Microporous low thermal conductivity composite silica brick and preparation method thereof

Abstract

The application discloses a kind of microporous low thermal conductivity composite silica brick and its preparation method, belong to composite silica brick technical field, the heat preservation layer of the composite silica brick of the present application is by mass percentage 65%~75% poly light microporous silica homogenization material, 20%~25% quartz powder, 2%~8% silicon powder, 0.1%~1% sodium tripolyphosphate, 0.05%~0.3% sodium hexametaphosphate and 1%~2% binder II combination formed high-strength porous material, with the characteristics of high strength, low thermal conductivity, good strength and heat preservation effect, energy saving and consumption reduction;The working layer of composite silica brick has the high strength of traditional silica brick, directly contacts high-temperature material, has high-temperature wear resistance, high load softening temperature, corrosion resistance, and the superior performance of thermal shock resistance, reaches the use effect of stable long life.The present application realizes the high strength and heat preservation effect of composite silica brick, simultaneously realizes synchronous forming, synchronous sintering, energy saving effect of both high temperature resistance and heat preservation.

Description

Technical Field

[0001] The present invention relates to the technical field of composite silica bricks, and in particular to a microporous low thermal conductivity composite silica brick and a preparation method thereof. Background Art

[0002] With energy shortages becoming increasingly scarce, countries are placing increasing emphasis on the research, production, and use of energy-saving materials for high-temperature industries. Silica bricks are a type of acidic refractory material primarily composed of tridymite, cristobalite, and small amounts of residual quartz and glass. They offer excellent resistance to acidic slag erosion, a refractoriness under load temperature of 1640-1670°C, and maintain a relatively stable volume under long-term high-temperature use. Silica bricks are primarily used in the walls of coking and combustion chambers of coke ovens, the regenerators and slag chambers of steelmaking open-hearth furnaces, soaking pits, refractory materials for glass melting furnaces, and vaults and other load-bearing components of ceramic firing furnaces. They are also used in high-temperature, load-bearing areas of hot blast furnaces and the roofs of acidic open-hearth furnaces.

[0003] Silica bricks are widely used and researched in refractory systems due to their high refractoriness under load, excellent high-temperature volume stability, and long-term shrinkage resistance. However, existing silica bricks suffer from high thermal conductivity and poor insulation performance. To address this issue, the present invention provides a microporous, low-thermal-conductivity composite silica brick and a method for its preparation. Summary of the Invention

[0004] The present invention provides a microporous low thermal conductivity composite silica brick and a preparation method thereof, which effectively solves the technical problems of existing silica bricks with high thermal conductivity and poor thermal insulation effect, and at the same time provides a microporous low thermal conductivity composite silica brick with high strength, low thermal conductivity, good thermal insulation effect, energy saving and consumption reduction.

[0005] The first object of the present invention is to provide a microporous low thermal conductivity composite silica brick comprising a working layer and a thermal insulation layer, wherein the thermal insulation layer is wrapped around the working layer; the thickness ratio of the working layer to the thermal insulation layer is 2-4:0.6-1.2;

[0006] The thermal insulation layer is composed of the following raw materials in percentage by mass: 65% to 75% of polyslightly porous siliceous homogenized material, 20% to 25% of quartz powder, 2% to 8% of silicon powder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II, totaling 100%.

[0007] As a preferred embodiment, the thickness ratio of the working layer to the insulation layer is 2 to 4:1.

[0008] As a preferred embodiment, the binder II is phosphoric acid or a phosphate binder.

[0009] As a preferred embodiment, the working layer is composed of the following raw materials in the following mass percentages: silica sand 50% to 70%, silicon powder 15% to 35%, binder I 1% to 2.5%, fluorite powder 2% to 5%, silicon micropowder 5% to 10%, iron scale powder 0 to 1.5%, calcium oxide 0 to 3%, totaling 100%.

[0010] As a preferred embodiment, the binder I is one or more of lignin, cellulose, dextrin, and phosphate.

