A method for improving the leaching of copper from roasted ores

Abstract

The present application relates to a method for improving the leaching rate of copper in roasted ore, belonging to the field of zinc hydrometallurgy. The present application uses the traditional process of neutral leaching + weak acid leaching + sub-heat acid leaching to leach the roasted ore, effectively improves the leaching rate of copper by adding excessive oxidizing agent and roasted ore in the neutral leaching and controlling the leaching time; and further reduces the copper residue and improves the leaching rate of copper by controlling the weak acid leaching and sub-heat acid leaching process. The method of the present application can increase the leaching rate of copper in roasted ore by 16.67%, reduce the amount of copper entering the acid leaching residue, improve the recovery rate of copper, reduce resource waste, increase the recovery amount of copper in roasted ore for zinc smelting enterprises, and increase the economic benefits of enterprises.

Description

Technical Field

[0001] This invention belongs to the field of zinc hydrometallurgy, specifically, it relates to the recovery and utilization of associated copper in zinc concentrate. Background Technology

[0002] Copper has good ductility, thermal conductivity, and electrical conductivity, making it an important non-ferrous metal with a wide range of applications.

[0003] Copper is often found as a byproduct in zinc concentrate, with high-copper zinc concentrate containing 1-3% copper. After desulfurization in a fluidized bed roaster, copper enters the roasted zinc ore. During leaching, copper is distributed in the neutral leaching solution and acid leaching residue. During the purification of the neutral leaching solution, copper enters the copper-cadmium slag. After leaching the zinc and cadmium from the copper-cadmium slag, the copper is recovered as copper slag. When the acid leaching residue is treated in a fuming furnace or rotary kiln, most of the copper distributed in the acid leaching residue is lost, except for a very small amount that enters the secondary zinc oxide dust, and is lost in the fuming furnace water quenching slag or rotary kiln slag.

[0004] In existing technologies, when using a neutral leaching + weak acid leaching process for roasted ore, the copper leaching rate is 30-40%. When using a neutral leaching + weak acid leaching + subthermal acid leaching process, the copper leaching rate is 50-60%. The leached copper is recovered and reused, while the unleached copper is largely lost in the slag from the fuming furnace or rotary kiln. Current roasted ore leaching processes result in low copper leaching rates and significant copper losses in the slag from the fuming furnace or rotary kiln, leading to resource waste, limiting the amount of high-copper-zinc concentrate that zinc smelters can purchase, and impacting their economic efficiency. Summary of the Invention

[0005] To overcome the problems existing in the background technology, the present invention provides a method for improving the copper leaching rate in roasted ore. Compared with the current zinc roasted ore leaching process, the copper leaching rate is increased by more than 16.67%, the amount of copper entering the acid leaching residue is reduced, the copper recovery rate is improved, resource waste is reduced, and the economic benefits of enterprises are increased.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] The roasted ore is subjected to neutral leaching, weak acid leaching, and subthermal acid leaching steps, so that copper ultimately enters the neutral leaching solution. The solutions from the weak acid leaching and subthermal acid leaching steps are returned to the neutral leaching step. An excess of roasted ore is added to the neutral leaching step, and the leaching time is controlled to prevent copper from precipitating into the slag. The acidity of the weak acid leaching step is controlled during the process and at the end point to prevent copper from precipitating into the slag. An excess of oxidant is added to the neutral leaching step to prevent copper from precipitating into the slag in the weak acid leaching and subthermal acid leaching steps.

[0008] Furthermore, the excessive addition of roasted ore means that the amount of roasted ore added is 1.1-1.3 times the theoretical amount.

[0009] Furthermore, the neutral leaching time is 1.0-1.5 hours.

[0010] Furthermore, the weak acid leaching process and endpoint: H2SO4 5-10 g / L.

[0011] Furthermore, during the leaching of subthermic acid, the leaching temperature is 70-85℃, the leaching time is 1.0-3.0h, and the process and endpoint are H2SO4 20-60g / L.

[0012] Furthermore, the oxidant is added in excess, meaning the amount of oxidant added is 1.2-1.4 times the theoretical amount.

[0013] Furthermore, the oxidant is one or both of manganese powder and zinc electrolytic anode mud.

[0014] Furthermore, a neutral acid leaching is performed, wherein the acid solution is prepared from a weak acid leaching solution, a subthermal acid leaching solution, and an acidic solution.

[0015] Furthermore, weak acid leaching and subthermal acid leaching are performed using an acidic solution, wherein the acidic solution is one or both of dilute sulfuric acid and zinc electrolytic waste liquid.

