High-value utilization method for all components of copper slag

Abstract

The invention provides a copper slag all-component high-value utilization method, which belongs to the technical field of metallurgical waste slag resource utilization, and comprises the following steps: heating copper slag in H2 / N2 atmosphere by adopting double-frequency alternating microwaves, and reducing an iron-containing compound into metal iron; after the reduced material is crushed, a metal iron concentrate is separated out through magnetic separation; the magnetic separation residues are mixed with a CaCl2-MgCl2-NaCl composite chlorinating agent, chlorination is conducted under the multi-temperature-zone gradient heating condition, and step-by-step chlorination volatilization of valuable metal such as copper, zinc and lead is achieved; the preparation method comprises the following steps: adding a TiO2-Cr2O3-ZrO2 composite nucleating agent and a CaO-MgO composite additive into chlorination residues, and carrying out melting, molding and non-equilibrium crystallization treatment, so as to prepare the diopside microcrystalline glass. According to the method, preferential extraction of iron in the copper slag and segmented efficient recovery of metals such as copper, zinc and lead are achieved, and the silicate tailings are thoroughly converted into a glass ceramic building material with a high additional value.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical waste slag resource utilization technology, specifically involving a method for high-value utilization of all components of copper slag. The method utilizes microwave activation-gradient chlorination synergistic drive to efficiently recover valuable metals (such as iron, copper, zinc, lead, etc.) from copper slag and prepare high-value-added microcrystalline glass building materials, achieving zero-pollution and high-value comprehensive utilization of copper slag. Background Technology

[0002] Copper slag is a major solid waste generated during copper smelting. Its main components include fir olivine (2FeO·SiO2), magnetite (Fe3O4), small amounts of metal sulfides, and valuable metals such as copper, zinc, and lead, as well as their compounds. With the rapid development of my country's copper industry, the annual production of copper slag is enormous. Its long-term storage not only occupies a large amount of land but may also release harmful heavy metal ions through weathering and rainwater leaching, causing serious pollution to soil, water sources, and the atmosphere, and bringing enormous environmental pressure.

[0003] Currently, the comprehensive utilization of copper slag mainly focuses on iron extraction and the recovery of small amounts of valuable metals. Traditional treatment methods include pyrometallurgical magnetic separation and hydrometallurgical leaching. For example, pyrometallurgical magnetic separation usually requires reduction roasting at high temperatures, resulting in high energy consumption and difficulty in effectively recovering low-magnetic or non-magnetic valuable metals such as copper, zinc, and lead. A large amount of valuable components remain in the tailings, making subsequent processing difficult. While hydrometallurgical leaching can selectively leach certain metals, it often requires the use of strong acids or alkalis, leading to equipment corrosion, secondary pollution (such as wastewater treatment), and high requirements for copper slag pretreatment, resulting in a long process and relatively high costs. Furthermore, the traditional approach to the tailings after copper slag treatment is to use them as low-value building materials or discard them directly, failing to realize their maximum value. How to achieve efficient, clean, and high-value utilization of all components (metals and non-metals) in copper slag is a significant challenge currently facing the field of copper slag resource utilization.

[0004] Therefore, there is an urgent need to develop a low-temperature, high-efficiency copper slag full-component utilization technology that integrates metal recycling and building materials, in order to solve the problems of high energy consumption, secondary pollution, and low added value of existing processes. Summary of the Invention

[0005] To address the problems of high energy consumption, low recovery rate of valuable metals, and difficulty in tailings treatment in existing copper slag treatment methods, this invention provides a method for the high-value utilization of all components of copper slag. This method ingeniously combines microwave high-efficiency heating, selective reduction, gradient chlorination volatilization, and microcrystalline glass preparation technology, aiming to achieve efficient recovery of valuable metals such as iron, copper, zinc, and lead from copper slag, and to transform the final tailings into high-value-added building materials, achieving the goal of maximizing resource utilization and zero environmental pollution. The specific technical solution is as follows:

[0006] A method for high-value utilization of all components of copper slag includes the following steps:

[0007] a) Microwave activation and reduction: Copper slag is heated in an H2 / N2 atmosphere using dual-frequency alternating microwaves to preferentially reduce iron-containing compounds in the copper slag to metallic iron;

[0008] b) Iron-rich aggregate separation: After crushing the reduced material obtained in step a), the metallic iron-rich aggregate is separated using magnetic separation technology;

[0009] c) Gradient chlorination volatilization: The residue after magnetic separation in step b) is mixed with CaCl2-MgCl2-NaCl composite chlorinating agent and chlorinated under gradient temperature conditions in multiple temperature zones to achieve stepwise and selective chlorination volatilization of valuable metals such as copper, zinc, and lead.

[0010] d) Preparation of glass-ceramics: The solid residue after chlorination in step c) is mixed with TiO2-Cr2O3-ZrO2 composite nucleating agent and CaO-MgO composite additive, and then melted, shaped and subjected to non-equilibrium crystallization treatment to prepare diopside glass-ceramics.

