Multi-stage vapor-liquid separation system of horizontal tube falling film evaporator

Abstract

The invention discloses a horizontal tube falling film evaporator multi-stage vapor-liquid separation system, which belongs to the technical field of multi-effect distillation and comprises an evaporator and a multi-stage vapor-liquid separator. An evaporator condensation side seal head is arranged on the condensation side of the evaporator, a multi-stage vapor-liquid separator is embedded into the upper portion in the evaporator condensation side seal head, the multi-stage vapor-liquid separator comprises a seal head partition plate, a corrugated baffle, a defoaming wire mesh and a vapor-liquid baffle, and the corrugated baffle, the defoaming wire mesh and the vapor-liquid baffle are sequentially arranged on the seal head partition plate from inside to outside. The upper part is a secondary steam outlet area output by the evaporator, and secondary steam carrying liquid drops output by the evaporator is sequentially subjected to turbulent flow and turn-back separation, corrugated baffle separation and defoaming wire mesh separation in an evaporator cylinder and then enters a next-effect evaporator; and the lower part is a condensed water collection outlet area output by the evaporator. The efficient optimal vapor-liquid separation effect under the working condition that the steam flow speed is 1-5.5 m / s can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of multi-effect distillation technology, and particularly relates to a multi-stage vapor-liquid separation system for a horizontal tube falling film evaporator. Background Technology

[0002] The hot-press multi-effect distillation water machine is a new type of high-efficiency medical injection water preparation equipment. The horizontal tube falling film evaporator is an important component of this equipment, mainly including a pure steam inlet system, a purified water distribution system, a vapor-liquid separation system, a distilled water system, and a residual water system. The main working principle of this evaporator is as follows: high-temperature and high-pressure pure steam enters the heat exchange tubes of the evaporator, while purified water forms a uniform liquid film on the outer surface of the heat exchange tubes through spraying or other means. The pure steam inside the tubes releases heat and condenses into distilled water, while the purified water outside the tubes absorbs heat and evaporates to produce secondary steam. The secondary steam carrying droplets passes through the vapor-liquid separation system to separate the droplets and become pure steam, which then enters the next effect evaporator.

[0003] For the preparation of medical water for injection, the conductivity and bacterial endotoxin levels are core indicators for evaluating the quality of water produced by a distillation water purifier, and these indicators are closely related to the vapor-liquid separation system in the evaporator. Based on the above working principle, the secondary steam generated by the evaporator will carry a large number of purified water droplets. Since the conductivity and bacterial endotoxin levels of the purified water do not meet the requirements for water for injection, if these purified water droplets enter the distilled water of the next effect evaporator with the secondary steam, it will seriously affect the water quality produced by the equipment. Therefore, before the secondary steam leaves the evaporator of that effect, it is necessary to use a vapor-liquid separation system to remove the purified water droplets it carries.

[0004] As a crucial component of horizontal tube falling film evaporators, the vapor-liquid separation system is a device that utilizes the density difference between the vapor and liquid phases to separate the vapor and liquid mixtures through a physical mechanism. Traditional vapor-liquid separation systems typically employ a single-wire demister to separate liquid droplets from the secondary steam. However, this approach has significant drawbacks: the vapor-liquid separation effect of a single separator is limited, and some droplets are still carried by the steam into the next-effect evaporator. Furthermore, the single-wire demister requires a relatively high secondary steam flow rate, achieving optimal vapor-liquid separation only at a steam flow rate of 1-3 m / s. In reality, fluctuations in operating conditions can easily lead to steam flow rate fluctuations, exceeding 3 m / s, resulting in a significant decrease in vapor-liquid separation efficiency and large fluctuations in the conductivity of the system's produced water. This negatively impacts the production quality of subsequent medical injection water, equipment operational stability, and industry compliance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a multi-stage vapor-liquid separation system for a horizontal tube falling film evaporator. By designing turbulence and backflow separation within the evaporator cylinder and employing a multi-stage separation method with a multi-stage vapor-liquid separator, while simultaneously optimizing the parameters of each component, the vapor-liquid separation effect is improved. This achieves efficient vapor-liquid separation under operating conditions with steam flow rates of 1~5.5 m / s, thereby enhancing the stability of the quality of water produced for injection and solving the problems of limited separation effect and poor adaptability to flow rate fluctuations in existing single-wire demisters.

