A low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kiln and a preparation method thereof

Abstract

The application discloses a low-thermal-conductivity periclase-magnesia-alumina spinel refractory material for a cement rotary kiln and a preparation method thereof. The refractory material is mainly composed of 1-2mm magnesia particles 3-5%, 0.1-0.9mm magnesia particles 30-48%, 1-2mm magnesia-alumina spinel particles 3-5%, 0.1-0.9mm magnesia-alumina spinel particles 8-20%, magnesia powder 17-32%, Mg(OH)2 powder 3-6% and magnesite powder 1-3% in terms of mass percentage. The 1-2mm magnesia particles, the 0.1-0.9mm magnesia particles, the 1-2mm magnesia-alumina spinel particles and the 0.1-0.9mm magnesia-alumina spinel particles are mixed, then a binder solution is added and mixed, and then the magnesia powder, the Mg(OH)2 powder and the magnesite powder are added and uniformly mixed to obtain a mixture; the mixture is sequentially subjected to machine pressing, drying and calcination to obtain the product low-thermal-conductivity periclase-magnesia-alumina spinel refratory material. The prepared periclase-magnesia-alumina spinel refractory material has low thermal conductivity, small pore size and good salt and alkali erosion resistance, and is suitable for the upper transition zone of the cement rotary kiln.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials for cement rotary kilns, specifically relating to a low thermal conductivity periclase-magnesium aluminum spinel refractory material for cement rotary kilns and its preparation method. Background Technology

[0002] Pernicopteranite-magnesia-alumina spinel refractories are widely used as lining materials for high-temperature kilns due to their excellent high-temperature strength, thermal shock stability, and erosion resistance. In recent years, with the steady advancement of the dual-carbon economy policy, high-temperature industries are facing enormous pressure to conserve energy and reduce emissions. Pernicopteranite-magnesia-alumina spinel used in cement rotary kilns has a high thermal conductivity, resulting in significant heat loss through the kiln surface. Therefore, there is an urgent need to prepare pernicopteranite-magnesia-alumina spinel refractories with low thermal conductivity to further achieve energy conservation and emission reduction in cement rotary kilns.

[0003] Currently, there are relevant literature reports on low thermal conductivity periclase-magnesia-alumina spinel refractory materials. For example: 1. Invention patent CN117362008A discloses a periclase-spinel and hollow sphere composite brick and its preparation method. This method uses fused magnesia as raw material to prepare a refractory layer and magnesium-alumina spinel hollow spheres as raw material to prepare a heat insulation layer. The main problems with this product are: First, the refractory layer and the heat insulation layer are made of different materials, and there is a large difference in the coefficient of thermal expansion between the two layers. During production and use, defects are easily generated between the layers, leading to product damage and reduced service life; Second, the surface of the hollow spheres is smooth, making it difficult to bond with the matrix, resulting in low product strength. In addition, the internal pore size is large. Once the dense layer is damaged, the heat insulation layer made of hollow spheres is difficult to meet the usage requirements. 2. Invention patent CN107337438B discloses a lightweight periclase-magnesia-alumina spinel refractory material and its preparation method. This invention uses porous periclase-magnesia-alumina spinel ceramic material particles, porous periclase-magnesia-alumina spinel ceramic material fine powder, and magnesia fine powder as raw materials to prepare lightweight periclase-magnesia-alumina spinel refractory materials. The porosity of the aggregate easily provides more pore channels for the penetration of corrosive media, reducing the material's corrosion resistance and shortening its service life. 3. Patent application CN103864434A discloses a lightweight periclase-magnesia-alumina spinel refractory material for cement rotary kilns and its preparation method. This invention uses porous periclase-magnesium aluminum spinel ceramic particles as aggregate, employing in-situ reaction of magnesite micro powder and active α-alumina micro powder to block the surface pores of the aggregate and form closed pores. However, it is worth noting that after the thermal decomposition of magnesite micro particles, the internal micro-nano pores merge and grow, and the micro particles undergo volume shrinkage, easily leaving annular pore defects around them, making it difficult to form a neck connection with the aggregate. During the reaction sintering process involving Al2O3, an expanded spinel ring forms on the surface of the magnesite micro particles, and the internal micro-nano pores, after merging and growing, easily form large pore defects inside. Due to the sintering stress between the shrinkage caused by the merging and growth of the internal pores and the expanded spinel ring, it is difficult to form internal pores on the surface and they cannot be completely sealed. Therefore, this technical route can neither block the surface pores of the aggregate nor form closed pores between magnesite powder and active α-alumina micro powder and between the powder and the aggregate. The resulting product has large pore size and uneven pore distribution.

