A heat-insulating riser and a method for manufacturing the same

Abstract

The application provides a heat-insulating riser and a preparation method thereof. The preparation method comprises the following steps: preparing a riser slurry and a silica sol; mixing the silica sol and the riser slurry and adjusting the pH to 6-8 to prepare a gel; and aging, modifying and drying the gel to obtain the heat-insulating riser; wherein the riser slurry comprises paper fibers, refractory fibers, floating beads and optionally phenolic resin; and the mass ratio of the silica sol to the riser slurry is 1:5-1:1. The preparation method of the application adopts a silica aerogel heat-insulating riser, and through a sol-gel method, silica aerogel particles are filled in the gaps of the refractory fibers and the floating beads, especially the gaps of the floating beads are divided into innumerable smaller compartments, the gas convection heat transfer is basically inhibited, the overall thermal conductivity of the riser is obviously reduced, and the heat-insulating performance of the riser is obviously improved.

Description

Technical Field

[0001] This application belongs to the field of materials technology, specifically relating to an insulating riser and its preparation method. Background Technology

[0002] There are two main types of risers: exothermic insulating riser sleeves and ordinary insulating riser sleeves. Insulating risers are mainly made of thermal insulation materials, with the aim of slowing down the solidification time of the molten metal inside the riser sleeve and improving feeding efficiency. Currently, insulating risers are mostly made of paper fiber, refractory fiber, and cenospheres as raw materials. Although their strength is moderate, the thermal conductivity of insulating risers is above 0.15 W / (m•K), which cannot meet the casting scenarios with higher requirements for thermal insulation performance. Summary of the Invention

[0003] To address the problems existing in the prior art, this application provides an insulating riser and its preparation method.

[0004] Specifically, this application relates to the following aspects:

[0005] A method for preparing an insulating riser includes the following steps:

[0006] Preparation of riser slurry and silica sol;

[0007] Silica sol and riser slurry were mixed and the pH was adjusted to 6-8 to prepare a gel.

[0008] The gel is aged, modified, and dried to obtain an insulating riser;

[0009] The riser slurry includes paper fiber, refractory fiber, cenospheres, and optionally phenolic resin;

[0010] The mass ratio of silica sol to riser slurry is 1:5 to 1:1.

[0011] Furthermore, the riser slurry contains 1.2-4 wt% paper fiber, 5-13 wt% refractory fiber, 7.5-17.5 wt% cenospheres, and optionally 1-2.5 wt% phenolic resin, with the remainder being solvent.

[0012] Furthermore, the solvent is ethanol with a content of 70-90%.

[0013] Furthermore, the silica sol is prepared by the following steps:

[0014] Tetraethyl orthosilicate, ethanol, and water were mixed evenly and the pH was adjusted to 2-3 for hydrolysis to obtain silica sol.

[0015] Furthermore, the mass ratio of tetraethyl orthosilicate, ethanol and water is 1:(10-14):(1-4).

[0016] Furthermore, when the riser slurry does not contain phenolic resin, the drying process is as follows: drying at 60℃ for 42-54 hours, drying at 80℃ for 2-6 hours, and drying at 120℃ for 1-3 hours.

[0017] Furthermore, when the riser slurry contains phenolic resin, the drying process is as follows: drying at 60℃ for 42-54 hours, drying at 80℃ for 2-6 hours, drying at 120℃ for 1-3 hours, and drying at 180℃ for 2-6 hours.

[0018] Furthermore, the refractory fiber is one or more of high-alumina fiber, aluminum silicate fiber, and rock wool fiber.

[0019] An insulating riser is obtained by the above-described preparation method.

[0020] An insulating riser includes silica aerogel, paper fiber, refractory fiber, and cenospheres, wherein the silica aerogel content in the insulating riser is 0.2-3 wt%, the paper fiber content is 5-15 wt%, the refractory fiber content is 20-40 wt%, and the cenosphere content is 30-70 wt%.

[0021] An insulating riser comprises silica aerogel, paper fiber, refractory fiber, cenospheres, and phenolic resin, wherein the silica aerogel content is 0.2-3 wt%, the paper fiber content is 5-15 wt%, the refractory fiber content is 20-40 wt%, the cenosphere content is 30-70 wt%, and the phenolic resin content is 4-10 wt%.

