Rare earth oxide modified fly ash low thermal conductivity grouting material and its preparation method and application

Abstract

The present invention provides a rare earth oxide modified fly ash low thermal conductivity grouting material, its preparation method and application. The grouting material comprises a rare earth fly ash mixture and a binder with a mass ratio of (58 - 80):(20 - 42). Among them, the rare earth fly ash mixture is composed of rare earth oxide and fly ash with a mass ratio of (1 - 12):(88 - 99). The grouting material described in the present invention has a thermal conductivity decreased by more than 30% compared with conventional grouting materials and has strong heat preservation performance.

Description

Technical Field

[0001] The present invention belongs to the field of refractory materials, and particularly relates to a rare earth oxide modified fly ash low thermal conductivity grouting material, its preparation method and application. Background Art

[0002] Rare earth oxides have a very wide range of application fields and can be used as polishing powders, catalysts, hydrogen storage materials, glass ceramics, PVC additives, rare earth alloys, etc. They have excellent chemical stability and high temperature stability and are applied in fields such as polishing, thermal barrier coatings, and catalysis. There is no report on the application of rare earth oxides in industrial furnace thermal insulation grouting materials.

[0003] Grouting materials use high-strength materials as aggregates and often use cement as a binder. A certain amount of water is added to it at the construction site, and it can be used after being stirred evenly. Grouting materials have good self-flowability, rapid hardening, early strength, etc. However, in the use process, it also has some limitations, such as high brittleness, relatively high thermal conductivity, poor high temperature resistance, etc. Especially when applied to the middle and high temperature working layers of high temperature industrial furnaces, it is more likely to show erosion, arching, cracking and other phenomena under the action of thermal stress caused by alternating heat and cold.

[0004] At present, there is almost no research on using solid waste fly ash as the main base material of high temperature industrial furnace grouting materials, and there is no report on using rare earth oxides to solve the problem of relatively high thermal conductivity of fly ash-based grouting materials.

[0005] Therefore, in order to solve the problem of relatively high thermal conductivity of fly ash-based grouting materials and respond to the concept of waste-free industry and environmental protection cities, a fly ash-based grouting material suitable for medium and high temperature conditions, with excellent heat preservation and certain mechanical strength is developed using rare earth oxides. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the defects in the prior art and provides a rare earth oxide modified fly ash low thermal conductivity grouting material, its preparation method and application. To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] In a first aspect, the present invention provides a rare earth oxide modified fly ash low thermal conductivity grouting material, which comprises a rare earth fly ash mixture and a binder with a mass ratio of (58 - 80) : (20 - 42), wherein the rare earth fly ash mixture is composed of rare earth oxide and fly ash with a mass ratio of (1 - 12) : (88 - 99).

[0008] Preferably, the fly ash is pretreated, and the pretreatment method includes the following steps:

[0009] The fly ash raw material is calcined at a high temperature of 750°C - 900°C for 1 - 10 h, and the calcined fly ash is ground by a high-energy air jet mill, and the particle size after grinding meets the requirement that the residue on a 1200-mesh sieve is ≤ 5%.

[0010] More preferably, the method for the pretreatment of fly ash comprises the following steps:

[0011] Put the fly ash raw material into a rotary kiln for roasting, heat it from room temperature to 200 °C at a rotation speed of 10 - 60 rpm and a heating rate of 3 - 15 °C / min, keep it warm for 0.5 - 2 h, then heat it to 750 - 900 °C at a heating rate of 7 - 20 °C / min, keep it warm for 1 - 10 h, and then discharge and air-cool it to room temperature.

[0012] More preferably, the fly ash comprises the following components by mass percentage: alumina 10% - 45%, silica 25% - 55%, calcium oxide ≤ 22%, magnesium oxide ≤ 5%, iron oxide ≤ 7%, potassium and sodium ≤ 5%, and the balance is insoluble matter.

[0013] Preferably, the particle size of the rare earth fly ash mixture is 7 μm ≤ D90 ≤ 13 μm.

[0014] Preferably, the rare earth oxide is one or more of lanthanum oxide, cerium oxide, samarium oxide, gadolinium oxide, erbium oxide, yttrium oxide, lanthanum cerium oxide, and lanthanum samarium oxide.

[0015] Preferably, the binder is one or more of melamine formaldehyde, furfural phenol, furfural acetone, furfuryl alcohol, polybutadiene, phenol aldehyde, organohalosilane polymer, silica sol, aluminum sol, zirconium sol, and CA70 cement.