[0004] As can be seen from the above, the main problems with existing periclase-magnesia-alumina spinel refractory materials for low thermal conductivity cement rotary kilns are as follows: First, due to the difference in thermal expansion coefficients, multi-layer composite bricks are prone to defects and peeling between layers, resulting in short service life and high risk. Second, the hollow spheres have poor bonding with the matrix, resulting in low product strength. Moreover, the large pore size inside the hollow spheres will exacerbate the material's damage once the outer shell of the hollow spheres is eroded. Third, the porosity of the aggregate will provide more pore channels for the penetration of alkali solutions and alkali vapors, affecting the material's resistance to alkali erosion. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the issues of large pore size, poor resistance to alkali corrosion, and high thermal conductivity in existing low thermal conductivity periclase-magnesium aluminum spinel refractory materials used in cement rotary kilns. This invention provides a low thermal conductivity periclase-magnesium aluminum spinel refractory material for cement rotary kilns and its preparation method. The periclase-magnesium aluminum spinel refractory material prepared using this invention has low thermal conductivity, small pore size, and good resistance to salt and alkali corrosion, making it suitable for the upper transition zone of cement rotary kilns and achieving energy saving and emission reduction effects.

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

[0007] On one hand, the present invention provides a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns. Expressed as a percentage by mass, the low thermal conductivity periclase-magnesia-alumina spinel refractory material is mainly composed of 3-5% 1-2mm magnesia sand particles, 30-48% 0.1-0.9mm magnesia sand particles, 3-5% 1-2mm magnesia-alumina spinel particles, 8-20% 0.1-0.9mm magnesia-alumina spinel particles, 17-32% magnesia sand powder, 3-6% Mg(OH)2 powder, and 1-3% magnesite powder.

[0008] According to the above-mentioned low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the MgO content in the magnesia particles is ≥97wt%.

[0009] According to the above-mentioned low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the Al2O3 content in the magnesium-alumina spinel particles is ≥65wt%.

[0010] According to the above-mentioned low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the particle size of the magnesia powder is <88μm; the MgO content in the magnesia powder is ≥97wt%.

[0011] According to the above-mentioned low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the particle size of the Mg(OH)2 powder is <50μm; the MgO content in the Mg(OH)2 powder is ≥99wt%.

[0012] According to the above-mentioned low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the particle size of the magnesite powder is <25μm; the MgO content in the magnesite powder is ≥45wt%.

[0013] On the other hand, a method for preparing a low thermal conductivity periclase-magnesium aluminum spinel refractory material for cement rotary kilns is provided, the preparation method comprising the following steps:

[0014] 1) Weigh out all raw materials according to the above-mentioned raw material ratio of low thermal conductivity periclase-magnesium aluminum spinel refractory;

[0015] 2) Place the aggregates of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles, and 0.1-0.9 mm magnesium aluminum spinel particles into a mixing mill and mix (mixing time is 3-8 min). Then add a binder solution accounting for 3-6% of the total weight of each raw material and mix (mixing time is 2-5 min). Then add the matrix magnesia powder, Mg(OH)2 powder, and magnesite powder and mix evenly (mixing time is 3-8 min) to obtain the mixture.

[0016] 3) Press the resulting mixture into shape using a machine;

[0017] 4) Dry the molded product;

[0018] 5) The dried product is calcined and then cooled to obtain a low thermal conductivity periclase-magnesium aluminum spinel refractory material.

[0019] According to the above preparation method of low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, the preparation method of the binder solution in step 2) is as follows: the binder and water are mixed at a mass ratio of 1.2 to 1.5:1, and then placed in a mixer and stirred for 20 to 30 minutes to obtain the binder solution.

[0020] According to the above-mentioned preparation method of low thermal conductivity periclase-magnesium aluminum spinel refractory material for cement rotary kilns, the binder is sodium lignosulfonate powder, calcium lignosulfonate powder, or dextrin powder.

[0021] According to the above preparation method of low thermal conductivity periclase-magnesium aluminum spinel refractory for cement rotary kilns, the pressure is controlled at 120-180 MPa during the machine pressing process in step 3); the drying temperature is controlled at 110-220℃ and the drying time is controlled at 24-36 h during the drying process in step 4); and the calcination rate is controlled at 3-6℃ / min during the calcination process in step 5), and the temperature is held at 1480-1620℃ for 4-6 h.