[0022] Furthermore, the refractory fiber is one or more of high-alumina fiber, aluminum silicate fiber, and rock wool fiber.

[0023] Beneficial effects of this application

[0024] Existing insulation risers commonly use cenospheres to improve insulation performance, but the large gaps between the cenospheres affect thermal conductivity. The preparation method of this application uses silica aerogel insulation risers. Through the sol-gel method, silica aerogel particles fill the gaps between refractory fibers and cenospheres. In particular, the gaps between the cenospheres are divided into numerous smaller compartments, which basically suppresses gas convection heat transfer and significantly reduces the overall thermal conductivity of the riser, thus significantly improving the insulation performance of the riser.

[0025] The insulating riser prepared in this application is particularly suitable for casting aluminum or magnesium alloys at casting temperatures below 700°C. Detailed Implementation

[0026] The present application is further illustrated below with reference to embodiments. It should be understood that the embodiments are only used to further illustrate and explain the present application and are not intended to limit the present application.

[0027] Unless otherwise defined, technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, materials and methods are described herein. In case of conflict, the definitions included herein shall prevail. Furthermore, materials, methods, and examples are for illustrative purposes only and are not intended to be limiting. The present application is further described below with reference to specific embodiments, but is not intended to limit the scope of the application.

[0028] To address the problems existing in the prior art, this application provides a method for preparing an insulating riser, comprising the following steps:

[0029] Step 1: Prepare riser slurry and silica sol;

[0030] Step 2: Mix the silica sol and riser slurry evenly and adjust the pH to 6-8 to prepare the gel;

[0031] Step 3: Aging, modifying and drying the gel to obtain an insulating riser;

[0032] The riser slurry includes paper fiber, refractory fiber, cenospheres, and optionally phenolic resin;

[0033] The mass ratio of silica sol to riser slurry is 1:5 to 1:1.

[0034] In step 1, paper fibers, refractory fibers, cenospheres, and phenolic resin risers are all commercially available. The paper fibers can be derived from various plant fibers, or from repulping products containing paper fibers.

[0035] Refractory fibers can be high-alumina fibers, aluminosilicate fibers, rock wool fibers, etc.

[0036] Phenolic resins are mainly synthesized chemically from phenolic and aldehyde compounds. They are thermosetting resins and can be either unmodified or modified thermosetting phenolic resins. The phenolic resins include, but are not limited to, phenolic resins modified with one or more of lignin, biomass, coal tar, asphalt, graphite, and alkylphenols.

[0037] In some embodiments, the phenolic resin can be a solid powdered phenolic resin with a 60-mesh pass rate of 100%, preferably a 180-mesh pass rate of 95%.

[0038] Cenospheres are spherical or near-spherical hollow particles found in fly ash, a byproduct of power plants. They range in size from 20 to 200 mesh and mainly contain 25-35% alumina and 60-75% silicon dioxide. Alternatively, they may be derived from perlite after artificial heating and expansion.

[0039] The slurry can be prepared using ethanol with a content of 70-90%. In some embodiments, the riser slurry comprises paper fiber, refractory fiber, and cenospheres, wherein the paper fiber content in the riser slurry is 1.2-4 wt%, for example, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, or 2.9 wt%. The refractory fiber content is 5-13 wt%, for example, it can be 5 wt%, 3.5 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, 4 wt%, and any value between these values; the refractory fiber content is 5-13 wt%, for example, it can be 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%. wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, and any value between these values; the content of the granules is 7.5-17.5 wt%, for example, it can be 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 14.5 wt%, 15 wt%, 15.5 wt%, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, and any value between these values.

[0040] In some embodiments, the riser slurry is composed of paper fiber, refractory fiber, cenospheres and ethanol at a content of 70-90%, wherein the content of paper fiber in the riser slurry is 1.2-4 wt%, the content of refractory fiber is 5-13 wt%, and the content of cenospheres is 7.5-17.5 wt%.

