Sodium borate-calcium-based composite flux, preparation method and application of sodium borate-calcium-based composite flux in fire refining of copper

Abstract

The invention belongs to the technical field of copper smelting flux, and particularly relates to a sodium borate-calcium-based composite flux, a preparation method and application of the sodium borate-calcium-based composite flux in copper fire refining. The sodium borate-calcium-based composite flux is composed of calcium carbonate, sodium borate, sodium carbonate and fluorite according to a specific proportion, and through the calcium-boron-sodium ternary synergistic effect, arsenic and antimony are efficiently removed, and meanwhile the yield of copper is increased. And the chemical erosion to the magnesite-chrome brick of the anode furnace is obviously reduced. Calcium oxide generated by high-temperature decomposition of calcium carbonate in the flux reacts with arsenic and antimony to generate stable calcium arsenate, sodium arsenate, calcium antimonate and sodium antimonate, so that efficient removal of arsenic and antimony is realized; b2O3 generated by decomposition of sodium borate and MgO in the magnesite-chrome brick form a high-melting-point Mg3B2O6 protection layer, the erosion rate of the magnesite-chrome brick is subjected to breakthrough control, the order of magnitude is reduced compared with a traditional process, and the melt viscosity is reduced through fluorite so as to promote slag-copper separation. The flux can completely replace a traditional sodium carbonate process, equipment transformation is not needed, the flux is suitable for crude copper containing high arsenic and antimony, the service life of a furnace lining is remarkably prolonged, and the copper grade is improved.

Description

Technical Field

[0001] This invention belongs to the field of copper smelting flux technology, specifically relating to a sodium borate-calcium based composite flux, its preparation method, and its application in copper pyrometallurgical refining. Background Technology

[0002] Pyrometallurgical refining, as a core process in non-ferrous metal smelting, plays a crucial role in the purification of metals such as copper and lead. The high arsenic, antimony, and lead content in complex mixed concentrates, the copper-containing intermediate materials produced during smelting, and the recycling of secondary copper-containing resources all contribute to the high arsenic, antimony, and lead content in the crude copper produced during pyrometallurgical copper smelting. If arsenic, antimony, and lead are not removed during the pyrometallurgical stage, arsenic will accumulate in the electrolyte during electrolysis, altering its properties. Simultaneously, antimony readily combines with arsenic and bismuth to form flocculent floating anode mud, which adheres to the cathode plate, forming protrusions and severely affecting the quality of the cathode copper. High arsenic content in the anode mud also directly impacts subsequent gold and silver recovery rates.

[0003] Traditional processes generally employ a two-step method for impurity removal: first, SiO2 is added to form slag and remove lead, generating lead silicate slag (PbO·SiO2), which is then removed by skimming. Subsequently, sodium carbonate (Na2CO3) is added to remove arsenic and antimony, and the peroxidation reaction generates sodium arsenate (Na3AsO4) and sodium antimonate (Na3SbO4), which enter the alkaline slag. However, this process has three significant drawbacks: First, in a high-temperature alkaline environment (1150-1250℃), the Na2O produced by the decomposition of Na2CO3 reacts violently with the magnesia-chrome bricks to generate low-melting-point phases (such as Na2CrO4 and Na2MgSiO4), causing structural spalling of the furnace lining material, exacerbating the erosion of the magnesia-chrome bricks, and reducing the furnace lining life to less than 6 months; Second, the step-by-step processing leads to a prolonged contact time between the melt and the refractory material, resulting in increased cumulative thermal erosion; Third, the sodium carbonate consumption is as high as 12.8-16 kg / t of crude copper, accounting for more than 15% of the auxiliary material cost, and the arsenic-containing alkaline slag produced is recycled, causing As and Sb enrichment, requiring additional sodium carbonate to be added to remedy the situation, increasing costs, and also causing the refractory bricks to erode more rapidly.

[0004] The invention patent with publication number CN102433438A discloses a method for treating waste copper. The selected slag-forming agent is composed of calcium carbonate, sodium chloride and silicon dioxide. Because the selected slag-forming agent has a weak bonding force with metal oxides, the impurity removal effect is also weak. The invention patent with publication number CN111876611B discloses a method for deep removal of arsenic, lead, zinc, and tin through pyrometallurgical refining of crude copper. This method uses NaHCO3-CaCO3-FeO x The -SiO2 system solved the removal of Pb and Zn, but did not solve the problem of deep removal of As (arsenic) and Sb (antimony).