[0022] The positive and beneficial effects of this invention are:

[0023] 1. This invention innovatively designs the source of pores in periclase-magnesium aluminum spinel refractory materials, and the manufactured products have a pore structure with small pore diameter and uniform pore distribution.

[0024] Firstly, there are elongated, interconnected large pores between dense magnesia and the matrix. Existing periclase-magnesia-alumina spinel refractories use dense magnesia or magnesium-alumina spinel particles as aggregates. During sintering, it is difficult for the dense aggregate to form a neck connection with the fine powder, and the sintering shrinkage of the aggregate and matrix is ​​mismatched, easily resulting in elongated large pores at the interface. The pore size increases with the aggregate particle size. This invention adopts a method of reducing aggregate particle size: First, the pore size at the aggregate-matrix interface is reduced; second, without changing the volume and mass of the fine powder, smaller aggregate particles occupy the positions of the original larger aggregate particles, increasing the pore volume of the product by utilizing the increased porosity between the aggregate particles; finally, smaller-graded aggregates are more likely to form neck connections with the fine powder particles, which can effectively avoid the generation of elongated pores at the interface caused by increased sintering stress between the aggregate and matrix during firing.

[0025] Secondly, the matrix contains micron-sized pores. In existing periclase-magnesia-alumina spinel materials, mass transfer between MgO microparticles is mainly through solid-phase sintering, with some reactive sintering involving Al2O3 and liquid-phase sintering involving high-temperature, low-melting-point phases generated by impurities. However, due to differences in particle size, inter-particle reaction degree, and thermal expansion coefficients between different phases in the matrix, the number of neck connections in the periclase-magnesia-alumina spinel material matrix is ​​relatively small, resulting in numerous isolated or interconnected micron-sized pores between MgO microparticles. This invention employs in-situ decomposition pore-forming technology, adding Mg(OH)2 powder and magnesite powder to the matrix. Mg(OH)2 microparticles and magnesite microparticles fill the pores between MgO microparticles and at the aggregate-matrix interface. The micro- and nano-pores generated after thermal decomposition refine the original pore structure, reducing pore size and making the pore distribution more uniform, further reducing the thermal conductivity of the product.

[0026] 2. The unique pore structure design of this invention can reduce the thermal conductivity of the product and improve its resistance to salt and alkali corrosion.

[0027] The product obtained by this invention has small and uniformly distributed pores at the aggregate / matrix interface and in the matrix, which can effectively reduce the thermal conductivity of the product and reduce heat loss through the furnace lining material, thus saving energy and protecting the environment; 2) Regarding the penetration of alkali vapor and alkali solution, the matrix part of the product of this invention has a complex pore structure. The significantly reduced pore size can reduce the effective porosity of alkali vapor and alkali solution penetration, increase the flow resistance of alkali vapor and alkali solution, and the uniformly distributed pores can absorb the volume expansion generated by the reaction of magnesium aluminum spinel with alkali, weaken the volume effect of the product reacting with alkali, and thus effectively improve the product's resistance to alkali corrosion.

[0028] 3. The low thermal conductivity periclase-magnesia-alumina spinel refractory material prepared by this invention was tested and found to have a bulk density of 2.70–2.80 g / cm³. 3Apparent porosity is 19-24%; compressive strength is 60-75 MPa; thermal conductivity is 1.8-2.0 W / (m·K) (1000℃).

[0029] Therefore, the periclase-magnesia-alumina spinel refractory material prepared by this invention has a low thermal conductivity, small pore size, and good resistance to salt and alkali corrosion, making it more suitable for the upper transition zone of cement rotary kilns and achieving energy saving and emission reduction. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments, but this does not limit the scope of protection of the present invention.

[0031] In the following examples, the magnesia particles used have an MgO content ≥ 97 wt%; the magnesium aluminum spinel particles have an Al2O3 content ≥ 65 wt%; the magnesia powder has a particle size < 88 μm; the magnesia powder has an MgO content ≥ 97 wt%; the Mg(OH)2 powder has a particle size < 50 μm; the Mg(OH)2 powder has an MgO content ≥ 99 wt%; the magnesite powder has a particle size < 25 μm; and the magnesite powder has an MgO content ≥ 45 wt%.

