Pickling filter cake retreatment method and application

Abstract

The invention belongs to the technical field of metal processing, and particularly relates to a retreatment method and application of a pickling filter cake. According to the acid pickling filter cake retreatment method, the acid pickling filter cake comprises an acid filter cake, the acid filter cake enters a buffer bin through a dryer, the buffer bin conveys the acid filter cake to a bucket elevator conveyor through an inclined spiral conveyor 1, the bucket elevator conveyor lifts materials to the roasting top end of a multi-section roasting furnace, and the materials enter the multi-section roasting furnace through double feeding turning plates to be roasted. The roasted materials are cooled through a roller cooler and then conveyed to a product bin through an inclined screw conveyor 2; flue gas generated by the multi-section roasting furnace enters the cyclone dust collector to remove dust, the dedusted flue gas is deacidified through the three-stage washing deacidification tower, the deacidified flue gas enters the washing purification tower to be desulfurized, and the desulfurized flue gas is pumped by the induced draft fan to a chimney to be discharged. The invention further provides a pickling filter cake retreatment device applied to the pickling filter cake retreatment method. According to the invention, the retreatment efficiency and environmental protection property of the pickling filter cake are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal processing, and in particular relates to a method and application of reprocessing a pickling filter cake. Background Art

[0002] In the field of metal processing, the cold rolling pickling process is one of the key steps to improve the surface quality of metals. During the pickling process, the pickling liquid removes the oxide scale and impurities on the metal surface, but it also produces a large amount of acidic waste liquid and pickling filter cake. The pickling filter cake contains metal oxides, residual acid and other impurities, which are difficult to treat solid wastes. If not properly treated, it may cause serious pollution to the environment. Therefore, the effective treatment and resource utilization of the pickling filter cake is an important technical problem currently faced.

[0003] Traditional methods for treating acid-washed filter cakes mainly include landfill, chemical neutralization and roasting. Among them, landfill will occupy a large amount of land resources and may cause long-term environmental pollution; although chemical neutralization can reduce acidity, secondary pollutants generated during the treatment process still need to be treated later. Roasting is considered to be one of the more effective treatment methods. It can decompose organic matter in the filter cake through high-temperature roasting and convert metal oxides into a more easily recyclable form, thereby realizing resource reuse.

[0004] At present, the main challenge facing roasting treatment is how to ensure efficient conversion of metal oxides while minimizing the emission of harmful gases, reducing energy consumption and improving the efficiency of acid-washed filter cake reprocessing. Summary of the invention

[0005] The present invention aims at the deficiencies of the prior art and provides a method and application for reprocessing a pickling filter cake.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present application provides a method for reprocessing a pickling filter cake, wherein the pickling filter cake includes an acid filter cake, which first falls into a dryer for drying, and then falls into a buffer silo after dehydration. The buffer silo conveys the acid filter cake to a bucket conveyor through an inclined screw conveyor 1, and the bucket conveyor lifts the material to the top layer of a multi-stage roasting furnace. The material then enters the multi-stage roasting furnace through a double feeding flap for roasting treatment. The roasted material is cooled by a drum cooler and then conveyed to a product bin for collection by an inclined screw conveyor 2; The flue gas generated by the multi-stage roasting furnace enters the cyclone dust collector to remove dust. The flue gas after dust removal passes through a 3-stage water washing and deacidification tower for deacidification. After deacidification, the flue gas enters a water washing purification tower for desulfurization treatment. The desulfurized flue gas is drawn to the chimney by an induced draft fan for discharge.

[0007] Preferably, the multi-stage roasting furnace comprises a plurality of roasting stages, each roasting stage comprises a burner, and the temperatures are controlled at 300°C, 500°C, 700°C and 900°C respectively.

[0008] It should be noted that the material is transported to the top furnace bed of the multi-stage roasting furnace by the feeding system. The temperature of each bed layer is set by adjusting the burner control valve, and the air-fuel ratio is accurately controlled to ensure the combustion effect. The oxygen content of each furnace layer is accurately controlled by air supply and flue gas backmixing control, and the oxidation heat release rate is controlled. The temperature of each furnace layer is controlled in layers to suppress the volatilization and decomposition of heavy metals while meeting the heavy metal roasting efficiency. At the same time, the incineration efficiency of residual carbon and organic matter is improved, and the heat consumption of the system is reduced. The flue gas generated during the roasting of the multi-stage roasting furnace is further removed from harmful gases and dust such as CO and NOx through the matching flue gas purification device, and enters the chimney for venting after meeting the emission requirements.