[0011] Optionally, in step a), the dual-frequency alternating microwave uses high-frequency microwaves and low-frequency microwaves, i.e., dynamically switching between 2.45 GHz and 915 MHz frequencies. The continuous emission time of each frequency is 10 to 300 seconds, meaning that after using one frequency for 10 to 300 seconds, the frequency is switched to another. The 2.45 GHz microwave has a high frequency and a short wavelength. It has a stronger bulk heating effect on materials, a faster heating speed, and can quickly raise the temperature of the entire material; it can be understood as the "main heating source." The 915 MHz microwave has a low frequency and a longer wavelength. It has stronger penetrating power and can heat larger and thicker materials. More importantly, the selective heating effect of low-frequency microwaves on certain polar molecules may differ from that of high-frequency microwaves, helping to distribute energy more evenly in the material and avoiding "hot spots."

[0012] Existing technologies typically employ single-frequency microwave heating, which has the following drawbacks: 1) Uneven heating: Single-frequency microwaves easily form standing waves within the material, leading to overheating (hot spots) at some points and underheating at others. This results in uneven reduction of iron; some iron is over-reduced to form excessive metallic iron that aggregates and grows, while some iron remains unreduced. 2) Poor selectivity: The fixed single-frequency heating mode may not optimally achieve selective heating between iron oxides and other components (such as silicate networks). Our goal is to allow iron oxides to preferentially and rapidly absorb energy for reduction, while other substances remain as stable as possible. 3) Risk of "thermal runaway": As temperature increases, the dielectric loss factor of the material changes. Single microwaves may cause a sharp rise in local temperature, making it difficult to control the reaction process and even causing the material to melt, disrupting subsequent magnetic separation.

[0013] Therefore, this invention, through the use of dual-frequency alternating microwaves, possesses the synergistic advantage of "rapid heating at 2.45GHz + homogenization and heat preservation at 915MHz". By alternating use, the material can be rapidly brought to the reaction temperature at 2.45GHz first, and then the 915MHz mode can be switched on, utilizing its strong penetrating power to uniformly diffuse heat from the inside out, allowing the reduction reaction to proceed in a more uniform and controllable temperature field. This lays the foundation for achieving "precise reduction".

[0014] Optionally, in step a), the power ratio of the 2.45GHz and 915MHz microwaves is (3-5):1, meaning the high-frequency microwaves serve as the main heating source, while the low-frequency microwaves serve as an auxiliary homogenization source to enhance the penetration and heating uniformity of the copper slag. Taking a total power of 8kW as an example, with a power ratio of 4:1, the 2.45GHz microwave power is 6.4kW, and the 915MHz microwave power is 1.6kW.

[0015] Optionally, in step a), the volume fraction of H2 in the H2 / N2 atmosphere is 20%–50% to effectively promote the selective reduction of iron oxides. The copper slag is heated to a reduction temperature of 600–900°C. Under these conditions, microwave energy is preferentially and efficiently absorbed by the iron-containing minerals in the copper slag and converted into heat energy. Simultaneously, H2 acts as a reducing agent, synergistically promoting the conversion of iron oxides into metallic iron. This process achieves the selective reduction of iron, laying the foundation for subsequent magnetic separation.

[0016] The reduction temperature range mentioned above is derived from the microwave absorption capacity of the material to be treated. Specifically, different materials have different abilities to absorb microwave energy (i.e., dielectric loss) in a microwave field. In glass-ceramics, iron oxides (Fe2O3, Fe3O4) are extremely strong microwave absorbers, while the main silicate glass phase has a weaker absorption capacity. Therefore, microwave energy is preferentially absorbed by the iron oxide particles, causing their local temperature to rise rapidly, reaching or even exceeding their reduction temperature, while the temperature of the surrounding glass matrix remains relatively low. This achieves "targeted heating."

[0017] This reduction temperature range also allows for kinetic control of the reduction of iron oxides. Since the reduction reaction (Fe₂O₃ → Fe₃O₄ → FeO → Fe) proceeds in steps, precise control of the dual-frequency alternating mode and the final heating temperature can control the reaction to stop at the step of forming metallic iron (Fe). If the heating temperature is too low, the reduction reaction is incomplete, producing a large amount of FeO, which cannot be magnetically separated. If the heating temperature is too high or the time is too long, the generated metallic iron particles grow excessively, aggregate, or react with silicates to form a difficult-to-handle low-melting-point eutectic phase. Simultaneously, this leads to over-melting of the glass matrix, encapsulating the iron particles, which is detrimental to magnetic separation.

[0018] Microwave activation has been studied in metallurgy, but its application is mostly limited to ore pretreatment or single-frequency heating. This invention, however, utilizes the selective absorption characteristics of iron oxides within a uniform and controllable thermal field created by dual-frequency microwaves. This allows for rapid and accurate local reduction of iron oxides into strongly magnetic metallic iron at relatively low overall material temperatures (e.g., below the softening point of the glass phase). The resulting particles are fine and dispersed, facilitating subsequent magnetic separation. Ultimately, this technology contributes to the high-value utilization of tailings slag.

