Method for controlling granularity of titanium dioxide by chlorination process

Abstract

The invention relates to the technical field of chlorination-process titanium dioxide production, in particular to a chlorination-process titanium dioxide particle size control method which comprises the following steps: mixing hot oxygen, aluminum trichloride and preheated titanium tetrachloride in an oxidizing furnace, and reacting to obtain primary titanium dioxide particles; the pressure of the tail of the oxidizing furnace is controlled to be 180-400 kPa, so that the pressure of the furnace end is controllable within the range of 280-500 kPa, and target regulation and control of the particle size of the primary titanium dioxide particles within the range of 160-350 nm are achieved by controlling the pressure of the system. According to the method, the particle size of the primary titanium dioxide particles can be efficiently and quickly controlled within the range of 160-350 nm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chlorination titanium dioxide production, and particularly relates to a method for controlling the particle size of chlorination titanium dioxide. BACKGROUND

[0002] Currently, there are two mainstream processes for producing titanium dioxide: the chlorination method and the sulfuric acid method. Compared with the sulfuric acid method, the chlorination method has the advantages of high automation, advanced technology, and high quality and environmental protection, and thus gradually becomes the main trend of the development of the titanium dioxide industry. Titanium dioxide has stable properties and is the best white pigment at present, and is widely used in the fields of coatings, plastics, papermaking, inks and the like. Chlorinated titanium dioxide with different particle sizes has a great influence on optical properties. For example, chlorinated titanium dioxide with a particle size of 220-240 nm has excellent visual whiteness, and has excellent hiding power and color removal in water-based and oil-based systems, and titanium dioxide with a particle size of 210±10 nm can well avoid the formation of ink knife lines; chlorinated titanium dioxide with a particle size of 180-200 nm has better white pigment properties in plastic and resin systems.

[0003] In the production process of chlorinated titanium dioxide, the basic principle of preparing the initial product is to use gaseous titanium tetrachloride and oxygen to fully mix in the reaction zone and react at a high temperature of 1600-2000 ℃. The speed of the gas phase oxidation reaction is millisecond level, and the initial product titanium dioxide is generated in an instant of contact of the reactants. The initial product titanium dioxide is processed by a coating process to manufacture titanium dioxide products that meet the requirements of different fields, and the particle size of the initial product has a great influence on the particle size of the titanium dioxide product. The post-processing process is only a fine adjustment of the particle size, so controlling the particle size of the initial product is a core and key link for controlling the type and quality grade of the chlorinated titanium dioxide product. In the existing initial product particle size control means, the use of additives KCl and AlCl3 is the most common, however, the use of additives is restricted by the performance control of the initial product rutile conversion rate, whiteness, brightness, color and color removal, and cannot well meet the initial product particle size control requirements. At the same time, the adjustment of process parameters such as the required concentration, flow, temperature and pressure of the additives is very tedious, and is easy to cause low production stability and efficiency. Therefore, how to efficiently and quickly control the particle size of the initial product of chlorinated titanium dioxide has become a problem to be solved. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to provide a method for controlling the particle size of chlorinated titanium dioxide, which efficiently and quickly realizes the controllability of the particle size of the initial product titanium dioxide particles in the range of 160-350 nm.

[0005] The present application provides a method for controlling the particle size of the initial product of chlorinated titanium dioxide, comprising the following steps:

[0006] Hot oxygen, aluminum trichloride, and preheated titanium tetrachloride are mixed in an oxidation furnace and reacted to obtain primary titanium dioxide particles. The furnace tail pressure is controlled at 180–400 kPa to achieve controllable furnace head pressure within the range of 280–500 kPa, and the particle size of the primary titanium dioxide particles is controlled within the range of 160–350 nm.

[0007] Preferably, the system implementing the control method includes:

[0008] Oxidation furnace;

[0009] A cooling duct connected to the gas outlet of the oxidation furnace;

[0010] A bag filter connected to the gas outlet of the cooling duct;

[0011] A pulping tank connected to the solid waste outlet of the bag filter;

[0012] A pressure regulating valve is installed at the gas outlet of the bag filter to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0013] Preferably, the particle size of the primary titanium dioxide particles can be precisely controlled to be 160–200 nm, 200–230 nm, 230–260 nm, or 260 nm–350 nm.

[0014] Preferably, when the furnace head pressure is 280-330 kPa, the particle size of the primary titanium dioxide particles is 160-200 nm.

[0015] Preferably, when the furnace head pressure is 380-420 kPa, the particle size of the primary titanium dioxide particles is 200-230 nm.

[0016] Preferably, when the furnace head pressure is 430-450 kPa, the particle size of the primary titanium dioxide particles is 230-260 nm.

