Mixing reaction device and application thereof in preparation of monodisperse nano calcium carbonate

Abstract

The invention provides a mixed reaction device and application thereof in preparation of monodisperse nano calcium carbonate. The mixing reaction device comprises a shell, a feeding cavity is formed in the upper portion of the interior of the shell and communicated with a feeding port, a stator is fixedly arranged on the lower portion of the interior of the shell and provided with a hollow cavity, a rotor is arranged in the hollow cavity, an adjustable gap is formed between the rotor and the stator, and the top of the gap is communicated with the feeding cavity. A plurality of diversion grooves are formed in the inner wall of the stator and the outer wall of the rotor in the circumferential direction at intervals, the rotor is connected with a driving shaft of a driving mechanism through a rotating shaft, a backflow opening is formed in the top of the shell, the two ends of the backflow opening are communicated with the feeding cavity and the backflow pipe respectively, and an outlet communicated with the bottom of the gap is formed in the bottom of the shell. The outlet is connected with the lower portion of a return pipe through a three-way valve, the middle of the return pipe is communicated with an air inlet, and an air inlet valve is arranged on the air inlet. The mixing reaction device can improve the dispersion degree and the surface modification degree of the calcium carbonate nanoparticles.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid reaction equipment, and in particular to a mixing and reaction device and its application in the preparation of monodisperse nano calcium carbonate. Background Art

[0002] The mixing and reaction device is a device for mixing raw materials and carrying out chemical reactions. At present, there are a series of problems in the calcium carbonate industry in China, such as simple production processes, serious product homogenization, low product added value, high energy and material consumption, unstable product quality, and the whiteness and fineness of products not meeting the high-quality requirements; at the same time, there are problems in the production technology of nano calcium carbonate, such as uneven particle size distribution, difficult separation, poor dispersion effect, and high import dependence on high-end nano calcium carbonate products.

[0003] CN 115608299 B discloses a micro-reaction device for preparing nano calcium carbonate, including a lower housing, a mixing housing, and an upper housing. A linear guide column cavity one is provided in the lower housing, and a square groove cavity one is also provided in the middle of the lower housing. The mixing housing is fitted in the square groove cavity one. An L-shaped guide column cavity two is provided in the upper housing. The inner end of the guide column cavity two is connected to the mixing housing, the mixing housing is connected to the guide column cavity one, the outer end of the guide column cavity two is connected to a dispersed phase inlet, and the two ends of the guide column cavity one are respectively connected to a continuous phase inlet and a continuous phase outlet. However, the micro-reaction environment provided by the above micro-reaction device is used to solve the problems of uneven particle size, low crystallinity, and irregular morphology in the preparation of nano calcium carbonate products by traditional autoclave reactors.

[0004] CN 115286028 B discloses a method and device for synthesizing highly dispersed nano calcium carbonate without using additives. The device includes a peristaltic pump, a constant temperature crystallizer, a membrane dispersion micro-reactor, a magnetic stirrer, and a low-temperature constant temperature bath; the membrane dispersion micro-reactor is arranged in the constant temperature crystallizer, the membrane dispersion micro-reactor is connected to the peristaltic pump, and the constant temperature crystallizer is connected to the low-temperature constant temperature bath; the membrane dispersion micro-reactor is a spiral hollow fiber tube, and a plurality of micropores are uniformly arranged on the wall surface of the hollow fiber tube; the equivalent diameter of the micropores is 0.45 μm; sodium carbonate solution is pumped into the membrane dispersion micro-reactor through the peristaltic pump to react with the calcium hydroxide and calcium chloride slurry to obtain calcite calcium carbonate with a particle size of 18.8 nm. However, the above patents all strengthen the mass transfer and reaction efficiency of the system by constructing a one-dimensional or two-dimensional micro-scale reaction environment, accelerate the nucleation process of calcium carbonate, and realize the relative separation of the nucleation and crystallization processes. However, reaction equipment, especially one-dimensional channel-type reaction devices, is prone to problems such as blockage.

[0005] In addition, nano-calcium carbonate has relatively high activity and surface energy, and is prone to agglomeration during the processes of preparation, storage, and application, thereby losing the essential characteristics of nanomaterials. In order to improve the monodispersity of nano-calcium carbonate, inhibit the agglomeration between particles, and enhance its dispersibility in polymer substrates when used as a polymer filler, it is necessary to use surfactants to conduct surface functional modification on nano-calcium carbonate, reduce its surface energy, modulate its surface hydrophilic-hydrophobic ability, inhibit the agglomeration between nanoparticles, and improve the monodispersity of nano-calcium carbonate and its compatibility with organic substrates. Traditional functional modification is carried out in a kettle / tank reactor. The reaction space is too large, which is prone to dead zones, and it is impossible to effectively depolymerize and break soft agglomerated particles. At the same time, the materials in the kettle / tank reactor are not evenly mixed, and the residence time is uneven, resulting in poor timeliness and uniformity during the surface functional modification of calcium carbonate, seriously affecting its performance when used as a polymer filler.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a mixing and reaction device and its application in the preparation of monodisperse nano-calcium carbonate. This mixing and reaction device can improve the dispersion degree and surface modification degree of calcium carbonate nanoparticles.

[0008] The present invention provides a mixing and reaction device, which includes a housing. An inlet chamber is provided above the interior of the housing. The inlet chamber is communicated with an inlet port. A stator is fixedly provided below the interior of the housing. The stator has a hollow cavity. A rotor is provided in the hollow cavity. There is an adjustable gap between the rotor and the stator. The top of the gap is communicated with the inlet chamber. A plurality of diversion grooves are circumferentially spaced on the inner wall of the stator and the outer wall of the rotor. The rotor is connected to the drive shaft of the drive mechanism through a rotating shaft. A reflux port is provided at the top of the housing. Both ends of the reflux port are respectively communicated with the inlet chamber and a reflux pipe. An outlet communicated with the bottom of the gap is provided at the bottom of the housing. The outlet is connected to the lower part of the reflux pipe through a three-way valve. The middle part of the reflux pipe is communicated with an air inlet. An air inlet valve is provided on the air inlet.

