Fluidized bed crystallization apparatus and method

Abstract

This application relates to a fluidized bed crystallization apparatus and method. The liquid to be treated is injected at high speed into the interior of the reaction crystallization cylinder through a tangential inlet pipe along the tangential direction. The inlet direction is tangential to the cylinder wall, creating a swirling flow field within the crystallization cylinder. This swirling flow field flows upwards through a coaxially arranged guide tube. The generatrix of the guide tube is a smooth curve that contracts in the middle and expands at both ends. The flow velocity increases significantly in the middle section, creating a local negative pressure zone. The pressure difference between this negative pressure zone and the two ends of the guide tube induces fluid outside the guide tube to enter the interior from the lower port and flow upwards, exiting from the upper port and re-entering the external swirling flow field, forming a closed internal circulation flow. The entire internal circulation process is driven entirely by the swirling kinetic energy generated by the tangential inlet, achieving a highly efficient and low-consumption internal circulation.

Description

Technical Field

[0001] This application relates to the field of water treatment and resource utilization equipment technology, and in particular to a fluidized bed crystallization device and method. Background Technology

[0002] As coal mining depths increase, the volume of water flowing from deep mines has risen significantly, and this water generally exhibits high mineralization, particularly with high concentrations of scale-forming ions such as calcium, magnesium, and sulfate. Direct discharge of this mine water not only wastes valuable water resources but may also lead to ecological risks such as salinization of surface water bodies. Conversely, reuse of this water can easily result in the formation of dense, hard, and difficult-to-remove inorganic scale layers on the inner walls of heat exchange equipment, pipelines, and treatment units, seriously threatening the long-term stable operation of the system.

[0003] Against this backdrop, fluidized bed crystallization technology has become a key technology option in the deep treatment and resource utilization of highly mineralized mine water because it can achieve efficient hardness removal while directionally converting scale-forming ions into crystalline products with certain commercial value (such as calcite-type calcium carbonate), thus combining environmental benefits and resource recovery potential.

[0004] Traditional fluidized bed crystallizers employ a vertical cylindrical structure, using an external high-power circulating pump to force the reaction liquid to circulate within the bed, or relying on an internal mechanical agitator to provide disturbance energy to maintain the suspended fluidized state of the seed crystals. In early engineering practice, this design effectively solved problems such as scaling and low mass transfer efficiency in static crystallizers, achieving relatively stable hardening removal. Its core logic lies in breaking the local supersaturation equilibrium through external energy input, promoting preferential crystal growth on the surface of suspended particles, thereby inhibiting homogeneous nucleation and heterogeneous nucleation on the vessel wall. However, with the expansion of mine water treatment scale, the increasing complexity of water quality, and the increasingly stringent requirements for the quality of resource-based products, the inherent contradictions of this mechanically-assisted fluidization mode have gradually become prominent, evolving into a key bottleneck restricting technological upgrades.

[0005] Fundamentally, existing technologies suffer from a profound structural disconnect in their fluid dynamics design—"fluidization maintenance" and "crystal protection" are placed under conflicting physical mechanisms. Specifically, to overcome the settling resistance caused by high-viscosity, high-density mine water, the system must rely on a high-intensity shear field to maintain particle suspension, which poses a devastating threat to the already formed crystal structure. The turbulent vortices generated by high-speed rotating impellers or high-velocity circulating pumps, while providing the necessary fluidization kinetic energy, also exert severe collision and shear stress on the crystals, causing large crystal particles to break up and inducing a large number of secondary nucleations. This not only significantly increases the proportion of fine crystals in the product, weakening its commercial value as an industrial filler or building material raw material, but also increases the load on subsequent solid-liquid separation units due to the large specific surface area and poor settling performance of fine crystals. Furthermore, traditional water inlet methods (such as bottom center jets or annular distributors) are unable to establish sufficient radial disturbance in the near-wall region of the cylinder, resulting in flow dead zones near the boundary layer. Within this region, solute diffusion is restricted, and localized supersaturation accumulates continuously, easily triggering uncontrolled heterogeneous nucleation. This leads to the rapid deposition of dense, hard scale on the vessel walls, forcing frequent system shutdowns for chemical cleaning or mechanical descaling, severely impacting continuous operating efficiency and equipment lifespan. Furthermore, existing equipment generally lacks the ability to control the entire crystal lifecycle, failing to effectively distinguish crystals at different growth stages. This results in a large number of insufficiently grown microcrystals being lost with the overflow, causing a decrease in resource recovery rate and increasing the difficulty of controlling effluent turbidity.

[0006] The above problems do not exist in isolation, but rather stem from the same underlying logical flaw: traditional fluidized bed crystallization systems treat the fluid dynamic environment as a single functional carrier, focusing only on its "transport" and "mixing" functions, while neglecting its synergistic potential in multiple dimensions such as crystal morphology control, interface scale prevention, and particle size classification.

[0007] Therefore, how to achieve efficient internal circulation is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0008] This application provides a fluidized bed crystallization apparatus to achieve efficient internal circulation.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A fluidized bed crystallization apparatus includes a reaction crystallization cylinder, a guide cylinder, and at least one tangential water inlet pipe, wherein: The flow guide tube is fixed inside the reaction crystallization tube and is coaxially arranged with the reaction crystallization tube; The guide tube is a rotating body with openings at both ends, and the generatrix of the guide tube is a smooth curve that contracts in the middle and expands at both ends. The tangential water inlet pipe is located at the lower part of the reaction crystallization cylinder and is used to introduce the liquid to be treated along the tangential direction of the reaction crystallization cylinder.

