Method for improving the soluble zinc rate of zinc calcine

Abstract

The application discloses a method for improving the soluble zinc rate of zinc calcine, and belongs to the technical field of zinc metallurgy. The method for improving the soluble zinc rate of zinc calcine comprises the following steps: mixing high-temperature zinc calcine and an activating agent to obtain primary treated sand; and performing reduction treatment on the primary treated sand by using a reducing gas in an inert gas atmosphere to obtain modified zinc calcine; and the activating agent is a mixture of a sulfate and an alkaline oxide. Through the selection of the activating agent, the structure of the insoluble compounds such as zinc ferrite and zinc silicate in the zinc calcine can be broken, and the bound zinc element can be released, so that the soluble zinc rate of the zinc calcine can be greatly improved.

Description

Technical Field

[0001] This application belongs to the field of zinc metallurgy technology, and in particular relates to a method for improving the soluble zinc content of zinc calcined sand. Background Technology

[0002] In the zinc metallurgical industry, zinc concentrate roasting is a key pretreatment process. Its purpose is to oxidize zinc sulfide in the zinc concentrate into zinc oxide, obtaining zinc roasted ore, which can then be used to extract zinc metal through processes such as acid leaching. However, in actual roasting, insoluble compounds such as zinc ferrite and zinc silicate are inevitably generated in the zinc roasted ore. The presence of these insoluble phases leads to a decrease in the soluble zinc content of the zinc roasted ore, and a large amount of zinc resources are bound in the leaching residue. This not only reduces the zinc recovery rate but also increases the difficulty and cost of subsequent residue treatment.

[0003] To improve the soluble zinc content of zinc calcined abrasive, existing technologies employ methods such as optimizing roasting process parameters, adding activators, or subjecting the calcined abrasive to secondary crushing. For example, prior art with publication number CN 118996144 A discloses a method for increasing the direct leaching rate of zinc in zinc calcined abrasive. This method involves directly dissolving zinc oxide and zinc ferrite in the zinc calcined abrasive through a single acid leaching stage, thereby releasing a large amount of zinc and increasing the direct leaching rate of zinc.

[0004] Although the above methods can improve the direct leaching rate of zinc in zinc calcined sand to some extent, the following problems still exist: First, the process requires additional consumption of copper powder and a large amount of sulfuric acid, resulting in high reagent costs. Furthermore, it cannot effectively utilize the residual heat of the calcined sand itself, leading to high energy consumption and poor economic efficiency and process rationality. Second, it only dissolves the insoluble phases already formed in the calcined sand through acid leaching, without fundamentally inhibiting the formation of insoluble compounds such as zinc ferrite and zinc silicate. When the content of insoluble phases in the calcined sand is high, the leaching effect will decrease significantly, and there is a clear upper limit to the improvement of the zinc leaching rate, making it difficult to meet the industrial production demand for high zinc resource recovery rates. Third, some processes require significant equipment modifications, resulting in poor industrial adaptability and the potential generation of excessive sulfur-containing tail gas, increasing environmental treatment costs.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of protection of this application. Summary of the Invention

[0006] This application discloses a method for improving the soluble zinc content of zinc calcined sand, aiming to solve the technical problems of poor soluble zinc content, high reagent consumption and energy costs, and poor industrial adaptability in existing methods.

[0007] To achieve the above objectives, the technical solution of this application is: The first aspect of this application provides a method for improving the soluble zinc content of zinc calcined sand, comprising: After mixing high-temperature zinc calcined sand and an activator, a primary treated sand is obtained; In an inert gas atmosphere, the primary processed sand is reduced using a reducing gas to obtain modified zinc calcined sand; The activator is a mixture of sulfate and basic oxide.

[0008] Preferably, in conjunction with the first aspect, the sulfate includes one or more of sodium sulfate, potassium sulfate, calcium sulfate, and ammonium sulfate; The alkaline oxides include one or more of calcium oxide and magnesium oxide.

[0009] Preferably, in conjunction with the first aspect, the mass ratio of the sulfate to the basic oxide is (1.8-3.5):1.

[0010] Preferably, in conjunction with the first aspect, the amount of alkaline oxide added in the activator is 1.02-1.08 times the SiO2 content in the high-temperature zinc calcined sand.