[0006] To achieve the above objectives, this invention proposes a multi-stage vapor-liquid separation system for a horizontal tube falling film evaporator.

[0007] A horizontal tube falling film evaporator multi-stage vapor-liquid separation system includes an evaporator and a multi-stage vapor-liquid separator; The evaporator has a condensing side end cap, and a multi-stage vapor-liquid separator is embedded in the upper part of the condensing side end cap. The multi-stage vapor-liquid separator includes an end cap partition and a corrugated baffle, a demister mesh, and a vapor-liquid baffle arranged sequentially from the inside to the outside. The end cap partition divides the evaporator condensing side end cap into upper and lower parts. The upper part is the secondary steam outlet area output by the evaporator, and the lower part is the condensate collection outlet area output by the evaporator. The corrugated baffle is composed of several corrugated stainless steel folded plates arranged sequentially along the secondary steam inlet direction. The bottom of each stainless steel folded plate is fixed to the end cap partition, and the top of each plate contacts the inner wall of the evaporator condensing side end cap. The demister mesh is arc-shaped and embedded between the evaporator condensing side end cap and the end cap partition. There is a pressure difference between the inside of the evaporator cylinder and the outlet area on the condenser side. This causes the secondary steam carrying liquid droplets to enter the secondary steam outlet area after being separated by turbulence and backflow inside the evaporator cylinder. Then, it passes through the corrugated baffles and demister wires of the multi-stage vapor-liquid separator in sequence before entering the next effect evaporator.

[0008] A further technical solution is that the evaporator condensing side end cap includes an end cap cylinder, a condensing side flange, and a steam inlet side flange. The evaporator cylinder is connected to the condensing side flange. The condensing side flange and the steam inlet side flange are respectively disposed on both sides of the end cap cylinder. The steam inlet side flange is connected to the next-effect evaporator cylinder. The multi-stage vapor-liquid separator has an arc-shaped structure and is embedded in the upper part of the head cylinder of the evaporator condenser side head; the condenser side flange is provided with reinforcing ribs, the head baffle of the multi-stage vapor-liquid separator is welded to the upper side of the reinforcing rib of the condenser side flange, and the two sides of the head baffle are respectively welded to the inner wall of the head cylinder; the head baffle has an inclination angle α with the horizontal plane.

[0009] A further technical solution is provided, wherein the minimum value of the inclination angle α between the head diaphragm and the horizontal plane is calculated using the following formula: ; in, This represents the minimum value of the tilt angle. m This represents the equivalent mass of the droplet that is separated from the vapor-liquid mixture. R Represents the radius of the spherical droplet. P The pressure difference between the inlet and outlet of the vapor-liquid separator. k=0.5~1 This is the shear force correction factor. The viscosity is the secondary vapor viscosity. Let g be the secondary steam velocity, and g be the acceleration due to gravity.

[0010] A further technical solution is that the corrugated stainless steel folded plate serves as the baffle blade of the corrugated baffle, and is an arc-shaped plate with a raised middle surface and inclined sides. All baffle blades are arranged in a uniform manner at a set interval, and the height of the baffle blades increases symmetrically from the sides to the middle, so that the upper and lower ends of all the file blades are respectively connected to the inner wall of the head cylinder and the upper surface of the head partition. The arc-shaped surface at the top of the demister is tangent to the inner wall of the head cylinder. The demister is a DP high-efficiency wire mesh with a set wire diameter and hole spacing.

[0011] A further technical solution involves the secondary steam carrying droplets output from the evaporator undergoing turbulence and backflow separation within the evaporator cylinder to achieve the first stage of vapor-liquid separation. Specifically, as the secondary steam carrying droplets flows toward the condenser outlet, the pressure difference between the evaporator cylinder and the condenser outlet region creates an airflow. Under the influence of airflow disturbance and droplet gravity, the droplets detach from the steam, thus completing the first stage of vapor-liquid separation. After the secondary steam carrying droplets enters the corrugated baffle, it impacts the three impact surfaces in sequence. After the impact, the droplets separate from the steam. The separated droplets flow back to the evaporator along the inclined end plate, completing the second stage of vapor-liquid separation. The secondary steam after passing through the corrugated baffle enters the demister wire mesh, where the tiny droplets mixed in with the secondary steam are separated into vapor and liquid. The separated droplets flow back to the evaporator along the inclined end plate, completing the third stage of vapor-liquid separation.

