Method for cooperating recovery of iron powder and copper sulfide concentrate from copper residue flotation tailings

Abstract

The application discloses a method for cooperatively recovering iron powder and copper sulfide concentrate from copper slag flotation tailings, and belongs to the technical field of metallurgical waste residue resource utilization. The copper slag flotation tailings are finely ground; an alkaline additive is added to adjust the alkalinity R to 0.6-1.2. The material is placed in air or oxygen-enriched air and kept at 650-900 DEG C for 20-60 min. Then the material is placed in a reducing atmosphere and kept at 700-1000 DEG C for 30-90 min. 0.5-3.0 wt% of a sulfidizing agent is added to the material; the material is kept at 900-1150 DEG C for 20-60 min in a weak reducing atmosphere. Then the material is annealed at 1050-1250 DEG C for 20-60 min; and then the material is cooled to room temperature in an inert atmosphere or a weak reducing atmosphere. The material is ground to separate the iron phase and copper sulfide, and low-intensity magnetic separation is performed to obtain magnetic iron powder and a non-magnetic mixture; the non-magnetic mixture is subjected to sulfidation flotation at pH 8-11 to recover copper sulfide concentrate. Through the multi-step thermochemical process of alkalinity adjustment, pre-oxidation, selective reduction and sulfidation segregation, the method realizes deep separation of the iron powder and the copper sulfide concentrate with low energy consumption, high selectivity and no pollution.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical waste slag resource utilization technology, specifically relating to a method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings. Background Technology

[0002] Copper slag flotation tailings are a secondary resource generated during copper smelting. They are usually acidic slags with low copper content. The iron phase is mainly composed of magnetite and ferromagnesian olivine, while the copper is mostly distributed in the form of copper sulfide beads or copper-rich droplets, which are tightly wrapped by the iron silicate phase. The particles are small and have a complex intergrowth relationship with the magnetic phase.

[0003] Currently, the common treatment for this type of tailings is a single-step high-temperature direct reduction, which uses solid carbon or coal-based materials as reducing agents combined with magnetic separation. While this method can yield high-grade iron powder, during the high-temperature, long-duration reduction process, copper easily diffuses into the iron phase and forms microalloys or solid solutions, causing copper to enter the magnetic products along with the magnetic iron powder. This makes effective phase separation of iron and copper difficult, limiting the downstream use of the iron powder, reducing the beneficiation and smelting value of copper, and resulting in resource waste and the risk of byproduct pollution.

[0004] Therefore, there is an urgent need to develop a method that can effectively break down the ferrosilicon network structure and dissociate the encapsulated copper phase in tailings under moderate temperature and conventional reagent conditions. By controlling the process in stages, copper-iron alloying can be suppressed, and copper can be precipitated as independent sulfide droplets. Combined with a low-intensity magnetic separation and flotation process, efficient separation and recovery of iron powder and copper sulfide concentrate can be achieved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings.

[0006] The objective of this invention is achieved as follows: the method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings includes the following steps: Alkalinity adjustment: Grind the copper slag flotation tailings into fine powder; add an alkaline additive, wherein the alkaline additive is one or more of limestone, dolomite, and cement kiln co-processing dust, and adjust the alkalinity R=(WCaO+WMgO) / (WSiO2+WAl2O3) of the system to 0.6-1.2. Pre-oxidation: Place the alkalinity-adjusted material in air or oxygen-enriched air and keep it at 650-900℃ for 20-60 min; Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere and kept at 700~1000℃ for 30~90min; Sulfidation: A sulfiding agent is added to the selectively reduced material; the sulfiding agent is any one or more of elemental sulfur, pyrite, and thiosulfate, and the amount added is 0.5~3.0 wt% of the total mass of the material; the material is kept at 900~1150℃ for 20~60 min under a weak reducing atmosphere. Annealing and cooling: Anneal the vulcanized material at 1050~1250℃ for 20~60min; then cool the material to room temperature in an inert atmosphere or a weak reducing atmosphere; Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation, which refers to a magnetic induction intensity of 0.1~0.3T, to obtain a mixture of magnetic iron powder and non-magnetic powder; the non-magnetic mixture is subjected to sulfide flotation under pH conditions of 8~11 to recover copper sulfide concentrate.

[0007] Compared with the prior art, the technical solution described in this invention has the following advantages: 1. By adding alkaline additives such as limestone and dolomite, CaO and MgO react with fir olivine, displacing FeO from the stable olivine structure and turning it into free, more active ferrous oxide, thus achieving the chemical deconstruction of copper slag flotation tailings.