[0009] Preferably, the lining material of the multi-stage roasting furnace is a high-chromium-nickel alloy, the high-chromium-nickel alloy is coated with an alumina ceramic coating with a thickness of 3-5 mm, and an aerogel insulation board is installed on the outside of the multi-stage roasting furnace.

[0010] Preferably, the materials of the multi-stage roasting furnace include furnace body materials, lining materials, roasting stage partition materials, and mechanical component materials; the furnace body materials include shell materials and external insulation materials, and the shell materials include carbon steel; the external insulation materials include aerogel insulation boards; the lining materials include high-temperature ceramic composite linings, and the high-temperature ceramic composite linings include high-alumina bricks and coatings, and the coatings include silicon carbide coatings and modified coatings; the roasting stage partition materials include honeycomb ceramic partitions.

[0011] Preferably, the raw material of the modified coating includes at least one of α-alumina, yttrium oxide, cerium oxide, titanium carbide nanoparticles, boron nitride micron sheets, monoclinic zirconium dioxide, tetragonal zirconium dioxide, and silica sol.

[0012] Preferably, the preparation method of the modified coating includes the following steps: mixing α-alumina, yttrium oxide and cerium oxide, adding silica sol, coarse ball milling to obtain a mixture, adding titanium carbide nanoparticles, boron nitride micron sheets, monoclinic zirconium dioxide, and tetragonal zirconium dioxide to the mixture, mixing and high-energy ball milling to form a multiphase composite slurry, and high-temperature curing or high-temperature sintering the multiphase composite slurry to form a modified coating on the surface of the high-alumina brick lining.

[0013] Preferably, air and mixed coal gas are introduced into the multi-stage roasting furnace; alkali solution is added to the water washing purification tower, and the alkali solution includes sodium hydroxide; process water is added to the drum cooler, and the drainage discharged from the drum cooler also enters the water washing purification tower; and the 3-stage water washing deacidification tower discharges acidic water.

[0014] It should be noted that the present invention uses the acid-washed filter cake as raw material, uses a multi-stage furnace to oxidize and roast the material, and effectively controls the temperature, residence time, and oxygen content of different layers in the multi-stage roasting furnace in layers, so that a series of physical and chemical processes such as waste drying and metal oxidation occur, so that the organic matter in the waste is oxidized and roasted, and the metal oxides in the filter cake are converted into a form that is easier to recover, and the roasting temperature is controlled to suppress the volatilization loss of some metals. At the same time, the flue gas generated during the roasting process can also be purified by a supporting flue gas system such as a water washing and deacidification tower.

[0015] Preferably, the inclination angle of the inclined screw conveyor 1 and the inclined screw conveyor 2 is 15-50 degrees, the diameter of the conveying pipe is 100-400 mm, and the lining is made of high wear-resistant material; the lifting height of the bucket conveyor is 2-8 meters, and the lifting speed is 2-4 meters / minute; the working temperature in the dryer is 100-250°C, the drying time is 10-15 minutes, and the moisture content of the dried material drops below 10%; the power of the induced draft fan is 20-60kW, and the air volume is 3000-8000 cubic meters / hour.

[0016] Second, provide applications: A pickling filter cake reprocessing device is used in the aforementioned pickling filter cake reprocessing method. The pickling filter cake reprocessing device includes a dryer, the dryer is connected to an inclined screw conveyor 1 through a buffer silo, the inclined screw conveyor 1 is connected to a double feed flap through a bucket conveyor, the double feed flap is connected to a multi-stage roasting furnace, the multi-stage roasting furnace is connected to an inclined screw conveyor 2 through a drum cooler, and the inclined screw conveyor 2 is connected to a product bin; the multi-stage roasting furnace is also connected to a three-stage water washing and deacidification tower through a cyclone dust collector, the three-stage water washing and deacidification tower is connected to an induced draft fan through a water washing purification tower, and the induced draft fan is connected to a chimney.

