Silica brick for coke oven and preparation method therefor
By using CaO-Al2O3 mineralizers and a pre-firing process to form an oxide coating layer and control the high-temperature reaction path, the thermal conductivity and density problems of coke oven silica bricks were solved, and high-performance silica bricks were prepared.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- INSPECTION & CERTIFICATION CO LTD MCC
- Filing Date
- 2025-11-14
- Publication Date
- 2026-05-21
AI Technical Summary
Existing silica bricks for coke ovens have unsatisfactory thermal conductivity and density. Traditional mineralizers are difficult to disperse evenly, and the release of gases from high-temperature decomposition affects the brick structure, leading to a decrease in thermal conductivity.
Using CaO-Al2O3 mineralizers, calcium nitrate tetrahydrate and high-silicon aluminum alloy powder are added to form an oxide coating layer through pre-firing. The high-temperature reaction path is controlled, and gaseous SiO(g) and Al2O(g) are used to diffuse and fill the pores, thereby improving the continuity of the brick structure and its thermal conductivity.
Coke oven silica bricks with dense structure, high strength, high load softening temperature, and excellent thermal conductivity were prepared, solving the problem of damage to the brick structure caused by the decomposition gas of traditional mineralizers and improving the density and thermal conductivity of the bricks.
Abstract
Description
Coke oven silica bricks and their preparation methods
[0001] Cross-reference to related applications
[0002] This application claims the benefit of Chinese Patent Application No. 202411646951.6, filed on November 18, 2024, the contents of which are incorporated herein by reference. Technical Field
[0003] This invention relates to the field of refractory materials technology, specifically to a coke oven silica brick and its preparation method. Background Technology
[0004] High thermal conductivity is currently the main direction for the energy-saving development of silica bricks for coke ovens. Traditionally, silica bricks are produced using a mixture of lime slurry and iron scale as mineralizers. However, this method has long suffered from problems such as difficulty in uniformly dispersing the mineralizer and the potential for gas generation during the high-temperature decomposition of lime slurry to damage the brick structure. In particular, the gas generated during the high-temperature decomposition of lime slurry is highly detrimental to the density of the brick, thus affecting the product's thermal conductivity.
[0005] Patent ZL202211303558.8, "A Silica Brick with Added Calcium Nitrate Tetrahydrate and Its Preparation Method," discloses the production of silica bricks using calcium nitrate tetrahydrate as a mineralizing agent. This involves introducing uniformly dispersed, highly active CaO into the brick through the decomposition of calcium nitrate tetrahydrate. However, the addition of calcium nitrate tetrahydrate still presents the problem of gas release from high-temperature decomposition, which is detrimental to the brick's density and thermal conductivity.
[0006] The above are the inventor's research findings, not all of which are existing technologies, and therefore cannot all be regarded as existing technologies. Summary of the Invention
[0007] The purpose of this invention is to overcome the problems of unsatisfactory thermal conductivity and density of silica bricks used in coke ovens, and to provide a coke oven silica brick and its preparation method. The coke oven silica bricks prepared by this method have the characteristics of dense structure, high strength, high load softening temperature and excellent thermal conductivity.
[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing coke oven silica bricks, comprising the following steps:
[0009] S1. Fine silica powder, calcium nitrate tetrahydrate, and high-silicon aluminum alloy powder are mixed to form mud 1; wherein, the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is controlled to be 10-60:1; the silicon content in the high-silicon aluminum alloy powder is above 20%;
[0010] S2. Pre-fire clay material 1 at 500-950℃;
[0011] S3. Mix the silica aggregate, binder and the material obtained after pre-firing in S2 together to make mud 2.
[0012] S4. Press the clay material 2 into brick blanks, and then dry and sinter them to obtain coke oven silica bricks.
[0013] A second aspect of the present invention provides coke oven silica bricks prepared by the above-described preparation method.