[0012] In a further technical solution, the corrugated baffle is used to remove large purified water droplets, and its optimal operating flow rate range is 3.5~5.5m / s, with a corresponding spacing of 30~50mm between the baffle blades; the optimal spacing between the baffle blades in the corrugated baffle is determined based on the secondary steam flow rate.

[0013] In a further technical solution, the demister mesh is used to remove small purified water droplets, and its optimal operating flow rate range is 1~3.5m / s, corresponding to a wire diameter of 0.15~0.25mm and a hole spacing of 150~200μm; the wire diameter and hole spacing parameters of the demister mesh are determined according to the secondary steam flow rate.

[0014] A further technical solution involves determining the thickness of the corrugated baffles and demister mesh in the multi-stage vapor-liquid separator based on the secondary steam flow rate, including: When the secondary steam flow rate is 1~3 m / s ; When the secondary steam flow rate is 3~4 m / s ; When the secondary steam flow rate is 4~5.5 m / s, ; in, For the thickness of the vapor-liquid separator, , These represent the thicknesses of the corrugated baffle and the demister mesh, respectively. .

[0015] A further technical solution is to improve the droplet removal efficiency of the corrugated baffle and the demister mesh. All results were obtained through an inertial collision efficiency model, which is as follows: ; in, Represents the Stokes number. For droplet density, The equivalent diameter of the droplet. The steam flow rate is... For vapor viscosity, The spacing between the corrugated baffle blades or the aperture of the demister mesh.

[0016] In a further technical solution, the vapor-liquid baffle is elongated, with its length matching the inner diameter of the end cap cylinder and its width being adjustable; the vapor-liquid baffle is located at the end of the demister mesh to prevent the separated droplets from being blown into the next effect evaporator by the airflow.

[0017] The above technical solutions have the following beneficial effects: 1. This invention proposes a multi-stage vapor-liquid separation system for a horizontal tube falling film evaporator. The main component is a multi-stage vapor-liquid separator. By adding corrugated baffles to a traditional multi-stage vapor-liquid separator and combining this with the structural characteristics of the evaporator cylinder, a three-stage vapor-liquid separation architecture is constructed: "turbulence and backflow separation within the evaporator cylinder + corrugated baffle separation + demister mesh separation." This allows for sequential separation through primary turbulence and backflow, secondary separation by corrugated baffles targeting large droplets, and tertiary separation by demister mesh focusing on small droplets, synergistically improving separation efficiency and performance. Furthermore, the parameters of each component in the three-stage vapor-liquid separation architecture are optimized to achieve efficient vapor-liquid separation over a wide flow rate range, specifically achieving optimal separation at steam velocities of 1~5.5 m / s. This improves the stability of the quality of water for injection and solves the problems of limited separation effect and sensitivity to flow rate fluctuations in traditional systems.

[0018] 2. The vapor-liquid separation system proposed in this invention has a wider range of adaptability to fluctuations in steam flow rate. For secondary steam with a high flow rate, the impact force when passing through the corrugated baffle is strong, which can separate most of the liquid droplets carried by the secondary steam. At the same time, the impact can reduce the steam flow rate, which is beneficial to the separation effect of the subsequent demister mesh. For secondary steam with a low flow rate, the corrugated baffle can separate some larger liquid droplets. After the gas-liquid mixture enters the subsequent demister mesh, it can achieve the optimal separation effect. Moreover, the separated droplets can reliably flow back along the inclined end plate, which can effectively avoid secondary pollution. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the reverse side structure of the evaporator condenser side end cap in the multi-stage vapor-liquid separation system proposed in the embodiments of the present invention; Figure 2 This is a schematic diagram of the structure of the multi-stage vapor-liquid separator in an embodiment of the present invention; Figure 3 This is a schematic diagram of the front structure of the evaporator condenser side end cap in the multi-stage vapor-liquid separation system proposed in the embodiments of the present invention; Figure 4 This is a cross-sectional view of the evaporator condenser side end cap in an embodiment of the present invention; Figure 5 This is a schematic diagram of secondary steam carrying liquid droplets entering and impacting the corrugated baffle in an embodiment of the present invention; Figure 6 This is a schematic diagram of the flow of various fluids in the evaporator of the hot-pressed multi-effect distillation water machine in an embodiment of the present invention; wherein, ( aThis is a schematic diagram of the overall exterior of the evaporator. b ( ) is a schematic diagram of the internal structure of the evaporator.

