A zinc oxide fume treatment control system and method

Abstract

The present application relates to the field of non-ferrous smelting solid waste resource utilization and pollution control technology, and specifically discloses a zinc oxide fume treatment control system and method. The system comprises a raw material slurry module, a first-stage leaching alkali control module, a second-stage leaching temperature control module and a calcification arsenic precipitation control module. In the first-stage leaching process, the efficient arsenic leaching balance point is dynamically captured according to the arsenic and zinc leaching rate variation curve with pH, and the leaching agent addition amount is accurately controlled; in the second-stage leaching, the heating temperature is real-time regulated according to the dissolved zinc rate; before the calcification arsenic precipitation, oxidation treatment is carried out, the oxidation-reduction potential is controlled based on the trivalent arsenic oxidation efficiency, and the lime milk addition amount is dynamically adjusted according to the arsenic concentration and zinc content in the precipitate during the arsenic precipitation process. The present application realizes efficient selective leaching and stable solidification of arsenic, effectively inhibits the loss of zinc, and has the advantages of high separation efficiency, high resource recovery rate and the like.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and pollution control technology in non-ferrous metal smelting, and specifically to a zinc oxide fume treatment control system and method. Background Technology

[0002] With the rapid development of the non-ferrous metal smelting industry, zinc oxide dust, as an important secondary resource generated during the smelting process, contains various valuable metal elements such as zinc, lead, indium, and silver, as well as toxic and harmful elements such as arsenic. The presence of arsenic not only seriously affects the recovery efficiency of valuable metals but also causes environmental pollution and threatens human health. Its safe disposal has become one of the key issues restricting the green and high-quality development of the lead and zinc smelting industry.

[0003] Currently, leaching-precipitation processes are commonly used to remove arsenic from zinc oxide flue gas. However, arsenic in zinc oxide from Osmelt furnaces mainly exists in a stable form. Arsenic exists in a certain form, making it difficult for traditional leaching processes to efficiently and selectively leach it. This results in problems such as low separation efficiency of arsenic from valuable metals, high consumption of leaching agents, high zinc content in the residue, and unstable solidification of arsenic.

[0004] The two-stage countercurrent alkaline leaching-lime precipitation process can selectively leach arsenic and separate zinc from arsenic. However, it lacks precise control methods for key parameters, such as the alkalinity at the end of the first-stage leaching, the temperature of the second-stage leaching, and the amount of lime slurry added for arsenic precipitation. This results in poor separation of zinc and arsenic, leading to resource waste and the risk of secondary pollution. There is an urgent need to develop a zinc oxide fume treatment system and method that can achieve precise control, efficient separation, and green, low-consumption operation. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a zinc oxide fume treatment control system and method, aiming to achieve efficient separation and solidification of arsenic and recycling of valuable metals.

[0006] The technical solution adopted by the present invention to solve its technical problem is as follows: The present invention provides a zinc oxide fume treatment and control system, including: a raw material slurry module: mixing zinc oxide fume with process water to obtain zinc oxide slurry.

[0007] The first-stage leaching alkali control module: A leaching agent is added to the zinc oxide slurry to carry out a first-stage leaching reaction. Based on the arsenic and zinc leaching rate change curves with pH in the reaction mixture, the equilibrium point for efficient arsenic leaching and inhibition of zinc dissolution is captured. The endpoint alkalinity is determined based on the equilibrium point and the amount of leaching agent added is controlled. After the first-stage leaching reaction is completed, solid-liquid separation is carried out to obtain a first-stage leaching residue and a first-stage leaching solution.

[0008] The two-stage leaching temperature control module uses a high-alkali new solution to carry out a secondary leaching reaction on the primary leaching residue. The heating temperature is adjusted in real time according to the rate of zinc dissolution in the mixed solution during the secondary leaching process.

[0009] Calcification and Arsenic Precipitation Control Module: Before arsenic precipitation, a section of the leachate is oxidized. The oxidation-reduction potential is controlled according to the oxidation efficiency of trivalent arsenic. After oxidation, lime milk is added to carry out the calcification and arsenic precipitation reaction. The amount of lime milk added is dynamically adjusted based on the changes in arsenic concentration in the reaction mixture and the changes in zinc content in the precipitate.

[0010] The present invention provides a method for controlling zinc oxide dust treatment, comprising the following steps: S1: mixing zinc oxide dust with process water to obtain zinc oxide slurry.

[0011] S2: Add leaching agent to zinc oxide slurry to carry out a first-stage leaching reaction. According to the arsenic and zinc leaching rate change curves with pH in the reaction mixture, capture the equilibrium point for efficient arsenic leaching and inhibit zinc dissolution. Based on the equilibrium point, determine the endpoint alkalinity and control the amount of leaching agent added. After the first-stage leaching reaction is completed, perform solid-liquid separation to obtain a first-stage leaching residue and a first-stage leaching solution.

[0012] S3: A high-alkali new solution is used to carry out a secondary leaching reaction on the first-stage leaching residue. The heating temperature is adjusted in real time according to the rate of zinc dissolution in the mixed solution during the secondary leaching process.

[0013] S4: Before arsenic precipitation, a section of the leachate is oxidized. The oxidation-reduction potential is controlled according to the oxidation efficiency of trivalent arsenic. After oxidation, lime milk is added to carry out the calcification and arsenic precipitation reaction. The amount of lime milk added is dynamically adjusted based on the changes in arsenic concentration in the reaction mixture and the changes in zinc content in the precipitate.

[0014] Compared with the prior art, the zinc oxide fume treatment control system and method of the present invention have the following beneficial effects: 1. The present invention monitors the arsenic and zinc leaching rate curves with pH changes in real time during a leaching process, dynamically captures the equilibrium point of efficient arsenic leaching and inhibits zinc dissolution, and thus accurately controls the endpoint alkalinity, significantly improving the arsenic leaching efficiency and reducing zinc loss.

