Working principle of gas-liquid separator

During cooling or pressurization of a saturated gas, some of the condensable gas components form small liquid droplets that flow along with the gas. The function of a gas-liquid separator is to treat gases containing a small amount of condensate, thereby enabling the recovery of the condensate or the purification of the gas phase. Its structure is generally a pressure vessel, with relevant air intake components and droplet capture components inside. The gas is generally discharged from the upper outlet, while the liquid phase is collected from the lower part.

There are two separation principles: First, separating a mixture by utilizing the difference in mass (weight) of its components (such as separation methods 1, 2, 3, 6). II. Separating mixtures by utilizing the different particle sizes in dispersed systems (such as separation methods 4 and 5). The separation methods include: 1. Gravity sedimentation: Due to the difference in density between gas and liquid, as the liquid flows together with the gas, it is affected by gravity and acquires a downward velocity, while the gas continues to flow in its original direction. In other words, there is a tendency for the liquid and gas to separate in a gravitational field; the liquid that moves downward adheres to the walls and collects there before being discharged through an outlet pipe. 2. Deflection separation: Due to the difference in density between gas and liquid, when they flow together, if an obstacle is encountered, the gas will be deflected aside, while the liquid, due to inertia, continues to move forward. The liquid that moves forward adheres to the surface of the obstacle and, under the effect of gravity, gathers together and is then discharged through a drain pipe. 3. Centrifugal separation: Due to the difference in density between gas and liquid, when they are mixed together and rotate, the liquid experiences a greater centrifugal force than the gas. As a result, the liquid tends to separate through centrifugal force; it adheres to the separation wall surface and gathers together under the influence of gravity, before being discharged through a drain pipe. 4. Screen separation: Due to the difference in particle sizes between gas and liquid, when they flow together, if they must pass through a screen, it works like sieving – the gas passes through while the liquid is trapped on the screen. Under the effect of gravity, the liquid flows downward to the bottom of the separator where it is discharged. . 5. Ultrafiltration separation: Due to the difference in particle sizes between gases and liquids, when they flow together, if filtration through micropores is necessary, it works like sieving – the gas passes through while the liquid is trapped on the microporous filter and flows downward under the effect of gravity to be discharged at the bottom of the separator. 6. Packing separation: Due to the difference in density between gas and liquid, when the two flow together, if they encounter an obstacle, the gas will be deflected away, while the liquid, due to inertia, continues to move forward. The liquid that moves forward adheres to the surface of the blocking packing and, under the effect of gravity, gathers together and is discharged through the outlet pipe. This post was last edited by zhangyong6404 on 2009-3-4 17:46.]

Our company uses liquid droplet catchers that feature baffle plates; the gas containing liquid is collected as liquid within the gas after several collisions with these baffle plates. :)

Can a cyclone separator be used as a gas-liquid separator?

Cyclone separator – for separating gas from solids. Centrifuge – for separating solids from liquids. For separating gas from liquids, tanks or towers are generally used

