-33 Lead < .01-44 Mercury < .0002-.49 Selenium .004-.96 Silver .01-2 Cyanides < .02-64, 000 Reagent cyanide 1.09-30.9 Fluoride 230-250,000 Reactive sulfide < .11-6.24 Aluminum 47, 000-222, 000 Antimony 13-33 Beryllium 6.2-17 Carbon 130, 000-690, 000 Cobalt 11-16 Copper 12-110 Magnesium 100-1, 700 Manganese 0-200 Nickel 16-40 Sodium 86, 000-220, 000 Thallium < .5 Tin 72-120 Vanadium 75-120 Zinc .1-63 Alumina 78, 000-260, 000 Calcium 5, 000-64, 000 Iron oxide 3, 000-28, 000 Phosphorus 50-300 Silicon oxide 7, 000-109, 000 Sulfur 0-3, 000 Fluorine 99, 000-182, 000 Ash% 57.1-79.5 Typical ash powder compositions are shown in Table 3.

Table 3 Composition of typical Ash dust The typical composition of the electric arc furnace powder is shown in Table 4 below.

Table 4 Composition of typical electric Arc Furnace Dust The family of glass compositions used in the process of the present invention is such that the glasses are lower in alkali oxides and higher in alkaline earth metal oxides than typical commercial glasses, such as soda-limestone-silicate glass. The use of glass having this composition decreases the structural stability, from an atomic perspective, of the glass above the glass transition temperature. This leads to the crystallization of the glass at higher proportions in the temperature range from the vitreous transition temperature to the liquid crystallization temperature, whereby a slab is produced which does not deform during a rapid cooking process. Figure 1 is a flow chart of the process for the process of the present invention. In this process, the material A of the industrial waste may optionally be mixed with other additives B. Other additives B may include small amounts of other glass-forming ingredients to bring the composition of material A into the range of glass oxide composition. desired, as shown in Table 1. Other additives B include sand, ash dust, titania, zirconia, limestone, dolomite, soda ash, and mixtures thereof. In addition, the different types of industrial waste materials can be combined to give an industrial waste material A having the desired composition of glass oxide. Other additives B may include a nucleation enhancing agent to increase the crystallization rate by improving the nucleation rate of the seeds to provide sites for development. These nucleating enhancing agents include MgO, Ti02, F, Cr203, sulfides, phosphates, and mixtures thereof. In addition, the nucleating agent may be present in the industrial waste material A itself. The industrial material A or any other additives B are mixed in the mixer 2 to produce the mixed material C. The mixed material C is processed in a melter 4 to form a glass melt D, where the glass melt D is a molten liquid uniform. Typically, casting occurs at a melting temperature of approximately 1100 ° to 1550 ° C from 0.25 to 6 hours. During the smelting process, the industrial waste material A and the other additives B decompose and react to form oxides of the metals present in the industrial waste material A and other additives B. The metal oxides react and combine to form a melt Glass D. An oxidizing atmosphere during the glass melting processes operates to oxidize the carbon and metals in their metallic state that are potentially present in the selected industrial waste material A. Typically, the melter is a cyclone melter.

