A copper melt smelting desulfurization process

Abstract

This invention relates to the field of copper smelting technology, and in particular to a desulfurization process for copper melt smelting, comprising the following steps: melting copper or copper alloy raw materials to obtain copper melt; removing the charcoal covering layer on the surface of the copper melt, and adding a desulfurization slagging agent composed of calcium oxide, sodium carbonate, magnesia, and refractory powder; heating the copper melt to 1250–1350°C and holding it at that temperature for 30–60 minutes; after the holding period, removing slag and taking samples for testing; if the sample meets the standards, adding charcoal to complete the desulfurization; otherwise, adding more desulfurization slagging agent. The ratio of the desulfurization slagging agent is matched with the reaction characteristics of sulfur in the copper melt, allowing it to fully react chemically with sulfur to generate sulfide slag that is easily separated from the copper melt, thus improving the thoroughness of desulfurization from the source; simultaneously, timed stirring is performed during the constant-temperature slagging process to promote full contact between the desulfurization slagging material and the copper melt, which helps to improve the uniformity of desulfurization and ensures a stable and reliable desulfurization effect.

Description

Technical Field

[0001] This invention relates to the field of copper smelting technology, and in particular to a desulfurization process for copper melt smelting. Background Technology

[0002] The smelting process is the core step in producing qualified copper materials, directly determining their subsequent processing performance and reliability. During the smelting of copper and copper alloys, factors such as oil content in raw materials and sulfur content in furnace lining materials can easily lead to excessive sulfur content in the molten copper after smelting. Since sulfur is infinitely soluble in copper, as a harmful impurity in copper processing, excessive sulfur content can cause a series of quality problems.

[0003] Given the serious harm that sulfur poses to the quality of copper, various copper material standards have imposed strict controls on sulfur content, generally requiring sulfur content to be ≤0.0050% (i.e. 50ppm). Therefore, desulfurization treatment has become a necessary step in the copper smelting process.

[0004] Currently, mature desulfurization technologies are only applied in the copper smelting industry, with the mainstream method being the oxidation process. This involves introducing compressed air into the furnace to achieve oxidative desulfurization, and the resulting sulfur-containing flue gas is recovered to produce sulfuric acid. However, this technology cannot be directly adapted to the smelting conditions of the copper processing industry, and the copper processing sector still lacks efficient and practical desulfurization technologies. The industry commonly uses the traditional method of adding new metals to dilute the sulfur content, which not only has extremely low desulfurization efficiency but also results in a large amount of metal raw material occupation and resource waste, high production costs, and unstable desulfurization effects. It is difficult to stably control the sulfur content of molten copper below 50 ppm, failing to meet the stringent sulfur content standards for high-end copper materials.

[0005] Therefore, it is urgent for technical personnel to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a copper melt smelting desulfurization process, which aims to solve the problems that existing desulfurization processes are unable to achieve deep desulfurization, cannot stably control the sulfur content of copper melt below the design allowable value, and thus cannot meet the strict requirements of copper material standards for sulfur content.

[0007] This invention relates to a copper melt smelting desulfurization process, comprising the following steps: S1. Place copper or copper alloy raw materials in a furnace and melt them to obtain copper melt; S2. Remove the charcoal covering layer from the surface of the copper melt and add a desulfurization slag-forming agent to the copper melt at a rate of 8-12 kg per ton of copper melt. The desulfurization slag-forming agent consists of 40-55% calcium oxide, 20-35% sodium carbonate, 2-5% magnesia, and the remainder refractory powder by mass percentage. S3. Heat the copper melt to 1250-1350℃ and hold for 30-60 minutes, stirring every 3-5 minutes during the holding period; S4. After the heat preservation is completed, remove the surface slag and take a sample to test the sulfur content. If the sulfur content is ≤50ppm, add charcoal to the copper melt again to cover it, and the desulfurization is completed. If the sulfur content is >50ppm, add the desulfurization slag-forming agent again, with an addition amount of 1 to 3 kg per ton of copper melt, and continue to heat preservation for 10 to 30 minutes. Then remove the slag and take a sample again for testing until the sulfur content is <50ppm.

[0008] As a further improvement to the technical solution disclosed in this invention, in S2, the desulfurization slag-forming agent is pre-dried and dehydrated at 300-500°C for 1-2 hours, and then added to the copper melt in the form of a uniform powder after cooling.