What I saw in our company was baffle separation

There are many separation structures used in gas-liquid separators, and the separation methods include: 1. Gravity sedimentation； 2. Baffle separation ； 3. Centrifugal separation ； 4. Screen separation ； 5. Ultrafiltration separation ； 6. Packing separation, etc. But overall, there are only two separation principles: first, separating a mixture by utilizing the difference in mass (weight) of its components (such as separation methods 1, 2, 3, 6). Gases and liquids have different densities; for the same volume, the mass of a gas is less than that of a liquid. II. Separating mixtures by utilizing the different particle sizes in dispersed systems (such as separation methods 4 and 5). The molecular arrangement in liquids is different from that in gases; gas molecules are far apart from each other, while liquid molecules are much closer together, which is why gas particles are smaller than liquid particles. I. Gravity settlement 1. Brief explanation of the principle of gravity settlement: Due to the difference in density between gas and liquid, when the liquid flows together with the gas, it is subjected to the force of gravity, resulting in a downward velocity, while the gas continues to flow in its original direction. In other words, there is a tendency for the liquid and gas to separate in a gravitational field; the liquid that moves downward adheres to the walls and accumulates there before being discharged through an outlet pipe. 2. Advantages and disadvantages of gravitational settling. Advantages: 1) Simple design. 2) The equipment is simple to manufacture. 3) Low resistance. Disadvantages: 1) The separation efficiency is the lowest. 2) The equipment is large in size. 3) It takes up a lot of space. 3. Improvements: Methods to improve gravity settling: 1) Install internal components and employ other separation methods. 2) Increase volume. 4. Since gas-liquid mixtures are always in a gravitational field, gravitational settling is also widespread. Due to the inherent limitations of gravity sedimentation, researchers were forced to develop more efficient gas-liquid separators, which led to the emergence of baffle separation and centrifugal separation. II. Bypass separation 1. Brief description of the principle of bypass separation: Due to the difference in density between gas and liquid, when they flow together, if an obstacle is encountered, the gas will be deflected aside, while the liquid, due to inertia, continues to move forward. The moving liquid adheres to the surface of the obstacle and, under the effect of gravity, gathers together and is discharged through a drain pipe. 2. Advantages and disadvantages of baffled separation: Advantages: 1) Higher separation efficiency compared to gravity sedimentation. 2) The volume-specific gravity settlement is greatly reduced, so the baffle separation structure can be used in (high) pressure vessels. 3) Stable job. Disadvantages: 1) The separation load range is narrow; beyond the specified flow rate of the gas-liquid mixture, the separation efficiency drops sharply. 2) The resistance is greater than the gravitational settlement. 　　 3. Improvements: Based on the principle of baffled separation, the faster the flow rate of the gas-liquid mixture, the greater its inertia, which means a stronger tendency for gas-liquid separation and therefore a higher separation efficiency. However, in practice the situation is exactly the opposite. Why is that? The reasons are as follows: 1) At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the separation load per unit time, and the shorter the residence time of the mixture in the separator. 2) As the gas flows in a tortuous path, it also pushes the liquid that has already adhered to the wall in the direction of the gas flow. If the liquid has not yet escaped this pushing force by the time it reaches the edge of the collection wall, then the liquid that is attached to the wall will be carried away by the gas again. At a constant gas-liquid ratio, the greater the flow rate of the gas-liquid mixture, the stronger the force exerted by the gas to push the liquid forward. As a result, the liquid reaches the edge of the collection wall in less time, while the time it takes for the liquid to reach the bottom remains unchanged. This means that more liquid that has already reached the wall is carried away without being separated. 3) Liquids do not have a fixed shape and are prone to breaking apart. As they come into contact with the wall, they form smaller droplets that return to the gas phase. As the flow velocity increases, the impact force of the liquid against the collection wall grows, leading to greater fragmentation. We know that the smaller the droplets, the less inertia they have, and thus they are more easily carried away by the gas. Now that the cause has been identified, how can it be improved? 1) Regarding the first point, the volume of the separator can be increased, which in turn reduces the flow velocity. 2) Regarding the second point, if we prevent the liquid that has already contacted the wall from flowing to the edge of the collection wall, or if we separate the gas from the liquid that has already contacted the wall so as to eliminate or reduce any driving force, the separation efficiency of the baffle separator will **improve**. 3) Regarding the third point, if we modify the rigid collection wall to reduce the impact force of droplets hitting the wall, then the separation efficiency of the deflector separator will also **improve**. III. Centrifugal separation 1. Brief description of the principle of centrifugal separation: Due to the difference in density between gas and liquid, when they are mixed together and rotate, the liquid experiences a greater centrifugal force than the gas. As a result, the liquid tends to separate through centrifugal force; it adheres to the separation wall surface and gathers together under the influence of gravity before being discharged through a drain pipe. 2. Advantages and disadvantages of centrifugal separation: Advantages: 1) Higher separation efficiency compared to gravitational sedimentation. 2) The volume-specific gravity sedimentation is greatly reduced, so centrifugal separation structures can be used in (high)-pressure vessels. 3) Stable job. Disadvantages: 1) The separation load range is narrow; beyond the specified flow rate of the gas-liquid mixture, the separation efficiency drops sharply. 2) The resistance is greater than the gravitational settlement. 　　 