[0016] Furthermore, the acid leaching residue produced in the subthermal acid leaching step is used to recover zinc through a fumigation furnace or rotary kiln.

[0017] Furthermore, the copper entering the neutral leachate is recovered after purification and cadmium leaching.

[0018] The beneficial effects of this invention are:

[0019] This invention effectively reduces the amount of copper entering the slag during the neutral leaching process by adding an excessive amount of oxidant and roasted ore in the neutral leaching process and by controlling the leaching time, thereby increasing the copper leaching rate.

[0020] This invention reduces the ZnS content in the leaching residue by controlling the acidity during the weak acid leaching process and the final acidity, thereby reducing the probability of copper entering the residue as CuS during weak acid leaching.

[0021] This invention reduces the probability of copper entering the slag as CuS during subthermal acid leaching by adding an excessive amount of oxidant during neutral leaching.

[0022] This invention, by controlling the acidity during the subthermal acid leaching process and the final acidity, enables CuFe2O4 to be leached while only a small amount of ZnFe2O4 is leached, thereby increasing the copper leaching rate and reducing the iron leaching rate.

[0023] This invention increases the copper leaching rate in roasted ore by 16.67%, reduces the amount of copper entering the acid leaching residue, improves the copper recovery rate in roasted ore, reduces resource waste, and enables zinc smelting enterprises to increase the amount of copper recovered from roasted ore, thereby increasing the economic benefits of the enterprises. Detailed Implementation

[0024] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0025] The method for increasing the copper leaching rate in roasted ore includes the following steps:

[0026] (1) Neutral leaching

[0027] Acidic solution, weak acid leaching solution and subthermal acid leaching solution are prepared into acid solution and oxidant is added. Roasted ore is added to acid solution for neutral leaching. The leaching temperature is controlled at 70-80℃, the leaching time is 1.0-1.5h, and the pH value at the leaching endpoint is 4.6-4.8, so that zinc and copper in roasted ore enter the solution.

[0028] The acid solution is prepared from a weak acid leachate, a subthermal acid leachate, and an acidic solution; the acidic solution is one or both of dilute sulfuric acid and zinc electrolysis waste liquid.

[0029] The amount of added oxidant is 1.2-1.4 times the theoretical amount.

[0030] The oxidant is one or both of manganese powder and zinc electrolytic anode mud.

[0031] The theoretical amount of oxidant is shown in reaction formula (1).

[0032] ZnS+MnO2+2H2SO4=ZnSO4+MnSO4+S+2H2O (1)

[0033] Copper in roasted ore exists primarily as CuO, and also contains Cu₂O and CuFe₂O₄. During neutral leaching, CuO and Cu₂O are mainly leached out in large quantities. Roasted ore also contains a small amount of ZnS. As a large amount of ZnO is leached from the roasted ore, ZnS becomes enriched in the neutral leaching pulp and combines with the already leached Cu. 2+ The following reaction occurs:

[0034] ZnS + CuSO4 = CuS↓ + ZnSO4 (2)

[0035] Through extensive experimental research, the inventors discovered that reaction (2) occurs across a wide range of acidities, from pH 4.5 up to 150 g / L H2SO4. Furthermore, the CuS generated by reaction (2) has a high electrode potential, meaning it is almost entirely unleached in subsequent weak acid and subthermal acid leaching steps. Therefore, once formed, CuS is ultimately lost in the acid leaching residue. In addition, the inventors found that by shortening the neutral leaching reaction time—from the conventional 2.0-3.0 h to 1.0-1.5 h, and using 1.1-1.3 times the theoretical amount of roasted ore—reaction (2) can be suppressed, thereby reducing the amount of copper entering the acid leaching residue and increasing the copper leaching rate. Therefore, controlling the neutral leaching time and the excess amount of roasted ore is crucial.

[0036] The theoretical quantity of roasted ore is shown in reaction formula (3).

[0037] ZnO + H₂SO₄ = ZnSO₄ + H₂O (3)

[0038] After the neutral leaching slurry is thickened and clarified, copper enters the middle and upper clarifiers, while the bottom clarifier flows into the weak acid leaching solution. After purification, the copper enters the copper-cadmium slag. After leaching zinc and cadmium from the copper-cadmium slag, the copper is recovered and reused as copper slag.