[0010] Optionally, in the above-mentioned fluidized bed crystallization device, the guide tube is a hyperboloid guide tube, and the generatrix trajectory of the hyperboloid guide tube conforms to the hyperboloid equation.

[0011] Optionally, in the above-mentioned fluidized bed crystallization device, the number of tangential water inlet pipes is three, and the three tangential water inlet pipes are evenly distributed along the circumference of the reaction crystallization cylinder, and the angle between the center lines of adjacent tangential water inlet pipes on the horizontal plane is 120°; the inlet cross section of each tangential water inlet pipe is elliptical, and the major axis of the ellipse is arranged tangentially.

[0012] Optionally, the fluidized bed crystallization device described above further includes a solid-liquid separation zone and a transition connecting section. One end of the transition connecting section is connected to the reaction crystallization cylinder, and the other end of the transition connecting section is connected to the solid-liquid separation zone. The solid-liquid separation zone is connected to the reaction crystallization cylinder through the transition connecting section.

[0013] Optionally, the fluidized bed crystallization device described above also includes a hydraulic classification discharge leg. The first end of the hydraulic classification discharge leg is connected to the bottom of the reaction crystallization cylinder. The second end of the hydraulic classification discharge leg is provided with a discharge valve. The side wall of the second end of the hydraulic classification discharge leg is provided with a washing water inlet for introducing washing water. The hydraulic classification discharge leg is conical, with the first end being the large-diameter end of the cone and the second end being the small-diameter end of the cone; or, the hydraulic classification discharge leg is a cylindrical-conical combination structure, with the first end being a cylindrical end and the second end being a conical end, the large-diameter end of the conical end being connected to the cylindrical end.

[0014] Optionally, in the above-mentioned fluidized bed crystallization device, a porous ceramic filter element is provided inside the hydraulic classification discharge leg, and the porous ceramic filter element is located between the discharge valve and the first end of the hydraulic classification discharge leg.

[0015] Optionally, in the above-mentioned fluidized bed crystallization device, the solid-liquid separation zone includes an inverted frustum section and a cylindrical section, the bottom of the inverted frustum section is connected to the transition connection section, and the top of the inverted frustum section is connected to the bottom of the cylindrical section. The inner wall of the inverted truncated cone section is coated with a hydrophobic coating, and the static water contact angle of the hydrophobic coating is greater than 110°. The top of the inverted truncated cone section is provided with an inverted conical three-phase separation baffle and an overflow weir. The inverted conical three-phase separation baffle is a conical shell with the cone apex facing downwards. The edge of the inverted conical three-phase separation baffle is connected to the inner wall of the inverted truncated cone section and / or the cylindrical section, and multiple guide holes are opened on the conical surface of the inverted conical three-phase separation baffle.

[0016] Optionally, the fluidized bed crystallization apparatus described above further includes a support frame, which is sleeved on the outside of the guide tube and fixedly connected to the guide tube. The support frame has at least one support arm extending radially along the guide tube, and the end of the support arm is fixedly connected to the inner wall of the reaction crystallization tube. The support arm and / or the interior of the support frame are filled with a high-damping material.

[0017] Optionally, the fluidized bed crystallization device described above also includes an online turbidity meter, a level gauge, and a controller. The online turbidity meter and the level gauge are installed at the first end of the hydraulic classification discharge leg. The controller is electrically connected to the online turbidity meter, the level gauge, and the discharge valve, respectively. The controller is configured to control the opening and closing of the discharge valve according to preset turbidity threshold and level threshold.

[0018] The fluidized bed crystallization apparatus provided by this invention, in use, allows the liquid to be treated to be injected at high speed into the interior of the reaction crystallization cylinder through a tangential inlet pipe located at the lower part of the cylinder, along the tangential direction. Because the inlet direction is tangential to the cylinder wall, a strong swirling flow field is formed within the cylinder. This swirling flow field flows upwards through a coaxially arranged guide tube. Since the generatrix of the guide tube is a smooth curve that contracts in the middle and expands at both ends, its flow cross-sectional area is the smallest in the middle, causing a significant increase in fluid velocity as it flows through this area, thus creating a local negative pressure zone in the middle of the guide tube. The pressure difference between this negative pressure zone and the two ends of the guide tube induces fluid outside the guide tube to enter the interior of the guide tube from its lower port and flow upwards, finally exiting from the upper port and re-entering the external swirling flow field, thereby forming a closed internal circulation flow. The entire internal circulation process is driven entirely by the swirling kinetic energy generated by the tangential water inlet, without relying on any external mechanical circulation pump or built-in stirring components. This effectively solves the problems of high energy consumption, crystal breakage, and scaling on the vessel wall caused by mechanical drive, as described in the background technology, and achieves efficient and low-consumption internal circulation.

[0019] This application also provides a fluidized bed crystallization method, using the fluidized bed crystallization apparatus as described in any of the preceding claims, comprising: Step S1: The liquid to be treated is injected tangentially into the reaction crystallization cylinder through the tangential water inlet pipe, and a swirling flow field is formed inside the reaction crystallization cylinder; Step S2: The pressure gradient generated in the middle of the guide tube by the swirling flow field induces the liquid to be treated to form a central backflow from bottom to top inside the guide tube, and form a closed internal circulation with the liquid to be treated outside the guide tube.

