The gas-liquid separator must ensure the diameter of the separated droplets

Reply to 1# woliaibo: In applications for gas-liquid separation that meet the requirements of industrial production, the removal efficiency of liquid droplets in the gas stream should be such that droplets larger than 10 microns are removed at a rate of 3N, meaning 99.9% removal of droplets larger than 10 microns is sufficient to meet the standards for normal industrial operations. For special occasions, there are also different requirements such as 8 microns*3N, 5 microns*3N, 3 microns*3N, 1 micron*3N, 0.3 micron*3N, etc. The removal of droplets larger than 5 microns can be achieved through aerodynamic methods, while the removal of droplets smaller than 3 microns requires the use of membrane cores with special coalescing properties. It should be noted that coalescing membrane cores and filtering elements have completely different functions; a filtering element with a size of 0.3 microns cannot ensure the removal of droplets sized at 0.3 microns * 3N, whereas only a coalescing membrane core of 0.3 microns can do so. In the previous discussions, I mentioned that filter elements can only effectively remove solid particles with a fixed equivalent diameter from the flow field in a quantitative manner; whereas for the quantitative removal of liquid droplets or gel particles with varying diameters in the flow field, dynamic removal and coalescing membrane cores are the only methods that can achieve this.

Reply to 2# luoli519: Can droplets in gases be removed using the principle of ultrafiltration? Using aerodynamic removal, the calculated cylinder diameter is too large

Reply 3# woliaibo: A super coalescing separator can be used to separate droplets from the air flow. However, the coalescing filter-type separator is only suitable for situations where the liquid content in the feed gas is low, the gas processing volume is not large, and the process requirements allow for intermittent shutdowns. The gas-liquid separators designed on our technical platform, under the same operating conditions, often have a diameter that is 30% or more smaller than that of filter element-type separators. I’m not sure if the design results for domestic technology platforms are the same. As far as I know, there is no relatively accurate kinetic model available in the country, which makes it impossible to carry out accurate design. The coalescing filter element separator is a separator with accurate quantification. For a kinetic separator to compete with it, the kinetic model must be accurate, and this cannot yet be achieved with domestic technology platforms.

Reply to 4# luoli519: Does a coalescing separator have two filter elements? One is a coalescing filter element and the other is a separation filter element. It can ensure the precision of separation, but the design isn’t very precise either; everything needs to be enlarged to ensure its operational capability, right?~~~~~

Reply to 5# woliaibo: The function of a coalescing filter element is to cause tiny liquid droplets to coalesce and grow into larger droplets; indeed, these larger droplets in the airflow still need to be separated from the airflow using other methods. Since the equivalent diameter of droplets decreases as they flow through mechanical orifices with the airflow, and then increases again due to surface tension after passing through those orifices, it is recommended that gas-liquid separation devices avoid using mechanical orifice-based components for quantitative separation (including filters, membrane screens, wire meshes, packing, and filter media).

Reply to 6# luoli519: Coalescence can only be applied to larger particles, while separation is usually very precise. Would combining coalescence with a cyclone separator yield better results?

Reply to 7# woliaibo: Yes, fine coalescence involves causing extremely small liquid droplets to collide with each other; through surface free energy, these countless tiny droplets are brought together to form larger droplets that are easier to separate. The dynamic and quantitative removal of such large droplets is generally achieved using multi-factor cyclone separators or high-efficiency dual-effect microchannel vane separators.

Reply to 8# luoli519: Fine coagulation means coagulating first and then separating, with two layers of mesh. Cyclone centrifugal separation is used for pretreatment; these three components are generally used together, right?

Reply to 9# woliaibo: To clarify further, any mechanical filtering device, including filters and membrane filters, cannot be used for the quantitative separation of liquid droplets from air streams. The so-called two-layer network can achieve coalescence, but it may not be able to achieve quantitative separation of droplets. As for cyclone separators, they can be used to separate liquids and solids from the gas phase. Domestic cyclone separators have very low separation accuracy due to their large diameter; it should be noted that within an appropriate range of gas flow velocities, the separation accuracy and efficiency are inversely proportional to the rotation radius of the gas flow in the cyclone separator. I wonder if anyone has seen multi-factor cyclone separators used abroad; their cyclone diameter is less than 50 millimeters. Compared to the cyclone separators in China, which have diameters of several meters, one can easily imagine their efficiency and precision. Domestic cyclone separators are typically used for pre-treatment, whereas multi-factor cyclone separators used abroad can be employed for fine-tuning the purification process, achieving 99.9% separation of liquid droplets with a diameter of 10 microns and solid particles with a diameter of 8 microns. It is recommended that everyone learn about this new technology and equipment from large enterprises such as Shenhua and Sichuan Petrochemical of CNPC, which use foreign multi-factor cyclone separators, in order to improve the separation technology and the design capabilities of complete sets of equipment among domestic engineering companies.

Reply to 10# luoli519: I know that the coagulation and separation devices available in China are not capable of achieving quantitative separation. We can’t figure it out either; our measuring devices aren’t accurate enough.