Process for reducing the silver content of zinc roasting leach residue

Abstract

The present application relates to a kind of process for reducing the silver content of zinc roasting ore leaching slag, belong to the field of silver recovery in zinc concentrate.The technical scheme of the present application includes: controlling roasting temperature 960-1050 ℃;Electric field dust and two-rotation dust are collected separately, and high-silver roasting dust is obtained;Boiler dust, one-rotation dust and roasting sand are mixed to obtain low-silver roasting ore;High-silver roasting dust is leached separately to obtain silver concentrate;Low-silver roasting ore is subjected to neutral and acid leaching to obtain leaching slag.The present application increases the amount of silver entering two-rotation dust and electric field dust, and produces silver concentrate by separately treating two-rotation dust and electric field dust with high silver content, which provides an additional channel for silver in zinc concentrate, even if the silver content of zinc concentrate entering the furnace is increased, the silver content of leaching slag can be reduced, which is beneficial for the subsequent treatment of leaching slag, reduces resource waste, and enables zinc smelting enterprises to increase the procurement proportion of high-silver zinc concentrate, increasing the economic benefits of enterprises.

Description

Technical Field

[0001] This invention belongs to the field of silver recovery technology in zinc concentrate, specifically, it relates to reducing the silver content in the leaching residue of zinc roasted ore. Background Technology

[0002] Silver is a valuable and rare metal widely used in industry, photography, jewelry, and currency manufacturing. The recovery of associated silver from zinc concentrate is a major source of silver. Zinc concentrate is roasted in a fluidized bed furnace to remove sulfur, resulting in roasted zinc ore. After zinc is leached from the roasted zinc ore, leaching residue is obtained. The silver in the zinc concentrate is ultimately concentrated in the leaching residue, and silver is primarily recovered from the zinc leaching residue.

[0003] The silver content in leaching residue is mainly affected by the silver content of zinc concentrate. In the current technology, zinc concentrate contains 60-140 g / t of Ag, and the corresponding leaching residue contains 150-350 g / t of Ag. If the Ag content in zinc concentrate is greater than 140 g / t, the silver content in the leaching residue obtained after leaching zinc from zinc roasted ore will increase. When the leaching residue with Ag content greater than 350 g / t is processed in subsequent stages, it will increase the loss of silver in the waste residue, resulting in resource waste. It also limits the amount of high-silver zinc concentrate that zinc smelting enterprises can purchase, thus affecting the economic benefits of zinc smelting enterprises. Summary of the Invention

[0004] To overcome the problems existing in the background technology, the present invention provides a process for reducing the silver content in the leaching residue of zinc roasted ore. By controlling the zinc roasting process, the proportion of silver entering the electric field dust and the vortex dust is increased, and the electric field dust and the vortex dust are collected and leached separately, thereby reducing the silver content in the leaching residue of zinc roasted ore.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: The process for reducing the silver content in zinc roasting ore leaching residue includes the following steps: (1) Collect the high-silver roasting dust from the zinc roasting system separately, and mix the low-silver roasting dust and roasting sand to obtain low-silver roasted ore; (2) The high silver roasting dust was leached and then separated into liquid and solid to obtain silver concentrate; (3) Leach the low-silver roasted ore, and after liquid-solid separation, obtain the leaching residue.

[0006] Furthermore, in step (1), the zinc roasting system roasts the zinc concentrate after it has been batched.

[0007] Furthermore, the high-silver baking dust mentioned in step (1) is two-stage vortex dust and / or electric field dust; the low-silver baking dust is boiler dust and single-stage vortex dust.

[0008] Furthermore, the leaching of the low-silver roasted ore in step (3) is either neutral leaching + weak acid leaching or neutral leaching + weak acid leaching + subthermal acid leaching.

[0009] Furthermore, in step (1), the zinc roasting system has a roasting temperature of 960-1050℃ for the zinc concentrate.

[0010] Furthermore, the leaching conditions in step (2) are: leaching temperature 70-90℃, leaching time 0.5-4h, and leaching endpoint acidity 0.005-100g / L.

