Method for preparing porous lightweight aggregate through coal-based solid waste coupling regulation

Abstract

The preparation method of the porous lightweight aggregate material comprises the following steps: uniformly mixing the raw materials; the mixed raw materials are treated and molded; roasting the formed material; wherein the raw materials in the step 1) comprise raw materials; the material comprises, by weight, 70-98 parts of gasification slag, 2-20 parts of coal gangue, 2-15 parts of waste glass and 0.2-2 parts of a pore-forming agent. The porous lightweight aggregate material with an excellent pore structure is obtained after working procedures such as coal-based solid waste, regulation and control, the adding amount of the coal-based solid waste can reach 80 wt% or above, the prepared porous lightweight aggregate has a good application prospect in the aspect of building materials, and the porous lightweight aggregate material has great significance in developing modes and methods for resource utilization of the coal-based solid waste and increasing the additional value of the waste and has wide application prospects. And compared with the conventional process, the temperature required by the preparation process is greatly reduced, so that the industrial popularization and application are facilitated.

Description

Technical Field

[0001] This invention relates to the preparation of building materials using the recycling of industrial solid waste resources, specifically to a method for preparing porous lightweight aggregates by coupling coal-based solid waste gasification slag and coal gangue. Background Technology

[0002] Gasification slag is a byproduct of the coal gasification process, while coal gangue is a solid waste generated during coal mining and washing. Both types of solid waste require resource utilization. Currently, gasification slag and coal gangue are not utilized on a large industrial scale, and the main disposal methods are stockpiling and landfilling. This poses safety hazards such as groundwater and soil pollution and also wastes land resources.

[0003] Currently, gasification slag and coal gangue are mainly utilized in building materials and carbon-slag mixing, which can achieve rapid and large-scale processing while ensuring harmlessness, and is an important way to reduce gasification slag. In addition, based on their characteristics, they can also be used to manufacture high-value-added products, such as adsorbents, catalyst carriers, and other application materials. For example, Chinese patent application publication number CN110452012A proposes a method for the synergistic resource utilization of coal gangue and coal gasification slag to prepare ceramsite. This method mainly uses coal gangue, gasification slag, and additives as main raw materials to prepare ceramsite materials in an oxidizing atmosphere of 800-1200℃. Chinese Patent Application Publication No. CN117510224A discloses a porous lightweight aggregate based on spodumene flotation tailings and its preparation method. This method uses spodumene flotation tailings (60-75%) and gasification slag (25-40%) as raw materials, holds them at 1050-1100℃ for 10-30 minutes, and then cools them to prepare a porous lightweight aggregate material. These utilization methods show that large-scale utilization of coal gangue and gasification slag remains difficult in practical applications and requires further improvement.

[0004] Therefore, in order to make full use of the valuable components in gasification slag and coal gangue, high-performance porous lightweight aggregate materials can be synthesized to greatly increase their added value. This not only meets the environmental protection requirements for the harmless, reduced-volume, and resource-based treatment of solid waste, but also has good social and economic benefits. Summary of the Invention

[0005] This invention provides a method for preparing porous lightweight aggregate materials using coal gasification slag and coal gangue, wherein the proportion of coal gasification slag used is relatively high, allowing for greater recycling of the coal gasification slag.

[0006] The second aspect of the present invention provides a method for preparing porous lightweight aggregate materials using coal gasification slag and coal gangue, wherein the obtained porous lightweight aggregate materials have not only low density but also relatively high strength.

[0007] The present invention provides a method for preparing a porous lightweight aggregate material, comprising: 1) Mix the ingredients thoroughly; 2) The mixed raw materials are processed and shaped; 3) The material formed in step 2) is then roasted; The raw materials for step 1) include: 70-98 parts by weight of gasification slag, 2-20 parts by weight of coal gangue, 2-15 parts by weight of waste glass, and 0.2-2 parts by weight of pore-forming agent.

[0008] Gasification residue is selected from raw materials rich in iron, calcium and other components.

[0009] In this raw material, gasification slag serves as the main component, significantly reducing the high-temperature viscosity of the melt. It also exhibits a synergistic foaming effect with the residual carbon and added pore-forming agents, resulting in an ideal closed-cell structure with fine and uniform pore size within a wider process window. The iron and calcium content in the gasification slag precipitates high-strength microcrystalline phases in situ during cooling, greatly strengthening the cell walls. The resulting porous lightweight aggregate material achieves extremely low density (excellent thermal insulation) while possessing compressive strength far exceeding that of similar products. With lower energy consumption (low-temperature sintering) and a high waste content (environmentally friendly and economical), an ideal material combining structural and functional properties (lightweight, high-strength, and thermally insulating) is manufactured.

