Method for recovering elemental sulfur from oxygen pressure leaching residues

Abstract

The invention discloses a method for recovering elemental sulfur from oxygen pressure leaching residues, which comprises the following steps: firstly, dissociating elemental sulfur from mineral substances by adopting a grinding process, and then adopting N, N '-diethyldithiocarbamate and neutral oil as collecting agents and sodium thioglycolate as an inhibitor in flotation operation; the N, N-diethyldithiocarbamate and neutral oil synergistic collecting system is adopted in flotation operation, under the organic inhibition effect of bifunctional sodium thioglycollate, the number of times of concentration can be reduced, the grade of the sulfur concentrate can be improved, high-grade sulfur concentrate is successfully obtained through roughing and concentration of the flotation column, the grade can reach 90% or above, and the recovery rate can reach 80% or above. In addition, the method does not need heating or roasting, the used medicament is acid-resistant, the filtrate can be recycled, and the method has the advantages of simple process, low energy consumption, high resource recovery rate and the like, is suitable for efficient recovery of elemental sulfur in the oxygen pressure leaching process waste residues of zinc, copper, nickel and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting and recycling technology, specifically relating to a method for recovering elemental sulfur from oxygen pressure leaching residue. Background Technology

[0002] Pressure leaching (POX) is the mainstream hydrometallurgical process for processing zinc, copper, and nickel sulfide concentrates. Under high temperature, high pressure, and acidic conditions, sulfide minerals are oxidized into elemental sulfur and metal sulfates. After flash evaporation and filtration, the resulting solid residue is the POX residue. The elemental sulfur content in this residue is typically between 20% and 45%, but it is in the form of fine particles (D50 approximately 10-40 μm), and is mostly encapsulated by pyrite, sphalerite, gangue, and calcium sulfate. The free sulfuric acid concentration in the slurry is 50-150 g / L, the pulp pH is below 1, and the Zn content is low. 2+ Fe 3+ / Fe 2+ The total amount of metal ions can reach several hundred grams per liter. More importantly, sulfur readily adsorbs Fe on its surface. 3+ Zn 2+ Pb 2+ and Ca 2+ These substances form a hydrophilic hydroxyl sulfate film, which severely blocks its natural hydrophobicity.

[0003] Traditional methods for sulfur recovery mainly include thermal filtration and return roasting. Thermal filtration requires melting and filtering at 120-135℃, resulting in severe equipment corrosion, high energy consumption, and significant safety risks. Return roasting re-oxidizes sulfur into SO2 for acid production, wasting elemental sulfur resources and increasing the load on tail gas treatment. Conventional flotation, due to issues such as fine particle size, high acidity, easy decomposition of collectors, and surface hydrophilic film shielding, can only obtain low-quality sulfur products, which is difficult to meet market requirements, and the sulfur flotation recovery rate is low.

[0004] Elemental sulfur is naturally hydrophobic and theoretically can be flotated. However, oxygen pressure leaching residue has the following characteristics: fine particle size, high sulfur content... 0 It often exists in the form of sulfides such as FeS2 and ZnS or sulfates (such as CaSO4), requiring complete dissociation; the pulp has high acidity (pH<1), and conventional xanthate collectors are easily decomposed; the solution contains a high concentration of Zn. 2+ Fe 3+ A hydrophilic hydroxyl-sulfate film forms on the sulfur surface, hindering collector adsorption; fine sulfur particles easily desorb from the bubble surface, resulting in low flotation efficiency. Therefore, there is an urgent need for a flotation technology that is adaptable to strong acid-high ionic environments, selective for fine sulfur particles, and environmentally friendly. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide a method for recovering elemental sulfur from oxygen pressure leaching residue.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for recovering elemental sulfur from oxygen pressure leaching residue, comprising the following steps: The oxygen pressure leaching residue slurry is ground, and the ground oxygen pressure leaching residue slurry is mixed with a collector and a depressant for flotation to obtain sulfur concentrate; the collector includes ethyl thiocyanate and neutral oil; the depressant includes sodium mercaptoacetate.