[0005] The invention patent with publication number CN103243223A discloses a method for removing tin from crude copper, which consists of four steps: preliminary oxidation and impurity removal from fritillary slag, low-temperature tin removal with NaOH-NaNO3 / KNO3, high-temperature tin removal with NaOH-NaNO3 / KNO3, and low-temperature reduction. The process is lengthy and costly, and it also exacerbates the erosion of refractory bricks.

[0006] The invention patent with publication number CN103725897A discloses a method for the continuous pyrometallurgical refining of waste copper to directly produce high-purity oxygen-free copper. The use of metaphosphate, phosphorus pentoxide, and carbonate in the oxidation stage achieved good results, effectively removing other impurity metal elements from the copper liquid after oxidation refining. However, the addition of phosphate may lead to Cu3P residue due to the low solubility of phosphorus, causing grain boundary segregation and reducing the ductility and conductivity of copper. During electrolysis, residual phosphorus exists in the form of Cu3P at the anode, leading to passivation, increased energy consumption, and increased anode sludge, affecting precious metal recovery. Incomplete slag formation from phosphate dissolves to generate PO4. 3- , with Cu 2+ Complexation reduces conductivity and leads to abnormal cathode deposition or dendrite growth. Simultaneously, soluble phosphorus may co-deposit on the cathode, impairing the conductivity of copper. Based on this research background, this patent proposes a low-cost technology for arsenic and antimony removal and magnesia-chrome brick protection using a sodium borate-calcium based composite flux. This technology achieves the triple goals of efficient arsenic and antimony removal, protection of magnesia-chrome bricks, and reduced production costs by optimizing the composition and preparation process of the composite flux. Summary of the Invention

[0007] This invention provides a sodium borate-calcium based composite flux, its preparation method, and its application in copper pyrometallurgical refining. This addresses the technical problems in the prior art, such as the inability to remove high arsenic, antimony, and lead content in complex mixed concentrates, the recycling of copper-containing intermediate materials and secondary copper-containing resources produced during smelting, which leads to high arsenic, antimony, and lead content in crude copper produced by copper pyrometallurgical refining and seriously affects the quality of cathode copper.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A sodium borate-calcium-based composite flux, wherein the sodium borate-calcium-based composite flux comprises 40–50% calcium carbonate, 20–30% sodium borate, 10–20% sodium carbonate, and 5–10% fluorite.

[0009] The calcium carbonate can be replaced by quicklime, and the sodium borate can be replaced by boric acid.

[0010] A method for preparing a sodium borate-calcium based composite flux includes the following steps: At 150°C, 40–50% calcium carbonate, 20–30% sodium borate, 10–20% sodium carbonate and 5–10% fluorite were dried for 2 hours. The dried calcium carbonate, sodium borate, sodium carbonate, and fluorite are mixed evenly.

[0011] The process of uniformly mixing the dried calcium carbonate, sodium borate, sodium carbonate, and fluorite involves placing the dried calcium carbonate, sodium borate, sodium carbonate, and fluorite into a mixer and mixing them at 100 rpm for 30 minutes to ensure uniform dispersion of each component.

[0012] The application of a sodium borate-calcium based composite flux in copper pyrometallurgical refining includes the following steps: Place crude copper into a crucible, heat it to the first temperature, and hold it at that temperature for time t1. Continue heating to the second temperature, hold at that temperature for time t2, and then add some sodium borate-calcium based composite flux to the crucible; Continue heating for time t3. After the temperature reaches the third temperature, add the remaining sodium borate-calcium-based composite flux and hold for time t4. Use a vent pipe to introduce compressed air into the bottom of the crucible at the first air flow rate, and continue blowing for t5 time. Continue to introduce compressed air at the second air flow rate, and continue blowing for t6 time before heat preservation.

[0013] The crude copper is placed in a crucible and heated to a first temperature, then held at that temperature for a time t1, where the first temperature is 800℃ and t1 = 30 minutes. Specifically, the crude copper is placed in a crucible and heated to 800℃ at a rate of 10℃ / min, then held at that first temperature for 30 minutes to ensure that the CaCO3 in the crude copper is partially decomposed into CaO.

