A formula and process for making high temperature calcined reinforced calcium silicate insulation products from low grade diatomite

Abstract

The application discloses a formula and a process for preparing high-temperature calcination reinforced calcium silicate heat-insulating products from low-grade diatomite, and comprises the following components: 10 parts of low-grade diatomite, 1-2 parts of silica ash, 3.5-4.5 parts of quicklime, 0.05-0.2 parts of industrial aluminum salt and 0.3-0.5 parts of reinforcing fiber. The process comprises the following steps: pretreating the low-grade diatomite, the quicklime, the industrial aluminum salt and the silica ash; mixing diatomite and silica ash slurry, calcium hydroxide, a solution of reinforcing agent and reinforcing fiber to obtain raw materials; performing hydration reaction on the raw materials to obtain slurry; performing pressure filtration on the slurry to form a molded piece; performing autoclave curing on the molded piece; and drying to obtain the calcium silicate heat-insulating product. The application uses low-grade diatomite to prepare qualified calcium silicate heat-insulating products, and the product prepared by the process does not decrease in residual compressive strength after being calcined at 650 DEG C for 16 hours, but increases by more than 10%, has a self-reinforcing effect after high-temperature calcination, and is beneficial to actual heat-insulating application of the product.

Description

Technical Field

[0001] This invention relates to a formula and process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth. Background Technology

[0002] The existing calcium silicate insulation products are generally prepared using the following steps: 1) Pretreatment of diatomaceous earth and quicklime: a) First, the diatomaceous earth is ground into powder using a vibratory mill and passed through a 150-300 mesh sieve. The diatomaceous earth must be grade 5 or above according to the standard of "Diatomaceous Earth" JC / T414-2017; b) The quicklime is slaked with water at a temperature of 60-80℃; 2) The diatomaceous earth and the slaked calcium hydroxide are measured according to a calcium-silicon ratio (molar ratio of calcium hydroxide to silicon dioxide) of 0.8, and then an appropriate amount of water is added according to a water-solid ratio of 7 / 1 to 9 / 1. The mixture is stirred evenly, and then a certain amount of reinforcing fiber is added. Continue stirring for 15-20 minutes. The reinforcing fiber is one or a mixture of alkali-resistant glass fiber, wood pulp, and cotton pulp, and the amount used is 2-5% of the total weight of diatomaceous earth and calcium hydroxide solids; 3) Place the stirred raw materials in a heat-insulating tank and carry out the hydration reaction at 95-99 degrees Celsius, and keep it statically heated for 6 hours; 4) Press and filter the slurry in the heat-insulating tank with a mold, and form it at a molding pressure of 8-15 MPa; 5) The molded parts are steam-cured at a steam pressure of 0.8-1.0 MPa for 18 hours; 6) Then dry it at 120-160℃ until the moisture content is less than or equal to 7%, and the type I calcium silicate insulation product is obtained.

[0003] First, the residual compressive strength of Type I calcium silicate insulation products prepared by this formula and process will decrease after uniform calcination at 650℃ for 16 hours, which will adversely affect practical applications. Second, to meet the production efficiency and the requirements for Type I products in the GB / T10699-2015 standard for calcium silicate insulation products, the raw material diatomaceous earth has high requirements, needing to be Grade 5 or above according to JC / T414-2017 standard (diatomaceous earth content greater than 30%, bulk density less than 0.60 g / cm³). If diatomaceous earth (diatom content less than 20%, compacted bulk density > 0.70 g / cm³) other than the grade 6 soil index specified in JC / T414-2017 standard is used, the reduced diatom content and high clay content will result in high slurry viscosity and poor fluidity when producing calcium silicate insulation products. This will lead to slow filter pressing and molding speed, poor strength of the pressed products, easy cracking after steam curing, and looseness after drying. The products will not meet the requirements of Type I products in the GB / T10699-2015 standard for calcium silicate insulation products.