[0016] Preferably, the preparation process of the rare earth oxide is as follows: heat the rare earth carbonate raw material from room temperature to 220 - 270 °C at a heating rate of 3 - 15 °C / min, keep it warm for 0.5 - 2 h, and then heat it to 900 °C - 1100 °C at a heating rate of 3 - 12 °C / min and keep it warm for 3 - 6 h.

[0017] In a second aspect, the present invention provides a preparation process for the rare earth oxide-modified fly ash low thermal conductivity grouting material, comprising the following steps:

[0018] Mix the modified fly ash and the rare earth oxide for 1 - 5 h, then grind them to 7 μm ≤ D90 ≤ 13 μm by a high-energy air mill, transfer them to a mixer for stirring, add the binder and stir for 0.5 - 12 h to obtain the rare earth oxide-modified fly ash low thermal conductivity grouting material.

[0019] In a third aspect, the present invention further provides an application of the above grouting material in the preparation of the working layer of an industrial kiln. Preferably, the working layer is the thermal insulation working layer of the industrial kiln body, furnace waist or furnace throat.

[0020] Fourthly, the present invention also provides a curing process for applying the above-mentioned rare earth oxide-modified fly ash low thermal conductivity grouting material, which includes the following steps: injecting the rare earth oxide-modified fly ash low thermal conductivity grouting material into a mold and heating it to 120°C - 180°C at a heating rate of 0.1 - 5°C / min and keeping it warm for 1 - 10 hours to cure and form.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The thermal conductivity of the grouting material described in the present invention is reduced by more than 30% compared with the conventional grouting material, and it has strong heat preservation performance. The thermal conductivity of the fly ash material after removing cenospheres is about 0.55 W / (m·K), and the thermal conductivity of rare earth oxides is between 0.2 - 0.4 W / (m·K). Adding rare earth oxides to the grouting material can effectively reduce the thermal conductivity by more than 15%.

[0023] (2) The rare earth oxides prepared by roasting rare earth carbonate in the grouting material described in the present invention have a stacked lamellar microstructure. The special lamellar structure increases the binding sites with the binder, and can increase the flexural strength of the grouting material by more than 50%.

[0024] (3) The particle size of the rare earth fly ash mixture in the grouting material described in the present invention satisfies 7μm ≤ D90 ≤ 13μm, which makes the powder material have a large specific surface area and high surface activity, and has excellent fluidity and dispersibility. Rare earth oxides can fill the pores of fly ash and increase the overall compressive strength of the grouting material by more than 30%.

[0025] (4) The linear change rate of the grouting material described in the present invention is reduced by more than 50%. The addition of rare earth oxides improves the compactness of the grouting material, which is evenly dispersed and has a low self-thermal conductivity, reduces the structural pores and apparent porosity after the grouting material is cured, and effectively enhances the stability of the linear change. Description of the Drawings

[0026] Figure 1 It is the microscopic morphology diagram of lanthanum cerium oxide described in Embodiment 1 of the present invention. Detailed Embodiments

[0027] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the technical field to which the present invention belongs. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods used are all conventional methods unless otherwise specified.

[0028] The present invention will be described in detail below with reference to the embodiments.

[0029] Embodiment 1

[0030] Pretreatment of fly ash: The fly ash raw material is placed in a rotary kiln for roasting, heated from 25°C to 200°C at a speed of 30 rpm and 10°C / min, kept warm for 2 h, then heated to 800°C at 10°C / min, kept warm for 5 h, and then discharged and air-cooled to 25°C. Its composition is 26% alumina, 45% silica, 11% calcium oxide, 3% magnesium oxide, 6.05% iron oxide, 2.25% potassium and sodium, and the balance is insoluble matter.

[0031] Preparation of rare earth oxides: Commercially available lanthanum cerium carbonate (purchased from Baotou Research Institute of Rare Earths) is placed in a corundum crucible of a muffle furnace, heated from room temperature to 270°C at 15°C / min, kept warm for 2 h, then heated to 1100°C at 10°C / min, kept warm for 5 h, and then cooled to room temperature with the furnace to obtain lanthanum cerium oxide in the form of stacked lamellae (as Figure 1 shown).