[0041] In some embodiments, the riser slurry comprises paper fiber, refractory fiber, cenospheres, and phenolic resin, wherein the paper fiber content in the riser slurry is 1.2-4 wt%, for example, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, or 2.9 wt%. The refractory fiber content is 3wt%, 3.1wt%, 3.2wt%, 3.3wt%, 3.4wt%, 3.5wt%, 3.6wt%, 3.7wt%, 3.8wt%, 3.9wt%, 4wt%, and any value between these values; the refractory fiber content is 5-13wt%, for example, it can be 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%. The content of phenolic resin is 1-2.5 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, and any value between these values; the content of cenospheres is 7.5-17.5 wt%, for example, it can be 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 14.5 wt%, 15 wt%, 15.5 wt%, 16 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, and any value between these values; the content of phenolic resin is 1-2.5%. The percentage (wt%) can be, for example, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, or any value between these values. In some embodiments, the riser slurry is composed of paper fiber, refractory fiber, cenospheres, phenolic resin, and ethanol at a content of 70-90%, wherein the riser slurry contains 1.2-4wt% paper fiber, 5-13wt% refractory fiber, 7.5-17.5wt% cenospheres, and 1-2.5wt% phenolic resin.

[0042] The addition of phenolic resin can improve the strength of the insulating riser, i.e. its compressive strength. The higher the riser strength, the less likely it is to break during use, making it easier to operate and less likely to shed slag, which would cause slag to fall into the molten metal and form defects. However, too much resin will increase the gas generation of the riser, which will increase the risk of defects such as porosity in the casting.

[0043] Silica sol is prepared by the following steps:

[0044] Tetraethyl orthosilicate, ethanol, and water were mixed evenly and the pH was adjusted to 2-3 for hydrolysis to obtain silica sol.

[0045] The silica content in silica sol is usually close to 100%.

[0046] In some embodiments, silica sol is prepared by the following steps: tetraethyl orthosilicate, ethanol, and water are mixed in a molar ratio of 1:(10-14):(1-4), and then 1 mol / L HCl (or a strong acid such as nitric acid or sulfuric acid) is added dropwise to adjust the pH of the mixed solution to 2-3. The solution is then hydrolyzed under magnetic stirring, for example, for 45 min. After hydrolysis, a sol is formed.

[0047] In step 2, a gel is prepared by the sol-gel method.

[0048] Existing insulation risers commonly use cenospheres to improve insulation performance, but the large gaps between the cenospheres affect thermal conductivity. The preparation method of this application introduces silica aerogel insulation risers. Through the sol-gel method, silica aerogel particles fill the gaps between refractory fibers and cenospheres. In particular, the gaps between the cenospheres are divided into numerous smaller compartments, which basically suppresses gas convection heat transfer and significantly reduces the overall thermal conductivity of the riser, thus significantly improving the insulation performance of the riser.

[0049] The mass ratio of silica sol to riser slurry is 1:5 to 1:1, for example, it can be 1:5, 1:4.5, 1:4, 1:3.5, 1:3, 1:2.5, 1:2, 1:1.5, 1:1.25, 1:1, and any value between these values.

[0050] When the silica content in the gel is too low, the resulting insulating riser has excessively high thermal conductivity and poor insulation performance. Similarly, when the silica content in the gel is too low, the resulting insulating riser has poor compressive strength.

[0051] In some implementations, step 2 includes the following steps: mixing silica sol and riser slurry evenly; adding 36.5% ammonia water to adjust the pH value to 6-8, pouring it into the riser mold, and letting it stand at room temperature for 1 hour to achieve gelation.

[0052] The aging and modification of the gel in step 3 can both be carried out using methods known in the art.

[0053] In some implementations, the aging step involves solvent exchange of the gel at 50°C in anhydrous ethanol for 6 hours.

[0054] In some implementations, the modification step is as follows: the aged gel is poured into a trimethylchlorosilane (10% by volume) modifier diluted with hexane and kept at 35°C for 24 hours.

[0055] The drying process in step 3 can be carried out using gradient heating, that is, drying by increasing the temperature in stages. This drying method is more conducive to maintaining the structure of the gel pores.

