Calcium and magnesium separation process for dolomite tailings

Abstract

The invention discloses a calcium-magnesium separation process for dolomite tailings, which belongs to the field of dolomite tailings treatment, and comprises the following steps: crushing the dolomite tailings by a crusher until the particle size is less than 5mm, and then grinding the dolomite tailings in a ball mill until the particle size reaches 200 meshes; a magnetic separator is adopted for magnetic separation, iron impurities in the tailings are removed, then impurities such as silicon are removed through a flotation method, and the pretreated dolomite tailings are obtained; putting the pretreated dolomite tailings into a high-temperature furnace, and calcining at 950 DEG C for 2 hours; according to the method, various innovative separation technologies are combined, efficient separation of calcium and magnesium can be achieved, the purity of calcium and magnesium products is improved, the production cost is reduced, and resource waste is reduced; the industrial preparation technology of nano magnesium oxide, nano magnesium hydroxide and nano calcium carbonate developed on the basis of the separation process breaks through the bottleneck of the prior art, improves the product quality and the production efficiency, and has a good industrial prospect.

Description

Technical Field

[0001] The invention relates to the technical field of dolomite tailings treatment, in particular to a dolomite tailings calcium and magnesium separation process. Background Art

[0002] Dolomite tailings, a common industrial waste, contain abundant calcium and magnesium resources. Effective processing and comprehensive utilization of these resources not only reduces the environmental impact of tailings but also enables resource recycling, resulting in significant economic and environmental benefits. However, existing methods for extracting magnesium from dolomite and preparing related products have numerous shortcomings.

[0003] Among the traditional methods for preparing magnesium products from dolomite, the pressurized carbonization method requires high-pressure equipment, large equipment investment, relatively low production capacity, and the purity of the by-product calcium salt is not high. The ammonium chloride-carbon dioxide method introduces more impurities during the preparation process, resulting in seriously impure calcium carbonate products. The ammonium sulfate one-step leaching method has the problem of easily exceeding the sulfate ion standard in the magnesium oxide product, and the production cycle is long and the cost is high. Although the ion exchange resin method has achieved calcium and magnesium separation to a certain extent, it has not fundamentally solved the problem of reducing costs. The magnesium chloride method is only applicable to specific areas with magnesium chloride resources, and its application range is limited.

[0004] Existing methods for preparing nano-magnesium oxide and nano-magnesium hydroxide are complex, requiring expensive reagents and sophisticated equipment, resulting in high costs. Furthermore, product quality is unstable and particle size distribution is uneven, making it difficult to meet the needs of large-scale industrial applications.

[0005] Therefore, there is a need for a dolomite tailings calcium and magnesium separation process that can effectively solve the problems of incomplete calcium and magnesium separation, high production cost, unstable product quality, etc. in the existing technology and realize efficient resource utilization of dolomite tailings. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a dolomite tailings calcium and magnesium separation process, which effectively solves the problems of incomplete calcium and magnesium separation, high production costs, and unstable product quality in the existing technology, and realizes the efficient resource utilization of dolomite tailings. Based on this separation process, breakthroughs are made in the key common technologies for the industrialization of nano-magnesium oxide, nano-magnesium hydroxide, and nano-calcium carbonate, and corresponding pilot production lines are built to meet the application needs of related materials in multiple fields in the downstream Guangdong-Hong Kong-Macao Greater Bay Area and promote the development of related industries.

[0007] Technical solution: To solve the above technical problems, according to one aspect of the present invention, more specifically, a dolomite tailings calcium and magnesium separation process comprises the following steps:

[0008] S1. Pretreatment stage: Dolomite tailings usually contain a variety of impurities and have a large particle size, which is not conducive to subsequent separation and reaction.

[0009] First, the dolomite tailings are crushed to a particle size of less than 5mm by a crusher to initially refine the tailings particles. During the crushing process, the high-speed rotating components inside the crusher impact and squeeze the tailings to reduce their particle size.

[0010] Then, the tailings are ground in a ball mill to a particle size of 200 mesh, further refining the particles, increasing the specific surface area, and improving the activity of subsequent reactions. The ball mill grinds the tailings particles into fine particles through the impact and grinding action of the steel balls. Then, a magnetic separator is used for magnetic separation, using the magnetic field to remove iron impurities in the tailings.

