Overhead condensers (OHC) in refinery applications such as atmospheric and vacuum distillation units often experience very corrosive environments due to condensation of hydrochloric acid, HCl. The acid is often neutralized using water washing and addition of a caustic solution such as ammonia (NH3) or an organic amine such as monoethanolamine (MEA) or dimethylethanolamine (DMEA). While neutralizing the HCl, addition of these bases can lead to chloride salt deposits with following possible pitting corrosion, under deposit corrosion and stress corrosion cracking of the tubes in the OHC. In this work, the recently developed grade UNS N08935 has been tested in a laboratory environment mimicking ammonium chloride under-deposit corrosion and aqueous acidic corrosion in OHC applications. The results from the testing will compare the performance of N08935 to super duplex stainless steel UNS S32750 and nickel base alloy UNS N06625 being exposed to different temperatures, HCl and NH3 concentrations and flow rates representative of crude unit overhead condenser operating conditions.

Subject
Water, Materials, Corrosion resistant alloys, Salts, Corrosion rate, Materials performance, Predicted corrosion rate, Nickel based alloys, Metal coupons, Under deposit corrosion, Pitting, Corrosion resistance, Alloys
Keywords:
Crude unit, Crude overhead, HCl, Ammonium chloride, Salt formation, Material selection
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2021
Association for Materials Protection and Performance (AMPP)
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