Sour Water Stripping

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.

Stripper OVHD

H₂S, NH₃, and water vapors leaving the top of the stripper create a natural environment for ammonium bisulfide corrosion. In the condensation area, where liquid water is present and the pH (ranging from 9 to 10) favors the stability of the HS⁻ ion, sour water corrosion is likely. Therefore, corrosion probes should be located in these areas.

If a corrosion inhibitor is injected into the overhead (OVHD) line, the probes should be installed downstream of any injection systems, as shown in Figure 1. Depending on inlet piping configuration and access Locations A and/or A’ may be considered for corrosion monitoring.

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