Coal gangue glazed tile and preparation method thereof

Abstract

The present application relates to a kind of coal gangue glazed tile and its preparation method, the coal gangue glazed tile includes brick and glaze, the brick according to percentage by weight, including coal gangue 55-60%, red mud 25-30%, kaolinite 10-15%, talcum powder 1-3%, sintering aid 0.1-0.3%;The glaze according to percentage by weight, including 18-20% calcined coal gangue, 25-30% quartz, 20-25% zirconium quartz, 8-10% calcite, 13-15% boric acid, 4-6% borax.The coal gangue glazed tile prepared in the present application uses a large amount of coal gangue as raw material, can effectively utilize the large amount of coal gangue produced in coal production, reduces the pollution of coal gangue to environment;The coal gangue glazed tile produced has excellent breaking strength, glaze crack resistance, pollution resistance and wear resistance;Meanwhile, red mud and talcum powder are used as sulfur-fixing agent, the combustible sulfur in coal gangue can be solidified, effectively reduce the emission of sulfur-containing waste gas, reduce production cost and pollution.

Description

Technical Field

[0001] This invention relates to a coal gangue glazed brick and its preparation method, belonging to the field of ceramic brick technology. Background Technology

[0002] Coal gangue is a solid waste generated during coal production and processing. Its annual emissions are equivalent to about 10% of the year's coal production. Long-term stockpiling of coal gangue occupies large amounts of land and causes spontaneous combustion, polluting the atmosphere and groundwater. The main chemical components of coal gangue are SiO2, Al2O3, Fe2O3, and CaO; its mineral composition includes kaolin, quartz, montmorillonite, feldspar, illite, and limestone. These minerals are commonly used raw materials for ceramic materials. Therefore, using coal gangue as a raw material to produce ceramic materials, especially high-volume ceramic bricks, provides a promising approach for the resource utilization of coal gangue. Coal gangue is a mixture of inorganic matter and a small amount of organic matter. The inorganic matter includes minerals and water, with highly variable mineral content and a very complex composition. It contains dozens of elements, the main ones being Si, Al, Fe, Ca, Mg, K, Na, S, Ti, and P. Therefore, the composition of coal gangue used as a raw material for ceramic bricks needs to be comprehensively considered to achieve good results. Patent CN106810206 B, entitled "A Method for Preparing Ultra-Flat Polished Glazed Ceramic Bricks Using Coal Gangue," specifies the following mass percentage composition of the bottom layer powder of the ceramic brick body: coal gangue 50-55%, kaolin 10-20%, albite 10-15%, calcite 10-15%, and wollastonite 10-15%. This method effectively utilizes waste resources, significantly reduces firing temperature and shortens the firing cycle, and substantially lowers production costs. However, the composition of coal gangue produced in different regions is complex, and some types of coal gangue cannot be used as raw materials for ceramic bricks. Furthermore, the presence of sulfur in coal gangue poses a pollution problem during the firing process. Publication No. CN 111848125 B, Invention Title: A Production Method of Sintered Brick Building Materials from Waste Gypsum, Red Mud, and Coal Gangue. In this patent, BaCl2 in the additive reacts fully with sulfur in the waste gypsum and coal gangue to generate BaSO4 and HCl, achieving the effect of removing sulfur trioxide. Reaction formula:

[0003] BaCl2 + SO3 + H2O = BaSO4 + 2HCl; SiO2 + 4HCl = SiCl4 + 2H2O; SiO2 and KNO3 react with red mud