[0015] 2. This invention uses real-time control of the two-stage leaching temperature based on the zinc dissolution rate to keep the reaction process in the optimal temperature range, thereby improving the zinc recovery rate and reducing energy consumption.

[0016] 3. This invention precisely controls the oxidation-reduction potential based on the oxidation efficiency of trivalent arsenic during the pre-precipitation oxidation process, thereby ensuring that arsenic can be completely removed in a more stable and easier-to-precipitate pentavalent form.

[0017] 4. This invention combines the dual detection of arsenic concentration and zinc content in the precipitate to dynamically adjust the amount of lime milk added to the calcified arsenic precipitation, thereby ensuring efficient arsenic precipitation while minimizing zinc entrainment loss. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a system module connection diagram of the present invention.

[0020] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0021] Figure 3 This is a flow chart of the two-stage countercurrent alkaline leaching-lime precipitation arsenic process of the present invention. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a zinc oxide fume treatment control system and method proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] The specific solution of the zinc oxide fume treatment control system and method provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Please see Figure 1 and Figure 3 The present invention illustrates a zinc oxide fume treatment control system provided in one embodiment of the present invention, including a raw material pulping module, a first-stage leaching alkali control module, a second-stage leaching temperature control module, and a calcification arsenic precipitation control module.

[0026] The raw material pulping module is connected to a first-stage leaching alkali control module, which is connected to a second-stage leaching temperature control module and a calcification arsenic precipitation control module.

[0027] The raw material slurry module is used to mix zinc oxide dust with process water to produce zinc oxide slurry.

[0028] In one embodiment of the present invention, zinc oxide dust is a product of the pyrometallurgical process. Its physical form is an extremely fine powder, but its chemical composition may be uneven; for example, the distribution of elements such as arsenic and zinc may exhibit segregation. Directly feeding it into the leaching reactor would lead to material loss and environmental pollution, and could also easily cause incomplete reactions due to material agglomeration. However, by slurrying, the solid powder is pre-mixed with process water to form a homogeneous slurry, ensuring that the material subsequently entering the leaching module is a fluid with uniform composition and concentration.

[0029] Considering that lower alkalinity can preferentially promote the dissolution of arsenic oxides while inhibiting the dissolution of zinc oxide, a sensitive control window is created for subsequent precise alkalinity control by capturing the equilibrium point of efficient arsenic leaching and inhibiting zinc dissolution. Meanwhile, room temperature operation can reduce unnecessary energy consumption while satisfying material homogenization, thus balancing separation efficiency and economy.

[0030] Based on this, in a preferred embodiment of the present invention, the specific process of preparing zinc oxide slurry includes: adding metered zinc oxide dust into a slurry tank at room temperature, adding a corresponding amount of process water, and starting the stirring device for stirring.

[0031] During the stirring process, dilute alkali solution is added dropwise to the slurry tank, and the pH value of the slurry is monitored in real time. When the pH value is within the preset low alkalinity range for slurrying, the addition of dilute alkali solution is stopped, and stirring is continued for a set time to obtain zinc oxide slurry.

[0032] It should be noted that the preset low alkalinity range for pulping is pH 8-10. Pulping of zinc oxide dust is controlled at room temperature and relatively low alkalinity to promote the release of volatile organic compounds (VOCs) from the zinc oxide dust. Dissolve.

[0033] In one embodiment of the present invention, after stopping the addition of dilute alkali solution, stirring is continued and maintained for 15-30 minutes to ensure the homogenization of the slurry and the completion of the initial reaction.

[0034] After a uniform zinc oxide slurry is obtained, it is pumped to a reactor for a first-stage countercurrent leaching reaction.

[0035] The first-stage leaching alkali control module is used to add leaching agent to zinc oxide slurry for a first-stage leaching reaction. Based on the arsenic and zinc leaching rate change curves with pH in the reaction mixture, the equilibrium point for efficient arsenic leaching and inhibition of zinc dissolution is captured. The endpoint alkalinity is determined based on the equilibrium point and the amount of leaching agent added is controlled. After the first-stage leaching reaction is completed, solid-liquid separation is performed to obtain a first-stage leaching residue and a first-stage leaching solution.

[0036] The goal of a primary countercurrent leaching reaction is to allow as much arsenic as possible to enter the solution while minimizing zinc dissolution. If the alkalinity (pH) is too low, the arsenic leaching rate will decrease, resulting in a large amount of arsenic remaining in the residue, which cannot be effectively removed subsequently. If the alkalinity (pH) is too high, zinc will dissolve in large quantities as zincates, leading to the loss of the target metallic zinc and increasing the burden on subsequent solution treatments. Furthermore, the primary countercurrent leaching process is crucial, and the quality of its product directly affects the operation of the subsequent two processes. Therefore, it is necessary to control the endpoint alkalinity of the primary countercurrent leaching reaction.

[0037] Considering that arsenic and zinc are amphoteric metals, their leaching rates exhibit a key overlapping and divergent range with respect to pH: in the lower pH range, arsenic leaching rate increases rapidly with increasing alkalinity, while zinc leaching rate remains at a low level; however, once the pH exceeds a certain critical value, zinc dissolution accelerates dramatically, while the increase in arsenic leaching rate plateaus. Therefore, by tracking this curve in real time, the optimal process equilibrium point can be precisely identified where arsenic leaching rate approaches its peak while zinc leaching rate has not yet significantly increased. By controlling the endpoint alkalinity at this point, the selectivity of arsenic-zinc separation can be maximized.

[0038] Based on this, in a preferred embodiment of the present invention, the specific process of controlling the amount of leaching agent added includes: D1: extracting the reference range of the endpoint alkalinity under the current countercurrent leaching conditions from the database, and using the lower limit of the reference range as the reference endpoint alkalinity.

