Emulsion degassing kettle with pressure partition

Abstract

The utility model discloses an emulsion degassing kettle with pressure partitions, which is characterized in that a stirring shaft is arranged in a degassing kettle body, and the degassing kettle body is divided into an upper negative pressure area and a lower positive pressure area by a conical partition plate; a notch is formed in the center of the conical partition plate, and a bubble cap capable of moving up and down along the stirring shaft covers the notch; the positive pressure area is an emulsion degassing main area; according to the present invention, the to-be-degassed emulsion, the defoaming agent and the like are injected into the positive pressure region, and during the degassing process, the high degassing pressure of the positive pressure region can improve the surface energy required by bubble generation, substantially compress the bubble volume, inhibit the bubble expansion and diffusion, shorten the bubble life, and cannot form the stable foam layer; as time goes on, the partial pressure of water vapor in the gas phase is gradually increased, the bubble cap is jacked up when the pressure of the positive pressure area is increased, and the pressure of the positive pressure area is released, so that the influence of the water vapor on the degassing efficiency is effectively solved, and the degassing time is greatly saved.

Description

Technical Field

[0001] This utility model relates to the field of chemical equipment technology, specifically to an emulsion degassing kettle with pressure partitions, used to efficiently remove residual monomers from polymer emulsions while suppressing foam formation. Background Technology

[0002] Emulsion degassing, an important step in polymer emulsion production, aims to remove unreacted monomers remaining in the emulsion. These unreacted monomers are volatile organic compounds (VOCs). The principle of emulsion degassing utilizes the low boiling point and volatility of monomers. The emulsion is heated at a relatively low pressure, causing the residual monomers to vaporize and be extracted as a gaseous phase, thereby reducing VOCs.

[0003] The core challenge of emulsion degassing lies in the generation of degassing foam. This problem is rooted in the emulsion system itself: during degassing, the surfactants in the emulsion significantly reduce the surface tension of the liquid, resulting in a structurally stable and durable foam layer at the gas-liquid interface. Combined with the vacuum environment, the bubbles expand rapidly. If not controlled in time, the foam can fill the entire degassing equipment, leading to a series of problems: 1. The foam inhibits the effective escape of residual monomers, significantly reducing degassing efficiency; 2. After the foam bursts, residual monomers and emulsion adhere to vacuum pipes, condensers, and vacuum pump chambers, causing equipment contamination, flow blockage, reduced heat exchange efficiency, and deterioration or even damage to the vacuum pump, significantly increasing maintenance burden and downtime risk; 3. The foam itself contains emulsion droplets; if a large amount is removed, it will result in direct product loss, severely reducing production yield.

[0004] Currently, the most effective way to suppress and eliminate foam is to inject defoamers during the degassing process. However, the amount added is difficult to control precisely: too little defoaming will not have any effect, while too much will damage the stability of the emulsion or impair the performance of the final product (such as gloss and film-forming properties). Therefore, foam control has become a key bottleneck restricting degassing efficiency, improving economic efficiency, ensuring safety, and optimizing product quality. It is a core pain point that urgently needs to be addressed in current technological upgrades. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an emulsion degassing vessel with pressure partitions. The vessel body is divided into a positive pressure zone and a negative pressure zone by a conical partition. The pressure is alternately released by the periodic opening and closing of the bubble cap, thereby reducing foam generation and improving degassing efficiency.

[0006] To achieve the above objectives, the specific technical solution of this utility model is as follows:

[0007] This utility model provides an emulsion degassing vessel with pressure partitioning, including a degassing vessel body, and a stirring shaft arranged on the central axis of the degassing vessel body; the interior of the degassing vessel body is divided into a negative pressure zone at the top and a positive pressure zone at the bottom by a conical partition; a notch is provided at the center of the conical partition, and a bubble cover that can move up and down along the stirring shaft is covered on the notch; the stirring shaft passes through the negative pressure zone, the bubble cover, and the notch of the conical partition from top to bottom and enters the positive pressure zone, and a stirring paddle is arranged on the stirring shaft in the positive pressure zone;

[0008] The negative pressure zone is equipped with a vacuum extraction port for connecting to external vacuum equipment; the positive pressure zone is equipped with an emulsion inlet, an emulsion outlet, a defoamer injection port, and a degassing steam inner extension pipe, and the outer wall of the reactor in the positive pressure zone is equipped with a semi-pipe jacket.

