What is full vacuum distillation?
Thread Content
We use liquid ring vacuum pumps or steam jet pumps to create a vacuum in the distillation process; the vacuum level can reach -98 KPa, with lower values of up to -95 KPa. This distillation process has been ongoing for 14 years. The liquid being distilled contains catalysts and high-boiling substances. Question: With such a high vacuum level, won’t those high-boiling substances evaporate? Currently, the measurement of high-boiling substances in the finished product occasionally exceeds the specified limits; the tower is operating in full reflux mode, yet these high-boiling substances still exceed the limits sometimes. Question: Is it correct to use full vacuum distillation in this case?
This post was last edited by *amingteda on 2022-12-13 20:14. Generally, this problem does not occur in full vacuum distillation. 1. It is necessary to clearly analyze whether the excessive heavy components at the tower top are the same ones monitored on a regular basis 2. Has there been any change in the concentration of the feed recomponents, such as an increase?
1. Is it continuous distillation? If so, is the feed temperature at the specified level? 2. Whether the packing or components inside the tower are in good condition. 3. Is the reflux distributor in good condition?
Check the data on the relationship between the boiling point of a substance and its vapor pressure. At this temperature, if the vapor pressure of the boiling mixture is still below 1 kPa, its concentration at the top of the tower will increase due to reflux, reaching a level that was once considered acceptable but is no longer so. Could it be that the boiling mixture in the entire system isn’t being removed in time, resulting in an increase in its concentration? Or perhaps the performance of the tower has declined due to blockages or fouling
Check the packing, distributor, and whether the temperature is too high; reduce the reflux ratio.
There are many reasons for the excessive levels of heavy components at the top of the tower: 1. Changes in feed composition and temperature； 2. Is the temperature at the bottom of the tower or the concentration of the components from the top of the tower controlled too low? ； 3. Is the temperature of the reflux higher than before? 4. Whether the feed contains water. 5. Packing or distributor issues.
It is likely that too many impurities are attached to the surface of the packing, which reduces the efficiency of distillation and increases the amount of heavy components at the top of the tower