[0004] my country has very few high-quality diatomite resources, but abundant reserves of low-grade diatomite. Utilizing low-grade diatomite (diatomite that does not meet the sixth-grade soil index specified in JC / T414-2017 standard, with a diatomite content of less than 20% and a tapped bulk density > 0.70 g / cm³) to prepare qualified calcium silicate insulation products has become a production direction with great market potential. Summary of the Invention

[0005] The purpose of this invention is to provide a technical solution for the formulation and process of making high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth, addressing the shortcomings of existing technologies.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A formula for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth is characterized by comprising the following components in parts by weight: 10 parts low-grade diatomaceous earth, 1-2 parts silica fume, 3.5-4.5 parts quicklime, 0.05-0.2 parts industrial aluminum salt, and 0.3-0.5 parts reinforcing fiber.

[0008] The process described above for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth is characterized by the following steps:

[0009] S1. Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts and silica fume;

[0010] a. First, use a vibratory mill to grind the low-grade diatomaceous earth into powder and pass it through a 150-300 mesh sieve to obtain diatomaceous earth powder;

[0011] b. Use water at a temperature of 60-70℃ to slake quicklime;

[0012] c. Prepare a 0.6 mol / L reinforcing agent solution by dissolving industrial aluminum salt in hot water;

[0013] d. Add water to silica fume at a water-to-solid ratio of 10:1, stir evenly, and then use ultrasonic equipment for wet decomposition to obtain silica fume slurry;

[0014] e. Stir and mix the diatomaceous earth powder and silica fume slurry evenly to obtain a diatomaceous earth and silica fume mixture slurry;

[0015] S2. The diatomaceous earth and silica fume mixture and the calcium hydroxide obtained from digestion are measured at a calcium-silicon ratio of 0.56 to 0.65, and water is added at a water-solid ratio of 7 / 1 to 9 / 1. The mixture is stirred evenly, and a reinforcing agent solution and reinforcing fibers are added during stirring to obtain the raw material.

[0016] S3. Place the mixed raw materials in a heat-insulating tank and carry out the hydration reaction at 95-100℃ for 4-6 hours. Continue stirring at low speed before the end of the heat-insulating period to obtain a slurry.

[0017] S4. Press and filter the slurry in the heat preservation tank using a mold. After the slurry cools to room temperature, measure the pH value to be 11.2-11.8.

[0018] S5. The molded parts are subjected to steam curing at a steam pressure of 0.8 to 1.0 MPa for 16 hours.

[0019] S6. Finally, dry at 120-160℃ to obtain calcium silicate heat insulation product.

[0020] This preparation process can produce qualified calcium silicate insulation products using low-grade diatomaceous earth (diatom content less than 20%, generally between 15% and 20%, tapped bulk density > 0.70 g / cm³) that does not meet the JC / T414-2017 standard. Due to the reduced diatom content and increased clay content, the calcium-silicon ratio is lowered from 0.8 to 0.56-0.65, alleviating the problem of excessive quicklime, improving the permeability of the slurry, and significantly increasing the pressing speed. The reinforcing agent, industrial aluminum salt solution, is slowly added under stirring, resulting in more uniform mixing, promoting crystallization, and simultaneously acting as a flocculator. The addition of pozzolanic silicate accelerates the hydration reaction and increases the gel content. Furthermore, the residual compressive strength of the product prepared by this process, after being uniformly calcined at 650℃ for 16 hours, does not decrease like ordinary calcium silicate insulation materials; instead, it increases by more than 10%, demonstrating enhanced compressive strength after high-temperature calcination, which is beneficial for practical insulation applications.

[0021] Furthermore, the diatom content in low-grade diatomite is less than 20%, and the tapped bulk density is >0.70 g / cm³. 3 .

[0022] Furthermore, during the digestion process in step S1 b, the mass ratio of water to quicklime is 8:1.

[0023] Furthermore, the industrial aluminum salt in step S1 process c is either aluminum sulfate or potassium aluminum sulfate.

[0024] Furthermore, in step S1 process e, the mass ratio of silica fume to diatomaceous earth is 1:10 to 1:5.

[0025] Furthermore, the total solids concentration in the diatomaceous earth and silica fume mixture slurry in step S1 process e is 15% to 25%.

[0026] Furthermore, the reinforcing agent solution in step S2 accounts for 0.3% to 1.0% of the total solid content.