[0017] Preferably, the three-stage water washing and deacidification tower includes water washing and deacidification tower 1, water washing and deacidification tower 2, and water washing and deacidification tower 3, the cyclone dust collector is connected to water washing and deacidification tower 1, water washing and deacidification tower 1 is connected to water washing and deacidification tower 3 through water washing and deacidification tower 2, and water washing and deacidification tower 3 is connected to a water washing purification tower; a mechanical vibration device is installed in the multi-stage roasting furnace, and the vibration frequency of the mechanical vibration device is 5-10Hz.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses a multi-stage roasting furnace and controls the layering temperature. The temperature of each roasting section is set to 300°C, 500°C, 700°C and 900°C respectively. The residence time of the material at different temperatures and the oxidation environment are accurately controlled, which can effectively inhibit the volatilization of heavy metals and the decomposition of impurities, so that the organic matter and metals in the pickling filter cake are fully oxidized and decomposed, thereby improving the resource utilization rate. The flue gas is treated by a cyclone dust collector and a 3-stage water washing and deacidification tower to effectively remove acidic gases and dust particles, and finally deeply purified by a water washing purification tower and discharged after meeting the standards. Equipped with a high-efficiency induced draft fan to ensure the smooth operation of the entire flue gas treatment system, significantly reduce emission pollution, and reduce the impact on the environment.

[0019] 2. The invention optimizes the multi-stage roasting furnace from multiple angles. The first optimization method is: the lining material of the multi-stage roasting furnace is a high-chromium-nickel alloy, and the high-chromium-nickel alloy is coated with an alumina ceramic coating with a thickness of 3-5 mm. An aerogel insulation board is installed on the outside of the multi-stage roasting furnace. The second optimization method: the materials of the multi-stage roasting furnace include furnace body materials, lining materials, roasting section partition materials, and mechanical parts materials; the furnace body materials include shell materials and external insulation materials, and the shell materials include carbon steel; the external insulation materials include aerogel insulation boards; the lining materials include high-temperature ceramic composite linings, and the high-temperature ceramic composite linings include high-aluminum bricks and coatings. The coatings include silicon carbide coatings and modified coatings; the roasting section partition materials include honeycomb ceramic partitions. The third optimization method: modify the coating, and the porosity of the modified coating gradually increases from the bottom layer to the surface layer to form gradient pores to relieve thermal stress. The bottom layer is a dense structure, and the outer layer has nano-scale micropores to increase the surface specific surface area and reaction activity. The synergistic effect of the multi-layer structure enables the modified coating to maintain long-term stability in extremely high temperature and corrosive environments.

[0020] Therefore, the present invention designs a high-efficiency, multi-stage roasting furnace and flue gas treatment system, and innovates in material and process control, thereby improving the efficiency and environmental protection of the acid-washed filter cake reprocessing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 The present invention is a flow chart of the acid-washed filter cake reprocessing. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The experimental methods used below are conventional methods unless otherwise specified, and the parts, equipment, materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels. The principles or mechanisms of the parts or equipment that can be purchased conventionally through commercial channels are well known, and the common names have been given below, so no further description is given.

[0024] The following provides a method and application for pickling filter cake reprocessing. The pickling filter cake reprocessing device is applied in the method for pickling filter cake reprocessing. The method for pickling filter cake reprocessing is explained in conjunction with the pickling filter cake reprocessing device.

[0025] Example 1 Reference Figure 1 , a pickling filter cake reprocessing device, the pickling filter cake is the pickling filter cake produced by the cold rolling pickling process, the pickling filter cake includes an acid filter cake, the acid filter cake enters the dryer, the dryer is connected to the buffer silo by pipeline, and a stirring device is provided inside the buffer silo to prevent the filter cake from depositing during storage. The buffer silo is made of corrosion-resistant materials, such as stainless steel, and has good sealing performance to prevent leakage. Among them, the material is heated and dried by jacket steam in the dryer, and condensed water can be discharged after drying.

