Multi-stage stirring tube type continuous micro-channel reactor

Abstract

The utility model discloses a multi-stage stirring tube type continuous micro-channel reactor, which relates to the field of pharmaceutical and chemical fine chemical equipment, and adopts the technical scheme that the multi-stage stirring tube type continuous micro-channel reactor comprises a cylindrical tubular shell with a large length-diameter ratio, a feeding hole is formed in one end of the cylindrical tubular shell, and a discharging hole is formed in the other end of the cylindrical tubular shell; the cylindrical tubular shell is internally provided with coaxial multi-stage stirring impellers and multi-stage radial blocking parts for separating the upper stirring impeller and the lower stirring impeller, the multi-stage stirring impellers are fixed on the same stirring shaft driven by a power source, and a first-stage stirring impeller and a first-stage radial blocking part form a first-stage mixing unit; the reactor has the effect that by designing the proportion of the axial length of the single-stage stirring impeller to the thickness of the single-stage radial baffle and the proportion of the diameter of the stirring impeller, the diameter of the radial baffle and the diameter of the inner cavity of the cylindrical tubular shell, the reactor can be well applied to the synthesis process of nanoparticles.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of pharmaceutical chemical fine chemical equipment, more specifically, it relates to a multistage stirring pipe type continuous microchannel reactor. BACKGROUND

[0002] In the prior art, for the synthesis process of micro-nano particles, it is often necessary to set up a strong stirring in the stirring reaction kettle and to realize the purpose of uniform mixing by means of optimizing the structure of the stirrer. For example, the intermittent stirring type carbonation method disclosed in CN1332207A adopts a low-temperature stirring bubble kettle type carbonation reactor to prepare calcium carbonate with different crystal structures and different particle sizes by adding a crystal shape control agent. This process can avoid the problems of high energy consumption, difficult process conditions to control and wide particle size distribution in the intermittent bubble type carbonation method without stirring; this method has become the main method for producing nano calcium carbonate in recent years because of the large gas-liquid contact area of the stirring, the uniform reaction, the narrow product particle size distribution, etc. However, due to many factors affecting the product particle size, it is difficult to control in the industrial production process, so there are still disadvantages such as poor repeatability and uneven particle size distribution; the intermittent or continuous kettle type (CSTR type) carbonation reactor has the disadvantages of large negative effect of scale-up test, long reaction period, low production capacity of single equipment, etc.

[0003] Even if the carbonation reaction process control and the surface modification of calcium carbonate particles are further improved, the following problems often cannot be avoided in the process of feeding and chemical reaction: 1) insufficient stirring and "dead zone" caused by stirring will cause scaling and other problems, which will cause local over-proportioning and lead to agglomeration of the product, which is almost impossible to avoid in a conventional stirring reaction kettle; 2) heat exchange problem of conventional reaction kettle: due to the limitation of insufficient specific surface area (surface area and volume ratio), the heat exchange efficiency of conventional stirring kettle is not high enough, and local overheating (hot spot) often occurs. Local overheating often leads to a decrease in yield and selectivity. 3) Problem of back mixing in the kettle: conventional single-pot reaction often uses the method of gradually adding reactants to prevent the reaction from being too violent, but in many reactions, the residence time of reactants, products or intermediate transition state products under reaction conditions will lead to the agglomeration of micro-nano particles or the uneven distribution of particle size. 4) Scale-up effect of conventional stirring reaction kettle: due to the limitation of the external size characteristics (such as length-diameter ratio) of the conventional reaction kettle, at the same time, as the reaction scale is gradually enlarged, the control of mass transfer and heat transfer is gradually weakened, so the scale-up effect of the stirring kettle will be very obvious.

[0004] In addition, compared with a conventional stirred reactor, the specific surface area of the micro reactor is very large, the mixing efficiency is extremely high, the heat exchange capacity is extremely strong, and the residence time distribution is extremely narrow. Therefore, CN110128851A discloses a preparation method for hydrophobic nano calcium carbonate by using a micro-pore reactor or a membrane dispersion micro reactor, which has the characteristics of small equipment volume, high production efficiency, stable product quality and the like. However, due to the very small size of the channel of the process fluid in the micro reactor, the slurry needs to be continuously circulated until the reaction is completed; at the same time, the equipment investment is high and the production capacity of a single device is small, so it is difficult to carry out large-scale industrial production. In addition, due to the absence of transmission equipment in actual operation, the system pressure drop is inevitably too large or agglomeration causes blockage, so that it cannot be operated for a long time.

