A heat-insulating castable for the thermal insulation layer of a lime rotary kiln, its preparation method and application

Abstract

The present invention discloses a heat-insulating castable for the insulation layer of a lime rotary kiln, its preparation method and application. A heat-insulating castable for the insulation layer of a lime rotary kiln according to the present invention comprises raw materials in the following parts by mass: 70 to 75 parts of premixed fine powder; 100 parts of cordierite particles; 9 to 12 parts of magnesium dihydrogen phosphate solution; wherein, the premixed fine powder comprises calcium magnesium melilite fine powder, enstatite fine powder, magnesium rhodonite fine powder and dodecacalcium heptaaluminate fine powder. The process for preparing the insulation layer of the lime rotary kiln with this castable is simple, without high-temperature firing or medium-temperature heat treatment, and the preparation cost is low; the heat-insulating castable for the insulation layer of the lime rotary kiln prepared can be quickly sintered and form good bonding strength under the condition of not exceeding 1000 °C, saving energy; the castable has a small thermal conductivity and a low thermal expansion coefficient; the castable does not need to add explosion-proof fibers and has good anti-explosion performance; the castable has good fluidity, is evenly dispersed, and has uniform heat transfer at high temperatures.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractory materials, and particularly relates to a heat-insulating castable for the insulation layer of a lime rotary kiln, a preparation method thereof, and an application thereof. Background Art

[0002] A lime rotary kiln belongs to a rotary heating device and is mainly used for calcining active lime. In the inner lining of a lime rotary kiln, the insulation layer (close to the cylinder side) does not participate in the calcination of active lime and is not in direct contact with media such as "smoke-gas-dust" on the hot surface. Its function is mainly to reduce the heat dissipation of the kiln body and lower the outer shell temperature of the kiln body.

[0003] At present, refractory materials for the insulation layer of a lime rotary kiln include various forms:

[0004] (1) In the form of precast bricks. The working lining and the refractory material of the insulation layer are integrally preformed to form an integrated structure, and then the precast bricks are masonry-fixed on the cylinder of the lime rotary kiln ( Zhang Honglei, Wang Yue, Ji Jiashan, et al. Development and Application of Composite Bricks for the Inner Lining of an Active Lime Rotary Kiln Refractories & Lime, 2014(1): 7-10 ). This technical means can better solve the integrity of the working layer and the insulation layer. However, during high-temperature service, the temperature of the working lining in contact with the hot surface is about 1500 - 1550 °C, and the heating temperature of the insulation layer generally does not exceed 1000 °C. Under a huge temperature gradient, the thermal expansion of the precast bricks is difficult to match synchronously, resulting in the peeling of the working lining and the insulation layer, and reducing the operation stability of the lime rotary kiln.

[0005] (2) By means of laying insulation cotton or heat-insulating boards. Laying insulation cotton or heat-insulating boards between the cylinder of the lime rotary kiln and the working lining can also play a role in reducing heat dissipation. This construction method is simple, the overall structure of the insulation layer is good, and the thermal conductivity coefficient of the insulation cotton or heat-insulating board is small, and the heat-insulating performance is good ( A Refractory and Energy-Saving Inner Lining Structure for a Lime Rotary Kiln CN202120249985.7 ). However, the strength of the insulation cotton or heat-insulating board is low, and it is extremely vulnerable to mechanical stress and crack, crush or even pulverize under the dynamic working conditions of the lime rotary kiln, deteriorating the working effect of the insulation layer, reducing the service life of the refractory material of the insulation layer, and even causing the kiln to stop.

[0006] (3) By means of masonry of heat-insulating bricks. Masonry of heat-insulating bricks in the lime rotary kiln is also one of the commonly used means to reduce heat loss ( A Three-Layer Lightweight Composite Brick and Its Preparation Method, CN201210079223.2 ). The heat-insulating bricks have high strength and small thermal conductivity coefficient, and at the same time solve the problems of the strength and heat insulation of the insulation layer. However, on the one hand, masonry of heat-insulating bricks increases the construction difficulty (the cylinder of the lime rotary kiln is circular), and there are also brick joints, resulting in uneven temperature distribution of the cylinder and causing deformation of the cylinder during the dynamic working process. In addition, the heat-insulating bricks are all fired at high temperature (fired at about 1300 - 1400 °C), thereby significantly increasing the material preparation cost.