[0004] The NaOH in the solution reacts fully to remove alkali and solidify sodium, making the product neutral. In the above reaction formula, HCl generated reacts with SiO2 to produce SiCl4 and H2O. The SiO2, BaCl2, and KNO3 in the additives react with SO3 and NaOH in the waste gypsum, red mud, and coal gangue, thoroughly removing sulfur and alkali, fixing sulfur and sodium, making the product neutral in pH, without blooming, meeting and exceeding national standards. The product prepared by this method is a common sintered brick, which is fundamentally different from glazed ceramic bricks. Therefore, this patent does not consider the bonding between the brick body and the glaze. It can be seen that the existing technology for preparing ceramic bricks using coal gangue lacks a comprehensive consideration of the physicochemical properties of coal gangue and auxiliary materials, resulting in coal gangue ceramic bricks with generally poor performance. Moreover, the preparation process involves a large amount of waste gas emission, difficult subsequent treatment, and high costs. Summary of the Invention

[0005] This invention provides a coal gangue glazed brick and its preparation method, which solves the problems of general ceramic brick performance and large amount of waste gas emissions in the existing process of producing ceramic bricks from coal gangue.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A coal gangue glazed brick includes a brick blank and a glaze. The brick blank, by weight percentage, includes 55-60% coal gangue, 25-30% red mud, 10-15% kaolinite, 1-3% talc powder, and 0.1-0.3% sintering aid.

[0008] The glaze, by weight percentage, comprises 18-20% calcined coal gangue, 25-30% quartz, 20-25% zircon, 8-10% calcite, 13-15% boric acid, and 4-6% borax.

[0009] Further, preferably, the loss on ignition of the coal gangue is 6-8%, and the total sulfur content is 0.3-0.5%.

[0010] Further, preferably: the plasticity index of the red mud is 7-20, preferably 11-17; the drying sensitivity coefficient is less than 1, and the loss on ignition is 2-5%.

[0011] Further, preferably: the loss on ignition of the kaolinite is 7-10%, and the loss on ignition of the talc powder is 7-10%.

[0012] Further, preferably: the sintering aid comprises, by weight percentage, 15-20% silicon carbide, 20-30% low melting point glass powder, and the balance being alumina.

[0013] The method for preparing coal gangue glazed bricks of the present invention includes the following steps:

[0014] (1) Crush and ball mill the raw materials for brick blanks.

[0015] (2) Remove iron from the ball-milled raw material and spray dry it;

[0016] (3) The spray-dried raw materials were aged for 24 hours;

[0017] (5) Ball mill the glaze, fineness: 325 mesh sieve, sieve residue 0.7-1.0%, specific gravity after milling: 1.86-1.90, flow rate after milling: 50-80m / s.

[0018] (4) Press the raw material into shape and dry it at 80-90℃ for 1-2 hours;

[0019] (6) Spray water on the dried brick blanks at a pressure of 0.4-0.5 MPa and a water volume of 7.5-15 g / m2.

[0020] (7) After spraying water, the brick blanks are sprayed with glaze. The glaze specific gravity is 1.85-1.88, the flow rate is 33-38m / s, and the glaze application amount is 560-570g / m2.

[0021] (7) Firing;

[0022] (8) Grind and polish the edges to obtain coal gangue glazed bricks.

[0023] Further, preferably: the ball milling in step (1) is specifically as follows: fineness: 2.0-2.5% residue on 250 mesh sieve; moisture: 33.8-36.6%; specific gravity: 1.66-1.71; flow rate: 35-65m / s.

[0024] Further, preferably: the moisture content of the powder after spray drying in step (2) is 6-8%, and the particle composition is as follows: 35-45% of particles above 40 mesh, 45-55% of particles from 40-60 mesh, 6-10% of particles from 60-80 mesh, 3-5% of particles from 80-100 mesh, and the remainder is particles below 100 mesh.

[0025] Furthermore, preferably: the pressing pressure in step (4) is 53000-55000KN, pressing 4 times, 8.1 times / minute.

[0026] Further, preferably: the firing process specifically involves: heating to 350-400℃ at a heating rate of 3-5℃ / min and firing for 20-30 minutes; heating to 700-750℃ at a heating rate of 3-5℃ / min and firing for 8-10 minutes; heating to 950-1000℃ at a heating rate of 2-3℃ / min and firing for 8-10 minutes; heating to 1100-1150℃ at a heating rate of 1-2℃ / min and firing for 40 minutes; and finally cooling down and firing at 1000℃ for 10 minutes.

