Novel high-strength low-thermal-conductivity insulating brick and preparation method thereof

Abstract

The invention relates to the technical field of preparation of insulating bricks, and discloses a novel high-strength low-heat-conductivity insulating brick and a preparation method thereof. The preparation method comprises the following steps: weighing the following raw materials in parts by weight: 20-30 parts of high-precision microbeads, 0-10 parts of fly ash, 20-25 parts of alumina clinker powder, 0-10 parts of waste brick powder, 20-25 parts of high-quality clay, 5-8 parts of siliceous micro powder, 8-12 parts of perforated perlite and 18-22 parts of aluminum-silicon-calcium powder; mixing and stirring: pouring the raw materials into a stirrer, firstly performing dry mixing until the components are uniform, then adding water for adjustment, and continuing wet mixing to obtain a mixed material; compression molding: adding the mixed material into a mold, and adopting a step-by-step compression molding process to obtain a green brick; and firing treatment: putting the green brick into a tunnel kiln, firing, preserving heat, and cooling to obtain the novel high-strength low-heat-conductivity insulating brick. The high-precision microbeads and the perforated perlite cooperate with each other, and the silicon-aluminum-calcium powder promotes sintering, so that high strength and low heat conductivity are realized; high-temperature stability is guaranteed through precise firing, the cost is reduced through solid waste doping, technological parameters are optimized, and large-scale production can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of insulating brick preparation, and particularly relates to a new high-strength low-thermal-conductivity insulating brick and a preparation method thereof. BACKGROUND

[0002] Insulating bricks are widely used in industrial kiln lining, building exterior wall insulation, heat pipe insulation and other fields, and the core requirement is to have sufficient mechanical strength and high temperature stability while ensuring low thermal conductivity. However, the existing technology has the following significant pain points: Firstly, to reduce the thermal conductivity, the traditional insulating brick often increases the porosity, but too high porosity will generally result in a normal temperature compressive strength lower than 3MPa, which is easy to break during transportation and masonry. If the strength is improved, the densification of raw materials will increase the thermal conductivity and greatly reduce the insulation effect.

[0003] Secondly, most insulating bricks have a linear change rate of more than-1.0% after being fired at 1300℃ or above, and the closed pore structure is easy to break, resulting in a sharp increase in thermal conductivity and a shortened service life. Thirdly, some technologies rely on high-purity natural raw materials such as high-alumina clay, which has high cost and large resource consumption. Industrial solid wastes such as fly ash and waste brick powder are difficult to effectively integrate into the formula due to improper processing, which easily leads to fluctuations in product performance.

[0004] Therefore, the technical personnel in the field urgently need to develop a new high-strength low-thermal-conductivity insulating brick and a preparation method thereof. SUMMARY

[0005] The purpose of the present application is to solve the problems in the prior art and provide a new high-strength low-thermal-conductivity insulating brick and a preparation method thereof.

[0006] Based on one purpose of the present application, the following technical solution is provided: a preparation method of a new high-strength low-thermal-conductivity insulating brick, comprising the following steps: S1, raw material preparation: the following raw materials are weighed according to weight parts: high-precision microbeads 20-30 parts, fly ash 0-10 parts, bauxite clinker powder 20-25 parts, waste brick powder 0-10 parts, high-quality clay 20-25 parts, siliceous micro powder 5-8 parts, open-cell perlite 8-12 parts, and aluminum-silicon-calcium powder 18-22 parts; The high-precision microbeads are prepared by ball milling fly ash to a particle size of 5-10um after pre-burning at 800-900℃ for 2-3h; The siliceous micro powder has a SiO2 content of ≥98% and a particle size of ≤1um; The high-quality clay has an Al2O3 content of ≥35%, an Fe2O3 content of ≤1.5%, and is aged for more than 72h; The open-pore perlite has an open porosity of 85% or more, a particle size of 2-5 mm, and a closed porosity of 70% or more. The aluminum-silicon-calcium powder has a CaO content of 25-30%, an Al2O3 content of 15-20%, and a particle size of 100-200 mesh. S2, mixing and stirring: the above raw materials are poured into a stirring machine, dry mixing is first performed until the components are uniform, then water is added for adjustment, and wet mixing is continued to obtain a mixture; S3, pressing and forming: the mixture is added to a mold, and a step-by-step pressing forming process is adopted to obtain a brick blank; S4, firing treatment: the brick blank is placed in a tunnel kiln, and after firing, heat preservation, and cooling, a new type of high-strength low-thermal-conductivity insulation brick is obtained.

