A method for removing mica from mechanical sand based on multi-field coupling

Abstract

This invention relates to the field of mineral processing technology, specifically disclosing a method for removing mica from manufactured sand based on multi-field coupling. The method first involves screening, drying, and characterizing the manufactured sand raw material. Then, the sand is mixed with water to form a slurry. By simultaneously and precisely controlling the temperature and pH of the slurry and adding a metal ion adjuster, a first coupling pretreatment is performed to selectively enhance the surface electrical properties of mica. The pretreated slurry is then fed into a high-voltage electrostatic separator, where a second coupling separation is performed in a high-voltage electrostatic field maintained at a constant temperature, achieving the separation of mica from clean sand. Simultaneously, the mica content of the product is monitored in real time, and feedback is used to adjust the pretreatment and separation parameters. Finally, the product is dehydrated, and the recycled water is reused. This invention solves the problems of low efficiency and poor stability of single separation methods through the synergistic effect of multiple fields—temperature field, reagent concentration field, and high-voltage electrostatic field—achieving efficient, stable, and clean removal of mica.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a method for removing mica from manufactured sand based on multi-field coupling. Background Technology

[0002] Manufactured sand, as an important substitute for natural sand, is increasingly widely used in construction engineering. However, manufactured sand parent rocks often contain mica minerals, which, after crushing, form flaky particles mixed within the sand grains. Mica has low hardness, poor strength, a smooth surface, and is hydrophilic. In concrete, it significantly reduces the bonding force between cement paste and aggregate, increases water consumption, and affects the strength, durability, and workability of concrete. Therefore, effectively removing mica from manufactured sand is a key step in improving its quality.

[0003] Currently, methods for removing mica from manufactured sand are mainly divided into two categories: physical sorting and surface modification. Physical sorting methods mainly include: Hydraulic classification and shaking table separation: Separation is achieved by utilizing the differences in particle size, shape, and density between mica and quartz, the main sand particles. However, mica flaky particles settle slowly in fluids and are easily mixed with fine-grained sand and gravel, resulting in low separation efficiency, significant loss of fine sand, and reduced yield.

[0004] Flotation: This method utilizes the differences in the physicochemical properties of mica and quartz surfaces. By adding collectors and frothers, mica adheres to air bubbles and floats to the surface for separation. This method is effective for fine-grained mica, but it has drawbacks such as high reagent costs, potential chemical residues in the final product that could affect concrete performance, and complex wastewater treatment.

[0005] High-voltage electrostatic separation: This method separates mica and quartz based on their differences in conductivity under a high-voltage electric field. Mica has relatively good conductivity and is easily polarized, adsorbing onto the electrodes. However, the separation efficiency of this method is greatly affected by material moisture content, particle size distribution, and surface cleanliness. Dust and fine particles generated during the production of manufactured sand easily adhere to the surface of mica, altering its electrical properties, and fluctuations in environmental humidity can lead to unstable separation efficiency.

[0006] The core problem with existing technologies lies in the difficulty of efficiently, stably, and economically separating flaky mica particles from the main minerals of manufactured sand (such as quartz and feldspar) in terms of density and magnetic properties, but which exhibit specific differences in morphology, surface electrical properties, and chemical activity. For example, electrostatic separation is sensitive to surface conditions; flotation relies on reagents and introduces chemical contamination; and simple gravity separation is inefficient. None of these methods systematically consider or utilize the specific response behavior of mica under the coupling effect of complex physical fields and chemical microenvironments.

[0007] Therefore, there is an urgent need for a new method that can overcome the above-mentioned defects and achieve efficient, clean, and stable separation of mica from sand through multi-field synergy and precise control. Summary of the Invention

[0008] To achieve the above objectives, this invention provides a method for removing mica from machine-made sand based on multi-field coupling, comprising the following steps: Step 1: Screening and drying pretreatment of the manufactured sand raw material to obtain the sand to be sorted; Step 2: Mix the sand to be sorted with water to form a first pre-treated slurry. Add pH adjuster and metal ion adjuster to the first pre-treated slurry. Simultaneously control the temperature and pH value of the first pre-treated slurry to perform the first coupled pre-treatment under the first target temperature range and target pH range to obtain the second pre-treated slurry. Step 3: After adjusting the second pre-treated slurry to the second target temperature, feed it into the high-voltage electrostatic separator; turn on the high-voltage electrostatic field of the high-voltage electrostatic separator and control the ambient temperature of the separation zone, so that the second pre-treated slurry is separated under the second coupling effect of the high-voltage electrostatic field and the temperature field, and mica particles and clean sand particles are collected respectively. Step 4: Real-time detection of mica content in the clean sand particles obtained after sorting, comparison of mica content with preset mica content target threshold, and dynamic adjustment of the amount of metal ion modifier added, the first target temperature range and the voltage of the high voltage electrostatic field based on the comparison results. Step 5: Dewater the products obtained after sorting, and recycle the dewatering water to prepare the first pretreatment slurry.

[0009] Preferably, step 1 specifically includes: Step 1.1: The manufactured sand raw material is screened to remove coarse particles with a particle size greater than 5 mm and silt with a particle size less than 0.075 mm, so as to obtain sand material to be sorted with a particle size range of 0.075 mm to 5 mm. Step 1.2: Dry the sand to be sorted at a temperature of 105°C to 110°C until constant weight; Step 1.3: Determine the mica content and average diameter-to-thickness ratio of the mica particles in the dried sand to be sorted, and determine the particle size distribution of the sand to be sorted; the mica content is determined using a mineral dissociation analyzer or microscopic image analysis technology; the average diameter-to-thickness ratio of the mica particles is obtained by statistical calculation of the projected area and thickness of the mica particles; the particle size distribution is determined using a laser particle size analyzer.

[0010] Preferably, step 2 specifically includes: Step 2.1: Mix the dried sand to be sorted with water at a solid-liquid mass ratio of 1:3 to 1:5 to form a uniform first pretreatment slurry in a mixing tank; Step 2.2: Simultaneously add a pH adjuster and a metal ion adjuster to the first pretreatment slurry; the pH adjuster is a sodium hydroxide solution or a sulfuric acid solution; the metal ion adjuster is a calcium chloride solution or an aluminum sulfate solution; Step 2.3: The temperature of the first pretreated slurry is raised and stabilized within the first target temperature range by the heating and temperature control system of the mixing tank. At the same time, the pH value of the first pretreated slurry is adjusted and stabilized within the target pH range by adding a pH adjuster. The first target temperature range and the target pH range are determined by laboratory condition tests for specific manufactured sand raw materials. The principle of determination is to maximize the surface zeta potential difference between mica particles and quartz particles. In the laboratory condition tests, different combinations of temperature and pH levels are set. The slurry is treated under each combination condition, and the surface zeta potential of the mica-enriched phase and the quartz-enriched phase particles are measured respectively. The temperature and pH range that maximizes the zeta potential difference between the two is selected as the first target temperature range and the target pH range. Step 2.4: Maintain the first target temperature range and target pH range, and continuously stir the first pretreated slurry for 10 to 20 minutes to complete the first coupled pretreatment and obtain the second pretreated slurry.