[0014] The temperature is further increased to the second temperature, and after holding at that temperature for t2 minutes, a portion of sodium borate-calcium-based composite flux is added to the crucible. The second temperature is 1150°C, and t2 = 20 minutes. Specifically, the temperature is increased to 1150°C at a rate of 5°C / min and held for 20 minutes to ensure that the crude copper is completely melted and forms a crude copper melt. 60% of the total mass of sodium borate-calcium-based composite flux is then added to the crude copper melt.

[0015] The heating process continues for time t3. After the temperature reaches the third temperature, the remaining sodium borate-calcium-based composite flux is added, and the temperature is maintained for time t4. Here, t3 = 10 minutes, the third temperature is 1200℃, and t4 is 10 minutes. Specifically, the temperature continues to rise, and after 10 minutes, when the temperature reaches 1200℃, the remaining sodium borate-calcium-based composite flux is added, and the temperature is maintained for 10 minutes.

[0016] The method involves using a vent pipe to introduce compressed air into the bottom of the crucible at a first air flow rate, and continuously blowing for a time t5, wherein the first air flow rate is 30 ml / min and t5 = 15 minutes; specifically, the lower end of the vent pipe is 1 cm from the bottom of the crucible, and compressed air is introduced into the crucible through the vent pipe at a pressure of 0.5 MPa, with the gas flow rate controlled at 30 ml / min, and continuously blowing for 15 minutes.

[0017] The process involves continuing to introduce compressed air at a second gas flow rate, continuously blowing for a time t6, and then holding the mixture at a constant temperature. The second gas flow rate is 50 ml / min, and t6 = 35 minutes. Specifically, after blowing for 15 minutes at a gas flow rate of 30 ml / min, the gas flow rate is controlled at 50 ml / min, and blowing continues for another 35 minutes. Then, the mixture is held at a constant temperature for 60 minutes to promote slag-copper stratification.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention significantly improves the overall performance of copper pyrometallurgical refining through the design of a calcium-boron synergistic system. This technical solution has the following outstanding advantages: (1) simple formulation and excellent performance, directly replacing the traditional sodium carbonate process; (2) no need to modify existing equipment, making implementation convenient; (3) while achieving efficient impurity removal and furnace lining protection, it significantly reduces overall costs, providing an economical and efficient solution for the copper pyrometallurgical refining process. Meanwhile, in traditional processes, sodium carbonate flux severely corrodes magnesia-chrome bricks, resulting in a furnace lining life of only 5-6 months, and the step-by-step impurity removal process is complex and energy-intensive. This invention utilizes CaO as the main alkaline carrier, reducing the amount of sodium salt used, and simultaneously generates a high-melting-point Mg3B2O6 protective layer through B2O3 and MgO, thereby reducing the furnace lining erosion rate and extending the furnace life to over 12 months. In addition, fluorite (CaF2) reduces the melt viscosity to <0.3 Pa·s, promoting slag-copper separation, while the B2O3-CaF2 eutectic effect lowers the flux melting point to 1100–1150℃, which is suitable for the copper refining temperature window.

[0019] From the perspective of industrial production, this invention offers industrial advantages such as simple operation and good equipment adaptability by precisely controlling the dosage and optimizing the addition method of the impurity removal agent. It can not only significantly improve the viscous flow characteristics of the melt and lower the melting point of the system, but also efficiently remove impurities such as arsenic and antimony, while effectively inhibiting the erosion of magnesium-chromium refractory materials. This method reduces the energy consumption of pyrometallurgical refining, while also having excellent process operability and equipment compatibility, and significantly extending the service life of the furnace lining. Attached Figure Description

[0020] Figure 1 This is a schematic diagram comparing the microscopic scanning electron microscope images of refractory brick erosion in an embodiment of the present invention. Detailed Implementation

[0021] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0022] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1 This embodiment proposes a sodium borate-calcium based composite flux, comprising 40-50% calcium carbonate, 20-30% sodium borate, 10-20% sodium carbonate, and 5-10% fluorite; the calcium carbonate can be replaced with quicklime, and the sodium borate can be replaced with boric acid. The preparation method is as follows: the raw materials, including 40-50% calcium carbonate, 20-30% sodium borate, 10-20% sodium carbonate, and 5-10% fluorite, are dried at 150°C for 2 hours to remove adsorbed moisture. Then, the dried calcium carbonate, sodium borate, sodium carbonate, and fluorite are added to a mixer in the specified proportions and mixed at 100 rpm for 30 minutes to ensure uniform dispersion of each component.