[0009] Further, the hollow cavity of the stator and the rotor are both frustum-shaped. The rotor is connected to a lifting mechanism, and the lifting mechanism can drive the rotor to move up and down relative to the stator to adjust the size of the gap.

[0010] Further, the size of the gap is adjustable within the range of 20 - 500 μm, and the size of the gap is, for example, 50 - 200 μm.

[0011] Further, the rotational speed of the rotor is adjustable within the range of 1000 - 6000 r / min.

[0012] Further, the inlet chamber is frustum-shaped in reverse, and the bottom of the inlet chamber is flush with the top of the stator.

[0013] Further, a Venturi tube is provided in the middle of the reflux pipe, and the throat of the Venturi tube is communicated with the air inlet.

[0014] The present invention also provides an application of the above mixing and reaction device in the preparation of monodisperse nano calcium carbonate.

[0015] The present invention also provides a method for preparing monodisperse nano calcium carbonate by using calcium-containing industrial solid waste, which is carried out by using the above mixing and reaction device. The method comprises the following steps:

[0016] S1: Add the calcium-containing solid waste and the ammonium salt solution into the mixing and reaction device through the feed port for mixing, transfer the mixture to a reaction kettle for reaction after mixing, and filter after the reaction to obtain a calcium-containing filtrate.

[0017] S2: Add the calcium-containing filtrate and the crystal form control agent into the mixing and reaction device through the feed port, and at the same time add the CO2-containing gas into the mixing and reaction device through the air inlet for mixing reaction. Filter after the mixing reaction to obtain nano calcium carbonate.

[0018] S3: Add the nano calcium carbonate and the aqueous solution containing surfactant into the mixing and reaction device through the feed port for mixing reaction. Centrifuge, wash and dry after the mixing reaction to obtain monodisperse nano calcium carbonate.

[0019] In step S1, the calcium-containing solid waste is selected from at least one of red mud, carbide slag, steel slag and yellow phosphorus furnace slag; the mass content of the ammonium salt in the ammonium salt solution is 9-20%, and the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium acetate; the mass ratio of the calcium-containing solid waste to the ammonium salt solution is (0.05-0.2):1; the temperature during mixing is 20-50 °C, the rotation speed of the rotor of the mixing and reaction device during mixing is 1000-5000 r / min, and the mixing time is 5-10 min; the temperature during the reaction is 60-120 °C, the time is 1-6 h; the mass content of calcium chloride in the calcium-containing filtrate is 5-14%.

[0020] In step S2, the crystal form control agent is selected from at least one of glucose, sodium polyphosphate, dodecylbenzenesulfonic acid, sodium dodecyl sulfate, polyethylene glycol, sodium sulfate, citric acid and oxalic acid; the mass ratio of the crystal form control agent to the nano calcium carbonate is (0.002-0.005):1; the CO2-containing gas is a mixture of N2 and CO2, and the mass content of CO2 in the CO2-containing gas is 2-100%. The CO2-containing gas can be self-aspirated into the mixing and reaction device through the Venturi tube, and the intake air volume of the CO2-containing gas is adjusted through the intake valve; the temperature during the mixing reaction is 20-50 °C, the rotation speed during mixing is 2000-6000 r / min, and the time is 1-10 min.

[0021] In step S3, the surfactant is selected from at least one of stearic acid, dodecylbenzenesulfonic acid, silane coupling agent, aluminate coupling agent and titanate coupling agent; the mass ratio of the surfactant to the nano calcium carbonate is (0.03 - 0.05):1; the temperature during the mixing reaction is 20 - 50 °C, the rotation speed of the rotor of the mixing reaction device during the mixing reaction is 1000 - 3000 r / min, and the mixing reaction time is 5 - 10 min; the temperature during drying is 60 - 100 °C, and the time is 6 - 12 h.

[0022] The monodisperse nano calcium carbonate prepared above has regular morphology, purity > 98.2%, chlorine content < 0.005%, alkalinity of 7.5 - 7.9, sedimentation volume of 2.8 - 3.8 mL / g, particle size of 10 - 100 nm, narrow particle size distribution, the product is white, and there are no visible impurities visually.

