In a NiTech® COBC, the mixing of process fluid is achieved by the combination of fluid oscillation and the presence of orifice baffles. Vortices are generated when process fluid flows through the orifice baffles, delivering uniform mixing in each chamber between adjacent baffles. This enhances heat and mass transfer rates to speed up the process and ensure a consistent processing environment.
The jacketed pipework provides a large surface area for heat transfer to the process medium (the CBD distillate/hydrocarbon solvent/CBD isolate seed crystals). Temperature zones are setup along the length of the COBC, starting from high temperature (at the start of the COBC) through to low temperature (at the end of the COBC). The process fluid enters at the bottom of the crystallizer and exits at the top.
This is the essence of the NiTech® crystallizer: optimal heat transfer combined with uniform mixing. These enable control of CBD isolate crystallization with high precision, resulting in CBD isolate yields near the theoretical maximum, high CBD isolate purities and CBD isolate crystals with more uniform particle size.
When performing CBD isolate crystallization, CBD distillate is diluted with a hydrocarbon solvent (typically heptane or pentane) in a feed tank, before being charged into the COBC via an external pump. Dilution reduces the viscosity of CBD distillate to improve flow and enhance the heat and mass transfer rates, which in turn accelerate the crystallization process.
Temperature zones along the COBC are typically operated at:
The process fluid cools as it flows through the COBC temperature zones. At the point when it is cooled to the solubility temperature of the solution (e.g. 5°C), the seed slurry (CBD isolate crystals suspended in CBD-saturated hydrocarbon solvent) is injected into the process fluid via a secondary charging point. CBD isolate seed crystals grow as the solution is further cooled, ensuring a well controlled crystallization process. At the end of the COBC, CBD isolate crystals emerge as solids suspended in the remaining process fluid and are recovered by downstream filtration before being washed and dried.
A simple flow diagram showing the typical setup of a NiTech® continuous crystallizer for CBD isolate production is show below.