Zinc smelting system and method based on retired cement kiln

Abstract

The invention discloses a zinc smelting system and method based on an out-of-service cement kiln, and the zinc smelting system is based on facility reconstruction of the out-of-service cement kiln and comprises a material pretreatment unit, a preheating and roasting unit, a heat supply unit, a roasting slag treatment unit and a flue gas treatment unit, a first air pipe is connected between a first cyclone cylinder and a second cyclone cylinder of the preheating and roasting unit, a discharging pipe of the second cyclone cylinder and a discharging pipe of a third cyclone cylinder are combined and then connected with a discharging pipe of a rotary kiln, a smoke chamber is arranged at the tail end of the rotary kiln and connected with a settling chamber, and the settling chamber is connected with the third cyclone cylinder. A kiln head of the rotary kiln is connected with a grate cooler, a second air pipe is connected between the end, close to the kiln head of the rotary kiln, of the grate cooler and the second cyclone, a discharging pipe of the first cyclone is communicated with the second air pipe, and the first air pipe is communicated with a discharging pipe of the material pretreatment unit. Materials entering the rotary kiln are preheated in advance by mainly utilizing airflow subjected to heat exchange of the grate cooler, so that the fire coal consumption of the rotary kiln is reduced.

Description

Technical Field

[0001] The present application relates to the technical fields of solid waste resource utilization and non-ferrous metal smelting, and in particular to a zinc smelting system and method based on retired cement kilns. Background Art

[0002] In the metallurgical industry, the disposal of zinc- and alkali-metal-containing dust and mud (such as steel dust and mud, zinc smelting slag, hot-dip galvanizing slag, etc.) is a common problem. If this type of solid waste is not handled properly, it will not only cause a waste of zinc resources and environmental pollution, but may also threaten the safe operation of the blast furnace due to the circulation and enrichment of zinc and alkali metals in the blast furnace system. The current mainstream disposal processes include cold-pressed pellets, rotary kilns, and rotary hearth furnaces, but each has its limitations: although the rotary kiln process is widely used and mature, it has problems such as easy ring formation in the kiln and limited room for improvement in dezincification efficiency; although the rotary hearth furnace process has high dezincification efficiency, it requires large equipment investment and high energy consumption, and the sulfur content of the product limits its application; other processes, such as the cold-pressed pellet process, are limited by the content of harmful elements and steelmaking applicability, while the small blast furnace process and the new melting furnace process are significantly restricted by industrial policies.

[0003] In the building materials industry, environmental protection upgrades and capacity optimization are leading to the gradual elimination of 2,000t / d and 2,500t / d cement production lines. This has resulted in the idleness of core equipment such as rotary kilns, preheaters, and coolers, as well as supporting facilities. How to efficiently utilize these idle resources and achieve industrial transformation has become a pressing challenge for the industry.

[0004] Traditional zinc smelting processes face problems such as high cost, high energy consumption, and insufficient solid waste resource utilization. The idleness of retired cement kilns causes asset waste, and there is a lack of a systematic solution that combines the disposal of metallurgical solid waste with the reuse of retired cement kilns. Summary of the Invention

[0005] To this end, the present application provides a zinc smelting system and method based on retired cement kilns to solve the technical problems in the prior art of high equipment investment cost, high energy consumption, insufficient solid waste resource utilization, and idle retired cement kilns in the building materials industry for zinc smelting.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] A first aspect of the present invention provides a zinc smelting system based on a retired cement kiln. The zinc smelting system is based on the facility reconstruction of the retired cement kiln and includes: a material pretreatment unit for pre-homogenizing the material and storing the homogenized material, and proportioning the zinc-containing waste and reduced coal;

[0008] The preheating and roasting unit includes a first cyclone, a second cyclone, a third cyclone, a smoke chamber, a sedimentation chamber, a rotary kiln, a grate cooler and a burner, wherein a first air duct is connected between the first cyclone and the second cyclone, and a discharge pipe of the second cyclone and a discharge pipe of the third cyclone are both connected to the discharge pipe of the rotary kiln, the smoke chamber is arranged at the kiln tail end of the rotary kiln, the top of the smoke chamber is connected to one end of the sedimentation chamber, and the other end of the sedimentation chamber is connected to the third cyclone, a kiln head cover is provided at the kiln head of the rotary kiln, the kiln head cover is used to connect the rotary kiln with the grate cooler and form a closed space, one end of the burner passes through the closed space and is inserted into the rotary kiln, a second air duct is connected between the second cyclone and the kiln head cover, the discharge pipe of the first cyclone is connected to the second air duct, and the first air duct is connected to the discharge pipe of the material pretreatment unit;

[0009] The roasting slag processing unit is used to process the roasting slag produced by the preheating and roasting units;

[0010] The flue gas treatment unit is used to treat the zinc-containing flue gas generated by the preheating and roasting units.

[0011] Optionally, the flue gas treatment unit includes a waste heat boiler, a desulfurization tower and a first dust collector, a first flue pipe is connected between the third cyclone and the desulfurization tower, a second flue pipe is connected between the desulfurization tower and the first dust collector, the waste heat boiler is connected in parallel to the first flue pipe and is connected to the desulfurization tower, and the first cyclone is connected to the first dust collector through the third flue pipe.

[0012] Optionally, the roasting slag processing unit includes a hammer crusher, a second dust collector and a slag storage, the hammer crusher is connected to the grate cooler, the second dust collector is arranged at one end of the grate cooler away from the rotary kiln, and the slag storage is used to store the slag crushed by the hammer crusher.

