Demister device for falling film evaporators
By designing a demister with an air-guiding mechanism and a gradually narrowing demister channel, the problem of poor demister effect and clogging in existing devices is solved by utilizing the physical properties of foam and the impact of the grid layer, thus achieving efficient steam demistering and stable flow.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG MEILI JIAN DAIRY CO LTD
- Filing Date
- 2023-11-21
- Publication Date
- 2026-06-05
AI Technical Summary
The existing demister devices for falling film evaporators are inadequate in terms of demister effect and efficiency, especially in that they are prone to clogging when the demister channel is narrow, and the demister effect is poor when the channel is wide.
A defoaming device was designed, including a vertically extending defoaming channel and an air-guiding mechanism inside the housing. The width of the defoaming channel gradually decreases along the air-guiding direction and is equipped with input and output defoaming grid layers. By utilizing the physical properties of foam and the guidance of the air-guiding mechanism, the foam in the steam is dispersed in the defoaming channel and broken by the impact of the grid layer.
It improves demister efficiency and stability, avoids channel blockage, and ensures the stability of steam flow and demister effect.
Smart Images
Figure CN117919739B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a defoaming device, particularly a defoaming device for a falling film evaporator. Background Technology
[0002] A falling film evaporator is a device used for distillation and dehydration, commonly found in chemical, pharmaceutical, and food processing industries. It separates and purifies substances by evaporating liquid inside heated tubes, forming a thin film on the tube walls, and finally condensing the film on the tube walls. Falling film evaporators typically have high heat and mass transfer efficiency, can handle high-concentration solutions, and are relatively energy-efficient. This type of equipment plays a vital role in the chemical industry, enabling the production and purification of chemicals.
[0003] The steam produced by a falling film evaporator contains a solution. The steam is usually sent to a condenser or the next-effect evaporator to improve utilization. Before the steam is output from the falling film evaporator, it needs to be defoamed. For example, the invention patent with prior art publication number CN200810195826.2 discloses a defoaming device for a tubular falling film evaporator. In this invention patent, the defoaming device is composed of several curved damping blades arranged in parallel with each other. A defoaming channel is formed between adjacent damping blades. The steam flow impacts the surface of the damping blades multiple times in the defoaming channel, causing the foam to break and thus completing the defoaming. This demisting method has defects and limitations: the smaller the distance between adjacent damping blades, that is, the narrower the demisting channel, the higher the frequency of collision between steam and damping blades when steam flows in the demisting channel, and the better the demisting effect. However, when foam breaks, it forms liquid. This liquid forms on the damping blades, and the narrower the demisting channel, the easier it is to cause blockage. Conversely, the wider the demisting channel, the less likely it is to cause blockage, but it will reduce the frequency of collision between steam and damping blades, resulting in a worse demisting effect. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a defoaming device for a falling film evaporator, which can improve the defoaming effect and efficiency.
[0005] The present invention is achieved through the following technical solution.
[0006] A demister for a falling film evaporator includes a housing having a steam inlet at the bottom and a steam outlet at the top; the housing contains at least one vertically extending demister channel and an induced draft mechanism; the demister channel has an inlet communicating with the steam inlet and an outlet communicating with the steam outlet; the induced draft mechanism guides steam into the inlet of the demister channel, and the width of the demister channel gradually decreases along the guiding direction of the induced draft mechanism.
[0007] As a further improvement of the present invention, the inlet of the demister channel is provided with an input demister mesh layer for initial demistering of the steam flowing into the demister channel.
[0008] As a further improvement of the present invention, the output port of the demister channel is provided with an output demister mesh layer for performing final demistering on the steam flowing out of the demister channel.
[0009] As a further improvement of the present invention, the mesh size of the input defoaming mesh layer is larger than that of the output defoaming mesh layer.
[0010] As a further improvement of the present invention, the area of the input port is larger than the area of the output port.