[0021] Among them, 1. Multi-stage vapor-liquid separator; 2. Head baffle; 3. Corrugated baffle; 4. Demister mesh; 5. Vapor-liquid baffle; 6. Evaporator condenser side head; 7. Head cylinder; 8. Condensation side flange; 9. Steam inlet side flange; 10. Reinforcing rib; 11. Inclined angle; 12. Pure steam inlet; 13. Purified water inlet; 14. Distilled water outlet; 15. Distilled water outlet; 16. First impact surface; 17. Second impact surface; 18. Third impact surface. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Example 1 In the process of preparing medical injection water using a hot-press multi-effect distillation water evaporator, high-temperature and high-pressure pure steam enters the heat exchange tubes of the evaporator to exchange heat and generate distilled water. Simultaneously, purified water evaporates in the shell side of the evaporator to generate secondary steam. This secondary steam comes into contact with the purified water liquid film or mixes with atomized spray droplets. Upon exiting the system, it carries a large number of purified water droplets. This secondary steam carrying the purified water droplets then enters the next effect evaporator. However, because the conductivity and bacterial endotoxin levels of the purified water droplets do not meet the requirements for injection water, they need to be separated from the pure steam. To address these issues, this embodiment proposes a multi-stage vapor-liquid separation system using a horizontal tube falling film evaporator. The main component of this system is a multi-stage vapor-liquid separator. This multi-stage vapor-liquid separator, together with the turbulence and backflow separation effects within the evaporator shell, forms the multi-stage vapor-liquid separation system.

[0025] The multi-stage vapor-liquid separation system proposed in this embodiment mainly includes an evaporator and a multi-stage vapor-liquid separator. The evaporator has a condenser-side end cap on its condenser side (i.e., the output side), and there is a pressure difference between the inside of the evaporator cylinder and the condenser-side outlet area. The upper part of the evaporator condenser-side end cap is embedded with a multi-stage vapor-liquid separator. Figure 1As shown, the evaporator condenser-side end cap 6 includes an end cap cylinder 7, a condenser-side flange 8, and a steam inlet flange 9. The condenser-side flange 8 and the steam inlet flange 9 are respectively located on both sides of the end cap cylinder 7. The evaporator cylinder is connected to the condenser-side flange 8, and the steam inlet flange 9 is connected to the next-effect evaporator. The multi-stage vapor-liquid separator 1 is embedded in the upper part of the end cap cylinder 7 between the condenser-side flange 8 and the steam inlet flange 9.

[0026] like Figure 2 As shown, the multi-stage vapor-liquid separator 1 includes a head baffle 2 and corrugated baffles 3, demister mesh 4, and vapor-liquid baffles 5 arranged sequentially from the inside out on the head baffle 2. The head baffle 2 divides the evaporator condenser side head 6 into upper and lower parts. The upper part is the secondary steam outlet area of ​​the evaporator. Figure 6 As shown, there is a pressure difference between the inside of the evaporator cylinder and the condenser outlet area. The secondary steam carrying liquid droplets output from the evaporator flows towards the condenser outlet. This secondary steam carrying liquid droplets passes through the turbulence and backflow separation in the evaporator cylinder, the corrugated baffle separation of the multi-stage vapor-liquid separator, and the demister wire separation before entering the next effect evaporator. The lower part is the condensate collection outlet area output from the evaporator, where the condensate generated in each heat exchange tube flows out from the tube opening and collects.

[0027] In this embodiment, the multi-stage vapor-liquid separator 1 has an arc-shaped structure, which is embedded in the upper part of the end cap cylinder 7 of the evaporator condenser side end cap. As another implementation, the multi-stage vapor-liquid separator 1 can also have a semi-circular structure.

[0028] Furthermore, in the multi-stage vapor-liquid separator 1, the bottom end plate 2 is used to support the corrugated baffle 3, the demister mesh 4, and the vapor-liquid baffle 5. The two sides of the end plate 2 are welded and fixed to the inner wall of the end plate cylinder 7, thereby fixing the entire multi-stage vapor-liquid separator.