[0011] Preferably, the matching relationship between the first target temperature range and the target pH range is as follows: within the first target temperature range of 55 degrees Celsius to 58 degrees Celsius, a target pH range of 10.5 to 11.0 is matched; under the matching relationship, the metal cations in the metal ion adjuster are selectively adsorbed on the surface of mica particles in a hydroxylated form.

[0012] Preferably, step 3 specifically includes: Step 3.1: Flow the second pretreated slurry through the heat exchanger to adjust the temperature of the second pretreated slurry to the second target temperature; the second target temperature is less than or equal to the lower limit of the first target temperature range of the first coupled pretreatment. Step 3.2: The second pretreated slurry, after temperature adjustment, is fed into the feeding device of the high-pressure electrostatic separator at a stable flow rate; the high-pressure electrostatic separator includes a grounded drum, a high-voltage static electrode, a heating and insulation cover, and a slurry atomizing feeder; Step 3.3: Turn on the DC high voltage power supply of the high voltage static electrode and raise the voltage to the working voltage value; the working voltage value is determined according to the particle size distribution of the sand to be sorted and the processing capacity of the high voltage electrostatic separator; the larger the median particle size of the particle size distribution and the larger the processing capacity, the higher the working voltage value; turn on the heating and heat preservation cover to maintain the ambient temperature of the high voltage electrostatic separator sorting area within the second target temperature range. Step 3.4: The second pre-treated slurry is dispersed into droplet particles by the slurry atomizing feeder and evenly sprinkled on the surface of the grounded rotating drum. Under the second coupling effect of the high voltage electrostatic field and the temperature field, the mica particles deviate from their trajectory due to the enhanced surface conductivity and fall into the mica collection tank. The clean sand particles are mainly thrown down along the centrifugal force direction and enter the clean sand collection tank.

[0013] Preferably, step 4 specifically includes: Step 4.1: The mica content in the clean sand particles discharged from the clean sand collection tank is detected in real time using an online grade analyzer; the online grade analyzer is an analyzer based on near-infrared spectroscopy technology; Step 4.2: The real-time detected mica content is transmitted to the central control unit, which compares the mica content with a preset target threshold for mica content; the target threshold for mica content is set to 1.0% to 1.5%. Step 4.3: If the central control unit determines that the real-time mica content is continuously higher than the target threshold for mica content, the central control unit will sequentially perform the following optimization and control operations: First, increase the addition rate of metal ion modifier to the first pretreatment slurry; then increase the set value of the first target temperature range of the first coupling pretreatment by 0.5 degrees Celsius to 2 degrees Celsius; finally, increase the working voltage of the high-voltage electrostatic field of the high-voltage separator by 1000 volts to 3000 volts. Step 4.4: If the central control unit determines that the real-time mica content is lower than the target threshold for mica content, then the current metal ion modifier addition rate, the first target temperature range setting value, and the working voltage value remain unchanged.

[0014] Preferably, the process of determining the working voltage value in step 3.3 is as follows: First, the median particle size D50, in millimeters, is obtained based on the particle size distribution of the sand to be separated; the rated processing capacity Q, in tons / hour, is obtained based on the design processing capacity of the high-voltage electrostatic separator; the initial working voltage value U, in kilovolts, is estimated using the following formula: ; The particle size voltage coefficient, whose value is determined through equipment calibration tests, is measured in kilovolts per millimeter (kV / mm). It reflects the degree to which the particle size of the material affects the required voltage.

[0015] The load handling voltage coefficient, whose value is determined through equipment calibration tests, is measured in kilovolts (kV). It reflects the degree to which the load handled by the equipment affects the required voltage.

[0016] The reference voltage, measured in kilovolts (kV), represents the initial voltage of the equipment under reference conditions. After obtaining the estimated value, actual sorting tests were conducted within the safe voltage range of the high-voltage electric separator. The optimization target was to minimize the mica content of the clean sand particles after sorting. The final working voltage value was then fine-tuned and determined.

[0017] Preferably, step 5 specifically includes: Step 5.1: The clean sand particles discharged from the clean sand collection tank are transported to the dewatering screen for dewatering to obtain a clean manufactured sand product with a moisture content of less than 8%; the underflow water generated by the dewatering screen is used as the first return water. Step 5.2: The tailings slurry formed by the mica particles discharged from the mica collection tank and water is transported to the thickening tank for sedimentation. The supernatant of the thickening tank is used as the second return water. Step 5.3: Collect the first and second return water into the return water tank and circulate it to Step 2 for preparing the first pretreated slurry; Step 5.4: Periodically test the pH value and conductivity of the return water in the return water tank. When the pH value is lower than the lower limit of the target pH range, add pH adjuster to the return water tank or stirring tank; when the conductivity is lower than the set threshold, add metal ion adjuster to the return water tank or stirring tank. The set threshold is determined by laboratory tests and is the conductivity value corresponding to the minimum ion concentration required to maintain the first coupling pretreatment effect.

[0018] Preferably, during the first coupling pretreatment in step 2.3, an online conductivity meter is used to monitor the conductivity changes of the first pretreated slurry in real time. The online conductivity meter feeds back the real-time monitored conductivity data to the central control unit. The central control unit has a pre-stored conductivity reference range, which is determined by laboratory tests and characterizes the slurry conductivity range of the metal ion modifier under the target adsorption state. If the real-time conductivity is continuously lower than the lower limit of the conductivity reference range, the central control unit increases the addition rate of the metal ion modifier. If the real-time conductivity is continuously higher than the upper limit of the conductivity reference range, the central control unit decreases the addition rate of the metal ion modifier.

[0019] The beneficial effects of this invention are: 1. This invention creatively solves the technical problems of low efficiency and poor stability of single-field separation technology by constructing a synergistic environment of multi-field coupling of "temperature-reagent concentration-high voltage electric field". By synchronously and precisely controlling the temperature and pH value / metal ion concentration of the pretreated slurry, it creatively enables metal ions to selectively adsorb onto the mica surface in a specific hydroxylated form, while having virtually no impact on quartz, actively and greatly enhancing the difference in surface electrical properties between the two. This coupled pretreatment mechanism creates unprecedentedly superior conditions for subsequent high-voltage electrostatic separation, resulting in a breakthrough improvement in separation efficiency and processing stability, fundamentally overcoming the defect of traditional electrostatic separation being overly sensitive to the surface state of materials.

