A method for preparing aluminum-silicon alloy by using flash-jet joule heat to impact coal gangue

Abstract

This invention provides a method for preparing aluminum-silicon alloys from coal gangue using flash Joule thermal shock, belonging to the field of pyrometallurgical technology. The core process includes three steps: pretreatment, acid washing for impurity removal, and thermal activation shock. First, the coal gangue undergoes low-temperature roasting and air jet milling pretreatment to obtain powder of a specific particle size. Then, targeted composite acid washing is used to remove impurities, preparing a high aluminum-silicon ratio activation precursor. Finally, the precursor is placed in a flash Joule thermal reactor, pretreated with argon plasma, and then subjected to instantaneous high-temperature shock by an electric current to complete the mineral transformation and obtain pure aluminum-silicon alloy. This invention transforms industrial solid waste coal gangue into high-value-added alloy products, solving the environmental problem of coal gangue stockpiling and overcoming the problems of long traditional aluminum-silicon alloy preparation processes, high energy consumption, and high raw material requirements. Through targeted impurity removal combined with the synergistic effect of plasma and Joule thermal shock, a high removal rate of impurity ions and a high retention rate of Al2O3 are achieved.

Description

Technical Field

[0001] This invention relates to the field of pyrometallurgical technology, and more specifically, to a method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing, and it is one of the largest industrial solid wastes emitted in my country. For a long time, the large-scale stockpiling of coal gangue has not only encroached on land resources but also released harmful substances through weathering and leaching, causing serious pollution to the surrounding soil, water bodies, and atmospheric environment, and posing safety hazards such as spontaneous combustion and landslides. Currently, landfilling and stockpiling are still the main methods of coal gangue disposal, resulting in enormous pressure on solid waste disposal and significant environmental risks. Aluminum-silicon alloys, due to their light weight, low coefficient of thermal expansion, good wear and corrosion resistance, and excellent casting properties, have wide applications in aerospace, automotive, and electronic packaging industries.

[0003] However, the traditional preparation of aluminum-silicon alloys mainly relies on electrolysis or the melting and blending of high-purity aluminum ingots and industrial silicon. The high requirements for raw materials and the long process result in high production costs. Although some technologies have attempted to use coal gangue for road paving, brick making, or underground filling, these methods generally suffer from limited disposal capacity and low added value, making it difficult to achieve large-scale and efficient utilization of coal gangue. Moreover, existing processes are constrained by lengthy processes and high energy consumption, making it difficult to obtain economic benefits in the preparation of aluminum-silicon alloys from coal gangue. How to invent a method for preparing aluminum-silicon alloys from coal gangue using flash Joule thermal shock to solve these problems has become an urgent issue for those skilled in the art. Summary of the Invention

[0004] To overcome the above shortcomings, this invention provides a method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue, aiming to solve the problem that existing processes are limited by lengthy procedures and high energy consumption, making it difficult to obtain economic benefits in the process of preparing aluminum-silicon alloys from coal gangue.

[0005] This invention is implemented as follows: This invention provides a method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue, comprising the following steps: S1, Preprocessing The coal gangue sample is pretreated to obtain powder; the pretreatment includes at least roasting and crushing. S2, Acid pickling to remove impurities The active powder was acid-washed with a composite acid to remove impurities, followed by solid-liquid separation and drying to obtain an activated precursor with a high aluminum-to-silicon ratio. S3, thermal activation shock The activated precursor is placed in a flash Joule heating reactor and subjected to instantaneous high-temperature shock by applying a high current; wherein, before or simultaneously with applying the high current, plasma treatment is applied to the surface of the activated precursor, and the final reaction product is an aluminum-silicon alloy.

[0006] Preferably, the calcination in S1 is low-temperature calcination, with a temperature of 300-400℃ and a calcination time of 1-1.5h; the crushing is air jet milling, and the particle size of the crushed powder meets the requirement of 90% ≤ 74μm.

[0007] Preferably, the composite acid in S2 is a targeted composite acid for different impurities: when the main purpose is to remove iron, the composite acid is a mixture of hydrochloric acid and citric acid; when the main purpose is to remove calcium and magnesium, the composite acid is a mixture of sulfuric acid and fluoroboric acid.

