A demister and demister system for preventing surface scaling in absorption towers

Abstract

This invention relates to a demister and system for preventing surface scaling in absorption towers. The demister includes a main frame, within which a demister assembly is fixedly connected. The demister assembly includes several demister tubes arranged side-by-side, with connecting pipes fixedly connected between adjacent demister tubes. Each demister tube and connecting pipe has a fixedly connected baffle plate arranged axially along its axis, dividing the interior of the demister tube and connecting pipe into a first chamber and a second chamber. The sidewall of the second chamber has several micropores. The sidewall of the main frame has a hot gas inlet, a hot gas outlet, and an anti-clogging liquid inlet, respectively. The hot gas inlet and outlet communicate with the first chamber, while the anti-clogging liquid inlet communicates with the second chamber. During operation, the demister dilutes and removes slurry droplets adhering to the surface of the demister tubes, thereby preventing evaporation and crystallization to form scale, effectively solving the problem of scaling and clogging in traditional demisters.

Description

Technical Field

[0001] This invention belongs to the technical field of demisters in absorption towers, and specifically relates to a demister for preventing surface scaling in absorption towers, and a demister system using the demister. Background Technology

[0002] Flue gas generated from the combustion of fuels such as coal in thermal power plants often contains a large amount of sulfur dioxide, which needs to be treated before being released. Currently, absorption towers are mainly used to absorb sulfur dioxide from the flue gas. When the flue gas enters the absorption tower, it flows upward, while a large amount of limestone slurry is sprayed downward inside the tower. The upward-flowing flue gas comes into countercurrent contact with the downward-sprayed slurry droplets, resulting in a violent reaction. The sulfur dioxide is absorbed and reacted by the limestone droplets, and then the flue gas continues to move upward and is discharged from the top of the absorption tower.

[0003] In this process, the flue gas containing sulfur dioxide reacts with the limestone slurry, leaving behind a large number of fine limestone / gypsum slurry droplets. These droplets contain chloride ions, fluoride ions, unreacted limestone, and gypsum, making them highly corrosive. If not removed, they will severely corrode downstream equipment, increasing maintenance costs. Therefore, demisters are typically installed in absorption towers to remove residual limestone / gypsum slurry droplets from the flue gas.

[0004] Existing technologies typically remove fine droplets by providing an adhesion surface to allow them to adhere to the demister surface. However, on the demister surface, due to flue gas temperature and airflow, the moisture in the droplets continuously evaporates, causing the solution to rapidly become supersaturated. The dissolved salts then crystallize and precipitate, firmly adhering to the demister surface and forming scale. This scale blocks the airflow channels on the demister surface, significantly increasing the resistance to flue gas flow. This forces the induced draft fan to increase its power to maintain airflow, thus significantly increasing plant power consumption. In severe cases, insufficient fan output may even force a reduction in unit load.

[0005] Currently, the common approach to avoid structural damage is to replace the demister. However, replacing the demister requires shutting down the absorption tower, which is time-consuming and labor-intensive. Therefore, this application provides a demister for absorption towers to prevent surface scaling, and a demister system using the demister to improve the above-mentioned problems. Summary of the Invention

[0006] The purpose of this invention is to provide a demister for absorption towers that prevents surface scaling, effectively alleviating scaling on the demister surface and avoiding a decrease in demister efficiency and an increase in system pressure differential caused by scaling on the demister surface.

[0007] To achieve the above objectives, the present invention provides a demister for preventing surface scaling in an absorption tower, comprising a main frame, within which a demister assembly is fixedly connected. The demister assembly includes several demister pipes arranged side by side, with a connecting pipe fixedly connected between adjacent demister pipes. Each demister pipe and connecting pipe has a baffle plate fixedly connected inside, and the baffle plate is arranged axially along the demister pipe and connecting pipe. The baffle plate divides the interior of the demister pipe and connecting pipe into a first chamber and a second chamber. The side wall of the second chamber has several micropores. The side wall of the main frame has a hot gas inlet, a hot gas outlet, and an anti-clogging liquid inlet, wherein the hot gas inlet and hot gas outlet are connected to the first chamber, and the anti-clogging liquid inlet is connected to the second chamber.

[0008] Furthermore, multiple layers of demisting components are fixedly connected along the axial direction in the main frame, and the gap between the demisting pipe in one layer of demisting component and the demisting pipe in the adjacent demisting component corresponds to the gap between the pipes in the adjacent demisting component.

