Method for vacuum directional vulcanization and arsenic removal of arsenic-containing solid waste from copper smelting

Abstract

The present application belongs to the technical field of non-ferrous metal smelting, and provides a method for the vacuum directional vulcanization and arsenic removal of arsenic-containing solid waste from copper smelting. In the present application, black copper sludge and contaminated acid sulfide slag are mixed and then smelted under vacuum conditions to achieve the directional vulcanization of the black copper sludge by the contaminated acid sulfide slag, so as to generate Cu2S and metal As; and then the vulcanization product is subjected to vacuum distillation according to the difference of saturated vapor pressures, such that As is condensed in a condensation area in a vapor form; and Cu2S is not volatilized and left in residues, thereby achieving the separation of Cu2S and metal As. The present application achieves the recovery of arsenic from the black copper sludge and the contaminated acid sulfide slag, such that non-toxic metal arsenic having an economic value is obtained; in addition, the generated Cu2S can be directly returned to a copper blowing system, thereby achieving the comprehensive utilization of valuable elements. After the treatment by means of the method of the present application, the recovery rate of Cu2S is higher than 90%, and the purity is greater than 95%, thereby satisfying the purity standard of copper matte in copper blowing; and the direct recovery rate of condensed As is higher than 90%, and the purity is greater than 99.5%.

Description

A method for removing arsenic from arsenic-containing solid waste from copper smelting by vacuum directional sulfidation

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on July 11, 2023, with application number CN202310847831.1 and invention name “A method for vacuum directional sulfidation dearsenicization of arsenic-containing solid waste from copper smelting”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of nonferrous metal smelting, and in particular to a method for removing arsenic from arsenic-containing solid waste from copper smelting by vacuum directional sulfidation. Background Art

[0003] In recent years, with the scarcity of copper resources, the mining of high-arsenic copper ores has been on the rise, especially in domestic concentrates, where some arsenic content can reach over 10% by weight. Depending on the characteristics of the smelting process, approximately 45-50% by weight of arsenic enters the smelting slag. Some plants have implemented slag beneficiation processes, resulting in approximately 10-15% by weight of arsenic entering the slag concentrate, 30-40% by weight entering the tailings, approximately 15% by weight entering the waste acid, and approximately 15% entering the anode copper. As the electrolysis process progresses, it gradually enters wet-process materials such as anode mud, black copper mud, and crude copper sulfate, ultimately generating arsenic-containing solid wastes such as tailings, slag concentrate, black copper mud, anode mud, crude copper sulfate, and sulfide slag.

[0004] Black copper mud is a black mud-like substance produced when impurities such as As, Pd, and Bi in the copper electrolyte are separated out at the cathode together with Cu during electrolytic copper removal and impurity removal. The main elements in black copper mud are Cu and As (containing about 40wt% copper and about 20wt% arsenic, mainly existing in the form of Cu3As), while other impurities (such as Bi, Pb, Sb, and S) are relatively low in content. Dirty acid sulfide slag is a sulfide precipitate with a relatively small solubility product formed by the addition of a sulfiding agent when purifying dirty acid using a sulfiding process in the copper smelting process. In addition to containing a large amount of As and S (containing about 40wt% arsenic and about 36wt% sulfur, mainly existing in the form of As2S3), the dirty acid sulfide slag also contains valuable elements such as Cu, Pb, and Re. Most copper smelting plants do not have a good product form for the recovery of As. Instead, they either store black copper mud and dirty acid sulfide slag or simply return to the furnace for smelting. Because black copper sludge and waste acid sulfide slag contain large amounts of As, storing them not only requires a large amount of space, but the As in them will undergo a series of reactions with air and water, causing significant environmental damage. If black copper sludge and waste acid sulfide slag are returned to the copper smelting process, impurities such as As, Sb, and Bi will circulate in the system, seriously affecting the direct metal recovery rate, reducing equipment production capacity, and increasing energy consumption.

[0005] Summary of the Invention

[0006] In view of this, the purpose of this application is to provide a method for vacuum directional sulfidation dearsenicization of arsenic-containing solid waste from copper smelting, which can achieve dearsenicization while comprehensively recovering valuable elements such as Cu and S in black copper mud and dirty acid sulfidation slag.