[0027] The beneficial effects of this invention are:

[0028] Coal gangue has a complex composition. While the chemical composition and physical properties of most coal gangue raw materials can basically meet the requirements for brick making, some problems exist: First, some coal gangue does not sinter. It is difficult to determine whether such raw materials are suitable for brick making based solely on chemical and physical properties, and firing tests must be conducted. Second, coal gangue with excessive calorific value will prolong the firing cycle and cause excessive black cores when the calorific value of the raw materials in the fired coal gangue exceeds the target, thus affecting product quality. Third, low-plasticity coal gangue will be difficult to shape. Fourth, SO2 or SO3 is generated during the roasting process of coal gangue. If not eliminated, it can not only damage the furnace but also pollute the air when emitted into the atmosphere. This invention fully considers the physicochemical properties of various raw materials, taking into account factors such as loss on ignition, total sulfur, plasticity index, and drying sensitivity coefficient. Based on the influence of different raw material ratios on the flexural strength, water absorption, glaze bonding strength, and sulfur fixation effect of the green body, coal gangue, red mud, kaolinite, and talc are used as raw materials. The CaO and Na2O in red mud and talc are used to solidify SO2 or SO3 in situ, reducing emissions. At the same time, kaolinite is used to adjust the flexural strength of the green body, and talc and sintering aids fill the voids in the sintering process, which can effectively improve product performance.

[0029] The coal gangue glazed bricks prepared by this invention use a large amount of coal gangue as raw material, which can effectively utilize the large amount of coal gangue produced in coal mine production and reduce the pollution of coal gangue to the environment. The produced coal gangue glazed bricks have excellent breaking strength, glaze crack resistance, pollution resistance and wear resistance. At the same time, red mud and talc powder are used as sulfur-fixing agents to solidify the combustible sulfur in coal gangue, effectively reducing the emission of sulfur-containing waste gas, reducing production costs and pollution. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] The coal gangue used in this invention has a SiO2 content of 55-70%, an Al2O3 content of 20-25%, a total sulfur content of 0.3-0.5%, and a loss on ignition of 6-8%. Within this range, the chemical composition of other raw materials can be used as ceramic brick materials. The specific composition of the raw materials used is shown in Table 1 below.

[0032] Table 1 Composition of different raw materials

[0033]

[0034] Low-melting-point glass powder should be lead-free, with a melting temperature of 600-700℃ and a coefficient of thermal expansion of 70-100*10. -7 The glass powder used in this embodiment is of grade D270.

[0035] The Influence of Total Sulfur Content on Coal Gangue Glazed Bricks in Examples 1-6

[0036] A coal gangue glazed brick includes a brick blank and a glaze. The brick blank, by weight percentage, includes 57% coal gangue, 25% red mud, 15% kaolinite, 2.8% talc powder, and 0.2% sintering aid.

[0037] The glaze, by weight percentage, comprises 20% calcined coal gangue, 25% quartz, 25% zircon, 10% calcite, 15% boric acid, and 5% borax.

[0038] The sintering aids, by weight percentage, consist of 18% silicon carbide, 25% low-melting-point glass powder, and the balance being alumina.

[0039] The total sulfur content in coal gangue was adjusted by calcining coal gangue and ferrous sulfide to 0%, 0.2%, 0.3%, 0.4%, 0.5%, and 0.6%, respectively.

[0040] The method for preparing coal gangue glazed bricks of the present invention includes the following steps:

[0041] (1) Crush and ball mill the raw material for brick blanks. The ball milling in step (1) is specifically as follows: fineness: 2.0% residue on 250 mesh sieve; moisture: 34.6%; specific gravity: 1.68; flow rate: 40m / s.