[0007] Preferably, in step 2, the stirring machine is a double-shaft paddle stirring machine, and the stirring speed is 300-350 r / min. During the wet mixing process, the machine is stopped every 5 min for 1 min to discharge the internal bubbles of the material.

[0008] Preferably, in step 2, the raw materials are poured into the stirring machine according to the principle of "light first, heavy later, and clinker first, raw material later". The water content of the material after water adjustment is 16-18%, the dry mixing time is 10-15 min, and the wet mixing time is 20-25 min.

[0009] Preferably, in step 3, a 4 MPa step-by-step pressing forming process is adopted: first, 1 MPa pressure is maintained for 1 min, then the pressure is increased to 4 MPa and maintained for 3 min to obtain a brick blank.

[0010] Preferably, in step 4, the inner firing atmosphere of the tunnel kiln is a weak oxidizing atmosphere, and the oxygen volume fraction is controlled to be 8-12%.

[0011] Preferably, in step 4, the firing is performed according to the following system: from room temperature to 600℃, the heating rate is 5-8℃ / min; from 600-1000℃, the heating rate is 3-5℃ / min; from 1000-1320℃, the heating rate is 2-3℃ / min; at 1320℃, the heat preservation time is 6 h, and after natural cooling to 500℃, air cooling is performed to room temperature.

[0012] Based on another object of the present application, a new type of high-strength low-thermal-conductivity insulation brick is provided, which is prepared by the above preparation method, and the performance indicators of the insulation brick meet the following requirements: The cold compressive strength is ≥4.3 MPa, and the cold compressive strength after 1300-1350℃ re-firing is 3.6-3.9 MPa; The cold thermal conductivity coefficient is ≤0.15 W / (m·K) at room temperature (25℃), and the thermal conductivity coefficient is ≤0.18 W / (m·K) at 800℃; Bulk density 0.55-0.60 g / cm3, closed pore rate ≥70%, linear change rate ≤-0.5% after re-firing at 1350 DEG C.

[0013] Compared with the prior art, the application has the beneficial effects that: The application solves the core problem that the traditional thermal insulation bricks are difficult to balance the strength, thermal insulation and high-temperature stability by "specific raw material ratio + precise process control".

[0014] I. The cold compressive strength of examples 1-3 is all ≥4.3 MPa (the highest is 4.5 MPa), which is increased by 45%-90% compared with the comparative examples; the cold thermal conductivity is ≤0.15 W / (m·K) (the lowest is 0.13 W / (m·K)), the thermal conductivity at 800 DEG C is ≤0.18 W / (m·K), which is much lower than that of the traditional thermal insulation bricks (0.20-0.30 W / (m·K)). This is due to the synergistic effect of high-precision beads (pre-burned ball milling) and open-pore perlite - the former fills the pores to improve the density, and the latter builds a closed thermal insulation cavity, and the siliceous powder (high SiO2) and aluminum-silicon-calcium powder promote low-temperature sintering to avoid excessive densification.

[0015] II. The high-temperature stability is significantly better than that of the prior art. The linear change rate of examples 1-3 after re-firing at 1350 DEG C is ≤-0.5% (the lowest is -0.2%), the closed pore rate is ≥70%, and the compressive strength is still ≥3.6 MPa; while the linear change rate of comparative examples 1-3 is all ≤-0.7%, the closed pore rate is ≤65%, and the strength is greatly reduced to ≤2.8 MPa. The key lies in the precise sintering at 1320 DEG C (to ensure that the crystals are fully developed without over-burning) and the weak oxidizing atmosphere (to inhibit the oxidation and decomposition of the raw materials), which avoids the structural cracking caused by insufficient sintering or improper atmosphere in the traditional process.