3. Improvements: Based on the principle of centrifugal separation, the faster the flow rate of the gas-liquid mixture, the greater the centrifugal force, which means a greater tendency for gas-liquid separation and therefore a higher separation efficiency. Yet in practice, the situation is exactly the opposite. Why is that? The reasons are as follows: 1) At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the separation load per unit time, and the shorter the residence time of the mixture in the separator. 2) As the gas swirls, it also pushes the liquid that has already adhered to the wall in the direction of the gas flow. The flow of this liquid downward is hindered, and as the thickness of the liquid layer attached to the wall increases, the effect of the gas-liquid shear force grows; in other words, the liquid that has adhered to the wall becomes more likely to return to the gas phase and be carried away. At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the force exerted by the gas to push the liquid forward. As a result, more liquid is separated per unit of time. Additionally, the thicker the liquid layer is, the more liquid that has already adhered to the wall gets carried away without being separated. 3) Liquids do not have a fixed shape and are prone to breaking apart. As they come into contact with the wall, they form smaller droplets that return to the gas phase. As the flow velocity increases, the impact force of the liquid against the collection wall grows, leading to greater fragmentation. We know that the smaller the droplets, the less inertia they have, and thus they are more easily carried away by the gas. Now that the cause has been identified, how can it be improved? 1) Regarding the first point, the volume of the separator can be increased, which in turn reduces the flow velocity. 2) Regarding the second point, if we separate the gas from the liquid that has already adhered to the wall, thereby preventing or reducing the driving force, the separation efficiency of the centrifugal separator will **increase**. 3) Regarding the third point, if we modify the rigid collection wall to reduce the impact force of droplets hitting it, then the separation efficiency of the centrifugal separator will also **improve**. IV. Packing Separation 1. Brief description of the principle of packing separation: Due to the difference in density between gas and liquid, when they flow together, if an obstacle is encountered, the gas will be deflected, while the liquid, due to inertia, continues to move forward. The liquid that moves forward adheres to the surface of the obstructing packing and, under the effect of gravity, gathers together and is discharged through a drain pipe. Since the packing has a much larger area of collecting walls for obstruction compared to ordinary baffle separation, and due to the repeated baffle actions, the liquid tends to adhere to these walls, its separation efficiency is improved. 2. Advantages and disadvantages of filler separation: Advantages: 1) The separation efficiency is higher than that of conventional baffled separation or conventional centrifugal separation. 2) Simple structure, only one packing frame needs to be made. 3) Its volume is smaller than that of ordinary baffle separators or ordinary centrifugal separators. Disadvantages: 1) The separation load range is narrower; once the specified flow rate of the gas-liquid mixture or the liquid-gas ratio is exceeded, the separation efficiency drops sharply. 2) The resistance is greater than that of ordinary baffle separators or ordinary centrifugal separators. 3) The work is relatively unstable, and it’s easy to carry liquid. 4) The filler is fragile. 5) The filler is prone to clogging. 6) The selection of filler is very important. 　 3. Improvements: From the principle of filler separation, the greater the flow rate of the gas-liquid mixture or the higher the liquid-to-gas ratio, the greater the tendency for gas-liquid separation, and thus the separation efficiency should be higher. However, in practice it is the opposite. Why is that? The reasons are as follows: 1) At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the separation load per unit time, and the shorter the residence time of the mixture in the separator. 2) As the gas causes turbulence, it also pushes the liquid that has already adhered to the wall in the direction of the gas flow. The flow of the liquid is hindered, and as the thickness of the liquid layer on the wall increases, the area available for gas flow decreases. This results in higher velocities of both the gas and the liquid. Under these combined effects, the liquid that has adhered to the wall can be easily carried away by the gas again. If the flow rate increases or the liquid-to-gas ratio increases, it will be relatively easier to carry liquid. 3) There are many types of fillers, each with different separation capabilities. However, all types of fillers can easily become clogged by solid impurities, as even the flow of liquid is complicated or even blocked; it is therefore normal for solid impurities to cause blockages at certain points. Now that the cause has been identified, how can it be improved? 1) Increase the volume of the separator, which in turn reduces the flow rate. 2) Use structured packing. 3) Insert a baffled separation or centrifugal separation in series in front of it. V. Screen Separation 1. Brief Explanation of the Principle of Screen Separation: Due to the difference in particle sizes between gases and liquids, when these two are mixed and flow together, if they must pass through a screen, it functions like a sieve – the gas passes through, while the liquid is trapped on the screen and, under the effect of gravity, flows downward to the bottom of the separator where it is discharged. The screening effect of the mesh is similar to that of baffled separation; however, its surface area for blocking and collection per unit volume is larger than that of the packing, there are more baffling occurrences per unit volume, and the pore size of the mesh is smaller due to the surface tension of the liquid, which enables it to perform a screening function. 2. Advantages and disadvantages of screen separation: Advantages: 1) The separation efficiency is higher than that of packing separation. 2) Simple structure, only one screen fixing device needs to be made. 3) The volume ratio of the filler separator is smaller. Disadvantages: 1) The separation load range is very narrow; once the specified flow rate of the gas-liquid mixture or the liquid-to-gas ratio is exceeded, the separation efficiency drops sharply. 2) The resistance is greater than that of ordinary baffle separators or ordinary centrifugal separators. 