(227c) Case Study: Salt Corrosion Controlled by Discontinuing Water Wash

Effective control of overhead system corrosion activity has become more challenging due to the increased prevalence of opportunity crude oils being processed today. Such crude oils can contain significantly higher levels of contaminants (for example chlorides, sulfur, naphthenic acids) than crude oils commonly processed in the past. Combine these more difficult-to-process crude oils with the fact that many refineries are operating well beyond design capacity, and the result is a substantially increased risk of overhead corrosion. Baker Petrolite has developed a comprehensive, engineering-based approach to address these problems using its TOPGUARD Overhead Corrosion Control Program.

For many systems, successful corrosion control can be simply achieved with the use of corrosion inhibitors and neutralizing amines. Alternately, corrosion issues can be addressed with non-chemical methods, such as operational changes, higher-grade metallurgy or water wash. Water washing in distillation column overhead systems is a proven method for controlling under-salt corrosion. However, not every system is a viable candidate for water wash. In fact, in some situations, equipment design can actually render a water wash system ineffective. A TOPGUARD troubleshooting effort on an atmospheric overhead system identified such a case. With a continuous water wash in place, heat exchanger life ranged from six to twelve months due to under-salt corrosion. An engineering evaluation of the system, utilizing the Ionic Model, identified an alternate approach which featured a change in neutralizer strategy coupled with a strict upper limit on overhead chloride levels. With the implementation of these new strategies, water wash injection was discontinued. As a result, heat exchanger life increased dramatically. During the three years of operation with the new strategy, the equipment has experienced no leaks or failures and routine monitoring gives no indication it needs to be replaced. Baker Petrolites TOPGUARD Program ensures that all aspects of equipment mechanical design are considered when selecting a proper corrosion control strategy.