A sintering machine head dust and silver extraction control system and method based on ORP dynamic feature recognition

Abstract

The present application relates to a kind of sintering machine head ash silver extraction control system and method based on ORP dynamic feature identification, belong to hydrometallurgy process control technical field, including washing sintering machine head ash salt elution, leaching in sodium chloride solution, make silver [AgCl2] ‑ Form into leaching solution;Through ORP online monitoring continuous acquisition redox potential changes with time curve E (t), real-time calculation first derivative dE / dt;According to the size of |dE / dt| division reaction stage, and accurately determine the reaction endpoint by identifying ORP curve inflection point;Different zinc powder segmented addition strategy is implemented according to reaction stage, and addition is stopped in endpoint stage;The present application realizes endpoint dynamic judgment by identifying ORP variation trend, zinc powder consumption is reduced to 50%-65% of theoretical amount, crude silver grade is increased to more than 90%, response time is shortened to within 10 seconds, and ORP characteristic curve library under different process conditions can also be established, to provide support for digitalization and intelligentization of hydrometallurgy.

Description

Technical Field

[0001] This invention relates to a control system and method for extracting gray silver from sintering die heads based on ORP dynamic feature recognition, belonging to the field of hydrometallurgical process control technology. Background Technology

[0002] Sintering machine head ash is solid waste collected by the electrostatic precipitator at the head of the steel sintering process. It contains various valuable elements such as silver, lead, zinc, copper, potassium, and thallium. Taking typical domestic sintering machine head ash as an example, the silver content is usually between 50-500 g / t, making it valuable for recycling. Currently, the main method for recovering silver from sintering machine head ash is chloride leaching followed by zinc powder replacement.

[0003] Chloride leaching utilizes the Cl in sodium chloride solution - With Ag + A stable silver chloride complex [AgCl2] is formed. - (Cumulative stability constant Kf = 1.1 × 10) 5 This process transfers silver from the solid phase to the liquid phase. After leaching, zinc powder is added to the silver-containing leachate. The reducing properties of zinc displace the silver from the solution, yielding crude silver powder.

[0004] Chinese patent CN120519706A discloses a method for recovering valuable metals from sintering machine head ash, and discloses the basic process flow of chloride leaching-zinc powder replacement.

[0005] The above-mentioned process route has been applied in both laboratory and industrial production, but the following technical problems have long existed: First, the displacement endpoint cannot be precisely controlled. In existing processes, the amount of zinc powder added is determined based on experience or a fixed feed rate, and cannot be dynamically adjusted according to the actual reaction progress. Since the gray silver content of different batches of sintering die heads varies greatly (50-500 g / t), a fixed feed rate often leads to two situations: insufficient addition results in incomplete silver displacement and a low recovery rate; excessive addition leaves a large amount of zinc powder residue in the crude silver, reducing the grade of the crude silver and increasing the cost of zinc powder consumption.

[0006] Second, the methods for monitoring the reaction process are severely outdated. Currently, determining the endpoint of the substitution mainly relies on ICP-OES or atomic absorption spectrometry analysis after sampling, which typically takes 1-2 hours from sampling and digestion to obtaining the detection results. This outdated detection method cannot provide a basis for process control in real-time production.

[0007] Third, there is a lack of a staged addition strategy based on reaction kinetics. Traditional methods use the same addition rate and batch size regardless of whether the reaction is in the rapid replacement phase or near the endpoint, resulting in the simultaneous problems of insufficient zinc powder supply during the rapid reaction phase (incomplete reaction) or excessive zinc powder near the endpoint (decrease in grade). Summary of the Invention

[0008] To address the technical problems existing in the prior art, this invention provides a control system and method for extracting gray silver from sintering machine heads based on ORP dynamic feature recognition. By acquiring the ORP change curve over time in real time, calculating the first derivative dE / dt, and identifying the ORP inflection point, it achieves real-time quantitative judgment of the displacement reaction process. The response time is shortened from 1-2 hours in traditional ICP-OES analysis to less than 10 seconds, realizing real-time process control.