[0017] Preferably, when the furnace head pressure is 480-500 kPa, the particle size of the primary titanium dioxide particles is 260-350 nm.

[0018] Preferably, the temperature of the preheated titanium tetrachloride is 450–590°C;

[0019] The temperature of the thermo-oxygenated oxygen is 790–870°C.

[0020] Preferably, when the furnace head pressure is 280-330 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 180-190 nm;

[0021] When the furnace head pressure is 380-420 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 210-220 nm.

[0022] When the furnace head pressure is 430-450 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 240-250 nm.

[0023] When the furnace head pressure is 480-500 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 250-300 nm.

[0024] The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013 to 0.015.

[0025] Preferably, the material flow rate is controlled by adjusting the pressure of the oxidation furnace, thereby making the grain growth time in the reaction controllable between 6.4 and 17 ms.

[0026] This invention achieves controllable particle size of primary titanium dioxide particles within the range of 160–350 nm. During the primary particle size control process, no changes to any raw material or process control parameters are required. The internal pressure adjustment of the oxidation furnace is achieved online, making it convenient and quick. The additive potassium chloride (KCl) in the original process can be specifically used to adjust the primary particle size distribution, and aluminum trichloride (AlCl3) can specifically control the conversion rate of rutile titanium dioxide without excessive adjustments. This results in a more uniform TiO2 primary particle size distribution, and the whiteness, brightness, and tinting strength are superior to similar products produced by other processes. Furthermore, the production method of this invention has the advantages of low cost and simple operation. If widely applied in the titanium dioxide chloride industry, it will bring significant economic benefits. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a control system for the particle size of titanium dioxide produced by the chloride process, provided as an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a method for controlling the particle size of titanium dioxide produced by the chloride process, comprising the following steps: mixing hot oxygen, aluminum trichloride, and preheated titanium tetrachloride in an oxidation furnace and reacting them to obtain primary titanium dioxide particles; controlling the furnace tail pressure of the oxidation furnace to 180–400 kPa to achieve controllable furnace head pressure within the range of 280–500 kPa; and achieving targeted control of the particle size of the primary titanium dioxide particles within the range of 160–350 nm.

[0030] This invention involves mixing hot oxygen, aluminum trichloride, and preheated titanium tetrachloride in an oxidation furnace and reacting them to obtain primary titanium dioxide particles.

[0031] The aluminum trichloride is a crystal form conversion agent.

[0032] In some embodiments of the present invention, the system implementing the control method includes:

[0033] Oxidation furnace;

[0034] A cooling duct connected to the gas outlet of the oxidation furnace;

[0035] A bag filter connected to the gas outlet of the cooling duct;

[0036] A pulping tank connected to the solid waste outlet of the bag filter;

[0037] A pressure regulating valve is installed at the gas outlet of the bag filter to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0038] Figure 1 This is a schematic diagram of a control system for the particle size of titanium dioxide produced by the chloride process, provided as an embodiment of the present invention.

[0039] The oxidation furnace, cooling duct, bag filter, and pulping tank form a closed system.

[0040] In some embodiments of the present invention, the system further includes a chlorination furnace. The chlorination furnace is connected to the gas outlet of the bag filter.

[0041] The main component of the tail gas from the oxidation system after gas-solid separation from the bag filter is chlorine; the mass content of chlorine in the tail gas is 70% to 90%, which can be recycled to the chlorination furnace.

[0042] The inventors discovered during their research that the only point where system pressure can be adjusted without affecting product quality is at the pipe connecting the bag filter outlet to the chlorination furnace. Specifically, a pressure regulating valve is installed on the pipe between the bag filter and the chlorination furnace to control the tail pressure of the oxidation furnace, thereby achieving control over the furnace head pressure.

[0043] In some embodiments of the present invention, the tail pressure of the oxidation furnace is controlled to be 180-230 kPa, 280-320 kPa, 330-350 kPa or 380-400 kPa.

[0044] In some embodiments of the present invention, the particle size of the primary titanium dioxide particles is controlled to be 160-200nm, 200-230nm, 230-260nm, or 260nm-350nm.

[0045] In some embodiments of the present invention, when the furnace head pressure is 280-330 kPa, the particle size of the primary titanium dioxide particles is 160-200 nm.

[0046] In some embodiments of the present invention, when the furnace head pressure is 380-420 kPa, the particle size of the primary titanium dioxide particles is 200-230 nm.

[0047] In some embodiments of the present invention, when the furnace head pressure is 430-450 kPa, the particle size of the primary titanium dioxide particles is 230-260 nm.

[0048] In some embodiments of the present invention, when the furnace head pressure is 480-500 kPa, the particle size of the primary titanium dioxide particles is 260-350 nm.