[0013] Optionally, a naturally drooping and retractable material blocking curtain is provided in the smoke chamber. The material blocking curtain is provided on a side of the smoke chamber close to the rotary kiln to prevent the material in the rotary kiln from being carried away by the smoke.

[0014] Optionally, a material retaining ring is provided on the inner wall side of the rotary kiln, and the height of the material retaining ring extends along the inner diameter of the rotary kiln.

[0015] Optionally, the preheating and roasting unit also includes a kiln tongue with an adjustable inclination angle, and the kiln tongue covers the cross-section of the smoke chamber, one end of the kiln tongue extends into the rotary kiln, and the kiln tongue includes an integrally formed tongue portion and a tube portion, the tube portion is a closed curved channel raised on the upper surface of the tongue portion, and the discharge pipe of the rotary kiln is connected to the tube portion.

[0016] A second aspect of the present invention provides a zinc smelting method based on a retired cement kiln, using a zinc smelting system based on a retired cement kiln provided by the first aspect of the present invention, and the specific method is as follows:

[0017] Homogenization, storage and batching of raw materials: the raw materials are pre-homogenized in the material pre-treatment unit, the pre-homogenized materials are stored and the zinc-containing waste and reduced coal are batched in proportion;

[0018] For preheating and roasting, the airflow in the kiln head hood enters the second cyclone through the second air duct, and the airflow in the second cyclone enters the first cyclone through the first air duct; the batched materials enter the first air duct, and under the action of the airflow, the materials enter the first cyclone and are preheated; the materials separated in the first cyclone enter the second air duct through its discharge pipe, and the materials enter the second cyclone and are preheated under the action of the airflow; when the temperature of the materials in the second cyclone reaches above 600℃, the materials in the second cyclone are sent to the second cyclone through its discharge pipe. The material is reduced and roasted in the rotary kiln, and the slag produced in the rotary kiln enters the grate cooler, and the generated flue gas enters the settling chamber through the smoke chamber; the slag is air-cooled in the grate cooler, and the air flow after heat exchange in the grate cooler enters the second cyclone through the second air duct; large particles in the flue gas settle in the settling chamber and enter the rotary kiln again, and the flue gas in the settling chamber enters the third cyclone and is separated in the third cyclone. The large particles of dust are returned to the rotary kiln through the discharge pipe of the third cyclone and the discharge pipe of the rotary kiln;

[0019] Slag treatment: the slag in the grate cooler enters the roasting slag treatment unit, which processes the slag;

[0020] Flue gas treatment: the flue gas in the third cyclone and the first cyclone enters the flue gas treatment unit respectively, the flue gas treatment unit treats the flue gas and obtains secondary zinc oxide product.

[0021] Optionally, the flue gas treatment includes: the flue gas in the third cyclone enters the desulfurization tower from the first flue pipe, and the remaining flue gas in the desulfurization tower enters the first dust collector from the second flue pipe; or / and the flue gas in the third cyclone enters the waste heat boiler from the first flue pipe, and the remaining flue gas of the waste heat boiler then enters the desulfurization tower, and the remaining flue gas in the desulfurization tower enters the first dust collector from the second flue pipe; the airflow in the first cyclone enters the first dust collector from the third flue pipe.

[0022] Optionally, the slag treatment includes: the slag in the grate cooler enters the hammer crusher for crushing, and the crushed slag is transported to the slag storage for storage; the hot air from the end of the grate cooler away from the rotary kiln enters the second dust collector for treatment.

[0023] Optionally, the zinc smelting method further comprises further smelting the secondary zinc oxide product, and the specific method is as follows:

[0024] The secondary zinc oxide product is directly placed in the first cyclone and the second cyclone in sequence; the burner supplies heat to the rotary kiln to control the temperature of the rotary kiln to be less than 900°C, and the secondary zinc oxide product in the second cyclone is sent into the rotary kiln for roasting through its discharge pipe; the secondary zinc oxide product in the rotary kiln becomes zinc roasted sand and is collected by a grate cooler.

[0025] Compared with the prior art, this application has at least the following beneficial effects:

[0026] This application provides a zinc smelting system based on retired cement kilns. By innovatively renovating retired cement kiln facilities and collaboratively designing various functional units, it effectively solves multiple technical problems existing in the prior art, and has significant technical advantages and economic and environmental benefits. Specific beneficial effects are as follows:

[0027] 1. Significantly reduce equipment investment costs and revitalize idle resources. By making full use of the existing facilities (such as rotary kilns, grate coolers, smoke chambers and other main structures) of retired cement kilns in the building materials industry for adaptive reconstruction, there is no need to build new dedicated zinc smelting kilns, which greatly reduces the initial equipment investment of the zinc smelting production line. At the same time, it revitalizes a large number of idle retired cement kiln resources in the building materials industry and avoids the waste of social assets.

[0028] 2. The unique layout of the first and second air ducts primarily achieves heat exchange from the grate cooler to the second cyclone and then to the first cyclone. The high-temperature airflow from the grate cooler is transported directly through the second air duct to the second cyclone, where it undergoes heat exchange with the material within. The airflow within the second cyclone then continues through the first air duct to the first cyclone, where it undergoes another heat exchange with the material within the first cyclone. The low-temperature material within the first cyclone is connected to the second air duct via the discharge pipe and then enters the second cyclone for a second preheating. This process not only achieves a gradient cooling of the high-temperature hot air but also raises the preheating temperature of the material entering the rotary kiln, significantly reducing the rotary kiln's heat consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more intuitively illustrate the prior art and the present application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be considered as limiting conditions for implementing the present application; for example, based on the technical concepts disclosed in this application and the exemplary drawings, those skilled in the art are capable of easily making routine adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components).