[0023] The mixing and reaction device of the present invention can be applied to the preparation of monodisperse nano-calcium carbonate using calcium-containing industrial solid waste. In the ammonium salt leaching stage of calcium-containing solid waste, the high-pressure liquid film shear and high-frequency oscillation effects formed by the stator and rotor of the mixing and reaction device during high-speed rotation are used to strengthen the crushing and reaction capabilities of calcium-containing solid waste particles, improving the contactability and reactivity between calcium-containing solid waste and ammonium salt solution. Air enters the reaction system precisely and controllably through the air inlet and air inlet valve at the throat of the Venturi tube to form nano-micro bubbles, accelerating the escape of ammonia during the reaction process, and increasing the leaching rate and leaching timeliness of calcium in calcium-containing solid waste; in the carbonization stage of calcium-containing filtrate, the Bernoulli principle is used to preliminarily premix the CO2-containing gas with the calcium-containing filtrate to obtain a first gas-liquid mixed flow containing large bubbles, which enters the inverted frustum-shaped feed cavity through the feed port set at the top of the shell, and then enters the micron-scale dynamic confinement micro-reaction space formed by the stator and rotor. The large bubbles are sheared into extremely small bubbles by the extrusion and shear effects during the high-speed rotation of the rotor to form a second gas-liquid mixed flow at the micron scale, increasing the gas-liquid contact area between CO2 and calcium-containing filtrate, improving the gas-liquid mass transfer process and micro mixing and reaction efficiency, suppressing the inhomogeneity of mass, temperature, and concentration in the system, making the reaction time of CO2 and calcium-containing filtrate match the mixing time between gas-liquid materials, precisely controlling the CO2 absorption rate and supersaturation degree of the reaction system during the reaction process, realizing the explosive nucleation and rapid growth of calcium carbonate, and thus obtaining nano-calcium carbonate with small particle size and narrow particle size distribution; in the surface functionalization treatment stage, the shear, fragmentation, and depolymerization capabilities of the high-speed rotating liquid film within the micron scale can disperse the soft agglomerates during the preparation and storage of nano-calcium carbonate, strengthening the reaction capabilities and reaction timeliness between surfactants and nano-calcium carbonate particles, and thus obtaining monodisperse nano-calcium carbonate. Compared with the existing kettle / tank reactors and related processes, the mixing and reaction device of the present invention has simple operation, short process flow, is easy to produce in batches and stably, has low cost, low energy consumption for preparing monodisperse nano-calcium carbonate, and has good industrialization prospects, providing an important way for the large-scale, low-cost, and resource utilization of industrial solid waste, the quality improvement and efficiency enhancement of nano-calcium carbonate products, and the technological progress of calcium carbonate and its related application industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of the mixing and reaction device of the present invention;

[0026] Figure 2Schematic structural diagram of the rotor of the mixing and reaction device of the present invention;

[0027] Figure 3 SEM photograph and energy spectrum surface scan diagram of the steel slag in Example 2;

[0028] Figure 4 SEM photograph and energy spectrum surface scan diagram of the steel slag after ammonium salt leaching of calcium in Example 2;

[0029] Figure 5 XRD pattern of the monodisperse nano-calcium carbonate prepared in Example 2;

[0030] Figure 6 SEM photograph of the monodisperse nano-calcium carbonate prepared in Example 2;

[0031] Figure 7 SEM photograph and energy spectrum surface scan diagram of the red mud solid waste used in Example 3;

[0032] Figure 8 SEM photograph of the monodisperse nano-calcium carbonate prepared in Example 3;

[0033] Figure 9 Particle size distribution curve of the monodisperse nano-calcium carbonate prepared in Example 4;

[0034] Figure 10 SEM photograph of the calcium carbonate prepared in Comparative Example 1;

[0035] Figure 11 Particle size distribution curve of the calcium carbonate prepared in Comparative Example 1;

[0036] Figure 12 SEM photograph of the calcium carbonate prepared in Comparative Example 2.

[0037] Explanation of reference numerals:

[0038] 1: housing; 2: feed chamber; 3: feed inlet; 4: stator; 5: rotor; 6: diversion groove; 7: diversion groove; 8: rotating shaft; 9: return port; 10: return pipe; 11: outlet; 12: three-way valve; 13: Venturi tube; 14: air inlet; 15: air inlet valve; 16: vent port; 17: discharge port. Detailed Description of the Invention

[0039] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms also include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1

[0043] Combined with Figure 1 、 Figure 2 As shown, the mixing and reversing device of this embodiment includes a housing 1. Above the interior of the housing 1, there is a feeding chamber 2, which is communicated with a feeding port 3. Below the interior of the housing 1, a stator 4 is fixedly provided. The stator 4 has a hollow cavity, and a rotor 5 is arranged in the hollow cavity. There is an adjustable gap between the rotor 5 and the stator 4, and the top of the gap is communicated with the feeding chamber 2. On the inner wall of the stator 4 and the outer wall of the rotor 5, a plurality of flow guiding grooves 6 and a plurality of flow guiding grooves 7 are respectively arranged at circumferential intervals. The rotor 5 is connected to the driving shaft of the driving mechanism through a rotating shaft 8. At the top of the housing 1, there is a reflux port 9. Both ends of the reflux port 9 are respectively communicated with the feeding chamber 2 and a reflux pipe 10. At the bottom of the housing 1, there is an outlet 11 communicated with the bottom of the gap. The outlet 11 is connected to the lower part of the reflux pipe 10 through a three-way valve 12. The middle part of the reflux pipe 10 is communicated with an air inlet 14, and an air inlet valve 15 is provided on the air inlet 14.

[0044] The housing 1 can be a cylindrical closed housing, and a feeding port 3, a reflux port 9, and an air vent 16 are independently provided at its top. The feeding port 3, the reflux port 9, and the air vent 16 are respectively communicated with the feeding chamber 2. The feeding port 3 is used to send materials to the feeding chamber 2, the reflux port 9 is used to make the materials in the gap flow back to the feeding chamber 2, and the air vent 16 is used for exhausting air.

[0045] Above the inside of the housing 1, a feed cavity 2 is provided. The feed cavity 2 is in the shape of an inverted frustum of a cone. The bottom of the feed cavity 2 is flush with the top of the stator 4, so as to facilitate the material in the feed cavity 2 to enter the gap between the stator 4 and the rotor 5 for mixing reaction. Below the inside of the housing 1, a stator 4 and a rotor 5 are provided. The stator 4 is arranged in the hollow cavity of the rotor 5. There is a gap between the stator 4 and the rotor 5, and this gap forms a dynamic confinement micro-reaction space at the micron scale, which is conducive to the formation of high-pressure liquid film shear and high-frequency oscillation effects during high-speed rotation, so as to strengthen the crushing and reaction capabilities of calcium-containing solid waste particles and improve the contactability and reactivity between calcium-containing solid waste and ammonium salt solution.

