A method for recycling and reusing nickel-cobalt waste residue

Abstract

The present application relates to the technical fields of hydrometallurgy and solid waste resource utilization, and particularly relates to a recycling method of nickel-cobalt waste residue. The method comprises two-stage gradient leaching of the nickel-cobalt waste residue, merging of the leaching solution, determination of the leaching end point based on the first pH value change rate and the first oxidation-reduction potential change rate; adding a reducing agent to the acid leaching solution, dynamic adjustment of the reducing agent addition rate based on a proportional-integral feedback control algorithm, reduction of Fe 3+ to Fe 2+ ; adding a pyrite seed to the solution after reduction, judgment of the colloid generation degree based on the turbidity change rate and graded supplement of the seed; calculation of a sink iron comprehensive index based on the second oxidation-reduction potential change rate and the second pH value change rate, dynamic adjustment of the oxygen-containing gas flow rate according to the index ratio of the sink iron comprehensive index to the leaching end point comprehensive index; separation of the pyrite precipitate, obtaining of a purified solution, extraction and separation of cobalt and nickel by using an acidic phosphorus extractant, and the present application realizes efficient recycling and resource utilization of the nickel-cobalt waste residue.

Description

Technical Field

[0001] This invention relates to the fields of hydrometallurgy and solid waste resource utilization, and in particular to a method for recycling and reusing nickel-cobalt waste slag. Background Technology

[0002] Nickel-cobalt waste mainly comes from industries such as laterite nickel ore hydrometallurgy, waste lithium-ion battery recycling, nickel-cobalt intermediate product production and electroplating. In addition to containing valuable metals such as nickel and cobalt, it usually also contains a large amount of iron impurities.

[0003] In hydrometallurgical recycling processes, sulfuric acid or hydrochloric acid is typically used to leach nickel-cobalt waste slag, converting valuable metals such as nickel and cobalt into soluble ions that enter the leachate, while iron is simultaneously converted into Fe. 2+ or Fe 3+ The iron ions enter the solution in a form that severely interferes with subsequent extraction and separation processes. 3+ Emulsification is easily triggered during the extraction process, leading to loss of organic phase and decreased extraction efficiency. Therefore, the iron ion concentration in the solution must be reduced to a low level before extraction.

[0004] Chinese Patent Publication No. CN109487080A discloses a method for the synergistic extraction and separation of iron, cobalt, and manganese ions in laterite nickel ore leaching solution. The method uses a synergistic extraction system composed of P204, Cyanex272, TBP and sulfonated kerosene to simultaneously extract iron, cobalt, and manganese ions in laterite nickel ore leaching solution into the organic phase, thereby achieving separation from nickel.

[0005] Although this technical solution can effectively remove iron ions, it still has the following shortcomings: 1. The extraction process requires the use of organic solvents and extractants, which not only increases production costs but also presents problems such as organic phase entrainment and residue, and may introduce new impurities; 2. The pH of the extraction system needs to be precisely controlled within a narrow range, resulting in a narrow operating window; 3. For leachates with high iron content, the consumption of extractant is large, resulting in reduced economic efficiency; 4. The small amount of extractant remaining in the raffinate needs further oil removal treatment, which increases the complexity of the process.

[0006] In summary, existing technologies for treating nickel-cobalt waste leachate containing high iron generally face a contradiction between iron removal efficiency and nickel-cobalt recovery rate: the more thorough the iron removal, the greater the amount of alkali added and the higher the pH, and the more severe the co-precipitation loss of nickel and cobalt. How to achieve efficient removal of iron ions and reduce nickel-cobalt loss at the same time without introducing additional impurities or significantly increasing the pH value is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] Therefore, the present invention provides a method for recycling and reusing nickel-cobalt waste slag, which overcomes the problems in the prior art where the iron removal process requires adjusting the pH to cause large losses due to nickel-cobalt co-precipitation, easy introduction of organic impurities and high cost, and poor iron slag filtration performance leading to operational difficulties.

[0008] To achieve the above objectives, the present invention provides a method for recycling and reusing nickel-cobalt waste slag, comprising: Nickel-cobalt waste residue is mixed with dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1, and then dissolved and filtered to obtain a first-stage leachate and a first-stage tailings rich in nickel and cobalt. The first stage tailings were mixed with concentrated sulfuric acid solution at a liquid-to-solid ratio of 2-4:1, and the solution was dissolved and filtered to obtain the second stage leachate containing a small amount of nickel and cobalt and the final tailings. The first and second leachates were combined. A comprehensive index for the leaching endpoint was determined based on the rate of change of the first pH value and the rate of change of the first redox potential. This index was used to determine the leaching reaction endpoint and to formulate a correction strategy, resulting in a product containing Ni. 2+ Co 2+ and Fe 3+ Acid leaching solution; A reducing agent is added to the acid leaching solution, and the target value of the redox potential is determined based on the measured parameters of the acid leaching solution. The addition rate of the reducing agent is dynamically adjusted through a proportional-integral feedback control algorithm to obtain a reduced solution. Pyrite seed crystals are added to the reduced solution, and the reaction system is adjusted to determine whether colloids are generated based on the rate of change of turbidity of the solution. The comprehensive index of iron deposition was determined based on the real-time detection of the rate of change of the second redox potential and the rate of change of the second pH value. The stability of the precipitated iron system is determined based on the comprehensive index of precipitated iron and the comprehensive index of leaching endpoint, so as to dynamically adjust the flow rate of oxygen-containing gas until the pyrite is completely precipitated. The precipitate of ferrous sulfate was separated to obtain a purified solution rich in nickel and cobalt. A saponified acidic phosphorus extractant was then added to preferentially extract Co. 2+ After back-extraction, cobalt sulfate solution and nickel sulfate solution were obtained respectively.

[0009] Furthermore, the process of merging the leachates includes: Nickel-cobalt waste residue is mixed with dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1, and then dissolved and filtered to obtain a first-stage leachate and a first-stage tailings rich in nickel and cobalt. The first stage tailings were mixed with concentrated sulfuric acid solution at a liquid-to-solid ratio of 2-4:1, and the solution was dissolved and filtered to obtain the second stage leachate containing a small amount of nickel and cobalt and the final tailings. The first leachate and the second leachate are combined to obtain the combined leachate.

[0010] Furthermore, the process of determining the endpoint of the leaching reaction includes: The weighted sum of the first pH value change rate and the first redox potential change rate is used to determine the leaching endpoint composite index. Based on the leaching endpoint composite index being greater than 0.2, it is determined that the leaching reaction has not reached the endpoint; The leaching reaction is determined to have reached its endpoint based on a comprehensive index of less than or equal to 0.2 and a duration of greater than or equal to 15 minutes.

[0011] Furthermore, the process of determining the correction strategy includes: The inflection point is determined based on the ratio of the rate of change of the first pH value to the ratio of the rate of change of the first redox potential. Adjust the stirring speed or aeration flow rate according to the inflection point combination state until the leaching endpoint comprehensive index reaches 0.2.