[0009] To achieve the above objectives, the technical solution adopted by this invention is a sintering die head gray-silver extraction control system based on ORP dynamic feature recognition, comprising: A reaction vessel used to hold silver-containing leaching solution; An ORP online monitoring electrode is inserted into the reaction vessel to collect redox potential signals in real time. The data processing unit, connected to the ORP online monitoring electrode, is used to receive potential signals and calculate the first derivative dE / dt and the second derivative d²E / dt², and to identify the reaction stage based on the magnitude and sign change of dE / dt. A zinc powder dosing device is connected to the data processing unit and adds zinc powder to the reactor according to a segmented dosing strategy based on instructions issued by the data processing unit.

[0010] Preferably, the data processing unit is preset with a first threshold and a second threshold to determine the relative magnitude of |dE / dt| with respect to the threshold.

[0011] A method for controlling the extraction of gray silver from sintering die heads based on ORP dynamic feature recognition includes the following steps: S1. Water washing and desalination: The ash from the sintering machine head is washed with water to remove soluble potassium and sodium salts, resulting in desalination residue. S2. Chloride leaching: Add the desalted residue obtained in step S1 to a sodium chloride solution and leach with stirring at 60℃-90℃ for 2-4 hours, maintaining a liquid-to-solid ratio of 3:1-5:1, so that silver is leached as [AgCl2]. - The chloride complex was transferred into the leachate to obtain a silver-containing leachate; S3, ORP online monitoring: The silver-containing leaching solution was transferred into the reaction vessel, and the ORP online monitoring electrode was inserted to continuously collect the redox potential change curve E(t) over time. S4. ORP Dynamic Feature Identification and Response Stage Judgment: The first derivative dE / dt of the ORP curve collected in step S3 is calculated in real time, and the response stage is identified based on the magnitude and sign change of dE / dt; the response stage includes: when |dE / dt|≥ the first threshold, it is a rapid response stage; When the second threshold <|dE / dt| < the first threshold, it is a transition phase; When |dE / dt|≤ the second threshold and E(t) reaches an inflection point, it is the reaction endpoint stage; The first threshold is 50-200mV / min, and the second threshold is 5-30mV / min; S5. Zinc powder staged addition control: The zinc powder addition strategy is dynamically controlled according to the reaction stage identified in step S4. In the rapid reaction stage, a large batch of rapid addition is used; in the transition stage, a medium batch of addition is used; and in the reaction endpoint stage, zinc powder addition is stopped. S6. Solid-liquid separation: The mixture after displacement is subjected to solid-liquid separation to obtain silver powder product and silver-poor post-liquid.

[0012] Preferably, in step S2, the concentration of the sodium chloride solution is 200-350 g / L, and the leaching temperature is 70-90℃; after leaching, the silver leaching rate of the desalination residue with a silver content of 50-500 g / t reaches more than 85%.

[0013] Preferably, in step S3, the ORP online monitoring acquires redox potential signals in real time through the ORP electrode at sampling intervals of 1-10 seconds, transmits the acquired potential signals to the data processing unit, and the data processing unit performs real-time calculations on the potential signals, including the calculation of the first derivative dE / dt and the second derivative d²E / dt², and determines the reaction stage based on the calculation results.

[0014] Preferably, in step S4, the first derivative dE / dt is calculated as follows: dE / dt=(E n -E n-k ) / (k·Δt), Among them, E n E is the ORP value of the nth sampling point. n-k Δt is the ORP value of the kth sampling point, Δt is the sampling interval, and k is the width of the smoothing window, which ranges from 3 to 10.

[0015] Preferably, in step S4, the method for identifying the ORP inflection point is as follows: Calculate the first derivative dE / dt and the second derivative d²E / dt² of the ORP curve. When the sign of d²E / dt² changes from negative to positive, and |dE / dt| is not greater than the second threshold for N consecutive sampling points, the ORP curve is determined to have an inflection point. The time corresponding to the inflection point is the reaction endpoint time.

[0016] Preferably, in step S5, the zinc powder staged addition control strategy is as follows: (a) Rapid reaction stage: |dE / dt|≥ the first threshold. At this time, the concentration of silver ions is high and the driving force of the reaction is large. Add 15%-25% of the theoretical zinc powder consumption in batches, with an addition interval of 2-5 minutes. (b) Transition stage: The second threshold <|dE / dt| < the first threshold. At this time, the silver ion concentration is moderate. Add 8% to 15% of the theoretical zinc powder consumption in one batch, with an addition interval of 5 to 8 minutes. (c) Reaction endpoint stage: |dE / dt|≤ the second threshold and the ORP inflection point is detected, stop adding zinc powder, continue stirring for 3-10 minutes and then perform solid-liquid separation.

