A steel dust sludge dezincification and collection device, method and slag material

Abstract

The present disclosure provides a steel dust and sludge dezincification and collection device, method and slag. The device comprises a heating and volatilization unit and a cooling and collection unit. The heating and volatilization unit comprises a furnace tube, a primary heating zone, a secondary heating zone and a crucible. The crucible is provided with a through hole at the bottom and is suspended in the furnace tube. The primary heating zone and the secondary heating zone are respectively arranged at the periphery of the lower segment and the upper segment of the furnace tube. The top outlet of the furnace tube is connected to the cooling and collection unit. The corresponding method comprises: loading the mixed and granulated material into the gas-permeable crucible; placing the crucible in the primary heating zone under an inert or reducing atmosphere, and heating to reduce and volatilize the zinc compounds; at the same time, the secondary heating zone forms a thermal barrier to prevent premature condensation of zinc vapor; the volatilized high-temperature zinc vapor enters the cooling and collection unit to condense into metallic zinc and is collected. The present disclosure solves the problems of uneven gas-solid contact, easy condensation and blockage of zinc vapor in the conveying pipeline, low collection efficiency and high energy consumption, and realizes efficient and high-purity recovery of zinc in steel dust and sludge.

Description

Technical Field

[0001] This disclosure relates to the field of metallurgical solid waste resource utilization and environmental protection technology, particularly to a device, method, and slag material for zinc removal and collection of steel dust and sludge during the steel smelting process. Background Technology

[0002] The steel industry is the foundation of the national economy, but its production process generates large amounts of iron-containing dust and sludge, which contains high concentrations of harmful elements such as zinc, lead, potassium, and sodium. In particular, converter and electric arc furnace dust can contain 5% to 30% zinc. If this zinc-containing dust and sludge is directly returned to the sintering or ironmaking process, zinc will accumulate in the blast furnace, leading to furnace lining erosion, poor furnace operation, increased energy consumption, and severely limiting the blast furnace's lifespan. If it is stockpiled or landfilled, it will cause serious land occupation and heavy metal environmental pollution risks. Therefore, zinc removal treatment of steel dust and sludge to achieve zinc resource recovery and iron resource recycling is an inevitable requirement for the green, low-carbon, and sustainable development of the steel industry.

[0003] Currently, technologies for recovering zinc from steel dust and sludge are mainly divided into two categories: hydrometallurgy and pyrometallurgy. While hydrometallurgy offers better selectivity, it generally suffers from problems such as long processes, high reagent consumption, severe equipment corrosion, and the generation of large amounts of difficult-to-treat waste liquid, posing challenges to both economic efficiency and environmental friendliness. In contrast, pyrometallurgy, especially the high-temperature volatilization method based on the carbothermic reduction principle, has become the mainstream technology for treating zinc-containing dust and sludge in industry due to its large processing capacity, fast reaction speed, and relatively mature process. However, traditional pyrometallurgical zinc removal technologies still face several significant technical bottlenecks: 1. Zinc vapor condensation and equipment blockage: Zinc has a boiling point of 907℃. After reduction and volatilization, zinc vapor is highly susceptible to condensation as it migrates to lower temperatures, causing it to drop below its dew point. This condensation often occurs on the inner walls of refractory materials in kilns or pipelines, forming hard nodules. This not only results in zinc loss and reduced recovery rates but also severely blocks airflow channels, increases system resistance, and may even force equipment shutdown for cleaning, significantly impacting operating rates and equipment lifespan.

[0004] 2. Energy efficiency and collection purity issues: To ensure the full volatilization of zinc, traditional processes often require maintaining the entire reaction zone at a high temperature, resulting in huge energy consumption. At the same time, zinc vapor is discharged along with gases such as CO and CO2. The efficiency of the condensation collection system and its ability to separate different condensation products are limited, leading to low zinc recovery rates and the need to improve the purity of the collected crude zinc and zinc oxide, resulting in high subsequent refining costs. Summary of the Invention

[0005] Therefore, this disclosure provides a device, method, and slag material for zinc removal and collection of steel dust and sludge, in order to at least solve the technical problem of zinc vapor easily condensing midway and affecting efficiency in the prior art.

