Method for preparing foamed glass from silicon slag after extracting aluminum from coal gangue

Abstract

The application discloses a method for preparing foamed glass from silicon slag after extracting aluminum from coal gangue, and belongs to the field of solid waste resource utilization and inorganic porous materials. The method comprises the following steps: mixing the silicon slag after extracting aluminum from coal gangue with a foam stabilizer by ball milling to obtain powder I; in the presence of water, mixing a gel agent, a surfactant and the powder I and performing shearing stirring to obtain a foamed ore pulp; the stirring rate of the shearing stirring is 1200-2000 r / min; pouring the gel foamed ore pulp into a mold, sintering the surface of the pulp by flame, and then performing solidification treatment to obtain a foamed glass blank; and performing drying treatment and sintering treatment on the foamed glass blank, and the foamed glass is obtained. The method can obtain a foamed glass material with ultra-low volume water absorption (less than 0.2%) and ultra-low thermal conductivity (<0.02 W / m.K).

Description

Technical Field

[0001] This invention relates to a method for preparing foamed glass from silica slag after aluminum extraction from coal gangue, belonging to the technical field of solid waste resource utilization and inorganic porous materials. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. Its accumulated volume is enormous, consuming vast amounts of land resources and causing environmental pollution. Rich in alumina and silica, coal gangue is often used in acid or alkali processes for aluminum extraction. After aluminum extraction, the SiO2 content is 60-80%. The output is huge, and currently, there is a lack of efficient large-scale utilization methods; it is mostly disposed of through stockpiling, causing secondary pollution and resource waste. How to achieve high-value-added resource utilization of the silica slag after aluminum extraction from coal gangue has become a critical issue urgently needing to be addressed in the field of solid waste treatment.

[0003] Foamed glass is an inorganic porous material made primarily from waste glass and slag through a high-temperature foaming process. It possesses excellent properties such as lightweight, fire resistance, corrosion resistance, and low thermal conductivity, making it widely used in building insulation, industrial pipeline insulation, and cold storage insulation. Compared to foamed ceramics, foamed glass has a significantly lower thermal conductivity, resulting in a lighter weight for the same volume, making it easier to transport, handle, and install. It also effectively reduces the load on building structures and performs better as an insulation material. Furthermore, foamed glass exhibits excellent water resistance, with low water absorption and permeability, giving it an irreplaceable advantage in humid environments or applications with extremely high waterproofing requirements (such as cold storage and underground structures).

[0004] Currently, the industrial production of foamed glass generally employs the powder sintering method, which involves mixing glass powder with a foaming agent (such as calcium carbonate or carbon black) and then softening the glass and decomposing the foaming agent at high temperatures (typically >850℃) to generate gas, forming a porous structure. However, this method has the following technical drawbacks: First, the size and distribution of bubbles are difficult to control precisely, easily leading to uneven pore size and large pore defects, affecting the stability of the product's mechanical properties and thermal insulation effect; second, the product has a high volumetric water absorption rate, causing it to easily absorb water and increase in weight in humid environments, which not only reduces the thermal insulation effect but may also cause freeze-thaw damage; third, the high thermal conductivity results in insufficient thermal insulation performance, making it difficult to meet the requirements of high-standard building energy-saving materials; fourth, the raw materials mainly rely on waste glass, limiting the available sources.

[0005] However, research on methods for preparing foamed glass using silica slag from coal gangue after aluminum extraction as the main raw material is still insufficient, and mature process routes are lacking. In summary, developing a method for preparing foamed glass using silica slag from coal gangue after aluminum extraction as the main raw material is of great significance for realizing the high-value utilization of coal gangue resources. Summary of the Invention