[0007] (4) Select heat-insulating castable. Select heat-insulating castable on the cylinder body of the lime rotary kiln to form a heat-insulating protective layer by casting molding ( A High-Alumina Heat-Insulating Castable, CN201510742472.9 ), such technical means are widely used, and the overall connectivity of the lightweight heat-insulating castable is good, the heat-insulating effect is remarkable, the construction performance is good, and the development cost of the material is also low. However, the service temperature of the heat-insulating layer of the lime rotary kiln cylinder generally does not exceed 1000 °C, and the sintering performance of the heat-insulating castable becomes a new difficulty at this temperature. When the heat-insulating castable is difficult to sinter quickly and generate strength, the dynamic operation of the lime rotary kiln cylinder directly leads to the shedding and damage of the heat-insulating castable. In addition, the cost of refractory raw materials such as high-aluminum materials, bauxite materials, mullite and corundum is high, which also greatly restricts the practical application of the heat-insulating castable for lime rotary kilns. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a heat-insulating castable for the heat-insulating layer of a lime rotary kiln, its preparation method and application. The process of preparing the heat-insulating layer of the lime rotary kiln with this castable is simple, without high-temperature firing or medium-temperature heat treatment, and the preparation cost is low; the heat-insulating layer of the lime rotary kiln prepared by using the heat-insulating castable of the present invention can be quickly sintered and form good bonding strength under the condition of not exceeding 1000 °C, saving energy; the heat-insulating layer of the lime rotary kiln has a small thermal conductivity and a low thermal expansion coefficient; the castable does not need to add explosion-proof fibers and has good anti-explosion performance; the castable has good fluidity, is evenly dispersed, and has uniform heat transfer at high temperature.

[0009] The present invention adopts the following technical solutions:

[0010] A heat-insulating castable for the heat-insulating layer of a lime rotary kiln, comprising the following raw materials in parts by mass: 70-75 parts of premixed fine powder; 100 parts of cordierite particles; 9-12 parts of magnesium dihydrogen phosphate solution; wherein, the premixed fine powder includes calcium magnesium melilite fine powder, enstatite fine powder, magnesium rhodonite fine powder and dodecacalcium heptaaluminate fine powder.

[0011] Further, the mass ratio of the calcium magnesium melilite fine powder: enstatite fine powder: magnesium rhodonite fine powder: dodecacalcium heptaaluminate fine powder is 100:(70-80):(45-60):(15-20).

[0012] Further, the concentration of the magnesium dihydrogen phosphate solution is 15-18 wt%.

[0013] Further, the particle size of the calcium magnesium melilite fine powder is 30-40 μm.

[0014] Further, the particle size of the enstatite fine powder is 50-60 μm.

[0015] Further, the particle size of the magnesium rhodonite fine powder is 70-80 μm.

[0016] Furthermore, the particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

[0017] Furthermore, the particle size of the cordierite particles is 0.1 - 4 mm, and the particle size is discontinuously distributed. The mass ratio of the [0.1 mm - 0.5 mm] particles, [1.5 mm - 2 mm] particles, and [3.5 mm - 4 mm] particles is (20 - 30):(60 - 65):(10 - 15).

[0018] For the preparation method of a heat - insulating castable for the insulation layer of a lime rotary kiln as described above, the premixed fine powder and cordierite particles are mixed evenly according to the mass ratio to obtain a mixture, and then a certain amount of magnesium dihydrogen phosphate solution is added to the mixture and stirred for a period of time to obtain the heat - insulating castable for the insulation layer of the lime rotary kiln.

[0019] Furthermore, stir for 8 - 12 minutes.