[0010] It utilizes industrial waste and can produce high-performance porous lightweight aggregate materials. Attached Figure Description

[0011] Figure 1 Flowchart of the method for preparing porous lightweight aggregate material according to the present invention.

[0012] Figure 2 XRD results of the porous lightweight aggregate material prepared in Example 1.

[0013] Figure 3 Porous lightweight aggregate material prepared in Example 3. Detailed Implementation

[0014] The method for preparing porous lightweight aggregate materials from coal gasification slag and coal gangue according to this application is described in further detail below. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0015] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0016] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0017] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0018] The terms "implementation," "an implementation / preferred implementation," "another implementation / preferred implementation," or "certain implementations" used in this specification refer to specific elements (e.g., specific features, structures, or characteristics) described in relation to the implementation being included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0019] Unless otherwise specified, experimental methods in the following examples are generally performed under standard conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to one skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be used in the methods of this application. The preferred embodiments and materials described herein are for illustrative purposes only.

[0021] The "gasification slag" of this application is a solid waste generated during the coal gasification process. Its main components include silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium oxide (CaO), iron oxide (Fe2O3), and a small amount of residual carbon.

[0022] The "coal gangue" in this application refers to black, grayish-black, or dark brown rocks that are extracted along with coal-bearing strata during coal mining and washing, but have a low carbon content and a high ash content (usually >50%). Coal gangue contains both inorganic and organic matter. The inorganic matter mainly consists of oxides of silicon, aluminum, calcium, magnesium, and iron, such as silicon dioxide (SiO2) and aluminum oxide (Al2O3). Its mineral composition is mostly kaolinite, montmorillonite, quartz, and mica. The organic matter contains a certain amount of residual carbon (C) and a small amount of volatile matter contained in coal.

[0023] The “waste glass” in this application includes soda-lime silicate glass, borosilicate glass, aluminosilicate glass, quartz glass, etc.

[0024] The term "loss on ignition" (LOI) refers to the percentage of mass a sample loses after being burned at high temperatures relative to its original mass. It is commonly used to analyze the content of flammable components such as organic matter and carbonates in materials.

[0025] A method for preparing a porous lightweight aggregate material includes: 1) Mix the ingredients thoroughly; 2) The mixed raw materials are processed and shaped; 3) The material formed in step 2) is then roasted; The raw materials for step 1) include 70-98 parts by weight of gasification slag, 2-20 parts by weight of coal gangue, 2-15 parts by weight of waste glass, and 0.2-2 parts by weight of pore-forming agent.

[0026] The gasification slag of this application contains a total silicon and aluminum content of 65-69 wt%, a calcium oxide content of 6-16 wt%, and an iron oxide content of 3-8 wt%. The remainder consists of other impurities (such as sulfides, other metal oxides, etc.).

[0027] In the sintering (calcination) process of the high-proportion gasification slag mixture, the high-content gasification slag, with its rich CaO and iron oxide (such as Fe2O3), constructs a unique self-fluxing system, enabling the mixture to generate a sufficient liquid phase at a low temperature of 1140℃, thus achieving energy saving and mildening of the high-temperature process. Efficient sintering is achieved at this relatively low foaming temperature, forming a high-strength calcium-iron pyroxene crystal phase.

[0028] Optional, the content of calcium oxide is 13-15 wt%; the content of iron oxide is 6-8 wt%.

[0029] In some embodiments, the gasification slag contains 2-4 wt% residual carbon (expressed as loss on ignition). For example, the residual carbon content is 3.52 wt%.

[0030] The presence of residual carbon in the gasification slag, acting as an "in-situ foaming agent," in synergy with a small amount of added pore-forming agent, is a prerequisite for achieving a uniform, fine, closed-cell structure in the product, thus enabling ultra-low density and excellent thermal insulation.

[0031] In some embodiments, the raw materials in step (1) contain 2-20 parts by weight of coal gangue.

[0032] The loss on ignition (LOI) of coal gangue is >22 wt%. Alternatively, the LOI of coal gangue can be between 22 and 25 wt%.