[0005] Therefore, in order to solve the above technical problems, the present application provides a multi-stage stirring pipe type continuous micro-channel reactor. Utility model content

[0006] In view of the deficiencies of the prior art, the purpose of the utility model is to provide a multi-stage stirring pipe type continuous micro-channel reactor.

[0007] In order to achieve the above-mentioned purpose, the utility model provides the following technical scheme: a multi-stage stirring pipe type continuous micro-channel reactor, which comprises a large-length-diameter-ratio cylindrical pipe type shell, one end of which is provided with a feeding port, and the other end is provided with a discharging port, the inside of the cylindrical pipe type shell is provided with a coaxial multi-stage stirring impeller and a multi-stage radial blocking component separating the upper and lower stirring impellers, the multi-stage stirring impeller is fixed on the same stirring shaft driven by a power source, the first-stage stirring impeller and the first-stage radial blocking component constitute a first-stage mixing unit, and the multi-stage stirring impeller and the multi-stage radial blocking component finally form a multi-stage mixing unit fixed in the inside of the cylindrical pipe type shell, the diameter of the radial blocking component is smaller than the inner cavity diameter of the cylindrical pipe type shell, the ratio of the length of the cylindrical pipe type shell to the inner cavity diameter is greater than 5:1, the number of mixing units composed of the stirring impeller and the radial blocking component is greater than 3, and the number of feeding ports is not less than 2.

[0008] Among them, the ratio of the axial length h1 of the single-stage stirring impeller to the thickness b of the single-stage radial blocking component is 5:1-1:10, the characteristic index x=d1*D / (d*d) between the diameter d1 of the stirring impeller, the diameter d of the radial blocking component and the inner cavity diameter D of the cylindrical pipe type shell is in the range of 0.1-2.

[0009] Preferably, the ratio of the axial length h1 of the single-stage stirring impeller to the thickness b of the single-stage radial blocking component is 5:1-1:3, the characteristic index x=d1*D / (d*d) between the diameter d1 of the stirring impeller, the diameter d of the radial blocking component and the inner cavity diameter D of the cylindrical pipe type shell is in the range of 0.2-0.5.

[0010] Preferably, the single-stage radial blocking component is a baffle or a block.

[0011] Preferably, the baffle and the block are circular ring-shaped or cylindrical, and the axial cylinder of both is engraved with a pattern structure.

[0012] Preferably, the stirring impeller is a six-straight-blade open stirring paddle, a six-straight-blade disc turbine paddle, a spiral stirring paddle, a propelling stirring paddle, a Brumagin stirring paddle, a gear-shaped blade, a four-inclined-blade paddle or a disc turbine paddle.

[0013] Preferably, the outer side wall of the cylindrical tube shell is matched with a sleeve type outer jacket to meet the process temperature control and heat exchange requirements.

[0014] Preferably, the end of the cylindrical tube shell is provided with a bearing, the stirring shaft is fixed with the inner ring of the bearing, the head of the stirring shaft is connected with a power source through a shaft coupling, and a spacer is nested between the inner and outer rings of the bearing, and the cylindrical tube shell is internally provided with a support shaft for supporting the radial blocking component.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] 1. The utility model combines the advantages of the micro-channel reactor and the active stirrer, increases the process conditions of the active stirring feeding on the basis of retaining the large specific surface area of the micro-channel equipment, and the high length-diameter ratio enables the reactor to have the advantages of the high-efficiency mixing and heat exchange of the micro-reactor, greatly strengthens the heat transfer and mass transfer effect, and thus solves the heat exchange problem of the conventional stirring reactor due to the insufficient surface area in the background technology.