[0007] Preferably, the oxygen pressure leaching residue has a content of 30%-50% in the slurry.

[0008] Preferably, the pH of the slurry of the oxygen-containing pressure leaching residue is <1.

[0009] Preferably, the particle size D50 of the ground oxygen pressure leaching residue is 14-20 μm.

[0010] More preferably, the particle size D50 of the ground oxygen pressure leaching residue is 15-19 μm.

[0011] More preferably, the particle size D50 of the ground oxygen pressure leaching residue is 16-18 μm.

[0012] More preferably, the particle size distribution of the ground oxygen pressure leaching residue also satisfies one or more of the following conditions: A) D10 is 3-5 μm; B) D25 is 8-10 μm; C)D75 is 24-26 μm D)D90 is 30-34 μm.

[0013] Preferably, the grinding equipment is an ultrafine grinding equipment.

[0014] More preferably, the grinding equipment is a vertical stirred mill or an IsaMill ultrafine mill.

[0015] This invention grinds oxygen pressure leaching residue to the above-mentioned particle size distribution. By controlling the fineness of the oxygen pressure leaching residue, the fine particles of elemental sulfur (S) are made more uniform. 0 The process allows for the complete dissociation of pyrite, sphalerite, sulfates, and silicates coexisting with the oxygen pressure leaching residue, thereby releasing the encapsulated elemental sulfur particles and creating the necessary conditions for subsequent flotation separation. Furthermore, the ultrafine grinding process effectively strips or destroys some of the hydrophilic metal-hydroxyl-sulfate complex film encapsulating the surface of elemental sulfur, significantly restoring and enhancing the natural hydrophobicity of elemental sulfur.

[0016] Preferably, the mass ratio of the collector to the oxygen pressure leaching residue is (100-400) g : 1 t.

[0017] Preferably, the mass ratio of the inhibitor to the oxygen pressure leaching residue is (100-300) g : 1 t.

[0018] Preferably, the mass ratio of the ethyl thionitrogen to oxygen pressure leaching residue is (30-80) g : 1 t.

[0019] Preferably, the mass ratio of the neutral oil to the oxygen pressure leaching residue is (100-200) g : 1 t.

[0020] Preferably, the neutral oil includes at least one of diesel, kerosene, and gasoline.

[0021] More preferably, the diesel fuel is light diesel fuel.

[0022] More preferably, the diesel fuel is a light diesel fuel that has been hydrotreated and has an aromatic content of <5%.

[0023] Preferably, the method further includes the following steps: adding ethyl thiocyanate to a sodium hydroxide solution to carry out a saponification reaction, and using the resulting ethyl thiocyanate solution as a collector.

[0024] More preferably, the saponification reaction is carried out at 50-70°C.

[0025] The present invention pre-treats ethyl thiocyanate by saponification, which is beneficial to its uniform dispersion in strong acid slurry.

[0026] Preferably, the method further includes the following steps: preparing sodium thioacetate into an aqueous solution and adjusting the pH of the thioacetic acid solution to 5-6 using sodium hydroxide.

[0027] More preferably, sodium mercaptoacetate is prepared as an aqueous solution with a pH of 5-6 to avoid instantaneous deactivation of mercaptoacetic acid when added to strongly acidic slurries.