[0007] In order to achieve the above-mentioned invention objectives, this application provides the following technical solutions:

[0008] The present application provides a method for removing arsenic from arsenic-containing solid waste from copper smelting by vacuum directional sulfidation, comprising the following steps:

[0009] Mixing black copper mud and dirty acid sulfide slag to obtain a mixture;

[0010] Pressing the mixture into a shape to obtain a green body;

[0011] The green body is melted under vacuum conditions to undergo sulfidation to obtain a sulfided product; the sulfided product includes Cu2S and metallic As;

[0012] The sulfide product is subjected to vacuum distillation to obtain metallic arsenic in the condensation zone, and the distillation residue is mainly Cu2S; the pressure of the vacuum distillation is 1-100 Pa, and the temperature is 1023-1273K; the temperature of the condensation zone is 373-573K.

[0013] Preferably, the arsenic content in the black copper mud is 10-20 wt%, and the copper content is 30-40 wt%.

[0014] Preferably, the arsenic content in the polluted acid sulfide slag is 38-42 wt%, and the sulfur content is 35-39 wt%.

[0015] Preferably, the mass ratio of the black copper mud to the dirty acid sulfide slag is 1:(0.2-5).

[0016] Preferably, the smelting temperature is 673-973 K, the holding time is 30-120 min, and the pressure is 1-10000 Pa.

[0017] Preferably, the compression molding pressure is 8 to 20 MPa.

[0018] Preferably, the vacuum distillation time is 30 to 120 minutes.

[0019] Preferably, before the smelting, the green body is dried.

[0020] Preferably, the average particle size of the mixture is 75 to 90 μm.

[0021] Preferably, the green body is a cylindrical body with a height of 5 to 10 mm and a diameter of 25 to 30 mm.

[0022] Preferably, Cu and As in the black copper mud mainly exist in the form of Cu3As.

[0023] Preferably, As and S in the polluted acid sulfide slag mainly exist in the form of As2S3.

[0024] Preferably, the drying temperature is 110° C. and the drying time is 4 hours.

[0025] Preferably, the recovery rate of Cu2S in the sulfidation product is higher than 90%, and the purity is greater than 95%.

[0026] Preferably, the direct yield of As in the sulfidation product is higher than 90% and the purity is higher than 99.5%.

[0027] The present application provides a method for vacuum directional sulfidation dearsenicization of arsenic-containing solid waste from copper smelting, comprising the following steps: mixing black copper mud and dirty acid sulfidation slag to obtain a mixture; pressing the mixture into shape to obtain a green body; smelting the green body under vacuum conditions to cause sulfidation to obtain a sulfide product; the sulfide product includes Cu2S and metallic As; vacuum distilling the sulfide product to obtain metallic arsenic in a condensation zone, and the distillation residue is mainly Cu2S; the vacuum distillation pressure is 1 to 100 Pa, and the temperature is 1023 to 1273K; the temperature of the condensation zone is 373 to 573K.

[0028] In the present application, black copper mud and dirty acid sulfided slag are mixed and then smelted under vacuum conditions to achieve directionally sulfided black copper mud by dirty acid sulfided slag to generate Cu2S and metallic As. Then, the sulfided product is vacuum distilled according to the difference in saturated vapor pressure. As is condensed in the condensation zone in the form of vapor; while Cu2S does not volatilize and remains in the residue, thereby achieving the separation of Cu2S and metallic As.

[0029] This application achieves the recovery of arsenic from black copper sludge and waste acid sulfide slag, obtaining non-toxic and economically valuable metallic arsenic. The generated Cu2S can be directly returned to the copper converting system, achieving comprehensive utilization of valuable elements. Results from the examples show that after treatment using this method, the recovery rate of Cu2S exceeds 90%, with a purity greater than 95%, meeting the purity standards for copper matte in copper converting. The direct recovery rate of condensed As exceeds 90%, with a purity greater than 99.5%.