3) The work is unstable, and it’s easy for liquid to get involved. 4) It gets clogged easily. 6) The mesh size and material selection of the screen are very important. 　 3. Improvement: Based on the principle of separation from a mesh screen, the higher the flow rate of the gas-liquid mixture or the greater the liquid-to-gas ratio, the greater the tendency for gas-liquid separation should be, and thus the separation efficiency should be higher. However, in practice it is the opposite. Why is that? The reasons are as follows: 1) At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the separation load per unit time, and the shorter the residence time of the mixture in the separator. 2) As the gas flows, it also pushes the liquid that has adhered to the wall in the direction of the gas flow. The downward movement of the liquid is hindered, and as the thickness of the liquid layer on the wall increases, the flow area available for the gas decreases, leading to liquid blockage. The flow velocities of both the gas and the liquid increase, and under these combined effects, the liquid that has adhered to the wall can be easily carried away by the gas again. If the flow rate increases or the liquid-to-gas ratio increases, liquid entrainment will occur easily. 3) Screens with different mesh counts have varying separation capabilities, but all types of screens are prone to being clogged by solid impurities, as even the flow of liquids is slow; it is therefore normal for solid impurities to cause blockages at certain points. 4) Different materials for the mesh result in varying separation capabilities, and the main reason for this is related to the wetting properties of liquids. If a material can reduce the wetting of liquids on its surface, it will facilitate the flow of those liquids. Ordinary meshes are typically made of regular steel wire or stainless steel wire, but no matter what type of mesh is used, it is not possible to completely overcome the issue of liquid wetting on the surface. Now that the cause has been identified, how can it be improved? 1) Increase the volume of the separator, which in turn reduces the flow rate. 2) Re-select the mesh count and material of the screen. 3) Insert a baffled separation or centrifugal separation in series in front of it. VI. Microfiltration Separation 1. Brief Explanation of the Principle of Microfiltration Separation: Due to the difference in particle sizes between gases and liquids, when these two are mixed and flow together, if microfiltration is required, it functions like sieving – the gas passes through, while the liquid is trapped on the microfilter and, under the effect of gravity, flows downward to the bottom of the separator where it is discharged. The sieving function of a microfiltration separator is true sieving; the diameter of its micropores is generally below 50 micrometers, which means that liquid particles larger than this pore diameter cannot pass through. Of course, its separation mechanism is relatively complex; since it is a microscopic process, in-depth research is required. The blocking and collection surface area of microfiltration separators is extremely high per unit volume, and the number of deflection and screening cycles per unit volume is greater than that of wire meshes. 2. Advantages and disadvantages of microfiltration separation. Advantages: 1) Extremely high separation efficiency. 2) Simple structure; only a microporous filter fixing device needs to be fabricated. 3) It has a smaller volume compared to the screen separator. Disadvantages: 1) The range of separable load is extremely narrow; once the specified flow rate of the gas-liquid mixture or the liquid-to-gas ratio is exceeded, the separation efficiency drops sharply. 2) Beyond the specified flow rate or liquid-to-gas ratio, liquid resistance occurs easily, resulting in a sharp increase in resistance. 3) The resistance is greater than that of ordinary baffle separators or ordinary centrifugal separators. 4) The working electrode is highly unstable and prone to carrying liquid. 5) Prone to clogging. 6) The type of microfiltration filter and the choice of material are very important. 　 3. Improvements: From the principle of microfiltration separation, the higher the flow rate of the gas-liquid mixture or the greater the liquid-to-gas ratio, the more difficult it is to separate the gas from the liquid. Why is that? The reasons are as follows: 1) At a constant gas-liquid ratio, the higher the flow rate of the gas-liquid mixture, the greater the separation load per unit time, and the shorter the residence time of the mixture in the separator. 2) The gas exerts a strong shear force on the liquid that has already adhered to the wall, leading to obvious problems: A The liquid cannot flow downward smoothly; as the thickness of the liquid layer attached to the wall increases, the flow area available for the gas decreases, which easily results in liquid blockages. Moreover, both the velocity of the liquid and that of the gas increase, and under these combined effects, the liquid that is already attached to the wall can be easily carried away by the gas again. If the flow rate increases or the liquid-to-gas ratio increases, liquid entrainment will occur easily. For liquid particles of type B, once they have passed through a microporous filter without being separated, it is no longer possible to separate them physically (except through adsorption separation), as their particle size is too small. 3) Microfiltrators with different pore diameters exhibit varying separation capabilities, but all types of microfiltrators are highly susceptible to clogging by solid impurities. 4) Different materials used for microfiltrators result in varying separation performances, and the main reason for this is related to the wetting property of liquids on their surfaces. If a material can reduce the wetting of liquids on its surface, it will facilitate the flow of the liquid and alleviate liquid resistance. Materials for microfiltrators include ceramics, glass fibers, and powder metallurgy; however, no matter what type of microfilter is used, it is not possible to completely solve the problems of liquid surface wetting and liquid resistance. Now that the cause has been identified, how can it be improved? 1) Increase the volume of the separator, which in turn reduces the flow rate. 2) Re-select the types and materials of the microfiltration filters. 3) Insert a baffled separation or centrifugal separation in series in front of it. Reference: http://www.epclean.com/Edu/Course/View/980.html Forum reference: http://bbs.hcbbs.com/thread-294099-1-1.html