[0009] Furthermore, several heat-conducting plates are fixedly connected to the side of the partition facing the second chamber. The demister and connecting pipe are made of heat-insulating material, or the outer wall of the demister and connecting pipe is fixedly connected to a heat-insulating structure. The partition and heat-conducting plates are made of heat-conducting material.

[0010] Maximum diameter of micropores Calculate using the following formula:

[0011]

[0012] in, To prevent the clogging fluid from being at the highest ambient temperature Surface tension at that time, To prevent the contact angle between the clogging fluid and the micropore wall, To prevent clogging, the density of the liquid is given, g is the acceleration due to gravity, and h is the height of the liquid surface.

[0013] The calculation method is as follows:

[0014]

[0015] in, To prevent clogging of the liquid at the gas-liquid critical point temperature, the highest ambient temperature was used in the temperature calculation here. The vapor-liquid critical temperature of water Thermodynamic temperatures are used in all cases.

[0016] Furthermore, the minimum spacing between adjacent micropores on the sidewall of the second chamber Calculate as follows:

[0017]

[0018] The actual distance between adjacent micropores is greater than Furthermore, the micropores are evenly distributed on the side wall of the second chamber.

[0019] Furthermore, when the demister tube is a circular tube, calculate the maximum diameter of the micropores. liquid level height Where R is the outer radius of the circular tube. The azimuth angle of the suspended droplet.

[0020] Another technical solution adopted in this application is:

[0021] A demisting system includes a demister installed inside an absorption tower. The anti-clogging liquid inlet of the demister is connected to a constant pressure valve via a pipeline. The constant pressure valve is connected to an anti-clogging liquid source via a pipeline. The hot gas inlet is connected to an upstream high-temperature flue gas source via a pipeline. A first air pump is installed between the hot gas inlet and the upstream high-temperature flue gas source. The hot gas outlet is connected to a second air pump via a pipeline. The output section of the air pump is connected to the flue gas inlet of the absorption tower via a pipeline.

[0022] Furthermore, the pipes between the upstream high-temperature flue gas source and the first gas pump, the pipes between the hot gas inlet and the first gas pump, the pipes between the hot gas outlet and the second gas pump, and the pipes between the second gas pump and the absorption tower are all covered with an insulation layer.

[0023] Furthermore, a one-way valve is installed between the hot gas outlet and the second air pump, and a three-way valve is installed on the pipe between the hot gas inlet and the first air pump. The three-way valve is connected to the inlet of the second air pump through the pipe.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The device provided by this invention heats the anti-clogging liquid in the second chamber by introducing high-temperature gas into the first chamber. As the temperature rises and the surface tension decreases, the liquid flows out through pre-set micropores. The outflowing liquid dilutes the limestone / gypsum slurry droplets adhering to the surface of the demister tube, preventing the droplets from crystallizing and precipitating due to water evaporation or solute supersaturation, thus fundamentally preventing scale formation. This solves the problem of increased flue gas resistance, higher energy consumption, and even forced shutdown caused by scale clogging in traditional demisters.

[0026] The system provided by this invention can directly extract high-temperature flue gas from an upstream high-temperature flue gas source as a heat source, realizing energy recycling and reducing additional energy consumption. Simultaneously, a constant pressure valve maintains stable pressure in the second chamber, preventing abnormal liquid leakage or untimely replenishment. The combination of a three-way valve, a one-way valve, an air pump, and insulated pipes allows for flexible switching of the flue gas path. When needed, hot gas is guided through the demister; when not needed, it bypasses and directly enters the absorption tower. The system operates flexibly, efficiently, and energy-savingly. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the structure of the demister for preventing surface scaling in the absorption tower of the present invention;

[0028] Figure 2 This is an axial cross-sectional view of the defogging component in this invention;

[0029] Figure 3 This is a schematic diagram of the connection of the defogging system in this invention.