[0020] 2. The intelligent closed-loop optimization system developed in this invention achieves adaptive and stable operation of the process. By monitoring product quality in real time using an online grade analyzer, the central control unit dynamically adjusts key parameters such as pretreatment dosage, temperature, and sorting voltage based on this feedback. This closed-loop system effectively compensates for interference caused by fluctuations in the mineral composition and particle size of the raw materials, giving the entire sorting process strong anti-disturbance capabilities and ensuring long-term stable production of high-quality manufactured sand with low mica content. This solves the industry pain point of unstable product quality due to raw material fluctuations in traditional methods.

[0021] 3. This invention, while ensuring highly efficient separation, also possesses significant environmental and economic advantages. The method primarily relies on a physical electric field and a small amount of recyclable inorganic reagents, avoiding product contamination and wastewater treatment problems associated with organic reagents in traditional flotation methods. The process water is recycled in a closed loop, significantly reducing fresh water consumption and wastewater discharge. Although temperature control and online monitoring are introduced, the resulting comprehensive improvement in separation efficiency, product qualification rate, and stability makes the overall production cost more competitive, providing a practical and feasible technical path for the green and low-carbon production of manufactured sand. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of the steps of the method of the present invention; Figure 2 This is a flowchart of step 1 of the method of the present invention; Figure 3 This is a flowchart of step 2 of the method of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0025] Please see Figures 1-3This invention provides a method for removing mica from machine-made sand based on multi-field coupling. Those skilled in the art can implement this invention based on the description herein. It should be noted that the specific details described should not be construed as limiting the invention. Any obvious substitutions, modifications, and improvements made without departing from the spirit of the invention are included within the scope of protection of this invention.

[0026] The core of this invention lies in creatively constructing and controlling a multi-field coupled synergistic process environment involving a temperature field, a reagent concentration field, and a high-voltage electric field. This method is not a simple superposition of multiple physical fields, but rather actively and selectively alters the surface physicochemical properties, especially the surface electrical properties, of the target mineral (mica) and gangue minerals (mainly quartz) through coupled pretreatment of temperature and specific chemical reagent concentrations. This allows for efficient and stable separation of the two minerals in the subsequent high-voltage electrostatic separation field due to the significant difference in their motion trajectories. Simultaneously, a closed-loop feedback system based on real-time detection dynamically optimizes the entire coupled separation process, ensuring the long-term stability of the treatment effect. The method comprises five main process stages: raw material pretreatment and characteristic analysis, construction and control of the coupled pretreatment environment, multi-field coupled separation operation, closed-loop feedback optimization of separation process parameters, and product post-treatment and media circulation.

[0027] The method of the present invention will now be described in detail with reference to a complete and continuous production process.

[0028] Step 1: Screen and dry the manufactured sand raw material to obtain the sand to be sorted.

[0029] The purpose of this step is to obtain raw materials that are physically homogeneous and surface-dry, and to provide basic data for the selection of subsequent process parameters.

[0030] Step 1 specifically includes the following sub-steps: Step 1.1: The raw materials from the manufactured sand production line are screened to remove non-compliant particles. Specifically, a vibrating screen is used to separate coarse particles larger than 5 mm, which can usually be returned to the front-end crushing system; simultaneously, fine mud particles smaller than 0.075 mm are separated. Ultimately, the resulting sand material has a particle size strictly controlled between 0.075 mm and 5 mm. This particle size range is the effective processing range for the subsequent high-voltage electrostatic separation process.

[0031] Step 1.2: The sand to be sorted obtained in Step 1.1 is fed into a drying device for drying. The purpose of drying is to completely remove the free water film adhering to the particle surface. The presence of free water will seriously interfere with the charging and conducting behavior of particles in a high-voltage electric field, leading to sorting failure. The drying process is carried out at a temperature of 105°C to 110°C, and heating is continued until the sand reaches constant weight. The criterion for constant weight is that the mass change is less than one-thousandth when weighed twice consecutively at an interval of 30 minutes.

[0032] Step 1.3: Key characteristic analysis of the dried sand to be sorted is performed to provide a basis for setting subsequent process parameters. First, the mica content in the sand is determined. A mineral dissociation analyzer or microscopic image analysis technique is used to analyze the prepared sand sample sections. The volume percentage of mica is calculated through mineral phase identification and statistics. Second, the morphological characteristics of the mica are analyzed, focusing on determining the average aspect ratio of the mica particles. The average value is calculated by measuring and statistically analyzing the projected area and thickness of a large number of mica particles; this parameter characterizes the platy nature of the mica. Finally, the particle size distribution of the entire sand to be sorted is determined. A laser particle size analyzer is used to obtain the cumulative particle size distribution curve of the sand, from which key indicators such as the median particle size (D50) are obtained. All the above analytical data are recorded and input into the central control unit.

[0033] Step 2: Mix the sand to be sorted with water to form a first pre-treated slurry. Add pH adjuster and metal ion adjuster to the first pre-treated slurry. Simultaneously control the temperature and pH value of the first pre-treated slurry to perform a first coupled pre-treatment under the first target temperature range and target pH range to obtain a second pre-treated slurry.

[0034] This step is the most creative embodiment of the present invention. Its purpose is to actively and selectively modify the surface properties of mica particles by precisely controlling the coupling effect of temperature and chemical environment.

[0035] Step 2 specifically includes the following sub-steps: Step 2.1: Mix the dried sand from Step 1 with water at a specific solid-liquid mass ratio. This solid-liquid mass ratio ranges from 1:3 to 1:5. The mixing is carried out in a pretreatment mixing tank equipped with a stirrer, where the sand and water are thoroughly mixed to form a uniformly suspended first pretreatment slurry.

[0036] Step 2.2: Two chemical adjusters are added simultaneously to the first pretreatment slurry. The first is a pH adjuster, used to adjust the acidity or alkalinity of the slurry; sodium hydroxide solution or sulfuric acid solution can be used. The second is a metal ion adjuster, used to provide metal cations that can specifically adsorb onto the mica surface; calcium chloride solution or aluminum sulfate solution can be used. Both adjusters are added to the stirred tank continuously or intermittently using a metering pump.

[0037] Step 2.3: Turn on the heating and temperature control system of the mixing tank, as well as the online pH meter. This is a key operation to achieve the coupling of the "temperature field and reagent concentration field". On the one hand, the heating system raises the temperature of the first pretreated slurry from room temperature and precisely stabilizes it within a specific first target temperature range. On the other hand, by adding a pH adjuster, the pH value of the first pretreated slurry is adjusted and precisely stabilized within a specific target pH range.