[0011] Because iron impurities will affect the purity of subsequent products, magnetic separators can effectively separate magnetic iron impurities;

[0012] Then, impurities such as silicon are removed by flotation. The flotation method uses the differences in the physical and chemical properties of the mineral surface to make impurities such as silicon adhere to bubbles, thereby separating them from the dolomite tailings, and finally obtaining pre-treated dolomite tailings.

[0013] S2. Preliminary separation of calcium and magnesium: The pretreated dolomite tailings are placed in a high-temperature furnace and calcined at 950°C for 2 hours. High-temperature calcination decomposes the calcium carbonate and magnesium carbonate in the dolomite tailings into calcium oxide and magnesium oxide. The calcined product is transferred to a digestion tank, and medium water is added. The digestion temperature is controlled at 65°C and the digestion time is controlled at 45 minutes.

[0014] Calcium oxide and magnesium oxide react with water to produce calcium hydroxide and magnesium hydroxide. Add an aqueous solution containing a small amount of tartaric acid to the digested slurry, adjust the solution pH to 10.5, and stir the reaction at 35°C for 1 hour.

[0015] Tartaric acid can complex with calcium ions, changing the dissolution equilibrium of calcium hydroxide and increasing its solubility, while having little effect on the solubility of magnesium hydroxide;

[0016] In this way, under the conditions of controlling the solution pH value to 10.5 and the temperature to 35°C, calcium hydroxide can be preferentially dissolved, and the preliminary separation of calcium and magnesium can be achieved by filtration to obtain calcium filtrate and magnesium-enriched residue;

[0017] S3. Deep separation and purification: Add water and disodium EDTA to the magnesium-enriched residue after preliminary separation, and react under stirring for 2 hours. Disodium EDTA acts as a complexing agent to fully complex the magnesium ions with the complexing agent.

[0018] The solution is passed through an exchange column filled with a strong acidic cation exchange resin for ion exchange purification to further remove impurity ions in the solution and obtain a high-purity magnesium solution. Carbon dioxide gas is introduced into the calcium filtrate, and the reaction temperature is controlled at 25°C for 1 hour to precipitate the calcium ions as calcium carbonate.

[0019] The high-purity nano calcium carbonate product is obtained by filtering, washing and drying at 100°C to remove impurities and moisture in the precipitate.

[0020] Furthermore, further, it also includes a product preparation technology based on the separation process, and the product preparation technology includes a preparation method of nano magnesium oxide and nano magnesium hydroxide:

[0021] Preparation method of nano-magnesium oxide: urea is added to the refined magnesium solution to make the urea concentration reach 0.5 mol / L, the reaction temperature is controlled at 80°C, and the reaction time is 4 hours;

[0022] Under these conditions, urea decomposes to produce carbonate ions, which react with magnesium ions to form a magnesium hydroxide precursor precipitate. The magnesium hydroxide precursor is transferred to a hydrothermal reactor and reacted at 200°C for 4 hours. The hydrothermal reaction can further crystallize the magnesium hydroxide precursor.

[0023] After the reaction, the product is filtered and washed to remove impurities, then calcined at 700°C for 3 hours to decompose the magnesium hydroxide into nanomagnesium oxide. During the reaction, 0.5% (mass fraction) of polyethylene glycol is added as a surfactant. The polyethylene glycol adsorbs on the surface of the nanomagnesium oxide particles, controlling the morphology of the nanomagnesium oxide to a flake shape and a particle size of 30-50 nm.

[0024] Preparation method of nano magnesium hydroxide: slowly add 2 mol / L ammonia water to the refined magnesium solution, and simultaneously add 0.2% (mass fraction) EDTA and 0.3% (mass fraction) PEG;

[0025] Ammonia provides hydroxide ions, which react with magnesium ions to form magnesium hydroxide. EDTA and PEG act as additives to regulate the reaction process, controlling the reaction temperature to 50°C and the reaction time to 2.5 hours.

[0026] After the reaction is completed, the product is processed by spray drying combined with freeze drying. Spray drying can quickly remove moisture, while freeze drying can further remove residual moisture and prevent agglomeration, resulting in a well-dispersed nano-magnesium hydroxide product with a particle size of 20-30nm.

