Continuous inorganic surface treatment system and method for titanium dioxide

Abstract

The present application relates to the field of titanium dioxide production, and discloses a continuous inorganic surface treatment system and method for titanium dioxide, which comprises: a plurality of treatment containers connected in sequence, the plurality of treatment containers comprising a dilution slurry preheating tank, at least one curing tank and a film-coating end material storage tank; a supply module configured to supply at least one of a dispersing agent, dilution water, a film-coating agent, a pH regulator and steam to the treatment containers correspondingly; a plurality of upwardly-protruding U-shaped pipes, each of which is connected between adjacent treatment containers and comprises a first horizontal section, a first vertical section, a second horizontal section and a second vertical section connected in sequence, wherein the first horizontal section is connected to the bottom of an upstream treatment container, the second horizontal section is higher than the first horizontal section and lower than the top of the upstream treatment container, and the outlet of the second vertical section is higher than the first horizontal section and connected to the top of a downstream treatment container. The present application can improve the stability of the quality of the film-coated titanium dioxide product.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology, specifically to a continuous inorganic surface treatment system and method for titanium dioxide. Background Technology

[0002] Currently, the post-processing of titanium dioxide mainly employs an intermittent coating process. This requires large-volume and numerous coating tanks, resulting in low production efficiency and quality variations between batches. To meet production demands, multiple batches often need to be processed simultaneously, requiring a large number of operators and leading to high labor intensity.

[0003] To improve production efficiency and reduce labor intensity, continuous coating processes can be used. However, in existing continuous coating processes, the processing time of materials in the container lacks effective control, resulting in deviations in the processing time of different batches of materials in the container, leading to poor product quality stability.

[0004] Therefore, how to achieve precise control of material handling time during continuous coating process in order to improve the stability of titanium dioxide coating product quality is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a continuous inorganic surface treatment system and method for titanium dioxide to solve the technical problem of how to improve the quality stability of titanium dioxide coated products.

[0006] According to one aspect of the present invention, a continuous inorganic surface treatment system for titanium dioxide is provided, comprising: a plurality of processing containers connected in sequence, the plurality of processing containers including a diluent slurry preheating tank, at least one curing tank and a coating end material storage tank; a supply module configured to supply the processing containers with at least one of a dispersant, diluent water, coating agent, pH adjuster and steam; and a plurality of upwardly protruding U-shaped tubes, each U-shaped tube being connected between adjacent processing containers and including a first transverse section, a first vertical section, a second transverse section and a second vertical section connected in sequence, wherein the first transverse section is connected to the bottom of an upstream processing container, the second transverse section is higher than the first transverse section and lower than the top of the upstream processing container, and the outlet of the second vertical section is higher than the first transverse section and connected to the top of a downstream processing container.

[0007] According to one embodiment of the present invention, at least one curing tank includes a zirconium-clad curing tank and an aluminum-clad curing tank connected in sequence. The supply module includes a zirconium coating agent supply unit, an aluminum coating agent supply unit, and a pH adjuster supply unit. The zirconium coating agent supply unit is connected to a U-shaped pipe upstream of the zirconium-clad curing tank, the aluminum coating agent supply unit is connected to a U-shaped pipe upstream of the aluminum-clad curing tank, and the pH adjuster supply unit is connected to the aluminum-clad curing tank.

[0008] According to one embodiment of the present invention, at least one processing container is provided with a pH meter, and the supply module includes a pH adjuster supply unit in fluid communication with at least one processing container; the system further includes a control unit configured to control the flow rate of the pH adjuster supplied to the corresponding processing container based on the detection result of the pH meter.

[0009] According to one embodiment of the present invention, the system further includes an initial slurry pipeline connected to the top of the dilution slurry preheating tank, and the supply module includes a dispersant supply unit, a dilution water supply unit, a pH adjuster supply unit, and a steam supply unit connected to the initial slurry pipeline.

[0010] According to one embodiment of the present invention, the system further includes a control unit and a washing device connected to the coating end material storage tank, the control unit being configured to: in response to the material quantity in the coating end material storage tank reaching a predetermined value, convey material to the washing device for washing.

[0011] According to another aspect of the present invention, a continuous inorganic surface treatment method for titanium dioxide is proposed, comprising: starting the system as described above, such that an initial slurry continuously and sequentially enters a plurality of treatment containers for treatment; wherein, before starting the system, the method further comprises: calculating the initial slurry flow rate based on the target yield per unit time and the initial slurry concentration; calculating the flow rate of other added materials based on the initial slurry flow rate and process requirements, the other added materials including dispersants, coating agents, pH adjusters, and dilution water; and determining the design volume of the corresponding treatment container based on the total flow rate of all materials entering the treatment container and the preset treatment time of the materials in the corresponding treatment container.

[0012] According to one embodiment of the present invention, calculating the flow rate of other added materials includes: calculating the dispersant flow rate based on the initial slurry flow rate and the required amount of dispersant added; calculating the coating agent flow rate based on the initial slurry flow rate and the required amount of coating agent added; and calculating the dilution water flow rate based on the initial slurry concentration, the initial slurry flow rate, and the required concentration after dilution. The method further includes: controlling the system based on the initial slurry flow rate, the dispersant flow rate, the dilution water flow rate, and the coating agent flow rate after system startup.

[0013] According to one embodiment of the present invention, at least one curing tank includes a zirconium-clad curing tank and an aluminum-clad curing tank connected in sequence, and a pH meter is provided inside the processing container; the method further includes: automatically adjusting the flow rate of pH adjuster based on the detection result of the pH meter, so that the pH value in the diluted slurry preheating tank is 9.5~10.5, the pH value in the aluminum-clad curing tank is 9.5~10.5 or 4.5~6.5, and the pH value in the coating end material storage tank is 6.8~7.5.

