Batch Pan

Next to natural solar evaporation, the batch pan (Figure 1) is one of the oldest methods of concentration. It is somewhat outdated in today's technology, but is still used in a few limited applications, such as the concentration of jams and jellies where whole fruit is present and in processing some pharmaceutical products. Up until the early 1960's, batch pan also enjoyed wide use in the concentration of corn syrups. With a batch pan evaporator, product residence time normally is many hours. Therefore, it is essential to boil at low temperatures and high vacuum when a heat sensitive or thermodegradable product is involved. The batch pan is either jacketed or has internal coils or heaters. Heat transfer areas normally are quite small due to vessel shapes, and heat transfer coefficients (HTC’s) tend to be low under natural convection conditions. Low surface areas together with low HTC's generally limit the evaporation capacity of such a system. Heat transfer is improved by agitation within the vessel. In many cases, large temperature differences cannot be used for fear of rapid fouling of the heat transfer surface. Relatively low evaporation capacities, therefore, limit its use.