KR101105159B1 - Fly ash containing composition for preparing chinaware - Google Patents

Abstract

The present invention relates to a composition for producing porcelain, wherein coal ash is added to a general porcelain base material, and 5 to 30% by weight of coal ash is added based on the total weight of the composition for producing porcelain.

Description

Fly Ash Containing Composition for Ceramics Production {FLY ASH CONTAINING COMPOSITION FOR PREPARING CHINAWARE}

The present invention relates to a coal ash containing composition for producing ceramics, and ceramics made from such compositions.

Pottery is a representative product of ceramics used in daily life, and its history is very long. The old earthenware found in ancient tombs, and the ceramics we are currently using, are made from clay and other materials that have been crushed and decomposed of rocks and minerals on the earth's surface, will be.

Pottery refers to a wide range of products and materials, from the edibles and tiles used to assemble or decorate buildings as part of ceramics, to porcelain, which is a tableware for everyday life.

Among the items that must be considered in the process of manufacturing ceramics are the characteristics of raw materials, formability, density and porosity, absorption rate, expansion coefficient, mechanical properties and many other items. From the chemical properties, the product properties and firing conditions are inferred. Therefore, depending on which material is used as a raw material, the manufacturing process and the physical properties of the product are determined.

Many research reports on ceramics do not have detailed research reports on the properties of the ceramics throughout the manufacturing process, but on specific properties of ceramics. Most of the research focuses on the densification and strength of ceramics.

However, in contrast to densification, if porcelain is made porous, it will have excellent properties in lightness, insulation, sound absorption, etc., but there are not many studies on it.

One research paper on how to make porcelain porous is to investigate the physical properties of fired objects by adding fly ash and fine hollow bodies called Shirasu ballon to ceramic raw materials. See Y. Koolayashi, O. Ohira, Y. Okashi, E. Kato J. Ceramic Society JAPAN 99 [6] 495-502 (1991); Okutani Nishikawa, T. Tanaka, KMiyatani, J. ceramic Soc Japan 110 [7] 688-692 (2002); And K. Sodeyama, Y. Sakka, Y. Kamino, K. Hamaishi, J. Ceram. Soc, Japan 106 [3] 333-338 (1998)].

They also examined the effect of the size of the coal ash and Shirasu ballon on the strength in order to simultaneously realize the weight reduction and high strength of the material.

Kumar et al. Investigated the properties of mechanical strength and density by adding pore coal ash to porcelain raw materials. See S. Kumar, K. K. Singh, P. Rachandrarao, Journal of Materials Science 36. 5917-5922 (2001); Jeong, Doo-young. Lee, Byung-Suk, Lee Kwang-Joon, Journal of the Korean Geotechnical Society, Vol. 17, No. 2, 59 ~ 172 (2001); Y. Kolayashi, E.Kato, J. Ceramic Society. Japan 106 [9] 938-941 (1998); And K. Dana. S. Das, S, Kumar, J. European Ceramic Society 24.3169-3175 (2004)].

Miyatani et al. Attempted to introduce waste holes by adding coal ash to porcelain substrates. E. Okutani, T. Tanaka, T. Nishikawa, K. Miyatani, Y. Sadaoka, J. Ceramic society. Japan III [5] 333-338 (2003).

Kausik et al. Investigated the reduction in weight and strength by adding lime and blast furnace solvents to traditional ceramic tiles to investigate their strength, porosity and density. [K. Dana, S. Kumar DAS Bull. Mater. Sci., Vol. 27 No. 2. 183-188 April (2004); And K, Dana, J. Dey, S. Kumur DAS, Ceramics International 31. 147-152 (2005)].

Kobayashi et al. Examined the weight reduction of materials due to changes in pores and microstructures caused by heating temperatures. See Y. Koolayashi, E. Kato, J. Ceramic Society. Japan 106 [9] 938-941 (1998); And in S. Bharim, S. S. Amritphale, N. Chandra, British Ceramic Transaction Vol. 102. No. 2 83 (2003).

Kobayash et al. Investigated the addition of alumina to magnetic materials to form fine, independent pores in the substrate in order to lighten the ceramics while maintaining the strength of the porcelain as much as possible. See Okutani Nishikawa, T. Tanaka, KMiyatani, J. ceramic Soc Japan 110 [7] 688-692 (2002); And T.Kurita. M. Fujiwara, N. Otsuka, K. Asaga, H. Fujimoto, J. Ceramic Soc Japan 106 [12] 1206-1209 (1998).

H.M.shah et al. Investigated the change of porcelain properties such as shrinkage and absorbency of porcelain by addition of coal ash. [Reference: Moon Jong-soo, Choi Tae-hyun, Ceramic Engineering (1), Cheng (2003)].

In this case, as the pore-forming agent, starch, which is hydrophilic, is dissolved in water and burned out in the combustion process, is used.

Starch has been reported to be able to lighten porcelain by generating bubbles during the firing process as a binder in the molding of ceramics.

Fly ash is a by-product of coal-fired power plants captured during the year of coal fired furnaces. The main components of coal ash, such as SiO ₂ and Al ₂ O ₃ , are the same as the main components of porcelain, but do not adversely affect ceramics produced. However, unburned carbon and iron contained in small amounts of coal ash adversely affect ceramics. It is expected that these components can be fully utilized as a raw material for porcelain by refining their content to less than 1%.

