Modeling the scale-up of contact drying processes

The conventional way of scaling up a contact drying process includes a pilot-scale step. Scaling up from lab scale to production scale without the use of a pilot plant saves time and money. A method has been developed to perform a scale-up from a 200-g bench-scale Rotavap drying process to production scale (approximately 1000 kg). A mathematical model, an improvement on the so-called Schlünder model, has been developed to simulate bench-scale drying processes. This simulation is used to determine the unknown mixing parameters by regression analysis. Besides the heat transfer resistances predicted by Schlünder an additional resistance term was found which is product dependent and can also be determined by regression. Ultimately the model can be used to predict the drying curve on production scale. In five out of eight cases the developed method accurately predicted drying behaviour. In three remaining cases the model did not apply due to extreme stickiness or aggregation during drying.