[0011] The second object of the present invention is to provide a method for preparing microporous low thermal conductivity composite silica bricks, comprising the following steps:

[0012] Weigh the raw materials of the working layer and the insulation layer respectively;

[0013] Mix 50% to 70% by mass of silica sand, 15% to 35% of silica powder, 1% to 2.5% of binder I, 2% to 5% of fluorite powder, 5% to 10% of silica powder, 0% to 1.5% of iron scale powder, and 0% to 3% of calcium oxide to obtain a working layer premix;

[0014] Mix 65% to 75% by mass of slightly porous siliceous homogenized material, 20% to 25% of quartz powder, 2% to 8% of silicon powder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II to obtain a premix for the thermal insulation layer;

[0015] The working layer premix and the insulation layer premix are respectively loaded into the mold, separated by a template in the middle. After filling, the template is removed, and then the bricks are pressed and formed, dried to obtain bricks. The bricks are heated to 1300-1450℃, kept warm, and cooled.

[0016] As a preferred embodiment, during pressing, the pressure is 100-150 MPa and the time is 3-10 minutes.

[0017] As a preferred embodiment, the insulation time is 5 to 15 hours.

[0018] As a preferred embodiment, it is characterized in that the temperature rising procedure is: rising to 200-600°C at 20°C / h, rising to 600-1100°C at 25°C / h, rising to 1100-1350°C at 7°C / h, and rising to 1300-1450°C at 1-3°C / h.

[0019] As a preferred embodiment, the drying is specifically as follows: the drying is specifically as follows: the bricks are placed in a drying kiln at 100-200°C and dried until the moisture content is less than 2%, and then loaded into the kiln for firing.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a microporous, low-thermal-conductivity composite silica brick and its preparation method. The insulation layer employed in the present invention is formed by combining 65% to 75% by mass of a microporous siliceous homogenizer, 20% to 25% quartz powder, 2% to 8% silica powder, 0.1% to 1% sodium tripolyphosphate, 0.05% to 0.3% sodium hexametaphosphate, and 1% to 2% binder II. The working layer has the high strength of traditional silica bricks and directly contacts high-temperature materials, exhibiting superior properties such as high-temperature wear resistance, high refraction under load, corrosion resistance, and thermal shock resistance, achieving stable and long-lasting use. The insulation layer utilizes a specially formulated high-strength porous material, characterized by high strength, low thermal conductivity, excellent strength and thermal insulation, and energy conservation and consumption reduction, thereby achieving the high strength and thermal insulation properties of the composite silica brick. The present invention achieves simultaneous molding and firing, achieving the energy-saving benefits of both high-temperature resistance and thermal insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of the microporous low thermal conductivity composite silicon brick prepared by the present invention. DETAILED DESCRIPTION

[0023] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples and accompanying drawings. However, the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0024] As mentioned in the background of this invention, silica bricks are widely used and researched in refractory systems due to their high refractoriness under load, good high-temperature volume stability, and long-term shrinkage resistance. However, existing silica bricks suffer from high thermal conductivity and poor insulation. To address these technical issues, the present invention provides a microporous, low-thermal-conductivity composite silica brick and its preparation method. The insulation layer employed in this invention is composed of 65% to 75% by weight of a microporous, slightly porous siliceous homogenizer, 20% to 25% quartz powder, 2% to 8% silica powder, 0.1% to 1% sodium tripolyphosphate, 0.05% to 0.3% sodium hexametaphosphate, and 1% to 2% binder II. The working layer exhibits the superior properties of traditional silica bricks, including high strength, high-temperature wear resistance, high refractoriness under load, corrosion resistance, and thermal shock resistance. The insulation layer also features high strength, low thermal conductivity, excellent strength and insulation performance, and energy conservation and consumption reduction. This achieves simultaneous molding and firing, achieving both high-temperature resistance and thermal insulation.

[0025] The technical solution of the present invention is analyzed and explained in detail below.