[0011] Furthermore, the neutral leaching conditions in step (3) are: leaching temperature 70-90℃, leaching time 1.0-3.0h, and leaching endpoint pH value 4.8-5.4; the weak acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and leaching endpoint pH value 2.0-3.5; the subthermal acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and leaching endpoint acidity 20-70g / L.

[0012] Furthermore, in step (1), after the roasted sand and boiler dust are ground, they are mixed with a vortex dust.

[0013] Furthermore, the neutral leachate from step (3) is purified, electrolyzed, and cast to produce zinc ingots.

[0014] Furthermore, the weak acid leachate and the subthermic acid leachate from step (3) are returned to the neutral leachate.

[0015] Furthermore, in steps (2) and (3), zinc electrolytic waste liquid or dilute sulfuric acid is used as the leaching agent for leaching.

[0016] The beneficial effects of this invention are: This invention improves the volatilization rate of silver by controlling the roasting process of zinc concentrate, thereby increasing the proportion of silver entering the vortex dust and electric field dust. The vortex dust and electric field dust are collected and leached separately. Even if the silver content of the zinc concentrate entering the furnace is increased, the silver content in the leaching residue can still be reduced. This allows zinc smelting enterprises to increase the proportion of high-silver zinc concentrate they purchase, thereby increasing the economic benefits of the enterprises. Attached Figure Description

[0017] Figure 1 This is a simplified process flow diagram of the present invention. Detailed Implementation

[0018] 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.

[0019] The method for reducing the silver content in zinc roasting ore leaching residue includes the following steps: (1) Zinc concentrate batching and roasting High-silver zinc concentrate and low-silver zinc concentrate are blended together, and the Ag content in the zinc concentrate after blending is greater than 140 g / t. The blended concentrate is then roasted in a fluidized bed furnace.

[0020] During the roasting process, roasted ore and roasted dust are produced, each accounting for approximately 50%. The roasted dust includes boiler dust, primary cyclone dust, secondary cyclone dust, and electric field dust. The inventors discovered that roasted dust contains more silver than roasted ore, especially secondary cyclone dust and electric field dust, which contain even higher amounts of silver. Increasing the roasting temperature further increases the silver content in secondary cyclone dust and electric field dust, while correspondingly decreasing the silver content in roasted ore. However, roasting temperatures above 1050℃ increase the amount of zinc ferrite generated during roasting, leading to a decrease in zinc leaching rate. Therefore, the roasting temperature of zinc concentrate was increased from the conventional 890-950℃ to 960-1050℃ to increase the proportion of silver in secondary cyclone dust and electric field dust in the zinc concentrate, control the amount of zinc ferrite generated, and simultaneously ensure the zinc leaching rate.

[0021] (2) Separation of high-silver roasted dust and low-silver roasted ore Among the zinc concentrate roasting products, roasted sand has the lowest silver content; among the roasting dust, the proportions of boiler dust, primary vortex dust, secondary vortex dust and electric field dust decrease from large to small, and the silver content also increases from low to high.

[0022] High-silver-content electric field dust and secondary vortex dust are collected separately to obtain high-silver roasting dust; boiler dust and roasted sand are ball-milled and then mixed with primary vortex dust to obtain low-silver roasted ore.

[0023] (3) High silver dust leach out separately High-silver roasted dust was leached separately using dilute sulfuric acid or electrolytic waste liquid as the leaching agent. The leaching conditions were: leaching temperature 70-90℃, leaching time 1-4 hours, and final acidity of 0.005-100 g / L. After liquid-solid separation, silver concentrate was obtained. Because the leaching pulp contained Cl... - In high-silver roasting dust, a small amount of Ag2SO4 will precipitate into the slag in the form of AgCl. Therefore, all the silver in high-silver roasting dust is enriched in silver concentrate, and the filtrate is used for neutral leaching of low-silver roasted ore.