[0024] In the aforementioned sodium borate-calcium-based composite flux, calcium carbonate is the primary alkaline carrier: calcium carbonate (40–50%) decomposes at high temperatures to generate calcium oxide (CaO), which reacts with arsenic and antimony to form stable calcium arsenate (Ca3(AsO4)2) and calcium antimonate (Ca3(SbO4)2), thereby reducing dependence on sodium salts. CaO exhibits significantly better chemical affinity for arsenic and antimony than traditional sodium salts, and its reaction free energy for the formation of arsenic / antimonate indicates higher thermodynamic stability, resulting in a significant improvement in the removal rate of arsenic and antimony.

[0025] 3CaO + As₂O₃ + O₂ = Ca₃(AsO₄)₂ 3CaO + Sb₂O₃ + 2O₂ = Ca₃(SbO₄)₂ Sodium carbonate as a co-oxidizing agent: Sodium carbonate (10–20%) acts as a co-oxidizing agent, utilizing its strong oxidizing properties to accelerate the initial oxidation reaction of arsenic and antimony. Simultaneously, it can effectively remove some arsenic and antimony. Furthermore, sodium ions (Na...) + The borate glass phase encapsulates the metal, limiting its migration ability and thus reducing the chemical erosion of magnesia-chrome bricks by sodium salts.

[0026] As₂O₃ + 2Na₂CO₃ + O₂ = 2Na₃AsO₄ + CO₂ Sb₂O₃ + 2Na₂CO₃ + O₂ = 2Na₃SbO₄ + CO₂ Sodium borate as a protective agent (20–30%): Sodium borate (20–30%) decomposes at high temperatures to generate boron oxide (B₂O₃), which reacts with magnesium oxide (MgO) in magnesia-chrome bricks to form high-melting-point magnesium borate (Mg₃B₂O₆, melting point 1360℃), forming a dense physical barrier layer on the furnace lining surface, thus reducing the depth of melt penetration. Simultaneously, the glassy network structure formed by B₂O₃ effectively binds free sodium ions (Na₂O₃). + This reduces its direct contact with the furnace lining, further inhibiting furnace lining erosion.

[0027] 3MgO + B₂O₃ = Mg₃B₂O₆ Fluorite as a flux: As a melt flow modifier, fluorite (5–10%) releases fluoride ions (F... - This disrupts the high-melting-point silicate network structure in the melt, promoting efficient slag-copper separation. Simultaneously, the eutectic effect of B₂O₃ and CaF₂ lowers the melting point of the flux system to 1100–1150℃, ensuring sufficient fluidity of the melt at refining temperatures of 1150–1200℃. - With Ca 2+ The CaF2 microcrystals generated are dispersed in the slag phase to form a "pseudo-particle" effect, which enhances the interfacial tension between the slag layer and the copper liquid, thereby improving the slag removal efficiency.

[0028] Therefore, based on the sodium borate-calcium based composite flux prepared above, this embodiment further proposes an application of the sodium borate-calcium based composite flux in copper pyrometallurgical refining. The sodium borate-calcium based composite flux is applied to copper pyrometallurgical refining. During the copper pyrometallurgical refining process, the sodium borate-calcium based composite flux is added to efficiently remove arsenic and antimony while inhibiting the corrosion of magnesia-chrome bricks, thus removing impurities during the copper pyrometallurgical refining process. The amount of sodium borate-calcium based composite flux added is 1.5%-2.5% of the mass of crude copper during the copper pyrometallurgical refining process. The method of applying the sodium borate-calcium based composite flux in copper pyrometallurgical refining includes the following steps: Place crude copper into a crucible, heat it to the first temperature, and hold it at that temperature for time t1. Continue heating to the second temperature, hold at that temperature for time t2, and then add some sodium borate-calcium based composite flux to the crucible; Continue heating for time t3. After the temperature reaches the third temperature, add the remaining sodium borate-calcium-based composite flux and hold for time t4. Use a vent pipe to introduce compressed air into the bottom of the crucible at the first air flow rate, and continue blowing for t5 time. Continue to introduce compressed air at the second air flow rate, and continue blowing for t6 time before heat preservation.