[0014] According to one embodiment of the present invention, the temperature inside each processing container is maintained at 60~65°C by controlling the steam flow rate.

[0015] According to one embodiment of the present invention, when the liquid level in the U-shaped tube upstream of the curing tank reaches the second transverse section during the first operation of the system, the corresponding coating agent is added to the curing tank.

[0016] In the technical solution of the present invention, the U-shaped tube and the upstream processing container form a communication device, and the liquid level in the upstream processing container will be stably maintained at the height corresponding to the second horizontal section at the top of the U-shaped tube. This allows for precise control of the amount of material in the upstream processing container. Furthermore, the upward-protruding U-shaped tube ensures that the material flows smoothly at a stable flow rate. Thus, a stable and sufficient material processing time can be achieved through a stable material quantity and a smooth flow process, thereby improving the stability of the titanium dioxide coating product quality. Attached Figure Description

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

[0018] Figure 1 A schematic diagram of a continuous inorganic surface treatment system for titanium dioxide according to an embodiment of the present invention is shown; Figure 2 SEM images of the titanium dioxide coating products obtained in Examples 1-2 and Comparative Examples 1-2 are shown.

[0019] Explanation of reference numerals in the attached figures: 10. Initial slurry storage tank; 12. Initial slurry pipeline; 20. Diluted slurry preheating tank; 22. First U-tube; 24. First pH meter; 30. Zirconium coating curing tank; 32. Second U-tube; 34. Second pH meter; 40. Aluminum coating curing tank; 42. Third U-tube; 44. Third pH meter; 50. Coating end material storage tank; 54. Fourth pH meter; 60. Washing equipment; 71. Dispersant supply unit; 72. Dilution water supply unit; 73. Zirconium coating agent supply unit; 74. Aluminum coating agent supply unit; 75. Alkali supply unit; 76. Acid supply unit; 77. Steam supply unit. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0023] refer to Figure 1 This invention proposes a continuous inorganic surface treatment system for titanium dioxide, comprising: a plurality of processing containers connected in sequence, the plurality of processing containers including a diluent slurry preheating tank 20, at least one curing tank and a coating end material storage tank 50; a supply module configured to supply the processing containers with at least one of a dispersant, diluent water, coating agent, pH adjuster and steam; and a plurality of upwardly protruding U-shaped tubes, each U-shaped tube being connected between adjacent processing containers and including a first horizontal section, a first vertical section, a second horizontal section and a second vertical section connected in sequence, wherein the first horizontal section is connected to the bottom of an upstream processing container, the second horizontal section is higher than the first horizontal section and lower than the top of the upstream processing container, and the outlet of the second vertical section is higher than the first horizontal section and connected to the top of a downstream processing container.

[0024] In the technical solution of this invention, the U-shaped tube and the upstream processing container form a communication device, and the liquid level in the upstream processing container will be stably maintained at the height corresponding to the second horizontal section at the top of the U-shaped tube. This allows for precise control of the amount of material in the upstream processing container. Furthermore, the upward-protruding U-shaped tube ensures that the material flows smoothly at a stable flow rate (the material is lifted from the upstream processing container to the top of the U-shaped tube, avoiding vortices caused by the high pressure at the bottom of the upstream processing container). Thus, a stable material quantity and a smooth flow process enable a stable and sufficient material processing time, thereby improving the stability of the titanium dioxide coating product quality.

[0025] In some embodiments, at least one curing tank includes a zirconium-clad curing tank 30 and an aluminum-clad curing tank 40 connected in sequence. A plurality of U-tubes include a first U-tube 22 connected between the diluted slurry preheating tank 20 and the zirconium-clad curing tank 30, a second U-tube 32 connected between the zirconium-clad curing tank 30 and the aluminum-clad curing tank 40, and a third U-tube 42 connected between the aluminum-clad curing tank 40 and the coating end material storage tank 50.

[0026] In some embodiments, the supply module includes a dispersant supply unit 71, a dilution water supply unit 72, a zirconium coating agent supply unit 73, an aluminum coating agent supply unit 74, an alkali supply unit 75, an acid supply unit 76, and a steam supply unit 77. The alkali supply unit 75 and the acid supply unit 76 are pH adjuster supply units. The alkali can be, for example, a NaOH solution, the acid can be, for example, a dilute sulfuric acid solution, the zirconium coating agent can be, for example, a zirconium sulfate solution, and the aluminum coating agent can be, for example, a sodium aluminate solution. Each supply unit may include a storage tank and / or a conveying pipeline, on which components such as automatic regulating valves, metering pumps, and flow meters may be installed to automatically control the opening and closing of the material supply and the flow rate. At least one processing vessel is equipped with an online pH meter to detect the pH value in real time, so as to adjust the flow rate of the pH adjuster (NaOH solution, dilute sulfuric acid) according to the pH control range required by the process. The system temperature can be controlled at 60~65°C by controlling the steam flow rate.

