A method and system for improving the grade of zinc oxide in the Wiltz process by heat treatment and cooling for energy saving.

Abstract

This invention discloses a heat treatment and controlled cooling energy-saving method for improving the grade of zinc oxide in the Wiltz process, belonging to the field of hazardous waste resource utilization technology. The method includes the treatment of dust-laden flue gas and the treatment of the resulting high-temperature kiln slag. This invention achieves full-component resource utilization by co-processing heat treatment and controlled cooling at the kiln tail with oxidative rapid cooling at the kiln head of zinc-lead hazardous waste. Specifically, precise temperature control at the kiln tail promotes the formation of high-purity crystalline structures in zinc oxide, increasing the product grade by 10%~15% and significantly reducing the cost of subsequent wet purification. At the kiln head, oxidative rapid cooling converts FeO in the kiln slag into Fe3O4 through a chemically exothermic reaction, effectively recovering more than 50% of the waste heat and chemical energy of iron oxides, reducing system energy consumption by 10%~20%. This invention also provides a system for implementing the above method.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste resource utilization technology, and relates to an improvement method for the traditional Wiltz rotary kiln process, specifically to a quality control and energy-saving method and system for improving the grade of secondary zinc oxide in the Wiltz process. Background Technology

[0002] The Waelz Process is currently the mainstream pyrometallurgical resource recovery process for treating zinc- and lead-containing hazardous wastes such as electric arc furnace dust and hydrometallurgical zinc slag. These zinc- and lead-containing hazardous wastes have complex compositions, typically containing pig iron and other heavy metals in addition to zinc and lead.

[0003] The basic principle of the Wiltz process is as follows: in a rotary kiln, a carbonaceous reducing agent is used to reduce zinc and lead oxides in the material into metal vapor. The metal vapor reacts with oxygen during the flow of flue gas to generate zinc oxide and lead oxide dust. Finally, the secondary zinc oxide product is collected by the dust collection system, thus achieving the enrichment and recovery of zinc and lead components.

[0004] The existing traditional Wiltz process has the following three main problems in industrial applications: 1) The secondary zinc oxide product has low grade and insufficient economic value. Traditional flue gas cooling processes involve long cooling paths and inefficient cooling control. Under these conditions, zinc and lead vapors in the high-temperature flue gas are prone to oxidation reactions with excess air during cooling. Simultaneously, a large amount of large-particle dust impurities carried in the flue gas cannot be effectively separated and directly enters the dust collection system with the airflow, resulting in a generally low grade of secondary zinc oxide produced, only 45%–60%. The high impurity content of the product severely limits its economic value and subsequent applications.

[0005] 2) The waste heat from high-temperature kiln slag is not recovered, and valuable components are not fully utilized, resulting in both energy waste and environmental risks. In traditional processes, the high-temperature kiln slag discharged from rotary kilns is usually directly water-quenched or stockpiled. The large amounts of carbon and iron resources and high-temperature heat contained in the slag are not effectively recovered and utilized, resulting in significant energy waste. At the same time, the heavy metals such as lead and zinc remaining in the slag cannot be further extracted, and direct stockpiling or disposal poses a potential risk of environmental leakage.

[0006] To address the aforementioned shortcomings, existing technologies have proposed some improvement solutions, but all of them have significant limitations: Chinese invention patent (patent number: ZL 201310309803.0) discloses a method for treating zinc leaching residue. This method simply sets up a flue gas cooling process to adapt to the temperature requirements of bag filter dust collectors, but does not carry out fine conditioning and temperature control for the high-temperature flue gas section, which makes it impossible to achieve efficient separation of zinc and lead components and impurities, thus making it difficult to effectively improve the grade of secondary zinc oxide products.

[0007] Befesa's SDHL process oxidizes iron in the kiln slag to ferrous oxide by introducing air at the end of the rotary kiln, while simultaneously preheating the air entering the kiln. However, the ferrous oxide generated by this process is not magnetic and cannot be directly recovered through magnetic separation. It needs to be further oxidized to magnetite (Fe3O4) before magnetic separation can be achieved. Furthermore, this process still uses the method of directly water quenching the high-temperature kiln slag, and the problem of waste heat is not solved.

