A method for recovering high-purity sulfur product from zinc-sulfur sludge by wet process

Abstract

This invention discloses a method for recovering high-purity sulfur from hydrometallurgical zinc slag. The method involves washing, drying, grinding, and sieving the hydrometallurgical zinc slag, then mixing it with a water-ethylene glycol solvent and adjusting the pH to the range of 2-10. The mixture is then transferred to a high-pressure reactor for a solvothermal reaction under mechanical stirring. After the reaction is complete, the mixture is cooled to room temperature, and the solid product is separated by water washing to obtain sulfur-rich slag and metal-enriched residue. The sulfur-rich slag is then physically cut to remove surface impurities, yielding the high-purity sulfur product. This method combines high-pressure solvothermal reaction with physical cutting to separate sulfur from metallic impurities in hydrometallurgical zinc slag, obtaining a high-purity sulfur product. This reduces the accumulation of sulfur-containing waste and the loss of sulfur resources. Furthermore, this method is simple, economical, and efficient, providing a new approach for the treatment of sulfur-containing waste.

Description

Technical Field

[0001] This invention relates to a method for treating sulfur slag from hydrometallurgical zinc smelting, and particularly to a method for recovering high-purity sulfur products from sulfur slag from hydrometallurgical zinc smelting, belonging to the field of comprehensive recycling of waste residues from non-ferrous metal smelting. Background Technology

[0002] With industrial development and increasing environmental protection requirements, the amount of sulfur-containing waste residue is constantly increasing. Domestic zinc smelting leaching projects produce approximately 600,000 tons of sulfur-containing leaching residue annually. After flotation treatment, this residue yields sulfur-rich slag with a sulfur content exceeding 70%, containing not only elemental sulfur (S) but also certain amounts of Zn, Pb, Ag, Fe, and other elements, making it highly valuable for recycling. Failure to promptly recycle and utilize this sulfur-containing waste residue will result in significant resource waste and lead to waste residue stockpiling problems. Therefore, effectively recovering sulfur from hydrometallurgical zinc smelting sulfur residue is not only beneficial for the comprehensive recovery of sulfur resources and valuable metals but also helps alleviate environmental pressure.

[0003] Sulfur recovery methods from hydrometallurgical slag are mainly divided into physical and chemical methods. Physical methods, based on the physical properties of sulfur, can be broadly categorized into flotation, hot filtration, and high-pressure decanting. These methods are simple, but their recovery efficiency is poor, with low purity and recovery rate, only serving to enrich sulfur. Chemical methods utilize solvents that can dissolve elemental sulfur to separate it, generally divided into organic and inorganic solvent methods. Inorganic solvent methods also suffer from low purity of recovered elemental sulfur, while organic solvent methods, although achieving higher purity, are highly toxic and consume large amounts of solvent, limiting their industrial application.

[0004] Hydrometallurgical zinc leaching residue is both hazardous waste and a sulfur-containing secondary resource; its safe disposal is significant for both comprehensive resource utilization and environmental protection. Current technologies struggle to achieve high-purity sulfur recovery from hydrometallurgical zinc leaching residue, primarily due to the coexistence of sulfur and metallic phases in the residue. These metallic phases are characterized by fine particles, diverse types, and varied morphologies, exhibiting strong binding with sulfur. This causes the molten sulfur to encapsulate the metallic phases during cooling, making separation difficult. While existing solutions address this challenge, they suffer from poor separation and recovery efficiency and low selectivity. For instance, Chinese patent CN115215300B discloses a method for recovering elemental sulfur from high-sulfur residue. This method employs a water-slurry-heat treatment-liquid-liquid interface rapid cooling phase separation approach. This innovative approach effectively achieves highly selective separation of elemental sulfur and impurities in high-sulfur residue, increasing the direct recovery rate of elemental sulfur. In this method, the sulfur distribution rate in the sulfur-rich block reaches a maximum of 97.24%, and the recovery rate can reach 92.04%. Although the sulfur distribution rate in the sulfur-rich block is relatively high and the sulfur recovery rate is high, the sulfur still contains many impurities that are difficult to separate, and the surface is also covered with a layer of metal sulfides. If high-purity sulfur is to be separated, other processes are still required to further separate the sulfur. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering sulfur from hydrometallurgical zinc slag. This method achieves high sulfur enrichment in hydrometallurgical zinc slag through a one-step high-pressure solvothermal reaction. High-purity sulfur can be recovered through simple physical cutting and stripping, with a purity of up to 99.9% and a high sulfur recovery rate. At the same time, valuable metals are efficiently enriched for subsequent recovery.