[0008] 2. The oxidation process in air or oxygen-rich air will destroy the original microstructure. The copper phase that was originally encapsulated will migrate and merge due to the change in interfacial energy. Pre-oxidation will achieve coarsening of copper phase grains, creating good grain size conditions for subsequent separation.

[0009] 3. By controlling the hydrogen concentration and reaction temperature, the highly reactive FeO is preferentially reduced to metallic iron nuclei. At the same time, the diffusion of copper into the iron lattice is suppressed, so that copper exists in the form of independent sulfides or metal droplets, thereby achieving the physical separation of iron and copper and avoiding the formation of copper-iron alloys.

[0010] 4. Through sulfidation treatment, copper oxide or metallic copper is converted into stable Cu2S or (Cu,Fe)S. These sulfides have a large wetting angle on the surface of metallic iron and are not easy to adhere to, thus avoiding copper being carried into the iron powder during magnetic separation, which would result in high copper content in the iron powder and copper loss.

[0011] 5. High-temperature annealing dissolves small iron particles, which then deposit onto larger particles, transforming the dispersed iron particles into dense, large particles, which is more conducive to magnetic separation. Subsequent weak magnetic separation processes are then employed to recover only the strongly magnetic, large iron powder particles, avoiding the mechanical entrainment of weakly magnetic copper sulfides.

[0012] In summary, the technical solution described in this invention, through a multi-step thermochemical process of "alkalinity adjustment - pre-oxidation - selective reduction - sulfide segregation", first unlocks the copper phase encapsulated in the magnesia-ferrolithium matrix, then inhibits the diffusion of copper into the iron phase and transforms it into independent sulfide droplets, significantly reducing the tendency of copper-iron alloying and solid solution. Combined with weak magnetic physical separation, it achieves deep separation of iron powder and copper sulfide concentrate with low energy consumption, high selectivity, and no pollution. Detailed Implementation

[0013] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the scope of protection of the present invention.

[0014] The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to the present invention includes the following steps: Alkalinity adjustment: Grind the copper slag flotation tailings into fine powder; add an alkaline additive, which is one or more of limestone, dolomite, and cement kiln co-processing dust, to adjust the alkalinity R=(WCaO+WMgO) / (WSiO2+WAl2O3) of the system to 0.6-1.2.

[0015] Pre-oxidation: The alkalinity-adjusted material is placed in air or oxygen-enriched air and kept at 650–900℃ for 20–60 min; this causes the ferromagnetic olivine to be partially oxidized into magnetite and / or hematite, while simultaneously unlocking the encapsulated copper phase and increasing its separable size.

[0016] Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere and kept at 700~1000℃ for 30~90min; the iron oxide is selectively reduced to a diffusely distributed metallic iron core, while the diffusion and wetting of copper into the iron phase is controlled, so that copper exists in the form of independent sulfide droplets or metallic copper microdroplets.

[0017] Sulfidation: A sulfiding agent is added to the selectively reduced material; the sulfiding agent is any one or more of elemental sulfur, pyrite, and thiosulfate, and the amount added is 0.5~3.0 wt% of the total mass of the material; the material is kept at 900~1150℃ for 20~60 min under a weak reducing atmosphere; the copper in the material is converted into Cu2S and / or (Cu,Fe)S droplets, and they grow and aggregate, while reducing the wettability between the copper phase and the iron phase and inhibiting copper-iron alloying.

[0018] Annealing and cooling: Anneal the sulfided material at 1050~1250℃ for 20~60min; causing the dispersed iron nuclei to migrate and aggregate into dense large-particle iron phase; then cool the material to room temperature in an inert atmosphere or weak reducing atmosphere to avoid re-oxidation of the iron phase.

[0019] Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation, which refers to a magnetic induction intensity of 0.1~0.3T, to obtain a mixture of magnetic iron powder and non-magnetic powder; the non-magnetic mixture is subjected to sulfide flotation under pH conditions of 8~11 to recover copper sulfide concentrate.

[0020] In the alkalinity adjustment process, grinding the copper slag flotation tailings means grinding it to a D50 of 0.05–0.15 mm. The total amount of alkaline additive added is 10–35 wt% of the mass of the copper slag flotation tailings. The preferred alkalinity R is 0.8–1.0.

[0021] In the pre-oxidation process, the oxygen volume fraction of the oxygen-enriched air is 25-50%. The pre-oxidation temperature is preferably 700-850℃, and the pre-oxidation time is preferably 30-50 minutes.

[0022] In the selective reduction process, the reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 5-30%, preferably 10-25%. The reduction temperature is preferably 800-950°C, and the reduction time is preferably 45-75 minutes.

[0023] In the sulfidation process, the sulfiding agent is preferably pyrite, added at 1.0–2.0 wt%, or elemental sulfur, added at 0.8–1.5 wt%. The sulfidation temperature is preferably 950–1100℃, and the sulfidation time is preferably 20–40 min.

