Device and method for controlling particle size of titanium dioxide generated by chlorination process

Abstract

The invention discloses a device and method for controlling the particle size of titanium dioxide generated by a chlorination process, and the device comprises an oxidation reactor used for converting titanium tetrachloride into rutile type titanium dioxide; an inlet of the growth zone is connected with an outlet of the oxidation reactor, and the growth zone is used for controlling the nucleation number and growth time of rutile titanium dioxide so as to obtain titanium dioxide particles with a target particle size; an inlet of the cooling guide pipe is connected with an outlet of the growth area, and the cooling guide pipe is used for cooling the titanium dioxide particles. According to the scheme provided by the invention, the average particle size of the titanium dioxide chloride primary product is controllable in a range of 180-280nm, and in the process of controlling the particle size of the primary product, the average retention time of TiO2 particles in a high-temperature area is controlled without changing any raw and auxiliary material process control parameters. The additive KCl in the original process can be specially used for adjusting the particle size distribution of the primary product, AlCl3 is also specially used for controlling the rutile conversion rate, and excessive adjustment is not needed, so that the particle size distribution of the TiO2 primary product is more uniform.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide particle size control, and more specifically to an apparatus and method for controlling the particle size of titanium dioxide produced by the chlorination process. Background Technology

[0002] Currently, there are two main processes for producing titanium dioxide: the chloride process and the sulfate process. Compared with the sulfate process, the chloride process has advantages such as high automation, advanced technology, and superior environmental friendliness, thus gradually becoming the main trend in the titanium dioxide industry. Titanium dioxide is stable and is currently the best white pigment, widely used in coatings, plastics, papermaking, inks, and other fields. Different particle sizes of titanium dioxide chloride have a significant impact on optical properties. For example, titanium dioxide chloride with a particle size of 220-240nm has excellent visual whiteness and excellent hiding power and tinting strength in water-based and oil-based systems. For inks, titanium dioxide with a particle size of 210±10nm can effectively prevent the formation of ink slashes. Titanium dioxide chloride with a particle size of 180nm-200nm exhibits better white pigment properties in plastic and resin systems.

[0003] In the production of titanium dioxide, the basic principle of preparing the initial oxidation product is to utilize gaseous titanium tetrachloride and oxygen, which are thoroughly mixed in the reaction zone and reacted at a high temperature of 1600-2000℃. This gas-phase oxidation reaction occurs at millisecond speeds, with the initial titanium dioxide being generated instantaneously upon contact with the reactants. This initial titanium dioxide undergoes a coating and post-processing process to manufacture finished titanium dioxide products that meet the needs of different fields. The particle size of the initial product has a significant impact on the particle size of the finished titanium dioxide product, and the post-processing process only fine-tunes its particle size. Therefore, controlling the particle size of the initial product is a core and crucial step in controlling the type and quality grade of the finished titanium dioxide product. Among existing methods for controlling the particle size of the initial product, the use of additives KCl and AlCl3 is the most common. However, the use of additives is constrained by the control of properties such as rutile conversion rate, whiteness, brightness, color, and bleaching power of the initial product, making it difficult to effectively meet the particle size control requirements. Furthermore, adjusting process parameters such as the required concentration, flow rate, temperature, and pressure of the additives is very cumbersome, easily leading to low production stability and efficiency.

[0004] Therefore, how to efficiently and quickly control the particle size of primary titanium dioxide chloride has become an urgent problem to be solved. Summary of the Invention

[0005] In view of this, in order to overcome at least one aspect of the above-mentioned problems, embodiments of the present invention provide an apparatus for controlling the particle size of titanium dioxide produced by the chlorination process, comprising: An oxidation reactor is used to convert titanium tetrachloride into rutile titanium dioxide. The growth zone, whose inlet is connected to the outlet of the oxidation reactor, is used to control the number of nuclei and the growth time of the rutile titanium dioxide to obtain titanium dioxide particles of the target particle size. A cooling conduit, the inlet of which is connected to the outlet of the growth zone, is used to cool the titanium dioxide particles.