[0046] There is no strict limit on the adjustable method of the gap size, as long as the gap size can be adjusted within the range of 20 - 500 μm. Specifically, the hollow cavity of the stator 4 and the rotor 5 are in the shape of frustums of a cone that match each other. The inclination angles of the side surfaces of the hollow cavity and the frustum of the rotor 5 are the same. At the same time, the sizes of the upper and lower bases of the frustum of the hollow cavity are both larger than those of the upper and lower bases of the frustum of the rotor 5. The stator 4 and the rotor 5 are coaxially arranged. When the stator 4 and the rotor 5 are relatively fixed, there is a fixed gap between the stator 4 and the rotor 5.

[0047] Furthermore, the rotor 5 can be connected to a lifting mechanism. The lifting mechanism can drive the rotor 5 to move up and down relative to the stator 4 to adjust the gap size, and the gap size can be adjusted within the range of 20 - 500 μm according to actual process requirements. It can be understood that when the rotor 5 moves upward relative to the stator 4, the gap between the stator 4 and the rotor 5 becomes smaller; when the rotor 5 moves downward relative to the stator 4, the gap between the stator 4 and the rotor 5 becomes larger.

[0048] In addition, a plurality of diversion grooves 6 are arranged at intervals along the circumferential direction on the inner wall of the stator 4, and the depth of the diversion grooves 6 is 1 - 2 mm; a plurality of diversion grooves 7 are arranged at intervals along the circumferential direction on the outer wall of the rotor 5, and the depth of the diversion grooves 7 is 1 - 2 mm. The diversion grooves 6 and the diversion grooves 7 can be arranged to penetrate from top to bottom along the inner wall of the stator 4 and the outer wall of the rotor 5; at the same time, the diversion grooves 6 and the diversion grooves 7 can be inclined, and the inclination angle is 45 - 75 degrees. The distance between adjacent diversion grooves 6 is 1 - 2 mm, and the distance between adjacent diversion grooves 7 is 1 - 2 mm.

[0049] The rotor 5 is connected to the drive shaft of the drive mechanism through the rotating shaft 8. The drive mechanism drives the rotor 5 to rotate through the drive shaft and the rotating shaft 8. The rotational speed of the rotor 5 is adjustable within the range of 1000 - 6000 r / min. During the high-speed rotation process of the stator 4 and the rotor 5, a high-pressure liquid film shearing and high-frequency oscillation effect are formed, thereby strengthening the crushing and reaction capabilities of calcium-containing solid waste particles, and enhancing the contactability and reactivity between the calcium-containing solid waste and the ammonium salt solution. At the same time, the gap between the stator 4 and the rotor 5 is a micron-scale dynamic confinement micro-reaction space. The CO2 large bubbles are sheared into extremely small bubbles by the extrusion and shearing effects during the high-speed rotation of the rotor 5 to form a micron-scale second gas-liquid mixed flow, increasing the gas-liquid contact area between CO2 and the calcium-containing filtrate, improving the gas-liquid mass transfer process and the microscopic mixing and reaction efficiency, suppressing the inhomogeneity of mass, temperature, and concentration in the system, making the reaction time of CO2 and the calcium-containing filtrate match the mixing time between the gas-liquid materials, precisely controlling the absorption rate of CO2 and the supersaturation degree of the reaction system during the reaction process, realizing the explosive nucleation and rapid growth of calcium carbonate, and thus obtaining nano-calcium carbonate with small particle size and narrow particle size distribution. In addition, the shearing, crushing, and depolymerization capabilities of the high-speed rotating liquid film within the micron scale can disperse the soft agglomerates during the preparation and storage of nano-calcium carbonate, strengthening the reaction ability and reaction timeliness between the surfactant and the nano-calcium carbonate particles, and thus obtaining monodisperse nano-calcium carbonate.

[0050] One end of the reflux pipe 10 is communicated with the reflux port 9, and the other end of the reflux pipe 10 forms a discharge port 17. When the mixing and reaction effect of the mixing and reaction device does not meet the preset requirements, the material can be refluxed to the mixing and reaction device through the reflux pipe 10 via the outlet 11 to continue the mixing reaction. When the mixing and reaction effect of the mixing and reaction device meets the preset requirements, the material can be discharged through the discharge port 17.

[0051] In particular, a Venturi tube 13 is provided in the middle of the reflux pipe 10. The throat of the Venturi tube 13 is communicated with the air inlet 14, and the CO₂-containing gas can be self-sucked into the mixing and reaction device through the Venturi tube 13. The outlet 11 is connected to the Venturi tube 13, and the CO₂-containing gas is introduced through the Venturi tube 13 to obtain a preliminary gas-liquid mixed flow. Subsequently, a second gas-liquid mixed flow is obtained in the micron-scale dynamic confinement microenvironment formed by the gap between the stator 4 and the rotor 5, strengthening the mixing and reaction ability between the gas and the liquid. The CO₂-containing gas enters the reaction system accurately and controllably through the air inlet 14 and the inlet valve 15 at the throat of the Venturi tube 13 to form nano-micro bubbles, accelerating the escape of ammonia during the reaction process, and improving the leaching rate and leaching timeliness of calcium in the calcium-containing solid waste. In addition, according to Bernoulli's principle, the CO₂-containing gas and the calcium-containing filtrate are preliminarily premixed through the pressure difference to obtain a first gas-liquid mixed flow containing large bubbles, which enters the inverted frustum-shaped feed cavity 2 through the feed port 3 provided at the top of the housing 1, and then enters the micron-scale dynamic confinement micro-reaction space formed by the stator 4 and the rotor 5 to shear the large bubbles into extremely small bubbles to form a micron-scale second gas-liquid mixed flow, improving the gas-liquid mass transfer process and the microscopic mixing and reaction efficiency.