[0027] Furthermore, the reinforcing fiber in step S2 is one or a mixture of more than one of alkali-resistant glass fiber, wood pulp and cotton pulp, and the total amount of reinforcing fiber is 2-3% of the total weight of diatomaceous earth, silica fume and calcium hydroxide solids.

[0028] Furthermore, in step S3, the stirring is carried out at a low speed for 30 minutes before the end of the heat preservation. The stirring paddle is a frame type and the speed is 10-30 r / min.

[0029] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0030] 1. Qualified calcium silicate insulation products can be made from low-grade diatomaceous earth (diatom content less than 20%, generally between 15 and 20%, and tapped bulk density > 0.70 g / cm³) that does not meet the JC / T414-2017 standard.

[0031] 2. Due to the decrease in diatom content and the increase in clay content, the calcium-silicon ratio was lowered from 0.8 to 0.56-0.65, which alleviated the problem of excessive quicklime and improved the permeability and mechanical properties of the slurry.

[0032] 3. Slowly add the reinforcing agent industrial aluminum salt solution while stirring to ensure more uniform mixing, promote crystallization reaction, and at the same time act as a flocculator.

[0033] 4. Adding silica fume with pozzolanic activity accelerates the hydration reaction and increases the gel content.

[0034] 5. The product prepared by this process does not show a decrease in residual compressive strength after being uniformly burned at 650℃ for 16 hours, unlike ordinary calcium silicate thermal insulation materials. Instead, it increases by more than 10%, demonstrating the effect of enhanced compressive strength after high-temperature burning. Detailed Implementation

[0035] This invention discloses a formula for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth, comprising the following components by weight: 10 parts low-grade diatomaceous earth, 1-2 parts silica fume, 3.5-4.5 parts quicklime, 0.05-0.2 parts industrial aluminum salt, and 0.3-0.5 parts reinforcing fiber.

[0036] This invention discloses a process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth, comprising the following steps:

[0037] S1. Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts, and silica fume; the silica fume is an industrial silicon byproduct.

[0038] a. First, use a vibratory mill to grind low-grade diatomaceous earth into powder and pass it through a 150-300 mesh sieve to obtain diatomaceous earth powder; the diatom content in the low-grade diatomaceous earth is less than 20%, and the tapped bulk density is >0.70 g / cm³. 3 .

[0039] b. Use water at a temperature of 60-70℃ to digest the quicklime; during digestion, the mass ratio of water to quicklime is 8:1.

[0040] c. Prepare a 0.6 mol / L reinforcing agent solution by mixing industrial aluminum salt with hot tap water; the industrial aluminum salt is either aluminum sulfate or potassium aluminum sulfate. Slowly add the reinforcing agent industrial aluminum salt solution while stirring to ensure more uniform mixing, promote the crystallization reaction, and simultaneously act as a flocculator.

[0041] d. Add silica fume (tap density 500-900 g / cm³) 3 The silica slurry was obtained by adding water and stirring evenly with water at a water-to-solid ratio of 10:1 and then wet decrypting it using an ultrasonic device. Adding silica ash with pozzolanic activity accelerated the hydration reaction and increased the gel content.

[0042] e. Mix diatomaceous earth powder and silica fume slurry evenly to obtain a diatomaceous earth and silica fume mixed slurry; the mass ratio of silica fume to diatomaceous earth is 1:10 to 1:5. The total solids concentration in the diatomaceous earth and silica fume mixed slurry is 15% to 25%.

[0043] S2. The diatomaceous earth and silica fume mixture, along with the slaked calcium hydroxide, are measured at a calcium-to-silicon ratio of 0.56–0.65. Water is then added at a water-to-solid ratio of 7 / 1–9 / 1. The mixture is stirred until homogeneous. During stirring, a reinforcing agent solution and reinforcing fibers are added to obtain the raw material. The reinforcing fibers are one or more of alkali-resistant glass fiber, wood pulp, and cotton pulp. The total amount of reinforcing fibers is 2–5% of the total weight of the diatomaceous earth, silica fume, and calcium hydroxide solids. The reinforcing agent solution accounts for 0.3–1.0% of the total solid content. Due to the reduced diatomaceous earth content and increased clay content, the calcium-to-silicon ratio is lowered from 0.8 to 0.56–0.65, alleviating the problem of excessive quicklime and improving the permeability of the slurry.