[0014] The third aspect of this invention provides a coke oven silica brick, the raw materials of which include fine silica powder, silica aggregate, calcium nitrate tetrahydrate, and a binder. The raw materials also include high-silicon aluminum alloy powder, wherein the silicon content of the high-silicon aluminum alloy powder is more than 20% by mass, and the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-60:1. Based on the total amount of fine silica powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, the mass percentage of calcium nitrate tetrahydrate is 10% to 30%, the mass percentage of high-silicon aluminum alloy powder is 0.1% to 3%, and the mass percentage of fine silica powder is 15% to 45%. The fine silica powder and silica aggregate are crystalline silica.
[0015] In the preparation method of this invention, coke oven silica bricks are produced using CaO-Al2O3 mineralizers. Specifically, CaO and Al2O3 are introduced into the material as mineralizers by adding calcium nitrate tetrahydrate and high-silicon aluminum alloy (preferably, high-purity crystalline silica is used simultaneously to reduce the Al2O3 introduced into the raw materials). Furthermore, pre-firing controls the reaction pathway of the high-silicon aluminum alloy within the brick at high temperatures, allowing it to provide Al2O3 mineralizer while simultaneously improving the thermal conductivity of the coke oven silica bricks through the diffusion and deposition of gaseous SiO(g). The role of pre-firing can be summarized in at least two aspects: firstly, it promotes the decomposition of calcium nitrate tetrahydrate to form uniformly dispersed, highly active CaO, while preventing the decomposition of calcium nitrate tetrahydrate during silica brick firing from damaging the brick structure; secondly, pre-firing oxidizes the surface of the high-silicon aluminum alloy powder to form an oxide coating layer. The melting point of high-silicon aluminum alloys is generally below 1000℃ (the higher the aluminum content, the lower the melting point). The oxide layer coating the alloy powder surface can encapsulate the alloy when the temperature exceeds its melting point during silica brick firing, preventing reaction. When the firing temperatures reach 1360℃ and 1430℃ respectively, the highly reactive CaO uniformly dispersed within the brick reacts with Al2O3 and SiO2 in the oxide coating layer on the alloy surface to form a liquid phase, thereby destroying the oxide coating layer. Since the ambient temperature when the coating layer is destroyed is much higher than the melting point of the alloy, the molten alloy reacts rapidly upon contact with air to form gaseous metal oxides Al2O(g) and SiO(g). Ultimately, the diffusion and oxidation deposition of Al2O(g) and SiO(g) within the brick fill the fine pores, improving the continuity of the brick's skeletal structure and thus enhancing the brick's thermal conductivity.
[0016] This invention uses CaO-Al2O3-based mineralizers to produce coke oven silica bricks, specifically by adding calcium nitrate tetrahydrate and high-silicon aluminum alloys to achieve at least the following beneficial effects:
[0017] (1) The pre-firing process of the powder forms an oxide coating layer on the alloy surface, and at the same time, it causes the mineralizer calcium nitrate tetrahydrate to decompose in advance, avoiding the decomposition of the powder during the firing process of the brick blank to generate gas that damages the brick structure and improving the density of the fired brick blank.
[0018] (2) Calcium nitrate tetrahydrate is transformed into a liquid phase due to frictional heat generation during the premixing process. Liquid phase mixing achieves uniform distribution of CaO in the powder, ensuring that the oxide coating layer on the alloy surface can be destroyed by CaO during the firing of silicon bricks.
[0019] (3) By pre-firing the oxide coating layer constructed on the alloy surface and the destruction of the oxide coating layer by CaO at high temperature, the high silicon aluminum alloy is transformed into gaseous metal oxides Al2O(g) and SiO(g) at high temperature. It can fill the small pores in the brick through diffusion and deposition, improve the continuity of the brick skeleton structure, and thus improve the heat transfer efficiency.
[0020] (4) The silica bricks of the present invention have a dense structure, high strength, high load softening temperature, and excellent thermal conductivity.