[0008] Preferably, the volume ratio of hydrochloric acid to citric acid is 3:1; the volume ratio of sulfuric acid to fluoroboric acid is 4:1; the molar concentration of the composite acid is 1-3 mol / L; the pickling solution-solid ratio is 8:1-18:1 mL / g; the pickling temperature is 50-80℃; and the pickling time is 0.5-2h.

[0009] Preferably, the activated precursor obtained in S2 has an Al2O3 content of ≥35% and an aluminum-silicon atomic ratio of 0.6-1.0.

[0010] Preferably, the high current in S3 is one or more combinations of pulse current, alternating current, constant current, or decaying current.

[0011] Preferably, the intensity of the high current is 40-100A, and the application duration is 50-1000ms; the peak temperature generated by the instantaneous high-temperature impact is 1500-3000℃.

[0012] Preferably, in step S3, argon plasma is used for plasma treatment, the power of the plasma gun is 1-2kW, and the plasma bombardment time on the sample surface is 5-10ms; within 10-20ms after the plasma bombardment ends, the flash evaporation Joule heating reaction device is started to apply a high current.

[0013] Preferably, the electrode is a parallel plate electrode or a coaxial electrode with adjustable electrode spacing, and a ceramic insulating component is provided between the electrode and the cavity; the high melting point conductive material is graphite; and the ceramic insulating component is made of alumina ceramic.

[0014] Preferably, the plasma spray gun is installed at the top or side of the reaction chamber, with the front end of the spray gun 3-5 cm away from the sample surface, and the jet direction at 30°-45° to the sample surface.

[0015] The beneficial effects of this invention are: 1. This invention transforms low-value-added coal gangue into aluminum-silicon alloys widely used in aerospace, automotive, and other fields through a complete process of pretreatment, acid washing for impurity removal, and thermal activation and impact. This not only improves the utilization efficiency of solid waste resources but also reduces the environmental risks and safety hazards caused by coal gangue stockpiling. At the same time, the targeted composite acid and plasma synergistic impurity removal design precisely adapts the acid system to different impurities, achieving a high impurity ion removal rate and controlling the Fe impurity content below 0.1%, while ensuring a high Al2O3 retention rate. This solves the problems of incomplete impurity removal and excessive aluminum loss in traditional processes.

[0016] 2. This invention employs flash Joule thermal shock technology to achieve rapid mineral transformation at millisecond-level instantaneous high temperatures. Compared with traditional high-temperature smelting methods, it reduces energy consumption and shortens the production cycle. Furthermore, the synergistic effect of plasma pretreatment and Joule thermal shock not only breaks the chemical bonds of aluminum-silicon minerals, putting the raw materials in a quasi-activated state and reducing the current intensity and energy consumption of subsequent reactions, but also removes encapsulated impurities, further improving the impurity removal effect. Meanwhile, the targeted composite acid system breaks through the bottleneck of traditional single acid in treating complex impurities, effectively dissolving insoluble impurity phases and reducing production costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of a method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue, provided by an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] I. Implementation Examples Example

[0021] S1. Pretreatment: Select coal gangue raw material with Al2O3 content of 42% and calcine it at 350℃ for 1.2h to remove some organic matter and crystal water, thereby reducing the energy consumption of subsequent crushing; then use a high-efficiency air jet mill for ultrafine grinding, control the particle size distribution to 90%≤74μm, and obtain coal gangue powder with large specific surface area and high reactivity, creating favorable conditions for subsequent acid leaching.

[0022] S2. Acid washing for impurity removal: A customized targeted composite acid (hydrochloric acid to citric acid volume ratio 3:1) was used. Taking advantage of the strong solubility of hydrochloric acid and the complexing ability of citric acid, acid washing was carried out at 3 mol / L concentration with a liquid-to-solid ratio of 10:1 mL / g at 80℃ for 1 hour, selectively dissolving impurity ions such as Fe and Ca. High-efficiency solid-liquid separation was achieved by plate and frame filtration. The obtained solid was dried at 110℃ for 3 hours to obtain the activated precursor. The test results showed that the Al2O3 content in the precursor remained at 41%, the aluminum-silicon atomic ratio was 0.8, and the impurity ion removal rate reached 95%, indicating that the acid washing process effectively preserved the main aluminum-silicon structure while removing impurities.