[0020] A preparation method for the insulation layer of a lime rotary kiln includes the following steps:

[0021] S1. Prepare the heat - insulating castable for the insulation layer of the lime rotary kiln by using the preparation method described in claim 8 or 9;

[0022] S2. Cast and form the heat - insulating castable for the insulation layer of the lime rotary kiln;

[0023] S3. Cure the formed sample at 25 - 30 °C for 4 - 6 hours and then demold it, and then cure it at 100 - 110 °C for 4 - 6 hours to obtain the insulation layer of the lime rotary kiln.

[0024] No special equipment or instruments are required in the preparation of the present invention, and the process is simple.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) When the heat - insulating castable for the insulation layer of the lime rotary kiln prepared by the present invention is cast to form the insulation layer of the lime rotary kiln, no sintering or heat treatment is required. Good early strength is formed through the chemical combination generated by the hydration - ionization of dodecacalcium heptaaluminate and magnesium dihydrogen phosphate solution, saving energy and resources.

[0027] (2) The present invention utilizes the low thermal conductivity characteristics of raw material components such as calcium - magnesium melilite, and combines with the large lattice voids of enstatite and magnesium rhodonite to form rapid sintering at a temperature not exceeding 1000 °C, forming closed pores inside the material. On the one hand, it reduces the thermal conductivity of the insulation layer of the lime rotary kiln, and at the same time reduces the thermal expansion coefficient of the insulation layer of the lime rotary kiln, and forms a high - strength solid - solution bond, improving the service strength of the insulation layer of the lime rotary kiln.

[0028] (3) The castable prepared by the present invention does not need to add explosion-proof fibers. By using the discontinuous distribution of particles such as cordierite to form the "loosest packing", it not only does not need to add other additives, reducing costs, but also increases the closed porosity of the insulation layer of the lime rotary kiln, reduces the thermal conductivity of the insulation layer of the lime rotary kiln, and reduces the heat loss of the lime rotary kiln.

[0029] (4) The present invention premixes according to the flow characteristics of each refractory aggregate component, improves the dispersibility and uniformity of the matrix fine powder, improves the flow performance of the castable components, is conducive to the construction of the castable, and at the same time ensures the good integrity of the insulation layer of the lime rotary kiln, which is conducive to uniform heat transfer at high temperatures.

[0030] The heat-insulating castable for the insulation layer of the lime rotary kiln prepared by the present invention is detected as follows: the vibration flow value of the heat-insulating castable for the insulation layer of the lime rotary kiln is 135 - 138 mm, the thermal conductivity of the insulation layer of the lime rotary kiln is 0.58 - 0.69 W / (m·K), the high-temperature hot-state compressive strength (1000°C × 0.5 h) is 54 - 57 MPa, and the thermal expansion rate (1000°C) is 0.14 - 0.21%.

[0031] Therefore, the process for preparing the insulation layer of the lime rotary kiln with this castable is simple, without high-temperature firing or medium-temperature heat treatment, and the preparation cost is low; the heat-insulating castable for the insulation layer of the lime rotary kiln prepared can be quickly sintered and form good bonding strength under the condition of not exceeding 1000°C, saving energy; the castable has a small thermal conductivity and a low thermal expansion coefficient; the castable does not need to add explosion-proof fibers and has good anti-burst performance; the castable has good fluidity, is evenly dispersed, and has uniform heat transfer at high temperatures. Description of the Drawings

[0032] Figure 1 It is a photograph of the appearance of the test sample of the heat-insulating castable for the insulation layer of the lime rotary kiln in Example 1 after heat treatment at 1000°C for 4 hours;

[0033] Figure 2 It is a SEM photograph of the test sample of the heat-insulating castable for the insulation layer of the lime rotary kiln in Example 1 after heat treatment at 1000°C for 4 hours;

[0034] Figure 3 For Figure 2 SEM photograph of the magnified microscopic area of the matrix. Detailed Embodiments

[0035] The following are specific embodiments of the present invention and in combination with the drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0036] Example 1

[0037] Step 1: Weigh the calcium magnesium melilite fine powder, enstatite fine powder, magnesium rhodonite fine powder, and dodecacalcium heptaaluminate fine powder according to the mass ratio of 100:75:60:16, add them to a roller mixer and mix for 42 minutes to obtain a premixed fine powder material;

[0038] Step 2: Weigh the cordierite granules and the premixed fine powder material according to the mass ratio of 100:73, add them to a planetary mixer and mix for 20 minutes to obtain a mixed material;

[0039] Step 3: Add a magnesium dihydrogen phosphate solution with a certain concentration to the mixed material and stir for 8 minutes to obtain the heat-insulating castable for the lime rotary kiln insulation layer.