[0019] Optionally, in step b), the particle size of the crushed material is controlled at 20-40μm, the magnetic separation field strength is 1-1.5T, and the iron recovery rate is ≥90%.

[0020] Further, after the reduction reaction is complete, the resulting material is cooled and then mechanically crushed to break the lumpy material into fine powder of 20-40 μm. This step aims to significantly increase the exposed area of ​​the metallic iron phase, improving the efficiency of subsequent magnetic separation. The crushed material is then fed into a magnetic separator for magnetic separation at a magnetic field strength of 1-1.5T. Because the reduced metallic iron is strongly magnetic, while other silicate, sulfide, and other matrices are weakly magnetic or non-magnetic, magnetic separation can efficiently separate iron-rich aggregates with an iron content ≥65%. This portion of iron-rich aggregates can be used directly as raw material for ironmaking or further refined.

[0021] Optionally, in step c), the amount of the CaCl2-MgCl2-NaCl composite chlorinating agent added is 15-30% of the mass of the non-magnetic residue, and the mass ratio of CaCl2, MgCl2, and NaCl is (40-70):(20-40):(5-15). This invention uses a composite chlorinating agent to achieve functional synergy: targeted chlorination of different heavy metals, as different heavy metal oxides have varying degrees of ease of chlorination and product volatility. It also creates a "step-like" chlorination reaction kinetic, continuously providing a chlorination atmosphere at high temperatures. This complementary and relay-like effect across temperature ranges greatly broadens the effective chlorination volatilization temperature window, ensuring that various heavy metals can be efficiently removed within their respective optimal temperature ranges. Furthermore, calcium and magnesium are also diopside glass elements (Ca(Mg,Al)(Si,Al)2O6).

[0022] Optionally, in step c), the multi-temperature gradient heating is performed by gradually increasing the temperature from 450℃ to 1050℃ to achieve selective volatilization of different metal chlorides in different temperature ranges. Further, the gradient heating program includes holding at 450-550℃ for 30-60 min, holding at 650-750℃ for 20-40 min, and holding at 900-1050℃ for 20-30 min to achieve selective volatilization of different metal chlorides in different temperature ranges. By controlling the gradient heating process, the recovery rates of valuable metals such as copper, zinc, and lead are all greater than 85%.

[0023] Specifically, the gradient heating procedure includes the following steps:

[0024] Step 1, Low Temperature Stage: The temperature is raised from room temperature to approximately 450-550℃ and held for 30-60 minutes. Within this temperature range, chlorides of volatile metals such as zinc begin to form and volatilize. This stage primarily involves a solid-gas reaction; the chlorinating agent reacts with ZnO in the material to produce gaseous ZnCl2. The main reaction equations are as follows:

[0025] ZnO(s) + (Mg,Ca)Cl2 (s)→ ZnCl2(g) + (Mg,Ca)O(s)

[0026] Choosing this temperature range offers the following advantages: 1) It utilizes the high volatility of ZnCl2. Specifically, metallic zinc chloride has a melting point of 290℃ and a boiling point of 732℃. However, in the temperature range of 450-550℃, it has a very high saturated vapor pressure, meaning it can directly sublimate into a gaseous state with extremely high efficiency, thus detaching from the material. 2) Kinetic advantages: At this relatively low temperature, the matrix of the material to be treated (microcrystalline glass tailings slag) has not yet been sintered and densified, and the porosity remains good. This provides a smooth channel for the inward diffusion of chlorine gas and the outward escape of the product gas (ZnCl2). 3) It avoids encapsulation: If treatment is carried out at high temperatures from the beginning, the surface of the material may first sinter to form a dense layer, encapsulating the internal Zn. Even if ZnCl2 is generated, it cannot volatilize, leading to removal failure.

[0027] Step 2, Intermediate Temperature Stage: Raise the temperature to 650-750℃ and hold for 20-40 minutes to promote the volatilization of copper and lead chlorination. The main reaction equations are as follows:

[0028] PbO(s) +(Mg,Ca)Cl2(s) → PbCl2(g) + (Ca,Mg)O(s)

[0029] CuO(s) +(Mg,Ca)Cl2(s) → CuCl2(g) + (Ca,Mg)O(s)

[0030] Choosing this temperature range offers the following advantages: 1) Satisfying reaction kinetics: PbCl2 has a boiling point of 950℃, lower than CuCl2, and therefore volatilizes before copper. CuCl2 has a boiling point of 993℃, but already has a high vapor pressure at this temperature. Compared to PbO, CuO requires stronger chlorination conditions and higher temperatures to form stable gaseous CuCl2 or Cu3Cl2. The temperature of 650-750℃ provides sufficient energy for the reaction, ensuring it proceeds at a considerable rate. 2) Ensuring product volatilization: The vapor pressures of PbCl2 and CuCl2 in this temperature range are sufficiently high for effective volatilization. CuCl2, in particular, shows a significantly increased volatilization rate above 700℃. The heating temperature at this step is higher than the volatilization temperature of Zn, but not yet high enough to completely melt and sinter the material, while simultaneously preparing for the next step of higher-temperature processing.

