A semi-silica high-temperature foamed insulating refractory material and its preparation method

Abstract

The present invention relates to a semi-siliceous high-temperature foamed insulating refractory material and a preparation method thereof, and relates to the technical field of insulating refractory materials. The present invention mainly comprises the following steps: 26-54wt% of a low-aluminum-aluminum siliceous natural raw material, 40-65.5wt% of silica, 0.5-4wt% of kyanite, 0.2-0.5wt% of a high-temperature foaming agent, and 4wt% of a soft clay binder are mixed according to mass percentage to obtain a mixed raw material; the mixed raw material is then wet-ground into 325 mesh, placed in a drying tower for dehydration, granulated, and formed under a pressure of 100-120 MPa to obtain a green body; and finally, the green body is placed in a high-temperature furnace at 1500-1580°C for 1-2 hours and calcined, and after cooling and taking out of the furnace, the semi-siliceous high-temperature foamed insulating refractory material is obtained. The semi-siliceous high-temperature foamed insulating refractory material of the present invention has silicon dioxide as its main chemical component, is foamed in situ by high-temperature calcination, and does not introduce low-melting-point flux. The prepared product has low thermal conductivity, good mechanical properties and high operating temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and in particular relates to a semi-silica high-temperature foamed heat-insulating refractory material and a preparation method thereof. Background Art

[0002] High-temperature foaming material is a ceramic-based high-porosity material with a three-dimensional network structure. It has excellent properties such as light weight and high strength, thermal insulation, sound insulation and noise reduction, corrosion resistance, and aging resistance. Among them, the closed porosity in the high-temperature foaming material is high, which greatly reduces the convective heat transfer efficiency during the heat transfer process, and therefore exhibits excellent thermal insulation performance. High-temperature foaming materials have received widespread attention and attention in the building insulation industry. The invention patent with publication number CN107353032A provides a method for preparing a foamed ceramic insulation board, which uses a large amount of low-melting-point alkaline oxides in industrial inorganic hazardous waste and refractory clay tailings as flux, foams at 1100~1300℃, and prepares a volume density of 0.3~0.8 g / cm 3 The invention patent with publication number CN113387720A uses coal gangue and potassium feldspar as the main raw materials, adds flux and foaming agent, and foams at 800-900℃ to obtain a foamed ceramic with a bulk density of 130-230kg / m 3 , a foamed thermal insulation material with a compressive strength of 2.5~3.3MPa. The implementation of the above invention patents has enriched the raw materials and preparation methods for high-temperature foaming materials, but a large amount of flux is introduced in the preparation process of high-temperature foaming materials, which are generally fired at below 1300°C. Their refractoriness is low and it is difficult to meet the conditions for use in high-temperature industries. In particular, the introduction of feldspar minerals or alkaline oxides will greatly reduce the temperature and liquid viscosity of liquid phase formation, thereby greatly reducing the use temperature of the foaming material. Therefore, it is necessary to further increase the high-temperature foaming temperature and refractoriness of high-temperature foaming materials and improve their high-temperature performance in order to meet the conditions for application in high-temperature industries.

[0003] Semi-silica refractory is a traditional high-temperature material used in high-temperature furnace linings such as permanent linings of steel ladles and preheating zones of cement kilns. It has the characteristics of low alkaline oxide impurity content, excellent acid resistance, and good volume stability at high temperatures of 1000-1400°C. Cai Shuping et al. (Trial Production of High-Silica Semi-Silica Bricks [J], Refractories (Technical Brief), 1999, 2:119) used silica and waste silica brick particles as aggregates, pyrophyllite and industrial alumina as fine powders, and iron-phosphorus as mineralizers. After calcination at 1330°C, a semi-silica brick with a volume density of 2.0 g / cm was prepared. 3Dense semi-silica bricks of about 10000 square meters. Traditional semi-silica refractories have low refractoriness and relatively simple functions, resulting in low added value for this type of product. Semi-silica refractories have low thermal conductivity, making them ideal insulating refractory materials. However, there are few reports on the research and development of semi-silica insulating refractories. Due to the chemical composition characteristics of semi-silica refractories, which have high SiO2 content and low Al2O3 content, they have stable performance in the insulation temperature range of kilns (1100-1400°C) and easily melt into a high-viscosity liquid phase at higher temperatures (≥1500°C), showing potential for the preparation of high-temperature foam insulation materials. Therefore, it is necessary to develop new process technologies to prepare semi-silica insulation materials with a large number of closed pore structures. This can improve the thermal insulation function of semi-silica refractories, reduce energy emissions from high-temperature facilities, and have a positive impact on the carbon standards of high-temperature industries. Summary of the Invention

[0004] The purpose of the present invention is to provide a semi-siliceous high-temperature foamed insulating refractory material and a preparation method thereof. The semi-siliceous high-temperature foamed insulating refractory material prepared by the present invention has the characteristics of low thermal conductivity, good mechanical properties and high operating temperature.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a semi-siliceous high-temperature foamed insulating refractory material comprises the following steps:

[0007] First, 26-54 wt% of a low-aluminum-aluminum siliceous natural raw material, 40-65.5 wt% of silica, 0.5-4 wt% of kyanite, 0.2-0.5 wt% of a high-temperature foaming agent, and 4 wt% of a soft clay binder are mixed according to mass percentage to obtain a mixed raw material;

[0008] Then, the mixed raw materials are wet-ground into 325 mesh, put into a drying tower for dehydration, granulated, and formed under a pressure of 100-120 MPa to obtain a green body;

[0009] Finally, the green body is placed in a high-temperature furnace at 1500-1580°C for 1-2 hours for calcination, and after being cooled and taken out of the furnace, a semi-siliceous high-temperature foamed insulating refractory material is obtained.