[0039] In one embodiment of the present invention, reference ranges for other reaction parameters under the current countercurrent leaching conditions, such as reaction temperature and reaction time, are extracted from the database, and the other reaction parameters are controlled within their respective reference ranges.

[0040] D2: Calculate the total amount of leaching agent added based on the reference endpoint alkalinity.

[0041] Considering that the total amount of alkali required to meet the reference endpoint alkalinity is subtracted from the amount of alkali carried in by the zinc oxide slurry itself, the difference represents the amount of alkali that needs to be replenished by the leaching agent. Therefore, the specific process for calculating the total amount of leaching agent to be added includes: calculating the required total amount of alkali based on the total volume of the slurry and the reference endpoint alkalinity, obtaining the amount of alkali carried in by the slurry, subtracting the amount of alkali carried in by the slurry from the required total amount of alkali to obtain the amount of alkali that needs to be replenished by the leaching agent, and then calculating the total amount of leaching agent to be added based on the alkali concentration of the leaching agent.

[0042] As an example, assume the zinc oxide slurry processing volume is 100 kg, the liquid-to-solid ratio is 3:1, the liquid phase alkali concentration is 10 g / L, the leaching agent alkali concentration is 80 g / L, and the reference endpoint alkalinity is 25 g / L. The specific process for calculating the total amount of leaching agent added is as follows: Based on the zinc oxide slurry processing volume and liquid-to-solid ratio, the initial liquid volume of the slurry is calculated to be 75 kg, and the amount of alkali introduced by the slurry = 75 L × 10 g / L = 750 g.

[0043] To simplify calculations, it is assumed that the liquid volume changes little before and after the reaction, and the total volume of the slurry is approximately equal to the initial liquid volume plus the leaching agent volume. The total volume of the slurry is assumed to be... The volume of the leaching agent is , (Equation 1); Total alkali required = The amount of alkali that needs to be added by the leaching agent = The volume of the leaching agent is (Equation 2); Solving the system of equations 1 and 2 simultaneously yields the following results. That is, approximately 96L of leaching agent with a concentration of 80g / L needs to be added.

[0044] In one embodiment of the present invention, the leachate from the two-stage countercurrent leaching is used as the leaching agent for the first-stage countercurrent leaching.

[0045] D3: Based on the total amount of leachate added, divide it into a one-time initial addition and a subsequent multiple addition according to preset rules, determine the proportion of each in the total addition, and set the number of subsequent multiple additions and the amount of each addition.

[0046] In one embodiment of the present invention, the amount of each distribution in the subsequent distribution can be the same or different.

[0047] Considering the time required for the leaching agent to react with the zinc oxide slurry, if the reaction is incomplete when measuring the arsenic leaching rate, zinc leaching rate, and pH value in the reaction mixture, significant errors will occur in the test results. This will cause the equilibrium point for efficient arsenic leaching and inhibition of zinc dissolution, captured based on the test data, to lag behind the actual equilibrium point, at which point a large amount of zinc may have already dissolved. Therefore, it is necessary to initially estimate the time required for the added leaching agent to react completely, and then perform testing after the reaction is complete to improve the accuracy and reliability of the test data.

[0048] D4. Extract historical leaching reaction data from the database, obtain the reaction completion time corresponding to different leaching agent addition amounts, and determine the reaction completion time corresponding to the initial one-time addition and the subsequent multiple additions.

[0049] D5: After the initial addition of the solution and complete reaction, test and record the arsenic and zinc leaching rates and pH value of the reaction mixture at this point as the initial monitoring data.

[0050] D6: The first addition of the product is carried out in the later stage. After the reaction is complete, the arsenic and zinc leaching rates and pH value of the reaction mixture are detected and recorded to obtain the first set of monitoring data.

[0051] D7: Based on the initial monitoring data and the first set of monitoring data, plot the arsenic and zinc leaching rates as a function of pH, and capture the equilibrium point for efficient arsenic leaching and inhibition of zinc dissolution based on the aforementioned curves.

[0052] If capture is successful, the pH value of the reaction mixture at the equilibrium point will be recorded as the actual endpoint alkalinity, and the addition of leaching agent will be stopped.

[0053] If capture fails, proceed to step D8.

[0054] It should be noted that a coordinate system was established with pH value on the x-axis and arsenic and zinc leaching rates on the y-axis, respectively, and the curves of arsenic and zinc leaching rates as a function of pH were plotted.

[0055] In a preferred embodiment of the present invention, considering that the equilibrium point of efficient arsenic leaching and inhibition of zinc dissolution is characterized on the arsenic and zinc leaching rate as a function of pH, when the pH exceeds a certain critical value, the dissolution of zinc will accelerate sharply, while the increase in arsenic leaching rate will tend to level off.

[0056] Based on this, the specific process of capturing the equilibrium point of efficient arsenic leaching and inhibiting zinc dissolution is as follows: obtain the tangent slope at the last data point on the curve of arsenic leaching rate versus pH. If the tangent slope is within the preset range of tangent slope corresponding to a gradual increase, then the last data point is determined as the high plateau point of arsenic leaching.

[0057] The increment of the zinc leaching rate at the last data point on the zinc leaching rate versus pH curve is calculated relative to the zinc leaching rate at its adjacent previous data point. If the increment reaches a preset leaching rate increment threshold or the zinc leaching rate at the last data point reaches a preset zinc leaching rate warning value, then the last data point is determined to be the zinc leaching spike point.

[0058] If the arsenic leaching rate curve changes with pH and shows a high plateau point, or the zinc leaching rate curve changes with pH and shows a sudden increase point, then the equilibrium point is determined to have been captured; otherwise, the equilibrium point is determined not to have been captured.

