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Once a reaction has been "worked-up," it is ready for product isolation. Product isolation can be accomplished by simple or complex distillation in the case of liquids, or separation from the mother liquor in the case of solids.
Liquid Products
Heat sensitive liquid products are typically isolated utilizing vacuum distillation with a conventional vessel or packed column. Other types of distillation equipment, such as wiped film evaporators, may be employed if the product is extremely heat sensitive. The equipment would typically be a reactor, condenser, and receiver and may in fact be the original reaction vessel. A packed column still would be used for the more complex distillation. Parsons has successfully designed many applications for liquid product isolation.
Impurities that are structurally similar to the product may be extremely difficult to separate even using a packed column. In those cases, Parsons has utilized simulated moving bed (SMB) technology to accomplish these separations.
Solid Products
Solid products are typically isolated via centrifugation. Centrifuges are available in a number of configurations such as vertical basket, horizontal basket, and inverting basket. Parsons has experience with the installation of each of these types. All of the related systems must be designed for cGMP since the centrifuge and mother liquor are both in contact with the final product.
As API products have become more potent and toxic, there has been an increasing trend to incorporate product isolation and drying in one unit to minimize the handling of the final product. The practicality of a device that can isolate, wash, and dry the crystals in one operation has great merit. Parsons' experience with these types of units shows that there are critical items that must be incorporated into the design such as heel loss, drying efficiency, and cleanability.
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