[0017] Preferably, in step S5, the theoretical zinc powder consumption is calculated according to the following formula: m_Zn(theory)=(C_Ag×V×M_Zn) / (2×M_Ag), Wherein, C_Ag is the silver concentration in the silver-containing leachate (mg / L), V is the volume of the leachate (L), M_Zn is the molar mass of zinc (65.38 g / mol), and M_Ag is the molar mass of silver (107.87 g / mol); The actual total amount of zinc powder added is controlled at 50%-70% of the theoretical consumption.

[0018] Preferably, in step S6, the silver-depleted liquid is returned to step S2 as a chloride leaching solution for recycling, and sodium chloride is added during the recycling process to maintain the concentration at 200-350 g / L; or the silver-depleted liquid is evaporated and crystallized to recover potassium chloride and sodium chloride.

[0019] Compared with the prior art, the present invention has the following technical effects: 1. This invention introduces ORP dynamic feature recognition into the control of the zinc powder displacement silver precipitation process in a chloride salt system. By real-time acquisition of the ORP change curve over time, calculation of the first derivative dE / dt, and identification of the ORP inflection point, real-time quantitative judgment of the displacement reaction process is achieved. The response time is shortened from 1-2 hours in traditional ICP-OES analysis to less than 10 seconds, realizing real-time process control. This differs from all existing technologies using fixed thresholds or empirical judgment methods.

[0020] 2. This invention employs a staged zinc powder dosing control strategy based on reaction kinetics to improve zinc powder utilization and crude silver grade. The reaction process is divided into three stages—rapid reaction, transition, and endpoint—based on the ORP change rate (|dE / dt|), with different zinc powder dosages and dosing intervals used in each stage. This strategy reduces actual zinc powder consumption to 50%-65% of the theoretical amount while increasing the crude silver grade to over 90%.

[0021] 3. The synergistic effect of the chloride leaching system and ORP dynamic control in this invention. In the chloride system, Ag is expressed as [AgCl2]- It exists in the form of Zn, with a standard reduction potential of approximately +0.225 V (vs SHE). 2+ / Zn is -0.763 V (vs SHE), and the potential difference between the two is 0.988 V. A large potential difference means that the ORP signal changes more significantly, the first derivative characteristics are more prominent, and the signal foundation is excellent.

[0022] 4. The establishment of the ORP curve feature library in this invention provides a data foundation for process optimization and quality control. By continuously collecting ORP change curves over time, an ORP feature curve library can be established under different silver contents and different chloride ion concentrations. This library can be used for process parameter optimization, abnormal operating condition diagnosis, and batch-to-batch consistency control, supporting process digitization.

[0023] 5. The post-silver depletion solution of this invention is recyclable, resulting in significant environmental benefits. The post-silver depletion solution after replacement is rich in Zn. 2+ and Cl - It can be directly returned to the leaching process for recycling, realizing a closed-loop circulation of chloride ions and water, reducing the consumption of fresh sodium chloride by 30%-50%, and reducing wastewater discharge by more than 80%. Attached Figure Description

[0024] Figure 1 This is a flow chart of the silver extraction process from sintering machine head ash in this invention.

[0025] Figure 2 This is a schematic diagram showing the ORP change curve over time and the division of reaction stages in this invention.

[0026] Figure 3 This is a schematic diagram illustrating the characteristics of |dE / dt| at each reaction stage in this invention. Detailed Implementation

[0027] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] like Figure 1 As shown, the core technical idea of ​​this invention is as follows: continuously collect E(t) curves through online monitoring of ORP → calculate the first derivative dE / dt in real time → identify the reaction stage based on the magnitude of |dE / dt| and the sign change of d²E / dt² → implement different zinc powder addition strategies according to the stage → accurately stop addition at the ORP inflection point to achieve dynamic judgment of the endpoint.

[0029] Example 1: ORP dynamic feature recognition control of zinc powder displacement silver immersion (1) Water washing and desalination. Take 5 kg of sintering machine head ash raw material, add 15 L of deionized water, stir and wash at 60℃ for 30 minutes, and separate the solid and liquid. The filter cake is the desalination residue. After water washing, the KCl and NaCl content in the desalination residue is reduced to below 1%.

