Application Note: Turbidity Measurement in Brine

To produce chlorine through electrolysis, purified brine is required. Turbidity measurements following precipitation and filtration allow real-time monitoring and help to detect filter breakthrough. This enhances process reliability, protects the expensive membrane in the electrolysis cell, and minimizes downtimes.

Background
Chlorine is a key raw material for the chemical, pharmaceutical, and crop protection industries. It is produced mainly by electrolysis of sodium chloride brine in either a diaphragm, membrane or mercury cell. In each process brine is electrolyzed by a direct electric current (DC) that converts chloride ions into elemental chlorine.

Salt is obtained from the mining of natural deposits or from seawater, and contains impurities, mainly minerals and metals. These can adversely affect the electrolytic cell by clogging and damaging the membrane or diaphragm. Therefore, the brine fed into the cells needs to be as pure as possible and free of contaminants.

The contaminants precipitate by adjusting the pH and by the addition of chemicals. Subsequently all precipitated and suspended contaminants are removed by filtration.

Turbidity measurement systems are particularly suitable for monitoring and increasing the efficiency of the precipitation and filtration processes.