In addition, since the coal ash has a specific gravity of 1.9 to 2.3, it is a light material with porous particles. Therefore, the material added to the porcelain raw material will greatly improve the weight and insulation of the porcelain.

When unburned carbon and iron are removed, the color of coal ash becomes light grayish white and can be used as a white porcelain raw material.

The manufacture of pottery using coal ash was reviewed by M · S Hermandez et al in the manufacture of new magnetized earthenware materials. [M.S. Hernandez-Crespo, J. Ma, Rincon, Ceramics International 27. 713-720 (2001).

The manufacture of new ceramics with coal ash added to existing raw materials requires various investigations such as molding strength, moisture demand, color, firing temperature, firing time, flexural strength, glaze selection, and coefficient of friction depending on the amount of coal ash added. Okutani et al. Attempted to reduce the weight of the base by adding coal ash to the existing porcelain base and introducing pores of open and discarded holes. See Okutani Nishikawa, T. Tanaka, KMiyatani, J. ceramic Soc Japan 110 [7] 688-692 (2002).

Kausik Dana investigated the shrinkage, apparent density, water absorption and flexural strength by adding coal ash to tile materials based on Kaolin-quartz-feldspar. [K. Dana. S. Das, S, Kumar, J. European Ceramic Society 24.3169-3175 (2004)]

Kumam et al. Investigated the changes in MOR strength, flexural strength and wear resistance by adding coal ash to ceramic materials. See Y. Koolayashi, E. Kato, J. Ceramic Society. Japan 106 [9] 938-941 (1998)]

In addition, many researchers added coal ash to porcelain to investigate the basics of porcelain properties such as flexural strength, shrinkage, and absorption, along with weight reduction. However, no comprehensive research has yet been published to manufacture tableware products in which coal ash is added to the production of existing products.

Although coal ash is an excellent industrial resource, it is treated as industrial waste, and only a part of it is used as an inexpensive industrial resource. However, refinement can be used as an expensive industrial resource. have.

In the present invention, the refined coal ash is added to the raw material blends of porcelain products currently produced and marketed to develop new porcelains having light and high thermal insulation properties by controlling various items on the porcelain properties such as molding strength, firing temperature, hygroscopicity, and shrinkage rate.

It is an object of the present invention to provide a composition for producing porcelain which is light and excellent in heat insulation without affecting other properties of porcelain and porcelain produced from such a composition.

In the present invention, the above-described object is achieved by refining coal ash and adding the refined porous coal ash to a porcelain base material, which is the main raw material of porcelain, in a specified amount and firing at a specific temperature.

According to the present invention, by providing a composition for producing porcelain by adding a specific amount of porous coal ash to the porcelain base material for producing porcelain, it is possible to produce a porcelain having excellent lightness and warmth without affecting other properties of the porcelain produced therefrom. It is possible. In addition, according to the present invention, by refining coal ash, which is treated as industrial waste, and used as a porcelain raw material, it is possible to greatly reduce the raw material cost in producing porcelain.

In the present invention, a light and large heat retention ceramics may be manufactured by adding 5 wt% to 30 wt% of refined porous coal ash based on the total weight of the porcelain composition to the porcelain base material to prepare the porcelain manufacturing composition. Found.

The present invention provides a composition for producing porcelain as a composition for producing porcelain, wherein coal ash is added to a general porcelain base material, and 5 to 30% by weight of coal ash based on the total weight of the composition for producing porcelain.

Preferably, the present invention is a composition for producing porcelain in which coal ash is added to the S / S clay component, which is a general porcelain material, which is based on the total weight of the composition for producing porcelain, and contains 5 to 30% by weight of coal ash. To provide. Here, the clay means a combination for ceramics with various raw materials controlled, and the S / S clay refers to the basic clay used in the present invention.

More preferably, the present invention is 10 to 12% by weight monotonite, 20 to 24% by weight of Indonesian silica, 10 to 15% by weight feldspar, 10 to 26% by weight of domestic alumina, 10 to 20% by weight of There is provided a composition for producing ceramics containing British clay, 1-3% by weight of bone ash, 1-3% by weight of Chinese talcum, and 5-30% by weight of domestic coal.

The present invention also comprises mixing and stirring the composition for producing ceramics of the present invention and water in a ratio of 1: 1 by weight, forming and drying, calcining by heating to a temperature of 1210 ℃ to 1220 ℃ in air, It provides a method for producing the contained ceramics.

The present invention also provides porcelain having a porosity produced by the process as shown in Figure 1 according to the method of the present invention.

Regarding the coal ash contained in the composition for producing ceramics of the present invention, in the present invention, the coal ash obtained from the coal power plant is pulverized and combusted by a ball mill according to the combustion method described above, and the unburned carbon powder is not more than 0.5% by weight. Porous coal ash was obtained and contained in the composition for producing ceramics of the present invention. Such refined porous coal ash is contained in the composition for producing pottery in an amount of 5% by weight to 30% by weight based on the total weight of the composition for producing pottery.

Coal ash contained in the composition for producing ceramics of the present invention is preferably 5 to 30% by weight based on the total weight of the composition, when the amount of coal ash is less than 5% by weight, the porosity is too high in the ceramics produced from the composition for producing ceramics A low problem arises, and when it is more than 30% by weight, a problem arises in that the strength of the porcelain produced from the composition for producing a porcelain is too weak.