[0027] In some embodiments, the system further includes an initial slurry storage tank 10 and an initial slurry pipeline 12 connecting the initial slurry storage tank 10 and the dilution slurry preheating tank 20, the initial slurry pipeline 12 being connected to the top of the dilution slurry preheating tank 20. The initial slurry can be a sand-milled slurry. The initial slurry pipeline 12 can be connected to a dispersant supply unit 71, a dilution water supply unit 72, a pH adjuster supply unit (alkali supply unit 75), and a steam supply unit 77, so that the dispersant, dilution water, and alkali (NaOH solution) are initially mixed with the initial slurry in the initial slurry pipeline 12 before entering the dilution slurry preheating tank 20 for further mixing, improving the mixing uniformity. Steam is used to provide a suitable temperature for the dilution process. The dilution slurry preheating tank 20 is equipped with a first pH detector 24 to detect the pH value in real time.

[0028] In some embodiments, the zirconium coating agent supply unit 73 is connected to a U-shaped pipe (first U-shaped pipe 22) upstream of the zirconium coating curing tank 30, so that the zirconium coating agent is initially mixed with the diluted slurry in the first U-shaped pipe 22 before entering the zirconium coating curing tank 30 for further mixing to fully carry out the zirconium coating reaction. A steam supply unit 77 is connected to the zirconium coating curing tank 30 to provide a suitable reaction temperature. A second pH meter 34 is installed inside the zirconium coating curing tank 30.

[0029] In some embodiments, the aluminum coating agent supply unit 74 is connected to a U-shaped pipe (second U-shaped pipe 32) upstream of the aluminum coating curing tank 40, so that the aluminum coating agent is initially mixed with the zirconium-coated slurry in the second U-shaped pipe 32 before entering the aluminum coating curing tank 40 for further mixing to fully carry out the aluminum coating reaction. A pH adjuster supply unit is connected to the aluminum coating curing tank 40 to provide suitable reaction pH conditions. A third pH meter 44 is installed inside the aluminum coating curing tank 40 to monitor the pH value in real time. A steam supply unit 77 is connected to the aluminum coating curing tank 40 to provide a suitable reaction temperature.

[0030] In some embodiments, the coating end material storage tank 50 is connected to a pH adjuster supply unit to adjust the coating end material to a suitable pH value. A fourth pH meter 54 is provided within the coating end material storage tank 50. In some embodiments, the system further includes a washing device 60 (e.g., a diaphragm washing device) connected to the coating end material storage tank 50.

[0031] In some embodiments, the system further includes a control unit for controlling the entire continuous inorganic surface treatment process. The control unit can control the flow rates of various materials to control appropriate material ratios, reaction temperatures, reaction pH conditions, yield per unit time, etc. The control unit can be configured to deliver material to the washing equipment 60 for washing in response to the material quantity in the coating end material storage tank 50 reaching a predetermined value. The control unit can be configured to control the flow rate of pH adjuster supplied to the corresponding processing container based on real-time detection results from a pH meter and preset pH conditions.

[0032] According to another aspect of the present invention, a continuous inorganic surface treatment method for titanium dioxide is proposed, comprising: starting the system as described above, so that the initial slurry is continuously and sequentially fed into a plurality of treatment containers for treatment.

[0033] Before starting the system, the method also includes: calculating the initial slurry flow rate based on the target output per unit time and the initial slurry concentration; calculating the flow rates of other added materials, including dispersants, coating agents, pH adjusters, and dilution water, based on the initial slurry flow rate and process requirements; and determining the design volume (nominal volume) of the corresponding treatment container based on the total flow rate of all materials entering the treatment container and the preset treatment time of the materials in the corresponding treatment container. A treatment container that meets the design volume requirements is then selected. When the target output changes significantly, a treatment container of a different volume can be used; when the target output changes only slightly, only the U-tubes of different heights need to be replaced to change the loading height inside the treatment container.

[0034] In some embodiments, calculating the flow rates of other added materials includes: calculating the dispersant flow rate based on the initial slurry flow rate and the required amount of dispersant; calculating the coating agent flow rate based on the initial slurry flow rate and the required amount of coating agent; and calculating the dilution water flow rate based on the initial slurry concentration, the initial slurry flow rate, and the required concentration after dilution. In some embodiments, the method further includes: controlling the continuous inorganic surface treatment process based on the initial slurry flow rate, the dispersant flow rate, the dilution water flow rate, and the coating agent flow rate after system startup.

[0035] In some embodiments, determining the design volume of the corresponding processing container includes: calculating the product of the total flow rate and the preset processing time to obtain the effective volume (the effective volume is the volume inside the processing container from the bottom to the height corresponding to the top of the downstream U-tube), dividing the effective volume by the loading coefficient to obtain the design volume of the corresponding processing container.

[0036] In some embodiments, the method further includes: automatically adjusting the flow rate of pH adjuster based on the detection results of a pH meter, so that the pH value in the diluted slurry preheating tank 20 is 9.5~10.5, the pH value in the aluminum cladding curing tank 40 is 9.5~10.5 or 4.5~6.5, and the pH value in the coating end material storage tank 50 is 6.8~7.5.

[0037] In some embodiments, the temperature inside each processing vessel is maintained at 60-65°C by controlling the steam flow rate.

[0038] In some embodiments, when the system is first run, when the liquid level in the U-tube upstream of the curing tank reaches the second transverse section, the corresponding coating agent is added to the curing tank.

[0039] The following description is based on specific embodiments and comparative examples.

[0040] Example 1 (Zirconium-aluminum continuous coating, wherein the aluminum coating adopts an alkaline co-flow process) Based on a daily output of 240 tons, a continuous coating system is designed to coat 1000 kg of TiO2 per hour.

[0041] I. Coating process parameter settings (1) The concentrations of the sand grinding slurry, C1=350g / L (based on TiO2), sodium hexametaphosphate dispersant, C2=100g / L (based on P2O5), zirconium sulfate coating agent, C3=100g / L (based on ZrO2), sodium aluminate coating agent, C4=100g / L (based on Al2O3), and aluminum sulfate solution coating agent, C5=100g / L (based on Al2O3), were obtained in advance.

