Online analysis in the Chlorine industry

Large-scale production of chlorine involves several steps and many pieces of equipment. The plant also simultaneously produces sodium hydroxide (caustic soda)hydrogen gas. A typical plant consists of brine production/treatment, cell operations, chlorine cooling & drying, chlorine compression & liquefaction, liquid chlorine storage & loading, caustic handling, evaporation, storage & loading and hydrogen handling.


Key to the production of chlorine is the operation of the brine saturation/treatment system. Maintaining a properly saturated solution with the correct purity is vital, especially for membrane, diaphragm and mercuric cells. At several points in this process the brine is tested for hardness and strength.

After the ion exchangers, the brine is considered pure, and is transferred to storage tanks to be pumped into the cell room. The pure brine is heated to the correct temperature to control exit brine temperatures according to the electrical load. Brine exiting the cell room must be treated to remove residual chlorine and control PH levels before being returned to the saturation stage. This can be accomplished via dechlorination towers with acid and sodium bisulphite addition.

Failure to remove chlorine can result in damage to the ion exchange units. Brine should be monitored for accumulation of both chlorate anions, sulphate anions, and either have a treatment system in place, or purging of the brine loop to maintain safe levels, since chlorate anions can diffuse through the Membrane and contaminate the caustic, while sulphate anions can damage the anode surface coating.

SERES Analysers tailored to the need of Soda and Chlorine production plant

Your facilities operate 24/7. However, you can be operating blind if your essential assets are monitored infrequently using manual measurements. AquaGas introduces SERES Environnement cost-effective monitoring solutions of 9 parameters enabling anytime, online insight into your essential assets to help you prevent unplanned shutdowns, improve reliability, and reduce maintenance costs.

water analyser onyx

Online analyser parameters targeted

  • CA+MG in Brine (0.1 TO 5 MG/L)
  • CA+MG TRACES in Brine (5 TO 100  µG/L)
  • NAOH / NA2CO3 in Brine (Ranges according to process)
  • SO4 in Brine (Ranges according to process)
  • ACTIVE CHLORINE CL0CL+ in Brine and chemical effluents (Ranges according to process)
  • CHLORIDES TRACES in a Sodium Solution, 30% and 50%
    (5 TO 100 MG/L)
  • NH4+ in Brine
  • NAOH/NA2CO3 in a Sodium Hypochlorite /Soda medium for the control of residual Alkalinity on a tail- gas exhaust in electrochlorination treatment tower (50 to 250 G/L NA)
  • NCL3 in Chlorine, in association with the determination of NH4, Chlorine precursor in Brine, on Diaphragm or membrane production processes.

Online analyser exclusive features

  • Multi parameter/range
  • Multistream capabilities (up to 6 streams)
  • Remote control
  • Powerful touchscreen interface
  • User programmable sampling sequences


Validated over the years in Chlorine production, chemical and petrochemical industries


Online Process Monitoring for

  • Chlorine production
  • Soda production
  • Electrochlorination
  • Gas emissions and liquid effluents treatment systems