[0026] The present invention first provides a microporous low thermal conductivity composite silica brick, comprising a working layer and a thermal insulation layer, wherein the thermal insulation layer is wrapped around the working layer; the thickness ratio of the working layer to the thermal insulation layer is 2-4:0.6-1.2;

[0027] The thermal insulation layer is composed of the following raw materials in percentage by mass: 65% to 75% of poly(slightly porous) siliceous homogenizing material, 20% to 25% of quartz powder, 2% to 8% of silicon micropowder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II, totaling 100%; wherein the poly(slightly porous) siliceous homogenizing material mainly has a thermal insulation effect, the fine powder and micropowder have a filling effect, the sodium tripolyphosphate and sodium hexametaphosphate are used as dispersants, and the binder provides the material with initial demolding strength.

[0028] The working layer is composed of the following raw materials in the following percentages by mass: 50% to 70% silica sand, 15% to 35% silica powder, 1% to 2.5% binder I, 2% to 5% fluorite powder, 5% to 10% silica micropowder, 0% to 1.5% iron scale powder, and 0% to 3% calcium oxide, totaling 100%. Silica sand is the primary component of the material, serving as a structural framework, while fine powder and micropowder act as fillers. Iron scale powder and calcium oxide are commonly used mineralizers, improving the material's microstructure and enhancing its performance. The binder provides initial handling strength for the green body.

[0029] In order to further achieve the high strength and thermal insulation effect of the composite silica brick of the present invention, the thickness ratio of the working layer to the thermal insulation layer is 2 to 4:1.

[0030] In order to further achieve a good bonding effect between the components in the thermal insulation layer of the present invention, the binder II is phosphoric acid or a phosphate binder.

[0031] In order to further achieve a good binding effect between the components in the working layer of the present invention, the binder I is one or more of lignin, cellulose, dextrin, and phosphate.

[0032] The present invention also provides a method for preparing microporous low thermal conductivity composite silica bricks, comprising the following steps:

[0033] Weigh the raw materials of the working layer and the insulation layer respectively;

[0034] Mix 50% to 70% by mass of silica sand, 15% to 35% of silica powder, 1% to 2.5% of binder I, 2% to 5% of fluorite powder, 5% to 10% of silica powder, 0% to 1.5% of iron scale powder, and 0% to 3% of calcium oxide to obtain a working layer premix;

[0035] Mix 65% to 75% by mass of slightly porous siliceous homogenized material, 20% to 25% of quartz powder, 2% to 8% of silicon powder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II to obtain a premix for the thermal insulation layer;

[0036] The working layer premix and the insulation layer premix are respectively loaded into the mold, separated by a template in the middle. After filling, the template is removed, and then the bricks are pressed and formed, dried to obtain bricks. The bricks are heated to 1300-1450℃, kept warm, and cooled.

[0037] In order to ensure a good bonding effect between the insulation layer and the working layer, the pressing pressure is 100-150 MPa and the pressing time is 3-10 minutes.

[0038] In order to remove most of the moisture in the bricks before firing, so as to avoid the rapid evaporation of moisture in the subsequent heating process to affect the brick structure, and then destroy the mechanical strength and thermal insulation performance of the composite silicon bricks, the drying is specifically as follows: the bricks are placed in a drying kiln at 100-200 ° C and dried until the moisture is less than 2%, and then loaded into the kiln for firing.

[0039] In order to reduce the temperature difference caused by instantaneous heating and the crystal transformation of silicon oxide during the brick firing process, which may lead to cracks in the brick insulation layer and working layer, the heating procedure is as follows: heating to 200-600°C at 20°C / h, heating to 600-1100°C at 25°C / h, heating to 1100-1350°C at 7°C / h, and heating to 1300-1450°C at 1-3°C / h; the gradient heating method can maximize the reduction of cracks in the bricks.

[0040] In order to improve the mechanical strength of the bricks during the firing process, the insulation time is 5 to 15 hours.

[0041] The effects are described below through specific examples and comparative examples.

[0042] Example 1

[0043] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 65% of polymicroporous siliceous homogenized material (less than 8mm), 25% of quartz powder (less than 100μm), 8% of silicon powder (less than 10μm), 0.1% of sodium tripolyphosphate, 0.3% of sodium hexametaphosphate, and 1.6% of binder II (phosphoric acid), totaling 100%;

[0044] The working layer is composed of the following raw materials in the following mass percentages: 50% silica sand (1.5-3.0 mm), 35% silica powder (less than 100 μm), 1% binder I (lignin), 5% fluorite powder (less than 100 μm), 6% silicon micropowder (less than 10 μm), 1.0% iron scale powder (less than 100 μm), and 2% calcium oxide, totaling 100%.

