Photo: Collected
The drying tower can be divided into five working sections, namely the grain storage section, drying section, softening section, cooling section, and unloading section.
One side of the grain section has a small transparent window, called a viewing window, to observe the position of the grain in the tower. The drying section is the main process of drying food, mainly hot air as a drying medium for food heating and water removal, the food moisture is reduced to a certain degree so that it is conducive to storage and ensures quality.
The interior of the drying tower is mainly composed of staggered pentagonal ventilation corner tubes. The corner tubes that the user can see from the outside are exhaust corner tubes, and the seven outward rectangular tubes are intake corner tubes. The hot air provided by the hot air fan enters the grain pile through the intake Angle tube, takes away the water vapor evaporated from the grain while passing through the grain layer, and is discharged into the atmosphere through the exhaust Angle tube.
In the drying section, due to the grain weight, flow from top to bottom, the hot air enters from the intake Angle tube and passes through the grain layer in the upward or downward direction. The hot air and the grain flow both flows in the same direction and in the opposite direction, so it is called mixed flow. When the hot air passes through the grain layer, it transfers heat and humidity between the grain grains, and the hot air transfers heat to the grain grains, so that the temperature rises. The grain grains are heated up, and the water evaporates into the air. The dry medium carries water vapor into the waste gas and is discharged through the exhaust Angle tube. In this process, the higher the grain temperature rises, the faster the water evaporates. In order to ensure the quality of the grain, that is, processing and edible, the temperature rise and drying time of grain in the drying section are strictly controlled. The principle is not only to reduce the moisture of grain but also not to damage the quality of grain.
In the drying section, the part without arranged ventilation Angle tube is a slow Su section. The hot grain flows down to the slow Su section, and there is no hot air in the slow Su section. Its main function is to slow down the stress formed in the grain during the drying process and promote the water inside the grain to move outward gradually so that the water inside the grain surface and the grain tend to balance. A slow selling process is beneficial to the next stage of drying and can ensure the quality of the baked grain, but it can not be used for oil crops.
After roasting, the grain is very hot and needs to be cooled before it can be stored. The dryer is provided with a cooling section, and the air cooler is responsible for providing cold air to the cold air section. The countercurrent cooling method is adopted to cool the baked grain. In the cooling process, the cold air first contacts the lower low-temperature grain, and absorbs the heat in the grain while running upward. The temperature of the cold air gradually increases, which can avoid the sharp cooling of the grain when the cold air contacts with the upper hot grain. Countercurrent cooling can improve the cooling effect of the cooling section and protect the quality of the grain from being affected. The grain temperature gradually decreases through the cooling section from top to bottom. When the temperature of the grain in the tower is within 4-8 degrees Celsius higher than the ambient temperature, the grain is discharged from the grain discharge section and stored in the warehouse. When the temperature is below 0 degrees Celsius, the grain temperature can be controlled at 0 degrees Celsius. In production, the cooling degree of grain can be judged by detecting the temperature of cooling waste gas.
The discharge section includes a discharge port, circulation conveyor, observation hole, and discharge device. The observation hole is mainly used to watch the discharge of grain in the tower. The commonly used grain discharging device is divided into a grid plate and six impeller-type two structures. Grid plate grain discharging mechanism by the leakage bucket, grain grid plate, crank connecting rod, and other components, normal grain discharging grid plate block in the funnel below, need to discharge grain, under the action of the crank connecting rod mechanism, drive fixed grain discharging grid plate frame reciprocating motion, so that grain discharging grid plate and leakage bucket sometimes separate, sometimes overlap, used to control grain discharging speed. The six-impeller-type grain discharge device is composed of a grain leakage bucket, six impellers, and speed-regulating motor, etc. The six impellers are blocked in the grain leakage bucket. When the grain needs to be drained, the speed-regulating motor drives the six impellers to rotate, the grain goes down, and the speed of the six impellers controls the grain discharge speed. The grain from the discharge device flows through the discharge port to the circulating conveyor. Circulation conveyor in addition to conveying food, but also through the reverse transmission, after a dry did not reach the safe water of the food, and then back to the elevator feed port, and then the food is loaded tower drying again, drying cycle times by the food moisture level, at this time the dryer into the circulating drying state.
Source:
Online/GFMM
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