Corrosion Monitoring in Refineries on Knowledge Library

Amine Unit

Mon, 01 Jan 0001 00:00:00 +0000

Corrosion Monitoring In Amine Unit

The importance of corrosion monitoring in amine units appears to have diminished over the last two decades. Several factors contribute to this trend. First, there has been a general shift toward upgrading metallurgy from carbon steel to stainless steel or higher alloys in the most critical areas, such as the hot lean outlet from the regenerator and the lean/rich exchanger. Second, the increased use of proprietary solvent mixtures with enhanced anti-corrosion properties and improved resistance to decomposition has played a significant role. Lastly, most corrosion damage in these systems is more often associated with localized amine stress corrosion cracking, flow-induced corrosion, or erosion-corrosion phenomena.

Crude Unit

Mon, 01 Jan 0001 00:00:00 +0000

Atmospheric (Crude) Distillation Unit (CDU)

Corrosion monitoring in crude distillation units traditionally focuses on the atmospheric tower’s overhead section (OVHD). While there are no fixed guidelines specifying exact locations for corrosion monitoring, there is some consensus on key focus areas, such as the OVHD main line and cooler outlets. The proper assessment of monitoring locations and the number of monitoring points will depend primarily on the type of OVHD system, considering its operating regime (1-drum, 2-drums) and the cooler piping system (balanced, unbalanced). Below, you will find guidelines for monitoring locations based on generic OVHD system types: 1 drum – balanced coolers; 1 drum – unbalanced coolers and 2 drums – balanced coolers.

Hydroprocessing

Mon, 01 Jan 0001 00:00:00 +0000

Corrosion Monitoring Hydroprocessing (hydrotreating/hydrocracking)

Corrosion monitoring in hydroprocessing units (such as hydrotreating and hydrocracking) is relatively uncommon. The core processes, hydrogenation and/or cracking, occur in a water-free environment at elevated temperatures, making typical uniform electrochemical corrosion unlikely. Corrosion generally takes place in the cooling-separation section of the unit and is often driven by the presence of alkaline sour water (ammonium bisulfide solution).

Common areas of corrosion include the reactor effluent air-cooler (REAC), sour water lines from cold separators, product strippers/stabilizers and fractionation. Even so, corrosion monitoring is not always recommended by process licensors, as proper design and material selection effectively mitigate the risks of elevated corrosiveness. When the concentrations of sulfur, nitrogen, and oxygenates in the hydroprocessing feed exceed the original design conditions, whether due to bio-feed co-processing or the use of high-sulfur side-cuts, corrosion can intensify and demanding stricter monitoring.

Sour Water Stripping

Mon, 01 Jan 0001 00:00:00 +0000

Corrosion Monitoring In Sour Water Stripping (SWS) Unit

Ammonium bisulfide corrosion (also known as alkaline sour water corrosion) is the primary damage mechanism and occurs in almost all parts of the SWS unit. However, its intensification is typically observed in the stripper’s overhead (OVHD) line and coolers, and rarely in the hot sour water (SW) feed line. In the stripper reboiler loop (if a reboiler is present), alkaline sour water corrosion is a rare phenomenon but may still occur depending on the unit’s operating regime and loading. Hot stripped sour water and cold sour water feed do not pose a serious corrosion threat.