[0030] Figure 1 A schematic diagram of a zinc smelting system based on a retired cement kiln provided in an embodiment of the present application;

[0031] Figure 2An axial partial cross-sectional view of a rotary kiln of a zinc smelting system based on a retired cement kiln provided in an embodiment of the present application;

[0032] Figure 3 A radial partial cross-sectional view of a rotary kiln of a zinc smelting system based on a retired cement kiln provided in an embodiment of the present application;

[0033] Figure 4 A schematic structural diagram of a kiln tongue of a zinc smelting system based on a retired cement kiln provided in an embodiment of the present application.

[0034] Description of reference numerals:

[0035] 1. First cyclone; 2. Second cyclone; 3. Third cyclone; 4. Smoke chamber; 5. Settling chamber; 6. Rotary kiln; 7. Grate cooler; 8. First air duct; 9. Second air duct; 10. Burner; 11. Waste heat boiler; 12. Desulfurization tower; 13. First dust collector; 14. First smoke pipe; 15. Second smoke pipe; 16. Third smoke pipe; 17. Hammer crusher; 18. Second dust collector; 19. Slag storage; 20. Material retaining curtain; 21. Material retaining ring; 22. Kiln tongue; 221. Tongue; 222. Pipe; 23. Pre-homogenization yard; 24. Batching station; 25. Homogenization storage; 26. Belt conveyor; 27. Discharge pipe of rotary kiln; 28. Hoist; 29. Chimney; 30. Fuel system; 31. Pulverized coal conveying pipeline; 32. Discharge pipe of material pretreatment unit; 33. Kiln head hood; a. Steam; b. Material transportation; c. Airflow. DETAILED DESCRIPTION

[0036] The present application will be further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0037] In order to maximize the use of idle equipment and facilities of retired cement kilns and carry out industrial transformation, while focusing on the company's solid waste resources and classifying and refining them for resource utilization, the technology for recycling retired cement kilns was born.

[0038] The technology for reusing retired kilns is to make full use of the sites, equipment and facilities of cement production, including rotary kilns, preheaters, coolers, various crushing and grinding systems, storage facilities and homogenization tanks, laboratories, control rooms, auxiliary facilities, etc., to innovate the technology for resource utilization of solid waste, so as to achieve the process of harmless disposal of solid waste and recovery of valuable components.

[0039] The following is combined with Figure 1-4 , this application is further described in detail through specific examples.

[0040] This embodiment provides a zinc smelting system based on a retired cement kiln, comprising: a material pretreatment unit, a preheating and roasting unit, a heat supply unit, a roasting slag treatment unit, and a flue gas treatment unit.

[0041] The material pretreatment unit is used to pre-homogenize the material and store the homogenized material, as well as to proportion the zinc-containing waste and reduced coal. The material pretreatment unit includes a pre-homogenization yard 23, a batching station 24 and a homogenization warehouse 25. Materials with large production volumes or materials with a certain moisture content are pre-homogenized through the pre-homogenization yard 23. The pre-homogenization principle adopts horizontal stacking and longitudinal cutting of the raw materials to ensure that the composition of different layers of materials is matched and homogenized. The main materials that have been pre-homogenized are transported to the main material warehouse in the batching station 24 for temporary storage. Other materials, such as different dry powder materials, are pressure-delivered to other material warehouses in the batching station 24 by transport vehicles. Each material in the batching station 24 is equipped with a metering device to adjust the delivery volume and batching ratio of different materials.

[0042] Among them, the raw material storage of the cement plant can be used to realize the classified storage of raw materials of different qualities, and the pre-homogenization yard 23 uses the limestone pre-homogenization yard 23 and equipment of the cement plant to complete the pre-homogenization of raw materials of different qualities, thereby achieving material homogeneity and stability.

[0043] The prepared materials are transported to the homogenization silo 25 for storage using the cement company's existing conveying facilities, such as belt conveyors 26 and elevators 28. Before entering the homogenization silo 25, adjustments can be made based on on-site production conditions, or the coarse product (secondary zinc oxide product) from the waste heat boiler 11, desulfurization tower 12, or first dust collector 13 can be added to adjust the zinc content of the materials in the homogenization silo 25. The homogenization silo 25 utilizes the cement plant's raw material silo, allowing for further homogenization of the materials before entering the preheating and roasting units through the principle of multi-point feeding and multi-point unloading. The discharge port of the homogenization silo 25 is equipped with metering facilities and material flow stabilization facilities.

[0044] Lead smelting slag, zinc smelting leaching slag, zinc-cobalt slag, zinc-copper slag, copper smelting and scrap copper recycling slag and fly ash, and fly ash from steel companies are used as zinc-containing solid wastes. The materials are sized, crushed, ground, and matched to control their specific surface area and reduce dust generation. After batching, the zinc content of the materials entering the rotary kiln 6 is guaranteed to be greater than 6%. Simultaneously, the sintering properties, silica content, and alumina content of the materials are controlled, and the liquid phase volume of the materials entering the kiln is designed to prevent ringing and crusting in the rotary kiln 6, which can lead to malfunctions and maintenance accidents.

[0045] Reducing coals such as carbon black, coke, anthracite, etc. are ground by the coal mill of the coal grinding system (the system of the original cement plant) and then enter the batching station 24 through the conveying facilities for batching, wherein zinc-containing waste and reducing coal are batched in proportion.

[0046] During the batching process, it is necessary not only to ensure the zinc content of the material entering the kiln, but also to ensure the liquid phase volume, iron oxide content, alkali content, silicate rate, lime saturation coefficient, aluminum oxygen rate, and trace element content in the material. The best control indicators can be matched according to the specific material composition to ensure that the material is easy to burn without crusting and egg formation, and to control the viscosity of the material.