[0023] S3. Thermal Activation Shock: The precursor is loaded into a sealed chamber of a flash Joule heating device designed for rapid high-temperature reactions (equipped with graphite parallel plate electrodes with adjustable electrode spacing, and internal alumina ceramic insulation to ensure electrical safety). The chamber is evacuated to 0.5 Pa to reduce oxygen interference. First, the plasma spray gun at the top of the chamber is activated (the front end of the spray gun is 4 cm from the sample surface, and the jet direction is at a 35° angle to the sample surface for optimal coverage). Argon gas is introduced as the ionization medium, and the sample surface is bombarded with 1.5 kW power for 8 ms to achieve surface activation and preheating. After the bombardment ends, a high-intensity pulsed current (80 A, lasting 1000 ms) is immediately applied after a 15 ms interval. The Joule heating effect is used to generate an instantaneous high-temperature shock with a peak temperature of 3000℃, which promotes the co-reduction and alloying of aluminum-silicon oxide. After the reaction, the mixture is rapidly cooled to room temperature to suppress component segregation, and finally, an aluminum-silicon alloy is obtained.

[0024] Product testing: The alloy composition has a Si content of 30.67%, an Al content of 69.25%, and an Fe impurity content of less than 0.05%, indicating that the alloy has high purity and meets the expected aluminum-silicon ratio.

[0025] Example 2 S1. Pretreatment: Coal gangue raw material with an Al2O3 content of 38% is selected and calcined at 320℃ for 1.0h. The calcination treatment effectively removes organic impurities and some bound water from the raw material, thereby improving the activity of subsequent reactions. After calcination, the material is efficiently crushed by an air jet mill, and the crushing particle size is strictly controlled to ensure that more than 90% of the particles have a particle size ≤74μm, thereby obtaining coal gangue powder with high specific surface area and good reactivity.

[0026] S2. Acid Pickling for Impurity Removal: A targeted composite acid (sulfuric acid to fluoroboric acid volume ratio 4:1) is used. This composite acid system combines the strong acid dissolving ability of sulfuric acid with the special decomposition effect of fluoroboric acid on silicate minerals, achieving selective removal of impurity ions such as iron and calcium. The molar concentration of the acid solution is controlled at 2 mol / L, and the acid pickling solution-to-solid ratio is 15:1 mL / g. The acid pickling is carried out with continuous stirring at 60℃ for 0.5 h. By optimizing the acid pickling conditions, the processing time is shortened while ensuring the impurity removal efficiency. Solid-liquid separation adopts membrane separation technology, which achieves efficient retention of fine particles and complete separation of liquid impurities. The separated solid is dried at 105℃ for 2.5 h to completely remove residual moisture and obtain an activated precursor. The test results show that the Al2O3 content in the precursor is 37%, the aluminum-silicon atomic ratio is 0.7, and the impurity ion removal rate reaches 92%, indicating that the acid pickling process effectively removes impurities while maintaining the main aluminum-silicon structure.

[0027] S3. Thermal Activation Shock: The obtained activated precursor is loaded into the reaction chamber equipped with a graphite coaxial electrode. The chamber is evacuated to 0.3 Pa to create a high-vacuum reaction environment to reduce oxidation interference. The plasma spray gun installed on the side of the chamber is started, and the distance between the front end of the spray gun and the sample surface is adjusted to 3 cm. The jet direction is at a 30° angle to the sample surface. Argon gas is introduced as the ionization medium, and the sample surface is bombarded with plasma at a power of 1.2 kW for 6 ms to achieve surface activation and uniform preheating of the material. After the bombardment ends, a constant current of 60 A is applied for 800 ms after a 12 ms interval. The Joule heating effect is used to generate a stable high temperature, with a peak temperature of 2000℃, which promotes the full reduction and alloying of aluminum-silicon oxide. After the reaction, the product is rapidly cooled to room temperature to obtain an aluminum-silicon alloy product.

[0028] Product testing: Composition analysis shows that the product contains 20.36% Si, 79.53% Al, and less than 0.1% Fe impurities. The alloy composition is mainly aluminum, which meets the expected target for high-aluminum alloys.

[0029] Example 3 S1. Pretreatment: Select coal gangue raw material with an Al2O3 content of 40% and roast it at a low temperature of 380℃ for 1.5h. The volatile matter and crystal water in the raw material are further removed by the high roasting temperature and time. After roasting, the material is finely crushed by air jet mill. The particle size of the product is strictly controlled so that more than 90% of the particles have a particle size ≤74μm, so as to obtain coal gangue powder with uniform particle size and high reactivity, which provides an ideal material state for the subsequent acid leaching process.

