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The batch cycle grain dryer is suitable equipment for drying rice in the southern rice region. Having mastered the main factors that affect the drying process of paddy rice, the importance attached to the operation can give better use to the effectiveness of the dryer.
Drying of rice is a complex process. Drying conditions are variable and there are many influencing factors. However, the drying medium - hot air, drying object - rice, drying equipment - drying machine structural performance and drying method selection - drying process is the main influencing factor.
One, hot air 1, hot air temperature. The temperature of the hot air determines the quantity of heat that is transmitted to the rice. When the temperature of the hot air is high, the water vaporization on the surface of the rice is accelerated and the water transfer rate inside the rice is accelerated. In addition, the temperature of the hot air increased, and the ability to take away the water from the rice increased. Therefore, an increase in the hot air temperature not only results in a faster drying rate, a shorter drying time, but also a lower unit heat loss. However, the hot air temperature must not be excessively increased. The hot air temperature is too high and the drying speed is accelerated, but it may affect the quality of rice. In the batch-type circulating dryer, the possibility of popping the waist of rice increases when the precipitation amplitude is more than 1.2%/h. Therefore, when rice is dried, the temperature of hot air should be raised without affecting the quality of rice.
2, hot air volume. Appropriately increasing the speed at which hot air passes through the rice can also accelerate the drying process of the rice. When the hot air temperature and rice water content are the same, the hot air flow rate is less than 0.5 m/s, and the drying effect is most obvious. The amount of induced draft and the pressure of the induced draft fan are the most important factors that affect the drying speed. In the case of relatively dry ambient air, the purpose of drying the rice can be achieved only by activating the "circulation" and "air supply" functions. With a small amount of air, the moisture of the grain cannot be fully taken away. If the air volume is too large, the grains will be sucked away and be lost. When the initial water content of rice is high, the hot air flow rate has a significant effect on the drying process of rice.
3, hot air relative humidity. Hot air humidity affects the moisture absorption capacity of the device. When the humidity of the hot air reaches saturation, it cannot continue to absorb moisture. Therefore, the drying rate becomes slower.
Second, rice 1, rice varieties. Different rice varieties have different chemical compositions, organizational structures, forms of moisture and rice dry matter, moisture absorption properties, and so on, so their drying characteristics and drying time are also different.
2, the moisture content of rice before drying. The content of rice water before drying can also affect the speed of the drying process. When the water content of rice is low, the main evaporation of the drying process is the micro-capillary water and adsorbed water of rice, and the evaporation of these moisture is relatively difficult, and therefore, the drying speed is slow. When the water content of rice is high, the water content of rice is mainly free water, and the drying speed is fast.
Third, the dryer structure performance 1, dryer type. With different types, the condition of hot air is different from the contact with rice and the form of rice movement. Therefore, the drying speed and drying uniformity are also different.
2, the dryer process quality. For example, if the drying section is not sealed properly, it will cause cold air to be sucked in, thereby reducing the hot air temperature and prolonging the drying time. Another example is a displacement mechanism. If a displacement impeller is used, the speed of the impeller determines the time for heating and slowing the circulation of the sulphur. The impeller rotates fast, the grain has a short residence time in the ventilation section, the heating time is short, the valley temperature is low, and the circulation is fast. The rotation of the impeller is slow, the rice has a long residence time in the ventilation section, and the heating time is long, but it also increases the bursting rate. Therefore, the speed of the impeller should be adjusted according to the specific conditions.
Fourth, the drying process is reasonable drying process should be: so that the internal moisture diffusion rate of rice is equal to or close to the external evaporation rate. Therefore, for paddy rice with different water content and the safe storage water selected after drying, different heating and slowing Su process, ie, gap drying, should be selected during operation. It is necessary to consider not only the dry quality of rice but also the drying efficiency. .