[0026] The buffer silo is connected to the inclined screw conveyor 1 by pipeline. The inclined screw conveyor 1 is a variable frequency inclined screw conveyor. The inclined screw conveyor 1 is connected to the bucket conveyor by pipeline. The inclined screw conveyor 1 is used to convey the material upward to the bucket conveyor. The bucket conveyor is a bucket elevator with a conveying function. The bucket conveyor is connected to the double feed flap by pipeline. The bucket conveyor is responsible for lifting the material to the double feed flap. The double feed flap can be a flap valve with a dual channel or a two-stage feed hammer flap. The double feed flap is connected to the multi-stage roasting furnace by pipeline. The purpose of such a setting is: (1) The main function of the double feed flap is to distribute the material from the conveying system to different areas of the roasting furnace in an orderly manner. (2) The dual channel distribution allows the double feed flap to switch between the two conveying channels, so that the material can choose one of the channel flow directions as needed, for example, to distribute the material to different sections of the multi-stage roasting furnace to ensure a uniform roasting effect. (3) The double feed flap can buffer and distribute the material flow, preventing the material from directly piling up in a certain position, thereby ensuring that the material enters the roasting area evenly. This is very important for temperature control and reaction uniformity during the roasting process. (4) The double feed flap has a good sealing structure, which can prevent dust leakage and intrusion of external gas, ensuring that the entire roasting process is carried out in a controlled atmosphere.

[0027] The multi-stage roasting furnace is a multi-stage furnace with roasting function. Air and mixed gas are introduced into the multi-stage roasting furnace. The multi-stage roasting furnace has two connection routes: The first one: The multi-stage roasting furnace is connected to the drum cooler by pipeline, the drum cooler is connected to the inclined screw conveyor 2 by pipeline, the inclined screw conveyor 2 is an inclined screw conveyor, and the inclined screw conveyor 2 is connected to the product bin by pipeline. Among them, process water is added to the drum cooler, and the process water in the drum cooler is mainly used to cool the high-temperature materials after roasting.

[0028] Article 2: The multi-stage roasting furnace is connected to the cyclone dust collector by pipeline, the cyclone dust collector is connected to the water washing and deacidification tower 1 by pipeline, the water washing and deacidification tower 1 is connected to the water washing and deacidification tower 2 by pipeline, the water washing and deacidification tower 2 is connected to the water washing and deacidification tower 3 by pipeline, the water washing and deacidification tower 3 is connected to the water washing and purification tower by pipeline, the water washing and purification tower is connected to the induced draft fan by pipeline, and the induced draft fan is connected to the chimney by pipeline, wherein alkali solution is added to the water washing and purification tower, and the alkali solution includes sodium hydroxide. Acidic water is discharged to the water washing and deacidification tower 3, the water washing and deacidification tower 2 and the water washing and deacidification tower 1. Among them, the water washing and deacidification tower 1, the water washing and deacidification tower 2, and the water washing and deacidification tower 3 are all deacidification towers with water washing and deacidification functions. In addition, the drainage discharged from the drum cooler can enter the water washing and purification tower. The drainage enters the water washing and purification tower mainly to purify the drainage, remove the acidity and other pollutants therein, so that the wastewater meets the standards for discharge or recycling, and reduce environmental pollution. The water washing and purification tower can be a water washing tower, a washing tower, or a desulfurization tower.

[0029] Example 2 In this embodiment, specific process steps are given: Feeding: The acid filter cake is transported to the site and unloaded into the raw material bin. Then the acid filter cake is lifted to the feed port of the dryer and falls into the dryer. Steam is introduced into the jacket of the dryer. After the material is heated by steam, it is initially dehydrated and the dehydrated material falls into the feed port at the top of the buffer silo. When the material falls into the buffer silo, a weighing module is also installed on the buffer silo. After the material falls into the buffer silo, it is pushed by the variable frequency inclined screw conveyor 1 at the bottom of the buffer silo and falls into the feed port of the bucket conveyor. After being lifted by the bucket conveyor, the material is lifted to the top layer of the multi-stage roasting furnace, and slides into the top furnace bed of the multi-stage roasting furnace through the double feeding flap, and the multi-stage roasting furnace is roasted. It should be noted that because the weighing signal of the buffer silo weighing module will be fed back to the motor variable frequency of the inclined screw conveyor 1, precise control of feeding is achieved.

