2 replies to this topic

[hana1]

Hello All.

I am a final year student don't worry Im not here to give you my project to work out lol! I am doing some reading before my next semester in Jan on reboilers and condensors, I am interested in knowing how faulted temperature controls of reboilers and condesers effect the distillation process. I have been reading through alot of books and web sites and found heaps of great info, but what I wanted to clear up on was If for e.g. the temperature or pressure of the reboiler/condenser is higher/lower then Its design temp/pressure how it would effect the distillation process

what I found on high reboiler temperature control over design condition effects;

Uneven distribution; where liquid distribution to the reboiler is uneven, I also found that It could burn out the reboiler tube bundle Im quite confused on this bit because it's beyond my scope, also It causes fouling due to tubes being unflooded. Can I say that these same effects are valid for faulted pressures or would the effects be different because everywhere (well most) literature go on about fouling, uneven distribution etc. In terms of condenser malfunction where for e.g. the cold reflux is returned instead of saturated liquid reflux, how can this cold reflux effect the distillation processs?


If someone can please direct me to a useful website or books to read I'd be ever so greatful.

Thank you all for reading.

[djack77494]

hana1,
THere seem to be two separate topics here that you'd like discussed. If I understand you correctly, you'd like to know how a failed control system would impact a condenser and (same for) a reboiler as one topic, and you'd like to know how said failure would impact the distillation process itself.

This is really too big a question to be adequately addressed in a forum like this. There are so many possible types of control approaches to distillation processes and so many options for the mechanical design of the heat exchange equipment that a relatively simple response would not do the topic justice. I will say that your one expressed concern regarding "burning out tubes" in a reboiler due to overtemperature seems overstated. Whether the heating fluid is on the shell or tube side, whether you have a pumped or thermosiphon reboiler, horizontal or vertical, etc., etc., I cannot imagine a well designed heat exchanger not being capable of withstanding zero flow of column bottoms to the reboiler. Yes, the tubes would reach a maximum temperature and the distillation column would slump (due to insufficient heat input), but the tubes would not "burn out". However, with very hot tubes, perhaps caused by poor distribution of the flow or by an inadequate bottoms flowrate, you would tend to promote fouling.



For further answers to your inquiry, you must do more reading. There are many excellent and practical books on distillation out there. I can recommend Kister's for example. After going through the available resources, if you have any more focused inquiries, please feel free to repost them. Good luck.

[hana1]

^ Hi. Thank you very much for the reply. I guess this subject is broad because i couldn't figure out where to start and where to finish, I have to design a condensor so i thought I'd gather info but it seems quite a challenge. I will hopefully try find the book you quoted and will get back for further assistance if necessary.