[0009] As a further improvement to the technical solution disclosed in this invention, the magnesia is preferably active fused magnesia with a magnesium oxide content of ≥96% and a particle size controlled at 30-60 mesh, while the particle size of calcium oxide and sodium carbonate is 50-80 mesh.

[0010] As a further improvement to the technical solution disclosed in this invention, in S3, the isothermal desulfurization process adopts argon bottom blowing stirring, the argon purity is ≥99.99%, and the flow rate is controlled at 1.5~3L / min.

[0011] As a further improvement to the technical solution disclosed in this invention, the stirring adopts an intermittent mode: stirring for 3 minutes, stopping for 2 minutes, and repeating the cycle until the heat preservation ends.

[0012] As a further improvement to the technical solution disclosed in this invention, the desulfurization slag-forming agent is added in stages: 70% is added initially, and the remaining 30% is added after heat preservation for 10 minutes.

[0013] As a further improvement to the technical solution disclosed in this invention, the entire desulfurization process is carried out in a closed medium-frequency furnace, and the furnace is maintained at a slightly positive pressure of 150-320 Pa.

[0014] As a further improvement to the technical solution disclosed in this invention, after desulfurization is completed and the copper melt is re-covered with charcoal, deoxidation treatment is performed on the copper melt; when the copper melt is pure copper, phosphorus copper is used for deoxidation, and the phosphorus content is controlled to be 10-50 ppm; when the copper melt is cupronickel, copper-magnesium master alloy containing 16-25% magnesium is used for deoxidation, and the addition ratio is 0.03-0.07%.

[0015] In practical applications, the copper melt smelting desulfurization process disclosed in this invention can achieve at least the following beneficial technical effects, specifically: 1) The desulfurization slagging agent formulation is matched with the reaction characteristics of sulfur in the copper melt, allowing it to fully react chemically with sulfur to generate sulfide slag that is easily separated from the copper melt, thus improving the thoroughness of desulfurization from the source. Furthermore, the dosage of the desulfurization slagging agent is rationally controlled during the smelting and desulfurization process to ensure the desulfurization reaction proceeds fully. 2) Heat the copper melt to a suitable temperature and hold it at that temperature to provide good thermodynamic conditions for the subsequent desulfurization reaction. In addition, timed stirring is carried out to promote full contact between the flux and the copper melt, which helps to improve the uniformity of desulfurization. After the holding time is completed, slag is removed and samples are taken for testing. If the sulfur content does not meet the standard, an appropriate amount of desulfurization slag-forming agent is added in time, and the holding time is extended. The test is repeated until the standard is met, forming a complete closed-loop process to ensure that the sulfur content of each batch of copper melt meets the standard requirements. Detailed Implementation

[0016] The technical solution disclosed in this invention will be further described in detail below with reference to specific embodiments. By implementing a copper melt smelting desulfurization process in conjunction with a desulfurization slag-forming agent, deep desulfurization of the copper melt is achieved, with the sulfur content stably controlled below 50 ppm and the purity of the copper melt meeting the standards. Specific embodiments are as follows: Desulfurization slagging agent The desulfurization slag-forming agent used in this invention, by mass percentage, consists of 40-55% calcium oxide, 20-35% sodium carbonate, 2-5% magnesia, and the balance being refractory powder.

[0017] The magnesia is active fused magnesia with a magnesium oxide content of ≥96% and a particle size controlled between 30 and 60 mesh; the calcium oxide and sodium carbonate have a particle size of 50 to 80 mesh; and the refractory powder has a particle size of 100 to 200 mesh.

[0018] The detailed preparation method of the desulfurization slagging agent includes the following steps: 1) Weigh out calcium oxide, sodium carbonate, activated fused magnesia and refractory powder according to the proportions, place each raw material in a drying oven and pre-dry at 100-120℃ for 2-3 hours to remove free moisture; 2) Add the pre-dried calcium oxide, sodium carbonate, and activated fused magnesia into a high-speed mixer and mix at a speed of 400-600 r / min for 8-12 min to obtain a base mixture; 3) Add refractory powder to the base mixture and continue mixing at 300-400 r / min for 10-15 min to obtain a uniformly mixed powder; 4) Place the uniformly mixed powder at 300-500℃ to dry and dehydrate for 1-2 hours, then cool to room temperature to obtain the desulfurization slagging agent product.