[0032] Preparation of grouting material: 95 parts of pretreated fly ash and 5 parts of lanthanum cerium oxide in the form of stacked lamellae are added and mixed in a three-dimensional powder mixer for 2 h, then ground in a high-energy air mill to D90 of 10 μm, and then transferred to a cement mortar mixer for low-speed stirring. 58 parts of the stirred powder are taken, 40 parts of phenol aldehyde and 2 parts of CA70 cement are added and stirred for 1 h to obtain lanthanum cerium oxide modified fly ash low thermal conductivity grouting material.

[0033] Curing of grouting material: The prepared lanthanum cerium oxide modified fly ash low thermal conductivity grouting material is poured into a casting mold. The mold filled with the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material is placed in an oven and kept warm at 70°C for 1 h, then heated at a rate of 0.15°C / min, and kept warm at 150°C for 2 h after reaching 150°C. After the temperature in the oven drops to room temperature, the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material spline is demolded, and the removed spline is tested. The results are shown in Table 1.

[0034] Example 2

[0035] Pretreatment of fly ash: The fly ash raw material is placed in a rotary kiln for roasting, heated from 25°C to 200°C at a speed of 30 rpm and 10°C / min, kept warm for 2 h, then heated to 800°C at 10°C / min, kept warm for 5 h, and then discharged and air-cooled to 25°C. Its composition is 29% alumina, 43% silica, 8% calcium oxide, 2% magnesium oxide, 3% iron oxide, 3% potassium and sodium, and the balance is insoluble matter.

[0036] Preparation of rare earth oxides: Commercially available cerium carbonate and samarium carbonate (purchased from Baotou Research Institute of Rare Earths) are respectively placed in corundum crucibles of a muffle furnace, heated from room temperature to 270°C at 15°C / min, kept warm for 2 h, then heated to 1100°C at 10°C / min, kept warm for 5 h, and then cooled to room temperature with the furnace to obtain cerium oxide and samarium oxide in the form of stacked lamellae respectively.

[0037] Preparation of grouting material: 97 parts of calcined fly ash, 2 parts of cerium oxide in the form of stacked lamellae, and 1 part of samarium oxide are added and mixed in a three-dimensional powder mixer for 2 h, then ground by a high-energy air flow mill to D90 of 12 μm, and then transferred to a cement mortar mixer for low-speed stirring. 58 parts of the stirred powder are taken, 40 parts of organohalosilane and 2 parts of silica sol are added and stirred for 1 h to obtain cerium oxide and samarium oxide modified fly ash grouting material.

[0038] Curing of grouting material: The prepared cerium oxide and samarium oxide modified fly ash low thermal conductivity grouting material is poured into a casting mold. The mold filled with cerium oxide and samarium oxide modified fly ash grouting material is placed in an oven at 70 °C for 1 h, then heated at a rate of 0.15 °C / min until it reaches 150 °C and kept at this temperature for 2 h. After the temperature in the oven drops to room temperature, the cerium oxide and samarium oxide modified fly ash grouting material sample strip is demolded, and the removed sample strip is tested. The results are shown in Table 1.

[0039] Example 3

[0040] Pretreatment of fly ash: The fly ash raw material is placed in a rotary kiln for roasting, heated from 25 °C to 200 °C at a speed of 30 rpm and 10 °C / min, kept at this temperature for 2 h, then heated to 800 °C at a speed of 10 °C / min and kept at this temperature for 5 h, and then discharged and air-cooled to 25 °C. Its composition is 24% aluminum oxide, 48% silicon oxide, 5% calcium oxide, 3% magnesium oxide, 5% iron oxide, 0.8% potassium and sodium, and the balance is insoluble matter.

[0041] Preparation of rare earth oxides: Commercially available (purchased from Baotou Research Institute of Rare Earths) lanthanum carbonate and gadolinium carbonate are respectively filled into corundum crucibles in a muffle furnace, heated from room temperature to 270 °C at a speed of 15 °C / min and kept at this temperature for 2 h, then heated to 1100 °C at a speed of 10 °C / min and kept at this temperature for 5 h, and then cooled to room temperature with the furnace to obtain lanthanum oxide and gadolinium oxide in the form of stacked lamellae respectively.

[0042] Preparation of grouting material: 92 parts of calcined fly ash, 5 parts of lanthanum oxide in the form of stacked lamellae, and 3 parts of gadolinium oxide are added and mixed in a three-dimensional powder mixer for 2 h, then ground by a high-energy air flow mill to D90 of 8 μm, and then transferred to a cement mortar mixer for low-speed stirring. 58 parts of the stirred powder are taken, 40 parts of furfural phenol and 2 parts of zirconium sol are added and stirred for 1 h to obtain lanthanum oxide and gadolinium oxide modified fly ash grouting material.