[0028] The directional collector used in this invention consists of ethyl thiocyanate (sodium diethyl dithiocarbamate, commonly known as EDTC) and neutral oil, constructing a synergistic collection system resistant to strong acids (pH < 1). Ethiocyanate exhibits good stability under strong acidic conditions. Its -CSS⁻ active groups can undergo stable chemisorption with the active sites on the surface of elemental sulfur, preferentially adsorbing onto the surface of dissociated elemental sulfur, thus imparting preliminary hydrophobicity. Neutral oil, acting as an auxiliary collector and covering agent, forms a hydrophobic oil film on the surface of sulfur particles through physical spreading, thickening the hydrophobic layer and promoting oil bridging, thereby promoting the aggregation of fine sulfur particles and improving their adhesion stability to bubbles, particularly beneficial for improving the recovery efficiency of fine-particle sulfur. The synergistic effect of both significantly improves the selective collection of fine elemental sulfur under strong acid and high metal ion conditions, and also enhances the flotation rate and foam stability, making it suitable for the efficient recovery of fine sulfur from oxygen pressure leaching residue.

[0029] The targeted inhibitor used in this invention is sodium mercaptoacetate. Sodium mercaptoacetate molecules contain two functional groups: a thiol group (-SH) and a carboxyl group (-COOH). The -SH group selectively adsorbs onto the surface of residual pyrite / sphalerite through the interaction of metal ions on the mineral surface, while the -COOH group inhibits collector adsorption through electrostatic repulsion or generates hydrophilic interactions, thereby effectively inhibiting the flotation of sulfide minerals. Sodium mercaptoacetate has minimal impact on elemental sulfur that has regained its hydrophobicity, achieving highly efficient flotation separation of elemental sulfur and sulfide minerals in a strongly acidic environment.

[0030] Preferably, the flotation operation uses a flotation column.

[0031] More preferably, the diameter of the flotation column is 0.6~6m and the height is 7~15m.

[0032] More preferably, the flotation column is a KYZ type flotation column.

[0033] The flotation equipment used in this invention employs flotation columns for flotation separation, utilizing their deep-cell static separation environment to reduce turbulent desorption. Compared to traditional flotation machines, flotation columns offer a longer mineralization path, a more stable froth layer, and better recovery of fine particles, making them particularly suitable for processing ultrafine elemental sulfur in this process. Roughing rapidly captures most of the liberated elemental sulfur, followed by two further cleaning processes to remove entrained impurities, ultimately yielding a high-grade elemental sulfur concentrate.

[0034] Preferably, the process parameters for the flotation operation are selected from at least one of the following: a) The aeration rate of the flotation column is 0.1-0.4 m³. 3 / h; b) The thickness of the foam layer in the flotation column is 5-30 cm; c) Flushing water flow rate: 0.1-2 L / min.

[0035] Preferably, the oxygen pressure leaching residue comprises elemental sulfur, iron sulfide minerals, zinc sulfide minerals, and silicate minerals.

[0036] Preferably, the flotation operation includes one roughing operation and two cleaning operations.

[0037] Preferably, the environmental conditions for the flotation operation are a temperature of 0-40℃ and a pressure of 0.8-1.2 standard atmospheres.

[0038] The beneficial effects of this invention are: This invention provides a method for recovering elemental sulfur from oxygen pressure leaching residue. First, a grinding process is used to dissociate elemental sulfur from minerals. Then, in the flotation operation, ethyl thiocyanate and neutral oil are used as collectors, and sodium mercaptoacetate is used as an inhibitor. Ethiocyanate is stable at pH < 1, and the process is carried out using -CSS. - The process involves chemical adsorption of sulfur; physical spreading of neutral oil to form an oil film, resisting high ionic strength interference and promoting the aggregation of fine elemental sulfur particles; and the -SH functional group of sodium thioacetate, which facilitates adsorption onto the surface of iron sulfide / zinc sulfide minerals, while its -COOH functional group hydrophilizes impurity minerals and complexes metal ions to reduce sulfur surface contamination. Therefore, the flotation operation of this invention employs a synergistic collection system of ethyl thiocyanate and neutral oil. Under the organic inhibition of the difunctional sodium thioacetate, not only are the number of cleaning cycles reduced, but the grade of sulfur concentrate is also improved. After roughing and cleaning in the flotation column, high-grade sulfur concentrate is successfully obtained, with a grade exceeding 90% and a recovery rate exceeding 80%. Furthermore, this method requires no heating or roasting, the reagents used are acid-resistant, and the filtrate can be recycled. It has advantages such as simple process, low energy consumption, and high resource recovery rate, and is suitable for the efficient recovery of elemental sulfur from oxygen pressure leaching process wastes of zinc, copper, nickel, etc., showing broad application prospects. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of recovering elemental sulfur from oxygen pressure leaching residue in Example 1; Figure 2 This is a particle size distribution diagram of the oxygen pressure leaching residue after grinding in Example 1; Figure 3 This is an overall diagram of the flotation column; Figure 4 This is a particle size distribution diagram of the oxygen pressure leaching residue after grinding in Example 2; Figure 5 This is a particle size distribution diagram of the oxygen pressure leaching residue after grinding, as shown in Comparative Example 1. Detailed Implementation