[0017] 2. The utility model broadens the use range of the micro-channel reactor or the stirring reaction kettle, and it can be found through CFD numerical simulation that the two materials can be completely mixed after the third-stage mixing unit, the stirring function of the product can ensure that the materials are quickly mixed after being fed and are not prone to the problems of micro-nano particle agglomeration or fouling, too large pressure drop or even blockage, the circulation gap formed by the radial blocking component enables the reactor to have the advantages of the high-efficiency mixing and heat exchange of the micro-reactor, the design of the radial blocking component also reduces the inter-stage back mixing, ensures good mixing in the stage, and the overall trend is a plug flow, avoids the disadvantages of the simple kettle stirring type or the conventional micro-channel reactor, such as insufficient stirring, existence of "dead zone", back mixing in the kettle, "amplification" effect of the reaction kettle, and too small channel size of the micro-reactor, which leads to large pressure drop or easy blockage, and thus solves the problems of insufficient stirring and "dead zone" of the conventional stirring reactor, back mixing in the kettle, amplification effect, and too small channel size of the micro-reactor in the background technology.

[0018] 3. The utility model discloses a single-stage stirring impeller axial length and single-stage radial baffle thickness ratio and the proportion design of stirring impeller diameter, radial baffle diameter and cylindrical pipe type shell inner chamber diameter, so that the reactor can be well applied to the synthesis process of nanoparticles.

[0019] 4. The utility model discloses a radial blocking part pattern design, when the reactant of synthesis micro-nano particle flows through the radial blocking part with pattern, these small scale flow phenomena can make reactant molecules fully contact in smaller space range, be favorable to micro-nano particle uniform nucleation. This is like creating more " meeting opportunity " for reactant molecules in the microcosmic world, makes the nucleation process of micro-nano particle more uniform, efficient, and can realize full mixing in different directions and positions. This all -round mixing effect helps to ensure that the growth environment of each micro-nano particle is relatively consistent, thereby obtaining the micro-nano particle product with narrower particle size distribution. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings described herein are used to provide further understanding of the utility model, and constitute a part of the application, the illustrative embodiment of the utility model and its explanation are used to explain the utility model, and do not constitute undue limitation to the utility model. In the drawings:

[0021] Figure 1 It is the structure schematic drawing of the utility model (including A partial structure enlargement and B partial cross section structure schematic drawing);

[0022] Figure 2 It is the stirring impeller type schematic drawing used in the utility model;

[0023] Figure 3 It is the annular pattern schematic drawing of radial blocking part in the cylindrical outside in the utility model;

[0024] Figure 4 For marking Figure 1 The parameter of each structure (the structure parameter of the key feature size of each component and the key feature size are marked) Figure 1

[0025] In the drawing: 1, cylindrical pipe type shell;2, feed inlet;3, discharge port;4, stirring impeller;5, radial blocking part;6, power source;7, stirring shaft;8, bearing;9, coupling;10, spacer;11, support shaft. DETAILED DESCRIPTION

[0026] As Figures 1-4 ​The utility model provides a kind of multistage stirring pipe type continuous microchannel reactor, including the cylindrical tubular shell 1 of big length-diameter ratio, its one end is provided with feed inlet 2, the other end is provided with discharge outlet 3, the inside of the cylindrical tubular shell 1 is provided with coaxial multistage stirring impeller 4 and the multistage radial blocking component 5 of separating upper and lower stirring impeller 4, multistage stirring impeller 4 is fixed on the same stirring shaft 7 driven by power source 6, primary stirring impeller 4 and primary radial blocking component 5 constitute primary mixing unit, by multistage stirring impeller 4 and multistage radial blocking component 5 finally form multistage mixing unit fixed in the inside of cylindrical tubular shell 1, the end of cylindrical tubular shell 1 is equipped with bearing 8, stirring shaft 7 is fixed with the inner ring of bearing 8 by being set in bearing 8, and bearing 8 is rotated to support stirring shaft 7, and its head is connected with power source 6 by coupling 9, the inner and outer rings of bearing 8 are nested with spacer 10, can accurately control the axial gap between the inner and outer rings of bearing 8, ensure that bearing 8 is in normal operation, the inside of the cylindrical tubular shell 1 is provided with the support shaft 11 of supporting radial blocking component 5, the diameter of radial blocking component 5 is less than the inner cavity diameter of cylindrical tubular shell 1.

[0027] The above-mentioned primary stirring impeller 4 and primary radial blocking component 5 constitute a primary mixing unit, which can form a multistage mixing unit fixed in the cylindrical tubular shell 1. When the stirring shaft 7 is directly driven by the motor or driven by the magnetic coupling (power source 6), the mixing function of the reactor can be realized.

