LensDrying of Polyols
Figure 1: Continuous crystallization and drying of polyols.
Crystallization Process

The process is based around a single-shaft LIST KneaderReactor configured as a combined crystallizer/dryer. Under the conditions in the mixing chamber, the water in the process mixture undergoes flash evaporation; the large cross-sectional area of the KneaderReactor allows this to take place without entrainment of liquid droplets or fines. As the solution becomes super-saturated, the polyols crystallize.

To achieve the desired final water content, the KneaderReactor is used as a dryer. After the evaporation stage, the crystals are still wet, sticky and capable of forming large agglomerates. The design of the LIST Crystallizer/Dryer provides effective drying with minimal product buildup and crust formation, and without the need to recycle dry product. Throughout the process, the large heat exchange surfaces ensure precise temperature control. The final dry crystalline product is discharged through a LIST Lock System.