[0009] The blister is lifted when the pressure in the positive pressure zone increases, connecting the positive pressure zone with the negative pressure zone. After the pressure in the positive pressure zone is released, it falls back to the notch position and together with the conical partition isolates the positive pressure zone and the negative pressure zone.

[0010] Considering that liquid droplets may be carried into the negative pressure zone during the degassing process, and these droplets are prone to condensation in the negative pressure zone, in the preferred embodiment, the height of the conical baffle gradually decreases from the inside to the outside along the radial direction, and the cone angle is 120° to 150°; a liquid receiving tank is provided at the edge where the conical baffle connects to the inner wall of the degassing vessel body, which is used to collect the condensate in the negative pressure zone, and the liquid receiving tank is connected to the drain port opened on the vessel body for discharging the condensate.

[0011] To ensure a tight seal when the blister pack contacts the notch, in a preferred embodiment, an annular flange is provided around the notch of the conical partition facing upwards; a groove is provided at the bottom of the blister pack opposite the annular flange; an O-ring is provided in the groove for sealing; when the annular flange is inserted into the groove, the positive pressure area and the negative pressure area are isolated.

[0012] To prevent the blister pack from being lifted too high and from hitting the top of the vessel body, a limiting plate is provided on the stirring shaft above the blister pack to limit the height of the blister pack's upward movement; furthermore, in order to enable the blister pack to move relative to the stirring shaft, the surface roughness of the stirring shaft Ra≤1.6, preferably Ra=0.4~0.8.

[0013] Preferably, the degassing steam inner extension pipe extends into the positive pressure zone from the bottom of the positive pressure zone, and its pipe diameter is DN50. The inserted part has several small holes with a diameter of 10 to 18 mm, and the total cross-sectional area of ​​the small holes is 2 to 4 times the cross-sectional area of ​​the degassing steam inner extension pipe.

[0014] To further monitor the safety of the degassing process and provide overpressure protection, the positive pressure zone is equipped with a liquid level switch port and a rupture disc port.

[0015] According to the preferred embodiment, the degassing vessel body has a length-to-diameter ratio of 2 to 6, and the semi-pipe jacket has a diameter of DN40 to DN80 for introducing heating or cooling media. The stirring impeller has a multi-layer blade structure, and the inner wall of the positive pressure zone is equipped with baffles.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention uses a conical baffle to divide the internal area of ​​the vessel into a positive pressure zone and a negative pressure zone, with a notch at the center. A bubble cover, capable of moving spontaneously based on the pressure difference and gravity between the two zones, is installed on this notch. The bubble cover creates a degassing + venting cycle throughout the degassing process. During the degassing stage, the two zones are separated. The emulsion is in the initial positive pressure stage in the positive pressure zone, where the temperature continuously increases with heat input, the viscosity decreases, and the saturated vapor pressure of the monomers in the emulsion increases. Therefore, the driving force for monomer mass transfer to the gas phase increases, accelerating the degassing rate. As time progresses, the partial pressure of water vapor in the gas phase gradually increases, causing the monomer partial pressure to decrease and the degassing rate to slow down. At this point, the bubble cover opens under the pressure difference, allowing for rapid pressure release and effectively solving the problem of water vapor affecting degassing efficiency, significantly saving degassing time.

[0018] This degassing reactor design can also effectively suppress the amount of foam generated and reduce the amount of defoamer used. This is because degassing mainly occurs in the positive pressure stage. Higher degassing pressure will increase the deformation energy required for bubble generation, while significantly compressing the bubble volume, inhibiting bubble expansion and diffusion, and shortening the bubble life, making it impossible to form a stable foam layer.

[0019] Other features and advantages of this invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1 A simplified structural diagram of an emulsion degassing reactor with pressure zones is shown.

[0021] Figure 2 A schematic diagram of the materials in an emulsion degassing vessel with pressure zones is shown.

[0022] Figure 3 A simplified diagram of the metal blister structure is shown.

