Operating Principle of horizontal thin film dryer

Horizontal thin film dryers are continuously operating contact dryers and are used for a broad range of applications under vacuum, atmospheric pressure and overpressure. They consist of a horizontally arranged heated shell with end covers and a rotor with bolted-on blades. The wet product fed through the inlet nozzle is picked up by the rotor blades, applied to the hot wall and simultaneously conveyed towards the outlet nozzle at the opposite end of the body. 

The generated vapours are streaming counter-currently to the product flow and leave the dryer close to the feed nozzle. Evaporating and conveying capacity are adapted by the appropriate rotor blade arrangement.  

Entrained particles from the dry zone are removed in the wet zone. Moisture levels of less than 1 % can be achieved. The residence time of the product typically is between 5 and 15 minutes.

Horizontal thin film dryers are also suitable for other applications apart from drying such as solid particle cooling and product melting. The outstanding heat transfer rate for hot solid products enables cooling of large amounts of solids without air in one compact machine compared to usually used cooling screws. In product melting, e.g. the melting of urea, the particles are heated and melted inside the dryer. The melt can be mixed with other liquid and solid additives to improve the properties of the final products.