A method for removing arsenic, antimony and bismuth from crude copper

Abstract

The present application belongs to the field of metallurgy, and discloses a method for removing arsenic, antimony and bismuth from crude copper, comprising the following steps: S1. Melting crude copper raw material to obtain molten copper liquid, and controlling the temperature of the molten copper liquid to be 1150-1250 DEG C; S2. Adding a slagging agent to the molten copper liquid, and introducing oxygen-containing gas to remove impurities from the molten copper liquid; first, maintaining the oxygen volume concentration at 0.1%-0.5%, adding a part of the slagging agent to react; then, increasing the oxygen volume concentration to 1.5%-3.0%, and adding the remaining slagging agent to react; wherein the slagging agent comprises an alkaline carbonate, an oxidizing agent and a crystal nucleus inducer; the oxidizing agent is sodium nitrate or / and potassium nitrate; S3. Allowing the molten copper liquid to be separated from the slag phase, and removing the slag to obtain refined copper liquid. The method can deeply remove arsenic, antimony and bismuth, and can reduce the amount of slag, and the slag system has good fluidity and is easy to separate, so that the copper purity is improved while the recovery rate is ensured.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for refining crude copper to remove arsenic, antimony, and bismuth. Background Technology

[0002] Copper, as a crucial basic industrial metal, directly determines a series of key performance indicators such as electrical conductivity, thermal conductivity, and mechanical strength through its purity level. In the pyrometallurgical refining process of copper, arsenic (As), antimony (Sb), and bismuth (Bi) are considered three particularly harmful impurity elements. These impurities not only severely weaken the electrical conductivity and ductility of copper materials but also cause various process defects in subsequent processing, such as electrolytic refining or continuous casting. For example, during electrolysis, they may cause passivation on the anode surface, hindering effective current conduction; while in the casting stage, they can easily lead to hot brittleness of the billet, reducing the quality of the finished product and the processing qualification rate, thus affecting the reliability and service life of the final product. Therefore, effectively controlling the content of these impurities is of great significance for ensuring the high-quality production of copper materials.

[0003] Traditionally, two processes are used to remove impurities such as arsenic, antimony, and bismuth from crude copper: oxidation volatilization and alkaline spraying for slag formation. Oxidation volatilization primarily involves simply blowing air or oxygen into the molten copper, using an oxidation reaction to convert some impurities into oxide forms. However, while this method can oxidize some impurities to a certain extent, the high solubility of arsenic, antimony, and bismuth oxides in molten copper, and the tendency of these impurities to form stable intermetallic compounds with copper, such as complex copper arsenides and copper antimony compounds, make complete separation of impurities difficult, thus posing significant challenges to subsequent deep refining processes.

[0004] The slag-forming method using caustic soda spray typically employs sodium carbonate as a slag-forming agent. It is injected into the molten copper, where the alkali reacts with impurity oxides to form slag, thus achieving separation. This method shows relatively good removal efficiency for arsenic, effectively reducing its content. However, its efficiency in removing antimony and bismuth is limited, often failing to meet the requirements for deep purification. Furthermore, when the amount of slag generated is too large, it can easily entrain some metallic copper, leading to a decrease in copper recovery rate and a corresponding increase in production costs. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a method for removing arsenic, antimony, and bismuth from crude copper. This method solves the problems of difficulty in deeply removing arsenic, antimony, and bismuth during copper refining and the difficulty in completely separating the slag from metallic copper after slag formation. The technical solution of this invention can obtain high-purity copper and ensure a high recovery rate.

[0006] The specific technical solution is as follows:

[0007] A method for refining crude copper to remove arsenic, antimony, and bismuth, characterized by comprising the following steps:

[0008] S1. Melt the crude copper raw material to obtain molten copper liquid, and control its temperature at 1150~1250℃;

[0009] S2. Add slag-forming agent to molten copper and introduce oxygen-containing gas to remove impurities from the molten copper.

[0010] First, maintain the oxygen volume concentration at 0.1%~0.5%, add 50wt%~70wt% of the total slagging agent, and react at 1150~1250℃ for 30~60 min; then increase the oxygen volume concentration to 1.5%~3.0%, add the remaining slagging agent, and react at 1150~1250℃ for 60~90 min.

[0011] The slag-forming agent comprises alkaline carbonate, an oxidant, and a crystal nucleation inducer; the oxidant is sodium nitrate and / or potassium nitrate.

