A magnesium-silicon-alumina checker brick for coke ovens and its preparation process

Abstract

This invention relates to the field of refractory material preparation technology, and particularly to a magnesium-silicon-alumina checker brick for coke ovens and its preparation process. The raw materials for the checker brick include: 55-75 parts of high-silicon, low-calcium reburned magnesia particles, 15-30 parts of high-silicon, low-calcium reburned magnesia fine powder, 5-12 parts of high-plasticity clay, and 0-7 parts of silica micro powder; with the addition of 0-5 parts of silica sol and 3-8 parts of water; the chemical composition of the finished product is MgO: 75%-90%, SiO2: 8%-15%, Al2O3: 1%-7%, and impurities ≤3%. Through composition and process design, a magnesium-silicon-alumina checker brick suitable for use in coke oven regenerators, with high energy storage and high heat exchange performance, is finally obtained. This can improve the heating efficiency of coke ovens, reduce coke oven heating energy consumption, reduce nitrogen oxide generation, and the manufacturing cost of the checker brick is low, which is beneficial to improving the economic and social benefits of enterprises.

Description

Technical Field

[0001] This invention relates to the field of refractory material preparation technology, and in particular to a magnesium-silicon-alumina checker brick for coke ovens and its preparation process. Background Technology

[0002] The coke oven is the core thermal equipment in the coking industry. Its working principle involves the combustion of coal gas in the combustion chamber, transferring heat to the coal in the carbonization chamber through a partition wall constructed of silica bricks, thus burning the coal into coke and recovering chemical products from the coal. The flue gas produced by the combustion of coal gas passes through the regenerator checker bricks, small flues, and main flue via inclined ducts, and is discharged into the atmosphere through the chimney after desulfurization and denitrification. The regenerator checker bricks trap heat from the flue gas through heat exchange, and then transfer the heat stored in the checker bricks to the counter-flowing coal gas and combustion air used for heating the combustion chamber through a reversing device. This heat exchange behavior is cyclical, and the checker bricks play a dual role in the operation of the coke oven: recovering waste heat from the coke oven heating flue gas and stabilizing the heating temperature of the coke oven combustion chamber. Provided that it can withstand the temperature and atmosphere of hot flue gas, if the checker bricks have high energy storage and heat exchange capacity, it will effectively improve the heat recovery efficiency of the coke oven heating flue gas (while reducing the flue gas emission temperature), reduce the temperature fluctuation of the combustion chamber, and thus reduce the energy consumption of coke oven heating, increase coke oven productivity, improve the quality of coke products, and of course increase the economic benefits of the enterprise.

[0003] For a long time, checker bricks used in coke ovens have mainly been made with an Al2O3 content of 30%–48% and a bulk density of 2.10–2.25 g / cm³. 3 Clay bricks. In the past two decades, with the development of coke ovens towards larger sizes, in order to improve the heat resistance of checker bricks, the use of bricks with an Al2O3 content of 45%–65% and a bulk density of 2.25–2.40 g / cm³ has emerged. 3 Technical solutions include using high-alumina bricks and andalusite bricks, or adding a silicon carbide coating when using traditional glued checker bricks. However, in general, the materials used for checker bricks in coke ovens are still limited to alumina-silicon based refractory materials, and the bulk density of the bricks is generally between 2.10 and 2.40 g / cm³. 3Within this range, the thermal conductivity is between 1.0 and 1.5 W / (m·K). Although high-alumina bricks and andalusite bricks with high Al2O3 content can fully meet the requirements of large coke ovens in terms of high temperature resistance and slag erosion resistance, their heat storage and heat exchange efficiency is relatively low among many refractory materials, and their effect on improving large coke ovens in terms of flue gas waste heat recovery and heating temperature stability is very limited. To date, practitioners in related fields have mainly focused on improving the heat resistance of checker bricks by improving the performance of aluminosilicate materials, while not paying enough attention to improving the heat storage and heat exchange efficiency of checker bricks. Furthermore, no one has proposed replacing existing aluminosilicate refractory materials with other materials in order to significantly improve the heat storage and heat exchange efficiency of checker bricks while ensuring heat resistance and coke oven gas ash resistance.