[0039] (2) Weak acid leaching

[0040] Acidic solution is added to the neutral leaching underflow for weak acid leaching. This step mainly leaches out excess zinc oxide and zinc silicate from the roasted ore, while also leaching copper. During weak acid leaching, the amount of leaching residue is further reduced, and the ZnS content in the leaching residue is further increased.

[0041] In existing technologies, the leaching time with weak acid is controlled at 1.0-4.0 h, the leaching temperature at 70-85 °C, and the pH value during and at the end of the leaching process at 2.0-3.0 (equivalent to 0.05-0.5 g / L of H₂SO₄). The inventors have discovered that even with the addition of excessive oxidant during neutral leaching, a large amount of Fe is still generated when the pH value during and at the end of the leaching process is 2.0-3.0. 2+ The reaction mechanism is as follows:

[0042] Fe(OH)3+H2SO4=Fe2(SO4)3+H2O (4)

[0043] Fe2(SO4)3+ZnS=2FeSO4+ZnSO4+S↓ (5)

[0044] Reaction (4): During neutral leaching, the hydrolyzed precipitate Fe(OH)3 undergoes a small amount of redissolved into the solution during weak acid leaching. The reduced amount of leaching residue leads to an increase in the ZnS content in the residue, and the low acidity is insufficient to allow the oxidant and Fe... 2+The reaction occurred, thus reaction (5) took place, resulting in the formation of Fe in the solution. 2+ In Fe 2+ During formation, the Cu leached 2+ It will also react with ZnS to form reaction (2), causing Cu 2+ The sediment settles into the slag.

[0045] Through extensive experimental research, the inventors have promoted the preferential reaction between ZnS and the oxidant by increasing the acidity of the weak acid leaching process and the acidity at the leaching endpoint (1).

[0046] After reaction (1) occurs, the ZnS content in the slag is reduced, thus avoiding the reaction of ZnS and Cu. 2+ A reaction occurs.

[0047] Extensive experimental research has revealed that during weak acid leaching, the process and endpoint acidity are extremely important for driving reaction (1). When the H2SO4 content is <5 g / L, reaction (1) proceeds poorly, making it difficult to prevent reaction (2) from occurring; when the H2SO4 content is >10 g / L, the pulp's thickening and clarifying properties are poor. Therefore, controlling the H2SO4 content during weak acid leaching to 5-10 g / L at both the process and endpoint, by driving reaction (1), can both prevent reaction (2) from occurring and ensure the pulp's thickening and clarifying properties.

[0048] After the weak acid leaching slurry is thickened and clarified, the supernatant (weak acid leaching solution) is returned to the neutral leaching step for leaching solution preparation, and the bottom flows into the subthermal acid leaching.

[0049] (3) Subthermic acid leaching

[0050] Acid solution is added to the weak acid leaching underflow for subthermal acid leaching. The main purpose of this step is to leach out metallic Cu and CuFe2O4 generated during the neutral and weak acid leaching steps of Cu2O leaching. The reaction formula is as follows:

[0051] Cu+MnO2+2H2SO4=CuSO4+MnSO4+2H2O (6)

[0052] CuFe2O4+4H2SO4=CuSO4+Fe2(SO4)3+4H2O (7)

[0053] CuFe₂O₄ is less stable than ZnFe₂O₄ under acidic conditions. Therefore, during subthermal acid leaching, controlling the leaching temperature to 70-85℃, the leaching time to 1.0-3.0 h, and the concentration of H₂SO₄ to 20-60 g / L will allow CuFe₂O₄ to leach out, while only a small amount of ZnFe₂O₄ will be leached out, thus avoiding the leaching of Fe. 3+ Enrichment occurs.

[0054] Because reaction (2) occurs over a very wide range of acidities, CuS precipitate will also be produced during subthermal acid leaching. Through extensive experimental research, the inventors discovered that when an excess of manganese powder is added during neutral leaching, reaction (1) will preferentially occur during subthermal acid leaching, thereby consuming ZnS in the residue and preventing reaction (2) from occurring. Through experimental comparison, the oxidant added during neutral leaching needs to be 1.2-1.4 times the theoretical amount.

[0055] After the subthermal acid leaching slurry is thickened, clarified, and filtered, the supernatant and filtrate (subthermal acid leaching solution) are returned to the neutral leaching solution. The filter residue is acid leaching residue, which is used to recover zinc through a fuming furnace or rotary kiln.

[0056] To illustrate the present invention more clearly, the following embodiments will be described in detail.

[0057] Example 1

[0058] The main components (%wt) of the roasted ore used in this embodiment are: Zn 56.82, Fe 12.06, Cu 1.16.

