Semibatch reactor pharmaceuticals

Batch and semibatch reactors are most often used for low production capacities, where the cost of labor and dead time are only a small fraction of the unit cost of the product. They are generally encountered in the area of specialty chemicals and polymers and in pharmaceuticals, in particular, in plants with a wide variety of products. Large batch reactors are used in fermentations for antibiotic production, an example of which is given in Fig. 8-1. 

The pharmaceuticals company AstraZeneca has recently reported on research that has taken place over a number of years in addressing a switch from batch or semibatch processing to continuous operation. Wemersson (2007) stated that continuous stirred tank reactors (CSTRs), tubular reactors and micro-reactors had been evaluated. Substantial testing has also been done using the Alfa Laval plate reactor (see Chapter 5). Critical variables examined as a function of reactor type have included heat transfer capacity, mixing capacity and flow characteristics. 

Feed purification generally involves absorption, adsorption, extraction, and/or distillation. Reaction involves agitated batch, agitated semibatch, continuous stirred tank, or continuous flow reactors. The continuous flow reactors may be empty or contain a mass of solid catalyst. Product separation and purification involves distillation in the petrochemical industry or extraction and crystallization in the extractive metallurgy and pharmaceutical industries absorption is used to a lesser extent. 

A large majority of reactions are run in the batch or semibatch mode, making the stirred vessel the mainstay of chemical reaction engineering in the pharmaceutical and specialty chemical industries. The reasons for this reactor choice include ... 

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