A pyro smelting process for preparing ultra-high purity copper by deeply removing trace impurities

Abstract

The application discloses a fire smelting process for preparing ultra-high purity copper by deeply removing trace impurities. It relates to the technical field of ultra-high purity copper preparation. The anode copper melt is heated to 1120-1150 DEG C, and under the closed micro-positive pressure condition of the cooperation of the micro-oxidation atmosphere and the inert carrier gas, the high-vapor-pressure impurities are naturally volatilized and removed by constant temperature and static setting. The temperature is uniformly raised to 1180-1220 DEG C, the weak oxidation atmosphere is switched, the composite slagging agent is added to the surface of the melt, and the slag is removed after constant temperature reaction. The temperature is uniformly reduced to 1080-1100 DEG C, the high-purity inert protective atmosphere is switched, the composite deoxidizer is added, and the slag is removed after the closed static setting, so that the ultra-high purity copper liquid is obtained. The application adopts three-stage step-by-step temperature control refining, that is, the low-temperature pre-removal of the easily-volatilized impurities, the medium-temperature accurate slagging for deeply removing the refractory metal impurities, and the deep deoxidization under the inert atmosphere. In the process of deoxidization, the trace impurity elements are removed, the impurity content in the copper melt is further reduced, and thus the ultra-high purity copper is obtained.

Description

Technical Field

[0001] This application relates to the field of ultra-high purity copper preparation technology, and in particular to a pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper. Background Technology

[0002] Ultra-high purity copper (purity ≥99.999%, 5N grade and above) is a core material for high-end electronic products such as semiconductor sputtering targets, high-frequency communication cables, quantum devices, and high-precision electronic lead frames. The purity of copper directly determines the electrical performance, thermal conductivity, and long-term reliability of these devices. As integrated circuit linewidths continue to shrink and communication frequencies continue to increase, the purity requirements for copper raw materials have risen from the traditional 3N~4N grade to 5N and even 6N grade and above.

[0003] Currently, the mainstream technology for the industrial production of ultra-high purity copper involves first electrolytic refining to increase the copper purity to around 99.99% (4N), and then reducing the total impurity content to below 10ppm through zone melting or vacuum electron beam melting, achieving a level of 5N or higher. However, this route has significant drawbacks: the process is lengthy, involving multiple steps such as electrolysis, drying, and vacuum melting; energy consumption is high, as both zone melting and electron beam melting require high vacuum environments and high-power heating; investment in specialized equipment is large, and maintenance costs are high; and production efficiency is low, making continuous mass production difficult.

[0004] Traditional pyrometallurgical refining is currently the mainstream technology in the copper smelting industry, offering advantages such as large processing capacity, low cost, and good compatibility with existing furnaces. Conventional pyrometallurgical refining can only increase copper purity to 99.5%~99.97% (3N~3N7 grade), with extremely low removal rates for trace impurities such as Ag, Sn, Bi, and Pb. These impurities are difficult to remove during atmospheric pressure oxidation. Under reducing conditions, it is difficult to form volatile compounds or easily separable slag phases. The residual concentration is usually still in the tens to hundreds of ppm range, which cannot be stably controlled below 1 ppm, and cannot meet the preparation requirements of 6N grade ultra-high purity copper.

[0005] Therefore, realizing the one-step pyrometallurgical process to directly prepare 6N-grade ultra-high purity copper from industrial crude copper or 4N-grade cathode copper has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to solve at least one of the above-mentioned technical problems and to develop a pyrometallurgical process for preparing copper with a purity of 6N or higher, this application provides a pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper.

[0007] On the one hand, this application provides a pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper, which includes the following steps: S1. Heat the molten copper anode to 1120~1150℃, and under a closed micro-positive pressure condition with a micro-oxidation atmosphere of 0.5%~1.0% oxygen volume fraction and an inert carrier gas, keep it at a constant temperature for 30~45 minutes to allow high vapor pressure impurities to evaporate and be removed naturally. S2. Heat the mixture at a constant rate to 1180~1220℃, switch to a weak oxidizing atmosphere with an oxygen volume fraction of 2%~3%, add 2.0%~2.8% of the copper liquid mass of the composite slag-forming agent to the surface of the melt, react at a constant temperature for 35~50 minutes, and then remove the slag. S3. Cool the liquid at a constant rate to 1080~1100℃, switch to a high-purity inert protective atmosphere with an oxygen volume fraction of <0.1ppm, add 0.08%~0.20% of the copper liquid mass of composite deoxidizer, seal and let stand for 40~60 minutes, then remove the slag to obtain ultra-high purity copper liquid. The composite slag-forming agent is composed of the following components by mass percentage: calcium oxide 35%~45%, silicon dioxide 20%~28%, sodium carbonate 12%~18%, aluminum oxide 8%~12%, cerium dioxide 3%~6%, and boron trioxide 2%~5%; The composite deoxidizer is composed of the following components by mass percentage: 40%~60% borax, 30%~50% carbonaceous reducing agent, and 5%~10% copper-phosphorus master alloy, wherein the phosphorus content of the copper-phosphorus master alloy is 10%~15%.

