Falling film crystallizer
By designing a composite flow field in the crystallizer, the synergistic effect of the scraper, circulating liquid inlet, and agitator is achieved, which solves the problem of bottom crystal aggregation and blockage, realizes dynamic suspension of crystals and stable discharge, and improves production continuity and product quality.
Patent Information
- Application Number
- CN202512048564.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-02-13
AI Technical Summary
Existing crystallizers tend to accumulate and clog at the bottom after the inner wall crystals are scraped off, resulting in poor production continuity, deterioration of crystal morphology, and the circulating flow field design cannot simultaneously achieve crystal suspension and flow stability.
The design employs a synergistic approach of scraper plate, circulating liquid inlet, bottom agitator, and side outlet to create a composite flow field of axial tumbling and radial dispersion. Combined with the centrifugal force of the agitator, this ensures crystal suspension and stable discharge, avoiding dead zones in the flow field.
This achieves a dynamic suspension state for the crystals, avoiding aggregation and blockage, ensuring production continuity and product quality stability, reducing energy consumption, and minimizing downtime for cleaning.
Smart Images
Figure CN121513489A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of chemical reaction equipment, in particular to a falling film crystallizer. BACKGROUND
[0002] Crystallization is one of the core unit operations for realizing material separation and purification in chemical, pharmaceutical, food and other industries, and the stability of the process and the yield and quality of the crystals directly affect the production efficiency and quality of the products. In industrial crystallization equipment, the problem of crystal adhesion on the inner wall of the crystallizer is a key bottleneck that has long hindered the continuity of production: when the solute in the solution is precipitated under a supersaturated state, a large amount of crystals will preferentially adhere to the inner wall of the crystallizer (especially the cooling wall surface), and if not removed in time, not only will the heat transfer efficiency of the wall surface be reduced, the uniformity of the supersaturation of the solution will be destroyed, but also the crystals will be caked and the particle size distribution will be uneven, and in severe cases, the equipment will be blocked and forced to shut down for cleaning.
[0003] To solve the problem of crystal adhesion on the inner wall, the existing technology generally uses a wall scraping device (such as a scraper or a doctor blade) to rotate against the inner wall of the crystallizer to scrape off the precipitated crystals. However, such devices can only achieve the "scraping" action, and the scraped crystals often directly fall to the conical body area at the bottom of the crystallizer, which is easy to quickly accumulate and compact due to the action of gravity, and then block the bottom discharge port, which is particularly prominent when dealing with high-viscosity solutions or large-particle-size crystals. For example, in the crystallization process of materials such as citric acid and sucrose, the blockage caused by the accumulation of crystals at the bottom of the traditional crystallizer requires frequent shutdown for dredging, which not only increases the operating cost, but also causes the crystal morphology to deteriorate and the product batch stability to decrease due to frequent start-stop.
[0004] To address the problem of crystal accumulation at the bottom, some existing technologies have tried some improvement schemes: some crystallizers have a single stirring device added at the bottom, but due to the limited stirring range, only the local area can be disturbed, and the uniform suspension of the crystals at the bottom cannot be achieved; another technology uses bottom gas blowing to promote mixing, but the introduction of gas can easily cause the solution to foam and the crystal form to be damaged, and after the bubbles escape, the crystals will still quickly settle; another scheme increases the diameter of the bottom discharge port to alleviate the blockage, but this will cause the separation efficiency of the crystals and the mother liquor to decrease, and increase the load of the subsequent filtration process. At the same time, the liquid circulation system of the existing crystallizer mostly uses a single inlet design, and the circulating liquid can only flow in a fixed direction, making it difficult to form a turbulent flow field covering the entire bottom cone, and unable to effectively inhibit the settlement and accumulation of the crystals.
[0005] In addition, the existing crystallizer liquid discharge mode is mostly direct discharge at the bottom, and the crystals are prone to secondary accumulation due to uneven flow rate during the discharge process, resulting in fluctuation of the discharge flow rate and affecting the continuity of subsequent processes such as filtration and drying. For example, in a melt crystallization device, the "bridge" phenomenon often occurs during the crystal settling process due to the lack of sustained suspension power, which blocks the discharge pipeline and forces the production to be interrupted. The traditional circulation system often only focuses on the temperature uniformity of the solution, without combining the circulation flow field with the crystal suspension demand, resulting in low energy utilization rate of the circulating liquid and the inability to achieve the dual goals of "suppressing accumulation" and "uniform suspension".