[0042] (2) Calculate the material flow rate according to the product coating process requirements: ① Determine the flow rate V1 (unit L / h) of the sand mill slurry based on the designed output. The designed output is k=1000 (calculated as TiO2, unit kg / h). Then V1=1000*k / C1=1000×1000(kg / h)÷350g / L =2857.14L / h.

[0043] ② The initial flow rate of the sodium hydroxide solution for pH adjustment is set according to the flow rate of the dispersant, and then dynamically adjusted according to the detection results of the first pH meter (to ensure that the pH of the diluted slurry is in the range of 9.5~10.5).

[0044] ③ The flow rate of the dispersant sodium hexametaphosphate solution is set to 0.3% of the ratio of its addition to titanium dioxide according to the coating process requirements, i.e., m1=(C2*V2) / (C1*V1)=0.3%, then its flow rate V2=V1*C1*m1 / C2=2857.14×350×0.3%÷100=30.0L / h.

[0045] ④ The ratio of the amount of zirconium sulfate solution added to titanium dioxide according to the coating process requirements is m2=0.4%, then its flow rate V3=V1*C1*m2 / C3=2857.14×350×0.4%÷100=40.0L / h.

[0046] ⑤ The flow rate of the coating agent sodium aluminate solution is 2.5% of the ratio of its addition to titanium dioxide according to the coating process requirements, i.e., m3=(C4*V4) / (C1*V1)=2.5%, then its flow rate V4=V1*C1*m3 / C4=2857.14×350×2.5%÷100=250L / h.

[0047] ⑥ The flow rate of dilute sulfuric acid is controlled within the pH range of 9.5 to 10.0, and is automatically adjusted based on the feedback results from the third pH meter.

[0048] ⑦ The dilution water flow rate V5, after dilution according to the process requirements, the concentration is C0=280g / L (based on TiO2), then the dilution water V5=(C1-C0)*V1 / C0=(350-280)*2857.14 / 280=714.29L / h.

[0049] ⑧ Adjust the final pH to 6.8~7.5 using dilute sulfuric acid, with the flow rate automatically adjusted based on the feedback from the fourth pH meter.

[0050] II. Continuous Coating Equipment and Connection Method (1) According to the zirconium-aluminum surface treatment process, a zirconium sulfate solution storage tank, a sodium aluminate solution storage tank, a sodium hydroxide solution storage tank, a dilute sulfuric acid solution storage tank, a sand grinding slurry storage tank, a diluted slurry preheating tank, a zirconium coating curing tank, an aluminum coating curing tank, and a coating end material storage tank are provided.

[0051] (2) Connect the steam pipeline to the dilution slurry preheating tank, the zirconium curing tank, and the aluminum curing tank respectively, and install automatic regulating valves on the pipelines so that the system temperature can be controlled at 60~65℃ by controlling the steam flow.

[0052] (3) Use a metering pump, flow meter and pipeline to connect the sand grinding slurry storage tank and the dilution slurry storage tank.

[0053] (4) Install the first to fourth online pH detectors in the dilution slurry preheating tank, zirconium coating curing tank, aluminum coating curing tank, and coating end material storage tank, respectively.

[0054] (5) Connect the dilution water, NaOH solution, and dispersant to the sand mill slurry feed pipe in sequence through the pipe, and install a flow meter and an automatic regulating valve on the pipe. By controlling the flow ratio of dilution water, dispersant and sand mill slurry feed, the dilution slurry is controlled according to the set concentration. After initial mixing in the pipe, it enters the dilution slurry preheating tank for preheating and further uniform mixing. The flow rate of pH adjuster is automatically adjusted according to the process requirements range based on the online pH feedback results.

[0055] (6) A zirconium coating ripening tank is installed at a suitable lower position at the rear end of the diluent preheating tank. The two are connected by an upward-protruding first U-shaped pipe to ensure that the uniformly mixed material in the preheating tank continuously enters the zirconium coating ripening tank. At the same time, the first coating agent (zirconia solution) storage tank is connected to the rear end of the first U-shaped pipe by a pipe, flow meter, and automatic valve, so that the zirconium sulfate solution and the preheated TiO2 diluent slurry are initially mixed evenly in the pipe before entering the zirconium coating ripening tank. The height from the bottom to the top of the first U-shaped pipe in the diluent preheating tank is... The corresponding effective volume is set as slurry mixing time × (slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate). The dilution mixing time is designed to be 0.5 hours, and the NaOH solution flow rate is estimated at 30 L / h based on the dispersant dosage. Therefore, the effective volume = 0.5 × (2857.14 + 280 + 30 + 30) = 1598.57 L. Based on a typical tank filling coefficient of 70%, the volume of the dilution preheating tank should be approximately 1598.57 ÷ 0.7 = 2283.67 L ≈ 2.3 m³. 3 .

