Materials Performance

DEC 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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39 MATERIALS PERFORMANCE: VOL. 57, NO. 12 DECEMBER 2018 two recommendations were made: perform an IEM study of the system to confirm sys- tem velocities and proper wash water requirements, and move the water injec- tion site to the top of the tower, spraying down from the second elbow to allow maxi- mum contact time between the spray drop- lets and the process vapor. Mitigation Strategies to Counter NH 4 Cl Corrosion Improved corrosion management can be achieved through operational and pro- cess control. Contaminant levels in the overh ead f luctuate over a wide range, thereby posing a huge challenge to corro- sion mitigation and unit reliability. Upgrad- ing materials from CS to CRAs is an option, but is cost prohibitive. Higher corrosion allowances may increase service life but will not reduce corrosion rates. Hence, the following strategies can be adopted: 1. IEM can be utilized to estimate pH and temperatures at the aqueous dew point, and determine deposit composition. Key inputs are over- head accumulator water and desalter wash water analyses. This helps iden- tify "tramp" amines and choose the most effective neutralizers. 2. Optimize water washing so that salt- forming constituents are absorbed in water prior to the advent of NH 4 Cl forming conditions. However, dis- solving salts is the only practical approach. Since salts form in areas inaccessible to wash droplets, proper d e si g n and lo cation of inje ction points are important factors to allow maximum contact time between the spray droplets and the process vapor. Poorly designed systems lead to inad- equate water being available to dis- solve away these salts, causing the c orro sion m e chani sm to shift to downstream units. 3. Accurate temperature profile mea- surement using infrared guns or cam- eras enables better determination of the water dew point and salt forma- tion point. 4. Corrosion rate and thickness moni- toring tool s, such as an int ernal rotary inspection system, ultrasonic thickness, or x-ray methods, can be placed at susceptible locations and wall thickness tracked frequently (two to three times annually), espe- cially at areas around the most recent failure. Electrical resistance probes and weight loss coupons should also be considered . Nonintrusive tech- niques (hydrogen permeation probes) can be used for real-time monitoring. References 1 Y.-M. Wu, "Calculations Estimate Process Stream Descriptions," Oil & Gas J. 91, 1 (1994). 2 A.J. Bagdasarian, D.J. Truax, "Chloride Stress Corrosion Cracking of Austenitic Stainless Steels in Hydroprocessing Units," CORRO- SION/97, paper no. 501 (Houston, TX: NACE International, 1997). 3 V.K. Braden, P.R. Petersen, "Crude Unit Over- head Corrosion Control," CORROSION/98, paper no. 585 (Houston, TX: NACE, 1998). 4 G.G. Duggan, R.G. Rechtien, "Application of Ionic Equilibria Process Simulation for At- mospheric Distillation Overhead Systems," CORROSION/98, paper no. 586 (Houston, TX: NACE, 1998). 5 A. Singh, C. Harvey, "Corrosion Management in Fractionator Feed Preheat Exchangers in Hydroprocessing Units," CORROSION 2000, paper no. 00687 (Houston, TX: NACE, 2000). 6 J.R . Rue, J.G. Edmondson, "Control of Salt- Initiated Corrosion in Crude Unit Overhead Systems," CORROSION 2001, paper no. 01538 (Houston, TX: NACE, 2001). 7 P.R . Petersen, et al., "Impact of Ammonium Chloride Salt Deposition on Refinery Opera- tions," CORROSION 2001, paper no. 01540 (Houston, TX: NACE, 2001). 8 C. Shargay, et al., "Design Considerations to Minimize Ammonium Chloride Corrosion in Hydrotreater RE AC 's," CORROSION 2001, paper no. 01543 (Houston, TX: NACE, 2001). 9 K. Toba, et al., "A New Approach to Prevent Corrosion of the Reactor Effluent System in HDS Units," CORROSION 2003, paper no. 03653 (Houston, TX: NACE, 2003). 10 R. Rechtien, G. Duggan, "Identifying the Im- pacts of Amine Contamination on Crude Units," CORROSION 2006, paper no. 06581 (Houston, TX: NACE, 2006). 11 NACE Publication 34109, "Crude Distillation Unit—Distillation Tower Overhead System" (Houston, TX: NACE, 2009). 12 G. Duggan, et al., "Multiple Corrosion Mech- anisms in a Crude Distillation Overhead Sys- tem," CORROSION 2009, paper no. 09332 (Houston, TX: NACE, 2009). 13 A. Sun, D. Fan, "Prediction, Monitoring and Control of Ammonium Chloride Corrosion in Ref inin g P ro c e sse s," C O RRO SIO N/2010, paper no. 10359 (Houston, TX: NACE, 2010). 14 K. Toba, et al., "Corrosion of Carbon Steel and Alloys in Ammonium Chloride Salt," CORROSION 2014, paper no. 4007 (Houston, TX: NACE, 2014). 15 C.D. Taylor, "Modeling Corrosion, Atom by Atom," Interface (Pennington, NJ: The Elec- trochemical Society, Winter 2014). 16 API 571, "Damage Mechanisms Af fecting Fixed Equipment in the Refining Industry " (Washington, DC: American Petroleum Insti- tute, 2011). is article is based on CORROSION 2017 paper no. 9574, presented in New Orleans, Louisiana, USA. SUDHAKAR MAHAJANAM is a senior cor- rosion specialist and corrosion team lead at Pinnacle Advanced Reliability Technol- ogies, Pasadena, Texas, USA, email: In his role, he provides materials and corrosion guid- ance to internal project teams and exter- nal clients. He has 25 years of experience in the field of metallurgy and corrosion, with 11+ years in oil and gas. Sudhakar currently holds certifications in API 571 and API 580. He has a B.S. degree in met- allurgical engineering from the Indian Institute of Technology Roorkee; M.S. and Ph.D. degrees in materials science and engineering from The Ohio State Univer- sity, and an M.B.A. from the University of Texas at Austin. He has published more than 30 papers and is a technical editor for several peer-reviewed journals. He received the SPE Outstanding Technical Editor award in 2010 and 2016 and the NACE Harvey Herro Award in 2005. He is a member of NACE. FRED ADDINGTON is a principal of corro- sion technology at Pinnacle Advanced Reliability Technologies, email: fred. He provides subject matter expertise to internal proj- ect teams and external clients. In his 30-year career, he has worked in steel production, nuclear power, and oil refin- ing. For the last 25 years, he has worked for owner/operators and service compa- nies in the area of corrosion mitigation and detection. He has a B.S. degree in metallurgical engineering from the Uni- versity of Texas at El Paso and is a mem- ber of NACE. AMANDA BARBA is a student at The Uni- versity of Texas Health Science Center, Houston, Texas, USA, email: abarbamme@ Prior to that, she provided con- sultative expertise at Pinnacle by assigning damage mechanisms and damage modes to refinery piping and equipment, thereby driving inspection on high-risk areas and reducing the probability of failure. She has a B.S. degree in metallurgical engineering from the University of Texas at El Paso. Underdeposit Corrosion in Crude Tower Overheads

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