[0028] One end of the cylindrical tubular shell 1 is formed with two or more feed inlets 2 (not less than two), and the other end is formed with one discharge outlet 3. Then, two or more materials are pumped into the tubular reactor at a certain flow rate by a feed pump (the materials can be gas or liquid). Subsequently, when the power source 6 is turned on at a certain speed, the materials pumped from the feed inlet 2 can be mixed by the stirring impeller 4 at the first stage (active stirring), and then the first-stage mixing unit is completed after the flow is converged by the first layer of radial blocking components 5. Then, the materials are gradually mixed or reacted by other mixing units, and finally, the system is discharged through the discharge outlet 3.

[0029] The number of mixing units composed of stirring impellers 4 and radial blocking components 5 is greater than 3, and in actual use, it is generally more than 10. When the number of mixing units is greater than 3, multistage mixing of materials can be realized, the uniformity of mixing can be improved, the plug flow can be enhanced to reduce backmixing, and the reaction progress can be flexibly controlled. The number of feed inlets 2 is not less than 2, which can meet the simultaneous feeding of multiple materials, facilitate the development of diversified reactions, and also can strengthen the mixing effect. Multiple material streams interact and the flow ratio can be flexibly controlled to optimize the overall reaction process.

[0030] The types of stirring impeller 4 include, but are not limited to, six straight blade open stirring paddle, six straight blade disc turbine paddle, ribbon stirring paddle, propeller stirring paddle, Brumakin stirring paddle, gear-shaped blade, four inclined blade paddle (45°PBT), disc turbine paddle (Rushton), among which the ribbon stirring paddle, propeller stirring paddle, four inclined blade paddle and Brumakin stirring paddle perform well in use, all of which can produce good material flow effect. Whether it is the simultaneous axial and circumferential movement of the ribbon stirring paddle, the high-efficiency axial flow generated by the propeller stirring paddle, the complex flow field formed by the four inclined blade paddle (45°PBT) containing axial and circumferential flow, or the strong convection generated by the Brumakin stirring paddle, all of them are helpful for the rapid flow and full mixing of the material in the reactor, reducing the stratification and aggregation of the material, and the stirring speed of the stirring impeller 4 can be controlled and adjusted, ranging from 0 to 1000 rpm, and in actual operation, the mixing effect is better at 200-1000 rpm. The ratio of the length of the cylindrical tubular shell 1 to the diameter of the inner cavity is greater than 5:1. If the length is relatively short compared to the inner cavity, the residence time of the material in the reactor will also be relatively short, and it is extremely easy to appear the condition of not being fully mixed. The ratio of the length of the cylindrical tubular shell 1 to the diameter of the inner cavity is preferably greater than 8:1, or even 10:1, so as to fully ensure the complete mixing of the material.

[0031] Further, a sleeve type outer jacket is matched on the outer side wall of the cylindrical tubular shell 1 to meet the process temperature control and heat exchange requirements.

[0032] In addition, the ratio of the axial length h1 of the single-stage stirring impeller 4 to the thickness b of the single-stage radial blocking component 5 is 5:1-1:10, preferably 5:1-1:3. In the process of synthesizing micro-nano particles, it is necessary to accurately control the mixing degree of the reaction material. The ratio of the axial length of the single-stage stirring impeller 4 to the thickness of the single-stage radial blocking component 5 is in the range of 5:1-1:10 (preferably 5:1-1:3). Compared with the reactor applied to high-viscosity system or solid-liquid two-phase process, the length of the stirring impeller 4 relative to the radial blocking component 5 is reduced, which greatly reduces the stirring intensity. Although the stirring intensity is relatively weak, it has certain benefits for the growth stage of micro-nano particles. After the micro-nano particles have been formed, weaker stirring can avoid the agglomeration of particles due to excessive shear force. Because the size of micro-nano particles is small and the surface energy is high, they are easy to adsorb and agglomerate with each other. Appropriate stirring intensity can reduce the probability of collision and agglomeration between particles while ensuring the mixing of materials.

[0033] At the same time, this ratio range can create an environment conducive to the growth of micro-nano particles. The appropriate h1 / b ratio makes the flow field in the reactor not only ensure the mixing of reactants, but also make the generated micro-nano particles grow in a relatively stable environment.