[0030] In the diagram: 1. Main frame; 2. Demisting assembly; 3. Demisting pipe; 4. Connecting pipe; 5. Partition; 6. First chamber; 7. Second chamber; 8. Hot gas inlet; 9. Hot gas outlet; 10. Anti-clogging liquid inlet; 11. Micropore; 12. Heat-conducting plate; 13. Demister; 14. Constant pressure valve; 15. Anti-clogging liquid source; 16. Upstream high-temperature flue gas source; 17. First air pump; 18. Second air pump; 19. One-way valve; 20. Three-way valve. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1:

[0033] like Figure 1 and Figure 2 As shown, a demister for preventing surface scaling in an absorption tower includes a main frame 1. A demister assembly 2 is fixedly connected inside the main frame 1. The demister assembly 2 includes several demister pipes 3 arranged side by side, and a connecting pipe 4 is fixedly connected between adjacent demister pipes 3. A partition 5 is fixedly connected inside each demister pipe 3 and the connecting pipe 4. The partition 5 is arranged axially along the demister pipe 3 and the connecting pipe 4. The partition 5 divides the interior of the demister pipe 3 and the connecting pipe 4 into a first chamber 6 and a second chamber 7. Several micropores 11 are opened on the side wall of the second chamber 7. A hot gas inlet 8, a hot gas outlet 9 and an anti-clogging liquid inlet 10 are respectively opened on the side wall of the main frame 1. The hot gas inlet 8 and the hot gas outlet 9 are connected to the first chamber 6, while the anti-clogging liquid inlet 10 is connected to the second chamber 7.

[0034] During device operation, hot gas is introduced into the first chamber 6, and anti-clogging liquid inlet 10 is introduced into the second chamber 7. The temperature of the hot gas is higher than the ambient temperature of the area where the demister is located. Under normal conditions, due to the surface tension of the liquid, the liquid in the second chamber 7 cannot flow out from the micropores 11. When droplets adhere to the demister tube 3, high-temperature gas can be introduced into the first chamber 6 to heat the anti-clogging liquid in the second chamber 7. As the temperature rises, the surface tension of the liquid decreases, causing it to flow out of the demister tube 3 and mix with the droplets adhering to the surface of the demister tube, preventing evaporation and crystallization to form scale. At the same time, as the liquid flows out of the demister tube 3, droplets continuously accumulate on the surface of the pipe and fall off, further reducing the possibility of scale formation.

[0035] Example 2:

[0036] Based on Example 1:

[0037] The main frame 1 is fixedly connected along the axial direction with multiple layers of demisting components 2, and the demisting pipe 3 in one layer of demisting component 2 corresponds to the gap of the demisting pipe 3 in the adjacent demisting component 2.

[0038] A number of heat-conducting plates 12 are fixedly connected to the side of the partition 5 facing the second chamber 7. The demist pipe 3 and the connecting pipe 4 are made of heat-insulating material, or the outer wall of the demist pipe 3 and the connecting pipe 4 is fixedly connected to a heat-insulating structure. The partition 5 and the heat-conducting plates 12 are made of heat-conducting material.

[0039] The multi-layered demister assembly 2 forms a tortuous flow channel, making it easier for flue gas to adhere to the demister pipe 3 during its ascent, effectively removing liquid droplets from the flue gas. Simultaneously, the heat-conducting plate 12 improves heating efficiency, thereby shortening the heating time and allowing the device to start up faster.

[0040] Example 3:

[0041] Based on Example 1:

[0042] The maximum diameter of micropore 11 Calculate using the following formula:

[0043]

[0044] in, To prevent the clogging fluid from being at the highest ambient temperature Surface tension at that time, To prevent the contact angle between the clogging fluid and the wall of the micropore 11, To prevent clogging, the density of the liquid is given, g is the acceleration due to gravity, and h is the height of the liquid surface.

[0045] The calculation method is as follows:

[0046]

[0047] in, To prevent clogging of the liquid at the gas-liquid critical point temperature, the highest ambient temperature was used in the temperature calculation here. The vapor-liquid critical temperature of water Thermodynamic temperatures are used in all cases.

[0048] The minimum spacing between adjacent micropores 11 on the side wall of the second chamber 7 Calculate as follows:

[0049]

[0050] The actual spacing between adjacent micropores 11 is greater than Furthermore, the micropores 11 are evenly distributed on the side wall of the second chamber 7.

[0051] When the demister tube 3 is a circular tube, calculate the maximum diameter of the micropore 11. liquid level height Where R is the outer radius of the circular tube. The azimuth angle of the suspended droplet.

[0052] In this embodiment, water is used as the anti-clogging fluid. The temperature at the location where the demister is installed in the absorption tower fluctuates between 50°C and 60°C. Therefore, in the calculations of this embodiment... Take 647.10K, Take 333.15K, from which we can derive It is 0.0663 N / m.