[0049] In some embodiments of the present invention, the temperature of the preheated titanium tetrachloride is 450–590°C; for example, 450–550°C.

[0050] In some embodiments of the present invention, the temperature of the hot oxygen is 790–870°C. The temperature of the hot oxygen can be maintained by the heat generated by the combustion of toluene.

[0051] In some embodiments of the present invention, the mass ratio of the hot oxygen, aluminum trichloride and preheated titanium tetrachloride is 2105:72:10000.

[0052] In some embodiments of the present invention, when the furnace head pressure is 280-500 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to be 160-350 nm; the mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0053] In some embodiments of the present invention, when the furnace head pressure is 280-330 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 180-190 nm; the mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0054] When the furnace head pressure is 380-420 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 210-220 nm; the mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0055] When the furnace head pressure is 430-450 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 240-250 nm; the mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0056] When the furnace head pressure is 480-500 kPa, the process further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 250-300 nm; the mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0057] In some embodiments of the present invention, the material flow rate is controlled by adjusting the pressure of the oxidation furnace, thereby making the grain growth time in the reaction controllable between 6.4 and 17 ms.

[0058] The initial titanium dioxide particles are rutile titanium dioxide.

[0059] This invention achieves controllable average particle size of primary titanium dioxide particles within the range of 160–260 nm. During the primary particle size control process, no changes to any raw material or process control parameters are required. The internal pressure adjustment of the oxidation furnace is achieved online, making it convenient and quick. The additive potassium chloride (KCl) in the original process can be specifically used to adjust the primary particle size distribution, and aluminum trichloride (AlCl3) can specifically control the conversion rate of rutile titanium dioxide without excessive adjustments. This results in a more uniform TiO2 primary particle size distribution, and the whiteness, brightness, and tinting strength are superior to similar products produced by other processes. Furthermore, the production method of this invention has the advantages of low cost and simple operation. If widely applied in the titanium dioxide chloride industry, it will bring significant economic benefits.

[0060] The present invention does not impose any special restrictions on the source of the raw materials used above, and they can be commercially available.

[0061] To further illustrate the present invention, the following detailed description of a method for controlling the particle size of titanium dioxide produced by the chloride process, in conjunction with embodiments, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0062] Example 1

[0063] Adopting such Figure 1 The control system shown includes:

[0064] Oxidation furnace;

[0065] A cooling duct connected to the gas outlet of the oxidation furnace;

[0066] A bag filter connected to the gas outlet of the cooling duct;

[0067] A pulping tank connected to the solid waste outlet of the bag filter;

[0068] A chlorination furnace connected to the gas outlet of the bag filter;

[0069] A pressure regulating valve is installed on the pipeline between the bag filter and the chlorination furnace to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0070] Oxygen is heated by the heat generated from the combustion of toluene to obtain hot oxygen at a temperature of 790–870°C. This hot oxygen is then mixed with titanium tetrachloride and AlCl3 at a temperature of 450–550°C in an oxidation furnace and reacted to obtain primary rutile titanium dioxide particles.

[0071] The mass ratio of the hot oxygen, aluminum trichloride, and preheated titanium tetrachloride is 2105:72:10000;

[0072] The tail pressure of the oxidation furnace is controlled at 180-230 kPa to achieve controllable head pressure within the range of 280-330 kPa. Potassium chloride is added to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 180-190 nm. The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0073] The grain growth time in the reaction is controllable between 6.4 and 17 ms.

[0074] Example 2

[0075] Adopting such Figure 1 The control system shown includes:

[0076] Oxidation furnace;

[0077] A cooling duct connected to the gas outlet of the oxidation furnace;

[0078] A bag filter connected to the gas outlet of the cooling duct;

[0079] A pulping tank connected to the solid waste outlet of the bag filter;

[0080] A chlorination furnace connected to the gas outlet of the bag filter;

[0081] A pressure regulating valve is installed on the pipeline between the bag filter and the chlorination furnace to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0082] Oxygen is heated by the heat generated from the combustion of toluene to obtain hot oxygen at a temperature of 790–870°C. This hot oxygen is then mixed with titanium tetrachloride and AlCl3 at a temperature of 450–550°C in an oxidation furnace and reacted to obtain primary rutile titanium dioxide particles.

[0083] The tail pressure of the oxidation furnace is controlled at 280-320 kPa to achieve controllable head pressure within the range of 380-420 kPa. Potassium chloride is added to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 210-220 nm. The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0084] The grain growth time in the reaction is controllable between 6.4 and 17 ms.