[0030] S2. Acid washing for impurity removal: A targeted composite acid (hydrochloric acid to citric acid volume ratio 3:1) was used. This composite acid system fully utilizes the strong acidity of hydrochloric acid and the complexing ability of citric acid to synergistically remove impurity ions such as iron and calcium. The molar concentration of the acid solution was controlled at 3 mol / L, and the liquid-to-solid ratio of the acid washing solution was increased to 20:1 mL / g. The acid washing was carried out with continuous stirring at 80℃ for 2 hours. The impurity removal effect was further improved by increasing the liquid-to-solid ratio and extending the reaction time. After the reaction, efficient solid-liquid separation was achieved by plate and frame filtration. The obtained solid was dried at 115℃ for 4 hours to obtain a uniformly dried activated precursor. The test results showed that the Al2O3 content in the precursor was 39%, the aluminum-to-silicon atomic ratio was 0.9, and the impurity ion removal rate reached 96%, indicating that the enhanced acid washing conditions achieved excellent impurity removal effect.

[0031] S3. Thermal Activation Shock: The obtained activated precursor is loaded into the reaction chamber, which is evacuated to 0.8 Pa to establish a suitable vacuum reaction environment. The plasma spray gun installed on the top of the chamber is started, and the distance between the front end of the spray gun and the sample surface is adjusted to 5 cm. The jet direction is at a 40° angle to the sample surface. Argon gas is introduced as the working gas, and the sample is bombarded with plasma at a power of 1.8 kW for 10 ms to achieve large-area activation and deep preheating of the material. After the bombardment ends, an alternating current with an intensity of 90 A and a duration of 800 ms is applied after an 18 ms interval. The skin effect of the alternating current and the electromagnetic stirring effect are used to promote the uniformity of the reaction. The peak temperature reaches 2500℃, achieving efficient reduction and alloying of aluminum-silicon oxide. After the reaction, the final product is obtained by rapid cooling.

[0032] Product testing: Composition analysis shows that the product contains 25.19% Si, 74.74% Al, and less than 0.05% Fe impurities. The alloy composition is moderate, the impurity content is low, and the product quality is excellent.

[0033] Example 4 S1. Pretreatment: Coal gangue raw material with an Al2O3 content of 35% was selected and subjected to low-temperature roasting at 300℃ for 1.0h. Roasting effectively removed volatile components and some bound water from the raw material. Subsequently, the roasted material was crushed using a high-efficiency air jet mill, and the particle size distribution was strictly controlled so that more than 90% of the particles had a particle size ≤74μm, resulting in coal gangue powder with uniform particle size and improved reactivity, which created favorable conditions for subsequent acid leaching to remove impurities.

[0034] S2. Acid washing for impurity removal: A targeted composite acid (hydrochloric acid to citric acid volume ratio 3:1) was used. This composite acid system fully utilizes the strong acid dissolving properties of hydrochloric acid and the organic complexing ability of citric acid to achieve selective dissolution of impurity ions. The molar concentration of the acid solution was controlled at 1 mol / L, and the solid-to-solid ratio of the acid washing solution was 10:1 mL / g. The acid washing was carried out under mild conditions of 50℃ with continuous stirring for 1.5 h, which ensured the impurity removal effect while reducing damage to the main structure. After the reaction, efficient solid-liquid separation was achieved by plate and frame filtration. The solid was collected and dried at 105℃ for 2 h to completely remove residual moisture and obtain the activated precursor. The test showed that the Al2O3 content in the precursor was 35%, the aluminum-silicon atomic ratio was 0.6, and the impurity ion removal rate reached 93%, indicating that the impurity removal effect was good under the conditions and the aluminum-silicon framework was preserved.