[0012] S3. Let it stand to separate the copper liquid from the slag phase, remove the slag, and obtain refined copper liquid.

[0013] The main components of the crude copper raw material include: Cu content ≥ 96.5 wt%, As content ≤ 1.0 wt%, Sb content ≤ 1.0 wt%, and Bi content ≤ 0.3 wt%.

[0014] The mechanism of the above method is as follows:

[0015] The slag-forming agent of this invention utilizes the synergistic effect of its components to efficiently fix arsenic, antimony, and bismuth into the slag phase. Sodium nitrate or potassium nitrate acts as an oxidant, decomposing at high temperatures to release active oxygen, enhancing the oxidation process of As, Sb, and Bi, transforming them from elemental or low-valence states into high-valence oxides that are easier to form slag. Furthermore, sodium nitrate or potassium nitrate simultaneously oxidizes and forms slag. During oxidation, alkaline carbonates, acting as the slag matrix, provide an alkaline environment, reacting with oxides of As, Sb, and Bi to form stable sodium salts (such as Na3AsO4, Na3SbO4, and Na3BiO4), fixing them in the slag. The nucleation inducer adjusts the physical properties of the slag (such as melting point and viscosity) and acts as a heterogeneous nucleation core, promoting the growth and aggregation of arsenic, antimony, and bismuth-containing compound particles, facilitating the separation of slag from molten copper. Therefore, the slag-forming agent of this invention significantly improves the removal efficiency of arsenic, antimony, and bismuth, and the slag system exhibits good fluidity, is easy to separate, and has a high direct copper recovery rate.

[0016] Simultaneously, this invention employs a two-step enhanced removal process, simultaneously oxidizing and forming slag. The weak oxidation process selectively removes arsenic and initially removes antimony and bismuth; at lower oxygen concentrations, arsenic, due to its high volatility, partially volatilizes as As₂O₃ while being partially oxidized to form slag; this stage also allows for the initial oxidation of some antimony and bismuth, which then enter the slag phase. The strong oxidation process deeply removes antimony and bismuth; increasing the oxygen concentration ensures that the remaining, more difficult-to-oxidize antimony and bismuth are fully oxidized and react with the slag-forming agent, ultimately entering the slag phase. Stepwise addition of the slag-forming agent avoids reagent waste and maintains the continuous activity of the slag. This two-step oxidation slag-forming process improves the removal rate of antimony and bismuth and reduces the amount of slag required, preventing the entrainment of metallic copper during slag removal.

[0017] Specifically, the main reaction equations are as follows:

[0018] 4NaNO3→2Na2O+O2↑+4NO2↑;

[0019] 4As + 3O2 → 2As2O3↑;

[0020] 4As + 5O₂ → 2As₂O₅;

[0021] 4Sb + 5O2 → 2Sb2O5;

[0022] 4Bi + 5O₂ → 2Bi₂O₅;

[0023] As₂O₅ + 3Na₂O → 2Na₃AsO₄;

[0024] Sb₂O₅ + 3Na₂O → 2Na₃SbO₄;

[0025] Bi₂O₅ + 3Na₂O → 2Na₃BiO₄;

[0026] 3Na2CO3+As2O5→2Na3AsO4+3CO2↑;

[0027] 3Na2CO3+Sb2O5→2Na3SbO4+3CO2↑;

[0028] 3Na2CO3+Bi2O5→2Na3BiO4+3CO2↑;

[0029] 6Na2CO3+3SiO2+As2O5→2Na3AsO4+6CO2↑+3Na2SiO3;

[0030] 6Na2CO3+3SiO2+Sb2O5→2Na3SbO4+6CO2↑+3Na2SiO3;

[0031] 6Na2CO3+3SiO2+Bi2O5→2Na3BiO4+6CO2↑+3Na2SiO3.

[0032] Specifically, in the above method, crude copper is melted and refined in a refining furnace.

[0033] Furthermore, in step S2: the slag-forming agent preferably contains 40wt%~60wt% alkaline carbonate, 20wt%~30wt% oxidant, and 20wt%~30wt% crystal nucleation inducer.

[0034] Furthermore, in step S2: the nucleation inducing agent is preferably calcium oxide and / or silicon dioxide.

[0035] Furthermore, in step S2: the alkaline carbonate is preferably sodium carbonate and / or potassium carbonate.

[0036] Furthermore, in step S2: the amount of slag-forming agent is preferably 0.5wt% to 2.0wt% of the crude copper raw material.