[0006] In view of this, those skilled in the art need to improve the existing crystallizer to overcome the above-mentioned defects. SUMMARY
[0007] The main purpose of the present application is to provide a falling film crystallizer to solve the problem of bottom accumulation and blockage after the crystal is scraped off the inner wall of the existing crystallizer.
[0008] In order to achieve the above-mentioned purpose, in a first aspect, the present application provides a falling film crystallizer, which comprises a vertical crystallizer shell, a liquid distributor arranged in the crystallizer shell from top to bottom, a wall scraping stirrer, a stirring assembly, a power driving assembly for driving the rotation of the wall scraping stirrer and the stirring assembly, the liquid outlet of the liquid distributor is adjacent to the inner wall of the crystallizer shell, a jacket sleeve is fixedly arranged outside the crystallizer shell, a circulating refrigerant fluid medium passes through the jacket sleeve, the temperature of the refrigerant fluid medium is ≥0℃, the side wall of the crystallizer shell is provided with a solution inlet connected with the liquid distributor, the lower end of the crystallizer shell is connected with a crystallizer lower cone, the bottom of the crystallizer lower cone is provided with a circulating liquid inlet, the side wall of the crystallizer lower cone is provided with a mixed liquid outlet, the mixed liquid outlet is connected with a filter assembly, and the liquid phase outlet of the filter assembly is connected with the circulating liquid inlet through a circulating pump.
[0009] Optionally, the liquid distributor is one of a centrifugal film forming liquid distributor and a forced film forming liquid distributor.
[0010] Optionally, the centrifugal film forming liquid distributor comprises a first shaft sleeve, a plurality of first connecting rods fixedly connected with the first shaft sleeve in the radial direction, a liquid distributor cylinder connected with the end of the first connecting rod through a first connecting flange, liquid distributor ring plates fixedly arranged on the upper and lower sides of the liquid distributor cylinder, a plurality of grid grooves are formed in the outer side wall of the liquid distributor cylinder, the solution inlet is arranged in the radial direction and faces the grid grooves, and the shaft sleeve is fixedly connected with the stirring shaft of the power driving assembly.
[0011] Optionally, the centrifugal film-forming liquid distribution device comprises a second shaft sleeve, a plurality of second connecting rods fixedly connected with the second shaft sleeve in a radial direction, a liquid distribution device inner cylinder connected with the end of the second connecting rods through a second connecting flange, a liquid distribution device outer cylinder fixedly arranged outside the liquid distribution device inner cylinder, and a liquid distribution device lower ring plate fixedly arranged at the bottom of the liquid distribution device outer cylinder and the liquid distribution device inner cylinder, wherein a plurality of liquid outlet holes are arranged on the liquid distribution device lower ring plate, and the solution inlet is arranged in an L shape and the vertical section of the solution inlet is opposite to the gap between the liquid distribution device outer cylinder and the liquid distribution device inner cylinder.
[0012] Optionally, the forced film-forming liquid distribution device comprises a circular annular film-forming distribution pipe, a plurality of openings are arranged at the bottom of the film-forming distribution pipe, a plurality of fixed plates are fixedly arranged on the inner side wall of the crystallizer shell, the film-forming distribution pipe is connected with the fixed plates through a fixed clamp, and a rib plate is arranged between the fixed plates and the inner side wall of the crystallizer shell.
[0013] Optionally, the power driving assembly comprises a central stirring shaft arranged along the axial direction of the crystallizer shell and a motor assembly connected with the central stirring shaft.
[0014] Optionally, the wall scraping stirrer comprises a plurality of layers of wall scraping assemblies arranged along the axial direction of the central stirring shaft, each layer of the wall scraping assemblies comprises a central shaft sleeve fixedly connected with the central stirring shaft, a plurality of first stirring paddles arranged in a radial direction and fixedly connected with the central shaft sleeve, the end of each layer of the first stirring paddles is provided with a block-shaped wall scraping plate or the ends of a plurality of layers of the first stirring paddles are connected through a strip-shaped wall scraping plate, the wall scraping plate is fixedly connected or rotatably connected with the stirring paddle, and a spring is arranged between the wall scraping plate and the stirring paddle.