[0056] In some implementations, when the riser slurry does not contain phenolic resin, the drying process involves drying at 60°C for 42-54 hours, at 80°C for 2-6 hours, and at 120°C for 1-3 hours in sequence.

[0057] In some implementations, when the riser slurry contains phenolic resin, the drying process involves sequential drying at 60°C for 42-54 hours, at 80°C for 2-6 hours, at 120°C for 1-3 hours, and at 180°C for 2-6 hours. The final temperature gradient of 180°C for 2-6 hours ensures complete curing of the phenolic resin, maximizing the riser's strength. Using four temperature gradients results in a stronger compressive strength in the molded riser. Using three temperature gradients leads to greater porosity collapse in the aerogel and improved thermal conductivity.

[0058] In some implementations, the method for preparing the insulating riser includes the following steps:

[0059] Step 1: Prepare riser slurry and silica sol;

[0060] Step 2: Mix the silica sol and riser slurry evenly and adjust the pH to 6-8 to prepare the gel;

[0061] Step 3: Aging, modifying and drying the gel to obtain an insulating riser;

[0062] The riser slurry contains 1.2-4 wt% paper fiber, 5-13 wt% refractory fiber, 7.5-17.5 wt% cenospheres, and optionally 1-2.5 wt% phenolic resin.

[0063] The mass ratio of silica sol to riser slurry is 1:5 to 1:1.

[0064] In some implementations, the method for preparing the insulating riser includes the following steps:

[0065] Step 1: Prepare riser slurry and silica sol;

[0066] Step 2: Mix the silica sol and riser slurry evenly and adjust the pH to 6-8 to prepare the gel;

[0067] Step 3: Aging, modifying and drying the gel to obtain an insulating riser;

[0068] The riser slurry contains 1.2-4 wt% paper fiber, 5-13 wt% refractory fiber, 7.5-17.5 wt% cenospheres, and optionally 1-2.5 wt% phenolic resin.

[0069] The mass ratio of silica sol to riser slurry is 1:5-1:1;

[0070] When the riser slurry does not contain phenolic resin, the drying process is as follows: drying at 60℃ for 42-54 hours, drying at 80℃ for 2-6 hours, and drying at 120℃ for 1-3 hours.

[0071] When the riser slurry contains phenolic resin, the drying process is as follows: drying at 60℃ for 42-54 hours, drying at 80℃ for 2-6 hours, drying at 120℃ for 1-3 hours, and drying at 180℃ for 2-6 hours.

[0072] This application also provides heat-insulating risers obtained by the above preparation method.

[0073] This application also provides an insulating riser, comprising silica aerogel, paper fiber, refractory fiber and cenospheres, wherein the silica aerogel content in the insulating riser is 0.2-3 wt%, the paper fiber content is 5-15 wt%, the refractory fiber content is 20-40 wt%, and the cenosphere content is 30-70 wt%.

[0074] This application also provides an insulating riser, comprising silica aerogel, paper fiber, refractory fiber, cenospheres, and phenolic resin, wherein the insulating riser contains 0.2-3 wt% silica aerogel, 5-15 wt% paper fiber, 20-40 wt% refractory fiber, 30-70 wt% cenospheres, and 4-10 wt% phenolic resin.

[0075] Paper fiber, refractory fiber, cenospheres, and phenolic resin risers are all commercially available. The refractory fiber may be one or more of high-alumina fiber, aluminosilicate fiber, and rock wool fiber.

[0076] Example

[0077] Unless otherwise specified, all contents mentioned in the following examples and comparative examples are by mass percentage.

[0078] The paper fiber was purchased from the Jinan Daily Printing Plant.

[0079] The refractory fiber was purchased from Shandong Redun High Temperature Materials Co., Ltd.

[0080] The microspheres were purchased from Hebei Chengtong Microsphere New Material Co., Ltd.

[0081] The phenolic resin is from Jinan Shengquan Group Co., Ltd., and its model number is PF4116.

[0082] Example 1

[0083] S1: Preparation of Insulating Riser Grout

[0084] Raw materials: 8 wt% paper fiber, 25 wt% high alumina fiber, 67 wt% cenospheres

[0085] The above raw materials were mixed with 80% ethanol to form a homogeneous slurry with a solid content of 25%.