[0008] The above technical solution employs a three-stage, step-by-step temperature control method to remove different impurities. It utilizes a medium-low temperature environment combined with a micro-oxidation closed system to preferentially remove high-vapor-pressure, volatile impurities such as Bi, Pb, Se, and Te through differences in saturated vapor pressure. Then, the temperature is raised to a medium temperature of 1180–1220°C. First, As and Sb are fixed by calcium oxide, silicon dioxide, and sodium carbonate. Then, utilizing the high lattice energy and lattice defect characteristics of cerium dioxide in the composite slag-forming agent, under weak oxidation conditions at 1180–1220°C, Ag and Sn oxides diffused to the slag-copper interface preferentially dissolve into the cerium dioxide lattice, forming CeO2 with a low melting point, low density, and extremely stable thermodynamics. xAg2O The ySnO2 multi-component complex salt phase, with added alumina to stabilize the slag phase structure and prevent reverse dissolution into the copper liquid, and the boron trioxide in the composite slag-forming agent, after melting, has a wetting angle >90° in the copper liquid and is non-wetting. During the floating process, it spontaneously forms a borax salt liquid film by relying on capillary force and low interfacial tension. This film has strong anisotropic interfacial energy, which can efficiently capture, encapsulate and dissolve trace amounts of amphoteric oxides such as As2O3 and Sb2O3 in the melt, and initiate a physical-chemical composite slag formation reaction. It floats up with the liquid film agglomeration, improving the removal rate. Taking advantage of the rapid drop in oxygen solubility during the low-temperature stage (1080~1100℃), and in conjunction with a boron-carbon-phosphorus composite deoxidizer, the oxygen content is reduced to below 0.3ppm under a high-purity inert atmosphere. During this process, the high-purity inert protective atmosphere acts as a stripping agent, continuously carrying away volatilized impurities from the copper melt, further reducing the content of impurity metals. The borax in the composite deoxidizer forms a borax salt film during the flotation process, adhering to trace amounts of oxides or elements such as As, Sb, and Sn in the copper melt, causing a slag reaction that removes them from the copper melt, further reducing their content in the copper melt.

[0009] Based on the above technical solution, in S2, the multi-component composite slag-forming agent is added in stages: first, calcium oxide, silicon dioxide and sodium carbonate are added, and after reacting for 20 minutes, aluminum oxide, cerium dioxide and boron trioxide are added.

[0010] The above technical solution achieves graded removal of impurities. First, most of the high-concentration As and Sb oxides are removed through the basic slag, and then trace amounts of difficult-to-remove impurities such as Ag and Sn are deeply captured through the activated slag collector, which significantly improves the utilization rate of slag-forming agent and the overall impurity removal efficiency.

[0011] Based on the above technical solution, in S1, the inert carrier gas is nitrogen or argon, and the micro-positive pressure inside the furnace is controlled at 200~500Pa.

[0012] The above technical solution uses inert carrier gas to achieve air lifting, which enhances the efficiency of volatile impurity discharge; the slightly positive pressure environment can prevent outside air and dust from seeping into the furnace and avoid introducing secondary impurities.

[0013] Based on the above technical solution, in S3, the high-purity inert carrier gas is nitrogen or argon, and the water content is ≤0.5ppm.

[0014] The above technical solution reduces water content, avoids the decomposition of water vapor at high temperatures to produce oxygen and hydrogen, prevents oxidation and hydrogen embrittlement defects in copper liquid, ensures the internal density of the product, and eliminates quality problems such as porosity and looseness.

[0015] Based on the above technical solution, in S2, the heating rate of the uniform heating is 0.8~1.2℃ / min.