[0011] As a further improvement of the present invention, the steam inlet is located at the center of the bottom of the casing, the steam outlet is located at the center of the top of the casing, and multiple demister channels are arranged around the steam inlet; the input port is formed in the lower part of the demister channels and faces the steam inlet; the output port is formed in the upper part of the demister channels and faces the steam outlet; the induced draft mechanism has an impeller located above the steam inlet and horizontally arranged.
[0012] As a further improvement of the present invention, the housing includes an outer cylinder, an inner cylinder, a bottom cover for providing the steam inlet, and a top cover for providing the steam outlet; a baffle tube is provided between the outer cylinder and the inner cylinder, the baffle tube having a plurality of vertically extending inner and outer folds formed by cyclically reverse folding, and a plurality of baffle walls with adjacent folds as edges; the inner folds of the baffle tube are connected to the outer wall of the inner cylinder, and the space enclosed by the adjacent baffle walls with the outer folds of the baffle tube as edges and the outer wall of the inner cylinder forms the demister channel.
[0013] As a further improvement of the present invention, the lower part of the inner cylinder has a lower annular hollow that exposes the baffle tube, and the inner folded edge divides the lower hollow into a plurality of the input ports; the upper part of the inner cylinder has an upper annular hollow that exposes the baffle tube, and the inner folded edge divides the upper hollow into a plurality of the output ports.
[0014] As a further improvement of the present invention, the lower part of the baffle wall has a through hole, so that the liquid formed after the foam bursts flows into the liquid collection space between the baffle and the outer cylinder.
[0015] As a further improvement of the present invention, the inner wall of the inner cylinder is provided with a partition that separates the space vertically, and the air-guiding mechanism is installed at the bottom of the partition.
[0016] The beneficial effects of this invention are:
[0017] Different sized bubbles are burst at different horizontal positions within the demister channel, and bubbles of the same size but in different groups are burst at different vertical positions within the demister channel. Therefore, the demister channel in this embodiment utilizes the physical properties of foam, and through the guiding action of the induced draft mechanism and the characteristics of the demister channel, ensures that the foam in the steam has different demister positions with wide dispersion in both the horizontal and vertical directions within the demister channel. After the foam is burst, it forms liquid on the wall of the demister channel, and the formed liquid is also widely dispersed on the wall of the demister channel, thus preventing blockage of the demister channel and ensuring the stability of steam flow and the efficiency of demistering. Attached Figure Description
[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings to aid in understanding the objectives and advantages of the present invention, wherein:
[0019] Figure 1 This is a schematic diagram of the demister device;
[0020] Figure 2 for Figure 1 AA sectional view;
[0021] Figure 3 for Figure 1 BB cross-sectional diagram;
[0022] Figure 4 for Figure 3 A magnified view of a portion of the image;
[0023] Figure 5 This is a schematic diagram of the baffle tube structure. Detailed Implementation
[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0025] The directional terms such as up, down, left, right, front, back, front, back, top, and bottom mentioned or possibly used in this specification are defined relative to the construction shown in the accompanying drawings. The terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. These are relative concepts and may therefore vary depending on their location and usage. Therefore, these or other directional terms should not be interpreted as restrictive.
[0026] Reference Figures 1-5A demisting device is used in a falling film evaporator. The steam generated by the falling film evaporator is sent to a condenser for condensation (single-effect operation) or to the next-effect evaporator as a heating medium. In this embodiment, the demisting device is installed in the falling film evaporator to remove condensation from the steam to be output by the falling film evaporator. The demisting device in this embodiment includes a shell 1, with a steam inlet 1a at the bottom and a steam outlet 1b at the top. The steam generated by the falling film evaporator enters the demisting device through the steam inlet 1a, undergoes demisting action, and is then output through the steam outlet 1b and sent to the condenser or the next-effect evaporator.