[0035] S3. Thermal Activation Shock: The obtained activated precursor is placed in the sealed chamber of the flash Joule thermal reaction apparatus. The chamber is evacuated to 0.1 Pa to create a low-oxygen reducing atmosphere. The plasma spray gun installed on the side of the chamber is started, and the distance between the front end of the spray gun and the sample surface is adjusted to 3 cm. The jet direction is at a 35° angle to the sample surface. Argon gas is introduced as the ionizing gas, and the sample surface is bombarded with plasma at a power of 1.0 kW for 5 ms to achieve surface activation and preheating. After the bombardment ends, a decaying current mode is applied at an intensity of 40 A for a duration of 600 ms after a 10 ms interval. The thermal field distribution is controlled by the current decay process to achieve an instantaneous high-temperature shock with a peak temperature of about 1800℃, which promotes the co-reduction and alloying process of aluminum-silicon oxide. After the reaction, the product is rapidly cooled to room temperature to obtain the final aluminum-silicon alloy product.

[0036] Product testing: Composition analysis shows that the product contains 12.38% Si, 87.49% Al, and less than 0.1% Fe impurities. The alloy composition meets expectations, with aluminum being the dominant alloy and low impurity content.

[0037] Example 5 S1. Pretreatment: Select coal gangue raw material with Al2O3 content of 43% and calcine it at 350℃ for 1.2h to effectively remove organic matter and crystal water; use air jet mill for fine crushing to make more than 90% of the material particles ≤74μm, and obtain coal gangue powder with high specific surface area and uniform particle size, which is beneficial to the uniform contact and mass transfer of reactants in subsequent acid washing and thermal activation processes.

[0038] S2. Acid washing for impurity removal: A targeted composite acid (hydrochloric acid to citric acid volume ratio 3:1) with a molar concentration of 2 mol / L and a solid-to-hydrochloric acid ratio of 10:1 mL / g was used. The acid washing was carried out at 80℃ with stirring for 1.5 h to efficiently remove impurity ions such as Fe and Ca by utilizing the synergistic effect of the composite acid. In the solid-liquid separation stage, membrane separation technology was used to achieve efficient retention of fine particles and complete separation of liquid impurities. The obtained solid was dried at 120℃ for 3 h to obtain a uniformly dried activated precursor. The test results showed that the Al2O3 content in the precursor was 42%, the aluminum-silicon atomic ratio was 1.0, and the impurity ion removal rate was 94%, indicating that the acid washing process effectively removed impurities while maintaining a good balance of aluminum and silicon elements.

[0039] S3. Thermal Activation Shock: The activation precursor is loaded into the reaction chamber, and a vacuum of 1.0 Pa is created to establish a low-pressure reaction environment. The plasma spray gun installed at the top of the chamber is started, and the nozzle tip is adjusted to 4 cm from the sample surface, with the jet direction at a 45° angle to the sample surface. Argon gas is introduced as the working gas, and the sample is bombarded with plasma at a power of 2.0 kW for 8 ms to achieve efficient activation and preheating of the material surface. 20 ms after the bombardment ends, a pulsed + constant composite current with a current intensity of 80 A and a duration of 1000 ms is applied. The rapid heating is achieved through the pulsed phase, followed by a constant phase to maintain the high-temperature reaction, with a peak temperature of 2100℃, which promotes the rapid reduction of aluminum-silicon oxide and the formation of a homogeneous alloy. After the reaction, the final product is obtained through a controllable cooling process.

[0040] Product testing: The product contains 30.95% Si, 68.98% Al, and less than 0.05% Fe impurities. The alloy composition is mainly aluminum with silicon as a secondary component, and the impurity content is low, meeting the requirements for high-quality aluminum-silicon alloys.

[0041] Control group 1 S1. Pretreatment: Completely consistent with Example 1.

[0042] S2, Acid washing to remove impurities: A single 3mol / L hydrochloric acid was used, and other parameters were the same as in Example 1; after drying, the Al2O3 content in the precursor was 38%, the aluminum-silicon atomic ratio was 0.75, and the impurity ion removal rate was 72%.

[0043] S3, Thermal activation shock: No plasma treatment was performed; a pulsed current (intensity 100A, other parameters are the same as in Example 1) was directly applied.

[0044] Product testing: Si content 28.32%, Al content 67.51%, Fe impurity content 0.35%, energy consumption increased by 300% compared to Example 1.

[0045] Control group 2 S1. Pretreatment: Coal gangue is directly crushed to 90% ≤ 74μm without low-temperature roasting and air jet mill activation.

[0046] S2, Acid washing and impurity removal: The parameters are the same as in Example 2; after drying, the Al2O3 content in the precursor is 36%, the aluminum-silicon atomic ratio is 0.68, and the impurity ion removal rate is 85%.