[0006] The first aspect of this disclosure provides a steel dust dezincification and collection device, including a heating and volatilization unit and a cooling and collection unit. The heating and volatilization unit includes a furnace tube, a primary heating zone, a secondary heating zone, and a crucible. A through hole is opened at the bottom of the crucible and it is suspended inside the furnace tube. The primary heating zone and the secondary heating zone are respectively located on the periphery of the lower section and the upper section of the furnace tube. The top outlet of the furnace tube is connected to the cooling and collection unit.

[0007] In one alternative embodiment, the through holes at the bottom of the crucible are arranged in an array, with a diameter of 2 mm to 10 mm and a center-to-center distance of 5 mm to 20 mm between adjacent through holes. The total area of ​​all through holes accounts for 25% to 60% of the area at the bottom of the crucible.

[0008] In an optional embodiment, it also includes a support structure, a wire hanging bracket, and an automatic lifting device. The support structure is fixed to the outer frame of the furnace tube, and a wire hanging bracket is provided at its top. An automatic lifting device is provided at the bottom of the wire hanging bracket, and the crucible is hoisted at the bottom of the automatic lifting device.

[0009] In one alternative embodiment, the primary heating zone and the secondary heating zone are each independently sealed; the secondary heating zone is located directly above the primary heating zone and before the furnace tube outlet.

[0010] In one optional embodiment, the cooling collection unit includes a chiller and a fan. The outlet of the secondary heating zone is connected to a collection box. The outlet of the collection box is connected to the chiller through a pipeline. A fan is installed on the pipeline. The air outlet of the collection box is connected to the air inlet of the chiller. The outlet of the chiller is connected to the inlet of the collection box. The chiller is connected to the exhaust gas purification system through an exhaust gas treatment interface.

[0011] A second aspect of this disclosure provides a method for zinc removal and collection of steel dust and sludge, based on the steel dust and sludge zinc removal and collection device provided in this disclosure, including the following steps: S1. Pretreatment: The zinc-containing steel dust and sludge to be treated are mixed evenly with a solid carbonaceous reducing agent in a certain proportion and made into granular material with a predetermined particle size. S2. Loading: Load the granular material obtained in step S1 into the crucible; S3. Furnace loading and atmosphere control: Transfer the crucible containing the material to the primary heating zone of the heating and volatilization unit; introduce an inert protective gas or reducing gas into the primary heating zone to establish and maintain the atmosphere required for the reaction; at the same time, turn on the cooling and collection unit. S4. Gradient heating and zinc volatilization: The temperature of the primary heating zone is controlled to rise to 950℃ to 1450℃, so that the zinc compounds in the material are reduced to generate zinc metal vapor; at the same time, the temperature of the secondary heating zone is controlled to be maintained at 950℃ to 1100℃, so that the rising zinc vapor remains gaseous when passing through the secondary heating zone, preventing it from condensing on the inner wall of the furnace tube. S5. Steam guidance and condensation collection: The fan drives the zinc vapor into the collection box, and the inside of the collection box is forcibly cooled by the cooling collection unit, so that the zinc vapor condenses into liquid or solid metallic zinc after contacting the cold wall surface and is deposited. S6. Post-processing: After the reaction is complete, stop heating and introduce inert protective gas to cool the equipment; collect the condensed zinc product and the residual zinc residue in the crucible.

[0012] In an optional embodiment, in step S4, the heating rate of the primary heating zone is 3°C / min to 15°C / min; the target temperature of the primary heating zone is 1200°C to 1350°C, and the target temperature of the secondary heating zone is 980°C to 1050°C; the temperature of the secondary heating zone is always not lower than 80% of the temperature of the primary heating zone and is higher than the boiling point of zinc.

[0013] In an optional embodiment, in step S4, after the target temperature is reached, a heat preservation treatment is required, and the heat preservation time is 30 minutes to 180 minutes; during the heat preservation period, the power of the secondary heating zone is adjusted to control its temperature fluctuation range within ±10℃.

[0014] In an optional embodiment, in step S5, the cooling collection unit is cooled by a closed-loop water cooling system, with the cooling water temperature controlled at 5°C to 30°C and the flow rate at 5 L / min to 20 L / min.