[0012] Furthermore, based on the potential deviation between the measured value of the redox potential and the target value of the redox potential, a feeding rate control signal is calculated using a proportional-integral feedback control algorithm to adjust the addition rate of the reducing agent in real time. The target value of the redox potential is determined dynamically based on the measured parameters of the acid leaching solution; The measured parameters include the measured values ​​of the redox potential, pH value, and temperature value at the endpoint of acid leaching.

[0013] Furthermore, the turbidity change rate of the solution is determined based on the amount of turbidity change within a preset time window; Based on the fact that the turbidity change rate is greater than the preset turbidity change rate, it is determined that the reaction system produces colloids; The amount of pyrite seed crystals to be added is determined by classifying the turbidity change rate difference between the turbidity change rate and the preset turbidity change rate. The amount added is directly proportional to the difference in the rate of change of turbidity; The preset turbidity change rate is 5 NTU / min.

[0014] Furthermore, the weighted summation of the rate of change of the second redox potential and the rate of change of the second pH value is used to determine the comprehensive index of iron precipitation; The index ratio is determined based on the ratio of the total iron leaching index to the total leaching endpoint index; Based on the index ratio being greater than 1.0, the iron sinking system is determined to be unstable.

[0015] Furthermore, the oxygen-containing gas flow rate is dynamically adjusted based on the deviation of the exponential ratio from the exponential ratio of 1.0; Among them, the adjustment range is directly proportional to the degree of deviation.

[0016] Furthermore, the preparation process of the pyrite seed crystals includes: The initial seed crystals prepared by the first chemical synthesis, or the recycled seed crystals after washing, drying and grinding the pyrite precipitate generated in the previous batch of iron precipitation reaction; The ferrous alum seed crystals include at least one of ferrous alum, sodium ferrous alum, or potassium ferrous alum.

[0017] Furthermore, the reducing agent includes at least one of iron powder, scrap iron, sodium sulfite, sodium bisulfite, sulfur dioxide, sodium metabisulfite, and ascorbic acid; The acidic phosphorus extractant includes at least one of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, di(2-ethylhexyl)phosphonic acid, and di(2,4,4-trimethylpentyl)phosphonic acid.

[0018] Compared with the prior art, the beneficial effects of the present invention are that it adopts a two-stage countercurrent leaching process. The first stage rapidly dissolves most of the nickel and cobalt with a high liquid-to-solid ratio, and the second stage deeply leaches the tailings of the first stage with fresh concentrated sulfuric acid. Through the tiered utilization of acid, the total acid consumption is reduced while the nickel leaching rate reaches more than 98% and the cobalt leaching rate reaches more than 97%, which is 8-10 percentage points higher than the traditional single-stage leaching.

[0019] Furthermore, this invention constructs a comprehensive index for the leaching endpoint based on the rate of change of the first pH value and the rate of change of the first redox potential. By comparing the weighted sum of the two parameters with 0.2, the leaching endpoint is determined, overcoming the shortcomings of single parameters being easily interfered with and having a high misjudgment rate. Experiments show that the accuracy rate of determining the leaching endpoint is over 95%. When the leaching endpoint has not been reached, the inflection point is determined by the ratio of the rate of change of the first pH value and the rate of change of the first redox potential. The stirring speed is adjusted in stages according to the deceleration state of the two parameters and the index difference, realizing the fine control of the leaching process and avoiding the blindness of traditional experience-based operations.

[0020] Furthermore, this invention employs a proportional-integral feedback control algorithm. Based on the dynamically calculated target value of the redox potential, the reducing agent addition rate is adjusted in real time according to the potential deviation between the measured value and the target value of the redox potential of the acid leaching solution. Compared to the traditional one-time addition method, the reducing agent consumption is reduced by 10%-20%, Fe 3+ The residual rate is less than 0.5%, and the accuracy rate of determining the reduction endpoint is over 95%.

[0021] Furthermore, this invention incorporates the turbidity change rate into the control of the iron precipitation process. By monitoring the turbidity change rate in real time, it determines whether colloids are generated and replenishes seed crystals in stages according to the turbidity difference. The amount of seed crystals replenished is 5% to 30% of the total amount of seed crystals. This mechanism can promptly suppress the formation of ferric hydroxide colloids, avoid the loss of nickel and cobalt by adsorption of colloids, and reduce the risk of impurity contamination caused by the introduction of external seed crystals.

[0022] Furthermore, this invention establishes a comprehensive iron precipitation index based on the second redox potential change rate and the second pH change rate. The iron precipitation process is judged by weighted summation, achieving selective precipitation of iron under low-acid conditions of pH 1.0 to 2.0. This reduces the nickel-cobalt loss rate from 5% to 15% in traditional methods to below 1%. The ratio of the leaching endpoint comprehensive index to the iron precipitation comprehensive index is used as a linkage verification index for determining the iron precipitation endpoint. When the ratio is less than or equal to 1.0, it indicates that the stability of the iron precipitation system is not lower than the leaching endpoint, confirming complete precipitation of pyrite. This mechanism provides a unified quantitative comparison of the stability of different process steps, increasing the accuracy of iron precipitation endpoint determination from 85% to 95%. Furthermore, the oxygen-containing gas flow rate is dynamically adjusted based on the difference between the index ratio and the target value. The adjustment range is proportional to the degree of deviation, achieving smooth, adaptive, and stepless adjustment, avoiding system disturbances caused by sudden flow changes.

[0023] Furthermore, this invention uses the pyrite precipitate generated from the iron precipitation reaction, after filtration, washing, drying and grinding, as a seed crystal for recycling in the iron precipitation step. This achieves self-sufficiency in seed crystals, eliminating the need to purchase them externally and significantly reducing production costs. At the same time, the recycled seed crystals originate from this system, and their composition is known and controllable, effectively avoiding the risk of contamination from impurities such as potassium, sodium and organic matter that may be introduced by external seed crystals, thus ensuring the purity of the nickel-cobalt products.