[0008] In summary, existing Wiltz processes and their improvements cannot simultaneously achieve the multiple objectives of improving the grade of secondary zinc oxide, recovering waste heat from kiln slag, and efficiently utilizing iron resources. Therefore, developing an improved Wiltz process that can simultaneously address these issues has significant practical implications and engineering application value. Summary of the Invention

[0009] To address the above problems, this invention provides a quality control and energy-saving method and system for improving the grade of secondary zinc oxide produced by the Wiltz process.

[0010] The specific solution of the present invention is as follows: First, this invention provides a method for improving the grade of zinc oxide in the Wiltz process by quality conditioning, cooling, and energy saving, the technical solution of which is as follows: A method for improving the grade of secondary zinc oxide in the Wiltz process, characterized by conditioning and cooling for energy saving, includes the treatment of dust-laden flue gas and the treatment of the resulting high-temperature kiln slag. The treatment of dust-laden flue gas includes the following steps: The dust-laden flue gas is sequentially conditioned and cooled, separated by cyclone separation and cooled and recovered to obtain low-temperature flue gas containing zinc oxide and lead oxide dust and large-particle impurity dust. The large-particle impurity dust is then subjected to reduction and volatilization treatment and converted into secondary kiln slag. Gas-solid separation was performed on low-temperature flue gas containing condensed zinc oxide and lead oxide dust to obtain high-grade secondary zinc oxide and clean exhaust gas. The treatment of the obtained high-temperature kiln slag includes the following steps: The obtained high-temperature kiln slag was oxidized and rapidly cooled to obtain cooled kiln slag. The cooled kiln slag was quenched with water to obtain kiln slag rich in Fe3O4. The obtained high-temperature kiln slag includes primary kiln slag and secondary kiln slag; the dust-containing flue gas and primary kiln slag are obtained by reducing and volatilizing zinc- and lead-containing hazardous waste, reducing agents, and fluxing agents.

[0011] This invention achieves the resource utilization of all components by synergistically treating zinc-lead hazardous waste through kiln tail conditioning and controlled cooling combined with kiln head oxidation and rapid cooling. Specifically, precise temperature control at the kiln tail promotes the formation of high-purity crystalline structures in zinc oxide, increasing product grade by 10%–15% and significantly reducing the cost of subsequent wet purification. At the kiln head, the oxidation and rapid cooling process converts FeO in the kiln slag into Fe3O4 through an exothermic chemical reaction, effectively recovering over 50% of the waste heat and chemical energy from iron oxides, reducing system energy consumption by 10%–20%.

[0012] Preferably, in the reduction and volatilization process, the temperature of the reduction section is 1000~1200℃.

[0013] Preferably, the conditioning and cooling process includes: injecting a conditioning medium into the dust-laden flue gas, causing the dust-laden flue gas to drop from 900-1100℃ to 600-650℃ in 2-10 seconds, thereby obtaining the conditioned and cooled dust-laden flue gas.

[0014] More preferably, the conditioning medium includes atomized water.

[0015] More preferably, the injection pressure of the atomized water is 2~4MPa and the particle size is 20~200um.

[0016] More preferably, the cyclone separation includes: performing cyclone separation on the conditioned and cooled dust-laden flue gas to obtain purified dust-laden flue gas and large-particle dust impurities, wherein the inlet wind velocity of the cyclone separation is 10~12m / s.

[0017] Further preferred embodiment of cooling recovery includes: using a cooling medium for forced cooling to reduce the temperature of the purified dust-laden flue gas to 150~200℃.

[0018] In a particularly preferred embodiment, the cooling medium is cold air, which is heated into hot air during the forced cooling process and then recycled back to the kiln head as primary air for combustion.

[0019] In a particularly preferred embodiment, the cooling medium is cold water, which absorbs heat during the forced cooling process, and the heat it carries is used for waste heat power generation.

