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PROBLEM
To provide some background on the process, a complex feed consisting of ACN, water, and traces of propionitrile, among a number of components, comes from an existing distillation column that removes all lower boiling impurities. Since the required purity of the recovered ACN could not be achieved in that single distillation column, Koch Modular was to provide a pressure swing distillation system to achieve it.
Although breaking of an azeotrope presents a challenge on its own, there are also challenges unique to modules being installed in places with unconventional climate restrictions in addition to those unique to pharmaceutical clients.
For example, because the module installation site was in the Caribbean, near the coast, and surrounded by salty sea breezes, deliberate thought was required when planning materials of construction to avoid any material corrosion.
Additionally, traces of propionitrile in the feed might also be present in the product stream if not carefully planned for its removal, presenting possible build-up concerns after repeated recycling of the ACN solvent. Not to mention, the FDA regulations that pharmaceutical clients are subject to can limit any modifications to be made to the system after process validation by the FDA.
SOLUTION
Koch Modular addressed climate challenges by choosing corrosion-resistant materials and appropriate coatings that can withstand the coastal environment.
Also, it was determined through pilot testing that traces of propionitrile in the purified and recycled ACN product could cause buildup issues, and an additional column was designed to guarantee elimination of even those trace amounts.
The concerns about the FDA process validation regulations was overcome by thorough process development and maintaining constant communication throughout the project timeline to ensure that no future modifications would be necessary.
RESULTS
Koch Modular provided a complete modular pressure swing distillation system designed to process the client’s feed and provide a recovered product containing at least 99.95 wt% ACN and <500 ppm water. Actual recovered product had <100 ppm water.
Ultimately, with the recovery of purified ACN, this system reduces any waste solvent disposal costs and offers cost-saving and environmental benefits. It also demonstrates the ability of Koch Modular engineers to work with the stringent regulations imposed on the pharmaceutical industry, and to optimize construction materials.