[0056] (7) Set up an aluminum curing tank at a suitable lower position at the rear end of the zircon curing tank. The two are connected by an upward-protruding second U-shaped pipe to ensure that the material in the zircon curing tank continuously enters the aluminum curing tank. At the same time, connect the second coating agent (sodium aluminate solution) storage tank to the rear end of the second U-shaped pipe with a pipe, flow meter and automatic valve so that the sodium aluminate solution and the zircon-coated TiO2 slurry are initially mixed evenly in the pipe before entering the aluminum curing tank. At the same time, connect the dilute sulfuric acid solution storage tank to the aluminum curing tank with a pipe, flow meter and automatic valve. The effective volume corresponding to the height from the bottom to the top of the second U-shaped pipe in the zirconium coating curing tank is the coating curing time of the first coating agent (zirconia sulfate) × (grinding slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate + zirconium sulfate solution flow rate). The zirconium coating curing time is designed to be 1 hour. Therefore, the effective volume = 1.0 × (2857.14 + 280 + 30 + 30 + 40) = 3237.14 L. Based on a typical storage tank filling coefficient of 70%, the volume of the zirconium coating curing tank is 3197.14 ÷ 0.7 = 4624.49 L ≈ 4.6 m³. 3 .

[0057] (8) A coating end material storage tank is set at a suitable lower position at the rear end of the aluminum cladding curing tank. The two are connected by an upward-protruding third U-shaped pipe to ensure that the material in the aluminum cladding curing tank is fully cured and continuously enters the coating end material storage tank. The effective volume corresponding to the height position from the bottom to the top of the third U-shaped pipe in the aluminum cladding curing tank is the aluminum cladding curing time × (grinding slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate + zirconium sulfate flow rate + dilution water flow rate). (Sulfuric acid flow rate + sodium aluminate flow rate), the aluminum cladding curing time is designed for 2.0 hours, using 20% ​​sulfuric acid in a parallel flow, with an estimated flow rate of approximately 100 L / h. Therefore, the volume = 2.0 × (2857.14 + 280 + 30 + 30 + 40 + 250 + 100) = 7174.28 L. Based on a typical tank filling coefficient of 70%, the volume of the aluminum cladding curing tank is 7174.28 ÷ 0.7 = 10248.97 L ≈ 10.2 m³. 3 .

[0058] (9) The pH adjuster (NaOH solution, dilute sulfuric acid solution) is connected to the coating end material storage tank through pipes, flow meters, automatic valves, etc. The flow rate of the pH adjuster is automatically adjusted according to the pH control requirements and the feedback result of the online pH detector.

[0059] (10) The volume of the finishing material storage tank is calculated as twice that of the aluminum cladding curing tank, which is 10.2 × 2 = 20.4 m³. 3 The system is then connected to a diaphragm washing unit via pumps and pipes. The processing capacity of the diaphragm washing unit should match the amount of titanium dioxide coated, i.e., the washing capacity should be greater than 1000 kg of titanium dioxide per hour.

[0060] (11) During the initial operation, the sand mill slurry, NaOH solution, and dispersant are fed simultaneously. When the diluted slurry is preheated and filled to the top of the first U-tube, the zirconium sulfate solution is fed. When the zirconium curing tank is filled to the top of the second U-tube, the sodium aluminate solution is fed. When the third pH meter detects that the pH reaches the range of 9.5 to 10.5, dilute sulfuric acid begins to flow concurrently into the aluminate curing tank and maintains this pH range. When the aluminate curing tank is filled to the top of the third U-tube, dilute sulfuric acid solution begins to be fed into the coating end material storage tank, maintaining the value detected by the fourth pH meter in the range of 6.8 to 7.5. When the material in the coating end material storage tank is sufficient for one batch of diaphragm washing feed, the feed pump is started for washing to obtain the inorganic coated filter cake.

[0061] The coated product A was obtained using the process described in Example 1.

[0062] Example 2 (Zirconium-aluminum cladding, wherein the aluminum cladding is produced using an acidic co-flow process) A continuous coating equipment is designed to coat 2000 kg of TiO2 per hour.

[0063] I. Coating process parameter settings (1) The concentrations of the sand-milling slurry, C1=350g / L (based on TiO2), sodium hexametaphosphate dispersant, C2=100g / L (based on P2O5), zirconium sulfate coating agent, C3=100g / L (based on ZrO2), sodium aluminate coating agent, C4=100g / L (based on Al2O3), and aluminum sulfate solution coating agent, C5=100g / L (based on Al2O3), were obtained in advance.

[0064] (2) Calculate the material flow rate according to the product coating process requirements: Calculate the material flow rate according to the product coating process requirements: ① Determine the flow rate V1 (unit L / h) of the sand mill slurry based on the designed output. The designed output is k=2000 (calculated as TiO2, unit kg / h). Then V1=1000*k / C1=1000×2000(kg / h)÷350g / L =5714.29L / h.

[0065] ② The initial flow rate of the sodium hydroxide solution for pH adjustment is set according to the flow rate of the dispersant, and then dynamically adjusted according to the detection results of the first online pH meter (to ensure that the pH of the diluted slurry is in the range of 9.5~10.5).

[0066] ③ The flow rate of the dispersant sodium hexametaphosphate solution is set to 0.3% of the ratio of its addition to titanium dioxide according to the coating process requirements, i.e., m1=(C2*V2) / (C1*V1)=0.3%, then its flow rate V2=V1*C1*m1 / C2=5714.29×350×0.3%÷100=60.0L / h.

[0067] ④ The ratio of the amount of zirconium sulfate solution added to titanium dioxide according to the coating process requirements is m2=0.4%, then its flow rate V3=V1*C1*m2 / C3=5714.29×350×0.4%÷100=80.0L / h.

[0068] ⑤ The flow rate of the coating agent sodium aluminate solution is 2.5% of the ratio of its addition to titanium dioxide according to the coating process requirements, i.e., m3=(C4*V4) / (C1*V1)=2.5%, then its flow rate V4=V1*C1*m3 / C4=5714.29×350×2.5%÷100=500L / h.

