Our LPG recovery plant operate a refrigeration unit which utilizes propane as the refrigerant. The propane refrigerant is used as cooling media in two HE, one of them is a Deethanizer Overhead Condenser where the deethanizer overhead vapor (consist of H2, C1, C2, C3, and a little iC4) is condensed to form liquid reflux, and the other HE is a feed gas chiller where the feed gas (consist of H2 and C1-C6+) is chilled and condensed.
Some month later we found that the propane in the refrigeration system was contaminated by lighter hydrocarbon such as C1 and C2, and we suspected that there is a leak within the Deethanizer Ovhd Condenser since the process side in the condenser has a higher pressure than the refrigerant side and also because of we didn't find any hydrocarbon heavier than C4 in the contaminated propane.
In almost the same time, we saw that the condensing presure is higher than normal and there was a decrease in the HE's chilling capability. I thought that the increase in condensing pressure is a possible consequence for the existence of some non condensable gas in the system. But I haven't had any idea whether the second phenomenon is caused by the same cause or not. Does anybody have any idea about this?
Thank you in advance.