KR20180072048A - Manufacturing method of ceramic tile - Google Patents

Abstract

The present invention relates to a method for manufacturing a ceramic tile comprising: a step of forming a base composition for a ceramic tile by mixing a base raw material including clay and fly ash into a solvent; a step of forming and drying the base composition for the ceramic tile; a step of forming a ceramic tile base layer by preliminarily sintering a dried result product; a step of forming a first glaze layer on an upper part of the ceramic tile base layer; a step of forming a second glaze layer on an upper part of the first glaze layer; and a step of secondarily sintering the result product on which the second glaze layer is formed. The clay and the fly ash are mixed in a weight ratio of 70:30 to 99:1. The present invention is provided to maintain mechanical properties such as flexural strength or the like by being compared with a conventional ceramic tile; and to reduce raw material costs by recycling the fly ash which is a by-product of coal thermal power generation, thereby securing price competitiveness.

Description

[0001] Manufacturing method of ceramic tile [0002]

The present invention relates to a method of manufacturing a ceramic tile, and more particularly, to a method of manufacturing a ceramic tile in which fly ash, which is a by-product of coal-fired power generation, is recycled to reduce raw material costs and ensure price competitiveness.

Every year in Korea, coal fly ash power plants generate more than 8 million tons of fly ash, and only a few of them are being reused as additives for cement and clay bricks. Most of the fly ash is currently landfied and can not be recycled. Therefore, there is an urgent need to solve environmental problems and the cost of waste disposal. The development of fly ash recycling technology is a big issue not only in Korea but also around the world.

The ceramic tile industry for construction is 12,355 million m ² worldwide, and the domestic market is over 800 billion won. In particular, since ceramic tiles have product prices that are several times higher than clay bricks, which are building materials, fly ash as a raw material is advantageous for securing product competitiveness.

The fly ash is mainly composed of silica (SiO ₂ ) and silica-alumina compound (SiO ₂ -Al ₂ O ₃ ), and contains iron oxide (Fe ₂ O ₃ ) and an alkali oxide partly, Body) component. However, since fly ash contains a large amount of unburned carbon, it may cause blistering and delamination due to CO ₂ in the high-temperature firing process of the ceramic tile and deterioration of mechanical properties due to the internal trap. In the case of pre-treatment for removal of unburned carbon contained in fly ash, it is necessary to study how to utilize the existing ceramic tile manufacturing process because the price of product due to process addition increases.

Korean Patent Registration No. 10-0184160

A problem to be solved by the present invention is to provide a ceramic tile which can maintain the mechanical properties such as bending strength as compared with conventional ceramic tiles but also can reduce the cost of raw materials by recycling fly ash which is a by- Method.

The present invention relates to a method for producing a ceramic tile, comprising the steps of: (a) mixing a raw material containing clay and fly ash into a solvent to form a base composition for a ceramic tile; (b) molding and drying the base composition for the ceramic tile; (d) forming a first glaze layer on top of the ceramic tile substrate; (e) forming a first glaze layer on the first glaze layer; (c) Forming a second glaze layer, and (f) secondary firing the resultant having the second glaze layer, wherein the clay and the fly ash are mixed at a weight ratio of 70:30 to 99: 1 To a ceramic tile.

The fly ash has a chemical composition of 52 to 64 wt% of SiO _2, 19 to 29 wt% of Al ₂ O ₃ , 1 to 11 wt% of Fe ₂ O ₃ , 0.1 to 5 wt% of CaO, 0.1 to 5.5 wt% of MgO, Na ₂ O 0.01~3% by weight, and may be a material containing K ₂ O 0.01~2.5 wt% of TiO ₂ 0.01~3% by weight.

The clay is SiO ₂ 64~72% by weight, chemical composition, Al ₂ O ₃ 9~19% by weight, Fe ₂ O ₃ 0.1~6% by weight, CaO 0.01~2.5 weight%, MgO 0.01~3% by weight, Na ₂ O, 0.01 to 4.5 wt% of K ₂ O, 0.01 to 4 wt% of K ₂ O, and 0.01 to 5 wt% of TiO ₂ .

In the step (a), the solvent may further contain 0.1 to 3 parts by weight of CaO powder per 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of MgO powder may be added to 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of Na ₂ O powder may be further added to the solvent relative to 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of K ₂ O powder may be further added to 100 parts by weight of the fly ash.

The first firing is preferably performed in an oxidizing atmosphere at a firing temperature of 1000 to 1250 캜.

And a step of maintaining unburned carbon contained in the fly ash at a temperature of 700 to 850 캜 before the temperature is raised to the firing temperature in the first firing step.

In step (a), 3 to 10 parts by weight of silicon (Si) powder may be further blended with 100 parts by weight of the fly ash.

According to the present invention, as compared with conventional ceramic tiles, fly ash, which is a by-product of coal-fired power generation, can be recycled while maintaining mechanical characteristics such as bending strength, thereby reducing raw material costs and securing price competitiveness. Ceramic tiles have a higher product price than many other clay bricks, which is a building material. Therefore, it is advantageous to secure product competitiveness when using fly ash as a raw material.