[0059] As an example, suppose we are currently conducting a second round of post-treatment, and the second set of monitoring data obtained after the reaction is complete, along with the previously monitored data, are shown in Table 1. The preset judgment thresholds are: the tangent slope range corresponding to slow growth is [-0.5, 0.5]% / pH (i.e., the slope is close to zero, indicating that growth has become very slow or reached a plateau); the zinc leaching rate increment threshold is 5% (i.e., the zinc leaching rate at the current point suddenly increases by more than 5 percentage points compared to the previous point); the zinc leaching rate warning value is 15% (i.e., a warning is triggered when the zinc leaching rate reaches 15%).

[0060] Table 1. Cumulative monitoring data sequence after the second deployment

[0061]

[0062] The specific process of capturing the equilibrium point of efficient arsenic leaching and inhibiting zinc dissolution is as follows: (1) Determine whether the arsenic leaching rate has a high plateau point: Obtain the last data point, i.e., data point 2 (pH=11.5, arsenic leaching rate=92%). Based on data point 1 and data point 2, calculate the tangent slope at data point 2 as approximately (92%-90%) / (11.5-11.0)=4% / pH. Since the calculated slope 4% / pH is not within the preset growth range [-0.5, 0.5], data point 2 is not determined to be a high plateau point of arsenic leaching.

[0063] (2) Determine whether the zinc leaching rate has a sudden increase: Obtain the last data point, i.e., data point 2 (pH=11.5, zinc leaching rate=4%); calculate the zinc leaching rate increment of data point 2 relative to data point 1 as 4%-3%=1%. Since the zinc leaching rate increment of 1%<5% (preset threshold) has not reached the increment threshold, and the zinc leaching rate of 4%<15% (preset warning value) has not reached the warning value, therefore, data point 2 is not determined to be a sudden increase point in zinc leaching.

[0064] (3) Comprehensive judgment on whether the equilibrium point has been captured: Since neither the high plateau point of arsenic leaching nor the sudden rise point of zinc leaching has appeared, it is finally determined that the equilibrium point has not been captured, and the next leaching agent addition and monitoring will continue.

[0065] It should be noted that this invention sets the criterion for capturing the equilibrium point of efficient arsenic leaching and inhibiting zinc dissolution based on the process principles of maximizing benefits and controlling risks. The appearance of a high plateau point in arsenic leaching means that further increasing alkalinity has a negligible effect on improving arsenic leaching, and the cost-effectiveness of adding more leaching agent is extremely low. On the other hand, the appearance of a sharp rise point in zinc leaching is a clear danger signal, indicating that the protective window for inhibiting zinc dissolution is about to end or has already ended. Continuing to add alkali will lead to a large amount of valuable zinc dissolution, which will not only increase the burden and cost of subsequent separation but also cause the loss of the target product. Therefore, the triggering of either of these two critical points signifies that the optimal balance between efficient arsenic leaching and inhibited zinc dissolution has been broken, and the reaction must be stopped immediately to lock in the optimal process range.

[0066] D8: Conduct a second round of dispensing. After the reaction is complete, detect and record the second set of monitoring data.

[0067] D9: Based on the initial monitoring data, the first set of monitoring data, and the second set of monitoring data, update the arsenic and zinc leaching rate curves as a function of pH, and capture the equilibrium point again.

[0068] If capture is successful, determine the actual endpoint alkalinity and stop adding leaching agent; if capture is still unsuccessful, proceed to step D10.

[0069] D10: Repeat steps D6 to D9. If the equilibrium point is not found when all the subsequent additions are completed, continue adding the leaching agent according to the subsequent addition plan until the equilibrium point is found.

[0070] After the first stage of countercurrent leaching reaction is completed, the slurry after the first stage of leaching is subjected to solid-liquid separation to obtain a first stage of leaching residue and a first stage of leaching solution. The first stage of leaching residue is sent to the second stage of countercurrent leaching process, and the first stage of leaching solution is sent to the calcification and arsenic precipitation process.

[0071] The two-stage leaching temperature control module is used to perform a secondary leaching reaction on the primary leaching residue using a high-alkali new solution, and to adjust the heating temperature in real time according to the rate of zinc dissolution in the mixed solution during the secondary leaching process.

[0072] Considering that the second-stage countercurrent leaching uses a high-alkali fresh solution to treat the first-stage leaching residue, the aim is to deeply extract residual zinc from the residue. Increasing the temperature can significantly accelerate the zinc leaching reaction rate and diffusion rate, thereby improving recovery efficiency. However, higher temperatures are not always better; excessively high temperatures can exacerbate the dissolution of impurities and may lead to uneconomical energy consumption. Therefore, it is necessary to regulate the heating temperature of the second-stage countercurrent leaching.

[0073] Since the rate of increase in dissolved zinc concentration is the most direct indicator of reaction progress, when the rate begins to slow down, it indicates a decrease in the driving force of the reaction, at which point the temperature can be appropriately increased; conversely, if the initial rate is already fast, excessively high temperatures are unnecessary to avoid energy waste. Based on this, the heating temperature can be adjusted according to the rate of zinc dissolution.

[0074] In a preferred embodiment of the present invention, the specific process of regulating the heating temperature is as follows: during the secondary leaching process, the concentration of dissolved zinc in the mixed solution is detected and the actual rate of zinc dissolution is plotted.

[0075] Extract the desired zinc dissolution rate variation curves under the current secondary leaching conditions from the database.

[0076] The actual zinc dissolution rate change curve is compared with the expected zinc dissolution rate change curve to calculate the degree of agreement between the two curves.

[0077] If the degree of agreement exceeds the set threshold, the current heating temperature is maintained; otherwise, the following control steps are performed: calculate the average zinc dissolution rate of the actual curve and the desired curve within the same time interval.

[0078] If the actual average value is greater than the expected average value, then it is determined that the heating temperature needs to be reduced.

[0079] If the actual average value is less than the expected average value, it is determined that the heating temperature needs to be increased.

