The aim of this work was to explore and test the concept of a novel direct nucleation
control method with external dissolution of fine crystals (E-DNC). It was postulated
that the heating cycles of the internal DNC method could be transferred from the crystallizer
jacket to an electrically heated recirculation tube, thereby using less energy and
requiring a shorter time compared to internal DNC. The conceptual model was explored
and developed by reviewing previous research on the topic and addressing known drawbacks.
Engineering experience and a heuristic approach led to the conclusion that five commonly
used controllers would suffice for a straightforward implementation of the method.
A simplified simulation was developed to compare the time and energy requirements
for the internal and external DNC methods, and it was concluded that external DNC
uses 37% less energy and 19% less time compared to internal DNC. The laboratory system
was then constructed by modifying the internal DNC apparatus with inexpensive and
commonly used components. A linear cooling experiment was performed to establish the
baseline for comparison with E-DNC experiments and to set the expected count range.
The E-DNC experiments were then conducted with the aim of obtaining larger crystal
sizes, and it was shown that the process could be designed in only three experiments.
Adjusting the heating rate and count limit led to a significant increase in median
crystal size (22.5%) compared to linear cooling.