In preparing the ceramics of the present invention, the composition for preparing ceramics of the present invention and water are mixed in a ratio of 1: 1 by weight, and such a ratio is a typical ratio in the art.

In producing the ceramics of the present invention, the firing temperature is preferably 1210 ° C to 1220 ° C. If the firing temperature is less than 1210 ℃ large pores remain on the surface of the porcelain shows that the firing is not complete, and if the firing temperature is more than 1220 ℃ pores increase again tends to be overfired.

The component and its characteristic of the general ceramics raw material contained in the composition for ceramics manufacture of this invention are described below.

In general, the porcelain base material is composed of silicate mineral as a skeletal material, feldspar mineral as a flux or adhesive material, and clay mineral as a plastic material. In particular, in the case of dishware mainly for spinning wheels, it is required to have appropriate plasticity necessary for molding. . This plasticity can be obtained mainly from clay minerals such as clay, kaolin, sericite, pottery, bentonite, and feldspar.

With the development of raw material refining technology, it is required that the raw materials used for the tableware have very pure color with almost no colored components.

All raw materials of pottery are first used by grinding, but there are some that must be pulverized because they must be collected in the form of powder in nature and collected in bulk.

Generally, the raw material computed in the state of powder is called a plastic raw material, and the raw material which should be grind | pulverized is called a non-plastic raw material. When making porcelain stocks, mix different ingredients homogeneously. The mixing ratio at this time is determined according to the combination ratio. Finally, the combination, namely clay, must be moldable. So even if the fired product has the desired properties, it cannot be called clay if it is not molded.

The characteristics of each component of the plastic raw material and the non-plastic raw material constituting such ceramic material are as follows.

<Pottery material>

1.plastic raw materials

1) clay material

(1) Clay

Clay is a raw material with excellent plasticity. The theoretical chemical composition of kaolinite Al ₂ O ₃ · 2SiO ₂ · 2H ₂ O is H ₂ O 13,9%, SiO ₂ 41.54%, Al ₂ O ₃ 39.3%, and the hot change is the crystallized water at 300 ~ 800 ℃. release and mullite 3Al ₂ O ₃ · 2SiO ₂ and generates, in more than 950 ℃ transitions to the ₂ O ₃ · 2SiO ₂ and 3Al glass (遊離) 4SiO _2.

Excessive use of clay in tableware causes severe color deterioration and severe cracks during drying, resulting in poor light transmittance and increased shrinkage. Therefore, the suitable amount is about 10 to 20%.

(2) Plastic clay (Ball clay)

Plastic clay is a secondary clay with high plasticity. It is a fine particle with a high dry strength and contains a lot of organic matter. Therefore, the calcined color is usually pressed and has a color from pale yellow to white.

(3) Bentonite

It is a bentonite and a fine-grained clay through a clay material composed mainly of montmorillonite Al ₂ O ₃ · 4SiO ₂ · 2H ₂ O in which ash or tuff have been modified.

It is used as a material to give plasticity and strength of the body, and the dry strength is increased, and it is impossible to add more than 2% to ceramic raw materials because it has a lot of iron and colloidal property.

2) Pyrophyllite

A mineral that constitutes the main constituent mineral of feldspar, which is represented by Al ₂ O ₃ · 4SiO ₂ · H ₂ O (Al ₂ Si ₄ O ₁₀ (OH) ₂ ) and has a white, pale yellow, pale green, or light blue color This is a dense mass.

Usually composed of fine scaly flakes, the plasticity is small, but shrinkage when heated, well sintered, less torsion and hydration expansion, easy to press molding

3) Sericite

It is a fine mineral of the muscovite and its surface has a gloss like silk. The formula of muscovite is K ₂ A ₁₄ (Si ₆ Al ₂ ) O ₂₀ (OH) ₄ .

Cicada's qualities as a raw material for porcelain are large plasticity, high dry strength, feldspar function, and fine grains without iron, especially iron sulfide.

4) Talc

Talc (3MgO · 4SiO ₂ · H ₂ O), like chloroplast, has less hydroxyl groups, so its adsorption is low and its plasticity is insufficient. Its color is colorless or white, and its impurity is light blue, brown and green. Feel feels soft and smooth.

It is used as a solvent or talc glaze and is characterized by small plastic shrinkage or hydration expansion.

2. Non-plasticized raw material

There are many kinds of non-plastic raw materials used as raw materials for ceramics, and products with different properties may be obtained depending on the method of using the non-plastic raw materials.

1) silica raw material

Silica is chemically composed of about 60% of the oxide constituting the crust with SiO ₂ , and industrially agglomerated is called silica or quartz. The chemical composition of silica (chemical composition) is a SiO ₂ more than 99.60%, the example in trace amounts, such as _{(Na 2 O + K 2 O} ). Silica raw materials include silica sand, quartzite, and quartz flint, and pulverized quartz is called flint. The effect of calcining quartz is that the structure and state of porcelain bases are good, and when it is used as a glaze, the gloss is improved, but the occurrence of pin holes is often seen.

Quartz improves the whiteness of the product, increases the light transmittance and strength, and can easily change the expansion ratio depending on the amount added.