[0069] ⑥ The flow rate of dilute sulfuric acid is controlled within the pH range of 9.5 to 10.0, and is automatically adjusted based on the feedback results from the third pH meter.

[0070] ⑦ The dilution water flow rate V5, after dilution according to the process requirements, the concentration is C0=280g / L (based on TiO2), then the dilution water V5=(C1-C0)*V1 / C0=(350-280)*5714.29 / 280=1428.58L / h.

[0071] ⑧ Adjust the final pH to 6.8~7.5 using dilute sulfuric acid, with the flow rate automatically adjusted based on the feedback from the fourth pH meter.

[0072] II. Continuous Coating Equipment and Connection Method (1) According to the zirconium-aluminum surface treatment process, a zirconium sulfate solution storage tank, a sodium aluminate solution storage tank, a sodium hydroxide solution storage tank, a dilute sulfuric acid solution storage tank, a sand grinding slurry storage tank, a diluted slurry preheating tank, a zirconium coating curing tank, an aluminum coating curing tank, and a coating end material storage tank are provided.

[0073] (2) Connect the steam pipeline to the dilution slurry preheating tank, the zirconium curing tank, and the aluminum curing tank respectively, and install automatic regulating valves on the pipelines so that the system temperature can be controlled at 60~65℃ by controlling the steam flow.

[0074] (3) Use a metering pump, flow meter and pipeline to connect the sand grinding slurry storage tank and the dilution slurry storage tank.

[0075] (4) Install the first to fourth online pH detectors in the dilution slurry preheating tank, zirconium coating curing tank, aluminum coating curing tank, and coating end material storage tank, respectively.

[0076] (5) Connect the dilution water, NaOH solution, and dispersant to the sand mill slurry feed pipe in sequence through the pipe, and install a flow meter and an automatic regulating valve on the pipe. By controlling the flow ratio of dilution water, dispersant and sand mill slurry feed, the dilution slurry is controlled according to the set concentration. After initial mixing in the pipe, it enters the dilution slurry preheating tank for preheating and further uniform mixing. The flow rate of pH adjuster is automatically adjusted according to the process requirements range based on the online pH feedback results.

[0077] (6) A zirconium coating ripening tank is installed at a suitable lower position at the rear end of the diluent preheating tank. The two are connected by an upward-protruding first U-shaped pipe to ensure that the uniformly mixed material in the preheating tank continuously enters the zirconium coating ripening tank. At the same time, the first coating agent (zirconia solution) storage tank is connected to the rear end of the first U-shaped pipe by a pipe, flow meter, and automatic valve, so that the zirconium sulfate solution and the preheated TiO2 diluent slurry are initially mixed evenly in the pipe before entering the zirconium coating ripening tank. The height from the bottom to the top of the first U-shaped pipe in the diluent preheating tank is as follows: The corresponding effective volume is calculated as slurry mixing time × (slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate). The dilution mixing time is designed to be 0.5 hours, and the NaOH solution flow rate is estimated at 60 L / h based on the dispersant dosage. Therefore, the effective volume = 0.5 × (5714.29 + 714.29 + 60 + 60) = 3274.29 L. Based on a typical tank filling coefficient of 70%, the volume of the dilution preheating tank should be approximately 1598.57 ÷ 0.7 = 4677.56 L ≈ 4.7 m³. 3 .

[0078] (7) Set up an aluminum curing tank at a suitable lower position at the rear end of the zircon curing tank. The two are connected by an upward-protruding second U-shaped pipe to ensure that the material in the zircon curing tank continuously enters the aluminum curing tank. At the same time, connect the second coating agent (sodium aluminate solution) storage tank to the rear end of the second U-shaped pipe with a pipe, flow meter and automatic valve so that the sodium aluminate solution and the zircon-coated TiO2 slurry are initially mixed evenly in the pipe before entering the aluminum curing tank. At the same time, connect the dilute sulfuric acid solution storage tank to the aluminum curing tank with a pipe, flow meter and automatic valve. The effective volume corresponding to the height from the bottom to the top of the second U-shaped pipe in the zirconium coating curing tank is the coating curing time of the first coating agent (zirconia sulfate) × (grinding slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate + zirconium sulfate solution flow rate). The zirconium coating curing time is designed to be 1 hour. Therefore, the effective volume = 1.0 × (5714.29 + 714.29 + 60 + 60 + 80) = 6474.28 L. Based on a typical storage tank filling coefficient of 70%, the volume of the zirconium coating curing tank should be approximately 6474.28 ÷ 0.7 = 9248.97 L ≈ 9.2 m³. 3 .

[0079] (8) A coating end material storage tank is set at a suitable lower position at the rear end of the aluminum cladding curing tank. The two are connected by an upward-protruding third U-shaped pipe to ensure that the material in the aluminum cladding curing tank is fully cured and continuously enters the coating end material storage tank. The effective volume corresponding to the height position from the bottom to the top of the third U-shaped pipe in the aluminum cladding curing tank is the aluminum cladding curing time × (grinding slurry flow rate + dilution water flow rate + dispersant flow rate + NaOH solution flow rate + zirconium sulfate flow rate + dilute sulfur (Acid flow rate + sodium aluminate flow rate), the cladding curing time is designed for 2.0 hours, using 20% ​​sulfuric acid in a parallel flow, with an estimated flow rate of approximately 200 L / h. Therefore, the effective volume = 2.0 × (5714.29 + 714.29 + 60 + 60 + 80 + 500 + 200) = 14348.56 L. Based on a typical tank filling coefficient of 70%, the volume of the cladding curing tank is 14348.56 ÷ 0.7 = 20497.94 L ≈ 20.5 m³. 3 .

