Development of In-House Novel Process Scheme to Mitigate BenSat Unit Oxygen Stripper Overhead System Corrosion with Reduced CAPEX

Abstract

As part of the worldwide drive to produce cleaner fuels via Benzene reduction in the Gasoline Pool, ADNOC Refining utilizes the Innovative Benzene Saturation Technology which selectively targets saturation of only the benzene fraction to minimize the loss of octane number. The Benzene Reduction Unit (BenSat Process)is designed to process combined full reformate stream from two existing reforming units and comprises of the Oxygen Stripper, Reformate Splitter columns and BenSat Process unit. Severe corrosion and leaks were observed in the Overhead Circuit of the BenSat Unit after 2 Years of operation. Detailed Root cause analysis indicated to variations and contaminants in the feed stream as the main cause for the corrosion. Based on lab result of corrosion deposit analysis, which showed a presence of 78% of Iron & 9.8% of Oxygen, and morphology of failure i.e. presence of pits and tubercles it was concluded that the most probable reason for the failure is Oxygen corrosion aggravated by the presence of chloride. As the contributing causes were identified to be continuous in nature, a comprehensive solution was required at ADNOC Refining to ensure that similar failures do not re-occur. An upgraded and expensive metallurgy for the entire overhead circuit was the obvious solution for such a problem. However even this solution only prolongs the effects of corrosion and does not mitigate the corrosion at the source. The Technical Team at ADNOC Refining (RRW) developed an economical and continuous chemical injection system to resolve the issue at the source itself. Given the sensitive nature of the platinum Catalyst in the downstream of the Oxygen Stripper System, the selection of appropriate chemicals was a challenge. A unique combination of Corrosion Inhibiting filmer and a Neutralizing Amine was selected while ensuring overall compatibility with the system. A Chemical Injection Skid Framework was designed, engineered and built in-house in record duration for immediate commissioning. Upon implementation of the chemical injection system, it was observed that corrosion halted completely within one month. The paper explains in detail the troubleshooting and implementation methodology. These methodologies further highlight how efficient team work is able to deliver in-house solutions in the shortest possible durations.