Monitoring the kinetics of heterogeneous crystal growth using an Intrinsic Exposed Core Optical Fibre Sensor

- The optical fibre sensor could accurately follow heterogeneous crystal growth kinetics at various temperatures of three crystal types.
- The optical fibre sensor could accurately follow heterogeneous crystal growth kinetics on a stainless steel surface.
- The optical fibre sensor could measure the change in heterogeneous crystal growth kinetics when applying a crystal growth inhibitor.
- The extracted kinetic parameters followed a literature crystal growth model.

The prevention of unwanted heterogeneous crystal growth, known as scale formation, requires accurate detection of the rate and amount of scale deposition on surfaces. An Intrinsic Exposed Core Optical Fibre Sensor (IECOFS) has been used to measure heterogeneous crystal growth kinetic parameters, such as the rate of crystal growth and the induction time. Measurements at different temperatures allowed the activation energy to be determined for three crystal types, with excellent agreement with literature values. Crystal growth kinetic parameters were determined for calcium carbonate with the IECOFS and were found to compare well with kinetic parameters extracted from crystal growth measurements on a stainless steel surface. Crystal growth kinetic measurements were also performed in the presence of a poly-acrylic-acid (PAA) crystal growth inhibitor. The IECOFS monitored a reduction in the crystal growth rate and an increase in the induction time, matching well with the expected behaviour of the PAA inhibitor and agreeing with a literature model of crystal growth.