[0047] Silicic acid rate:

[0048]

[0049] Aluminum oxygen rate:

[0050]

[0051] Lime saturation coefficient:

[0052]

[0053] The silicate content is as high as possible, greater than 0.5, the alumina content is greater than 0.1, and the lime saturation coefficient is greater than -0.6. The calorific value of the ingredients is controlled to be around 1200 kal / kg by controlling the carbon content, and the total iron content is controlled to be less than 30%.

[0054] The preheating and roasting unit includes a first cyclone 1, a second cyclone 2, a third cyclone 3, a smoke chamber 4, a settling chamber 5, a rotary kiln 6, a grate cooler 7 and a burner 10. The first cyclone 1 and the second cyclone 2 are connected to the first air duct 8. The discharge pipe of the second cyclone 2 and the discharge pipe of the third cyclone 3 are both connected to the discharge pipe of the rotary kiln 6. The smoke chamber 4 is arranged at the kiln tail end of the rotary kiln 6. The top of the smoke chamber 4 is connected to one end of the settling chamber 5. The settling chamber 5 is connected to the first cyclone 1 and the second cyclone 2. The other end of the chamber 5 is connected to the third cyclone 3. A kiln head hood 33 is provided at the kiln head of the rotary kiln 6. The kiln head hood 33 is used to connect the rotary kiln 6 with the grate cooler 7 and form a closed space. One end of the burner 10 passes through the closed space and is inserted into the rotary kiln 6. The second air duct 9 is connected between the second cyclone 2 and the kiln head hood 33. The discharge pipe of the first cyclone 1 is connected to the second air duct 9, and the first air duct 8 is connected to the discharge pipe 32 of the material pretreatment unit.

[0055] The roasting slag processing unit is used to process the roasting slag produced by the preheating and roasting units, and includes a hammer crusher 17, a second dust collector 18 and a slag storage 19. The hammer crusher 17 is connected to the grate cooler 7. The second dust collector 18 is arranged at the end of the grate cooler 7 away from the rotary kiln 6. The slag storage 19 is used to store the slag crushed by the hammer crusher 17.

[0056] The flue gas treatment unit is used to treat the zinc-containing flue gas generated by the preheating and roasting units, and includes a waste heat boiler 11, a desulfurization tower 12 and a first dust collector 13. A first flue pipe 14 is connected between the third cyclone 3 and the desulfurization tower 12, and a second flue pipe 15 is connected between the desulfurization tower 12 and the first dust collector 13. The waste heat boiler 11 is connected in parallel to the first flue pipe 14 and is connected to the desulfurization tower 12. The first cyclone 1 is connected to the first dust collector 13 through the third flue pipe 16.

[0057] Different from the existing general rotary kiln 6 smelting method of secondary zinc oxide, in this application, the first cyclone 1 and the second cyclone 2 are arranged outside the rotary kiln 6 to preheat the material entering the rotary kiln 6, and the cooling of the material is carried out in the grate cooler 7. The water quenching of the roasting slag is changed to air cooling to relieve the load of the rotary kiln 6, thereby improving the capacity of the rotary kiln 6 of the same specification and further reducing the heat consumption of roasting.

[0058] The coal grinding system of the cement plant realizes the fuel grinding when alternative fuels are needed and when supplementary fuels are needed.

[0059] The cement plant's clinker storage can be used as a slag storage 19. After being cooled by a grate cooler 7, the slag is crushed by a hammer crusher 17 and then transported by a chain bucket conveyor to the slag storage 19 for storage. The slag can then be further ground using the cement plant's cement mill system. After being ground and sorted, the slag is then stored in different locations.

[0060] The compressed air, electricity, and water required for this application are still provided by the original cement plant's utility system. The entire zinc smelting system in this application utilizes a central control room for monitoring, adjustment, and operation, improving the stability of the rotary kiln 6 calcination operation and reducing fluctuations. The original cement plant's laboratory system is also utilized to sample and test raw materials, slag, and products, adjust material mixes, and control product quality. The original cement plant's waste heat power generation system is retained, utilizing waste heat boiler 11 to cool flue gases and simultaneously generate steam a.

[0061] Cement plants typically lack desulfurization measures. The zinc smelting system of this application requires the addition of desulfurization equipment. Desulfurization utilizes a wet process, utilizing the cement plant's existing humidification tower, which is modified by injecting alkali solution or a solid desulfurizer. A reactive filler bed can be added to the humidification tower to form a desulfurization tower 12. The cement plant's dust collectors are functionally designed, with a first dust collector 13 and a second dust collector 18 installed separately to treat flue gas from different areas.

[0062] The core calcining equipment in cement plants (retired cement kilns) is the rotary kiln (6). The aspect ratio of the rotary kiln (6) is the primary factor affecting its calcination or roasting performance. In existing technology, the aspect ratio of rotary kilns (6) used in zinc smelting is generally around 15, while cement plants typically use a ratio of 15 or greater, fully compatible with zinc smelting processes. (Utilizing other ancillary facilities in retired cement kilns, preliminary assessments suggest that a φ4.0×60 rotary kiln producing 2,500 tons of cement clinker per day could be converted to secondary zinc oxide smelting, processing 500-1,000 tons of zinc-containing waste per day and 150,000 to 300,000 tons of zinc-containing waste annually. This technology is designed to process 200,000 tons of zinc-containing waste annually.)