[0080] The heating temperature adjustment value is determined based on the preset mapping relationship between the average deviation of the zinc dissolution rate and the heating temperature adjustment value.

[0081] It should be noted that the method for plotting the actual zinc dissolution rate change curve is as follows: the reaction mixture is sampled at fixed time intervals, the zinc dissolution concentration in the mixture is detected, and the increase in zinc dissolution concentration per unit time is calculated based on the results of two consecutive sampling tests. The zinc dissolution rate corresponding to each sampling time point is determined, and the actual zinc dissolution rate change curve is plotted accordingly.

[0082] As an example, suppose the reaction mixture is sampled at 20, 30, and 40 minutes after the start of the second leaching, and the dissolved zinc concentrations are measured to be 150 g / L (20 min), 159 g / L (30 min), and 171 g / L (40 min), respectively. The instantaneous zinc dissolution rate is calculated as follows: 20-30 minute rate = (159-150) / 10 = 0.9 g / L / min; 30-40 minute rate = (171-159) / 10 = 1.2 g / L / min. The actual zinc dissolution rate curve is plotted as a broken line that rises from 0.9 g / L / min to 1.2 g / L / min.

[0083] Extract the expected zinc dissolution rate change curve under the zinc oxide raw material and process conditions from the database (assuming it is a curve that rises steadily from 0.8 g / L / min to 1.1 g / L / min).

[0084] The actual curve and the expected curve are superimposed on the same time axis, and their degree of agreement is calculated (e.g., by calculating the root mean square error RMSE or correlation coefficient). Let's assume that the calculated degree of agreement is 83%.

[0085] Since the fit is 83% less than the set threshold of 90%, the heating temperature needs to be adjusted.

[0086] The actual average zinc dissolution rate over the 20-40 minute time interval was calculated to be 1.05 g / L / min, while the expected average zinc dissolution rate was 0.95 g / L / min. Since the actual average (1.05) is greater than the expected average (0.95), the actual zinc dissolution rate is determined to be too fast, and the adjustment direction is to reduce the heating temperature.

[0087] The average deviation of the zinc dissolution rate was calculated to be 0.10 g / L / min. The preset mapping relationship was consulted (for example, the heating temperature is reduced by 1.0℃ for every 0.01 g / L / min deviation). The heating temperature adjustment was determined to be 10.0℃ (reduction).

[0088] The control system lowers the heating temperature of the reactor by 10.0℃.

[0089] The secondary leaching process continues. In the next sampling cycle (e.g., at the 50th and 60th minutes), the above process is repeated. The process continues to be compared and dynamically adjusted based on the latest actual zinc dissolution rate change curve until the consistency meets the requirements or the leaching process ends.

[0090] It should be noted that by intelligently comparing the zinc dissolution rate curve plotted in real time with the expected curve, it can not only determine whether adjustment is needed, but also accurately diagnose the problem of excessive zinc leaching rate, and quantitatively reduce the reaction temperature accordingly. This ensures leaching efficiency while effectively suppressing the dissolution of large amounts of impurities and avoiding unnecessary energy waste, thus achieving precise and closed-loop control of the two-stage leaching process.

[0091] After the two-stage countercurrent leaching reaction is completed, the slurry after the two-stage leaching is subjected to solid-liquid separation to obtain the two-stage leaching solution and the final leaching residue. The two-stage leaching solution is returned to the first-stage leaching as a leaching agent, and the final leaching residue is used for valuable metal recovery.

[0092] The calcification and arsenic precipitation control module is used to oxidize a section of leachate before arsenic precipitation. It controls the oxidation-reduction potential based on the oxidation efficiency of trivalent arsenic. After oxidation, lime milk is added to carry out the calcification and arsenic precipitation reaction. The amount of lime milk added is dynamically adjusted based on the changes in arsenic concentration in the reaction mixture and the changes in zinc content in the precipitate.

[0093] In a leachate, arsenic often exists as arsenite, which has extremely high solubility and far lower reactivity with calcium ions than arsenate. Direct lime precipitation of trivalent arsenic would produce highly soluble but unstable calcium arsenite, resulting in extremely low precipitation efficiency and easy re-dissolution of the residue in the environment, causing secondary pollution. Controlling the redox potential can force the efficient and complete oxidation of trivalent arsenic in the solution to pentavalent arsenic, creating conditions for the subsequent formation of calcium arsenite minerals with extremely low solubility and extremely stable chemical properties. Therefore, to ensure the complete removal of arsenic in its more stable and easily precipitated pentavalent form, precise control of the redox potential during the oxidation process is necessary.

[0094] Furthermore, considering that insufficient lime slurry during the arsenic precipitation process can lead to incomplete precipitation, excessive residual arsenic concentration in the solution, and low yield and poor stability of the resulting calcium arsenate precipitate, which is prone to re-dissolution during subsequent treatment and causes secondary pollution, excessive lime slurry not only causes re-dissolution of the amphoteric zinc, resulting in the loss of valuable metals, but also contaminates the arsenic slag, reduces its purity, and causes excessive calcium ions to react with sulfate ions in the solution to form a large amount of gypsum, unnecessarily increasing the slag volume and encapsulating the effective components, thus inhibiting the arsenic precipitation efficiency, it is necessary to control the amount of lime slurry added.

[0095] The oxidation efficiency of trivalent arsenic to pentavalent arsenic reflects whether the oxidation-reduction potential (ORP) setting meets the actual process requirements. If the oxidation efficiency is insufficient, the ORP setting is increased to enhance the oxidation driving force; if the efficiency has met the target, the ORP is kept stable.

[0096] Based on this, in a preferred embodiment of the present invention, the specific process of controlling the oxidation-reduction potential is as follows: before oxidation treatment, the initial concentrations of trivalent and pentavalent arsenic in a leachate are detected.