[0020] The fluidized bed crystallization method provided by the present invention uses the fluidized bed crystallization apparatus as described in any of the above embodiments, and therefore has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here. Attached Figure Description

[0021] The accompanying drawings, incorporated in and forming part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort. One or more embodiments are illustrated by way of example through the corresponding images in the accompanying drawings. These exemplary descriptions do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0022] Figure 1 This is a schematic diagram of the overall structure of the fluidized bed crystallization apparatus provided in the embodiments of this application; Figure 2 This is a schematic diagram of the tangential water inlet pipe provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the hydraulic classification discharge leg provided in an embodiment of this application; Figure 4 This is a schematic diagram of the solid-liquid separation zone provided in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures: 1. Reaction crystallization cylinder; 2. Transition connecting section; 3. Solid-liquid separation zone; 4. Flow guide cylinder; 5. Tangential water inlet pipe; 6. Hydraulic classification discharge leg; 7. Discharge valve; 8. Washing water inlet; 9. Porous ceramic filter element; 10. Inverted truncated cone section; 11. Cylindrical section; 12. Hydrophobic coating; 13. Inverted conical three-phase separation baffle; 14. Overflow weir; 15. Flow guide hole; 16. Support frame; 17. Support arm; 18. High damping material; 19. Controller; 20. Online turbidity meter; 21. Level gauge. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0026] For ease of description, spatial relative terms may be used in the text to describe the relative position or movement of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "front," "back," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure undergoes a positional flip, orientation change, or change of motion, these directional indications will change accordingly. For instance, an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0027] See Figure 1 and Figure 2 This application provides a fluidized bed crystallization device, including a reaction crystallization cylinder 1, a guide cylinder 4, and at least one tangential water inlet pipe 5. The guide cylinder 4 is fixed inside the reaction crystallization cylinder 1 and is coaxially arranged with the reaction crystallization cylinder 1. The guide cylinder 4 is a rotating body with open ends. The generatrix of the guide cylinder 4 is a smooth curve that contracts in the middle and expands at both ends. The tangential water inlet pipe 5 is arranged at the lower part of the reaction crystallization cylinder 1 and is used to introduce the liquid to be treated along the tangential direction of the reaction crystallization cylinder 1.

[0028] Specifically, the tangential inlet pipe 5 injects the liquid to be treated (mine water) into the bottom of the reaction crystallization cylinder 1 at a specific angle and flow rate, forming a swirling flow field with strong centrifugal characteristics. This swirling flow field, on the one hand, pushes the crystal particles towards the inner wall of the reaction crystallization cylinder 1 through centrifugal force, forming a dynamic particle layer; on the other hand, due to the special geometric configuration of the guide cylinder 4, the flow velocity of the swirling fluid increases significantly when flowing through the middle of the guide cylinder 4. According to Bernoulli's equation, the increased velocity leads to a decrease in static pressure, thus forming a local negative pressure zone in the middle region of the guide cylinder 4. This negative pressure zone, together with the pressure difference between the upper and lower ports of the guide cylinder 4, induces the fluid to enter the interior of the guide cylinder 4 from the outside through the lower port and flow out from the upper port, forming a stable bottom-up central backflow. This central backflow and the external swirling flow form a closed loop in space, i.e., an internal circulation flow field.

[0029] The internal circulation flow field possesses multiple synergistic effects. First, the centrifugal force of the swirling flow field causes crystal particles to continuously adhere to the inner wall of the reaction crystallization cylinder 1, and under the drive of the spiral upward flow, they undergo spiral sliding motion along the inner wall surface. This motion process generates continuous and gentle friction between the particle layer and the inner wall, effectively stripping away the initially attached crystal nuclei and preventing the formation of dense, hard scale—this is the "particle self-friction" anti-scaling mechanism. Second, since the internal circulation is entirely driven by the fluid's own kinetic energy, it avoids the direct impact and shearing of the crystals by high-speed rotating components, thus significantly reducing the crystal breakage rate and promoting the growth and stable production of large-particle, high-purity calcite-type calcium carbonate crystals. Finally, the smooth curved surface design of the guide cylinder 4 eliminates the local vortex dead zones caused by traditional mechanical agitators or distributors, ensuring the uniformity and continuity of the flow field throughout the reaction zone and fundamentally suppressing the abnormal accumulation of boundary layer supersaturation.

[0030] The fluidized bed crystallization apparatus provided by this invention, in use, allows the liquid to be treated to be injected at high speed into the interior of the reaction crystallization cylinder 1 through a tangential water inlet pipe 5 located at the lower part of the reaction crystallization cylinder 1, along the tangential direction of the reaction crystallization cylinder 1. Because the water inlet direction is tangential to the cylinder wall of the reaction crystallization cylinder 1, a strong swirling flow field is formed within the reaction crystallization cylinder 1. This swirling flow field flows upwards through a coaxially arranged guide cylinder 4. Since the generatrix of the guide cylinder 4 is a smooth curve that contracts in the middle and expands at both ends, the flow cross-sectional area in its middle is the smallest, and the flow velocity increases significantly when the fluid flows through this point, thus forming a local negative pressure zone in the middle of the guide cylinder 4. The pressure difference between this negative pressure zone and the two ends of the guide cylinder 4, together with the pressure difference, induces fluid outside the guide cylinder 4 to enter the interior of the guide cylinder 4 from the lower port and flow upwards, finally flowing out from the upper port of the guide cylinder 4 and re-entering the external swirling flow field, thereby forming a closed internal circulation flow. The entire internal circulation process is driven entirely by the swirling kinetic energy generated by the tangential water inlet, without relying on any external mechanical circulation pump or built-in stirring components, thus achieving efficient and low-consumption internal circulation.

[0031] To optimize the above technical solution, the guide tube 4 is a hyperboloid guide tube 4, and the generatrix trajectory of the hyperboloid guide tube 4 conforms to the hyperboloid equation.