[0004] This invention argues that, considering the operating conditions of coke ovens, changing the material of the checker bricks from an aluminum-silicon system to a magnesium-silicon-aluminum system can fundamentally improve the heat resistance (determined by the load softening start temperature) and coke oven gas ash resistance of the checker bricks. Furthermore, the heat storage capacity (determined by bulk density) and heat exchange capacity (determined by thermal conductivity) of the checker bricks will also be greatly improved. This will significantly enhance the heating efficiency and temperature stability of the coke oven, ultimately resulting in significant economic benefits.

[0005] Magnesium-aluminum-silicon (MgASi) refractories are common refractory materials, characterized by good high-temperature resistance and excellent resistance to alkaline slag erosion. They are widely used in high-temperature and ultra-high-temperature fields such as iron and steel smelting, ferroalloy smelting, cement and glass preparation, and heating furnaces. They are also used to make heat storage / heat exchange checker bricks in equipment such as glass kiln regenerators, blast furnace hot blast stoves, and heating furnaces. However, due to their high thermal expansion coefficient, poor thermal shock resistance, and inability to withstand acidic slags, as well as their significantly higher price compared to ordinary alumina-silicon materials, there is no precedent for their application in coke ovens (where the temperature is relatively low and economic efficiency is required). Furthermore, MgASi refractories are lean materials and easily hydrate, while coke oven checker bricks are characterized by thin walls and narrow pores, requiring the clay material to have a high water content and exceptionally good plasticity during molding, which conventional MgASi materials cannot meet.

[0006] On the other hand, high-silicon, low-calcium magnesite in my country is generally discarded and unusable. This invention calcines it to produce inexpensive high-silicon, low-calcium recalcined magnesia, which has good hydration resistance. By adding highly plastic binders and anti-hydration binders, a magnesium-silicon-alumina refractory material with MgO-SiO2-Al2O3 as its main components is finally produced. Its price is lower than that of conventional alumina-silicon refractories, but its heat storage and thermal conductivity are significantly better than those of conventional alumina-silicon refractories. Using magnesium-silicon-alumina refractories to prepare checker bricks for coke ovens can achieve efficient energy storage and heat exchange, thereby improving the heating efficiency of coke ovens, improving the stability of coke oven heating temperature, and reducing nitrogen oxide emissions from coke ovens at the source. This has important practical significance and application value for promoting energy conservation and emission reduction in the coking industry and its transformation towards a green and low-carbon future. Summary of the Invention