[0097] During the oxidation process, the redox potential is increased at an equal gradient from its initial value, while samples are taken at equal time intervals to detect the concentration of pentavalent arsenic in a section of the leachate.

[0098] When the rate of increase in pentavalent arsenic concentration is slowed down, the oxidation efficiency of trivalent arsenic is detected and calculated.

[0099] The oxidation efficiency is compared with a preset target value: if the target value is reached, the current oxidation-reduction potential is maintained.

[0100] If the value is lower than the target value, the amount of redox potential adjustment is determined and controlled based on the preset regulation rules.

[0101] It should be noted that the oxidation efficiency of trivalent arsenic is the ratio of the difference between the current concentration and the initial concentration of pentavalent arsenic to the initial concentration of trivalent arsenic.

[0102] As an example, assume that the initial trivalent arsenic concentration in a leachate is 5 g / L; the initial pentavalent arsenic concentration is 0.2 g / L; the target oxidation efficiency for oxidizing trivalent arsenic to pentavalent arsenic is >95%; and the arsenate concentration in the solution is measured every 5 minutes.

[0103] During the oxidation process, the oxidation-reduction potential (ORP) value slowly increased from the initial +200mV to +350mV. At the same time, the concentration of arsenate (pentavalent arsenic) increased significantly from 0.2g / L. The analyzer data showed that its concentration increased steadily at a rate of about 0.1g / L per minute.

[0104] Until the ORP value reached +480mV, the rate of increase in arsenate concentration slowed significantly, decreasing from 0.1 g / L per minute to 0.02 g / L. After reaching approximately 4.8 g / L, the concentration began to fluctuate between 4.8 and 4.9 g / L, with the change curve becoming relatively flat. The calculated oxidation efficiency was (4.85 - 0.2) / 5.0 = 93%, which has not yet reached the target of >95%.

[0105] Based on the preset regulation rule (for every 1% decrease in oxidation efficiency, ORP increases by 10mV), the ORP was increased from +480mV to +500mV, and the arsenate concentration was finally stabilized at 4.98g / L.

[0106] The calculated oxidation efficiency is (4.98-0.2) / 5.0=95.6%, which meets the process requirements and stabilizes the ORP at +500mV.

[0107] It should be noted that the trivalent arsenic concentration is the arsenite concentration, and the pentavalent arsenic concentration is the arsenate concentration.

[0108] It should be noted that the difference in pentavalent arsenic concentration between two consecutive sampling tests can be used to determine whether the rate of increase in concentration has slowed down.

[0109] After the leaching solution oxidation treatment is completed, the formal calcification and arsenic precipitation reaction begins.

[0110] During the arsenic precipitation process, monitoring the decreasing trend of residual arsenic concentration in the solution can determine whether the precipitation reaction is nearing completion, thus establishing the lower limit for the amount of lime slurry to be added. When the arsenic concentration stops decreasing, it indicates that the reaction has reached chemical equilibrium, and continuing to add lime slurry would be wasteful. Furthermore, monitoring the zinc content in the calcium arsenate slag can determine whether zinc re-dissolution or zinc co-precipitation has occurred. Once the zinc content in the slag begins to rise abnormally, it indicates that the amount of lime slurry added has exceeded the window for selective arsenic precipitation, thus allowing the determination of the lower limit for the amount of lime slurry to be added.

[0111] Based on this, in a preferred embodiment of the present invention, the specific process of dynamically adjusting the amount of lime slurry added is as follows: lime slurry is added in stages to a section of the oxidized leachate according to a preset lime slurry step-by-step addition scheme.

[0112] After each addition of lime slurry and after the reaction was complete, samples were taken and the arsenic concentration in the supernatant and the zinc content in the precipitate were tested.

[0113] Based on the test results, a dual judgment is made as to whether the cumulative amount of lime slurry added has reached either the lower or upper limit.

[0114] If, after a certain addition of lime slurry, the cumulative addition reaches either the lower limit or the upper limit, then the addition of lime slurry shall be stopped.

[0115] Otherwise, continue with the next round of lime slurry addition until either limit is reached.

[0116] The lower limit of the amount of lime slurry added is based on ensuring complete arsenic precipitation, while the upper limit is based on inhibiting excessive zinc co-precipitation.

[0117] Based on this, the specific process of the dual judgment is as follows: detect the arsenic concentration of the current supernatant. If the current arsenic concentration has not changed compared with the arsenic concentration measured after the last addition of lime milk, or if the current arsenic concentration has dropped below the preset target concentration value, then it is determined that the cumulative addition of lime milk has reached the lower limit; otherwise, it is determined that the lower limit has not been reached.

[0118] The zinc content in the current precipitate is detected. If the current zinc content reaches or exceeds the set zinc content control threshold, it is determined that the cumulative amount of lime slurry added has reached the upper limit; otherwise, it is determined that the upper limit has not been reached.

[0119] In one embodiment of the present invention, the target concentration of arsenic in the supernatant is 1.0 mg / L, and the control threshold of zinc content in the precipitate is 3%.

[0120] After calcification and arsenic precipitation, the slurry is subjected to solid-liquid separation to obtain calcium arsenate slag and arsenic-precipitated liquid. The calcium arsenate slag is safely landfilled as hazardous waste, while the arsenic-precipitated liquid can be partially returned to the system for recycling or treated to meet discharge standards.

[0121] Please see Figure 2 As shown, the present invention provides a method for controlling zinc oxide dust treatment, comprising the following steps: S1: mixing zinc oxide dust with process water to obtain zinc oxide slurry.

[0122] S2: Add leaching agent to zinc oxide slurry to carry out a first-stage leaching reaction. According to the arsenic and zinc leaching rate change curves with pH in the reaction mixture, capture the equilibrium point for efficient arsenic leaching and inhibit zinc dissolution. Based on the equilibrium point, determine the endpoint alkalinity and control the amount of leaching agent added. After the first-stage leaching reaction is completed, perform solid-liquid separation to obtain a first-stage leaching residue and a first-stage leaching solution.