[0016] The above technical solution ensures a uniform rise in melt temperature, avoiding local overheating that could lead to copper evaporation and loss; at the same time, it allows sufficient time for impurities dissolved in copper to precipitate uniformly, creating favorable conditions for subsequent slag-forming reactions and improving impurity removal stability.

[0017] Based on the above technical solution, in S3, the cooling rate of the uniform cooling is 1.0~1.5℃ / min.

[0018] The above technical solution utilizes the thermodynamic property that the solubility of oxygen in copper drops sharply at low temperatures to promote the precipitation of dissolved oxygen; at the same time, it allows sufficient time for the products generated by the deoxidation reaction to float and separate, thereby improving the deoxidation depth and melt purity.

[0019] Based on the above technical solution, in S3, the composite deoxidizer is wrapped with copper foil and then pressed into the melt.

[0020] The above technical solution prevents the deoxidizer from prematurely oxidizing and becoming ineffective due to contact with air during the addition process, ensuring that the deoxidation reaction is fully carried out inside the melt; at the same time, it avoids secondary pollution caused by the introduction of air, thereby improving deoxidation efficiency and product purity.

[0021] In summary, a three-stage, step-by-step, graded, temperature-controlled refining process is adopted: first, low-temperature pre-removal of volatile impurities; second, medium-temperature precise slag formation for deep removal of refractory metal impurities; and finally, deep deoxidation under an inert atmosphere. During the deoxidation process, trace impurity elements are also removed, further reducing the impurity content in the copper melt, thereby obtaining ultra-high purity copper. Detailed Implementation

[0022] Traditional pyrometallurgical refining uses a conventional, single high-temperature oxidation-reduction process, which cannot simultaneously process multiple types of impurities and always has an upper limit on purity. Many studies have broken down the smelting process into several different temperature ranges and removed different impurities at different temperatures. Although this can improve the removal rate of some impurities, the effect is poor in the further refining of copper, making it difficult to achieve the preparation of 6N grade ultra-high purity copper.

[0023] This application uses 4N grade anode copper as raw material and improves the purity of copper to 6N grade through three-stage temperature control and the combined effects of furnace atmosphere and slag-forming agent / deoxidizer.

[0024] Firstly, a mild temperature and a weak oxidizing atmosphere are used to remove volatile impurities with low boiling points and easy vaporization, such as bismuth, lead, selenium, and tellurium. The saturated vapor pressure of these impurities, including elemental impurities and low-valence oxides, is much higher than that of metallic copper. Within the current mild temperature range, they can spontaneously escape from the interior of the molten copper to the surface of the melt without the need for high temperatures, and are then carried out of the system by the carrier gas in the furnace. Simultaneously, the weak oxidizing atmosphere can convert some elemental impurities into more easily vaporized low-valence oxides, further accelerating the separation speed. This also avoids the re-dissolution of impurities under high-temperature conditions, significantly improving the stability and removal rate of volatile impurities.

[0025] Secondly, in the medium-temperature range, non-volatile and chemically stable solid metals and non-metallic impurities such as silver, tin, arsenic, and antimony are removed. After heating, a suitable temperature environment for oxidation reaction is created. First, silver, tin, arsenic, and antimony are fully oxidized to generate corresponding metal oxides. Then, arsenic and antimony oxides are fixed by calcium oxide, silicon dioxide, and sodium carbonate in the slag-forming agent. Through the complexation and combination reaction between aluminum oxide, cerium dioxide, and boron trioxide in the slag-forming agent and the chemically stable silver and tin oxides, a stable and less dense composite salt substance is generated, which aggregates and floats into the slag layer. Separation is achieved by skimming the slag.

[0026] Finally, deep deoxidation is completed in a low-temperature inert environment. The solubility of oxygen in the copper melt decreases significantly as the melt temperature decreases, and after cooling, a large amount of dissolved oxygen spontaneously enters a supersaturated precipitation state. Then, a composite deoxidizer suitable for the low-temperature environment is added, which reacts rapidly with free oxygen to generate harmless and easily floating deoxidation products. During this process, the high-purity inert protective atmosphere can play a role in gas lifting, continuously carrying away the volatilized impurities from the copper melt, further reducing the content of impurity metals. During the floating process, the borax in the composite deoxidizer forms a borax salt film, which adheres to trace amounts of oxides or elements such as As, Sb, and Sn in the copper melt, causing a slag reaction and detaching them from the copper melt, further reducing their content in the copper melt. At the same time, the sealed inert environment isolates the outside air, preventing the copper melt from absorbing oxygen and oxidizing again. During this process, it is not necessary to stir the melt, avoiding affecting the already separated metal phase and slag phase.