[0044] S3. Place the mixed raw materials in an insulated tank and carry out the hydration reaction at 95-100℃ for 4-6 hours. 30 minutes before the end of the insulation, continuously stir at a low speed of 10-30 r / min to obtain the slurry.

[0045] S4. While the slurry in the heat-insulating tank is still hot, press and filter it using a mold. After the slurry cools to room temperature, measure the pH value to be 11.2-11.8.

[0046] S5. The molded parts are subjected to steam curing at a steam pressure of 0.8 to 1.0 MPa for 16 hours.

[0047] S6. Finally, dry at 120-160℃ to obtain calcium silicate heat insulation product.

[0048] This preparation process can use low-grade diatomaceous earth (diatom content less than 20%, generally between 15% and 20%, tapped bulk density > 0.70 g / cm³) that does not meet the JC / T414-2017 standard to produce qualified calcium silicate insulation products.

[0049] Example 1

[0050] A process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth includes the following steps:

[0051] 1) Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts, and silica fume;

[0052] a. First, use a vibratory mill to grind low-grade diatomaceous earth (according to JC / T414-2017 standard test, diatom content 18%, tapped bulk density 0.72 g / cm³, SiO2 content 66.78%) into powder and pass it through a double-layer 150 mesh sieve.

[0053] b. Use 8 parts of water at 70℃ to digest 1 part of quicklime. After aging for 10 days, remove part of the clear liquid from the top layer and prepare a lime slurry with a CaO content of 13.5% and a solid impurity content of about 5%.

[0054] c. Prepare anhydrous aluminum sulfate into a 0.6 mol / L aqueous solution;

[0055] d. Add 10kg of silica fume (SiO2 content 92%) to 100kg of water, stir evenly, and then ultrasonically decrypt for 15 minutes;

[0056] e. Add 100 kg of diatomaceous earth powder and 401 kg of water to the above silica fume slurry and stir until evenly mixed. The weight ratio of silica fume to diatomaceous earth is 1:10, and the total solids concentration is 18%.

[0057] 2) Measure the diatomaceous earth and the lime slurry obtained from digestion according to a calcium-silicon ratio of 0.56, add 294 kg of lime slurry, and then add 531 kg of water according to a water-to-solid ratio of 7.7:1. Stir with a propeller at 600 rpm for 15 minutes. During this stirring, slowly add 3 L of anhydrous aluminum sulfate solution, 2.5 kg of cotton fiber and 0.8 kg of easily dispersible alkali-resistant glass fiber. The total amount of anhydrous aluminum sulfate and reinforcing fiber accounts for about 0.4% and 2% of the total solids contained in the diatomaceous earth, silica fume and lime slurry, respectively.

[0058] 3) Pump the mixed raw materials into a heat preservation tank using a mud pump and keep them at 98℃ for 5 hours. Then, continuously stir the mixture in the heat preservation tank using a frame stirring method for 30 minutes at a speed of 20 r / min, for a total heat preservation time of 5.5 hours.

[0059] 4) Place the slurry in the heat preservation tank into the mold, and while it is still hot, press it on a hydraulic press equipped with the mold at a pressure of 13 MPa to form the slurry. After the slurry cools, the pH value is 11.24.

[0060] 5) The molded parts are subjected to autoclaving at a steam pressure of 0.9 MPa and a temperature of 180°C for 16 hours;

[0061] 6) Then dry with hot air at 150℃ to obtain calcium silicate insulation products. According to GB / T10699-2015 "Calcium Silicate Insulation Products", its density, mass moisture content, compressive strength, flexural strength, thermal conductivity, and uniform temperature burning performance were measured, as shown in Table 1.

