Recently we have faced with a severe failure in reach/lean MEA exchanger in our ammonia plant.The surface of tubes in reach MEA side completly corroded in the areas confind to inlet and outlet of tubesheet.The outer surface of tubes in lean side was in good condition.Tube material was s/s304.Any comments regards to the type and mechnism of corrosion would be appreciated. m.jorat

Failure of exchanger tubes - MEA process for CO2 removal - Ammonia Plant Tube failures ued to be experienced often in plants adopting MEA process for CO2 removal in ammonia plants. Problem could be due to higher than design temperature operation at the inlet and outlet ends in rich MEA and loss of inhibitor. Splashing of rich MEA at higher than design temp can generate vapors with higher velocity with resulting deposit formation . Tubes might have been designed for normal rich MEA flow conditions. To stop inlet impingement in rich MEA exchangers, some plants have provided impingement distributors (if space is available) or simple impingement plates at the inlet end of rich MEA exchanger. Second option some plants have used more inhibitors with MEA with amineguard. Some plants have switched over to modified or activated MDEA process (Bayer A.G Germany developed this process in 1970's). A couple of plants who switched over from MEA to activated or modified MDEA did not experience such tube failure problems compared to plants which still operated with original MEA deisgn without additional amine guard as inhibitors. The fact that failures are being experienced with S.S 304 tubes could be due to liquid- vapor conditions prevailing in the rich MEA exchanger (i.e., possibility of rich MEA devoid of inhibiotor due to higher velocity from liquid-vapor impingement at the inlet and outlet ends of rich MEA exchanger ( This can possibly result in depositiion of some formates awhich can degenerate to form formic acid). S.S 304 behavior will dramatically alter if the temperature is > 200 deg F if due to formic acid formation - if this had taken place . MEA Analysis and deposit analysis on the failed tubes - if tubes had been taken out for failure analysis would help a lot. Process improvements with more inhibitor (MEA with amine guard) or from long term solving of problem to switch over for modifed MDEA process may solve this problem. These are long term solutions. Trust this is of some use C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai India July 10, 2004 E-mail:nishi@vsnl.com >Masoud: > >You might analyze the rich amine solution for chloride >content and formate salts, which can degrade to formic acid. > High levels of formate salts can be quite corrosion to >304SS/316SS. > >Hope this helps! > > > >David Hendrix >The Hendrix Group Inc.

One of this discussion group suggested that formate solutions were quite corrosive. We provide concentrated formate solutions for use in high pressure high temperature oil wells where they are highly valued for being non-corrosive, particularly in acid gas environments. See http://www.eandpnet.com/ep/previous/1104/1104coverstory.htm for a recent article on the (non)corrosivity of formate solutions. John Downs Cabot Specialty Fluids e-mail : john_downs@cabot-corp.com >Recently we have faced with a severe failure in reach/lean >MEA exchanger in our ammonia plant.The surface of tubes in >reach MEA side completly corroded in the areas confind to >inlet and outlet of tubesheet.The outer surface of tubes in >lean side was in good condition.Tube material was s/s304.Any >comments regards to the type and mechnism of corrosion would >be appreciated. >m.jorat