[0034] The characteristic index x = d1*D / (d*d) between the diameter d1 of the stirring impeller 4, the diameter d of the radial blocking component 5 and the diameter D of the inner cavity of the cylindrical tubular shell 1 ranges from 0.1 to 2, preferably from 0.2 to 0.5. Firstly, the proportional relationship can ensure sufficient space for mixing of the reactants and growth of the micro-nano particles in the reactor. For example, in the synthesis of calcium carbonate nano-particles, the slurry and solution need to be mixed sufficiently in a suitable space, and the suitable range can ensure that the two reactants can be in sufficient contact in the reasonable flow field generated by the stirring impeller 4 after entering the reactor, thereby providing good conditions for nucleation of the micro-nano particles.

[0035] Secondly, for micro-nano particle synthesis, a smaller range (0.2-0.5) is helpful to form a relatively stable reaction zone. In this range, the stirring impeller 4 rotates in a suitable space to generate a flow field that can mix the reactants in a local area without causing uneven dispersion of the reactants or excessively slow reaction due to excessive space. This is particularly important for nanoscale reactions, because the generation of micro-nano particles requires precise control of the concentration and contact time of the reactants, and suitable reaction space can improve the selectivity and efficiency of the reaction.

[0036] Compared with the reactor applied to high-viscosity systems or solid-liquid two-phase processes: since the high-viscosity system targeted by the above reactor has poor flowability due to strong intermolecular forces, the design emphasizes generating sufficient shear force to overcome viscous force through a suitable structure to promote overall mixing, so that the value of X is larger, which can fully ensure the lateral area of the stirring impeller 4 to promote stirring, and also make the gap between the radial blocking component 5 and the inner wall of the cylindrical tubular shell 1 related to the size. If solid material is involved, the gap cannot be too small, and sufficient space is needed for the solid particles to pass through smoothly. If it is a micro-nano particle, the size of the annular gap can be appropriately reduced, which is closer to a micro-channel reactor.

[0037] The size of the above annular gap D-d is 50-1000 microns, preferably 150-500 microns.

[0038] The radial blocking component 5 in the utility model can be a baffle or a block, which can be circular or cylindrical, or can be a structure with patterns engraved on the axial cylinder. The above patterns can strengthen the mixing and heat transfer of the material between the adjacent two stirring impellers.

[0039] Specifically, first, in the micro-nano synthesis process, the degree of micro-mixing of reactants plays a key role in the nucleation and growth of micro-nano particles. Compared with a single baffle, the radial blocking component 5 (baffle or baffle) with a pattern can enhance mixing at the microscale. The pattern structure can disrupt the laminar flow state of the fluid, generating more small-scale eddies and turbulence. For example, when the reactants (such as metal salt solution and precipitant) for synthesizing micro-nano particles flow through the radial blocking component 5 with a pattern, these small-scale flow phenomena can enable reactant molecules to contact each other in a smaller spatial range, facilitating uniform nucleation of micro-nano particles. This is like creating more "meeting opportunities" for reactant molecules in the micro world, making the nucleation process of micro-nano particles more uniform and efficient.

[0040] Second, for micro-nano particle synthesis, the uniformity of mixing is extremely high. A single baffle can only provide a relatively simple flow field guide, while a patterned structure can enable full mixing of the fluid in different directions and positions when passing through the radial blocking component 5. This all-round mixing effect helps to ensure that the growth environment of each micro-nano particle is relatively uniform, resulting in a narrower particle size distribution of the micro-nano particle product.

[0041] Finally, in the micro-nano synthesis process, many reactions are very sensitive to temperature. The radial blocking component 5 with a pattern can significantly improve the heat transfer efficiency, which is extremely beneficial to temperature control in the micro-nano synthesis process. The pattern structure increases the contact area between the radial blocking component 5 and the fluid, enabling heat to be transferred more quickly and uniformly in the reaction system. For example, some nanomaterial synthesis reactions that require a specific temperature, such as the synthesis of metal oxide nanoparticles by thermal decomposition, precise temperature control can be achieved through efficient heat transfer. The pattern structure is like laying a denser "heat exchange network" in the reactor, enabling the reaction system to better maintain the required temperature range and avoid local overheating or undercooling that affects the growth of micro-nano particles.