[0062]

[0063] Table 1

[0064] The type I calcium silicate insulation products prepared by this process conform to the standard GB / T10699-2015 "Calcium Silicate Insulation Products", and their density physical properties reach a density ≤240kg / m³. 3 The product must meet the following requirements: moisture content ≤ 7.5%, compressive strength ≥ 0.65 MPa, flexural strength ≥ 0.33 MPa, thermal conductivity (100℃) ≤ 0.065 W / (m·K), linear shrinkage rate ≤ 2% during uniform calcination, no through cracks, and remaining compressive strength ≥ 0.4 MPa, with the remaining compressive strength increasing by 16% compared to before uniform calcination.

[0065] Example 2

[0066] A process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth includes the following steps:

[0067] 1) Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts, and silica fume, a byproduct of the metallic silicon industry;

[0068] a. First, use a vibratory mill to grind low-grade diatomaceous earth (according to JC / T414-2017 standard test, diatom content 16%, tapped bulk density 0.79 g / cm³, SiO2 content 65.64%) into powder and pass it through a double-layer 180 mesh sieve.

[0069] b. Use 8 parts of water at 65℃ to digest 1 part of quicklime. After aging for 10 days, remove part of the clear liquid from the top layer and prepare a lime slurry with a CaO content of 13.7% and a solid impurity content of about 5%.

[0070] c. Dissolve potassium aluminum sulfate in hot water at 80 degrees Celsius to prepare a 0.6 mol / L aqueous solution;

[0071] d. Add 10kg of silica fume (SiO2 content 92%) to 100kg of water, stir evenly, and then ultrasonically decrypt for 15 minutes;

[0072] e. Add 66.7 kg of diatomaceous earth powder and 262 kg of water to the above silica fume slurry and stir until evenly mixed. The weight ratio of silica fume to diatomaceous earth is 3:20, and the total solids concentration is 17.5%.

[0073] 2) Measure the diatomaceous earth and the lime slurry obtained from digestion according to a calcium-silicon ratio of 0.60, add 217 kg of lime slurry, and then add 452 kg of water according to a water-to-solid ratio of 8.4:1. Mix and stir evenly, and stir with a propeller at 600 rpm for 15 minutes. During this stirring, slowly add 6 L of potassium aluminum sulfate solution, 2 kg of cotton fiber and 0.7 kg of easily dispersible alkali-resistant glass fiber. The total amount of potassium aluminum sulfate and reinforcing fiber accounts for about 0.8% and 2% of the total solids contained in diatomaceous earth, silica fume and lime slurry, respectively.

[0074] 3) Pump the mixed raw materials into an insulated tank and keep them at 98℃ for 4.5 hours. Then, continue to stir in the insulated tank for 30 minutes, for a total of 5 hours.

[0075] 4) Place the slurry in the heat preservation tank into the mold, and while it is still hot, press it into shape under a pressure of 11 MPa on a hydraulic press equipped with the mold. After the slurry cools, the pH value is 11.43.

[0076] 5) The molded parts are subjected to autoclaving at a steam pressure of 0.8 MPa and a temperature of 175°C for 16 hours;

[0077] 6) Then dry with hot air at 143℃ to obtain calcium silicate insulation products. According to GB / T10699-2015 "Calcium Silicate Insulation Products", its density, mass moisture content, compressive strength, flexural strength, thermal conductivity, and uniform temperature burning performance were measured, as shown in Table 2.

[0078]

[0079]

[0080] Table 2

[0081] The type I calcium silicate insulation products prepared by this process conform to the standard GB / T10699-2015 "Calcium Silicate Insulation Products", and their density physical properties reach a density ≤240kg / m³. 3 The product must meet the following requirements: moisture content ≤ 7.5%, compressive strength ≥ 0.65 MPa, flexural strength ≥ 0.33 MPa, thermal conductivity (100℃) ≤ 0.065 W / (m·K), uniform calcination performance linear shrinkage ≤ 2%, no through cracks, and remaining compressive strength ≥ 0.4 MPa, with the remaining compressive strength increasing by 15% compared to before uniform calcination.

[0082] Example 3

[0083] A process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth includes the following steps:

[0084] 1) Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts, and silica fume;

[0085] a. First, use a vibratory mill to grind low-grade diatomaceous earth (according to JC / T414-2017 standard test, diatom content 15%, tapped bulk density 0.82 g / cm³, SiO2 content 65.88%) into powder and pass it through a double-layer 150 mesh sieve.