[0123] S3: A high-alkali new solution is used to carry out a secondary leaching reaction on the first-stage leaching residue. The heating temperature is adjusted in real time according to the rate of zinc dissolution in the mixed solution during the secondary leaching process.

[0124] S4: Before arsenic precipitation, a section of the leachate is oxidized. The oxidation-reduction potential is controlled according to the oxidation efficiency of trivalent arsenic. After oxidation, lime milk is added to carry out the calcification and arsenic precipitation reaction. The amount of lime milk added is dynamically adjusted based on the changes in arsenic concentration in the reaction mixture and the changes in zinc content in the precipitate.

[0125] In summary, this invention achieves highly efficient selective leaching and stable solidification of arsenic by dynamically capturing the equilibrium point for efficient arsenic leaching and inhibiting zinc dissolution based on the arsenic and zinc leaching rate curves with pH changes during the first-stage leaching process, and precisely controlling the amount of leaching agent added. In the second-stage leaching, the heating temperature is adjusted in real time based on the zinc dissolution rate. Oxidation treatment is performed before calcification precipitation of arsenic, and the redox potential is controlled based on the oxidation efficiency of trivalent arsenic. Furthermore, the amount of lime slurry added is dynamically adjusted during arsenic precipitation based on the arsenic concentration and the zinc content in the precipitate. This invention achieves highly efficient selective leaching and stable solidification of arsenic, while effectively inhibiting zinc loss, and has advantages such as high separation efficiency and high resource recovery rate.

[0126] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0127] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A zinc oxide fume treatment control system, characterized by, The application relates to a zinc oxide ore leaching method and device. The method comprises the following steps: a raw material slurry module: zinc oxide fume is stirred and mixed with process water to obtain a zinc oxide ore slurry; a first-stage leaching alkali control module: a leaching agent is added into the zinc oxide ore slurry to perform a first-stage leaching reaction, an efficient arsenic leaching balance point is captured and zinc dissolution is inhibited according to a pH variation curve of arsenic and zinc leaching rates in a reaction mixture, a final point alkali degree is determined based on the balance point, the leaching agent addition amount is controlled, and solid-liquid separation is performed after the first-stage leaching reaction is completed to obtain a first-stage leaching residue and a first-stage leaching solution; a second-stage leaching temperature control module: a high-alkali new solution is used to perform a second-stage leaching reaction on the first-stage leaching residue, and the heating temperature is controlled in real time according to a zinc dissolution rate in the mixture during the second-stage leaching process; a calcification arsenic precipitation control module: the first-stage leaching solution is subjected to oxidation treatment before arsenic precipitation, the oxidation-reduction potential is controlled according to the oxidation efficiency of trivalent arsenic, lime milk is added to perform a calcification arsenic precipitation reaction after the oxidation is completed, and the lime milk addition amount is dynamically adjusted based on the arsenic concentration variation in the reaction mixture and the zinc content variation in the precipitate. The specific process of controlling the leaching agent addition amount comprises the following steps: D1: a reference interval of the final point alkali degree under the current first-stage countercurrent leaching condition is extracted from a database, and the lower limit value of the reference interval is taken as a reference final point alkali degree; D2: the total leaching agent addition amount is calculated based on the reference final point alkali degree; D3: the total leaching agent addition amount is divided into a front one-time addition amount and a rear split addition amount according to a preset rule, the proportions of the two in the total addition amount are determined, and the number of times and the addition amount of each time of the rear split addition are set; D4: historical leaching reaction data are extracted from the database, the reaction completion time required for different leaching agent addition amounts is obtained, and the reaction completion time required for the front one-time addition and the rear split addition is respectively determined; D5: after the front one-time addition amount is added and the reaction is completed, the arsenic and zinc leaching rates and the pH value of the reaction mixture at this time are detected and recorded as monitoring starting data; D6: the first rear split addition is performed, and after the reaction is completed, the arsenic and zinc leaching rates and the pH value of the reaction mixture are detected and recorded to obtain a first group of monitoring data; D7: the arsenic and zinc leaching rate variation curve with the pH value is drawn according to the monitoring starting data and the first group of monitoring data, and the balance point of efficient arsenic leaching and zinc dissolution inhibition is captured based on the variation curve; if the balance point is successfully captured, the pH value of the reaction mixture when the balance point appears is recorded as the actual final point alkali degree, and the leaching agent addition is stopped; if the balance point is not successfully captured, step D8 is executed; D8: the second rear split addition is performed, and after the reaction is completed, a second group of monitoring data is obtained; D9: the arsenic and zinc leaching rate variation curve with the pH value is updated according to the monitoring starting data, the first group of monitoring data and the second group of monitoring data, and the balance point is captured again; if the balance point is successfully captured, the actual final point alkali degree is determined, and the leaching agent addition is stopped; if the balance point is not successfully captured, step D10 is executed; D10: the process of steps D6 to D9 is repeatedly executed, and if the balance point is not successfully captured when the rear split addition amount is completely added, the leaching agent is continuously added according to the rear split addition scheme until the balance point is captured. ​ ​ ​ The specific process of regulating the heating temperature comprises the following steps: detecting the dissolved zinc concentration in the mixed solution during the secondary leaching process and drawing an actual dissolved zinc rate change curve; extracting an expected dissolved zinc rate change curve under the current secondary leaching condition from a database; comparing the coincidence degree of the actual dissolved zinc rate change curve and the expected dissolved zinc rate change curve, and calculating the coincidence degree of the two curves; if the coincidence degree exceeds a set threshold, maintaining the current heating temperature unchanged, otherwise, performing the following regulation steps: calculating the average value of the dissolved zinc rate of the actual curve and the expected curve in the same time interval; if the actual average value is greater than the expected average value, determining that the heating temperature needs to be lowered; if the actual average value is less than the expected average value, determining that the heating temperature needs to be raised; and determining the heating temperature adjustment value according to a preset mapping relationship between the average value deviation of the dissolved zinc rate and the heating temperature adjustment value. The specific process of controlling the oxidation-reduction potential comprises the following steps: detecting the initial concentrations of trivalent arsenic and pentavalent arsenic in the primary leaching solution before the oxidation treatment; during the oxidation process, making the oxidation-reduction potential start from an initial value and rise at an equal gradient, and meanwhile, sampling and detecting the concentration of pentavalent arsenic in the primary leaching solution at an equal time interval; when the recognition of the pentavalent arsenic concentration increase slows down, detecting and calculating the current oxidation efficiency of trivalent arsenic; comparing the oxidation efficiency with a preset oxidation efficiency target value: if the target value is reached, maintaining the current oxidation-reduction potential; if the target value is not reached, determining the oxidation-reduction potential adjustment value based on a preset regulation rule and performing control. The specific process of dynamically adjusting the addition amount of lime milk comprises the following steps: adding lime milk into the primary leaching solution after oxidation in batches according to a preset lime milk step-by-step feeding scheme; after each addition of lime milk and after the reaction is completed, sampling and detecting the arsenic concentration in the supernatant of the reaction mixture and the zinc content in the precipitate; according to the detection results, performing a double judgment on whether the cumulative addition amount of lime milk reaches a lower limit value or an upper limit value; if the cumulative addition amount reaches any one of the limit values after the addition of lime milk, stopping the feeding of lime milk; otherwise, continuing to perform the next round of lime milk feeding until any one of the limit values is reached.