2) Feldspar quality raw material

In the ceramic industry, solvents are often added to the substrate to lower the temperature at which the liquid phase is produced during firing. When this liquid cools, it becomes glass and binds the particles in the body. Because of the presence of solvents, pottery or porcelain may be firmly rigid even when fired at 1100 to 1300 ° C., thereby making them impermeable.

The feldspars are minerals with similar chemical formulas, and the most important ones in the ceramic industry include potassium feldspar, sodium feldspar, feldspar, fluorite, dolomite, biotite, and mica.

Usually, the three main ingredients of porcelain manufacturing are clay, silica and feldspar, which give plasticity for molding, give dry strength and produce mullite at high temperature, and silica increase whiteness and increase strength to improve the skeleton of the body. The feldspar is a solvent to improve the tissue structure of the body.

3) limestone raw material

The chemical composition of pure limestone is 56% of CaO and 44% of CO ₂ , and is decomposed at about 900 ° C. by thermal decomposition as follows:

CaCO _3- > CaO + CO ₂ (Fin Hole Formation)

In the manufacture of ceramics, less than 3% of limestone is used in the possession of ceramics, which increases shrinkage and mechanical strength, and serves to reduce porosity or increase light transmittance.

4) Pottrey stone

It is not a mineral name but refers to a raw material from which ceramics can be made by sweet firing, that is, a combination stone made by nature.

Generally 70% quartz, clay mineral is mainly mica, white dense rock containing 30% kaolin, and its physical properties such as composition, structure, chemical composition, and refractory depends on the kind of the main mineral.

5) Bone ash

It is an important raw material for bone china and is made by calcining bovine bone. As raw material bones, bones of various animals were used, but nowadays, bovine bones are used because they have less iron oxide and can be baked in white.

Bone ash is mostly used as a raw material of bone ash magnetic, but acts as a flux to increase the whiteness and light transmittance of the base.

In addition, alumina may be used in the manufacture of ceramics. When alumina is added, the ceramics have a high fire resistance, strong chemical resistance at any temperature, high mechanical strength, high abrasion resistance, high hardness, and excellent thermal shock resistance. Suitable amounts of alumina required for the porcelain to have the properties as described above are 10 to 26% by weight, based on the total porcelain manufacturing composition.

The porcelain holding material contained in the composition for producing a porcelain of the present invention may contain a peptizing agent, a coagulant, a lubricant, a drying accelerator, and the like, as other auxiliary materials, depending on the properties and processes of the blended raw material.

The refined porous coal ash contained in the composition for producing pottery of the present invention is a refined porous coal ash produced by purifying the remaining material used to obtain energy in a coal power plant.

Such characteristics of coal ash and its purification method are as follows:

<Characteristics of Coal Ash and its Purification Method>

1. Characteristics of Fly Ash

1) Coal Ash Generation Process

In coal-fired power plants, coal is pulverized (passed 200 to 70% of 200Mesh sieve) and injected into the furnace at high speed with hot air in a floating state at a temperature range of 1,500 ± 200 ℃, which is above the melting point of most minerals contained in coal. It burns instantly. At this time, the material remaining after burning is called ash (ash), and anthracite coal is 26 to 50%, bituminous coal is generated about 8 to 15% and divided into bottom ash, fly ash, etc. according to the location after the combustion.

Bottom ash is attached to the furnace wall, superheater, reheater, etc. and falls to the boiler floor due to its own weight. The particle size varies from 1 to 25 mm depending on the power plant. 15 to 20% or so.

Coal ash refers to ashes gathered in the hopper under the coal mill or air preheater and ash collected in the hopper under the dust collector. The particle size of the coal gathered in the hopper under the coal mill or air preheater is 0.3 to 10mm, which is about 5% of the ash generated. to be. The particle size of the dust collected by the electrostatic precipitator and collected in the lower hopper of the dust collector varies depending on the type of coal or combustion conditions, but it is usually 10 to 30㎛ and 75 to 80% of the ash generated is mostly recycled to coal ash. system to the fly ash silo.

2) Chemical Characteristics of Fly Ash

The chemical properties of the coal ash provided to find the unburned carbon content in the crude coal ash sample are shown in Table 1 below.

Table 1. Chemical composition (wt%) of coal ash samples purchased from Seocheon thermal power plant

ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO K ₂ O Na ₂ O Ig. Loss Content (% by weight) 51.32 29.2 3.30 4.08 1.03 3.41 0.22 7.44

3) Mineralogical Characteristics of Fly Ash

In general, the coal is analyzed mineralogically before combustion, and it is mainly composed of quartz, feldspar, kaolin, mica, iron oxide, iron oxide, etc. in addition to danso, but after coal is burned with strong heat, it is mostly mulliteized. Outside is made of quartz and magnetite.

4) Particle size distribution of coal ash

Although the granularity of coal ash is mainly in the range of 1 to 100 μm, in order to investigate the particle size distribution characteristics of the provided coal ash samples, 170 mesh (90 μm) and 325 mesh (43 μm) sieves are included in the Tyler standard sieves. Using a rotary sieve shaker (Rotary Sieve Shaker) taking a given amount of a sample to perform a four-minute experiment and the results are shown in Table 2 below.

