ABSTRACT The evolution of steam nucleation during a strike in discontinuous evaporating crystallizers for sucrose production is investigated utilizing a newly designed model. Steam nucleation at the wall of the calandria tubes becomes less likely as the strike progresses due to the increasing massecuite level. Other sources of steam bubbles have to be involved to explain ongoing evaporation. Novel to the chosen approach in this study is the consideration of sucrose crystals as active steam nucleation sites. The modeling results are compared with evaporation rates of industrial pans. Data from the process control system of three different sugar factories allow generating reference data for different process points of the strike. Simulation results match reference values qualitatively using input parameters from the literature. Adjustment of the massecuite velocities and heat transfer coefficients to the different operating points results not only in good agreement of experimental and calculated data but also reflects a realistic evolution of the process states. For all observed cases sucrose crystals take over the steam nucleation process at some point during the strike. The evaporation rates achieved this way agree with industrial data. The results affirm the initial hypothesis that steam nucleation on sucrose crystals plays a role in the industrial operation. This opens the field for subsequent questions regarding process design and operation as well as consequences for the surface of the sucrose crystals.
Geisendörfer et al. (Sun,) studied this question.