84
K. Igarashi and H. Ooshima
Drowning out crystallization is an effective method selected next to cooling crystallization, but the cost of the solvent used for that cannot be ignored. When repeatedly
using a solvent, two or more solvents must be separated to pure solvents again by
distillation or the like.
Evaporation of solvent is also used for crystallization of highly water-soluble
compounds like sugars and amino acids. It is the simple method, but changes in
various phenomena such as the thermal stability of the solute and the increase in
viscosity due to concentration must be estimated in advance.
In any case, in crystallization from a solution, the solution should be supersaturated
by a suitable method, and induce crystallization.
5.2 Production of Crystals with a Large and Narrow Size
Distribution Using Internal Fines Dissolver [5]
5.2.1 Introduction
As mentioned above, industrial crystallization is expected to produce solids having
not only a particular composition but also a desired crystal size distribution (CSD),
because CSD often determines handling and many end-use properties. A product
with unimodal and narrow size distribution and large mean size is often desired.
It is well known that CSD is dependent on the primary nucleation, growth kinetics,
and also on secondary nucleation that is mainly caused by a collision between crystals
and the impeller in the crystallizer.
We have proposed a novel crystallizer. The crystallizer, named as WWDJ-batch
crystallizer, is equipped with a double-deck jacket and Wall Wetter™, which is a
slurry sprinkler. The structure of the crystallizer is quite simple, as shown below.
It is easy to wash and clean the inside of the vessel. This is a severe demand in
the production of pharmaceuticals. The crystallizer allowed the batch production of
large crystals with a narrow crystal size distribution (CSD) through the selective
dissolution of fine crystals that progresses simultaneously with crystallization.
In this section, we describe the production of the large crystals of glycine with a
narrow CSD using the WWDJ-batch crystallizer.
5.2.2 Apparatus
The WWDJ (Wall Wetter/Double-deck Jacket) batch crystallizer is illustrated in
Fig. 5.1a. The crystallizer is a cylindrical glass vessel with a round bottom, covered
with a double-deck jacket. The working volume of this crystallizer is 1.7 L. The
crystallizer was equipped with a four-blade propeller. It was also equipped with a
K. Igarashi and H. Ooshima
Drowning out crystallization is an effective method selected next to cooling crystallization, but the cost of the solvent used for that cannot be ignored. When repeatedly
using a solvent, two or more solvents must be separated to pure solvents again by
distillation or the like.
Evaporation of solvent is also used for crystallization of highly water-soluble
compounds like sugars and amino acids. It is the simple method, but changes in
various phenomena such as the thermal stability of the solute and the increase in
viscosity due to concentration must be estimated in advance.
In any case, in crystallization from a solution, the solution should be supersaturated
by a suitable method, and induce crystallization.
5.2 Production of Crystals with a Large and Narrow Size
Distribution Using Internal Fines Dissolver [5]
5.2.1 Introduction
As mentioned above, industrial crystallization is expected to produce solids having
not only a particular composition but also a desired crystal size distribution (CSD),
because CSD often determines handling and many end-use properties. A product
with unimodal and narrow size distribution and large mean size is often desired.
It is well known that CSD is dependent on the primary nucleation, growth kinetics,
and also on secondary nucleation that is mainly caused by a collision between crystals
and the impeller in the crystallizer.
We have proposed a novel crystallizer. The crystallizer, named as WWDJ-batch
crystallizer, is equipped with a double-deck jacket and Wall Wetter™, which is a
slurry sprinkler. The structure of the crystallizer is quite simple, as shown below.
It is easy to wash and clean the inside of the vessel. This is a severe demand in
the production of pharmaceuticals. The crystallizer allowed the batch production of
large crystals with a narrow crystal size distribution (CSD) through the selective
dissolution of fine crystals that progresses simultaneously with crystallization.
In this section, we describe the production of the large crystals of glycine with a
narrow CSD using the WWDJ-batch crystallizer.
5.2.2 Apparatus
The WWDJ (Wall Wetter/Double-deck Jacket) batch crystallizer is illustrated in
Fig. 5.1a. The crystallizer is a cylindrical glass vessel with a round bottom, covered
with a double-deck jacket. The working volume of this crystallizer is 1.7 L. The
crystallizer was equipped with a four-blade propeller. It was also equipped with a