[0029] As a further implementation method, such as Figure 3 As shown, a reinforcing rib 10 is welded inside the condensing side flange 8, and the end cap diaphragm 2 is welded to the upper side of the reinforcing rib 10 inside the condensing side flange to further strengthen the fixation of the multi-stage vapor-liquid separator.

[0030] like Figure 4As shown, the end cap baffle 2 in the multi-stage vapor-liquid separator 1 is inclined, that is, the end cap baffle 2 has an inclination angle of 11 with the horizontal plane. The inclination angle of the end cap baffle (i.e., the angle of inclination 11) is set to ensure reliable backflow of the droplets separated by the corrugated baffle and the demister mesh. Specifically, the inclination angle α of the end cap baffle is calculated and determined as follows: the droplets separated from the vapor-liquid separation are equivalent to spherical droplets with mass m and radius R. The droplets are subjected to the pressure difference force between the inlet and outlet, the drag force of the airflow, and gravity on the end cap baffle. To avoid contamination of the injection water by the droplets, the separated droplets should not be blown out of the end cap baffle by the airflow. Therefore, the resultant force of the pressure difference force and the drag force of the airflow should be less than the effect of gravity, that is: ; Among them, the force of pressure difference P is the pressure difference between the inlet and outlet of the gas-liquid separator, and A is the projected area of ​​the liquid droplet; according to the shear flow model, the airflow drag force , k =0.5~1 is the shear force correction factor, which is determined by experimental calibration; μ is the viscosity of the secondary steam; v is the flow rate of the secondary steam; gravitational force. .

[0031] Furthermore, substituting the parameters into the above calculation formula and rearranging, we obtain the minimum value of the inclination angle α, which is: .

[0032] like Figure 5 As shown, the corrugated baffle 3 is composed of several corrugated stainless steel folded plates that serve as baffle blades. Each corrugated stainless steel folded plate is an arc-shaped plate with a central convex surface and inclined sides. Several corrugated stainless steel plates are arranged sequentially along the secondary steam inlet direction. The bottom of each stainless steel folded plate is fixed to the end cap partition, and its top contacts the inner wall of the evaporator condenser end cap (it can be connected and fixed if necessary). Furthermore, all baffle blades are arranged in a uniform, predetermined interval, with the height of the baffle blades increasing symmetrically from the sides to the middle, so that the upper and lower ends of all baffle blades are connected to the inner wall of the end cap cylinder and the upper surface of the end cap partition, respectively. The main function of the corrugated baffle 3 is to remove larger purified water droplets. Its optimal working effect corresponds to a secondary steam flow rate range of 3.5~5.5 m / s, with a corresponding baffle blade spacing of 30~50 mm. The optimal blade spacing is determined based on the steam flow rate; the higher the secondary steam flow rate, the larger the blade spacing.

[0033] Specifically, to achieve the best working effect of the corrugated baffle, the critical flow velocity V for separation by the corrugated baffle is determined based on the principle of fluid motion inertia separation. b ,for: ; in,d The equivalent diameter of the separated droplets; The density of the separated droplets; The density of the secondary steam; g It is the acceleration due to gravity; The drag coefficient is 0.44 for the equivalent droplet; all the above parameter values ​​can be determined based on the material properties and operating conditions.

[0034] Next, based on the critical flow velocity determined by the above calculations, the blade spacing is determined to guide the evaporator design. In this embodiment, when the critical flow velocity is greater than 5.5 m / s, the separation effect of the corrugated baffle decreases significantly, requiring adjustment of the evaporator design dimensions; when the critical flow velocity is 3.5~5.5 m / s, the optimal blade spacing is determined based on the flow velocity value. The blade spacing can be determined according to the evaporator size and engineering experience. For evaporators of conventional sizes, the blade spacing is 30~50 mm.

