The set up was equipped with two in-line measurement instruments. A K-Patents Process Refractometer (K-Patents PR-23-AP) and a FBRM D600 probe were used to monitor the liquid phase and chord length distribution, respectively. The position of the probes was chosen in the high mixing zone, i.e. near the agitator. The measurements from both probes were recorded every 2 min. As the measurement by FBRM and in-line refractometer change in a continuous way, the data at every 1 h is considered for the comparison. The complete experimental setup used in this study is shown in Fig. 1.