[0015] A third aspect of this disclosure is to provide a dezincified slag material obtained by processing steel dust using the method provided in this disclosure, which is then used in the steel smelting process or as a raw material for building materials.

[0016] This disclosure provides a zinc removal and collection device, method, and slag material for steel dust and sludge. The device includes a heating and volatilization unit and a cooling and collection unit. The heating and volatilization unit includes a furnace tube, a primary heating zone, a secondary heating zone, and a crucible. The crucible has a through hole at its bottom and is suspended inside the furnace tube. The primary and secondary heating zones are respectively located on the periphery of the lower and upper sections of the furnace tube. The top outlet of the furnace tube is connected to the cooling and collection unit. The corresponding method includes: after mixing and granulating, the material is loaded into a permeable crucible; under an inert or reducing atmosphere, the crucible is placed in the primary heating zone, and the temperature is raised to reduce and volatilize the zinc compounds; simultaneously, a thermal barrier is formed in the secondary heating zone to prevent premature condensation of zinc vapor; the volatilized high-temperature zinc vapor enters the cooling and collection unit, condenses into metallic zinc, and is collected. This disclosure solves the problems of uneven gas-solid contact, easy condensation and blockage of zinc vapor in the conveying pipeline, low collection efficiency, and high energy consumption, achieving efficient and high-purity recovery of zinc from steel dust and sludge. The process steps and equipment structure of this disclosure are synergistically optimized to create and maintain a physicochemical environment conducive to efficient zinc volatilization, smooth transport and rapid condensation, solving the problem of zinc vapor condensation and blockage, and enabling efficient zinc collection, low energy consumption, simple operation and stable operation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the main structure of a steel dust dezincification and collection device provided in an embodiment of this disclosure; Figure 2 This is a side view of a steel dust dezincification and collection device provided in an embodiment of the present disclosure; Figure 3 This is a schematic diagram of a method for zinc removal and collection of steel dust and sludge provided in an embodiment of this disclosure.

[0019] In the diagram: 101 - Furnace tube, 102 - Primary heating zone, 103 - Secondary heating zone, 104 - Crucible, 105 - Automatic lifting device, 106 - Wire hanging bracket, 107 - Support structure, 108 - Ladder, 109 - Inlet valve, 201 - Collection box, 202 - Gas outlet, 203 - Water outlet, 204 - Water inlet, 205 - Fan, 206 - Tail gas treatment interface, 207 - Chiller, 208 - Alkali absorption tower. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0021] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0023] Furthermore, the technical features involved in the different embodiments of this disclosure described below can be combined with each other as long as they do not conflict with each other.

[0024] This disclosure provides a device for removing zinc from steel dust and sludge and collecting it. See also... Figure 1 , Figure 2 The furnace tube 101 includes a heating and volatilization unit and a cooling and collection unit. The heating and volatilization unit includes a furnace tube 101, a primary heating zone 102, a secondary heating zone 103, and a crucible 104. The crucible 104 has a through hole at its bottom and is suspended inside the furnace tube 101. The primary heating zone 102 and the secondary heating zone 103 are respectively located on the periphery of the lower and upper sections of the furnace tube 101. The top outlet of the furnace tube 101 is connected to the cooling and collection unit.

[0025] In one embodiment provided in this disclosure, the through holes at the bottom of the crucible 104 are arranged in an array, with a hole diameter of 2 mm to 10 mm, a center-to-center distance of 5 mm to 20 mm between adjacent through holes, and the total area of ​​all through holes accounts for 25% to 60% of the bottom area of ​​the crucible.

[0026] Understandably, during loading, the diameter of the through-hole is no larger than the particle size of the material, allowing the material to naturally accumulate inside the crucible and form a permeable bed. Crucible 104 is made of alumina.

[0027] In one embodiment provided in this disclosure, a support structure 107, a wire hanging bracket 106, and an automatic lifting device 105 are also included. The support structure 107 is fixed to the outer frame of the furnace tube 101. The top of the support structure 107 is provided with a wire hanging bracket 106, and the bottom of the wire hanging bracket 106 is provided with an automatic lifting device 105. The bottom of the automatic lifting device 105 is used to suspend the crucible 104.