Table 2. Particle Size Distribution of Fly Ash Samples

Mesh Wt. (%) Unburned LOI Carbon
(wt.%) Distribution of Unburned Carbon
(wt.% of LOI) +170 15.1 22.3 51.70 -170 +325 12.8 4.3 8.45 -325 72.1 3.6 39.85 Total 100.0 - 100.0

5) Color

Many are greyish white but vary from pale yellow to dark brown, depending on the content of carbon, iron and moisture.

6) Specific gravity and density

Coal ash has a specific gravity of 1.9 to 2.3, about 1.9 for sub-bituminous coal and up to 2.96 for iron-rich bituminous coal, which is about 2/3 of the specific gravity of cement.

2. Purification of Unburned Carbon in Fly Ash

The refining technology of unburned carbon in coal ash is very extensively studied and can be classified into wet and dry methods. In the case of the wet method, the flotation screening method is typical, and the dry method includes the air classification method, the combustion method, and the electrostatic separation method.

1) Floating Screening

Suspension screening takes advantage of the difference in wettability of unburned carbon with hydrophobicity and coal ash with hydrophilicity. In order to increase barge efficiency, insoluble oils such as surfactants and collectors (Frother) are used, which increase the hydrophobicity of the unburned carbon particles and facilitate the generation of fine bubbles. At this time, the bubbles of fine particles are selectively attached only to the hydrophobic unburned carbon particles, and the unburned carbon particles are moved from the water to the air layer and recovered by overflow, and the coal ash remains dispersed in the water and discharged and separated downward. do. This flotation screening method is an old technology, which is widely used in the mineral treatment and waste treatment fields, and recently, interest in the use of unburned carbon in coal ash has been amplified.

2) Air classification method

The air classification method is a method of separating coal ash and unburned carbon by using centrifugal force generated by rotation of air or a mechanical device, and this method is different from the case where the difference in particle size, shape and density is large. It is advantageous when the powders are present as a separate substance rather than as a compound. In the case of unburned carbon separation in coal ash, since the large particles contain a large amount of unburned carbon, it has been promoted for the longest time as a particle size separation method to remove it, and unlike other methods, the secondary particles have a uniform particle size. There is an advantage.

3) combustion method

Combustion is a method of first grinding coal ash and then heating and removing unburned carbon remaining in coal ash. Since low calories, low mobility and volatility do not exist, long residence time and excess air amount are required to burn coal ash without supplementary fuel. do.

4) Electrostatic Separation Method

The electrostatic separation technology is the best among the dry separation technologies, but most of them are being studied as a laboratory small amount of processing technology for theoretical research in the coal refining field.

In the present invention, by adding the coal ash as described above to the porcelain holding material having the composition and properties as described above to prepare a composition for producing porcelain.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example

Example  One

<Production of Composition for Pottery Manufacturing>

1. Porcelain holding raw material

The components of the S / S clay used as a raw material for porcelain is made by mixing various raw materials such as clays, kaolins, pottery, feldspar, and silica, and chemical components are shown in Table 3 below.

Table 3. Chemical Composition of S / S Topsoil

ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ TiO ₂ CaO MgO Na ₂ O K ₂ O Ig loss P ₂ O Trace impurities weight% 61.3 27 0.15 0.08 1.59 0.85 1.07 1.05 5.82 0.87 0.22

The distribution curve of these particles is shown in FIG. From the distribution curve of FIG. 2, the diameter at 50% was 4.88 mu, and the average particle size was 8.03 mu, and it was confirmed that the grain size was appropriate as porcelain clay. The distribution curves also show that the particle distribution is aggregated in the average particle size. Therefore, the distribution and average particle size of the coal ash to be added to the main raw material S / S cover also indicate the reference value which should have similar value as the main raw material S / S cover.

2. Preparation of Refined Porous Fly Ash

Coal ash used in this experiment was the first refined coal ash from the coal ash supplier, which was obtained by burning domestic anthracite coal at Seocheon thermal power plant in Chungnam.

The first refined coal ash contains 6.55% of unburned carbon powder, and if used as a raw material for porcelain, black spots may appear on the surface of the product by black unburned carbon powder, which may cause product defects. In addition, porcelain raw materials are composed of inorganic compounds, and these are formed by firing. If unburned carbon, which is an organic material, is included in the porcelain raw material, the porcelain, which is an inorganic material, and an unburned carbon powder, which is organic, cannot be combined. Therefore, the bond strength of the unburned carbon powder is weakened and the strength is decreased, and cracks are likely to occur due to the impact, friction, heat or other causes that the ceramic products receive during use.

 Therefore, it is not suitable to use coal ash as a raw material for porcelain unless the unburned carbon content is refined to about 0.5%.

 In this experiment, some refined products were purchased by the combustion method, and in order to further refine the coal ash, which was first pulverized and burned the unburned carbon powder remaining in the coal ash, greatly reducing the unburned carbon powder was used in the experiment. This method is expected to be able to obtain high-refining coal ash with low cost, and refined coal ash by this method.

 Unburned carbon powder in coal ash generated during domestic anthracite combustion is contained 3 to 4 times higher than unburned carbon powder produced from combustion of bituminous coal which is imported briquettes. Coal ash from Seocheon thermal power plant using domestic anthracite coal was first purified by the company, and the results of the analysis of the components using the element analyzer (model: CS2000) according to KSL 4007-2001 were analyzed. same.