1 is a view showing a structure of a wall tile.
Figs. 2 and 3 are photographs showing Roller hearth kiln for firing ceramic tiles used in Experimental Example.
4 is a graph showing the results of particle size analysis of fly ash.
5 is a graph showing the results of X-ray diffraction analysis of fly ash.
6 and 7 are photographs of a fiedl emission-scanning electron microscope (FE-SEM) showing the microstructure of fly ash.
8 is a graph showing the measurement results of the absorption rate (WA) and the porosity (P) of the ceramic tile substrate according to the amount of fly ash added.
FIG. 9A is a field emission scanning electron microscope (FE-SEM) image showing the surface microstructure of the post-firing standard specimen ST, FIG. 9B is a field emission scanning electron microscope 9C is a field scanning electron microscope (FE-SEM) photograph showing the surface microstructure of the specimen after firing (FC2), and FIG. 9D is a photograph showing the surface microstructure of the specimen (FC3) after firing (FE-SEM) photograph, and FIG. 9E is a field emission scanning electron microscope (FE-SEM) photograph showing the surface microstructure of the specimen after firing (FC4).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

A method of manufacturing a ceramic tile according to a preferred embodiment of the present invention includes the steps of: (a) mixing a base material containing clay and fly ash into a solvent to form a base composition for a ceramic tile; (b) (C) forming a ceramic tile base layer by first firing the dried resultant, (d) forming a first glaze layer on the ceramic tile base layer, and (e) forming a second glaze layer on top of the first glaze layer, and (f) secondarily firing the resultant with the second glaze layer, wherein the clay and the fly ash are mixed at 70:30 To 99: 1.

The fly ash has a chemical composition of 52 to 64 wt% of SiO _2, 19 to 29 wt% of Al ₂ O ₃ , 1 to 11 wt% of Fe ₂ O ₃ , 0.1 to 5 wt% of CaO, 0.1 to 5.5 wt% of MgO, Na ₂ O 0.01~3% by weight, and may be a material containing K ₂ O 0.01~2.5 wt% of TiO ₂ 0.01~3% by weight.

The clay is SiO ₂ 64~72% by weight, chemical composition, Al ₂ O ₃ 9~19% by weight, Fe ₂ O ₃ 0.1~6% by weight, CaO 0.01~2.5 weight%, MgO 0.01~3% by weight, Na ₂ O, 0.01 to 4.5 wt% of K ₂ O, 0.01 to 4 wt% of K ₂ O, and 0.01 to 5 wt% of TiO ₂ .

In the step (a), the solvent may further contain 0.1 to 3 parts by weight of CaO powder per 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of MgO powder may be added to 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of Na ₂ O powder may be further added to the solvent relative to 100 parts by weight of the fly ash.

In the step (a), 0.1 to 3 parts by weight of K ₂ O powder may be further added to 100 parts by weight of the fly ash.

The first firing is preferably performed in an oxidizing atmosphere at a firing temperature of 1000 to 1250 캜.

And a step of maintaining unburned carbon contained in the fly ash at a temperature of 700 to 850 캜 before the temperature is raised to the firing temperature in the first firing step.

In step (a), 3 to 10 parts by weight of silicon (Si) powder may be further blended with 100 parts by weight of the fly ash.

Hereinafter, a method of manufacturing a ceramic tile according to a preferred embodiment of the present invention will be described in more detail.

The inventors of the present invention have studied whether fly ash can be used as a raw material substitute for securing price competitiveness in a ceramic tile industry which is a typical building material.

The fly ash is mainly composed of silica (SiO ₂ ) and silica-alumina compound (SiO ₂ -Al ₂ O ₃ ), and contains iron oxide (Fe ₂ O ₃ ) and an alkali oxide partly, Body) component. However, since fly ash contains a large amount of unburned carbon, it may cause blistering and delamination due to CO ₂ in the high-temperature firing process of the ceramic tile and deterioration of mechanical properties due to the internal trap. It is important to utilize the existing ceramic tile manufacturing process as the pre-treatment process for removing unburned carbon contained in the fly ash is performed, because the product price due to the process increase.

Ceramic tiles are generally used for building interior, and are divided into wall tiles (floor tiles) and floor tiles (floor tiles).

Ceramic tile is an eco-friendly building material made of earth, and has excellent strength and durability due to high-temperature firing above 1000 ℃.

Among the ceramic tiles, the wall tile is formed on the surface of the glaze layer by the gasification of the glaze composition, thereby maintaining the cleanliness through prevention of contamination, and adding aesthetic and various functions. Accordingly, wall tiles are widely used not only as toilets but also as interior materials for living environments such as kitchens and floors.

1 is a view showing a structure of a wall tile.