[0006] In some embodiments, the growth zone has a length of 30m to 50m and a diameter of 170mm to 300mm; The pressure inside the oxidation reactor is 380 kPa to 450 kPa, and the larger the diameter of the growth zone, the lower the pressure inside the oxidation reactor.

[0007] In some embodiments, the apparatus further includes: A collector, connected to the outlet of the cooling conduit, is used to collect the generated titanium dioxide particles.

[0008] In some embodiments, the apparatus further includes: A cooling water tank is provided, in which the growth zone and the cooling conduit are disposed.

[0009] In some embodiments, the cooling conduit includes: The first cooling conduit has its inlet connected to the outlet of the growth zone; The second cooling conduit has its inlet connected to the outlet of the first cooling conduit.

[0010] In some embodiments, the length of the first cooling conduit is 30m to 45m and the diameter is 160mm to 200mm; the length of the second cooling conduit is 40m to 60m and the diameter is 150mm to 200mm.

[0011] In some embodiments, the present invention also provides a method for controlling the particle size of titanium dioxide produced by the chlorination process, comprising the steps of: An oxidation reactor is filled with excess hot oxygen, and toluene and titanium tetrachloride are added to the oxidation reactor to obtain rutile titanium dioxide. The number of nuclei and the growth time of the rutile titanium dioxide are controlled by the growth zone to obtain titanium dioxide particles of the target particle size. The titanium dioxide particles are cooled using cooling conduits.

[0012] In some embodiments, the method further includes: The temperature of the titanium dioxide particles is controlled to be 400℃~600℃ when they enter the cooling conduit from the growth zone.

[0013] In some embodiments, the method further includes: The residence time of the titanium dioxide particles in the growth zone is controlled to be 500ms~900ms.

[0014] In some embodiments, the method further includes: Add aluminum trichloride and / or potassium chloride to the oxidation reactor.

[0015] This invention offers one of the following beneficial technical effects: The proposed solution achieves controllable average particle size of the initial titanium dioxide (TiO2) product within the range of 180-280 nm. During the initial particle size control process, no changes to any raw material or auxiliary process control parameters are required, and the average residence time of TiO2 particles in the high-temperature zone is controlled. The additive KCl in the original process can be specifically used to adjust the initial particle size distribution, and AlCl3 can be specifically used to control the rutile conversion rate, eliminating the need for excessive adjustments and resulting in a more uniform TiO2 initial particle size distribution. Attached Figure Description

[0016] 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 embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of an apparatus for controlling the particle size of titanium dioxide produced by the chlorination process, provided as an embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] According to one aspect of the present invention, embodiments of the present invention provide an apparatus for controlling the particle size of titanium dioxide produced by the chlorination process, such as... Figure 1 As shown, it includes: An oxidation reactor is used to convert titanium tetrachloride into rutile titanium dioxide. The growth zone, whose inlet is connected to the outlet of the oxidation reactor, is used to control the number of nuclei and the growth time of the rutile titanium dioxide to obtain titanium dioxide particles of the target particle size. A cooling conduit, the inlet of which is connected to the outlet of the growth zone, is used to cool the titanium dioxide particles.

[0021] The proposed solution achieves controllable average particle size of primary titanium dioxide (TiO2) in the range of 180-280 nm. During the primary particle size control process, no changes to any raw material or process control parameters are required, and the average residence time of TiO2 particles in the high-temperature zone is controlled. The additive KCl in the original process can be specifically used to adjust the primary particle size distribution, and AlCl3 is specifically used to control the rutile conversion rate, eliminating the need for excessive adjustments and resulting in a more uniform TiO2 primary particle size distribution.

[0022] In some embodiments, the growth zone has a length of 30m to 50m and a diameter of 170mm to 300mm, wherein the pressure inside the oxidation reactor is 380kPa to 450kPa, and the larger the diameter of the growth zone, the lower the pressure inside the oxidation reactor.