[0033] In the mixed raw materials, the high loss on ignition of coal gangue forms abundant initial micropores in the early stage of sintering, which serve as "pre-set nucleation points". These micropores work synergistically with residual carbon in the gasification slag and added pore-forming agents to further obtain a uniform and fine ideal pore structure in the final product.

[0034] The total content of calcium oxide and iron oxide (Fe2O3) in coal gangue is less than 9 wt%.

[0035] The coal gangue of this application, with its low flux and high silica-alumina properties, effectively balances the excessively low high-temperature viscosity that may result from a large amount of calcium-rich iron gasification slag, stabilizing the viscosity of the entire system within the window most suitable for low-temperature (1140℃) foaming. This allows the mixture to exhibit foaming stability at low temperatures and the resulting product to have high strength properties.

[0036] In the preparation method of the porous lightweight aggregate material provided in this application, the main raw material used is gasification slag, which is an inexpensive waste. By controlling the content of calcium oxide and iron oxide in the gasification slag, and combining it with coal gangue and pore-forming agents, an ideal closed-cell structure with fine pore size and uniform distribution can be formed during low-temperature sintering. During the cooling process, a high-strength microcrystalline phase precipitates in situ, which greatly strengthens the cell walls. As a result, the final porous lightweight aggregate material has extremely low density (excellent thermal insulation) while also possessing compressive strength and durability far exceeding those of similar products.

[0037] The pore-forming agent includes silicon carbide.

[0038] In some embodiments, the gasification slag of this application is selected from solid waste generated during the coal gasification process.

[0039] The main components of the gasification slag include: 48-50 wt% SiO2, 16-20 wt% Al2O3, 13-15 wt% CaO, 6-8 wt% Fe2O3, and 2-4% carbon (based on loss on ignition). Specifically, for example, 48.47 wt% SiO2, 18.80 wt% Al2O3, 14.52 wt% CaO, 7.25 wt% Fe2O3, and 3.52 wt% carbon (based on loss on ignition). The remainder consists of other metal oxides.

[0040] Alternatively, the gasification slag may contain small amounts of MgO, K2O, and Na2O in addition to the components mentioned above. For example, 1.46 wt% MgO, 0.97 wt% K2O, and 0.93 wt% Na2O.

[0041] The coal gangue in this application is selected from solid waste discharged during coal mining or coal washing. The composition and content of solid waste discharged from coal mining and coal washing vary in different regions.

[0042] The main components of the coal gangue in this application include: 50-55 wt% SiO2, 15-18 wt% Al2O3, 3-5 wt% CaO, 2-4 wt% Fe2O3, and 22-25% carbon (based on loss on ignition). For example, the coal gangue contains 50.76 wt% SiO2, 16.90 wt% Al2O3, 3.59 wt% CaO, 2.41 wt% Fe2O3, and 22.34 wt% carbon (based on loss on ignition). The remainder consists of other metal oxides.

[0043] Alternatively, in addition to the main components mentioned above, coal gangue may also contain small amounts of MgO, K2O, and Na2O. For example: 0.37 wt% MgO, 0.89 wt% K2O, and 0.16 wt% Na2O.

[0044] The main components of the waste glass in this application are waste glass products generated from daily consumption or industry.

[0045] The main components of the waste glass in this application include: 65-68 wt% SiO2, 17-20 wt% Na2O, and 8-10 wt% CaO. Specifically, for example, 66.55 wt% SiO2, 17.26 wt% Na2O, and 8.71 wt% CaO.

[0046] This waste glass is a strong fluxing material rich in alkali metal oxides (especially Na2O), which can further promote the formation of melt at low temperatures during sintering of the mixture.

[0047] Optionally, in addition to the main components mentioned above, waste glass may also contain oxides such as iron oxide, magnesium oxide, aluminum oxide, and potassium oxide. For example: Fe₂O₃, 4.55 wt% MgO, 0.55 wt% K₂O, and 1.55 wt% Al₂O₃. A small amount of carbon (based on sintering weight) of 0.13 wt%.

[0048] In some embodiments, the raw materials for step 1) include 70-98 parts by weight of gasification slag, 2-20 parts by weight of coal gangue, 2-15 parts by weight of waste glass, and 0.3-1 parts by weight of pore-forming agent. For example, 75 parts by weight of gasification slag, 18 parts by weight of coal gangue, 6.5 parts by weight of waste glass, and 0.5 parts by weight of pore-forming agent; or 71 parts by weight of gasification slag, 19.5 parts by weight of coal gangue, 9 parts by weight of waste glass, and 0.5 parts by weight of pore-forming agent.