[0006] To address the problems existing in the prior art, one of the objectives of this invention is to provide a method for preparing foamed glass from silica slag after aluminum extraction from coal gangue. This method uses silica slag after aluminum extraction from coal gangue as the core raw material, combining mechanical shear foaming, gel casting, and surface flame sintering processes. By optimizing the foaming and stabilizing system, foamed glass materials with both ultra-low volume water absorption (less than 0.2%) and ultra-low thermal conductivity (<0.02 W / m·K) are obtained at a relatively low sintering temperature. This achieves high-value-added utilization of coal gangue slag, and features a simple process flow, low energy consumption, wide availability of raw materials, and excellent product performance, thus having good prospects for widespread application.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing foamed glass from silica slag after aluminum extraction from coal gangue, the method comprising:

[0008] (1) Powder I is obtained by ball milling and mixing the silica slag after aluminum extraction from coal gangue with a foam stabilizer;

[0009] (2) In the presence of water, the gelling agent, surfactant and powder I are mixed and sheared to obtain foam slurry; the shearing and stirring rate is 1200~2000 r / min;

[0010] (3) The gel foam slurry is cast into a mold, the surface of the slurry is sintered by flame, and then cured to obtain a foamed glass blank; the conditions for flame sintering include: flame temperature of 300~1300℃, flame distance from slurry surface of 10~30cm, and sweeping speed of 1~2m / s.

[0011] (4) The foamed glass preform is dried and sintered to obtain the final product.

[0012] In the existing technology, foamed glass is mostly made from waste glass and powder sintering method. The foaming process depends on the decomposition reaction of the foaming agent at high temperature. The pore structure is difficult to control precisely, resulting in high energy consumption, product performance fluctuation, high water absorption rate and poor heat preservation performance. The key innovation of this invention is: (1) In this invention, the silica slag after aluminum extraction from coal gangue is mixed evenly with the foam stabilizer, which can reduce the surface tension of the liquid and promote nucleation. In the subsequent high-speed shearing process, the entrained air instantly forms a large number of stable bubbles. At the same time, it can ensure the formation of uniform and delicate foam and prevent the bubbles from merging, collapsing or cracking. At the same time, the foam stabilizer can also regulate the viscosity and surface tension of the high-temperature melt to prevent the bubbles from merging and growing during the sintering process. (2) This invention combines mechanical shearing foaming, gel casting, and surface flame sintering processes. High-speed shearing disperses gas in the slurry to form microbubbles, which are then rapidly solidified with the help of a gelling agent, stably fixing the bubbles within the preform. This results in a fine-sized, uniformly distributed pore structure during room-temperature foaming. The surface flame sintering process ensures that the foamed glass also possesses a high closed-cell rate. Furthermore, the synergistic effect of the various features of this invention enables the preparation of foamed glass with high closed-cell rate and low thermal conductivity. This invention uses silica slag from coal gangue after aluminum extraction as the main raw material (SiO2 content 60-80 wt%) to prepare foamed glass. Combined with the other technical features of this application, foamed glass materials with ultra-low volumetric water absorption and ultra-low thermal conductivity can be obtained without the addition of waste glass.

[0013] In this invention, the silicon slag after aluminum extraction from coal gangue refers to the high-silica powder material after aluminum extraction from coal gangue through acid leaching or alkali leaching.

[0014] As a preferred embodiment, the ball milling time is 10-20 minutes, and the ball-to-material ratio is 4-12:1.

[0015] As a preferred embodiment, the mass ratio of the foam stabilizer to the silica slag after aluminum extraction from coal gangue is 0.01~0.06:1. The amount of foam stabilizer added is very sensitive. If the amount of foam stabilizer is too small, the bubbles will be unstable and collapse immediately; if the amount of foam stabilizer is too large, the foam will be too stable, causing the cell walls to fail to rupture at the appropriate time (i.e., "closed-cell"), resulting in product shrinkage or excessive hardness.

[0016] As a preferred embodiment, in step (2), the dry weight ratio of the gelling agent to the free SiO2 in the silica slag after aluminum extraction from coal gangue is 0.02-0.03:1. The relative content of SiO2 and Na2O in the silica slag after aluminum extraction from coal gangue varies depending on the aluminum extraction process (acid method or alkali method). Sodium silicate, formed by the reaction of SiO2 and Na2O, has a certain gelling effect. The gelling agent mainly acts on the free SiO2 and silicate minerals that have not combined with Na2O. If the gelling agent dosage is too high, the slurry fluidity is poor, the system viscosity rises sharply, mixing and molding become difficult, and the foaming ratio will be affected. If the gelling agent dosage is too low, gelling is insufficient, the green body strength is low, it is easily damaged during demolding and handling, and it is prone to collapse and cracking during high-temperature sintering.