[0006] To achieve the above-mentioned technical objectives, this invention provides a method for recovering high-purity sulfur products from hydrometallurgical zinc slag. The method involves washing, drying, grinding, and sieving the hydrometallurgical zinc slag to obtain sulfur slag powder. The sulfur slag powder is then mixed with a water-ethylene glycol solvent, and the pH is adjusted to the range of 2–10. The mixture is then transferred to a high-pressure reactor for a solvothermal reaction under mechanical stirring. After the reaction is complete, the mixture is cooled to room temperature. The solid product is separated by water washing to obtain sulfur-rich slag and metal-enriched residue. The sulfur-rich slag is then subjected to physical cutting and ultrasonic stripping to remove surface impurities, yielding the high-purity sulfur product.

[0007] The key to this invention's recovery of high-purity sulfur from hydrometallurgical zinc slag lies in the use of a special solvent medium and appropriate pH conditions during a high-pressure solvothermal reaction. This, combined with mechanical stirring and a high-temperature, high-pressure environment, enables the high-purity enrichment of sulfur. After cooling, the metal sulfides coating the sulfur block are physically removed, yielding high-purity sulfur with a purity of 99.9%, eliminating the need for further purification. In achieving high-purity sulfur enrichment during the high-pressure solvothermal reaction, the compatibility of the solvent medium with sulfur and the control of pH conditions are crucial. Under the interfacial forces of the solvent medium and in a suitable pH environment, coupled with mechanical stirring and high temperature and pressure, the hydrophobic sulfur in the slag continuously aggregates to form an independent sulfur-rich phase. Simultaneously, various impurities in the sulfur are eliminated, while hydrophilic residues are enriched. The interior of the sulfur-rich phase is almost entirely high-purity sulfur, and the metal sulfides coating its surface are easily removed mechanically, resulting in high-purity sulfur with a purity of 99.9%, requiring no further purification.

[0008] As a preferred embodiment, the volume ratio of water to ethylene glycol in the water-ethylene glycol mixed solvent is 1:0.5 to 1.5. This preferred combined solvent medium, on the one hand, facilitates the aggregation of sulfur through interfacial tension; on the other hand, it facilitates the effective removal of gangue phase impurities such as sulfates from the sulfur, and promotes the high-purity aggregation of hydrophobic sulfur. Extensive experiments have shown that neither water-based solvents nor short-chain alcohol solvents alone can achieve the same technical effects as the water-ethylene glycol combined solvent medium.

[0009] As a preferred embodiment, the mass percentage composition of the water-ethylene glycol mixed solvent and the sulfur slag powder is 35-95%:5-65%. Alternatively, the mass percentage composition of the water-ethylene glycol mixed solvent and the sulfur slag powder is 65-85%:15-35%. Studies have found that under these preferred conditions, in synergy with other conditions, it helps to further improve the recovery rate and purity of elemental sulfur, as well as the selective separation of elemental sulfur from other metallic phases. It also effectively enriches other metallic elements in high-sulfur slag and reduces the content of elemental sulfur, thus contributing to obtaining more valuable residues. If the solvent dosage is too high, the sulfur in the slag is difficult to densely aggregate, thereby affecting the sulfur recovery rate. If the solvent dosage is too low, liquid sulfur at high temperatures is difficult to separate from other impurities, and subsequently, upon cooling, the sulfur crystals will re-encapsulate with the impurities, making it difficult to separate the sulfur from the metallic phase.