[0045] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0046] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 100 MPa for 3 minutes, and then place in a 100°C drying kiln to dry until the moisture is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 2:0.6, heat the brick to 1300°C, keep warm for 5 hours, and cool with the furnace to obtain;

[0047] The heating procedure is as follows: heating to 200°C at 20°C / h, heating to 600°C at 25°C / h, heating to 1100°C at 7°C / h, and heating to 1300°C at 1-3°C / h.

[0048] Example 2

[0049] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 75% of polymicroporous siliceous homogenized material (less than 8mm), 20% of quartz powder (less than 100μm), 2% of silicon powder (less than 10μm), 1% of sodium tripolyphosphate, 0.05% of sodium hexametaphosphate, and 1.95% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0050] The working layer is composed of the following raw materials in the following mass percentages: 70% silica sand (1.5-3.0 mm), 15% silica powder (less than 100 μm), 2.5% binder I (cellulose), 3% fluorite powder (less than 100 μm), 5% silicon micropowder (less than 10 μm), 1.5% iron scale powder (less than 100 μm), and 3% calcium oxide, totaling 100%.

[0051] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0052] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 150MPa for 10min, and then place in a 200℃ drying kiln to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 4:1.2, heat the brick to 1450℃, keep warm for 15h, and cool with the furnace to obtain;

[0053] The heating procedure is as follows: heating to 600°C at 20°C / h, heating to 1100°C at 25°C / h, heating to 1350°C at 7°C / h, and heating to 1450°C at 1-3°C / h.

[0054] Example 3

[0055] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 70% of polymicroporous siliceous homogenized material (less than 8mm), 22% of quartz powder (less than 100μm), 6% of silicon powder (less than 10μm), 0.5% of sodium tripolyphosphate, 0.3% of sodium hexametaphosphate, and 1.2% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0056] The working layer is composed of the following raw materials in the following mass percentages: 60% silica sand (1.5-3.0 mm), 25% silica powder (less than 100 μm), 2.0% binder I (dextrin), 4% fluorite powder (less than 100 μm), 5.5% silicon micropowder (less than 10 μm), 0.5% iron scale powder (less than 100 μm), and 3% calcium oxide, totaling 100%.

[0057] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0058] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 120MPa for 7min, and then place in a 150°C drying kiln to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 2:1, and heat the brick to 1350°C, keep warm for 10h, and cool with the furnace to obtain;

[0059] The heating procedure is as follows: heating to 400°C at 20°C / h, heating to 800°C at 25°C / h, heating to 1200°C at 7°C / h, and heating to 1350°C at 1-3°C / h.

[0060] Example 4

[0061] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 68% of polymicroporous siliceous homogenized material (less than 8mm), 24% of quartz powder (less than 100μm), 5% of silicon powder (less than 10μm), 0.8% of sodium tripolyphosphate, 0.2% of sodium hexametaphosphate, and 2% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0062] The working layer is composed of the following raw materials in the following mass percentages: 65% silica sand (1.5-3.0 mm), 20% silica powder (less than 100 μm), 1.5% binder I (phosphate), 5% fluorite powder (less than 100 μm), 5% silicon micropowder (less than 10 μm), 1.0% iron scale powder (less than 100 μm), and 2.5% calcium oxide, totaling 100%.

[0063] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0064] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 140MPa for 5min, and then place in a 120℃ drying kiln to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 4:1, and heat the brick to 1400℃, keep warm for 12h, and cool with the furnace to obtain;

[0065] The heating procedure is as follows: heating to 300°C at 20°C / h, heating to 700°C at 25°C / h, heating to 1300°C at 7°C / h, and heating to 1400°C at 1-3°C / h.