[0016] III. The process is stable and can be scaled up for production, and the environmental protection and economy are considered. The formula incorporates industrial solid wastes such as fly ash (0-10 parts) and waste brick powder (0-10 parts), with a maximum utilization rate of 20% (example 3), replacing part of the high-cost natural raw materials (such as bauxite clinker powder), reducing the raw material cost by 15%-20%; the bulk density is 0.55-0.60 g / cm3, which is 20%-30% lighter than that of the traditional thermal insulation bricks (0.7-0.9 g / cm3), reducing the transportation and masonry energy consumption. At the same time, the "double-shaft paddle stirring + step-by-step pressurization + staged temperature rising sintering" process solves the problems of mixed bubbles and uneven compaction density, and the performance index fluctuation of examples 1-3 is ≤8%, which is much lower than that of the comparative examples (15%-25%), ensuring the stable quality of industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is the process flow chart of the application in the examples. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be described below in combination with the drawings Figure 1 and the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0019] Embodiment One 1. Raw material ratio (weight parts): High-precision microbeads 25 parts (850℃ pre-burning 2.5h, particle size 7μm), Fly ash 5 parts, bauxite clinker powder 22 parts, waste brick powder 3 parts, High-quality clay 23 parts (Al2O3 38%, Fe2O3 1.2%, stale 96h), Siliceous powder 6 parts (SiO2 99%, particle size 0.8μm), Open-cell perlite 10 parts (open-cell rate 88%, particle size 3mm, closed-cell rate 75%), Aluminum-silicon-calcium powder 16 parts (CaO 28%, Al2O3 18%, 150 mesh).

[0020] 2. Preparation process: Double-shaft paddle type mixer (rotation speed 320r / min), according to the principle of “light first, heavy later, clinker first, raw material later”, the materials are put in and dry mixed for 12min; Water is added to adjust the moisture content to 17%, and wet mixing is performed for 22min (stop every 5min for 1min to exhaust air); stepwise pressurization (1MPa for 1min→4MPa for 3min); Tunnel kiln with weak oxidizing atmosphere (oxygen volume fraction 10%), firing system: room temperature→600℃ (heating rate 6℃ / min)→1000℃ (heating rate 4℃ / min)→1320℃ (heating rate 2.5℃ / min, holding for 6h), air cooling to room temperature after 500℃. 3. Performance index: Normal temperature compressive strength 4.4MPa, 1350℃ re-fired compressive strength 3.9MPa; Normal temperature thermal conductivity 0.14W / (m·K), 800℃ thermal conductivity 0.17W / (m·K); Bulk density 0.57g / cm³, closed-cell rate 73%, linear change rate after 1350℃ re-firing -0.3% Embodiment Two 1. Raw material ratio (weight parts): High-precision microbeads 20 parts (800℃ pre-burning 3h, particle size 5μm), Fly ash 10 parts, bauxite clinker powder 25 parts, waste brick powder 0 parts, High-quality clay 25 parts (Al2O3 35%, Fe2O3 1.4%, stale 72h), Silica powder 5 parts (SiO298%, particle size 1 μm), Open-cell perlite 8 parts (open-cell ratio 85%, particle size 2 mm, closed-cell ratio 70%), Alumina-silicate-calcium powder 18 parts (CaO 25%, Al2O3 20%, 100 mesh). 2. Preparation process: Double-shaft paddle-type mixer (rotation speed 300 r / min), dry mixing 10 min; Moisture content 16%, wet mixing 20 min (exhaust same as before); Stepwise pressurization (same as in Example 1); Tunnel kiln oxygen volume fraction 8%, firing schedule: room temperature→600℃ (5℃ / min)→1000℃ (3℃ / min)→1320℃ (2℃ / min, holding for 6 h), air cooling after 500℃.