Referring to FIG. 1, a first glaze layer 20 is formed on a base layer 10 formed by mixing raw materials such as clay to form a molded body, and the first glaze layer is formed on the substrate layer 10, The second glaze composition is applied to the upper part of the glaze layer 20 to form the second glaze layer 30, and then the second glaze composition is subjected to secondary firing. The primary glaze layer 20 is referred to as the Engobe layer and serves as an intermediate layer capable of concealing the color of the substrate layer 10 and controlling thermal expansion of the substrate layer 10 and the secondary glaze layer 30 . The second glaze layer 30 has a function of strengthening (protecting) and decorating the surface of the ceramic tile.

In order to produce the ceramic tile having the above-described structure, first, the base material for the ceramic tile is added to the solvent and mixed to form the base composition for the ceramic tile. The raw materials include clay and fly ash as raw materials constituting the basic skeleton of the ceramic tile. The clay may be a clay containing chemical composition components SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, MgO, Na ₂ O, K ₂ O and TiO ₂ . For example, the clay is SiO ₂ 64~72% by weight, chemical composition, Al ₂ O ₃ 9~19% by weight, Fe ₂ O ₃ 0.1~6% by weight, CaO 0.01~2.5 weight%, MgO 0.01~3% by weight, 0.01 to 4.5% by weight of Na ₂ O, 0.01 to 4% by weight of K ₂ O and 0.01 to 5% by weight of TiO ₂ . The fly ash may be a by-product of coal-fired power generation, and may include a chemical composition containing SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, MgO, Na ₂ O, K ₂ O and TiO ₂ . For example, the fly ash has a composition of 52 to 64 wt% of SiO _2, 19 to 29 wt% of Al ₂ O ₃ , 1 to 11 wt% of Fe ₂ O ₃ , 0.1 to 5 wt% of CaO, 0.1 to 5.5 wt% 0.01 to 3 wt% of Na ₂ O, 0.01 to 2.5 wt% of K ₂ O, and 0.01 to 3 wt% of TiO ₂ . The clay and the fly ash are mixed in a weight ratio of 70:30 to 99: 1, more preferably 80:20 to 95: 5, and most preferably 85:15 to 95: 5. In the following Experimental Examples, when the weight ratio of the clay and the fly ash was 60:40, the properties such as bending strength were rapidly lowered. It is preferable to mix the clay and fly ash in the weight ratio in the above range Do. As the solvent, distilled water, ethanol, methanol or the like may be used. The raw material may further contain raw materials such as stonite, clay, pyrophyllite, and limestone.

The solvent may further contain 0.1 to 3 parts by weight of CaO powder per 100 parts by weight of the fly ash. The CaO powder acts as a flux that affects the densification of the substrate layer during the first firing process. During the firing process, CO ₂ gas due to oxidation of unburned carbon contained in fly ash and O ₂ gas due to reduction of iron oxide may be discharged from the surface to form pores. However, the CaO powder serving as a flux may be additionally By mixing, it is possible to increase the density while suppressing the formation of pores, thereby increasing the mechanical properties such as bending strength.

The solvent may further contain 0.1 to 3 parts by weight of MgO powder per 100 parts by weight of the fly ash. The MgO powder acts as a flux that affects the densification of the substrate during the first firing process. The pores may be formed as CO ₂ gas due to oxidation of unburned carbon contained in fly ash and O ₂ gas due to reduction of iron oxide are discharged from the surface during the firing process. However, the MgO powder serving as a flux may be additionally By mixing, it is possible to increase the density while suppressing the formation of pores, thereby increasing the mechanical properties such as bending strength.

The solvent may further contain 0.1 to 3 parts by weight of Na ₂ O powder per 100 parts by weight of the fly ash. The Na ₂ O powder acts as a flux that affects the densification of the substrate layer during the first firing process. During the firing process, CO ₂ gas due to the oxidation of unburned carbon contained in the fly ash and O ₂ gas due to the reduction of iron oxide may be discharged from the surface to form pores. However, the Na ₂ O powder serving as a flux It is possible to increase the compactness while suppressing the formation of pores, thereby increasing the mechanical properties such as the bending strength.

0.1 to 3 parts by weight of K ₂ O powder may be further mixed with 100 parts by weight of the fly ash in the solvent. The K ₂ O powder acts as a flux that affects the densification of the substrate layer during the first firing process. During the firing process, CO ₂ gas due to oxidation of unburned carbon contained in fly ash and O ₂ gas due to reduction of iron oxide may be discharged from the surface to form pores. However, the K ₂ O powder It is possible to increase the compactness while suppressing the formation of pores, thereby increasing the mechanical properties such as the bending strength.

The solvent may further contain 3 to 10 parts by weight of silicon (Si) powder per 100 parts by weight of the fly ash. When the silicon (Si) powder is added, SiC is formed by reacting with the unburned carbon contained in the fly ash during the firing as well as the effect of removing the unburned carbon contained in the fly ash, There is an effect that the strength can be increased.

The mixing may be performed by various methods such as ball mill, planetary mill, attrition mill, and the like.