[0028] In one embodiment provided in this disclosure, the primary heating zone 102 and the secondary heating zone 103 are each independently sealed; the secondary heating zone 103 is located directly above the primary heating zone 102 and before the outlet of the furnace tube 101.

[0029] In one embodiment of this disclosure, the cooling collection unit includes a chiller 207 and a fan 205. The outlet of the secondary heating zone 103 is connected to a collection box 201. The outlet 203 of the collection box 201 is connected to the chiller 207 via a pipeline. The fan 205 is installed on the pipeline. The air outlet 202 of the collection box 201 is connected to the air inlet of the chiller 207. The outlet 203 of the chiller 207 is connected to the inlet 204 of the collection box 201. The chiller 207 is connected to an exhaust gas purification system via an exhaust gas treatment interface 206. The cooling water discharged from the outlet 203 of the chiller 207 enters the inlet 204 of the collection box 201, thereby cooling the collection box 201. After cooling and absorbing heat to raise its temperature, the circulating water returns to the chiller 207 through the outlet 203 of the collection box 201 for cooling circulation.

[0030] For example, the exhaust gas purification system may be an alkaline absorption tower 208.

[0031] This device can be inspected and maintained via ladder 108.

[0032] This disclosure provides a method for zinc removal and collection of steel dust and sludge, based on the steel dust and sludge zinc removal and collection device provided in this disclosure. (See also...) Figure 3 This includes the following steps: S1. Pretreatment: The zinc-containing steel dust and sludge to be treated are mixed evenly with a solid carbonaceous reducing agent in a certain proportion and made into granular material with a predetermined particle size. In this step, zinc-containing steel dust and sludge are mixed with a solid carbonaceous reducing agent at a certain mass ratio. After uniform mixing, an appropriate amount of binder is added to form pellets or granules, producing granular material with a particle size of 5–20 mm, which is then dried. This step aims to increase the material's permeability, improve reaction kinetics, and prevent fine powder from being carried away by the airflow.

[0033] S2. Loading: Load the granular material obtained in step S1 into crucible 104; In this step, the pretreated granular material is loaded into a dedicated alumina crucible 104. The crucible 104 is unique in that it has multiple uniformly arranged arrays of through-holes at its bottom. The material naturally accumulates within the crucible 104, forming a fixed bed with good gas permeability. This design ensures that the reactant gas can uniformly penetrate the entire material layer from bottom to top, greatly enhancing gas-solid mass and heat transfer and avoiding reaction dead zones found in traditional loading methods.

[0034] S3. Furnace loading and atmosphere control: Transfer the crucible 104 containing the material to the primary heating zone 102 of the heating and volatilization unit; introduce an inert protective gas or reducing gas into the primary heating zone 102 to establish and maintain the atmosphere required for the reaction; at the same time, turn on the cooling and collection unit. In this step, the crucible 104 loaded with materials can be smoothly and accurately lifted into the center of the vertical furnace tube 101 using an automatic lifting device 105, placing it in the constant temperature zone of the primary heating zone 102. For example, the automatic lifting device 105 can be a commercially available hydraulic lift, which can be operated by external remote control or buttons to lift and move the crucible 104. After sealing the furnace tube 101, the inlet spherical valve 109 is opened to introduce inert protective gases such as high-purity nitrogen and argon, or reducing gases such as CO and H2, or a mixture thereof, into the furnace tube 101. The gas flow rate is controlled at 0.5–5.0 L / min to remove air, establish the required reaction atmosphere, and carry the volatilized zinc vapor as a carrier gas. Simultaneously, the cold water circulation system of the cooling collection unit is started. In this disclosure, the cold water circulation system uses a chiller 207 and related pipelines to prepare for subsequent condensation.

[0035] S4. Gradient heating and zinc volatilization: The temperature of the primary heating zone 102 is controlled to rise to 950°C to 1450°C, so that the zinc compounds in the material are reduced to generate zinc metal vapor; at the same time, the temperature of the secondary heating zone 103 is controlled to be maintained at 950°C to 1100°C, so that the rising zinc vapor remains gaseous when passing through the secondary heating zone, preventing it from condensing on the inner wall of the furnace tube 101. First, the primary heating zone is heated to the target temperature at a rate of 5–10 °C / min, which is 950–1450 °C, preferably 1200–1350 °C. At this high temperature, compounds such as zinc oxide (ZnO) and zinc ferrite (ZnFe₂O₄) in the material are carbothermally reduced: ZnO(s) + C(s) → Zn(g) + CO(g), ZnFe₂O₄(s) + 4C(s) → Zn(g) + 2Fe(s) + 4CO(g). Zinc escapes in the form of vapor.