[0019] Copper melt smelting desulfurization process Example 1 S1. Pure copper raw material is placed in the furnace and melted to obtain copper melt; the desulfurization process is carried out in a closed medium frequency furnace, and the furnace is maintained at a slight positive pressure of 200Pa. S2. Remove the charcoal covering layer from the surface of the copper melt and add the desulfurization and slag-forming agent in stages; by mass percentage: calcium oxide 45%, sodium carbonate 30%, activated fused magnesia 3%, and the remainder is refractory powder; the total amount added is 10 kg per ton of copper melt. S3. Heat the copper melt to 1300℃ and hold for 45 minutes. The isothermal desulfurization process uses argon gas with a purity ≥99.99% for bottom blowing and stirring at a flow rate of 2.0 L / min. The stirring is done in an intermittent mode: stir for 3 minutes, stop for 2 minutes, and repeat until the holding period ends. S4. After the heat preservation is completed, the surface slag is removed, and the sulfur content is sampled and tested to be 32ppm. Charcoal is added back to the copper melt for covering, and phosphorus copper is used for deoxidation. Desulfurization is completed.

[0020] Example 2 S1. Place the cupronickel raw material in the furnace and melt it to obtain copper melt; the desulfurization process is carried out in a closed medium frequency furnace, and the furnace is maintained at a slight positive pressure of 200Pa. S2. Remove the charcoal covering layer from the surface of the copper melt and add the desulfurization and slag-forming agent in stages; by mass percentage: calcium oxide 50%, sodium carbonate 25%, activated fused magnesia 4%, and the remainder is refractory powder; the total amount added is 10 kg per ton of copper melt. The specific steps for adding the desulfurization slag-forming agent in stages are as follows: First, add 70% of the total amount of the desulfurization slag-forming agent, stir evenly and keep warm for 10 minutes to allow the desulfurization slag-forming agent to initially and fully contact and react with the copper melt; then add the remaining 30% of the desulfurization slag-forming agent, continue to stir evenly, and complete all the feeding operations. S3. Heat the copper melt to 1300℃ and hold for 45 minutes. The isothermal desulfurization process uses argon gas with a purity ≥99.99% for bottom blowing and stirring at a flow rate of 2.0 L / min. The stirring is done in an intermittent mode: stir for 3 minutes, stop for 2 minutes, and repeat until the holding period ends. S4. After the heat preservation is completed, the surface slag is removed, and the sulfur content is tested to be 56 ppm. Desulfurization slag-forming agent is added again at a rate of 2 kg per ton of copper melt, and the heat preservation is continued for 20 minutes. After that, the slag is removed and the sample is tested again, and the sulfur content is 26 ppm. Charcoal is added back to cover the copper melt, and copper-magnesium intermediate alloy containing 20% ​​magnesium is used for deoxidation at a ratio of 0.05%. Desulfurization is completed. It should be noted that the desulfurization slagging agent should be added a maximum of 2 times, and the total amount of desulfurization slagging agent added per ton of copper melt should not exceed 12 kg; if the sulfur content is still >50 ppm after 2 additions, the addition should be stopped and the smelting should be restarted.

[0021] Example 3 S1. Place the copper alloy raw material in the furnace and melt it to obtain copper melt; the desulfurization process is carried out in a closed medium frequency furnace, and the furnace is maintained at a slight positive pressure of 200Pa. S2. Remove the charcoal covering layer from the surface of the copper melt and add the desulfurization and slag-forming agent in stages; by mass percentage: calcium oxide 40%, sodium carbonate 35%, activated fused magnesia 5%, and the remainder is refractory powder; the total amount added is 10 kg per ton of copper melt. S3. Heat the copper melt to 1300℃ and hold for 45 minutes. The isothermal desulfurization process uses argon gas with a purity ≥99.99% for bottom blowing and stirring at a flow rate of 2.0 L / min. The stirring is done in an intermittent mode: stir for 3 minutes, stop for 2 minutes, and repeat until the holding period ends. S4. After the heat preservation is completed, the surface slag is removed, and the sulfur content is sampled and tested to be 38ppm. Charcoal is added back to cover the copper melt, and phosphorus copper is used for deoxidation. Desulfurization is completed.