[0042] (2) Remove iron from the ball-milled raw material and spray dry it. The moisture content of the powder after spray drying in step (2) is 6.3%, and the particle composition is as follows: 36.7% of particles above 40 mesh, 48.8% of particles between 40 and 60 mesh, 7.6% of particles between 60 and 80 mesh, 3.8% of particles between 80 and 100 mesh, and 3.1% of particles below 100 mesh.

[0043] (3) The spray-dried raw materials were aged for 24 hours;

[0044] (5) The glaze is ball-milled with a fineness of 325 mesh sieve, a sieve residue of 0.8%, a specific gravity of 1.87, and a flow rate of 60 m / s.

[0045] (4) Press the raw material into shape, dry it at 80°C for 2 hours. The pressing pressure in step (4) is 54000KN, and the pressing is done 4 times at 8.1 times / minute.

[0046] (6) Spray water onto the dried brick blanks at a pressure of 0.4 MPa and a flow rate of 10 g / m³. 2 ;

[0047] (7) After spraying water, the brick blanks are sprayed with glaze. The glaze specific gravity is 1.86, the flow rate is 35m / s, and the glaze application rate is 560g / m. 2 .

[0048] (8) Firing, specifically: heating to 380°C at a heating rate of 3°C / min and firing for 25 min; heating to 720°C at a heating rate of 4°C / min and firing for 8 min; heating to 980°C at a heating rate of 2°C / min and firing for 10 min; heating to 1150°C at a heating rate of 1°C / min and firing for 40 min; finally cooling down and firing at 1000°C for 10 min.

[0049] (8) Grind and polish the edges to obtain 800mm×800mm×10.5mm coal gangue glazed bricks.

[0050] Performance index determination

[0051] The sulfur fixation rate is calculated using the following formula:

[0052] Sulfur fixation rate = (weight of finished brick × sulfur content of finished brick) / (weight of brick blank × sulfur content of brick blank) × 100%.

[0053] The sulfur content of finished bricks and brick blanks was determined using the method for determining total sulfur in coal (GB / T214-2007).

[0054] The performance of ceramic tiles was determined using the methods described in GB / T 4100-2015 Ceramic Tiles. Specific data are shown in Table 2.

[0055] Table 2 Performance data of ceramic bricks prepared with different sulfur contents

[0056]

[0057] Sulfur is present in coal gangue, posing a sulfur pollution problem during the sintering process. Therefore, sulfur fixation is a key issue to consider during coal gangue sintering. Adding sulfur-fixing components converts combustible sulfur into solid compounds, effectively reducing sulfur emissions and simplifying subsequent waste gas treatment. Table 2 shows that the breaking strength of ceramic bricks increases sequentially from high to low total sulfur content in coal gangue. When the total sulfur content exceeds 0.49%, the breaking strength of ceramic bricks changes significantly. This is because sulfur-fixing products are generated during the sintering process of coal gangue. These products fill the voids inside the ceramic bricks, increasing their density and strength, thereby improving their mechanical properties and durability. Simultaneously, the sulfur-fixing products have good corrosion resistance, resisting the erosion of some chemical substances and enhancing the corrosion resistance of the ceramic bricks. However, when the sulfur content is too high, the high concentration of sulfur-fixing products forms voids inside the ceramic brick, which reduces the density of the brick and thus affects its mechanical properties and durability. Therefore, controlling the total sulfur content of coal gangue is of great importance for coal gangue glazed bricks.

[0058] Examples 7-11: Effect of Loss on Ignition on Coal Gangue Glazed Bricks

[0059] The experiment was basically the same as in Example 4, except that charcoal was added to adjust the loss on ignition of coal gangue to 7%, 8%, 9%, 10%, and 11% respectively, and the effect of loss on ignition on coal gangue glazed bricks was investigated. The specific experimental data are shown in Table 3.