[0024] Furthermore, in the vulcanization process, a sulfate auxiliary is preferably added, with the amount added being 1.0 to 4.0 wt% of the total mass of the material; the sulfate auxiliary is preferably sodium sulfate, with the amount added preferably being 1.0 to 3.0 wt%.

[0025] In the vulcanization process and the annealing and cooling process, the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 1-4%.

[0026] In the annealing and cooling process, the annealing temperature is preferably 1100-1200℃, and the annealing time is preferably 20-40 min.

[0027] In the separation process, the magnetic induction intensity is preferably 0.15~0.25T. The pH value of the sulfide flotation is preferably 9~10, and xanthate collectors and / or dioxin collectors are used.

[0028] Example 1

[0029] Alkalinity adjustment: Grind the copper slag flotation tailings to a D50 of 0.10 mm. Add 15-20 wt% dolomite from the copper slag flotation tailings to adjust the alkalinity R of the system to 0.85-0.95.

[0030] Pre-oxidation: Place the alkalinity-adjusted material in an air atmosphere and keep it at 780-820℃ for 30-50 minutes.

[0031] Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere with a hydrogen / nitrogen volume fraction of 10-20% and kept at 880-920℃ for 50-70 minutes.

[0032] Sulfidation: Add 1.0–2.0 wt% pyrite and 1.0–2.0 wt% sodium sulfate to the selectively reduced material; keep the material at 980–1040 °C for 25–35 min in a weakly reducing atmosphere with a hydrogen / nitrogen volume fraction of 2%.

[0033] Annealing and cooling: Anneal the vulcanized material at 1120-1180℃ for 20-30 minutes; then cool the material to room temperature in an inert atmosphere.

[0034] Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation with a magnetic induction intensity of 0.18~0.22T to obtain a mixture of magnetic iron powder and non-magnetic powder. The non-magnetic mixture is subjected to sulfide flotation at a pH of 9~10, using xanthate collectors and / or dioxin collectors to recover copper sulfide concentrate.

[0035] Recovery results: Magnetic iron powder has an Fe grade of 89-91% and contains 0.25-0.40% Cu, with an iron recovery rate of 86-89%; copper concentrate has a Cu grade of 18-26% and a copper recovery rate of 78-84%.

[0036] Example 2

[0037] Alkalinity adjustment: Grind the copper slag flotation tailings to a D50 of 0.08~0.12mm. Add limestone at 20~25wt% of the copper slag flotation tailings to adjust the alkalinity R of the system to 0.95~1.05.

[0038] Pre-oxidation: Place the alkalinity-adjusted material in oxygen-enriched air with an oxygen volume fraction of 25% and keep it at 700-760℃ for 40-50 minutes.

[0039] Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere with a hydrogen / nitrogen volume fraction of 10-15% and kept at 820-880℃ for 60-75 minutes.

[0040] Sulfurization: Add 0.8–1.5 wt% of elemental sulfur and 1.5–3.0 wt% of sodium sulfate to the selectively reduced material; keep the material at 960–1020 °C for 20–30 min in a weakly reducing atmosphere with a hydrogen / nitrogen volume fraction of 3%.

[0041] Annealing and cooling: Anneal the vulcanized material at 1100-1150℃ for 20-30 minutes; then cool the material to room temperature in an inert atmosphere.

[0042] Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation with a magnetic induction intensity of 0.20~0.25T to obtain a mixture of magnetic iron powder and non-magnetic powder. The non-magnetic mixture is subjected to sulfide flotation at a pH of 9~10, using xanthate collectors and / or dioxin collectors to recover copper sulfide concentrate.

[0043] Recovery results: Magnetic iron powder has an Fe grade of 88-90% and contains 0.30-0.45% Cu, with an iron recovery rate of 85-87%; copper concentrate has a Cu grade of 20-30% and a copper recovery rate of 75-82%.

[0044] Example 3

[0045] Alkalinity adjustment: Grind the copper slag flotation tailings to a D50 of 0.06~0.10mm. Add 10~15wt% of dolomite from the copper slag flotation tailings to adjust the alkalinity R of the system to 0.8~0.9.

[0046] Pre-oxidation: Place the alkalinity-adjusted material in oxygen-enriched air with an oxygen volume fraction of 30% and keep it at 820-860℃ for 20-30 minutes.

[0047] Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere with a hydrogen / nitrogen volume fraction of 20-30% and kept at 900-950℃ for 40-60 minutes.