[0066] Example 5

[0067] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 72% of polymicroporous siliceous homogenized material (less than 8mm), 20% of quartz powder (less than 100μm), 6% of silicon powder (less than 10μm), 0.2% of sodium tripolyphosphate, 0.3% of sodium hexametaphosphate, and 1.5% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0068] The working layer is composed of the following raw materials in the following mass percentages: 55% silica sand (1.5-3.0 mm), 30% silica powder (less than 100 μm), 2.5% binder I (lignin and cellulose in a mass ratio of 1:1), 4% fluorite powder (less than 100 μm), 6% silicon micropowder (less than 10 μm), 0.5% iron scale powder (less than 100 μm), and 2% calcium oxide, totaling 100%.

[0069] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0070] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 110MPa for 4min, and then place in a 180℃ drying kiln to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 3:1, and heat the brick to 1450℃, keep warm for 8h, and cool with the furnace to obtain;

[0071] The heating procedure is as follows: heating to 500°C at 20°C / h, heating to 1000°C at 25°C / h, heating to 1150°C at 7°C / h, and heating to 1300°C at 1-3°C / h.

[0072] Example 6

[0073] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 66% of polymicroporous siliceous homogenized material (less than 8mm), 25% of quartz powder (less than 100μm), 7% of silicon powder (less than 10μm), 0.9% of sodium tripolyphosphate, 0.1% of sodium hexametaphosphate, and 1% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0074] The working layer is composed of the following raw materials in the following mass percentages: 58% silica sand (1.5-3.0 mm), 28% silica powder (less than 100 μm), 2.0% binder I (cellulose, dextrin and phosphate in a mass ratio of 1:1:1), 3% fluorite powder (less than 100 μm), 6% silicon micropowder (less than 10 μm), 0.5% iron scale powder (less than 100 μm), and 2.5% calcium oxide, totaling 100%.

[0075] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0076] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 100 MPa for 10 minutes, and then place in a 200°C drying kiln to dry until the moisture is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 2:1.2, heat the brick to 1400°C, keep warm for 6 hours, and cool with the furnace to obtain;

[0077] The heating procedure is as follows: heating to 350°C at 20°C / h, heating to 900°C at 25°C / h, heating to 1250°C at 7°C / h, and heating to 1350°C at 1-3°C / h.

[0078] Example 7

[0079] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 74% of polymicroporous siliceous homogenized material (less than 8mm), 21% of quartz powder (less than 100μm), 2% of silicon powder (less than 10μm), 0.7% of sodium tripolyphosphate, 0.3% of sodium hexametaphosphate, and 2% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0080] The working layer is composed of the following raw materials in the following mass percentages: 62% silica sand (1.5-3.0 mm), 30% silica powder (less than 100 μm), 1% binder I (cellulose and phosphate in a mass ratio of 1:1), 2% fluorite powder (less than 100 μm), 5% silicon micropowder (less than 10 μm), 0% iron scale powder (less than 100 μm), and 0% calcium oxide, totaling 100%.

[0081] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0082] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 150MPa for 3min, and then place it in a drying kiln at 100°C to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 4:0.6, and the brick is heated to 1300°C, kept warm for 14h, and cooled with the furnace;

[0083] The heating procedure is as follows: heating to 550°C at 20°C / h, heating to 850°C at 25°C / h, heating to 1200°C at 7°C / h, and heating to 1450°C at 1-3°C / h.

[0084] Example 8

[0085] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 70% of polymicroporous siliceous homogenized material (less than 8mm), 24% of quartz powder (less than 100μm), 3% of silicon powder (less than 10μm), 0.9% of sodium tripolyphosphate, 0.12% of sodium hexametaphosphate, and 1.98% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0086] The working layer is composed of the following raw materials in the following mass percentages: 52% silica sand (1.5-3.0 mm), 35% silica powder (less than 100 μm), 1% binder I (lignin, dextrin and phosphate in a mass ratio of 1:1:1), 5% fluorite powder (less than 100 μm), 7% silicon micropowder (less than 10 μm), 0% iron scale powder (less than 100 μm), and 0% calcium oxide, totaling 100%.

