c) Vacuum belt dryer
Brand and model: ISESA.
Capacity: Depends on the solution to be dried
Description: The dryer consists of a Teflon treadmill of a 495 cm long and 43 cm wide, mounted horizontally inside a stainless steel cylinder, which is kept under vacuum. The treadmill moves on 5 flat heat exchangers, which can be fed with vapor, a thermal fluid or cooling water. The solution to be dried (which must have a viscosity of approximately 1000 centipoises) is fed in one end of the dryer, so that their distribution is uniform across the width of the treadmill. The treadmill moves continuously at a rate of 5 – 25 cm/min, in terms of which the solution comes successively into contact with the surface of 5 heat exchangers, which are maintained at specified temperatures. The energy transferred from the surface of the exchanger to the solution through the Teflon tape, causing a gradual evaporation of the solvent. If the material to be dried has plastic characteristics, usually the last exchanger is used as a cooler. At the end of the dryer, a mechanical device scrapes off the solid of the treadmill and is evacuated to a container.