[0031] Step 3, High-Temperature Section: Heat to 900-1050℃ and hold for 20-30 minutes to ensure complete chlorination recovery of less volatile metals such as manganese (this step can be ignored if the content of manganese and other metals in the copper slag is extremely low). The main reaction equations are as follows:

[0032] MnO(s) +(Mg,Ca)Cl2(s) → MnCl2(g) + (Ca,Mg)O(s)

[0033] Choosing this temperature range offers the following advantages: 1) Overcoming thermodynamic limitations: MnCl2 has a boiling point as high as 1190℃, making it the most difficult metal to volatilize among the listed metals. Only at temperatures above 900℃ can its vapor pressure be high enough to achieve effective volatilization. 2) Enhancing mass transfer: At this high temperature, the material has usually undergone partial softening or sintering, but with a sufficiently long holding time, the escape of MnCl2 gas can still be ensured. This step ensures that all volatile heavy metal impurities are deeply and thoroughly removed, which is a key guarantee for obtaining high-purity tailings slag. If the content of Mn and other metals in the material is extremely low, this step can be omitted, reflecting the flexibility of the process.

[0034] Optionally, in step d), the amount of the TiO2-Cr2O3-ZrO2 composite nucleating agent added is 2-4% of the mass of the residue after chlorination treatment, and the mass percentage of each component is TiO2:(30-50)wt%, Cr2O3:(10-20)wt%, ZrO2:(30-50)wt%, whose synergistic effect can effectively induce the subsequent crystallization process. The amount of the CaO-MgO composite additive added is 30-50% of the mass of the residue after chlorination treatment, and the mass percentage of each component is CaO:(50-70)wt%, MgO:(30-50)wt%.

[0035] In the field of glass-ceramics, it is common to use TiO2 or ZrO2 alone as nucleating agents, especially TiO2. However, the advantages of introducing all three, particularly Cr2O3, and combining it with the other two are: 1) The unconventionality of Cr2O3: Cr2O3 is rarely used as a primary nucleating agent because its dark color (greenish) severely affects the appearance of the glass, and its nucleation behavior and mechanism differ significantly from common Ti and Zr ions. Those skilled in the art are generally motivated to avoid using Cr2O3 to prevent coloration. 2) The uniqueness of the three-component synergistic mechanism: The TiO2-Cr2O3-ZrO2 composite nucleating agent constitutes a novel "three-component synergistic system." Interactions such as the formation of composite oxides, energy barrier complementarity, and stepwise crystallization occur among these three components, overcoming the shortcomings of a single nucleating agent. 3) Complementary Energy Barriers: ZrO2 nucleation requires high energy (high energy barrier), but the nuclei are stable; Cr2O3 can effectively lower the nucleation energy barrier; TiO2 creates an "easy-to-nucleate" overall environment through phase separation in the intermediate temperature range. The combination of the three achieves a "seamless" energy barrier coverage from high to medium temperatures. 4) Multiphase Induction: In complex tailings slag microcrystalline glass systems, multiple crystalline phases may coexist. The above-mentioned composite nucleating agent system can induce the precipitation of different crystalline phases simultaneously or stepwise. For example, ZrO2 may induce a high-silicon phase, Cr2O3 may induce an iron-rich phase (such as spinel), while ZrO2 dominates the precipitation of the main crystalline phase (such as pyroxene), ultimately forming an interlocking multiphase microcrystalline structure, which usually leads to superior mechanical properties. 5) Temperature range transition: During the cooling / heat treatment process, ZrO2 first precipitates at high temperature → TiO2 then initiates liquid phase separation and nucleation in the intermediate temperature range → Cr2O3 continuously provides low-energy-barrier nucleation sites throughout the process. This "relay" ensures efficient and continuous nucleation dynamics throughout the entire crystallization temperature range.

[0036] Optionally, in step d), the non-equilibrium crystallization process includes rapidly heating to the crystallization temperature range and holding at that temperature, followed by rapid cooling to obtain diopside microcrystalline glass with excellent properties. Further, the non-equilibrium crystallization process includes: heating to 1250-1350℃ at a rate of 15-25℃ / min for melting, rapidly quenching to 650-750℃ and holding for 1-2 hours for nucleation, and then heating to 950-1050℃ at 10-15℃ / min for crystallization for 30-60 minutes to promote the growth of diopside (Ca(Mg,Al)(Si,Al)2O6) crystals.

[0037] Optionally, the final diopside microcrystalline glass has the main crystalline phase Ca(Mg,Al)(Si,Al)2O6, the crystal size is 0.5-2μm, and the flexural strength is ≥120MPa.

[0038] This method achieves preferential extraction of iron from copper slag, efficient segmented recovery of copper, zinc, lead and other metals, and 100% conversion of silicate tailings into high-value-added microcrystalline glass building materials. The overall metal recovery rate is higher than that of traditional processes, while energy consumption is reduced.