[0021] (5) The preparation method of the present invention is simple, the raw materials are abundant and cost-effective, the firing process is easy to control, and it is suitable for the industrial production of large silica bricks. Detailed Implementation
[0022] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0023] In existing technology, there is no precedent for producing silica bricks using Al2O3 and CaO as mineralizers. Al2O3 has always been considered an impurity phase in silica bricks, with its content generally between 0.3% and 1.3%. This is because when CaO and Al2O3 coexist in silica bricks, the amount of liquid phase increases sharply with the increase of the Al2O3 / CaO ratio, a phenomenon particularly pronounced above 1500℃ and especially above 1600℃. However, if the CaO content in silica bricks is increased to above 2% (the CaO content in traditional coke oven silica bricks is generally below 2%), a small amount of Al2O3 can also improve the refractoriness of the silica bricks. The operating temperature of coke ovens is generally between 1000-1300℃, which is far from 1500℃. Therefore, it is technically feasible to apply a CaO-Al2O3 mineralizer with a high CaO ratio to coke oven silica bricks. However, if lime milk is continued to be used as a calcium mineralizer, its disadvantage of being difficult to disperse evenly will become more pronounced with the increase of the amount added. Using calcium nitrate tetrahydrate as a calcium mineralizer can achieve uniformity, but the problem of gas release generated by high-temperature decomposition still needs to be solved.
[0024] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0025] In a first aspect, the present invention provides a method for preparing coke oven silica bricks, comprising the following steps:
[0026] S1. Mix fine silica powder, calcium nitrate tetrahydrate, and high-silicon aluminum alloy powder to prepare mud 1;
[0027] S2. Pre-fire clay material 1 at 500-950℃;
[0028] S3. Mix the silica aggregate, binder and the material obtained after pre-firing in S2 together to make mud 2.
[0029] S4. Press the clay material 2 into brick blanks, and then dry and sinter them to obtain coke oven silica bricks.
[0030] Controlling the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder to 10-60:1 is beneficial for constructing a material composition with high CaO and low Al2O3 in the material.
[0031] In the preparation method of this invention, coke oven silica bricks are produced using CaO-Al2O3 mineralizers. Specifically, CaO and Al2O3 are introduced into the material as mineralizers by adding calcium nitrate tetrahydrate and high-silicon aluminum alloy (preferably, high-purity crystalline silica is used simultaneously to reduce the Al2O3 introduced into the raw materials). Furthermore, pre-firing controls the reaction pathway of the high-silicon aluminum alloy within the brick at high temperatures, allowing it to provide Al2O3 mineralizers while simultaneously improving the thermal conductivity of the coke oven silica bricks through the diffusion and deposition of gaseous SiO(g). Pre-firing promotes the decomposition of calcium nitrate tetrahydrate to form uniformly dispersed, highly active CaO, while preventing the decomposition of calcium nitrate tetrahydrate during silica brick firing from damaging the brick structure. On the other hand, pre-firing oxidizes the surface of the high-silicon aluminum alloy powder to form an oxide coating layer. The melting point of high-silicon aluminum alloys is generally below 1000℃ (the higher the aluminum content, the lower the melting point). The oxide layer coating the alloy powder surface can encapsulate the alloy when the temperature exceeds its melting point during silica brick firing, preventing reaction. When the firing temperatures reach 1360℃ and 1430℃ respectively, the highly reactive CaO uniformly dispersed within the brick reacts with Al2O3 and SiO2 in the oxide coating layer on the alloy surface to form a liquid phase, thereby destroying the oxide coating layer. Since the ambient temperature when the coating layer is destroyed is much higher than the melting point of the alloy, the molten alloy reacts rapidly upon contact with air to form gaseous metal oxides Al2O(g) and SiO(g). Ultimately, the diffusion and oxidation deposition of Al2O(g) and SiO(g) within the brick fill the fine pores, improving the continuity of the brick's skeletal structure and thus enhancing the brick's thermal conductivity.