[0030] (2) Chloride leaching. The desalted residue was added to a 300 g / L sodium chloride solution at a liquid-to-solid ratio of 3:1 and leached by stirring in an 80°C constant temperature water bath for 3 hours. After leaching, the solution was filtered to obtain 15 L of silver-containing leachate. ICP-OES analysis showed that the silver concentration in the leachate was 83.8 mg / L, and the silver leaching rate was 89.8%.

[0031] (3) Online monitoring of ORP. The silver-containing leaching solution was transferred to a 20 L glass reactor, and stirring was started (300 rpm). The ORP monitoring electrode was inserted, and the initial ORP value of +185 mV was recorded after the reading stabilized. The sampling interval was set to 5 seconds, and the curve of ORP change over time E(t) was continuously collected.

[0032] (4) Staged zinc powder addition and ORP dynamic characteristic identification. The theoretical zinc powder consumption was calculated to be 381 mg based on the silver content in the leachate. Zinc powder (100 mesh) was added in stages according to the following strategy: ① Rapid reaction phase: When |dE / dt|≥100 mV / min, add the first batch of zinc powder at 20% of the theoretical amount (76mg); after 5 minutes, if |dE / dt| is still ≥100 mV / min, add the second batch (76mg). ② Transition phase: When |dE / dt| drops below 100 mV / min and >15 mV / min, add 12% (46 mg) of the theoretical amount, and extend the dosing interval to 6 minutes; ③ Reaction endpoint determination: When |dE / dt| at 5 consecutive sampling points is less than 15mV / min, and d²E / dt² changes from negative to positive (the ORP curve shows an inflection point), and the ORP value drops to -18mV, the reaction endpoint is determined to have been reached, and the addition of zinc powder is stopped.

[0033] The actual cumulative zinc powder dosage was 229 mg, which is 60.1% of the theoretical amount. The total time from the first batch of zinc powder to the determination of the endpoint was approximately 28 minutes.

[0034] (5) Solid-liquid separation. The reaction mixture was vacuum filtered, and the filter cake was washed three times with deionized water and dried at 80°C to obtain 1.353 g of silver powder. ICP-OES analysis showed that the silver powder grade was 92.3%. The silver concentration in the filtrate (silver-poor liquid) was 0.59 mg / L, and the silver replacement recovery rate was 99.3%.

[0035] Comparative Example 1: The traditional fixed zinc powder addition process was exactly the same as Example 1, except for the zinc powder addition method.

[0036] Zinc powder was added in a single dose, 1.5 times the theoretical zinc powder consumption (572 mg), and the mixture was filtered after reacting for 60 minutes. 1.705 g of silver powder was obtained, and ICP-OES analysis showed a silver powder purity of 73.6%. The silver concentration in the liquid after silver depletion was 0.17 mg / L, and the silver replacement recovery rate was 99.8%.

[0037]

[0038] As shown in the table, compared with the traditional process, the present invention reduces the amount of zinc powder used by 59.9% and increases the crude silver grade by 18.7 percentage points. Although the silver recovery rate of Comparative Example 1 is slightly higher by 0.5 percentage points, it is less economical at the cost of consuming 149% more zinc powder and reducing the crude silver grade.

[0039] Example 2: ORP dynamic feature recognition effect of raw materials with different silver contents This embodiment examines sintering machine head ash raw materials with silver contents of 50 g / t, 150 g / t, 280 g / t, and 500 g / t. Following the process conditions of Example 1, water washing and desalination, chloride leaching, and ORP dynamic characteristic identification to control zinc powder replacement were performed. The results show that for sintering machine head ash raw materials with silver contents ranging from 50 to 500 g / t, the method of this invention can accurately identify the ORP inflection point and determine the reaction endpoint. The actual zinc powder dosage remained stable between 59% and 63% of the theoretical amount, and the crude silver grade was consistently above 90%.

[0040] Example 3: Quantitative Verification of ORP Curve Features and First Derivative Identification This embodiment performs a detailed dynamic feature analysis on the ORP change curve over time in Embodiment 1 to verify the reliability of the first derivative identification and inflection point criterion.

[0041] (1) ORP curve acquisition: The sampling interval is 5 seconds, and a total of 336 data points are collected during the entire replacement process (28 minutes × 60 seconds / 5 seconds = 336 points).

[0042] (2) First derivative calculation: Using a smooth window of k=5 and Δt=5 seconds, calculate the dE / dt value at each point.