They can also be used for bath, kettle, open crucible, or electric smelters. A particularly preferred form of caster 4 is the Combustion and Casting System manufactured by Vortec Corporation, Collegeville, Pa. The oxidation is carried out in the suspension preheater of the Combustion and Casting System, in which the molten material C is suspended in an oxidant fluid. Preferably, the suspension preheater is a whirling, counter-rotating suspension preheater. The smelting and oxidation system is described in U.S. Patent No. 4,957,527 to Hnat, which is incorporated by reference herein. See also U.S. Patent No. 4,544,394 to Hnat, which is incorporated by reference herein. Figure 2 is a perspective view of the Combustion and Casting System, useful in the practice of the process of the present invention. The main components of the apparatus of the invention include a preheater chamber type 100, the cyclone casting chamber 200 at the discharge end of the preheater chamber 100, and the cyclone outlet assembly 300 at the discharge end of the chamber. casting 200. Other components, such as a gasifier and the plasma torch preheater can be incorporated in this system. See U.S. Patent No. 4,957,527. As shown in Figure 3, the fuel 30 is introduced into the top or head end 102 of the preheater 100. The fuel 30 is introduced together with material from the glass batch 10 through the injector assembly 104 which is located at the head end 102 of the preheater 100, and which is coaxial with the longitudinal axis of the preheater chamber 100. The preheating step is very important for the invention. The well-stirred suspension / clogging flow preheater 100 improves thermal transfer by convection to the particulate material, while providing combustion stabilization when combustion occurs within the preheater vessel. Due to the intense mixing, rapid heat release takes place in the combustion processes. By selecting the proper injection site and speed, the interaction of the particulate mineral material with the preheater walls can be either minimized or maximized. The axial injection will tend to minimize the interaction with the preheater wall, while the tangential injection tends to maximize the interaction with the reactor wall, particularly where high levels of turbulence are used. As shown in Figure 4, preheated air or other suitable gaseous oxidizing material 20a, 20b is introduced into the preheater 100 through two or more inlet gates 106a, 106b. These gaseous oxidizing materials 20a, 20b are introduced in such a way that they produce turbulent mixing of the injected fuel 30 with the oxidizing material 20a, 20b and the glass batch material 10 (for example crusted composition B of Figure 1). The result is a mixture of fuel, oxidant, and glass-forming materials in the upper region 108 of the preheater 100. Within the upper region 108, the gases present are either well stirred or mixed, but the particulate material (e.g. glass-forming materials) in the region 108 is not necessarily agitated or evenly distributed throughout the volume of the region 108. When a counter-rotating preheater is used, as shown in Figures 3 and 4, the inlet gates 106a, 106b are tangential to the container walls and are separated at different levels. The jets are typically vertically spaced in the order of ^ to 2 diameters of separation reactor. The combustion of the fuel 30 and the oxidizing material 20a, 20b within the upper region 108 of the preheater 100 results in a high intensity heat release and also results in a rapid heat transfer rate to the particulate material (e.g. glass-forming materials) suspended in the gas flow within this region. Ignition within the preheater occurs via mixing and agitation of the fuel and oxidant within the well-stirred region of the reactor. The ignition occurs inside the preheater with the help of a pilot burner or a conventional electric ignition assembly. In the preferred embodiment, preheating of high temperature air is provided (>500 ° C) via a commercially available heat recovery unit. In these cases, the radiation coming from the walls of the reactor coated with refractory material, preferred, will establish in general the autoignition of the various mixtures of fuel and oxidant that are going to be used. The force of circulation in the upper region 108 of the preheater 100 is created by the contractuating vortices or the colliding jets, thereby providing the primary means of stabilizing the flame within the preheater. Without this strong recirculation of the combustion gases, the extinguishing of the flame tends to occur due to the extinguishing of the flame by the inert batch materials or other mineral material within the preheater assembly. This is particularly true for mineral material, such as limestone, which releases substantial amounts of C02 upon heating. When using low heating value fuels, auxiliary gas injection, separate igniters, or pilot burners may also be used to achieve flame stabilization within the preheater. When the preheater 100 is a cylindrical combustion chamber, primary flame and heat release occurs in the upper region 108, which occupies a chamber volume with a length-to-diameter ratio of approximately 0.5: 1-3.0: 1. , preferably 1: 1. The strong mixture of fuel and oxidant within this region allows the effective combustion of many types of fuels, including gaseous, liquid, solid or liquid-solid suspension fuels. Current below the upper region 108 within the preheater 100 is the lower region 110 or piston-like expense, where a piston-like expense of the gas and solid or liquid particles is produced, and where the final combustion of the fuel 30 is completed. By piston-type expense, it is understood that the recirculation patterns of the gas have been lowered and the main flow direction is parallel to the longitudinal axis of the reactor. The effective length-to-diameter ratio of the piston-type expenditure region 110 is again about 0.5: 1-3.0: 1, preferably 1: 1. The gaseous materials, the fuel 30, the oxidants 