[0047] S3, Thermal activation shock: Same as the parameters in Example 2.

[0048] Product testing: Si content 18.74%, Al content 77.32%, Fe impurity content 0.21%, reaction time extended by 50% compared to Example 2.

[0049] Control group 3 S1. Pretreatment: Completely consistent with Example 1.

[0050] S2, Acid washing to remove impurities: Completely consistent with Example 1.

[0051] S3. Thermal activation: The traditional high-temperature smelting method is adopted, without plasma treatment. The smelting temperature is 1500℃ and the holding time is 2h.

[0052] Product testing: Si content 27.15%, Al content 66.83%, Fe impurity content 0.42%, energy consumption 1200 times that of Example 1, and production cycle extended to 2 hours.

[0053] II. Performance Testing 1. Purity and composition testing of activated precursors The activated precursor samples prepared in Examples 1-5 and Control Groups 1-3 were used to determine the mass fractions of major components such as Al2O3, Fe2O3, CaO, and MgO in the samples using X-ray fluorescence spectrometry. The Al2O3 retention rate (the ratio of Al2O3 content in the activated precursor to the Al2O3 content in the raw coal gangue) and the content of impurities (Fe2O3, Fe2O3, CaO, MgO, etc.) were calculated. 3 +、Ca 3 +, Mg 3 The total removal rate (including acid washing and impurity removal processes) was used to evaluate the impact of the acid washing process on the purity of the precursor.

[0054] 2. Testing of the composition and impurity content of aluminum-silicon alloy products Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the composition of the aluminum-silicon alloys produced in each group of reactions, focusing on the mass fractions of Al and Si and the content of Fe (Fe is a major harmful impurity in coal gangue that directly affects the alloy performance), to verify the process's ability to ensure the purity of the target product.

[0055] 3. Process energy consumption and reaction efficiency testing The total power consumption of each group of experiments was recorded by the power control system of the flash Joule heating reaction device, and the energy consumption per unit mass of sample (J / g) was calculated in combination with the sample mass. At the same time, the total time from the start of plasma treatment to the end of the reaction was recorded. The production cycle of the traditional high-temperature melting method (control 3) was compared to evaluate the energy consumption advantage and reaction efficiency of the process of the present invention.

[0056] III. Results Analysis The results of the above performance tests are summarized in Table 1 below:

[0057] Table 1: Performance Test Results for Each Group

[0058] The following key conclusions can be drawn from the test results: The synergistic effect of targeted composite acid and plasma in removing impurities is significant: Examples 1-5 use targeted composite acid (hydrochloric acid-citric acid or sulfuric acid-fluoroboric acid) pickling combined with plasma surface bombardment. The total removal rate of impurity ions reaches 92%-96%, and the Fe content of impurities is controlled at <0.05%-<0.1%. Compared with control group 1 (single hydrochloric acid + no plasma), the Fe content is reduced by more than 77%, and compared with control group 3 (conventional smelting), it is reduced by more than 88%. Moreover, the Al2O3 retention rate is maintained at 93%-97%, achieving a precise balance between efficient impurity removal and aluminum element retention, and solving the problems of incomplete impurity removal or excessive loss of aluminum elements in traditional processes.

[0059] The flash joule heating process has significant advantages in energy consumption and efficiency: the unit mass energy consumption of Examples 1-5 is only 100-300 J / g, and the total reaction time is as short as 60 ms and as long as 1020 ms. In contrast, the unit energy consumption of the traditional high-temperature melting method in Control Group 3 is 400-1500 times that of the Examples, and the production cycle is as long as 2 hours. This fully verifies the technical advantages of the present invention, such as millisecond-level heating and high energy utilization, and solves the problems of long process and high energy consumption in traditional processes.

[0060] Verification of the necessity of the pretreatment step: Control group 2 did not undergo low-temperature roasting and air jet milling pretreatment. The impurity ion removal rate dropped to 85%, the reaction time was extended by 50%, and trace amounts of unreacted silicon mineral phase appeared in the product. This indicates that low-temperature roasting can activate the coal gangue lattice and air jet milling can increase the specific surface area, creating favorable conditions for subsequent acid washing and thermal shock reaction.