[0024] Leaching temperature, leaching time, and final acidity at the leaching endpoint determine the yield and silver grade of silver concentrate. When all three are taken at their lower limits, the yield of silver concentrate is the highest, but the silver grade of silver concentrate is the lowest; when all three are taken at their upper limits, the yield of silver concentrate is the lowest, but the silver grade of silver concentrate is the highest.

[0025] (4) Leaching of low-silver roasted ore Using dilute sulfuric acid or electrolytic waste liquid as the leaching agent, low-silver roasted ore undergoes neutral + weak acid leaching or neutral + weak acid leaching + subthermal acid leaching. After liquid-solid separation, leaching residue is obtained. All the silver in the low-silver roasted ore is enriched in the leaching residue, with a silver content of less than 300 g / t. The acidic leaching solution is then subjected to neutral leaching. The supernatant produced from neutral leaching is purified, electrolyzed, and smelted to produce zinc ingots; the leaching residue is sent for further processing. The neutral leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-3.0h, and final pH value 4.8-5.4; the weak acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and final pH value 2.0-3.5; the subthermal acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and final acidity 20-70g / L.

[0026] To illustrate the present invention more clearly, the following embodiments will be described in detail. Example 1

[0027] The main components (%wt) of the zinc concentrate used in this embodiment after batching are: Zn 46.72, H2O 10.81, Fe 11.06, Ag 210 g / t.

[0028] The zinc concentrate after batching was added to a fluidized bed furnace for roasting and desulfurization, with the roasting temperature controlled at 1050℃. Secondary vortex dust and electric field dust were collected separately to obtain high-silver roasted dust, with the main components (%wt): Zn 42.36, Fe 12.53, Ag 960 g / t. Roasted sand and boiler dust were ball-milled and then mixed with primary vortex dust to obtain low-silver roasted ore, with the main components (%wt): Zn 55.85, Fe 12.66, Ag 140 g / t.

[0029] The high-silver roasted dust was leached separately using zinc electrolysis waste liquid as the leaching agent. The leaching conditions were: leaching temperature 70℃, leaching time 1h, and final acidity of 0.005g / L (pH 4.0). After liquid-solid separation, silver concentrate was obtained with a yield of 34.22%. The main components of the silver concentrate (%wt) were: Zn 20.09, Fe 23.36, and Ag 2810g / t. All the silver in the high-silver roasted dust was enriched in the silver concentrate. The filtrate was then subjected to neutral leaching of low-silver roasted ore.

[0030] Using dilute sulfuric acid as the leaching agent, the low-silver roasted ore underwent neutral leaching and weak acid leaching respectively. The neutral leaching conditions were: leaching temperature 70℃, leaching time 1.0 h, and final pH value 5.4; the weak acid leaching conditions were: leaching temperature 90℃, leaching time 1.0 h, and final pH value 2.0. After liquid-solid separation, leaching residue was obtained. The main components of the leaching residue (%wt) were: Zn 15.32, Fe 24.53, Ag 280 g / t. All the silver in the low-silver roasted ore was enriched in the leaching residue, which was sent for subsequent processing. The acidic leaching solution was returned to the neutral leaching solution, which was then purified, electrolyzed, and cast to produce zinc ingots.

[0031] Comparative Example 1

[0032] The zinc concentrate from Example 1, after being batched, was subjected to the same fluidized bed roasting conditions as in Example 1. The vortex dust and electric field dust were not collected separately, but were mixed with the roasted ore to obtain roasted ore. The main components of the roasted ore (%wt) were: Zn 54.45, Fe 12.31, Ag 240 g / t.

[0033] Using the low-silver roasted ore leaching conditions of Example 1, the roasted ore was subjected to neutral and weak acid leaching respectively. After liquid-solid separation, leaching residue was obtained. The main components of the leaching residue (%wt) were: Zn 15.23, Fe 23.83, Ag 478 g / t. All the silver in the roasted ore was enriched in the leaching residue.

