A process for continuously removing chlorine from bismuth salts in the supernatant of medium leaching

Abstract

The present invention discloses a process for continuously removing chlorine from the supernatant of the intermediate leaching. The supernatant of the intermediate leaching is used as the solution to be treated. The chlorine removal agent, bismuth oxide, is pickled and activated under high acid conditions. The activated bismuth oxide is added to the elevated tank and continuously and stably added to the supernatant of the intermediate leaching for chlorine removal. An alkali solution is used to adjust the pH of the slurry after chlorine removal. The slurry after pH adjustment is subjected to liquid-solid separation using a filter press. The obtained filtrate is returned to the intermediate leaching thickener of the hydrometallurgical zinc smelting, and the obtained filter residue is subjected to regeneration treatment. An alkali solution is pre-prepared in the alkali solution tank and continuously input into the alkali washing tank, and an alkali washing reaction is carried out with the filter residue under high temperature and high alkali conditions. The alkali washing solution obtained after liquid-solid separation using a filter press is used to recover chlorine, and the obtained alkali washing residue is treated. The alkali washing residue is discharged to the pickling tank for pickling and activation and then reused in the chlorine removal process. By using the present invention, the chloride ions in the supernatant of the intermediate leaching of a hydrometallurgical zinc smelting system with high silicon and low iron can be removed.

Description

Technical Field

[0001] The invention relates to the field of zinc hydrometallurgy nonferrous smelting, and in particular to a process for continuously removing chlorine from a bismuth salt from a leaching supernatant. Background Art

[0002] During the hydrometallurgical zinc smelting process, zinc-containing materials such as zinc roasted sand, zinc oxide, various soot, and other zinc-containing materials (zinc slag, production auxiliary materials, etc.) contain chlorine, and almost all of this chlorine enters the leachate. Chloride ions have a small radius and easily penetrate into the anode through the tiny pores of the anodic protective film, where they interact with lead, causing anode corrosion. Lead sulfate is mechanically entrained into the cathode, where it discharges and precipitates with lead ions, reducing the quality of the electrolytic zinc.

[0003] Common chlorine removal methods used by domestic zinc smelting enterprises include silver sulfate precipitation method, copper slag method, bismuth salt method, ion exchange method, etc. The silver sulfate precipitation method is to add silver sulfate to the new solution to react with chloride ions to generate insoluble silver chloride precipitate. This method is simple to operate and has good chlorine removal effect, but it is costly and has a low silver regeneration recovery rate. It has no practical value in industry. The copper slag method uses the interaction between copper and copper ions and chloride ions in the solution to generate insoluble cuprous chloride (Cu2Cl2) precipitate. The bismuth salt method is to react bismuth oxide with Bi2Cl2 under acidic conditions. 3+ It reacts with chloride ions to form bismuth chloride, which is then hydrolyzed to form an insoluble bismuth oxychloride precipitate. The bismuth oxychloride is then washed with alkali under high temperature conditions to regenerate bismuth oxide, which can be reused to reduce production costs. The ion exchange method uses the exchangeable anions of the ion exchange resin to react with the chloride ions in the new solution, so that the chlorine in the solution is adsorbed on the resin, and the corresponding exchangeable anions on the resin enter the solution. The copper slag method is widely used in industry, but the copper slag method has strict requirements on the copper content of the copper slag. The low copper content has poor chlorination effect. Therefore, it is urgent to develop a dechlorination process with strong applicability, simple and continuous process, water-saving and high dechlorination efficiency.

[0004] Chinese patent application CN113930806A discloses a wet electrolytic zinc dechlorination and chlorine recovery process. The process first acidifies bismuth oxide to obtain bismuth ions, which react with chloride ions and hydrolyze to form bismuth oxychloride precipitates. The dechlorination process can remove more than 80% of the chlorine in the high-chloride zinc sulfate solution. In the regeneration process, the chlorine basically overflows in the form of hydrogen chloride gas, and the chlorine resolution rate can reach more than 90%. The hydrogen chloride is absorbed by water to prepare dilute hydrochloric acid. Chinese patent application CN102154552A discloses a method for removing chlorine from a chlorine-containing zinc sulfate solution using bismuth trioxide. This method can remove Cl in the solution. -When the concentration drops below 300 mg / L, the regeneration dechlorination rate of Bi2O3 can reach over 98%. Chinese Patent Application CN113930806A discloses a method for purifying and removing chlorine from manganese sulfate electrolyte, using the activated product bismuthyl sulfate to remove chloride ions from manganese sulfate electrolyte, with a chlorine removal rate reaching over 95.0% and a bismuth utilization rate exceeding 98.0%. These methods can achieve good chlorine removal effects, but the above methods have not been applied to relevant chlorine removal in the middle leaching supernatant, with complex process flows and no continuous operation achieved, high equipment and labor costs, and do not meet the requirements of industrial production. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention aims to provide a process for continuously removing chlorine with bismuth salts from the middle leaching supernatant.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A process for continuously removing chlorine with bismuth salts from the middle leaching supernatant, comprising the following steps:

[0008] S1. Prepare the middle leaching supernatant of hydrometallurgical zinc smelting as the solution to be treated;

[0009] S2. Pickle and activate the chlorine removal agent bismuth oxide under high acid conditions;

[0010] S3. Add the activated bismuth oxide to the elevated tank, and then continuously and stably add it to the middle leaching supernatant in step S1 for chlorine removal;

[0011] S4. Adjust the pH of the slurry finally obtained in step S3 using alkali solution;

[0012] S5. Perform liquid-solid separation on the slurry after adjusting the pH using a filter press, return the obtained filtrate to the middle leaching thickener of hydrometallurgical zinc smelting, and transfer the obtained filter residue to step S6 for regeneration treatment;

[0013] S6. Prepare alkali solution in the alkali solution tank in advance, continuously input the alkali solution into the alkali washing tank, perform an alkali washing reaction with the filter residue under high temperature and high alkali conditions, recover chlorine from the alkali washing solution obtained after liquid-solid separation using a filter press, and transfer the obtained alkali washing residue to step S7 for treatment;

[0014] S7. Discharge the alkali washing residue to the pickling tank for pickling and activation, and then reuse it in the chlorine removal process to achieve the reuse of bismuth salts.

[0015] Furthermore, set up stirring reaction tank 1# and stirring reaction tank 2#. The activated bismuth oxide and the middle leaching supernatant both continuously enter stirring reaction tank 1# for reaction, and the reacted slurry continuously enters stirring reaction tank 2# for pH adjustment.

[0016] Further, in step S2, pickling activation is carried out using waste acid liquor or concentrated sulfuric acid, and the initial acidity is controlled at 190 - 200 g / L.

[0017] Further, in step S3, the high-level tank is equipped with a stirring mechanism to prevent the dechlorinating agent from precipitating and caking.

[0018] Further, in step S4, the concentration of the alkali liquor > 70 g / L.

[0019] Further, in step S3, the temperature during the dechlorination reaction process is 30 - 50 °C, and the reaction time is 1.0 - 1.5 h.

[0020] Further, in step S4, the pH of the slurry is adjusted to 2.5 - 3.5.

[0021] Further, in step S6, the temperature of the alkali washing reaction is 85 °C, the alkalinity is not less than 70 g / L, the reaction time is 1.0 - 1.5 h, the final alkalinity > 30 g / L. If the alkalinity does not meet > 30 g / L during the reaction process, alkali liquor needs to be supplemented.

[0022] Further, in step S5, at least two filter presses are set for pressure filtration, and each filter press is used alternately to achieve continuous pressure filtration operation.

[0023] Further, in step S6, at least two alkali washing tanks are set for alkali washing respectively, and each alkali washing tank is used alternately to achieve continuous alkali washing operation.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. Using the present invention, the removal of chloride ions from the middle leaching supernatant in the hydrometallurgical zinc smelting system with high silicon and low iron can be achieved;

[0026] 2. The present invention can achieve continuous operation, thereby achieving high-load and efficient dechlorination. Moreover, no waste residue and waste water are generated during the dechlorination process, and chlorine can be further recycled in the form of sodium chloride.