[0021] 3. Performance index: Normal-temperature compressive strength 4.3 MPa, 1350℃ re-fired compressive strength 3.7 MPa; Normal-temperature thermal conductivity 0.15 W / (m·K), 800℃ thermal conductivity 0.18 W / (m·K); Bulk density 0.55 g / cm³, closed-cell ratio 71%, linear change rate after 1350℃ re-firing -0.4% Example Three 1. Raw material ratio (weight parts): High-precision microbeads 30 parts (900℃ pre-burning 2 h, particle size 10 μm), Fly ash 0 parts, bauxite clinker powder 20 parts, waste brick powder 10 parts, High-quality clay 20 parts (Al2O3 40%, Fe2O3 1.0%, stale 120 h), Silica powder 8 parts (SiO2 99.5%, particle size 0.5 μm), Open-cell perlite 12 parts (open-cell ratio 90%, particle size 5 mm, closed-cell ratio 78%), Alumina-silicate-calcium powder 22 parts (CaO 30%, Al2O3 15%, 200 mesh). 2. Preparation process: Double-shaft paddle-type mixer (rotation speed 350 r / min), dry mixing 15 min; Moisture content 18%, wet mixing 25 min (exhaust same as before); Stepwise pressurization (same as in Example 1); Tunnel kiln oxygen volume fraction 12%, firing schedule: room temperature→600℃ (8℃ / min)→1000℃ (5℃ / min)→1320℃ (3℃ / min, holding for 6 h), air cooling after 500℃.

[0022] 3. Performance indicators: Normal temperature compressive strength 4.5 MPa, 1350℃ re-fired compressive strength 4.0 MPa; Normal temperature thermal conductivity 0.13 W / (m·K), 800℃ thermal conductivity 0.16 W / (m·K); Bulk density 0.60 g / cm³, closed porosity 76%, 1350℃ re-fired linear change rate -0.2%.

[0023] Comparative Example 1 (no high-precision micro beads, replaced by fly ash) Raw material adjustment: delete high-precision micro beads, fly ash increased to 40 parts, and the rest of the raw materials are the same as Example 1.

[0024] Performance indicators: normal temperature compressive strength 2.7 MPa (60% less than Example 1), 1350℃ re-fired compressive strength 1.9 MPa; normal temperature thermal conductivity 0.23 W / (m·K) (64% higher than Example 1), 800℃ thermal conductivity 0.28 W / (m·K); bulk density 0.72 g / cm³, closed porosity 52%, 1350℃ re-fired linear change rate -1.2%.

[0025] Comparative Example 2 (firing temperature reduced to 1250℃, not reaching 1320℃) Process adjustment: the raw materials are the same as Example 1, the maximum firing temperature is changed to 1250℃ (6h holding), and the rest of the process is the same. Performance indicators: normal temperature compressive strength 3.2 MPa (32% lower than Example 1), 1350℃ re-fired compressive strength 2.3 MPa; normal temperature thermal conductivity 0.18 W / (m·K), 800℃ thermal conductivity 0.22 W / (m·K); bulk density 0.65 g / cm³, closed porosity 61%, 1350℃ re-fired linear change rate -0.9%.

[0026] Comparative Example 3 (one-time pressure forming, not step-by-step pressure) Process adjustment: the raw materials are the same as Example 1, the forming process is changed to "direct 4 MPa pressure for 4 min", and the rest of the process is the same. Performance indicators: normal temperature compressive strength 3.5 MPa (24% lower than Example 1), 1350℃ re-fired compressive strength 2.8 MPa; normal temperature thermal conductivity 0.16 W / (m·K), 800℃ thermal conductivity 0.19 W / (m·K); bulk density 0.62 g / cm³, closed porosity 65%, 1350℃ re-fired linear change rate -0.7%.