[0010] Furthermore, the low-aluminum-aluminum siliceous natural raw material is one or both of high-silicon pyrophyllite and silicon-rich sillimanite, and the particle size is ≤200 mesh.

[0011] Furthermore, the SiO2 content in the high-silicon pyrophyllite is 75%~85wt%, and the Al2O3 content is 15%~20wt%.

[0012] Furthermore, the SiO2 content in the silicon-rich sillimanite is 65% to 70wt%, and the Al2O3 content is 30% to 40wt%.

[0013] Furthermore, the silica is taken from natural minerals, wherein the SiO2 content is ≥99.0wt% and the raw material particle size is ≤200 mesh.

[0014] Furthermore, the high-temperature foaming agent is one or two of TiN, TiAlN, SiC, and B4C, and the raw material particle size is ≤400 mesh.

[0015] Furthermore, the soft clay binder is one of Guangxi white mud, ball clay, and kaolin clay.

[0016] Furthermore, the semi-siliceous high-temperature foamed insulating refractory material prepared by the preparation method has a main crystalline phase of cristobalite, a secondary crystalline phase of mullite, and contains ≥30% of a silicon-rich glass phase.

[0017] Furthermore, the semi-siliceous high-temperature foamed insulating refractory material prepared by the preparation method has a closed porosity between 60% and 90%, a compressive strength between 8 and 20 MPa, a refractoriness under load between 1350 and 1450°C, and a thermal conductivity between 0.08 and 0.22 W / (m·k).

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention uses low-aluminum aluminum-siliceous natural raw materials and silica as the main raw materials. The raw materials are of high purity, low alkaline oxide impurity content, and no flux is introduced, which greatly improves the use temperature of the high-temperature foaming material. During the heating process of the blank, the decomposition of kyanite and sillimanite in the raw materials and the volume expansion effect accompanied by the transformation of the silica crystal form produce a large number of evenly distributed initial micropores; during the high-temperature calcination stage, the added high-temperature foaming agent further assists in pore formation, and the resulting high-temperature foaming material has a uniform pore size distribution. The prepared semi-siliceous high-temperature foaming insulation refractory material has cristobalite as the main crystal phase, and the secondary crystal phase mullite grains are needle-shaped and interspersed between the silicon-rich glass phase, which plays a role in improving the strength and toughness of the foaming insulation material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a photo of the high-temperature foamed ceramic prepared in Example 1 of the present invention;

[0021] Figure 2 This is the XRD pattern of the high-temperature foamed ceramic prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions and effects of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto. Example 1

[0023] The present embodiment provides a method for preparing a semi-siliceous high-temperature foamed insulating refractory material, comprising the following steps:

[0024] A mixed raw material is obtained by mixing 42.25wt% of high-silicon pyrophyllite, 49.25wt% of silica, 4% of kyanite, 0.5% of SiC and 4wt% of Guangxi white mud according to mass percentage; the mixed raw material is then wet-ground into 325 mesh, placed in a drying tower for dehydration, granulated, and formed under a pressure of 120MPa to obtain a green body; finally, the green body is placed in a high-temperature furnace and calcined at 1510°C for 1h, and after cooling and taking out of the furnace, a semi-siliceous high-temperature foamed insulating refractory material is obtained.

[0025] The high-silicon pyrophyllite raw material in this example has a SiO2 content of 78.83wt% and an Al2O3 content of 18.55wt% after burning; the SiO2 content in the silica is 99.56wt%; the Al2O3 content in the kyanite is 50.0wt%, and the raw material particle size is ≤325 mesh; the particle sizes of the SiC and Guangxi white mud raw materials are both ≤400 mesh.

[0026] The technical indicators of the high-temperature foamed insulating refractory material prepared in this example are: closed porosity of 89.0% and bulk density of 0.38g / cm 3 , compressive strength is 10.5 MPa, refractoriness under load is 1400℃, thermal conductivity is 0.12W / (m·k). Figure 1 It can be seen that the internal pore distribution and pore size of the prepared high-temperature foamed ceramics are uniform, the pore walls are thin and the pores are highly circular. Example 2

[0027] The present embodiment provides a method for preparing a semi-siliceous high-temperature foamed insulating refractory material, comprising the following steps:

[0028] 12.54 wt% of silicon-rich sillimanite, 33.2 wt% of high-silicon pyrophyllite, 49.56 wt% of silica, 0.5 wt% of kyanite, 0.2 wt% of SiC and 4 wt% of Guangxi white mud are mixed according to mass percentage to obtain a mixed raw material; the mixed raw material is then wet-ground into 325 mesh, placed in a drying tower for dehydration, granulated, and formed under a pressure of 120 MPa to obtain a green body; finally, the green body is placed in a high-temperature furnace and calcined at 1550°C for 1 hour, and after cooling and taking out of the furnace, a semi-siliceous high-temperature foamed insulating refractory material is obtained.