[0023] In the diagram: 1-Degassing vessel body; 2-Half-pipe jacket; 3-Agitator shaft; 4-Bubble cap limiting plate; 5-Bubble cap; 6-Conical baffle; 7-Notch; 8-Liquid receiving tank; 9-Agitator; 10-Steam inner extension pipe; 11-Emulsion outlet; 12-Vacuum extraction port; 13-Emulsion inlet; 14-Rupture disc outlet; 15-Drain outlet; 16-Defoamer injection port; 17-Positive pressure zone vacuum extraction port; 18-Liquid level switch port; 19-Cooling (heating) water inlet and outlet; 20-Manhole; 21-Baffle plate; 22-Sealing ring groove; 23-O-ring seal; 24-Stuffing gland; 25-Stuffing gland. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0025] Figures 1 to 3 As shown, to effectively reduce the amount of foam generated and the height of the foam layer during degassing, and to reduce the amount of defoamer added, this utility model provides an emulsion degassing kettle with pressure partitions, such as... Figure 1 and Figure 2 As shown, the degassing vessel body is divided into upper and lower parts by a conical partition 6. The upper part is connected to an external vacuum pump through a vacuum extraction port 12, and is drawn to negative pressure by the vacuum pump, referred to as the negative pressure zone. The lower part is the positive pressure zone, where the tank wall is equipped with a semi-tube jacket 2. The positive and negative pressure zones are connected by a notch 7 at the center of the partition, and a "bowl-shaped" bubble cap 5 covers the notch. The bubble cap 5 can move up and down along the stirring shaft 3. In the initial state, the bubble cap 5 covers the notch 7, and the two areas are separated from each other. During emulsion degassing, the positive pressure zone... The monomers and moisture will enter the gas phase space in large quantities, causing the pressure in the positive pressure zone to rise. When the pressure rises to a certain value, the bubble cap 5 will be "lifted" and move upward along the stirring shaft 3. At this time, the two regions are connected, the positive pressure zone begins to be evacuated, the pressure drops rapidly, and the bubble cap 5 will move downward under its own gravity until it completely covers the gap 7. The two regions are completely isolated again, and the positive pressure zone begins a new round of pressure accumulation. During the above process, the negative pressure zone is always being evacuated and maintained at a certain vacuum level.

[0026] According to a specific embodiment of this utility model, the degassing vessel body adopts a vertical structure with a length-to-diameter ratio of 2 to 6. A larger length-to-diameter ratio can increase the gas flow rate inside the vessel, which is conducive to the rapid discharge of gas from the vessel. A stirring shaft 3 is arranged on the central axis of the degassing vessel body; the stirring shaft passes through the notch of the positive pressure zone, the bubble cap, and the conical partition from top to bottom and enters the negative pressure zone. A stirring paddle 9 is arranged on the stirring shaft in the negative pressure zone; the surface roughness Ra of the stirring shaft is ≤1.6, preferably Ra = 0.4 to 0.8.

[0027] In one specific embodiment, a bubble cap limiting plate 4 is provided on the stirring shaft 3 to restrict the upward movement of the bubble cap. If the stirring shaft is composed of multiple segments, the splicing flange can be used as the bubble cap limiting plate. The height of the limiting plate from the notch in the partition is preferably no more than 0.6m to prevent the bubble cap from taking too long to fall back or from tilting during the fall, thus preventing it from falling back properly. The bubble cap has a hollow "bowl-shaped" structure, through which the stirring shaft can pass. Figure 3 As shown: The inside of the blister pack has a groove 22, and an O-ring 23 is embedded in the groove. It can fit tightly with the annular flange on the partition notch to improve the sealing performance. The O-ring is made of fluororubber (FKM). When the blister pack can be made of metal materials such as S30408, S30403, S31608 or aluminum alloy, the part in contact with the stirring shaft is provided with a packing seal 24 and filled with soft sealing material. The sealing packing is made of materials that are wear-resistant, acid and alkali resistant, highly elastic, not easily broken, have a low coefficient of friction, and good self-lubricating properties, such as phenolic fiber and polytetrafluoroethylene fiber. The sealing packing is sealed by a packing gland 25. The packing gland 25 is made of engineering plastics with self-lubricating and corrosion resistance, such as polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), and polypropylene (PP).

[0028] Blister 5 can also be made of engineering plastics. If engineering plastics are selected as the material for the blister, there is no need to set filler seals. Engineering plastics should be self-lubricating, low in density, not easily broken, resistant to acid and alkali corrosion, and have a maximum working temperature of ≥150℃, such as PEEK, PTFE, PP, etc.