[0023] Specifically, such as Figure 1 As shown, the oxidation reactor is the core reaction unit for the chlorination process to prepare titanium dioxide. Titanium tetrachloride raw material undergoes a high-temperature oxidation reaction with oxygen within the reactor, generating rutile titanium dioxide crystal nuclei. The reactor's outlet and the growth zone inlet can be connected by a sealed flange to ensure that the high-temperature reaction products (typically 1600-2000℃) enter the growth zone without loss, avoiding temperature fluctuations caused by leakage that could affect crystal nucleus growth.

[0024] The growth zone is the core functional unit for controlling particle size. Its length and diameter parameters directly determine the high-temperature residence time and flow state of the titanium dioxide particles. Therefore, its length can be set to 30m~50m and its diameter to 170mm~300mm. This size range can ensure that the particles flow in a stable plug flow state in a high-temperature environment (1600-2000℃), avoiding uneven particle residence time caused by back-mixing. For example, if the length of the growth zone is less than 30m, the particle residence time is insufficient, the crystal nucleus growth is inadequate, and fine powder with too small a particle size is easily generated; if the length is greater than 50m, it will result in an excessively large equipment footprint and excessive particle growth, with the particle size exceeding the target range; if the diameter is less than 170mm, it will cause the material flow rate to be too fast and the residence time to be shortened; if the diameter is greater than 300mm, the material flow rate will be too slow, and particle agglomeration is likely to occur, affecting the uniformity of particle size.

[0025] The pressure inside the oxidation reactor is 380 kPa to 450 kPa. The larger the diameter of the growth zone, the lower the pressure inside the oxidation reactor. That is, when the diameter of the growth zone is 300 mm, the pressure inside the oxidation reactor is 380 kPa. As the diameter of the growth zone gradually decreases, the pressure inside the oxidation reactor gradually increases until the diameter of the growth zone is 170 mm, at which point the pressure inside the oxidation reactor is 450 kPa.

[0026] In some embodiments, the apparatus further includes: A collector, connected to the outlet of the cooling conduit, is used to collect the generated titanium dioxide particles.

[0027] Specifically, such as Figure 1 As shown, the titanium dioxide particles cooled by the cooling conduit remain in an air-entrained state. The collector can efficiently separate the particles from the carrier gas through filtration, preventing product loss. For titanium dioxide particles with a target particle size (180~280nm), a bag filter can be used to achieve directional collection of qualified particles while retaining a small amount of agglomerated large particles. The collector is sealed to the cooling conduit to prevent particle oxidation or contamination caused by outside air. Simultaneously, the lower outlet of the bag filter is precisely connected to the pulping tank, allowing the collected, dried titanium dioxide particles to be directly transported to the pulping stage.

[0028] In some embodiments, the apparatus further includes: A cooling water tank is provided, in which the growth zone and the cooling conduit are disposed.

[0029] In some embodiments, the cooling conduit includes: The first cooling conduit has its inlet connected to the outlet of the growth zone; The second cooling conduit has its inlet connected to the outlet of the first cooling conduit.

[0030] In some embodiments, the length of the first cooling conduit is 30m to 45m and the diameter is 160mm to 200mm; the length of the second cooling conduit is 40m to 60m and the diameter is 150mm to 200mm.

[0031] Specifically, the cooling water tank provides a stable temperature environment for the growth zone through water bath cooling, helping to maintain the high-temperature conditions required for particle nucleation and growth. Parameters such as the flow rate of the 25°C ambient temperature demineralized water in the cooling water tank and the volume of the cooling water tank can be adjusted according to production capacity needs. For example, the cooling water tank is 70m long, 15m wide, and has a cooling water flow rate of 260m³ / h. The segmented cooling conduit achieves gradient cooling under the cooling effect of the water tank, gradually reducing the particle temperature from the high temperature of the growth zone to 400°C~600°C at the outlet of the growth zone. After further cooling by the cooling conduit, the particles enter the bag filter. During filtration, the particles continue to cool naturally. This temperature range avoids violent vaporization when high-temperature particles directly enter the pulper and come into contact with the solvent, ensuring operational safety. Simultaneously, a suitable temperature enhances the wetting effect of the solvent on the particles, contributing to the preparation of a uniform slurry.

