Gas-liquid co-current rotating liquid film reactor and its application in preparation of metal hydroxide

Abstract

The application discloses a gas-liquid phase parallel flow rotating liquid film reactor and application thereof in preparation of metal hydroxide. The application is based on the basic process of preparing metal hydroxide from a gas-liquid phase precipitation method, and a gas-liquid phase multi-fluid parallel flow rotating liquid film reactor is designed through computational fluid dynamics simulation analysis, multiple gas-liquid fluid inlets are constructed, and the traditional vertical inlet is improved into tangential feeding along the rotating direction, so that the forced mixing process of the gas-liquid two phases in the reaction space is improved, the microscopic mixing and nucleation process of the reactants are strengthened, the inlet anti-overflow device is added, the upward overflow of the increased inlet flow fluid is avoided, the quality control of the product is strengthened, the efficient control of the nucleation particle size and distribution is realized, the production efficiency and product quality can be improved, the product with small particle size and narrow particle size distribution is obtained, the product particle size can be controlled in the range of 15-200 nm, and the primary particle size distribution range can be reduced to 30-60 nm.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic functional material preparation devices, specifically relating to a gas-liquid phase co-flow rotating liquid film reactor and its application in the preparation of metal hydroxides. Background Technology

[0002] Metal hydroxides are alkaline and readily decompose upon heating to produce metal oxides. Most are sparingly or only slightly soluble in water, such as magnesium hydroxide, aluminum hydroxide, and rare earth hydroxides. Metal hydroxide raw materials are readily available, simple to prepare, and exhibit excellent performance, making them widely used in various fields such as acid absorption, tail gas treatment, building materials, and military applications. For example, magnesium hydroxide, as an important inorganic salt compound of magnesium, has a wide range of uses, including as a flame retardant, neutralizer for acidic wastewater, precipitant for heavy metal wastewater, flue gas desulfurizer, cosmetic and food additive, and is also an important raw material for the production of magnesium oxide. Especially as an inorganic flame retardant, it has gained increasing popularity over the past two decades due to its high decomposition temperature, strong smoke suppression ability, excellent flame retardant effect, and the absence of toxic or corrosive substances after decomposition. The particle size distribution and morphology of hydroxides have a significant impact on their performance; therefore, preparing hydroxides with small particle size and narrow particle size distribution is of great importance for their application.

[0003] Precipitation is one of the most commonly used methods for synthesizing hydroxides. Its advantages include a simple reaction process and ease of large-scale industrial production. Common precipitation methods include liquid-liquid phase precipitation and gas-liquid phase precipitation. Traditional precipitation methods for preparing hydroxides suffer from inconsistent particle sizes and wide particle size distributions due to the inability to separate nucleation and crystallization processes, significantly impacting product performance and large-scale production. To address these issues, our team invented a rotating liquid film reactor (CN20121010556.7), which allows for rapid turbulent mixing of fluids within a confined space, resulting in a precipitation reaction that yields products with small particle sizes and narrow particle size distributions. This reactor has already achieved large-scale application in the preparation of layered composite metal hydroxides and hydroxides through liquid-liquid phase reactions. However, due to the differences in fluid characteristics and collision reaction mechanisms between gas-liquid and liquid-liquid phases, this reactor can only be used for liquid-liquid phase precipitation reactions, not gas-liquid phase precipitation reactions. Gas-liquid phase reaction is an important route for preparing inorganic materials such as hydroxides, and it has been widely used in the preparation of various materials such as magnesium hydroxide, aluminum hydroxide, and rare earth hydroxides. Therefore, the development of gas-liquid phase rotating liquid film reactors is of great significance for improving the particle size and morphology control of hydroxides such as magnesium hydroxide and for large-scale production. Summary of the Invention

[0004] To enhance the gas-liquid phase reactant mixing process within the reactor, improve micro-mixing and nucleation of reactants, and achieve efficient control over the particle size and distribution of gas-liquid phase precipitation reaction products, while simultaneously improving production efficiency and product quality, this invention provides a gas-liquid phase co-flow rotating liquid film reactor and its application in the preparation of metal hydroxides.