2. A zinc oxide fume treatment control system according to claim 1, characterized in that: The specific process of preparing the zinc oxide ore slurry comprises the following steps: Under normal temperature conditions, the metered zinc oxide dust is added into a slurry tank, and a corresponding amount of process water is added, and a stirring device is started to stir; During the stirring process, dilute alkali is added dropwise into the slurry tank, and the pH value of the slurry is monitored in real time, until the pH value is in a preset low alkalinity interval of slurry, the dropwise addition of dilute alkali is stopped, and the stirring is continued for a set time to prepare the zinc oxide ore slurry.

3. A zinc oxide fume treatment control system as claimed in claim 1, wherein: The specific process of calculating the total addition amount of leaching agent comprises the following steps: According to the total volume of the slurry liquid and the reference end-point alkalinity, the required total alkali amount is calculated, and the slurry-borne alkali amount is obtained, the required total alkali amount is subtracted by the slurry-borne alkali amount to obtain the alkali amount to be supplemented by the leaching agent, and the total addition amount of the leaching agent is calculated in combination with the alkali concentration of the leaching agent.

4. A zinc oxide fume treatment control system as claimed in claim 1, wherein: The specific process of capturing the balance point of efficient arsenic leaching and inhibiting zinc dissolution comprises the following steps: obtaining a tangent slope at a last data point on the curve of arsenic leaching rate changing with pH, if the tangent slope is in a preset interval of tangent slopes corresponding to a slow increase, the last data point is determined as an arsenic leaching high plateau point; calculating an increment of zinc leaching rate of a last data point on the curve of zinc leaching rate changing with pH relative to a zinc leaching rate of a last adjacent data point, if the increment reaches a preset threshold of leaching rate increment or the zinc leaching rate of the last data point reaches a preset zinc leaching rate warning value, the last data point is determined as a zinc leaching sudden rising point; if the curve of arsenic leaching rate changing with pH has a high plateau point or the curve of zinc leaching rate changing with pH has a sudden rising point, it is determined that the balance point is captured, otherwise it is determined that the balance point is not captured.

5. A zinc oxide fume treatment control system according to claim 4, wherein: The specific process of the double determination is as follows: detecting an arsenic concentration of a current supernatant, if the current arsenic concentration does not change compared with an arsenic concentration measured after last lime milk is put or the current arsenic concentration has decreased to below a preset target concentration value, it is determined that the cumulative amount of the current lime milk has reached a lower limit, otherwise it is determined that the lower limit is not reached; detecting a zinc content in a current precipitate, if the current zinc content reaches or exceeds a preset zinc content control threshold, it is determined that the cumulative amount of the current lime milk has reached an upper limit, otherwise it is determined that the upper limit is not reached.

6. A method of controlling zinc oxide fume treatment by a system for controlling zinc oxide fume treatment according to any one of claims 1 to 5, characterized by the steps of, The method comprises the following steps: S1: mixing zinc oxide dust with process water to prepare a zinc oxide ore slurry; S2: adding a leaching agent to the zinc oxide ore slurry to perform a first leaching reaction, according to a curve of arsenic and zinc leaching rates changing with pH in a reaction mixture, a balance point of efficient arsenic leaching and inhibited zinc dissolution is captured, a terminal alkalinity is determined based on the balance point and a leaching agent addition amount is controlled, and after the first leaching reaction is completed, solid-liquid separation is performed to obtain a first leaching residue and a first leaching liquid; S3: using a high-alkali new liquid to perform a secondary leaching reaction on the first leaching residue, according to a dissolved zinc rate in the mixture during the secondary leaching process, a heating temperature is adjusted in real time; S4: before arsenic precipitation, the first leaching liquid is subjected to oxidation treatment, according to an oxidation efficiency of trivalent arsenic, an oxidation-reduction potential is controlled, after oxidation is completed, lime milk is added to perform a calciumization arsenic precipitation reaction, based on changes of arsenic concentration in the reaction mixture and changes of zinc content in the precipitate, an addition amount of the lime milk is dynamically adjusted.

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