[0036] The secondary heating zone 103 is synchronously controlled. Located directly above the primary heating zone 102 and before the outlet of furnace tube 101, its temperature is independently controlled and maintained between 950 and 1100°C. This secondary heating zone forms a high-temperature "thermal barrier" or "thermal channel," playing a crucial role: it ensures that all zinc vapor rising from the primary heating zone 102 maintains a temperature above the boiling point of zinc as it passes through the upper part of furnace tube 101. This effectively inhibits the condensation or heterogeneous nucleation of zinc vapor on the relatively low-temperature inner wall of furnace tube 101, fundamentally solving the industry problem of zinc vapor clogging the transport channel. The independent and precise temperature control of the dual zones, compared to traditional single-zone heating, optimizes heat distribution and reduces overall energy consumption while ensuring reaction efficiency.

[0037] S5. Steam guidance and condensation collection: Fan 205 drives zinc vapor into collection box 201. The cooling collection unit forces the inside of collection box 201 to cool it, so that the zinc vapor condenses into liquid or solid metallic zinc after contacting the cold wall surface and is deposited. In this step, under the slight negative pressure of the fan 205 at the end of the cooling collection unit, the high-temperature gas containing zinc vapor flows through the high-temperature "hot channel" and quickly enters the connected collection box 201. The wall of the collection box 201 is continuously cooled by a closed-loop circulating cooling water system, and the water temperature is controllable. When the high-temperature zinc vapor comes into contact with the low-temperature wall of the collection box 201, rapid condensation occurs. By precisely controlling the cooling water temperature and flow rate, the condensation rate can be regulated, promoting the deposition of zinc in liquid or dense solid form, which is beneficial to improving the purity of the product and the convenience of subsequent collection. Studies have shown that rapid cooling helps to obtain a higher zinc recovery rate and affects the physical morphology of the product. The condensed metallic zinc accumulates at the bottom of the collection box 201, while the uncondensed exhaust gas is discharged from the outlet 202 above the collection box 201, connected to the chiller 207, and then connected to the exhaust gas treatment system via the exhaust gas treatment interface 206 for purification treatment to meet environmental emission requirements.

[0038] S6. Post-processing: After the reaction is completed, stop heating and introduce inert protective gas to cool the equipment; collect the zinc product obtained from condensation in the collection box 201 and the residual zinc-de-zinc residue in the crucible 104 respectively.

[0039] In this step, heating is turned off after the predetermined reaction time is reached. The apparatus is allowed to cool naturally or via a programmed cooling process while a protective gas supply continues. Once the temperature has dropped to a safe range, the collection box 201 is opened first, and the solidified zinc ingots or zinc powder are removed. Then, the crucible 104 is lifted from the furnace tube 101 using an automatic lifting device 105, and the dezincified residue is poured out. This residue has a zinc content that can be reduced to below 1%, and its main components are iron oxides and metallic iron. It can be used as a high-quality raw material for ironmaking or as building material, achieving a closed-loop cycle of iron elements.

[0040] In one embodiment provided in this disclosure, in step S1, the solid carbonaceous reducing agent is one or more of coke powder, coal powder or graphite powder, and its addition amount is such that the molar ratio of carbon to zinc in the mixture is fixed at 1.0.

[0041] In step S3, the inert protective gas is nitrogen or argon; the reducing gas is carbon monoxide, hydrogen, or a mixture thereof; the gas flow rate is controlled at 0.5 L / min to 5.0 L / min to maintain a slight positive pressure inside the furnace tube 101 and ensure that the reaction gas passes through the material layer. The transfer of the crucible 104 in step S3 is accomplished by an automatic lifting device 105, which is also used in step S6 to safely remove the reacted crucible 104 from the high-temperature furnace tube 101.