The specific gravity and unburned carbon content by KSM 004 using a gas pycnometer (Model Accupyc 1330, Micrometer) are shown in Table 4.

Table 4. Unburned Carbon Content and Specific Gravity of Coal Ash Purchased from Seocheon Thermal Power Plant

Unburned Carbon (wt%) importance 6.553 2.315

  Coal ash, first purified by the combustion method, still contains a large amount of unburned carbon, about 6-7%. In order to use coal ash as a raw material for porcelain, unburned carbon powder contained in coal ash must be 0.5% or less. Therefore, in order to purify the unburned carbon powder to less than 0.5%, the coal ash is first pulverized, and the unburned carbon powder contained in the coal ash particles is exposed to the outside and burned in a combustion furnace, so that the unburned carbon powder can be burned and removed. In addition, coal ash should be similar to the particle size distribution of S / S soil in order to add light ash to S / S soil to make light and warmth ceramics. Therefore, coal ash should be first pulverized into fine particles having a particle size distribution similar to that of the main raw material S / S soil, in order to remove unburned carbon dust. The particle size distribution of coal ash is important because the distribution of particles used as porcelain raw materials greatly affects various properties of ceramics such as plastic strength, molding strength, impact strength, and firing temperature. The distribution of roughly refined coal ash by combustion method is shown in Table 5. The 10% average particle size is 7.38mu, the 50% average particle size is 32.43mu, the 90% average particle size is 77.71mu and the total average is 38.28mu. The particle size distribution of the coal ash refined by the primary combustion method is too large than the average particle size of 8.03mu of S / S clay and contains too much unburned carbon powder, so the primary refined coal ash cannot be used as a raw material for ceramics. It was.

 In the ceramic sintered material such as ceramics, large raw material particles adversely affect molding strength, plastic strength, impact strength, etc., and thus, the first refined coal ash was pulverized to have a particle size distribution value similar to that of S / S clay in the secondary refining process.

Table 5. Diameter vs. cumulative value of primary refined coal ash (standard range in bottom position volume)

X 0.30 0.50 0.70 1.00 1.40 2.00 2.60 3.20 4.00 5.00 Q3 1.20 2.14 2.43 2.61 2.89 3.70 4.58 5.33 6.17 7.17 q3 0.65 0.40 0.19 0.11 0.18 0.50 0.74 0.79 0.83 0.98 X 6.00 8.00 1.00 12.00 15.00 20.00 25.00 32.00 36.00 45.00 Q3 8.25 10.68 13.41 16.35 21.03 29.34 37.87 49.32 55.30 66.96 q3 1.30 1.85 2.68 3.54 4.60 6.34 8.38 10.17 11.14 11.46 X 56.00 63.00 90.00 112.0 140.0 180.0 224.0 280.0 315.0 400.0 Q3 77.92 83.23 94.74 98.31 99.76 100.00 100.00 100.00 100.00 100.00 q3 10.99 9.89 7.08 3.58 1.43 0.21 0.00 0.00 0.00 0.00

    X: diameter / mu, Q3: cumulative value /%, q3: density /%

<Manufacture of Pottery>

0.5 kg of refined coal ash is added to 9.5 kg of S / S clay, which is the basic clay as described above, and then kneaded to form and dry the molded product. Was prepared.

The porcelain was prepared in the same manner as described above, except that 1, 2, and 3 kg of refined coal ash was added to 9, 8, and 7 kg of S / S clay respectively.

<Physical Properties Test on Manufactured Ceramics>

1. Thermal conductivity

The measurement of the thermal conductivity of ceramics was made by measuring the sample into 35mm diameter and 3mm thick, and k = k _R * (T _R / _△ t) * (L / L _R ) in the thermal conductivity measuring apparatus (Thermal conductivity measuring apparatus TD-TCA40). The thermal conductivity K value was measured by the formula.

K: Thermal conductivity of the specimen (cal / cm · sec · ℃)

L: thickness of specimen (mm)

K _R : Thermal conductivity of standard thermal conductor (copper: 320 Kcal / m · h ℃)

L _R Length of standard thermal conductor (30mm)

_△ T _R : Average temperature difference of standard thermal conductor

_ΔT : Temperature difference at specimen contact (△ t ℃)

 The thermal conductivity of porcelain substrates according to the amount of coal ash added to the clay showed a tendency of decreasing the thermal conductivity in proportion to the amount of coal ash as shown in Table 6, but the degree of change was not small. However, when 30% of coal ash is added, the thermal conductivity decreases by about 15% compared to that of clay, indicating that the addition of coal ash helps the warmth of ceramics.

Table 6. Thermal conductivity (cal / cm · sec · ℃)

A B C D E F T1 116.4 116.9 116.9 116.4 116.4 116.7 T2 116.1 116.6 116.5 116.1 116.1 116.4 T3 115.7 116.3 116.1 115.7 115.5 115.8 T4 115.3 116.0 115.8 115.4 115.5 115.8 T5 24.5 22.6 25.3 30.5 29.0 24.7 T6 24.2 22.3 25.0 30.2 28.7 24.4 L 0.0043 0.0040 0.0041 0.0040 0.0043 0.0043 △ T 90.5 93.1 90.2 84.6 86.2 90.8 K 1.77483 1.37487 1.69697 1.63909 1.57773 1.51542

A: S / S
B: coal ash
C: S / S clay 95% + coal 5%
D: S / S top cover 90% + coal 10%
E: S / S topdressing 80% + coal ash 20%
F: 70% of S / S clay + 30% of coal ash
T: Temperature measuring point

2. apparent porosity

 Since porcelain consists of the body itself and voids, it is possible to estimate roughly the properties of porcelain products by knowing its quantitative ratio.