[0032] According to the present invention, preferably, the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-40:1, for example, it can be a specific mass ratio or any range between two such ratios, such as 10:1, 12:1, 15:1, 18:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 35:1, 38:1, 40:1, etc. Preferably, the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-20:1. Controlling the mass ratio within the above-mentioned preferred range is beneficial to further improve the performance of the obtained brick.
[0033] In this invention, the term "high-silicon aluminum alloy" has the conventional definition in the art, and the high-silicon aluminum alloy powder can be, for example, one or more mixtures of Al-20Si and silicon-aluminum alloys with higher silicon content.
[0034] According to the present invention, preferably, the silicon content in the high-silicon aluminum alloy powder is above 20%, which is beneficial to the formation of gaseous SiO(g) at high temperature and to increase the density of the silicon dioxide skeleton in the material.
[0035] Preferably, based on the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, the mass percentage of calcium nitrate tetrahydrate is 10%–30%, for example, specific mass percentages such as 10%, 15%, 20%, 25%, and 30%; the mass percentage of high-silicon aluminum alloy powder is 0.1%–3%, for example, specific mass percentages such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3%; and the mass percentage of silica fine powder is 15%–45%, for example, specific mass percentages such as 15%, 18%, 20%, 25%, 30%, 35%, 40%, and 45%. Using appropriate mass ratios of silica fine powder, calcium nitrate tetrahydrate, and high-silicon aluminum alloy powder is more conducive to the transformation of quartz to tridymite during the firing process of silica bricks.
[0036] In this invention, "silica aggregate" refers to large-particle silica raw materials that play a skeletal role in silica bricks, and there are no particular limitations on its source.
[0037] According to some preferred embodiments of the present invention, the silica aggregate comprises a first silica aggregate and a second silica aggregate.
[0038] Preferably, the particle size of the first silica aggregate is ≤2.5mm and >0.5mm, and the particle size of the second silica aggregate is ≤0.5mm. Using two different particle sizes of the first and second silica aggregates is more conducive to the formation of a dense packing of particles in the material.
[0039] In this invention, the particle size refers to the maximum particle diameter, determined by sieving.
[0040] More preferably, based on the total amount of fine silica powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, first silica aggregate, and second silica aggregate, the first silica aggregate has a mass percentage of 10% to 40%, for example, specific mass percentages such as 10%, 15%, 20%, 25%, 30%, 35%, and 40%, and the second silica aggregate has a mass percentage of 30% to 70%, for example, specific mass percentages such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, and 70%. Under these preferred conditions, the mechanical strength of the material is further improved.
[0041] In this invention, the binder can be a conventional choice in the art, and preferably, the binder is selected from molasses and / or sulfite pulp waste liquor.
[0042] According to some preferred embodiments of the present invention, the mass amount of the binder is 0.5% to 5% of the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, for example, it can be a specific mass percentage such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%.
[0043] Preferably, the silica powder and silica aggregate are crystalline silica, which helps to reduce the Al2O3 introduced into the raw materials and is more conducive to the formation of a high CaO and low Al2O3 material ratio in the material.
[0044] In this invention, preferably, the particle size of the silica powder is ≤200 mesh and the particle size of the high-silicon aluminum alloy powder is ≤80 mesh. Using suitable low-particle-size high-silicon aluminum alloy powder and silica powder is more conducive to the formation of the passivation layer on the surface of the powder and the reaction to form gaseous metal oxides during high-temperature sintering.
[0045] In this invention, "mesh" adopts the Chinese standard and refers to the number of mesh holes per square centimeter.
[0046] In various aspects of this invention, in step S2, the pre-firing temperature is 500-950℃, for example, it can be a specific temperature such as 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, or any range between two. Preferably, the pre-firing time in step S2 is 1-6 hours, for example, it can be a specific time such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any range between two. Preferably, the pre-firing time is 2-6 hours.
[0047] In this invention, the drying and calcination processes in step S4 can be performed using methods conventional in the art.