[0010] As a preferred embodiment, the pH is adjusted to be within the range of 3 to 7. A pH between 3 and 7 is more conducive to improving the purity and recovery rate of sulfur. If the pH is too low, the solution is in an acidic environment, and the high-temperature liquid sulfur crystallizes faster, which is not conducive to separating it from other impurities. If the pH is too high, the solution is in an alkaline environment, which can dissolve some of the sulfur and reduce the sulfur recovery rate.

[0011] As a preferred embodiment, the solvothermal reaction conditions are: a reaction at 120–180°C for 0.5–12 hours. The solvothermal reaction temperature is further preferably 125–175°C, and most preferably 125–145°C. The solvothermal reaction time is further preferably 1.5–6 hours. Within a certain range of reaction temperature and time, it is beneficial for sulfur to melt better and release the impurities encapsulated within. If the reaction temperature is too high, the sulfur undergoes ring-opening to form high-viscosity polymeric sulfur. When the polymeric sulfur cools rapidly, it binds tightly to the impurities, making it difficult to separate and preventing the formation of high-purity sulfur-rich slag. If the reaction temperature is too low, the melting temperature of sulfur is not reached, making it difficult to release the impurities encapsulated by the sulfur, and thus preventing the obtaining of high-purity sulfur-rich slag.

[0012] As a preferred embodiment, the mechanical stirring rate during the solvothermal reaction is 200–1400 r / min. A further preferred mechanical stirring rate is 1000–1400 r / min. High-speed mechanical stirring promotes the formation of the sulfur-enriched phase. Experiments show that without stirring, the sulfur slag and solvent separate into layers, and the solvent fails to promote slurry dispersion, making it difficult to form a high-purity sulfur-enriched phase.

[0013] As a preferred embodiment, the cooling process involves cooling to room temperature using a circulating water cooling method.

[0014] This invention addresses the technical problems of poor separation and recovery of elemental sulfur and metallic impurities in hydrometallurgical zinc slag, resulting in poor separation selectivity and difficulty in obtaining high-purity sulfur. By synergistically controlling the pH and solvent type in the high-pressure solvothermal reaction stage, and combining it with high-temperature and high-pressure hydrothermal conditions and mechanical stirring, this invention can achieve highly selective separation of sulfur and metallic impurities in hydrometallurgical zinc slag, enabling ultra-pure recovery of sulfur and enrichment of valuable metals in the residue.

[0015] The present invention relates to a method that does not have specific requirements regarding the sulfur content and impurity composition of the hydrometallurgical zinc slag, and good separation selectivity can be obtained using this method. For example, the hydrometallurgical zinc slag is a hydrometallurgical zinc oxygen pressure leaching residue.

[0016] The method of the present invention can be used for sulfur recovery from hydrometallurgical zinc slag with any sulfur content, and is particularly suitable for sulfur enrichment of sulfur-containing solid waste that is difficult to recover directly by molten hot filtration.

[0017] The preferred method for recovering high-purity sulfur products from hydrometallurgical zinc smelting slag, provided by the present invention, is as follows:

[0018] 1) The raw slag from the wet zinc smelting process is washed until the pH is around 2, then dried, ground and sieved, with the particle size controlled at around 200 mesh, to obtain sulfur slag.

[0019] 2) Mix sulfur slag with water-ethylene glycol solvent at a mass percentage of 35-95%:5-65% (preferably 65-85%:15-35%). After mixing, adjust the pH of the solution to 2-10 (preferably 3-7) with acid / alkali. Then seal it in a reactor, control the stirring speed at 200-1400 r / min (preferably 1000-1400 r / min), and heat it to 120-180℃ and keep it at that temperature for 0.5-12 h (preferably 3-6 h).

[0020] 3) Cool the reacted material to room temperature using circulating water;

[0021] 4) Wash the sample obtained in step 3) with water to separate the sulfur-rich slag with a black surface and a yellow interior and the pure black residue.