[0086] S2: Sol preparation

[0087] Tetraethyl orthosilicate, anhydrous ethanol, and water were mixed in a molar ratio of 1:12:3 and stirred magnetically for 20 minutes. After thorough mixing, 1 mol / L HCl was added dropwise to adjust the pH of the mixed solution to 2-3. Hydrolysis was then carried out under magnetic stirring for 45 minutes, resulting in the formation of a sol.

[0088] S3: Gel Preparation

[0089] Mix the sol and riser slurry at a mass ratio of 4:6 until homogeneous. Add 1 mol / L ammonia water to adjust the pH to 6-8, pour into the riser mold, and let stand at room temperature for 1 hour (until gelation).

[0090] S4: Aging

[0091] The gel was subjected to solvent exchange in anhydrous ethanol at 50°C for 6 hours.

[0092] S5: Modified

[0093] After aging, pour out anhydrous ethanol, add trimethylchlorosilane (TMCS, 10% by volume) modifier diluted with n-hexane, seal and keep at 35°C for 24 hours for modification.

[0094] S6: Drying

[0095] Pour off the liquid portion, seal and clean with n-hexane at 50°C twice and replace the solvent twice, 12 hours each time. Finally, remove the n-hexane liquid and place the gel in a constant temperature oven to dry stepwise, drying at 60°C for 48 hours and at 120°C for 2 hours to obtain the riser.

[0096] Example 2

[0097] The only difference between Example 2 and Example 1 is that the mass ratio of sol to riser slurry is 2:8.

[0098] Example 3

[0099] The only difference between Example 3 and Example 1 is that the mass ratio of sol to riser slurry is 1:1.

[0100] Example 4

[0101] The only difference between Example 4 and Example 1 is that the high-alumina fiber content in the raw materials is 37wt% and the cenosphere content is 55wt%.

[0102] Example 5

[0103] The only difference between Example 5 and Example 1 is that the high-alumina fiber content in the raw materials is 50wt% and the cenosphere content is 42wt%.

[0104] Example 6

[0105] S1: Preparation of Insulating Riser Grout

[0106] Raw materials: 8 wt% paper fiber, 25 wt% high alumina fiber, 61 wt% cenospheres, 6 wt% phenolic resin.

[0107] The above raw materials were mixed with 80% ethanol to form a homogeneous slurry with a solid content of 25%.

[0108] S2: Sol preparation

[0109] Tetraethyl orthosilicate, anhydrous ethanol, and water were mixed in a molar ratio of 1:12:3 and stirred magnetically for 20 minutes. After thorough mixing, 1 mol / L HCl was added dropwise to adjust the pH of the mixed solution to 2-3. Hydrolysis was then carried out under magnetic stirring for 45 minutes, resulting in the formation of a sol.

[0110] S3: Gel Preparation

[0111] Mix the sol and riser slurry at a mass ratio of 4:6 until homogeneous. Add 1 mol / L ammonia water to adjust the pH to 6-8, pour into the riser mold, and let stand at room temperature for 1 hour (until gelation).

[0112] S4: Aging

[0113] The gel was subjected to solvent exchange in anhydrous ethanol at 50°C for 6 hours.

[0114] S5: Modified

[0115] After aging, pour out anhydrous ethanol, add trimethylchlorosilane (TMCS, 10% by volume) modifier diluted with n-hexane, seal and keep at 35°C for 24 hours for modification.

[0116] S6 drying:

[0117] Pour off the liquid portion, seal and clean with n-hexane at 50°C twice and replace the solvent twice, 12 hours each time. Finally, pour out the n-hexane liquid and place the gel in a constant temperature oven to dry step by step.

[0118] S6: Dry at 60℃ for 48 h, at 80℃ for 4 h, at 120℃ for 2 h, at 180℃ for 2 h, and cure at room temperature.

[0119] Example 7

[0120] The difference between Example 7 and Example 6 is that the content of high-alumina fiber and phenolic resin in the raw materials are different, as detailed in Table 1.