[0052] The mixing and reaction device of this embodiment can be applied to the preparation of monodisperse nano-calcium carbonate from calcium-containing industrial solid waste, and the method is as follows:

[0053] S1: Add the calcium-containing solid waste and the ammonium salt solution into the mixing and reaction device through the feed port 3 for mixing, transfer the mixture to a reaction kettle for reaction after mixing, and filter after the reaction to obtain a calcium-containing filtrate;

[0054] S2: Add the calcium-containing filtrate and the crystal form control agent into the mixing and reaction device through the feed port 3, and at the same time add the CO₂-containing gas into the mixing and reaction device through the air inlet 14 for mixing reaction, and filter after the mixing reaction to obtain nano-calcium carbonate;

[0055] S3: Add the nano-calcium carbonate and the aqueous solution containing the surfactant into the mixing and reaction device through the feed port 3 for mixing reaction, and centrifuge, wash and dry after the mixing reaction to obtain monodisperse nano-calcium carbonate.

[0056] In step S1, the calcium-containing solid waste is selected from at least one of red mud, carbide slag, steel slag and yellow phosphorus furnace slag; the mass content of the ammonium salt in the ammonium salt solution is 9-20%, and the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium acetate; the mass ratio of the calcium-containing solid waste to the ammonium salt solution is (0.05-0.2):1; the temperature during mixing is 20-50°C, the rotation speed of the rotor 5 of the mixing and reaction device during mixing is 1000-5000 r / min, and the mixing time is 5-10 min; the temperature during the reaction is 60-120°C, the time is 1-6 h; the mass content of calcium chloride in the calcium-containing filtrate is 5-12%.

[0057] In step S2, the crystal form control agent is selected from at least one of glucose, sodium polyphosphate, dodecylbenzenesulfonic acid, sodium dodecyl sulfate, polyethylene glycol, sodium sulfate, citric acid, and oxalic acid; the mass ratio of the crystal form control agent to nano calcium carbonate is (0.002 - 0.005):1; the CO₂-containing gas is a mixture of N₂ and CO₂, and the mass content of CO₂ in the CO₂-containing gas is 2 - 100%. The CO₂-containing gas can be self-aspirated into the mixing and reaction device through the Venturi tube 13, and the intake air volume of the CO₂-containing gas is adjusted through the intake valve 15; the temperature during the mixing reaction is 20 - 50°C, the rotation speed during mixing is 2000 - 6000 r / min, and the time is 1 - 10 min.

[0058] In step S3, the surfactant is selected from at least one of stearic acid, dodecylbenzenesulfonic acid, silane coupling agent, aluminate coupling agent, and titanate coupling agent; the mass ratio of the surfactant to nano calcium carbonate is (0.03 - 0.05):1; the temperature during the mixing reaction is 20 - 50°C, the rotation speed of the rotor 5 of the mixing and reaction device during the mixing reaction is 1000 - 3000 r / min, and the mixing reaction time is 5 - 10 min; the temperature during drying is 60 - 100°C, and the time is 6 - 12 h.

[0059] The monodisperse nano calcium carbonate prepared above has regular morphology, purity > 98.2%, chlorine content < 0.006%, alkalinity of 7.5 - 7.8, sedimentation volume of 2.8 - 3.8 mL / g, particle size of 10 - 100 nm, narrow particle size distribution, the product is white, and there are no visible impurities visually.

[0060] The mixing and reaction device in this embodiment uses dynamic confinement microscale high-pressure liquid film shearing, high-frequency oscillation, strong turbulent flow action, friction shearing action, etc. to deeply extract calcium from calcium-containing solid waste. By using the Venturi tube intake air method and the enhanced mixing and reaction ability within the dynamic confinement microscale, it controls the mass transfer and mixing and reaction process, carbonization rate, composition and particle size of nano calcium carbonate, as well as the degree and uniformity of surface functional graft modification of nano calcium carbonate, realizing the high-value utilization of solid waste resources and the quality improvement and efficiency enhancement of nano calcium carbonate products.

[0061] Compared with the existing kettle / tank reactors and related processes, the mixing and reaction device of this embodiment integrates crushing, depolymerization, and enhanced mixing and reaction. By utilizing the enhanced mixing, dispersion, and reaction capabilities within the dynamic confinement space and the precisely controllable gas introduction method, it can achieve deep leaching of calcium components in calcium-containing solid waste, improve the carbonation rate and carbonation timeliness of calcium-containing filtrate, precisely control the composition, purity, particle size, dispersion, and surface and interface properties of nano-calcium carbonate, realize large-scale, low-cost, and resource utilization of industrial calcium-containing solid waste, as well as quality improvement and efficiency enhancement of nano-calcium carbonate products. It has simple operation, a short process flow, is easy to produce in batches stably, has low cost and low energy consumption for preparing monodisperse nano-calcium carbonate, and has good industrialization prospects. It provides an important way for large-scale, low-cost, and resource utilization of industrial solid waste, quality improvement and efficiency enhancement of nano-calcium carbonate products, and technological progress in calcium carbonate and its related application industries.

[0062] Example 2

[0063] The method for preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment is carried out using the mixing and reaction device of Example 1, and the steps are as follows:

[0064] (1) Calcium leaching from calcium-containing solid waste with ammonium salt

[0065] Dissolve 50 g of ammonium chloride in 200 mL of water to form a clear ammonium chloride solution, and the mass content of ammonium chloride in the ammonium chloride solution is 20%.