[0015] Optionally, the jacket cylinder is provided with a jacket inner flow guide plate.
[0016] Optionally, the top of the crystallizer shell is fixedly provided with an oval head, the oval head is provided with a top gas phase balance port and a manhole, and the power driving assembly is arranged on the oval head.
[0017] Optionally, the stirring assembly comprises a spiral wall scraping plate fixedly arranged on the central stirring shaft in a spiral shape and a second stirring paddle arranged in a radial direction and staggered on the central stirring shaft, and the spiral wall scraping plate is fixedly connected with the second stirring paddle.
[0018] The falling film crystallizer and method have the beneficial effects that, compared with the prior art, the crystallizer structure solves the problem of traditional crystallizer bottom crystal accumulation and blockage from the aspects of flow field dynamics and crystal suspension mechanism through the synergistic design of the wall scraping plate, the circulating liquid inlet, the bottom agitator and the side discharge port; after the crystals scraped by the wall scraping plate fall to the bottom cone, the high-speed circulating liquid introduced by the circulating liquid inlet at the lowest part of the crystallizer forms an upward turbulent flow field at the bottom of the cone; according to the momentum transfer principle of fluid mechanics, the kinetic energy of the circulating liquid pushes the deposited crystals at the bottom to mix with the solution, breaking the sedimentation balance of the crystals; at the same time, the rotation of the agitator at the bottom of the stirring shaft forms a radial shear flow field, which is coupled with the axial flow field of the circulating liquid to form a composite flow field of "axial turbulence + radial dispersion" in the cone area, so that the crystal particles are uniformly wrapped in the solution, avoiding the formation of local high concentration areas due to gravity sedimentation, and fundamentally inhibiting the aggregation and "bridging" phenomenon of the crystals; and the filtered solution reenters from the bottom circulating liquid inlet through the circulating pump, forming a closed circulation system: on the one hand, the continuous input of the circulating liquid provides stable power for the crystal suspension, so that the crystals are always in a "dynamic suspension" state, without the need for additional disturbance devices, and the energy utilization rate is improved; on the other hand, the continuous action of the circulating flow field keeps the mixed solution of the crystals and the solution at a uniform concentration and flow rate, so that when the mixed solution is discharged from the side discharge port of the lower cone, the crystal sedimentation caused by sudden change of flow rate can be avoided, realizing "continuous and stable discharge in a suspended state", eliminating the secondary blockage risk of the traditional bottom discharge mode; secondly, the conical structure of the lower cone of the crystallizer matches the position design of the circulating liquid inlet and the agitator: the inclined wall surface of the cone can guide the turbulent flow field of the circulating liquid to diffuse to the whole domain, avoiding flow field dead angles; and the agitator is located at the center of the bottom of the cone, and the centrifugal force generated by the rotation of the agitator can disperse the crystal particles to the cone wall, which is complementary to the centripetal flow of the circulating liquid, ensuring that the crystals at all positions in the cone area can be covered by the flow field, realizing "dead angle-free suspension", and completely solving the problem of local accumulation at the bottom of the traditional crystallizer; thus, the structure realizes the whole-process synergy of "wall scraping-suspension-circulation-discharge": the wall scraping plate ensures that there is no crystal adhesion on the inner wall, maintaining the heat transfer efficiency; the composite flow field of the circulating liquid and the agitator ensures that the crystals are always in a suspended state, avoiding aggregation and blockage; the side discharge port discharges under the crystal suspension state, ensuring stable flow; and the filtered solution is recycled, which not only maintains the uniformity of the supersaturation degree of the solution, but also provides continuous power for the suspension. This synergistic mechanism makes the crystallization process not need to stop for cleaning and blockage, significantly improves the production continuity, avoids the damage to the crystal morphology caused by accumulation, and ensures the stability of the product quality. BRIEF DESCRIPTION OF DRAWINGS
[0019] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety. The drawings are not intended to limit the application and are merely used to explain more fully of the present application. In the drawings: Figure 1 is a schematic view of the present application; Figure 2 is a schematic view of a liquid applicator Figure 1 (Example One); Figure 3 is a schematic view of a liquid applicator Figure 2 (Example One); Figure 4 is a schematic view of a liquid applicator Figure 3 (Example One); Figure 5 is a schematic view of a liquid applicator Figure 4 (Example Two); Figure 6 is a schematic view of a liquid applicator Figure 5 (Example Two); Figure 7 is a schematic view of a liquid applicator Figure 6 (Example Two); Figure 8 is a schematic view of a liquid applicator Figure 7 (Example Three); Figure 9 is a schematic view of a liquid applicator Figure 8 (Example Three); Figure 10 is a schematic view of a liquid applicator Figure 9 (Example Three); Figure 11 is a schematic view of a wall scraping agitator (Example One); Figure 12 is a schematic view of a wall scraping agitator (Example Four); Figure 13 is a schematic view of an agitator assembly.