[0037] Furthermore, in step S3: it is preferable to let it stand for 20 to 30 minutes.

[0038] Furthermore, in step S3: the obtained refined copper liquid can be cast into a copper anode plate.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] This invention utilizes a novel slag-forming agent to enhance the oxidation process of As, Sb, and Bi, transforming them from elemental or low-valence states into high-valence oxides that are easier to form slag, and generating stable sodium salts (such as Na3AsO4, Na3SbO4, and Na3BiO4), which are then fixed in the slag. Simultaneously, a nucleation inducer promotes the growth and aggregation of arsenic, antimony, and bismuth-containing compound particles, facilitating the separation of the slag from the molten copper. The slag-forming agent leverages the synergistic effect of its components to efficiently fix arsenic, antimony, and bismuth in the slag phase, significantly improving the removal efficiency of these substances. It can reduce the total amount of As, Sb, and Bi in the molten copper to below 0.2 wt%, and the slag system exhibits good fluidity, is easy to separate, and has a high direct copper recovery rate.

[0041] This invention employs a two-step enhanced removal process, which involves slag formation during oxidation. In the weak oxidation stage, some arsenic can be volatilized in the form of As2O3. The strong oxidation process deeply removes antimony and bismuth, allowing them to be fully oxidized and react with the slag agent. This improves the removal rate of antimony and bismuth while reducing the amount of slag, preventing the inclusion of metallic copper during slag removal, thereby reducing the impurity content in the anode copper. Attached Figure Description

[0042] Figure 1 This is a flowchart of the method for refining crude copper to remove arsenic, antimony, and bismuth in this invention. Detailed Implementation

[0043] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0044] Example 1

[0045] The crude copper used for refining arsenic, antimony, and bismuth is mainly composed of the following components: Cu 96.94 wt%, As 0.85 wt%, Sb 0.92 wt%, and Bi 0.29 wt%.

[0046] The steps are as follows:

[0047] S1. Melt the crude copper raw material in a refining furnace to obtain molten copper liquid, and control its temperature at 1150℃;

[0048] S2. Add slag-forming agent to molten copper and introduce oxygen-containing gas to remove impurities from the molten copper; the amount of slag-forming agent is 0.5 wt% of the crude copper raw material.

[0049] By controlling the oxygen flow rate, a two-step enhanced removal reaction is carried out. First, the reaction is carried out under a weak oxidizing atmosphere: the oxygen volume concentration in the furnace is maintained at 0.1%, 50 wt% of the total slagging agent is added, and the reaction is carried out at 1180℃ for 60 min, so that arsenic is preferentially oxidized, volatilized, and slagging is formed. Then, the reaction is carried out under a strong oxidizing atmosphere: the oxygen volume concentration is increased to 1.5%, the remaining slagging agent is added, and the reaction is carried out at 1180℃ for 90 min, so as to deeply remove antimony and bismuth.

[0050] The slag-forming agent consists of 40wt% sodium carbonate, 30wt% sodium nitrate, and 30wt% calcium oxide.

[0051] S3. Keep the liquid at a constant temperature for 25 minutes to allow the copper liquid to fully separate from the slag phase enriched with arsenic, antimony, and bismuth. Remove the slag to obtain high-purity refined copper liquid, and then cast the refined copper liquid into copper anode plates.

[0052] Example 2

[0053] The crude copper used for refining arsenic, antimony, and bismuth is mainly composed of the following components: Cu 97.58 wt%, As 0.54 wt%, Sb 0.43 wt%, and Bi 0.28 wt%.

[0054] The steps are as follows:

[0055] S1. Melt the crude copper raw material in a refining furnace to obtain molten copper liquid, and control its temperature at 1250℃;

[0056] S2. Add a slag-forming agent to the molten copper liquid and introduce oxygen-containing gas to remove impurities from the molten copper liquid; the amount of slag-forming agent is 2.0 wt% of the crude copper raw material.

[0057] By controlling the oxygen flow rate, a two-step enhanced removal reaction is carried out. First, the reaction is carried out under a weak oxidizing atmosphere: the oxygen volume concentration in the furnace is maintained at 0.3%, 70 wt% of the total slagging agent is added, and the reaction is carried out at 1250℃ for 30 min, so that arsenic is preferentially oxidized and volatilized and slagging is formed. Then, the reaction is carried out under a strong oxidizing atmosphere: the oxygen volume concentration is increased to 3.0%, the remaining slagging agent is added, and the reaction is carried out at 1250℃ for 60 min, so as to deeply remove antimony and bismuth.