Hereinafter, the mixing process by the ball mill method will be described in detail. The raw materials are charged into a ball milling machine and mixed. Followed by rotating at a constant speed using a ball miller to pulverize the raw materials uniformly while mixing them. The ball used for the ball mill may be a ball made of a ceramic such as alumina or zirconia, and the balls may be all the same size or may be used together with balls having two or more sizes. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are controlled so as to be mixed with the desired particle size while pulverizing. For example, the size of the balls may be set in a range of about 1 mm to 50 mm in consideration of the size of the particles, and the rotational speed of the ball miller may be set in a range of about 100 to 500 rpm. The ball mill is preferably carried out for 1 to 48 hours in consideration of the target particle size and the like.

The base resin composition for a ceramic tile has a slurry shape, and the base resin material is dispersed in a solvent to form a solid content in the base resin composition for a ceramic tile. It is preferable to mix the solvent so that the solids content of the ceramic tile base composition becomes 40 to 70%.

The substrate composition for a ceramic tile obtained by the above-described method can form a substrate layer for a ceramic tile through a molding, drying and primary firing step to be described later.

More specifically, the base composition for a ceramic tile is molded into a desired shape and dried. The molding can be performed by a variety of known methods such as slip casting, press molding, and the like. Further, before the forming step, the base composition for ceramic tile may be further subjected to a step of de-ironing, a step of classification and filtration, and the like. The drying process is preferably performed at a temperature ranging from room temperature to 150 ° C for 10 minutes to 48 hours. Most of the solvent component is removed by the drying process.

The base resin composition for ceramic tile may be sprayed using a spray dryer to prepare spherical granular powder, which may be molded into a mold. The inlet temperature of the spray dryer is maintained at 120 to 180 캜, more preferably 140 to 150 캜, and the outlet temperature is maintained at 50 to 150 캜, more preferably 60 to 110 캜, the spraying pressure is 30 to 100 kPa, , It is adjusted in the range of 50 to 60 kPa.

The molded product is firstly baked at a temperature of about 1000 to 1250 占 폚.

Hereinafter, the first firing step will be described in detail.

The molded product is charged into a furnace such as an electric furnace, and a primary firing process is performed. The first firing step is preferably performed at a temperature of about 1000 to about 1,250 DEG C for about 1 to about 48 hours. It is desirable to keep the pressure inside the furnace constant during the first firing.

The first firing is preferably performed at a temperature of about 1000 to 1250 ° C. When the firing temperature is less than 1000 캜, the thermal or mechanical characteristics of the ceramic tile may be poor due to incomplete firing. When the firing temperature exceeds 1250 캜, energy consumption is high, which is uneconomical.

The firing temperature is preferably raised at a heating rate of 1 to 50 ° C / min. If the heating rate is too slow, the time is long and productivity is deteriorated. If the heating rate is too high, thermal stress is applied due to a rapid temperature rise It is preferable to raise the temperature at the temperature raising rate in the above range.

The first firing is preferably carried out at a firing temperature for 1 to 48 hours. If the firing time is too long, the energy consumption is high, so it is not only economical but also it is difficult to expect further firing effect. If the firing time is small, the physical properties of the ceramic tile may not be good due to incomplete firing.

It is preferable that the primary firing is performed in an oxidizing atmosphere (for example, oxygen (O ₂ ) or air atmosphere).

After the first firing process is performed, the furnace temperature is lowered to unload the first fired product. The furnace cooling may be effected by shutting down the furnace power source to cool it in a natural state, or optionally by setting a temperature decreasing rate (for example, 10 DEG C / min). It is preferable to keep the pressure inside the furnace constant even while the furnace temperature is lowered.

And a step of removing unburned carbon contained in the fly ash by maintaining the temperature at 700 to 850 ° C before the temperature is raised to the firing temperature in the first firing step.

A primary glaze layer (Engobe layer) is formed on the first sintered ceramic tile substrate layer. A first glaze composition is prepared to form a first glaze layer on the first sintered ceramic tile substrate layer, and the first glaze composition is sown and dried on the first sintered ceramic tile substrate surface. The first glaze layer is preferably formed to a thickness of about 50 to 300 mu m. The first glaze composition is in a slurry state including a solid content and a solvent, and the solvent is preferably contained in the first glaze composition in an amount of 30 to 80 parts by weight based on 100 parts by weight of the solid content.

The second glaze composition is applied onto the first glaze layer and dried to form a second glaze layer. The second glaze composition is in a slurry state including a solid content and a solvent, and the solvent is preferably contained in the second glaze composition in an amount of 30 to 80 parts by weight based on 100 parts by weight of the solid content. The second glaze layer is preferably formed to a thickness of about 70 to 500 mu m.

