I have a question regarding the forced circulation in reboilers
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The reboiler of the existing negative-pressure distillation column in the unit (vertical, thermosiphonic type) frequently experiences blockages in its tube side due to polymers. I was thinking that this reboiler could be equipped with a column bottom circulation pump in order to achieve forced circulation ? If it can be changed, how should it be changed and what needs to be taken into consideration?
Using a pump for forced circulation can only help to extend the lifespan of the reboiler; it does not solve the problem at its root. It is best to take measures within the process itself, and if that’s not possible, the reboiler should be operated in a one-in-one-out configuration, which allows for online cleaning without having to stop production.
At the moment, I want to extend the usage period. I was wondering if there are any other devices that have undergone similar modifications, and whether it’s possible to do the same
This post was last edited by sifangok on 2017-4-11 23:32. Let’s figure out the reason first! Generally, there are few backups for reboilers. Except for materials with high viscosity and heat sensitivity, forced circulation is not usually used; any changes to the equipment should be discussed first with the design team. To find out the reason, sometimes it’s enough to just change a parameter; don’t act recklessly.
Find out the reason first before discussing technical upgrades; also, work in conjunction with the design institute!
It is possible to convert a thermosyphon reboiler into a system with forced circulation by adding a pump, and there is no problem with this, as one of the purposes of designing thermosyphon reboilers is to save costs by reducing the need for circulation pumps. However, based on my experience with similar devices (e.g., styrene, acrylonitrile), the measure of using circulation pumps to address polymer clogging introduces new problems; the filters at the pump inlets tend to get clogged frequently. If it is necessary to use such pumps, it is advisable to install two pumps, one in operation and one as a backup, which is a more reliable approach.
Sure, the polymer negative pressure towers here use pumps for forced circulation. The filter screens at the pump inlet often get clogged, so it is necessary to install two filter screens, one in use and one as a backup.
Recently, I had to clean a reboiler – over 1,500 tubes were blocked by nearly 3/4 of them. I hired a professional cleaning company, but they were unable to clean it; the tubes were filled with polymers. They could clear only 3-4 tubes per hour. Eventually, we took the risk of opening the blind flanges on the shell side, and after applying steam for heating, the cleaning speed increased. It took half a month to clean one such reboiler – it was a truly frustrating process. By adding a circulation pump, cleaning the filter becomes relatively simpler
It can be added, but attention must be paid to the selection of the pump. On one hand, temperature and the type of medium are factors to consider, and on the other hand, the circulation rate also needs to be taken into account. Perhaps it would be possible to replace the reboiler with a forced-circulation falling-film evaporator in order to keep the temperature inside the tank relatively low