Paddle dryers are conduction dryers used for drying of sludge, paste or wet powder. Paddle dryer consists of horizontal container with single or double shafts mounted with hollow paddles. The paddles are specially designed to make them self-cleaning. The container is provided with jacket. Steam or hot oil is passed through the container jacket as well as the paddles so that all the internal surfaces are heated up. The wet product is fed to the dryer at one end and travels to the other end while it comes in contact with hot surface of paddles and container and gets dried. The dry product is discharged at the bottom from the paddle dryer. For heat sensitive products or for products having solvent in them the paddle dryer is operated under vacuum.