In one embodiment, the solid content of the first glaze composition ranges from 55 to 67 wt% of SiO _{2, 8 to} 14.5 wt% of Al ₂ O ₃ , 0.01 to 0.8 wt% of Fe ₂ O ₃ , 0.1 to 6 wt% of TiO ₂ , By weight of MgO, 0.1 to 4% by weight of Na ₂ O _3, 0.1 to 4% by weight of K ₂ O, 0.01 to 0.8% by weight of P ₂ O ₅ and 1.5 to 7.5% by weight of ZrO ₂ may be, the second solid component of the glaze composition is SiO _2, 41~53 wt%, Al ₂ O ₃ 8~20 wt%, K ₂ O 0.1~4% by weight, ZrO _2, 2~12% by weight, Fe ₂ O _{3 to 13} wt%, B ₂ O ₃ 5 to 17 wt%, CaO 0.1 to 8 wt%, and P ₂ O _{5 2 to} 12 wt%.

The glaze layer forms a vitreous film on the surface of the tile on which the micro pores are present to induce the strength enhancement and the reduction of the absorption rate, and exhibits the inherent color and texture. For example, the first baked ceramic tile substrate (or the ceramic tile substrate on which the greenhouse layer is formed) is immersed in the glaze composition, or the glaze composition is applied to the surface of the ceramic tile substrate layer with a brush, (Or the upper surface of the embossed layer), or a method of spraying the glaze composition onto the surface of the ceramic tile substrate layer (or the upper surface of the embossed layer) with a spraying device.

The ceramic tile having the second glaze layer is charged into a furnace such as an electric furnace, and a secondary firing process is performed.

Hereinafter, the secondary firing step will be described in detail.

The resultant (ceramic tile) having the second glaze layer is charged into a furnace such as an electric furnace, and a secondary firing process is performed. The secondary firing is preferably performed at a temperature of about 1000 to 1100 DEG C for a predetermined time (e.g., about 2 to 10 minutes). It is desirable to keep the pressure inside the furnace constant during the secondary firing.

The secondary baking is preferably performed at a temperature of about 1000 to 1100 ° C. If the firing temperature is less than 1000 ° C, the solid content of the glaze composition may be incompletely melted and the surface of the ceramic tile may not be smooth or gloss (shine) characteristics may be poor. When the firing temperature exceeds 1100 ° C, to be.

The firing temperature is preferably raised at a heating rate of 1 to 50 ° C / min. If the heating rate is too slow, the time is long and productivity is deteriorated. If the heating rate is too high, thermal stress is applied due to a rapid temperature rise And the ceramic tile oil surface may not be smooth due to rapid temperature rise.

The secondary baking is preferably carried out at a baking temperature for 1 to 48 hours. If the firing time is too long, the energy consumption is high, so it is not only economical but also it is difficult to expect further firing effect. If the firing time is small, the physical properties of the ceramic tile may not be good due to incomplete firing.

The secondary firing is preferably performed in an oxidizing atmosphere (for example, oxygen (O ₂ ) or air atmosphere).

After the secondary firing process is performed, the furnace temperature is lowered to unload the secondary fired product. The furnace cooling may be effected by shutting down the furnace power source to cool it in a natural state, or optionally by setting a temperature decreasing rate (for example, 10 DEG C / min). It is preferable to keep the pressure inside the furnace constant even while the furnace temperature is lowered.

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited to the following experimental examples.

<Experimental Example>

A study on the application of fly ash from a coal - fired power plant to the construction of ceramic tile wall tile without pretreatment. The basic properties of fly ash were investigated and the mechanical properties of the ceramic tile were investigated. Since the ceramic tile wall tile is a glazed tile and the firing process is usually a fast firing process that is completed within 40 minutes, the same firing process is applied in this experiment, - Ceramic tiles were produced.

In this experiment, five samples (FC 1 to 4 and ST) of ceramic wall tile substrates including fly ash (TOKAI KOGYO Ltd., JPN) were prepared and the clay (Clay) and fly ash The composition is shown in Table 1, and the mixing ratio of clay and fly ash in each sample is shown in Table 2.

SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO Na ₂ O K ₂ O B ₂ O ₃ TiO ₂ Loss on Ignition Clay (Clay) 68.2 14.6 2.3 0.5 0.8 1.1 0.2 0 1.8 10.5 Fly ash 58.7 24.5 5.8 2.2 2.4 0.8 0.6 0 0.8 4.2

Samples FC1 FC2 FC3 FC4 ST Clay 90wt%
Fly ash 10wt% Clay 80wt%
Fly ash 20wt% Clay 70wt%
Fly ash 30wt% Clay 60wt%
Fly ash 40wt% Clay 100wt%

Fly ash was added to the distilled water to remove the hollow body shape that was floating on the bottom, and only the material sinking to the bottom was obtained and dried. The composition of the ceramic wall tile substrate was the average value of the analysis results of domestic D and T companies .

The wall tile base and fly ash were added to distilled water, respectively, and the mixture was ball milled for 2 hours using a 10 mm zirconia ball. After mixing with a ball mill, spherical granules were prepared by spraying at a rate of 10 L / h using a spray drier (Spray Dryer, EYERA SD-1000, JPN). At this time, the inlet temperature was maintained at 140 to 150 ° C, the outlet temperature was maintained at 60 to 110 ° C, and the spray pressure was controlled within the range of 50 to 60 kPa.