[0030] This application realizes the coordinated treatment of two arsenic-containing solid wastes, namely, copper smelting acid sulfide slag and black copper mud. The process flow is short, the operation is simple, the resource recovery rate is improved, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a flow chart of the method for vacuum directional sulfidation dearsenicization of arsenic-containing solid waste from copper smelting of the present application;

[0032] Figure 2 is a graph showing the variation of saturated vapor pressure of different substances with temperature;

[0033] FIG3 is an XRD diagram of the black copper mud raw material in Example 1;

[0034] FIG4 is an XRD pattern of the distillation residues of Examples 1 and 2;

[0035] FIG5 is an SEM image of the mixed condensation products collected in the condensation zone of Example 1 and Example 2. DETAILED DESCRIPTION

[0036] The present application provides a method for removing arsenic from arsenic-containing solid waste from copper smelting by vacuum directional sulfidation, comprising the following steps:

[0037] Mixing black copper mud and dirty acid sulfide slag to obtain a mixture;

[0038] Pressing the mixture into a shape to obtain a green body;

[0039] The green body is melted under vacuum conditions to undergo sulfidation to obtain a sulfided product; the sulfided product includes Cu2S and metallic As;

[0040] The sulfide product is subjected to vacuum distillation to obtain metallic arsenic in the condensation zone, and the distillation residue is mainly Cu2S; the pressure of the vacuum distillation is 1-100 Pa, and the temperature is 1023-1273K; the temperature of the condensation zone is 373-573K.

[0041] The present application mixes black copper mud and dirty acid sulfide slag to obtain a mixture.

[0042] In the present application, the black copper mud is preferably arsenic-containing solid waste generated on the surface of cathode copper during the copper refining process. The arsenic content in the black copper mud is preferably 10-20 wt%, more preferably 13-18 wt%, and the copper content is preferably 30-40 wt%, more preferably 32-38 wt%. In the present application, the Cu and As in the black copper mud are primarily present in the form of Cu3As. In the present application, the black copper mud inevitably also contains impurities such as Bi, Pb, and S.

[0043] In the present application, the waste acid sulfide slag is preferably arsenic-containing solid waste generated by treating waste acid in an acid production system using a sulfidation process. The waste acid sulfide slag preferably contains 38-42 wt% arsenic and 35-39 wt% sulfur. In the present application, As and S in the waste acid sulfide slag primarily exist in the form of As2S3. The waste acid sulfide slag inevitably also contains valuable elements such as Cu, Pb, and Re.

[0044] In the present application, the mass ratio of the black copper mud to the dirty acid sulfide slag is preferably 1:(0.2-5), more preferably 1:(1-4), and further preferably 1:(2-3).

[0045] The present application has no special requirements for the mixing process, and any method known in the art that can uniformly mix the black copper mud and the dirty acid sulfide slag can be used.

[0046] In the present application, the average particle size of the mixture is preferably 75 to 90 μm, more preferably 80 to 85 μm.

[0047] After obtaining the mixed material, the present application presses the mixed material into a shape to obtain a green body.

[0048] In the present application, the pressure of the press molding is preferably 8-20 MPa, more preferably 9-11 MPa. In the present application, the green billet is preferably a cylindrical billet with a height of preferably 5-10 mm and a diameter of preferably 25-30 mm. The press molding of the mixture in the present application facilitates more complete contact between the black copper mud and the dirty acid sulfide slag, reduces the volatilization of the sulfide reactant As2S3, and promotes a more complete directional sulfide reaction process.

[0049] After obtaining the green body, the present application melts the green body under vacuum conditions to cause sulfidation to occur, thereby obtaining a sulfidation product; the sulfidation product includes Cu2S and metallic As.

[0050] Before the smelting, the present application preferably further comprises drying the green body. In the present application, the drying temperature is preferably 110° C. and the drying time is preferably 4 hours.

[0051] In the present application, the smelting is preferably carried out in a vacuum reduction furnace; the smelting temperature is preferably 673-973K, more preferably 700-900K, and even more preferably 730-873K; the holding time of the smelting is preferably 30-120min, more preferably 40-100min, and even more preferably 60-80min; the smelting pressure is preferably 1-10000Pa, more preferably 100-9000Pa, and even more preferably 1000-8000Pa. In the smelting process of the present application, the main chemical reaction occurring is: 2Cu3As+As2S3=3Cu2S+4As.

[0052] In the present application, the sulfide product includes Cu2S and metallic As, and inevitably contains other impurity elements or sulfides of other impurity elements.