[0020] Preferably, the oxidation and rapid cooling of the obtained high-temperature kiln slag includes: introducing natural cold air into the obtained high-temperature kiln slag and cooling it for 5 to 10 minutes to reduce the temperature of the obtained high-temperature kiln slag to 500 to 600°C.

[0021] More preferably, the natural cool air is oxygen-rich air or natural air.

[0022] More preferably, during the oxidative cooling process of the obtained high-temperature kiln slag, the natural cold air is heated to 900~1000℃ and recycled as secondary air for combustion at the kiln head.

[0023] Preferably, zinc- and lead-containing hazardous waste includes one or more of the following: electric furnace dust, zinc leaching residue, non-ferrous smelting dust, or low-grade zinc-containing tailings sand.

[0024] Preferably, the reducing agent includes: a fuel with fixed carbon.

[0025] More preferably, carbon-fixed fuels include coke powder and pulverized coal.

[0026] Preferably, the flux includes lime or cement kiln ash.

[0027] More preferably, the zinc-lead hazardous waste, reducing agent, and flux are pretreated before the reduction and volatilization treatment.

[0028] More preferably, the pretreatment includes mixing, granulation, or pelletizing.

[0029] Second, the present invention provides a system for implementing the above method, the technical solution of which is as follows: A tempering and cooling energy-saving system for improving the grade of secondary zinc oxide produced by the Wiltz process, used to achieve the above-mentioned tempering and cooling energy-saving method for improving the grade of secondary zinc oxide produced by the Wiltz process, comprising: The Wiltz rotary kiln is used for the reduction and volatilization treatment of zinc- and lead-containing hazardous waste, reducing agents, and fluxes to obtain dust-containing flue gas and primary kiln slag; it is also used for the reduction and volatilization treatment of large-particle dust to obtain secondary kiln slag. The flue gas conditioning device is used to condition and cool dusty flue gas, separate it into cyclones, and cool and recover it to obtain low-temperature flue gas with condensed zinc oxide and lead oxide dust and large-particle dust. The dust collection device is used to perform gas-solid separation on low-temperature flue gas containing condensed zinc oxide and lead oxide dust to obtain high-grade zinc oxide and clean exhaust gas. An oxidation quenching device is used to oxidize and quench the obtained high-temperature kiln slag to obtain cooled kiln slag. A water quenching device is used to quench and cool the cooled kiln slag to obtain kiln slag rich in Fe3O4.

[0030] Preferably, the flue gas conditioning device includes a conditioning and cooling unit, a selective impurity and dust removal unit, and a surface forced convection heat exchange unit connected in sequence, wherein, The conditioning and cooling unit is used to condition and cool the dust-laden flue gas to obtain the conditioned and cooled dust-laden flue gas. The selective dust removal unit is used to perform cyclone separation on the dust-laden flue gas after conditioning and cooling to obtain purified dust-laden flue gas and large-particle dust. The surface forced convection heat exchange unit is used to cool and recover the purified dust-laden flue gas, resulting in low-temperature flue gas with condensed zinc oxide and lead oxide dust.

[0031] Preferably, the dust collection device includes a baghouse dust collector.

[0032] Preferably, the oxidation quenching device further includes: a flow control valve and a fixed air-filled grate with an inclination angle of 10~15°.

[0033] Preferably, the surface forced convection heat exchange unit is also equipped with cleaning components such as ultrasonic cleaning and / or mechanical vibration.

[0034] The beneficial effects of this invention include: 1) Significantly enhance product quality and added value This invention, unlike traditional simple "cooling" dust collection, involves conditioning and cooling the high-temperature dusty flue gas containing zinc and lead at the kiln tail. By precisely controlling the temperature curve, it promotes the formation of a high-purity crystalline structure of zinc oxide. Furthermore, by selectively condensing and precisely removing impurities condensed on large dust particles, it significantly improves the quality of secondary zinc oxide products (by 10% to 15%). This not only increases the added value of the product but also significantly reduces the metallurgical costs of subsequent wet purification.