[0029] In the above method steps, the first temperature is 800℃, t1 = 30 minutes; the second temperature is 1150℃, t2 = 20 minutes; t3 = 10 minutes; the third temperature is 1200℃, t4 = 10 minutes; the first gas flow rate is 30 ml / min, t5 = 15 minutes; the second gas flow rate is 50 ml / min, t6 = 35 minutes. Specifically: crude copper is placed in a crucible and heated to 800℃ at a rate of 10℃ / min, and held at the first temperature for 30 minutes to ensure that the CaCO3 in the crude copper is partially decomposed into CaO. Subsequently, the temperature is increased to 1150℃ at a rate of 5℃ / min and held for 20 minutes to ensure that the crude copper is completely melted and forms a crude copper melt. 60% by mass of sodium borate-calcium based composite flux is then added to the crude copper melt. The molten copper continues to heat up. After 10 minutes, when the temperature reaches 1200℃, the first addition of 60% sodium borate-calcium-based composite flux has completely melted into the molten copper. At this point, the remaining 40% sodium borate-calcium-based composite flux is added to the melt. The total amount of sodium borate-calcium-based composite flux added in both additions is 1.5% of the mass of the molten copper. After adding the remaining 40% sodium borate-calcium-based composite flux, wait 10 minutes to allow all the sodium borate-calcium-based composite flux to completely melt. Insert an alumina vent tube, with the lower end of the alumina vent tube 1 cm from the bottom of the crucible. Pressurized air is introduced into the bottom of the melt through the alumina vent tube at a pressure of 0.5 MPa, with the gas flow rate controlled at 30 ml / min. Continue blowing for 15 minutes, then control the gas flow rate at 50 ml / min and continue blowing for 35 minutes. After the compressed gas in the crucible is blown twice, it is kept at the temperature for another 60 minutes to promote slag-copper stratification. Then the melt is slowly cooled and samples are taken to analyze the removal rates of arsenic, antimony and lead in the samples. The specific data are shown in Table 1 below.

[0030] Example 2 Based on the application of sodium borate-calcium-based composite flux in copper pyrometallurgical refining proposed in Example 1, in this example, each raw material in the sodium borate-calcium-based composite flux was dried at 150°C for 2 hours to remove adsorbed moisture. Then, 40% calcium carbonate, 10% fluorite, 30% sodium borate, and 20% sodium carbonate were added to a mixer in proportion and mixed at 100 rpm for 30 minutes to ensure uniform dispersion of each component. Crude copper was placed in a crucible and heated. The heating program was as follows: heating to 800°C at 10°C / min, then holding at that temperature for 30 minutes until CaCO3 in the crude copper partially decomposed into CaO; subsequently, heating to 1150°C at a rate of 5°C / min and holding for 20 minutes to ensure complete melting of the crude copper, forming a crude copper melt. 60% by mass of the sodium borate-calcium-based composite flux was then added to the crude copper melt. In this embodiment, the total amount of sodium borate-calcium based composite flux added twice is 1.5% of the mass of crude copper.

[0031] After adding the remaining 40% sodium borate-calcium based composite flux, wait 10 minutes to allow all the sodium borate-calcium based composite flux to completely melt. Insert the corundum vent tube, with the lower end of the corundum vent tube 1 cm from the bottom of the crucible. Introduce compressed air into the bottom of the melt through the corundum vent tube at a pressure of 0.5 MPa, controlling the gas flow rate at 30 ml / min, and continue blowing for 15 minutes. Then, control the gas flow rate at 50 ml / min and continue blowing for 35 minutes. After the compressed gas blowing is complete, continue holding at the temperature for 60 minutes to promote slag-copper stratification. Then, slowly cool the melt and take samples to analyze the removal rates of arsenic, antimony, and lead in the samples. The specific data are shown in Table 1 below.

