We are detecting high contents of basic nitrogen in the LPG from Merox unit. We have two LPG Merox, one for FCC and coquer and another one for crude distillation. This nitrogen concentrates downstream in the n-C4 fraction and causes fail of maximum nitrogen specification for commercial C4.
Previous to both LPG Merox units we have amine contactors (with MDEA) to remove SH2. We suspect that amine solubility and withdrawn is the problem, but we do not have nitrogen compounds speciation analysis  available.
 
A potential solution is to install a water wash after the amine contactor to remove potential amine withdrawn. It seems that this solution achieves to reduce amine levels to <1ppm.
 
– Does anyone has experience with this water washing after amine plants?
– Besides amines (MDEA), could it be possible to have other nitrogen compounds in LPG?: NH3 coming from the cracking of nitrogen compounds in FCC / coquer.  Acetonitrile and propionitrile are also mentioned as contaminants in C4 streams. Could also be present light amines (methylamine, ethylamine), resulting from the cracking in FCC / coquer?
– In case we have other nitrogen compounds of the above metioned the water wash after amine contactor will be effective to remove that kind of basic nitrogen?
 
Thank you very much in advanced for your kind collaboration.