[0048] Preferably, in step S4, the drying process includes: drying the brick blank at a temperature of less than 200°C for 24 to 48 hours until the residual moisture content is <1.0 wt%.
[0049] More preferably, the sintering process includes: heating to a maximum of 1450-1510℃, for example, a specific temperature such as 1450℃, 1460℃, 1470℃, 1480℃, 1490℃, 1500℃, 1510℃, or any range between the two, and holding at that temperature for 24-48 hours for firing. The above-mentioned preferred sintering conditions are more conducive to the sintering reaction in the material.
[0050] A second aspect of the present invention provides a coke oven silica brick, which is prepared by the coke oven silica brick preparation method described in the first aspect.
[0051] The third aspect of this invention provides a coke oven silica brick, the raw materials of which include fine silica powder, silica aggregate, calcium nitrate tetrahydrate, and a binder. The raw materials also include high-silicon aluminum alloy powder, wherein the silicon content in the high-silicon aluminum alloy powder is more than 20%, and the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-60:1, preferably 10-40:1. Based on the total amount of fine silica powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, the mass percentage of calcium nitrate tetrahydrate is 10% to 30%, the mass percentage of high-silicon aluminum alloy powder is 0.1% to 3%, and the mass percentage of fine silica powder is 15% to 45%. The fine silica powder and silica aggregate are crystalline silica.
[0052] Preferably, the particle size of the silica powder is ≤200 mesh, and the particle size of the high-silicon aluminum alloy powder is ≤80 mesh.
[0053] Preferably, the mass amount of the binder is 0.5% to 5% of the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate.
[0054] The present invention will be described in detail below through embodiments.
[0055] In the following examples and comparative examples, unless otherwise specified, the high-silicon aluminum alloys are all Al-30Si, that is, the silicon content is 30% by mass and the balance is aluminum; the particle size of the high-silicon aluminum alloy powder is ≤80 mesh.
[0056] The particle size of the first silica aggregate is ≤2.5mm and >0.5mm, and the particle size of the second silica aggregate is ≤0.5mm.
[0057] The binder used in the following examples and comparative examples is sulfite pulp waste liquor.
[0058] The particle size of the silica powder is ≤200 mesh.
[0059] The testing methods involved are as follows:
[0060] (1) Apparent porosity (%) was determined in accordance with GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products".
[0061] (2) Bulk density (g / cm³) 3 The density, apparent porosity and true porosity of dense shaped refractory products were determined according to GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products".
[0062] (3) The room temperature compressive strength (MPa) was determined in accordance with GB / T 5072-2023 "Test Method for Room Temperature Compressive Strength of Refractory Materials".
[0063] (4) The load softening temperature (°C) was determined in accordance with GB / T 5989-2023 "Test method for load softening temperature of refractory materials (differential heating method)".
[0064] (5) The thermal conductivity (W / (m·k)) was determined in accordance with GB / T 5990-2021 "Test methods for thermal conductivity, specific heat capacity and thermal diffusivity of refractory materials (hot wire method)".
[0065] Example 1
[0066] First, 15 wt% fine silica powder, 1.5 wt% high-silicon aluminum alloy, and 20 wt% calcium nitrate tetrahydrate are mixed and pre-fired at 900℃ for 2 hours. Then, the pre-fired material is mixed evenly with 25 wt% first silica aggregate, 38.5 wt% second silica aggregate, and 3 wt% binder of the above mixture to form a mud, which is then pressed into shape. After a drying process, the brick blanks are dried at a temperature below 200℃ for 30 hours until the residual moisture content is <1.0 wt%. After drying, they are placed in a tunnel kiln and fired at 1470℃ for 40 hours to obtain silica bricks.
[0067] The obtained silica bricks were tested and found to have an apparent porosity of 18.0% and a bulk density of 1.91 g / cm³. 3 It has a room temperature compressive strength of 62.7 MPa, a load softening temperature of 1669℃, and a thermal conductivity of 2.65 W / (m·K).