[0032] Specifically, the hyperboloid guide tube 4 is a special type of rotating body whose geometry is precisely described by the hyperbolic equation. Extending axially from the geometric center of the guide tube 4 to both ends, the radial radius exhibits a continuous and smooth expansion trend. At the geometric center (i.e., the middle part of the guide tube 4), the radial radius is minimized, forming a throat. This results in smoother velocity changes and a more reasonable pressure gradient distribution as the fluid flows through the guide tube 4. The hyperboloid shape ensures that no local eddies or boundary layer separation occur during fluid acceleration at the throat, and the pressure reduction process is smooth and controllable, thus forming a stable and uniform negative pressure zone inside the guide tube 4. Simultaneously, the smooth transition characteristics of the hyperboloid allow for smooth flow of return fluid entering the interior from the outside of the guide tube 4, reducing flow resistance.

[0033] Furthermore, the equation of the hyperboloid is as follows:

[0034] in, Let be the coordinates along the axis of the guide tube 4, with the origin located at the geometric center of the guide tube 4; To correspond to the axial position The radial coordinate at the location; and These are positive real geometric parameters, which control the radial and axial expansion rates of the guide tube 4, respectively.

[0035] It should be noted that the reaction crystallization cylinder 1 is cylindrical and can be made of stainless steel, making it suitable for mine water treatment applications with a working temperature range of 10°C to 45°C. The guide cylinder 44 is integrally formed using a centrifugal casting process, and its surface is precision polished to a surface roughness Ra≤0.8μm, in order to minimize fluid resistance and avoid local turbulence-induced crystal nucleus adhesion.

[0036] The swirling flow field generated by a single tangential water inlet pipe 5 may be non-uniform, especially in large-scale industrial plants, where a single-point water inlet makes it difficult to establish a stable and symmetrical swirling flow field throughout the entire reaction crystallization zone. To optimize the above technical solution, the number of tangential water inlet pipes 5 is three, which are evenly distributed along the circumference of the reaction crystallization cylinder 1, with the centerlines of adjacent tangential water inlet pipes 5 forming an angle of 120° on the horizontal plane; the inlet cross-section of each tangential water inlet pipe 5 is elliptical, with the major axis of the ellipse arranged tangentially.

[0037] The centerlines of adjacent tangential inlet pipes 5 form a 120° angle on the horizontal plane. This design ensures that the three inlet points are at 120° angles to each other, allowing the liquid to be treated to be injected into the reaction crystallization cylinder 1 simultaneously from three symmetrical directions, resulting in a highly axially symmetric swirling flow field. The inlet cross-section of each tangential inlet pipe 5 is elliptical, with the major axis of the ellipse arranged tangentially. Compared to a circular inlet, the elliptical inlet provides a larger flow area and better flow guidance, reducing inlet resistance while ensuring the fluid is injected at the optimal tangential angle. During operation, the three tangential jets superimpose and reinforce each other within the reaction crystallization cylinder 1, forming a stable and powerful swirling flow field.

[0038] Specifically, the ratio of the inner diameter of the tangential water inlet pipe 5 to the diameter of the reaction crystallization cylinder 1 is between 1:15 and 1:20, preferably 1:18.5. The tangential water inlet pipe 5 and the reaction crystallization cylinder 1 are connected by a flange, and a sealing gasket is provided at the connection.

[0039] Specifically, three uniformly distributed tangential water inlet pipes 5 ensure the axisymmetry and uniformity of the swirling flow field within the reaction crystallization cylinder 1, eliminating flow field deviation and dead zones that may occur with single-point water inlet. This uniform swirling flow field ensures that the crystal particles are subjected to balanced forces throughout the reaction zone, thereby avoiding excessive local aggregation or sedimentation.

[0040] To optimize the above technical solution, the fluidized bed crystallization device also includes a solid-liquid separation zone 3 and a transition connection section 2. One end of the transition connection section 2 is connected to the reaction crystallization cylinder 1, and the other end of the transition connection section 2 is connected to the solid-liquid separation zone 3. The solid-liquid separation zone 3 is connected to the reaction crystallization cylinder 1 through the transition connection section 2.

[0041] Specifically, in application, the fluidized bed crystallization device consists of a solid-liquid separation zone 3, a transition section 2, and a reaction crystallization cylinder 1 from top to bottom. The lower reaction crystallization cylinder 1 is responsible for crystal growth and internal circulation, while the upper solid-liquid separation zone 3 is responsible for clarifying the water and retaining the crystals within the device. The transition section 2 ensures that the fluid rising from the reaction crystallization cylinder 1 can smoothly transition to the solid-liquid separation zone 3, avoiding turbulence caused by abrupt changes in cross-section. During operation, the mixture that has completed the crystallization reaction enters the transition section 2 through the top of the reaction crystallization cylinder 1. After the flow rate gradually decreases, it enters the solid-liquid separation zone 3, where clarification and separation are completed.

[0042] By adding a solid-liquid separation zone 3 and a transition connecting section 2, functional zoning for reaction crystallization and solid-liquid separation is achieved. Specifically, the solid-liquid separation zone 3 provides ample space and time for the sedimentation of fine crystals, effectively reducing the loss of microcrystals with overflow and improving the recovery rate of crystal products. At the same time, the turbidity of the clarified effluent is significantly reduced, alleviating the load on subsequent treatment units. The buffering effect of the transition connecting section 2 ensures a smooth transition of the flow field from the reaction crystallization cylinder 1 to the solid-liquid separation zone 3, avoiding crystal disturbance and secondary suspension caused by sudden changes in flow velocity.