[0029] In one specific embodiment, the conical baffle of the degassing vessel is a cone, with its height gradually decreasing radially from the inside to the outside, and a cone angle of 120° to 150°. A liquid receiving groove, made of the same material as the vessel body, is provided at the edge where the conical baffle connects to the inner wall of the degassing vessel body for easy welding. The liquid receiving groove is used to collect condensate from the negative pressure zone and is connected to a drain port on the vessel body for discharging the condensate. The condensate in the negative pressure zone can flow into the liquid receiving groove at the bottom of the baffle; the liquid receiving groove, as part of the baffle, is 150mm deep and 250mm wide. The top notch of the conical baffle has a diameter of 500mm, and a 150mm high, 5mm thick annular flange is formed around the notch. This annular flange can be inserted into the groove inside the bubble cap and fits against the O-ring seal inside the groove to improve sealing. If the tangent of the lower end cap of the equipment is used as a reference, the baffle is located at 2 / 3 of the length of the straight section of the equipment.

[0030] In one specific embodiment, a stirring paddle 9 is provided on the stirring shaft in the positive pressure zone. The stirring paddle 9 has a multi-layer blade structure and the rotation speed is adjustable from 0 to 60 rpm. A turbulence baffle 21 is provided on the inner wall of the positive pressure zone of the degassing vessel to enhance the stirring effect.

[0031] A steam extension pipe 10 is installed in the positive pressure zone. It is inserted from the bottom of the degassing vessel. The diameter of the extension pipe is DN50. Several small holes with a diameter of 10-18mm (e.g., 10mm) are opened in the inserted part to facilitate the rapid diffusion of degassing steam. The sum of the cross-sectional areas of the small holes is equal to 2-4 times the cross-sectional area of ​​the pipe to ensure that the amount of steam injected meets the requirements of emulsion stripping.

[0032] In one specific embodiment, a DN150 emulsion outlet 11 is provided at the bottom of the positive pressure zone of the degassing reactor for discharging the degassed emulsion; two vacuum extraction ports 12 are provided at the top of the negative pressure zone of the degassing reactor, the two ports are arranged symmetrically at 180°, and the size is DN200; an emulsion inlet 13 with a size of DN150 is provided tangentially along the cylinder wall of the positive pressure zone for injecting the emulsion to be degassed; a rupture disc port 14 is provided below the conical baffle for overpressure protection of the equipment; a drain port 15 with a size of DN50 connected to the liquid receiving tank is used to discharge condensate; an antifoaming agent injection port 16 is provided at the upper part (gas phase space) of the positive pressure zone of the degassing reactor for injecting antifoaming agent; preferably, a positive pressure zone vacuum extraction port 17 with a size of DN250 is provided at the top of the positive pressure zone, and a switch valve is provided on the pipeline connected to it and connected to the vacuum pipeline of the negative pressure zone at the top of the degassing reactor. If the bubble cap cannot move upward due to a malfunction, the switch valve on the pipeline can be temporarily opened to connect the positive pressure zone and the negative pressure zone. A liquid level switch port 18 is provided at the upper part (gas phase space) of the positive pressure zone of the degassing vessel to determine the position of foam; a cooling (heating) water inlet and outlet 19 is provided on the half-pipe jacket of the positive pressure zone of the degassing vessel, and the inlet and outlet dimensions are the same as the half-pipe dimensions; a manhole 20 is provided at the top of the degassing vessel and the tank wall for equipment maintenance and cleaning.

[0033] The emulsion degassing reactor proposed in this utility model can be operated using the following process:

[0034] When the degassing vessel is working normally, the negative pressure zone is maintained at a constant vacuum level (generally 20KPa~40KPa) by an external vacuum pump. After the emulsion is heated by degassing steam or a half-pipe jacket in the positive pressure zone, the monomers and some water in the emulsion will evaporate into the gas phase space, causing the pressure in the positive pressure zone to rise. This creates an upward thrust on the contact surface between the bubble cap 5 and the notch 7. When the thrust is large enough to overcome the resistance of the upward movement of the bubble cap 5 (the weight of the bubble cap itself + the pressure in the negative pressure zone + the friction between the bubble cap and the stirring shaft), the bubble cap will be pushed upward. At this time, the two pressure zones are connected, and the monomers and water vapor in the gas phase of the positive pressure zone are extracted. When the pressures of the two zones tend to be equal, the bubble cap falls back under the action of gravity and finally covers the notch of the partition plate. At this time, the positive and negative pressure zones are isolated again, and the emulsion completes one degassing and exhaust cycle.

