Hot vapour bypass

[chemprocess]

Hi All,

From your experience, does hot vapour bypass actually work well?

I have read a lot of articles and it suggested that it only works if you use condenser to cool the vapour from the column.

But our problem is there is no source of cooling water around that area. We are forced to use Fin Fan cooler instead of condenser.

Will the hot vapour bypass still work?


Background on the project:
We are venting LPG from the top of Debutaniser Column, the column operation pressure is around 1100 kPag. If you required any other information. Pleaselet me know.

Thank you in advance for your help.

 

[sshep]

Chemprocess,

Does a hot vapor by-pass really work well? My experience is that this does not always work well, but there are alot of flavors of such a configuration. In all cases the dependence on non-thermal equilibrium in the reciever is suspect- i.e. hot vapor in the vapor space and subcooled liquid in the reciever. The very concept is fraught with a degree of risk and design difficulty. Turbulance in the reciever will lead to much higher than expected bypassing requirement and this seems a very common problem (control valve wide open and pressure still too low). How to vent any non-condensibles is another problem because the vapor is hot and rich in condensibles. Some sort of vent condenser will usually be needed in cases of non-condensibles present.

Hot vapor bypass can work with air cooled condensers as well as water, but elevations are often a problem with fin-fans because these are usually located high- i.e. a good design has a liquid full line from condenser outlet to reciever. On the otherhand you can get subcooling in an air-cooler just as with cooling water by using a proper outlet design (seal loop).

Check out this paper if you have not already done so:

http://www.distillationgroup.com/technical/p081_06m15.htm

Note: this link takes you into the hot vapor bypass text, but there are other good sections also.

best wishes,
sshep