[0040] Among them, the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite granules is 11:100, and the concentration of the magnesium dihydrogen phosphate solution is 15 wt%.

[0041] The particle size of the calcium magnesium melilite fine powder is 30 - 40 μm.

[0042] The particle size of the enstatite fine powder is 50 - 60 μm.

[0043] The particle size of the magnesium rhodonite fine powder is 70 - 80 μm.

[0044] The particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

[0045] The particle size of the cordierite granules is 0.1 - 4 mm, and the particle size is discontinuously distributed. Among them, the mass ratio of the [0.1 mm - 0.5 mm] granules, [1.5 mm - 2 mm] granules, and [3.5 mm - 4 mm] granules is 20:60:15.

[0046] The heat-insulating castable for the lime rotary kiln insulation layer prepared in this example is cast and molded, demolded after curing at 25°C for 4 hours, and then cured at 110°C for 4 hours to obtain a test sample of the heat-insulating castable for the lime rotary kiln insulation layer. After testing, the vibration flow value (GB / T4513.4 - 2017) is 136 mm, the thermal conductivity (GB / T36133 - 2019) is 0.59 W / (m·K), the hot compressive strength at high temperature (1000°C × 0.5 h) (GB / T34218 - 2017) is 57 MPa, and the thermal expansion rate (GB / T7320 - 2018) (1000°C) is 0.16%.

[0047] Figure 1 Shown in the figure is the appearance photo of the test sample of the heat-insulating castable for the lime rotary kiln insulation layer in Example 1 after heat treatment at 1000°C for 4 hours. It can be seen that the appearance structure of the test sample is intact without any damage, indicating that the test sample has good demolding strength and high-temperature strength;

[0048] Figure 2This is a SEM photo of the test sample of the thermal insulation castable of the lime rotary kiln thermal insulation layer of Example 1 after heat treatment at 1000°C for 4 hours. It can be seen that the internal structure of the test sample is dense, and the pores formed are all closed pores, without through-connected pores, indicating that the test sample is lightweight and heat-insulating;

[0049] Figure 3 for Figure 2 From the SEM photograph of the enlarged microscopic area of the matrix, it can be seen that the pore structure of the matrix area of the test sample is uniform, and the grains are connected in a three-dimensional network chain, indicating that the test sample has uniform pores and high strength.

[0050] Example 2

[0051] Step 1: mix the fine powder of calcite: the fine powder of enstatite: the fine powder of magnesia rhodonite: the fine powder of calcium dodecanite in a mass ratio of 100:70:45:15, add the mixture into a roller mixer and mix for 45 minutes to obtain a premixed fine powder;

[0052] Step 2: add the cordierite particles to the premixed fine powder in a mass ratio of 100:75 into a planetary mixer and mix for 15 minutes to obtain a mixture;

[0053] Step 3: Add a certain concentration of magnesium dihydrogen phosphate solution to the mixture and stir for 12 minutes to obtain the lime rotary kiln insulation layer insulation castable.

[0054] The mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles is 12:100, and the concentration of the magnesium dihydrogen phosphate solution is 17 wt %.

[0055] The particle size of the fine powder of calcite is 30-40 μm.

[0056] The particle size of the enstatite fine powder is 50 to 60 μm.

[0057] The particle size of the magnesium rhodonite fine powder is 70 to 80 μm.

[0058] The particle size of the fine powder of dodecaluminate heptaaluminate is 10 to 25 μm.

[0059] The particle size of cordierite particles is 0.1 to 4 mm, and the particle size is discontinuously distributed, wherein the mass ratio of [0.1 mm to 0.5 mm] particles, [1.5 mm to 2 mm] particles, and [3.5 mm to 4 mm] particles is 30:65:10.