The granulated powder thus prepared was dried in an oven at 100 ° C for 24 hours, charged into a circular metal mold (diameter 30 mm) and uniaxially pressurized at a pressure of 20 MPa and a pressure of 20 MPa to form a molded body.

Roller hearth kiln (length: 10 m, maximum temperature: 1400 ° C, manufactured by Mir heating system), which is applied to the actual ceramic tile mass production process, was used for the firing process of the formed bodies (FC1 to FC4). 2 and 3 show Roller hearth kiln for firing ceramic tiles used in the present experiment. Ceramic wall tiles are manufactured by double firing through first firing for the green body and second firing after glazing. In this experiment, in order to check the applicability of fly ash to the substrate, general first firing process conditions (Maximum temperature 1150 ℃, car time 40min) was applied. However, in order to remove unburned carbon contained in fly ash, the railway time was extended by 10 minutes in the range of 750 ° C, while the standard sample (ST) without fly ash proceeded to the condition of 40 minutes in total without the holding time.

After the tile samples produced through the firing process is dried for 3 hours in a thermostat of 150 ℃ to measure the dry weight (W _1), immerse the specimens in distilled water and boiling for 3 hours or more and then cooled to room temperature while suspended in water, create a catcher sample The weight was measured (W ₂ ). The porosity (P) and the water absorption (WA) of the tile specimen were calculated by taking the catcher sample out of the water, wiping the surface with water and measuring the weight (W ₃ ). The porosity P can be calculated as shown in Equation 1 below and the absorption rate WA can be calculated as shown in Equation 2 below.

[Equation 1]

&Quot; (2) &quot;

The crystal structure of fly ash was observed using an X-ray diffractometer (XRD, Rigaku, D / 2500 VL / PC) and the microstructural changes due to the shape and sintering of the powder were determined by field emission scanning electron microscopy Field emission scanning electron microscope (FE-SEM, JEOL, JSM-6390) analysis was used. The chemical composition of the ceramic tile substrate and fly ash was analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES, OPTIMA 5300 DV, Perkinelmer). Unburned carbon contained in the fly ash Were analyzed using Carbon-Sulfur Analyzer (CS, CS-230, LECO). In addition, the bending strength of the ceramic tile specimen was measured by a 3-point bending strength method using a universal testing machine (UTM Inspekt 250, Sweden).

(σ _b3: 3-point bending strength (MPa), P: maximum load (N), L at the time when the specimen is destroyed: the distance between the bottom point (m), ω: the test piece butterfly (m), t a: specimen thickness (m)

3. Results and Discussion

Fly ash is composed mainly of silica-alumina and can be used as a raw material of ceramic tile base. However, fly ash generated by high combustion process of pulverized coal contains unburned unburned coal. As shown in Table 1, the chemical composition of fly ash is mainly composed of silica (58.7%) and alumina (24.5%), and other components include iron oxide (Fe ₂ O ₃ , 5.8%), calcium oxide (CaO, 2.2% Magnesium oxide (MgO, 2.4%), and sodium oxide (Na ₂ O, 0.8%). Oxides such as K ₂ O, Na ₂ O, CaO, and MgO act as a flux that affects the densification during sintering. From the results, it can be seen that the fly ash is almost similar in composition and content to the ceramic wall tile, and can be used alternatively.

However, the analysis results using the carbon-sulfur analyzer (CS) for fly ash are shown in Table 3 below. In the analysis using carbon-sulfur analyzer (CS), fly ash had unburned carbon content ranging from 13.8% to 18.9% in three samples, and average unburned carbon content in fly ash was found to be 15.6% .

Samples #One #2 # 3 Avg. C / S 14.2 13.8 18.9 15.6

As such, the high content of unburned carbon contained in the fly ash has a great influence on the firing process and final properties of the ceramic tile. Carbon is generally oxidized and removed from the surface during the high-temperature firing process. However, carbon trapped inside the tile substrate causes swelling and delamination phenomena, and carbon such as black-core Defects are generated and ultimately the absorption rate and strength are lowered. Therefore, an optimization process for the amount of use is required to mix the fly ash with the ceramic tile substrate.

FIG. 4 is a graph showing the results of particle size analysis of fly ash, FIG. 5 is a graph showing the results of X-ray diffraction analysis of fly ash, FIGS. 6 and 7 are graphs showing the microstructure of fly ash This is a fiedl emission-scanning electron microscope (FE-SEM) photograph.

From the results of the particle size analysis of FIG. 4, the particle size of fly ash was widely distributed from 0.1 μm to several hundred μm, and D ₅₀ was measured at 38 μm. The distribution of the particle size is similar to that of the conventional ceramic tile base material, and since the composition is similar to that of the conventional ceramic tile base material, the fly ash is easily mixed with the tile base since there is no large difference in the base and specific gravity.