[0027] The demister device in this embodiment has a hollow housing 1, which contains at least one vertically extending demister channel r and an induced draft mechanism 2. The demister channel r has an inlet r1 connected to the steam inlet 1a and an outlet r2 connected to the steam outlet 1b. The induced draft mechanism 2 guides steam into the inlet r1 of the demister channel r, and the width of the demister channel r gradually decreases along the guiding direction of the induced draft mechanism 2.
[0028] The extension direction of the demister channel r is vertical, and the width direction of the demister channel r is horizontal. Steam enters the demister channel r under the action of the induced draft mechanism 2, and its movement within the demister channel r can be decomposed into movement in two directions: one is vertical movement along the extension direction of the demister channel r, and the other is horizontal movement along the direction of narrowing width of the demister channel r.
[0029] Foam in steam is typically formed by bubbles encased in a thin film of liquid, and these bubbles vary in size. Therefore, bubbles of different sizes move at different speeds within the demister channel r. Specifically, their vertical and horizontal movement speeds differ, resulting in a wider distribution of foam entering the demister channel r from the inlet r1 at the same time. The horizontal movement of the foam follows the direction in which the width of the demister channel r gradually decreases. When the foam reaches the corresponding width of the demister channel r in the horizontal direction, it can be crushed. In existing technologies, the foam bursts due to multiple impacts on the damping blades as steam flows within the demister channel r, making it highly dependent on the steam flow velocity. Insufficient steam flow velocity leads to low demister efficiency. However, in this embodiment, by varying the width of the demister channel r, the walls of the demister channel r can crush the foam as soon as it reaches a position matching the width of the demister channel r. This demister method has lower requirements for steam flow velocity and significantly improves both demister efficiency and success rate.
[0030] Clearly, the horizontal position at which the foam is burst is directly related to the size of the foam and the width of the defoaming channel r. That is, foams of different sizes are burst at different horizontal positions within the defoaming channel r. Furthermore, the foams within the defoaming channel r are not independent entities, but rather foam clusters formed by multiple foams adhering together. In other words, even foams of the same size within different foam clusters move at different speeds within the defoaming channel r. That is, while foams of different sizes are burst at the same horizontal position within the defoaming channel r, their vertical positions within the defoaming channel r differ.
[0031] In summary, foams of different sizes are burst at different horizontal positions within the demister channel r, and foams of the same size but located in different foam groups are burst at different vertical positions within the demister channel r. Therefore, the demister channel r in this embodiment utilizes the physical properties of foam, and through the guiding action of the induced draft mechanism 2 and the characteristics of the demister channel r, ensures that the foam in the steam has different demister positions with wide dispersion in both the horizontal and vertical directions within the demister channel r. After the foam is burst, it forms liquid on the wall of the demister channel r, and the formed liquid is also widely dispersed on the wall of the demister channel r, thus preventing blockage of the demister channel r and ensuring the stability of steam flow and the efficiency of demistering.
[0032] In this embodiment, the inlet r1 of the demister channel r is provided with an input demister mesh layer 31. The input demister mesh layer 31 has uniformly distributed mesh holes. Steam flows into the inlet r1 through the mesh holes of the input demister mesh layer 31, and the foam it carries is impacted and ruptured. The input demister mesh layer 31 performs initial demistering on the steam before the demister channel r.
[0033] In this embodiment, the output port r2 of the demister channel r is provided with an output demister mesh layer 32. The output demister mesh layer 32 has uniformly distributed mesh holes. After the steam passes through the demister channel r for demistering, there may still be residual foam. At this time, the steam flows out of the output port r2 through the mesh holes of the output demister mesh layer 32. The residual foam is broken by impact, and the output demister mesh layer 32 performs the final demistering on the steam.
[0034] Before entering the inlet r1, the steam carries a large amount of foam of varying sizes. Larger foam particles need to be removed by the input demister mesh layer 31. After passing through the demister channel r, the remaining foam is primarily micro-foam, which needs to be eliminated by the output demister mesh layer 32. Therefore, in this embodiment, the mesh size of the input demister mesh layer 31 is larger than that of the output demister mesh layer 32, allowing the input demister mesh layer 31 to eliminate larger foam particles, while the output demister mesh layer 32 eliminates micro-foam particles.