[0042] The present utility model is explained in detail by the following four embodiments, the first three embodiments are the parameter matching of the reactor from different scales including laboratory, pilot and production level equipment; the latter is the simulation results and actual experimental results of the reactor in different application scenarios, including the continuous reaction process of synthesizing micro-nano particle CaCO3.

[0043] Embodiment one, laboratory level multi-stage stirring

[0044] The number of stages is 5, the length (h2) of the cylindrical tubular shell 1 and the diameter ratio of the inner cavity (D) = h2*5 / D = 5.2;

[0045] h1 / b = 3, x = d1*D / (d*d) = 0.6, circular ring gap (D-d) / 2 = 0.2 mm = 200 microns

[0046] Reference of the above corresponding letters: axial length of the stirring impeller 4 (h1); baffle thickness (b); diameter of the stirring impeller 4 (d1); inner cavity diameter of the cylindrical tubular shell 1 (D); diameter of the baffle (d); characteristic index (x) between the diameter of the stirring impeller 4, the diameter of the baffle and the inner cavity diameter of the cylindrical tubular shell 1.

[0047] With 2 feed ports 2 and one discharge port 3, the first inlet channel diameter (wa); the second inlet channel diameter (wb) and the outlet channel diameter (wc)

[0048] Specific parameters: inlet channel diameter wa=wb=6.25 mm, outlet channel diameter wc=6.25 mm,

[0049] Inner cavity diameter of the cylindrical tubular shell 1 (D) = 50 mm, diameter of the baffle (d) = 49.6 mm, diameter of the stirring impeller 4 (d1) = 29.5 mm, diameter of the stirring shaft 7 (d2) = 14 mm,

[0050] Axial length of the stirring impeller 4 (h1) = 30 mm, height of the single-stage mixing unit (h2) = 52 mm, baffle thickness (b) = 10 mm.

[0051] Embodiment two, pilot-scale multi-stage stirring mixing reactor

[0052] The number of stages is 8, the ratio of the length of the cylindrical tubular shell 1 (h2) to the inner cavity diameter (D) = h2*8 / D = 9.6;

[0053] h1 / b = 1, x = d1*D / (d*d) = 0.956, circular ring gap (D-d) / 2 = 0.5 mm = 500 microns

[0054] Reference of the above corresponding letters: axial length of the stirring impeller 4 (h1); baffle thickness (b); diameter of the stirring impeller 4 (d1); inner cavity diameter of the cylindrical tubular shell 1 (D); diameter of the baffle (d); characteristic index (x) between the diameter of the stirring impeller 4, the diameter of the baffle and the inner cavity diameter of the cylindrical tubular shell 1.

[0055] With 2 feed ports 2 and one discharge port 3, the first inlet channel diameter (wa); the second inlet channel diameter (wb) and the outlet channel diameter (wc)

[0056] Specific parameters: inlet channel diameter wa=wb=20 mm, outlet channel diameter wc=20 mm,

[0057] The inner diameter (D) of the cylindrical tubular shell 1 is 300 mm, the baffle diameter (d) is 299 mm, the stirring impeller 4 diameter (d1) is 285 mm, and the stirring shaft 7 diameter (d2) is 80 mm,

[0058] The axial length (h1) of the stirring impeller 4 is 300 mm, the single-stage mixing unit height (h2) is 360 mm, and the baffle thickness (b) is 300 mm.

[0059] Embodiment three, production level multi-stage stirring mixing reactor structure parameters

[0060] The length (h2) of the cylindrical tubular shell 1 and the inner diameter (D) ratio is h2*10 / D=11.25;

[0061] h1 / b=0.5, x=d1*D / (d*d)=0.985, the circular ring gap (D-d) / 2=0.8 mm=800 microns

[0062] The above corresponding letter reference: the axial length (h1) of the stirring impeller 4; the baffle thickness (b); the stirring impeller 4 diameter (d1); the inner diameter (D) of the cylindrical tubular shell 1; the baffle diameter (d); the characteristic index (x) between the stirring impeller 4 diameter, the baffle diameter and the inner diameter of the cylindrical tubular shell 1.