[0068] Example 2
[0069] First, 15 wt% fine silica powder, 0.5% high-silicon aluminum alloy, and 15 wt% calcium nitrate tetrahydrate are mixed and pre-fired at 800℃ for 3 hours. Then, the pre-fired material is mixed with 25 wt% first silica aggregate, 44.5 wt% second silica aggregate, and 3 wt% binder of the above mixture to form a uniform mud, which is then pressed into shape. After a drying process, the brick blanks are dried at a temperature below 200℃ for 30 hours until the residual moisture content is <1.0 wt%. After drying, they are placed in a tunnel kiln and fired at 1450℃ for 40 hours to obtain silica bricks.
[0070] The obtained silica bricks were tested and found to have an apparent porosity of 18.4% and a bulk density of 1.88 g / cm³. 3 It has a room temperature compressive strength of 58.6 MPa, a load softening temperature of 1672℃, and a thermal conductivity of 2.51 W / (m·K).
[0071] Example 3
[0072] First, 15 wt% fine silica powder, 2.5% high-silicon aluminum alloy, and 25 wt% calcium nitrate tetrahydrate are mixed and pre-fired at 950℃ for 3 hours. Then, the pre-fired material is mixed with 25 wt% first silica aggregate, 32.5 wt% second silica aggregate, and 4 wt% binder of the above mixture to form a uniform mud, which is then pressed into shape. After a drying process, the brick blanks are dried at a temperature below 200℃ for 30 hours until the residual moisture content is <1.0 wt%. After drying, they are placed in a tunnel kiln and fired at 1480℃ for 30 hours to obtain silica bricks.
[0073] The obtained silica bricks were tested and found to have an apparent porosity of 17.8% and a bulk density of 1.92 g / cm³. 3 It has a room temperature compressive strength of 69.8 MPa, a load softening temperature of 1659℃, and a thermal conductivity of 2.79 W / (m·K).
[0074] Example 4
[0075] The procedure was carried out in accordance with Example 1, except that the pre-burning time was different, specifically 1 hour.
[0076] The obtained silica bricks were tested and found to have an apparent porosity of 18.2% and a bulk density of 1.89 g / cm³. 3 It has a room temperature compressive strength of 59.8 MPa, a load softening temperature of 1662℃, and a thermal conductivity of 2.53 W / (m·K).
[0077] Example 5
[0078] The experiment was conducted in accordance with Example 1, except that the silicon content in the high-silicon aluminum alloy powder was different, resulting in a silicon to aluminum mass content ratio of 1:4.
[0079] The obtained silica bricks were tested and found to have an apparent porosity of 18.1% and a bulk density of 1.90 g / cm³. 3 It has a room temperature compressive strength of 61.5 MPa, a load softening temperature of 1663℃, and a thermal conductivity of 2.60 W / (m·K).
[0080] Comparative Example 1
[0081] The procedure was carried out in accordance with Example 1, except that no high-silicon aluminum alloy powder was added.
[0082] The obtained silica bricks were tested and found to have an apparent porosity of 18.3% and a bulk density of 1.88 g / cm³. 3 It has a room temperature compressive strength of 58.1 MPa, a load softening temperature of 1671℃, and a thermal conductivity of 2.21 W / (m·K).
[0083] Comparative Example 2
[0084] The experiment was conducted in accordance with Example 1, except that the amount of high-silicon aluminum alloy powder added was different. The amount of high-silicon aluminum alloy powder was controlled so that the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder was 5:1.
[0085] The obtained silica bricks were tested and found to have an apparent porosity of 17.9% and a bulk density of 1.92 g / cm³. 3 It has a room temperature compressive strength of 63.5 MPa, a load softening temperature of 1605℃, and a thermal conductivity of 2.66 W / (m·K).
[0086] Comparative Example 3
[0087] The process was carried out in accordance with Example 1, except that pre-firing was not performed. Instead, all raw materials were mixed and then directly stirred and mixed before being pressed into brick blanks, dried, and sintered.