[0060] Table 3 Performance data of ceramic bricks prepared with different loss on ignition

[0061]

[0062]

[0063] Loss on ignition (LOI) refers to the percentage of material mass loss caused by the volatilization of volatile components (such as moisture and organic matter) in ceramic materials during high-temperature firing. For glazed ceramic tiles, the raw materials used are mostly minerals, and these glazes contain organic matter. Therefore, LOI directly affects the performance of glazed ceramic tiles. This invention strictly controls the LOI of various raw materials, thereby effectively improving product performance. Table 3 shows that as LOI increases, the breaking strength and modulus of rupture of the prepared glazed ceramic tiles decrease, while the water absorption increases. This indicates that excessive LOI can lead to voids during the sintering process, poor bonding with the glaze, and other problems, resulting in high water absorption, reduced breaking strength, and lower modulus of rupture. It also significantly impacts glaze crack resistance, stain resistance, and abrasion resistance, leading to substandard products in glaze crack resistance tests and reduced stain resistance and abrasion resistance grades.

[0064] Examples 12-16: Effect of Red Mud Addition on Coal Gangue Glazed Bricks

[0065] The results were basically the same as in Example 7, except that the proportions of red mud, coal gangue and kaolin in the glazed tile material were adjusted to investigate the effect of red mud on the glazed tile. The specific results are shown in Table 4.

[0066] Table 4 Performance data of ceramic bricks prepared with different red mud contents

[0067]

[0068]

[0069] The purpose of adding red mud in this invention is to solidify the sulfur in coal gangue. Simultaneously, the addition of red mud can increase the sintering temperature and strength, enhancing the physical properties of coal gangue glazed bricks. As shown in Table 4, excessive addition of red mud increases the brittleness of the coal gangue glazed bricks, making them more prone to breakage or wear; too much red mud reduces their destructive power, making them more susceptible to external damage. However, insufficient addition results in a low sulfur fixation rate, leading to micropores in the coal gangue ceramic bricks during sintering and reducing their performance.

[0070] Examples 17-24: Effect of Additive Dosage on Coal Gangue Glazed Bricks

[0071] It is basically the same as Example 12, except for the amount and composition of the sintering aid, as shown in Table 5.

[0072] Table 5 Performance data of ceramic bricks prepared with different red mud contents

[0073]

[0074]

[0075] Coal gangue glazed bricks contain organic matter, which easily leads to poor bonding between the brick body and the glaze during firing, resulting in glaze cracking and poor resistance to glaze cracking, staining, and wear in the prepared ceramic bricks. This invention addresses this by adding a sintering aid containing low-melting-point glass powder, thereby giving the ceramic bricks superior performance.

[0076] Silicon carbide, a sintering aid, is a high-temperature resistant, wear-resistant, and high-hardness material with excellent thermal conductivity and chemical corrosion resistance. In the sintering process of coal gangue ceramic bricks, silicon carbide acts as a flux, lowering the sintering temperature, promoting densification of the green body, and improving product strength and thermal stability. Low-melting-point glass powder melts into a liquid phase during sintering, filling the voids between green body particles, promoting densification, and increasing product density and strength. Alumina, in the sintering process of coal gangue ceramic bricks, can improve the thermal stability and wear resistance of the green body, while also promoting densification and increasing product strength. Furthermore, alumina can synergistically interact with other components in coal gangue to further enhance product performance.

[0077] A mixture of silicon carbide, low-melting-point glass powder, and alumina, as a sintering aid for coal gangue ceramic bricks, can reduce the sintering temperature and increase the densification of the green body through synergistic and mutual promotion, thereby improving the density, strength, and thermal stability of the product and helping to improve the quality and production efficiency of coal gangue glazed bricks.

[0078] Examples 25-29

[0079] It is basically the same as Example 1, except that the ratio of raw materials is different, as shown in Table 6.

[0080] Table 6. Raw material ratios for different embodiments

[0081]

[0082] The performance of Examples 25-29 was tested, and the specific data are shown in Table 7.

