Regarding poor liquid drainage from the separator

1. Fluctuations in feed rate, temperature, and vacuum level can cause this phenomenon. 2. A small diameter of the liquid discharge pipe, partial blockage in it, or an obstruction in the downstream path can also lead to this issue. Stabilize the operating parameters and address the problem gradually

If the process parameters don’t fluctuate, could it be a problem with the demisting plate inside?

The increase in material viscosity is caused by the accumulation of material volume.

When materials accumulate on the demisting plate, it should lead to poor exhaust flow, thereby causing pressure to rise; this in turn promotes liquid drainage and should not result in suction

Waiting for the final result from your side. .

Is it a two-stage evaporation design by Saiding?

I think the principle is more or less like this: when the exhaust is not unobstructed and pressure builds up, it forces the liquid out to relieve that pressure; it takes some time to restore the pressure, and when the system pressure drops below the static pressure of the liquid, suction is created, and this process repeats itself – it’s a bit similar to surging!

What the original poster mentioned is an evaporator, whose gas-phase outlet is equipped with a fiber demister; after passing through this fiber demister, the gas stream is connected to the vacuum system. The liquid separated by the fiber demister can be smoothly discharged to the bottom of the separator through the downcomer at the beginning of operation ； After operating for a period of time, the liquid separated by the fiber demister remains in the downcomer, and the liquid level in this tube is higher than the liquid level at the bottom of the separator; sometimes, the liquid collected at the bottom of the separator even gets sucked back into the downcomer. After cleaning the fiber demister, the liquid separated by it can be discharged smoothly to the bottom of the separator through the downcomer ； After operating for a while, the liquid separated by the fiber demister would remain in the downcomer, causing the liquid level in that tube to be higher than the liquid level at the bottom of the separator; sometimes, this even led to the liquid collected at the bottom of the separator being sucked back into the downcomer. Drawing on our many years of experience in the design and operation of high-efficiency gas-liquid separators both domestically and internationally, I propose the following suggestions: 1. The problem lies in the selection of the separator. In operations using thin-film evaporators, the system either has high viscosity, is thermally sensitive and prone to self-polymerization or polycondensation, or crystallization occurs within the system; in such cases, a vacuum system is often required to enhance the evaporation process. Fiber-based separators such as screens and filters must not be used in such operating conditions. This is because the viscous froth, macromolecular gels, or saline froth carried by the secondary steam are carried by the airflow into the fiber internals, where they concentrate and aggregate or even crystallize, gradually blocking the flow channels within the fiber internals and causing the pressure drop to increase over time. Since the vacuum system is connected to the gas-phase outlet of the separator, the airflow exits from one section of the evaporator, enters the inlet side of the separator, passes through the fiber internals and the liquid-phase collection system, and then enters the vacuum system from the gas-phase outlet side of the separator. It can be seen that the absolute pressure on the inlet side of the fiber internals is high and the vacuum level is low, while the absolute pressure on the liquid-drop discharge side of the fiber internals is low and the vacuum level is high. Moreover, the pressure equilibrium equation for the fluid connection on both sides of the fiber internals is essentially satisfied: P (inlet side of fiber internals) = –ΔP (pressure drop during operation of fiber internals) + P (liquid-drop discharge side of fiber internals) + P (static head of the liquid level in the liquid-drop discharge pipe). At the beginning of operation, the fiber internals were clean and unobstructed; the DP (operational pressure drop across the fiber internals) was very low =~0, and P (the liquid level on the outlet side of the fiber internals) =~ P (the inlet side of the fiber internals) ； Thus, P (static head of the downcomer liquid level) =~0, and the downcomer discharges normally. After operating for a while, the fiber internals become clogged, resulting in poor airflow; the -DP (pressure drop across the fiber internals) increases significantly. Moreover, P (the pressure on the liquid outlet side of the fiber internals) is connected to the vacuum system, so the absolute pressure is very low ； For liquid levels in downcomer types, a higher liquid level is required in order to generate sufficient static head P (the static head of the liquid level in the downcomer) that can counteract the large pressure difference resulting from the operational pressure drop —DP (caused by the operation of the fibrous internals). As a result, the liquid level inside the downcomer becomes very high, which leads to poor drainage; in some cases, the liquid at the bottom of the separator is even drawn back into the downcomer to help establish this static head. 2. Solution: Make use of the existing separator housing, and at the same time upgrade the original fiber-based separation internals to high-efficiency vaned gas-liquid demisting separation internals along with an online washing system. This approach enables technical upgrades to be carried out while minimizing investment costs, thereby completely resolving the issue. We carried out similar technical upgrades on 4 evaporation crystallizers with a diameter of 7600 mm for a European multinational company’s factory in China; the internal components were manufactured and installed at a Chinese factory according to the designs, offering excellent cost-effectiveness and saving substantial amounts of money. 3. Compared with traditional foam separators with fiber structures, the feather-leaf type high-efficiency gas-liquid foam separator offers numerous advantages such as resistance to clogging, ease of cleaning and regeneration, high separation efficiency, lower operating pressure, smaller equipment size, no need to replace internal components, and reduced maintenance costs. It represents an excellent upgrade over traditional fiber-based foam separators, and this technology has been used to upgrade traditional fiber separators in nearly 100 installations worldwide. For detailed technical information, you can visit the direct link http://bbs.hcbbs.com/thread-1354813-1-1.html on this HCH Chemicals forum to learn more in detail. For more technical details and solutions, you can contact professional separation technology companies for collaboration.