[0053] In this embodiment, the demister's pipe is a circular pipe with a radius of 25mm, and the pipe material is polypropylene. Therefore, the maximum diameter of the micropores 11 can be determined. The actual design uses 1.40 mm instead of 0.001397 mm. This refers to the minimum spacing between micropores on the pipe. The value is 0.00520m, but the actual design uses 5.25mm.

[0054] By limiting the diameter of the micropores, it can be ensured that the liquid inside the demister tube 3 does not flow out of the micropores 11 when the temperature is at ambient temperature. When the liquid is heated, the surface tension decreases, and the liquid can flow out to dilute the droplets on the surface of the demister tube 3, thus preventing scaling.

[0055] Example 4:

[0056] Based on Example 1:

[0057] like Figure 3 As shown, a demisting system includes a demister 13 installed in an absorption tower. The anti-clogging liquid inlet 10 of the demister 13 is connected to a constant pressure valve 14 via a pipe. The constant pressure valve 14 is connected to an anti-clogging liquid source 15 via a pipe. The hot gas inlet 8 is connected to an upstream high-temperature flue gas source 16 via a pipe. A first air pump 17 is installed between the hot gas inlet 8 and the upstream high-temperature flue gas source 16. The hot gas outlet 9 is connected to a second air pump 18 via a pipe. The output section of the air pump is connected to the flue gas inlet of the absorption tower via a pipe.

[0058] The pipes between the upstream high-temperature flue gas source 16 and the first air pump 17, the pipes between the hot gas inlet 8 and the first air pump 17, the pipes between the hot gas outlet 9 and the second air pump 18, and the pipes between the second air pump 18 and the absorption tower are all covered with an insulation layer.

[0059] A one-way valve 19 is provided between the hot air outlet 9 and the second air pump 18, and a three-way valve 20 is provided on the pipe between the hot air inlet 8 and the first air pump 17. The three-way valve 20 is connected to the inlet of the second air pump 18 through the pipe.

[0060] In this system, the upstream high-temperature flue gas source 16 is used as the hot gas, which can effectively utilize the temperature of the high-temperature flue gas itself. However, the absorption tower has certain requirements for the temperature of the flue gas when treating high-temperature flue gas. Therefore, the first air pump 17 and the second air pump 18 are set to accelerate the transportation of high-temperature flue gas and reduce the heat exchange time. At the same time, the setting of the insulation layer can effectively reduce the heat loss. While effectively utilizing the high-temperature flue gas, it can also avoid the flue gas temperature from being too low.

[0061] Meanwhile, the constant pressure valve can maintain a certain pressure in the second chamber 7, which can prevent the continuous introduction of liquid into the second chamber 7 from causing liquid leakage from the micropore 11, and can also prevent the response speed from decreasing due to untimely liquid replenishment.

[0062] Demister working principle:

[0063] Under normal conditions, no gas is introduced into the first chamber 6 of the demister, while anti-clogging liquid is introduced into the second chamber 7. At this time, the temperature of the anti-clogging liquid is the ambient temperature. The pre-designed diameter of the micropores 11 causes the anti-clogging liquid to be unable to flow out of the micropores 11 under the action of its surface tension, and thus it is stored in the demister tube 3.

[0064] When the demister is in operation, high-temperature flue gas is introduced into the first chamber 6 to heat the anti-clogging fluid in the second chamber 7. As the temperature of the anti-clogging fluid increases, its surface tension decreases, and the liquid flows out from the micropores 11, diluting the droplets adhering to the demister surface and preventing evaporation and crystallization to form scale. Simultaneously, as the liquid accumulates on the demister surface, the influence of gravity on it increases, causing the accumulated droplets to fall under the influence of gravity, further reducing scale formation.

[0065] Working principle of the defogging system:

[0066] When the demister 13 does not need to be started, the three-way valve 20 connects the first air pump 17 and the second air pump 18, directly sending the high-temperature flue gas into the absorption tower.

[0067] When the demister 13 needs to be started, the three-way valve 20 connects the first air pump 17 and the hot gas inlet 8, sending high-temperature flue gas into the demister 13. Then, the high-temperature flue gas is discharged from the hot gas outlet 9 and enters the absorption tower through the second air pump 18. During this process, the anti-clogging liquid source 15 supplies anti-clogging liquid to the demister 13 through the constant pressure valve 14. When the pressure of the anti-clogging liquid in the demister 13 decreases, the constant pressure valve 14 opens to send in the anti-clogging liquid. When the pressure in the demister 13 recovers, the constant pressure valve 14 closes to maintain the pressure environment.