[0029] In this example, the SiO2 content of the pyrophyllite raw material after burning is 82.71wt%, and the Al2O3 content is 16.01wt%; the SiO2 content of the sillimanite raw material after burning is 65.33wt%, and the Al2O3 content is 33.65wt%; the SiO2 content in the silica is 99.56wt%; the Al2O3 content in the kyanite is 50.0wt%, and the raw material particle size is ≤325 mesh; the particle size of the SiC and Guangxi white mud raw materials are both ≤400 mesh.

[0030] The technical indicators of the high-temperature foamed insulating refractory material prepared in this example are: closed porosity of 76.5% and bulk density of 0.56g / cm 3 , compressive strength is 14.2MPa, refractoriness under load is 1440℃, thermal conductivity is 0.18W / (m·k). Figure 2 The XRD pattern of high-temperature foamed ceramics shows that the main crystal phase is cristobalite phase and the secondary crystal phase is mullite phase. Example 3

[0031] The present embodiment provides a method for preparing a semi-siliceous high-temperature foamed insulating refractory material, comprising the following steps:

[0032] 35wt% of silicon-rich sillimanite, 60wt% of silica, 0.5% of kyanite, 0.5% of SiC and 4wt% of Guangxi white mud are mixed according to mass percentage to obtain a mixed raw material; the mixed raw material is then wet-ground into 325 mesh, placed in a drying tower for dehydration, granulated, and formed under a pressure of 120MPa to obtain a green body; finally, the green body is placed in a high-temperature furnace and calcined at 1530°C for 1h, and after cooling and taking out of the furnace, a semi-siliceous high-temperature foamed insulating refractory material is obtained.

[0033] In this example, the SiO2 content of the sillimanite raw material after burning is 65.33 wt%, and the Al2O3 content is 33.65 wt%; the SiO2 content in the silica is 99.56 wt%; the Al2O3 content in the kyanite is 50.0 wt%, and the raw material particle size is ≤325 mesh; the particle sizes of the SiC and Guangxi white mud raw materials are both ≤400 mesh.

[0034] The technical indicators of the high-temperature foamed insulating refractory material prepared in this example are: closed porosity of 80.5% and bulk density of 0.45g / cm 3 , compressive strength is 12.3MPa, load softening temperature is 1420℃, and thermal conductivity is 0.16W / (m·k).

[0035] The high-temperature foaming agent in the above embodiment may also be TiN, TiAlN or B4C.

[0036] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a semi-siliceous high-temperature foamed insulating refractory material, characterized in that: The method comprises the following steps: First, 26-54 wt% of a low-aluminum-aluminum siliceous natural raw material, 40-65.5 wt% of silica, 0.5-4 wt% of kyanite, 0.2-0.5 wt% of a high-temperature foaming agent, and 4 wt% of a soft clay binder are mixed according to mass percentage to obtain a mixed raw material; Then, the mixed raw materials are wet-ground into 325 mesh, put into a drying tower for dehydration, granulated, and formed under a pressure of 100-120 MPa to obtain a green body; Finally, the green body is placed in a high temperature furnace at 1500-1580℃ for 1-2 hours for calcination, and after cooling out of the furnace, a semi-siliceous high temperature foamed insulating refractory material is obtained; The low-aluminum-aluminum siliceous natural raw material is one or both of high-silicon pyrophyllite and silicon-rich sillimanite, with a particle size of ≤200 mesh; The high-silicon pyrophyllite has a SiO2 content of 75% to 85wt% and an Al2O3 content of 15% to 20wt%; The SiO2 content in the silicon-rich sillimanite is 65% to 70wt%, and the Al2O3 content is 30% to 40wt%; The silica is taken from natural minerals, wherein the SiO2 content is ≥99.0wt% and the raw material particle size is ≤200 mesh; The semi-siliceous high-temperature foamed insulating refractory material has a main crystalline phase of cristobalite, a secondary crystalline phase of mullite, and contains ≥30% of a silicon-rich glass phase; The semi-siliceous high-temperature foamed insulating refractory material has a closed porosity of 60% to 90%, a compressive strength of 8 to 20 MPa, a refractoriness under load of 1350 to 1450°C, and a thermal conductivity of 0.08 to 0.22 W / (m·k).

2. The method for preparing a semi-siliceous high-temperature foamed insulating refractory material according to claim 1, characterized in that: The high-temperature foaming agent is one or two of TiN, TiAlN, SiC, and B4C, and the raw material particle size is ≤400 mesh.

3. The method for preparing a semi-siliceous high-temperature foamed insulating refractory material according to claim 1, characterized in that: The soft clay binder is one of Guangxi white mud, ball clay and kaolin clay.

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