[0032] Example 1:

[0033] The present invention relates to a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, which, expressed as a percentage by mass, consists of 4% 1-2mm magnesia sand particles, 30% 0.1-0.9mm magnesia sand particles, 5% 1-2mm magnesia-alumina spinel particles, 20% 0.1-0.9mm magnesia-alumina spinel particles, 32% magnesia sand powder, 6% Mg(OH)2 powder, and 3% magnesite powder.

[0034] The aggregate consists of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesia-alumina spinel particles, and 0.1-0.9 mm magnesia-alumina spinel particles; magnesia powder, Mg(OH)₂ powder, and magnesite powder are used as the matrix, and the sum of the aggregate and matrix constitutes the raw material. The magnesia particles used contain 97 wt% MgO; the magnesia-alumina spinel particles contain 65 wt% Al₂O₃; the magnesia powder contains 98 wt% MgO; the Mg(OH)₂ powder contains 99 wt% MgO; and the magnesite powder contains 45 wt% MgO.

[0035] The detailed steps of the preparation method of low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns in this embodiment are as follows:

[0036] 1) Weigh out all raw materials according to the raw material ratio of the low thermal conductivity periclase-magnesium aluminum spinel refractory material described in Example 1;

[0037] 2) Place the aggregates of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles, and 0.1-0.9 mm magnesium aluminum spinel particles into a mixer and mix for 3 minutes; then add a binder solution accounting for 3% of the total weight of each raw material and mix for 3 minutes; then add the matrix magnesia powder, Mg(OH)2 powder, and magnesite powder and mix for 3 minutes to obtain the mixture.

[0038] The preparation process of the binder solution is as follows: Sodium lignosulfonate powder and water are mixed at a mass ratio of 1.2:1, and then stirred in a mixer for 20 minutes to obtain the binder solution.

[0039] 3) The resulting mixture is machine-pressed at 120 MPa;

[0040] 4) Dry the molded product at 110℃ for 24 hours;

[0041] 5) After drying, heat to 1480℃ at a rate of 3℃ / min and hold for 5 hours; cool to obtain the product, low thermal conductivity periclase-magnesium aluminum spinel refractory material.

[0042] The low thermal conductivity periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have an apparent porosity of 24% and a bulk density of 2.70 g / cm³. 3 The compressive strength is 60MPa and the thermal conductivity is 1.8W / (m·K) (1000℃).

[0043] Example 2:

[0044] The present invention relates to a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, which, expressed as a percentage by mass, consists of 3% 1-2mm magnesia sand particles, 41% 0.1-0.9mm magnesia sand particles, 4% 1-2mm magnesia-alumina spinel particles, 16% 0.1-0.9mm magnesia-alumina spinel particles, 30% magnesia sand powder, 4% Mg(OH)2 powder, and 2% magnesite powder.

[0045] The aggregate consists of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesia-alumina spinel particles, and 0.1-0.9 mm magnesia-alumina spinel particles; magnesia powder, Mg(OH)₂ powder, and magnesite powder are used as the matrix, and the sum of the aggregate and matrix constitutes the raw material. The magnesia particles used contain 97.5 wt% MgO; the magnesia-alumina spinel particles contain 68 wt% Al₂O₃; the magnesia powder contains 97.5 wt% MgO; the Mg(OH)₂ powder contains 99.5 wt% MgO; and the magnesite powder contains 45.5 wt% MgO.

[0046] The detailed steps of the preparation method of low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns in this embodiment are as follows:

[0047] 1) Weigh out all raw materials according to the raw material ratio of the low thermal conductivity periclase-magnesium aluminum spinel refractory material described in Example 2;

[0048] 2) Place the aggregates of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles, and 0.1-0.9 mm magnesium aluminum spinel particles into a mixer and mix for 5 minutes; then add a binder solution accounting for 6% of the total weight of each raw material and mix for 5 minutes; then add the matrix magnesia powder, Mg(OH)2 powder, and magnesite powder and mix for 5 minutes to obtain the mixture.

[0049] The preparation process of the binder solution is as follows: Sodium lignosulfonate powder and water are mixed at a mass ratio of 1.3:1, and then placed in a mixer and stirred for 25 minutes to obtain the binder solution;

[0050] 3) The resulting mixture is machine-pressed at 160 MPa;

[0051] 4) Dry the molded product at 150℃ for 28 hours;

[0052] 5) After drying, heat to 1520℃ at a rate of 4℃ / min and hold for 4 hours; cool to obtain the product, low thermal conductivity periclase-magnesium aluminum spinel refractory material.