[0039] Compared with the prior art, the present invention has the following significant advantages:

[0040] 1. High metal recovery rate: Through microwave selective reduction and gradient chlorination volatilization, the stepwise and efficient recovery of valuable metals such as iron, copper, zinc and lead from copper slag is achieved. In particular, the recovery rate of low magnetic metals such as copper, zinc and lead is greater than 85%, which is much higher than that of traditional single treatment methods.

[0041] 2. Significantly reduced energy consumption: Microwave heating is highly efficient and rapid, resulting in a substantial reduction in energy consumption compared to traditional high-temperature roasting. The gradient chlorination process also reduces unnecessary energy consumption through optimized temperature programming.

[0042] 3. 100% Resource Utilization of Tailings: All silicate tailings that are difficult to process in traditional processes are transformed into high-performance microcrystalline glass, achieving zero-waste treatment of copper slag and completely solving the environmental pollution problem of copper slag.

[0043] 4. Reasonable process flow: It organically combines metal recycling and tailings utilization, with clear steps, controllable operation, and easy industrial implementation.

[0044] 5. Environmentally friendly: The entire process is carried out in a controlled atmosphere, reducing the generation of harmful gases; the tailings are utilized at a high value, avoiding the environmental risks associated with stockpiling.

[0045] 6. Significant economic benefits: By efficiently recovering valuable metals and preparing high-value-added microcrystalline glass, not only are the costs of copper slag treatment reduced, but new economic value is also created, resulting in significant economic and environmental benefits. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 The X-ray diffraction pattern of the copper slag sample before reaction in Example 1;

[0048] Figure 2 The image shows the X-ray diffraction pattern of the glass-ceramic sample obtained in Example 1. Detailed Implementation

[0049] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0050] This invention provides a method for high-value utilization of all components of copper slag, comprising the following steps:

[0051] Step 1: Microwave activation and reduction and iron enrichment

[0052] Optionally, in step a), the copper slag to be treated is first pretreated by crushing it to an appropriate particle size, such as 60-100 μm, and then the pretreated copper slag is fed into a microwave reactor. The dual-frequency alternating microwave uses high-frequency microwave and low-frequency microwave, i.e., 2.45 GHz and 915 MHz frequencies, to dynamically switch for heating, with a preferred power ratio controlled at (3-5):1. The duration of each frequency microwave is 60 seconds, i.e., irradiation is performed at 2.45 GHz for 60 seconds, followed by automatic switching to 915 MHz for 60 seconds, and this cycle is repeated to balance penetration depth and heating efficiency. Under a mixed atmosphere of H2 / N2 (preferably with a volume fraction of H2 of 20% to 50%), the copper slag is heated to a reduction temperature range of 600-900℃. Under these conditions, microwave energy is preferentially and efficiently absorbed by the iron-containing minerals in the copper slag and converted into heat energy, while H2 acts as a reducing agent, synergistically promoting the conversion of iron oxides into metallic iron. This process achieves selective reduction of iron, laying the foundation for subsequent magnetic separation.

[0053] Step 2: Crushing and magnetic separation of iron-rich aggregates

[0054] After the reduction reaction is complete, the resulting material is cooled and then mechanically crushed to break the lumpy material into fine powder of 20-40 μm. This step aims to significantly increase the exposed area of ​​the metallic iron phase, thereby improving the efficiency of subsequent magnetic separation. The crushed material is then fed into a magnetic separator and subjected to magnetic separation at a magnetic field strength of 1-1.5T. Because the reduced metallic iron is strongly magnetic, while other silicate and sulfide matrices are weakly magnetic or non-magnetic, magnetic separation can efficiently separate iron-rich aggregates with an iron content ≥65%. These iron-rich aggregates can be used directly as raw materials for ironmaking or further refined.

[0055] Step 3: Gradient chlorination volatilization to recover valuable metals

[0056] The non-magnetic residue remaining after magnetic separation (mainly containing silicate matrix and small amounts of incompletely reduced or unseparated copper, zinc, lead, and other compounds) is mixed evenly with a pre-prepared CaCl2-MgCl2-NaCl composite chlorinating agent. The preferred mass ratio of CaCl2, MgCl2, and NaCl in this composite chlorinating agent is (40-70):(20-40):(5-15), which synergistically improves chlorination efficiency and selectivity. The amount of CaCl2-MgCl2-NaCl composite chlorinating agent added is 15-30% of the mass of the non-magnetic residue.

[0057] The mixture is placed in a multi-temperature zone reactor and chlorinated according to a designed gradient heating program. The multi-temperature zone gradient heating gradually increases from approximately 450°C to approximately 1050°C to achieve selective volatilization of different metal chlorides within different temperature ranges. Specifically: first, the temperature is raised from room temperature to approximately 450-550°C and held for 30-60 minutes. Within this temperature range, chlorides of volatile metals such as zinc begin to form and volatilize. Then, the temperature is raised to 650-750°C and held for 20-40 minutes to promote the volatilization of copper and lead chlorides. Finally, the temperature is raised to 900-1050°C and held for 20-30 minutes to ensure sufficient chlorination recovery of less volatile metals such as manganese (this step can be ignored if the content of manganese and other metals in the copper slag is extremely low). By precisely controlling the gradient heating process, the chlorination recovery rate of valuable metals such as copper, zinc, and lead is greater than 85%. The volatilized metal chloride gases can be recovered into corresponding metal or compound products through subsequent condensation, washing, and other processes.