[0066] The calcium-containing industrial solid waste in this embodiment uses steel slag, which is an irregular block at the micron scale and mainly contains components such as calcium, silicon, iron, aluminum, magnesium, and phosphorus. Among them, the distributions of calcium, silicon, and phosphorus elements are consistent, and the distributions of iron, magnesium, manganese, etc. are consistent. The calcium content in the steel slag is 47.95% calculated as CaO, the silicon content is 10.92% calculated as SiO2, the iron content is 27.45% calculated as Fe2O3, the manganese content is 4.23% calculated as MnO, and the phosphorus content is 2.33% calculated as P2O5; the morphology and element distribution are as Figure 3 shown.

[0067] Weigh 40 g of steel slag and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of steel slag to ammonium chloride solution to be 0.160:1.

[0068] Add the above suspension to the mixing and reaction device through the feed port 3. The rotation speed of the rotor 5 of the mixing and reaction device is 5000 r / min, the gap between the stator 4 and the rotor 5 is set to 100 μm, rotate and mix at 25 °C for 10 min, then transfer it to the reaction kettle, react at 120 °C for 3 h, and obtain an insoluble residue phase and a calcium-containing filtrate through filtration.

[0069] (2) Carbonation of calcium-containing filtrate

[0070] The calcium-containing filtrate obtained in step (i) and the crystal form control agent sodium polyphosphate are introduced into the mixing and reaction device through the feed port 3. At the same time, a mixed gas of N2 and CO2 is introduced into the mixing and reaction device through the gas inlet 14 to mix and react with the calcium-containing filtrate. The mass content of CO2 in the mixed gas is 80%. The intake volume of the CO2-containing gas is adjusted to 500 mL / min through the intake valve 15. The mass ratio of ammonium polyphosphate to calcium carbonate is 0.005:1. The rotation speed of the rotor 5 of the mixing and reaction device is controlled at 6000 r / min, and the reaction is carried out by rotation at 25 °C for 3 min. After centrifugation and washing, it is dried at 60 °C for 12 h to obtain nano calcium carbonate.

[0071] (III) Surface functionalization treatment

[0072] The nano calcium carbonate obtained in step (ii) is dispersed into an aqueous solution containing dodecylbenzenesulfonic acid, and then introduced into the mixing and reaction device through the feed port 3 for rapid surface functionalization modification. The mass ratio of dodecylbenzenesulfonic acid to calcium carbonate is 0.05:1. The rotation speed of the rotor 5 of the mixing and reaction device is 3000 r / min, and the reaction is carried out by rotation at 50 °C for 10 min. After centrifugation and washing, it is dried at 60 °C for 12 h to obtain monodisperse nano calcium carbonate.

[0073] Calculate the mass ratio of the dissolved calcium oxide in the steel slag to the total calcium oxide in the steel slag, and the calcium extraction rate of the steel slag is 81.2%. The scanning electron microscope and energy spectrum surface scan of the slag phase after ammonium salt leaching of calcium in the steel slag are as Figure 4 shown. The content of calcium element decreases significantly, and the content of iron element increases significantly. The percentage content of calcium chloride in the obtained calcium-containing filtrate is 13.3%, and the yield of monodisperse nano calcium carbonate is 93.8%.

[0074] The monodisperse nano calcium carbonate prepared in this example has regular morphology, the purity of calcium carbonate is 98.4%, the chlorine content is 0.004%, the alkalinity is 7.5, and the sedimentation volume is 3.4 mL / g; the average particle size measured by the particle size distribution is 50 nm, the particle size distribution is narrow, the product is white, and there are no visible impurities visually. From Figure 5 the XRD pattern, it can be seen that the monodisperse nano calcium carbonate is of vaterite crystal structure, and its scanning electron microscope photograph is as Figure 6 shown. From Figure 6 it can be seen that the monodisperse nano calcium carbonate is spherical-like particles, the particle size distribution is narrow, and the particle size is about 55 nm.

[0075] Example 3

[0076] The method for preparing monodisperse nano calcium carbonate using calcium-containing industrial solid waste in this example is carried out using the mixing and reaction device of Example 1, and the steps are as follows:

[0077] (I) Ammonium salt leaching of calcium-containing solid waste

[0078] Dissolve 25 g of ammonium chloride in 250 mL of water to form a clear ammonium chloride salt solution, and the mass content of ammonium chloride in the ammonium chloride salt solution is 9%.

[0079] The calcium-containing industrial solid waste in this example uses red mud, which is micron-sized irregular blocks and mainly contains elements such as calcium, silicon, iron, titanium, and aluminum. The calcium content in red mud calculated as CaO is 48.21%, the silicon content calculated as SiO2 is 15.51, the iron content calculated as Fe2O3 is 16.75%, the titanium content calculated as TiO2 is 6.52%, and the aluminum content calculated as Al2O3 is 5.76%; the morphology and element distribution are as Figure 7 shown.

[0080] Weigh 40 g of red mud and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of red mud to ammonium chloride solution to be 0.145:1.

[0081] Add the above suspension into the mixing and reaction device through the feed port 3. The rotation speed of the rotor 5 of the mixing and reaction device is 6000 r / min, the gap between the stator 4 and the rotor 5 is set to 50 μm, rotate and mix at 25 °C for 10 min, then transfer it to the reaction kettle, react at 120 °C for 3 h, and obtain an insoluble residue phase and a calcium-containing filtrate through filtration.