[0027] 3. In the present invention, feeding the dechlorinating agent into the high-level tank can achieve uniform and continuous addition of the dechlorinating agent, stabilizing the reaction process and index control;

[0028] 4. In the hydrometallurgical zinc smelting system with high silicon and low iron, the removal of chloride ions from the middle leaching supernatant can be achieved;

[0029] 5. The present invention sets two consecutive reaction stirring tanks to simultaneously meet the process requirements of the dechlorination process and the pH adjustment of the dechlorination slurry, ensuring the continuity of the process;

[0030] 6. The present invention provides an alkali preparation tank, so that the alkali solution can be continuously transported, stably adjusting the pH of the slurry after dechlorination and the alkalinity of the alkali washing process, while avoiding the safety hazards caused by people directly adding alkali on the tank surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of the method of Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0033] Example 1

[0034] This embodiment provides a process for continuous dechlorination of bismuth salt from the supernatant solution. Figure 1 As shown, the specific process is:

[0035] (1) Prepare 30ml of supernatant solution for immersion 3 The mixture is continuously fed into stirring reaction tank 1# and then continuously fed into stirring reaction tank 2# for stirring reaction, wherein the chloride ion content is 700 mg / L;

[0036] (2) Add 3m3 of water to the pickling tank in advance. 3 Sulfuric acid and 3m 3 After adding bismuth oxide or the subsequent alkaline washing slag to the waste acid solution, the acidity should be tested at 190-200g / L, and the reaction should be stirred for 1.5 hours. The slurry concentration should be less than or equal to 40%. If the concentration is too high, dilute it with condensed water to prevent pump blockage.

[0037] (3) Transport the activated dechlorination agent to the high-level tank and control the flow rate to 2.5m 3 / h, and continuously added to stirred reactor 1# to react with the supernatant of the intermediate leaching to remove chlorine. The dechlorinated slurry enters stirred reactor 2#. The dechlorination reaction temperature is 30°C, and the liquid level in stirred reactor 1# is maintained at 4.0 meters;

[0038] (4) Add sodium hydroxide to the alkali preparation tank in advance to prepare an alkali solution with an alkalinity of >70 g / L. Use a variable frequency pump to continuously transport the alkali solution to stirred reactor tank 2# to adjust the pH of the slurry obtained after dechlorination in step (4). Adjust the flow rate according to the alkalinity. Adjust the pH of the slurry after dechlorination to 2.5. Maintain the liquid level in stirred reactor tank 2# at 2.3 meters.

[0039] (5) The dechlorinated slurry is filtered by a filter press, and the filtration process is continuous. The filtrate enters the reaction tank and returns to the medium leaching thickener, while the filter residue enters step (6). At least two filter presses are set to be responsible for the filtration in this step, and each filter press is used alternately, so that the continuous operation of the filtration process can be achieved.

[0040] (6) Alkali solution is pre-added to the alkali washing tank. The filter residue from step (5) is discharged into the alkali washing tank. At this time, the alkalinity is detected to be not less than 70 g / L, and the temperature is raised to 85 °C for reaction for 1.5 h. During the reaction process, the alkalinity is detected. If it is lower than 30 g / L, alkali solution should be added in time to ensure complete alkali washing recovery. At least two alkali washing tanks are set to be responsible for the alkali washing in this step, and each alkali washing tank is used alternately.

[0041] (7) After alkali washing, filtration is carried out. The filtrate is the post-alkali washing solution. When the chlorine content reaches 20 g / L, it is sent to the downstream water treatment to recover chlorine, and the alkali washing residue returns to step (2) for pickling activation and reuse.

[0042] Using the method of this example, the chlorine content in the medium leaching supernatant decreased from 700 mg / L to 96 mg / L, and the dechlorination rate was 86%. The Bi content in the dechlorinated slurry was 5.1 mg / L, and the bismuth loss was small. 3+ content is 5.1 mg / L, and the bismuth loss is small.

[0043] Example 2

[0044] This example provides a process for continuously removing chlorine from bismuth salts in the medium leaching supernatant. As Figure 1 shown, the specific process is as follows:

[0045] (1) Prepare 35 m of medium leaching supernatant and continuously enter the stirring reaction tank 1#, and then continuously enter the stirring reaction tank 2# for stirring reaction, with the chloride ion content of 705 mg / L; 3 continuously enter the stirring reaction tank 1#, and then continuously enter the stirring reaction tank 2# for stirring reaction, with the chloride ion content of 705 mg / L;

[0046] (2) Pre-add 3 m of sulfuric acid and 3 m of waste acid solution to the pickling tank. After adding bismuth oxide or the subsequent alkali washing residue, the acidity needs to be detected to be 190 - 200 g / L, and stir and react for 1.5 h. The pulp needs to be detected to be less than or equal to a concentration of 40%. If the concentration is too high, use condensed water to dilute it to prevent the pump body from being blocked; 3 sulfuric acid and 3 m of 3 waste acid solution. After adding bismuth oxide or the subsequent alkali washing residue, the acidity needs to be detected to be 190 - 200 g / L, and stir and react for 1.5 h. The pulp needs to be detected to be less than or equal to a concentration of 40%. If the concentration is too high, use condensed water to dilute it to prevent the pump body from being blocked;

[0047] (3) The activated dechlorination agent is transported to the high-level tank, and the flow rate is controlled at 3.5 m 3 / h, and continuously added to the stirring reaction tank 1# to react with the medium leaching supernatant for dechlorination. The dechlorinated slurry enters the stirring reaction tank 2#. The dechlorination reaction temperature is 50 °C, and the liquid level of the stirring reaction tank 1# is maintained at 4.0 - 4.5 meters.

