According to the characteristics of Camellia oleifera seeds, the tea seeds are covered with a layer of dense and separated tea seed shells, which hinders the heat transfer and water evaporation process of the tea seed kernels. The traditional drying method has a long cycle, which is low efficiency and is not environmental friendly. The use of air energy dryer greatly reduces the drying time of camellia oleifera seeds. The drying time of each batch of camellia seeds is about 20 hours. The drying process is carried out in 5 key steps:
First step: the temperature is controlled at 55 °C for no more than 2 hours. It is heated only without dehumidification. It is heated evenly and reaches an average and consistent temperature. The water begins to evaporate into the air. The rate of water vaporization also increases rapidly.
Second step: you should begin to heat up and dehumidify, the temperature is controlled at 60°C, the humidity is reduced from the initial 75% to 55%, and the time is about 6 hours. The removal speed of the surface moisture of the camellia seeds diffuses to the surrounding medium, and the moisture content drops very quickly.
Third step: maintain the constant speed for drying and set the temperature at 60 °C. Use continuous dehumidification mode to remove humidity to 40% for 4 hours.
Fourth step: the humidity is reduced to 30% at this stage, and the temperature is increased by 3°C, and the drying time remains unchanged, drying for 4 hours.
Finally, reduce the humidity to 20%, keep the temperature unchanged, the drying time is 4 hours, the air humidity is 20%. The humidity of camellia seeds is about 10-12%. In general, it takes 20 hours for a 12P heat pump dryer to dry the camellia seeds thoroughly.