[0011] Preferably, in conjunction with the first aspect, the temperature of the high-temperature zinc calcined sand is 580-1000 ℃; The mixing time of the high-temperature zinc calcined sand and activator is 10-30 min.

[0012] Preferably, in conjunction with the first aspect, the inert gas includes one or more of nitrogen, argon, and CO2.

[0013] Preferably, in conjunction with the first aspect, the reducing gas is sulfur dioxide; The volume fraction of the reducing gas is 85-99.5%.

[0014] Preferably, in conjunction with the first aspect, the volume fraction of oxygen in the inert gas atmosphere is ≤2.8%.

[0015] Preferably, in conjunction with the first aspect, the reduction temperature is 600-800 ℃ and the reduction time is 15-45 min.

[0016] Preferably, in conjunction with the first aspect, after the reduction is completed, the modified zinc calcined sand is cooled to room temperature, and an inert gas atmosphere is maintained during the cooling process; The soluble zinc content of the modified zinc calcinate is ≥94%.

[0017] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: The method for improving the soluble zinc content of zinc calcined abrasive provided in this application involves reacting high-temperature zinc calcined abrasive with a compound activator of sulfate and alkaline oxide, followed by reduction under low oxygen conditions. On the one hand, the entire activation and reduction reaction is completed using the residual heat of the high-temperature zinc calcined abrasive itself, with temperature control achieved solely through the flow rate and velocity of inert gas, eliminating the need for additional heating devices and reducing production energy consumption. On the other hand, by selecting the appropriate activator, the structure of insoluble compounds such as zinc ferrite and zinc silicate in the zinc calcined abrasive can be broken down, releasing the bound zinc element and significantly improving the soluble zinc content of the zinc calcined abrasive. Furthermore, the process used in this application can be directly integrated into production lines, with controllable operating conditions and costs, requiring no large-scale equipment modifications and facilitating industrial-scale promotion. Attached Figure Description

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

[0019] Figure 1 This is a process flow diagram of a method for improving the soluble zinc content of zinc calcined sand provided in an embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0022] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0023] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0024] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0025] It should be noted that all raw materials and / or reagents in the embodiments of this application are purchased on the market or prepared according to conventional methods known to those skilled in the art, and are all industrial-grade raw materials, meeting the cost and supply requirements of industrial production.

[0026] In a first aspect, this application provides a method for improving the soluble zinc content of zinc calcined sand, comprising: After mixing high-temperature zinc calcined sand and an activator, a primary treated sand is obtained; In an inert gas atmosphere, the primary processed sand is reduced using a reducing gas to obtain modified zinc calcined sand; The activator is a mixture of sulfate and basic oxide.

[0027] In this embodiment, the sulfate includes one or more of sodium sulfate, potassium sulfate, calcium sulfate, and ammonium sulfate; the alkaline oxide includes one or more of calcium oxide and magnesium oxide. This application, by using a mixture of sulfate and alkaline oxide as an activator, can effectively break down the structure of insoluble compounds such as zinc ferrite and zinc silicate in zinc calcined ore, releasing the bound zinc element and fundamentally and significantly increasing the soluble zinc rate of zinc calcined ore, stabilizing it to over 94%, reducing zinc resource waste, and improving zinc resource recovery rate.

[0028] It should be noted that this application directly utilizes the heat and residual heat of the high-temperature zinc calcined sand to complete the activation and reduction reaction, without the need for additional heating devices for supplemental heating. The system temperature is gently controlled by the flow rate and velocity of the inert gas, so that the temperature is stabilized in the range of 600-800 ℃ required for the reduction reaction. This maximizes the utilization of the residual heat of the calcined sand, effectively reduces energy consumption in the production process, and further improves the economic efficiency of the process.

[0029] It should be noted that the process used in this application can be directly connected to existing zinc metallurgical production lines. The operating conditions and costs are controllable, and there is no need for large-scale modification of existing equipment. Furthermore, the process parameters (temperature, time, gas concentration, etc.) are highly controllable, adaptable to existing production equipment, and easy to promote and apply on a large scale.