[0024] Furthermore, this invention effectively overcomes the technical challenges of high pH adjustment during iron removal, which leads to significant losses from nickel-cobalt co-precipitation; easy introduction of organic impurities during iron removal extraction; and poor filtration performance of iron slag. By achieving highly efficient selective precipitation of iron under low pH conditions, the nickel-cobalt loss rate is significantly reduced from 5%-15% in traditional methods to below 1%. By replacing extraction with precipitation for iron removal, the use and residue problems of organic extractants are completely avoided. Through seed-induced generation of large-particle pyrite crystals, the filtration time is shortened by more than 80%, significantly improving solid-liquid separation efficiency. This invention can achieve excellent technical indicators such as total nickel recovery rate of over 95%, total cobalt recovery rate of over 95%, and iron removal rate of over 99%, while significantly reducing reagent consumption, simplifying the operation process, and reducing solid waste emissions. It has significant economic benefits, environmental benefits, and promising prospects for industrial application. Attached Figure Description

[0025] Figure 1This is a flowchart of the method for recycling and reusing nickel-cobalt waste slag according to an embodiment of the present invention; Figure 2 This is a logic diagram illustrating the determination of the leaching reaction endpoint as described in an embodiment of the present invention. Figure 3 This is a logic diagram for determining whether a colloid is generated in a reaction system, as described in an embodiment of the present invention. Figure 4 This is a logic diagram illustrating the determination of the stability of the iron-sinking system as described in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0027] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] Please see Figure 1 The diagram shows a flowchart of the method for recycling and reusing nickel-cobalt waste slag according to an embodiment of the present invention. The method for recycling and reusing nickel-cobalt waste slag according to an embodiment of the present invention includes: Step S1: Mix the nickel-cobalt waste residue with dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1, dissolve and filter to obtain the first stage leachate and the first stage tailings rich in nickel and cobalt. Step S2: Mix the first stage tailings with concentrated sulfuric acid solution at a liquid-to-solid ratio of 2-4:1, dissolve and filter to obtain the second stage leachate containing a small amount of nickel and cobalt and the final tailings. Step S3: Combine the first and second leachates, determine the leaching endpoint comprehensive index based on the first pH value change rate and the first redox potential change rate, determine the leaching reaction endpoint, and determine the correction strategy to obtain Ni-containing solution. 2+ Co 2+ and Fe 3+ Acid leaching solution; Step S4: Add a reducing agent to the acid leaching solution, determine the target value of the redox potential based on the measured parameters of the acid leaching solution, and dynamically adjust the addition rate of the reducing agent through a proportional-integral feedback control algorithm to obtain the reduced solution. Step S5: Add ferrous sulfate seed crystals to the reduced solution. Determine whether colloids are generated in the reaction system based on the rate of change of turbidity of the solution, and adjust the amount of ferrous sulfate seed crystals added accordingly. Step S6: Determine the comprehensive index of iron deposition based on the real-time detected rate of change of the second redox potential and the rate of change of the second pH value; Step S7: Determine the stability of the precipitated iron system based on the comprehensive index of precipitated iron and the comprehensive index of leaching endpoint, so as to dynamically adjust the flow rate of oxygen-containing gas until the pyrite is completely precipitated. Step S8: Separate the pyrite precipitate to obtain a purified solution rich in nickel and cobalt. Add saponified acidic phosphorus extractant to preferentially extract Co. 2+ After back-extraction, cobalt sulfate solution and nickel sulfate solution were obtained respectively.

[0029] Specifically, the nickel-cobalt waste slag is crushed and ground to a particle size of 74-150μm, and then added to a reaction vessel with a 5%-20% dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1. Stirring is started, the reaction temperature is controlled at 70-90℃, and the reaction time is 1-2 hours. After the reaction is completed, solid-liquid separation is carried out by a filter press or a vacuum filter to obtain the first stage leachate rich in nickel and cobalt and the first stage tailings.

[0030] Specifically, the first tailings obtained in step S1 are transferred to another reactor, and a fresh concentrated sulfuric acid solution with a concentration of 70%-98% is added. The liquid-solid ratio is controlled at 2-4:1, and the mixture is stirred and reacted at 80-95℃ for 2-4 hours. After the reaction is completed, the solid and liquid are separated to obtain a second leaching solution containing a small amount of nickel and cobalt and the final tailings. The final tailings are washed and stored or used as building material raw materials.

[0031] In this embodiment of the invention, a high liquid-to-solid ratio and a low concentration of dilute sulfuric acid are used to ensure good fluidity of the slurry while rapidly dissolving most of the nickel and cobalt in the waste residue. The high liquid-to-solid ratio reduces the viscosity of the slurry, minimizes mechanical entrainment losses, and allows for a faster reaction rate, enabling the main leaching reaction to be completed in a shorter time. However, the tailings in the first stage still contain a small amount of unleached nickel and cobalt, mainly encased inside the waste residue particles or associated with sparingly soluble minerals. Therefore, step S2 uses a fresh concentrated sulfuric acid solution and a lower liquid-to-solid ratio to increase the acid concentration and reaction temperature, enabling deep leaching of the tailings. The higher acid concentration enhances the leaching kinetics, which can destroy the structure of sparingly soluble minerals, exposing and dissolving the encased nickel and cobalt. The low liquid-to-solid ratio ensures a higher acid concentration while reducing the volume of subsequent leaching solution.

[0032] Specifically, the first and second leachates are combined in the same reactor, stirring is started, and the temperature is maintained at 80-90℃. An online pH meter and an online ORP meter are installed on the reactor to collect pH and redox potential values ​​in real time, and the rate of change of the first pH value and the rate of change of the first redox potential are continuously monitored and calculated.

[0033] Please see Figure 2 As shown, it is a logic diagram for determining the endpoint of the leaching reaction according to an embodiment of the present invention.

[0034] Specifically, the process of determining the leaching endpoint composite index includes: The weighted sum of the first pH value change rate and the first redox potential change rate is used to determine the leaching endpoint composite index. If the leaching endpoint composite index is less than or equal to 0.2, it indicates that the rate of change of the first pH value and the rate of change of the first redox potential are both at a low level, the leaching system tends to be stable and is close to the leaching endpoint. At this time, if the duration is greater than or equal to 15 minutes, it is finally determined that the leaching reaction has reached the endpoint and stirring is stopped. If the duration is less than 15 minutes, monitoring and stirring are continued. Since the leaching endpoint composite index is greater than 0.2, it indicates that the system is not yet stable, and the leaching reaction has not reached the endpoint.

[0035] In this embodiment of the invention, the 15 minutes is the time from when the leaching endpoint composite index first drops below 0.2. If the leaching endpoint composite index rises back above 0.2 during this period, the timer is reset to zero.

[0036] Specifically, in response to the leaching reaction not reaching its endpoint, an inflection point is determined based on the ratio of the rate of change of the first pH value to the rate of change of the first redox potential, in order to determine a correction strategy.

[0037] Specifically, the rate ratio of the first pH change rate is determined based on the ratio of the first pH change rate in the current time period to the first pH change rate in the previous time period.

[0038] When the ratio of the rate of change of the first pH value is greater than 1, it indicates that the rate of change of the first pH value is still increasing and the inflection point has not yet been reached. When the rate ratio of the first pH value change rate is 1, it indicates that the first pH value change rate has reached its peak, the inflection point. When the ratio of the first pH value change rate to the first pH value change rate is less than 1, it indicates that the first pH value change rate has begun to decrease and the inflection point has passed. Specifically, the rate ratio of the first redox potential change rate is determined based on the ratio of the absolute value of the first redox potential change rate in the current time period to the absolute value of the first redox potential change rate in the previous time period.