[0059] The amount of manganese powder added to the acid solution was 1.4 times the theoretical amount, and the amount of roasted ore added was 1.3 times the theoretical amount. The leaching temperature was controlled at 85℃, the leaching time was 1.5h, and the final pH value was 4.8. After the neutral leaching slurry was thickened and clarified, neutral leachate and neutral underflow were produced.

[0060] Zinc electrolytic waste liquid was added to the neutral underflow for weak acid leaching, and the weak acid leaching process and endpoint H2SO4 were controlled at 10g / L. After the weak acid leaching slurry was thickened and clarified, weak acid leachate and weak acid underflow were produced. The weak acid leachate was returned to the neutral leaching process to prepare acid solution.

[0061] Dilute sulfuric acid was added to the weak acid underflow for subthermal acid leaching. The leaching temperature was controlled at 70℃ and the leaching time was 3.0h. The process and endpoint were H2SO4 20g / L. After the subthermal acid leaching slurry was thickened, clarified, and filtered, subthermal acid leaching solution and acid leaching residue were produced. The subthermal acid solution was returned to the neutral leaching solution to prepare acid solution, and the acid leaching residue was sent to the fumigation furnace for treatment.

[0062] Based on the acid leaching residue rate and copper content in the acid leaching residue, the copper leaching rate is 80.03%. The calculation method is: Leaching rate = (amount of acid leaching residue * copper content in acid leaching residue) / (amount of zinc roasted ore * copper content in zinc roasted ore). The algorithm is the same in the following examples.

[0063] Example 2

[0064] The main components (%wt) of the roasted ore used in this embodiment are: Zn 59.38, Fe 8.76, Cu 0.52.

[0065] Manganese powder and zinc electrolytic anode mud were added to the acid solution as oxidants, with the oxidant amount being 1.2 times the theoretical amount. The amount of roasted ore added was 1.1 times the theoretical amount. The leaching temperature was controlled at 70℃, the leaching time was 1.0 h, and the final pH value was 4.6. After the neutral leaching slurry was thickened and clarified, neutral leachate and neutral underflow were produced.

[0066] Dilute sulfuric acid was added to the neutral underflow for weak acid leaching, and the weak acid leaching process and endpoint H2SO4 5g / L were controlled. After the weak acid leaching slurry was thickened and clarified, weak acid leachate and weak acid underflow were produced. The weak acid leachate was returned to the neutral leaching process to prepare acid solution.

[0067] Zinc electrolysis waste liquid was added to the weak acid underflow for subthermal acid leaching. The leaching temperature was controlled at 80℃ and the leaching time was 1.0 h. The process and endpoint H2SO4 was 60 g / L. After the subthermal acid leaching slurry was thickened, clarified, and filtered, subthermal acid leaching solution and acid leaching residue were produced. The subthermal acid leaching solution was returned to neutral leaching to prepare acid solution, and the acid leaching residue was processed in a rotary kiln.

[0068] Based on the acid leaching residue rate and the copper content in the acid leaching residue, the copper leaching rate was 72.23%.

[0069] Example 3

[0070] The main components (%wt) of the roasted ore used in this embodiment are: Zn 58.74, Fe 9.39, Cu 0.83.

[0071] Acid solution was added to zinc electrolytic anode mud, with the amount of anode mud added being 1.3 times the theoretical amount, and roasted ore added being 1.2 times the theoretical amount. The leaching temperature was controlled at 78℃, the leaching time was 1.2h, and the final pH value was 4.7. After the neutral leaching slurry was thickened and clarified, neutral leachate and neutral underflow were produced.

[0072] Zinc electrolytic waste liquid was added to the neutral underflow for weak acid leaching, and the weak acid leaching process and endpoint H2SO4 7g / L were controlled. After the weak acid leaching slurry was thickened and clarified, weak acid leachate and weak acid underflow were produced. The weak acid leachate was returned to the neutral leaching process to prepare acid solution.

[0073] Subthermal acid leaching was carried out by adding dilute sulfuric acid to the weak acid bottom stream, controlling the leaching temperature at 75℃ and the leaching time at 2.0h. The process and endpoint were H2SO4 at 40g / L. After the subthermal acid leaching slurry was thickened, clarified, and filtered, subthermal acid leaching solution and acid leaching residue were produced. The subthermal acid leaching solution was returned to the neutral leaching process to prepare acid solution, and the acid leaching residue was sent to the fuming furnace for treatment.

[0074] Based on the acid leaching residue rate and the copper content in the acid leaching residue, the copper leaching rate was 76.69%.