[0048] (4) Add sodium hydroxide to the alkali preparation tank in advance to prepare the alkali solution, with the requirement that the alkalinity > 70 g / L. Use a variable-frequency pump to continuously transport the alkali solution to the stirring reaction tank 2# to adjust the pH of the slurry obtained after dechlorination in step (4). Adjust the flow rate according to the alkalinity, and adjust the pH of the dechlorinated slurry to 3.5. Maintain the liquid level in the stirring reaction tank 2# at 3.5 meters.

[0049] (5) The dechlorinated slurry is filtered by a filter press. The filtrate enters the reaction tank and returns to the medium leaching thickener, and the filter cake enters step (6). Set at least two filter presses (such as Figure 1 the filter presses 1#, 2#, 3#, 4# as described) to be responsible for the filtration in this step. Each filter press is used alternately, so that continuous operation of the filtration process can be achieved.

[0050] (6) Pre-add the alkali solution in the alkali washing tank. The filter cake from step (5) is discharged into the alkali washing tank. At this time, detect that the alkalinity is not less than 70 g / L, heat up to 85 °C, and react for 2.0 h. Detect the alkalinity during the reaction. If it is lower than 30 g / L, add alkali solution in time to ensure complete alkali washing recovery. Set at least two alkali washing tanks to be responsible for alkali washing (such as Figure 1 the alkali washing tanks 1# and 2# as shown), and each alkali washing tank is used alternately, so that the alkali washing operation can be carried out continuously.

[0051] (7) After alkali washing, perform filtration. The filtrate is the post-alkali washing liquid. When the chlorine content reaches 20 g / L, it is sent to the downstream water treatment to recover chlorine, and the alkali washing residue returns to step (2) for pickling activation and reuse.

[0052] In the method of this embodiment, the chlorine content in the medium leaching supernatant drops from 705 mg / L to 78 mg / L, the dechlorination rate is 89%, and the Bi content of the dechlorinated slurry is 3+ 8.9 mg / L, and the bismuth loss is small.

[0053] Example 3

[0054] This embodiment provides a process for continuously removing chlorine from bismuth salts from medium leaching supernatant, as Figure 1 shown, and the specific process is as follows:

[0055] (1) Prepare 40 m of medium leaching supernatant 3 , continuously enter the stirring reaction tank 1#, and then continuously enter the stirring reaction tank 2# for stirring reaction, and the chloride ion content therein is 680 mg / L;

[0056] (2) Pre-add 3 m of sulfuric acid and 3 m of 3 in the pickling tank 3For the waste acid solution, after adding bismuth oxide or the subsequent obtained alkali-washing residue, the acidity needs to be detected at 190 - 200 g / L, and stirred for reaction for 1.5 h. The pulp needs to be detected with a concentration less than or equal to 40%. If the concentration is too high, use condensed water for dilution to prevent the pump body from being blocked;

[0057] (3) The activated chlorine remover is transported to the high-level tank, and the flow rate is controlled at 3.5 m 3 / h, and continuously added to the stirring reaction tank 1# to react with the supernatant of the medium leaching for chlorine removal. The pulp after chlorine removal enters the stirring reaction tank 2#. The temperature of the chlorine removal reaction is 45°C, and the liquid level of the stirring reaction tank 1# is maintained at 4.0 m.

[0058] (4) Add sodium hydroxide in the alkali preparation tank in advance to prepare the alkali solution, and the required alkalinity > 70 g / L. Use a variable-frequency pump to continuously transport the alkali solution to the stirring reaction tank 2# to adjust the pH of the pulp obtained after chlorine removal in step (4). Adjust the flow rate according to the alkalinity, and adjust the pH of the pulp after chlorine removal to 3. Maintain the liquid level of the stirring reaction tank 2# at 3.5 m.