[0039] When the ratio of the rate of change of the first redox potential is greater than 1, it indicates that the rate of change of the first redox potential is still increasing and the inflection point has not yet been reached. When the ratio of the rate of change of the first redox potential is 1, it indicates that the rate of change of the first redox potential has reached its peak, the inflection point. When the ratio of the rate of change of the first redox potential is less than 1, it indicates that the rate of change of the first redox potential has begun to decrease and the inflection point has passed.

[0040] Specifically, when the ratio of the rate of change of the first pH value is ≥1 and the ratio of the rate of change of the first redox potential is ≥1, it indicates that neither the rate of change of the first pH value nor the rate of change of the first redox potential has slowed down, the inflection point of the two parameters has not yet appeared, and the leaching reaction is still in the rapid reaction stage. At this time, the current reaction conditions should be maintained and monitoring should continue, without adjusting the operating parameters.

[0041] When the ratio of the rate of change of the first pH value is <1 and the ratio of the rate of change of the first redox potential is <1, it indicates that both the rate of change of the first pH value and the rate of change of the first redox potential have begun to decelerate, the inflection points of both parameters have appeared, and the leaching reaction has entered the decelerating reaction stage from the rapid reaction stage. At this time, the stirring speed should be gradually reduced based on the difference between the comprehensive index of the leaching endpoint and the index of 0.2, so that the system can smoothly approach the endpoint and avoid system disturbance due to excessive stirring.

[0042] When the ratio of the rate of change of the first pH value is <1 and the ratio of the rate of change of the first redox potential is ≥1, it indicates that the rate of change of the first pH value has begun to decelerate and the inflection point has passed, but the rate of change of the first redox potential has not yet decelerated and the inflection point has not been reached. That is, the acid consumption reaction has entered the deceleration stage while the redox system is still changing rapidly. At this time, the stirring speed should be increased in a gradient based on the difference between the comprehensive index of the leaching endpoint and the index of 0.2 to promote the establishment of redox equilibrium.

[0043] When the ratio of the rate of change of the first pH value is ≥1 and the ratio of the rate of change of the first redox potential is <1, it indicates that the rate of change of the first pH value has not yet decelerated and the inflection point has not been reached, but the rate of change of the first redox potential has begun to decelerate and the inflection point has passed. That is, the acid consumption reaction is still proceeding rapidly while the redox system has entered the deceleration stage. At this time, the current pH conditions should be maintained, and the aeration flow rate should be gradually reduced based on the difference between the leaching endpoint comprehensive index and 0.2 to ensure that the two coordinate to approach the endpoint.

[0044] In this embodiment of the invention, the first stage leaching solution has a high nickel-cobalt concentration but low acidity, while the second stage leaching solution has a low nickel-cobalt concentration but high acidity. After the two liquids are combined, they need to be re-equilibrated. The pH and redox potential of the combined solution will change in the initial stage of mixing, and trace amounts of residual leaching reaction may also exist. Step S3 determines whether the leaching reaction has truly reached its endpoint by real-time monitoring of the rate of change of the first pH value and the rate of change of the first redox potential of the combined solution. When the leaching reaction is underway, H... + Consumed, pH continues to rise, Fe 3+ Concentration changes cause continuous changes in redox potential; as the reaction nears completion, H... + The consumption rate approaches zero, the rate of change of the first pH value approaches zero, and at the same time, Fe... 3+ / Fe2+ As the ratio stabilizes, the rate of change of the first redox potential also approaches zero; therefore, the combined determination of two parameters is more reliable than that of a single parameter, and can avoid misjudgment caused by probe drift or local reaction.

[0045] In this embodiment of the invention, the acid leaching solution obtained in step S3 is transferred to a reduction reactor, the temperature is maintained at 60-90℃, stirring is started, and an online ORP meter is started for continuous monitoring. A target value of oxidation-reduction potential is set in the control system. The target value of oxidation-reduction potential is dynamically calculated based on the measured parameters of the leaching endpoint of the acid leaching solution in step S3. The allowable fluctuation range is set to the target value ±50mV, and the sampling period of the proportional-integral control algorithm is set to 1 second. The reducing agent feeding system consists of a reducing agent storage tank, a metering pump, and a controller. The controller uses a proportional-integral feedback control algorithm to dynamically adjust the feeding rate based on the deviation between the measured value and the target value of the oxidation-reduction potential.

[0046] Specifically, the reducing agent includes at least one of iron powder, scrap iron, sodium sulfite, sodium bisulfite, sulfur dioxide, sodium metabisulfite, and ascorbic acid, without introducing additional impurity ions.

[0047] Specifically, the measured parameters include the measured values ​​of redox potential, pH value, and temperature value.

[0048] Specifically, the process of determining the target value of the redox potential includes: The target value of the redox potential is determined based on the measured values ​​of the redox potential, pH value, and temperature value at the leaching endpoint of the acid leaching solution.

[0049] Specifically, the measured redox potential at the leaching endpoint of the acid leaching solution is used as the benchmark value. The reduction in redox potential is subtracted from the benchmark value to obtain the first correction value; the reduction in redox potential is the required reduction in potential from the leaching endpoint to the pre-reduction endpoint. Then, the pH difference between the acid leaching solution's pH value and the reference pH value of 1.5 is calculated, and this difference is multiplied by a pH correction factor to obtain a pH correction term. The pH correction term is subtracted from the first correction value to obtain the second correction value. When the acid leaching solution's pH value is higher than 1.5, the pH correction term is positive, further reducing the target value; when the acid leaching solution's pH value is lower than 1.5, the pH correction term is negative, correspondingly increasing the target value. Finally, the temperature difference between the acid leaching solution's temperature and the reference temperature of 80°C is calculated, and this difference is multiplied by a temperature correction factor to obtain a temperature correction term. This temperature correction term is subtracted from the second correction value to obtain the target value of the redox potential. When the temperature of the leaching solution is above 80℃, the temperature correction term is positive, further reducing the target value; when the temperature of the leaching solution is below 80℃, the temperature correction term is negative, correspondingly increasing the target value.

[0050] In this embodiment of the invention, the preset reduction of the redox potential is the amount of reduction required between the measured value of the redox potential of the acid leaching solution at the reaction endpoint and the target value of the pre-reduced redox potential.

[0051] In this embodiment of the invention, the pH correction coefficient is a correction coefficient for the redox potential as a function of pH.

[0052] In this embodiment of the invention, the temperature correction coefficient is a correction coefficient for the change of redox potential with temperature.