[0027] Furthermore, a variety of pilot production lines were built based on the separation process:

[0028] Tailings Treatment and Resource Utilization Pilot Production Line: This production line includes tailings pretreatment equipment (crusher, ball mill, magnetic separator, flotation machine), calcium and magnesium separation equipment (calciner, digester, reactor, filter), nano-calcium carbonate production equipment (carbonization tower, dryer), and nano-magnesium oxide and nano-magnesium hydroxide production equipment (reactor, hydrothermal reactor, drying equipment). Equipped with an automated control system, this system provides real-time monitoring and precise control of process parameters such as temperature, pressure, flow rate, and pH value, ensuring process stability and consistent product quality.

[0029] The pilot production line for comprehensive dolomite utilization integrates dolomite tailings treatment, calcium and magnesium separation, and magnesium oxide and calcium carbonate product preparation processes. It features waste heat, waste gas, and wastewater recovery and reuse. Waste heat generated during the production process is used to preheat materials, reducing energy consumption. Carbon dioxide from waste gas is recovered for use in calcium carbonate production, reducing CO2 emissions. Wastewater is treated and recycled, achieving efficient resource utilization and environmentally friendly production.

[0030] High-end calcium carbonate application pilot production line: Targeted at the needs of the papermaking, rubber, and coatings sectors in the Guangdong-Hong Kong-Macao Greater Bay Area, this production line is equipped with equipment for surface modification of calcium carbonate using fatty acids and titanate coupling agents. This surface modification improves the dispersibility and compatibility of calcium carbonate in various substrates. In the papermaking sector, adding the modified calcium carbonate to paper improves its whiteness, strength, and printability. In the rubber sector, it enhances its hardness, abrasion resistance, and aging resistance. In the coatings sector, it improves its hiding power, gloss, and stability.

[0031] Furthermore, the separation process and product preparation technology are applied in multiple fields:

[0032] In the engineering plastics sector, the prepared nanomagnesium oxide and nanomagnesium hydroxide are added to engineering plastics such as polycarbonate and nylon to improve their flame retardancy, mechanical properties, and thermal stability. For example, nanomagnesium oxide and nanomagnesium hydroxide were added to polycarbonate at a 3% mass fraction and blended using a twin-screw extruder. Test results showed that the oxygen index of the polycarbonate after addition increased by 20%, tensile strength by 15%, and heat deflection temperature by 10°C, meeting the higher flame retardancy and mechanical properties required of engineering plastics.

[0033] In the field of biodegradable plastic masterbatches, nano-calcium carbonate and nano-magnesium oxide are added to polylactic acid and starch-based plastic masterbatches to improve the processing, mechanical, and degradation properties of biodegradable plastics. By adding 5% (by mass) nano-calcium carbonate and 2% (by mass) nano-magnesium oxide to polylactic acid biodegradable plastic masterbatches, the processing fluidity and mechanical properties of the polylactic acid are improved through optimized processing techniques (such as controlling processing temperature and screw speed). This also increases its degradation rate in natural environments, meeting the application needs of biodegradable plastics in packaging, agriculture, and other fields.

[0034] In the shoe masterbatch field, nano-magnesium oxide, nano-magnesium hydroxide, and nano-calcium carbonate are added to polyurethane and ethylene-vinyl acetate copolymer shoe masterbatches to enhance their wear resistance, antibacterial properties, and comfort. Nano-magnesium oxide, nano-magnesium hydroxide, and nano-calcium carbonate were added to polyurethane shoe masterbatches in a ratio of 2:1:3, and shoe sole samples were prepared through injection molding. Test results showed that the wear resistance of the soles increased by 30%, and the antibacterial properties exceeded 99%. The soles also exhibited enhanced elasticity and comfort, providing a high-performance raw material option for the shoe industry.

[0035] The beneficial effects of the dolomite tailings calcium and magnesium separation process of the present invention are:

[0036] (1) The present invention adopts a combination of multiple innovative separation technologies to achieve efficient separation of calcium and magnesium, improve the purity of calcium and magnesium products, reduce production costs, and reduce resource waste; the industrial preparation technology of nano-magnesium oxide, nano-magnesium hydroxide, and nano-calcium carbonate developed based on this separation process breaks through the bottleneck of existing technologies, improves product quality and production efficiency, and has good industrialization prospects.