[0027] In summary, this application achieves stepwise and in-depth removal of volatile impurities, refractory metal impurities, and oxygen impurities through three-stage gradient temperature control, combined with the furnace atmosphere and the effects of slagging agents / deoxidizers. This increases the purity of copper to 6N grade.

[0028] To further clarify the technical solution and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments and comparative examples. It should be understood that these embodiments are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions in the art or as recommended by the equipment manufacturer. Unless otherwise specified, the raw materials and reagents used in the embodiments are commercially available products.

[0029] Composite slag-forming agent: Weigh out 40% calcium oxide, 25% silicon dioxide, 15% sodium carbonate, 10% aluminum oxide, 5% cerium dioxide, and 5% boron trioxide by mass ratio, dry them separately at 200℃ for 2 hours to remove water of crystallization, and set aside for later use.

[0030] Composite deoxidizer: Weigh out 55% borax, 40% activated carbon, and 5% Cu-15P master alloy by mass ratio, mix them evenly, and wrap them in high-purity copper foil with a thickness of 0.1mm to form small balls with a diameter of 5cm. Each ball weighs 100g and is ready for use.

[0031] Anode copper raw materials: Bi 5ppm, Pb 6ppm, Se 1ppm, Te 0.5ppm, Ag 15ppm, Sn 8ppm, As 3ppm, Sb 2ppm, O 64ppm, Cu 99.99%, purity grade 4N; after surface cleaning, it is broken into small pieces of 10~20cm and air-dried naturally for 24 hours to remove surface adsorbed moisture. Example 1 This embodiment is a pilot-scale test in the laboratory, as detailed below: A medium-frequency induction furnace is used, with high-purity nitrogen and oxygen cylinders connected to the furnace inlet. A gas flow meter and an online oxygen content detector are installed, along with an internal pressure sensor to monitor changes in internal pressure in real time.

[0032] Add 0.5 tons of anode copper blocks to the furnace in batches, close the furnace door, and purge the furnace air with nitrogen for 5 minutes, controlling the nitrogen flow rate at 10 Nm³ / h. Turn on the medium-frequency power supply and heat to 1100℃ at a rate of 10℃ / min. After the copper material is completely melted, continue heating to 1130℃. Adjust the nitrogen flow rate to 8 Nm³ / h, slowly introduce oxygen, and control the oxygen volume fraction in the furnace to remain stable at 0.8%. Adjust the opening of the furnace exhaust valve to maintain a slight positive pressure of 350 Pa in the furnace. The furnace was kept at a constant temperature for 40 minutes, during which the furnace temperature, oxygen content, and pressure data were recorded every 10 minutes. The flue gas generated by volatilization entered the bag filter through the top flue to collect heavy metal dust. After the pre-vaporization was completed, multiple samples were taken from the upper, middle, and lower parts of the melt using a quartz sampler. After cooling, the surface was thoroughly cleaned and sent to GD-MS for elemental analysis. The results were taken as the average value of multiple points, as shown in Table 1, which shows the content of the eight impurity elements and oxygen element that are of key interest in this application.

[0033] The temperature was uniformly increased to 1200℃ at a rate of 1.0℃ / min, while maintaining a constant nitrogen flow rate. After reaching 1200℃, the oxygen flow rate was adjusted to maintain a stable oxygen volume fraction of 2.5% in the furnace. First, 9 kg of calcium oxide, silicon dioxide, and sodium carbonate were evenly sprinkled onto the surface of the melt, and the reaction was allowed to proceed for 20 minutes. Then, 3 kg of alumina, cerium dioxide, and boron trioxide were evenly sprinkled onto the surface of the melt, and the reaction continued for another 25 minutes. No stirring was performed during the reaction; the slag-copper reaction was achieved through natural convection of the melt. After the reaction, the floating slag layer was thoroughly removed using a slag skimmer, avoiding stirring the lower layer of molten copper. After slag removal, multiple samples were taken from the melt for testing, and the results are shown in Table 1.