[0035] At the same flow rate, the smaller the foam, the more difficult it is to break upon impact. Therefore, in this embodiment, the area of the inlet r1 is larger than the area of the outlet r2, which increases the flow rate of steam when passing through the outlet r2. This enhances the impact force of the residual micro foam on the output defoaming grid layer 32, thus facilitating the impact and breakage of the micro foam.
[0036] In this embodiment, the casing 1 is configured as a vertical cylindrical structure. The steam inlet 1a is located at the center of the bottom of the casing 1, and the steam outlet 1b is located at the center of the top of the casing 1. Multiple demister channels r are arranged around the steam inlet 1a within the casing 1. The inlets r1 of these demister channels r are formed at the lower part of the demister channel r and facing the steam inlet 1a, while the outlets r2 are formed at the upper part of the demister channel r and facing the steam outlet 1b. The induced draft mechanism 2 has an impeller 21, which is located above the steam inlet 1a and is horizontally positioned. Steam flows vertically into the casing 1 through the steam inlet 1a. Under the rotation of the impeller 21, the steam is blown outwards and enters the inlets r1 of each demister channel r. After passing through these demister channels r, the steam flows out through the outlets r2. The demistered steam converges towards the center and flows out of the casing 1 through the steam outlet 1b.
[0037] In this embodiment, the housing 1 includes an outer cylinder 11, an inner cylinder 12, a top cover 14, and a bottom cover 13. The outer cylinder 11 and the inner cylinder 12 are coaxially arranged. The steam inlet 1a is located at the center of the bottom cover 13, and the steam outlet 1b is located at the center of the top cover 14. A baffle 15 is provided in the space between the outer cylinder 11 and the inner cylinder 12. The baffle 15 has multiple vertically extending inner folded edges 15a and outer folded edges 15b formed by cyclically reverse folding, and multiple baffle walls 151 with adjacent folded edges as edges. The inner folded edges 15a of the baffle 15 are connected to the outer cylinder 11 wall of the inner cylinder 12. Therefore, multiple vertically extending spatial channels are formed between the baffle 15 and the inner cylinder 12. That is, the spatial channel enclosed by the adjacent baffle walls 151 with the outer folded edges 15b of the baffle 15 and the outer wall of the inner cylinder 12 forms the demisting channel r. The baffle walls 151 form the two walls of the demisting channel r. The two baffle walls 151 gradually transition from the two mutually spaced inner folded edges 15a to the same outer folded edge 15b, so that the width of the demisting channel r gradually decreases along the airflow direction of the impeller 21, which is suitable for the function of crushing foam to remove it.
[0038] As for the outer flange 15b of the baffle 15, it can be connected to the inner wall of the outer cylinder 11 or it can have a gap, which has no effect on the formation of the defoaming channel r.
[0039] In this embodiment, the lower part of the inner cylinder 12 has a lower annular perforation, which exposes the baffle cylinder 15. The inner folded edge 15a of the baffle cylinder 15 divides the lower perforation into multiple inlet ports r1. The upper part of the inner cylinder 12 has an upper annular perforation that exposes the baffle cylinder 15. The inner folded edge 15a divides the upper perforation into multiple outlet ports r2. The vertical width of the lower annular perforation is greater than that of the upper annular perforation, making the area of the inlet ports r1 larger than the area of the outlet ports r2. In addition, the inlet demisting mesh layer 31 and the outlet demisting mesh layer 32 are both set as annular single-layer or multi-layer wire mesh structures, assembled at the lower annular perforation and the upper perforation.
[0040] In this embodiment, the foam is crushed in the defoaming channel r to form liquid, which flows on the baffle wall 151. Therefore, through holes 151a are provided at the lower part of the baffle wall 151. The number of through holes 151a depends on the actual application. The liquid generated by the foam crushing can flow down along the baffle wall 151 and flow into the space between the baffle cylinder 15 and the outer cylinder 11 through the through holes 151a. This space serves as a liquid collection space s to collect the liquid. In addition, a pipeline can be provided to connect to the outer cylinder 11 to discharge and collect this liquid.