Claims

1. A demister for preventing surface scaling in an absorption tower, characterized in that, The system includes a main frame (1), in which a demisting assembly (2) is fixedly connected. The demisting assembly (2) includes several demisting pipes (3) arranged side by side, and a connecting pipe (4) is fixedly connected between adjacent demisting pipes (3). A partition (5) is fixedly connected inside each demisting pipe (3) and the connecting pipe (4), and the partition (5) is arranged along the axial direction of the demisting pipe (3) and the connecting pipe (4). The partition (5) divides the interior of the demisting pipe (3) and the connecting pipe (4) into a first chamber (6) and a second chamber (7). The side wall of the second chamber (7) is provided with several micropores (11). The side wall of the main frame (1) is provided with a hot air inlet (8), a hot air outlet (9) and an anti-clogging liquid inlet (10), respectively. The hot air inlet (8) and the hot air outlet (9) are connected to the first chamber (6), while the anti-clogging liquid inlet (10) is connected to the second chamber (7).

2. The demister for preventing surface scaling in an absorption tower according to claim 1, characterized in that, The main frame (1) is fixedly connected along the axial direction with multiple layers of demisting components (2), and the demisting pipe (3) in one layer of demisting component (2) corresponds to the gap of the demisting pipe (3) in the adjacent demisting component (2).

3. The demister for preventing surface scaling in an absorption tower according to claim 1, characterized in that, The partition (5) is fixedly connected with several heat-conducting plates (12) on the side facing the second chamber (7). The demister (3) and the connecting pipe (4) are made of heat-insulating material, or the outer wall of the demister (3) and the connecting pipe (4) is fixedly connected with a heat-insulating structure. The partition (5) and the heat-conducting plates (12) are made of heat-conducting material.

4. The demister for preventing surface scaling in an absorption tower according to claim 1, characterized in that, The maximum diameter of the micropore (11) Calculate using the following formula: in, To prevent the clogging fluid from being at the highest ambient temperature Surface tension at that time, To prevent the contact angle between the clogging fluid and the wall of the micropore (11), To prevent clogging, the density of the liquid is given, g is the acceleration due to gravity, and h is the height of the liquid surface. The calculation method is as follows: in, To prevent clogging of the liquid at the gas-liquid critical point temperature, the highest ambient temperature was used in the temperature calculation here. The vapor-liquid critical temperature of water Thermodynamic temperatures are used in all cases.

5. The demister for preventing surface scaling in an absorption tower according to claim 4, characterized in that, The minimum spacing between adjacent micropores (11) on the sidewall of the second chamber (7) Calculate as follows: The actual distance between the adjacent micropores (11) is greater than Furthermore, the micropores (11) are evenly distributed on the side wall of the second chamber (7).

6. The demister for preventing surface scaling in an absorption tower according to claim 5, characterized in that, When the demister (3) is a circular tube, calculate the maximum diameter of the micropore (11). liquid level height Where R is the outer radius of the circular tube. The azimuth angle of the suspended droplet.

7. A defogging system, characterized in that, The demister for preventing surface scaling in the absorption tower according to any one of claims 1 to 6 includes a demister (13) installed in the absorption tower. The anti-clogging liquid inlet (10) of the demister (13) is connected to a constant pressure valve (14) through a pipeline. The constant pressure valve (14) is connected to an anti-clogging liquid source (15) through a pipeline. The hot gas inlet (8) is connected to an upstream high-temperature flue gas source (16) through a pipeline. A first air pump (17) is provided between the hot gas inlet (8) and the upstream high-temperature flue gas source (16). The hot gas outlet (9) is connected to a second air pump (18) through a pipeline. The output section of the air pump is connected to the flue gas inlet of the absorption tower through a pipeline.

8. The defogging system according to claim 7, characterized in that, The pipes between the upstream high-temperature flue gas source (16) and the first air pump (17), the pipes between the hot gas inlet (8) and the first air pump (17), the pipes between the hot gas outlet (9) and the second air pump (18), and the pipes between the second air pump (18) and the absorption tower are all covered with an insulation layer.

9. The defogging system according to claim 7, characterized in that, A one-way valve (19) is provided between the hot air outlet (9) and the second air pump (18), and a three-way valve (20) is provided on the pipe between the hot air inlet (8) and the first air pump (17). The three-way valve (20) is connected to the inlet of the second air pump (18) through the pipe.

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