Design Aspects of Chemical Injection Systems in Crude Distillation Unit Overhead Section - A Case Study

Abstract Corrosion in Crude Distillation Unit (CDU) overhead is a well-known challenge over the years, therefore, many mitigation measures are being utilized to control it. One of the recognized damage mechanisms in the overhead circuit is Hydrochloric Acid Corrosion. This mode of failure is dependent on the calculated dew point where vapors containing water and hydrogen chloride condense. In such cases, the initial water droplets formed can be highly corrosive due to their low pH. To mitigate this damage mechanism, a chemical injection system is commonly used, incorporating neutralizing amines and corrosion inhibitors, along with wash water. This paper will showcase the design aspects of these chemical injection systems to provide optimum corrosion protection measures for the CDU overhead circuit. This includes, but is not limited to, material of construction, injection location, injection tip design, insertion length, …etc. Additionally, the paper will present a case study where improper design of chemical injection systems can lead to an accelerated deterioration of the material, leading to severe wall thinning or leak incidents that could jeopardize the operating facility.