[0063] The zinc smelting system of the present application generally divides the thermal system within the rotary kiln 6 from the kiln tail to the kiln head into three sections, from low to high temperature, namely the secondary preheating section, the high-temperature section, and the cooling section. The high-temperature section is the primary reaction section where zinc is reduced and precipitated. Zinc melts and volatilizes into the flue gas at a kiln temperature of 1100°C. The high-temperature section has a temperature of 1100-1300°C, the secondary preheating section has a temperature of 650-1000°C, and the cooling section is controlled at a temperature of 900-1000°C, thereby controlling ring formation in the rotary kiln 6. The cooling section is located in the first section of the rotary kiln 6, with the majority of the cooling being done in the grate cooler 7.

[0064] In the zinc smelting system of the present application, Figure 2 As shown, the smoke chamber 4 adopts a "vertical cabinet" type smoke chamber 4 with a large cross-section and a height greater than 3m, which ensures that the flue gas flow rate is within a certain range, can settle large particles of material, and at the same time prevent material dust from entering the flue gas, thereby minimizing the dust content. The discharge pipe of the rotary kiln 6 is connected to a kiln tongue 22 (i.e., "tongue") for the material to enter the rotary kiln 6 at one end close to the rotary kiln 6. The kiln tongue 22 is tilted and the tilt angle is adjustable, so that the angle at which the material enters the rotary kiln 6 can be adjusted, ensuring appropriate impact of the material and reducing dust. Specifically, the kiln tongue 22 covers the cross-section of the smoke chamber 4, and one end of the kiln tongue 22 extends into the rotary kiln 6. As shown Figure 4 As shown, kiln tongue 22 comprises an integrally formed tongue portion 221 and a tube portion 222. Tube portion 222 is a closed, curved channel protruding from the upper surface of tongue portion 221. The feed pipe of rotary kiln 6 is connected to tube portion 222. The angle of kiln tongue 22, adjustable at its angle, ensures adequate impact for incoming materials. Materials are conveyed through the closed, curved tube portion 222, minimizing the impact on the ventilation area of smoke chamber 4 and dust generation. Large particles falling from settling chamber 5 enter rotary kiln 6 directly through tongue portion 221.

[0065] like Figure 3As shown, a material retaining curtain 20 is installed in the smoke chamber 4. The material retaining curtain 20 is installed on the side of the smoke chamber 4 near the rotary kiln 6. The material retaining curtain 20 is hung from the top of the smoke chamber 4 and naturally hangs down from above. The material retaining curtain 20 has a rolling curtain function, which is used to prevent the material in the rotary kiln 6 from being carried away by the smoke. Specifically, the material retaining curtain 20 is composed of several heat-resistant steel chains. It is hung from the top of the smoke chamber 4 and naturally hangs down from above. At the same time, a connecting mechanism is designed to be raised and lowered from the outside, realizing the rolling curtain function, enhancing ventilation in the kiln. Alternatively, it can be used to adjust the ventilation area of the rotary kiln 6.

[0066] The kiln head and tail of the rotary kiln 6 are each equipped with a retaining ring 21, extending along the inner diameter of the rotary kiln 6. Specifically, the retaining ring 21 is made of an inorganic material that is resistant to high temperatures and wear. The retaining ring 21 is set at a height of 100 mm along the inner diameter of the rotary kiln 6. At the kiln tail, near the smoke chamber 4, it is located 300 mm from the end of the kiln tongue 22. This retaining ring 21 prevents material from moving toward the smoke chamber 4, maintaining the thickness of the material layer in the rotary kiln 6. At the kiln head, a retaining ring 21 is installed at the point where the burner 10 extends into the kiln, 1000 mm from the end of the burner 10. This retaining ring 21 extends the material residence time, ensures a certain cooling zone in the rotary kiln 6, and prevents the vitrification of the kiln slag.

[0067] The first cyclone 1 and the second cyclone 2 preheat the material to at least 600°C before entering the rotary kiln 6, thereby reducing the load on the rotary kiln 6, reducing the length of the rotary kiln 6, increasing the output of the rotary kiln 6, and further improving the heat recovery efficiency. The preheating adopts the first cyclone 1 and the second cyclone 2 in series, so that the hot air exchanges heat with the solid material, and the heat exchange efficiency with the material in the rotary kiln 6 is significantly improved. The hot air for heat exchange comes from the second air duct 9 connected to the kiln head hood 33. After heat exchange with the material, the temperature of the hot air is reduced to below 200°C, and it is discharged after entering the first dust collector 13. The first cyclone 1, the second cyclone 2, and the third cyclone 3 adopt a high-efficiency and low-resistance design, and the original cyclones and corresponding air ducts of the cement enterprise are modified to optimize the local wind speed. The wind speed is reasonably designed and matched. Specifically, the zinc smelting system of the present application utilizes a cyclone of a certain specification, adopts a low wind speed, and preheats in advance. An adjustable spreading device is used in the first cyclone 1 and the second cyclone 2, that is, the cross-sectional wind speed of the first cyclone 1 and the second cyclone 2 is adjustable, wherein the cross-sectional wind speed is determined according to the particle size of the material.

[0068] It should be noted that, at the initial stage of operation of the rotary kiln 6, the rotary kiln 6 is first preheated by the burner 10, and the heat generated by the burner 10 enters the second air duct 9 through the kiln head hood 33, thereby realizing the initial preheating of the materials in the first cyclone 1 and the second cyclone 2. After the materials enter the rotary kiln 6, as the materials burn, the heat supply of the burner 10 can be stopped. At this time, the heat of the second air duct 9 mainly comes from the heat exchanged by the grate cooler 7.