[0005] The aforementioned gas-liquid multifluid parallel-flow rotating liquid film reactor consists of a closed casing as the stator, with the upper end of the stator sealed. Inside the stator is a rotatable conical rotor, with a motor connected to the bottom of the rotor. The reactor body comprises the stator and the freely rotating rotor connected to the motor. Multiple liquid inlets are symmetrically arranged on both sides of the stator, with liquid fed tangentially along the rotor's rotation direction. The liquid inlets are located between the stator and the rotor, with their lower ends below the upper edge of the rotor, situated in the upper half of the rotor. A gas inlet is constructed at the center of the stator, allowing gas to enter the upper half of the rotor, where a gas disperser is installed. The reaction liquid is injected through the liquid inlet at a height of 1 / 4 to 1 / 2 of the rotor inlet, either on the same side or opposite side. Gas is injected through the gas inlet and flows out uniformly through the gas disperser, with the gas outlet height lower than the liquid outlet height. A discharge port is located at the lower end of the stator.

[0006] The feed inlets are arranged in four crosses, six evenly distributed at an angle of 60°, or eight evenly distributed at an angle of 45°.

[0007] Add an anti-overflow device: Two round hole-type adjusting bolts with a height of 10-20cm are opened on the horizontal surface above the stator and connected to the internal rotor.

[0008] The inner wall of the stator and the surface of the rotor are engraved with threads in the direction of 10° to 170°.

[0009] The stator is secured by a protective sleeve.

[0010] The stator-rotor gap is 0.1–0.5 mm; the rotor height is 5–25 cm.

[0011] The rotor tilt angle is the angle between the vertical rotor hypotenuse and the base, ranging from 36° to 86°. An angle between 60° and 75° is beneficial for increasing turbulent mixing, improving product yield, and enhancing nucleation efficiency.

[0012] The orifice diameter of the disperser is 1-3 mm.

[0013] The rotor speed range is 50 to 8000 rpm, and the fluid mixing velocity in the reactor is 7 m / s to 150 m / s.

[0014] The above-mentioned gas-liquid multifluid co-flow rotating liquid film reactor is used in the preparation of metal hydroxides.

[0015] The metal hydroxide is magnesium hydroxide, aluminum hydroxide, or lanthanum hydroxide. Ammonia gas is introduced through the gas inlet, and a magnesium salt solution, aluminum salt solution, or lanthanum salt solution is introduced through the liquid inlet.

[0016] The internal flow field of fluid mixing in a gas-liquid phase multifluid co-flow rotating liquid film reactor was simulated using fluid dynamics calculations. A turbulence model was adopted at low rotation speed to increase the inlet mass flow rate, enhance the fluid mixing effect, and thus improve the nucleation efficiency of coprecipitation reaction and control the product grain size. Increasing the rotor speed increased the fluid mixing speed in the reactor, resulting in more uniform fluid mixing and improved product yield in the reactor.