[0063] With 2 feed ports 2 and one discharge port 3, the first inlet channel diameter (wa); the second inlet channel diameter (wb) and the outlet channel diameter (wc)

[0064] The specific parameters are: the inlet channel diameter wa=wb=50 mm, the outlet channel diameter wc=50 mm,

[0065] The inner diameter (D) of the cylindrical tubular shell 1 is 800 mm, the baffle diameter (d) is 798.4 mm, the stirring impeller 4 diameter (d1) is 785 mm, and the stirring shaft 7 diameter (d2) is 150 mm,

[0066] The axial length (h1) of the stirring impeller 4 is 700 mm, the single-stage mixing unit height (h2) is 850 mm, and the baffle thickness (b) is 1400 mm.

[0067] Embodiment four, continuous synthesis of micro-nano CaCO3 particles with narrow particle size distribution

[0068] In actual industrial production, the kettle type stirrer is prone to fouling, and the equipment requirements are high, and the equipment maintenance and cleaning are difficult; and in the micro-channel reactor, the reactant concentration cannot be too high, otherwise the heat release is intense and easy to agglomerate and block.

[0069] In the seed reactor of industrial production of calcium carbonate nanoparticles, the two materials of Ca(OH)2 slurry and Na2CO3 solution are successfully synthesized into nano calcium carbonate in a new type of reactor.

[0070] The Ca(OH)2 slurry and Na2CO3 liquid phase reaction system are used to prepare CaCO3 calcium carbonate nanoparticles synthesis process, and the laboratory level multi-stage stirring tubular continuous micro-channel reactor described in embodiment one is used, and the stirring impeller is four inclined blade paddles (45°PBT).

[0071] The specific steps are as follows:

[0072] Step one: dissolve Ca(OH)2 in deionized water with a concentration of 0.25 mol / L as a dilute slurry dispersed phase. Dissolve Na2CO3 in deionized water with a concentration of 0.5 mol / L as a continuous phase; adopt the laboratory level multi-stage stirring tubular continuous micro-channel reactor described in embodiment one;

[0073] Step two: Ca(OH)2 dilute slurry and Na2CO3 solution are pumped into the mixing reactor from two feed ports 2 under the action of constant flow pump, the volume flow rate of Ca(OH)2 is 80 mL / min, the volume flow rate of Na2CO3 solution is 40 mL / min, the temperature is kept at room temperature, and the stirring impeller 4 stirring rate is 120 rpm. Ca(OH)2 reacts with Na2CO3 to generate calcium carbonate, when the calcium carbonate in the aqueous phase reaches saturation, the calcium carbonate generated at the interface precipitates to form small calcium carbonate particles which flow out of the equipment with the continuous phase.

[0074] Step three: dilute the particles in a calcium carbonate saturated solution and terminate the reaction. After ultrasonic dispersion, drop onto a glass slide and dry naturally at room temperature, measure to obtain calcium carbonate particles with a particle size range of 55-85 nanometers and an average particle size of 65 nanometers. The laboratory level multi-stage stirring tubular continuous micro-channel reactor described in embodiment one can continuously produce more than 105 hours without blocking and the process and product quality are stable. As a comparison, the corning heart-shaped micro-reactor can only maintain less than 6 hours to produce a large pressure drop or blockage and needs to clean the equipment, although the difference in particle size range and average particle size is not large.

[0075] In summary, the present application combines the advantages of the micro-channel reactor and the active stirrer, increases the active stirring (active stirring refers to the process of driving the multi-stage stirring impeller 4 to rotate by directly driving or magnetically coupling the stirring shaft 7, so that the materials entering the reactor are forced to mix under the action of the stirring impeller 4. Unlike natural convection or passive diffusion mixing methods, active stirring is a powered and active mixing method, which is the feature of the active stirrer), while the high aspect ratio enables the reactor to have the advantages of high-efficiency mixing and heat exchange of the micro-reactor, greatly enhances the heat and mass transfer effect, and widens the use range of the micro-channel reactor or the stirred reactor. Through CFD numerical simulation, it is found that after the third mixing unit, the two materials can be completely mixed. The stirring function of the product can ensure that the materials are mixed quickly after being fed and are not prone to agglomeration or fouling, which can cause excessive pressure drop or even blockage. The annular flow gap formed by the radial blocking part 5 enables the reactor to have the advantages of high-efficiency mixing and heat exchange of the micro-reactor, and the design of the radial blocking part 5 can also reduce the inter-stage back mixing and ensure good mixing in the stage, thereby avoiding the shortcomings of pure kettle stirrers or conventional micro-channel reactors, such as insufficient stirring, existence of "dead zone", insufficient heat exchange, existence of local "hot spots", problems of back mixing in the kettle, "amplification" effect of the reactor, and problems of large pressure drop or easy blockage caused by too small micro-channel size. In addition, through the proportion design of the axial length of the single-stage stirring impeller and the thickness of the single-stage radial baffle, as well as the proportion design of the diameter of the stirring impeller 4, the diameter of the radial baffle 5, and the diameter of the inner cavity of the cylindrical tube shell 1, the reactor can be well applied to the synthesis process of nanoparticles.