[0030] The first route: the roasted material is cooled by a drum cooler and then transported to the product bin for collection by an inclined screw conveyor 2. In addition, regarding dust and metal recovery: the dust collected during the roasting process is processed together with metal oxides for resource recovery to achieve metal recovery. Air and mixed coal gas are introduced during roasting. Air: Provides oxygen to support the oxidation reaction. During the roasting process, the acidic filter cake may contain unoxidized metal components (such as iron, zinc, etc.). The presence of oxygen causes these metals to oxidize to form corresponding oxides, thereby achieving the purpose of removal and stabilization. Mixed coal gas: Adding mixed coal gas provides fuel for the roaster. Its combustion releases heat, maintaining the high temperature environment of each section in the roaster, and ensuring the decomposition and oxidation of impurities in the filter cake.

[0031] The second route: The flue gas generated by the multi-stage roasting furnace first passes through a cyclone dust collector to remove large particles of dust, with a separation efficiency of 90%. The flue gas after dust removal by the cyclone dust collector passes through three water washing and deacidification towers (water washing and deacidification tower 1, water washing and deacidification tower 2, and water washing and deacidification tower 3) in turn. The spray flow rate of each tower is 200 liters / hour, which is used to neutralize the acidic substances in the flue gas. After deacidification, the flue gas enters the water washing purification tower, and a 10% sodium hydroxide lye is added to carry out flue gas desulfurization treatment, with a desulfurization efficiency of 95%. The treated flue gas is pumped to the chimney through an induced draft fan for discharge. The induced draft fan provides the necessary flow power for the flue gas to ensure the smooth flow of the flue gas in each treatment unit.

[0032] In addition, the water washing and deacidification tower will discharge acidic water after treating the material. If additional cooling or washing of the water washing and deacidification tower is required, process water can be added to the water washing and deacidification tower 3. The process water can be recycled and flows from the water washing and deacidification tower 3 to the water washing and deacidification tower 2 and then to the water washing and deacidification tower 1. The process water contacts the flue gas in the water washing and deacidification tower to dissolve the acidic components (such as hydrogen chloride, sulfur oxides, etc.) in the flue gas, dissolving the acidic substances in the water to form acidic water, and the acidic water is discharged from the water washing and deacidification tower 1. The process water is gradually recycled in different tower sections to improve the use efficiency of the process water.

[0033] Example 3 Specific parameter settings are provided in this embodiment. The specific parameter settings are provided to better implement the technical solution of the present application, but other reasonable parameters are not excluded: The inclination angle of the inclined screw conveyor 1 and the inclined screw conveyor 2 can be 30 degrees, the diameter of the conveying pipe is 200 mm, and the lining is made of high wear-resistant material to reduce friction.

[0034] The bucket conveyor is responsible for lifting the materials to the multi-stage roasting furnace. Its lifting height is 6 meters and the lifting speed is 2 meters / minute. It adopts a chain bucket structure to ensure stability during the conveying process.

[0035] The operating temperature in the dryer is 150°C and the drying time is controlled within 15 minutes to ensure that the moisture content of the material drops below 10% before roasting.

[0036] The induced draft fan has a power of 45kW and an air volume of 5,000 cubic meters per hour. It uses variable frequency control to adapt to different working conditions. The treated and purified flue gas is finally discharged through the chimney, which is 30 meters high to ensure the effective diffusion of the flue gas and reduce the impact on the environment.

[0037] Example 4 Further optimized dust removal: A bag filter is installed after the cyclone dust collector to further remove fine dust particles, with a filtration efficiency of 99%.

[0038] Example 5 In this example, the multi-stage roasting furnace is further optimized.

[0039] The multi-stage roasting furnace adopts a modular design, with a total of multiple roasting sections, preferably 4, each section is 2 meters long, with a total length of 8 meters, and each section can independently control the temperature and oxygen content.

[0040] Each roasting section is equipped with an independent multi-point burner, and the temperature is controlled at 300℃, 500℃, 700℃ and 900℃ respectively. The burner uses natural gas as fuel and is equipped with a combustion control valve to accurately control the air-fuel ratio and ensure full combustion.