[0032] Example 3 Based on the application of sodium borate-calcium-based composite flux in copper pyrometallurgical refining proposed in Example 1, in this example, each raw material in the sodium borate-calcium-based composite flux was dried at 150°C for 2 hours to remove adsorbed moisture. Then, 45% calcium carbonate, 10% fluorite, 25% sodium borate, and 20% sodium carbonate were added to a mixer in proportion and mixed at 100 rpm for 30 minutes to ensure uniform dispersion of each component. Crude copper was placed in a crucible and heated. The heating program was as follows: heating to 800°C at 10°C / min and holding for 30 minutes to partially decompose CaCO3 into CaO; then heating to 1150°C at 5°C / min and holding for 20 minutes to ensure complete melting of the melt; first, 60% of the total mass of sodium borate-calcium-based composite flux was added. After another 10 minutes, the temperature reached 1200°C, and the remaining 40% of sodium borate-calcium-based composite flux was added. In this embodiment, the total amount of sodium borate-calcium based composite flux added twice is 2% of the mass of crude copper.

[0033] After adding the remaining 40% sodium borate-calcium based composite flux, wait 10 minutes to ensure the flux is completely melted. Then, insert the corundum vent tube (1 cm from the bottom of the crucible) and introduce compressed air into the bottom of the melt at a pressure of 0.5 MPa, with a gas flow rate controlled at 30 ml / min, and continue blowing for 15 minutes. Subsequently, control the gas flow rate at 50 ml / min and continue blowing for another 35 minutes. After the compressed gas blowing is completed, hold the melt at a temperature for 60 minutes to promote slag-copper stratification. Then, slowly cool the melt and take samples to analyze the removal rates of arsenic, antimony, and lead. The specific data are shown in Table 1 below.

[0034] Example 4 Based on the application of sodium borate-calcium-based composite flux in copper pyrometallurgical refining proposed in Example 1, in this example, each raw material in the sodium borate-calcium-based composite flux was dried at 150°C for 2 hours to remove adsorbed moisture. Then, 50% calcium carbonate, 10% fluorite, 20% sodium borate, and 20% sodium carbonate were added to a mixer in proportion and mixed at 100 rpm for 30 minutes to ensure uniform dispersion of each component. Crude copper was placed in a crucible and heated. The heating program was as follows: heating to 800°C at 10°C / min and holding for 30 minutes to partially decompose CaCO3 into CaO; then heating to 1150°C at 5°C / min and holding for 20 minutes to ensure complete melting of the melt; first, 60% of the total mass of sodium borate-calcium-based composite flux was added. After another 10 minutes, the temperature reached 1200°C, and the remaining 40% of sodium borate-calcium-based composite flux was added. In this embodiment, the total amount of sodium borate-calcium based composite flux added twice is 2.5% of the mass of crude copper.

[0035] After adding the remaining 40% sodium borate-calcium based composite flux, wait 10 minutes to allow all the sodium borate-calcium based composite flux to completely melt. Insert the corundum vent tube, with the lower end of the corundum vent tube 1 cm from the bottom of the crucible. Introduce compressed air into the bottom of the melt through the corundum vent tube at a pressure of 0.5 MPa, controlling the gas flow rate at 30 ml / min. Continue blowing for 15 minutes, then control the gas flow rate at 50 ml / min and continue blowing for 35 minutes. After the compressed gas blowing is complete, continue holding at the temperature for 60 minutes to promote slag-copper stratification. Then, slowly cool the melt and take samples to analyze the removal rates of arsenic, antimony, and lead in the samples. The specific data are shown in Table 1 below.

[0036] Example 5 In a further preferred embodiment of the present invention, the traditional arsenic and antimony removal agent used in the copper pyrometallurgical refining process is added to the crude copper in two separate batches using the same application method as in Examples 2, 3, and 4. The samples after impurity removal using the traditional arsenic and antimony removal agent in the copper pyrometallurgical refining process are then sampled, and the removal rates of arsenic, antimony, and lead in the samples are analyzed. The specific data are shown in Table 1 below.

