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ABSTRACT
Investigations of fouling in heat exchangers are mainly focused on two factors: commercial impact due to energy losses, and environmental impact manifested through higher CO2 emissions. The purpose of this paper is to introduce a third factor relating to safety in operations. This paper presents two case studies, one for a hydroprocessing unit with feed/effluent heat exchangers and another for preheat train exchangers installed upstream of the atmospheric furnace in a refinery crude unit. Due to a wide range of process temperatures examined in both case studies, the heat exchangers in the network are subject to various fouling mechanisms. As illustrated in the pictures of actual tube bundles, some of the exchangers within the network are heavily fouled, while the other exchangers operate in nearly clean conditions. Detailed simulations indicate that nonuniform fouling results in heat exchanger operating temperatures that are significantly higher than those predicted by conventional analyses using uniform fouling. Higher than anticipated process fluid temperatures may result in exceeding the threshold limits for certain corrosion mechanisms and/or significantly higher than expected rates of corrosion.
Nomenclature
| API | = | American Petroleum Institute |
| API RP | = | American Petroleum Institute Recommended Practice |
| ASME | = | American Society of Mechanical Engineers |
| HTHA | = | high-temperature hydrogen attack |
| HTRI | = | Heat Transfer Research, Inc. |
| NACE | = | National Association of Corrosion Engineers |
| NHT | = | naphtha hydrotreater |
| PFD | = | process flow diagram |
| PWHT | = | postweld heat treatment |
| Rf | = | overall fouling resistance combining tube-side and shell-side fouling resistances, m2-K/W |
| TAN | = | total acid number |
| TEMA | = | Tubular Exchanger Manufacturers Association |
| Uclean | = | overall heat transfer coefficient at clean conditions, W/m2-K |
| Uobserved | = | overall heat transfer coefficient observed during operation, W/m2-K |
Additional information
Notes on contributors
Les Jackowski
Les Jackowski is a consulting heat exchanger engineer in Chevron's Energy Technology Company in Richmond, CA. He specializes in development and application of fouling mitigation and enhanced heat transfer surfaces technologies. Prior to joining Chevron, he worked for major engineering companies including Eichleay Engineers, Technip, and Parsons. He received an M.S. degree in mechanical engineering in 1981 from Warsaw University of Technology (WUT) and Ph.D. in heat and mass transfer in 1987 from WUT as well. His postodoctoral experience includes research work for Swiss Federal Institute of Technology (ETH) and University of California, Los Angeles. He is a registered Mechanical Engineer in the state of California.
Peter Risse
Peter Risse is the chief materials engineer for Chevron Lummus Global (CLG) within Chevron's Energy Technology Company in Richmond, CA. He and his team oversee materials selections for new capital projects and materials-related technical service for CLG licensee units. His responsibilities include leading CLG's fabrication shop audits, review of reactor fabrication, aid with unit troubleshooting, fixed equipment asset reliability, remaining life predictions in the hydroprocessing units. and performing field inspections. He has more than 30 years of experience in the refining industry. He holds a B.S. degree in chemical engineering from the University of Rhode Island and an M.S. degree in materials science from the University of California at Berkeley. He is a registered Corrosion and Metallurgical Professional Engineer in the state of California.
Rich Smith
Rich Smith works in Chevron's Manufacturing Process Technology Team as a Business Improvement Network leader supporting hydrotreaters and hydrocrackers, a position he assumed in January 2013. Prior to this, his roles included managing facility planning for manufacturing, managing oils planning and then facility planning for the Richmond, CA, refinery, and roles in the Richmond refinery technical and operations organizations. He is a native of Downers Grove, IL, and grew up in Nevada and Oregon. He graduated from Oregon State University in 1985 with a bachelor's degree in chemical engineering. He received his Professional Engineer's license in chemical engineering in 1989.