[0053] Specifically, the process of dynamically adjusting the addition rate of the reducing agent includes: The measured values ​​of the redox potential are read in real time at a preset sampling period. The potential deviation between the measured value and the target value is calculated, and the potential deviation is multiplied by a proportional coefficient and an integral coefficient respectively. The proportional coefficient is used to adjust the feeding rate in real time based on the magnitude of the current potential deviation; the larger the potential deviation, the faster the feeding rate, and the smaller the potential deviation, the slower the feeding rate. The integral coefficient is used to accumulate and sum the potential deviations at all past moments. When the potential deviation persists for a long time, the integral term gradually increases, driving the continuous adjustment of the feeding rate until the potential deviation is completely eliminated. The proportional term and the integral term are added together to obtain the feeding rate control signal. The value range of the control signal is 0% to 100%, which is used to control the feeding rate of the metering pump. Through the above proportional-integral feedback control, real-time, smooth, and precise adjustment of the reducing agent addition rate is achieved.

[0054] In this embodiment of the invention, at the initial stage of reduction, the measured value of the oxidation-reduction potential is much higher than the target value, the deviation is large, the proportional term outputs a large control signal, and the metering pump adds the reducing agent at a high rate. As the reduction reaction proceeds, the measured value of the oxidation-reduction potential gradually decreases, the deviation decreases, and the feeding rate automatically slows down. When the measured value of the oxidation-reduction potential stabilizes within the range of the target value ±50mV and the duration reaches 5 minutes, the controller determines that the reduction is complete and stops adding the reducing agent.

[0055] In this embodiment of the invention, based on the response requirement of the second redox potential change rate, the redox potential change rate is usually 1-10 mV / second during the pre-reduction process. A sampling period of 1 second can ensure that the controller captures at least 1-10 mV of change in each sampling interval, which is sufficient to reflect the dynamic trend of the reduction reaction. If the sampling period is too long, such as 10 seconds, key changes may be missed, resulting in control lag. If the sampling period is too short, such as 0.1 seconds, the controller will be under increased burden and may amplify measurement noise.

[0056] In this embodiment of the invention, Fe 3+ Reduced to Fe 2+The reaction exhibits asymptotic characteristics near the endpoint; even after the redox potential enters the target range, trace amounts of Fe may still exist in the solution at a concentration of approximately 0.1-0.5 g / L. 3+ Sufficient time is needed for these residual Fe 3+ Continuing the reaction, experiments showed that from the moment the redox potential first entered the target range to the point where Fe... 3+ It typically takes 3-5 minutes for the concentration to drop below 0.1 g / L, and a 5-minute stabilization time ensures that Fe... 3+ It was fully restored.

[0057] In this embodiment of the invention, the reduced solution obtained in step S4 is transferred to an iron precipitation reactor, and ferrous sulfate seed crystals are added. The ferrous sulfate seed crystals are derived from the ferrous sulfate precipitate recycled in this step. After washing, drying, and grinding, they are added in a certain proportion. Stirring is started, and the temperature is heated to 70-100°C. The rate of change of the second redox potential, the rate of change of the second pH value, and the turbidity of the solution are collected in real time.

[0058] Specifically, the ferrous sulfate seed crystals include at least one of ferrous sulfate sulfonium ...

[0059] Specifically, the preparation process of the ferrous sulfate seed crystals includes: S51. During the initial run, if there are no circulating seed crystals, obtain the initial seed crystals in the following manner: Towards Fe 3+ Add ammonium sulfate or sodium sulfate to a sulfuric acid solution with a concentration of 10-20 g / L to control the NH4+ content. 4+ Or Na + with Fe 3+ The molar ratio is 1:3. The pH is adjusted to 1.3-1.5 with sodium carbonate, heated to 90-95℃, and stirred for 2-3 hours to form ferrous sulfate precipitate. After the reaction is complete, the ferrous sulfate precipitate is obtained by filtration, washed 2-3 times with deionized water to remove entrained solution, dried at 60-80℃ to constant weight, and ground to a particle size of 5-20μm to obtain the initial seed crystals. S52. Recycling of seed crystals during continuous operation: During continuous operation, the pyrite seed crystals originate from the pyrite precipitate generated in steps S5, S6, and S7 of the iron precipitation reaction. After filtering the pyrite precipitate generated in the previous batch of iron precipitation reaction, it is washed 2-3 times with deionized water to remove entrained Ni. 2+ Co 2+ The solution is dried at 60-80℃ to constant weight, and then ground to a particle size of 5-20μm to obtain recycled seed crystals, which are added to the iron precipitation reaction in this batch at a ratio of 3-5g / L. S53, Maintaining the activity of seed crystals: When the activity of seed crystals used for a long time decreases, that is, when the iron precipitation time is prolonged, the precipitate becomes finer, and the iron removal rate is less than 90%, freshly prepared seed crystals should be added at 10%-20% of the total amount, or all of them should be replaced with fresh seed crystals.

[0060] Please see Figure 3 As shown, it is a logic diagram for determining whether a reaction system produces colloids according to an embodiment of the present invention.

[0061] Specifically, the process of adjusting the amount of ferrous sulfate seed crystals added includes: During the iron precipitation reaction, the turbidity of the solution is monitored in real time. The turbidity change rate is determined based on the ratio of the turbidity change within a preset time window to the length of the time window, with units of NTU / min. The turbidity change is determined based on the difference between the measured turbidity value at the current moment and the measured turbidity value at the previous moment.

[0062] Based on the fact that the turbidity change rate is greater than the preset turbidity change rate of 5 NTU / min, it is determined that ferric hydroxide colloid has been generated in the solution. Based on the turbidity change rate being less than or equal to a preset turbidity change rate of 5 NTU / min, it is determined that no colloids were generated in the system.

[0063] In this embodiment of the invention, the preset turbidity change rate is used to determine whether ferric hydroxide colloid is generated during the iron precipitation reaction.

[0064] Specifically, in response to the formation of ferric hydroxide colloid in the solution, the difference between the turbidity change rate and the preset turbidity change rate is calculated. Based on the fact that the difference in the rate of change of turbidity is less than or equal to the first preset turbidity difference of 2 NTU / min, fresh crystal seeds are added at 5%-10% of the total number of crystal seeds to slightly enhance the seed seed induction effect and inhibit further formation of colloids. Based on the turbidity change rate difference being greater than the first preset turbidity difference of 2 NTU / min and less than or equal to the second preset turbidity difference of 5 NTU / min, fresh crystal seeds are added at 10%-20% of the total number of crystal seeds to significantly enhance the crystal seed induction effect and promote the conversion of colloids into pyrite crystals. Based on the turbidity change rate difference being greater than the second preset turbidity difference of 5 NTU / min, fresh seed crystals are added at a rate of 20%-30% of the total seed crystals, and the seed crystal activity is checked. If necessary, all seed crystals are replaced with fresh seed crystals to quickly restore the selectivity of the iron deposition reaction.

[0065] Specifically, the process of dynamically adjusting the oxygen-containing gas flow rate includes: In response to the absence of colloid formation in the system, the rates of change of the second redox potential and the second pH value during the iron deposition reaction are collected in real time. These rates are then multiplied by their respective weighting coefficients and summed to calculate the iron deposition index. The iron deposition index is a dimensionless parameter; a smaller value indicates that the iron deposition system is closer to the endpoint, while a larger value indicates a greater deviation from the endpoint.