[0060] The heat-insulating castable for the lime rotary kiln insulation layer prepared in this example was cast into shape, demolded after curing at 28°C for 6 hours, and then cured at 105°C for 5 hours to obtain a test sample of the heat-insulating castable for the lime rotary kiln insulation layer. After testing, the vibration flow value was 138 mm, the thermal conductivity was 0.65 W / (m·K), the high-temperature hot-state compressive strength (1000°C × 0.5 h) was 55 MPa, and the thermal expansion rate (1000°C) was 0.20%.

[0061] Example 3

[0062] First step: Ingredients were proportioned according to the mass ratio of calcium magnesium melilite fine powder : enstatite fine powder : magnesium rhodonite fine powder : dodecacalcium heptaaluminate fine powder being 100 : 80 : 58 : 20, and added to a roller mixer and mixed for 50 minutes to obtain pre-mixed fine powder materials;

[0063] Second step: Ingredients were proportioned according to the mass ratio of cordierite particles : pre-mixed fine powder materials being 100 : 72, added to a planetary mixer, and mixed for 16 minutes to obtain a mixed material;

[0064] Third step: A certain concentration of magnesium dihydrogen phosphate solution was added to the mixed material and stirred for 10 minutes to obtain the heat-insulating castable for the lime rotary kiln insulation layer.

[0065] Among them, the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles was 9 : 100, and the concentration of the magnesium dihydrogen phosphate solution was 15 wt%.

[0066] The particle size of the calcium magnesium melilite fine powder was 30 - 40 μm.

[0067] The particle size of the enstatite fine powder was 50 - 60 μm.

[0068] The particle size of the magnesium rhodonite fine powder was 70 - 80 μm.

[0069] The particle size of the dodecacalcium heptaaluminate fine powder was 10 - 25 μm.

[0070] The heat-insulating castable for the lime rotary kiln insulation layer prepared in this example was cast into shape, demolded after curing at 30°C for 5 hours, and then cured at 110°C for 6 hours to obtain a test sample of the heat-insulating castable for the lime rotary kiln insulation layer. After testing, the vibration flow value was 135 mm, the thermal conductivity was 0.62 W / (m·K), the high-temperature hot-state compressive strength (1000°C × 0.5 h) was 56 MPa, and the thermal expansion rate (1000°C) was 0.17%.

[0071] The particle size of the cordierite particles was 0.1 - 4 mm, and the particle size was discontinuously distributed, among which the mass ratio of the [0.1 mm - 0.5 mm] particles, [1.5 mm - 2 mm] particles, and [3.5 mm - 4 mm] particles was 25 : 62 : 13.

[0072] Example 4

[0073] Step 1: Weigh the calcium magnesium melilite fine powder, enstatite fine powder, magnesium rhodonite fine powder, and dodecacalcium heptaaluminate fine powder at a mass ratio of 100:70:54:18, add them to a roller mixer and mix for 40 minutes to obtain a premixed fine powder material;

[0074] Step 2: Weigh cordierite particles and the premixed fine powder material at a mass ratio of 100:70, add them to a planetary mixer and mix for 18 minutes to obtain a mixed material;

[0075] Step 3: Add a magnesium dihydrogen phosphate solution with a certain concentration to the mixed material and stir for 10 minutes to obtain a heat-insulating castable for the insulation layer of a lime rotary kiln.

[0076] Among them, the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles is 10:100, and the concentration of the magnesium dihydrogen phosphate solution is 18 wt%.

[0077] The particle size of the calcium magnesium melilite fine powder is 30 - 40 μm.

[0078] The particle size of the enstatite fine powder is 50 - 60 μm.

[0079] The particle size of the magnesium rhodonite fine powder is 70 - 80 μm.

[0080] The particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

[0081] The particle size of the cordierite particles is 0.1 - 4 mm, and the particle size is discontinuously distributed. Among them, the mass ratio of the [0.1 mm - 0.5 mm] particles, [1.5 mm - 2 mm] particles, and [3.5 mm - 4 mm] particles is 20:60:10.