[0007] This invention provides a magnesium-silicon-alumina checker brick for coke ovens and its preparation process, mainly addressing the problem of low heat storage efficiency in current coke oven checker bricks. It employs high-silicon, low-calcium reburned magnesia particles and fine powder with excellent hydration resistance to prevent cracking during brick drying and reduce production costs. The addition of high-plasticity clay powder ensures good molding performance of the clay. The addition of binders such as silica powder, silica sol, and sodium silicate further prevents magnesium oxide hydration during brick drying, increases the dry strength of the brick, and lowers the firing temperature. Through the design of scientific particle size distribution and molding pressure, the bulk density of the checker brick is increased and the porosity is reduced. Ultimately, a magnesium-silicon-alumina checker brick suitable for use in coke oven regenerators, with high energy storage and heat exchange performance, is obtained. This improves the heating efficiency of coke ovens, reduces heating energy consumption, and reduces nitrogen oxide generation. Furthermore, the manufacturing cost of the checker brick is low, which is beneficial to improving the economic and social benefits of enterprises.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A type of magnesia-silicon-alumina checker brick for coke ovens, wherein the raw material of the checker brick is composed of the following components in parts by weight: 55-75 parts of high-silicon, low-calcium, deburned magnesia granules, 15-30 parts of high-silicon, low-calcium, deburned magnesia fine powder, 5-12 parts of high-plasticity clay, and 0-7 parts of silica powder; with the addition of 0-5 parts of silica sol and 3-8 parts of water; the chemical composition of the high-silicon, low-calcium, deburned magnesia granules and high-silicon, low-calcium, deburned magnesia fine powder, by mass fraction, is: MgO ≥ 80%, MgO + SiO 2+Al2O3 ≥ 94%, CaO ≤ 2%, with the remainder being impurities; the microstructure is characterized by periclase grains surrounded by a complete silicate glass phase; the high-plasticity clay is obtained by sodium treatment or mud precipitation of bentonite or kaolin, and the mass ratio of SiO2 to Al2O3 in the high-plasticity clay is 2.0 to 5.0; the chemical composition of the finished checker bricks, by mass fraction, is MgO: 75% to 90%, SiO2: 8% to 15%, Al2O3: 1% to 7%, and the total amount of other impurities ≤ 3%; the mineral crystal phases in the checker bricks, by weight ratio, include periclase: 50% to 70%, forsterite: 20% to 40%, magnesium aluminum spinel: 0% to 10%, and the remainder being a glass phase.

[0009] The particle size of the high-silicon, low-calcium calcined magnesia is 0–3 mm.

[0010] The particle size of the high-silicon, low-calcium, reburned magnesia fine powder is ≤0.074mm.

[0011] The particle size of the highly plastic clay is ≤0.074mm.

[0012] The particle size of the silica micro powder is ≤0.045mm.

[0013] The silica micro powder is an industrial byproduct of the production of Si or Si-Fe alloys in an electric arc furnace. It has a SiO2 content of ≥90% and an average particle size of 0.1–0.2 μm after complete dispersion.

[0014] A process for preparing magnesium-silicon-alumina checker bricks for coke ovens includes the following steps: (1) Add the two types of high-silicon, low-calcium calcined magnesia particles of different sizes into the mixing mill and mix for 1 to 3 minutes; (2) Pour the silica sol and water into the mixer and mix for 3-5 minutes; (3) Add high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay, and silica micro powder to a mixer and mix for 10-15 minutes; (4) The mixed mud is loaded into the mold of the press and compressed into shape. The molding pressure is 100-200 MPa. (5) After the brick blanks are dried and dehydrated, they are fired at a temperature of 1350-1450℃ to obtain magnesium-silicon-alumina checker bricks.

[0015] The performance indicators of the finished checker bricks are: bulk density ≥ 2.65 g / cm³ 3 Apparent porosity ≤24%, room temperature compressive strength ≥30MPa, load softening start temperature ≥1450℃, permanent linear change ≥-0.3% after heating at 1400℃ for 3 hours, and thermal conductivity ≥2.5W / (m·K) at 1000℃.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) The coke oven magnesia-silica-alumina checker bricks of the present invention are mainly made of high-silicon, low-calcium, reburned magnesia (including granules and fine powder). This magnesia is obtained by sintering low-grade magnesite or magnesite beneficiation waste. It has the following characteristics in its microstructure: periclase grains are surrounded by a complete silicate glass phase. This structure can effectively prevent the hydration of periclase, and therefore is suitable for the manufacture of coke oven checker bricks with high moisture content. The high-temperature resistance of high-silicon, low-calcium, reburned magnesia is lower than that of ordinary magnesia, but it can fully meet the needs of coke oven regenerators with relatively low operating temperatures. In addition, high-silicon, low-calcium, reburned magnesia not only has a cost advantage (low price), but also helps the comprehensive utilization of magnesite resources in my country.