[0038] The first target temperature range and target pH range were pre-determined in the laboratory through systematic two-factor condition experiments on manufactured sand raw materials from specific origins and with specific mineral compositions. The determining principle was to maximize the surface zeta potential difference between mica and quartz particles. The experimental method was as follows: In a small laboratory container, a slurry with the same solid-liquid ratio as in production was prepared, the amount of metal ion modifier added was fixed, and a series of temperature levels (e.g., 40°C, 50°C, 60°C, 70°C) and a series of pH levels (e.g., 9, 10, 11, 12) were systematically varied. Under each temperature-pH combination, after thorough stirring for a certain period of time (e.g., 15 minutes), the supernatant was collected and the surface zeta potential of the mica-enriched and quartz-enriched phase particles was measured using a zeta potential analyzer. By analyzing the data under all combinations, the optimized temperature and pH range that maximized the zeta potential difference between the two phases was identified, and this range was defined as the first target temperature range and target pH range in production. For example, for a certain type of manufactured granite sand, the optimized region might be a first target temperature range of 55°C to 58°C and a target pH range of 10.5 to 11.0. Within this optimized region, the metal cations in the metal ion modifier (such as Ca²⁺) + Under specific temperature and pH conditions, it is more likely to exist in hydroxylated forms (such as CaOH). + It selectively and firmly adsorbs onto the aluminum-oxygen octahedral active sites on the surface of mica particles, thereby significantly altering the surface electrical properties of mica (reducing its negative zeta potential) while having minimal effect on the quartz surface.

[0039] Step 2.4: Maintain the first target temperature range and target pH range determined above, and continuously stir the first pretreated slurry for 10 to 20 minutes. This process ensures that the adsorption reaction between metal ions and the mica surface is fully carried out, completing the first coupling pretreatment. The slurry at this point is called the second pretreated slurry. During the pretreatment process, an online conductivity meter can also be used to monitor changes in the slurry conductivity as an auxiliary reference for the adsorption behavior of metal ions.

[0040] Step 3: After adjusting the second pretreatment slurry to the second target temperature, feed it into the high-voltage electrostatic separator; turn on the high-voltage electrostatic field of the high-voltage electrostatic separator and control the ambient temperature of the separation zone, so that the second pretreatment slurry is separated under the second coupling effect of the high-voltage electrostatic field and the temperature field, and mica particles and clean sand particles are collected respectively.

[0041] The purpose of this step is to achieve the physical separation of mica and quartz sand using a high-voltage electrostatic field while maintaining the temperature environment necessary for pretreatment.

[0042] Step 3 specifically includes the following sub-steps: Step 3.1: Before being transported to the high-voltage electrostatic separator, the second pretreated slurry obtained in Step 2 passes through a heat exchanger. The heat exchanger adjusts the temperature of the second pretreated slurry to a second target temperature. This second target temperature is typically set to be less than or equal to the lower limit of the first target temperature range selected in the first coupled pretreatment in Step 2. The purpose is to maintain the stability of the surface modification state of the mica particles and prevent changes in surface properties due to a sudden drop in temperature.

[0043] Step 3.2: The second pretreated slurry, after temperature adjustment, is fed into the feeding device of the high-pressure electrostatic separator at a stable and controllable flow rate. The high-pressure electrostatic separator typically includes the following core components: a grounded, rotatable metal drum (grounded drum); an electrode placed parallel to the drum and subjected to high-voltage direct current (high-voltage static electrode); an insulating shell enclosing the separation zone (heating and insulation cover); and a device that can uniformly disperse the slurry onto the surface of the drum (slurry atomizing feeder).

[0044] Step 3.3: Start the high-voltage electrostatic separator. First, turn on the DC high-voltage power supply to the high-voltage electrostatic electrodes, raising the voltage to a preset operating voltage value. This operating voltage value needs to be determined comprehensively based on the particle size distribution of the sand to be separated (especially the median particle size D50) and the processing capacity of the equipment. Generally speaking, the coarser the particles and the larger the processing capacity, the higher the required operating voltage value. A feasible method for determining this value is to first use an empirical formula. ; The particle size voltage coefficient, whose value is determined through equipment calibration tests, is measured in kilovolts per millimeter (kV / mm). It reflects the degree to which the particle size of the material affects the required voltage.

[0045] The load handling voltage coefficient, whose value is determined through equipment calibration tests, is measured in kilovolts (kV). It reflects the degree to which the load handled by the equipment affects the required voltage.

[0046] The reference voltage, measured in kilovolts (kV), represents the initial voltage of the equipment under reference conditions. Then, fine-tuning is performed during actual operation to achieve the best sorting effect. Next, the heating and insulation cover is turned on to maintain its internal temperature within the second target temperature range, thereby creating a stable temperature field in the sorting area, which forms a second coupling environment with the high-voltage electrostatic field.

[0047] Step 3.4: The second pre-treated slurry is dispersed into fine droplets or particle groups by a slurry atomizing feeder and uniformly fed onto the grounded drum surface. The drum rotates at a constant speed. In the high-voltage electrostatic field, due to the first coupling pre-treatment, the surface conductivity of the mica particles is significantly enhanced, while the surface conductivity of the quartz particles remains essentially unchanged. Particles with different conductivity exhibit different charging and discharging behaviors upon contact with the drum. Mica particles with better conductivity are more easily charged and less affected by the mirror attraction of the drum. Simultaneously, they are more easily polarized and attracted under the induction of the high-voltage electrode. Therefore, their trajectory deviates from the drum earlier and falls into the mica collection tank located below the high-voltage electrostatic electrode under gravity. Quartz particles with poor conductivity, however, are less prone to charge dissipation. They are firmly adsorbed by the drum and rotate along a long arc, mainly relying on centrifugal force to be thrown into the clean sand collection tank located tangentially to the drum. Thus, the mica and clean sand are separated.

[0048] Step 4: Real-time detection of mica content in the clean sand particles obtained after sorting, comparison of mica content with preset target threshold for mica content, and dynamic adjustment of the amount of metal ion modifier added, the first target temperature range, and the voltage of the high-voltage electrostatic field based on the comparison results.

[0049] This step constitutes an intelligent closed-loop feedback control system, ensuring that the process can adaptively adjust to fluctuations in raw materials and maintain optimal sorting results.

[0050] Step 4 specifically includes the following sub-steps: Step 4.1: Install an online grade analyzer at the outlet of the clean sand collection tank to continuously monitor the mica content in the outflowing clean sand particles in real time. This online grade analyzer can be a rapid analysis device based on principles such as near-infrared spectroscopy or X-ray fluorescence.

