pH Measurement in Sour Water Stripper

Sour water is acidic, corrosive wastewater produced by refineries. It must be stripped using steam to remove the ammonia and hydrogen sulfide gases before being reused or released to the environment.

The pH level of the sour water stripper is carefully controlled at approximately a pH of 8 to ensure adequate removal of both gases. 

The reference electrode in a pH sensor provides a stable voltage potential independent of the measured solution. The reference electrode degrades over time, requiring eventual replacement. The Rosemount RBI pH Sensor contains five reference junctions, significantly delaying reference poisoning.

More than one type of pH sensor can be selected for a particular process. While many pH sensors are discarded after use, some pH sensors can be rebuilt and reused.
 

The Rosemount 3500P pH Sensor, on the other hand, contains just two reference junctions, but the reference junction and reference electrolyte are rebuildable.

This video outlines the maintenance process for deciding between replaceable or rebuildable sensor outlines the maintenance process for deciding between replaceable or rebuildable sensor.

The Rosemount 5081 Transmitter is a two-wire device that is rated Class 1, Div 1 for explosion proof and may be suitable in this environment of flammable vapors. The Rosemount 1058 Transmitter is a four-wire device rated for Class 1, Div 2 environments.
 

The hazardous area classification of the site will help determine the applicable transmitter.