[0040] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0041] The sulfur recovery efficiency of the following examples and comparative examples was calculated using the following formula: Recovery rate = (Concentrate yield × Concentrate grade) / (100 × Raw ore grade) × 100%; For purity testing methods, please consult the Quality Inspection Center of Danxia Smelting Plant.

[0042] The following examples and comparative examples involved pretreatment of ethyl thiocyanate, diesel fuel, and sodium acetate, as detailed below: 1) To prepare ethyl thiocyanate, first add ethyl thiocyanate to a 5% NaOH solution and saponify it at 60℃ for 5 minutes to ensure it is evenly dispersed in the strong acid slurry.

[0043] 2) Prepare neutral oil by selecting light diesel oil that has been hydrotreated and has an aromatic content of <5%, and form an O / W type emulsion through an online shear emulsifier.

[0044] 3) Prepare sodium mercaptoacetate by preparing a 5% aqueous solution before adding it to the flotation column, and adjust the pH to 5-6 with 0.5% NaOH to prevent the strong acid from being deactivated instantaneously.

[0045] The oxygen pressure leaching residue slurry treated in the following examples and comparative examples is an oxygen pressure leaching residue slurry with a concentration of 30w%-35w%, wherein, by mass percentage, the oxygen pressure leaching residue contains 35.2% elemental sulfur, 20.5% pyrite, 15.3% sphalerite, and 29.0% silicate gangue, the slurry pH is 0.8, and the total concentration of metal ions is 105 g / L.

[0046] Example 1 Example 1 provides a process for recovering elemental sulfur from oxygen pressure leaching residue, the process flow diagram of which is shown below. Figure 1 As shown, the specific process steps are as follows: S1. The sample used in the experiment was oxygen pressure leaching residue slurry. The oxygen pressure leaching residue slurry was ground to D50 = 17 μm using a vertical stirred mill. The particle size distribution after fine grinding is as follows: Figure 2 As shown, the specific particle size distribution is as follows: D10(μm): 4.384; D25(μm): 8.847; D50(μm): 17.395; D75(μm): 25.100; D90(μm): 31.963; D97(μm): 37.731; D(3,2)(μm): 9.682; D(4,3)(μm): 17.754; S2. Add the finely ground oxygen pressure leaching slurry to a KYZ flotation column. Figure 3Add 200 g / t of sodium thioglycolate as an inhibitor, 50 g / t of ethyl thiocyanate as a collector, and 150 g / t of diesel oil. The flotation process parameters are: flotation column aeration rate of 0.25 m. 3 / h, foam layer thickness 20cm, flushing water flow rate 0.8L / min; adopting a process of one roughing and two cleaning, first roughing is carried out to obtain roughing concentrate and roughing tailings, and then after two cleaning stages, the final cleaning II concentrate is sulfur concentrate, the sulfur grade in the sulfur concentrate is 92.31%, and the elemental sulfur recovery rate is 84.38%.