[0051] Step 4.2: The online grade analyzer transmits the real-time detected mica content data to the central control unit. The central control unit has a preset target threshold for mica content, which is set according to the final product quality standard (e.g., Class I construction sand standard), typically between 1.0% and 1.5%. The central control unit compares and judges the real-time mica content against this target threshold.

[0052] Step 4.3: The central control unit executes the adjustment strategy based on the comparison results. If the mica content detected in real time remains higher than the target threshold, it indicates that the current sorting effect is not up to standard. The central control unit will automatically fine-tune the key process parameters in sequence according to the preset logic: First, increase the addition rate of the metering pump for adding metal ion modifier in Step 2 to increase the effective ion concentration in the slurry; Second, increase the first target temperature setting of the pretreatment mixing tank in Step 2 by 0.5 degrees Celsius to 2 degrees Celsius; Third, increase the working voltage of the high-voltage electrostatic electrode in Step 3 by 1000 volts to 3000 volts. These three adjustments aim to synergistically enhance the surface modification effect of mica and the electric field separation strength. After adjustment, the system will run stably for a period of time (e.g., 15-20 minutes) and the effect will be evaluated again.

[0053] Step 4.4: If the mica content detected in real time is lower than or equal to the target threshold, the central control unit determines that the current sorting effect is good, maintains all controlled parameters (metal ion adjuster addition rate, first target temperature setpoint, working voltage value) unchanged, and the system enters stable operation monitoring mode.

[0054] Step 5: Dewater the products obtained after sorting, and recycle the dewatering water to prepare the first pretreatment slurry.

[0055] This step achieves the final treatment of the product and the closed-loop recycling of water resources, demonstrating the environmental friendliness and economic efficiency of the method.

[0056] Step 5 specifically includes the following sub-steps: Step 5.1: The clean sand particles discharged from the clean sand collection tank typically contain about 10-20% moisture. They are then conveyed to a dewatering screen (such as a linear vibrating screen) for dewatering, yielding a final clean manufactured sand product with a moisture content of less than 8%. The water passing through the dewatering screen is called the first return water.

[0057] Step 5.2: The mica-rich tailings slurry discharged from the mica collection tank is transported to a thickener (such as an inclined plate thickener) for solid-liquid separation. The underflow (mica sludge) from the thickener is pumped to a filter press for further processing into sludge cake. The supernatant overflowing from the thickener is called the secondary return water, which is relatively clear.

[0058] Step 5.3: The first and second return water are collected in the plant's return water tank. The water in the return water tank is pumped back to the pretreatment mixing tank in Step 2.1 as supplementary water for preparing the first pretreatment slurry, thereby achieving a large-scale closed-loop circulation of process water.

[0059] Step 5.4: To ensure the stability of the chemical environment of the circulating water system, the pH value and conductivity of the water in the return water tank need to be tested regularly. The testing frequency can be once every 2 to 4 hours. Based on the test results, automatically or manually replenish the consumed chemical agents to the system: if the pH value is lower than the lower limit of the target pH range set in Step 2.3, add pH adjuster to the return water tank or pretreatment mixing tank; if the conductivity is lower than a minimum threshold determined experimentally to maintain a good pretreatment effect, add metal ion adjuster. In this way, the dynamic balance of the chemical environment of the entire circulating system is maintained.

[0060] Example This embodiment uses manufactured granite sand from a region in southeastern China as the treatment target. The parent rock of this manufactured sand typically contains 3% to 8% mica (mainly muscovite). After being processed by jaw crusher, cone crusher, and vertical shaft impact crusher, the mica is mostly present in flaky form within sand grains ranging from 0.075 mm to 5 mm, severely affecting the strength and durability of the prepared concrete. This is a quality bottleneck that the local building materials industry urgently needs to address. This embodiment applies the method described in this invention to deeply remove mica from this manufactured sand.

[0061] Step 1: Pretreatment and property analysis of manufactured sand raw materials; Approximately 500 kg of raw material is obtained from the vibrating screen of the granite manufactured sand production line. First, it is passed through a double-layer vibrating screen; the upper screen has a 5 mm mesh size, and the lower screen has a 0.075 mm mesh size. Coarse particles larger than 5 mm are returned to the crushing system, while the silt smaller than 0.075 mm is collected for other uses. Finally, approximately 420 kg of sand with a particle size between 0.075 mm and 5 mm is obtained for sorting.

[0062] Take approximately 10 kg of sand to be separated and place it in an electrically heated drying oven at 108 degrees Celsius. Weigh the sand every 30 minutes until the weight difference between two consecutive weighings is less than one-thousandth, at which point constant weight is considered achieved. This process takes approximately 4 hours. The purpose of drying is to completely remove the adsorbed water film on the particle surface, as the presence of free water severely shields the inherent electrical properties of the particle surface, leading to the failure of subsequent electrostatic separation.

[0063] Approximately 1 kg of sand was randomly sampled from multiple points after drying as a representative sample. This sample was analyzed using a mineral liberation analyzer. A slide was prepared from the sample, and different mineral phases were identified using backscattered electron imaging. The analysis software automatically calculated the mica volume content to be 5.2% and measured the projected area and thickness of over 2000 mica particles, calculating an average diameter-to-thickness ratio of 28:1, confirming the significant platy morphology of the mica. Simultaneously, another sample was tested using a laser particle size analyzer. The results showed that the median particle size (D50) of this sand to be sorted was 0.85 mm, with particles ranging from 0.15 mm to 0.6 mm accounting for the highest proportion.

[0064] Step 2: Construct and regulate the coupled preprocessing environment; Preparation of pretreatment slurry: Add the dried sand material to be sorted from step 1 (approximately 420 kg) and 1260 kg of industrial water (solid-liquid mass ratio 1:3) together into a stainless steel pretreatment mixing tank equipped with a stirrer, jacket heating and temperature sensor to form slurry.

[0065] Two conditioning solutions were added simultaneously to the stirred tank: a 10% sodium hydroxide solution for pH adjustment and a 5% calcium chloride solution for metal ion adjustment. An online pH meter and an online conductivity meter were installed in the stirred tank, with their probes immersed below the surface of the slurry.