[0043] To optimize the above technical solution, the fluidized bed crystallization device also includes a hydraulic classification discharge leg 6. The first end of the hydraulic classification discharge leg 6 is connected to the bottom of the reaction crystallization cylinder 1. The second end of the hydraulic classification discharge leg 6 is provided with a discharge valve 7. The side wall of the second end of the hydraulic classification discharge leg 6 is provided with a washing water inlet 8 for introducing washing water. The hydraulic classification discharge leg 6 is conical, with the first end being the large-diameter end of the cone and the second end being the small-diameter end of the cone; or, the hydraulic classification discharge leg 6 is a cylindrical-conical combination structure, with the first end being a cylindrical end and the second end being a conical end, and the large-diameter end of the conical end being connected to the cylindrical end.

[0044] Specifically, the inverted conical or conical structure of the hydraulic classification discharge leg 6 utilizes the principle of gravity settling. As the crystal particles entering the hydraulic classification discharge leg 6 move downwards, the cross-sectional area gradually decreases, resulting in a relatively increased upward velocity of the fluid and creating a natural particle size classification effect. During operation, washing water is introduced in reverse from the washing water inlet 8 on the side wall, forming an upward water flow within the hydraulic classification discharge leg 6. Large crystal particles with a settling velocity greater than the washing water flow velocity can overcome the resistance of the reverse water flow and continue to sink, eventually being discharged through the discharge valve 7. Meanwhile, small crystals with a settling velocity less than the washing water flow velocity are lifted by the reverse water flow and return to the reaction crystallization cylinder 1 to continue growing. This achieves online hydraulic classification of the crystals, ensuring that the discharged crystals are larger in size and of higher quality, significantly improving the commercial value of the crystals. The reverse-introduced washing water not only plays a classification role but also cleans fine impurities adhering to the crystal surface, improving product purity. The inverted conical or cylindrical-conical combination structure design of the hydraulic classification discharge leg 6 makes the classification process stable and controllable, with high classification accuracy. The tiny crystals that were lifted back into the reaction chamber were given the opportunity to continue growing, thus avoiding a waste of resources.

[0045] Specifically, the ratio of the internal circulation flow rate to the washing water inlet flow rate introduced by the washing water inlet 8 is preferably between 0.3:1 and 0.6:1.

[0046] In some embodiments, the flow rate of the reverse washing water introduced into the lower sidewall of the discharge leg is precisely controlled within the range of 1.5 mm / s to 2.5 mm / s. According to Stokes' law of settling, the settling velocity of the particles... It can be represented as:

[0047] in, Particle density, For fluid density, It is the acceleration due to gravity. Particle size, Let be the fluid dynamic viscosity. Therefore, setting the wash water flow rate is equivalent to setting a critical settling particle size. Larger particles (typically larger than 200 μm) with settling velocities greater than this flow rate can overcome the resistance of the reverse flow and continue to settle and eventually be discharged; while finer particles (typically smaller than 200 μm) with settling velocities less than this flow rate are lifted by the reverse flow and returned to the reaction crystallization cylinder 1 to continue growth. This process achieves online hydraulic classification of crystals, ensuring the uniformity of particle size and high quality of the discharged product.

[0048] The above-mentioned grading process is achieved entirely using the principles of fluid mechanics, requiring no additional power, thus meeting the design requirements for energy conservation and emission reduction.

[0049] See Figure 3 In order to optimize the above technical solution, a porous ceramic filter element 9 is provided inside the hydraulic classification discharge leg 6. The porous ceramic filter element 9 is located between the discharge valve 7 and the first end of the hydraulic classification discharge leg 6.

[0050] Specifically, the porous ceramic filter element 9 is made of high-purity alumina and other ceramic materials sintered at high temperature, possessing a uniform microporous structure with a pore size range of 50μm to 100μm and a porosity of not less than 35%. This specific pore size range enables it to effectively intercept fine crystals with a particle size less than 100μm, while allowing water and dissolved ions to pass through. During operation, the fine crystals flowing downstream with the sedimentation flow first pass through the porous ceramic filter element 9 before reaching the discharge valve 7. Crystals with a particle size larger than the filter element's pore size are intercepted above the filter element and cannot enter the cavity of the discharge valve 7. The intercepted microcrystals can be reintroduced into the reaction crystallization cylinder 1 to participate in the subsequent crystallization process under the continuous flushing of the reverse washing water. The high porosity of the filter element ensures low water flow resistance and does not affect the normal drainage function of the discharge leg. This arrangement effectively prevents fine crystals from entering the discharge valve 7, ensuring the long-term reliable operation of the discharge system. At the same time, the intercepted crystals can be returned to the reaction crystallization cylinder 1 to continue growing, which not only avoids resource waste but also further improves the recovery rate of crystal products.

[0051] See Figure 4To optimize the above technical solution, the solid-liquid separation zone 3 includes an inverted truncated cone section 10 and a cylindrical section 11. The bottom of the inverted truncated cone section 10 is connected to the transition connection section 2, and the top of the inverted truncated cone section 10 is connected to the bottom of the cylindrical section 11. The inner wall of the inverted truncated cone section 10 is coated with a hydrophobic coating 12, and the static water contact angle of the hydrophobic coating 12 is greater than 110°. The top of the inverted truncated cone section 10 is provided with an inverted conical three-phase separation baffle 13 and an overflow weir 14. The inverted conical three-phase separation baffle 13 is a conical shell with the cone apex facing downward. The edge of the inverted conical three-phase separation baffle 13 is connected to the inner wall of the inverted truncated cone section 10 and / or the cylindrical section 11, and multiple guide holes 15 are opened on the conical surface of the inverted conical three-phase separation baffle 13.