  Apparent porosity = volume of opening part / volume of (material part + waste part + open pore part) X 100

The measurement was calculated by measuring the catcher weight, the dry weight, and the weight in water.

  Apparent porosity = (catcher weight-dry weight) / (catcher weight-water weight) X 100

Table 7. Apparent Porosity Variation with Proportion of Coal Ash Added

       Sample temperature (℃) S / S 5 wt% 10% by weight 20 wt% 30 wt% 1250 0.60 0.00 6.00 0.60 0.00 1245 0.00 0.00 0.00 0.00 0.00 1240 0.00 0.00 0.00 0.00 0.00 1230 0.00 0.00 0.00 0.00 0.12 1220 0.00 0.00 0.00 0.25 1.22 1215 0.00 0.00 0.18 0.50 1.60 1210 0.00 0.17 0.37 0.64 3.14 1205 0.26 0.17 0.48 1.69 4.44 1200 0.49 0.63 1.35 2.75 4.84 1190 1.09 1.39 2.47 4.08 6.96 1175 2.40 2.63 4.11 5.61 7.80 1160 3.70 4.54 5.83 7.27 10.68 1140 6.50 6.22 7.84 9.67 12.20

As shown in FIG. 3 and Table 7, the apparent porosity of the basic clay starts to have a value of almost 0 at around 1210 ° C. when the firing temperature is gradually increased from 1140 ° C. From these temperatures, the rate of absorption reaches almost zero, and at higher temperatures, all have a value of zero. Therefore, when the apparent porosity (A _p ) is determined, the optimum firing temperature is near the temperature at which the value starts at 0 at 1210 ° C.

As shown in Figures 4, 5, 6, and 7 shows the apparent porosity when 5, 10, 20, 30% of coal ash is added to the basic soil. The temperature at which the apparent porosity (A _P ) starts at 0 rises about 5 ° C. above the basic soil when 5% is added, and when the temperature increases by 10 ° C., the A _p value starts to occur at 0 °. However, when 30% of the coal ash is added, the apparent porosity becomes zero at the experimental temperature of 1240 ° C. That is, the addition of coal ash indicates that the porosity increases with an increase in the appropriate firing temperature. Source of firing temperature rises This phenomenon because the added coal ash has a porous ipjayi possessing combined with those of the addition is to have more of the pores are glassy been produced in the process is the apparent porosity (A _P) value to close these pores To make it zero, a higher firing temperature is required.

3. Disposal Power Test

Table 8 shows the experimental results on the change in waste porosity (C _p ) according to the amount of coal ash added to S / S soil, which is the basic soil, and FIG. 8 is S / S soil, and FIG. 9, FIG. 10, FIG. 11 and FIG. The change in the value of waste porosity (C _p ) with the temperature of 5, 10, 20, 30% coal ash in S soils.

The waste porosity (Cp) of the clay at the low firing temperature of 1140 ℃ has a small value of 11.59, but the waste porosity (C _p ) near 1210 ℃, the temperature at which the firing temperature rises and the apparent porosity (A _p ) becomes zero. The value will be 14.71 and will remain close to this value even at higher temperatures. The addition of coal ash to the basic soil has a constant value of about 14.7, even at slightly higher firing temperatures, depending on the amount added. As the amount of added coal ash increases, the waste porosity Cp increases, and as the amount of added ash increases, the waste porosity Cp increases from a lower temperature. This phenomenon can be seen that the higher the amount of coal ash, the higher the porosity due to the addition of coal porosity, and the larger the pore size at lower temperatures, the smaller the apparent porosity (Ap) and the smaller particles in these pores. It is estimated that the open pores are turned into discarded pores due to the glass generated during the migration and firing process.

The coal ash content and disposed of porosity (C _p) between the added amount is discarded porosity of the green body up to 20% from the value (C _p) value and substantially have the same value, even the ash amount of 30% disposed of porosity (C _p) value of clay The value of waste porosity (C _p ) can be as high as 30% of coal ash. However, it is difficult to add 30% of coal ash as the absorption rate, which is an important property of ceramics, is high. do.

Table 8. Changes in Waste Rates with Coal Ash Rate

         Sample temperature (℃) S / S 5 wt% 10% by weight 20 wt% 30 wt% 1250 14.65 15.43 15.94 15.95 15.85 1245 14.48 15.49 15.79 16.03 15.92 1240 14.47 15.46 15.76 16.01 15.96 1230 14.53 15.33 15.77 15.93 15.86 1220 14.40 14.90 15.66 15.75 15.45 1215 14.45 14.71 15.44 15.78 15.00 1210 14.71 14.68 15.16 15.59 14.73 1205 14.81 14.77 15.14 15.04 14.63 1200 14.97 14.88 14.88 14.59 13.94 1190 14.75 14.50 14.34 14.02 13.00 1175 14.00 13.97 13.27 13.33 13.27 1160 13.43 12.46 12.61 12.62 11.76 1140 11.59 11.41 11.47 11.19 10.91

4. Change in firing temperature and pore shape

Investigate the surface of the fired body with coal ash by scanning electron microscope (SEM) to investigate the size and distribution of pores according to the firing temperature and the amount of coal ash added. The possibility of use as a tool for estimating the approximate value of the appropriate firing temperature was investigated based on the confirmation of the occurrence.