[0066] Initiate the coupling pretreatment process: Turn on the agitator and set the speed to 200 rpm to ensure the slurry is fully suspended and free of obvious vortices. Simultaneously execute the following two core control operations: First, temperature control: The jacketed steam heating system is turned on, and the slurry temperature is gradually increased from the initial 25 degrees Celsius. In this embodiment, the determination of the first target temperature range is the result of optimization through previous system laboratory condition tests. For this specific granite manufactured sand, we designed a two-factor, multi-level condition test in the laboratory. In a 2-liter beaker, a slurry with a solid-liquid ratio of 1:3 was prepared, and the amount of calcium chloride added was fixed (100 g / ton of sand based on calcium ions). The system changed the pretreatment temperature (30 degrees Celsius, 40 degrees Celsius, 50 degrees Celsius, 60 degrees Celsius, 70 degrees Celsius) and pH value (8, 9, 10, 11, 12). Under each temperature-pH combination condition, after stirring for 15 minutes, the upper suspension of the slurry was taken, and the zeta potential of the mica-enriched phase and quartz-enriched phase obtained by sedimentation separation was measured using a zeta potential analyzer.

[0067] Experiments revealed a strong coupling effect between temperature and pH on the zeta potential of mica surface. At low temperatures (e.g., 40°C), even with a high pH (e.g., 11), calcium ion adsorption on the mica surface was slow, resulting in a limited positive shift in the zeta potential. At high temperatures (e.g., 70°C), if the pH was also high (e.g., 12), the zeta potential on the quartz surface experienced a significant negative shift (a decrease in absolute value), leading to a reduction in the potential difference between the two. Through data processing, an optimized region was identified that maximized the difference in zeta potential between the mica and quartz surfaces. For the raw materials in this embodiment, the first target temperature range corresponding to this optimized region was 55°C to 58°C, and the target pH range was 10.5 to 11.0. Within this region, the zeta potential on the mica surface decreased from approximately -35 mV to approximately -5 mV, while the zeta potential on the quartz surface remained stable at approximately -30 mV, increasing the difference from approximately 5 mV to approximately 25 mV. This dramatic widening of the difference is due to the fact that, under specific temperature and pH coupling conditions, calcium ions react as CaOH... + Predominantly in hydroxylated form, it undergoes specific adsorption on the surface of the mica aluminum oxide octahedral layer, partially neutralizing the negative charge of mica.

[0068] Therefore, in the industrial production of this embodiment, we set and stabilized the pretreatment temperature at 56 degrees Celsius.

[0069] Second, chemical environment control: A 10% sodium hydroxide solution was added dropwise using a peristaltic pump to precisely adjust and stabilize the pH of the slurry at 10.8. During this process, an online conductivity meter showed that the conductivity gradually increased from an initial value of approximately 100 microsiemens / cm and stabilized at approximately 450 microsiemens / cm, indirectly reflecting the addition and partial adsorption of calcium ions. Simultaneously, according to the reagent regimen established in the laboratory, a 5% calcium chloride solution was added at a constant rate using another peristaltic pump to ensure that the calcium ion concentration in the slurry remained stable at 100 g / ton of sand.

[0070] The temperature was maintained at 56 degrees Celsius and the pH at 10.8, and the mixture was continuously stirred for 15 minutes. Throughout the process, the central control unit monitored and recorded the temperature, pH, and conductivity data in real time to ensure the stability of the coupled pretreatment environment.

[0071] Step 3: Multi-field coupling sorting operation; The slurry, which has undergone sufficient pretreatment in step 2 and is still maintained at 56 degrees Celsius, is pumped to the feeding system of the high-pressure roller electrostatic separator via a slurry pump. Before entering the feeding system, the slurry flows through a plate heat exchanger, the temperature of which is set to 56 degrees Celsius on the hot side to ensure that the slurry temperature does not decrease during transportation; that is, the second target temperature in this embodiment is 56 degrees Celsius.

[0072] The main components of the high-pressure roller electrostatic separator include: a grounded stainless steel drum with a diameter of 400 mm and a width of 800 mm, a knife-shaped high-pressure static electrode (with a distance of 65 mm) arranged parallel to the axis of the drum, an electric heating insulation cover wrapped around the separation zone, and a slurry atomizing feeder located above the drum.

[0073] Start-up of the equipment: First, turn on the DC high-voltage power supply of the high-voltage static electrode and raise the voltage to the operating voltage value. This operating voltage value is not fixed, but is initially set based on the particle size distribution (D50 = 0.85 mm) measured in step 1 and the processing capacity of this equipment (approximately 8 tons / hour). Generally, the coarser the particles and the larger the processing volume, the higher the required electric field strength. The initial setting is 35 kV, referring to empirical formulas and considering the equipment's safety range. Then, turn on the heating and insulation cover and set its temperature to 55 degrees Celsius to make the air temperature in the sorting zone close to the slurry temperature, preventing changes in particle surface characteristics due to heat dissipation.

[0074] The pretreated slurry enters the slurry atomizing feeder, which contains a high-speed rotating disc that breaks the slurry into fine droplets and evenly distributes them onto the surface of the grounded rotating drum. The drum rotates at 25 rpm. In a 35 kV high-voltage electrostatic field, the surface of the mica particles has been selectively modified through coupling pretreatment, resulting in significantly enhanced conductivity (manifested as a decrease in surface resistance), while the surface electrical properties of the quartz particles change very little. According to the principle of electrostatic separation, the more conductive mica particles, when in contact with the rotating drum, can quickly conduct away the acquired charge, thus experiencing less mirror attraction from the drum; simultaneously, they are more easily polarized and attracted under the induction of the high-voltage electrode. As a result of the coupling effect of multiple forces (electric force, centrifugal force, and gravity), the trajectory of the mica particles deviates significantly: they detach from the drum surface earlier and fall in a parabolic trajectory into the mica collection trough (tailings trough) located directly below the high-voltage electrostatic electrode. Quartz particles with poor electrical conductivity are not easily charged when they come into contact with the drum. They are attracted by a strong mirror force and move along a longer arc with the drum. They are mainly thrown into the quartz sand collection tank (concentrate tank) located in the tangential direction of the drum by centrifugal force.

[0075] Step 4: Closed-loop feedback optimization of sorting process parameters; Online grade analyzers based on near-infrared spectroscopy were installed at the outlets of the mica and quartz sand collection tanks, respectively. These instruments scan the material flowing through their detection windows in real time, once every 30 seconds, and quickly analyze the mica content (for concentrate streams) or quartz content (for tailings streams) using a built-in spectral model.

[0076] The product quality target set in this embodiment is that the mica content in the concentrate (clean manufactured sand) does not exceed 1.5%. This mica content target threshold is determined based on the requirements for the content of harmful substances in Class I sand in the "Construction Sand" standard, combined with the actual needs of downstream high-performance concrete preparation.

[0077] The central control unit receives data in real time from two online grade analyzers. During the initial operation phase (first 30 minutes), the mica content in the concentrate is displayed as 1.8%, slightly higher than the target threshold of 1.5%. The central control unit initiates an optimization and control program based on preset control logic. This logic is based on a process knowledge base: when the mica content in the concentrate exceeds the standard, the primary suspicion is insufficient surface modification of the mica or inadequate electric field separation.