[0034] The furnace was cooled to 1090℃ at a uniform rate of 1.2℃ / min, with the oxygen valve closed during the cooling process, and only high-purity nitrogen was introduced. After cooling to 1090℃, ultra-high-purity nitrogen was switched on, with the nitrogen flow rate controlled at 5 Nm³ / h, maintaining a slight positive pressure of 300 Pa inside the furnace. Six deoxidizer balls were slowly pressed into the center of the melt using a long-handled tool, and the tool was immediately removed after pressing to avoid introducing air. The furnace was sealed and allowed to stand for 50 minutes without any operation, relying on natural convection of the melt to achieve the deoxidation reaction. After standing, a small amount of slag on the surface was gently removed with a slag skimmer. Multiple samples were taken and sent to GD-MS for full elemental analysis. The results are shown in Table 1; the purity of copper was >99.9999%, reaching the 6N grade.

[0035] Table 1. Detection results of impurity elements at each stage of Example 1 Example 2 This embodiment is for industrial-scale production, as detailed below: The existing 10-ton rotary anode furnace is used, equipped with a conventional flue gas treatment system, gas control system and temperature measurement system.

[0036] Ten tons of anode copper blocks were added to the furnace in batches. The furnace door was closed, and nitrogen was introduced to purge the air inside the furnace for 5 minutes. The temperature was then increased to 1130°C at a rate of 10°C / min, with a nitrogen flow rate of 600 Nm³ / h, an oxygen volume fraction of 0.6%, and a slight positive pressure of 300 Pa. The rotary kiln was rotated slowly at 0.5 r / min to promote surface renewal of the melt. The mixture was kept at a constant temperature for 45 minutes, during which samples were taken every 15 minutes to test the impurity content. After pre-evaporation, multiple samples were taken and sent to GD-MS for elemental analysis. The results are shown in Table 2.

[0037] The temperature was increased to 1200℃ at a rate of 1.0℃ / min, with an oxygen volume fraction of 2.3%. 0.2 tons of composite slagging agent were added, followed by the addition of calcium oxide, silicon dioxide, and sodium carbonate, reacting for 20 min, then the addition of alumina, cerium dioxide, and boron trioxide, reacting for 25 min. The rotary kiln was maintained at a speed of 0.5 r / min, relying on the rotation of the furnace body for natural stirring. After the reaction was completed, the entire slag layer was removed by tilting the furnace. After slag removal, multiple samples were taken and sent for GD-MS elemental analysis; the results are shown in Table 2.

[0038] The temperature was lowered to 1090℃ at a rate of 1.2℃ / min, and ultra-high purity nitrogen protection was switched on, with an oxygen content of <0.1ppm. 10kg of composite deoxidizer pellets were added, wrapped in copper foil to form larger pellets, and then placed into the furnace. The rotary kiln was stopped and allowed to stand in a sealed environment for 55 minutes. Surface slag was gently removed. Multiple samples were taken and sent to GD-MS for elemental analysis. The results are shown in Table 2; the copper purity was >99.9999%, reaching 6N grade.

[0039] Table 2. Detection results of impurity elements at each stage of Example 2 Comparative Example 1 Add 0.5 tons of anode copper blocks into the furnace in batches, close the furnace door, and allow natural ventilation to raise the temperature to 1100℃ for melting; continue to raise the temperature to 1230℃, and after the copper material has completely melted, start the oxidation stage.

[0040] The furnace door was opened, and compressed air was introduced at a flow rate of 15 Nm³ / h for strong oxidation. The melt was continuously stirred during the oxidation process to promote the reaction. Oxidation was carried out at a constant temperature for 25 minutes until copper flowers appeared on the surface of the molten copper. Multiple samples were taken and sent to GD-MS for elemental analysis. The results are shown in Table 3.

[0041] 10 kg of a quartz-borax binary slag (60% quartz sand, 40% borax) was added to the surface of the melt. The mixture was stirred for 20 min to ensure full contact between the slag phase and the molten copper. After removing the floating slag layer, 2.5 kg of dry charcoal powder was added for strong reduction. The reduction was continued for 20 min until the surface of the molten copper exhibited a mirror-like luster, indicating that the reduction had reached its endpoint. Multiple samples were taken and sent to GD-MS for elemental analysis. The results are shown in Table 3. The purity of the copper was 99.9951%, reaching 4N5.

[0042] Table 3. Detection results of impurity elements at each stage of Comparative Example 1 Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example does not include the rare earth slag removal process, while the other steps are the same as in Example 1.

[0043] The slag-forming agent consists of 45 wt% calcium oxide, 28 wt% silicon dioxide, 22 wt% sodium carbonate, and 5 wt% boron trioxide, which are mixed evenly and then uniformly sprinkled onto the surface of the melt in one go.