[0083] Table 7 Performance data of coal gangue glazed bricks prepared in different embodiments

[0084]

[0085]

[0086] As shown in Table 7, the coal gangue glazed bricks prepared by this invention use a large amount of coal gangue as raw material, which can effectively utilize the large amount of coal gangue produced in coal mine production and reduce the pollution of coal gangue to the environment. The produced coal gangue glazed bricks have excellent breaking strength, glaze crack resistance, pollution resistance and wear resistance. At the same time, red mud and talc powder are used as sulfur-fixing agents, which can solidify the combustible sulfur in coal gangue, effectively reduce the emission of sulfur-containing waste gas, reduce production costs and reduce pollution.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A glazed brick made from coal gangue, characterized in that: The material includes brick blanks and glaze. The brick blanks, by weight percentage, consist of 55-60% coal gangue, 25-30% red mud, 10-15% kaolinite, 1-3% talc powder, and 0.1-0.3% sintering aids. The glaze, by weight percentage, comprises 18-20% calcined coal gangue, 25-30% quartz, 20-25% zircon, 8-10% calcite, 13-15% boric acid, and 4-6% borax. The coal gangue has a loss on ignition of 6-8% and total sulfur of 0.3-0.5%; the red mud has a plasticity index of 7-20, a drying sensitivity coefficient of less than 1, and a loss on ignition of 7-8%; the kaolinite has a loss on ignition of 7-10%; and the talc powder has a loss on ignition of 7-10%. The sintering aids, by weight percentage, include 15-20% silicon carbide, 20-30% low-melting-point glass powder, and the balance being alumina.

2. A method for preparing coal gangue glazed bricks as described in claim 1, characterized in that, Includes the following steps: (1) Crush and ball-mill the raw materials for brick blanks. (2) Remove iron from the ball-milled raw material and spray dry it; (3) The spray-dried raw materials were aged for 24 hours; (4) Ball mill the glaze material to a fineness of 325 mesh sieve, with a sieve residue of 0.7-1.0%, a specific gravity at the outlet of the mill of 1.86-1.90, and an outlet flow rate of 50-80 m / s; (5) Press the raw material into shape and dry it at 80-90℃ for 1-2 hours; (6) Spray water onto the dried brick blanks at a pressure of 0.4-0.5 MPa and a water volume of 7.5-15 g / m². (7) After spraying water, the brick blanks are sprayed with glaze. The glaze specific gravity is 1.85-1.88, the flow rate is 33-38m / s, and the glaze application amount is 560-570g / m2; (8) Firing; (9) Grind and polish the edges to obtain coal gangue glazed bricks.

3. The preparation method according to claim 2, characterized in that: The ball milling in step (1) is specifically as follows: fineness: 2.0-2.5% residue on 250 mesh sieve; moisture: 33.8-36.6%; specific gravity: 1.66-1.71; flow rate: 35-65m / s.

4. The preparation method according to claim 2, characterized in that: In step (2), the moisture content of the spray-dried powder is 6-8%, and the particle composition is as follows: 35-45% for particles above 40 mesh, 45-55% for particles of 40-60 mesh, 6-10% for particles of 60-80 mesh, 3-5% for particles of 80-100 mesh, and the remainder is particles below 100 mesh.

5. The preparation method according to claim 2, characterized in that: In step (4), the pressing pressure is 53000-55000KN, and the pressing is performed 4 times at 8.1 times / minute.

6. The preparation method according to claim 2, characterized in that: The firing process is as follows: heating at a rate of 3-5℃ / min to 350-400℃ and firing for 20-30 minutes; heating at a rate of 3-5℃ / min to 700-750℃ and firing for 8-10 minutes; heating at a rate of 2-3℃ / min to 950-1000℃ and firing for 8-10 minutes; heating at a rate of 1-2℃ / min to 1100-1150℃ and firing for 40 minutes; and finally cooling down and firing at 1000℃ for 10 minutes.

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