[0078] The regulatory action will be implemented in three steps, with each step being a fine-tuning step: 1. Increase the rate of metal ion modifier addition: Increase the pump speed of calcium chloride solution addition by 5% to slightly increase the calcium ion concentration in the slurry from 100 g / ton of sand to about 105 g / ton of sand.

[0079] 2. Simultaneously fine-tune the pretreatment temperature: Increase the temperature setting of the pretreatment mixing tank from 56 degrees Celsius to 56.8 degrees Celsius.

[0080] 3. Fine-tuning the working voltage of the electrostatic separator: Increase the voltage of the high-voltage electrostatic electrode from 35 kV to 36 kV.

[0081] These adjustments are designed to work synergistically: a slightly higher calcium ion concentration and temperature promote the adsorption of more calcium hydroxyl compounds on the mica surface, further increasing its electrical difference with quartz; while increasing the voltage enhances the electric field separation force. Approximately 15 minutes after the adjustments were implemented (considering system lag time), the online grade analyzer showed that the mica content in the concentrate gradually decreased and stabilized at 1.4%. The central control unit then stopped adjusting and entered a stable operation monitoring mode. If subsequent detection values ​​deviate again, the system will repeat this closed-loop feedback optimization process. This system ensures that the process can adaptively maintain optimal separation performance when faced with small fluctuations in raw material prices.

[0082] Step 5: Product post-processing and media circulation; The concentrate sand discharged from the quartz sand collection tank (approximately 398 kg / hour), with a moisture content of about 15%, is conveyed to a linear dewatering screen. The screen yields clean manufactured sand with a moisture content of less than 8%, which is then packaged for later use. The underflow from the dewatering screen, along with the tailings slurry discharged from the mica collection tank, enters a thickening tank. The supernatant overflow from the thickening tank enters a return water tank and is pumped back to the pretreatment slurry preparation stage in step 2 as makeup water for recycling. The underflow from the thickening tank (mainly mica sludge) is pumped to a filter press for treatment.

[0083] To maintain a stable chemical environment in the circulating water system, water samples are taken periodically (every 4 hours) from the return water tank to test its pH value and calcium ion concentration (using titration). Based on the test results, a small amount of sodium hydroxide solution and calcium chloride solution is automatically added to the pretreatment mixing tank to compensate for the reagents consumed during product removal and adsorption, thus maintaining the pH value and ion concentration of the circulating water system near the set range and achieving closed-loop circulation and minimized reagent consumption.

[0084] Effect verification: To objectively evaluate the effectiveness of the method of this invention, parallel comparative experiments were conducted using three existing technologies on the same batch of granite manufactured sand raw materials. All experiments aimed to reduce the mica content from 5.2% to the lowest possible level and examined its recovery rate (concentrate yield) and stability.

[0085] 1. Comparative Example 1 (Hydraulic Classification Method): A hydrocyclone array was used for classification and desliming. By adjusting the feed pressure and underflow orifice size, attempts were made to separate mica flake particles into the overflow by utilizing their slow settling characteristic. After multiple parameter adjustments, under optimal conditions, the underflow concentrate yield was 85%, but the mica content only decreased to 3.5%, and the loss of fine sand (<0.3 mm) was severe.

[0086] 2. Comparative Example 2 (Conventional Flotation): Flotation was carried out at room temperature using an amine cationic collector (dodecylamine) and a frother (pine oil). The flotation was performed under acidic conditions (pH=3) with stirring and slurry preparation followed by aeration. The concentrate yield was 88%, and the mica content could be reduced to 1.0%. However, the concentrate surface retained a chemical odor, and the generated wastewater had a high chemical oxygen demand (COD), requiring complex treatment.

[0087] 3. Comparative Example 3 (Conventional High-Voltage Electrostatic Separation): Without the coupling pretreatment in step 2, the sand dried in step 1 is directly fed into the high-voltage electrostatic separator described in step 3. Separation is performed under the same 35 kV voltage. Due to the lack of selective modification of the mica surface, the electrical differences between mica and quartz are small, resulting in extremely poor separation. The concentrate yield is as high as 95%, but the mica content is still 4.8%, indicating almost no separation effect.

[0088] 4. Method of this invention embodiment: adopts the complete process of steps 1 to 5 above.

[0089] The key technical indicators of the four schemes are compared in Table 1: Table 1 Comparison of Key Technical Indicators Conclusion: This invention, through active regulation of surface electrical properties via temperature-concentration coupled pretreatment, combined with subsequent heat-insulating high-pressure electrostatic separation and closed-loop feedback optimization, successfully reduced mica content from 5.2% to 1.4% without using harmful organic agents and while maintaining a high sand recovery rate (93%). Furthermore, the process was stable and the wastewater was easily treatable. The overall performance of this method is significantly superior to traditional single physical separation or chemical flotation methods.

[0090] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for removing mica from mechanical sand based on multi-field coupling, characterized in that, Includes the following steps: Step 1: Screening and drying pretreatment of the manufactured sand raw material to obtain the sand to be sorted; Step 2: Mix the sand to be sorted with water to form a first pre-treated slurry. Add pH adjuster and metal ion adjuster to the first pre-treated slurry. Simultaneously control the temperature and pH value of the first pre-treated slurry to perform the first coupled pre-treatment under the first target temperature range and target pH range to obtain the second pre-treated slurry. Step 3: After adjusting the second pre-treated slurry to the second target temperature, feed it into the high-voltage electrostatic separator; turn on the high-voltage electrostatic field of the high-voltage electrostatic separator and control the ambient temperature of the separation zone, so that the second pre-treated slurry is separated under the second coupling effect of the high-voltage electrostatic field and the temperature field, and mica particles and clean sand particles are collected respectively. Step 4: Real-time detection of mica content in the clean sand particles obtained after sorting, comparison of mica content with preset mica content target threshold, and dynamic adjustment of the amount of metal ion modifier added, the first target temperature range and the voltage of the high voltage electrostatic field based on the comparison results. Step 5: Dewater the products obtained after sorting, and recycle the dewatering water to prepare the first pretreatment slurry.

2. The method for removing mica from machine-made sand based on multi-field coupling according to claim 1, characterized in that, Step 1 specifically includes: Step 1.1: The manufactured sand raw material is screened to remove coarse particles with a particle size greater than 5 mm and silt with a particle size less than 0.075 mm, so as to obtain sand material to be sorted with a particle size range of 0.075 mm to 5 mm. Step 1.2: Dry the sand to be sorted at a temperature of 105°C to 110°C until constant weight; Step 1.3: Determine the mica content and average diameter-to-thickness ratio of the mica particles in the dried sand to be sorted, and determine the particle size distribution of the sand to be sorted.

