The thermosiphon reboiler performs poorly
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The reboiler of the distillation tower is of the thermosyphon type. Under normal conditions, the temperature at the bottom of the tower is 224 degrees, while the temperature at the outlet of the material in the reboiler’s heat transfer tube side is around 226 degrees; heating is provided by hot oil at 280 degrees. Currently, the temperature at the bottom of the tower is low, while the temperature at the exit of the reboiler’s heat transfer tubes is too high; for example, the temperature at the bottom of the tower is 215 degrees, and that at the reboiler’s exit is 237 degrees. Moreover, the temperature of the hot oil after further heating is much higher than before. It seems that the evaporation rate of the tower is insufficient. The bottom of this tower is equipped with a partition; this has occurred before as well, and later on, by raising the liquid level on the product side to over 90%, heat exchange became normal. But now raising the liquid level doesn’t work either; to bring it to normal temperature, a lot more hot oil needs to be added. The analysis indicates that the material cannot circulate in large quantities; it is possible that there is blockage in the pipeline section. As a result, after the material undergoes phase change and vaporization, it is further heated, leading to a higher outlet temperature. However, the reduced circulation volume results in insufficient temperature inside the reactor. Everyone, do you agree, or are there any other explanations?
It’s scaled up; it needs to be cleaned. How long has it been in use?
I’ve been using it for 5 years. It turns out that it happens like this sometimes, but it gets better after a few days. Are there any other measures that can help improve the situation besides cleaning? After all, parking is quite a hassle. Within less than 2 years of operation, the liquid level increased; it turned out that a leak in the partition was to blame, which caused poor circulation. It will be fine after the upgrade. But recently, even with a high liquid level, such situations have occurred from time to time
It’s time to clean it after 5 years; after all, the equipment will develop scale, and there’s really no other solution.
Check whether the material pipelines entering and leaving the reboiler are too small
This should be fine; it worked well before, except for the issue of elevated liquid levels. But now problems keep arising.
Based on the phenomena I mentioned, can it be determined that it is caused by scaling in the pipe? One is to confirm whether it’s this issue so as to inform the manager, and the other is to see if there are any process adjustments that can be made
Based on the analysis of the observed phenomena, raising the liquid level increased the flow rate and enhanced the heat transfer coefficient in the tube side, which restored normal heat transfer; it appears that there may be scaling on the tube side of the heat exchanger. Raising or lowering the liquid level now is also ineffective; a large amount of hot oil needs to be added to bring the temperature back to normal, as scaling on the side of the heat transfer oil is severe.
Both the tube side and the shell side should be checked for scaling. On the material side, increasing the reflux rate can help circulate more light components through the reboiler; additionally, a forced circulation line can be used to clear any blockages, which will ensure proper operation for about half a year. Find some time to clean it up later.
Could you draw a diagram to explain what the partition is like in detail, and what kind of material it is made of?
If scaling is severe on the heat transfer oil side, under the same heat oil conditions, the exit temperature of the material in the tube side is significantly higher than normal, but the temperature at the bottom of the tower is very low. So I don’t think it’s a problem on the heat transfer oil side