[0017] (2) The magnesium-silicon-alumina checker bricks for coke ovens described in this invention utilize the characteristics of periclase, such as high bulk density, good thermal conductivity, and high specific heat. By controlling the raw material composition and proportion, the bulk density of the checker bricks is ensured to be ≥2.65 g / cm³. 3 With a thermal conductivity ≥2.5 W / (m·K), its heat storage performance and thermal conductivity are superior to those of aluminosilicate checker bricks (whose bulk density is generally between 2.15 and 2.25 g / cm³). 3 The efficiency is greatly improved, meaning it has higher energy storage and heat exchange efficiency, which can significantly reduce the emission temperature of coke oven flue gas, reduce coke oven heating energy consumption, reduce the temperature change of coke oven combustion chamber, and reduce the amount of nitrogen oxides generated.

[0018] (3) The coke oven magnesia-silica-alumina checker bricks of the present invention incorporate a lower proportion (5%~12%) of high-plasticity clay in the batching process to reduce the firing temperature of the product. The firing temperature of the present invention (1350~1450℃) is 200~300℃ lower than that of conventional magnesia-silica refractory bricks, and is basically the same as that of ordinary high-alumina bricks. At the same time, the present invention, with fewer impurities, modifies the originally barren (non-plastic) magnesia material into a highly plastic clay material, thereby enabling the production of thin-walled, narrow-pore coke oven checker brick blanks through compression, and giving the brick blanks high bonding strength after drying. During the firing process, minerals such as kaolinite in the high-plasticity clay lose their crystal water and structural water, forming highly active amorphous SiO2 and Al2O3. At lower temperatures, amorphous SiO2 and Al2O3 come into contact with MgO particles to form a low-viscosity acid salt liquid phase. Through the liquid phase sintering mechanism, under conditions far below the sintering temperature of magnesia bricks (1550–1750℃), the hard magnesia particles are moistened, pulled closer, rearranged, and fill the voids, generating magnesia olivine (M2S) and a small amount of magnesium aluminum spinel (MA). Together with the residual silicate glass phase, they form a composite bonding matrix, achieving rapid densification of the brick body, increasing the bulk density and compressive strength of the brick body, reducing apparent porosity and thermal expansion rate, thereby improving the thermal conductivity and thermal shock stability of the checker bricks.

[0019] (4) The magnesium-silicon-alumina checker bricks for coke ovens described in this invention incorporate silica micropowder in the batching process. This silica micropowder is an industrial byproduct of Si or Si-Fe alloy production in a submerged arc furnace. In the submerged arc furnace, when quartz is reduced by carbonaceous material to form Si, a large amount of SiO gas is generated. This gas is discharged outside the furnace, comes into contact with air, and is rapidly oxidized and condensed to form ultrafine amorphous SiO2 powder. After dust collection and treatment, silica micropowder with SiO2 ≥ 90% (mass content) is obtained. Silica micropowder is a micron-sized amorphous SiO2 powder with a particle size much smaller than magnesia particles and fine magnesia powder. It can perfectly fill the gaps between magnesia particles to achieve the densest packing, thereby significantly improving the density of the brick blank and the bulk density of the fired brick. Moreover, silica micropowder has extremely high surface energy and strong chemical reactivity. It can react with MgO particles at lower temperatures to form a highly dispersed solid-phase reaction, forming a uniformly distributed forsterite network. This, in turn, induces beneficial microcracks at the microscopic level, thereby improving thermal shock stability by consuming elastic strain energy.

[0020] (5) The magnesium-silicon-alumina checker bricks for coke ovens described in this invention incorporate silica sol as a binder in the batching. Silica sol is a colloidal solution of nano-sized SiO2 particles dispersed in water. It has a large specific surface area and high activity, and can uniformly coat the surface of magnesia particles, causing the free magnesium oxide in the raw materials to undergo the following chemical reaction: MgO + SiO2 + nH2O → MgO·SiO2·nH2O, thereby preventing cracking of the brick blanks during the drying process due to the generation and decomposition of magnesium hydroxide. During the pressing of the clay, the silica sol at the particle contact points partially evaporates due to moisture evaporation or the colloidal structure is destroyed by pressure. The nano-SiO2 particles condense and solidify at the contact points, forming a strong "solid-solid" bonding bridge, thereby giving the brick blanks high green strength and drying strength. In addition, the silica sol has a high SiO2 content and is a nano-active material. The reaction is complete, and the required SiO2 can be precisely introduced with a small amount of addition, generating a beneficial high-temperature bonding phase in key parts, avoiding the negative impact caused by the introduction of coarse particles or impurities.