[0017] It should be noted that the calculation method for the mass of free SiO2 in the silica slag after aluminum extraction from coal gangue is: m(SiO2) = 60 g / mol × [n(SiO2) - 1.2n(Na2O)], where n(SiO2) represents the amount of substance of SiO2 and n(Na2O) represents the amount of substance of Na2O.

[0018] As a preferred embodiment, in step (2), the mass ratio of the surfactant, powder I, and water (on a dry basis) is 0.002~0.004:0.8~1.2:1. If the amount of surfactant is too high, it will damage the liquid film strength, leading to bubble coalescence, system collapse ("collapsed bubbles"), unstable bubbles, a large number of open pores, uneven distribution, and large pore size, which will seriously affect the water absorption rate and heat preservation performance of the product; if the amount of surfactant is too low, stable foam cannot be formed, and the foaming ratio is low and insufficient.

[0019] As a more preferred embodiment, in step (2), the mass ratio of the surfactant, the powder I, and the water on a dry basis is 0.002~0.004:1:1.

[0020] As a preferred method, the flame sintering conditions include: a flame temperature of 600~1200℃ and a flame distance of 15~30cm from the slurry surface. A suitable defoaming process helps eliminate open-cell structures on the surface, increases the closed-cell rate, and enhances waterproofing and thermal insulation performance. Experiments have shown that foamed glass prepared under these preferred conditions has a lower volumetric water absorption rate.

[0021] As a preferred embodiment, the shearing stirring rate is 1500~2000 r / min, and the time is 30~60 min. Insufficient shearing force during shearing stirring fails to break up the entrained air into microbubbles, causing large bubbles to easily merge, float, or even rupture, resulting in uneven foam pore size and low closed-cell rate. Excessive shearing force cuts the bubbles too finely, resulting in extremely thin bubble walls. Before solidification, the foam is prone to localized collapse or excessive closed-cell formation, leading to severe shrinkage upon cooling, causing deformation or cracking of the foamed glass. In this preferred embodiment, it is ensured that the gas is sufficiently sheared and dispersed into microbubbles and uniformly distributed in the slurry, forming a stable foam with high aeration.

[0022] As a preferred embodiment, the foam stabilizer is selected from at least one of trisodium phosphate, tripotassium phosphate, boric acid, and borax. The aforementioned foam stabilizer can adjust slurry properties, strengthen the bubble film, assist in controlling the gelation process, stabilize wet preform foam, adjust melt viscosity, inhibit Ostwald curing, promote uniform nucleation, and assist in controlling melt foam, playing a role in stabilizing bubbles during the room-temperature casting and / or high-temperature sintering foaming stages.

[0023] As a preferred embodiment, the gelling agent is selected from at least one of carboxymethyl cellulose, soluble starch, and sodium alginate. The gelling agent is of industrial or analytical grade. In this preferred embodiment, the viscosity of the slurry can be increased, the stability of the foam can be enhanced, and the merging or escape of bubbles before solidification can be prevented.

[0024] As a preferred embodiment, the surfactant is selected from at least one of sodium dodecyl sulfonate, dodecylamine, hexadecyl methyl ammonium bromide, and Sapindus saponins. The surfactant is commercially available as industrially pure or analytically pure. In this preferred embodiment, the gas-liquid interfacial tension is reduced, promoting bubble formation and refinement, which is beneficial for obtaining a uniform microfoam structure.