[0030] It should be noted that this application utilizes the synergistic effect of activators and reduction reactions to inhibit the formation of insoluble phases, improve zinc recovery, reduce the amount of leaching residue generated, and lower the difficulty and cost of subsequent leaching residue treatment. At the same time, it selects non-toxic and easily treated inert gases and reducing gases to avoid generating harmful pollutants, which meets the development needs of green metallurgy.

[0031] It should be noted that this application also avoids interference from oxidation reaction by controlling the low oxygen content conditions in the inert gas atmosphere and parameters such as reduction temperature and time, ensuring the quality stability of modified zinc calcined sand and meeting the standard of soluble zinc rate, thus providing a guarantee for the stable operation of the subsequent acid leaching zinc extraction process.

[0032] In this embodiment, the preferred mass ratio of sulfate to alkaline oxide is (1.8-3.5):1. This ratio range is determined based on the synergistic effect mechanism of the two components, reaction efficiency, and actual industrial production requirements. A ratio that is too low or too high will affect the improvement of the soluble zinc content in the modified zinc calcinate and may also cause process problems. When the ratio is below 1.8:1, the amount of sulfate is relatively insufficient. On the one hand, it cannot fully decompose to produce enough SO3, making it difficult to fully react with ZnO in the zinc calcinate to form easily soluble ZnSO4. On the other hand, it also cannot allow sufficient sulfate cations (Na+) to be generated. + K + NH4 +(etc.) Embedded in the zinc ferrite lattice, it is difficult to effectively destroy the stable structure of zinc ferrite, thus failing to lay a sufficient foundation for subsequent reduction reactions; on the other hand, the alkaline oxides are relatively excessive. Excess alkaline oxides will react with sulfates and zinc oxides generated in the system, which can easily cause zinc calcinate to clump, affecting not only the fluidization and mixing effect of the material, but also increasing the difficulty of subsequent conveying and reaction processes. At the same time, excessive alkaline oxides will increase the acid consumption of the subsequent acid leaching process, increasing production costs. When the ratio exceeds 3.5:1, the amount of sulfate used is excessively redundant. Firstly, it exceeds the reaction requirements with alkaline oxides and the insoluble phase in zinc calcinate. The excess sulfate cannot participate in the activation reaction, resulting in a waste of raw materials and increasing the cost of activator. Secondly, excess sulfate will decompose at high temperatures to produce a large amount of SO3. SO3 exceeding the system's reaction capacity will be discharged with the tail gas, which not only reduces the utilization rate of sulfur but also increases the load on tail gas treatment, failing to meet the requirements of green metallurgy. Thirdly, excess sulfate will form a coating layer on the surface of zinc calcinate, hindering the contact between the subsequent reducing gas SO2 and the insoluble phase inside the zinc calcinate, leading to insufficient reduction reaction and ultimately affecting the improvement of soluble zinc rate.

[0033] By selecting a ratio range of (1.8-3.5):1, precise proportioning and synergistic effects of sulfate and alkaline oxide can be achieved. This ensures that the sulfate provides sufficient SO3 and cations to fully destroy and modify the structure of insoluble phases such as zinc ferrite and zinc silicate. At the same time, the alkaline oxide reacts fully with SiO2 in zinc calcinate to generate stable calcium silicate / magnesium silicate, inhibiting the formation of zinc silicate. Furthermore, there is no excess redundancy of either component, which will not cause problems such as agglomeration, raw material waste, or increased tail gas load. Under the premise of ensuring activation reaction efficiency and maximizing the soluble zinc rate, the smoothness of the process and the controllability of production costs are taken into account.

[0034] In this embodiment, the amount of alkaline oxide added to the activator is 1.02-1.08 times the SiO2 content in the high-temperature zinc calcinate. This amount ensures that the alkaline oxide preferentially reacts with the SiO2 in the zinc calcinate to form stable calcium silicate, avoiding the combination of SiO2 and ZnO to form insoluble zinc silicate. It also avoids excessive alkaline oxide leading to calcinate agglomeration or an increase in subsequent acid leaching residue. Taking calcium oxide as an example, the specific chemical reaction is as follows:

[0035] In this embodiment, the temperature of the high-temperature zinc calcined abrasive is preferably 580-1000 °C; the mixing time of the high-temperature zinc calcined abrasive and the activator is preferably 10-30 min. The high-temperature zinc calcined abrasive is the zinc calcined abrasive from the fluidized bed cooler overflowing from the fluidized bed furnace. Activation is performed using the residual heat of the zinc calcined abrasive overflowing from the fluidized bed furnace, eliminating the need for additional heating and reducing energy consumption. This temperature range ensures a full reaction between the activator and the zinc calcined abrasive, where the sulfate decomposes to produce SO3, which reacts with ZnO to form easily soluble ZnSO4. Simultaneously, the cations in the sulfate (such as Na+)... + K + It can embed itself into the zinc ferrite lattice, disrupting its stable structure and laying the foundation for subsequent reduction reactions. Taking sodium sulfate as an example, the specific chemical reaction is as follows:

[0036]

[0037] In this embodiment, the inert gas includes one or more of nitrogen, argon, and CO2. The volume fraction of oxygen in the inert gas atmosphere is ≤2.8%. The inert gas used in this application is an industrial-grade gas. By introducing inert gas, the air inside the cooling cylinder can be quickly replaced, controlling the oxygen content to ≤2.8%, preventing oxidation reactions when SO2 is subsequently introduced, and preventing the reduction products (such as FeO, Fe3O4) from being re-oxidized, ensuring stable reduction performance. Simultaneously, by adjusting the inert gas flow rate and velocity, the system temperature can be gently adjusted, maintaining the residual heat of the high-temperature calcined sand at the 600-800℃ required for the reduction reaction, without the need for additional heating. The specific chemical reactions are as follows (side reactions to be suppressed):

[0038]

[0039]

[0040]

[0041] In this embodiment, the reduction temperature is preferably 600-800 °C, and the reduction time is preferably 15-45 min. The mixing and activation process of zinc calcinate and the activator, as well as the initial reaction of SO2 with the sparingly soluble phase, are both slightly exothermic reactions. Therefore, they can be naturally maintained within the reaction window without additional heating; temperature control can be achieved simply by fine-tuning the inert gas flow rate. At this time, defects appear in the zinc ferrite lattice due to the decrease in temperature, and Fe... 3+ Enhanced activity; SO2 can efficiently convert Fe 3+ Reduced to Fe 2+The generated FeO can combine with SO3 in the system to form easily soluble FeSO4, and ZnO can combine with SO3 to form easily soluble ZnSO4, further increasing the soluble zinc content. Simultaneously, some Fe2O3 is reduced to Fe3O4, thereby further inhibiting the formation of zinc ferrite. Controlling the reaction time ensures complete reduction of zinc ferrite, avoiding incomplete reaction that could lead to insufficient improvement in the soluble zinc content. The specific chemical reaction is as follows:

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] In this embodiment, after the reduction is completed, the modified zinc calcined abrasive is cooled to room temperature while maintaining an inert gas atmosphere during the cooling process; the soluble zinc content of the modified zinc calcined abrasive is ≥94%. Cooling under an inert atmosphere prevents the modified zinc calcined abrasive from being oxidized during the cooling process, ensuring the quality of the final product; at the same time, specifying the soluble zinc content of the modified zinc calcined abrasive ensures that the process can stably achieve the goal of increasing the zinc leaching rate, meeting the requirements of zinc recovery rate in industrial production.

[0048] It should be noted that the activation step in this application is carried out in a fluidized cooling cylinder, and the reduction is carried out in a cooling cylinder. The zinc calcined sand overflows from the boiling furnace and enters the fluidized cooler, where it is mixed with the activator and activated and reacted. Then, it is sent to the cooling cylinder, which has been pretreated with inert gas. Relying on the residual heat of the calcined sand itself, the temperature is finely controlled by the flow rate of the inert gas, and it undergoes a reduction reaction with the introduced SO2 to finally obtain zinc calcined sand with high solubility.

[0049] The technical solution of this application will be further described below with reference to specific embodiments, but the scope of protection of this application is not limited to the following embodiments.

