Seeking advice on challenges encountered with distillation towers
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I’ve run into a rather tricky problem recently. It involves a regular distillation tower that operates under negative pressure, with steam at 1.4 Mpa serving as the heat source. The amount of steam entering the reboiler is controlled using a control valve; previously, a steam flow rate of around 30% through the valve was sufficient to achieve a flow rate of 3 t/h. Recently, however, even with the valve fully open at 100%, the flow rate remains only 3 t/h. The steam pressure is fine, and the trap at the reboiler outlet was also inspected and found to be in good condition. As a result, the temperature at the bottom of the tower fails to increase, which is quite confusing. I would be very grateful if experts could help resolve this issue. Thank you!
We also have similar problems on site; actually, it’s easy to identify the issue by checking certain parameters. If there is a pressure gauge inside the heat exchanger, check whether the pressure on the steam side of the heat exchanger is much higher now than before It is precisely because the pressure on the secondary side of the control valve increases, which in turn reduces the pressure difference before and after the control valve, that the flow rate remains constant while the opening degree increases. Why is the pressure on the steam side of the heat exchanger high? The reason is simple: the heat exchange efficiency declines, and the steam does not have enough time to condense. There is adhesion of material on the process side of the heat exchanger, which affects its heat exchange efficiency; it may be necessary to clean the heat exchanger. If the pressure on the steam side remains the same as before, then there is a problem with the control valve or flow meter; it’s sufficient to remove them and check them (of course, in that case, the actual amount of steam entering the heat exchanger could be much higher than 3 t/h, and the temperature and pressure inside the distillation tower will also be different; you can simply compare the operating parameters). It’s not scary to encounter problems; what’s scary is failing to actually take the data and compare it. Once you have all these details right in front of you, everything will become clear!
It’s probably still a problem with the strainer; try opening the bypass slightly!
Check if the composition of the material at the bottom of the tower has changed
If the device is fine, it must be that the materials have changed
I fully agree with your view; I too doubt this situation, but I can’t be sure. The pressure at the site has indeed increased. We plan to open and clean the reboiler soon. Thank you!
Looking forward to seeing the photos when you open the heat exchanger, to see how much is stuck to the tube walls