[0025] As a preferred embodiment, the particle size of the silica slag after aluminum extraction from coal gangue is no greater than 10 μm, and the SiO2 content is 60-80 wt%, the Al2O3 content is 1-10 wt%, and the Na2O content is 4-24 wt%. Although the chemical composition of the silica slag after aluminum extraction from coal gangue may vary depending on the aluminum extraction process (acid method or alkali method) and the Al2O3 extraction rate, the silica slag after aluminum extraction from coal gangue under this preferred condition can meet the raw material composition ratio for foamed glass with low volume water absorption.

[0026] As a preferred embodiment, the temperature of the mold during injection molding is 60~80℃, and more preferably 70~80℃.

[0027] As a preferred embodiment, the curing treatment temperature is 30~80℃, and the time is 8~24h. Appropriate temperature and holding time are beneficial for the complete curing and shaping of the blank, avoiding deformation or cracking during demolding.

[0028] As a preferred embodiment, the drying process is performed by heating to 100-120°C at a rate of 2-8°C / min and holding at that temperature for 1-4 hours. An appropriate heating rate can prevent rapid moisture evaporation from causing cracking of the green body.

[0029] As a preferred embodiment, the sintering treatment is carried out at a temperature of 800~1000℃ for a time of 0.5~1h. During the sintering process, the powder melts and encapsulates air bubbles, forming a closed-cell foam structure.

[0030] As a preferred approach, cooling is performed after sintering. Slow cooling (annealing) after sintering is a key step in eliminating internal stress and preventing cracking of the product.

[0031] Compared with the prior art, the present invention has at least the following advantages:

[0032] (1) This invention uses silicon slag after aluminum extraction from coal gangue as the main raw material, realizing the high-value-added resource utilization of solid waste, and has significant environmental and economic benefits.

[0033] (2) This invention adopts mechanical shear foaming, gel casting and surface flame sintering process. By optimizing the foaming and stabilizing system, without the need for external high temperature foaming agent, the gas is dispersed in the slurry by high speed shearing to form micro bubbles. The bubbles are stabilized and fixed by the synergistic effect of the gel system and the surface flame sintering defoaming process. A fully closed-cell foam structure with small pore size and uniform distribution is obtained. This breaks through the limitation of the traditional powder sintering method for preparing foamed glass, which makes it difficult to accurately control the size and structure of bubbles. It greatly improves the thermal insulation performance and waterproof performance.

[0034] (3) By adding a specific foam stabilizer, the present invention effectively controls the viscosity and surface tension of the glass melt during the sintering stage, inhibits bubble coalescence, and ensures that the final product has excellent properties such as high closed-cell rate, high water resistance (volume water absorption rate less than 0.2%) and ultra-low thermal conductivity (<0.02 W / m·K).

[0035] (4) The foamed glass products prepared by the present invention have uniform pore structure, ultra-low water absorption rate and ultra-low thermal conductivity, and excellent performance. They can be widely used in building insulation, industrial pipeline insulation, cold storage insulation and other fields. Detailed Implementation

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] In this invention, room temperature refers to 25±2℃.

[0038] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0040] Volumetric water absorption rate was tested according to GB / T 5486-2008 standard; thermal conductivity was tested according to GB / T 10294-2008 standard.

[0041] In the following examples, 1 portion means 10g.

[0042] Example 1

[0043] The silica slag after aluminum extraction from coal gangue is a high-silica powder material obtained after aluminum extraction from coal gangue by alkaline leaching; its particle size is less than 10μm, and its SiO2 content is 72 wt%, Al2O3 content is 4 wt%, Na2O content is 16 wt%, and other components content is 8 wt%.

[0044] Step 1: Take 100 parts of the silica slag after aluminum extraction from coal gangue, add 5 parts of trisodium phosphate foam stabilizer, place it in a ball mill and ball mill for 15 minutes. The ball-to-material ratio is 8:1 to obtain powder I.

[0045] Step 2: In the presence of water, carboxymethyl cellulose, sodium dodecyl sulfonate, and powder I are mixed and stirred at 1600 r / min under high shear for 45 min to fully shear and disperse the gas absorbed into the slurry, forming a foam slurry with high aeration. The mass ratio of sodium dodecyl sulfonate, powder I, and water on a dry basis is 0.003:1:1, and the mass ratio of carboxymethyl cellulose on a dry basis to free SiO2 in the silica slag after aluminum extraction from coal gangue on a dry basis is 0.025:1.

