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At a chemical site in northern Germany pure synthetic glycerine is produced from epichlorohydrin. The synthetic glycerine is used in the particularly quality-sensitive areas of the cosmetics and food industries and especially in the pharmaceutical industry where each ingredient must be of the highest purity.

Technical glycerine synthesis from epichlorohydrin is carried out by means of hydrolysis with an aqueous sodium hydroxide (NaOH) solution. For optimum reaction control, the quantities must be dosed in the correct stoichiometric proportions. In other words, measurement is essential. Both the mass flow and concentration of the caustic are important for correct dosage of the NaOH solution.

The glycerine plant draws a 30% sodium hydroxide solution from the integrated network at the chemical site. The solution is then further diluted with the addition of water. Up until now, laboratory samples were used to check whether the correct concentration of the diluted solution was maintained. However, process engineers were looking for a suitable method to continuously monitor concentration and density in real time.

Non-invasive, ultrasonic measurement proved to be the ideal solution for this measuring task. The PIOX S non-invasive ultrasonic process analyser simultaneously measures all the necessary quantities:

The volume flow rate, the concentration of NaOH in the solution, the density and the mass flow rate.
Since the clamp-on ultrasonic transducers are simply mounted on the outside of the pipeline, they are not subject to any wear and tear by the medium. There is no need to interrupt production when setting up the measuring point. PIOX S proves to be convincing as a reliable process controller. Dilution is now automatically controlled thanks to the non-invasive, continuous measurement of concentration, density and mass flow which ensures the desired concentration is achieved at all times.


  • Simultaneous, non-invasive  measurement of concentration, density and mass flow
  • Automatic control of the amount of water added in order to ensure the desired concentration
  • Reliable and continuous process control - the specified quality is permanently ensured
  • Effective process optimisation
  • Measuring point can be set up very easily without opening the existing pipeline and during ongoing operation
  • Virtually wear-free measurement