[0066] The second pH change rate refers to the change in pH value per unit time during the iron precipitation reaction, measured in millivolts per minute; the second redox potential change rate refers to the change in redox potential per unit time during the iron precipitation reaction, measured in millivolts per minute.

[0067] In the iron precipitation reaction, the oxidation of ferrous ions to ferric ions is the main reaction. The rate of change of the second redox potential directly reflects the progress of the reaction, and the rate of change of the second pH value reflects the precipitation and acid production process of ferrous sulfate. Both are important criteria and are equally important. Therefore, the weight coefficients of the two are preferably each 50%. This ratio was determined through orthogonal experiment optimization.

[0068] Please see Figure 4 As shown, it is a logic diagram for determining the stability of the iron sinking system according to an embodiment of the present invention.

[0069] Specifically, the ratio of the leaching endpoint comprehensive index to the iron sinking comprehensive index is calculated. The ratio is a dimensionless parameter, specifically the quotient obtained by dividing the iron sinking comprehensive index by the leaching endpoint comprehensive index.

[0070] In this embodiment of the invention, the index ratio is used to characterize the relative relationship between the stability of the iron leaching system and the stability of the leaching endpoint.

[0071] Based on the index ratio being less than or equal to 1.0, it indicates that the stability of the iron precipitation system is not lower than the leaching endpoint, that is, the iron precipitation reaction has reached an equilibrium state equivalent to or higher than the leaching reaction. At this point, it is determined that the ferrous sulfate precipitation is complete, and the introduction of oxygen-containing gas is stopped. Based on the index ratio being greater than 1.0, it indicates that the stability of the iron leaching system is slightly lower than the leaching endpoint, and the iron leaching reaction has not yet reached complete equilibrium. At this point, it is necessary to continue to introduce oxygen-containing gas for 5-10 minutes, and then determine the endpoint after the index ratio drops below the preset index ratio.

[0072] Specifically, in response to the fact that the iron deposition reaction has not yet reached complete equilibrium, the oxygen-containing gas flow rate is dynamically adjusted according to the deviation of the exponential ratio from the exponential ratio of 1.0.

[0073] The specific adjustment method is as follows: calculate the deviation of the index ratio from the index ratio of 1.0, multiply the index ratio deviation by the flow rate adjustment coefficient, and the resulting product is the ventilation flow rate adjustment range; when the product is positive, increase the ventilation flow rate, and when the product is negative, decrease the ventilation flow rate.

[0074] In this embodiment of the invention, the comprehensive index of the leaching endpoint is a reliable benchmark value obtained through rigorous progressive judgment. It truly reflects the comprehensive fluctuation level of the reaction system when it reaches equilibrium. When the iron leaching reaction is underway, the comprehensive index of iron leaching is calculated in real time and compared with the comprehensive index of the leaching endpoint to determine whether the stability of the iron leaching system has reached or exceeded the standard of the leaching endpoint. When the index ratio is less than or equal to 1.0, it indicates that the comprehensive index of iron leaching is less than or equal to the comprehensive index of the leaching endpoint, that is, the stability of the iron leaching system is not lower than the leaching endpoint, which means that the iron leaching reaction has reached an equilibrium state equivalent to or higher than the leaching reaction. When the index ratio is greater than 1.0, it indicates that the stability of the iron leaching system is lower than the leaching endpoint, and the reaction needs to continue or the operating parameters need to be adjusted. Through the linkage verification of the comprehensive index of the leaching endpoint and the comprehensive index of iron leaching, the stability indicators of different steps are uniformly quantified and compared, realizing the closed-loop stability assessment of the entire process, and further improving the reliability and accuracy of the determination of the iron leaching endpoint.

[0075] In this embodiment of the invention, the iron in the reduced solution is in the form of Fe. 2+ In this embodiment of the invention, Fe is present by introducing oxygen-containing gas. 2+ Slowly oxidized to Fe 3+ The newly generated Fe 3+ The ferrous sulfate crystals react with sulfate and monovalent cations on their surface to form a ferrous sulfate precipitate. 3Fe 3+ +NH4 + +2SO4 2- +6H₂O→NH₄Fe₃(SO₄)₂(OH)₆+6H + ; The key to this step lies in slow oxidation and seed induction, if Fe... 3+ If the formation is too rapid, it will form amorphous ferric hydroxide colloid, lose its selectivity, and adsorb nickel and cobalt. This can be addressed by controlling the aeration flow rate to prevent Fe from forming. 2+ Slow oxidation, Fe 3+ The resulting crystals were captured and precipitated by the active sites on the seed crystal surface, achieving heterogeneous nucleation rather than homogeneous nucleation, producing large, easily filterable pyrite crystals. This step employs three-parameter coupled control: the rate of change of the second redox potential reflects the Fe... 3+ The balance between generation and consumption, the rate of change of the second pH value reflecting the progress of the ferrous sulfate precipitation reaction, and the turbidity of the solution reflecting the physical state of the precipitation, with an increase in turbidity indicating the presence of colloids, are all assessed in synergy. This approach is more reliable than using a single parameter and can promptly detect the risk of colloid formation and adjust the operation accordingly.

[0076] Specifically, the slurry obtained in step S7 is subjected to solid-liquid separation, filtered to obtain ferrous sulfate precipitate and a purified liquid rich in nickel and cobalt. The ferrous sulfate precipitate is washed with deionized water 2-3 times to remove the entrained solution. Part of the precipitate is dried and ground and then recycled as seed crystals for steps S5-S7.

[0077] The purified solution is pumped into an extraction mixer, and pre-saponified acidic phosphorus extractant is added. Sulfonated kerosene is used as a diluent, and the volume ratio of the organic phase to the aqueous phase (O / A) is controlled between 1:1 and 2:1. The pH is adjusted to 4.0-5.5 with dilute sulfuric acid or sodium hydroxide. After thorough mixing in the extraction mixer, the solution enters a clarifier for stratification. The organic phase is loaded with Co. 2+ The aqueous phase is a nickel sulfate solution; the supported organic phase is mixed with 1-2 mol / L dilute sulfuric acid at a certain ratio and back-extracted. After mixing, the mixture is clarified and separated into layers. The organic phase is regenerated and can be recycled. The aqueous phase is a cobalt sulfate solution; finally, cobalt sulfate solution and nickel sulfate solution are obtained respectively, realizing the deep separation and recovery of nickel and cobalt.

[0078] Specifically, the acidic phosphorus extractant is an acidic phosphorus type extractant with the general formula XYP(O)OH, which achieves selective extraction of metal ions through a cation exchange mechanism. In this embodiment of the invention, the acidic phosphorus extractant includes at least one of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, di(2-ethylhexyl)phosphoric acid, and di(2,4,4-trimethylpentyl)phosphonic acid.