[0020] 1, power driven assembly, 2, oval head, 3, crystallizer shell, 4, liquid distributor, 5, solution inlet, 6, jacketed coolant outlet, 7, jacketed coolant inlet, 8, wall-scraping agitator, 9, jacketed cylinder, 10, jacketed inner baffle, 11, crystallizer lower cone, 12, mixed liquid outlet, 13, agitator assembly, 14, circulating liquid inlet, 15, top gas phase balance port, 16, manhole; 17, liquid distributor cylinder; 19, liquid distributor ring plate; 20, first connecting flange; 21, first connecting rod; 22, first shaft sleeve; 23, inclined rib; 24, liquid distributor outer cylinder; 25, liquid distributor inner cylinder; 26, liquid distributor lower ring plate; 27, second connecting flange; 28, second connecting rod; 29, second shaft sleeve; 30, film-forming distribution pipe; 31, rib plate; 32, fixed plate; 33, fixed clamp; 34, first agitator blade; 35, block-shaped wall-scraping plate; 36, strip-shaped wall-scraping plate; 37, second agitator blade; 38, spiral-belt wall-scraping plate. DETAILED DESCRIPTION
[0021] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.
[0022] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.
[0023] In the present application, the terms "up", "down", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.
[0024] And, the above-mentioned partial terms can be used to represent other meanings in addition to the orientation or positional relationship, for example, the term "upper" can also be used to represent a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances.
[0025] In addition, the meaning of the term "a plurality of" should be two and more than two.
[0026] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0027] As shown in Figures 1-4 、 Figure 11 、 Figure 13 The falling film crystallizer of the present embodiment includes a vertical crystallizer shell 3, a liquid distributor 4, a wall scraping stirrer 8, a stirring assembly 13, a power drive assembly 1 driving the rotation of the wall scraping stirrer 8 and the stirring assembly 13, which are sequentially arranged from top to bottom in the crystallizer shell, the liquid outlet of the liquid distributor 4 is adjacent to the inner wall of the crystallizer shell 3, a jacket cylinder 9 is fixedly arranged outside the crystallizer shell 3, and a jacket inner flow guide plate 10 is arranged in the jacket cylinder 9, and a jacket coolant outlet 6 and a jacket coolant inlet 7 are respectively arranged on the jacket cylinder 9, a circulating coolant fluid medium is circulated in the jacket cylinder 9, the temperature of the coolant fluid medium is ≥0℃, a solution inlet 5 is arranged on the side wall of the crystallizer shell 3 and is connected with the liquid distributor 4, a crystallizer lower cone 11 is connected to the lower end of the crystallizer shell 3, a circulating liquid inlet 14 is arranged at the bottom of the crystallizer lower cone 11, a mixed liquid outlet 12 is arranged on the side wall of the crystallizer lower cone 11, a filter assembly is connected to the mixed liquid outlet 12, and the liquid phase outlet of the filter assembly is connected with the circulating liquid inlet 14 through a circulating pump.
[0028] Working principle: The saturated solution enters the crystallizer from the feed inlet at the upper part of the crystallizer, is uniformly distributed and sprayed on the inner wall of the crystallizer cylinder by the liquid distributor 4, and flows down along the inner wall in a film shape. The jacket of the crystallizer is connected with a coolant, which cools the cylinder of the crystallizer, so that the saturated solution is condensed and crystallized on the inner wall of the crystallizer. The stirring transmission system with a motor and a speed reducer drives the stirring shaft to rotate, so that the wall scraping plate rotates along the inner wall of the crystallizer and scrapes off the crystallized crystals. The crystals fall into the bottom cone of the crystallizer. In order to prevent the crystals from gathering and blocking the discharge port at the bottom of the cone, a circulating liquid inlet 14 is arranged at the lowest part of the crystallizer. When in operation, the circulating liquid is introduced to make the mixture of the solution and the crystals at the bottom churn upward, and under the action of the stirrer at the bottom of the stirring shaft, the crystals can be suspended in the solution. The discharge port is opened on the side of the lower cone 11 of the crystallizer, so that the crystals together with the solution enter the next filtering process, and the filtered solution reenters the crystallizer from the circulating liquid inlet 14 at the bottom of the crystallizer through the circulating pump.