[0069] Zinc-containing smoke and material dust emitted by the materials in the rotary kiln 6 exit the smoke chamber 4 of the rotary kiln 6 and then enter the settling chamber 5 (the settling chamber 5 is a modified decomposition furnace of a cement plant). The zinc-containing materials in the flue gas remain in the settling chamber 5 for a long time and are fully converted into zinc oxide. At the same time, as the flue gas velocity decreases, a portion of large particles of material settles down and enters the rotary kiln 6 again through the kiln tongue 22. The remaining majority of the material enters the third cyclone 3 for cyclone separation. After separation, the large particles of dust continue to enter the rotary kiln 6 to react again. The settling in the settling chamber 5 and the separation in the third cyclone 3 can significantly increase the yield of secondary zinc oxide. The flue gas containing a large amount of secondary zinc oxide products passes through the third cyclone 3 and enters the waste heat boiler 11, then enters the desulfurization tower 12, and finally passes through the first dust collector 13 to collect the products. The remaining flue gas is dust-removed and discharged after meeting the standards. The secondary zinc oxide products are collected in this process.

[0070] The waste heat boiler 11, as an auxiliary device, can significantly recover heat, further reducing smelting heat consumption. Cement plants are generally equipped with a waste heat power generation boiler at the kiln tail. The zinc smelting system of this application can utilize retired waste heat power generation equipment to direct the flue gas from the third cyclone 3 through the first flue pipe 14 into the waste heat boiler 11. The flue gas is cooled from 700-800°C to below 200°C, which is then used for power generation and grid connection or to provide steam a. The waste heat boiler 11 is also used to collect a portion of the secondary zinc oxide product.

[0071] In the above process, the waste heat boiler 11, the desulfurization tower 12 and the first dust collector 13 can all collect secondary zinc oxide products. The secondary zinc oxide products collected by different equipment can be graded and classified for recycling. According to product requirements, the secondary zinc oxide products can be stored or enter the rotary kiln 6 for a second time for re-roasting and smelting.

[0072] The secondary zinc oxide is roasted in rotary kiln 6 for a second time, further removing the chlorine content from the secondary zinc oxide product, improving the product grade and selling price. The secondary zinc oxide product is directly placed into first cyclone 1 and second cyclone 2, followed by delivery to rotary kiln 6. Burner 10 provides external heat within rotary kiln 6, ensuring an oxidizing atmosphere and controlling the temperature below 900°C. Chlorine and other impurities in the secondary zinc oxide are captured by the flue gas treatment unit, and the secondary zinc oxide is ultimately collected as zinc roasted sand by grate cooler 7.

[0073] The kiln head hood 33, installed at the kiln head of the rotary kiln 6, connects the kiln 6 with the grate cooler 7, forming an enclosed space. A portion of the hot air from the grate cooler 7 enters the rotary kiln 6 as combustion air, while another portion is introduced into the first and second cyclones 1 and 2 via the second air duct 9 to preheat the material. The cooling fan installed outside the grate cooler 7 has been modified, with its cooling area and distribution recalculated. A hammer crusher 17 is installed at the front of the grate cooler 7 to break up the kiln slag and enhance the cooling effect.

[0074] The iron oxide in the material in the rotary kiln 6 is reduced and roasted to elemental iron, which becomes the main component of the slag. The slag is cooled by heat exchange in the grate cooler 7. The cooled material is crushed by the hammer crusher 17 at the end of the grate cooler 7 and transported to the slag storage 19 for storage. The slag stored in the slag storage 19 can subsequently be separated for iron by the iron ore concentrate refining and sorting system (the existing system of the cement plant). The cold air in the grate cooler 7 exchanges heat with the slag to form 700°C hot air. The hot air enters the second cyclone 2, the first cyclone 1, and the first dust collector 13 through the third smoke pipe 16 in sequence through the second air duct 9. The excess 100°C hot air from the grate cooler 7 is removed by the second dust collector 18 and discharged through the chimney 29.

[0075] The roasting flue gas from the zinc smelting system of this application is disposed of and discharged through environmental protection facilities. All flue gas enters the original cement kiln exhaust chimney 29, which is equipped with online monitoring facilities for flue gas emissions. Desulfurization equipment, such as a desulfurization tower 12, is also installed before discharge. Denitrification utilizes the original cement plant's SNCR system. The entire system produces no solid waste, and kiln dust circulates within the system. After iron is extracted from the kiln slag, it can be recycled as a raw material in the cement plant.

[0076] The burner 10 is preferably a four-channel pulverized coal burner. During normal combustion and production of materials in the rotary kiln 6, the burner 10 only needs to provide high-pressure air or compressed air to provide the combustion-supporting air required for reduction roasting of the rotary kiln 6. The burner 10 can also be used as an auxiliary measure for local combustion adjustment to prevent local crusting in the rotary kiln 6. For example, the burner 10 can be connected to the pulverized coal through the connected pulverized coal conveying pipe 31 to provide heat and reducing coal for the rotary kiln 6 to prevent crusting in the rotary kiln 6. Secondly, when the rotary kiln 6 is ignited, the burner 10 can also be connected to the fuel system 30 to ignite the rotary kiln 6 or bake the rotary kiln 6.