[0035] 2) Achieve optimal system energy consumption and cascade utilization of thermal energy. This invention employs an oxidative rapid cooling process at the kiln head to replace traditional water quenching of kiln slag. By blowing natural cold air (oxygen-enriched air or natural air) into the resulting high-temperature kiln slag, and utilizing the exothermic chemical reaction of FeO → Fe3O4 in the slag, combined with efficient air heat exchange, more than 50% of the waste heat and chemical energy of iron oxides in the kiln slag are effectively recovered. The recovered heat is used to preheat secondary air, reducing the overall energy consumption of the system by 10% to 20% compared to the traditional Wilhelm process. This achieves the dual benefits of "energy saving in calcination" and "iron extraction from kiln slag."

[0036] 3) Achieve full-component recycling of resources and environmental friendliness This invention achieves deep resource utilization of zinc- and lead-containing hazardous waste through a combined design of kiln tail product extraction and kiln head energy-saving iron extraction. While efficiently recovering zinc and lead volatiles, it also enriches and recovers iron from kiln slag, which would otherwise be discarded as solid waste, achieving "zero emissions" of hazardous waste and full-component resource utilization, thus eliminating the environmental burden of traditional processes.

[0037] 4) Forming significant economic and environmental synergies In this invention, the two steps of extracting high-value products at the kiln tail and recovering low-value waste heat at the kiln head are not simply superimposed, but rather a synergistic combination that mutually enhances each other. At the kiln tail, high-grade zinc oxide is obtained through temperature control and precise impurity separation, significantly improving the process's economics; at the kiln head, heat energy and iron recovery effectively reduce operating costs. This synergistic effect gives this invention significant advantages over the traditional Wilhelm process, both economically and environmentally. Attached Figure Description

[0038] Figure 1 A process flow diagram of a quality control and energy-saving method for improving the grade of secondary zinc oxide in the Wiltz process; Figure 2 A schematic diagram of a quality control and energy-saving system for improving the grade of secondary zinc oxide produced by the Wiltz process; Figure 3 This is a schematic diagram of the flue gas conditioning device.

[0039] Implementation methods The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0040] 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. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0041] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0042] Unless otherwise specified, all percentages in the examples and comparative examples are mass percentages.

[0043] Example 1 This embodiment provides a method for improving the grade of secondary zinc oxide in the Wiltz process by quality conditioning, cooling, and energy saving. The process flow diagram is shown below. Figure 1 As shown, the specific steps include: 1. Pretreatment: The electric furnace dust (containing 25% zinc, 2% lead, and 30% iron) is mixed with coke powder and lime, granulated, and then dried to obtain solid material.

[0044] In some implementations, zinc-lead hazardous waste is one or more of zinc leaching residue, non-ferrous smelting dust, or low-grade zinc-containing tailings sand.

[0045] In some embodiments, the reducing agent is pulverized coal.

[0046] In some embodiments, the flux is cement kiln ash.

[0047] 2. Reduction and volatilization: Solid materials are added to the Wiltz rotary kiln. At a reduction temperature of 1000℃, lead and zinc are reduced and volatilized into the flue gas, and oxidized into zinc oxide and lead oxide dust in the kiln, forming dust-laden flue gas discharged from the kiln tail; the unvolatilized solid materials move towards the kiln head to form primary kiln slag.

[0048] In some embodiments, the temperature of the reduction section is controlled at 1100°C or 1200°C.

[0049] 3. Treatment of dust-laden flue gas and treatment of the resulting high-temperature kiln slag.

[0050] The treatment of dust-laden flue gas includes: sequentially conditioning and cooling the flue gas, cyclone separation, cooling recovery, and gas-solid separation to obtain high-grade zinc oxide and clean exhaust gas. Specifically, A. Conditioning and Cooling: The dust-laden flue gas enters the conditioning and cooling unit, which is equipped with multi-stage spray guns that spray atomized water with a pressure of 2MPa and a particle size of 20um, so that the dust-laden flue gas is cooled from 950℃ to 650℃ in 10s, resulting in the conditioned and cooled dust-laden flue gas.