[0032] In some embodiments, the cooling conduit is not limited to two sections; the number of sections and the size of each section can be changed according to production capacity requirements to adapt to different production needs.

[0033] In some embodiments, the present invention also provides a method for controlling the particle size of titanium dioxide produced by the chlorination process, comprising the steps of: An oxidation reactor is filled with excess hot oxygen, and toluene and titanium tetrachloride are added to the oxidation reactor to obtain rutile titanium dioxide. The number of nuclei and the growth time of the rutile titanium dioxide are controlled by the growth zone to obtain titanium dioxide particles of the target particle size. The titanium dioxide particles are cooled using cooling conduits.

[0034] In some embodiments, the method further includes: The temperature of the titanium dioxide particles is controlled to be 400℃~600℃ when they enter the cooling conduit from the growth zone.

[0035] In some embodiments, the method further includes: The residence time of the titanium dioxide particles in the growth zone is controlled to be 500ms~900ms.

[0036] In some embodiments, the method further includes: Add aluminum trichloride and / or potassium chloride to the oxidation reactor.

[0037] Specifically, a certain amount of toluene can be injected into a reactor filled with excess hot oxygen and burned. A certain amount of preheated refined titanium tetrachloride is added, along with AlCl3 and potassium chloride, so that titanium tetrachloride can fully react in the oxidation reactor and be converted into rutile TiO2. Without changing the raw material and auxiliary material process control parameters, the length of the growth zone is set to 30m~50m and the diameter to 170mm~300mm. The material temperature at the outlet of the growth zone is controlled to be 400℃~600℃. The average residence time of titanium dioxide particles in the high-temperature zone is further controlled to be within the range of 500ms~900ms, so as to control the number of grain nucleation and the growth time.

[0038] Finally, the reaction product, rutile TiO2 particles, was introduced into a cooling conduit at the end of the growth zone and collected after further cooling within the conduit.

[0039] The proposed solution achieves controllable average particle size of primary titanium dioxide (TiO2) in the range of 180-280 nm. During the primary particle size control process, no changes to any raw material or process control parameters are required, and the average residence time of TiO2 particles in the high-temperature zone is controlled. The additive KCl in the original process can be specifically used to adjust the primary particle size distribution, and AlCl3 is specifically used to control the rutile conversion rate, eliminating the need for excessive adjustments and resulting in a more uniform TiO2 primary particle size distribution.

[0040] Example 1 The cooling water tank is 70m long and 15m wide, with a flow rate of 260m³ / h of ambient water at 25℃. The generation zone has a diameter of 300mm and a length of 50m. The first cooling conduit has a diameter of 160mm and a length of 45m, and the second cooling conduit has a diameter of 150mm and a length of 60m. The TiCl4 flow rate in the oxidation reactor is 12t / h. The flow rates of KCl, AlCl3, and O2 are matched according to conventional process parameters. The material temperature range at the outlet of the generation zone can be controlled to be 400~550℃, and the residence time of TiO2 particles in the high-temperature zone is 800~900ms. The titanium dioxide produced has an average particle size of 230nm~280nm.

[0041] Example 2: The cooling water tank is 70m long and 15m wide, with a flow rate of 260m³ / h of ambient water at 25℃ (this condition remains unchanged). The growth zone has a diameter of 170mm and a length of 30m. The first cooling conduit has a diameter of 180mm and a length of 42m, while the second cooling conduit has a diameter of 190mm and a length of 50m. The TiCl4 flow rate in the oxidation reactor is 12t / h. The flow rates of KCl, AlCl3, and O2 are matched according to conventional process parameters. The material temperature range at the outlet of the first cooling conduit can be controlled to be 550~600℃, and the residence time of TiO2 particles in the high-temperature zone is 500~700ms. Titanium dioxide with an average particle size of 180nm~220nm can be produced.