[0077] The zinc smelting system of the present application can make full use of the control room control facilities and equipment of the retired cement enterprise, including overall fuel supply and adjustment, various material metering and feedback, online gas analyzer, various temperature, pressure, flow monitoring, cylinder scanning, speed adjustment, Karman opening adjustment, current monitoring, etc. It can ensure the precise control of the calcination system in the rotary kiln 6, reduce energy waste, and improve work efficiency. The central control operating system of the cement enterprise's production system can still be used, and the operating parameters of the rotary kiln 6 can be monitored and adjusted, such as the kiln speed, the rotary kiln 6 cylinder scanning temperature, various temperature and pressure parameters, kiln current, etc., and the system operation can be comprehensively judged and adjusted to prevent the formation of crust and eggs in the kiln, raw burning and over-burning, and improve the kiln operation rate. It can be an effective measure to change the operation rate of the rotary kiln 6 method. The laboratory as an auxiliary system detects and analyzes the components of incoming materials, intermediate process materials, and the kiln batching process, and forms a unique material formula to ensure product output and quality.

[0078] This embodiment also provides a zinc smelting method based on a retired cement kiln, characterized in that a zinc smelting system based on a retired cement kiln is adopted, and the specific method is as follows:

[0079] Homogenization, storage and batching of raw materials: the raw materials are pre-homogenized in the material pre-treatment unit, the pre-homogenized materials are stored and the zinc-containing waste and reduced coal are batched in proportion;

[0080] Preheating and roasting: The airflow in the kiln head cover 33 enters the second cyclone 2 through the second air duct 9, and the airflow in the second cyclone 2 enters the first cyclone 1 through the first air duct 8; the batched material enters the first air duct 8, and under the action of the airflow, the material enters the first cyclone 1 and is preheated. The material separated in the first cyclone 1 enters the second air duct 9 through its discharge pipe, and the material enters the second cyclone 2 and is preheated under the action of the airflow; when the temperature of the material in the second cyclone 2 reaches above 600℃, the material in the second cyclone 2 is sent to the rotary kiln through its discharge pipe. 6; the material undergoes a first reduction roasting in the rotary kiln 6, and the slag produced in the rotary kiln 6 enters the grate cooler 7, and the generated flue gas enters the settling chamber 5 through the smoke chamber 4; the slag is air-cooled in the grate cooler 7, and the air flow after heat exchange in the grate cooler 7 enters the second cyclone 2 through the second air duct 9; the large particles in the flue gas settle in the settling chamber 5 and enter the rotary kiln 6 again, and the flue gas in the settling chamber 5 enters the third cyclone 3 and is separated in the third cyclone 3. The large particles of dust return to the rotary kiln 6 through the discharge pipe of the third cyclone 3 and the discharge pipe of the rotary kiln 6;

[0081] Slag treatment: the slag in the grate cooler 7 enters the roasting slag treatment unit, which processes the slag;

[0082] Flue gas treatment: the flue gas in the third cyclone 3 and the first cyclone 1 enters the flue gas treatment unit respectively, which treats the flue gas and obtains secondary zinc oxide product.

[0083] The heat of the air flow in the kiln head hood 33 includes the heat from the burner 10, the heat from the combustion of the rotary kiln 6 and the heat from the heat exchange of the grate cooler 7. When the rotary kiln 6 is first ignited, the heat entering the second air duct 9 mainly comes from the heat from the burner 10. After the material in the rotary kiln 6 is normally burned, the heat entering the second air duct 9 mainly comes from the heat from the heat exchange of the grate cooler 7.

[0084] Flue gas treatment includes: the flue gas in the third cyclone 3 enters the desulfurization tower 12 from the first flue pipe 14, and the remaining flue gas in the desulfurization tower 12 enters the first dust collector 13 from the second flue pipe 15; or / and the flue gas in the third cyclone 3 enters the waste heat boiler 11 from the first flue pipe 14, and the remaining flue gas of the waste heat boiler 11 then enters the desulfurization tower 12, and the remaining flue gas in the desulfurization tower 12 enters the first dust collector 13 from the second flue pipe 15; the airflow in the first cyclone 1 enters the first dust collector 13 from the third flue pipe 16.

[0085] The slag treatment includes: the slag in the grate cooler 7 enters the hammer crusher 17 for crushing, and the crushed slag is transported to the slag storage 19 for storage; the hot air at the end of the grate cooler 7 away from the rotary kiln 6 enters the second dust collector 18 for treatment.

[0086] The zinc smelting method also includes further smelting of the secondary zinc oxide product, the specific method is as follows:

[0087] The secondary zinc oxide product produced by the primary roasting in the rotary kiln 6 is directly placed in the first cyclone 1 and the second cyclone 2 in sequence; the burner 10 provides heat to the rotary kiln 6 to control the temperature of the rotary kiln 6 to be less than 900°C, and the secondary zinc oxide product from the second cyclone 2 is fed into the rotary kiln 6 for roasting through its discharge pipe; the secondary zinc oxide product in the rotary kiln 6 becomes zinc roasted sand and is collected by the grate cooler 7.

[0088] The technical features of the above embodiments can be combined arbitrarily (as long as there is no contradiction in the combination of these technical features). In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A zinc smelting system based on a retired cement kiln, characterized in that: The zinc smelting system is based on the reconstruction of retired cement kilns and includes: A material pre-treatment unit, used for pre-homogenizing the material and storing the homogenized material, as well as proportioning the zinc-containing waste and the reduced coal; The preheating and roasting unit includes a first cyclone, a second cyclone, a third cyclone, a smoke chamber, a sedimentation chamber, a rotary kiln, a grate cooler and a burner, wherein a first air duct is connected between the first cyclone and the second cyclone, and a discharge pipe of the second cyclone and a discharge pipe of the third cyclone are both connected to the discharge pipe of the rotary kiln, the smoke chamber is arranged at the kiln tail end of the rotary kiln, the top of the smoke chamber is connected to one end of the sedimentation chamber, and the other end of the sedimentation chamber is connected to the third cyclone, a kiln head cover is provided at the kiln head of the rotary kiln, the kiln head cover is used to connect the rotary kiln with the grate cooler and form a closed space, one end of the burner passes through the closed space and is inserted into the rotary kiln, a second air duct is connected between the second cyclone and the kiln head cover, the discharge pipe of the first cyclone is connected to the second air duct, and the first air duct is connected to the discharge pipe of the material pretreatment unit; The roasting slag processing unit is used to process the roasting slag produced by the preheating and roasting units; The flue gas treatment unit is used to treat the zinc-containing flue gas generated by the preheating and roasting units.