[0086] b. Use 8 parts of water at 67℃ to digest 1 part of quicklime. After aging for 10 days, remove part of the clear liquid from the top layer and prepare a lime slurry with a CaO content of 13.3% and a solid impurity content of about 5%.

[0087] c. Dissolve potassium aluminum sulfate in hot water at 80 degrees Celsius to prepare a 0.6 mol / L aqueous solution;

[0088] d. Add 15kg of silica fume (SiO2 content 92%) to 150kg of water, stir evenly, and then sonicate for 15 minutes.

[0089] e. Add 75 kg of diatomaceous earth powder and 271 kg of water to the above silica fume slurry and stir until evenly mixed. The weight ratio of silica fume to diatomaceous earth is 1:5, and the total solids concentration is 17.6%.

[0090] 2) Measure the diatomaceous earth and the lime slurry obtained from digestion according to a calcium-silicon ratio of 0.65, add 288 kg of lime slurry, and then add 548 kg of water according to a water-to-solid ratio of 8.4:1. Mix and stir evenly, and stir with a propeller at 600 rpm for 15 minutes. During this stirring, slowly add 5.5 L of potassium aluminum sulfate solution, 2 kg of cotton fiber, 1 kg of wood pulp and 0.8 kg of easily dispersible alkali-resistant glass fiber. The total amount of potassium aluminum sulfate and reinforcing fiber accounts for about 0.6% and 3% of the total solids contained in diatomaceous earth, silica fume and lime slurry, respectively.

[0091] 3) Pump the mixed raw materials into an insulated tank and keep them at 98℃ for 4 hours. Then, continue to stir in the insulated tank in a frame for 30 minutes, for a total of 4.5 hours.

[0092] 4) Place the slurry in the heat preservation tank into the mold, and while it is still hot, press it on a hydraulic press equipped with the mold under a pressure of 10 MPa to form the slurry. After the slurry cools down, the pH value is 11.67.

[0093] 5) The molded parts were steam-cured at 0.8 MPa steam pressure and 175℃ for 16 hours; 6) Then, they were dried with hot air at 152℃ to obtain the calcium silicate insulation product. According to GB / T10699-2015 "Calcium Silicate Insulation Products", its density, moisture content, compressive strength, flexural strength, thermal conductivity, and uniform temperature burning performance were measured, as shown in Table 3.

[0094]

[0095] Table 3

[0096] The type I calcium silicate insulation products prepared by this process conform to the standard GB / T10699-2015 "Calcium Silicate Insulation Products", and their density physical properties reach a density ≤240kg / m³. 3 The product must meet the following requirements: moisture content ≤ 7.5%, compressive strength ≥ 0.65 MPa, flexural strength ≥ 0.33 MPa, thermal conductivity (100℃) ≤ 0.065 W / (m·K), linear shrinkage rate ≤ 2% during uniform calcination, no through cracks, and remaining compressive strength ≥ 0.4 MPa, with the remaining compressive strength increasing by 21% compared to before uniform calcination.

[0097] Comparative Example 1

[0098] The production of calcium silicate insulation products using low-grade diatomaceous earth according to conventional formulas and processes includes the following steps:

[0099] 1) Pre-treat low-grade diatomaceous earth and quicklime;

[0100] a. First, use a vibratory mill to grind low-grade diatomaceous earth (according to JC / T414-2017 standard test, diatom content 18%, tapped bulk density 0.72 g / cm³, SiO2 content 66.78%) into powder, pass it through a double-layer 150-mesh sieve, take 80 kg of the diatomaceous earth powder and add 370 kg of water, stir evenly, and prepare a diatomaceous earth slurry with a solid content of 17.8%;

[0101] b. Use 8 parts of water at 70℃ to digest 1 part of quicklime. After aging for 10 days, remove part of the clear liquid from the top layer and prepare a lime slurry with a CaO content of 13.5% and a solid impurity content of about 5%.

