Lower column liquid level of air separation distillation tower
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The liquid level in the lower section of the air separation distillation column cannot be controlled properly. The instrumentation staff checked and found that the transmitters are functioning normally, the pressure transfer pipes are unobstructed, the liquid is being discharged in the correct direction, and the electric heating system is also working properly. Process engineers always suspect problems with the instruments; it is difficult to maintain the liquid level at the desired parameters, although the valves operate properly. The process instruments were used in conjunction to blow nitrogen into the pressure pipe on the positive pressure side, in an attempt to force the liquid phase inside; this was done for an hour with no results. It’s impossible to determine the cause of the problem at the moment; it’s hard to tell whether the reading shows the actual liquid level. I hope experienced teachers can help analyze the reasons.
Try using a float level gauge or a double-flange level gauge.
From an instrumentation perspective: 1. Try to increase the damping time a bit； 2. Two small accumulation tanks should be installed on the high and low pressure sides where pressure is taken, insulated, and the liquid within them should be drained regularly ； 3. Is the pressure measurement location inappropriate? From a process perspective: 1. Try to modify the PID parameters ； 2. Switch to manual mode, open the valve to a certain degree, and try making adjustments. 3. Has there been a significant change in the feed rate or the pressure of the tower? This post was last edited by NEWAUTO on 2008-3-2 17:24.]
The liquid being blown out through the negative signal pressure tube may be caused by an excessively high level of liquid in that section; draining the liquid from there will prevent any liquid from being blown out through the negative signal tube. If this does not resolve the issue, try using the positive signal corresponding to the resistance in the lower tower as a substitute for the positive signal related to the liquid level there (since these two signal tubes are at the same height in the lower tower, they can be used interchangeably). Give it a try!
What are the reasons for the decrease in the light liquid level in a distillation tower?
We use equipment that has been modified; we handle the overall installation. For the cold boxes, ordinary differential pressure transmitters are used, and ordinary copper pipes are employed for the pressure guiding tubes – no heat tracing is used, and it works very well. I think the problem lies with the process itself; sometimes when the process adjustments aren’t proper, people tend to blame the instruments
Generally, air separation towers are equipped with heating elements at the bends of the pressure tapping points in the normal phase to ensure complete vaporization of the liquid phase; check for current to confirm that the heating elements are functioning properly. Additionally, positive-pressure tapping ports usually have two outlets; try replacing them to see if it works properly. I used to encounter this problem often too; sometimes just opening the positive pressure pipe and blowing into it would solve it. As for the liquid in your negative pressure tube, it’s possible that the liquid level is set too high; lowering it should resolve the issue.
Note: If the problem still isn’t resolved, try using the positive signal from the resistance in the lower tower as a substitute for the positive signal related to the liquid-air level (since these two signal tubes are at the same height in the lower tower, they can be used as substitutes). Give it a try! Correction: If the problem still isn’t resolved, try using the positive signal from the resistance in the lower tower as a substitute for the negative signal related to the liquid-air level (since these two signal tubes are at the same height in the lower tower, they can be used as substitutes). Try it!