[0059] (5) The pulp after chlorine removal is filtered by a filter press. The filtrate enters the reaction tank and returns to the medium leaching thickener, and the filter residue enters step (6). Set at least two filter presses to be responsible for the filtration of this step, and the two filter presses are used alternately, so that the continuous operation of the filtration process can be realized.

[0060] (6) Add alkali solution to the alkali-washing tank in advance. The filter residue in step (5) is discharged into the alkali-washing tank. At this time, the alkalinity is detected to be not less than 70 g / L, heated to 85°C, and reacted for 2.0 h. During the reaction process, the alkalinity is detected. If it is lower than 30 g / L, alkali solution should be added in time to ensure complete alkali-washing recovery. Set at least two alkali-washing tanks to be responsible for alkali-washing, and each alkali-washing tank is used alternately, so that the alkali-washing operation can be carried out continuously.

[0061] (7) After alkali-washing, filtration is carried out. The filtrate is the solution after alkali-washing. After the chlorine content reaches 20 g / L, it is sent to the downstream water treatment to recover chlorine, and the alkali-washing residue is returned to step (2) for pickling activation and reuse.

[0062] In this embodiment, the chlorine content in the supernatant of the medium leaching drops from 680 mg / L to 83 mg / L, the chlorine removal rate is 88%, and the Bi content of the pulp after chlorine removal is 9.2 mg / L, with a small loss of bismuth. 3+ For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all these changes and deformations should be included in the protection scope of the claims of the present invention.

[0063] For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all these changes and deformations should be included in the protection scope of the claims of the present invention.

Claims

1. A process for continuously removing chlorine from bismuth salts in the supernatant of medium leaching, characterized in that, It includes the following steps: S1. Prepare the middle leaching supernatant of zinc hydrometallurgy as the solution to be treated; S2. Pickle and activate bismuth oxide, the chlorine remover, under high acid conditions; S3. Add the activated bismuth oxide into the elevated tank, and then continuously and stably add it into the middle leaching supernatant in step S1 for chlorine removal; S4. Use the alkali solution to adjust the pH of the slurry finally obtained in step S3; S5. Use a filter press to perform liquid-solid separation on the slurry after pH adjustment. The obtained filtrate is returned to the middle leaching thickener of zinc hydrometallurgy, and the obtained filter residue is transferred to step S6 for regeneration treatment; S6. Prepare the alkali solution in the alkali solution tank in advance, continuously input the alkali solution into the alkali washing tank, and carry out the alkali washing reaction with the filter residue under high temperature and high alkali conditions. Recover chlorine from the alkali washing solution obtained after liquid-solid separation by the filter press, and transfer the obtained alkali washing residue to step S7 for treatment; S7. Discharge the alkali washing residue into the pickling tank for pickling and activation, and then reuse it in the chlorine removal process to realize the reuse of bismuth salt; Set up stirring reaction tank 1# and stirring reaction tank 2#. The activated bismuth oxide and the middle leaching supernatant continuously enter stirring reaction tank 1# for reaction, and the reacted slurry continuously enters stirring reaction tank 2# for pH adjustment; In step S5, at least two filter presses are set for filtration, and each filter press is used alternately to realize continuous filtration operation; In step S6, at least two alkali washing tanks are set respectively for alkali washing, and each alkali washing tank is used alternately to realize continuous alkali washing operation.

2. The process according to claim 1, characterized in that, In step S2, use waste acid solution or concentrated sulfuric acid for pickling activation, and control the initial acidity at 190 - 200 g / L.

3. The process according to claim 1, characterized in that, In step S3, the elevated tank is equipped with a stirring mechanism to prevent the chlorine remover from precipitating and caking.

4. The process according to claim 1, characterized in that, In step S4, the concentration of the alkali solution > 70 g / L.

5. The process according to claim 1, characterized in that, In step S3, the temperature during the chlorine removal reaction process is 30 - 50 °C, and the reaction time is 1.0 - 1.5 h.

6. The process according to claim 1, characterized in that, In step S4, the pH of the slurry is adjusted to 2.5 - 3.

5.

7. The process according to claim 1, characterized in that, In step S6, the alkali washing reaction temperature is 85 °C, the alkalinity is not less than 70 g / L, the reaction time is 1.0 - 1.5 h, the final alkalinity > 30 g / L, and if the alkalinity does not meet > 30 g / L during the reaction process, alkali solution needs to be supplemented.

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