What could be the reasons for the high moisture content of the finished product at the bottom of the tower?
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We have a floating valve column here that uses an DMF aqueous solution for the separation and extraction of DMF; the finished product is obtained at the bottom of the column, through vacuum distillation. The moisture content in the normal product is below 0.7%. These past couple of days, all parameters have remained unchanged, but the moisture content at the bottom of the column has risen to around 2%, and the output is also unstable. I would like to ask everyone if there could be any issues (the column has not yet been disassembled).
Can incomplete dehydration earlier lead to excessive water intake later?
The increase in water content at the bottom of the tower indicates that there are still parameter changes, you just haven’t noticed them; adjustments should be made promptly； If it still fails after adjustment, then there might be a leak in the reboiler, with steam leaking into the product in the tower bottom. We have a tower in which the product is collected at the bottom of the tower; the high moisture content is caused by insufficient temperature at the bottom of the tower, inadequate steam supply, or fluctuations in steam pressure ； Second, the product at the bottom of the tower will only be of satisfactory quality once it has accumulated to a certain amount ； Third, the reboiler is leaking.
There is a slight leak at the tube sheet of the reboiler tubes, allowing steam to enter the material and resulting in an elevated moisture level. Thank you
Two possibilities； First, the moisture content in the feed composition has increased; second, there is a leak in the reboiler. The second possibility seems more likely. You can conduct an analysis of the feed composition – if there is a high amount of water present, you can use material balance calculations for the top and bottom streams of the tower to estimate how much water is introduced and how much water is removed. If the water level is normal, then it’s the reboiler at the bottom of the tower that is leaking
If it’s the situation you described, then it’s necessary to stop the machine in order to repair the tube sheet of the reboiler tubes
This should be solvable using the common problem-solving approach