[0051] B. Cyclone Separation: The dust-laden flue gas after conditioning and cooling enters the selective dust removal unit, which is a cyclone type with an inlet air velocity controlled at 10m / s. Under this condition, large-particle-size (i.e., particle size of 25~80um and above) dust particles are centrifuged and removed, returned to the Wiltz kiln for reprocessing, and converted into secondary kiln slag. Zinc oxide and lead oxide dust particles with a particle size ≤20um will pass through with the flue gas, resulting in purified dust-laden flue gas. The separation behavior of dust particles with a particle size of 20~25um is uncertain; some are removed by centrifugation, while others pass through with the flue gas.

[0052] C. Cooling and Recovery: The purified dust-laden flue gas enters the surface forced convection heat exchange unit, which uses cold air or cold water for forced cooling to reduce the temperature of the purified dust-laden flue gas to 150℃. During this process, zinc oxide and lead oxide dust in the flue gas condense, resulting in low-temperature flue gas with condensed zinc oxide and lead oxide dust.

[0053] In some embodiments, the conditioning and cooling unit is equipped with multi-stage spray guns that spray atomized water with a pressure of 4MPa and a particle size of 200um, so that the flue gas can be rapidly reduced from 950°C to 600°C in 2s.

[0054] In some embodiments, the inlet velocity of the selective dust removal unit is controlled at 12 m / s.

[0055] In some embodiments, the surface forced convection heat exchange unit uses cold air or cold water for forced cooling to reduce the temperature of the purified dust-laden flue gas to 200°C.

[0056] In some embodiments, a temperature measuring point is provided at the outlet of the conditioning and cooling unit to adjust the atomized water flow rate according to the outlet temperature feedback signal, so as to achieve precise temperature control.

[0057] In some embodiments, the forced convection heat exchange unit is cooled by cold air, which is heated into hot air during the heat exchange process and then recycled as primary air for combustion at the kiln head.

[0058] In some embodiments, the surface forced convection heat exchange unit is cooled by cold water, which absorbs heat during the heat exchange process, and the heat it carries is used for waste heat power generation.

[0059] In some embodiments, the surface forced convection heat exchange unit uses a variable frequency fan and a temperature measuring point is set at the outlet. The fan frequency is adjusted by the feedback from the outlet temperature measuring point to accurately control the temperature of the purified dust-containing flue gas at the outlet.

[0060] In some embodiments, in order to prevent zinc oxide dust from agglomerating on the heat exchange surface, the surface forced convection heat exchange unit is also provided with cleaning components such as ultrasonic cleaning and / or mechanical rapping.

[0061] D. Gas-solid separation: Low-temperature flue gas containing zinc oxide and lead oxide dust enters the bag filter. After gas-solid separation, high-grade zinc oxide (mainly zinc oxide) and clean exhaust gas are obtained.

[0062] The high-temperature treatment of the obtained high-temperature kiln slag includes: the obtained high-temperature kiln slag is subjected to oxidative rapid cooling and water quenching to obtain kiln slag rich in Fe3O4. The obtained high-temperature kiln slag includes primary kiln slag and secondary kiln slag. Specifically, A. Oxidative quenching: The obtained high-temperature kiln slag enters the oxidative quenching device, where oxygen-enriched air is blown into it by a blower. The high-temperature kiln slag remains in the device for 5 minutes (i.e., the cooling time is 5 minutes), and is discharged after the temperature drops to 600℃, resulting in cooled kiln slag. Simultaneously, the oxygen-enriched air is heated to 1000℃ during the heat exchange process and can be reused as secondary air for combustion at the kiln head.

[0063] B. Water quenching: The cooled kiln slag is then quenched in a water quenching device to obtain kiln slag rich in Fe3O4.

[0064] In some embodiments, the obtained high-temperature kiln slag is kept in an oxidation quenching device for 10 minutes, and discharged after the temperature drops to 500°C to obtain cooled kiln slag; at the same time, oxygen-enriched air is heated to 900°C during the heat exchange process.