[0043] Curing of grouting material: The prepared cerium oxide and samarium oxide modified fly ash low thermal conductivity grouting material is poured into a casting mold. The mold filled with lanthanum oxide and gadolinium oxide modified fly ash grouting material is placed in an oven at 70 °C for 1 h, then heated at a rate of 0.15 °C / min until it reaches 150 °C and kept at this temperature for 2 h. After the temperature in the oven drops to room temperature, the lanthanum oxide and gadolinium oxide modified fly ash grouting material sample strip is demolded, and the removed sample strip is tested. The results are shown in Table 1.

[0044] Example 4

[0045] The preparation process is the same as that of Example 1, except that: the mass fraction of lanthanum cerium oxide in the form of stacked lamellae is 1 part, and the mass fraction of fly ash after pretreatment is 99 parts. The mass fraction of powder in the grouting material is 80 parts, the mass fraction of phenol aldehyde is 15 parts, and the mass fraction of CA70 cement is 5 parts. The test results of the test pieces are shown in Table 1.

[0046] Example 5

[0047] The preparation process is the same as that of Example 1, except that: the mass fraction of lanthanum cerium oxide in the form of stacked lamellae is 12 parts, and the mass fraction of fly ash after pretreatment is 88 parts. The test results of the test pieces are shown in Table 1. The mass fraction of powder in the grouting material is 70 parts, the mass fraction of phenol aldehyde is 20 parts, and the mass fraction of CA70 cement is 10 parts.

[0048] Comparative Example 1

[0049] Take 100 parts of commercially available grouting material, and its components are 26% high alumina powder, 33% pyrophyllite, 5% calcined kaolin, 1% borax, 12% silicon carbide, and 1% lithium oxide. 40 parts of phenol aldehyde and 2 parts of CA70 cement are added to the powder and stirred for 1 h to obtain the grouting material, which is poured into the castable mold. After heat preservation at 70 °C for 1 h, the temperature is raised at a rate of 0.15 °C / h. After rising to 150 °C, it is heat-preserved for 2 h.. After the temperature in the oven drops to room temperature, the grouting material test piece is demolded, and the removed test piece is tested. The results are shown in Table 1.

[0050] Comparative Example 2

[0051] Pretreatment of fly ash: The fly ash raw material is placed in a rotary kiln for roasting, heated from 25 °C to 200 °C at a speed of 30 rpm and 10 °C / min, heat-preserved for 2 h, then heated to 800 °C at a speed of 10 °C / min and heat-preserved for 5 h, and then discharged and air-cooled to 25 °C. Its components are 26% aluminum oxide, 45% silicon oxide, 11% calcium oxide, 3% magnesium oxide, 6.05% iron oxide, 2.25% potassium and sodium, and the balance is insoluble matter.

[0052] Preparation of grouting material: 58 parts of roasted fly ash are mixed in a three-dimensional powder mixer for 2 h, then ground by a high-energy air mill to D90 of 10 μm, and then transferred to a cement mortar mixer for low-speed stirring. 40 parts of phenol aldehyde and 2 parts of CA70 cement are added and stirred for 1 h to obtain the fly ash grouting material.

[0053] Curing of grouting material: The prepared fly ash grouting material is poured into the castable mold. The mold filled with fly ash grouting material is placed in an oven and heat-preserved at 70 °C for 1 h, then the temperature is raised at a rate of 10 °C / h. After rising to 150 °C, it is heat-preserved for 2 h. After the temperature in the oven drops to room temperature, the fly ash grouting material test piece is demolded, and the removed test piece is tested. The results are shown in Table 1.

[0054] Comparative Example 3

[0055] Pretreatment of fly ash: The fly ash raw material is placed in a rotary kiln for roasting, heated from 25°C to 200°C at a speed of 30 rpm and 10°C / min, held for 2 h, then heated to 800°C at 10°C / min, held for 5 h, and then discharged and air-cooled to 25°C. Its composition is 26% aluminum oxide, 45% silicon oxide, 11% calcium oxide, 3% magnesium oxide, 6.05% iron oxide, 2.25% potassium and sodium, and the balance is insoluble matter.

[0056] Preparation of rare earth oxides: Commercially available lanthanum cerium carbonate (purchased from Baotou Research Institute of Rare Earths) is placed in a corundum crucible in a muffle furnace, heated from room temperature to 270°C at 15°C / min, held for 2 h, then heated to 1100°C at 10°C / min, held for 5 h, and then cooled to room temperature with the furnace.