[0061] Furthermore, the "hydrochloric acid + citric acid (3:1)" system for high-Fe coal gangue achieved a 93%-96% removal rate of impurity ions, which is 29%-33% higher than that of hydrochloric acid alone (72%). The chelating effect of citric acid effectively prevents Fe... 3 +Reprecipitation, while reducing Al 3+Loss (Al retention rate increased by 3%-6%); For the "sulfuric acid + fluoroboric acid (4:1)" system for high calcium and magnesium coal gangue, the removal rate of calcium and magnesium impurities reaches 92%, which is 35% higher than that of sulfuric acid alone (68%). Fluoroboric acid can dissolve insoluble calcium and magnesium silicates, breaking through the bottleneck of traditional acid systems in the treatment of complex impurities; Plasma bombardment (5-10ms) destroys the Si-O-Al chemical bonds of aluminum-silicon minerals, putting the raw materials in a quasi-activated state, and the subsequent Joule heating current intensity can be reduced by 20%-30% (e.g., from 100A to 80A in Example 1), and energy consumption is reduced accordingly; In addition, high-energy particle bombardment strips away encapsulated impurities, which further increases the removal rate of impurity ions by 5%-8%, especially for Fe-type encapsulated impurities, which is the key guarantee for the Fe content of the example <0.05%.

[0062] It should be noted that the specific model and specifications need to be selected and determined based on the actual specifications of the device. The specific selection and calculation method adopts the existing technology in this field, so it will not be described in detail here.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue, characterized in that, Includes the following steps: S1, Preprocessing The coal gangue sample is pretreated to obtain powder; the pretreatment includes at least roasting and crushing. S2, Acid pickling to remove impurities The active powder was acid-washed with a composite acid to remove impurities, followed by solid-liquid separation and drying to obtain an activated precursor with a high aluminum-to-silicon ratio. S3, thermal activation shock The activated precursor is placed in a flash Joule heating reactor and subjected to instantaneous high-temperature shock by applying a high current; wherein, before or simultaneously with applying the high current, plasma treatment is applied to the surface of the activated precursor, and the final reaction product is an aluminum-silicon alloy.

2. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 1, characterized in that, The calcination in S1 is low-temperature calcination, with a temperature of 300-400℃ and a calcination time of 1-1.5h; the crushing is air jet milling, and the particle size of the crushed powder meets the requirement of 90% ≤ 74μm.

3. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 2, characterized in that, The composite acid in S2 is a targeted composite acid for different impurities: when the main purpose is to remove iron, the composite acid is a mixture of hydrochloric acid and citric acid; when the main purpose is to remove calcium and magnesium, the composite acid is a mixture of sulfuric acid and fluoroboric acid.

4. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 3, characterized in that, The volume ratio of hydrochloric acid to citric acid is 3:1; the volume ratio of sulfuric acid to fluoroboric acid is 4:1; the molar concentration of the composite acid is 1-3 mol / L; the pickling solution-solid ratio is 8:1-18:1 mL / g; the pickling temperature is 50-80℃; and the pickling time is 0.5-2h.

5. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 1, characterized in that, The activated precursor obtained in S2 has an Al2O3 content of ≥35% and an aluminum-silicon atomic ratio of 0.6-1.

0.

6. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 1, characterized in that, The high current in S3 is one or more combinations of pulse current, alternating current, constant current, or decaying current.

7. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 6, characterized in that, The intensity of the high current is 40-100A, and the duration of application is 50-1000ms; the peak temperature generated by the instantaneous high-temperature impact is 1500-3000℃.

8. The method for preparing aluminum-silicon alloy using flash Joule thermal shock coal gangue according to claim 7, characterized in that, In S3, argon plasma is used for plasma treatment. The power of the plasma spray gun is 1-2kW, and the plasma bombardment time on the sample surface is 5-10ms. Within 10-20ms after the plasma bombardment ends, the flash evaporation Joule heating reaction device is started to apply a high current.

9. A method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue according to claim 8, characterized in that, The electrode is a parallel plate electrode or a coaxial electrode with an adjustable electrode spacing. A ceramic insulating component is provided between the electrode and the cavity. The high-melting-point conductive material is graphite. The ceramic insulating component is made of alumina ceramic.

10. A method for preparing aluminum-silicon alloys using flash Joule thermal shock coal gangue according to claim 9, characterized in that, The plasma spray gun is installed at the top or side of the reaction chamber, with the front end of the spray gun 3-5 cm away from the sample surface, and the jet direction at 30°-45° to the sample surface.

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