[0041] A mechanical vibration device is installed in the multi-stage roasting furnace. The vibration frequency of the mechanical vibration device is between 5-10Hz. Its function is to control the residence time of the material in the roasting furnace to ensure uniform heating and sufficient reaction of the material.

[0042] Example 6 In this embodiment, the materials of the multi-stage roasting furnace are further optimized as follows: The lining material of the multi-stage roasting furnace is a high-chromium-nickel alloy, which has the function of preventing acidic gas from corroding the furnace body and prolonging the service life of the device.

[0043] The high chromium-nickel alloy is coated with an alumina ceramic coating with a thickness of 3-5 mm. Its function is to reduce the direct thermal shock of high temperature to the furnace body and improve thermal efficiency.

[0044] Aerogel insulation panels are installed on the outside of the multi-stage roasting furnace to improve the thermal insulation performance of the multi-stage roasting furnace, reduce heat loss, and improve the energy efficiency of the roasting system.

[0045] Example 7 In this example, the reaction comprising: Main reactions: Oxidation reaction of organic matter: The organic matter contained in the filter cake undergoes oxidation reaction under the action of high temperature and oxygen to generate carbon dioxide and water.

[0046] Formation of metal oxides: The metal elements (including iron and zinc) in the filter cake react with oxygen under high temperature conditions to generate corresponding metal oxides (including Fe2O3 and ZnO).

[0047] Main reactions of flue gas treatment: Deacidification reaction: Acidic gases (including HCl, SO2) in flue gas react with water and alkali solution to form neutral salts.

[0048] Desulfurization reaction: SO2 reacts with alkali solution (NaOH) to produce sodium sulfate.

[0049] Example 8 In this example, the multi-stage roasting furnace is further optimized: 1. Furnace material Shell material: Q235 carbon steel is selected as the main structural material of the furnace body. It has good strength and machinability and can support the weight of the entire furnace body.

[0050] External insulation material: Aerogel insulation board with ultra-low thermal conductivity can significantly reduce heat loss, ensure temperature control outside the furnace, and reduce energy consumption.

[0051] 2. Lining material High temperature ceramic composite lining: High alumina bricks: High alumina bricks (Al2O3 content ≥ 75%) are used as the basic material for lining, which have excellent high temperature resistance and chemical corrosion resistance, and can resist the corrosion of acidic gases in the furnace.

[0052] Silicon carbide coating: A layer of silicon carbide coating is applied on the surface of the high alumina brick lining, with a thickness of about 3-5 mm. This coating has excellent thermal conductivity and wear resistance, which helps to improve the temperature uniformity in the furnace and extend the service life of the lining.

[0053] 3. Baking section partition material Honeycomb ceramic structure: Honeycomb ceramic partitions are used between each baking area. This structure helps to improve the uniformity and temperature resistance of airflow, increase mechanical strength, and prevent deformation under high temperature conditions.

[0054] 4. Mechanical parts materials Drivetrain: Shafts and gears: 42CrMo alloy steel is used. This material has high strength and high wear resistance and is suitable for high temperature and heavy load transmission systems inside roasting furnaces.

[0055] Bearings: Ceramic bearings are selected because they have excellent high temperature and corrosion resistance and can work for a long time in the high temperature environment inside the roasting furnace.

[0056] 5. Pipe and connection materials Corrosion-resistant stainless steel pipes: 316L stainless steel is selected as the connecting pipe material for flue gas pipes and material transportation. It has excellent acid and alkali corrosion resistance and is suitable for use in high-temperature flue gas and corrosive environments.

[0057] 6. Flange and sealing materials: Flange: Use carbon steel flange to facilitate pipe connection and ensure the strength of the connection.

[0058] Sealing gasket: Use expanded graphite gasket, which has good high temperature resistance and sealing performance to prevent smoke leakage.

[0059] 7. Burner material of roasting section Burner main material: The burner is made of heat-resistant alloy (Inconel 600), which is suitable for long-term use under high temperature and can withstand high temperatures above 1000°C.

[0060] Nozzle material: Ceramic nozzles are selected, which have high thermal shock resistance and corrosion resistance, and are suitable for long-term use in the burner.