[0042] In one embodiment provided in this disclosure, in step S4, the heating rate of the primary heating zone 102 is 3°C / min to 15°C / min; the target temperature of the primary heating zone 102 is 1200°C to 1350°C, and the target temperature of the secondary heating zone 103 is 980°C to 1050°C; the temperature of the secondary heating zone 103 is always not lower than 80% of the temperature of the primary heating zone 102, and is higher than the boiling point of zinc.

[0043] In one embodiment provided in this disclosure, in step S4, after the target temperature is reached, a heat preservation treatment is required, and the heat preservation time is 30 minutes to 180 minutes; during the heat preservation period, the power of the secondary heating zone 103 is adjusted to control its temperature fluctuation range within ±10℃.

[0044] In one embodiment provided in this disclosure, in step S5, the cooling collection unit is cooled by a closed-loop water cooling system, such as a chiller 207 and related pipelines, with the cooling water temperature controlled at 5°C to 30°C and the flow rate at 5 L / min to 20 L / min.

[0045] The present disclosure will be further described below with reference to specific embodiment 1.

[0046] The raw material is converter dust from a steel plant. The chemical composition (wt%) of the converter dust is as follows: TFe content 35.2%, Zn content 12.8%, Pb content 0.9%, C content 2.1%, SiO2 content 4.5%, CaO content 8.3%, and moisture content <1%. Among them, TFe represents the total amount of all iron-containing compounds, and the rest are common elements or compounds.

[0047] S101. Pretreatment: Take 10 kg of dried dust and mix it evenly with 1.5 kg of coke powder with a particle size <1 mm. Add an appropriate amount of water and make green balls with a diameter of 10-15 mm on a disc pelletizer. Dry them in an oven at 105℃ for 4 hours.

[0048] S102. Loading: Load the dried pellets into the special alumina crucible 104, with the loading height being about 2 / 3 of the height of the crucible 104.

[0049] S103. Furnace Loading and Atmosphere Control: Activate the automatic lifting device 105 to slowly lower the crucible 104 into the 80mm inner diameter corundum furnace tube 101, positioning the bottom of the crucible 104 at the center of the primary heating zone 102. Close the furnace tube 101, open the inlet gas valve 109, and introduce high-purity nitrogen at a flow rate of 1.5 L / min as a protective gas for 10 minutes to displace the air inside the furnace tube 101. Start the chiller 207, set the cooling water temperature to 15℃ and the flow rate to 12 L / min, and turn on the blower 205 to maintain a slight negative pressure operation.

[0050] S104. Gradient Heating and Zinc Volatilization: Start heating. Control the primary heating zone 102 to heat up to 1300℃ at a rate of 8℃ / min, while simultaneously controlling the secondary heating zone 103 to heat up to 1000℃ at the same rate. After reaching the target temperature, start timing and hold for 90 minutes. During the holding period, the temperature of the secondary heating zone 103 is controlled at 1000±5℃. Switch the atmosphere to a mixture of nitrogen and carbon monoxide, adjusting the flow rate to 2.0 L / min to enhance the reducing atmosphere.

[0051] S105. Steam Guidance and Condensation Collection: High-temperature zinc vapor, guided by negative pressure, enters the water-cooled collection tank 201 through the 1000℃ secondary heating zone 103 and rapidly condenses. The exhaust gas is discharged through the outlet 202, connected to the chiller 207 for further cooling, and then connected to the exhaust gas treatment system, namely the alkaline absorption tower 208, through the exhaust gas treatment interface 206 for purification treatment.

[0052] S106. Post-processing: After the heat preservation is completed, turn off the heating power and switch back to pure nitrogen for programmed cooling. When the temperature of furnace tube 101 drops below 100℃, turn off the chiller 207 and the blower 205. Open furnace tube 101 and collection box 201, lift out crucible 104, and pour out the residue. The residue is in the form of porous sponge iron. Analysis shows that its zinc content is 0.8wt% and the iron grade has increased to 58.5%.

[0053] This disclosure provides an embodiment of a dezincified slag material obtained by processing steel dust and sludge using the method provided in this disclosure. The slag material can be used in the steel smelting process or as a building material raw material.