[0022] Comparative Example 1 S1. Place pure copper raw material in a furnace and melt it to obtain copper melt; S2. Remove the charcoal covering layer from the surface of the copper melt and add calcium carbonate-based desulfurizer in one go, at a rate of 5 kg per ton of copper melt. The calcium carbonate-based desulfurizer is composed of 75% calcium carbonate, 12% fluorite, and 13% talc by mass percentage.

[0023] S3. Heat the copper melt to 1300℃ and hold for 45 minutes.

[0024] S4. After the insulation is completed, remove the surface slag and proceed directly to the next process.

[0025] The desulfurization performance of the copper melts obtained in Examples 1-3 and Comparative Example 1 was tested, and the test results are shown in the table below: Test results show that the copper melt smelting desulfurization process and supporting special desulfurization and slag-forming agent used in Examples 1-3 of this invention have significantly better desulfurization effects than traditional processes. They can stably achieve deep desulfurization of copper melt, keeping the sulfur content consistently below 50 ppm, meeting the stringent sulfur content requirements of high-end copper materials. Furthermore, the desulfurization uniformity is excellent, and the slag and copper melt are thoroughly separated, effectively preventing slag phase inclusions from being carried into the melt. Simultaneously, the oxidation increment of the copper melt is low, maximizing the protection of the copper melt's purity and ensuring a 100% desulfurization compliance rate for each batch. Among these, Example 2 shows the best overall performance in terms of desulfurization depth, desulfurization uniformity, slag separation effect, and melt oxidation control.

[0026] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A copper melt smelting desulfurization process, characterized in that, Includes the following steps: S1. Place copper or copper alloy raw materials in a furnace and melt them to obtain copper melt; S2. Remove the charcoal covering layer from the surface of the copper melt and add a desulfurization and slag-forming agent to the copper melt at a rate of 8-12 kg per ton of copper melt. The desulfurization and slag-forming agent is composed of 40-55% calcium oxide, 20-35% sodium carbonate, 2-5% magnesia, and the balance refractory powder by mass percentage. S3. Heat the copper melt to 1250-1350℃ and hold for 30-60 minutes, stirring every 3-5 minutes during the holding period; S4. After the heat preservation is completed, remove the surface slag and take a sample to test the sulfur content. If the sulfur content is ≤50ppm, add charcoal to the copper melt again to cover it, and the desulfurization is completed. If the sulfur content is >50ppm, add the desulfurization slag-forming agent again, with an addition amount of 1 to 3 kg per ton of copper melt, continue to keep it heated for 10 to 30 minutes, then remove the slag and take a sample again to test until the sulfur content is <50ppm.

2. The copper melt smelting desulfurization process according to claim 1, characterized in that, In S2, the desulfurization slag-forming agent is pre-dried and dehydrated at 300-500℃ for 1-2 hours, and then added to the copper melt in the form of a uniform powder after cooling.

3. The copper melt smelting desulfurization process according to claim 2, characterized in that, The magnesia is active fused magnesia with a magnesium oxide content of ≥96% and a particle size controlled between 30 and 60 mesh, while the calcium oxide and sodium carbonate have a particle size of 50 to 80 mesh.

4. The copper melt smelting desulfurization process according to claim 1, characterized in that, In S3, the isothermal desulfurization process uses argon bottom blowing and stirring, with argon purity ≥99.99% and flow rate controlled at 1.5~3L / min.

5. The copper melt smelting desulfurization process according to claim 4, characterized in that, The stirring is done in an intermittent mode: stir for 3 minutes, then stop for 2 minutes, and repeat this cycle until the heat preservation is finished.

6. The copper melt smelting desulfurization process according to claim 1, characterized in that, The desulfurization slag-forming agent is added in stages: 70% is added initially, and the remaining 30% is added after holding the temperature for 10 minutes.

7. The copper melt smelting desulfurization process according to claim 1, characterized in that, The entire desulfurization process is carried out in a closed medium-frequency furnace, and the furnace is maintained at a slightly positive pressure of 150-320 Pa.

8. The copper melt smelting desulfurization process according to any one of claims 1-7, characterized in that, After desulfurization is completed and the copper melt is re-covered with charcoal, it undergoes deoxidation treatment. When the copper melt is pure copper, phosphorus copper is used for deoxidation, and the phosphorus content is controlled at 10-50 ppm. When the copper melt is cupronickel, copper-magnesium master alloy containing 16-25% magnesium is used for deoxidation, with an addition ratio of 0.03-0.07%.

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