As a result of the X-ray diffraction analysis of FIG. 5, quartz (SiO ₂ ) phase, mullite (3Al ₂ O ₃ .2SiO ₂ ) phase and amorphous silica phase of 20 ^° region were observed. However, a small amount of alkali oxides and unburned carbon were not found in the X-ray diffraction analysis. Since unburned carbon has amorphous amorphous carbon structure, it is judged that it is not included in the amorphous peak of 20 ^o region. The fraction of quartz and mullite phases except amorphous phase was analyzed by X-ray diffraction quantitative analysis program, and the fraction was 36.2% and 63.8%, respectively. Quartz phase and mullite were found to be the basic composition of porcelain Each of which has a great influence on glass formation and strength.

From the results of the microstructure analysis of Figs. 6 and 7, it can be seen that the fly ash is composed of spherical particles having a size of several tens of micrometers and angular-shaped particles having a smaller particle size.

The energy dispersive X-ray spectroscopy (EDS) analysis confirmed that most of the rounded particles were Si and O, while the angular particles of small grain size were the elements of Si, Al, Ca, Na, and Fe Was measured. The spherical particles contained in the fly ash mainly consisted of glassy phase, so spherical particles identified in the microstructure results can be judged as amorphous silica phase in the X-ray diffraction analysis.

Water absorption is an important property affecting the durability of ceramic tiles as a building material. 8 shows the measurement results of the water absorption (WA) and the porosity (P) of the ceramic tile substrate according to the addition amount of fly ash, and Table 4 shows the measurement results.

FC1 FC2 FC3 FC4 ST Water Absroption (%) 10.8 12.4 14.6 22.1 10.3 Porosity (%) 19.2 20.4 21.8 27.6 18.4

The absorption rate of the standard specimen (ST) without fly ash was 10.3%, and the absorption rate did not significantly increase from 10.8% (FC1) to 14.6% (FC3) as the amount of fly ash was increased. However, it can be seen that the absorption rate of the FC4 specimen with the addition amount of fly ash of 40% increases sharply to 22.1%. The porosity of the standard specimen (ST) was 13.2% and the porosity was not significantly increased from 14.6% to 17.8% as the amount of fly ash was increased (FC1 → FC3). Able to know. However, in the specimen of FC4, the porosity increased sharply to 22.3%. From these results, it can be seen that the permeability and the porosity are similar to each other. The porosity calculated by Archimedes' measurement means open porosity, and the increase in porosity and absorption rate at 40% (FC4) of fly ash means that many open pores are formed on the surface of the substrate during the firing process.

9A to 9E show the results of observation of the microstructure of the surface of the ceramic tile substrate after firing according to the addition amount of fly ash with a field emission scanning electron microscope (FE-SEM). 8A is for the standard specimen ST, FIG. 8B is for FC1, FIG. 8C is for FC2, FIG. 8D is for FC3, and FIG. 8E is for FC4.

Referring to FIGS. 9A to 9E, it can be confirmed that a dense fine structure is formed as a whole through the firing process in the case of the standard specimen (ST). In addition, in the case of the fly ash mixed specimen, no micropores were observed in the case of FC1 (with 10wt% of fly ash) as the addition amount increased, but FC2 (with 20wt% of fly ash) and FC3 In the case of adding 30wt% of fly ash, it was confirmed that the fine pores gradually increase on the surface of the specimen. Particularly, in the case of the addition amount of fly ash of 40 wt% (FC4), not only fine pores but also rough surface pores having a size of 100 mu m are observed. These results indicate that the unburned carbon contained in the fly ash is oxidized and gasified on the surface to volatilize, and then the surface is densified. However, it is judged that pores remain on the surface due to the presence of excess unburned carbon. In addition, iron oxide contained in fly ash contributes to the surface and internal pores of the substrate. The iron oxide is reduced in the high-temperature firing process and discharges oxygen (O ₂ ) gas. Part of the iron oxide forms pores on the inside and the surface of the substrate . The pores formed in such a substrate degrade the densification of the ceramic tile and affect the strength of the tile.

Table 5 shows the changes in bending strength (flexural strength, modulus strength) after firing according to the addition amount of fly ash.

Samples
Bending Strength (N / cm) Measured value (mean) Std. dev. Number ST 68.3 ± 3.4

10

FC1 76.2 ± 4.1 FC2 66.2 ± 4.5 FC3 64.6 ± 5.2 FC4 42.1 ± 5.8

The bending strength of the ceramic tile is measured by applying a load to a smooth bar specimen with a universal tester while applying a compressive stress to the top of the test piece and a tensile stress to the bottom. Because the tensile strength of the ceramic is smaller than that of the compressive strength, cracks are generated in the lower part of the specimen and are rapidly broken, and the bending strength is measured. The flexural strength of the standard specimen (ST) was 68.3 N / cm. The specimen with fly ash was not significantly different from the standard specimen up to 30 wt% (FC3), but FC1 (10 wt% Of the total population. This increase in flexural strength (FC1) is considered to be due to the fact that the alkali metal oxide contained in the fly ash accelerates the densification in the firing process. However, in the case of FC4 (40 wt%) specimen, it was confirmed that the bending strength was greatly reduced to 42.1 N / cm. This decrease in bending strength is attributed to the fact that numerous pores on the surface of the substrate contribute to crack initiation as excess fly ash is added and the bending strength decreases.