[0037] Table 1

[0038] The results in Table 1 above show that in Example 2, the sodium borate-calcium based composite flux prepared with 40% calcium carbonate, 10% fluorite, 30% sodium borate, and 20% sodium carbonate achieved arsenic and antimony removal rates of 95.24% and 90.25%, respectively, while the lead removal rate reached 89.36%. In Example 3, the sodium borate-calcium based composite flux prepared with 45% calcium carbonate, 10% fluorite, 25% sodium borate, and 20% sodium carbonate achieved arsenic and antimony removal rates of 96.07% and 92.46%, respectively, while the lead removal rate reached 91.48%. In Example 4, the sodium borate-calcium based composite flux prepared with 50% calcium carbonate, 10% fluorite, 20% sodium borate, and 20% sodium carbonate achieved arsenic and antimony removal rates of 95.34% and 91.08%, respectively, while the lead removal rate reached 90.11%. In Example 5, the traditional copper refining impurity removal agent achieved arsenic and antimony removal rates of 41% and 54%, respectively, while the lead removal rate was 73.8%. The results indicate that the sodium borate-calcium based composite flux proposed in this invention, through the synergistic effect of calcium and boron and a staged feeding strategy, achieves arsenic and antimony removal rates significantly higher than those produced by traditional sodium borate-calcium based composite fluxes, raising the arsenic and antimony removal rate to a level that meets the requirements of electrolysis.

[0039] In another preferred embodiment of the present invention, the sodium borate-calcium based composite flux is subjected to an erosion test on magnesia-chrome bricks to ensure that it can effectively inhibit the erosion of magnesia-chrome bricks during copper refining. The specific implementation method is as follows: Magnesium chrome bricks were cut into standard test blocks (2cm×2cm×5cm), dried at 105℃ for 2 hours, and then placed in 4 corundum crucibles with a spacing of ≥1cm between the test blocks in each corundum crucible. Sodium borate-calcium based composite flux prepared in Examples 2, 3, 4 and 5 were spread evenly on the bottom of four crucibles respectively. The added mass of sodium borate-calcium based composite flux was 60% of the total mass, and the particle size of sodium borate-calcium based composite flux was ≤0.074 mm, so that the sodium borate-calcium based composite flux covered the bottom 1 / 3 height of the magnesia-chrome brick test block. When the temperature is increased to 1200℃ at 5℃ / min, the sodium borate-calcium-based composite flux is melted to form a melt. After the temperature is kept constant, the remaining 40% sodium borate-calcium-based composite flux is evenly spread on the surface of the melt through a quartz feeding tube. The entire process was carried out under a nitrogen protective atmosphere and maintained at a constant temperature for 2 hours. After cooling, scanning electron microscopy (SEM) was used to determine the etching depth of the samples in the three crucibles. The SEM images of the magnesia-chrome brick etching obtained in Example 2 are shown below. Figure 1 As shown in (b), the scanning electron microscope image of the magnesia-chrome brick erosion obtained in Example 3 is as follows. Figure 1 (c) shows the scanning electron microscope image of the magnesia-chrome brick erosion obtained in Example 4. Figure 1As shown in (d), the scanning electron microscope image of the magnesia-chrome brick erosion obtained in Example 5 is as follows. Figure 1 As shown in (a). By Figure 1 A comparison of four scanning electron microscope images shows that the sodium borate-calcium-based composite flux proposed in this invention significantly inhibits the erosion of magnesia-chrome bricks. Therefore, this invention achieves a dual optimization effect through the application of sodium borate-calcium-based composite flux in the copper pyrometallurgical refining process: on the one hand, it increases the arsenic and antimony removal rate to meet the requirements of electrolysis; on the other hand, it significantly reduces the erosion rate of magnesia-chrome brick furnace linings. Furthermore, combining the impurity removal effects of the sodium borate-calcium-based composite fluxes prepared with three different component ratios in Examples 2 to 4, and the erosion inhibition effects produced after erosion experiments on magnesia-chrome bricks with the three sodium borate-calcium-based composite fluxes, it is finally concluded that the sodium borate-calcium-based composite flux prepared with 45% calcium carbonate, 10% fluorite, 25% sodium borate, and 20% sodium carbonate in Example 3 has the best erosion inhibition effect and impurity removal effect in copper pyrometallurgical refining.

[0040] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A sodium borate-calcium based composite flux, characterized in that, The sodium borate-calcium-based composite flux comprises 40–50% calcium carbonate, 20–30% sodium borate, 10–20% sodium carbonate, and 5–10% fluorite.

2. The sodium borate-calcium based composite flux according to claim 1, characterized in that, The calcium carbonate can be replaced by quicklime, and the sodium borate can be replaced by boric acid.