[0037] (2) The pilot production line constructed by the present invention provides an important platform for the industrial application of technology, which can effectively verify and optimize the production process and provide technical support and practical experience for large-scale industrial production; the expansion of downstream applications, especially in the fields of engineering plastics, degradable plastic masterbatches, shoe material masterbatches, etc., can meet the demand for high-performance materials in related industries in the Guangdong-Hong Kong-Macao Greater Bay Area, promote industrial upgrading and sustainable development, and have significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0039] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0041] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] Reference Figure 1 , a dolomite tailings calcium and magnesium separation process, the embodiment is as follows:

[0044] Pretreatment: Dolomite tailings are initially crushed using a jaw crusher to a particle size of less than 5mm. The crushed tailings are then fed into a ball mill, which operates at an appropriate speed and grinds them to a particle size of 200 mesh. A magnetic separator is used to remove iron impurities, with the magnetic field strength adjusted based on the iron content and magnetic properties of the tailings. Flotation is then used to remove impurities such as silicon. During the flotation process, the type and dosage of flotation reagents, as well as the agitation speed and aeration volume of the flotation equipment, are adjusted to produce pretreated dolomite tailings.

[0045] Initial separation of calcium and magnesium: The pretreated dolomite tailings are placed in a high-temperature furnace using electrical heating and calcined at 950°C for 2 hours. The calcined product is transferred to a digestion tank equipped with a stirring device. An appropriate amount of medium water is added. The digestion temperature is controlled at 65°C and the digestion time is 45 minutes using the heating and cooling systems. An aqueous solution containing a small amount of tartaric acid is added to the digested slurry. The amount of tartaric acid added is accurately calculated based on the calcium ion content in the slurry. The pH of the solution is adjusted to 10.5. The reaction is stirred at 35°C for 1 hour to dissolve the calcium hydroxide. The calcium and magnesium are initially separated by filtration through a plate and frame filter press, resulting in a calcium filtrate and a magnesium-enriched residue.

[0046] Deep separation and purification: Add an appropriate amount of water and disodium EDTA to the magnesium-enriched residue and allow the reaction to proceed for 2 hours with stirring. The stirring speed is controlled within a certain range to ensure that the magnesium ions are fully complexed with the complexing agent. The solution is then passed through an exchange column filled with a strong acidic cation exchange resin. The column size and resin loading are designed based on the solution flow rate and ion concentration. Ion exchange purification is performed to obtain a high-purity magnesium solution. Carbon dioxide gas is introduced into the calcium filtrate, with the flow rate controlled by a gas flowmeter. The reaction temperature is maintained at 25°C and the reaction time is 1 hour, allowing the calcium ions to precipitate as calcium carbonate. Filtration, multiple washings, and drying at 100°C yield a high-purity nano-calcium carbonate product.

[0047] Example 2

[0048] Preparation of products based on calcium and magnesium separation:

[0049] Preparation of Nano-MgO: Analytical-grade urea was added to a purified magnesium solution to a urea concentration of 0.5 mol / L. The reaction vessel was placed in a thermostatic water bath, maintained at 80°C, and reacted for 4 hours to produce a magnesium hydroxide precursor precipitate. The magnesium hydroxide precursor was then transferred to a stainless steel hydrothermal reactor and reacted at 200°C for 4 hours. After the reaction, the product was filtered through a centrifugal filter and washed multiple times with deionized water. It was then calcined in a muffle furnace at 700°C for 3 hours to produce the nano-MgO product. During the reaction, 0.5% (mass fraction) of polyethylene glycol was added as a surfactant. This addition, prior to the reaction, controlled the morphology of the nano-MgO to a flake-like shape with a particle size of 30-50 nm.

[0050] Preparation of Nano-Magnesium Hydroxide: 2 mol / L ammonia water is slowly added to a refined magnesium solution, along with 0.2% (mass fraction) EDTA and 0.3% (mass fraction) PEG. The reaction is stirred at 50°C for 2.5 hours. After the reaction, the product is processed using a combination of spray drying and freeze drying. The product is initially dried using a spray dryer, then further dried in a freeze dryer to prevent agglomeration. This results in a well-dispersed nano-magnesium hydroxide product with a particle size of 20-30 nm.

