5 Control of Crystal Size Distribution and Polymorphs …
85
Fig. 5.1 Schematic diagrams of the WWDJ-crystallizer (a) and Wall-wetter™ (b)
Wall Wetter [6] that is a slurry sprinkler, namely a device specially designed for
sprinkling slurry or a solution on the wall of the crystallizer headspace.
The Wall Wetter adopted in this study comprised two-channel bars with a Jshaped cross-section, as shown in Fig. 5.1b. The device was fixed to the agitation
shaft at a given angle. The slurry was raised along the channel by centrifugal force
and sprinkled on the upper wall, then fell down the wall. During the fall, it can be
expected that crystals dissolve partially so that fine crystals disappear if the upper
jacket temperature is higher than that of the lower jacket. The surviving large crystals
are also expected to grow further, at the expense of fine crystals, after returning to
the lower crystallization phase.
5.2.3 Crystallization of Glycine Using WWDJ-Crystallizer
The cooling crystallization of glycine was carried out using WWDJ-crystallizer.
First, the temperatures of the upper and lower jackets of the WWDJ-crystallizer
were adjusted to 55.6 °C. An aqueous solution (1.7 L) of 250 mg/mL glycine was
prepared at 70 °C and then quickly introduced into the crystallizer. After the solution
temperature reached 55.6 °C, the solution was cooled at a constant cooling speed,
10 °C/h, where the final temperature of the solution and lower jacket were set at 25 °C
85
Fig. 5.1 Schematic diagrams of the WWDJ-crystallizer (a) and Wall-wetter™ (b)
Wall Wetter [6] that is a slurry sprinkler, namely a device specially designed for
sprinkling slurry or a solution on the wall of the crystallizer headspace.
The Wall Wetter adopted in this study comprised two-channel bars with a Jshaped cross-section, as shown in Fig. 5.1b. The device was fixed to the agitation
shaft at a given angle. The slurry was raised along the channel by centrifugal force
and sprinkled on the upper wall, then fell down the wall. During the fall, it can be
expected that crystals dissolve partially so that fine crystals disappear if the upper
jacket temperature is higher than that of the lower jacket. The surviving large crystals
are also expected to grow further, at the expense of fine crystals, after returning to
the lower crystallization phase.
5.2.3 Crystallization of Glycine Using WWDJ-Crystallizer
The cooling crystallization of glycine was carried out using WWDJ-crystallizer.
First, the temperatures of the upper and lower jackets of the WWDJ-crystallizer
were adjusted to 55.6 °C. An aqueous solution (1.7 L) of 250 mg/mL glycine was
prepared at 70 °C and then quickly introduced into the crystallizer. After the solution
temperature reached 55.6 °C, the solution was cooled at a constant cooling speed,
10 °C/h, where the final temperature of the solution and lower jacket were set at 25 °C