[0041] In this embodiment, a partition 16 is provided on the inner wall of the inner cylinder 12. The partition 16 divides the space vertically. The induced draft mechanism 2 is installed at the bottom of the partition 16. The partition 16 is used to install the induced draft mechanism 2 on the one hand, and on the other hand, it can prevent the steam inlet 1a and the steam outlet 1b from being directly connected, so that the steam must pass through the demister channel r before it can flow out from the steam outlet 1b.
[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A defoaming device for a falling film evaporator, characterized in that, The device includes a housing (1) having a steam inlet (1a) at the bottom and a steam outlet (1b) at the top; the housing (1) is provided with at least one vertically extending demister channel (r) and a draft fan (2); the demister channel (r) has an inlet (r1) connected to the steam inlet (1a) and an outlet (r2) connected to the steam outlet (1b); the draft fan (2) is used to guide steam into the inlet (r1) of the demister channel (r), and the width of the demister channel (r) gradually decreases along the guiding direction of the draft fan (2); The inlet (r1) of the demister channel (r) is provided with an input demister mesh layer (31) for initial demistering of the steam flowing into the demister channel (r); The outlet (r2) of the demister channel (r) is provided with an output demister mesh layer (32) for performing final demistering on the steam flowing out of the demister channel (r); The mesh size of the input defoaming mesh layer (31) is larger than that of the output defoaming mesh layer (32), and the area of the input port (r1) is larger than that of the output port (r2). The steam inlet (1a) is located at the center of the bottom of the housing (1), and the steam outlet (1b) is located at the center of the top of the housing (1). Multiple demister channels (r) are provided and arranged around the steam inlet (1a). The input port (r1) is formed in the lower part of the demister channel (r) and faces the steam inlet (1a). The output port (r2) is formed in the upper part of the demister channel (r) and faces the steam outlet (1b). The induced draft mechanism (2) has an impeller (21) located above the steam inlet (1a) and arranged horizontally. The housing (1) includes an outer cylinder (11), an inner cylinder (12), a bottom cover (13) for providing the steam inlet (1a), and a top cover (14) for providing the steam outlet (1b). A baffle cylinder (15) is provided between the outer cylinder (11) and the inner cylinder (12). The baffle cylinder (15) has multiple vertically extending inner folded edges (15a) and outer folded edges (15b) formed by cyclically reverse folding, and multiple baffle walls (151) with adjacent inner folded edges (15a) or outer folded edges (15b) as edges. The inner folded edges (15a) of the baffle cylinder (15) are connected to the outer wall of the inner cylinder (12), and the space enclosed by the adjacent baffle walls (151) with the outer folded edges (15b) of the baffle cylinder (15) and the outer wall of the inner cylinder (12) forms the demister channel (r).
2. The defoaming device for a falling film evaporator according to claim 1, characterized in that, The lower part of the inner cylinder (12) has a lower annular cutout that exposes the baffle tube (15), and the inner folded edge (15a) divides the lower cutout into a plurality of the input ports (r1); the upper part of the inner cylinder (12) has an upper annular cutout that exposes the baffle tube (15), and the inner folded edge (15a) divides the upper cutout into a plurality of the output ports (r2).
3. The defoaming device for a falling film evaporator according to claim 1, characterized in that, The lower part of the baffle wall (151) has a through hole (151a) so that the liquid formed after the foam bursts flows into the liquid collection space (s) between the baffle cylinder (15) and the outer cylinder (11).
4. The defoaming device for a falling film evaporator according to claim 1, characterized in that, The inner wall of the inner cylinder (12) is provided with a partition (16) that separates the space vertically, and the air-guiding mechanism (2) is installed at the bottom of the partition (16).