[0088] The obtained silica bricks were tested and found to have an apparent porosity of 20.5% and a bulk density of 1.82 g / cm³. 3 It has a room temperature compressive strength of 49.1 MPa, a load softening temperature of 1640℃, and a thermal conductivity of 2.05 W / (m·K).
[0089] As can be seen from the comparison of the above embodiments and comparative examples, the silica bricks prepared by the preparation method provided by the present invention have the advantages of dense structure, high strength, high load softening temperature and excellent thermal conductivity.
[0090] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for producing a coke oven silica brick, characterized by, Includes the following steps: S1. Fine silica powder, calcium nitrate tetrahydrate, and high-silicon aluminum alloy powder are mixed to form mud 1; wherein, the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is controlled to be 10-60:1; the silicon content in the high-silicon aluminum alloy powder is above 20%; S2. Pre-fire clay material 1 at 500-950℃; S3. Mix the silica aggregate, binder and the material obtained after pre-firing in S2 together to make mud 2. S4. Press the clay material 2 into brick blanks, and then dry and sinter them to obtain coke oven silica bricks.
2. The production method according to claim 1, characterized by, Based on the total amount of fine silica powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, the mass percentage of calcium nitrate tetrahydrate is 10%–30%, the mass percentage of high-silicon aluminum alloy powder is 0.1%–3%, and the mass percentage of fine silica powder is 15%–45%.
3. The production method according to claim 1 or 2, characterized by, The silica aggregate includes a first silica aggregate and a second silica aggregate, wherein the particle size of the first silica aggregate is ≤2.5mm and >0.5mm, and the particle size of the second silica aggregate is ≤0.5mm; Preferably, based on the total amount of fine silica powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, first silica aggregate, and second silica aggregate, the mass percentage of the first silica aggregate is 10% to 40%, and the mass percentage of the second silica aggregate is 30% to 70%. Preferably, the mass amount of the binder is 0.5% to 5% of the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate.
4. The production method according to any one of claims 1 to 3, characterized by, The particle size of the silica fine powder is ≤200 mesh, and the particle size of the high-silicon aluminum alloy powder is ≤80 mesh; Preferably, the silica powder and silica aggregate are crystalline silica.
5. The method of any one of claims 1-4, wherein, The mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-40:
1.
6. The method of any one of claims 1-5, wherein, The preheating time in S2 is 1-6 hours.
7. The method of any one of claims 1-6, wherein, In S4, the drying process includes: drying the brick blank at a temperature of less than 200°C for 24 to 48 hours until the residual moisture content is <1.0 wt%; Preferably, the sintering process includes: heating to a maximum of 1450-1510℃ and holding at that temperature for 24-48 hours before firing.
8. A coke oven silica brick characterized by, It is prepared by the method for preparing coke oven silica bricks as described in any one of claims 1-7.
9. A coke oven silica brick characterized by, The raw materials for the coke oven silica bricks include fine silica powder, silica aggregate, calcium nitrate tetrahydrate, and binder. The raw materials for the coke oven silica bricks also include high-silicon aluminum alloy powder, in which the silicon content is above 20%, and the mass ratio of calcium nitrate tetrahydrate to high-silicon aluminum alloy powder is 10-40:1; based on the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate, the mass percentage of calcium nitrate tetrahydrate is 10%-30%, the mass percentage of high-silicon aluminum alloy powder is 0.1%-3%, and the mass percentage of silica fine powder is 15%-45%; the silica fine powder and silica aggregate are crystalline silica.
10. The silica brick according to claim 9, characterized in that The particle size of the silica fine powder is ≤200 mesh, and the particle size of the high-silicon aluminum alloy powder is ≤80 mesh; Preferably, the mass amount of the binder is 0.5% to 5% of the total amount of silica fine powder, calcium nitrate tetrahydrate, high-silicon aluminum alloy powder, and silica aggregate.