[0043] (3) Results of reaction stage division: ①0-8 minutes: |dE / dt|=120-280mV / min, which is determined to be the rapid response phase. During this phase, ORP drops rapidly from +185 mV to +20mV. ②8-22 minutes: |dE / dt|=15-80mV / min, which is judged as the transition phase, and ORP slowly decreases from +20 mV to -10 mV; ③ 22-28 minutes: |dE / dt| < 15 mV / min, and d²E / dt² changes from negative to positive at the 26th minute (the ORP curve changes from a steep drop to a flattening, showing an inflection point), which is determined to be the end stage of the reaction.

[0044] (4) Verification of inflection point criteria: Based on the ICP-OES hourly sampling analysis (the reaction endpoint is when the silver ion concentration drops to 0.8 mg / L, corresponding to the 27.5th minute), the ORP inflection point identification endpoint of this invention is the 26th minute, with an error of only 1.5 minutes and a relative error of 5.5%, proving that the identification of ORP dynamic features is accurate and feasible.

[0045] (5) Compared with the traditional fixed threshold method: If a fixed ORP threshold of -16mV is used as the endpoint criterion, the fixed threshold method will show obvious deviation when the silver content of the raw material changes (e.g., the endpoint ORP is about -25mV when it is 500 g / t). However, the dynamic identification method based on the ORP change rate of the present invention does not depend on a fixed absolute ORP threshold, and has adaptability to raw materials with different silver contents, which is better than the fixed threshold method.

[0046] like Figure 2 As shown, the curve illustrates the change in ORP value over time during the zinc-silver substitution reaction. The horizontal axis represents reaction time (minutes), and the vertical axis represents ORP value (mV). The graph indicates three reaction stages: the rapid reaction stage (0-8 min), where ORP rapidly decreases from +185 mV to +20 mV; the transition stage (8-22 min), where ORP slowly decreases from +20 mV to -10 mV; and the final reaction stage (22-28 min), where ORP levels off and reaches an inflection point (d²E / dt²=0), with the final ORP value being approximately -16 mV.

[0047] Figure 3 The characteristics of |dE / dt| (absolute value of the rate of change of ORP) at each reaction stage are shown. During the rapid reaction stage, |dE / dt| ≥ 100 mV / min; during the transition stage, 15 mV / min < |dE / dt| < 100 mV / min; and during the final reaction stage, |dE / dt| < 15 mV / min. The dashed lines in the figure indicate the first threshold (100 mV / min) and the second threshold (15 mV / min).

[0048] Example 4: Recycling of Silver-Depleted Fluid The silver-depleted solution (containing Zn) obtained in Example 1 2+ Approximately 15.3 g / L, Cl - Approximately 295g / L, Ag +After adding sodium chloride (0.59 mg / L) to a concentration of 300 g / L, the solution was recycled as a leachate. The same batch of sintering machine head ash (silver content 280 g / t) was used for leaching and ORP dynamic characteristic identification control replacement according to the process conditions of Example 1. This was repeated for 5 cycles. The results showed that the process parameters remained stable across the 5 cycles, with the silver leaching rate and crude silver grade fluctuating within 1.5 percentage points. ORP dynamic characteristic identification effectively determined the reaction endpoint in each cycle.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A control system for extracting gray silver from a sintering die head based on ORP dynamic feature recognition, characterized in that: include, A reaction vessel used to hold silver-containing leaching solution; An ORP online monitoring electrode is inserted into the reaction vessel to collect redox potential signals in real time. The data processing unit, connected to the ORP online monitoring electrode, is used to receive potential signals and calculate the first derivative dE / dt and the second derivative d²E / dt², and to identify the reaction stage based on the magnitude and sign change of dE / dt. A zinc powder dosing device is connected to the data processing unit and adds zinc powder to the reactor according to a segmented dosing strategy based on instructions issued by the data processing unit.

2. The sintering head gray silver extraction control system based on ORP dynamic feature recognition according to claim 1, characterized in that: The data processing unit is preset with a first threshold and a second threshold, which are used to determine the relative magnitude of |dE / dt| with the threshold.