[0046] Step 3: Pour the foamed slurry into an 80℃ high-temperature mold. After the slurry has poured and leveled, quickly sweep the surface of the slurry with a flame jet at a temperature of 900℃, a flame distance of 20cm, and a sweeping speed of 2m / s. After defoaming, cure at 50℃ for 12 hours, then demold to obtain the foamed glass preform.

[0047] Step 4: Heat the foamed glass preform to 110°C at a heating rate of 5°C / min, dry it for 2 hours, then sinter it at 850°C for 0.8 hours, and finally place it in an annealing furnace to slowly cool it to room temperature for 30 hours to obtain the finished foamed glass product.

[0048] Tests showed that the foamed glass prepared in this embodiment had a uniform pore distribution, a volume water absorption rate of 0.16%, and a thermal conductivity of 0.018 W / m·K.

[0049] Example 2

[0050] The silica slag after aluminum extraction from coal gangue is a high-silica powder material after aluminum extraction from coal gangue by acid leaching; its particle size is less than 10μm, and its SiO2 content is 80 wt%, Al2O3 content is 5 wt%, Na2O content is 4 wt%, and other components content is 11 wt%.

[0051] Step 1: Take 100 parts of the silica slag after aluminum extraction from coal gangue, add 3 parts of borax foam stabilizer, place it in a ball mill and ball mill for 12 minutes, with a ball-to-material ratio of 10:1, to obtain powder I;

[0052] Step 2: In the presence of water, soluble starch (CAS: 9005-84-9, analytical grade (AR), Tianjin Kemei Chemical Reagent Co., Ltd. or Nanjing Chemical Reagent Co., Ltd.), hexadecyl methyl ammonium bromide, and powder I are mixed and stirred at 1500 r / min under high shear for 50 min to fully shear and disperse the gas absorbed in the slurry, forming a foam slurry with high aeration. The mass ratio of hexadecyl methyl ammonium bromide, powder I, and water on a dry basis is 0.002:1:1, and the mass ratio of soluble starch on a dry basis to free SiO2 in the silica slag after aluminum extraction from coal gangue on a dry basis is 0.03:1.

[0053] Step 3: Inject the foamed mineral slurry into a 70℃ high-temperature mold. After the slurry is poured and leveled, quickly sweep the surface of the slurry with a flame jet. The flame temperature is 600℃, the flame distance is 15cm, and the sweeping speed is 1m / s. After defoaming, cure at 60℃ for 10 hours, demold, and obtain the foamed glass preform.

[0054] Step 4: Heat the foamed glass preform to 105°C at a heating rate of 6°C / min, dry it for 2 hours, then sinter it at 860°C for 1 hour, and finally place it in an annealing furnace to slowly cool it to room temperature for 35 hours to obtain the finished foamed glass product.

[0055] According to the test results, the volume water absorption rate of the foamed glass prepared in this embodiment is 0.19%, and the thermal conductivity is 0.017 W / m·K.

[0056] Example 3

[0057] The silica slag after aluminum extraction from coal gangue is a high-silica powder material obtained after aluminum extraction from coal gangue by alkaline leaching; its particle size is less than 10μm, and its SiO2 content is 75wt%, Al2O3 content is 1wt%, Na2O content is 19wt%, and the content of other components is 5wt%.

[0058] Step 1: Take 100 parts of the silica slag after aluminum extraction from coal gangue, add 4 parts of tripotassium phosphate foam stabilizer and 1 part of boric acid foam stabilizer, place in a ball mill and ball mill for 18 minutes, with a ball-to-material ratio of 4:1, to obtain powder I;

[0059] Step 2: In the presence of water, sodium alginate, dodecylamine, and powder I are mixed and stirred at 1800 r / min under high shear for 35 min to fully shear and disperse the gas absorbed into the slurry, forming a foam slurry with high aeration. The mass ratio of dodecylamine, powder I, and water on a dry basis is 0.004:1:1, and the mass ratio of sodium alginate on a dry basis to free SiO2 in the silica slag after aluminum extraction from coal gangue on a dry basis is 0.02:1.