[0082] (II) Carbonization of the calcium-containing filtrate

[0083] Introduce the calcium-containing filtrate obtained in step (I) and the crystal form control agent citric acid into the mixing and reaction device through the feed port 3. At the same time, introduce the mixed gas of N2 and CO2 into the mixing and reaction device through the air inlet 14 to carry out a mixing reaction with the calcium-containing filtrate. The mass content of CO2 in the mixed gas is 20%. Adjust the intake amount of the CO2-containing gas to 1000 mL / min through the intake valve 15. The mass ratio of citric acid to calcium carbonate is 0.003:1. The rotation speed of the rotor 5 of the mixing and reaction device is 4000 r / min, rotate and react at 25 °C for 3 min, after centrifugation and washing, dry at 60 °C for 12 h to obtain nano calcium carbonate.

[0084] (III) Surface functionalization treatment

[0085] Disperse the nano calcium carbonate obtained in step (II) into an aqueous solution containing stearic acid, and then introduce it into the mixing and reaction device through the feed port 3 for rapid surface functionalization modification. The mass ratio of stearic acid to calcium carbonate is 0.05:1. The rotation speed of the rotor 5 of the mixing and reaction device is 2000 r / min, rotate and react at 50 °C for 10 min, after centrifugation and washing, dry at 60 °C for 12 h to obtain monodisperse nano calcium carbonate.

[0086] The mass ratio of the dissolved calcium oxide in the red mud to the total calcium oxide in the red mud was calculated, and the calcium extraction rate of the red mud was 52.6%; the percentage content of calcium chloride in the obtained calcium-containing filtrate was 9.7%; the yield of monodisperse nano-calcium carbonate was 96.4%.

[0087] The monodisperse nano-calcium carbonate prepared in this example has regular morphology, the purity of calcium carbonate is 98.3%, the chlorine content is 0.005%, the alkalinity is 7.6, the sedimentation volume is 3.8 mL / g, the average particle size is 40 nm, the particle size distribution is narrow, the product is white, there are no visible impurities visually, and the scanning electron microscope photos are as Figure 8 shown. From Figure 8 it can be seen that the monodisperse nano-calcium carbonate is spherical nanoparticles with a narrow particle size distribution and a particle size of about 40 nm.

[0088] Example 4

[0089] The method for preparing monodisperse nano-calcium carbonate from calcium-containing industrial solid waste in this example was carried out using the mixing and reaction device of Example 1, and the steps are as follows:

[0090] (1) Calcium extraction from calcium-containing solid waste with ammonium salt

[0091] 30 g of ammonium chloride was dissolved in 200 mL of water to form a clear ammonium chloride solution, and the mass content of ammonium chloride in the ammonium chloride solution was 13%.

[0092] 20 g of the steel slag of Example 2 was weighed and dispersed in the above ammonium chloride solution to form a stable suspension, and the mass ratio of the steel slag to the ammonium chloride solution was controlled to be 0.086:1.

[0093] The above suspension was added to the mixing and reaction device through the feed port 3. The rotation speed of the rotor 5 of the mixing and reaction device was 4000 r / min, the gap between the stator 4 and the rotor 5 was set to 200 μm, and it was rotated and reacted at 25 °C for 10 min, and then transferred to the reaction kettle and reacted at 120 °C for 3 h. After filtration, the insoluble residue phase and the calcium-containing filtrate were obtained.

[0094] (2) Carbonization of calcium-containing filtrate

[0095] The calcium-containing filtrate and the crystal form control agent polyethylene glycol obtained in step (1) were introduced into the mixing and reaction device through the feed port 3. At the same time, a mixed gas of N2 and CO2 was introduced into the mixing and reaction device through the air inlet 14 to carry out a mixing reaction with the calcium-containing filtrate. The mass content of CO2 in the mixed gas was 20%. The intake amount of the CO2-containing gas was adjusted to 500 mL / min through the intake valve 15. The mass ratio of polyethylene glycol to calcium carbonate was 0.003:1. The rotation speed of the rotor 5 of the mixing and reaction device was 6000 r / min, and it was rotated and reacted at 25 °C for 3 min. After centrifugation and washing, it was dried at 60 °C for 12 h to obtain nano-calcium carbonate.

[0096] (III) Surface functionalization treatment

[0097] Disperse the nano-calcium carbonate obtained in step (II) into an aqueous solution containing stearic acid, and then introduce it into the mixing and reaction device through the feed port 3 for rapid surface functionalization modification. The mass ratio of stearic acid to calcium carbonate is 0.05:1. The rotation speed of the rotor 5 of the mixing and reaction device is 3000 r / min, and it is rotated and reacted at 50 °C for 10 min. After centrifugation and washing, it is dried at 60 °C for 12 h to obtain monodisperse nano-calcium carbonate.

[0098] Calculate the mass ratio of the dissolved calcium oxide in the steel slag to the total calcium oxide in the steel slag, and the calcium extraction rate of the steel slag is 79.5%; the percentage content of calcium chloride in the obtained calcium-containing filtrate is 7.18%; the yield of monodisperse nano-calcium carbonate is 95.8%.

[0099] The monodisperse nano-calcium carbonate prepared in this example has regular morphology, the purity of calcium carbonate is 98.7%, the chlorine content is 0.005%, the alkalinity is 7.8, the sedimentation volume is 2.8 mL / g, the average particle size is 98 nm, the particle size distribution is narrow, the product is white, there are no visible impurities visually, and the particle size distribution curve is as Figure 9 shown.

[0100] Control Example 1

[0101] Except for using an existing mixing and reaction device (ZJRIII-4 type three-stage emulsifying pump of Anhui Zhongjing Huasheng Technology Co., Ltd.) to replace the mixing and reaction device in Example 2, the rest are the same as in Example 2.