[0021] (6) The magnesium-silicon-alumina checker bricks for coke ovens described in this invention, by controlling the composition, proportion, and preparation process of the raw materials, ensure that the final composition of the finished product (by mass fraction) is: 75%–90% MgO, 10%–15% SiO2, 1%–7% Al2O3, and ≤3% other impurities. The main mineral crystal phases of the finished product (by weight) contain 50%–70% periclase, 20%–40% forsterite, and the remainder is magnesium-alumina spinel. The finished product has a high melting deformation temperature and resistance to coal gas ash melting erosion. The load softening start temperature is ≥1450℃, and the high temperature resistance is much higher than the highest temperature in the high temperature zone of the coke oven regenerator (approximately 1320℃). Long-term use in the high temperature zone of the regenerator will not cause softening and collapse problems, which can significantly improve the service life of the checker bricks in the coke oven regenerator.

[0022] (7) The coke oven magnesium-silicon-aluminum checker brick of the present invention uses high-silicon, low-calcium, recalcined magnesia as the main raw material with optimized three-stage particle size distribution. The brick blank is formed by machine pressing plastic molding with a molding pressure between 100 and 200 MPa. The preparation process is simple and can be produced using conventional equipment. Detailed Implementation

[0023] The present invention discloses a magnesium-silicon-alumina checker brick for coke ovens. The raw material of the checker brick is composed of the following components in parts by weight: 55-75 parts of high-silicon, low-calcium, calcined magnesia granules, 15-30 parts of high-silicon, low-calcium, calcined magnesia fine powder, 5-12 parts of high-plasticity clay, 0-7 parts of silica micro powder; 0-5 parts of silica sol and 3-8 parts of water.

[0024] The particle size of the high-silicon, low-calcium recalcined magnesia particles is 0–3 mm. The particle size of the high-silicon, low-calcium recalcined magnesia fine powder is ≤0.074 mm. The chemical composition of the high-silicon, low-calcium recalcined magnesia particles and the high-silicon, low-calcium recalcined magnesia fine powder (collectively referred to as high-silicon, low-calcium recalcined magnesia) by mass fraction is: MgO ≥ 80%, MgO + SiO 2+ Al2O3 ≥ 94%, CaO ≤ 2%, with the remainder being impurities. The main mineral components of high-silicon, low-calcium recalcined magnesia include periclase, forsterite, and a small amount of silicate glass phase. The microstructure is characterized by periclase grains being surrounded by a complete layer of silicate glass phase.

[0025] The high-plasticity clay has a particle size ≤0.074mm. It is obtained from bentonite or kaolin through sodium treatment or mud sedimentation, and the mass ratio of SiO2 to Al2O3 in the high-plasticity clay is 2.0–5.0. Bentonite's main component is montmorillonite, with interlayers primarily composed of Ca. 2+ (Calcium-based), moderately plastic, and expands well with water absorption. Kaolin's main component is kaolinite, which has good plasticity. Sodium treatment uses sodium... + Ca 2+Displacement increases interlayer repulsion and spacing, allowing water to penetrate more easily, thus significantly improving plasticity, expansion ratio, and bonding strength. Commonly used sodium-displacing agents include sodium carbonate, sodium fluoride, sodium chloride, and sodium sulfate. Sodium displacing involves crushing and grinding the raw materials to form a slurry, then adding the sodium-displacing agent and stirring. After a period of settling and aging, sodium-displacing clay is obtained. The plasticity of clay is determined by the content of fine-grained clay minerals (montmorillonite, kaolinite), interlayer cations, and colloids. Coarse-grained impurities (quartz, feldspar, rock fragments) are infertile impurities that damage plasticity and reduce the ductility and bonding strength of the clay. Slurry sedimentation (such as wet slurry preparation followed by settling or cyclone classification sedimentation) follows the law of gravity settling. Large, high-density impurities (quartz, sand, coarse soil particles) settle quickly and are separated after settling to the bottom. Ultrafine-grained clay minerals are suspended in the upper clear slurry; their strong plasticity, when enriched and retained, yields highly plastic clay.