[0058] The slag-forming agent consists of 60wt% sodium carbonate, 20wt% sodium nitrate, and 20wt% calcium oxide.

[0059] S3. Keep the liquid at a constant temperature for 20 minutes to allow the copper liquid to fully separate from the slag phase enriched with arsenic, antimony, and bismuth. Remove the slag to obtain high-purity refined copper liquid, and then cast the refined copper liquid into copper anode plates.

[0060] Example 3

[0061] The crude copper used for refining arsenic, antimony, and bismuth is mainly composed of the following components: Cu 97.89 wt%, As 0.34 wt%, Sb 0.62 wt%, and Bi 0.19 wt%.

[0062] The steps are as follows:

[0063] S1. Melt the crude copper raw material in a refining furnace to obtain molten copper liquid, and control its temperature at 1200℃;

[0064] S2. Add slag-forming agent to molten copper and introduce oxygen-containing gas to remove impurities from the molten copper; the amount of slag-forming agent is 1.5 wt% of the crude copper raw material.

[0065] By controlling the oxygen flow rate, a two-step enhanced removal reaction is carried out. First, the reaction is carried out under a weak oxidizing atmosphere: the oxygen volume concentration in the furnace is maintained at 0.5%, 60 wt% of the total slagging agent is added, and the reaction is carried out at 1150℃ for 45 min, so that arsenic is preferentially oxidized, volatilized, and slagging is formed. Then, the reaction is carried out under a strong oxidizing atmosphere: the oxygen volume concentration is increased to 2.0%, the remaining slagging agent is added, and the reaction is carried out at 1150℃ for 75 min, so as to deeply remove antimony and bismuth.

[0066] The slag-forming agent consists of 50 wt% sodium carbonate, 30 wt% sodium nitrate, and 20 wt% calcium oxide.

[0067] S3. Keep the liquid at a constant temperature for 25 minutes to allow the copper liquid to fully separate from the slag phase enriched with arsenic, antimony, and bismuth. Remove the slag to obtain high-purity refined copper liquid, and then cast the refined copper liquid into copper anode plates.

[0068] Example 4

[0069] The crude copper used for refining arsenic, antimony, and bismuth is mainly composed of the following components: Cu 97.47wt%, As 0.31wt%, Sb 0.29wt%, and Bi 0.22wt%.

[0070] The steps are as follows:

[0071] S1. Melt the crude copper raw material in a refining furnace to obtain molten copper liquid, and control its temperature at 1200 ℃;

[0072] S2. Add slag-forming agent to molten copper and introduce oxygen-containing gas to remove impurities from the molten copper; the amount of slag-forming agent is 1.5 wt% of the crude copper raw material.

[0073] By controlling the oxygen flow rate, a two-step enhanced removal reaction is carried out. First, the reaction is carried out under a weak oxidizing atmosphere: the oxygen volume concentration in the furnace is maintained at 0.5%, 50wt% of the total slagging agent is added, and the reaction is carried out at 1180℃ for 60 min, so that arsenic is preferentially oxidized and volatilized and slagging is formed. Then, the reaction is carried out under a strong oxidizing atmosphere: the oxygen volume concentration is increased to 2.0%, the remaining slagging agent is added, and the reaction is carried out at 1180℃ for 80 min, so as to deeply remove antimony and bismuth.

[0074] The slag-forming agent consists of 45 wt% sodium carbonate, 30 wt% potassium nitrate, and 25 wt% silicon dioxide.

[0075] S3. Keep the liquid at a constant temperature for 30 minutes to allow the copper liquid to fully separate from the slag phase enriched with arsenic, antimony, and bismuth. Remove the slag to obtain high-purity refined copper liquid, and then cast the refined copper liquid into copper anode plates.

[0076] Comparative Example 1

[0077] Referring to Example 1, the difference from Example 1 is that in step S2: the slag-forming agent does not contain sodium nitrate, and the composition ratio and amount of other components remain unchanged.

[0078] Other technical features are the same as in Example 1.

[0079] Comparative Example 2

[0080] Referring to Example 1, the difference from Example 1 is that in step S2, the oxygen volume concentration in the reaction under the original weak oxidizing atmosphere is adjusted to 1.5%.

[0081] Comparative Example 3

[0082] Referring to Example 1, the difference from Example 1 is that in step S2, the oxygen volume concentration in the reaction under the original strong oxidizing atmosphere is adjusted to 0.1%.