[0058] Finally, a small amount of CaCl2-MgCl2-NaCl composite chlorinating agent that did not participate in the chlorination reaction is leached out using circulating water, and then an evaporation and crystallization operation is carried out. By detecting the composition of the crystallized chlorinating agent, some CaCl2, MgCl2 and NaCl substances are added to prepare a CaCl2-MgCl2-NaCl composite chlorinating agent with a pre-set composition for recycling. The water vapor obtained from the evaporation is condensed and then enters the circulating water for continued use.

[0059] Step 4: Preparation of microcrystalline glass

[0060] The solid residue after chlorination is mainly a silicate material rich in silicon, aluminum, calcium, and other elements, and contains virtually no or only trace amounts of valuable metals. After drying and pulverizing this residue, a composite nucleating agent composed of TiO2, Cr2O3, and ZrO2 is uniformly mixed in at a ratio of 2-4% by weight of the residue, and a CaO-MgO composite additive is uniformly mixed in at a ratio of 30%-50% by weight of the residue. The preferred mass percentages of each component in the composite nucleating agent are TiO2:(30-50)wt%, Cr2O3:(10-20)wt%, and ZrO2:(30-50)wt%, whose synergistic effect can effectively induce the subsequent crystallization process. The mixture is placed in a high-temperature furnace and rapidly heated to 1250-1350℃ at a rate of 15-25℃ / min to obtain a homogeneous glass melt.

[0061] Then, the melt is rapidly quenched to 650-750℃ and held for 1-2 hours to initiate the nucleation stage of the non-equilibrium crystallization process. Finally, the temperature is increased to the crystallization temperature range of 950-1050℃ at a rate of 10-15℃ / min and held for 30-60 minutes to promote the growth of diopside (Ca(Mg,Al)(Si,Al)2O6) crystals. This non-equilibrium crystallization process yields diopside microcrystalline glass with excellent properties. Its main crystalline phase is Ca(Mg,Al)(Si,Al)2O6, with fine crystal sizes of 0.5-2μm and a flexural strength ≥120MPa, making it suitable as a high-performance building or decorative material.

[0062] Example 1

[0063] Take 500g of copper slag produced by a copper smelter (XRF analysis showed that the main components were: total iron (TFe as FeO) 57.9wt%, SiO2 31.2wt%, Al2O 34.5wt%, CaO 1.6wt%, Cu 0.9wt%, Zn 0.8wt%, Pb 0.6wt%, etc.). Figure 1 The X-ray diffraction pattern of the copper slag before the reaction indicates that the main phase is Fe2SiO4, with the presence of Fe3O4 and Fe3(Al)2O4. 0.2 Fe 1.8 (SiO4)3、(Ca 0.63 Fe 2.37 The copper slag contains phases such as Fe2(SiO4)3. The copper slag is then treated as follows:

[0064] a) Microwave Activation and Reduction: 100g of copper slag, crushed to 75μm, was spread evenly in a quartz crucible and placed in a microwave reaction chamber. This was done in 5 batches. A 40% (v / v) H2 / N2 mixture was introduced at a flow rate of 1.5L / min. Heating was performed using alternating dual-frequency microwaves (2.45GHz and 915MHz, power ratio 4:1, duration of each frequency for 60 seconds). The heating rate was controlled, increasing to 600℃ at 15℃ / min, then slowly increasing to 850℃ at 5℃ / min, and holding for 0.5 hours. The microwave was then turned off, and the mixture was continued until the temperature dropped below 200℃. The reduced material was then removed. This completed the selective reduction of iron oxides. After the reaction, the reduced material was obtained.

[0065] b) Iron-rich aggregate separation: The reduced material was removed, ball-milled to a particle size of 20μm, and then subjected to magnetic separation with a magnetic field strength of 1.2T. Iron-rich aggregate and magnetic separation tailings were obtained. The iron content in the iron-rich aggregate reached 72.0%, with a weight of 285.1g.

[0066] c) Gradient chlorination volatilization: Magnetic separation tailings (151.8g) were mixed evenly with a CaCl2-MgCl2-NaCl composite chlorinating agent (weighed at a mass ratio of 60:30:10, totaling 30g). The mixture was placed in a tubular chlorination furnace, and gradient chlorination was performed according to the following procedure: heating to 500℃ at a rate of 10℃ / min and holding for 45min; then heating to 700℃ at a rate of 8℃ / min and holding for 30min. A small amount of N2 was introduced to aid volatilization, and the outlet was connected to a stainless steel condenser collection system. Different condensers were used at different temperature stages during the heating process to collect different metal chlorides. After the reaction was completed, the volatilized metal chlorides at each temperature stage were collected (which can be subsequently processed to recover metals). A total of 8.77g of copper chloride, 7.16g of zinc chloride, and 3.58g of lead chloride were collected. The resulting solid residue, after chlorination treatment and leaching with the composite chlorinating agent, was then dried.