[0017] The beneficial effects of this invention are as follows: Starting from the basic process of preparing metal hydroxides by precipitation, this invention simulates the fluid mixing process of a gas-liquid phase multi-fluid co-flow rotating liquid film reactor using computational fluid dynamics (CFD). The reactor operates within a speed range of 50 rpm to 8000 rpm, and a turbulence model is selected. Based on the reaction of metal hydroxide synthesis by precipitation, combined with the RNG k-ε model, the mass fraction of metal hydroxides generated in the reactor is analyzed. The results show that a rotating liquid film reactor with a gas-liquid phase multi-fluid inlet can effectively improve product yield, increase the flow velocity within the reactor, and enhance the mixing effect of the gas and liquid phases. When the reactor rotor speed increases, the fluid mixing speed within the reactor accelerates, enhancing the mixing and mass transfer effect between fluids. The highest product yield and optimal fluid mixing effect are achieved when the rotor tilt angle is within the range of 60° to 75°, and the fluid mixing speed within the reactor remains stable and uniform. By adding two circular adjusting bolts with a height of 10–20 cm to the horizontal plane above the stator, connecting to the anti-overflow device of the internal rotor, fluid overflow is prevented while increasing the flow rate, thus improving the yield and the mixing efficiency within the reactor, and enhancing the control of product quality. This invention designs a gas-liquid phase multifluid co-flow rotating liquid film reactor, allowing fluids to rapidly flow into the reactor through multiple inlets. This increases the volumetric flow rate of the reacting fluid per unit time, and under rotor motion, enhances the fluid mixing effect and efficiency, resulting in a more complete precipitation reaction and a product with smaller particle size and narrower particle size distribution. The fluid flows in from approximately 1 / 4 to 3 / 4 of the stator-rotor gap, avoiding reactant overflow that occurs when the inlet mass flow rate increases. Adjusting the rotor angle significantly improves the product yield of the fluid mixture. The turbulent flow of the fluid in the rotor-stator gap enhances the forced mixing process of the two-phase fluids within the reaction space, strengthens the micro-mixing and nucleation process of reactant ions, and achieves efficient control over the nucleation particle size and distribution. This also improves production efficiency and product quality, resulting in a product with smaller particle size and narrower particle size distribution. The product particle size can be controlled within the range of 15–200 nm, and the primary particle size distribution range of the product can be reduced to 30 nm–60 nm. The maximum yield of magnesium hydroxide is increased from 30% to over 95%. Attached Figure Description

[0018] Figure 1 A front structural schematic diagram of the gas-liquid multi-fluid parallel-flow rotating liquid film reactor of the present invention, 1-gas inlet, 2-liquid inlet, 3-overflow prevention device, 4-stator shell, 5-rotor, 6-outlet, 7-motor, 8-slit adjustable bolt, 9-stator, 10-base.

[0019] Figure 2 Top views of 4, 6, and 8 liquid inlets, respectively.

[0020] Figure 3 This is the XRD pattern of layered composite magnesium hydroxide from Example 1.

[0021] Figure 4 This is a SEM image of the layered composite aluminum hydroxide from Example 1.

[0022] Figure 5 This is a laser particle size distribution diagram of lanthanum hydroxide obtained in Example 2. Detailed Implementation

[0023] Example 1:

[0024] like Figure 1 The gas-liquid phase multifluid co-flow rotating liquid film reactor shown consists of a closed casing as the stator, with the upper end of the stator closed; a rotatable conical rotor is located inside the stator, with a motor connected below the rotor; the reactor body is composed of the stator and the freely rotatable rotor connected to the motor; the gap between the stator and the rotor is 0.1-0.5 mm; the inner wall of the stator and the surface of the rotor are engraved with threads in the direction of 80°; the rotor height is 8 cm; the rotor tilt angle range is 72°; an anti-overflow device is added: a round hole type adjusting bolt with a height of 10 cm is added to the horizontal plane above the stator, connecting to the internal rotor; four cross-shaped liquid inlets are symmetrically constructed on the left and right sides of the stator, the liquid inlets are located between the stator and the rotor, and the lower end of the inlet is lower than the upper edge of the rotor, the reaction liquid is injected tangentially along the direction of rotor rotation; the gas inlet is located in the upper middle part of the rotor, and the gas flows out through a gas disperser with a diameter of 1 mm; the rotor tilt angle is the angle between the vertical rotor hypotenuse and the bottom edge;

[0025] The above-mentioned gas-liquid multifluid co-flow rotating liquid film reactor was applied to the preparation of magnesium hydroxide, and the specific operation is as follows:

[0026] MgCl2 and NH3 are reacted in the ratio of NH3 / Mg 2+ A molar ratio of 2.5:1 is injected within the same feed time, where [Mg 2+ Ammonia gas with a concentration of 1.0 mol / L was added to four liquid inlets at a rate of 0.1 L / min. The calculated flow rate of ammonia gas required within the corresponding time period was 4.48 L / min, which was then introduced through the gas inlets. The slit between the reactor stator and rotor was 0.1 mm, and the rotor speed was 5000 rpm. The resulting slurry was crystallized in a crystallization reactor at 100℃ for 3 hours. After filtration, washing, and drying, the product was obtained. The average particle size of the product was 50 nm, and the particle size distribution was 30–70 nm.