[0049] Optional, the raw materials for step 1) include 70-98 wt% gasification slag, 2-20 wt% coal gangue, 2-15 wt% waste glass and 0.2-2 wt% pore-forming agent.

[0050] In step 1), the particle size of the gasification slag and coal gangue is less than or equal to 74 μm.

[0051] The particle size of the exhaust glass and pore-forming agent is less than or equal to 74μm.

[0052] Existing technologies can be used to crush gasification slag, coal gangue, and waste glass.

[0053] The silicon carbide foaming agent is in powder form, and its particle size (or fineness) preferably meets the requirement of D90 ≤ 45μm (325 mesh), more preferably D90 ≤ 38μm (400 mesh). Silicon carbide powder of this specification can be directly and uniformly mixed with other raw materials without additional pulverization, which can ensure uniform foaming and the formation of a good cell structure during sintering.

[0054] For example, step 1) of this application uses ball milling for mixing. Specifically, gasification slag, coal gangue, waste glass, and pore-forming agent are mixed in a ball mill.

[0055] The ball mill described in this application can be any of the ball mill types disclosed in the prior art.

[0056] When mixing in a ball mill, the rotation speed is approximately 200-500 r / min.

[0057] The ball milling time can be 2-4 hours.

[0058] The molding process in step 2) of this application can be any method available in the prior art, such as a granulator.

[0059] In some embodiments, in step 2), the mixed raw materials are granulated to a particle size of 5-15 mm.

[0060] In the process of preparing porous lightweight aggregate materials, by miniaturizing the foaming unit, the unavoidable temperature gradient and long-range gas migration problems during the sintering process of large-sized green bodies are fundamentally eliminated, thereby producing "ideal" foamed ceramic balls with highly uniform and defect-free internal pore structures.

[0061] The final product obtained by this preparation method is no longer limited to plates or blocks, but becomes a basic functional unit with extremely high application flexibility. It can be directly used as a high-performance thermal insulation filler, lightweight aggregate and functional filter material, which greatly expands the application boundaries of foamed ceramics.

[0062] The preparation method described in this application avoids energy-consuming and waste-generating processes such as cutting and grinding in traditional foamed ceramic production, significantly improving product yield and production efficiency, and reducing overall costs.

[0063] In some embodiments, the calcination conditions in step 3) include calcination at a temperature of 600-1200°C.

[0064] Optionally, in an air environment, first raise the temperature to about 600℃ and hold it at about 600℃ for a certain period of time; then raise the temperature to 1100-1180℃ and hold it for a certain period of time.

[0065] During the calcination process, holding the mixture at a low temperature of 600℃ for a certain period of time allows for the gradual release of decomposition gases from the mixed raw materials, effectively preventing cracking of the green body before foaming and ensuring a high yield. Subsequently, at the foaming holding temperature of 1100-1180℃, the mixed raw materials of this application constitute a unique low-melting-point system. Under the physical and chemical properties of this system, the melt reaches the most suitable viscosity for foaming within this temperature range, while activating the 'composite foaming' mechanism of silicon carbide and residual carbon from gasification slag, and promoting the precipitation of high-strength crystalline phases such as calcium iron pyroxene.

[0066] Through the aforementioned stepped heating and insulation system, the adverse effects of unstable coal gangue components can be suppressed in the high solid waste raw material system of this application, while also 'stimulating' the foaming and strengthening functions of gasification slag and glass. This allows the raw material, mainly composed of solid waste (gasification slag), to be stably transformed into high-quality foamed ceramics with uniform and fine pores and high mechanical strength.

[0067] Preferably, the temperature is increased to about 600°C at a rate of 8-10°C / min.

[0068] Increase the temperature by 8-10℃ / min to 1100-1180℃.

[0069] During the roasting process, the holding time at each temperature range is controlled between 20 and 70 minutes.

[0070] By increasing the temperature gradient through the above-mentioned calcination process, residual carbon is used to create pores, the glass phase is densified, and pores are formed by adding pore-forming agents. After cooling in the furnace, porous lightweight aggregate material is obtained.

[0071] The porous lightweight aggregate material has a compressive strength of 1-8 MPa and a density of 40-930 kg / m³. 3 The porous lightweight composite material of this application has better thermal insulation performance.

[0072] The porous lightweight aggregate material obtained in this application can be used as ceramsite aggregate. It can be used in building materials (such as concrete) and other fields.