20a, 20b, and the entrained mixed materials C within the piston-like expense region 110, are accelerated through the convergence section 112 of the preheater chamber 100. From the 112, the gas materials and the entrained batch are distributed to the cyclone type smelting chamber 200 where secondary combustion occurs at an average temperature that exceeds the melting point of the glass product, and where the separation, dispersion, mixing, and the melting of the materials of the preheated batch occurs along the walls 202. It is the intention of the present invention to heat the mixed arsenals C in suspension and minimize the formation of liquid glass along the 100 preheater walls. However, when low melting point species are included as part of the mixture, some liquid glass species formation will occur along the walls of the preheater due to condensation of the vapor phase or turbulent deposition. The glass melt D formed on the walls 202 of the cyclone casting chamber 200 and the hot gases 32 coming from the cyclone chamber, leave the cyclone casting chamber 200 through the exhaust pipe assembly 300 which it is preferably placed tangential to the walls of the cyclone melting chamber. An outlet channel along the longitudinal axis of the cyclone melter is also possible. It is also desirable to separate the exhaust products from the melt D in a gas separation and interface assembly. In this arrangement, the glass melt D and hot gases 32 leave the cyclone melting chamber 200 through a tangential outlet channel to a reservoir (not shown). The hot gases 32 exit the tank through an escape hatch located in the roof of the tank. The reservoir also provides sufficient quantities of molten glass product 16 to interconnect with the slab forming equipment., downstream. After the cast step, the glass melt D (1) is either cast in water to create a solid glass product such as glass frit E or (2) cooled in a controlled manner to produce a solid glass product , such as cooled product F. In the first option, in a shut-off step 6, the glass melt D is drained into the water at a temperature of about 40 ° to 95 ° C for 0.5 to 10 minutes to quench the melt glass D. The quenching process freezes the glass structure and mechanically stresses the material due to the induced large thermal gradients, which leads to cooling and fracture of the glass melt D in the glass frit E with a particle size typically smaller than 5 mm. The resulting glass frit E is then dried by any suitable method. The glass frit E coming from the shutdown step can be managed using two alternative modes. In the first embodiment, the glass frit E is devitrified in the devitrification step 10 to form a granular crystallized product G. After the devitrification step 10, the granular crystalline material G is introduced into the slab processing process. In the second embodiment, the glass frit E is directly introduced into the slab manufacturing process, without a devitrification step. The first embodiment de-vitrifies the glass frit E in a devitrification step 10 to convert the glass frit E into a crystalline material G. The devitrification step 10 is typically carried out in a tank, in an oven, or in an oven. The devitrification of the glass frit E is carried out by thermal treatment of the material with a specific thermal treatment cycle. The exact heat treatment cycle is dependent on the composition of the glass to be devitrified and would be apparent to a person skilled in the art. Preferably, during the heat treatment cycle, the glass frit E is heated below its vitreous transition temperature at a temperature of about 800 to 1200 ° C. More preferably, the devitrification step 10 includes heating the glass frit at a rate of 200 ° to 1000 ° C per hour up to 800 ° to 1200 ° C, retaining the glass frit at a constant temperature of 0 2 hours, and then cooling the frit at a speed of 200 ° to 2000 ° C per hour up to room temperature. More preferably, during the heat treatment, the glass frit E is maintained at a temperature of less than 100 ° C above its vitreous transition temperature to improve the formation of the crystalline nuclei in the bulk material of the glass frit E Then, as the temperature increases to the maximum, the nucleation rate decreases and the crystalline growth rate increases. The nuclei that have formed, develop and consume the rest of the glass. During the devitrification step 10, a primary crystalline phase occurs where the primary crystalline phase consists of nepheline, diopside, anorthite, wollastonite, melilite, merite, spinel, akermanite, gelenite, crystalline phases based on iron substitutions in the crystalline phase and mixtures thereof. For purposes of this application, the term "primary crystalline phase" is defined as the crystalline phase constituting at least 50% by weight of the crystalline material in the product resulting from the devitrification step 10. In the second embodiment, the glass frit E It is introduced into the slab manufacturing process without any additional processing. The heat treatment to form a devitrified material occurs during the firing of the slab bodies, (discussed below). In an alternative step, the glass melt D is cooled in a controlled manner. The cooling of the glass melt D in a cooling step 8 under a controlled temperature profile will lead to a devitrified product F at room temperature. Typically, the cooling step 8 takes place in a tank. Preferably, the cooling step 8 includes decreasing the temperature of the glass melt D at a rate of 200 to 1000 ° C per hour, to produce the devitrified product F. This devitrified product F can then be introduced directly into the step of grinding of the slab making process. The product F resulting from controlled cooling is similar to the crystalline material obtained by the devitrification step 10 described above. It is desirable to introduce additional nucleation sites into the glass by grinding products E, F, or G in a powder with a particle size of less than 200 microns, and preferably