Why is the liquid level in the reflux tank lower as the temperature at the bottom of the distillation tower increases?
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In a typical distillation column system, when the temperature at the top of the column becomes too low compared to the specified value, the liquid level in the reflux tank drops. At this point, the steam supply to the bottom of the column is increased, which raises the temperature there significantly above the specified level; yet the liquid level in the reflux tank still does not increase!
Heat the bottom of the tower too quickly; do it slowly； At this point, if you stop heating, the liquid level at the bottom of the tower will rise rapidly, and it is possible for the tower to be flooded
The best thing to do is: stop and try not to drive again
Reduce the reflux and increase the top temperature of the tower
It’s simple: first, we need to analyze the root cause of the decrease in the liquid level in the reflux tank. This has nothing to do with the temperature of the overhead condenser. We should first check whether there is a significant increase in the pressure at the top of the tower; if it’s a vacuum tower, a fluctuation of 10 kPa can result in too little liquid accumulating on the upper trays of the distillation column, preventing the light components from evaporating promptly. Increasing the steam supply at this time may cause a temporary rise in the liquid level of the reflux tank, but this is just an illusion. After about ten minutes, the liquid level in the reflux tank will drop rapidly. The real reason for this is that excessive steam leads to a rapid rise in temperature, resulting in no liquid remaining on the upper trays, while the reflux tank continues to be emptied through reflux. It’s not that the components cannot be evaporated. To address this issue, we first need to determine the proportion of light components by taking samples, then reduce the amount of reflux taken from the tank. Second, we can reduce the reflux rate and lower the temperature at the bottom of the tower. Third, we can increase the feed and steam supply while keeping the reflux unchanged. The most reliable approach is the third one, although it’s also the most difficult to implement. The second option is less reliable
It would be best to accompany this question with a flowchart; visual aids make things more intuitive and facilitate discussion. First, clarify what a “classic distillation system” is, and then discuss the problems that arise from not controlling the parameters according to the operating specifications, as well as the reasons behind them. For reference.
Haha, a classic distillation system features reflux and heating, with no side streams. . . . . ;P
Is the pressure difference of the tower high? Has there already been a situation of the tower being flooded?
Xiao Ming is an expert; at least he has a thorough understanding of the basic theories! PS: For such issues, explaining them using the three concepts of balance is the clearest approach!
The number of variables in a distillation column is not limited to just the top temperature, the liquid level in the reflux tank, the vapor at the bottom of the column, and the bottom temperature – these are far from enough. For example, when running a business with a store, one needs to calculate the profits and losses for a month; you only report the purchases and sales, but most other factors aren’t taken into account. How can one calculate this accurately?
Raise the top temperature to the normal range first before checking