3. A method for preparing a sodium borate-calcium based composite flux, based on the sodium borate-calcium based composite flux according to any one of claims 1 to 2, characterized in that, Includes the following steps: At 150°C, 40–50% calcium carbonate, 20–30% sodium borate, 10–20% sodium carbonate and 5–10% fluorite were dried for 2 hours. The dried calcium carbonate, sodium borate, sodium carbonate, and fluorite are mixed evenly.

4. The method for preparing a sodium borate-calcium based composite flux according to claim 3, characterized in that, The process of uniformly mixing the dried calcium carbonate, sodium borate, sodium carbonate, and fluorite involves placing the dried calcium carbonate, sodium borate, sodium carbonate, and fluorite into a mixer and mixing them at 100 rpm for 30 minutes to ensure uniform dispersion of each component.

5. The application of a sodium borate-calcium-based composite flux in copper pyrometallurgical refining, based on the sodium borate-calcium-based composite flux according to any one of claims 1 to 2, characterized in that, Includes the following steps: Place crude copper into a crucible, heat it to the first temperature, and hold it at that temperature for time t1. Continue heating to the second temperature, hold at that temperature for time t2, and then add some sodium borate-calcium based composite flux to the crucible; Continue heating for time t3. After the temperature reaches the third temperature, add the remaining sodium borate-calcium-based composite flux and hold for time t4. Use a vent pipe to introduce compressed air into the bottom of the crucible at the first air flow rate, and continue blowing for t5 time. Continue to introduce compressed air at the second air flow rate, and continue blowing for t6 time before heat preservation.

6. The application of the sodium borate-calcium based composite flux according to claim 5 in copper pyrometallurgical refining, characterized in that, The process involves placing crude copper into a crucible, heating it to a first temperature, and holding it at that temperature for a time t1, where the first temperature is 800℃ and t1 = 30 minutes. Specifically, crude copper is placed in a crucible, heated to 800℃ at a rate of 10℃ / min, and held at that first temperature for 30 minutes to ensure that the CaCO3 in the crude copper is partially decomposed into CaO.

7. The application of the sodium borate-calcium based composite flux according to claim 5 in copper pyrometallurgical refining, characterized in that, The temperature is further increased to the second temperature, and after holding at that temperature for t2 minutes, a portion of sodium borate-calcium-based composite flux is added to the crucible. The second temperature is 1150°C, and t2 = 20 minutes. Specifically, the temperature is increased to 1150°C at a rate of 5°C / min and held for 20 minutes to ensure that the crude copper is completely melted and forms a crude copper melt. 60% of the total mass of sodium borate-calcium-based composite flux is then added to the crude copper melt.

8. The application of the sodium borate-calcium based composite flux according to claim 5 in copper pyrometallurgical refining, characterized in that, The heating process continues for time t3. After the temperature reaches the third temperature, the remaining sodium borate-calcium-based composite flux is added, and the temperature is maintained for time t4. Here, t3 = 10 minutes, the third temperature is 1200℃, and t4 is 10 minutes. Specifically, the temperature continues to rise, and after 10 minutes, when the temperature reaches 1200℃, the remaining sodium borate-calcium-based composite flux is added, and the temperature is maintained for 10 minutes.

9. The application of the sodium borate-calcium based composite flux according to claim 5 in copper pyrometallurgical refining, characterized in that, The process involves using a vent pipe to introduce compressed air into the bottom of the crucible at a first air flow rate, and continuously blowing for a time t5, where the first air flow rate is 30 ml / min and t5 = 15 minutes. Specifically, the lower end of the vent pipe is 1 cm from the bottom of the crucible, and compressed air is introduced into the crucible at a pressure of 0.5 MPa through the vent pipe, with the gas flow rate controlled at 30 ml / min, and the blowing is continued for 15 minutes.

10. The application of the sodium borate-calcium based composite flux according to claim 5 in copper pyrometallurgical refining, characterized in that, The process involves continuing to introduce compressed air at a second gas flow rate, continuously blowing for a time t6, and then holding the mixture at a constant temperature. The second gas flow rate is 50 ml / min, and t6 = 35 minutes. Specifically, after blowing for 15 minutes at a gas flow rate of 30 ml / min, the gas flow rate is controlled at 50 ml / min, and blowing continues for another 35 minutes. Then, the mixture is held at a constant temperature for 60 minutes to promote slag-copper stratification.

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