[0026] The silica micro powder has a particle size ≤0.045mm. Preferably, the silica micro powder is an industrial by-product of the production of Si or Si-Fe alloys in a submerged arc furnace (submerged arc furnace), with a SiO2 mass content ≥90% and an average particle size of 0.1~0.2μm after complete dispersion.

[0027] The chemical composition of the finished checker bricks, by mass fraction, is MgO: 75%–90%, SiO2: 10%–15%, Al2O3: 1%–7%, and the total amount of other impurities is ≤3%. The mineral crystalline phases in the checker bricks, by weight ratio, include periclase: 50%–70%, forsterite: 20%–40%, magnesium aluminum spinel: 0–10%, and the remainder is a glassy phase.

[0028] The performance indicators of the finished checker bricks are: bulk density ≥ 2.65 g / cm³ 3 Apparent porosity ≤24%, room temperature compressive strength ≥30MPa, load softening start temperature ≥1450℃, permanent linear change ≥-0.3% after heating at 1400℃ for 3 hours, and thermal conductivity ≥2.5W / (m·K) at 1000℃.

[0029] The preparation process of a magnesium-silicon-alumina checker brick for coke ovens according to the present invention includes the following steps: (1) Add the two types of high-silicon, low-calcium calcined magnesia particles of different sizes into the mixing mill and mix for 1 to 3 minutes; (2) Pour the silica sol and water into the mixer and mix for 3-5 minutes; (3) Add high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay, and silica micro powder to a mixer and mix for 10-15 minutes; (4) The mixed mud is loaded into the mold of the press and compressed into shape. The molding pressure is 100-200 MPa. (5) After the brick blanks are dried and dehydrated, they are fired at a temperature of 1350-1450℃ to obtain magnesium-silicon-alumina checker bricks.

[0030] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0031] Example 1:

[0032] In this embodiment, the raw material composition (parts by weight) of the magnesium-silicon-aluminum checker brick is as follows: 65 parts of high-silicon, low-calcium calcined magnesia particles with a particle size of 0-3mm, 24 parts of high-silicon, low-calcium calcined magnesia fine powder with a particle size of ≤0.074mm, 10 parts of high-plasticity clay with a particle size of ≤0.074mm, 1 part of silica micro powder; 4 parts of silica sol and 3 parts of water are added.

[0033] The preparation process of magnesium-silicon-aluminum checker bricks is as follows: 1) Premix high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay and silica micro powder.

[0034] 2) Add the high-silicon, low-calcium calcined magnesia particles into the mixer and mix for 2 minutes.

[0035] 3) Add silica sol and water to the mixer and mix for 3 minutes.

[0036] 4) Add the premixed powder from step 1) into the mixer and continue mixing for 15 minutes.

[0037] 5) Load the mixed mud into the press mold and press it to 100MPa for molding.

[0038] 6) After the brick blanks are dried and dehydrated, they are sent into the kiln and fired at a temperature of 1370-1400℃.