[0035] In the initial stage of positive pressure, the temperature of the emulsion will continuously rise with the input of heat, the viscosity will decrease, and the saturated vapor pressure of the monomer in the emulsion will increase. Therefore, the driving force for the mass transfer of monomer to the gas phase will increase, and the removal rate will accelerate. As time goes by, the partial pressure of water vapor in the gas phase will gradually increase, causing the partial pressure of monomer to decrease and the removal rate to decrease. At this time, the bubble cap will open in time, and the pressure will be released quickly, effectively solving the problem of the influence of water vapor on the degassing efficiency and saving degassing time to a large extent.

[0036] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A degassing vessel for emulsions with pressure zones, comprising a degassing vessel body, characterized in that, A stirring shaft is installed on the central axis of the degassing vessel body; the interior of the degassing vessel body is divided into a negative pressure zone at the top and a positive pressure zone at the bottom by a conical partition; a notch is provided at the center of the conical partition, and a bubble cover that can move up and down along the stirring shaft is covered on the notch; the stirring shaft passes through the negative pressure zone, the bubble cover, and the notch of the conical partition from top to bottom and enters the positive pressure zone, and a stirring paddle is installed on the stirring shaft in the positive pressure zone; The negative pressure zone is equipped with a vacuum extraction port for connecting to external vacuum equipment; the positive pressure zone is equipped with an emulsion inlet, an emulsion outlet, a defoamer injection port, and a degassing steam inner extension pipe, and the outer wall of the reactor in the positive pressure zone is equipped with a semi-pipe jacket. The blister is lifted when the pressure in the positive pressure zone increases, connecting the positive pressure zone with the negative pressure zone. After the pressure in the positive pressure zone is released, it falls back to the notch position and together with the conical partition isolates the positive pressure zone and the negative pressure zone.

2. The emulsion degassing reactor according to claim 1, characterized in that, The conical baffle gradually decreases in height from the inside to the outside along the radial direction, with a cone angle of 120° to 150°. A liquid receiving tank is provided at the edge where the conical baffle connects to the inner wall of the degassing vessel body. This tank is used to collect condensate from the negative pressure zone. The liquid receiving tank is connected to a drain port on the vessel body to discharge the condensate.

3. The emulsion degassing reactor according to claim 1, characterized in that, The conical partition has an annular flange facing upwards at the notch position; the bottom of the blister has a groove opposite to the annular flange; an O-ring seal is installed in the groove for sealing; when the annular flange is inserted into the groove, the positive pressure area and the negative pressure area are isolated.

4. The emulsion degassing reactor according to claim 1, characterized in that, The blister pack material is S30408, S30403, S31608, aluminum alloy, or engineering plastic; if it is made of metal, a packing seal and a packing gland are provided at the contact part between the blister pack and the stirring shaft to ensure the seal between the blister pack and the stirring shaft, and the sealing packing in the packing seal is phenolic fiber or polytetrafluoroethylene fiber.

5. The emulsion degassing reactor according to claim 1, characterized in that, A limiting plate is provided on the stirring shaft above the bubble cap to limit the height of the bubble cap; the surface roughness Ra of the stirring shaft is ≤1.

6.

6. The emulsion degassing reactor according to claim 1, characterized in that, The degassing steam inner extension pipe extends into the positive pressure zone from the bottom of the positive pressure zone. Its pipe diameter is DN50, and the inserted part has several small holes with a diameter of 10 to 18 mm. The total cross-sectional area of ​​the small holes is 2 to 4 times the cross-sectional area of ​​the degassing steam inner extension pipe.

7. The emulsion degassing reactor according to claim 1, characterized in that, The positive pressure zone is equipped with a level switch port and a rupture disc port for safety monitoring and overpressure protection.

8. The emulsion degassing reactor according to claim 1, characterized in that, The degassing reactor body has a length-to-diameter ratio of 2 to 6; the semi-pipe jacket has a diameter of DN40 to DN80 and is used to introduce heating or cooling media.

9. The emulsion degassing reactor according to claim 1, characterized in that, The impeller has a multi-layered blade structure, and the inner wall of the positive pressure zone is equipped with a baffle.

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