[0075] Comparative Examples

[0076] The roasted ore from Example 3 was used, and the roasted ore was leached using existing technical conditions of neutral leaching + weak acid leaching + subthermal acid leaching.

[0077] Manganese powder was added to the acid solution according to the theoretical amount. The amount of roasted ore added was 1.05 times the theoretical amount. The leaching temperature was controlled at 80℃, the leaching time was 2.5h, and the final pH value was 4.7. After the neutral leaching slurry was thickened and clarified, neutral leachate and neutral underflow were produced.

[0078] Zinc electrolysis waste liquid is added to the neutral underflow for weak acid leaching, and the pH value is controlled at 2.5 during and at the end of the weak acid leaching process. After the weak acid leaching slurry is thickened and clarified, weak acid leachate and weak acid underflow are produced. The weak acid leachate is returned to the neutral leaching process to prepare acid solution.

[0079] Subthermal acid leaching was carried out by adding dilute sulfuric acid to the weak acid bottom stream, controlling the leaching temperature at 80℃ and the leaching time at 3.0h. The process and endpoint were H2SO4 at 40g / L. After thickening, clarifying and filtering the subthermal acid leaching slurry, subthermal acid leaching solution and acid leaching residue were produced. The subthermal acid leaching solution was returned to neutral leaching to prepare acid solution, and the acid leaching residue was sent to a fumigation furnace for treatment.

[0080] Based on the acid leaching residue ratio and the copper content in the acid leaching residue, the copper leaching rate is 60.02%.

[0081] As can be seen from the comparative examples, when manganese powder was added at the theoretical amount, the roasted ore was added in excess by 1.05 times, the neutral leaching time was 2.5 hours, and the weak acid leaching process and the final pH value were controlled at 2.5, the copper leaching rate was reduced by 16.67% compared to Example 3. This indicates that the excess amount of oxidant, the excess amount of roasted ore, the neutral leaching time, and the acidity of the weak acid leaching process and the final pH value are extremely important for improving the copper leaching rate.

[0082] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for improving the copper leaching rate in roasted ore, comprising subjecting the roasted ore to neutral leaching, weak acid leaching, and subthermal acid leaching steps, respectively, so that copper ultimately enters the neutral leaching solution; wherein the leaching solutions from the weak acid leaching and subthermal acid leaching are returned to the neutral leaching step; characterized in that: In the neutral leaching step, an excessive amount of roasted ore is added, specifically 1.1-1.3 times the theoretical amount, to control the leaching time and prevent copper precipitation into the slag; in the weak acid leaching step, the process and endpoint acidity are controlled to prevent copper precipitation into the slag; in the neutral leaching step, an excessive amount of oxidant is added to prevent copper precipitation into the slag in the weak acid leaching and subthermal acid leaching steps. The neutral leaching time is 1.0-1.5 hours, with a final pH value of 4.6-4.

8. The weak acid leaching process and endpoint involve H₂SO₄ at a concentration of 5-10 g / L. During the weak acid leaching process, ZnS preferentially reacts with the oxidant, avoiding Cu... 2+ The reaction with ZnS causes copper to precipitate into the slag; the subthermal acid leaching process and endpoint: H2SO4 20-60 g / L; The roasted ore is zinc roasted ore, and the copper in the zinc roasted ore mainly exists in the form of CuO, and also contains Cu2O and CuFe2O4. The oxidant is one or both of manganese powder and zinc electrolytic anode mud.

2. The method according to claim 1, characterized in that, When leaching with subthermic acid, the leaching temperature is 70-85℃ and the leaching time is 1.0-3.0h.

3. The method according to claim 1, characterized in that, Excessive addition of oxidant in the neutral leaching step refers to adding an amount of oxidant that is 1.2-1.4 times the theoretical amount.

4. The method according to claim 1, characterized in that, The solution is neutrally leached with an acid solution, which is prepared by a weak acid leaching solution, a subthermal acid leaching solution, and an acidic solution.

5. The method as described in claim 1, characterized in that, Weak acid leaching and subthermal acid leaching are performed using an acidic solution, wherein the acidic solution is one or both of dilute sulfuric acid and zinc electrolytic waste liquid.

6. The method according to claim 1, characterized in that, The acid leaching residue produced in the subthermal acid leaching step is used to recover zinc through a fumigation furnace or rotary kiln.

7. The method according to claim 1, characterized in that, Copper entering the neutral leachate is recovered after purification and cadmium leaching.