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We are having a NATCO EDD desalter in one of our crude units and of late we are facing reduced desalting. The outlet salts have been consistently above 1 ptb and sometimes we find inlet and outlet salts to be almost equal. we tried to balance the salt removal across the desalter and tried to do a chloride balance across the crude/prefrac columns, but unable to close the material balance.
 
Answers
05/12/2013 A: Prabu Natarajan, Natco Uk Ltd, prabunatarajanuk@yahoo.com
Need to check the inlet & Outlet BS&W. If dehydration is working properly then in theory, Desalting should also be taking place. If the inlet & outlet salt is identified as same, then its better to check the mix valve to make sure that it doesnt creat stable emulsion which will end up having high water carry over & high salt outlet. Need bit more information on what's coming in and what's going out to understand what is actually happening.
28/03/2012 A: chandrasekhar kurcharlapati, toyo engineering, k_chandra_sekhar@yahoo.com
Does wash water have more salts than specified?
22/11/2011 A: Christopher Turner, Snamprogetti Ltd, chris.turner@snampro.co.uk
What are the inlet outlet vol% water and compositions?
21/11/2011 A: sam lordo, Becht Engineering, salordo@comcast.net
If you have a heavy crude ( <25 API/0.90 spgr) please review your operation with NATCO for suitability of the equipment application. Of course you should try to optimize all of the parameters that you can. With that said the question of salt balances; it is my experience that you only have a relatively good chance to do a good balance around the desalter itself. As soon as in involve the downstream equipment you need to make sure that you are sampling ALL of the streams as the chloride does distribute across the entire tower (most sites only do a couple of the streams), with that said the only chloride that you are measuring is that which has left the process, it does not account for what may be sticking in the tower, exchangers, etc.
The other aspect is what type of chloride measurement are you making. If it is an extraction, is a complete extraction (ie, multiple water washes)? Is it total chloride by combustion?