[0029] The operating temperature in the entire crystallizer is controlled to be above 0℃, so as to prevent the water in the solution from being condensed into ice on the inner wall of the crystallizer and thereby affecting the normal operation of the crystallizer. Meanwhile, a gas phase balance port is arranged at the top of the crystallizer to ensure that the pressure and temperature in the crystallizer are constant, the solubility of the container in the solvent is unchanged, and the crystallizer can be continuously operated for a long period.
[0030] In the embodiment, the liquid distributor 4 is a centrifugal film-forming liquid distributor 4, which comprises a first shaft sleeve 22, a plurality of first connecting rods 21 fixedly connected with the first shaft sleeve 22 in the radial direction, a liquid distributor cylinder 17 connected with the ends of the first connecting rods 21 through first connecting flanges 20, liquid distributor ring plates 19 fixedly arranged on the upper and lower sides of the liquid distributor cylinder 17, a plurality of grid grooves formed in the outer side wall of the liquid distributor cylinder 17, and a solution inlet 5 arranged in the radial direction and opposite to the grid grooves. The shaft sleeve is fixedly connected with the stirring shaft of the power driving assembly 1. Since the liquid distributor cylinder 17 is in a rotating state, the solution entering the solution inlet 5 falls and forms a film along the inner wall under the action of centrifugal force after entering the grid grooves. The two ends of the first connecting rods 21 are respectively provided with inclined ribs 23.
[0031] The solution inlet 5 of the conventional scraped plate crystallizer generally enters the inside of the equipment in the tangential direction of the cylinder, without a liquid distribution disc. The inlet mode of the present application is to enter the equipment vertically to the cylinder wall, and a liquid distribution disc is arranged in the crystallizer. Under the action of the liquid distribution disc, the solution can be uniformly formed into a film on the cylinder wall. Under the action of the coolant in the jacket, the efficiency of the solute to be crystallized into crystals is greatly increased.
[0032] In addition, the conventional scraper type crystallizer generally adopts evaporation mode operation, and the jacket heat medium adopts steam or heat conducting oil and the like. In a high temperature environment, the allowable stress of the metal material of the cylinder wall will decrease, resulting in that the thickness of the inner cylinder wall of the crystallizer will greatly increase under the same operating pressure, especially for a large scale crystallizer, thereby increasing the manufacturing cost of the equipment. The crystallizer of the present application is operated in a low temperature environment close to 0 DEG C, and the allowable stress of the metal material of the cylinder wall is unchanged, and the effect of reducing the manufacturing cost of the large scale crystallizer is very obvious. The falling film crystallizer of the present application mainly utilizes the principle that the solubility of solute in solution decreases with the decrease of temperature, and the operation is carried out at a low temperature above 0 DEG C, so the requirement for the jacket coolant is lower, the overall energy consumption is low, the operation cost of the device is reduced, and the safety of the device is improved.
[0033] In addition, the top of the crystallizer shell 3 is fixedly provided with an oval head 2, the oval head 2 is provided with a top gas phase balance port 15 and a manhole 16, and the power driven assembly 1 is arranged on the oval head 2. The flat cover structure at the top of the conventional scraper type crystallizer is replaced by the oval head 2 structure. The stress of the flat cover is not good, which directly affects the large scale of the equipment, and the stress of the oval head is much better than that of the flat cover, which is suitable for the large scale of the equipment, and the manufacturing cost of the equipment is considered.
[0034] As shown in Figure 1 The power driven assembly 1 includes a central stirring shaft arranged along the axial direction of the crystallizer shell 3, and a motor assembly connected with the central stirring shaft. The motor assembly includes a motor, a speed reducer and a transmission structure thereof. In the embodiment, the central stirring shaft drives the liquid distributor 4, the wall scraping stirrer 8 and the stirring assembly 13 to rotate together.