[0054] This disclosure is based on a device for zinc removal and collection of steel dust and sludge. The core steps of the method include: mixing and granulating zinc-containing dust and sludge with a reducing agent; loading the material into a special alumina crucible 104 with an array of through holes at the bottom; placing the crucible 104 in a primary heating zone 102 under an inert or reducing atmosphere and heating it to 950-1450°C to reduce and volatilize the zinc compounds; simultaneously, maintaining the temperature of the secondary heating zone 103 at 950-1100°C in the furnace tube 101 area above the material to form a thermal barrier to prevent premature condensation of zinc vapor; the volatilized high-temperature zinc vapor enters the cooling and collection unit under negative pressure, and is forcibly condensed into metallic zinc by circulating cooling water on the wall and collected. This disclosure utilizes a "bottom-ventilated crucible loading" method. Dual-zone gradient heating The synergistic process of "closed-loop forced condensation" solves key technical problems in traditional pyrometallurgical zinc removal, such as uneven gas-solid contact, easy condensation and blockage of zinc vapor in the conveying pipeline, low collection efficiency and high energy consumption, and realizes efficient and high-purity recovery of zinc from steel dust and sludge.

[0055] Specifically: 1. Extremely high zinc removal efficiency and recovery rate: The bottom-perforated crucible 104 ensures full contact between the reducing gas and the material. Combined with optimized high-temperature reaction conditions, the zinc volatilization rate remains stable at over 95%. The dual-temperature zone design, coupled with a highly efficient closed-loop water cooling system, effectively prevents the loss of zinc vapor during transportation, resulting in a zinc condensation recovery rate exceeding 90%, and an overall zinc recovery rate significantly higher than traditional processes.

[0056] 2. Completely solves the problem of equipment blockage: The "thermal barrier" formed by the secondary heating zone 103 is one of the core innovations of this disclosure. It actively maintains the high temperature of the zinc vapor transport path, keeping it in a gaseous state before entering the cooling and collection unit. This fundamentally eliminates the problem of zinc condensation and nodule formation on the inner walls of key components such as furnace tube 101 and valves, greatly improving the continuous operation stability and service life of the equipment, and reducing maintenance costs and downtime risks.

[0057] 3. Optimized Energy Efficiency: A dual-temperature zone independent temperature control strategy is adopted, applying the highest temperature only to the reaction zone, while maintaining a relatively low temperature in the conveying zone, but still above the boiling point of zinc. Compared with the traditional process of heating the entire large kiln to the highest temperature, this gradient heating mode can theoretically distribute heat energy more precisely, reduce ineffective heat loss, and has the potential to reduce energy consumption per unit product.

[0058] 4. High level of operational safety and automation: The entire process utilizes an automatic lifting device 105 for loading and unloading the crucible 104, achieving mechanization and automation of high-temperature material handling, greatly reducing the safety risks (such as high-temperature burns, dust exposure) and labor intensity of manual operation. The modular equipment design also facilitates maintenance and repair.

[0059] 5. Environmentally friendly and highly adaptable: The method is conducted in a closed system with centralized exhaust gas treatment, effectively controlling fugitive emissions of dust and harmful gases. The equipment can be flexibly designed for centralized processing in large steel enterprises, as well as for small and medium-sized steel plants or as a pilot-scale platform for technology verification, providing efficient solutions for application scenarios of different scales. Furthermore, this method has broader adaptability to the zinc content of raw materials.

[0060] 6. High product value and thorough resource utilization: The recovered product is metallic zinc ingots or high-grade zinc powder, with an economic value far exceeding that of crude zinc oxide powder produced by traditional processes. The residue after zinc removal has a high iron content and low levels of harmful elements, allowing it to be directly returned to the main steel production process, truly realizing the full-scale and high-value utilization of iron and zinc resources in dust and sludge.

[0061] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A device for zinc removal and collection of steel dust and sludge, characterized in that, It includes a heating and volatilization unit and a cooling and collection unit. The heating and volatilization unit includes a furnace tube, a primary heating zone, a secondary heating zone, and a crucible. The crucible has a through hole at its bottom and is suspended inside the furnace tube. The primary heating zone and the secondary heating zone are respectively located on the periphery of the lower and upper sections of the furnace tube. The top outlet of the furnace tube is connected to the cooling and collection unit.