2. The zinc smelting system based on a retired cement kiln according to claim 1, characterized in that: The flue gas treatment unit includes a waste heat boiler, a desulfurization tower and a first dust collector. A first flue pipe is connected between the third cyclone and the desulfurization tower, and a second flue pipe is connected between the desulfurization tower and the first dust collector. The waste heat boiler is connected in parallel to the first flue pipe and is connected to the desulfurization tower. The first cyclone is connected to the first dust collector through the third flue pipe.

3. The zinc smelting system based on a retired cement kiln according to claim 1, characterized in that: The roasting slag processing unit includes a hammer crusher, a second dust collector and a slag storage. The hammer crusher is connected to the grate cooler. The second dust collector is arranged at one end of the grate cooler away from the rotary kiln. The slag storage is used to store the slag crushed by the hammer crusher.

4. The zinc smelting system based on a retired cement kiln according to claim 1, characterized in that: The smoke chamber is provided with a naturally drooping and retractable material blocking curtain, which is arranged on the side of the smoke chamber close to the rotary kiln to prevent the material in the rotary kiln from being carried away by the smoke.

5. The zinc smelting system based on a retired cement kiln according to claim 1, characterized in that: A material retaining ring is provided on the inner wall side of the rotary kiln, and the height of the material retaining ring extends along the inner diameter of the rotary kiln.

6. The zinc smelting system based on a retired cement kiln according to claim 1, characterized in that: The preheating and roasting unit also includes a kiln tongue with an adjustable inclination angle, and the kiln tongue covers the cross-section of the smoke chamber. One end of the kiln tongue extends into the rotary kiln. The kiln tongue includes an integrally formed tongue portion and a tube portion. The tube portion is a closed curved channel raised on the upper surface of the tongue portion, and the discharge pipe of the rotary kiln is connected to the tube portion.

7. A zinc smelting method based on a retired cement kiln, characterized in that: A zinc smelting system based on a retired cement kiln according to any one of claims 1 to 6 is used, and the specific method is as follows: Homogenization, storage and batching of raw materials: the raw materials are pre-homogenized in the material pre-treatment unit, the pre-homogenized materials are stored and the zinc-containing waste and reduced coal are batched in proportion; For preheating and roasting, the airflow in the kiln head hood enters the second cyclone through the second air duct, and the airflow in the second cyclone enters the first cyclone through the first air duct; the batched materials enter the first air duct, and under the action of the airflow, the materials enter the first cyclone and are preheated; the materials separated in the first cyclone enter the second air duct through its discharge pipe, and the materials enter the second cyclone and are preheated under the action of the airflow; when the temperature of the materials in the second cyclone reaches above 600℃, the materials in the second cyclone are sent to the second cyclone through its discharge pipe. The material is reduced and roasted in the rotary kiln, and the slag produced in the rotary kiln enters the grate cooler, and the generated flue gas enters the settling chamber through the smoke chamber; the slag is air-cooled in the grate cooler, and the air flow after heat exchange in the grate cooler enters the second cyclone through the second air duct; large particles in the flue gas settle in the settling chamber and enter the rotary kiln again, and the flue gas in the settling chamber enters the third cyclone and is separated in the third cyclone. The large particles of dust are returned to the rotary kiln through the discharge pipe of the third cyclone and the discharge pipe of the rotary kiln; Slag treatment: the slag in the grate cooler enters the roasting slag treatment unit, which processes the slag; Flue gas treatment: the flue gas in the third cyclone and the first cyclone enters the flue gas treatment unit respectively, the flue gas treatment unit treats the flue gas and obtains secondary zinc oxide product.

8. The zinc smelting method based on a retired cement kiln according to claim 7, characterized in that: Flue gas treatment includes: the flue gas in the third cyclone enters the desulfurization tower from the first flue pipe, and the remaining flue gas in the desulfurization tower enters the first dust collector from the second flue pipe; or / and the flue gas in the third cyclone enters the waste heat boiler from the first flue pipe, the remaining flue gas of the waste heat boiler then enters the desulfurization tower, and the remaining flue gas in the desulfurization tower enters the first dust collector from the second flue pipe; the airflow in the first cyclone enters the first dust collector from the third flue pipe.

9. The zinc smelting method based on a retired cement kiln according to claim 7, characterized in that: The slag treatment includes: the slag in the grate cooler enters the hammer crusher for crushing, and the crushed slag is transported to the slag storage for storage; the hot air from the end of the grate cooler away from the rotary kiln enters the second dust collector for treatment.

10. The zinc smelting method based on a retired cement kiln according to claim 7, characterized in that: The zinc smelting method further comprises smelting the secondary zinc oxide product, and the specific method is as follows: The secondary zinc oxide product is directly placed in the first cyclone and the second cyclone in sequence; the burner supplies heat to the rotary kiln to control the temperature of the rotary kiln to be less than 900°C, and the secondary zinc oxide product in the second cyclone is sent into the rotary kiln for roasting through its discharge pipe; the secondary zinc oxide product in the rotary kiln becomes zinc roasted sand and is collected by a grate cooler.

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