[0022] 5) The sulfur-rich slag is mechanically cut and peeled to remove the surface metal sulfides, thus obtaining high-purity sulfur blocks.

[0023] This method provides a reference for the recovery of elemental sulfur from sulfur-containing waste residues generated in the hydrometallurgical industry, and promotes the high-purity and high-efficiency recovery of elemental sulfur from sulfur-containing waste residues.

[0024] Compared with the prior art, the advantages of the technical solution of this invention are as follows:

[0025] 1) The method for recovering sulfur from sulfur slag by combining high-pressure solvothermal reaction and physical cutting and stripping with phase separation control provided by this invention achieves highly selective separation of sulfur from metallic impurities in hydrometallurgical zinc slag through synergistic control of pH and solvent type during the high-pressure solvothermal reaction stage, combined with high-temperature and high-pressure hydrothermal conditions and mechanical stirring. This improves the recovery rate and purity of elemental sulfur, resulting in high-grade sulfur. Simultaneously, it enriches metallic elements in the residue, facilitating the recovery of valuable metals from the residue. Furthermore, this method does not require the addition of additional modifiers, does not affect the changes in the original phases, is beneficial for improving sulfur purity, and has a short process flow and is easy to operate.

[0026] 2) The technology of this invention can significantly enrich sulfur through high-pressure solvothermal reaction. The sulfur purity in the sulfur-rich slag is comparable to that of sulfur concentrate obtained by multi-stage flotation in current industry. The purity of elemental sulfur can reach 92%, and the recovery rate is about 80%. Furthermore, through simple physical cutting and peeling, the black impurities on the outer layer of the sulfur-rich slag can be removed to obtain a high-purity pure yellow sulfur product inside the sulfur-rich slag. The purity of the sulfur product can reach more than 99%, which is comparable to industrial-grade sulfur products; no further purification treatment is required.

[0027] 3) This invention achieves the effective enrichment of other components in the sulfur slag of hydrometallurgical zinc smelting. For example, it can enrich valuable metal elements such as Ag, Fe, and Zn in the residue of oxygen pressure leaching slag of hydrometallurgical zinc smelting.

[0028] 4) It provides a reference for the recovery of elemental sulfur from sulfur-containing waste residues generated in the hydrometallurgical industry and other chemical industries. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of sulfur recovery from sulfur slag in the wet zinc smelting process of this invention.

[0030] Figure 2 The XRD patterns are shown for the raw sulfur slag from the wet zinc smelting process, the sulfur-rich slag and residue formed when the mass percentage concentration of sulfur slag was 25% and the water + ethylene glycol ratio was 1:1 in Example 1, and the undissolved CS2 sample in the sulfur-rich slag. Figure 2 It can be seen that the main component of the sulfur-rich slag is elemental sulfur, containing some ZnS and FeS2; the composition of the residue and the undissolved CS2 sample in the sulfur-rich slag is more complex, containing aluminosilicates, silicates, PbSO4, CaSO4, SiO2, ZnS, FeS2 and a small amount of sulfur and other mineral phases.

[0031] Figure 3 This is a SEM-EDS surface scan of the residue produced in Example 1 when the mass percentage concentration was 25% and the water + ethylene glycol ratio was 1:1. Figure 3 The distribution of bright areas of elements in the surface scan results and Figure 2 The XRD results of the residues corroborate each other.

[0032] Figure 4 The effect of pH of the mixed solution on the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks in the wet zinc smelting process was investigated in Example 1. The results show that when the pH of the mixed solution is 5, the yield of sulfur-rich slag can reach 70.56% and the recovery rate of high-purity sulfur blocks can reach 54.42%. Detailed Implementation

[0033] To facilitate understanding of the technical means, objectives, and effects achieved by this invention, the technical solutions described below are further described in detail with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0035] Unless otherwise specified, the reagents used in this embodiment are all commercially available products or prepared by conventional means, and the equipment used is all conventional equipment in the art. The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0036] The following case uses hydrometallurgical zinc slag, which is oxygen pressure leaching residue from hydrometallurgical zinc production. The elemental composition of the hydrometallurgical zinc slag is as follows: Fe 1.3276%, Zn 1.7767%, Pb 5.2507%, Cu 0.045%, Ag 0.2767%, S 66.2928%, Si 5.8304%, Ca 3.5286%.