[0052] Specifically, the hydrophobic coating 12 is formed by spraying and curing a composite sol of fluorinated silane coupling agent and nano-silica. Preferably, the hydrophobic coating 12 is formed by dispersing heptadecafluorodecyltrimethoxysilane and nano-silica in an ethanol-water mixed solvent at a mass ratio of 3:1 to form a composite sol with a solid content of 8%, which is then cured at 120°C for 2 hours. The coating thickness is 30μm to 40μm.

[0053] Specifically, the cone angle of the preferred inverted conical three-phase separation baffle 13 is 120°, and the multiple guide holes 15 are distributed in a concentric circle array.

[0054] During operation, the rising fluid enters the inverted truncated cone section 10. As the cross-section gradually expands, the flow velocity decreases. Large crystal particles settle back to the reaction crystallization cylinder 1 under the action of gravity. The hydrophobic coating 12 of the inverted truncated cone section 10 significantly reduces the adhesion of the solid-liquid interface, making it easier for the small crystals attached to the wall to slide off, thus avoiding secondary deposition on the wall of the inverted truncated cone section 10. At the same time, the conical surface of the inverted cone-shaped three-phase separation baffle 13 can guide the gas (such as CO2 (carbon dioxide) released during the reaction) upward through the guide hole 15 to escape, blocking solid particles from leaking out with the overflow, ensuring that the turbidity of the effluent is stable and meets the standard. The liquid flows to the overflow weir 14 through the guide hole 15. This arrangement makes the turbidity of the effluent stable and meets the standard, and the crystal retention rate is significantly improved, providing a guarantee for obtaining high-quality clarified effluent.

[0055] To optimize the above technical solution, the fluidized bed crystallization device also includes a support frame 16. The support frame 16 is sleeved on the outside of the guide cylinder 4 and fixedly connected to the guide cylinder 4. The support frame 16 is provided with at least one support arm 17 extending radially along the guide cylinder 4. The end of the support arm 17 is fixedly connected to the inner wall of the reaction crystallization cylinder 1. The support arm 17 and / or the support frame 16 are filled with a high damping material 18.

[0056] Specifically, the support frame 16 has a ring-shaped structure, tightly fitted onto the outside of the guide tube 4 and fixedly connected to the outer wall of the guide tube 4. The support frame 16 has four radial support arms 17, which are symmetrically distributed in a cross shape along the circumference of the support frame 16. The end of each radial support arm 17 is fixedly connected to the inner wall of the reaction crystallization cylinder 1. Through the symmetrically distributed radial support arms 17, multi-point uniform support is achieved for the guide tube 4, ensuring the coaxiality of the guide tube 4 within the reaction crystallization cylinder 1. Simultaneously, it effectively disperses the radial and circumferential forces generated by fluid impact, improving the installation stability and vibration resistance of the guide tube 4.

[0057] Specifically, the high-damping material 18 (such as a silicone rubber-based composite damper) filled inside the support arm 17 has the ability to absorb vibration energy. During operation, when the excitation energy generated by the fluid flow is transmitted to the support arm 17, the high-damping material 18 dissipates the vibration energy into heat energy through internal friction, thereby suppressing structural resonance.

[0058] To optimize the above technical solution, the fluidized bed crystallization device also includes an online turbidity meter 20, a level gauge 21, and a controller 19. The online turbidity meter 20 and the level gauge 21 are installed at the first end of the hydraulic classification discharge leg 6. The controller 19 is electrically connected to the online turbidity meter 20, the level gauge 21, and the discharge valve 7, respectively. The controller 19 is configured to control the opening and closing of the discharge valve 7 according to the preset turbidity threshold and the level threshold.

[0059] Specifically, the online turbidity meter 20 is used to monitor the turbidity of the supernatant in the hydraulic classification discharge leg 6 in real time, reflecting the purity of the discharged crystals; the level gauge 21 is used to measure the crystal accumulation height in real time, reflecting the cumulative amount of crystals in the hydraulic classification discharge leg 6. The controller 19 is configured to control the opening and closing of the discharge valve 7 according to preset turbidity and level thresholds. During operation, the controller 19 continuously receives monitoring signals from the turbidity meter and the level gauge 21. When the turbidity is lower than the preset threshold (e.g., the supernatant is clear, indicating that the settled crystals are pure) and the crystal accumulation height reaches the preset threshold (indicating that there are enough crystals to be discharged), the controller 19 issues a command to open the discharge valve 7 for intermittent discharge; the discharge continues for a set time and then automatically closes, completing one discharge cycle. This arrangement achieves precision and automation in the discharge process, ensuring that the discharged crystals are high-purity, large-particle-size, high-quality products, and avoiding water waste caused by ineffective discharge. Real-time monitoring and automatic control reduce manual intervention and improve the operating efficiency and reliability of the fluidized bed crystallizer. By setting reasonable turbidity and material level thresholds, the fluidized bed crystallizer can discharge material at the optimal time, which not only ensures product quality but also prevents the risk of blockage caused by excessive crystal accumulation, thus achieving efficient operation.

[0060] In some embodiments, the online turbidimeter 20 is an infrared scattering type with a range of 0–100 NTU (Nephelometric Turbidity Unit, a unit of scattering turbidity used to characterize the degree of turbidity of liquids) and an accuracy of ±0.5 NTU. The probe is installed in the upper clear liquid zone of the hydraulic classification discharge leg 6. The gamma-ray level gauge 21 is a non-contact type with a radiation source of Cs(cesium)-137 and an activity of 10 mCi (millicuries). The detector is a NaI(Tl) scintillator (i.e., sodium iodide doped with thallium(Tl)). It can measure the crystal accumulation height in real time. The controller 19 is configured to: when the online turbidimeter 20 reading remains below 5 NTU for more than 30 seconds, and the level gauge 21 detects that the crystal accumulation height has reached 1.2 m, issue a command to open the discharge valve 7, discharge for 20 seconds, and then automatically close it, completing one intermittent discharge cycle.