[0073] The technical solution proposed in this application for preparing porous lightweight aggregate materials by coupled utilization of coal gasification slag and coal gangue is of great significance for increasing the added value of coal gasification slag and coal gangue and exploring ways to utilize industrial solid waste.

[0074] Compared with existing technologies, this application introduces waste glass and coal gangue into an ultra-high melting point gasification slag (70-98 parts) system, precisely controlling the melt viscosity and stabilizing the foaming window at a lower temperature (e.g., 1140°C). This allows the low melting point gasification slag-based system of this invention to achieve efficient foaming and sintering at a lower temperature (e.g., 1140°C) without relying on the high temperatures required by traditional high silica sand formulations. This not only significantly reduces energy consumption but also achieves a cell structure with uniform pore size and excellent strength under mild process conditions.

[0075] This application utilizes mechanical activation technology (such as ball milling) to fully release the active silicon and aluminum components; then optimizes the coupled molding and sintering process using a particle size gradient mixing method; simultaneously, it enhances the sintering liquid phase generation capacity through waste glass refinement treatment, significantly reducing the sintering temperature; finally, it successfully prepares high-strength, low-cost ceramsite aggregate with a coal gangue / gasification slag content of up to 80% by applying advanced belt roasting technology combined with component optimization control process. This ceramsite aggregate can effectively replace natural sand and gravel aggregates, providing key technical support for the large-scale application of coal gangue / gasification slag resource products in concrete.

[0076] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0077] In the following examples and comparative examples, the "gasification slag" originated from a company in Yili, and its main chemical composition is: SiO2 48.47%, Al2O3 18.80%, CaO 14.52%, Fe2O3 7.25%, MgO 1.46%, K2O 0.97%, Na2O 0.93%, and loss on ignition 3.52%. This gasification slag is a typical "calcium- and iron-rich" raw material rich in CaO and Fe2O3. The "coal gangue" originated from a company in Yili, and its main chemical composition is: SiO2 50.76%, Al2O3 16.90%, CaO 3.59%, Fe2O3 2.41%, MgO 0.37%, K2O 0.89%, Na2O 0.16%, and loss on ignition 22.34%. This coal gangue is a raw material characterized by high loss on ignition and low flux oxide content. The main chemical components of the "waste glass" are: SiO2 66.55%, Al2O3 1.55%, CaO 8.71%, Fe2O3 0.26%, MgO 4.55%, K2O 0.55%, Na2O 17.26%, and loss on ignition 0.13%. This waste glass is a strong fluxing material rich in Na2O.

[0078] The steps for preparing porous lightweight aggregate materials in the examples and comparative examples are shown in the appendix. Figure 1 .

[0079] Example 1: The gasification slag and coal gangue were pulverized to a particle size of less than or equal to 74 μm, and the waste glass and silicon carbide were also pulverized to a particle size of less than or equal to 74 μm. The raw materials comprised 71.5 wt% gasification slag, 17.8 wt% coal gangue, 8.9 wt% waste glass, and 1.8 wt% silicon carbide. All the raw materials were then mixed uniformly in a ball mill at 400 rpm for 3 hours. The resulting powder was then granulated to a particle size of 5-15 mm. The calcined powder was then heated in air, gradually increasing the temperature at 10°C / min to 600°C for 60 minutes, followed by a further increase at 10°C / min to 1150°C. o Sintering was carried out at temperature C for 50 minutes, and then the porous lightweight aggregate material was obtained after cooling. Figure 2 The XRD results of the prepared material are shown in the figure.

[0080] As attached Figure 2 The XRD pattern shown clearly reveals the phase composition of the gasified slag-based ceramsite sintered body. Based on the spectral characteristics, the main phases are quartz, calcium feldspar, and sodium feldspar, along with a certain amount of glassy phase (“bumpy peaks”). The calcium / sodium feldspar phase, as an important liquid phase forming agent, melts at high temperatures, which is the main source of the glassy phase; while the quartz phase, as a high-melting-point framework solid phase, does not melt at the experimental temperature.

