VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
(OP)
I have a question about a partial condenser. When I am condensing a liquid out of a gas mixture, I always thought there needed to be a gas outlet at the top of the partial condenser and a separate flowpath for the non-condensibles to prevent accumulation and vapor binding of the condenser. I am being told by a more experienced engineer that a liquid outlet at the bottom of the shell is all that is needed. He says the liquid draining out of the condenser to the separator drum will pull the noncondensibles with it, and there will be no accumulation problem. Besides, he argues, there is nowhere else for the noncondensibles to go. I keep seeing a big bubble of noncondensibles in the condenser in my mind's eye, thereby reducing the effective area of the condenser. Is it just me?





RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
Regards
StoneCold
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
Does the sytem operate under vacuum?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
ppeng01:
The answer is YES. You must allow for the CO2 to exit the cooler-condenser (as we used to call it) through a nozzle that allows for it to continue on downstream – Preferably without even going through what you call the reflux accumulator drum. I have designed and installed about 7 to 10 of these same, exact CO2 cooler-condensers in the past. I even manufactured 3 of them – together with the condensate accumulator (reflux accumulator drum). I've always consolidated my condensed "weak amine solution" that is condensed in the Stripper overheads cooler in such a manner in order to use it as a wash for the gases exiting the top of the Amine absorber tower. This has always helped me to reduce the normal amine losses that are experienced as leaving with the treated gases. I never use a reflux on a CO2 Stripper; a reflux is not needed in this application because it does no help in establishing an equilibrium at the top of the Stripper and it only adds another steam consumption load to the amine reboiler and increases the amount of water vapor going up the Stripper. Most – or all of the CO2 will essentially strip out in the top 2 theoretical stages in the Stripper.
I am attaching a sketch of what I mean and what I think you are doing in order to fully explain to you how the CO2 is cooled and the associated water + trace amine are condensed and separated in a CO2 removal process. I believe you are trying to do the same thing and are having trouble trying to explain it and convince others; I hope this helps to reinforce what you are trying to do.
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
ppeng01, I think both design options are acceptable. There are many partial condensers where the liquid and vapour leave through the same pipe at the bottom (to the overhead receiver). On some, but not all, I have seen a small vent line from the top of the condenser to the drum.
For total condensers it is a different story, and I think a vent line is requried to remove noncondensibles from the condenser.
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
RE: VENT NON-CONDENSIBLES IN PARTIAL CONDENSER?
In treating really rich or gas streams with over 15% ethane and heavier, the cooled still overhead can cause cooling and condensation of heavier hydrocarbons which leads to foaming.
In smaller amine plants, we would just pump those condensed still overheads into the bottom of the still column, saves a bundle of opx and equipment if the contactor operates at 1000 psi.