[0051] Example 3

[0052] Pilot production line:

[0053] Tailings Treatment and Resource Utilization Pilot Production Line: Based on the aforementioned process, a pilot production line with an annual processing capacity of 1,000 tons of dolomite tailings was constructed. The production line includes pretreatment equipment (crusher, ball mill, magnetic separator, flotation cell), calcium-magnesium separation equipment (calciner, digester, reactor, filter), nano-calcium carbonate production equipment (carbonization tower, dryer), and nano-magnesium oxide and nano-magnesium hydroxide production equipment (reactor, hydrothermal reactor, drying equipment). An automated control system monitors and controls parameters such as temperature, pressure, flow rate, and pH value during the production process in real time. This automated control system utilizes a programmable logic controller (PLC) for data acquisition and processing. Sensors transmit parameters from various devices to the PLC, which then controls actuators according to pre-set programs, automating the production process.

[0054] Dolomite Comprehensive Utilization Pilot Production Line: A comprehensive pilot production line was built, integrating processes such as dolomite tailings treatment, calcium and magnesium separation, and magnesium oxide and calcium carbonate product production. The waste heat generated by high-temperature calcination during production is used to preheat the material entering the ball mill through a heat exchanger. Carbon dioxide from the exhaust gas is recovered through an absorption tower and used for the carbonization reaction in the calcium carbonate production process. After treatment processes such as sedimentation, filtration, and ion exchange, the wastewater is recycled in the digester and other water-using processes, achieving efficient resource utilization and environmentally friendly production.

[0055] High-end calcium carbonate application pilot production line: Targeting the papermaking, rubber, coatings, and other fields, a pilot production line with an annual production capacity of 2,000 tons of high-end calcium carbonate products has been established. Calcium carbonate is surface-modified using fatty acids. By controlling the modifier dosage, reaction temperature, and reaction time, the dispersibility and compatibility of calcium carbonate in different matrices are improved. In the papermaking industry, the modified calcium carbonate is added to paper. By adjusting the addition amount and papermaking process parameters, the paper's whiteness, strength, and printability are improved. In the rubber industry, the modified calcium carbonate is mixed with rubber raw materials and kneaded in internal mixers and open mills to improve the rubber's hardness, wear resistance, and anti-aging properties. In the coatings industry, the modified calcium carbonate is added to coating formulations and dispersed in a high-speed disperser to improve the coating's hiding power, gloss, and stability.

[0056] Example 4

[0057] Downstream application examples:

[0058] In the engineering plastics sector, the prepared nano-magnesium oxide and nano-magnesium hydroxide were added to polycarbonate at a 3% mass fraction and blended using a twin-screw extruder. Parameters such as screw speed and temperature distribution were optimized based on the material's characteristics. Test results showed that the oxygen index of the polycarbonate after addition increased by 20%, tensile strength by 15%, and heat deflection temperature by 10°C, meeting the higher flame retardancy and mechanical properties required of engineering plastics.

[0059] In the field of biodegradable plastic masterbatches, the addition of 5% (by mass) nano-calcium carbonate and 2% (by mass) nano-magnesium oxide to polylactic acid (PLA) biodegradable plastic masterbatches improves the processing fluidity and mechanical properties of the PLA through optimized processing techniques (such as controlling processing temperature and screw speed). This also increases its degradation rate in natural environments, meeting the application needs of biodegradable plastics in packaging, agriculture, and other fields. Performance testing of the modified PLA using a thermogravimetric analyzer and mechanical testing equipment revealed a 10% improvement in processing fluidity, an 8% increase in tensile strength, and a 20% reduction in degradation time in a simulated natural environment.

[0060] In the shoe masterbatch field, nano-magnesium oxide, nano-magnesium hydroxide, and nano-calcium carbonate were added to polyurethane shoe masterbatch in a ratio of 2:1:3, and sole samples were prepared through injection molding. During the injection molding process, parameters such as injection temperature, pressure, and holding time were controlled.

[0061] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A dolomite tailings calcium and magnesium separation process, characterized in that: The following steps are involved: S1, pretreatment stage: the dolomite tailings are crushed to a particle size of less than 5mm by a crusher, and then ground in a ball mill to a particle size of 200 mesh; a magnetic separator is used to remove iron impurities in the tailings, and then silicon impurities are removed by flotation to obtain pretreated dolomite tailings; S2. Preliminary separation of calcium and magnesium: the pretreated dolomite tailings were placed in a high-temperature furnace and calcined at 950°C for 2h; The calcined product was transferred to a digestion tank, and medium water was added. The digestion temperature was controlled at 65°C and the digestion time was 45 min. An aqueous solution containing a small amount of tartaric acid was added to the digested slurry, and the pH value of the solution was adjusted to 10.

