Recently IDI worked on a Cannabidiol (CBD) extraction process design. Part of the overall design was specifying a low temperature (-40°C) chiller system. One of the major challenges of this system was related to requirements for the use of food grade cooling solutions.
Typically, chiller systems are designed using Ethylene Glycol (EG) as a baseline cooling fluid. In instances where food contact is required, EG is generally substituted with Propylene Glycol (PG), and in most cases it is a simple substitution only requiring minor changes to accommodate the differing properties. Differences include but are not limited to increased viscosity, thermal properties, and toxicity. In the case of this CBD process, it became a major hurdle.
During the system design it was calculated that the PG was too viscous at the required temperature of the system. Fluids that have a high viscosity are difficult to pump, lose significant velocity during piping transfers, and perform poorly in heat exchangers. IDI utilized our process knowledge to determine solutions to the problem; ultimately IDI recommended the usage of an alternative food safe heat transfer fluid that better met the requirements of the system.
Also, as a part of the process design IDI recommended the use of a pre-insulated piping system. Pipe insulation was important to the process to ensure accurate temperature delivery across the processing equipment. Cost savings are achieved using this type of system, even though the raw materials cost is higher, instillation costs are lower. By Elizabeth Mack, Mechanical/Process Engineer