[0102] Calculate the mass ratio of the dissolved calcium oxide in the steel slag to the total calcium oxide in the steel slag, and the calcium extraction rate of the steel slag is 68.3%; the percentage content of calcium chloride in the obtained calcium-containing filtrate is 10.56%, and the yield of monodisperse nano-calcium carbonate is 89.2%.

[0103] Combined with Figure 10 、 Figure 11 , the nano-calcium carbonate prepared in this control example has a spherical secondary aggregate morphology composed of 50-nm primary particles. The average particle size of the aggregates measured by the particle size distribution curve is 3 μm, the purity of calcium carbonate is 97.3%, the chlorine content is 0.083%, the alkalinity is 7.9, the sedimentation volume is 2.6 mL / g, and the average particle size is 2.7 μm.

[0104] Control Example 2

[0105] Except for using a conventional mechanical stirring device to replace the mixing and reaction device in the carbonization step of the calcium-containing filtrate, the rest are the same as in Example 2; that is, in this control example, the rotation reaction in the carbonization step of the calcium-containing filtrate is carried out under mechanical stirring conditions, and then centrifugation, washing, and drying are carried out to obtain nano-calcium carbonate.

[0106] The calcium carbonate prepared in this example has an irregular morphology. It is a spherical particle aggregate composed of primary particles of about 10 nm, accompanied by irregular blocks of about 300 nm. The average particle size measured by the particle size distribution curve is 1.8 μm. The purity of calcium carbonate is 97.4%, the chlorine content is 0.065%, the alkalinity is 7.6, the sedimentation volume is 2.3 mL / g, and the scanning electron microscope photograph is as Figure 12 shown. As can be seen from Figure 12 it, spherical particles and irregular blocks appear simultaneously, and the particle size of the spherical aggregate is about 1.5 μm.

[0107] Comparative Example 3

[0108] Except that a conventional mechanical stirring device is used to replace the mixing and reaction device in the calcium extraction step of the calcium-containing solid waste with ammonium salt, the rest is the same as in Example 2; that is, in this comparative example, rotational mixing in the calcium extraction step of the calcium-containing solid waste with ammonium salt is carried out under mechanical stirring conditions, and then it is transferred to a reaction kettle for reaction.

[0109] The mass ratio of the dissolved calcium oxide in the steel slag to the total calcium oxide in the steel slag is calculated, and the calcium extraction rate of the steel slag is obtained as 56.3%, and the percentage content of calcium chloride in the obtained calcium-containing filtrate is 8.5%.

[0110] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mixing device, characterized in that: It includes a shell, a feed chamber is provided at the upper part of the shell, the feed chamber is connected with the feed port, a stator is fixedly provided at the lower part of the shell, the stator has a hollow cavity, a rotor is provided in the hollow cavity, an adjustable gap is provided between the rotor and the stator, the top of the gap is connected with the feed chamber, a plurality of guide grooves are provided at intervals along the circumferential direction on the inner wall of the stator and the outer wall of the rotor, the rotor is connected with the driving shaft of the driving mechanism through a rotating shaft, a reflux port is provided at the top of the shell, the two ends of the reflux port are connected with the feed chamber and the reflux pipe respectively, an outlet connected with the bottom of the gap is provided at the bottom of the shell, the outlet is connected with the lower part of the reflux pipe through a three-way valve, the middle part of the reflux pipe is connected with the air inlet, and an air inlet valve is provided on the air inlet.

2. The mixing and reflection device according to claim 1, characterized in that: The hollow cavity of the stator and the rotor are both in a truncated cone shape. The rotor is connected to a lifting mechanism, and the lifting mechanism can drive the rotor to move up and down relative to the stator to adjust the size of the gap.

3. The mixing and reflection device according to claim 2, characterized in that: The gap size is adjustable in the range of 20-500μm.

4. The mixing and reflection device according to claim 1, characterized in that: The rotor speed is adjustable within the range of 1000-6000r / min.

5. The mixing and reflection device according to claim 1, characterized in that: The feed cavity is in the shape of an inverted truncated cone, and the bottom of the feed cavity is flush with the top of the stator.

6. The mixing and reflection device according to claim 1, characterized in that: A venturi tube is arranged in the middle of the return pipe, and the throat of the venturi tube is communicated with the air inlet.

7. Use of the mixing reaction device described in any one of claims 1 to 6 in the preparation of monodisperse nano-calcium carbonate.

8. A method for preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste, characterized in that: The method is carried out using the mixing reaction device described in any one of claims 1 to 6, and comprises the following steps: S1: adding calcium-containing solid waste and ammonium salt solution into a mixing device through a feed port for mixing, transferring the mixed solid waste and ammonium salt solution into a reactor for reaction, filtering the mixed solid waste and obtaining a calcium-containing filtrate. S2: adding the calcium-containing filtrate and the crystal form control agent into the mixing device through the feed port, and adding the CO2-containing gas into the mixing device through the gas inlet for mixed reaction, and filtering after the mixed reaction to obtain nano calcium carbonate; S3: adding the nano-calcium carbonate and the aqueous solution containing the surfactant into a mixing device through a feed port for mixed reaction, centrifuging, washing and drying after the mixed reaction to obtain monodispersed nano-calcium carbonate.

9. The method according to claim 8, characterized in that In step S1, the speed of the rotor of the mixing device during mixing is 1000-5000 r / min, and the mixing time is 5-10 min; in step S2, the speed of the rotor of the mixing device during the mixing reaction is 2000-6000 r / min, and the mixing reaction time is 1-10 min; in step S3, the speed of the rotor of the mixing device during the mixing reaction is 1000-3000 r / min, and the mixing reaction time is 5-10 min.

10. The method according to claim 8, characterized in that The intake amount of CO2-containing gas is regulated by the intake valve.

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