[0082] Cast and form the heat-insulating castable for the insulation layer of the lime rotary kiln prepared in this example, demold it after curing for 4 hours at 28 °C, and then cure it for 5 hours at 100 °C to obtain a test sample of the heat-insulating castable for the insulation layer of the lime rotary kiln. After testing, the vibration flow value is 136 mm, the thermal conductivity is 0.66 W / (m·K), the high-temperature hot-state compressive strength (1000 °C × 0.5 h) is 54 MPa, and the thermal expansion rate (1000 °C) is 0.15%.

[0083] Comparative Example 1

[0084] Step 1: Weigh the calcium magnesium melilite fine powder, enstatite fine powder, magnesium rhodonite fine powder, and dodecacalcium heptaaluminate fine powder at a mass ratio of 100:40:54:18, add them to a roller mixer and mix for 40 minutes to obtain a premixed fine powder material;

[0085] Step 2: Weigh the cordierite particles and the premixed fine powder at a mass ratio of 100:50, add them to a planetary mixer, and mix for 18 minutes to obtain a mixed material.

[0086] Step 3: Add a magnesium dihydrogen phosphate solution with a certain concentration to the mixed material and stir for 10 minutes to obtain the insulating castable for the lime rotary kiln insulation layer.

[0087] Among them, the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles is 10:100, and the concentration of the magnesium dihydrogen phosphate solution is 18 wt%.

[0088] The particle size of the calcium magnesium melilite fine powder is 30 - 40 μm.

[0089] The particle size of the enstatite fine powder is 50 - 60 μm.

[0090] The particle size of the rhodonite fine powder is 70 - 80 μm.

[0091] The particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

[0092] The particle size of the cordierite particles is 0.1 - 4 mm, and the particle size shows a discontinuous distribution. Among them, the mass ratio of the [0.1 mm - 0.5 mm] particles, the [1.5 mm - 2 mm] particles, and the [3.5 mm - 4 mm] particles is 20:60:10.

[0093] Cast and form the insulating castable for the lime rotary kiln insulation layer prepared in this comparative example. After curing for 4 hours at 28°C and then demolding, and then curing for 5 hours at 100°C, the test samples are obtained. After testing, the vibration flow value is 115 mm, the thermal conductivity is 0.44 W / (m·K), the high-temperature hot-state compressive strength (1000°C × 0.5 h) is 23 MPa, and the thermal expansion rate (1000°C) is 0.38%.

[0094] It can be found that reducing the addition amount of the enstatite fine powder and reducing the amount of the premixed fine powder result in a decrease in the dispersibility of the castable and a weakening of the fluidity, which in turn leads to a decrease in the sintering solid solution degree under high-temperature heat treatment conditions, weakening the sintering performance of the castable, and a significant decrease in its mechanical strength (high-temperature hot-state compressive strength).

[0095] Comparative Example 2

[0096] Step 1: Weigh the calcium magnesium melilite fine powder, enstatite fine powder, rhodonite fine powder, and dodecacalcium heptaaluminate fine powder at a mass of 100:80:58:20, add them to a roller mixer and mix for 50 minutes to obtain a premixed fine powder.

[0097] Step 2: Weigh the cordierite particles and the premixed fine powder at a mass ratio of 100:72, add them to a planetary mixer, and mix for 16 minutes to obtain a mixed material.

[0098] Step 3: Add a magnesium dihydrogen phosphate solution with a certain concentration to the mixture and stir for 10 minutes to obtain the insulating castable for the lime rotary kiln insulation layer.

[0099] Among them, the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles is 4:100, and the concentration of the magnesium dihydrogen phosphate solution is 5 wt%.

[0100] The particle size of the calcium magnesium melilite fine powder is 30 - 40 μm.

[0101] The particle size of the enstatite fine powder is 50 - 60 μm.

[0102] The particle size of the rhodonite fine powder is 70 - 80 μm.

[0103] The particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

[0104] The particle size of the cordierite particles is 0.1 - 4 mm, and the particle size is discontinuously distributed. Among them, the mass ratio of the [0.1 mm - 0.5 mm] particles, [1.5 mm - 2 mm] particles, and [3.5 mm - 4 mm] particles is 20:60:10.