less than 50 microns. This greatly increases the devitrification speed of the glass. In this way, the glass frit E, the devitrified product F or the crystalline material G can be ground in the grinding step 12 to produce glass particles H. The glass particles are then processed in a typical process for the manufacture of glass. slabs The glass particles H are mixed with an additive I to form a glass powder mixture J having a composition of 55 to 99% by weight of glass particles and 1 to 45% by weight of additive I. The additive I it can be any additive typically common in the slab industry, such as clays, silica, dolomite, limestone, organic or inorganic binders, and fluxes. The additive I typically comprises a binder that increases the strength before firing of the slab body after pressing, and controls the properties of the final ceramic body. The binders used in the process can be organic or inorganic. Inorganic binders typically consist of fine clay materials such as bentonite and highly plastic clay (or potters). When organic binders are used, typical additions of 1 to 5 weight percent of the binder to the glass particles are required. For the manufacture of slabs using clay binders, 70 to 90% by weight of the slab body can be glass particles H, with the remainder 10 to 30% by weight comprising clay. The additive I can also include fluxes to lower the firing temperature of the slabs. In addition, the composition of the additive I can be adjusted to obtain the desired properties (such as porosity, water absorption, and thermal expansion) for the final product. This allows a desired type of slab to be obtained (for example, pavers, wall slabs, and roofing shingles). In a ball milling step 14, the glass powder mixture J is mixed in a ball mill with water to further reduce the particle size of the ingredients and uniformly mix the batch. The suspension K generated by the ball mill is then spray-dried in a conventional spray-drying step 16 to form a free-flowing granular feed L for the slab presses. In the pressing step 18, the hydraulic slab presses form the granular feed L of free flow from 100 to 600 kg / cm2 in shaped slabs M. After a pressing step 18, the shaped slabs M are dried in step of drying 20 by an additional process of drying slabs. The resulting non-glazed slabs N can be glazed, in a glazing step 22 to produce a glazed slab O. The glazing step 22 is a traditional glazing step for slabs well known to those skilled in the art. The glazed slab 0 is fired in a slab 24 ignition step, traditional 800 ° to 1250 ° C from 0.3 to 2 hours to produce a final product P. Preferably, the cycle time is less than 1 hour. Alternatively, unglazed N-slabs may be subjected to cooking step 24 without glazing to produce the final product P which can be glazed and subsequently annealed. During the cooking step 24, the glass frit E and the crystalline material G and the product F behave in different ways. Where the products are produced by the method in which devitrification occurs prior to the formation of the slabs (e.g., the product F and the crystalline material G), this ceramic material is not significantly softened during the cooking step 24, due to the high melting temperature of the crystalline materials. The union of the particles in the slab bodies occurs mainly due to the clays and the additive I that react and that form a small amount of a liquid phase that binds the ceramic particles together. Second, a smaller amount of sintering may occur between the ceramic particles to aid in the bonding of the particles together. In the case where the glass was mixed in the slab body without prior devitrification (e.g., from glass frit E), devitrification of the glass occurs during the cooking step 24. The glass is initially softened during the process of cooking at temperatures slightly above the vitreous transition temperature (500 to 750 ° C depending on the composition of the glass) to a very viscous liquid (viscosity of 1014 to 1016 poises). When the body of the slab is heated to a greater degree, the glass softens (for example, the viscosity decreases) and begins to flow. In addition, the crystalline nuclei are formed and the development of crystals occurs, leading to the crystallization of the glass melt. Crystallization consumes a greater part of the glass melt. The crystalline development can also nucleate on the surface of the glass particles (for example, surface crystallization). The surface crystallization leads to the volume of the glass material being devitrified at a high speed due to the high surface to volume ratio of the glass powders. The crystalline phase is strongly dependent on the composition of the glass. The melting temperature of the crystalline phases is typically higher than the processing temperature of the ceramic slabs (e.g.,> 1150 ° C). In this way, during the cooking step 24, a slab having a primary crystalline phase is produced, where the primary crystalline phase consists of nepheline, diopside, anortite, wollastonite, melilite, merwinite, spinel, akermanite, gelenite, crystalline phases in iron substitutions in the crystalline phase and mixtures thereof. The method of the present invention produces a ceramic slab having a composition from 35 to 60% by weight of SiO2, from 3 to 25% by weight of A1203, from 0 to 25% by weight of CaO, from 0 to 20% of MgO, from 0.5 to 15% by weight of Fe203, from 0 to 15% by weight of Na20, from 0 to 5% by weight of K20, from 15 to 30% by weight of CaO + MgO, from 0 to 15% by weight of Na20 + K20, and from 0 to 5% by weight of other oxides. The other oxides include oxides of copper, manganese, chromium, nickel, zinc, arsenic, lead, gold, silver, sulfur, and mixtures thereof. In addition, the ceramic slab has a primary crystalline phase, where the primary crystalline phase consists of nepheline, diopside, anortite, wollastonite, melilite, merwinite, spinel, akermanite, gelenite, crystalline phases based on iron substitutions in the crystalline phase, and mixtures thereof.

