The operating principle is based on 2 heated or cooled (drum coolers) and counter-rotating rollers, which roll on the product against each other. The product is added from above. The product distributes evenly in the roller gap and is held in the corresponding position with the core components. The rotary movement creates a product film on the rollers. Changes in the roller gap, the rotation speed, circumference and temperature of the rollers, as well as the degree of the vacuum are directly dependent of each other and have a direct impact on the drying speed and the drying result. The knives arranged on both sides remove the dried or cooled, mostly skin-shaped to clumpy product from the roller body. Any potential knife abrasion is actively prevented and does not occur.