[0037] Example 1

[0038] The effect of mixed solution pH on the selectivity of separation of elemental sulfur and impurities in hydrometallurgical zinc smelting slag;

[0039] The implementation process of this example is as follows: The sulfur slag from the wet zinc smelting process was prepared with solvent water and ethylene glycol (specific volume ratio 1:1) to a concentration (mass percentage) of 25%. The pH of the mixture was adjusted to 2-10. The materials were loaded into a reactor, and the stirring speed inside the reactor was controlled at 1000 r / min. The temperature was raised to 135℃ and held for 1.5 h. Then, the mixture was cooled to room temperature by circulating water and discharged from the reactor. The materials were washed and separated to obtain sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and peeled to remove the surface metal sulfides to obtain sulfur blocks with a purity of over 99.5%. The yield of sulfur-rich slag and the recovery rate and purity of high-purity sulfur blocks are shown in Table 1. The effect of the pH of the mixed solution on the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks showed that pH had a significant impact on both the yield and recovery rate. The weakly acidic environment with pH = 5 was conducive to the removal of impurities from the sulfur-rich slag, achieving a sulfur-rich slag yield of 70.56% and a high-purity sulfur block recovery rate of 54.42%.

[0040] Table 1. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0041] pH Unadjusted pH pH=2 pH=3 pH=5 pH=7 pH = 9 Sulfur-rich slag yield (%) 37.6 61 64.7 70.6 63.2 62.8 Sulfur block recovery rate (%) 23.33 51.2 52.82 54.42 52.71 51.41 Sulfur block purity (%) 95.4 99.5 99.7 99.9 99.6 99.1

[0042] Example 2

[0043] The effect of solvent type on the selectivity of separation of elemental sulfur and impurities in hydrometallurgical zinc smelting slag;

[0044] The implementation process of this example is as follows: The hydrometallurgical zinc slag was prepared into a 25% concentration (by mass percentage) using different solvents (water, ethanol, ethylene glycol, n-pentanol, and water + ethylene glycol in a 1:1 volume ratio). The pH of the mixture was adjusted to 5. The materials were then loaded into a reactor, and the stirring speed was controlled at 1200 r / min while the temperature was raised to 130℃ and maintained for 2.5 h. Afterward, the mixture was cooled to room temperature using circulating water and discharged. The materials were washed and separated to obtain sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and peeled to remove the surface metal sulfides, yielding sulfur blocks. The yield of sulfur-rich slag and the recovery rate and purity of high-purity sulfur blocks are shown in Table 2. The effect of solvent type on yield and recovery rate shows that polar solvents have a greater impact on yield and recovery rate. The presence of highly polar water is beneficial for removing impurities from the sulfur-rich slag, achieving a sulfur-rich slag yield of 75.1% and a high-purity sulfur block recovery rate of 59.48%.

[0045] Table 2. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0046] Solvent types water ethanol Ethylene glycol n-Pentanol Water + Ethylene Glycol Sulfur-rich slag yield (%) 67.8 67.5 72.1 57.3 75.1 Sulfur block recovery rate (%) 55.72 51.45 56.90 42.48 59.48 Sulfur block purity (%) 97.3 98.2 98.5 97.6 99.9

[0047] Example 3

[0048] The effect of solid-liquid ratio on the selectivity of separation of elemental sulfur and impurities in sulfur slag from wet zinc smelting;