[0035] like Figure 1 and Figure 2 As shown, the demister mesh is arc-shaped and embedded between the evaporator condenser-side end cap and the end cap baffle. The arc-shaped surface at the top of the demister mesh is tangent to the inner wall of the end cap cylinder. The main function of the demister mesh 4 is to remove tiny purified water droplets. This demister mesh uses a DP type (i.e., high-efficiency type) mesh with a set wire diameter and aperture spacing. Its optimal operating flow rate range is 1~3.5m / s. In this embodiment, a 100-mesh DP high-efficiency type mesh is used, with a wire diameter of 0.15~0.25mm and an aperture spacing of 150~200μm.

[0036] In this embodiment, the wire diameter and aperture spacing parameters of the demister mesh can also be determined based on the secondary steam flow rate. Specifically, to achieve the best working effect of the demister mesh, the critical flow rate of the demister mesh is first calculated. ,for: ; Wherein, K is the wire mesh coefficient, which is determined according to the wire mesh type. The coefficient for DP high-efficiency wire mesh is 0.08~0.12. The density of the separated droplets; The density of the secondary steam.

[0037] Next, based on the calculated critical flow rate, the wire diameter and hole spacing parameters of the demister mesh are determined to guide the design of the evaporator, which will not be elaborated here.

[0038] Furthermore, the thickness of the corrugated baffles and demister mesh in the multi-stage vapor-liquid separator can be determined based on the secondary steam flow rate. Specifically, let the thickness of the vapor-liquid separator be... The thicknesses of the corrugated baffle and the demister wire mesh are respectively and , To ensure effective vapor-liquid separation, There exists a minimum value, and ≥300mm, while the corrugated baffle of the multi-stage vapor-liquid separator And defoaming wire mesh The value of is related to the secondary steam velocity, and is as follows: when the secondary steam velocity is 1~3 m / s, When the secondary steam velocity is 3~4 m / s, When the secondary steam velocity is 4~5.5 m / s, .

[0039] Based on the above system, a three-stage vapor-liquid separation architecture is constructed, consisting of "turbulence and backflow separation within the evaporator cylinder + corrugated baffle separation in the vapor-liquid separator + demister mesh separation in the vapor-liquid separator." For example... Figure 6 As shown, the entire water production process is as follows: First, high-temperature and high-pressure pure steam enters the evaporator through pure steam inlet 12, where it undergoes heat exchange inside the heat exchange tubes to generate distilled water, which flows out from distilled water outlet 15. Simultaneously, purified water enters the evaporator through purified water inlet 13, where it undergoes heat exchange and evaporation in the shell side of the evaporator to generate secondary steam. The secondary steam comes into contact with the purified water liquid film or mixes with atomized spray droplets to generate secondary steam carrying the purified water droplets. Meanwhile, the remaining purified water flows out through the residual water outlet 14 located at the bottom of the evaporator.

[0040] Secondly, the vapor-liquid separation process is carried out using the three-stage vapor-liquid separation architecture constructed above, including: (1) The secondary steam carrying droplets generated by the evaporation of purified water in the evaporator first completes the first stage of vapor-liquid separation within the shell side of the evaporator by utilizing the principles of airflow disturbance and gravity, through turbulence and backflow separation. Specifically, there is a pressure difference between the shell side of the evaporator and the condenser outlet area. As the secondary steam carrying droplets flows towards the condenser outlet, some droplets are removed under the action of airflow disturbance. At the same time, the condenser outlet is located at the upper right of the evaporator shell side. Since the density of droplets is greater than that of pure steam, some purified water droplets are separated from the pure steam under the action of gravity during the flow towards the condenser outlet, completing the first stage of vapor-liquid separation. Droplets that have not yet separated after turbulence and backflow separation enter the multi-stage vapor-liquid separator along with the secondary steam from the condenser outlet.

[0041] (2) The secondary steam after the recirculation separation enters the corrugated baffle for secondary separation. The corrugated baffle is composed of a series of corrugated stainless steel baffles, such as... Figure 5As shown, after the vapor-liquid mixture enters, it impacts three impact surfaces in sequence: the first impact surface 16, the second impact surface 17, and the third impact surface 18. After impact, the droplets separate from the vapor. Most of the larger droplets detach from the secondary vapor during their flow inside the corrugated baffle. Some droplets impact the wall, forming smaller droplets. Due to the angle of the bottom end cap baffle, the separated droplets flow back to the evaporator, completing the second stage of vapor-liquid separation. The secondary vapor continues to carry the smaller droplets, flowing towards the next-effect evaporator under the influence of pressure difference.