[0083] Comparative Example 4

[0084] The difference from Example 1 is that oxidation is performed first, and then a slag-forming agent is added for slag formation; specifically, step S2 is: maintaining the oxygen volume concentration in the furnace at 1.5% and reacting at 1180°C for 60 min; after the reaction is completed, the slag-forming agent is added and reacted at 1180°C for 90 min.

[0085] test

[0086] The purity of the copper anode plates obtained in each embodiment and comparative example, as well as the contents of arsenic, antimony, and bismuth, were tested; and the copper recovery rate was calculated. The copper content was determined according to the Chemical Analysis Methods for Crude Copper, Black Copper, and Anode Copper, Part 1: Determination of Copper Content (YS / T521.1-2024). The contents of arsenic, antimony, and bismuth were determined according to the Chemical Analysis Methods for Anode Copper, Part 3: Determination of Tin, Iron, Arsenic, Antimony, Bismuth, Lead, Zinc, and Nickel Contents by Inductively Coupled Plasma Atomic Emission Spectrometry (YS / T 1230.3-2018). The purity of the copper anode plates and the contents of arsenic, antimony, and bismuth are shown in Table 1, and the copper recovery rate is shown in Table 2.

[0087] Table 1. Purity of copper anode plates in each embodiment and comparative example, and their contents of arsenic, antimony, and bismuth.

[0088]

[0089] Table 2. Copper recovery rates for each embodiment and comparative example.

[0090]

[0091] As shown in Table 1, the sum of As, Sb, and Bi contents in the copper anode plates of Examples 1-4 is less than 0.2 wt%, while the sum of As, Sb, and Bi contents in Comparative Examples 1-4 is greater than 0.2 wt%. As shown in Table 2, the copper recovery rate of Examples 1-4 is greater than 99.5%, while the copper recovery rate of Comparative Examples 1-4 is less than 99.3%, especially in Comparative Example 4 where the copper recovery rate is only 99.08%. This is mainly because oxidation is performed first, followed by the addition of a slag-forming agent, resulting in less removal of impurities As, Sb, and Bi in the form of oxide volatilization; most of them must be removed by the slag-forming agent. Furthermore, adding the slag-forming agent all at once is less effective than adding it in two stages, and the slag-copper separation is incomplete. Furthermore, the high solubility of As, Sb, and Bi oxides in molten copper, coupled with the tendency of these impurity elements to form stable intermetallic compounds with copper, leads to incomplete reaction with the slag-forming agent, making complete separation of impurities difficult. Therefore, the copper recovery rate is significantly lower than that of the Examples. In conclusion, the method of this invention can effectively remove impurities from crude copper.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the removal of arsenic, antimony and bismuth from crude copper characterized in that, The method comprises the following steps: S1. Melting the raw copper material to obtain molten copper liquid, and controlling the temperature of the molten copper liquid to be 1150-1250℃; S2. Adding a slagging agent to the molten copper liquid, and introducing an oxygen-containing gas to remove impurities from the molten copper liquid; First, the oxygen gas volume concentration is maintained at 0.1%-0.5%, 50wt%-70wt% of the total amount of the slagging agent is added, and the reaction is carried out at 1150-1250℃ for 30-60 min; then, the oxygen gas volume concentration is increased to 1.5%-3.0%, the remaining slagging agent is added, and the reaction is carried out at 1150-1250℃ for 60-90 min; The slagging agent comprises an alkaline carbonate, an oxidizing agent, and a crystal nucleus inducer; the oxidizing agent is sodium nitrate or / and potassium nitrate; the alkaline carbonate is sodium carbonate or / and potassium carbonate; and the crystal nucleus inducer is calcium oxide or / and silicon dioxide. The amount of the slagging agent is 0.5wt%-2.0wt% of the raw copper material; S3. Static setting, separation of the copper liquid and the slag phase, and removal of the slag to obtain refined copper liquid.

2. The method of claim 1, wherein, In step S2, the components of the slagging agent comprise 40wt%-60wt% of the alkaline carbonate, 20wt%-30wt% of the oxidizing agent, and 20wt%-30wt% of the crystal nucleus inducer.

3. The method according to claim 1 or 2, characterized in that, In step S3, the static setting is performed for 20-30 min.

4. The method according to claim 1 or 2, characterized in that, The main components of the raw copper material include Cu content ≥96.5wt%, As content ≤1.0wt%, Sb content ≤1.0wt%, and Bi content ≤0.3wt%.

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