[0039] The physicochemical properties of the magnesium-silicon-aluminum checker bricks prepared in this embodiment were tested and are as follows: Table 1 - Performance indicators of magnesium-silicon-alumina checker bricks prepared in Example 1:

[0040] Example 2:

[0041] In this embodiment, the raw material composition (parts by weight) of the magnesium-silicon-aluminum checker brick is as follows: 70 parts of high-silicon, low-calcium calcined magnesia particles with a particle size of 0-3mm, 18 parts of high-silicon, low-calcium calcined magnesia fine powder with a particle size of ≤0.074mm, 8 parts of high-plasticity clay with a particle size of ≤0.074mm, 4 parts of silica micro powder; 6.5 parts of water added.

[0042] The preparation process of magnesium-silicon-aluminum checker bricks is as follows: 1) Premix high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay and silica micro powder.

[0043] 2) Add the high-silicon, low-calcium calcined magnesia particles into the mixer and mix for 2 minutes.

[0044] 3) Add 5 parts water to the mixer and mix for 3 minutes.

[0045] 4) Add the premixed powder from step 1) into the mixer and mix for 5 minutes.

[0046] 5) Add 1.5 parts water to the mixer and continue mixing for 10 minutes.

[0047] 6) Load the mixed mud into the press mold and press it to 100MPa for molding.

[0048] 7) After the shaped brick blanks are dried and dehydrated, they are sent into the kiln and fired at a temperature of 1400-1430℃.

[0049] The physicochemical properties of the magnesium-silicon-aluminum checker bricks prepared in this embodiment were tested and are as follows: Table 2 - Performance indicators of magnesium-silicon-alumina checker bricks prepared in Example 2:

[0050] Example 3:

[0051] In this embodiment, the raw material composition (parts by weight) of the magnesium-silicon-aluminum checker brick is as follows: 65 parts of high-silica, low-calcium calcined magnesia particles with a particle size of 0-3mm, 23 parts of high-silica, low-calcium calcined magnesia fine powder with a particle size of ≤0.074mm, 12 parts of high-plasticity clay with a particle size of ≤0.074mm; plus 5 parts of silica sol and 3 parts of water.

[0052] The preparation process of magnesium-silicon-aluminum checker bricks is as follows: 1) Add the high-silicon, low-calcium calcined magnesia particles into the mixer and mix for 2 minutes.

[0053] 2) Add silica sol and water to the mixer and mix for 3 minutes.

[0054] 4) Add the high-silicon, low-calcium calcined magnesia fine powder and high-plasticity clay to the mixer and continue mixing for 15 minutes.

[0055] 5) Load the mixed mud into the press mold and press it to 100MPa and 200MPa respectively.

[0056] 6) After the brick blanks are dried and dehydrated, they are sent into the kiln and fired at a temperature of 1380-1420℃.

[0057] The physicochemical properties of the magnesium-silicon-aluminum checker bricks prepared in this embodiment were tested and are as follows: Table 3 - Performance indicators of magnesium-silicon-alumina checker bricks prepared in Example 3:

[0058] Example 4:

[0059] In this embodiment, the raw material composition (parts by weight) of the magnesium-silicon-aluminum checker brick is as follows: 68 parts of high-silicon, low-calcium calcined magnesia particles with a particle size of 0-3mm, 20 parts of high-silicon, low-calcium calcined magnesia fine powder with a particle size of ≤0.074mm, 9 parts of high-plasticity clay with a particle size of ≤0.074mm, 3 parts of silica micro powder; 3 parts of silica sol and 4 parts of water are added.

[0060] The preparation process of magnesium-silicon-aluminum checker bricks is as follows: 1) Premix high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay and silica micro powder.

[0061] 2) Add the high-silicon, low-calcium calcined magnesia particles into the mixer and mix for 2 minutes.

[0062] 3) Add silica sol and water to the mixer and mix for 3 minutes.

[0063] 4) Add the premixed powder from step 1) into the mixer and continue mixing for 10 minutes.

[0064] 5) Load the mixed mud into the press mold and press it to 150MPa for molding.

[0065] 6) After the brick blanks are dried and dehydrated, they are sent into the kiln and fired at a temperature of 1380-1420℃.