[0079] Example 1

[0080] The method for recycling and reusing nickel-cobalt waste slag according to an embodiment of the present invention includes: Raw material: a nickel-cobalt waste residue, main components: Ni 5.2%, Co 0.8%, Fe 18.5%.

[0081] Step-by-step acid leaching: First stage: 100g of waste residue, 500mL of 10% dilute sulfuric acid, liquid-to-solid ratio 5:1, temperature 85℃, time 1.5h, filter to obtain first stage leachate and first stage tailings.

[0082] Second stage: The first stage tailings, fresh concentrated sulfuric acid with a concentration of 98%, is diluted to 30% according to process requirements, with a liquid-to-solid ratio of 3:1, a temperature of 90℃, and a time of 2 hours. The second stage leachate and the final tailings are obtained by filtration.

[0083] Combined leachate: Ni leaching rate 98.2%, Co leaching rate 97.5%, Fe leaching rate 92.1%.

[0084] Determination of leaching endpoint: The leaching endpoint composite index was calculated as follows: 0.6 × |0.001| / 0.003 + 0.4 × |0.8| / 2 = 0.2 + 0.16 = 0.36. After stabilizing for 15 minutes, the leaching endpoint composite index dropped to 0.18, and the leaching endpoint was determined.

[0085] Pre-restoration: The target value of the oxidation-reduction potential = 580 - 120 - 60 × (1.3 - 1.5) - 2 × (85 - 80) = 580 - 120 + 12 - 10 = 462 mV; After adding iron powder under PI control, the oxidation-reduction potential stabilizes at 455-465 mV after 30 minutes, then the feeding is stopped. 3+ The residual rate was 0.3%.

[0086] Seed-induced iron deposition: Add 4 g / L of ferric sulfate seed crystals, temperature 90℃, aeration flow rate 1.0 L / (min·L), initial turbidity 15 NTU, turbidity change rate 3 NTU / min (normal), calculate the iron precipitation index = 0.5 × |1.2| / 2 + 0.5 × |0.001| / 0.003 = 0.3 + 0.17 = 0.47; index ratio = 0.47 / 0.18 = 2.61 > 1.0, increase aeration to 1.644 L / (min·L), after 30 minutes the iron precipitation index decreases to 0.19, index ratio = 0.19 / 0.18 = 1.06, continue aeration for 10 minutes, after 40 minutes the iron precipitation index decreases to 0.15, index ratio = 0.83 ≤ 1.0, stop aeration, sedimentation is complete; filtration time: 8 minutes, filter cake moisture content 25%.

[0087] Extraction and separation: Saponification of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (saponification rate 70%) was performed at a ratio of O / A = 1.5:1, pH = 5.0, with a Co extraction rate of 96.2% and a Ni retention rate of 98.5%. Back-extraction yielded a cobalt sulfate solution (Co 45 g / L), and the raffinate was a nickel sulfate solution (Ni 48 g / L).

[0088] The results showed that the total recovery rate of nickel was 96.5%, the total recovery rate of cobalt was 95.8%, and the iron removal rate was 99.2%.

[0089] Comparative Example 1 This comparative example uses the traditional ferrous sulfate method. The difference from Example 1 is that the acid leaching is a single-stage leaching, i.e., the liquid-to-solid ratio is 4:1, the sulfuric acid concentration is 15%, the temperature is 85°C, and the leaching time is 2 hours, without a second stage of deep leaching; the iron removal method involves directly adding sodium carbonate to the acid leaching solution to adjust the pH to 1.5, adding sodium sulfate, heating to 90°C, without adding seed crystals, and allowing natural precipitation.

[0090] The results showed that the Ni leaching rate was 89.5% and the Co leaching rate was 87.2%, indicating that the single-stage leaching efficiency was low. The iron precipitation time was 4 hours, the filtration time was 45 minutes, the Ni loss rate was 8.5%, the Co loss rate was 7.2%, the total nickel recovery rate was 82.5%, and the total cobalt recovery rate was 81.0%. It can be seen that the nickel and cobalt recovery rates of Example 1 were increased by about 15 percentage points, and the filtration time was shortened by about 80%.

[0091] Comparative Example 2 The difference between this comparative example and Example 1 is that the index ratio is not calculated, and the endpoint is determined only by the comprehensive index of iron sinking being ≤0.2.

[0092] The results showed that when the comprehensive index of iron leaching first dropped to 0.20, the actual leaching endpoint comprehensive index was 0.25, the index ratio was 0.8, and after aeration was stopped, residual Fe in the solution was... 2+ Incomplete precipitation occurred, and the purified solution after filtration contained 0.8 g / L of Fe. Slight emulsification occurred during extraction, and the Co extraction rate dropped to 88.5%.

[0093] It can be seen that without linkage verification, the accuracy rate of endpoint determination is about 85%, with 1 out of 5 batches being misjudged; with linkage verification, the accuracy rate of endpoint determination is 95%, and the misjudgment rate is significantly reduced.

[0094] Comparative Example 3 The difference between this comparative example and Example 1 is that inflection point identification and graded adjustment are not performed. The endpoint is determined solely by whether the comprehensive index of the leaching endpoint is less than or equal to 0.20. If the endpoint is not reached, the current reaction conditions are maintained until the endpoint is reached, without adjusting the stirring speed or aeration flow rate. Other operating conditions are the same as in Example 1.

[0095] The results showed that it took 55 minutes for the leaching endpoint composite index to drop from 0.36 to 0.20, while it only took 15 minutes in Example 1, with the leaching time extended by about 40 minutes. Due to the failure to reduce the stirring speed in time, the system was still subjected to excessive stirring disturbance near the endpoint, and the leaching endpoint composite index rebounded twice, requiring a re-timing. The endpoint determination accuracy was 88%, which was 7 percentage points lower than the 95% of Example 1.

[0096] It is evident that inflection point identification and graded adjustment can effectively shorten leaching time, avoid system disturbances, and improve the efficiency of endpoint determination.

[0097] Comparative Example 4 The difference between this comparative example and Example 1 is that the target value of the redox potential is not dynamically calculated based on the measured parameters at the endpoint of the acid leaching solution, but a fixed target value of 450mV is used. Other operating conditions are the same as in Example 1.

[0098] The results showed that the measured redox potential at the leaching endpoint of this batch of acid leaching solution was 580 mV, while the fixed target value of 450 mV resulted in insufficient addition of reducing agent, Fe 3+ The residual rate was 2.1%, while it was only 0.3% in Example 1; the reduction reaction time was extended to 50 minutes, while it was 30 minutes in Example 1; the residual Fe... 3+ After entering the iron precipitation step, ferric hydroxide colloid is formed, with a Ni loss rate of 2.8% and a Co loss rate of 2.3%; the total nickel recovery rate is 94.0% and the total cobalt recovery rate is 93.2%, which are 2.5 and 2.6 percentage points lower than those in Example 1, respectively.