[0121] Comparative Example 1

[0122] S1: Preparation of Insulating Riser Grout

[0123] Raw materials: 8 wt% paper fiber, 25 wt% high alumina fiber, 61 wt% cenospheres, 6 wt% phenolic resin.

[0124] The above raw materials are mixed with water to form a uniform slurry with a solid content of 25%.

[0125] S2: Immerse the riser mold in the slurry. The riser mold is connected to a vacuum negative pressure pipe. The water in the slurry will be drawn away by the negative pressure, while the riser material remains on the screen of the riser mold. The semi-finished product is then demolded.

[0126] S3: The semi-finished product enters the drying kiln and is dried step by step at a temperature of 180℃ for 2 hours.

[0127] Comparative Example 2

[0128] The only difference between Comparative Example 2 and Example 1 is that the mass ratio of sol to riser slurry is 6:4.

[0129] Comparative Example 3

[0130] The only difference between Comparative Example 3 and Example 1 is that the mass ratio of sol to riser slurry is 1:9.

[0131] The specific parameters of the above embodiments and comparative examples are shown in Table 1.

[0132] Table 1

[0133]

[0134] Test case

[0135] The performance of the risers prepared above was tested.

[0136] 1) Thermal conductivity measurement method: The HOT Disk thermal constant analyzer was used for measurement. The HOT Disk thermal constant analyzer was purchased from KANGONAS Instruments Trading (Shanghai) Co., Ltd., manufacturer: Hot Disk GmbH, Sweden, model: TPS2500 S; the test temperature was 25℃±1℃.

[0137] Methods for determining compressive strength: Refer to GB / T 2684-2009 Test Methods for Foundry Sand and Mixtures.

[0138] Percentage decrease in thermal conductivity = (thermal conductivity of Comparative Example 1 - thermal conductivity) / thermal conductivity of Comparative Example 1 × 100%. That is, the percentage decrease in thermal conductivity compared to Comparative Example 1. A positive value indicates a decrease, and a negative value indicates an increase.

[0139] Percentage increase in compressive strength = (Comparative strength - Comparative example 1 compressive strength) / Comparative example 1 compressive strength × 100%. That is, the percentage change in compressive strength compared to Comparative example 1 (2.0 Kn). A negative value indicates a decrease, and a positive value indicates an increase.

[0140] The test results are shown in Table 2.

[0141] Table 2

[0142]

Claims

1. A method for preparing an insulating riser, comprising the following steps: Preparation of riser slurry and silica sol; Silica sol and riser slurry were mixed and the pH was adjusted to 6-8 to prepare a gel. The gel is aged, modified, and dried to obtain an insulating riser; The riser slurry contains paper fiber, high alumina fiber, cenospheres, and phenolic resin; The mass ratio of silica sol to riser slurry is 1:5 to 1:1.25; The riser pulp contains 1.2-4 wt% paper fiber, 5-10 wt% high alumina fiber, 7.5-17.5 wt% cenospheres, 1-2.5 wt% phenolic resin, and the remainder is solvent. The phenolic resin is a thermosetting phenolic resin; The silica sol is prepared by the following steps: Tetraethyl orthosilicate, ethanol and water were mixed evenly and the pH was adjusted to 2-3 for hydrolysis to obtain silica sol; The drying process involves sequentially drying at 60℃ for 42-54 hours, at 80℃ for 2-6 hours, at 120℃ for 1-3 hours, and at 180℃ for 2-6 hours.

2. The preparation method according to claim 1, wherein the solvent is ethanol with a content of 70-90%.

3. The preparation method according to claim 1, wherein the mass ratio of tetraethyl orthosilicate, ethanol and water is 1:(10-14):(1-4).

4. An insulating riser, obtained by the preparation method according to any one of claims 1-3.

5. An insulating riser, comprising silica aerogel, paper fiber, high alumina fiber, cenospheres, and phenolic resin, wherein the silica aerogel content is 0.2-3 wt%, the paper fiber content is 5-15 wt%, the high alumina fiber content is 20-40 wt%, the cenosphere content is 30-70 wt%, and the phenolic resin content is 4-10 wt%, wherein the phenolic resin is a thermosetting phenolic resin.

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