[0049] The implementation process of this example is as follows: The sulfur slag from the wet zinc smelting process was prepared into materials with concentrations (mass percentages) of 5%, 15%, 25%, 35%, 45%, 55%, and 65% using a solvent (water + ethylene glycol volume ratio of 1:1.5). The pH of the mixture was adjusted to 5. Each material was then loaded into a reactor, and the stirring speed was controlled at 900 r / min while the temperature was raised to 135℃ and maintained for 1.5 h. Afterward, the material was cooled to room temperature using circulating water and discharged from the reactor. The material was washed and separated to obtain sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and ultrasonically peeled to remove the surface metal sulfides, yielding sulfur blocks with a purity of over 99.5%. The yield of the sulfur-rich slag and the recovery rate of the high-purity sulfur blocks are shown in Table 3. The results of the study on the effect of solid-liquid ratio on yield and recovery rate showed that as the solid-liquid ratio increased, the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks both increased first and then decreased. When the solvent content decreased to a certain level, sulfur-rich slag would not be formed. Specifically, when the solid-liquid ratio was 25%, the yield of sulfur-rich slag was 63.4% and the recovery rate of high-purity sulfur blocks was 49.97%.

[0050] Table 3. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0051] Solvent content 5％ 15％ 25％ 35％ 45％ 55％ Sulfur-rich slag yield (%) 43.3 58.7 69.4 63.9 49.8 47.5 Sulfur block recovery rate (%) 37.37 34.62 50.97 41.08 28.55 21.42

[0052] The elemental composition and content of the sulfur-rich slag and residue obtained at a mass percentage concentration of 25% are shown in Table 4:

[0053] Table 4. Composition and content (%) of major elements in sulfur-rich slag and residue

[0054]

[0055] Example 4

[0056] The study investigated the effect of reaction temperature on the selectivity of separating elemental sulfur and impurities in the sulfur slag from the hydrometallurgical zinc smelting process, mainly focusing on:

[0057] The sulfur slag from the wet zinc smelting process was prepared into a 30% (w / w) solution using a solvent (water + ethylene glycol, volume ratio 1:1). The pH of the mixture was adjusted to 5. The solution was then loaded into a reactor, and the stirring speed was controlled at 800 r / min. The temperature was raised to 125℃, 135℃, 145℃, 155℃, and 165℃, and held for 1.5 h. The mixture was then cooled to room temperature using circulating water before being discharged. The material was washed and separated to obtain sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and peeled to remove the surface metal sulfides, yielding sulfur blocks with a purity of over 99.5%. The yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks are shown in Table 5. The effect of reaction temperature on yield and recovery rate showed that both the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks increased first and then decreased with increasing reaction temperature. If the temperature continues to rise, elemental sulfur will polymerize to form highly viscous sulfur, at which point high-purity sulfur blocks cannot be obtained, and the interior of the sulfur-rich slag is pure black. Therefore, an appropriate reaction temperature is more conducive to the formation of high-purity sulfur blocks. Specifically, at a reaction temperature of 135℃, the yield of sulfur-rich slag was 60.3%, and the recovery rate of high-purity sulfur blocks was 47.91%.

[0058] Table 5. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0059]

[0060]

[0061] Example 5

[0062] The effect of stirring speed on the selectivity of separating elemental sulfur and impurities in wet zinc smelting slag was investigated.

[0063] The sulfur slag from the wet zinc smelting process was prepared into a 25% concentration solution using a solvent (water + ethylene glycol, volume ratio 1:1). The pH of the mixture was adjusted to 5. The solution was then loaded into a reactor, and the stirring speed was controlled at 400 r / min, 600 r / min, 800 r / min, 1000 r / min, 1200 r / min, and 1400 r / min, respectively. The temperature was raised to 135°C and held for 2 hours. The mixture was then cooled to room temperature using circulating water before being discharged. The material was washed to separate sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and peeled to remove the surface metal sulfides, yielding sulfur blocks with a purity of over 99.5%. The yield of the sulfur-rich slag and the recovery rate of the high-purity sulfur blocks are shown in Table 6. The results of the effect of stirring speed on yield and recovery rate showed that as the stirring speed increased, the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks both increased first and then decreased. Specifically, when the stirring speed was 1000 rpm / min, the yield of sulfur-rich slag was 58.6% and the recovery rate of high-purity sulfur blocks was 48.83%.