[0034] Comparative Example 1 shows that if the high-silver-content dicyclone dust and electric field dust are not separated and leached separately, the silver content of the roasted ore increases, leading to an increase in the silver content of the leaching residue. Leaching residue with Ag > 350 g / t will result in increased silver loss into the waste residue during subsequent processing, causing resource waste. Example 2

[0035] The main components (%wt) of the zinc concentrate used in this embodiment after batching are: Zn 49.69, H2O 10.01, Fe 7.96, Ag 160 g / t.

[0036] The zinc concentrate after batching was added to a fluidized bed furnace for roasting and desulfurization, with the roasting temperature controlled at 960℃. Secondary vortex dust and electric field dust were collected separately to obtain high-silver roasted dust, with the main components (%wt): Zn 49.16, Fe 9.12, Ag 610 g / t. Roasted sand and boiler dust were ball-milled and then mixed with primary vortex dust to obtain low-silver roasted ore, with the main components (%wt): Zn 59.89, Fe 9.30, Ag 124 g / t.

[0037] The high-silver roasted dust was leached separately using dilute sulfuric acid as the leaching agent. The leaching conditions were: leaching temperature 90℃, leaching time 4h, and final acidity 100g / L. After liquid-solid separation, silver concentrate was obtained with a yield of 18.96%. The main components of the silver concentrate (%wt) were: Zn 9.26, Fe 11.33, and Ag 3220g / t. All the silver in the high-silver roasted dust was enriched in the silver concentrate. The filtrate was then subjected to neutral leaching of the low-silver roasted ore.

[0038] The low-silver roasted ore was subjected to neutral leaching and weak acid leaching. The neutral leaching conditions were: leaching temperature 90℃, leaching time 3.0h, and final pH value 4.8. The weak acid leaching conditions were: leaching temperature 70℃, leaching time 4.0h, and final pH value 3.5. After liquid-solid separation, leaching residue was obtained. The main components of the leaching residue (%wt) were: Zn 15.76, Fe 21.50, Ag 276g / t. All the silver in the low-silver roasted ore was enriched in the leaching residue, which was sent for further processing. The acidic leaching solution was then subjected to neutral leaching. The neutral leaching solution was purified, electrolyzed, and cast to produce zinc ingots.

[0039] Comparative Example 2

[0040] Using the zinc concentrate from Example 2 after batching, the fluidized bed roasting temperature was controlled at 900°C. The secondary vortex dust and electric field dust were collected separately to obtain high-silver roasting dust, with the following composition (%wt): Zn 48.89, Fe 9.33, Ag 420 g / t. The roasted sand and boiler dust were ball-milled and then mixed with the primary vortex dust to obtain low-silver roasted ore, with the following composition (%wt): Zn 60.03, Fe 9.86, Ag 152 g / t.

[0041] The high-silver roasted dust was leached separately under the same leaching conditions as in Example 2. After liquid-solid separation, silver concentrate was obtained with a yield of 21.98%. The composition of the silver concentrate (%wt) was: Zn 13.05, Fe 13.63, Ag 1910 g / t. All the silver in the high-silver roasted dust was enriched in the silver concentrate.

[0042] The low-silver roasted ore was subjected to neutral leaching and weak acid leaching under the same conditions as in Example 2. After liquid-solid separation, leaching residue was obtained. The main components of the leaching residue (%wt) were: Zn 12.44, Fe 20.77, Ag 360 g / t. All the silver in the low-silver roasted ore was enriched in the leaching residue, which was then sent for further processing.

[0043] Comparative Example 2 shows that if a conventional roasting temperature is used, the proportion of silver entering the vortex dust and electric field dust decreases, while the proportion entering the low-silver roasted ore increases, resulting in Ag content in the leaching residue exceeding 350 g / t, which still leads to an increase in the silver content in the leaching residue. Therefore, increasing the roasting temperature is extremely important. Example 3

[0044] The main components (%wt) of the zinc concentrate used in this embodiment after batching are: Zn 57.89, H2O 10.23, Fe 9.46, Ag 190 g / t.