3. The method for controlling the extraction of gray silver from the sintering machine head based on ORP dynamic feature recognition as described in claim 2, characterized in that: Includes the following steps: S1. Water washing and desalination: The ash from the sintering machine head is washed with water to remove soluble potassium and sodium salts, resulting in desalination residue. S2. Chloride leaching: Add the desalted residue obtained in step S1 to a sodium chloride solution and leach with stirring at 60℃-90℃ for 2-4 hours, maintaining a liquid-to-solid ratio of 3:1-5:1, so that silver is leached as [AgCl2]. - The chloride complex was transferred into the leachate to obtain a silver-containing leachate; S3, ORP online monitoring: The silver-containing leaching solution was transferred into the reaction vessel, and the ORP online monitoring electrode was inserted to continuously collect the redox potential change curve E(t) over time. S4. ORP Dynamic Feature Identification and Response Stage Judgment: The first derivative dE / dt of the ORP curve collected in step S3 is calculated in real time, and the response stage is identified based on the magnitude and sign change of dE / dt; the response stage includes: when |dE / dt|≥ the first threshold, it is a rapid response stage; When the second threshold <|dE / dt| < the first threshold, it is a transition phase; When |dE / dt|≤ the second threshold and E(t) reaches an inflection point, it is the reaction endpoint stage; S5. Zinc powder staged addition control: The zinc powder addition strategy is dynamically controlled according to the reaction stage identified in step S4. In the rapid reaction stage, a large batch of rapid addition is used; in the transition stage, a medium batch of addition is used; and in the reaction endpoint stage, zinc powder addition is stopped. S6. Solid-liquid separation: The mixture after displacement is subjected to solid-liquid separation to obtain silver powder product and silver-poor post-liquid.

4. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S2, the concentration of the sodium chloride solution is 200-350 g / L, and the leaching temperature is 70-90℃; after leaching, the silver leaching rate of the desalination residue with a silver content of 50-500 g / t reaches more than 85%.

5. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S3, the ORP online monitoring acquires redox potential signals in real time through the ORP electrode at sampling intervals of 1-10 seconds, and transmits the acquired potential signals to the data processing unit. The data processing unit performs real-time calculations on the potential signals, including the calculation of the first derivative dE / dt and the second derivative d²E / dt², and determines the reaction stage based on the calculation results.

6. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S4, the first derivative dE / dt is calculated as follows: dE / dt=(E n -HAVE BEEN n-k ) / (k·Δt), Among them, E n E is the ORP value of the nth sampling point. n-k Δt is the ORP value of the kth sampling point, Δt is the sampling interval, and k is the width of the smoothing window, which ranges from 3 to 10.

7. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S4, the method for identifying the ORP inflection point is as follows: Calculate the first derivative dE / dt and the second derivative d²E / dt² of the ORP curve. When the sign of d²E / dt² changes from negative to positive, and |dE / dt| is not greater than the second threshold for N consecutive sampling points, the ORP curve is determined to have an inflection point. The time corresponding to the inflection point is the reaction endpoint time.

8. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S5, the zinc powder staged addition control strategy is specifically as follows: (a) Rapid reaction stage: |dE / dt|≥ the first threshold. At this time, the concentration of silver ions is high and the driving force of the reaction is large. Add 15%-25% of the theoretical zinc powder consumption in batches, with an addition interval of 2-5 minutes. (b) Transition stage: The second threshold <|dE / dt| < the first threshold. At this time, the silver ion concentration is moderate. Add 8%-15% of the theoretical zinc powder consumption in batches, with an addition interval of 5-8 minutes. (c) Reaction endpoint stage: |dE / dt|≤ the second threshold and the ORP inflection point is detected, stop adding zinc powder, continue stirring for 3~10 minutes and then perform solid-liquid separation.

9. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 8, characterized in that: In step S5, the theoretical zinc powder consumption is calculated according to the following formula: m_Zn(theory)=(C_Ag×V×M_Zn) / (2×M_Ag), Wherein, C_Ag is the silver concentration in the silver-containing leachate (mg / L), V is the volume of the leachate (L), M_Zn is the molar mass of zinc (65.38 g / mol), and M_Ag is the molar mass of silver (107.87 g / mol); The actual total amount of zinc powder added is controlled at 50%-70% of the theoretical consumption.

10. The method for controlling the extraction of gray silver from sintering machine heads based on ORP dynamic feature recognition according to claim 3, characterized in that: In step S6, the silver-depleted liquid is returned to step S2 as a chloride leaching solution for recycling. During the recycling process, sodium chloride is added to maintain the concentration at 200-350 g / L; or the silver-depleted liquid is evaporated and crystallized to recover potassium chloride and sodium chloride.

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