[0080] (9) The pH adjuster (NaOH solution, dilute sulfuric acid solution) is connected to the coating end material storage tank through pipes, flow meters, automatic valves, etc. The flow rate of the pH adjuster is automatically adjusted according to the pH control requirements and the feedback result of the online pH detector.

[0081] (10) The volume of the coating finishing material storage tank is calculated as twice that of the aluminum cladding curing tank, which is 20.5 × 2 = 41.0 m³. 3 The system is then connected to a diaphragm washing unit via pumps and pipes. The processing capacity of the diaphragm washing unit should match the amount of titanium dioxide coated, i.e., the washing capacity should be greater than 2000 kg of titanium dioxide per hour.

[0082] (11) During the initial operation, the sand mill slurry, NaOH solution, and dispersant are fed simultaneously. When the diluted slurry is preheated and filled to the top of the first U-tube, the zirconium sulfate solution is fed. When the zirconium curing tank is filled to the top of the second U-tube, the sodium aluminate solution is fed. When the third pH meter detects that the pH reaches the range of 5.5 to 6.5, dilute sulfuric acid begins to flow concurrently into the aluminate curing tank and maintains this pH range. When the aluminate curing tank is filled to the top of the third U-tube, the NaOH solution is fed into the coating end material storage tank, maintaining the value detected by the fourth pH meter in the range of 6.8 to 7.5. When the material in the coating end material storage tank is sufficient for one batch of diaphragm washing feed, the feed pump is started for washing to obtain the inorganic coated filter cake.

[0083] The coated product C was obtained using the process described in Example 2.

[0084] Comparative Example 1 (Zirconium-aluminum intermittent cladding, wherein the aluminum cladding uses an alkaline co-flow process). Equipment specifications: Based on a production capacity of 240t / d, the intermittent coating process takes approximately 9.5 hours per batch; assuming each batch coats 20t, 12 batches are required. This 12-batch production per day necessitates 6 coating tanks, with each tank coating 2 batches. Each coating tank is approximately 110m³ in size (the final slurry concentration after coating is approximately 260kg / m³). 3 Assuming a 70% load, the required volume for 20 tons is: 20 × 1000 ÷ 260 ÷ 70% = 109.89 m³ 3 ).

[0085] Operating procedures: The main processes for intermittent zirconium-aluminum coating and alkaline aluminum coating are as follows: (1) The feed volume of the sand grinding slurry (350g / L) is approximately 57.14m. 3 It takes about 30 minutes; (2) Dilute the slurry to 280 g / L, and heat the slurry to 60~65℃, which takes about 15 minutes; (3) Add the dispersant and stir until homogeneous, which takes about 45 minutes; (4) Slowly add 0.4% zirconium sulfate solution and let it mature for a period of time, about 120 minutes, at which time the pH is in the range of 2 to 3; (5) Slowly add about 2.5% sodium aluminate solution. When the pH reaches 9.5~10.5, add dilute sulfuric acid in parallel. After adding, let it mature for a period of time, which takes about 180 minutes. (6) Slowly add dilute sulfuric acid to adjust the pH to 6.8~7.5 and let it mature for a period of time, about 150 minutes; (7) After the coating is completed, the material is transferred to the coating completion material storage tank, which takes about 30 minutes.

[0086] The coating time for a single batch is 30 + 15 + 45 + 120 + 180 + 150 + 30 = 570 min = 9.5 h. The coating product B was obtained using the process of Comparative Example 1.

[0087] Comparative Example 2 (Zirconium-aluminum intermittent cladding, wherein the aluminum cladding uses an acidic co-flow process). Equipment specifications: Based on a production capacity of 480 t / d, the intermittent coating time for each batch is approximately 9.5 hours; assuming each batch coats 20 t, 24 batches are required. This 24-batch production per day necessitates 12 coating tanks, with each tank coating 2 batches. Each coating tank is approximately 110 m² in size. 3 (The final slurry concentration after coating is approximately 260 kg / m³) 3 Assuming a 70% load, the required volume for 20 tons is: 20 × 1000 ÷ 260 ÷ 70% = 109.89 m³ 3 ).

[0088] Operating procedures: The main processes for intermittent zirconium-aluminum coating and acidic aluminum coating are as follows: (1) The feed volume of the sand grinding slurry (350g / L) is approximately 57.14m. 3 It takes about 30 minutes; (2) Dilute the slurry to 280 g / L, and heat the slurry to 60~65℃, which takes about 15 minutes; (3) Add the dispersant and stir until homogeneous, which takes about 45 minutes; (4) Slowly add 0.4% zirconium sulfate solution and let it mature for a period of time, about 120 minutes, at which time the pH is in the range of 2 to 3; (5) Slowly add about 2.5% sodium aluminate solution. When the pH reaches 5.5~6.5, add dilute sulfuric acid in parallel. After adding, let it mature for a period of time, which takes about 180 minutes. (6) Slowly add NaOH solution to adjust the pH to 6.8~7.5 and let it mature for a period of time, about 150 minutes; (7) After the coating is completed, the material is transferred to the coating completion material storage tank, which takes about 30 minutes; The coating time for a single batch is 30 + 15 + 45 + 120 + 180 + 150 + 30 = 570 min = 9.5 h. The coating product D was obtained using the process of Comparative Example 2.

[0089] Table 1 shows a comparison of the tank size and number of tanks in the continuous coating process of Examples 1-2 and the intermittent coating process of Comparative Examples 1-2.