[0053] After obtaining the sulfide product, the present application performs vacuum distillation on the sulfide product to obtain metallic arsenic in the condensation zone, and the distillation residue is mainly Cu2S; the pressure of the vacuum distillation is 1~100Pa, and the temperature is 1023~1273K; the temperature of the condensation zone is 373~573K.

[0054] In the present application, the pressure of the vacuum distillation is 1-100 Pa, preferably 10-90 Pa, more preferably 20-80 Pa; the temperature of the vacuum distillation is 1023-1273 K, preferably 1073-1223 K, more preferably 1100-1173 K; the temperature of the condensation zone is 373-573 K, preferably 400-550 K, more preferably 450-500 K. In the present application, the time of the vacuum distillation is preferably 30-120 min, more preferably 50-100 min, and even more preferably 60-90 min.

[0055] In this application, the sulfide product is vacuum distilled based on the difference in saturated vapor pressure. The saturated vapor pressure of metallic As is significantly different from that of Cu2S and other impurities (see Figure 2). Therefore, the temperature can be controlled to separate the metallic As, and As condenses in the condensation zone in the form of vapor. However, the saturated vapor pressure difference between Cu2S and other impurities is not large, and thus cannot be completely separated by vacuum distillation. However, the content of other impurities is relatively low, so the recovery rate and purity of Cu2S in the residue can ultimately reach a high level, thereby achieving the separation of Cu2S and metallic As.

[0056] Figure 1 is a process flow chart of the method of the present application. As shown in Figure 1, the present application mixes black copper mud and dirty acid sulfide slag to obtain a mixture; the mixture is pressed into shape to obtain a green body; the green body is smelted under vacuum conditions to undergo sulfidation to obtain a sulfide product; the sulfide product includes Cu2S and metallic As; the sulfide product is vacuum distilled to obtain metallic arsenic in the condensation zone, and the distillation residue is mainly Cu2S. After treatment by the method of the present application, the recovery rate of Cu2S is higher than 90%, and the purity is greater than 95%, meeting the purity standard of copper matte in copper converting; the direct recovery rate of condensed As is higher than 90%, and the purity is greater than 99.5%.

[0057] The method for vacuum directional sulfidation arsenic removal from arsenic-containing solid waste from copper smelting provided by the present application is described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present application.

[0058] Example 1

[0059] Taking the black copper mud and dirty acid sulfide slag of a domestic copper smelter as an example (composition is shown in Table 1), the materials were mixed in a mass ratio of black copper mud to dirty acid sulfide slag of 1:1.5 to obtain a mixture with an average particle size of 80 μm. The mixture was pressed into a cylindrical green body with a diameter of 30 mm and a height of 10 mm under a pressure of 20 MPa; the green body was placed in a drying oven at a temperature of 110°C for 4 h; the dried green body was placed in a vacuum reduction furnace; the system pressure was controlled to 7500 Pa, and the temperature was raised from room temperature to 773K at a rate of 15°C / min and kept warm for 60 min to generate a sulfide product, the main component of which was Cu 2S and metallic As; then, the sulfide product is vacuum distilled, the system pressure is controlled at 10Pa, the temperature is raised from room temperature to 1023K at a heating rate of 15°C / min, and the temperature is kept at 573K for 60 minutes. The temperature of the condensation area is controlled at 573K, and the separation of Cu2S and As in the sulfide product is achieved based on the difference in saturated vapor pressure; the distillation residue is Cu2S, and the condensation area is metallic arsenic. After treatment by the above method, the recovery rate of Cu2S reaches 92.35%, and the purity reaches 95.56%, which meet the purity standard of copper matte in copper refining; the direct recovery rate of the condensed As reaches 92.79%, and the purity reaches 99.51%.