[0053] The low thermal conductivity periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have an apparent porosity of 23% and a bulk density of 2.75 g / cm³. 3 The compressive strength is 64MPa and the thermal conductivity is 1.85W / (m·K) (1000℃).

[0054] Example 3:

[0055] This invention relates to a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, expressed as a mass percentage, consisting of 5% 1-2mm magnesia sand particles, 48% 0.1-0.9mm magnesia sand particles, 3% 1-2mm magnesia-alumina spinel particles, 18% 0.1-0.9mm magnesia-alumina spinel particles, 17% magnesia sand powder, 6% Mg(OH)2 powder, and 3% magnesite powder.

[0056] The aggregate consists of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesia-alumina spinel particles, and 0.1-0.9 mm magnesia-alumina spinel particles; magnesia powder, Mg(OH)₂ powder, and magnesite powder are used as the matrix, and the sum of the aggregate and matrix constitutes the raw material. The magnesia particles used contain 98 wt% MgO; the magnesia-alumina spinel particles contain 70 wt% Al₂O₃; the magnesia powder contains 97 wt% MgO; the Mg(OH)₂ powder contains 99 wt% MgO; and the magnesite powder contains 46 wt% MgO.

[0057] The detailed steps of the preparation method of low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns in this embodiment are as follows:

[0058] 1) Weigh out all raw materials according to the raw material ratio of the low thermal conductivity periclase-magnesium aluminum spinel refractory material described in Example 3;

[0059] 2) Place the aggregates of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles, and 0.1-0.9 mm magnesium aluminum spinel particles into a mixer and mix for 7 minutes; then add a binder solution accounting for 4% of the total weight of each raw material and mix for 4 minutes; then add the matrix magnesia powder, Mg(OH)2 powder, and magnesite powder and mix for 7 minutes to obtain the mixture.

[0060] The preparation process of the binder solution is as follows: binder dextrin powder and water are mixed at a mass ratio of 1.4:1, and then placed in a mixer and stirred for 25 minutes to obtain the binder solution;

[0061] 3) The resulting mixture is machine-pressed at 180 MPa;

[0062] 4) Dry the molded product at 180℃ for 32 hours;

[0063] 5) After drying, heat to 1560℃ at a rate of 5℃ / min and hold for 5 hours; cool to obtain the product, low thermal conductivity periclase-magnesium aluminum spinel refractory material.

[0064] The low thermal conductivity periclase-magnesia-alumina spinel refractory material prepared in this embodiment was tested and found to have an apparent porosity of 22% and a bulk density of 2.78 g / cm³. 3 The compressive strength is 70MPa and the thermal conductivity is 1.9W / (m·K) (1000℃).

[0065] Example 4:

[0066] The present invention relates to a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, which, expressed as a percentage by mass, consists of 5% 1-2mm magnesia sand particles, 48% 0.1-0.9mm magnesia sand particles, 5% 1-2mm magnesia-alumina spinel particles, 8% 0.1-0.9mm magnesia-alumina spinel particles, 30% magnesia sand powder, 3% Mg(OH)2 powder, and 1% magnesite powder.

[0067] The aggregate consists of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesia-alumina spinel particles, and 0.1-0.9 mm magnesia-alumina spinel particles; magnesia powder, Mg(OH)₂ powder, and magnesite powder are used as the matrix, and the sum of the aggregate and matrix constitutes the raw material. The magnesia particles used contain 97.5 wt% MgO; the magnesia-alumina spinel particles contain 72 wt% Al₂O₃; the magnesia powder contains 97.5 wt% MgO; the Mg(OH)₂ powder contains 99.5 wt% MgO; and the magnesite powder contains 45 wt% MgO.

[0068] The detailed steps of the preparation method of low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns in this embodiment are as follows:

[0069] 1) Weigh out all raw materials according to the raw material ratio of the low thermal conductivity periclase-magnesium aluminum spinel refractory material described in Example 1;

[0070] 2) Place the aggregates of 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles, and 0.1-0.9 mm magnesium aluminum spinel particles into a mixer and mix for 8 minutes; then add a binder solution accounting for 5% of the total weight of each raw material and mix for 2 minutes; then add the matrix magnesia powder, Mg(OH)2 powder, and magnesite powder and mix for 8 minutes to obtain the mixture.