[0061] This application also provides a fluidized bed crystallization method, using a fluidized bed crystallization apparatus as described in any of the above claims, comprising: Step S1: The liquid to be treated is injected tangentially into the reaction crystallization cylinder 1 through the tangential water inlet pipe 5, and a swirling flow field is formed inside the reaction crystallization cylinder 1; Step S2: The pressure gradient generated in the middle of the guide tube 4 by the swirling flow field induces the liquid to be treated to form a central backflow from bottom to top inside the guide tube 4, and form a closed internal circulation with the liquid to be treated outside the guide tube 4.

[0062] The fluidized bed crystallization method also includes using the centrifugal force generated by the swirling flow field to drive crystal particles to slide against the wall during the internal circulation process, generating a particle self-friction effect to peel off the crystal nuclei on the wall, and using the hydraulic classification discharge leg 6 to introduce reverse-flowing washing water, controlling the flow rate of the washing water to intercept large crystal particles and lift small crystals back to the reaction crystallization cylinder 1.

[0063] The fluidized bed crystallization method provided by the present invention uses the fluidized bed crystallization apparatus as described in any of the above embodiments, and therefore has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0064] Example 1: During operation, pretreated mine water is injected tangentially into the reaction crystallizer 1 through the tangential inlet pipe 5. The inlet pressure is controlled at 0.30 MPa and the flow rate at 85 m³ / h, creating a stable swirling flow field within the reaction crystallizer 1. Actual measurements show that under these conditions, the Reynolds number of the swirling flow field is 12500, the tangential velocity is 2.25 m / s, the axial velocity component is 0.18 m / s, and the crystal particle concentration is maintained at 12 g / L. The measured internal circulation flow rate is 38 m³ / h, with a ratio of 0.45:1 to the inlet flow rate. The washing water flow rate is controlled at 2.0 mm / s, and the calculated critical settling particle size is approximately 210 μm. The controller 19 monitors the turbidity of the supernatant and the crystal accumulation height in the hydraulic classification discharge leg 6 in real time. When the turbidity is below 5 NTU and the material level reaches 1.2 m, the discharge valve is opened for 20 seconds to discharge the material.

[0065] The average crystal size of Example 1 was 285 μm, the particle size distribution span was 0.82, the crystal breakage rate was 3.1%, the scaling rate on the vessel wall was 0.02 mg / cm²·d, the effluent turbidity was 1.2 NTU, and the discharge frequency was 6 times / day. SEM (Scanning Electron Microscope) images showed that the crystals had a regular rhombohedral morphology, and XRD (X-ray Diffraction) patterns showed that the main peak was calcite, with no aragonite or spherulite impurities, indicating high crystallinity. The experimental data from Example 1 demonstrate that the fluidized bed crystallization device provided in this application is significantly superior to traditional mechanically stirred fluidized bed crystallization devices and conventional vortex fluidized beds in terms of energy consumption, crystal quality, scale prevention performance, and effluent quality.

[0066] To verify the technical effects of the present invention, the following embodiments and comparative experiments were conducted.

[0067] The fluidized bed crystallization device and operating parameters described above were used to treat high-salinity mine water from a coal mine (TDS: Total Dissolved Solids ≈ 3500 mg / L, Ca²⁺ ≈ 100 mg / L). + (Calcium ions) ≈ 420 mg / L, HCO3 - (Bicarbonate ion concentration ≈ 1200 mg / L). The system was run continuously for 30 days, and key performance indicators were recorded.

[0068] Comparative Example 1: A traditional mechanically stirred fluidized bed crystallization device was used, equipped with a bottom impeller agitator (120 rpm), without an internal circulation guide structure or hydraulic staged discharge legs, and the discharge was initiated by a timed start method. Other influent water quality and flow conditions were the same as in Example 1.

[0069] Comparative Example 2: A conventional cyclone fluidized bed device was used, with only tangential water inlet, no streamlined guide tube 4, no internal circulation flow field, and the discharge leg was straight cylindrical. There was no washing water or filter element. Other conditions were the same as in Example 1.

[0070] The experimental results are summarized in the table below:

[0071] Among them, the smaller the Span value, the more concentrated the particle size distribution; the crystal breakage rate is calculated by the change of D50 before and after sieving; the scaling rate is determined by periodically scraping the deposits on the vessel wall and weighing them; the energy consumption includes the total power consumption of the water pump, agitator (if any) and control system.

[0072] Experimental data show that Example 1 is significantly superior to the two comparative examples in all key indicators. Its average crystal size is larger and its distribution is narrower, proving that the internal circulation flow field and hydraulic classification mechanism effectively promote crystal growth and screening; the crystal breakage rate is extremely low, confirming the protection of crystal integrity by the mechanical shear-free environment; the scaling rate on the vessel wall is almost negligible, verifying the effectiveness of the "particle self-friction" anti-scaling mechanism; the effluent turbidity is consistently up to standard, and the unit energy consumption is reduced by approximately 50%, demonstrating the comprehensive advantages of this invention in terms of energy efficiency and water quality.