[0044] After completion, multiple samples were taken and sent to GD-MS for full elemental analysis. The results are shown in Table 4. The purity of copper was 99.9984%, reaching the 4N8 grade.

[0045] Table 4. Results of impurity element detection at each stage of Comparative Example 2 Comparative Example 3 The difference between this comparative example and Comparative Example 1 is that the composite slag-forming agent in Example 1 is used to replace the quartz-borax binary slag; otherwise, they are the same as in Comparative Example 1.

[0046] After the reaction was completed, multiple samples were taken and sent to GD-MS for elemental analysis. The results are shown in Table 5. The purity of copper was 99.9971%, reaching 4N7.

[0047] Table 5. Results of impurity element detection at each stage of Comparative Example 3 As shown in Example 1, the technical solution of this application can refine 4N grade pure copper to 6N grade ultra-high purity copper in the pilot stage. As shown in Example 2, the technical solution of this application can still achieve 6N grade copper purity and oxygen content not higher than 0.3ppm in mass production.

[0048] Comparative Example 1 used conventional pyrometallurgical refining, which only improved the copper purity from 4N to 4N6, resulting in limited purification capacity, especially for impurities such as Ag and Sn, with a very low removal rate. In Comparative Example 2, the composite slag-forming agent did not contain alumina and cerium dioxide, and the removal rate of impurities such as Ag and Sn was significantly lower than that of Example 1. Comparative Example 3, based on Comparative Example 1, used the composite slag-forming agent used in Example 1 of this application, which improved the removal rate of impurities such as Ag and Sn, but the removal rate was still low, and the copper purity did not reach the 5N level.

[0049] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper, characterized in that, Includes the following steps: S1. Heat the molten copper anode to 1120~1150℃, and under a closed micro-positive pressure condition with a micro-oxidation atmosphere of 0.5%~1.0% oxygen volume fraction and an inert carrier gas, keep it at a constant temperature for 30~45 minutes to allow high vapor pressure impurities to evaporate and be removed naturally. S2. Heat the mixture at a constant rate to 1180~1220℃, switch to a weak oxidizing atmosphere with an oxygen volume fraction of 2%~3%, add 2.0%~2.8% of the copper liquid mass of the composite slag-forming agent to the surface of the melt, react at a constant temperature for 35~50 minutes, and then remove the slag. S3. Cool the liquid at a constant rate to 1080~1100℃, switch to a high-purity inert protective atmosphere with an oxygen volume fraction of <0.1ppm, add 0.08%~0.20% of the copper liquid mass of composite deoxidizer, seal and let stand for 40~60 minutes, then remove the slag to obtain ultra-high purity copper liquid. The composite slag-forming agent is composed of the following components by mass percentage: calcium oxide 35%~45%, silicon dioxide 20%~28%, sodium carbonate 12%~18%, aluminum oxide 8%~12%, cerium dioxide 3%~6%, and boron trioxide 2%~5%; The composite deoxidizer is composed of the following components by mass percentage: 40%~60% borax, 30%~50% carbonaceous reducing agent, and 5%~10% copper-phosphorus master alloy, wherein the phosphorus content of the copper-phosphorus master alloy is 10%~15%.

2. The pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper according to claim 1, characterized in that, In S2, the multi-component composite slag-forming agent is added in stages: first, calcium oxide, silicon dioxide, and sodium carbonate are added, and after reacting for 20 minutes, aluminum oxide, cerium dioxide, and boron trioxide are added.

3. The pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper according to claim 1, characterized in that, In S1, the inert carrier gas is nitrogen or argon, and the positive pressure inside the furnace is controlled at 200~500Pa.

4. The pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper according to claim 1, characterized in that, In S3, the high-purity inert carrier gas is nitrogen or argon, and the water content is ≤0.5ppm.

5. The pyrometallurgical smelting process for preparing ultra-high purity copper by deep removal of trace impurities according to claim 1, characterized in that, In S2, the heating rate of the uniform heating is 0.8~1.2℃ / min.

6. The pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper according to claim 1, characterized in that, In S3, the cooling rate of the uniform cooling is 1.0~1.5℃ / min.

7. The pyrometallurgical process for deep removal of trace impurities to prepare ultra-high purity copper according to claim 1, characterized in that, In S3, the composite deoxidizer is wrapped in copper foil and then pressed into the melt.

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