[0064] Table 6. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0065] Rotational speed (rpm / min) 400 600 800 1000 1200 1400 Sulfur-rich slag yield (%) 37.3 40.2 47.9 58.6 49.7 39.1 Sulfur block recovery rate (%) 21.33 32.57 37.38 48.83 42.17 35.49

[0066] Example 6

[0067] The effect of holding time on the selectivity of separating elemental sulfur and impurities in the sulfur slag of wet zinc smelting was investigated.

[0068] The sulfur slag from the wet zinc smelting process was prepared into a 25% concentration solution using a solvent (water + ethylene glycol, volume ratio 1:1). The pH of the mixture was adjusted to 5. The solution was then loaded into a reactor, and the stirring speed was controlled at 1100 r / min. The temperature was raised to 130℃ and held for 1.5 h, 2 h, 3 h, 6 h, and 12 h. Afterward, the mixture was cooled to room temperature using circulating water and discharged. The material was washed and separated to obtain sulfur-rich slag and residue. The sulfur-rich slag was mechanically cut and ultrasonically peeled to remove the surface metal sulfides, yielding sulfur blocks with a purity of over 99.5%. The yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks are shown in Table 7. The effect of holding time on yield and recovery rate is as follows. Figure 4 As shown, the yield of sulfur-rich slag and the recovery rate of high-purity sulfur blocks increase with the extension of the heat preservation time, but the increasing trend is not particularly obvious. In order to shorten the process time, the present invention preferably uses a heat preservation time of 1.5h. When the heat preservation time is 1.5h, the yield of sulfur-rich slag is 65.8% and the recovery rate of high-purity sulfur blocks is 53.27%.

[0069] Table 7. Yield of sulfur-rich slag and recovery rate of high-purity sulfur blocks

[0070] Insulation time 1.5h 2h 3h 6h 12h Sulfur-rich slag yield (%) 58.6 60.4 62.8 63.5 65.8 Sulfur block recovery rate (%) 48.83 49.98 51.97 52.03 53.27

[0071] Comparative Example 1

[0072] Compared with Example 5, the main difference is that the reaction process was not stirred (i.e., the stirring speed was 0). The results showed that no sulfur-rich slag was formed, indicating that the non-stirring condition was not conducive to the selective separation of sulfur and metal impurities.

[0073] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A process for recovering high purity sulphur product from a zinc sulphuric acid pressure leach residue, characterised in that: The wet-zinc-ore slag is washed, dried, ground and sieved to obtain sulfur slag powder; the sulfur slag powder is mixed with a water-glycol mixed solvent and adjusted to a pH in the range of 2-10, and then transferred into a high-pressure reaction kettle for a solvothermal reaction under mechanical stirring; after the reaction is completed, the solid product is separated by water washing to obtain sulfur-rich slag and metal-rich residue; the sulfur-rich slag is physically cut to peel off the surface impurities to obtain high-purity sulfur product. The mass percentage composition of the water-glycol mixed solvent and the sulfur slag powder is 35-95% : 5-65%. The solvothermal reaction is carried out at a temperature of 120-180℃ for 0.5-12h.

2. The method for recovering high-purity sulfur product from zinc sulphuric acid plant sludge according to claim 1, characterized in that: The volume ratio of water to glycol in the water-glycol mixed solvent is 1:0.5-1.

5.

3. The method for recovering high-purity sulfur product from zinc sulphuric acid plant sludge according to claim 1, characterized in that: The pH adjustment is in the range of 3-7.

4. The method for recovering high-purity sulfur product from zinc sulphuric acid plant sludge according to claim 1, characterized in that: The mechanical stirring rate in the process of the solvothermal reaction is 200-1400r / min.

5. The method of recovering high purity sulfur product from zinc sulphuric acid plant sludge according to claim 1, characterized in that: The cooling process is cooling to room temperature by circulating water cooling.

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