[0099] It is evident that by dynamically calculating the target value based on the measured parameters of the leaching endpoint, the leaching endpoint status of different batches of waste residue can be adaptively tracked, ensuring the consistency of the reduction effect.

[0100] Comparative Example 5 The difference between this comparative example and Example 1 is that turbidity monitoring was not performed, and seed crystals were not added when colloids were formed in the system. Other operating conditions were the same as in Example 1.

[0101] The results showed that due to the failure to monitor turbidity changes in a timely manner during the iron precipitation reaction, the formation of ferric hydroxide colloid was not inhibited in time, resulting in the colloid adsorbing a large amount of Ni from the solution. 2+ and Co 2+ The loss rate of Ni was 4.2% and the loss rate of Co was 3.8%, while the loss rates of Ni and Co in Example 1 were both less than 1%. At the same time, the colloid caused the filtration time to be extended to 20 minutes, while Example 1 only required 8 minutes. The total recovery rate of nickel was 93.8% and the total recovery rate of cobalt was 92.9%, which were 2.7 and 2.9 percentage points lower than those in Example 1, respectively.

[0102] It is evident that turbidity monitoring and graded crystal replenishment can promptly suppress the formation of ferric hydroxide colloids, prevent the loss of nickel and cobalt due to adsorption by colloids, and improve filtration performance.

[0103] Please refer to Table 1, which compares the experimental results of Example 1 and Comparative Examples 1-5.

[0104]

[0105] Table 1 The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recycling and reusing nickel-cobalt waste slag, characterized in that, include: Nickel-cobalt waste residue is mixed with dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1, and then dissolved and filtered to obtain a first-stage leachate and a first-stage tailings rich in nickel and cobalt. The first stage tailings were mixed with concentrated sulfuric acid solution at a liquid-to-solid ratio of 2-4:1, and the solution was dissolved and filtered to obtain the second stage leachate containing a small amount of nickel and cobalt and the final tailings. The first and second leachates were combined. A comprehensive index for the leaching endpoint was determined based on the rate of change of the first pH value and the rate of change of the first redox potential. This index was used to determine the leaching reaction endpoint and to formulate a correction strategy, resulting in a product containing Ni. 2+ Co 2+ and Fe 3+ Acid leaching solution; A reducing agent is added to the acid leaching solution, and the target value of the redox potential is determined based on the measured parameters of the acid leaching solution. The addition rate of the reducing agent is dynamically adjusted through a proportional-integral feedback control algorithm to obtain a reduced solution. Pyrite seed crystals are added to the reduced solution, and the reaction system is adjusted to determine whether colloids are generated based on the rate of change of turbidity of the solution. The comprehensive index of iron deposition was determined based on the real-time detection of the rate of change of the second redox potential and the rate of change of the second pH value. The stability of the precipitated iron system is determined based on the comprehensive index of precipitated iron and the comprehensive index of leaching endpoint, so as to dynamically adjust the flow rate of oxygen-containing gas until the pyrite is completely precipitated. The precipitate of ferrous sulfate was separated to obtain a purified solution rich in nickel and cobalt. A saponified acidic phosphorus extractant was then added to preferentially extract Co. 2+ After back-extraction, cobalt sulfate solution and nickel sulfate solution were obtained respectively.

2. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The process of merging leachates includes: Nickel-cobalt waste residue is mixed with dilute sulfuric acid solution at a liquid-to-solid ratio of 5-8:1, and then dissolved and filtered to obtain a first-stage leachate and a first-stage tailings rich in nickel and cobalt. The first stage tailings were mixed with concentrated sulfuric acid solution at a liquid-to-solid ratio of 2-4:1, and the solution was dissolved and filtered to obtain the second stage leachate containing a small amount of nickel and cobalt and the final tailings. The first leachate and the second leachate are combined to obtain the combined leachate.

3. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The process of determining the endpoint of the leaching reaction includes: The weighted sum of the first pH value change rate and the first redox potential change rate is used to determine the leaching endpoint composite index. Based on the leaching endpoint composite index being greater than 0.2, it is determined that the leaching reaction has not reached the endpoint; The leaching reaction is determined to have reached its endpoint based on a comprehensive index of less than or equal to 0.2 and a duration of greater than or equal to 15 minutes.

4. The method for recycling and reusing nickel-cobalt waste slag according to claim 3, characterized in that, The process of determining the correction strategy includes: The inflection point is determined based on the ratio of the rate of change of the first pH value to the ratio of the rate of change of the first redox potential. Adjust the stirring speed or aeration flow rate according to the inflection point combination state until the leaching endpoint comprehensive index reaches 0.

2.

5. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, Based on the potential deviation between the measured value and the target value of the redox potential, the feeding rate control signal is calculated according to the proportional-integral feedback control algorithm to adjust the addition rate of the reducing agent in real time. The target value of the redox potential is determined dynamically based on the measured parameters of the acid leaching solution; The measured parameters include the measured values ​​of the redox potential, pH value, and temperature value at the endpoint of acid leaching.

6. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The rate of turbidity change of the solution is determined based on the amount of turbidity change within a preset time window; Based on the fact that the turbidity change rate is greater than the preset turbidity change rate, it is determined that the reaction system produces colloids; The amount of pyrite seed crystals to be added is determined by classifying the turbidity change rate difference between the turbidity change rate and the preset turbidity change rate. The amount added is directly proportional to the difference in the rate of change of turbidity; The preset turbidity change rate is 5 NTU / min.

7. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The weighted sum of the rates of change of the second redox potential and the rates of change of the second pH value was used to determine the comprehensive index of iron precipitation. The index ratio is determined based on the ratio of the total iron leaching index to the total leaching endpoint index; Based on the index ratio being greater than 1.0, the iron sinking system is determined to be unstable.

8. The method for recycling and reusing nickel-cobalt waste slag according to claim 7, characterized in that, The oxygen-containing gas flow rate is dynamically adjusted based on the deviation of the exponential ratio from 1.

0. Among them, the adjustment range is directly proportional to the degree of deviation.

9. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The preparation process of the pyrite seed crystals includes: The initial seed crystals prepared by the first chemical synthesis, or the recycled seed crystals after washing, drying and grinding the pyrite precipitate generated in the previous batch of iron precipitation reaction; The ferrous alum seed crystals include at least one of ferrous alum, sodium ferrous alum, or potassium ferrous alum.

10. The method for recycling and reusing nickel-cobalt waste slag according to claim 1, characterized in that, The reducing agent includes at least one of iron powder, scrap iron, sodium sulfite, sodium bisulfite, sulfur dioxide, sodium metabisulfite, and ascorbic acid. The acidic phosphorus extractant includes at least one of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, di(2-ethylhexyl)phosphonic acid, and di(2,4,4-trimethylpentyl)phosphonic acid.

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