FIG. 13 is a photograph enlarged 500 times to examine the distribution and size of pores at a temperature of about 1220 ° C for S / S clay firing, which is the basic clay, and FIGS. It is a 500 times magnified photograph to investigate the distribution and size of pores at the temperature of 1220 ℃ which is the proper temperature of S / S clay, the basic clay.

13 is a lot of pores at 1200 ℃ and less bubbles at 1210 ℃, since the smooth surface without bubbles at 1220 ℃ based on this the appropriate firing temperature of S / S clay is 1210 to 1220 ℃ can see. At 1240 ° C, many bubbles reappear, suggesting that they are underfiring.

In FIG. 14 with 10% added coal ash, it was found that there were large pores at 1200 ° C., resulting in less unbaked state, small pores still remaining at 1210 ° C., and almost smooth at 1220 ° C. It is estimated to be near, and at 1240 ℃, many pores are generated and it can be seen that the underfiring starts.

Coal ash is added 20% In Figure 15 is baked at 1210 ℃ to 1220 ℃ to smooth the surface and not much porosity. However, at 1240 ° C, cotton is slightly less smooth than 1210 ° C to 1220 ° C and some pores are generated. The addition of 30% of coal ash in FIG. 16 is similar to that of 10% and 20% addition of coal ash, but at a low temperature of 1200 ° C. and a high temperature of 1240 ° C. or more, pores are shown to have larger pores compared to those containing less coal ash. The optimum temperature range appears to be narrower.

Also, the form of pores on the surface was similar to that of added or no coal ash, so no singularity could be found.

Although it is difficult to determine the appropriate firing temperature by SEM image, it is possible to use it as a tool to help determine the approximate firing temperature range.

As evidenced from the above tests and the results, the coal ash whose main component is the same as the raw material of porcelain is porous fine particles, and thus it can be used for the production of light and high insulation porcelain. In addition, when the coal ash is added to the porcelain base material in an amount of 5 to 30% by weight based on the total weight of the porcelain manufacturing material, it has been proved that the thermal conductivity is significantly lowered and the heat retention is improved.

Example  2

Commercially available materials include 1.1 kg of monolithic stone, 2.2 kg of Indonesian quartz, 1.3 kg of feldspar, 1.8 kg of domestic alumina, 1.5 kg of British clay, 0.2 kg of bone ash and 0.2 kg 1.7 kg of domestic coal was added to the mixture of the Chinese talcum and kneaded to form a porcelain by firing the molded product at various firing temperatures after molding and drying in a similar manner to Example 1.

The heat conductivity, apparent porosity, waste porosity, and changes in firing temperature and pore shape of the porcelain prepared as described above were tested as in Example 1 above. Similar results were obtained.

As described above, the present invention is described in detail with reference to the embodiments, but the present invention is not limited to these embodiments, and those skilled in the art can understand that various changes are possible within the technical idea of the present invention. There will be.

1 is a manufacturing flowchart of a composition for producing a ceramic according to the present invention including S / S clay to which coal ash is added.

2 is a particle distribution curve of S / S clay contained in the composition for producing pottery of the present invention.

Figure 3 shows the apparent porosity according to the firing temperature of the porcelain produced by the composition is not added to the ash, Figures 4 to 7 shows the apparent porosity according to the temperature of the porcelain produced by the composition for producing porcelain of the present invention Drawing.

8 shows the waste porosity according to the firing temperature of the porcelain produced by the composition is not added to the coal ash, Figures 9 to 12 shows the discarded porosity according to the temperature of the porcelain produced by the composition for producing porcelain of the present invention Drawing.

FIG. 13 is a photograph enlarged 500 times to examine the distribution and size of pores at a temperature of about 1220 ° C. of S / S soil, which is the basic soil, and FIGS. 14, 15, and 16 show coal ash on the soil, respectively. It is a 500 times magnified photograph to investigate the distribution and size of pores at the temperature of 1220 ℃ which is the proper temperature of S / S clay, which is the basic soil.

Claims (5)

A composition for producing porcelain, wherein coal ash is added to the porcelain base material of S / S clay having the composition shown in Table 1, wherein 5 to 30% by weight of coal ash is added based on the total weight of the composition for porcelain production. TABLE 1 ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ TiO ₂ CaO MgO Na ₂ O K ₂ O Ig loss P ₂ O Trace impurities weight% 61.3 27 0.15 0.08 1.59 0.85 1.07 1.05 5.82 0.87 0.22 delete delete The composition for preparing ceramics according to claim 1 and water are mixed and stirred in a ratio of 1: 1 by weight, molded and dried, and calcined by heating to a temperature of 1210 ° C. to 1220 ° C. in air, thereby containing coal ash. How to manufacture pottery. Porcelain produced by the method according to claim 4 having a porosity.

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