[0102] 2) Measure the diatomaceous earth and the lime slurry obtained from digestion according to a calcium-silicon ratio of 0.80, add 295 kg of lime slurry, and then add 472 kg of water according to a water-solid ratio of 8.0:1. Stir at 600 rpm for 15 minutes. During this stirring, gradually add 2 kg of reinforcing fiber cotton pulp, 1 kg of wood pulp, and 1 kg of alkali-resistant glass fiber. Then continue stirring for 20 minutes. The total amount of reinforcing fiber accounts for about 3% of the total solid content of diatomaceous earth and lime slurry.

[0103] 3) Pump the mixed raw materials into an insulated tank using a mud pump and keep them at 98℃ for 6 hours;

[0104] 4) Place the slurry from the heat preservation tank into the mold, and while it is still hot, press it into shape under a pressure of 13 MPa on a hydraulic press equipped with the mold. After the slurry cools, the pH value is 11.9.

[0105] 5) The molded parts are subjected to autoclaving at a steam pressure of 0.9 MPa and a temperature of 180°C for 16 hours;

[0106] 6) Then dry with hot air at 150℃ to obtain calcium silicate insulation products. According to GB / T10699-2015 "Calcium Silicate Insulation Products", its density, mass moisture content, compressive strength, flexural strength, thermal conductivity, and uniform temperature burning performance were measured, as shown in Table 1.

[0107]

[0108]

[0109] Type I calcium silicate insulation products containing reinforcing fibers, prepared using low-grade diatomaceous earth and conventional processes, achieve a density ≤240 kg / m³. 3 The product has a moisture content of ≤7.5% and a thermal conductivity (100℃) of ≤0.065W / (m·K). However, its compressive strength, flexural strength, and uniform temperature burning performance all fail to meet the requirements of the standard GB / T10699-2015 "Calcium Silicate Insulation Products", which stipulates that the moisture content should be ≤2%, there should be no through cracks, and the remaining compressive strength should be ≥0.4MPa. Furthermore, the remaining compressive strength is 13% lower than that before uniform temperature burning.

[0110] Comparative Example 2

[0111] The production of calcium silicate insulation products using high-grade diatomaceous earth according to conventional formulas and processes includes the following steps:

[0112] 1) Pre-treat high-grade diatomaceous earth and quicklime;

[0113] a. First, use a vibratory mill to grind high-grade diatomaceous earth (according to JC / T414-2017 standard test, diatom content 32%, tapped bulk density 0.55 g / cm³, SiO2 content 65.37%) into powder, pass it through a double-layer 150-mesh sieve, take 80 kg of the diatomaceous earth powder and add 370 kg of water, stir evenly, and prepare a diatomaceous earth slurry with a solid content of 17.8%;

[0114] b. Use 8 parts of water at 70℃ to digest 1 part of quicklime. After aging for 10 days, remove part of the clear liquid from the top layer and prepare a lime slurry with a CaO content of 13.5% and a solid impurity content of about 5%.

[0115] 2) Measure the diatomaceous earth and the lime slurry obtained from digestion according to a calcium-silicon ratio of 0.80, add 289 kg of lime slurry, and then add 470 kg of water according to a water-solid ratio of 8.0:1. Stir at 600 rpm for 15 minutes. During this stirring, gradually add 2 kg of reinforcing fiber cotton pulp, 1 kg of wood pulp, and 1 kg of alkali-resistant glass fiber. Then continue stirring for 20 minutes. The total amount of reinforcing fiber accounts for about 3% of the total solid content of diatomaceous earth and lime slurry.

[0116] 3) Pump the mixed raw materials into an insulated tank using a mud pump and keep them at 98℃ for 6 hours;

[0117] 4) Place the slurry in the heat preservation tank into the mold, and while it is still hot, press it into shape under a pressure of 12 MPa on a hydraulic press equipped with the mold. After the slurry cools, the pH value is 11.5.

[0118] 5) The molded parts are subjected to autoclaving at a steam pressure of 0.9 MPa and a temperature of 180°C for 16 hours;

[0119] 6) Then dry with hot air at 150℃ to obtain calcium silicate insulation products. According to GB / T10699-2015 "Calcium Silicate Insulation Products", its density, mass moisture content, compressive strength, flexural strength, thermal conductivity, and uniform temperature burning performance were measured, as shown in Table 1.

