(481g) Challenges and Successes in Continuous Chemical Processing

Process development for chemicals involves various stages that challenge chemical engineers to become innovative and creative with respect to the design of various unit operations. Batch processing simplifies unit operations but is not the most efficient or safest method to produce chemicals. In addition, there are processes that simply cannot be done using batch processing. These challenges frequently present themselves at the kilo lab scale. Nalas scales up dozens of chemical processes each year at their kilo lab that frequently require continuous process unit operations. These challenges have afforded excellent opportunities to apply chemical engineering principles across a multitude of chemical reactions, extractions, distillations, crystallizations, and isolations. No two processes are the same, each with their own unique challenge in solution.

Traditional reaction challenges include poor heat and mass transfer as reactor volume increases. Batch reactors are limited with respect to cooling capacity due to the reduced surface area to volume ratio of larger vessels compared to smaller vessels. Reaction temperature that was easily controlled in the laboratory becomes increasingly difficult or impossible to control at larger scales. This poses a scaleup safety and sustainability challenge. The use of smaller, continuous reactors has historically obviated these challenges. Recent advances in reactor design have afforded the opportunity for process intensification, reducing waste streams and frequently improving yield. These advances also result in higher throughput and smaller square footage reactor design that result in lower capital and operational costs. A continuous reaction often requires additional unit operations for purification and isolation of the desired material. Continuous extraction also reduces waste streams through process intensification. For example, the use of counter current centrifugal extractors has been demonstrated to dramatically reduce the required extraction solvent volume. The reduction of extraction solvent results in reduced demand on the subsequent continuous distillation. Again, this results in increased throughput with the benefit of lower capital and operational costs.

Several vignettes have been prepared for discussion based on our experience with continuous unit operations.