[0047] Example 2 Example 2 provides a process for recovering elemental sulfur from oxygen pressure leaching residue, the process flow diagram of which is shown below. Figure 1 As shown, the specific process steps are as follows: S1. The sample used in the experiment was oxygen pressure leaching residue slurry. The oxygen pressure leaching residue slurry was ground to D50 = 14 μm using a vertical stirred mill. The particle size distribution after fine grinding is as follows: Figure 4 As shown, the specific particle size distribution is as follows: D10(μm): 3.934; D25(μm): 6.741; D50(μm): 14.325; D75(μm): 22.409; D90(μm): 31.963; D97(μm): 35.521; D(3,2)(μm): 8.461; D(4,3)(μm): 15.344; S2. Add the finely ground oxygen pressure leaching slurry to a KYZ flotation column. Figure 3 Add 200 g / t of sodium thioglycolate as an inhibitor, 50 g / t of ethyl thiocyanate as a collector, and 150 g / t of diesel oil. The flotation process parameters are: flotation column aeration rate of 0.25 m. 3 / h, foam layer thickness 20cm, rinsing water flow rate 0.8L / min; adopting a process of one roughing, one cleaning and two scavenging, the final fine II concentrate is sulfur concentrate, the sulfur grade in the sulfur concentrate is 81.13%, and the elemental sulfur recovery rate is 76.76%.

[0048] Comparative Example 1 Comparative Example 1 provides a process for recovering elemental sulfur from oxygen pressure leaching residue, the specific process steps of which are as follows: S1. The sample used in the experiment was oxygen pressure leaching residue slurry. The oxygen pressure leaching residue slurry was directly floated without grinding, and its particle size distribution was as follows: Figure 5As shown, the specific particle size distribution is as follows: D10 (μm): 6.406; D25 (μm): 12.195; D50 (μm): 20.142; D75 (μm): 29.112; D90 (μm): 40.406; D97 (μm): 53.594; D(3,2)(μm): 13.954; D(4,3)(μm): 22.085; S2. Add the oxygen pressure leaching residue slurry to a KYZ flotation column ( Figure 3 Add 200 g / t of sodium thioglycolate as an inhibitor, 50 g / t of ethyl thiocyanate as a collector, and 150 g / t of diesel oil. The flotation process parameters are: flotation column aeration rate of 0.25 m. 3 / h, foam layer thickness 20cm, rinsing water flow rate 0.8L / min; adopting a process of one roughing and one cleaning and two scavenging, the final fine II concentrate is sulfur concentrate, the sulfur grade in the sulfur concentrate is 92.31%, and the elemental sulfur recovery rate is 84.38%.

[0049] Comparing the sulfur grade and sulfur recovery rate of Examples 1-2 and Comparative Example 1, it can be seen that insufficient dissociation is caused by not grinding the oxygen pressure leaching residue, while excessive grinding causes ore slime interference, resulting in low flotation indicators. When the ultrafine grinding particle size D50 = 17μm is controlled, the minerals can be fully dissociated and the hydrophilic film can be stripped, laying the foundation for efficient flotation.

[0050] Comparative Example 2 Comparative Example 2 provides a process for recovering elemental sulfur from oxygen pressure leaching residue. The specific process steps are as follows: S1. The sample used in the experiment was oxygen pressure leaching residue slurry. The oxygen pressure leaching residue slurry was ground to D50=17μm using a vertical stirred mill, and the particle size distribution after fine grinding was the same as in Example 1.

[0051] S2. The finely ground oxygen pressure leaching slurry is added to the flotation machine, and 200 g / t of sodium mercaptoacetate inhibitor, 50 g / t of ethyl thiocyanate collector and 150 g / t of diesel are added. The sulfur grade in the final sulfur concentrate is 74.24%, and the elemental sulfur recovery rate is 66.72%.