5. The solution was stirred and reacted at 35°C for 1 hour to dissolve the calcium hydroxide. The calcium and magnesium were initially separated by filtration to obtain a calcium filtrate and a magnesium-enriched residue. S3. Deep separation and purification: water and disodium EDTA added to the magnesium-enriched filter residue after preliminary separation are reacted under stirring for 2 hours to fully complex the magnesium ions with the complexing agent; The solution is passed through an exchange column filled with a strongly acidic cation exchange resin to perform ion exchange purification to obtain a high-purity magnesium solution; Carbon dioxide gas was introduced into the calcium filtrate, and the reaction temperature was controlled at 25°C and the reaction time was 1 hour to precipitate the calcium ions in the form of calcium carbonate. After filtering, washing and drying at 100°C, high-purity nano calcium carbonate product is obtained.

2. A dolomite tailings calcium and magnesium separation process according to claim 1, characterized in that: Also included is a product preparation technology based on the separation process, which includes a preparation method of nano-magnesium oxide and nano-magnesium hydroxide; the preparation method of nano-magnesium oxide is as follows: Urea was added to the refined magnesium solution to make the urea concentration reach 0.5 mol / L, the reaction temperature was controlled at 80°C, and the reaction time was 4 h to obtain a magnesium hydroxide precursor precipitate; The magnesium hydroxide precursor was transferred to a hydrothermal reactor and reacted at 200°C for 4 hours. After the reaction, the product was filtered, washed, and then calcined at 700°C for 3 hours to obtain the nano-magnesium oxide product. During the reaction, 0.5% polyethylene glycol was added as a surfactant to adjust the morphology of nano-magnesium oxide to be flaky and the particle size was controlled at 30-50nm.

3. A dolomite tailings calcium and magnesium separation process according to claim 2, characterized in that: The nano magnesium hydroxide preparation method is as follows: Slowly add 2 mol / L ammonia water to the refined magnesium solution, and simultaneously add 0.2% EDTA and 0.3% PEG. Control the reaction temperature at 50°C and the reaction time for 2.5 h. After the reaction is completed, the product is treated by spray drying combined with freeze drying to prevent agglomeration, thereby obtaining a nano magnesium hydroxide product with good dispersibility and a particle size of 20-30 nm.

4. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: Based on the separation process, a pilot production line for tailings treatment and resource utilization is built. The production line includes tailings pretreatment equipment, calcium-magnesium separation equipment, nano-calcium carbonate preparation equipment, nano-magnesium oxide and nano-magnesium hydroxide preparation equipment, and is equipped with an automated control system.

5. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: Based on the separation process, a pilot production line for comprehensive utilization of dolomite is built. The production line integrates dolomite tailings treatment, calcium and magnesium separation, and magnesium oxide and calcium carbonate product preparation processes, and has the functions of waste heat, waste gas, and wastewater recovery and reuse.

6. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: Based on the separation process, a high-end calcium carbonate application pilot production line was built. The production line was built to meet the needs of the papermaking, rubber, and coating fields in the Guangdong-Hong Kong-Macao Greater Bay Area, and was equipped with equipment for surface modification of calcium carbonate using fatty acids and titanate coupling agents.

7. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: The separation process and product preparation technology are applied to the field of engineering plastics, specifically adding the prepared nano-magnesium oxide and nano-magnesium hydroxide to polycarbonate and nylon engineering plastics to improve the flame retardancy, mechanical properties and thermal stability of the engineering plastics.

8. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: The separation process and product preparation technology are applied to the field of degradable plastic masterbatches, specifically adding nano-calcium carbonate and nano-magnesium oxide to polylactic acid and starch-based plastic masterbatches to improve the processing performance, mechanical properties and degradation performance of degradable plastics.

9. A dolomite tailings calcium and magnesium separation process according to claim 3, characterized in that: The separation process and product preparation technology are applied to the field of shoe masterbatches, specifically adding nano-magnesium oxide, nano-magnesium hydroxide and nano-calcium carbonate to polyurethane and ethylene-vinyl acetate copolymer shoe masterbatches to improve the wear resistance, antibacterial properties and comfort of the shoe materials.

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