[0027] The crystal structure of the product was characterized using an XRD-6000 X-ray powder diffractometer from Shimadzu Corporation of Japan. Figure 3The XRD pattern shows characteristic diffraction peaks of Mg(OH)2 at approximately 2θ = 4.8°, 38.0°, 50.8°, and 58.7°. The peaks are sharp and the baseline is low, indicating that the product has a complete crystal structure.

[0028] The grain size and morphology were observed using a Hitachi H-800 transmission electron microscope. Figure 4 These are scanning electron microscope images. As can be seen from the images, the particle size of the prepared product is between 30 and 60 nm.

[0029] Example 2:

[0030] like Figure 1 The gas-liquid phase multifluid co-flow rotating liquid film reactor shown consists of a closed casing as the stator, with the upper end of the stator closed; a rotatable conical rotor is located inside the stator, with a motor connected below the rotor; the reactor body is composed of the stator and the freely rotatable rotor connected to the motor; the gap between the stator and the rotor is 0.3 mm; the inner wall of the stator and the surface of the rotor are engraved with threads in the direction of 40°; the rotor height range is 10 cm; the rotor tilt angle is 75°; an anti-overflow device is added: a round hole type adjusting bolt with a height of 12 cm is added to the horizontal plane above the stator, connecting to the internal rotor; multiple liquid inlets are symmetrically arranged on the left and right sides of the stator, forming six evenly arranged liquid inlets, the liquid inlets are located between the stator and the rotor, and the lower end of the inlet is lower than the upper edge of the rotor, the reaction liquid is injected tangentially along the direction of rotor rotation, the gas inlet is located in the upper middle part of the rotor, and the gas flows out through a gas disperser with a diameter of 2 mm; the rotor tilt angle is the angle between the vertical rotor hypotenuse and the bottom edge;

[0031] The above-mentioned gas-liquid multifluid co-flow rotating liquid film reactor was applied to the preparation of aluminum hydroxide, and the specific operation is as follows:

[0032] AlCl3 and NH3 are reacted in the ratio NH3 / Al 3+ A molar ratio of 4:1 is injected within the same feed time, where [Al] 3+ Ammonia gas with a concentration of 1.0 mol / L was added to six liquid inlets at a rate of 0.1 L / min. The calculated flow rate of ammonia gas required within the corresponding time period was 8.96 L / min, which was then introduced into the gas inlets. The rotor speed was 4000 rpm. The resulting slurry was crystallized in a crystallization reactor at 60°C for 6 hours. After filtration, washing, and drying, Al(OH)3 was obtained. The average particle size of the product was 90 nm, and the particle size distribution was 60-160 nm.

[0033] The particle size of the samples was measured using a Mastersizer 2000 laser particle size analyzer from Malvern, UK. Figure 5 This is a laser particle size distribution map. As can be seen from the map, the average particle size of the product is 96 nm, d 90=152nm.

[0034] Example 3:

[0035] like Figure 1 The reactor, a gas-liquid multifluid co-flow rotating liquid film reactor, consists of a closed casing as the stator, with the upper end of the stator sealed. Inside the stator is a rotatable conical rotor, with a motor connected below the rotor. The reactor body is composed of the stator and the freely rotatable rotor connected to the motor. The gap between the stator and the rotor is 0.2 mm. The inner wall of the stator and the surface of the rotor are engraved with threads in a 60° direction. The rotor height ranges from 12 cm. The rotor tilt angle is 70°. An anti-overflow device is added: a circular hole-type adjusting bolt with a height of 15 cm is added to the horizontal plane above the stator, connecting to the internal rotor. Multiple liquid inlets are symmetrically arranged on the left and right sides of the stator, forming eight evenly arranged liquid inlets. The inlets are located between the stator and the rotor, with the lower end of the inlet below the upper edge of the rotor. The reaction liquid is injected tangentially along the direction of rotor rotation. The gas inlet is located in the upper middle part of the rotor, and the gas flows out through a gas disperser with a diameter of 3 mm. The rotor tilt angle is the angle between the vertical rotor hypotenuse and the bottom edge.