[0060] Step 3: Inject the foamed mineral slurry into an 80℃ high-temperature mold. After the slurry is poured and leveled, quickly sweep the surface of the slurry with a flame jet. The flame temperature is 1000℃, the flame distance is 30cm, and the sweeping speed is 2m / s. After defoaming, cure at 45℃ for 18 hours, demold, and obtain the foamed glass preform.

[0061] Step 4: Heat the foamed glass preform to 115°C at a heating rate of 7°C / min, dry it for 1.5 h, then sinter it at 900°C for 0.6 h, and finally place it in an annealing furnace to slowly cool it to room temperature for 25 h to obtain the finished foamed glass product.

[0062] According to the test, the volume water absorption rate of the foamed glass prepared in this embodiment is 0.11%, and the thermal conductivity is 0.019 W / m·K.

[0063] Example 4

[0064] The silica slag after aluminum extraction from coal gangue is a high-silica powder material after aluminum extraction from coal gangue by alkaline leaching; its particle size is less than 10μm, and its SiO2 content is 73wt%, Al2O3 content is 9wt%, Na2O content is 11wt%, and the content of other components is 7wt%.

[0065] Step 1: Take 100 parts of the silica slag after aluminum extraction from coal gangue, add 6 parts of trisodium phosphate foam stabilizer, place it in a ball mill and ball mill for 20 minutes. The ball-to-material ratio is 12:1 to obtain powder I.

[0066] Step 2: In the presence of water, sodium alginate, soapberry saponins and powder I are mixed and stirred at 2000 r / min under high shear for 30 min to fully shear and disperse the gas absorbed in the slurry, forming a foam slurry with high aeration. The mass ratio of dodecylamine, powder I and water on a dry basis is 0.003:1:1, and the mass ratio of sodium alginate on a dry basis to free SiO2 in the silica slag after aluminum extraction from coal gangue on a dry basis is 0.03:1.

[0067] Step 3: Inject the foamed mineral slurry into a 70℃ high-temperature mold. After the slurry is poured and leveled, quickly sweep the surface of the slurry with a flame jet. The flame temperature is 600℃, the flame distance is 15cm, and the sweeping speed is 1m / s. After defoaming, cure at 55℃ for 15 hours, demold, and obtain the foamed glass preform.

[0068] Step 4: Heat the foamed glass preform to 100°C at a heating rate of 2°C / min, dry it for 3 hours, then sinter it at 1000°C for 1 hour, and finally place it in an annealing furnace to slowly cool it to room temperature for 40 hours to obtain the finished foamed glass product.

[0069] According to the test results, the volume water absorption rate of the foamed glass prepared in this embodiment is 0.19%, and the thermal conductivity is 0.015 W / m·K.

[0070] Example 5

[0071] This embodiment is carried out using a method similar to that of Example 1, except that the amount of trisodium phosphate foam stabilizer is adjusted to 7 parts.

[0072] According to the test results, the volume water absorption rate of the foamed glass prepared in this embodiment is 0.17%, and the thermal conductivity is 0.03 W / m·K.

[0073] Comparative Example 1

[0074] This comparative example was conducted using a method similar to that of Example 1, except that the amount of trisodium phosphate foam stabilizer was adjusted to 0 parts.

[0075] Tests showed that the volumetric water absorption rate of the foamed glass prepared in this comparative example was 0.19%, and the thermal conductivity was 0.058 W / m·K.

[0076] Comparative Example 2

[0077] Steps one and two are the same as in Example 1;

[0078] Step 3: Inject the gel foam slurry into an 80℃ high-temperature mold, then cure it at 50℃ for 12 hours, demold it, and obtain the foamed glass preform;

[0079] Step four is the same as in Example 1.