[0050] The raw materials used in the following examples are as follows: The feed amount is based on 100 kg of zinc calcined ore (containing 4.3 kg of SiO2, with an initial soluble zinc content of 88.3%). The specific mass of each component of the activator is calculated according to the process parameters. The zinc calcined ore is taken from the product of fluidized bed roasting in a zinc smelter. Its main components (mass fraction) are: Zn 48.2%, Fe 8.5%, SiO2 4.3%, CaO 1.2%, with an initial soluble zinc content of 88.3%. Sulfates and basic oxides are all industrial grade; the inert gas is industrial grade nitrogen; the reducing gas SO2 has a purity ≥99.5%.

[0051] Basis for calculating the theoretical reaction amount of SiO2: Theoretical reaction amount of SiO2 = mass of zinc calcined sand × mass fraction of SiO2 × (molar mass of basic oxides / molar mass of SiO2).

[0052] Example 1 The method for improving the soluble zinc content of zinc calcined sand provided in this embodiment is illustrated in the flowchart below. Figure 1 As shown, it specifically includes: S101: Take 6.53 kg of industrial-grade sodium sulfate and 3.63 kg of industrial-grade calcium oxide (the mass ratio of sodium sulfate to calcium oxide is 1.8:1), mix them evenly to obtain an activator. Add the above activator to the fluidized bed cooler overflowing from the boiling furnace (zinc calcined sand temperature 580℃), wherein the amount of calcium oxide added is 1.02 times the theoretical reaction amount of SiO2 in the zinc calcined sand, stir and activate for 10 min to obtain primary treated sand.

[0053] S102: The primary treated sand is fed into a cooling cylinder, and industrial-grade nitrogen is introduced into the cooling cylinder. By adjusting the nitrogen flow rate, the internal air is replaced while the system temperature is stabilized at 600 ℃, and the oxygen content in the cooling cylinder is controlled at 2.5%. SO2 gas with a volume fraction of 85% is introduced to carry out a reduction reaction for 15 min. After the reaction is completed, Al-modified zinc calcined sand is obtained.

[0054] The solubility of the Al-modified zinc calcinate obtained in this example was found to be 94.1%.

[0055] It should be noted that the mixing and activation process of zinc calcined sand and activator, as well as the reaction between SO2 and the sparingly soluble phase in the initial stage of reduction, are both slightly exothermic reactions. The heat released can slightly increase the system temperature without the need for additional heating.

[0056] Example 2 The method for improving the soluble zinc content of zinc roasted sand provided in this embodiment specifically includes: S201: Take 7.53 kg of industrial-grade potassium sulfate and 3.01 kg of industrial-grade magnesium oxide (the mass ratio of potassium sulfate to magnesium oxide is 2.5:1), mix them evenly to obtain an activator. Add the above activator to the fluidized bed cooler overflowing from the boiling furnace (zinc calcined sand temperature 750℃), wherein the amount of magnesium oxide added is 1.05 times the theoretical reaction amount of SiO2 in the zinc calcined sand, stir and activate for 20 min to obtain primary treated sand.

[0057] S202: The first-processed sand is fed into a cooling cylinder, and industrial-grade nitrogen is introduced into the cooling cylinder. By adjusting the nitrogen flow rate, the internal air is replaced while the system temperature is stabilized at 700 ℃, and the oxygen content in the cooling cylinder is controlled at 1.8%. SO2 gas with a volume fraction of 92.5% is introduced to carry out a reduction reaction for 30 min. After the reaction is completed, A2-modified zinc calcined sand is obtained.

[0058] The solubility of the A2-modified zinc calcinate obtained in this example was found to be 95.3%.

[0059] Example 3 The method for improving the soluble zinc content of zinc roasted sand provided in this embodiment specifically includes: S301: Take 15.17 kg of industrial-grade ammonium sulfate and 4.33 kg of industrial-grade calcium oxide (the mass ratio of ammonium sulfate to calcium oxide is 3.5:1), mix them evenly to obtain an activator. Add the above activator to the fluidized bed cooler overflowing from the boiling furnace (zinc calcined sand temperature 1000℃), wherein the amount of calcium oxide added is 1.08 times the theoretical reaction amount of SiO2 in the zinc calcined sand, stir and activate for 30 min to obtain primary treated sand.