[0027] Embodiments of the application have been described above, with examples of the description being illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations of the described embodiments are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method for preparing a novel high-strength, low-thermal-conductivity insulating brick, characterized in that, Includes the following steps: S1. Raw material preparation: Weigh the following raw materials by weight: 20-30 parts high-precision microspheres, 0-10 parts fly ash, 20-25 parts bauxite clinker powder, 0-10 parts waste brick powder, 20-25 parts high-quality clay, 5-8 parts silica micro powder, 8-12 parts open-pore perlite, and 18-22 parts alumina-silica-calcium powder. The high-precision microspheres are prepared by pre-calcining fly ash at 800-900℃ for 2-3 hours and then ball milling it to a particle size of 5-10μm. The silica micropowder has a SiO2 content of ≥98% and a particle size of ≤1μm; The high-quality clay has an Al2O3 content of ≥35% and an Fe2O3 content of ≤1.5%, and has been aged for more than 72 hours. The open-pore perlite has an open pore rate of ≥85%, a particle size of 2-5mm, and a closed pore rate of ≥70%. The aluminum-silicon-calcium powder has a CaO content of 25-30%, an Al2O3 content of 15-20%, and a particle size of 100-200 mesh. S2. Mixing and stirring: Pour the above raw materials into a mixer, first dry mix until the components are uniform, then add water to adjust, and continue wet mixing to obtain a mixture. S3. Press molding: The mixture is added to the mold and a step-by-step press molding process is used to obtain the brick blank; S4. Firing treatment: The brick blanks are placed in a tunnel kiln, fired, kept warm, and cooled to obtain a new type of high-strength, low-thermal-conductivity insulating brick.

2. The preparation method of the novel high-strength, low-thermal-conductivity insulating brick according to claim 1, characterized in that: In step 2, the mixer is a twin-shaft paddle mixer with a mixing speed of 300-350 r / min. During the wet mixing process, the mixer is stopped for 1 minute every 5 minutes to remove air bubbles from the material.

3. The preparation method of the novel high-strength, low-thermal-conductivity insulating brick according to claim 1, characterized in that: In step 2, the raw materials are poured into the mixer according to the principle of "lighter materials first, heavier materials later, and cooked materials first, raw materials later". The moisture content of the materials is adjusted by adding water to 16-18%, the dry mixing time is 10-15 minutes, and the wet mixing time is 20-25 minutes.

4. The preparation method of the novel high-strength, low-thermal-conductivity insulating brick according to claim 1, characterized in that: In step 3, a step-by-step pressure molding process of 4MPa is adopted: first, the pressure is maintained at 1MPa for 1 minute, and then the pressure is increased to 4MPa and maintained for 3 minutes to obtain the brick blank.

5. The preparation method of the novel high-strength, low-thermal-conductivity insulating brick according to claim 1, characterized in that: In step 4, the internal firing atmosphere of the tunnel kiln is a weakly oxidizing atmosphere, and the oxygen volume fraction is controlled at 8-12%.

6. The preparation method of the novel high-strength, low-thermal-conductivity insulating brick according to claim 1, characterized in that: In step 4, the firing process is carried out according to the following schedule: from room temperature to 600℃, the heating rate is 5-8℃ / min; from 600 to 1000℃, the heating rate is 3-5℃ / min; from 1000 to 1320℃, the heating rate is 2-3℃ / min; hold at 1320℃ for 6 hours, cool naturally to 500℃, and then air-cool to room temperature.

7. A novel high-strength, low-thermal-conductivity insulating brick, prepared by any one of the preparation methods described in claims 1-6, characterized in that: The performance indicators of the thermal insulation bricks meet the following requirements: Compressive strength at room temperature ≥4.3MPa; compressive strength at room temperature after reheating at 1300-1350℃ 3.6-3.9MPa. Thermal conductivity at room temperature (25℃) ≤ 0.15 W / (m·K), thermal conductivity at 800℃ ≤ 0.18 W / (m·K); Bulk density 0.55-0.60 g / cm³, closed-cell rate ≥70%, linear change rate after reheating at 1350℃ ≤-0.5%.

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