[0045] The zinc concentrate after batching was added to a fluidized bed furnace for roasting and desulfurization, with the roasting temperature controlled at 1000℃. Secondary vortex dust and electric field dust were collected separately to obtain high-silver roasted dust, with the following composition (%wt): Zn 47.25, Fe 10.84, Ag 910 g / t. Roasted sand and boiler dust were ball-milled and then mixed with primary vortex dust to obtain low-silver roasted ore, with the following composition (%wt): Zn 58.88, Fe 10.96, Ag 128 g / t.

[0046] The high-silver roasted dust was leached separately using zinc electrolysis waste liquid as the leaching agent. The leaching conditions were: leaching temperature 80℃, leaching time 2.5h, and final acidity 50g / L. After liquid-solid separation, silver concentrate was obtained with a yield of 28.91%. The composition of the silver concentrate (%wt) was: Zn 15.31, Fe 18.66, Ag 3150g / t. All the silver in the high-silver roasted dust was enriched in the silver concentrate. The filtrate was then subjected to neutral leaching of low-silver roasted ore.

[0047] The low-silver roasted ore was subjected to neutral, weak acid, and subthermal acid leaching. The neutral leaching conditions were: leaching temperature 80℃, leaching time 2.0 h, and final pH value 5.0. The weak acid leaching conditions were: leaching temperature 80℃, leaching time 2.0 h, and final pH value 3.0. The subthermal acid leaching conditions were: leaching temperature 70-90℃, leaching time 1.0-4 h, and final acidity 20-70 g / L. After liquid-solid separation, leaching residue was obtained. The composition of the leaching residue (%wt): Zn 11.42, Fe 25.69, Ag 320 g / t. All the silver in the low-silver roasted ore was enriched in the leaching residue, which was sent for further processing. The weak acid and subthermal acid leaching solutions were then subjected to neutral leaching. The neutral leaching solution was purified, electrolyzed, and cast to produce zinc ingots.

[0048] 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 process for reducing the silver content in leaching residue from zinc roasted ore, characterized in that, Includes the following steps: (1) Collect the high-silver roasting dust from the zinc roasting system separately; mix the low-silver roasting dust and roasting sand to obtain low-silver roasted ore; (2) The high silver roasting dust was leached and then separated into liquid and solid to obtain silver concentrate; (3) Leach the low-silver roasted ore, and after liquid-solid separation, obtain the leaching residue; In step (1), the zinc roasting system has a roasting temperature of 960-1050℃; the high silver roasting dust mentioned in step (1) is two-stage dust and / or electric field dust, and the low silver roasting dust is boiler dust and single-stage dust.

2. The process according to claim 1, characterized in that, In step (1), the zinc roasting system roasts the zinc concentrate after it has been batched.

3. The process according to claim 1, characterized in that, The low-silver roasted ore leaching in step (3) is a combination of neutral leaching and weak acid leaching or neutral leaching, weak acid leaching, and subthermal acid leaching.

4. The process according to claim 1, characterized in that, The leaching conditions for step (2) are: leaching temperature 70-90℃, leaching time 0.5-4h, and leaching endpoint acidity 0.005-100g / L.

5. The process according to claim 1 or 3, characterized in that, The neutral leaching conditions in step (3) are: leaching temperature 70-90℃, leaching time 1.0-3.0h, and leaching endpoint pH value 4.8-5.4; the weak acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and leaching endpoint pH value 2.0-3.5; the subthermal acid leaching conditions are: leaching temperature 70-90℃, leaching time 1.0-4h, and leaching endpoint acidity 20-70g / L.

6. The process according to claim 1, characterized in that, In step (1), the roasted sand is ground with boiler dust and then mixed with a vortex dust.

7. The process according to claim 5, characterized in that, The neutral leachate from step (3) is purified, electrolyzed, and cast to produce zinc ingots; the weak acid leachate and subthermal acid leachate from step (3) are returned to the neutral leachate.

8. The process according to any one of claims 1, 3, or 4, characterized in that, The leaching in steps (2) and (3) uses zinc electrolytic waste liquid or dilute sulfuric acid as the leaching agent.

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