[0071] The preparation process of the binder solution is as follows: Sodium lignosulfonate powder and water are mixed at a mass ratio of 1.5:1, and then stirred in a mixer for 30 minutes to obtain the binder solution.

[0072] 3) The resulting mixture is machine-pressed at 140 MPa;

[0073] 4) Dry the molded product at 220℃ for 36 hours;

[0074] 5) After drying, heat to 1620℃ at a rate of 6℃ / min and hold for 6 hours; cool to obtain the product, low thermal conductivity periclase-magnesium aluminum spinel refractory material.

[0075] The low thermal conductivity periclase-magnesium aluminum spinel refractory material prepared in this embodiment was tested and found to have an apparent porosity of 19% and a bulk density of 2.80 g / cm³.3 The compressive strength is 75MPa and the thermal conductivity is 2.0W / (m·K) (1000℃).

[0076] Based on the relevant performance test data of the products prepared according to the above embodiments of the present invention, the bulk density of the magnesia-magnesia-alumina spinel refractory material prepared by the present invention is 2.70–2.80 g / cm³. 3 The apparent porosity is 19–24%; the compressive strength is 60–75 MPa; and the thermal conductivity is 1.8–2.0 W / (m·K) (1000℃). Therefore, the periclase-magnesia-alumina spinel refractory material prepared by this invention has low thermal conductivity, small pore size, and good resistance to salt and alkali corrosion, making it suitable for the upper transition zone of cement rotary kilns and achieving energy saving and emission reduction effects.

Claims

1. A low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, characterized in that, Expressed as a percentage by mass, the low thermal conductivity periclase-magnesia-alumina spinel refractory material is mainly composed of 3-5% 1-2mm magnesia particles, 30-48% 0.1-0.9mm magnesia particles, 3-5% 1-2mm magnesia-alumina spinel particles, 8-20% 0.1-0.9mm magnesia-alumina spinel particles, 17-32% magnesia powder, 3-6% Mg(OH)2 powder, and 1-3% magnesite powder.

2. The low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 1, characterized in that: The MgO content in the magnesia particles is ≥97wt%.

3. The low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 1, characterized in that: The magnesium aluminum spinel particles contain ≥65wt% Al2O3.

4. The low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 1, characterized in that: The particle size of the magnesia powder is <88μm; the MgO content in the magnesia powder is ≥97wt%.

5. The low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 1, characterized in that: The particle size of the Mg(OH)2 powder is <50μm; the MgO content in the Mg(OH)2 powder is ≥99wt%.

6. The low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 1, characterized in that: The particle size of the magnesite powder is <25μm; the MgO content in the magnesite powder is ≥45wt%.

7. A method for preparing a low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns, characterized in that, The preparation method includes the following steps: 1) Weigh out all raw materials according to the raw material proportioning ratio of the low thermal conductivity periclase-magnesium aluminum spinel refractory material as described in claim 1; 2) Mix 1-2 mm magnesia particles, 0.1-0.9 mm magnesia particles, 1-2 mm magnesium aluminum spinel particles and 0.1-0.9 mm magnesium aluminum spinel particles, then add 3-6% of a binder solution by weight of each raw material and mix; then add matrix magnesia powder, Mg(OH)2 powder and magnesite powder and mix evenly to obtain a mixture. 3) Press the resulting mixture into shape using a machine; 4) Dry the molded product; 5) The dried product is calcined and then cooled to obtain a low thermal conductivity periclase-magnesium aluminum spinel refractory material.

8. The method for preparing low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 7, characterized in that, The preparation method of the binder solution in step 2) is as follows: the binder and water are mixed at a mass ratio of 1.2 to 1.5:1, and then the mixture is stirred in a mixer for 20 to 30 minutes to obtain the binder solution.

9. The preparation method of the low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 7, characterized in that: The binder is sodium lignosulfonate powder, calcium lignosulfonate powder, or dextrin powder.

10. The method for preparing low thermal conductivity periclase-magnesia-alumina spinel refractory material for cement rotary kilns according to claim 7, characterized in that: In step 3), the pressure during machine pressing is controlled at 120–180 MPa; in step 4), the drying temperature is controlled at 110–220 °C and the drying time is controlled at 24–36 h; in step 5), the calcination rate is 3–6 °C / min and the temperature is raised to 1480–1620 °C and held for 4–6 h.