2. The iron and steel dust dezincification and collection device according to claim 1, characterized in that, The through holes at the bottom of the crucible are arranged in an array, with a diameter of 2 mm to 10 mm and a center-to-center distance of 5 mm to 20 mm between adjacent through holes. The total area of ​​all through holes accounts for 25% to 60% of the area at the bottom of the crucible.

3. The iron and steel dust dezincification and collection device according to claim 1, characterized in that, It also includes a support structure, a wire hanging bracket, and an automatic lifting device. The support structure is fixed to the outer frame of the furnace tube, and a wire hanging bracket is provided at the top of the support structure. An automatic lifting device is provided at the bottom of the wire hanging bracket, and the crucible is suspended at the bottom of the automatic lifting device.

4. The iron and steel dust dezincification and collection device according to claim 1, characterized in that, The primary heating zone and the secondary heating zone are each independently sealed; the secondary heating zone is located directly above the primary heating zone and before the furnace tube outlet.

5. The iron and steel dust dezincification and collection device according to claim 1, characterized in that, The cooling collection unit includes a chiller and a fan. The outlet of the secondary heating zone is connected to a collection box. The outlet of the collection box is connected to the chiller through a pipeline. A fan is installed on the pipeline. The air outlet of the collection box is connected to the air inlet of the chiller. The outlet of the chiller is connected to the inlet of the collection box. The chiller is connected to the exhaust gas purification system through an exhaust gas treatment interface.

6. A method for zinc removal and collection of steel dust and sludge, based on the steel dust and sludge zinc removal and collection device according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Pretreatment: The zinc-containing steel dust and sludge to be treated are mixed evenly with a solid carbonaceous reducing agent in a certain proportion and made into granular material with a predetermined particle size. S2. Loading: Load the granular material obtained in step S1 into the crucible; S3. Furnace loading and atmosphere control: Transfer the crucible containing the material to the primary heating zone of the heating and volatilization unit; introduce an inert protective gas or reducing gas into the primary heating zone to establish and maintain the atmosphere required for the reaction; at the same time, turn on the cooling and collection unit. S4. Gradient heating and zinc volatilization: The temperature of the primary heating zone is controlled to rise to 950°C to 1450°C, so that the zinc compounds in the material are reduced to generate zinc metal vapor; at the same time, the temperature of the secondary heating zone is controlled to be maintained at 950°C to 1100°C, so that the rising zinc vapor remains gaseous when passing through the secondary heating zone, preventing it from condensing on the inner wall of the furnace tube. S5. Steam guidance and condensation collection: The fan drives the zinc vapor into the collection box, and the inside of the collection box is forcibly cooled by the cooling collection unit, so that the zinc vapor condenses into liquid or solid metallic zinc after contacting the cold wall surface and is deposited. S6. Post-processing: After the reaction is complete, stop heating and introduce inert protective gas to cool the equipment; collect the condensed zinc product and the residual zinc residue in the crucible.

7. The method for zinc removal and collection of steel dust and sludge according to claim 6, characterized in that, In step S4, the heating rate of the primary heating zone is 3℃ / min to 15℃ / min; the target temperature of the primary heating zone is 1200℃ to 1350℃, and the target temperature of the secondary heating zone is 980℃ to 1050℃; the temperature of the secondary heating zone is always not lower than 80% of the temperature of the primary heating zone and is higher than the boiling point of zinc.

8. The method for zinc removal and collection of steel dust and sludge according to claim 6, characterized in that, In step S4, after reaching the target temperature, a heat preservation treatment is required, with a heat preservation time of 30 to 180 minutes. During the heat preservation period, the power of the secondary heating zone is adjusted to control the temperature fluctuation range within ±10℃.

9. A method for zinc removal and collection of steel dust and sludge according to claim 6, characterized in that, In step S5, the cooling collection unit is cooled by a closed-loop water cooling system, with the cooling water temperature controlled at 5°C to 30°C and the flow rate at 5 L / min to 20 L / min.

10. A dezincified slag material obtained by treating steel dust and sludge using the steel dust and sludge dezincification and collection method described in claim 6, characterized in that, The slag is fed into the steel smelting process or used as a raw material for building materials.

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