[0052] Comparing the sulfur grade and sulfur recovery rate of Example 1 and Comparative Example 2, it can be seen that for a strong acid, high salt oxygen pressure leaching residue system with D50 = 17 μm, the flotation column is significantly better than the traditional flotation machine in terms of both concentrate grade and recovery rate. The flotation column is more suitable for the efficient recovery process of elemental sulfur in oxygen pressure leaching residue of the present invention.

[0053] Comparative Example 3 Comparative Example 3 provides a process for recovering elemental sulfur from oxygen pressure leaching residue, and the specific process steps are as follows: S1. The sample used in the experiment was oxygen pressure leaching residue slurry. The oxygen pressure leaching residue slurry was ground to D50=17μm using a vertical stirred mill. The particle size distribution before and after fine grinding was the same as in Example 1.

[0054] S2. Add the finely ground oxygen pressure leaching slurry to a KYZ flotation column. Figure 3 The collectors butyl xanthate (50 g / t) and pine oil (150 g / t) were added. The flotation process parameters were: flotation column aeration rate 0.25 m. 3 / h, foam layer thickness 20cm, rinsing water flow rate 0.8L / min; adopting a process of one roughing and one cleaning and two scavenging, the final fine II concentrate is sulfur concentrate, the sulfur grade in the sulfur concentrate is 76.11%, and the elemental sulfur recovery rate is 68.16%.

[0055] Comparing the sulfur grade and sulfur recovery rate of Example 1 and Comparative Example 3, it can be seen that under strong acid (pH<1) and high Zn content conditions, sulfur recovery rate is significantly higher than that of Example 3. 2+ / F3 2+ In the environment, traditional xanthate systems fail to achieve flotation due to reagent decomposition and surface hydrophilic film shielding. The ethyl thiocyanate-neutral oil synergistic collector system of this invention, combined with the bifunctional sodium mercaptoacetate, provides a stable collector and effective surface film removal, achieving efficient separation of elemental sulfur and sulfide minerals. The concentrate grade and recovery rate are significantly better than those of traditional methods.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for recovering elemental sulfur from oxygen pressure leaching residue, characterized in that, Includes the following steps: The oxygen pressure leaching residue slurry is ground, and the ground oxygen pressure leaching residue slurry is mixed with a collector and a depressant for flotation to obtain sulfur concentrate; the collector includes ethyl thiocyanate and neutral oil; the depressant includes sodium mercaptoacetate.

2. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The particle size D50 of the ground oxygen pressure leaching residue is 14-20 μm.

3. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The mass ratio of the collector to the oxygen pressure leaching residue is (100-400) g : 1 t; And / or, the mass ratio of the inhibitor to the oxygen pressure leaching residue is (100-300) g : 1 t.

4. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 3, characterized in that, The mass ratio of the ethyl thiocyanate to oxygen pressure leaching residue is (30-80) g : 1 t; And / or, the mass ratio of the neutral oil to the oxygen pressure leaching residue is (100-200) g : 1 t.

5. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The neutral oil includes at least one of diesel, kerosene, and gasoline; Preferably, the diesel fuel is light diesel fuel.

6. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The flotation operation uses a flotation column; Preferably, the flotation column has a diameter of 0.6 to 6 m and a height of 7 to 15 m.

7. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 6, characterized in that, The process parameters for the flotation operation are selected from at least one of the following: a) The aeration rate of the flotation column is 0.1-0.4 m³. 3 / h; b) The thickness of the foam layer in the flotation column is 5-30 cm; c) Flushing water flow rate: 0.1-2 L / min.

8. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The oxygen pressure leaching residue includes elemental sulfur, iron sulfide minerals, zinc sulfide minerals, and silicate minerals.

9. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The flotation process includes one roughing operation and two cleaning operations.

10. The method for recovering elemental sulfur from oxygen pressure leaching residue according to claim 1, characterized in that, The environmental conditions for the flotation operation are a temperature of 0-40℃ and a pressure of 0.8-1.2 standard atmospheres.

Images