[0067] d) Preparation of microcrystalline glass: 144.2 g of the dried solid residue after chlorination treatment was mixed evenly with 4 g of TiO2-Cr2O3-ZrO2 composite nucleating agent (weighed at a mass ratio of 40:10:50) and 60 g of CaO-MgO composite additive (weighed at a mass ratio of 60:40). The mixture was placed in a high-temperature furnace and heated to 1300℃ at a rate of 20℃ / min for melting, and held at that temperature for 30 min. The melt was then poured into a preheated copper mold, rapidly quenched to 700℃, and placed in a crystallization furnace for 1.5 h for nucleation. The temperature was then increased to 1000℃ at a rate of 12℃ / min and held for 45 min. Finally, the temperature was cooled to room temperature.

[0068] Figure 2The X-ray diffraction pattern of the obtained glass-ceramic sample was obtained. It was confirmed that the main crystalline phase was diopside (PDF#41-1370, PDF#88-0847, PDF#89-0836), with a crystal size of about 1.2 μm. The flexural strength was measured to be 125 MPa by a universal testing machine.

[0069] In Example 1, after subsequent treatment, the recovered metal chlorides achieved copper, zinc, and lead recovery rates of 92%, 86%, and 87%, respectively, all exceeding 85%. Compared with traditional oxidation and reduction roasting followed by magnetic separation and acid leaching, the recovery rates of iron, copper, zinc, and lead in copper slag were all improved to a certain extent.

[0070] Example 2

[0071] A small amount of manganese-containing copper concentrate was added to the copper concentrate mixture from the same source as the copper slag in Example 1, resulting in manganese content in the copper slag. All copper smelting processes were identical to those in Example 1, yielding manganese-containing copper slag. 500g of the above manganese-containing copper slag was analyzed by XRF, and the main components were found to be: total iron (TFe as FeO) 57.2wt%, SiO2 31.4wt%, Al2O3 4.7wt%, CaO 1.9wt%, Cu 0.8wt%, Zn 0.7wt%, Pb 0.7wt%, Mn 0.5wt%, etc. The copper slag was then treated as follows:

[0072] a) Microwave Activation and Reduction: 100g of copper slag, crushed to 75μm, was spread evenly in a quartz crucible and placed in a microwave reaction chamber. This was done in 5 batches. A 40% (v / v) H2 / N2 mixture was introduced at a flow rate of 1.5L / min. Heating was performed using alternating dual-frequency microwaves (2.45GHz and 915MHz, power ratio 4:1). The heating rate was controlled, increasing to 600℃ at 15℃ / min, then slowly increasing to 850℃ at 5℃ / min, and holding at that temperature for 0.5 hours. The microwave was then turned off, and the mixture was continued to flow until the temperature dropped below 200℃. The reduced material was then removed. This completed the selective reduction of iron oxides. After the reaction, the reduced material was obtained.

[0073] b) Iron-rich aggregate separation: The reduced material was removed, ball-milled to a particle size of 20μm, and then subjected to magnetic separation with a magnetic field strength of 1.2T. Iron-rich aggregate and magnetic separation tailings were obtained. The iron content in the iron-rich aggregate reached 72.2%, with a weight of 284.6g.

[0074] c) Gradient chlorination volatilization: Magnetic separation tailings (152.1 g) are mixed thoroughly with a CaCl2-MgCl2-NaCl composite chlorinating agent (weighed at a mass ratio of 60:30:10, totaling 30 g). The mixture is placed in a tubular chlorination furnace, and gradient chlorination is performed according to the following procedure: The temperature is increased to 500℃ at a rate of 10℃ / min and held for 45 min; then increased to 700℃ at a rate of 8℃ / min and held for 30 min; finally, the temperature is increased to 1020℃ at a rate of 5℃ / min and held for 30 min. A small amount of N2 is introduced to aid volatilization, and the outlet is connected to a stainless steel condenser collection system. Different condensers are used at different temperature stages during the heating process to collect different metal chlorides separately. After the reaction was completed, the volatilized metal chlorides at each temperature range were collected (the metals could be recovered later). A total of 7.68g of copper chloride (recovery rate 91%), 6.35g of zinc chloride (recovery rate 87%), 4.09g of lead chloride (recovery rate 87%), and 4.88g of manganese chloride (recovery rate 85%) were collected. Then, the solid residue after chlorination treatment and leaching with composite chlorinating agent and drying was obtained.