[0042] Example 3: The cooling water tank is 70m long and 15m wide, with a flow rate of 260m³ / h of ambient water at 25℃ (this condition remains unchanged). The growth zone has a diameter of 200mm and a length of 40m. The second cooling conduit has a diameter of 200mm and a length of 45m, and the third cooling conduit has a diameter of 200mm and a length of 60m. The TiCl4 flow rate in the oxidation reactor is 12t / h. The flow rates of KCl, AlCl3, and O2 are matched according to conventional process parameters. The material temperature range at the outlet of the first cooling conduit can be controlled to be 520~570℃, and the residence time of TiO2 particles in the high-temperature zone is 650~800ms. The titanium dioxide produced has an average particle size of 200nm~250nm.

[0043] By coordinating the adjustment of the growth zone size and the cooling conduit size, the outlet temperature of the growth zone (400℃~600℃) and the high-temperature residence time of TiO2 particles (500ms~900ms) can be precisely controlled, thereby enabling the directional preparation of titanium dioxide of different specifications in the range of 180nm~280nm. The particle size control has high precision and wide coverage, which can meet the differentiated needs of titanium dioxide particle size for different application scenarios.

[0044] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0045] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0046] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0047] 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 different aspects of the invention 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. An apparatus for controlling the particle size of titanium dioxide produced by the chlorination process, characterized in that, include: An oxidation reactor is used to convert titanium tetrachloride into rutile titanium dioxide. The growth zone, whose inlet is connected to the outlet of the oxidation reactor, is used to control the number of nuclei and the growth time of the rutile titanium dioxide to obtain titanium dioxide particles of the target particle size. A cooling conduit, the inlet of which is connected to the outlet of the growth zone, is used to cool the titanium dioxide particles.

2. The apparatus as claimed in claim 1, characterized in that, The growth zone has a length of 30m to 50m and a diameter of 170mm to 300mm; The pressure inside the oxidation reactor is 380 kPa to 450 kPa, and the larger the diameter of the growth zone, the lower the pressure inside the oxidation reactor.

3. The apparatus as described in claim 1, characterized in that, The device further includes: A collector, connected to the outlet of the cooling conduit, is used to collect the generated titanium dioxide particles.

4. The apparatus as described in claim 3, characterized in that, The device further includes: A cooling water tank is provided, in which the growth zone and the cooling conduit are disposed.

5. The apparatus as claimed in claim 1, characterized in that, The cooling conduit includes: The first cooling conduit has its inlet connected to the outlet of the growth zone; The second cooling conduit has its inlet connected to the outlet of the first cooling conduit.

6. The apparatus as claimed in claim 5, characterized in that, The first cooling conduit has a length of 30m to 45m and a diameter of 160mm to 200mm; the second cooling conduit has a length of 40m to 60m and a diameter of 150mm to 200mm.

7. A method for controlling the particle size of titanium dioxide produced by the chlorination process, characterized in that, Perform the following steps using the apparatus as described in any one of claims 1-6: An oxidation reactor is filled with excess hot oxygen, and toluene and titanium tetrachloride are added to the oxidation reactor to obtain rutile titanium dioxide. The number of nuclei and the growth time of the rutile titanium dioxide are controlled by the growth zone to obtain titanium dioxide particles of the target particle size. The titanium dioxide particles are cooled using cooling conduits.

8. The method as described in claim 7, characterized in that, Also includes: The temperature of the titanium dioxide particles is controlled to be 400℃~600℃ when they enter the cooling conduit from the growth zone.

9. The method as described in claim 7, characterized in that, Also includes: The residence time of the titanium dioxide particles in the growth zone is controlled to be 500ms~900ms.

10. The method as described in claim 7, characterized in that, Also includes: Add aluminum trichloride and / or potassium chloride to the oxidation reactor.

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