[0036] The above-mentioned gas-liquid multifluid co-flow rotating liquid film reactor was applied to the preparation of lanthanum hydroxide, and the specific operation is as follows:

[0037] LaCl3 and ammonia were reacted according to the ratio NH3 / La 3+ A molar ratio of 5:1 is injected within the same feed time, where [La] 3+ =1.0 mol / L, added to 8 liquid feed ports at a rate of 0.1 L / min; the calculated flow rate of ammonia gas required within the corresponding time period was 11.2 L / min introduced into the gas feed port, with a rotor speed of 3000 rpm. The resulting slurry was crystallized in a crystallization reactor at 120℃ for 1 h, and after filtration, washing, and drying, La(OH)3 was obtained. The average particle size of the product was 100 nm, and the particle size distribution was 80-140 nm.

Claims

1. A gas-liquid multi-fluid co-current rotating liquid film reactor characterized by, The reactor is composed of a closed stator with a closed upper end, a rotatable conical rotor in the stator, and a motor connected to the lower end of the rotor. The reactor body is composed of the stator and the rotatable rotor connected to the motor. A plurality of liquid inlets are symmetrically arranged on the left and right sides of the stator, and the liquid is fed tangentially along the direction of rotation of the rotor. The liquid inlets are located between the stator and the rotor, and the lower end of the liquid inlets is lower than the upper edge of the rotor, located in the upper half of the rotor. A gas inlet is constructed at the center of the stator, and the gas is fed into the upper half of the rotor. A gas disperser is arranged in the rotor. The reaction liquid is injected into the rotor at a position of 1 / 4-1 / 2 of the height of the rotor inlet in the same side or opposite side manner through the liquid inlets. The gas is injected through the gas inlet and uniformly flows out through the gas disperser, and the gas outlet height is lower than the liquid outlet height. A discharge outlet is arranged at the lower end of the stator. The stator-rotor gap is 0.1-0.5 mm, and the rotor height is 5-25 cm. The pore size of the disperser is 1-3 mm.

2. The gas-liquid multi-fluid co-current rotating liquid film reactor according to claim 1, wherein, The inlets are four cross-shaped cross-arranged, six uniformly distributed at an included angle of 60°, or eight uniformly distributed at an included angle of 45°.

3. The gas-liquid multi-fluid co-current rotating liquid film reactor according to claim 1, wherein, An anti-overflow device is added, two round hole type adjusting bolts are opened on the opposite sides of the horizontal plane above the stator, the height is 10-20 cm, and the inside rotor is connected.

4. The gas-liquid multi-fluid co-current rotating liquid film reactor according to claim 1, wherein, The inner wall of the stator and the surface of the rotor are engraved with threads with a direction of 10°-170°.

5. The gas-liquid multi-fluid co-current rotating liquid film reactor according to claim 1, wherein, The rotor inclination angle is the included angle between the slant edge and the base edge of the rotor in the vertical direction, and the range is 36°-86°.

6. The gas-liquid multi-fluid co-current rotating liquid film reactor according to claim 1, wherein, The rotor rotation speed range is 50-8000 rpm, and the fluid mixing flow rate in the reactor is 7 m / s-150 m / s.

7. The gas-liquid multi-fluid co-current rotating liquid film reactor according to any one of claims 1-6 is used in the preparation of metal hydroxide.

8. Use according to claim 7, characterized in that, The metal hydroxide is magnesium hydroxide, aluminum hydroxide or lanthanum hydroxide; ammonia gas is fed from the gas inlet, and magnesium salt solution, aluminum salt solution or lanthanum salt solution is fed from the liquid inlet.

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