EXAMPLES EXAMPLE 1 Glass frits prepared from coal ash dust of coal-fired installation were processed in a glass that is suitable for the production of floor slab bodies. The glass was devitrified before being crushed into particles and mixed with additives in a powder for the pressing of slabs. The slabs were pressed and fired from this material, using a standard, industrial press for slabs, and the rotary crucible furnace. The slab bodies produced had desirable processing behavior and final properties for the commercial slab industry.

The composition of installation boiler ash dust ignited with mineral coal is given in Table 5: Table 5 Based on this analysis, the ash dust required the addition of a flux to lower the melting temperature to less than 1500 ° C. The ash dust was mixed with 20% by weight of limestone to lower the melting temperature. The glass was then melted in a cyclone glass melter at a temperature of about 1450 ° C. This type of smelter allowed the efficient oxidation of the non-ignited coal in the ash dust. The glass produced from the melter was poured into water to produce a frit with a particle size of less than 1 cm. In the resulting composition of the glass produced from this casting process as determined by chemical analysis, it is given in Table 6: Table 6 After drying, the glass frit was devitrified to convert the material of a glass to a crystalline product. The devitrification process was performed in an electric box furnace in batches of 27.2 kg to 54.4 kg (60 to 120 pounds). The material was spread on the oven floor to a depth of approximately 10 cm (4 inches). The glass frit was then heated to approximately 1100 ° C for 4.5 hours. The temperature profile of the heat treatment is given in Figure 5. In Region 1 of Figure 5, the glass was heated at a constant speed. The increase in the heating rate of the material in region 2 of Figure 5 was related to the heat released from the glass as crystallization occurs. The material was then kept at a constant temperature for about 1.5 hours, as shown in region 3 of Figure 5. The resulting devitrified material was then allowed to slowly cool to room temperature in several hours, as shown in Region 4 of Figure 5. The heat treatment process resulted in the color of the glass frit changing from black to brown due to the change in the atomic structure of the material. The resulting crystalline material was crushed with a hammer mill to obtain a powder with a particle size of about 5 mm. Additives were added such that the prepared batch consisted of 91% by weight of crystallized frit, 6% by weight of borosilicate glass frit, 2% by weight in bentonite, and 1% by weight of organic binder. The borosilicate glass frit provided a liquid phase for bonding the ceramic particles together during the firing process, because the bentonite and the organic binder increased the strength before baking the slabs before firing. A wet ball mill reduced the particle size of the crystallized glass pieces and mixed the batch ingredients. The resulting suspension was spray dried to remove water from the system and to form free flowing agglomerates from the particles. The spray-dried powder was a suitable feedstock for slab presses. The resulting spray-dried powder was pressed on 30 x 30 cm slabs with a pressure of 320 kg / cm2. The resulting slabs before firing were dried to remove any remaining, glazed, and cooked water. The slabs were cooked at a temperature of 1170 ° C in a 36-minute cooking cycle (cold to cold). The resulting slabs produced in this example were suitable for application as floor slabs and pavers. The following properties were determined for the prepared slabs. Density 1.75 kg / cm2 Black core none Shrinkage with cooking 7% Water absorption 1.5% Rupture module 500 kg / cm2 EXAMPLE 2 Glasses prepared from municipal solid waste incinerator ash (* MSW ") were processed in a glass that is suitable for the production of slab bodies The glass used in this example was not devitrified prior to slab formation The slabs were pressed and fired using standard industrial slab equipment The slab bodies produced had desirable processing behavior and final properties for the commercial slab industry The composition of the MS ash used in the vitrification process is given in Table 7: Table 7 To prepare a glass of this composition no additives were required for glass formation. The MSW ash was melted in a cyclone type glass melter. The oxidizing atmosphere of this type of melter prevents selected heavy metals such as lead from being reduced from their metallic state. The glass was processed at a temperature of 1275 ° C. The resulting glass melt was poured into water to prepare a glass frit. The composition of the glass frit is given in Table 8: Table 8 The glass frit, without devitrification, was reduced to a particle size < 5.0 mm with a matulos mill. The additives were added such that the composition of the slab lot was 66% by weight of the glass frit, 28% by weight of flexible clay, and 6% by weight of quartz. The batch materials were ground in a wet ball mill to reduce the size of the glass particles and to mix the batch materials. The resulting material was dried and ground to break up the large agglomerates. The resulting powder was then added to 5% by weight of water and passed through a mesh with 0.7 mm openings, to produce a granular material for pressing the slabs. The lot of the slabs was pressed to form slabs, with the dimensions of 16 x 8 cm with approximately 300 kg / cm2 of pressure. The resulting slabs were dried and cooked in a 45 minute cooking cycle (cold to cold). The different samples were cooked at 1040 °, 1080 °, and 1120 ° C to determine the effects of the cooking temperature. The properties of the slabs cooked at 1080 ° C were as follows: Black core none Shrinkage with cooking '4.40% Water absorption 2.53% Rupture module 752 kg / cm2 The properties of the slabs cooked at 1040 ° C and 1120 ° C were essentially the same. This indicates that the dimensions and properties of the final product will be relatively independent of changes in the cooking temperature.