[0042] (3) After passing through the corrugated baffle, the secondary steam enters the demister wire mesh to separate the tiny liquid droplets mixed in the steam. The separated droplets flow back to the evaporator through the inclined end plate to complete the third stage of steam-liquid separation, achieving efficient steam-liquid separation under the condition of steam flow rate of 1~5.5m / s.

[0043] As a further implementation, in the above process, the efficiency η of droplet removal from the corrugated baffle is calculated using an inertial collision efficiency model, which is as follows: ; Among them, Stokes number It can be represented as: ; in, The equivalent droplet density for removal; The equivalent droplet diameter is detached and removed; v is the secondary vapor velocity. denoted as , where is the viscosity of the secondary steam; D is the blade spacing of the corrugated baffle.

[0044] Preferably, the droplet removal efficiency of the demister mesh is calculated using the same method as that of the corrugated baffle, the only difference being... In the calculation formula, parameter D is the mesh size.

[0045] As a further implementation method, based on the quality of the raw water and the removal efficiency calculated above, the quality of the product water can be calculated during the evaporator design. If the product water quality cannot meet the design requirements, the evaporator design scheme and the design parameters of the multi-stage vapor-liquid separation system need to be adjusted to achieve qualified product water quality.

[0046] Finally, the multi-stage vapor-liquid separator proposed in this embodiment is also equipped with a vapor-liquid baffle. The vapor-liquid baffle is elongated and its length is consistent with the inner diameter of the end cap cylinder. Its width is adjustable. By setting the vapor-liquid baffle at the end of the demister wire mesh, the separated droplets can be prevented from being blown into the next effect evaporator under the action of the vapor flow.

[0047] Based on the multi-stage vapor-liquid separation system proposed in this embodiment, when facing secondary steam with a high flow rate, the impact force when passing through the corrugated baffle is strong, which can separate most of the liquid droplets carried by the secondary steam. At the same time, the impact can reduce the steam flow rate, which is beneficial to the separation effect of the subsequent demister mesh. When facing secondary steam with a low flow rate, the corrugated baffle can separate some larger droplets. After the gas-liquid mixture enters the subsequent demister mesh, it can achieve the optimal separation effect. Moreover, compared with the traditional wire mesh demister, this multi-stage vapor-liquid separation system can achieve the optimal vapor-liquid separation effect under operating conditions with a steam flow rate of 1~5.5m / s.

[0048] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-stage vapor-liquid separation system for a horizontal tube falling film evaporator, characterized in that, Includes evaporators and multi-stage vapor-liquid separators; The evaporator has a condensing side end cap, and a multi-stage vapor-liquid separator is embedded in the upper part of the condensing side end cap. The multi-stage vapor-liquid separator includes an end cap partition and a corrugated baffle, a demister mesh, and a vapor-liquid baffle arranged sequentially from the inside to the outside. The end cap partition divides the evaporator condensing side end cap into upper and lower parts. The upper part is the secondary steam outlet area output by the evaporator, and the lower part is the condensate collection outlet area output by the evaporator. The corrugated baffle is composed of several corrugated stainless steel folded plates arranged sequentially along the secondary steam inlet direction. The bottom of each stainless steel folded plate is fixed to the end cap partition, and the top of each plate contacts the inner wall of the evaporator condensing side end cap. The demister mesh is arc-shaped and embedded between the evaporator condensing side end cap and the end cap partition. There is a pressure difference between the inside of the evaporator cylinder and the outlet area on the condenser side. This causes the secondary steam carrying liquid droplets to enter the secondary steam outlet area after being separated by turbulence and backflow inside the evaporator cylinder. Then, it passes through the corrugated baffles and demister wires of the multi-stage vapor-liquid separator in sequence before entering the next effect evaporator.

2. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 1, characterized in that, The evaporator condensing side end cap includes an end cap cylinder, a condensing side flange, and a steam inlet side flange. The evaporator cylinder is connected to the condensing side flange. The condensing side flange and the steam inlet side flange are respectively located on both sides of the end cap cylinder. The steam inlet side flange is connected to the next-effect evaporator cylinder. The multi-stage vapor-liquid separator has an arc-shaped structure and is embedded in the upper part of the head cylinder of the evaporator condenser side head; the condenser side flange is provided with reinforcing ribs, the head baffle of the multi-stage vapor-liquid separator is welded to the upper side of the reinforcing rib of the condenser side flange, and the two sides of the head baffle are respectively welded to the inner wall of the head cylinder; the head baffle has an inclination angle α with the horizontal plane.

3. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 2, characterized in that, The formula for calculating the minimum angle α between the head diaphragm and the horizontal plane is: ； in, The minimum tilt angle is given, m represents the equivalent mass of the liquid droplet separated from the vapor-liquid separator, R represents the radius of the spherical droplet, P is the pressure difference between the inlet and outlet of the vapor-liquid separator, and k = 0.5~1 is the shear force correction coefficient. The viscosity is the secondary vapor viscosity. Let g be the secondary steam velocity, and g be the acceleration due to gravity.

4. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 2, characterized in that, The corrugated stainless steel folded plate serves as the baffle blade of the corrugated baffle. It is an arc-shaped plate with a raised center forming a raised surface and the two sides of the raised surface being inclined surfaces. All baffle blades are arranged in a uniform manner at a set interval, and the height of the baffle blades increases symmetrically from the sides to the middle, so that the upper and lower ends of all the file blades are connected to the inner wall of the head cylinder and the upper surface of the head partition, respectively. The arc-shaped surface at the top of the demister is tangent to the inner wall of the head cylinder. The demister is a DP high-efficiency wire mesh with a set wire diameter and hole spacing.

5. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 4, characterized in that, The secondary steam carrying droplets output from the evaporator undergoes turbulence and backflow separation within the evaporator cylinder for the first stage of vapor-liquid separation. During the flow of the secondary steam carrying droplets toward the condenser outlet, the pressure difference between the evaporator cylinder and the condenser outlet region creates an airflow. Under the influence of airflow disturbance and droplet gravity, the droplets detach from the steam, completing the first stage of vapor-liquid separation. After the secondary steam carrying droplets enters the corrugated baffle, it impacts the three impact surfaces in sequence. After the impact, the droplets separate from the steam. The separated droplets flow back to the evaporator along the inclined end plate, completing the second stage of vapor-liquid separation. The secondary steam after passing through the corrugated baffle enters the demister wire mesh, where the tiny droplets mixed in with the secondary steam are separated into vapor and liquid. The separated droplets flow back to the evaporator along the inclined end plate, completing the third stage of vapor-liquid separation.

6. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 4, characterized in that, The corrugated baffle is used to remove large purified water droplets, and its optimal operating flow rate range is 3.5~5.5m / s, with a corresponding spacing of 30~50mm between the baffle blades; the optimal spacing between the baffle blades in the corrugated baffle is determined based on the secondary steam flow rate.

7. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 4, characterized in that, The demister mesh is used to remove small purified water droplets. Its optimal operating flow rate range is 1~3.5m / s, corresponding to a wire diameter of 0.15~0.25mm and a hole spacing of 150~200μm. The wire diameter and hole spacing parameters of the demister mesh are determined according to the secondary steam flow rate.

8. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 4, characterized in that, The thickness of the corrugated baffles and demister wire mesh in the multi-stage vapor-liquid separator is determined based on the secondary steam flow rate, including: When the secondary steam flow rate is 1~3 m / s ; When the secondary steam flow rate is 3~4 m / s ; When the secondary steam flow rate is 4~5.5 m / s, ; in, For the thickness of the vapor-liquid separator, , These represent the thicknesses of the corrugated baffle and the demister mesh, respectively. .

9. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 1, characterized in that, The droplet removal efficiency of the corrugated baffle and demister mesh All were calculated using the inertial collision efficiency model; the inertial collision efficiency model is as follows: ； in, Represents the Stokes number. For droplet density, The equivalent diameter of the droplet. The steam flow rate is... For vapor viscosity, The spacing between the corrugated baffle blades or the aperture of the demister mesh.

10. The multi-stage vapor-liquid separation system of the horizontal tube falling film evaporator as described in claim 1, characterized in that, The vapor-liquid baffle is elongated, with its length matching the inner diameter of the head cylinder and its width adjustable. The vapor-liquid baffle is located at the end of the demister mesh to prevent the separated droplets from being blown into the next effect evaporator by the airflow.

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