[0048] Sulfidation: Add 0.5-1.0 wt% pyrite to the selectively reduced material; keep the material at 1000-1080℃ for 20-30 min in a weakly reducing atmosphere of 4% hydrogen / nitrogen by volume.

[0049] Annealing and cooling: Anneal the vulcanized material at 1150-1200℃ for 20-30 minutes; then cool the material to room temperature in the same weak reducing atmosphere as the previous step.

[0050] Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation with a magnetic induction intensity of 0.15~0.20T to obtain a mixture of magnetic iron powder and non-magnetic powder. The non-magnetic mixture is subjected to sulfide flotation at a pH of 8~9, using xanthate collectors and / or dioxin collectors to recover copper sulfide concentrate.

[0051] Recovery results: The magnetic iron powder has an Fe grade of 88-91% and contains 0.28-0.45% Cu, with an iron recovery rate of ≥85%; the copper concentrate has a Cu grade of 17-24% and a copper recovery rate of approximately 76-80%.

[0052] Example 4

[0053] — Comparative Example (Single-step high-temperature direct reduction combined with magnetic separation) Comparative process: No alkalinity R adjustment, pre-oxidation, or sulfidation is performed; after single-step reduction at ≥1200℃ for 60–90 min, magnetic separation is carried out with a magnetic induction intensity of 0.2 T.

[0054] Recovery results: The magnetic iron powder has an Fe grade of 88-90% and contains 0.8-1.2% Cu. A large amount of copper enters with the magnetic products, making it difficult to obtain independent copper concentrate. Compared with the technical solution described in this invention, the magnetic products have high copper inclusions and low copper diversion recovery rate.

[0055] Example 5

[0056] —Comparative example (alkalinity not adjusted, only pre-oxidation combined with reduction treatment) Comparative process: No limestone or dolomite is added to adjust the alkalinity; the rest of the process is the same as in Example 1.

[0057] Recovery results: The slag phase has high viscosity and poor metal phase migration, resulting in decreased magnetic separation efficiency; the Fe grade of the magnetic iron powder is 86-88%, containing 0.6-0.9% Cu, and the grade and recovery rate of copper concentrate are significantly reduced.

Claims

1. A method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings, characterized in that, The process includes the following steps: Alkalinity adjustment: Grind the copper slag flotation tailings into fine powder; add an alkaline additive, wherein the alkaline additive is one or more of limestone, dolomite, and cement kiln co-processing dust, and adjust the alkalinity R=(WCaO+WMgO) / (WSiO2+WAl2O3) of the system to 0.6-1.

2. Pre-oxidation: Place the alkalinity-adjusted material in air or oxygen-enriched air and keep it at 650-900℃ for 20-60 minutes; Selective reduction: The pre-oxidized and reconstructed material is placed in a reducing atmosphere and kept at 700~1000℃ for 30~90min; Sulfidation: A sulfiding agent is added to the selectively reduced material; the sulfiding agent is any one or more of elemental sulfur, pyrite, and thiosulfate, and the amount added is 0.5~3.0 wt% of the total mass of the material; the material is kept at 900~1150℃ for 20~60 min under a weak reducing atmosphere. Annealing and cooling: Anneal the vulcanized material at 1050~1250℃ for 20~60min; then cool the material to room temperature in an inert atmosphere or a weak reducing atmosphere; Separation: The cooled material is ground until the iron phase and copper sulfide are dissociated, and then subjected to low-intensity magnetic separation, which refers to a magnetic induction intensity of 0.1~0.3T, to obtain a mixture of magnetic iron powder and non-magnetic powder; the non-magnetic mixture is subjected to sulfide flotation under pH conditions of 8~11 to recover copper sulfide concentrate.

2. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the alkalinity adjustment process, the alkalinity R is 0.8 to 1.

0.

3. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the pre-oxidation process, the pre-oxidation temperature is 700-850℃ and the time is 30-50 minutes.

4. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the selective reduction process, the reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 5-30%.

5. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the selective reduction process, the reduction temperature is 800–950°C and the time is 45–75 min.

6. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the sulfidation process, the sulfiding agent is pyrite, with an addition amount of 1.0 to 2.0 wt% or elemental sulfur, with an addition amount of 0.8 to 1.5 wt%.

7. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the vulcanization process, the sulfate auxiliary is sodium sulfate, and the amount added is 1.0 to 3.0 wt%.

8. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the vulcanization process, the vulcanization temperature is 950–1100°C and the time is 20–40 minutes.

9. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the annealing and cooling process, the annealing temperature is 1100-1200℃ and the time is 20-40 minutes.

10. The method for co-recovering iron powder and copper sulfide concentrate from copper slag flotation tailings according to claim 1, characterized in that, In the sorting process, the magnetic induction intensity is 0.15~0.25T.