[0065] In some embodiments, the obtained high-temperature kiln slag enters an oxidation quenching device, and natural air is blown into the obtained high-temperature kiln slag by a blower in the device.

[0066] In some embodiments, the blower flow rate can be precisely controlled to ensure that all iron in the kiln slag is oxidized to magnetic iron. Precise control includes variable frequency speed regulation of the blower and a flow control valve located below the grate in the device, which can automatically adjust the air volume according to the material layer thickness.

[0067] Experimental results: Using the method provided by this invention, the zinc oxide product obtained from dust collection contains 65%~72% zinc oxide (ZnO) and 5% lead (Pb), both superior to the traditional Wiltz process (ZnO is generally 55%~60%, and Pb is generally 4%~4.5%). Fe3O4-rich kiln slag, after magnetic separation, can yield iron concentrate with an iron content of 40%~50%. Furthermore, calculations show that the heat recovery per ton of slag is equivalent to 40~45 kg of standard coal.

[0068] Example 2 This embodiment provides a quality control and energy-saving system for improving the grade of secondary zinc oxide produced by the Wiltz process, and its structural schematic diagram is shown below. Figure 2 As shown. Includes: The Wiltz rotary kiln is used for the reduction and volatilization treatment of zinc- and lead-containing hazardous waste, reducing agents, and fluxes to obtain dust-containing flue gas and primary kiln slag; it is also used for the reduction and volatilization treatment of large-particle dust to obtain secondary kiln slag. The flue gas conditioning device is used to condition and cool dusty flue gas, separate it into cyclones, and cool and recover it to obtain low-temperature flue gas with condensed zinc oxide and lead oxide dust and large-particle dust. The dust collection device is used to perform gas-solid separation on low-temperature flue gas containing condensed zinc oxide and lead oxide dust to obtain high-grade zinc oxide and clean exhaust gas. An oxidation quenching device is used to oxidize and quench the obtained high-temperature kiln slag to obtain cooled kiln slag, wherein the obtained high-temperature kiln slag includes primary kiln slag and secondary kiln slag. A water quenching device is used to quench and cool the cooled kiln slag to obtain kiln slag rich in Fe3O4.

[0069] Specifically, the structural schematic diagram of the flue gas conditioning device is as follows: Figure 3 As shown, it includes a conditioning and cooling unit, a selective dust removal unit, and a surface forced convection heat exchange unit connected in sequence.

[0070] Among them, the conditioning and cooling unit is used to condition and cool the dust-laden flue gas to obtain the conditioned and cooled dust-laden flue gas; The selective dust removal unit is used to separate the dust-laden flue gas after conditioning and cooling by cyclone separation to obtain purified dust-laden flue gas. The surface forced convection heat exchange unit is used to cool and recover the purified dust-laden flue gas, resulting in low-temperature flue gas with condensed zinc oxide and lead oxide dust.

[0071] In some embodiments, the dust collection device is a baghouse dust collector.

[0072] In some embodiments, the oxidation quenching device further includes a flow control valve and a fixed air-filled grate with an inclination angle of 10-15°. The resulting high-temperature kiln slag is piled up on the air-filled grate via a slope to form a material layer of a certain thickness (generally 500-800 mm). The cold air (including oxygen-enriched air or natural air) blown in by the blower penetrates the material layer from the bottom of the grate and is heated during the heat exchange process, and is reused as secondary air for combustion at the kiln head.

[0073] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for improving the grade of secondary zinc oxide in the Wiltz process by quality conditioning and cooling for energy saving, characterized in that, This includes the treatment of dust-laden flue gas and the treatment of the resulting high-temperature kiln slag. The treatment of the dust-laden flue gas includes the following steps: The dust-laden flue gas is sequentially subjected to conditioning and cooling, cyclone separation and cooling recovery to obtain low-temperature flue gas with condensed zinc oxide and lead oxide dust and large-particle impurity dust. The large-particle impurity dust is then subjected to reduction and volatilization treatment and converted into secondary kiln slag. The low-temperature flue gas containing condensed zinc oxide and lead oxide dust is subjected to gas-solid separation to obtain high-grade secondary zinc oxide and clean exhaust gas. The treatment of the obtained high-temperature kiln slag includes the following steps: The obtained high-temperature kiln slag is subjected to oxidative rapid cooling to obtain cooled kiln slag; The cooled kiln slag was then water-quenched to obtain kiln slag rich in Fe3O4. The obtained high-temperature kiln slag includes the primary kiln slag and the secondary kiln slag; the dust-laden flue gas and the primary kiln slag are obtained by reducing and volatilizing zinc- and lead-containing hazardous waste, reducing agents, and fluxing agents.

2. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 1, characterized in that, In the reduction and volatilization process, the temperature of the reduction section is 1000~1200℃.

3. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 1, characterized in that, The conditioning and cooling process includes: injecting a conditioning medium into the dust-laden flue gas to reduce the temperature of the dust-laden flue gas from 900-1100℃ to 600-650℃ in 2-10 seconds, thereby obtaining the conditioned and cooled dust-laden flue gas.

4. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 3, characterized in that, The conditioning medium includes atomized water; the injection pressure of the atomized water is 2~4MPa, and the particle size is 20~200um.

5. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 3, characterized in that, The cyclone separation includes: performing cyclone separation on the conditioned and cooled dust-laden flue gas to obtain purified dust-laden flue gas and large-particle dust impurities, wherein the inlet wind velocity of the cyclone separation is 10~12m / s.

6. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 5, characterized in that, The cooling recovery includes: using a cooling medium for forced cooling to reduce the temperature of the purified dust-laden flue gas to 150~200℃.

7. The method for improving the grade of secondary zinc oxide in the Wiltz process by quality control and energy saving according to claim 1, characterized in that, The oxidation and rapid cooling of the obtained high-temperature kiln slag includes: introducing natural cold air into the obtained high-temperature kiln slag and cooling it for 5-10 minutes to reduce the temperature of the obtained high-temperature kiln slag to 500-600℃.

8. A quality control and energy-saving system for improving the grade of secondary zinc oxide produced by the Wiltz process, characterized in that, The system is used to implement the quality control and energy-saving method for improving the grade of secondary zinc oxide by the Wiltz process as described in any one of claims 1-7, including: The Wiltz rotary kiln is used for the reduction and volatilization treatment of zinc- and lead-containing hazardous waste, reducing agents, and fluxes to obtain dust-containing flue gas and primary kiln slag; it is also used for the reduction and volatilization treatment of large-particle dust to obtain secondary kiln slag. The flue gas conditioning device is used to condition and cool dusty flue gas, separate it into cyclones, and cool and recover it to obtain low-temperature flue gas with condensed zinc oxide and lead oxide dust and large-particle dust. The dust collection device is used to perform gas-solid separation on low-temperature flue gas containing condensed zinc oxide and lead oxide dust to obtain high-grade zinc oxide and clean exhaust gas. An oxidation quenching device is used to oxidize and quench the obtained high-temperature kiln slag to obtain cooled kiln slag. A water quenching device is used to quench and cool the cooled kiln slag to obtain kiln slag rich in Fe3O4.

9. The quality control and energy-saving system for improving the grade of secondary zinc oxide produced by the Wiltz process according to claim 8, characterized in that, The flue gas conditioning device includes a conditioning and cooling unit, a selective dust removal unit and a surface forced convection heat exchange unit connected in sequence. The conditioning and cooling unit is used to condition and cool the dust-laden flue gas to obtain the conditioned and cooled dust-laden flue gas. The selective dust removal unit is used to perform cyclone separation on the conditioned and cooled dust-laden flue gas to obtain purified dust-laden flue gas and large-particle dust. The surface forced convection heat exchange unit is used to cool and recover the purified dust-laden flue gas to obtain low-temperature flue gas with condensed zinc oxide and lead oxide dust.

10. The quality control and energy-saving system for improving the grade of secondary zinc oxide using the Wiltz process according to claim 8, characterized in that, The oxidation quenching device also includes a flow control valve and a fixed air-filled grate with an inclination angle of 10~15°.

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