[0061] 8. External protection and support materials Furnace support frame: Made of Q345B steel, it has good weldability and mechanical properties and can stably support the overall weight of the multi-stage roasting furnace.

[0062] Example 9 In this example, the coating material in Example 8 is modified: Improvements will be made in material selection, multi-level control of microstructure, and processing steps.

[0063] raw material: α-Alumina: 10-15 μm, Sumitomo Chemical, 99.99% purity, α-alumina powder.

[0064] Yttrium Oxide: 99.99% purity, high purity yttrium oxide powder.

[0065] Cerium Oxide: 99.99% purity, high purity cerium oxide powder.

[0066] Titanium carbide nanoparticles: 99.99% purity, nano titanium carbide powder.

[0067] Boron nitride micron flakes: 99.99% purity, hexagonal boron nitride powder.

[0068] Monoclinic zirconium dioxide: 20nm-50nm, 99.9% purity.

[0069] Tetragonal zirconium dioxide: 20nm-50nm, 99.9% purity.

[0070] Preparation method: The first stage of ball milling (coarse ball milling): 67 wt% of α-alumina, 5 wt% of yttrium oxide and 5 wt% of cerium oxide were mixed, 3 wt% of silica sol was added, and the mixture was coarsely ball milled for 6 hours to obtain a mixture.

[0071] The second stage of ball milling (nanoscale dispersion): 8 wt% titanium carbide nanoparticles, 7 wt% boron nitride microplatelets, 2.5 wt% monoclinic zirconium dioxide, and 2.5 wt% tetragonal zirconium dioxide were added to the mixture, and after mixing, high-energy ball milling was performed for 12 hours to form a multiphase composite slurry.

[0072] The method of using the multi-phase composite slurry is to cure or sinter the multi-phase composite slurry at high temperature on the surface of the high-alumina brick lining.

[0073] It should be noted that after such modification, a multi-layer structure can be obtained: first prepare the bottom layer, which can be used as a bonding layer, α-alumina as a matrix, providing basic hardness and heat resistance, yttrium oxide and cerium oxide are mixed with it, and are strongly bonded to the matrix through ball milling and silica sol, and oxygen vacancies are generated by cerium oxide to enhance thermal conductivity and thermal expansion matching. Then prepare the protective layer, superimpose the bottom layer to make a composite reinforcement layer, titanium carbide nanoparticles and boron nitride micron sheets are mixed with two zirconium dioxides to form a two-phase structure to ensure the balance between toughness and hardness, and self-lubricity is achieved through boron nitride micron sheets. After the multi-phase composite slurry is cured or sintered on the surface of the high-alumina brick lining, a coating is formed on its surface. The porosity of the coating gradually increases from the bottom layer to the surface layer to form a gradient porosity to relieve thermal stress. The bottom layer is a dense structure, and the outer layer has nano-scale micropores to increase the surface specific surface area and reactivity. The synergistic effect of the multi-layer structure enables the coating to maintain long-term stability in extremely high temperature and corrosive environments.

[0074] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for reprocessing a pickling filter cake, characterized in that: The acid filter cake includes an acid filter cake, which first falls into a dryer for drying, and then falls into a buffer silo after dehydration. The buffer silo conveys the acid filter cake to a bucket conveyor through an inclined screw conveyor 1. The bucket conveyor lifts the material to the top layer of the multi-stage roasting furnace. The material then enters the multi-stage roasting furnace through a double feeding flap for roasting. The roasted material is cooled by a drum cooler and then conveyed to a product bin for collection by an inclined screw conveyor 2. The flue gas generated by the multi-stage roasting furnace enters the cyclone dust collector to remove dust. The flue gas after dust removal passes through a 3-stage water washing and deacidification tower for deacidification. After deacidification, the flue gas enters a water washing purification tower for desulfurization treatment. The desulfurized flue gas is drawn to the chimney by an induced draft fan for discharge.

2. The method for reprocessing the pickling filter cake according to claim 1, characterized in that: The multi-stage roasting furnace includes a plurality of roasting stages, each of which includes a burner, and the temperatures are controlled at 300° C., 500° C., 700° C. and 900° C. respectively.