[0060] Table 1 Main chemical components of black copper mud and waste acid sulfide slag (%)

[0061] Example 2

[0062] Taking the black copper mud and dirty acid sulfide slag of a domestic copper smelter (the main chemical composition is shown in Table 2) as an example, the materials were mixed in a mass ratio of 1:2 to obtain a mixture with an average particle size of 85 μm. The mixture was pressed into a cylindrical green body with a diameter of 30 mm and a height of 10 mm under a pressure of 20 MPa; the green body was placed in a drying oven at a temperature of 110 ° C for 4 h; the dried green body was placed in a vacuum reduction furnace; the system pressure was controlled to 6000 Pa, and the temperature was increased from room temperature to 973 K at a rate of 15 ° C / min, and kept warm for 120 min to generate sulfide products, mainly Cu2 S and metallic As; then, the sulfide product is subjected to vacuum distillation, the system pressure is controlled at 10Pa, the temperature is raised from room temperature to 1273K at a rate of 15°C / min, and the temperature is kept for 60 minutes. The temperature of the condensation area is controlled at 473K, and the Cu2S and As in the sulfide product are separated according to the difference in saturated vapor pressure; the distillation residue is Cu2S, and the condensation area is metallic arsenic. After treatment by the above method, the recovery rate of Cu2S reaches 94.75%, and the purity reaches 97.23%, which meet the purity standard of copper matte in copper refining; the direct recovery rate of As by directionally condensed reaches 96.59%, and the purity reaches 99.89%.

[0063] Table 2 Main chemical components of black copper mud and waste acid sulfide slag (%)

[0064] Structural characterization:

[0065] The black copper mud of Example 1 was characterized by XRD, and the results are shown in Figure 3. As shown in Figure 3, the main components of the black copper mud are Cu3As and a small amount of PbSO4.

[0066] The distillation residues of Examples 1 and 2 were characterized by XRD, and the results are shown in Figure 4. As shown in Figure 4, in both embodiments, the system pressure was controlled at 10 Pa, the vacuum distillation reaction temperatures were 1023 and 1273 K, respectively, and the reaction time was 60 min, resulting in the final residue being Cu2S.

[0067] The mixed condensation products from the condensation zones of Example 1 and Example 2 were characterized by SEM, and the results are shown in FIG5 .

[0068] Although the above embodiment provides a detailed description of the present application, it is only a part of the embodiments of the present application rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present application.

Claims

1. A method for removing arsenic from arsenic-containing solid waste from copper smelting by vacuum directional sulfidation, characterized in that: The following steps are involved: Mixing black copper mud and dirty acid sulfide slag to obtain a mixture; Pressing the mixed material into a shape to obtain a green body; The green body is melted under vacuum conditions to undergo sulfurization to obtain a sulfurized product; The sulfidation product includes Cu2S and metal As; The sulfide product is subjected to vacuum distillation to obtain metallic arsenic in the condensation zone, and the distillation residue is mainly Cu2S; the pressure of the vacuum distillation is 1-100 Pa, and the temperature is 1023-1273K; the temperature of the condensation zone is 373-573K.

2. The method according to claim 1, characterized in that The black copper mud has an arsenic content of 10-20 wt % and a copper content of 30-40 wt %.

3. The method according to claim 1, characterized in that The arsenic content in the polluted acid sulfided slag is 38-42wt%, and the sulfur content is 35-39wt%.

4. The method according to any one of claims 1 to 3, characterized in that: The mass ratio of the black copper mud to the dirty acid sulfide slag is 1:(0.2-5).

5. The method according to claim 1, characterized in that The smelting temperature is 673-973K, the holding time is 30-120min, and the pressure is 1-10000Pa.

6. The method according to claim 1, characterized in that The pressure of the compression molding is 8-20 MPa.

7. The method according to claim 1, characterized in that The vacuum distillation time is 30 to 120 minutes.

8. The method according to claim 1 or 5, characterized in that: Before the smelting, the green body is dried.

9. The method according to claim 1, 2 or 3, characterized in that: The average particle size of the mixture is 75-90 μm.

10. The method according to claim 1 or 6, characterized in that: The green blank is a cylindrical blank with a height of 5 to 10 mm and a diameter of 25 to 30 mm.

11. The method according to claim 2, characterized in that The Cu and As in the black copper mud mainly exist in the form of Cu3As.

12. The method according to claim 3, characterized in that The As and S in the polluted acid sulfide slag mainly exist in the form of As2S3.

13. The method according to claim 8, characterized in that The drying temperature is 110° C. and the drying time is 4 hours.

14. The method according to claim 1, characterized in that The recovery rate of Cu2S in the sulfidation product is higher than 90%, and the purity is higher than 95%.

15. The method according to claim 1, characterized in that The direct yield of As in the sulfidation product is higher than 90%, and the purity is higher than 99.5%.

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