[0060] S302: The primary treated sand is fed into a cooling cylinder, and industrial-grade CO2 is introduced into the cooling cylinder. By adjusting the nitrogen flow rate, the internal air is replaced while the system temperature is stabilized at 800 ℃, and the oxygen content in the cooling cylinder is controlled at 2.8%. SO2 gas with a volume fraction of 99.5% is introduced to carry out a reduction reaction for 45 min. After the reaction is completed, A3-modified zinc calcined sand is obtained.

[0061] The solubility of the A3-modified zinc calcinate obtained in this example was found to be 95.7%.

[0062] In addition, to verify the overall performance of the methods provided in the above embodiments, this application provides the following comparative examples for detailed explanation.

[0063] Comparative Example 1 The method composition ratio, preparation operation, and process parameters provided in this comparative example are basically the same as those in Example 3. The difference is that only ammonium sulfate is used as the activator in this comparative example. After the reaction is completed, B1-modified zinc calcinate is obtained.

[0064] Comparative Example 2 The method composition ratio, preparation operation, and process parameters provided in this comparative example are basically the same as those in Example 3. The difference is that no inert gas is introduced in this comparative example, that is, the reduction reaction is carried out in the air with an oxygen content of 21%. After the reaction is completed, B2-modified zinc calcinate is obtained.

[0065] The soluble zinc content described in this application is determined using a conventional acid leaching method common in the zinc metallurgical industry. The specific process is as follows: A certain mass of modified zinc calcined sand sample is weighed and placed in a dilute sulfuric acid leaching system (liquid-to-solid ratio ≥ 5:1, sulfuric acid concentration 150~200 g / L, leaching temperature 60~80 ℃, stirring rate 300~400 r / min). After leaching at a constant temperature for 1~2 h, solid-liquid separation is achieved using vacuum filtration. The mass concentration of zinc ions in the leaching solution is determined using an atomic absorption spectrophotometer, and the mass of leached zinc is calculated. The total zinc mass in the sample is determined using an X-ray fluorescence spectrometer.

[0066] Finally, the test results were obtained by calculating the soluble zinc rate as (leaked zinc mass / total zinc mass of the sample) × 100%.

[0067] Table 1 shows a comparison of the soluble zinc rate effects of the embodiments and comparative examples of this application: Table 1 Comparison of treatment effects

[0068] By comparing the soluble zinc rate of the examples and comparative examples, both Comparative Example 1 and Comparative Example 2 were lower than that of Example 3. Compared with Comparative Example 1, which used only ammonium sulfate as an activator without adding alkaline oxides, Comparative Example 1 had a soluble zinc rate 4.9% lower than that of Example 3. This indicates that sulfate alone cannot effectively activate the insoluble phase structures such as zinc ferrite and zinc silicate. It cannot inhibit the formation of zinc silicate from the source through the reaction of alkaline oxides with SiO2, nor can it form a synergistic effect with sulfate to enhance the destructive effect on the zinc ferrite lattice. It can only achieve a limited increase in zinc dissolution through sulfate decomposition, ultimately resulting in a significantly limited improvement in the soluble zinc rate.

[0069] Compared with Comparative Example 2, which did not introduce an inert gas and whose reduction reaction was carried out in an air atmosphere (oxygen content 21%), the soluble zinc rate in Comparative Example 2 was 4.5% lower than that in Example 3. This indicates that in an air environment, a high oxygen content can trigger multiple side reactions: on the one hand, the reducing gas SO2 is oxidized to SO3, reducing its reduction efficiency for zinc ferrite; on the other hand, the intermediate products such as FeO generated in the reduction reaction are rapidly oxidized to Fe2O3 / Fe3O4, and the insoluble phase is regenerated. At the same time, the stability of the reduction reaction cannot be guaranteed, ultimately resulting in a significant decrease in the soluble zinc rate.

[0070] This application can also be compared in terms of process energy consumption, raw material / reagent costs, leaching residue generation, industrial feasibility, and green metallurgy, specifically: Regarding process energy consumption: This application directly utilizes the residual heat of the high-temperature zinc calcined sand at 580-1000℃ to complete the activation and reduction reactions, and only finely adjusts the temperature by the flow rate of inert gas, without additional electric / thermal energy consumption, and the waste heat utilization rate is ≥90%.