[0080] Tests showed that the volumetric water absorption rate of the foamed glass prepared in this comparative example was 3.41%, and the thermal conductivity was 0.037 W / m·K. The sample without surface flame sintering had a higher porosity, increased water permeability, increased water absorption, and intensified internal heat convection, resulting in deteriorated waterproof and thermal insulation performance.

[0081] Comparative Example 3

[0082] This comparative example was conducted using a method similar to that of Example 1, except that the mass ratio of carboxymethyl cellulose (on a dry basis) to free SiO2 in the silica slag after aluminum extraction from coal gangue in step two was adjusted to 0.04:1 (on a dry basis).

[0083] Tests showed that the volumetric water absorption rate of the foamed glass prepared in this comparative example was 0.16%, and the thermal conductivity was 0.061 W / m·K. During the foaming process, the slurry exhibited poor fluidity, the system viscosity increased sharply, mixing and molding became difficult, and the foaming ratio decreased.

[0084] Comparative Example 4

[0085] This comparative example was conducted using a method similar to that of Example 1, except that in step two, the mass ratio of sodium dodecyl sulfonate (dry basis), powder I (dry basis), and water was adjusted to 0.005:1:1.

[0086] Tests showed that the volumetric water absorption rate of the foamed glass prepared in this comparative example was 1.28%, and the thermal conductivity was 0.097 W / m·K. Excessive surfactant dosage damaged the liquid film strength, leading to bubble coalescence and system collapse ("bubble collapse"). The bubbles were unstable, resulting in numerous unevenly distributed, large-sized open pores, which negatively impacted the product's water absorption rate and thermal insulation performance.

[0087] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue, characterized in that: The method includes: (1) Powder I is obtained by ball milling and mixing the silica slag after aluminum extraction from coal gangue with a foam stabilizer; (2) In the presence of water, the gelling agent, surfactant and powder I are mixed and sheared to obtain foam slurry; the shearing and stirring rate is 1200~2000 r / min; (3) The gel foam slurry is cast into a mold, the surface of the slurry is sintered by flame, and then cured to obtain a foamed glass blank; the conditions for flame sintering include: flame temperature of 300~1300℃, flame distance from slurry surface of 10~30cm, and sweeping speed of 1~2m / s. (4) The foamed glass preform is dried and sintered to obtain the final product.

2. The method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1, characterized in that: The mass ratio of the foam stabilizer to the silica slag after aluminum extraction from coal gangue is 0.01~0.06:1; And / or, the foam stabilizer is selected from at least one of trisodium phosphate, tripotassium phosphate, boric acid, and borax.

3. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: In step (2), the amount of gelling agent used on a dry basis and the mass ratio of free SiO2 in the silica slag after aluminum extraction from coal gangue on a dry basis are 0.02-0.03:

1.

4. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: In step (2), the mass ratio of the surfactant, powder I, and water on a dry basis is 0.002~0.004:0.8~1.2:

1.

5. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The conditions for flame sintering include: flame temperature of 600~1200℃ and flame distance of 15~30cm from the surface of the slurry.

6. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The shearing and stirring rate is 1500~2000 r / min, and the time is 30~60 min.

7. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The gelling agent is selected from at least one of carboxymethyl cellulose, soluble starch and sodium alginate; And / or, the surfactant is selected from at least one of sodium dodecyl sulfonate, dodecylamine, hexadecyl methyl ammonium bromide and soapberry saponin.

8. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The particle size of the silica slag after aluminum extraction from the coal gangue is no greater than 10 μm, and the SiO2 content is 60~80 wt%, the Al2O3 content is 1~10 wt%, and the Na2O content is 4~24 wt%.

9. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The curing process is carried out at a temperature of 30~80℃ for 8~24 hours.

10. A method for preparing foamed glass from silica slag after aluminum extraction from coal gangue according to claim 1 or 2, characterized in that: The drying conditions are as follows: heating to 100-120°C at a heating rate of 2-8°C / min and holding at that temperature for 1-4 hours; And / or, the sintering treatment is performed at a temperature of 800~1000℃ for a time of 0.5~1h.