[0035] As shown in Figure 11 In the embodiment, the wall scraping stirrer 8 includes a plurality of layers of wall scraping assemblies distributed along the axial direction of the central stirring shaft. Each layer of the wall scraping assemblies includes a central shaft sleeve fixedly connected with the central stirring shaft, and a plurality of first stirring paddles 34 arranged radially and fixedly connected with the central shaft sleeve. The end portion of each layer of the first stirring paddles 34 is provided with a block-shaped wall scraping plate 35. The wall scraping plate and the first stirring paddle 34 are connected through a hinge, and a supporting spring is arranged therebetween, so that the wall scraping plate can tightly adhere to the inner wall of the crystallizer cylinder during work.
[0036] As shown in Figure 13As shown, in the embodiment, the stirring assembly 13 includes a spiral scraping wall plate 38 fixedly arranged on the central stirring shaft, and a second stirring paddle 37 arranged radially and staggered on the central stirring shaft, the spiral scraping wall plate 38 is fixedly connected with the second stirring paddle 37, and the spiral scraping wall plate 38 and the second stirring paddle 37 are usually connected by fasteners or welded; the roundness requirement of the spiral scraping wall plate 38 to the inner wall of the crystallizer cylinder is very high, which must be controlled within 1.5 mm, and the longitudinal weld and the girth weld of the crystallizer cylinder must be ground flat.
[0037] Embodiment two, As Figures 5-7 shown, the difference from the first embodiment is that the liquid distributor 4 in the embodiment also adopts a centrifugal film-forming liquid distributor 4, but the centrifugal film-forming liquid distributor 4 includes a second shaft sleeve 29, a plurality of second connecting rods 28 fixedly connected with the second shaft sleeve 29, a liquid distributor inner cylinder 25 connected with the end of the second connecting rod 28 through a second connecting flange 27, a liquid distributor outer cylinder 24 fixedly arranged outside the liquid distributor inner cylinder 25, and a liquid distributor lower ring plate 26 fixedly arranged at the bottom of the two, a plurality of liquid outlet holes are formed in the liquid distributor lower ring plate 26, the solution inlet 5 is arranged in an L shape and its vertical section is opposite to the gap between the liquid distributor outer cylinder 24 and the liquid distributor inner cylinder 25, the solution inlet 5 enters the gap between the inner cylinder and the outer cylinder, and the solution is thrown out from the liquid outlet holes on the liquid distributor lower ring plate 26 under the centrifugal force, thereby uniformly falling along the inner wall of the crystallizer to form a film.
[0038] Embodiment three, As Figures 8-10 shown, the difference from the first embodiment is that the liquid distributor 4 in the embodiment adopts a forced film-forming liquid distributor 4, that is, it is not fixed with the central stirring shaft, and it only includes the forced film-forming liquid distributor 4 which includes a circular annular film-forming distribution pipe 30, a plurality of openings are formed at the bottom of the film-forming distribution pipe 30, a plurality of fixed plates 32 are fixedly arranged on the inner side wall of the crystallizer shell 3, the film-forming distribution pipe 30 is connected with the fixed plate 32 through a fixed clamp 33, and a rib plate 31 is further arranged between the fixed plate 32 and the inner side wall of the crystallizer shell 3, the solution inlet 5 falls from the bottom openings of the film-forming distribution pipe 30 under the action of pressure, thereby uniformly falling along the inner wall of the crystallizer to form a film, and the above structure can greatly reduce the overall weight of the liquid distributor 4, not only reducing the cost, but also reducing the load.
[0039] Embodiment four, As Figure 12The difference between the embodiment and the embodiment one is that the wall scraping plate in the embodiment is a strip-shaped wall scraping plate 36, and the wall scraping plate is connected with the end of the first stirring paddle 34. The number of the wall scraping paddle groups is selected according to the diameter of the crystallizer, and the number is usually 4-6 groups. The strip-shaped wall scraping plate and the stirring paddle are usually connected by fasteners or welded connection; or the wall scraping plate is connected with the stirring paddle by springs. When the wall scraping plate works, the centrifugal force generated by the rotation of the stirring shaft can make the wall scraping plate closely contact with the inner wall of the crystallizer cylinder.
[0040] When the strip-shaped wall scraping plate is connected with the stirring paddle by fasteners or welding, the roundness of the inner wall of the crystallizer cylinder must be very high, and must be controlled within 1.5 mm. The longitudinal weld and the girth weld of the crystallizer cylinder must be ground flat.