[0071] Regarding raw material / reagent costs: The activator used in this application is industrial-grade sulfate / alkaline oxide, which is readily available and has a low unit price; the amount of activator added is controlled, there is no raw material redundancy, and the effective utilization rate is ≥95%.

[0072] Leaching residue production: This application breaks down the insoluble phases of zinc ferrite / zinc silicate from the source through activators and reduction reactions, allowing zinc to dissolve fully. Furthermore, the alkaline oxides react with SiO2 to generate calcium / magnesium silicate, without excessive alkaline oxides causing an increase in residue. The acid leaching residue yield is reduced by 1.5%-5% compared to the original roasted sand, and by more than 1% compared to existing technologies.

[0073] Green metallurgy: In this application, the SO3 generated from sulfate decomposition fully reacts with ZnO / FeO to form soluble sulfate, with no excess SO3. x Emissions and exhaust gas treatment load are reduced by more than 80%; this application does not generate heavy metals or waste acid; oxidation side reaction is suppressed: the oxidation rate (%) of reduction products (FeO / Fe3O4) can be characterized by phase detection. The oxidation rate of this application under inert atmosphere (O2≤2.8%) is ≤5%, while the oxidation rate of Comparative Example 2 under air atmosphere is ≥30%.

[0074] Industrial feasibility: The activation in this application is completed in a fluidized bed cooler and the reduction is completed in a cooling cylinder, which can be directly connected to the existing zinc metallurgical roasting production line without large-scale equipment modification costs; at the same time, the process parameters (temperature, time, gas concentration) are all within the industrial conventional controllable range, and the operation is easy.

[0075] Meanwhile, the modified zinc calcined ore of this application, because zinc exists in the form of soluble sulfate / zinc oxide, has a shorter acid leaching time of less than 1 hour (compared to 2-3 hours for the original calcined ore), a sulfuric acid consumption of more than 3%, and a zinc leaching rate of more than 1.2 times. It can be directly adapted to the existing acid leaching process without the need to adjust the process parameters.

[0076] In summary, the above embodiments and comparative examples fully demonstrate that the compound activator of sulfate and alkaline oxide used in this application, under an inert gas atmosphere with an oxygen volume fraction ≤2.8%, can break the structure of insoluble phases such as zinc ferrite and zinc silicate, while ensuring that the reduction reaction proceeds efficiently and stably, and can significantly increase the soluble zinc rate of zinc calcined sand to over 94%.

[0077] 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.

[0078] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for improving the soluble zinc content of zinc calcined sand, characterized in that, include: After mixing high-temperature zinc calcined sand with an activator, a primary treated sand is obtained; In an inert gas atmosphere, the primary processed sand is reduced using a reducing gas to obtain modified zinc calcined sand; The activator is a mixture of sulfate and basic oxide.

2. The method according to claim 1, characterized in that, The sulfates include one or more of sodium sulfate, potassium sulfate, calcium sulfate, and ammonium sulfate; The alkaline oxides include one or more of calcium oxide and magnesium oxide.

3. The method according to claim 2, characterized in that, The mass ratio of the sulfate to the basic oxide is (1.8-3.5):

1.

4. The method according to claim 1, characterized in that, The amount of alkaline oxide added in the activator is 1.02-1.08 times the SiO2 content in the high-temperature zinc calcined sand.

5. The method according to claim 1, characterized in that, The temperature of the high-temperature zinc calcined sand is 580-1000 ℃; The mixing time for the high-temperature zinc calcined sand and activator is 10-30 min.

6. The method according to claim 1, characterized in that, The inert gas includes one or more of nitrogen, argon, and CO2.

7. The method according to claim 1, characterized in that, The reducing gas is sulfur dioxide; The volume fraction of the reducing gas is 85%-99.5%.

8. The method according to claim 1, characterized in that, The volume fraction of oxygen in an inert gas atmosphere is ≤2.8%.

9. The method according to claim 1, characterized in that, The reduction temperature is 600-800 ℃, and the reduction time is 15-45 min.

10. The method according to claim 1, characterized in that, After the reduction is completed, the modified zinc calcined sand is cooled to room temperature, and an inert gas atmosphere is maintained during the cooling process. The soluble zinc content of the modified zinc calcinate is ≥94%.

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