[0073] Furthermore, the crystals produced in Example 1 were analyzed by SEM and XRD. SEM images showed that the crystals had a regular rhombohedral morphology, a smooth surface, and no obvious defects or debris. XRD patterns showed that the main peaks completely matched the calcite standard card (JCPDS No. 05-0586), and no aragonite or spherulite impurities were detected. The crystals exhibited high crystallinity and excellent purity, meeting the standards for industrial-grade calcium carbonate products.

[0074] In summary, this invention constructs a highly integrated and self-consistent fluid dynamics system through precisely designed structural units such as the guide tube 4, tangential water inlet pipe 5, hydraulic classification discharge leg 6, and solid-liquid separation zone 2. This system can stably achieve efficient resource utilization of mine water, obtain high-quality calcium carbonate crystal by-products, and ensure long-term scale-free, low-consumption, and reliable operation of the system.

[0075] It should be noted that the fluidized bed crystallization device provided by this invention can be used in the field of water treatment and resource utilization equipment technology or other fields. Other fields refer to any field other than the field of water treatment and resource utilization equipment technology. The above are merely examples and do not limit the application areas of the fluidized bed crystallization device provided by this invention.

[0076] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0077] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0078] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A fluidized bed crystallization apparatus, characterized in that, It includes a reaction crystallization cylinder, a guide cylinder, and at least one tangential water inlet pipe, wherein: The flow guide tube is fixed inside the reaction crystallization tube and is coaxially arranged with the reaction crystallization tube; The guide tube is a rotating body with openings at both ends, and the generatrix of the guide tube is a smooth curve that contracts in the middle and expands at both ends. The tangential water inlet pipe is located at the lower part of the reaction crystallization cylinder and is used to introduce the liquid to be treated along the tangential direction of the reaction crystallization cylinder.

2. The fluidized bed crystallization apparatus according to claim 1, characterized in that, The guide tube is a hyperboloid guide tube, and the generatrix trajectory of the hyperboloid guide tube conforms to the hyperboloid equation.

3. The fluidized bed crystallization apparatus according to claim 1, characterized in that, The number of tangential water inlet pipes is three, and the three tangential water inlet pipes are evenly distributed along the circumference of the reaction crystallization cylinder. The angle between the center lines of adjacent tangential water inlet pipes on the horizontal plane is 120°. The inlet cross section of each tangential water inlet pipe is elliptical, and the major axis of the ellipse is arranged tangentially.

4. The fluidized bed crystallization apparatus according to claim 1, characterized in that, It also includes a solid-liquid separation zone and a transition connecting section. One end of the transition connecting section is connected to the reaction crystallization cylinder, and the other end of the transition connecting section is connected to the solid-liquid separation zone. The solid-liquid separation zone is connected to the reaction crystallization cylinder through the transition connecting section.

5. The fluidized bed crystallization apparatus according to claim 1 or 4, characterized in that, It also includes a hydraulic classification discharge leg, the first end of which is connected to the bottom of the reaction crystallization cylinder, the second end of which is provided with a discharge valve, and the side wall of the second end of which is provided with a washing water inlet for introducing washing water. The hydraulic classification discharge leg is conical, with the first end being the large-diameter end of the cone and the second end being the small-diameter end of the cone; or, the hydraulic classification discharge leg is a cylindrical-conical combination structure, with the first end being a cylindrical end and the second end being a conical end, the large-diameter end of the conical end being connected to the cylindrical end.

6. The fluidized bed crystallization apparatus according to claim 5, characterized in that, The hydraulic classification discharge leg is equipped with a porous ceramic filter element, which is located between the discharge valve and the first end of the hydraulic classification discharge leg.

7. The fluidized bed crystallization apparatus according to claim 4, characterized in that, The solid-liquid separation zone includes an inverted frustum section and a cylindrical section. The bottom of the inverted frustum section is connected to the transition connection section, and the top of the inverted frustum section is connected to the bottom of the cylindrical section. The inner wall of the inverted truncated cone section is coated with a hydrophobic coating, and the static water contact angle of the hydrophobic coating is greater than 110°. The top of the inverted truncated cone section is provided with an inverted conical three-phase separation baffle and an overflow weir. The inverted conical three-phase separation baffle is a conical shell with the cone apex facing downwards. The edge of the inverted conical three-phase separation baffle is connected to the inner wall of the inverted truncated cone section and / or the cylindrical section, and multiple guide holes are opened on the conical surface of the inverted conical three-phase separation baffle.

8. The fluidized bed crystallization apparatus according to claim 4, characterized in that, It also includes a support frame, which is sleeved on the outside of the flow guide tube and fixedly connected to the flow guide tube. The support frame has at least one support arm extending radially along the flow guide tube. The end of the support arm is fixedly connected to the inner wall of the reaction crystallization tube. The support arm and / or the interior of the support frame are filled with a high-damping material.

9. The fluidized bed crystallization apparatus according to claim 5, characterized in that, It also includes an online turbidity meter, a level gauge, and a controller. The online turbidity meter and the level gauge are installed at the first end of the hydraulic classification discharge leg. The controller is electrically connected to the online turbidity meter, the level gauge, and the discharge valve, respectively. The controller is configured to control the opening and closing of the discharge valve according to a preset turbidity threshold and a level threshold.

10. A fluidized bed crystallization method, characterized in that, The fluidized bed crystallization apparatus as described in any one of claims 1 to 9 comprises: Step S1: The liquid to be treated is injected tangentially into the reaction crystallization cylinder through the tangential water inlet pipe, and a swirling flow field is formed inside the reaction crystallization cylinder; Step S2: The pressure gradient generated in the middle of the guide tube by the swirling flow field induces the liquid to be treated to form a central backflow from bottom to top inside the guide tube, and form a closed internal circulation with the liquid to be treated outside the guide tube.

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