EXAMPLE 3 Glass prepared from crucible coatings worn from the reduction of aluminum, were processed to prepare dense ceramic bodies. The glass used in this example was not devitrified prior to the formation of the slab. The samples were prepared on a laboratory scale. The glass in the pressed bodies seemed to devitrify completely without the body becoming deformed during the cooking process. The ceramic bodies produced have desirable properties for application in the slab industry. Worn-out crucible coatings (* SPL ") from aluminum reduction consist of a combination of graphite block and insulating refractory brick.The insulating brick is mainly composed of Si02, A1203, and CaO.In addition to carbon, the graphite blocks contain residual cryolite (Na3AlF6), cyanides, and aluminate metal.A typical oxide composition of the combined graphite block and the insulating refractory brick is given in Table 9: Table 9 The SPL material was mixed with additional glass forming oxides in adequate amounts to produce a glass batch for the devitrification process which contained 60.0 wt.% SPL, 15.0 wt.% Limestone, 12.5 wt.% Sand, and 12.5 percent by weight glass pieces of container waste. The glass was then melted in a cyclone type glass melter at approximately 1300 ° C. A cyclone melter allowed the efficient oxidation of carbon from the graphite block. The glass produced from the melter was poured into water to produce a frit with a particle size of less than 1 cm. The resulting composition of the glass produced from this casting process as determined by chemical analysis, is given in Table 10: Table 10 A hammer mill was used to reduce the size of the glass frit to less than 0.5 mm. The particle of the glass frit was further reduced, to less than 50 μm, by wet-ball milling. Two batches were mixed with the compositions of the glass frit at 80 percent by weight and kaolin at 20 percent by weight, and glass frit at 70 percent by weight and kaolin at 30 percent by weight. The powder was mixed with 2 weight percent water and pressed into disks with a circular die and a laboratory press. The diameter of the disks was 5.7 cm. The pressure used for the pressing was 70 kg / cm2. The discs were cooked in a box oven at 1100 ° C. The time required to reach the maximum temperature was 2 hours. The temperature was maintained at the maximum temperature for 20 minutes. The discs were cooled to room temperature in a period of about 3 hours. Both disc compositions resulted in ceramic bodies that looked like traditional, baked clay bodies. The properties for the discs for the two compositions are: Property 20% by weight 30% by weight of kaolin kaolin Density 2.12 2.16 Black core None None Shrinkage with cooking 6.62% 6.73 Water absorption 13.25% 6.92% Although the invention has been described in detail for purposes of illustration, it is understood that such details are solely for that purpose, and variations may be made therein by those of skill in the art, without departing from the spirit and scope of the invention, the which is defined by the following claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of. the invention