3. The method for removing mica from machine-made sand based on multi-field coupling according to claim 1, characterized in that, Step 2 specifically includes: Step 2.1: Mix the dried sand to be sorted with water at a solid-liquid mass ratio of 1:3 to 1:5 to form a uniform first pretreatment slurry in a mixing tank; Step 2.2: Simultaneously add a pH adjuster and a metal ion adjuster to the first pretreatment slurry; the pH adjuster is a sodium hydroxide solution or a sulfuric acid solution; the metal ion adjuster is a calcium chloride solution or an aluminum sulfate solution; Step 2.3: The temperature of the first pretreated slurry is raised and stabilized within the first target temperature range by the heating and temperature control system of the mixing tank. At the same time, the pH value of the first pretreated slurry is adjusted and stabilized within the target pH range by adding a pH adjuster. Step 2.4: Maintain the first target temperature range and target pH range, and continuously stir the first pretreated slurry for 10 to 20 minutes to complete the first coupled pretreatment and obtain the second pretreated slurry.

4. The method for removing mica from machine-made sand based on multi-field coupling according to claim 3, characterized in that, The specific matching relationship between the first target temperature range and the target pH range is as follows: within the first target temperature range of 55 degrees Celsius to 58 degrees Celsius, a target pH range of 10.5 to 11.0 is matched.

5. The method for removing mica from machine-made sand based on multi-field coupling according to claim 1, characterized in that, Step 3 specifically includes: Step 3.1: Flow the second pretreated slurry through the heat exchanger to adjust the temperature of the second pretreated slurry to the second target temperature; the second target temperature is less than or equal to the lower limit of the first target temperature range of the first coupled pretreatment. Step 3.2: The second pretreated slurry, after temperature adjustment, is fed into the feeding device of the high-pressure electrostatic separator at a stable flow rate; the high-pressure electrostatic separator includes a grounded drum, a high-voltage static electrode, a heating and insulation cover, and a slurry atomizing feeder; Step 3.3: Turn on the DC high voltage power supply of the high voltage static electrode and raise the voltage to the working voltage value; the working voltage value is determined according to the particle size distribution of the sand to be sorted and the processing capacity of the high voltage electrostatic separator; the larger the median particle size of the particle size distribution and the larger the processing capacity, the higher the working voltage value; turn on the heating and heat preservation cover to maintain the ambient temperature of the high voltage electrostatic separator sorting area within the second target temperature range. Step 3.4: The second pre-treated slurry is dispersed into droplet particles by the slurry atomizing feeder and evenly sprinkled on the surface of the grounded rotating drum. Under the second coupling effect of the high voltage electrostatic field and the temperature field, the mica particles deviate from their trajectory due to the enhanced surface conductivity and fall into the mica collection tank. The clean sand particles are mainly thrown down along the centrifugal force direction and enter the clean sand collection tank.

6. The method for removing mica from machine-made sand based on multi-field coupling according to claim 1, characterized in that, Step 4 specifically includes: Step 4.1: The mica content in the clean sand particles discharged from the clean sand collection tank is detected in real time using an online grade analyzer; the online grade analyzer is an analyzer based on near-infrared spectroscopy technology; Step 4.2: The real-time detected mica content is transmitted to the central control unit, which compares the mica content with a preset target threshold for mica content; the target threshold for mica content is set to 1.0% to 1.5%. Step 4.3: If the central control unit determines that the real-time mica content is continuously higher than the target threshold for mica content, the central control unit will sequentially perform the following optimization and control operations: First, increase the addition rate of metal ion modifier to the first pretreatment slurry; then increase the set value of the first target temperature range of the first coupling pretreatment by 0.5 degrees Celsius to 2 degrees Celsius; finally, increase the working voltage of the high-voltage electrostatic field of the high-voltage separator by 1000 volts to 3000 volts. Step 4.4: If the central control unit determines that the real-time mica content is lower than the target threshold for mica content, then the current metal ion modifier addition rate, the first target temperature range setting value, and the working voltage value remain unchanged.

7. The method for removing mica from machine-made sand based on multi-field coupling according to claim 5, characterized in that, The process of determining the working voltage value in step 3.3 is as follows: First, the median particle size D50 is obtained based on the particle size distribution of the sand to be separated, in millimeters; the rated processing capacity Q is obtained based on the design processing capacity of the high-voltage electrostatic separator, in tons / hour; the initial working voltage value U, in kilovolts, is estimated using the following formula: ; The particle size voltage coefficient, measured in kilovolts per millimeter, reflects the degree to which the particle size of the material affects the required voltage. The load capacity voltage coefficient, measured in kilovolts, reflects the degree to which the load handled by the equipment affects the required voltage. Reference voltage, measured in kilovolts, represents the initial voltage of the equipment under reference conditions; After obtaining the estimated value, actual sorting tests were conducted within the safe voltage range of the high-voltage electric separator. The optimization target was to minimize the mica content of the clean sand particles after sorting. The final working voltage value was then fine-tuned and determined.

8. The method for removing mica from machine-made sand based on multi-field coupling according to claim 1, characterized in that, Step 5 specifically includes: Step 5.1: The clean sand particles discharged from the clean sand collection tank are transported to the dewatering screen for dewatering to obtain a clean manufactured sand product with a moisture content of less than 8%; the underflow water generated by the dewatering screen is used as the first return water. Step 5.2: The tailings slurry formed by the mica particles discharged from the mica collection tank and water is transported to the thickening tank for sedimentation. The supernatant of the thickening tank is used as the second return water. Step 5.3: Collect the first and second return water into the return water tank and circulate it to Step 2 for preparing the first pretreated slurry; Step 5.4: Regularly test the pH value and conductivity of the return water in the return water tank. When the pH value is lower than the lower limit of the target pH range, add pH adjuster to the return water tank or mixing tank; when the conductivity is lower than the set threshold, add metal ion adjuster to the return water tank or mixing tank.

9. A method for removing mica from machine-made sand based on multi-field coupling according to claim 3, characterized in that, During the first coupling pretreatment in step 2.3, an online conductivity meter is used to monitor the conductivity changes of the first pretreated slurry in real time. The online conductivity meter feeds back the real-time conductivity data to the central control unit. The central control unit stores a conductivity reference range, which characterizes the slurry conductivity range of the metal ion modifier under the target adsorption state. If the real-time conductivity is continuously lower than the lower limit of the conductivity reference range, the central control unit increases the addition rate of the metal ion modifier. If the real-time conductivity is continuously higher than the upper limit of the conductivity reference range, the central control unit decreases the addition rate of the metal ion modifier.

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