[0076] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any person skilled in the art can easily implement the present application according to the drawings and the above description. However, any equivalent changes, modifications and evolutions made by those skilled in the art within the scope of the technical solutions of the present application, using the disclosed technical content, are also equivalent embodiments of the present application. Meanwhile, any equivalent changes, modifications and evolutions made by those skilled in the art according to the essential technology of the present application, are also within the protection scope of the technical solutions of the present application.

Claims

1. A multi-stage stirred tube continuous microchannel reactor characterized by: The cylindrical tubular shell (1) with a large length-to-diameter ratio is provided with a feed inlet (2) at one end and a discharge outlet (3) at the other end. The cylindrical tubular shell (1) is provided with a coaxial multi-stage stirring impeller (4) and a multi-stage radial blocking component (5) that separates the upper and lower stirring impellers (4). The multi-stage stirring impellers (4) are fixed on the same stirring shaft (7) driven by a power source (6). The first-stage stirring impeller (4) and the first-stage radial blocking component (5) form a first-stage mixing unit. The multi-stage mixing unit is finally formed by the multi-stage stirring impellers (4) and the multi-stage radial blocking component (5) and is fixed inside the cylindrical tubular shell (1). The diameter of the radial blocking component (5) is smaller than the inner diameter of the cylindrical tubular shell (1). The ratio of the length of the cylindrical tubular shell (1) to the inner diameter of the cavity is greater than 5:

1. The number of mixing units formed by the stirring impellers (4) and the radial blocking component (5) is greater than 3. The number of feed inlets (2) is not less than 2. The ratio of the axial length h1 of the single-stage stirring impeller (4) to the thickness b of the single-stage radial blocking component (5) is 5:1-1:

10. The characteristic index x = d1*D / (d*d) between the diameter d1 of the stirring impeller (4), the diameter d of the radial blocking component (5), and the inner diameter D of the cylindrical tubular shell (1) is 0.1-2.

2. A multi-stage stirred tube continuous microchannel reactor according to claim 1, wherein: The ratio of the axial length h1 of the single-stage stirring impeller (4) to the thickness b of the single-stage radial blocking component (5) is 5:1-1:

3. The characteristic index x = d1*D / (d*d) between the diameter d1 of the stirring impeller (4), the diameter d of the radial blocking component (5), and the inner diameter D of the cylindrical tubular shell (1) is 0.2-0.

5.

3. A multi-stage stirred tube continuous microchannel reactor according to claim 1, wherein: The single-stage radial blocking component (5) is a baffle or a block.

4. A multi-stage stirred tube continuous microchannel reactor according to claim 3, wherein: The baffle and the block are in the shape of a ring or a cylinder, and the axial cylinder of both is engraved with a patterned structure.

5. A multi-stage stirred tube continuous microchannel reactor according to claim 1, wherein: The impeller (4) is a six-bladed open impeller, a six-bladed disc turbine impeller, a ribbon impeller, a propulsion impeller, a Brumatin impeller, a gear-shaped blade, a four-bladed impeller, or a disc turbine impeller.

6. A multi-stage stirred tube continuous microchannel reactor according to claim 1, wherein: The outer wall of the cylindrical tubular shell (1) is fitted with a sleeve-type outer jacket to meet the process temperature control and heat exchange requirements.

7. A multi-stage stirred tube continuous microchannel reactor according to claim 1, wherein: The cylindrical tubular shell (1) is equipped with a bearing (8) at its end. The stirring shaft (7) is sleeved in the bearing (8) and fixed to the inner ring of the bearing (8). Its head is connected to the power source (6) through a coupling (9). A spacer (10) is nested between the inner and outer rings of the bearing (8). The cylindrical tubular shell (1) is provided with a support shaft (11) inside to support the radial blocking component (5).

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