[0085] Example 3

[0086] Adopting such Figure 1 The control system shown includes:

[0087] Oxidation furnace;

[0088] A cooling duct connected to the gas outlet of the oxidation furnace;

[0089] A bag filter connected to the gas outlet of the cooling duct;

[0090] A pulping tank connected to the solid waste outlet of the bag filter;

[0091] A chlorination furnace connected to the gas outlet of the bag filter;

[0092] A pressure regulating valve is installed on the pipeline between the bag filter and the chlorination furnace to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0093] Oxygen is heated by the heat generated from the combustion of toluene to obtain hot oxygen at a temperature of 790–870°C. This hot oxygen is then mixed with titanium tetrachloride and AlCl3 at a temperature of 450–550°C in an oxidation furnace and reacted to obtain primary rutile titanium dioxide particles.

[0094] The tail pressure of the oxidation furnace is controlled at 330-350 kPa to achieve controllable furnace head pressure within the range of 430-450 kPa. Potassium chloride is added to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 240-250 nm. The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0095] The grain growth time in the reaction is controllable between 6.4 and 17 ms.

[0096] Example 4

[0097] Adopting such Figure 1 The control system shown includes:

[0098] Oxidation furnace;

[0099] A cooling duct connected to the gas outlet of the oxidation furnace;

[0100] A bag filter connected to the gas outlet of the cooling duct;

[0101] A pulping tank connected to the solid waste outlet of the bag filter;

[0102] A chlorination furnace connected to the gas outlet of the bag filter;

[0103] A pressure regulating valve is installed on the pipeline between the bag filter and the chlorination furnace to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

[0104] Oxygen is heated by the heat generated from the combustion of toluene to obtain hot oxygen at a temperature of 790–870°C. This hot oxygen is then mixed with titanium tetrachloride and AlCl3 at a temperature of 450–550°C in an oxidation furnace and reacted to obtain primary rutile titanium dioxide particles.

[0105] The mass ratio of the hot oxygen, aluminum trichloride, and preheated titanium tetrachloride is 2105:72:10000;

[0106] The tail pressure of the oxidation furnace is controlled at 380-400 kPa to achieve controllable head pressure within the range of 480-500 kPa. Potassium chloride is added to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 250-300 nm. The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013-0.015.

[0107] The grain growth time in the reaction is controllable between 6.4 and 17 ms.

[0108] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the particle size of primary titanium dioxide produced by the chloride process, comprising the following steps: Hot oxygen, aluminum trichloride, and preheated titanium tetrachloride are mixed in an oxidation furnace and reacted to obtain primary titanium dioxide particles. The furnace tail pressure is controlled at 180–400 kPa to achieve controllable furnace head pressure within the range of 280–500 kPa, and the particle size of the primary titanium dioxide particles is controlled within the range of 160–350 nm.

2. The control method according to claim 1, characterized in that, The system implementing the control method includes: Oxidation furnace; A cooling duct connected to the gas outlet of the oxidation furnace; A bag filter connected to the gas outlet of the cooling duct; A pulping tank connected to the solid waste outlet of the bag filter; A pressure regulating valve is installed at the gas outlet of the bag filter to control the tail pressure of the oxidation furnace, thereby achieving control of the furnace head pressure.

3. The control method according to claim 1, characterized in that, The particle size of the primary titanium dioxide particles can be precisely controlled to be 160–200 nm, 200–230 nm, 230–260 nm, or 260 nm–350 nm.

4. The control method according to claim 1, characterized in that, When the furnace head pressure is 280–330 kPa, the particle size of the primary titanium dioxide particles is 160–200 nm.

5. The control method according to claim 1, characterized in that, When the furnace head pressure is 380–420 kPa, the particle size of the primary titanium dioxide particles is 200–230 nm.

6. The control method according to claim 1, characterized in that, When the furnace head pressure is 430-450 kPa, the particle size of the primary titanium dioxide particles is 230-260 nm.

7. The control method according to claim 1, characterized in that, When the furnace head pressure is 480-500 kPa, the particle size of the primary titanium dioxide particles is 260-350 nm.

8. The control method according to claim 1, characterized in that, The temperature of the preheated titanium tetrachloride is 450–590°C. The temperature of the thermo-oxygenated oxygen is 790–870°C.

9. The control method according to claim 1, characterized in that, When the furnace head pressure is 280-330 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 180-190 nm. When the furnace head pressure is 380-420 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 210-220 nm. When the furnace head pressure is 430-450 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 240-250 nm. When the furnace head pressure is 480-500 kPa, the method further includes: adding potassium chloride to the oxidation furnace to control the particle size of the primary titanium dioxide particles to 250-300 nm. The mass ratio of titanium tetrachloride to potassium chloride is 1000:0.013 to 0.

015.

10. The control method according to claim 1, characterized in that, By adjusting the pressure of the oxidation furnace, the material flow rate can be controlled, thereby making the grain growth time in the reaction controllable between 6.4 and 17 ms.

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