[0081] Example 2 The gasification slag and coal gangue were pulverized to a particle size of less than or equal to 74 μm, and the waste glass and silicon carbide were also pulverized to a particle size of less than or equal to 74 μm. The raw materials comprised 72.5 wt% gasification slag, 18.1 wt% coal gangue, 9.1 wt% waste glass, and 0.3 wt% silicon carbide. All the raw materials were then mixed uniformly in a ball mill at 400 rpm for 3 hours. The resulting powder was then granulated to a particle size of 5-15 mm. The calcined powder was then heated in air, gradually increasing the temperature at 10°C / min to 600°C for 60 minutes, followed by further heating at 10°C / min to 1170°C. o Sintering was carried out at a temperature of 60 min, and the porous lightweight aggregate material was obtained after cooling.

[0082] Example 3 The gasification slag and coal gangue were pulverized to a particle size of less than or equal to 74 μm, and the waste glass and silicon carbide were also pulverized to a particle size of less than or equal to 74 μm. The raw materials comprised 72.4 wt% gasification slag, 18.1 wt% coal gangue, 9.05 wt% waste glass, and 0.45 wt% silicon carbide. All the raw materials were then mixed uniformly in a ball mill at 400 rpm for 3 hours. The resulting powder was then granulated to a particle size of 5-15 mm. The calcined powder was then heated in air, gradually increasing the temperature at 10°C / min to 600°C for 60 minutes, followed by further heating at 10°C / min to 1170°C. o Sintering was carried out at a temperature of 60 min, and the porous lightweight aggregate material was obtained after cooling. Figure 3 The diagram shows the preparation of porous lightweight aggregate materials.

[0083] As attached Figure 3 As shown, the pores are predominantly closed pores, tending to be circular, and are relatively uniform. The uniformity of the pores has a direct impact on compressive strength.

[0084] Comparative Example 1 The gasification slag and coal gangue were crushed to a particle size of less than or equal to 74 μm, and the waste glass and silicon carbide were also crushed to a particle size of less than or equal to 74 μm. The raw materials contained 58.8 wt% gasification slag, 39.2 wt% coal gangue, 0 wt% waste glass, and 2 wt% silicon carbide. All the above raw materials were mixed evenly in a ball mill at 400 r / min for 3 hours. The mixed powder was then granulated in a granulator to a particle size of 5-15 mm. The powder was then calcined in an air atmosphere, preheated at room temperature by gradually increasing the temperature to 600℃ at 10℃ / min for 60 min, and then sintered by increasing the temperature to 1150℃ at 10℃ / min and holding for 60 min. After cooling, a porous lightweight aggregate material was obtained.

[0085] Results and comparisons: Under the same sintering regime, the porous lightweight aggregate material prepared in Comparative Example 1 had insufficient internal foaming and low porosity, with a measured bulk density greater than 1.0 g / cm³ (1.58 g / cm³). This result is significantly higher than the density of the product obtained in Example 3, proving that when the content of gasification slag is lower than the lower limit required by this invention, the insufficient content of the main flux in the system leads to excessively high viscosity of the high-temperature melt, making foaming difficult and preventing the preparation of qualified lightweight high-strength ceramsite.

[0086] Comparative Example 2 Gasification slag and coal gangue are crushed to a particle size of less than or equal to 74 μm, and waste glass and silicon carbide are also crushed to a particle size of less than or equal to 74 μm. The raw materials contain 63 wt% gasification slag, 15.7 wt% coal gangue, 19.7 wt% waste glass, and 1.6 wt% silicon carbide. All the above raw materials are mixed evenly in a ball mill at 400 r / min for 3 hours. The mixed powder is then granulated to a particle size of 5-15 mm. The powder is then calcined in an air atmosphere, preheated at room temperature by gradually increasing the temperature to 600℃ at 10℃ / min for 60 min, and then sintered by increasing the temperature to 1150℃ at 10℃ / min and holding for 60 min. After cooling, a porous lightweight aggregate material is obtained.

[0087] Results and comparisons: Under the same sintering regime, the porous lightweight aggregate material prepared in Comparative Example 2 exhibited significant over-firing. Due to the high amount of waste glass (19.7%), exceeding the preferred range, the melt viscosity and surface tension of the system were excessively low at high temperatures. This excessive melting state resulted in insufficient bubble wall strength during foaming, failing to effectively encapsulate the gas. Numerous bubbles merged to form interconnected large channels, ultimately leading to gas escape, structural collapse, or the formation of open pores. While the resulting product may have a lower density, the pore size was extremely uneven, exhibiting numerous structural defects, leading to a significant deterioration in compressive strength. This result demonstrates that excessively high waste glass content disrupts the high-temperature physical property balance of the system. Although it enhances the fluxing effect, it severely damages melt stability and bubble wall strength, failing to form the uniform, high-strength closed-cell structure required by this invention. This verifies the necessity of controlling the waste glass content within an appropriate range (preferably 2-15%) to obtain excellent overall performance.