[0120]

[0121] Type I calcium silicate insulation products containing reinforcing fibers, prepared using low-grade diatomaceous earth and conventional processes, achieve a density ≤240 kg / m³. 3 The product must meet the following requirements: moisture content ≤ 7.5%, compressive strength ≥ 0.65 MPa, flexural strength ≥ 0.33 MPa, thermal conductivity (100℃) ≤ 0.065 W / (m·K), linear shrinkage rate ≤ 2% during uniform calcination, no through cracks, and remaining compressive strength ≥ 0.4 MPa, but the remaining compressive strength must be 16% lower than before uniform calcination.

[0122] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to achieve substantially the same technical effect are all covered within the protection scope of the present invention.

Claims

1. A process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth, characterized in that... Includes the following steps: S1. Pre-treat low-grade diatomaceous earth, quicklime, industrial aluminum salts and silica fume; a. First, the low-grade diatomaceous earth is ground into powder using a vibratory mill and then passed through a 150-300 mesh sieve to obtain diatomaceous earth powder; b. The quicklime is slaked with water at a temperature of 60-70℃ to obtain lime slurry; c. Prepare a 0.6 mol / L reinforcing agent solution by dissolving the industrial aluminum salt in hot water; d. The silica fume is mixed with water at a water-to-solid ratio of 10:1 and then wet-decomposed using an ultrasonic device to obtain silica fume slurry. e. Stir and mix the diatomaceous earth powder and the silica fume slurry evenly to obtain a diatomaceous earth and silica fume mixed slurry; S2. The diatomaceous earth and the digested calcium hydroxide are measured at a calcium-silicon molar ratio of 0.56 to 0.

65. Lime slurry is added to the diatomaceous earth and silica fume mixture, and water is added at a water-to-solid ratio of 7 / 1 to 9 / 1. The mixture is stirred evenly. During stirring, the reinforcing agent solution and reinforcing fibers are added to obtain the raw material. S3. Place the stirred raw materials in a heat-insulating tank and carry out the hydration reaction at 95-100°C for 4-6 hours. Continue stirring at low speed until the end of the heat-insulating process to obtain a slurry. S4. The slurry in the heat preservation tank is pressed and filtered using a mold. After the slurry is cooled to room temperature, the pH value is measured to be 11.2 to 11.

8. S5. The molded parts are subjected to steam curing at a steam pressure of 0.8 to 1.0 MPa for 16 hours. S6. Finally, dry at 120-160℃ to obtain calcium silicate heat insulation product. The calcium silicate insulation product is composed of the following parts by weight: 10 parts low-grade diatomaceous earth, 1-2 parts silica fume, 3.5-4.5 parts quicklime, 0.05-0.2 parts industrial aluminum salt, and 0.3-0.5 parts reinforcing fiber; The low-grade diatomaceous earth contains less than 20% diatoms and has a tapped bulk density > 0.70 g / cm³. 3 .

2. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: During the digestion process in step S1b, the mass ratio of water to quicklime is 8:

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3. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: The industrial aluminum salt mentioned in step S1, process c, is either aluminum sulfate or potassium aluminum sulfate.

4. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: The mass ratio of silica fume to diatomaceous earth in step S1 process e is 1:10 to 1:

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5. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: The total solids concentration in the diatomaceous earth and silica fume mixture slurry in step S1 process e is 15% to 25%.

6. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: The reinforcing agent solution in step S2 accounts for 0.3 to 1.0% of the total weight of diatomaceous earth, silica fume, and the solid calcium hydroxide obtained from digestion.

7. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: The reinforcing fiber in step S2 is one or a mixture of more than one of alkali-resistant glass fiber, wood pulp and cotton pulp, and the total amount of the reinforcing fiber is 2 to 3% of the total weight of the diatomaceous earth, the silica fume and the calcium hydroxide solid.

8. The process for producing high-temperature calcination-reinforced calcium silicate insulation products using low-grade diatomaceous earth according to claim 1, characterized in that: In step S3, stir continuously at a low speed for 30 minutes before the end of the heat preservation period, with a speed of 10-30 r / min.

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