Claims (30)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A process for the formation of ceramic slabs that have the appearance of slabs produced from clays, characterized the process because it comprises: melting a material to form a glass melt; the treatment of the glass melt to produce a solid glass product; grinding the solid glass product to produce glass particles having a particle size of less than 200 microns; mixing the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99% by weight of glass particles and 45-1% by weight of a first additive; the formation of the mixture of glass powder in slabs by dry pressing, where the slabs have a primary crystalline phase selected from the group consisting of nepheline, diopside, anortite, wollastonite, melilite, merwinite, spinel, akermanite, gelenite, phases crystalline based on iron substitutions in the crystalline phase, and mixtures thereof; and devitrification of the solid glass product before the grinding step or the glass particles in the slab after said forming step.

2. A process according to claim 1, characterized in that the material used to form the glass melt contains from 35 to 60% by weight of SiO2, from 3 to 25% by weight of A1203, from 0 to 25% by weight of CaO. , from 0 to 20% by weight of MgO, from 0.5 to 15% by weight of Fe203, from 0 to 15% by weight of Na20, from 0 to 5% by weight of K20, from 15 to 30% by weight of CaO + MgO, from 0 to 15% by weight of Na20 + K20, and from 0 to 5% by weight of other oxides.

3. A process according to claim 2, characterized in that the other oxides are selected from the group consisting of oxides of copper, manganese, chromium, nickel, zinc, arsenic, lead, gold, silver, sulfur, and mixtures thereof.

4. A process according to claim 1, further characterized in that it comprises: the addition of a nucleating enhancing agent to the material used to form the glass melt, to increase the speed of said devitrification.

5. A process according to claim 4, characterized in that the nucleation enhancing agent is selected from the group consisting of MgO, Ti02, F, Cr20, sulfides, phosphates, and mixtures thereof.

6. A process according to claim 1, characterized in that the first additive is a binder selected from the group consisting of clay, organic material, inorganic material, and mixtures thereof.

7. A process according to claim 1, further characterized in that it comprises: mixing the material used to form the glass melt, with a second additive selected from the group consisting of sand, ash dust, dolomite, soda ash, limestone , titania, zirconia, and mixtures thereof before the casting step to form a mixture.

8. A process according to claim 1, characterized in that the treatment comprises: the quenching of the glass melt to produce a glass frit.