[0090] Table 1 Comparison of Size and Quantity of Continuously Coated and Intermittently Coated Storage Tanks

[0091] As shown in Table 1, a continuous coating system with a capacity of 240 t / d requires 5 storage tanks, each 4.6 m in size. 3 ~20.4m 3 The quantities are not equal, while the intermittent coating process with the same output requires 6 storage tanks, each 110m in size. 3 The above demonstrates that the investment in intermittent coating equipment is significantly greater than that in continuous coating. Furthermore, continuously coated products exhibit better stability, while intermittently coated products show batch-to-batch variations.

[0092] Figure 2 SEM images of the continuous coating products obtained in Examples 1-2 and the intermittent coating products obtained in Comparative Examples 1-2 are shown, where A is continuous coating (aluminum basic co-flow), B is intermittent coating (aluminum basic co-flow), C is continuous coating (aluminate co-flow), and D is intermittent coating (aluminate co-flow). Figure 2 It is evident that both continuous and intermittent coating can coat the surface of titanium dioxide particles with a uniform film, thus continuous coating can completely replace intermittent coating.

[0093] In summary, this invention proposes a continuous inorganic surface treatment system and method for titanium dioxide. The system and method enable continuous production of inorganic coating for titanium dioxide, improve product quality stability, and simultaneously increase production efficiency and reduce labor intensity.

[0094] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A continuous inorganic surface treatment system for titanium dioxide, characterized in that, include: A plurality of processing containers connected in sequence, the plurality of processing containers including a slurry preheating tank, at least one maturation tank and a coating end material storage tank; The supply module is configured to supply the processing container with at least one of a dispersant, diluent water, coating agent, pH adjuster, and steam. Multiple upward-protruding U-shaped tubes, each U-shaped tube connecting adjacent processing containers and including a first horizontal segment, a first vertical segment, a second horizontal segment, and a second vertical segment connected in sequence, wherein the first horizontal segment is connected to the bottom of the upstream processing container, the second horizontal segment is higher than the first horizontal segment and lower than the top of the upstream processing container, and the outlet of the second vertical segment is higher than the first horizontal segment and connected to the top of the downstream processing container.

2. The system according to claim 1, characterized in that, The at least one curing tank includes a zirconium-coated curing tank and an aluminum-coated curing tank connected in sequence. The supply module includes a zirconium coating agent supply unit, an aluminum coating agent supply unit, and a pH adjuster supply unit. The zirconium coating agent supply unit is connected to the U-shaped pipe upstream of the zirconium-coated curing tank. The aluminum coating agent supply unit is connected to the U-shaped pipe upstream of the aluminum-coated curing tank. The pH adjuster supply unit is connected to the aluminum-coated curing tank.

3. The system according to claim 1, characterized in that, At least one of the processing containers is equipped with a pH meter, and the supply module includes a pH adjuster supply unit in fluid communication with at least one of the processing containers; the system also includes a control unit configured to control the flow rate of the pH adjuster supplied to the respective processing container based on the detection result of the pH meter.

4. The system according to claim 1, characterized in that, It also includes an initial slurry pipeline connected to the top of the diluted slurry preheating tank, and the supply module includes a dispersant supply unit, a dilution water supply unit, a pH adjuster supply unit, and a steam supply unit connected to the initial slurry pipeline.

5. The system according to claim 1, characterized in that, It also includes a control unit and a washing device connected to the coating end material storage tank, the control unit being configured to: in response to the material quantity in the coating end material storage tank reaching a predetermined value, deliver material to the washing device for washing.

6. A continuous inorganic surface treatment method for titanium dioxide, characterized in that, include: The system as described in any one of claims 1-5 is started, such that the initial slurry is continuously and sequentially fed into the plurality of processing containers for processing; Before starting the system, the method further includes: Calculate the initial slurry flow rate based on the target output per unit time and the initial slurry concentration; The flow rates of other added materials are calculated based on the initial slurry flow rate and process requirements. These other added materials include dispersants, coating agents, pH adjusters, and dilution water. The design volume of the corresponding processing container is determined based on the total flow rate of all materials entering the processing container and the preset processing time of the materials in the corresponding processing container.

7. The method according to claim 6, characterized in that, Calculating the flow rates of other added materials includes: calculating the dispersant flow rate based on the initial slurry flow rate and the required amount of dispersant; calculating the coating agent flow rate based on the initial slurry flow rate and the required amount of coating agent; and calculating the dilution water flow rate based on the initial slurry concentration, the initial slurry flow rate, and the required concentration after dilution. The method further includes: after starting the system, controlling the flow rate based on the initial slurry flow rate, the dispersant flow rate, the dilution water flow rate, and the coating agent flow rate.

8. The method according to claim 6, characterized in that, The at least one curing tank includes a zirconium-coated curing tank and an aluminum-coated curing tank connected in sequence, and the processing container is equipped with a pH meter; the method further includes: automatically adjusting the flow rate of the pH adjuster based on the detection result of the pH meter, so that the pH value in the diluted slurry preheating tank is 9.5~10.5, the pH value in the aluminum-coated curing tank is 9.5~10.5 or 4.5~6.5, and the pH value in the coating end material storage tank is 6.8~7.

5.

9. The method according to claim 6, characterized in that, The temperature inside each of the processing containers is maintained at 60-65°C by controlling the steam flow rate.

10. The method according to claim 6, characterized in that, When the system is first run, when the liquid level in the U-shaped tube upstream of the curing tank reaches the second transverse section, the corresponding coating agent is added to the curing tank.

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