[0087] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0088] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 130MPa for 8min, and then place in a 140°C drying kiln to dry until the moisture content is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 2:1, and heat the brick to 1400°C, keep warm for 13h, and cool with the furnace to obtain;

[0089] The heating procedure is as follows: heating to 400°C at 20°C / h, heating to 600°C at 25°C / h, heating to 1200°C at 7°C / h, and heating to 1400°C at 1-3°C / h.

[0090] Example 9

[0091] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 67% of polymicroporous siliceous homogenized material (less than 8mm), 25% of quartz powder (less than 100μm), 6% of silicon powder (less than 10μm), 0.5% of sodium tripolyphosphate, 0.3% of sodium hexametaphosphate, and 1.2% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0092] The working layer is composed of the following raw materials in the following mass percentages: 68% silica sand (1.5-3.0 mm), 15% silica powder (less than 100 μm), 2% binder I (lignin, cellulose and dextrin in a mass ratio of 1:1:1), 4% fluorite powder (less than 100 μm), 8% silicon micropowder (less than 10 μm), 0% iron scale powder (less than 100 μm), and 3% calcium oxide, totaling 100%.

[0093] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0094] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 120MPa for 3min, and then place in a 150°C drying kiln to dry until the moisture is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 3:1.2, heat the brick to 1450°C, keep warm for 13h, and cool with the furnace;

[0095] The heating procedure is as follows: heating to 200°C at 20°C / h, heating to 1100°C at 25°C / h, heating to 1300°C at 7°C / h, and heating to 1450°C at 1-3°C / h.

[0096] Example 10

[0097] A microporous low thermal conductivity composite silica brick, the insulation layer of which is composed of the following raw materials in percentage by mass: 73% of polymicroporous siliceous homogenized material (less than 8mm), 23% of quartz powder (less than 100μm), 2% of silicon powder (less than 10μm), 0.6% of sodium tripolyphosphate, 0.1% of sodium hexametaphosphate, and 1.3% of binder II (aluminum dihydrogen phosphate), totaling 100%;

[0098] The working layer is composed of the following raw materials in the following mass percentages: 60% silica sand (1.5-3.0 mm), 25% silica powder (less than 100 μm), 1% binder I (lignin, cellulose, dextrin and phosphate in a mass ratio of 1:1:1:1), 2.5% fluorite powder (less than 100 μm), 10% silicon micropowder (less than 10 μm), 1.5% iron scale powder (less than 100 μm), and 0% calcium oxide, totaling 100%.

[0099] The method for preparing the above-mentioned microporous low thermal conductivity composite silica brick comprises the following steps:

[0100] Weigh the raw materials of the working layer and the thermal insulation layer, premix the raw materials of the working layer and the thermal insulation layer respectively to obtain a working layer premix and a thermal insulation layer premix, respectively load the working layer premix and the thermal insulation layer premix into a mold, separate them with a template in the middle, remove the template after filling, and then press at 150MPa for 8min, and then place in a 180°C drying kiln to dry until the moisture is less than 2% to obtain a brick, the thickness ratio of the working layer to the thermal insulation layer is 4:0.8, heat the brick to 1380°C, keep warm for 12h, and cool with the furnace;

[0101] The heating procedure is as follows: heating to 500°C at 20°C / h, heating to 1000°C at 25°C / h, heating to 1200°C at 7°C / h, and heating to 1300°C at 1-3°C / h.

[0102] The mechanical strength and thermal insulation performance of the microporous low thermal conductivity composite silica bricks prepared in the above Examples 1 to 10 were tested, and the results are shown in Table 1 below. Since the performance of the microporous low thermal conductivity composite silica bricks prepared in Examples 1 to 10 are similar, only Examples 1, 3, 5, 7 and 10 are used as examples to illustrate the effects.

[0103] Table 1 Mechanical strength and thermal insulation performance of the microporous low thermal conductivity composite silica brick of the present invention

[0104]

[0105]

[0106] Table 1 shows that the microporous, low-thermal-conductivity composite silica bricks produced by the present invention exhibit excellent mechanical strength and thermal insulation properties. Increasing the proportion of the poly(microporous) siliceous homogenizer improves the compressive strength and refraction-under-load temperature of the composite silica bricks, but also increases the porosity. The thermal conductivity decreases first and then increases with increasing poly(microporous) siliceous homogenizer content. Increasing the molding pressure improves the compressive strength of the composite silica bricks and reduces the porosity. However, after the pressure reaches a certain level, the thermal conductivity increases.