9. A process according to claim 8, characterized in that the devitrification step comprises the devitrification of the glass frit before the grinding step.

10. A process according to claim 9, characterized in that the devitrification is carried out in a tank or in an oven.

11. A process according to claim 9, characterized in that the devitrification comprises: maintaining the glass frit at a temperature below 100 ° C above the vitreous transition temperature.

12. A process according to claim 9, characterized in that the devitrification comprises: the heating of the glass frit at a temperature of 200 ° to 1000 ° C per hour up to 800 ° to 1200 ° C; the maintenance of the glass frit at a constant temperature of 0 to 2 hours; and cooling the glass frit at a rate of 200 ° to 2000 ° C per hour at room temperature.

13. A process according to claim 9, characterized in that the devitrification is carried out at a temperature of 800 ° to 1200 ° C.

14. A process according to claim 1, characterized in that the step of devitrification comprises: the cooling of the glass melt.

15. A process according to claim 14, characterized in that the cooling step comprises the reduction of the temperature of the glass melt at a speed of 200 to 1000 ° C per hour.

16. A process according to claim 1, characterized in that the step of devitrification comprises: the thermal treatment of the slab under effective conditions to achieve nucleation.

17. A process according to claim 16, characterized in that the heat treatment comprises the firing of the slab at a temperature of 800 to 1250 ° C.

18. A process according to claim 17, characterized in that the heat treatment has a cycle time of less than 2 hours.

19. A process according to claim 6, characterized in that the first additive comprised from 1 to 20% by weight of the mixture.

20. A process according to claim 3, characterized in that it further comprises the oxidation of the material used to form the glass melt, under conditions effective to oxidize the metals and the carbonaceous material present in the material.

21. A process according to claim 20, characterized in that the oxidation is carried out in a suspension preheater, in which the glass is suspended in an oxidation fluid.

22. A process according to claim 20, characterized in that the preheater in suspension in a swirl-type, counter-rotating suspension preheater.

23. A process according to claim 1, further comprising: mixing the glass particles and the first additive with water to form a suspension and spray drying the suspension to produce a granular feed before the forming step.

, 24. A process according to claim 1, characterized in that it also comprises: the glaze of the slab.

25. A product, characterized in that it is prepared by the process according to claim 2.

26. A product, characterized in that it is prepared by the process according to claim 9.

27. A product, characterized in that it is prepared by the process according to claim 16.

28. A product, characterized in that it is prepared by the process according to claim 24.

29. A ceramic slab, characterized in that it has a composition of 35 to 60% by weight of SiO2, from 3 to 25% by weight of A1203, from 0 to 25% by weight of CaO, from 0 to 20% by weight of MgO, from 0.5 to 15% by weight of Fe2Os, from 0 to 15% by weight of Na20, from 0 to 5% by weight of K20, from 15 to 30% by weight of CaO + MgO, from 0 to 15% by weight of Na20, + K20, and from 0 to 5% by weight of other oxides.

30. A ceramic slab according to claim 27, characterized in that the other oxides are selected from the group consisting of oxides of copper, manganese, chromium, nickel, zinc, arsenic, lead, gold, silver, sulfur, and mixtures thereof . MANUFACTURE OF CERAMIC SLABS FROM INDUSTRIAL WASTE SUMMARY OF THE INVENTION The present invention relates to a process for the formation of ceramic slabs that have the appearance of slabs produced from clays. The process includes melting a material to form a glass melt, treating the glass melt to produce a solid glass product, grinding the solid glass product to produce glass particles having a particle size of less than 200. micrometers, mixing the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99% glass particles and 45 to 1% by weight of a first additive, the formation of the mixture of glass powder in slabs by dry pressing, where the slabs have a primary crystalline phase selected from the group consisting of nepheline, diopside, anortite, wollastonite, melilite, merwinite, spinel, akermanite, gelenite, crystalline phases based on iron substitutions in the crystalline phase, and mixtures thereof. The process includes a devitrification step where the solid glass product is devitrified before the milling step or the glass particles in the slab are devitrified after the forming step.