3. The method for reprocessing the pickling filter cake according to claim 1, characterized in that: The lining material of the multi-stage roasting furnace is a high-chromium-nickel alloy, and the high-chromium-nickel alloy is coated with an alumina ceramic coating with a thickness of 3-5 mm. An aerogel insulation board is installed on the outside of the multi-stage roasting furnace.

4. The method for reprocessing the pickling filter cake according to claim 1, characterized in that: The materials of the multi-stage roasting furnace include furnace body materials, lining materials, roasting section partition materials, and mechanical component materials; the furnace body materials include shell materials and external insulation materials, and the shell materials include carbon steel; the external insulation materials include aerogel insulation boards; the lining materials include high-temperature ceramic composite linings, and the high-temperature ceramic composite linings include high-alumina bricks and coatings, and the coatings include silicon carbide coatings and modified coatings; the roasting section partition materials include honeycomb ceramic partitions.

5. The method for reprocessing the pickling filter cake according to claim 4, characterized in that: The raw materials of the modified coating include at least one of alpha-alumina, yttrium oxide, cerium oxide, titanium carbide nanoparticles, boron nitride micron sheets, monoclinic zirconium dioxide, tetragonal zirconium dioxide and silica sol.

6. The method for reprocessing the pickling filter cake according to claim 5, characterized in that: The preparation method of the modified coating comprises the following steps: mixing α-alumina, yttrium oxide and cerium oxide, adding silica sol, coarse ball milling to obtain a mixture, adding titanium carbide nanoparticles, boron nitride micron sheets, monoclinic zirconium dioxide and tetragonal zirconium dioxide to the mixture, mixing and high-energy ball milling to form a multiphase composite slurry, and high-temperature curing or high-temperature sintering the multiphase composite slurry to form a modified coating on the surface of a high-alumina brick lining.

7. The method for reprocessing the pickling filter cake according to claim 1, characterized in that: Air and mixed coal gas are introduced into the multi-stage roasting furnace; alkali solution including sodium hydroxide is added to the water washing purification tower; process water is added to the drum cooler, and the drainage discharged from the drum cooler also enters the water washing purification tower; acidic water is discharged from the 3-stage water washing deacidification tower.

8. The method for reprocessing the pickling filter cake according to claim 1, characterized in that: The inclination angles of the inclined screw conveyor 1 and the inclined screw conveyor 2 are both 15-50 degrees, the diameter of the conveying pipe is 100-400 mm, and the lining is made of high wear-resistant materials; the lifting height of the bucket conveyor is 2-8 meters, and the lifting speed is 2-4 meters / minute; the working temperature in the dryer is 100-250℃, the drying time is 10-15 minutes, and the moisture content of the dried material drops below 10%; the power of the induced draft fan is 20-60kW, and the air volume is 3000-8000 cubic meters / hour.

9. A pickling filter cake reprocessing device, the pickling filter cake reprocessing device is used in the pickling filter cake reprocessing method according to any one of claims 1 to 8, characterized in that: The pickling filter cake reprocessing device comprises a dryer, the dryer is connected to an inclined screw conveyor 1 through a buffer silo, the inclined screw conveyor 1 is connected to a double feed flap through a bucket conveyor, the double feed flap is connected to a multi-stage roasting furnace, the multi-stage roasting furnace is connected to an inclined screw conveyor 2 through a drum cooler, and the inclined screw conveyor 2 is connected to a product silo; the multi-stage roasting furnace is also connected to a three-stage water washing and deacidification tower through a cyclone dust collector, the three-stage water washing and deacidification tower is connected to an induced draft fan through a water washing purification tower, and the induced draft fan is connected to a chimney.

10. The pickling filter cake reprocessing device according to claim 9, characterized in that: The three-stage water-washing and deacidifying tower comprises water-washing and deacidifying tower 1, water-washing and deacidifying tower 2 and water-washing and deacidifying tower 3. The cyclone dust collector is connected to water-washing and deacidifying tower 1. Water-washing and deacidifying tower 1 is connected to water-washing and deacidifying tower 3 through water-washing and deacidifying tower 2. Water-washing and deacidifying tower 3 is connected to a water-washing and purification tower. A mechanical vibration device is installed in the multi-stage roasting furnace. The vibration frequency of the mechanical vibration device is 5-10 Hz.

Images