Heated air flows horizontally through the screens. Metering rolls, at the bottom of the screens, control the rate of rice flow through the dryer. Rice is removed from the metering rolls with screw conveyors. This type of dryer has several disadvantages compared with other types of continuous flow dryers.
Rice tends to flow straight down between the screens, without much horizontal movement.
This means that the rice close to the hot air plenum is always exposed to the hottest air and dries more than the rice next to the screen near the air exhaust. Also rice next to the screens flows slower than the rice in the middle between the two screens. This leads to even more variability in the amount of drying experienced by individual grains. Some dryer designs include mixing sections to reduce variability. Two other dryers are designed to mix the rice as it flows through the dryer.