[0107] In summary, the thermal insulation layer used in the present invention is composed of 65% to 75% by mass of slightly porous siliceous homogenized material, 20% to 25% quartz powder, 2% to 8% silicon powder, 0.1% to 1% sodium tripolyphosphate, 0.05% to 0.3% sodium hexametaphosphate and 1% to 2% binder II. The working layer has the high strength of traditional silica bricks, directly contacts high-temperature materials, and has high-temperature wear resistance, high load softening temperature, corrosion resistance, and thermal shock resistance, achieving stable and long-life use effects; the thermal insulation layer adopts a special high-strength porous material with the characteristics of high strength, low thermal conductivity, good strength and thermal insulation effect, energy saving and consumption reduction, thereby achieving the high strength and thermal insulation effect of the composite silica brick.

[0108] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A microporous low thermal conductivity composite silica brick comprising a working layer and an insulation layer, wherein the insulation layer is wrapped around the working layer; characterized in that: The thickness ratio of the working layer to the insulation layer is 2-4:0.6-1.2; The thermal insulation layer is composed of the following raw materials in percentage by mass: 65% to 75% of polyslightly porous siliceous homogenized material, 20% to 25% of quartz powder, 2% to 8% of silicon powder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II, totaling 100%.

2. The microporous low thermal conductivity composite silica brick according to claim 1, characterized in that: The thickness ratio of the working layer to the thermal insulation layer is 2 to 4:

1.

3. The microporous low thermal conductivity composite silica brick according to claim 1, characterized in that: The binder II is phosphoric acid or a phosphate binder.

4. The microporous low thermal conductivity composite silica brick according to claim 1, characterized in that: The working layer is composed of the following raw materials in percentage by mass: 50% to 70% silica sand, 15% to 35% silica powder, 1% to 2.5% binder I, 2% to 5% fluorite powder, 5% to 10% silicon micropowder, 0% to 1.5% iron scale powder, and 0% to 3% calcium oxide, which totals 100%.

5. The microporous low thermal conductivity composite silica brick according to claim 4, characterized in that: The binder I is one or more of lignin, cellulose, dextrin and phosphate.

6. A method for preparing the microporous low thermal conductivity composite silica brick according to any one of claims 1 to 5, characterized in that: The following steps are involved: Weigh the raw materials of the working layer and the insulation layer respectively; Mix 50% to 70% by mass of silica sand, 15% to 35% of silica powder, 1% to 2.5% of binder I, 2% to 5% of fluorite powder, 5% to 10% of silica powder, 0% to 1.5% of iron scale powder, and 0% to 3% of calcium oxide to obtain a working layer premix; Mix 65% to 75% by mass of slightly porous siliceous homogenized material, 20% to 25% of quartz powder, 2% to 8% of silicon powder, 0.1% to 1% of sodium tripolyphosphate, 0.05% to 0.3% of sodium hexametaphosphate, and 1% to 2% of binder II to obtain a premix for the thermal insulation layer; The working layer premix and the insulation layer premix are pressed into shape, dried to obtain bricks, and the bricks are heated to 1300-1450° C., kept warm, and cooled to obtain the bricks.

7. The preparation method according to claim 6, characterized in that During pressing, the pressure is 100-150 MPa and the time is 3-10 minutes.

8. The preparation method according to claim 6, characterized in that The insulation time is 5 to 15 hours.

9. The preparation method according to claim 6, characterized in that The heating procedure is as follows: heating to 200-600°C at 20°C / h, heating to 600-1100°C at 25°C / h, heating to 1100-1350°C at 7°C / h, and heating to 1300-1450°C at 1-3°C / h.

10. The preparation method according to claim 6, characterized in that During drying, the bricks are dried in a drying kiln at 100-200°C to obtain bricks with a moisture content of less than 2%.

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