[0105] Cast and form the insulating castable for the lime rotary kiln insulation layer prepared in this comparative example. Demold it after curing at 30 °C for 5 hours, and then cure it at 110 °C for 6 hours to obtain the insulating castable for the lime rotary kiln insulation layer. After testing, the vibration flow value is 103 mm, the thermal conductivity is 1.27 W / (m·K), the high-temperature hot-state compressive strength (1000 °C × 0.5 h) is 14 MPa, and the thermal expansion rate (1000 °C) is 0.11%.

[0106] It can be found that reducing the mass ratio of the magnesium dihydrogen phosphate solution to the cordierite particles and reducing the concentration of the magnesium dihydrogen phosphate solution weaken the modified combination of the cordierite particles and other components, weaken the bonding strength between the material components, and reduce the fluidity of the castable; at the same time, the reduction of the concentration of the magnesium dihydrogen phosphate solution leads to poor heat treatment sintering performance, and further weakens the high-temperature mechanical strength of the castable.

[0107] Where not covered above, it shall apply to the prior art.

[0108] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration purposes and not for limiting the scope of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways of substitution, but will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should all be included within the protection scope of the present invention.

Claims

1. A heat-insulating castable for the insulation layer of a lime rotary kiln, characterized in that, It includes raw materials in the following parts by mass: 70 - 75 parts of premixed fine powder; 100 parts of cordierite particles; 9 - 12 parts of magnesium dihydrogen phosphate solution; wherein, the premixed fine powder includes calcium magnesium melilite fine powder, enstatite fine powder, rhodonite fine powder and dodecacalcium heptaaluminate fine powder; The mass ratio of the calcium magnesium melilite fine powder : enstatite fine powder : rhodonite fine powder : dodecacalcium heptaaluminate fine powder is 100 : (70 - 80) : (45 - 60) : (15 - 20).

2. The heat-insulating castable for the insulation layer of a lime rotary kiln according to claim 1, characterized in that, The concentration of the magnesium dihydrogen phosphate solution is 15 - 18 wt%.

3. The thermal insulation castable for the insulation layer of a lime rotary kiln according to claim 1, wherein, The particle size of the calcium magnesium melilite fine powder is 30 - 40 μm.

4. The heat-insulating castable for the insulating layer of a lime rotary kiln according to claim 1, characterized in that, The particle size of the enstatite fine powder is 50 - 60 μm.

5. The heat-insulating castable for the insulation layer of a lime rotary kiln as described in claim 1, wherein The particle size of the rhodonite fine powder is 70 - 80 μm; the particle size of the dodecacalcium heptaaluminate fine powder is 10 - 25 μm.

6. The heat-insulating castable for the insulation layer of a lime rotary kiln according to claim 1, wherein The particle size of the cordierite particles is 0.1 - 4 mm, and the particle size is discontinuously distributed, wherein the mass ratio of the [0.1 mm - 0.5 mm] particles, [1.5 mm - 2 mm] particles and [3.5 mm - 4 mm] particles is (20 - 30) : (60 - 65) : (10 - 15).

7. The preparation method of a heat-insulating castable for the thermal insulation layer of a lime rotary kiln according to any one of claims 1-6, characterized in that, Mix the premixed fine powder and cordierite particles evenly according to the mass ratio to obtain a mixture, and then add a certain amount of magnesium dihydrogen phosphate solution to the mixture and stir for a period of time to obtain the heat - insulating castable for the insulation layer of the lime rotary kiln.

8. The preparation method according to claim 7, characterized in that, Stir for 8 - 12 minutes.

9. A preparation method for the thermal insulation layer of a lime rotary kiln, characterized in that, It includes the following steps: S1. Prepare the heat - insulating castable for the insulation layer of the lime rotary kiln by using the preparation method described in claim 7 or 8; S2. Cast and form the heat - insulating castable for the insulation layer of the lime rotary kiln; S3. Cure the formed sample at 25 - 30 °C for 4 - 6 hours and then demold it, and then cure it at 100 - 110 °C for 4 - 6 hours to obtain the insulation layer of the lime rotary kiln.

Images