4. Conclusion

The effect of fly ash, which is a coal thermal power generation waste, on the ceramic tile material after the rapid calcination process applied to the production of the ceramic tile wall was verified. Fly ash is composed of alumina, iron oxide (Fe ₂ O ₃ ) and other alkali metal oxides (CaO, Na ₂ O, etc.) as main components of silica. Phase analysis shows that quartz phase, mullite and silica glass phase exist . Based on these results, fly ash is similar to existing ceramic tile substrate and is likely to be an alternative material. However, analysis using carbon - sulfur analyzer (CS) requires optimization process because it contains more than 16% unburned carbon content. The surface porosity of the ceramic specimens with the fly ash was increased as the amount of added fly ash was increased. Particularly, when the amount of fly ash was more than 40wt%, coarse surface pores of several tens of micrometers or more were observed along with micropores. These pores are considered to be due to the fact that surface magnetization can not be achieved due to the CO ₂ gas due to the oxidation of unburned carbon contained in the fly ash during the firing process and O ₂ gas due to the reduction of the iron oxide from the surface. In the evaluation of physical properties of ceramic wall tile specimens, the addition of 10wt% (FC1) of fly ash showed almost the same water absorption (10.8%) and porosity (19.2%) and bending strength increased 76.2N / cm ). On the other hand, it was confirmed that the water absorption and porosity were increased in specimens of 20 wt% or more, and specimens having a fly ash content of 40 wt% were abruptly decreased in physical properties. The reason why the ceramic tile property was improved when 10 wt% of fly ash was added is because the alkaline metal oxide such as CaO and Na ₂ O contained in the fly ash acts as a flux in the firing process and the density increases.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, This is possible.

10: Substrate layer
20: First glaze layer
30: Second glaze layer

Claims (10)

(a) mixing a base stock comprising clay and fly ash into a solvent to form a base composition for a ceramic tile;
(b) molding and drying the base composition for a ceramic tile;
(c) firstly firing the dried product to form a ceramic tile base layer;
(d) forming a first glaze layer above the ceramic tile substrate;
(e) forming a second glaze layer on the first glaze layer; And
(f) secondarily firing the resultant having the second glaze layer formed thereon,
Wherein the clay and the fly ash are mixed at a weight ratio of 70:30 to 99: 1.
According to claim 1, wherein said fly ash is a chemical composition with SiO ₂ 52~64 wt%, Al ₂ O ₃ 19~29 weight%, Fe ₂ O ₃ 1~11 wt%, CaO 0.1~5 wt%, MgO 0.1 By weight of Na ₂ O, 0.01 to 2.5% by weight of K ₂ O, and 0.01 to 3% by weight of TiO _{2, based on the total} weight of the ceramic tiles.
The clay according to claim 1, wherein the clay has a chemical composition of 64 to 72 wt% of SiO _{2, 9 to} 19 wt% of Al ₂ O ₃ , 0.1 to 6 wt% of Fe ₂ O ₃ , 0.01 to 2.5 wt% of CaO, 3 to 3 wt%, Na ₂ O: 0.01 to 4.5 wt%, K ₂ O: 0.01 to 4 wt%, and TiO _2: 0.01 to 5 wt%.
The method according to claim 1, wherein, in the step (a)
Wherein the solvent is further mixed with 0.1 to 3 parts by weight of CaO powder per 100 parts by weight of the fly ash.
The method according to claim 1, wherein, in the step (a)
Wherein the solvent is further mixed with 0.1 to 3 parts by weight of MgO powder per 100 parts by weight of the fly ash.
The method according to claim 1, wherein, in the step (a)
And 0.1 to 3 parts by weight of Na ₂ O powder is further mixed with 100 parts by weight of the fly ash in the solvent.
The method according to claim 1, wherein, in the step (a)
Wherein the solvent is further mixed with 0.1 to 3 parts by weight of K ₂ O powder per 100 parts by weight of the fly ash.
The method according to claim 1, wherein the first firing is performed in an oxidizing atmosphere at a firing temperature of 1000 to 1250 캜.
The method as claimed in claim 9, further comprising the step of removing unburned carbon contained in the fly ash by maintaining the temperature at 700 to 850 캜 before the temperature is raised to the firing temperature in the first firing step &Lt; / RTI &gt;
The method according to claim 1, wherein, in the step (a)
Wherein 3 to 10 parts by weight of silicon (Si) powder is further mixed with 100 parts by weight of the fly ash.

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