[0075] d) Preparation of glass-ceramics: 142.5 g of the dried solid residue after chlorination was mixed evenly with 4 g of TiO2-Cr2O3-ZrO2 composite nucleating agent (weighed at a mass ratio of 40:10:50) and 60 g of CaO-MgO composite additive (weighed at a mass ratio of 60:40). The mixture was placed in a high-temperature furnace and heated to 1300℃ at a rate of 20℃ / min for melting, and held for 30 min. The melt was then poured into a preheated copper mold, rapidly quenched to 700℃, and placed in a crystallization furnace for 1.5 h for nucleation. The temperature was then increased to 1000℃ at a rate of 12℃ / min and held for 45 min. Finally, the temperature was cooled to room temperature. The X-ray diffraction pattern of the obtained glass-ceramic sample showed peak shapes that were basically consistent with those of Example 1. It was confirmed that the main phase was still diopside (PDF#41-1370, PDF#88-0847, PDF#89-0836).

[0076] Comparative Example 1

[0077] Step a) uses single-frequency 2.45GHz microwave heating, and the other steps are the same as in Example 1.

[0078] Step b) yielded iron-rich aggregate and magnetic separation tailings. The iron-rich aggregate contained 61.1% iron and weighed 302.6 g. Compared to Example 1, the iron recovery rate decreased to 82% using single-frequency microwave heating.

[0079] Comparative Example 2

[0080] Step d) Add a binary nucleating agent containing TiO2 and ZrO2, and the other steps are the same as in Example 1.

[0081] The X-ray diffraction pattern of the obtained glass-ceramic sample was basically consistent with that of Example 1. It was confirmed that the main phase was still diopside (PDF#41-1370, PDF#88-0847, PDF#89-0836), but the average crystal size was approximately 3.4 μm, and the flexural strength measured by the universal testing machine was only 94 MPa. This indicates that replacing the ternary nucleating agent with a binary nucleating agent did not change the phase composition of the glass-ceramic, but the grain size increased, leading to a decrease in performance.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for high-value utilization of all components of copper slag, characterized in that, Includes the following steps: a) Microwave activation and reduction: Copper slag is heated in an H2 / N2 atmosphere using dual-frequency alternating microwaves to preferentially reduce iron-containing compounds in the copper slag to metallic iron; b) Iron-rich aggregate separation: After crushing the reduced material obtained in step a), the metallic iron-rich aggregate is separated using magnetic separation technology; c) Gradient chlorination volatilization: The residue after magnetic separation in step b) is mixed with CaCl2-MgCl2-NaCl composite chlorinating agent and chlorinated under gradient temperature conditions in multiple temperature zones to achieve stepwise and selective chlorination volatilization of valuable metals such as copper, zinc, and lead. d) Preparation of glass-ceramics: The solid residue after chlorination in step c) is mixed with TiO2-Cr2O3-ZrO2 composite nucleating agent and CaO-MgO composite additive, and then melted, shaped and subjected to non-equilibrium crystallization treatment to prepare diopside glass-ceramics.

2. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step a), the dual-frequency alternating microwave uses dynamic switching between 2.45 GHz and 915 MHz frequencies.

3. The method for high-value utilization of all components of copper slag according to claim 2, characterized in that, In step a), the power ratio of the 2.45GHz to the 915MHz microwave is (3-5):

1.

4. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step a), the volume fraction of H2 in the H2 / N2 atmosphere is 20% to 50%, and the copper slag is heated to a reduction temperature of 600-900℃.

5. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step b), the particle size of the crushed material is 20-40μm, and the magnetic separation field strength is 1-1.5T.

6. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step c), the amount of CaCl2-MgCl2-NaCl composite chlorinating agent added is 15-30% of the mass of the non-magnetic residue, and the mass ratio of CaCl2, MgCl2 and NaCl is (40-70):(20-40):(5-15).

7. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step c), the multi-temperature gradient heating includes: holding at 450-550℃ for 30-60 min, holding at 650-750℃ for 20-40 min, and holding at 900-1050℃ for 20-30 min.

8. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step d), the amount of TiO2-Cr2O3-ZrO2 composite nucleating agent added is 2-4% of the mass of the residue after chlorination treatment, and the mass percentage of each component is TiO2: (30-50)wt%, Cr2O3: (10-20)wt%, ZrO2: (30-50)wt%; the amount of CaO-MgO composite additive added is 30-50% of the mass of the residue after chlorination treatment, and the mass percentage of each component is CaO: (50-70)wt%, MgO: (30-50)wt%.

9. The method for high-value utilization of all components of copper slag according to claim 1, characterized in that, In step d), the non-equilibrium crystallization process includes: heating to 1250-1350℃ at a rate of 15-25℃ / min for melting, rapidly quenching to 650-750℃ and holding for 1-2 hours for nucleation, and then heating to 950-1050℃ at a rate of 10-15℃ / min for crystallization for 30-60 minutes.

10. The method for high-value utilization of all components of copper slag according to any one of claims 1 to 9, characterized in that, By controlling the gradient heating process, the recovery rates of valuable metals such as copper, zinc, and lead are all greater than 85%; the main crystalline phase of the diopside microcrystalline glass obtained is Ca(Mg,Al)(Si,Al)2O6, the crystal size is 0.5-2μm, and the flexural strength is ≥120MPa.

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