[0088] The performance of the lightweight aggregates prepared in Examples 1-3 above was tested using the following methods: 1.1h water absorption rate test: based on "Lightweight aggregates and their test methods Part 1: Lightweight aggregates" and "Lightweight aggregates and their test methods Part 2: Lightweight aggregates test methods".

[0089] 2. Apparent density test: Measure the mass and volume of the product, and calculate the apparent density according to the formula density = mass / volume. Based on "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" and "Lightweight Aggregates and Their Test Methods Part 2: Lightweight Aggregates Test Methods".

[0090] 3. Powder True Density Test: The lightweight aggregate was ground into powder, and the true density was tested using the American AccuPyc II 1340 fully automatic true density tester.

[0091] 4. Porosity test: Porosity is calculated according to the formula: Porosity = (1 - Apparent density / True density) × 100%. This is based on "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" and "Lightweight Aggregates and Their Test Methods Part 2: Lightweight Aggregates Test Methods".

[0092] 5. Compressive strength test: The compressive strength of the lightweight aggregate was tested using a micro-controlled compressive and flexural testing machine. The test was conducted according to "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" and "Lightweight Aggregates and Their Test Methods Part 2: Lightweight Aggregates Test Methods".

[0093] The test results are shown in the table.

[0094] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a porous lightweight aggregate material, comprising: 1) Mix the ingredients thoroughly; 2) The mixed raw materials are processed and shaped; 3) The material formed in step 2) is then roasted; The raw materials for step 1) include: 70-98 parts by weight of gasification slag, 2-20 parts by weight of coal gangue, 2-15 parts by weight of waste glass, and 0.2-2 parts by weight of pore-forming agent. Preferably, the gasification slag contains a total silicon and aluminum content of 65-69 wt%, a calcium oxide content of 6-16 wt%, and an iron oxide content of 3-8 wt%.

2. The preparation method according to claim 1, characterized in that, The gasification residue contains 13-15 wt% calcium oxide and 6-8 wt% iron oxide.

3. The preparation method according to claim 1 or 2, characterized in that, The gasification slag contains 2-6 wt% residual carbon (preferably 2-4 wt%). Preferably, the main components of the gasification slag include: 48-50 wt% SiO2, 16-20 wt% Al2O3, 13-15 wt% CaO, 6-8 wt% Fe2O3 and 2-4% carbon.

4. The preparation method according to claim 1 or 2, characterized in that, In step (1), the content of coal gangue in the raw materials is 2-20 parts by weight; Loss on ignition (LOI) of coal gangue >22 wt%; Preferably, the main components of coal gangue include: 50-55 wt% SiO2, 15-18 wt% Al2O3, 3-5 wt% CaO, 2-4 wt% Fe2O3, and 22-25% carbon.

5. The preparation method according to any one of claims 1-4, characterized in that, In step (1), the weight of waste glass is 2-15. Preferably, the main components of waste glass include: 65-68 wt% SiO2, 17-20 wt% Na2O, and 8-10 wt% CaO.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (1), the raw materials include 70-98 parts by weight of gasification slag, 2-20 parts by weight of coal gangue, 2-15 parts by weight of waste glass and 0.3-1 parts by weight of pore-forming agent.

7. The preparation method according to any one of claims 1-5, characterized in that, The particle size of gasification slag and coal gangue is less than or equal to 74μm; The particle size of the exhaust glass and pore-forming agent is less than or equal to 74μm; Pore-forming agents include silicon carbide.

8. The preparation method according to any one of claims 1-5, characterized in that, The roasting conditions for step 3) include roasting at a temperature of 600-1200℃; Preferably, in an air atmosphere, the temperature is first raised to about 600°C and held at about 600°C for a certain period of time; then the temperature is raised to 1100-1180°C and held for a certain period of time.

9. The preparation method according to claim 8, characterized in that, Heating to 600℃ at a rate of 8-10℃ / min; Preferably, the temperature is increased to 1100-1180℃ at a rate of 8-10℃ / min; Even more preferably, during the roasting process, the holding time at each temperature range is controlled between 20 and 70 minutes.

10. A porous lightweight aggregate material obtained by any one of the preparation methods of claims 1-9.

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