[0066] The physicochemical properties of the magnesium-silicon-aluminum checker bricks prepared in this embodiment were tested and are as follows: Table 4 - Performance indicators of magnesium-silicon-alumina checker bricks prepared in Example 4:

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A magnesium-silicon-alumina checker brick for coke ovens, characterized in that, The raw materials for checker bricks consist of the following components by weight: 55-75 parts of high-silicon, low-calcium calcined magnesia particles, 15-30 parts of high-silicon, low-calcium calcined magnesia fine powder, 5-12 parts of high-plasticity clay, and 0-7 parts of silica micropowder; plus 0-5 parts of silica sol and 3-8 parts of water; the chemical composition of the high-silicon, low-calcium calcined magnesia particles and the high-silicon, low-calcium calcined magnesia fine powder, by mass fraction, is: MgO ≥ 80%, MgO + SiO 2+ Al2O3 ≥ 94%, CaO ≤ 2%, with the remainder being impurities; the microstructure is characterized by periclase grains surrounded by a complete silicate glass phase; the high-plasticity clay is obtained by sodium treatment or mud precipitation of bentonite or kaolin, and the mass ratio of SiO2 to Al2O3 in the high-plasticity clay is 2.0 to 5.0; the chemical composition of the finished checker bricks, by mass fraction, is MgO: 75% to 90%, SiO2: 8% to 15%, Al2O3: 1% to 7%, and the total amount of other impurities ≤ 3%; the mineral crystal phases in the checker bricks, by weight ratio, include periclase: 50% to 70%, forsterite: 20% to 40%, magnesium aluminum spinel: 0% to 10%, and the remainder being a glass phase.

2. The magnesium-silicon-alumina checker brick for coke ovens according to claim 1, characterized in that, The particle size of the high-silicon, low-calcium calcined magnesia is 0–3 mm.

3. The magnesium-silicon-alumina checker brick for coke ovens according to claim 1, characterized in that, The particle size of the high-silicon, low-calcium, reburned magnesia fine powder is ≤0.074mm.

4. The magnesium-silicon-alumina checker brick for coke ovens according to claim 1, characterized in that, The particle size of the highly plastic clay is ≤0.074mm.

5. A magnesium-silicon-alumina checker brick for coke ovens according to claim 1, characterized in that, The particle size of the silica micro powder is ≤0.045mm.

6. A magnesium-silicon-alumina checker brick for coke ovens according to claim 5, characterized in that, The silica micro powder is an industrial byproduct of the production of Si or Si-Fe alloys in a submerged arc furnace. It has a SiO2 content of ≥90% and an average particle size of 0.1–0.2 μm after complete dispersion.

7. A preparation process for magnesium-silicon-alumina checker bricks for coke ovens as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Add the two types of high-silicon, low-calcium calcined magnesia particles of different sizes into the mixing mill and mix for 1 to 3 minutes; (2) Pour the silica sol and water into the mixer and mix for 3-5 minutes; (3) Add high-silicon, low-calcium calcined magnesia fine powder, high-plasticity clay, and silica micro powder to a mixer and mix for 10-15 minutes; (4) The mixed mud is loaded into the mold of the press and compressed into shape. The molding pressure is 100-200 MPa. (5) After the brick blanks are dried and dehydrated, they are fired at a temperature of 1350-1450℃ to obtain magnesium-silicon-alumina checker bricks.

8. The preparation process of a magnesium-silicon-alumina checker brick for coke ovens according to claim 7, characterized in that, The performance indicators of the finished checker bricks are: bulk density ≥ 2.65 g / cm³ 3 Apparent porosity ≤24%, room temperature compressive strength ≥30MPa, load softening start temperature ≥1450℃, permanent linear change ≥-0.3% after heating at 1400℃ for 3 hours, and thermal conductivity ≥2.5W / (m·K) at 1000℃.

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