[0057] 87 parts of pretreated fly ash are added with 13 parts of stacked lamellar lanthanum cerium oxide, mixed in a three-dimensional powder mixer for 2 h, ground to D90 of 10 μm by a high-energy air mill, and then transferred to a cement mortar mixer for low-speed stirring. 58 parts of the stirred powder are taken, added with 40 parts of phenol aldehyde and 2 parts of CA70 cement, and stirred for 1 h to obtain lanthanum cerium oxide modified fly ash low thermal conductivity grouting material.

[0058] Curing of grouting material: The prepared lanthanum cerium oxide modified fly ash low thermal conductivity grouting material is poured into a casting mold. The mold filled with the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material is placed in an oven at 70°C for 1 h, then heated at a rate of 0.15°C / min, and held at 150°C for 2 h after reaching 150°C. After the temperature in the oven drops to room temperature, the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material sample bar is demolded, and the removed sample bar is tested. The results are shown in Table 1.

[0059] It can be seen from the data results in Table 1 that the specific surface area of lanthanum cerium oxide is large. After adding too much lanthanum cerium oxide, the bonding force generated after the polycondensation reaction of the binder is insufficient, resulting in a significant decrease in the mechanical strength of the grouting material after molding.

[0060] Comparative Example 4

[0061] Pretreatment of fly ash: 95 parts of fly ash raw material are placed in a rotary kiln for roasting, heated from 25°C to 200°C at a speed of 30 rpm and 10°C / min, held for 2 h, then heated to 800°C at 10°C / min, held for 5 h, and then discharged and air-cooled to 25°C. Its composition is 26% aluminum oxide, 45% silicon oxide, 11% calcium oxide, 3% magnesium oxide, 6.05% iron oxide, 2.25% potassium and sodium, and the balance is insoluble matter.

[0062] Preparation of rare earth oxide: After pretreatment, 5 parts of commercially available lanthanum cerium oxide were added to fly ash and mixed in a three-dimensional powder mixer for 2 hours. Then, it was ground by a high-energy air mill until D90 reached 10 μm, and then transferred to a cement mortar mixer for low-speed stirring. 40 parts of phenol aldehyde and 2 parts of CA70 cement were added and stirred for 1 hour to obtain lanthanum cerium oxide modified fly ash low thermal conductivity grouting material.

[0063] Curing of grouting material: The prepared lanthanum cerium oxide modified fly ash low thermal conductivity grouting material was poured into a castable mold. The mold containing the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material was placed in an oven and kept at 70 °C for 1 hour, then heated at a rate of 0.15 °C / min until it reached 150 °C and kept at this temperature for 2 hours. After the temperature in the oven dropped to room temperature, the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material sample was demolded and the removed sample was tested. The results are shown in Table 1.

[0064] It can be seen from the data results in Table 1 that commercially available lanthanum cerium oxide mostly has a scattered irregular spherical and partial lamellar structure, and particles with a larger specific surface area require more binder to wrap, resulting in insufficient bonding force after the binder polycondensation reaction, leading to a decrease in the mechanical strength of the grouting material after molding.

[0065] Comparative Example 5

[0066] 95 parts of fly ash raw material were taken. Its composition is 29.3% alumina, 38.7% silica, 13% calcium oxide, 4.31% magnesium oxide, 6.55% iron oxide, 3.17% potassium and sodium, and the balance is insoluble matter. Commercially available (Baotou Research Institute of Rare Earths) lanthanum cerium carbonate was placed in a corundum crucible of a muffle furnace and heated from room temperature to 270 °C at a rate of 15 °C / min and kept at this temperature for 2 hours, then heated to 1100 °C at a rate of 10 °C / min and kept at this temperature for 5 hours, and then cooled to room temperature with the furnace. After pretreatment, 5 parts of lanthanum cerium oxide after high-temperature roasting were added to fly ash and mixed in a three-dimensional powder mixer for 2 hours. Then, it was ground by a high-energy air mill until D90 reached 10 μm, and then transferred to a cement mortar mixer for low-speed stirring. 40 parts of phenol aldehyde and 2 parts of CA70 cement were added and stirred for 1 hour to obtain lanthanum cerium oxide modified fly ash low thermal conductivity grouting material.