[0041] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A falling film crystallizer, characterized in that, The crystallizer includes a vertical crystallizer shell, a liquid distributor, a wall-scraping agitator, a stirring assembly, and a power drive assembly for rotating the wall-scraping agitator and the stirring assembly, arranged sequentially from top to bottom within the crystallizer shell. The liquid outlet of the liquid distributor is adjacent to the inner wall of the crystallizer shell. A jacketed cylinder is fixedly installed outside the crystallizer shell, and a circulating refrigerant fluid medium with a temperature ≥0℃ flows through the jacketed cylinder. A solution inlet connected to the liquid distributor is provided on the side wall of the crystallizer shell. A lower cone of the crystallizer is connected to the lower end of the crystallizer shell. A circulating liquid inlet is provided at the bottom of the lower cone of the crystallizer, and a mixed liquid outlet is opened on its side wall. A filter assembly is connected to the mixed liquid outlet, and the liquid phase outlet of the filter assembly is connected to the circulating liquid inlet through a circulating pump.
2. A falling film crystallizer as described in claim 1, characterized in that: The liquid distributor is one of a centrifugal film-forming liquid distributor or a forced film-forming liquid distributor.
3. A falling film crystallizer as described in claim 2, characterized in that: The centrifugal film-forming liquid distributor includes a first bushing, a plurality of first connecting rods radially fixedly connected to the first bushing, a liquid distributor cylinder connected to the ends of the first connecting rods through a first connecting flange, and liquid distributor ring plates fixedly disposed on the upper and lower sides of the liquid distributor cylinder. The outer side wall of the liquid distributor cylinder is provided with a plurality of grid grooves. The solution inlet is radially disposed and directly opposite the grid grooves. The bushing is fixedly connected to the stirring shaft of the power drive assembly.
4. A falling film crystallizer as described in claim 2, characterized in that: The centrifugal film-forming liquid distributor includes a second bushing, a plurality of second connecting rods radially fixedly connected to the second bushing, and an inner cylinder of the distributor connected to the ends of the second connecting rods through a second connecting flange. An outer cylinder of the distributor is fixedly installed on the outside of the inner cylinder of the distributor, and a lower ring plate of the distributor is fixedly installed at the bottom of both. A plurality of liquid outlet holes are opened on the lower ring plate of the distributor. The solution inlet is L-shaped and its vertical section is directly opposite the gap between the outer cylinder of the distributor and the inner cylinder of the distributor.
5. A falling film crystallizer as described in claim 2, characterized in that: The forced film-forming liquid distributor includes a circular film-forming distribution tube with several openings at the bottom. Several fixing plates are fixedly installed on the inner wall of the crystallizer shell. The film-forming distribution tube is connected to the fixing plates by fixing clips. Ribs are also provided between the fixing plates and the inner wall of the crystallizer shell.
6. A falling film crystallizer as described in claim 1, characterized in that: The power drive assembly includes a central stirring shaft arranged along the axial direction of the crystallizer shell and a motor assembly connected to the central stirring shaft.
7. A falling film crystallizer as described in claim 6, characterized in that: The scraper-type agitator includes several layers of scraper assemblies distributed along the axial direction of the central agitation shaft. Each layer of the scraper assembly includes a central bushing fixedly connected to the central agitation shaft and several first agitation blades radially arranged and fixedly connected to the central bushing. Each layer of first agitation blades has a block-shaped scraper plate at its end, or the ends of multiple layers of first agitation blades are connected by strip-shaped scraper plates. The scraper plates are fixedly or rotatably connected to the agitation blades, and a spring is provided between them.
8. A falling film crystallizer as described in claim 1, characterized in that: The jacket cylinder is provided with an inner guide plate.
9. A falling film crystallizer as described in claim 1, characterized in that: An elliptical head is fixedly installed on the top of the crystallizer shell. The elliptical head is provided with a top gas phase balance port and a manhole. The power drive assembly is installed on the elliptical head.
10. A falling film crystallizer as described in claim 6, characterized in that: The stirring assembly includes a spiral ribbon scraper fixedly mounted on the central stirring shaft and a second stirring blade radially and alternately arranged on the central stirring shaft, wherein the spiral ribbon scraper is fixedly connected to the second stirring blade.