[0067] Curing of grouting material: The prepared lanthanum cerium oxide modified fly ash low thermal conductivity grouting material was poured into a castable mold. The mold containing the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material was placed in an oven and kept at 70 °C for 1 hour, then heated at a rate of 0.15 °C / min until it reached 150 °C and kept at this temperature for 2 hours. After the temperature in the oven dropped to room temperature, the lanthanum cerium oxide modified fly ash low thermal conductivity grouting material sample was demolded and the removed sample was tested. The results are shown in Table 1.

[0068] It can be seen from the data results in Table 1 that fly ash without pretreatment contains hollow glass microspheres, unburned organic matter, residual carbon and adsorbed water. The above substances seriously affect the adhesion of the binder, resulting in a significant decrease in the mechanical strength of the grouting material after molding.

[0069] Table 1: Performance Data Sheet of Grouting Material

[0070]

[0071] The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A rare earth oxide modified fly ash low thermal conductivity grouting material, characterized in that: It includes a rare earth fly ash mixture with a mass ratio of (58 - 80):(20 - 42) and a binder. Among them, the rare earth fly ash mixture is composed of rare earth oxides and fly ash with a mass ratio of (1 - 12):(88 - 99); the fly ash has been pretreated, and the pretreatment method includes the following steps: Roast the fly ash raw material at a high temperature of 750°C - 900°C for 1 - 10 h. After roasting, the fly ash is ground by a high-energy air mill, and the particle size after grinding meets the requirement that the residue on a 1200-mesh sieve is ≤ 5%; The particle size of the rare earth fly ash mixture is 7μm ≤ D90 ≤ 13μm; The preparation process of the rare earth oxides is as follows: Heat the rare earth carbonate raw material from room temperature to 220 - 270°C at a rate of 3 - 15°C / min, hold for 0.5 - 2 h, and then heat to 900°C - 1100°C at a rate of 3 - 12°C / min and hold for 3 - 6 h.

2. The rare earth oxide modified fly ash low thermal conductivity grouting material according to claim 1, characterized in that: The method for the pretreatment of the fly ash includes the following steps: Place the fly ash raw material into a rotary kiln for roasting. Heat it from room temperature to 200°C at a rotation speed of 10 - 60 rpm and a heating rate of 3 - 15°C / min, hold for 0.5 - 2 h, then heat to 750 - 900°C at a rate of 7 - 20°C / min, hold for 1 - 10 h, and then discharge and air-cool to room temperature.

3. The rare earth oxide modified fly ash low thermal conductivity grouting material according to claim 1, wherein: The fly ash includes the following components by mass percentage: alumina 10% - 45%, silica 25% - 55%, calcium oxide ≤ 22%, magnesium oxide ≤ 5%, iron oxide ≤ 7%, potassium and sodium ≤ 5%, and the balance is insoluble substances.

4. The rare earth oxide modified fly ash low thermal conductivity grouting material according to claim 1, characterized in that: The rare earth oxides are one or more of lanthanum oxide, cerium oxide, samarium oxide, gadolinium oxide, erbium oxide, yttrium oxide, lanthanum cerium oxide, and lanthanum samarium oxide.

5. The rare earth oxide modified fly ash low thermal conductivity grouting material according to claim 1, characterized in that: The binder is one or more of melamine formaldehyde, furfural phenol, furfural acetone, furfuryl alcohol, polybutadiene, phenol aldehyde, organohalosilane polymer, silica sol, aluminum sol, zirconium sol, and CA70 cement.

6. The preparation process of the rare earth oxide-modified fly ash low thermal conductivity grouting material according to any one of claims 1-5, characterized in that: It includes the following steps: Mix the modified fly ash and rare earth oxides for 1 - 5 h, then grind them by a high-energy air mill to 7μm ≤ D90 ≤ 13μm, transfer them to a mixer for stirring, add the binder and stir for 0.5 - 12 h to obtain a rare earth oxide-modified fly ash low-thermal-conductivity grouting material.

7. Use of the grouting material according to any one of claims 1-5 in preparing the working layer of an industrial furnace, characterized in that: The working layer is the thermal insulation working layer of the industrial furnace body, furnace waist or furnace throat.

8. A curing process for applying the rare earth oxide-modified fly ash low-thermal-conductivity grouting material according to any one of claims 1 - 5, including the following steps: Inject the rare earth oxide-modified fly ash low-thermal-conductivity grouting material according to any one of claims 1 - 5 into a mold, and then heat it to 120°C - 180°C at a heating rate of 0.1 - 5°C / min and hold for 1 - 10 h to be cured and formed.

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