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物料的干燥过程分为哪些阶段?

2020-01-13 来源:http://www.zhongyanjixie.com 发布人:众焱小编 浏览量:
[导读]:  干燥试验可以确定物料的干燥过程。在干燥机干燥条件下,即干燥机干燥介质的温度、湿度、流量以及与物料在干燥过程中的接触量都是设定不...
  干燥试验可以确定物料的干燥过程。在干燥机干燥条件下,即干燥机干燥介质的温度、湿度、流量以及与物料在干燥过程中的接触量都是设定不变的数值,观察干燥机干燥物料在干燥过程中的水分、温度以及干燥机干燥速度的变化。如果测试。应用一定的温度、湿度、风速的热风烘干机来干燥少量的湿物料,基本上是接近干燥机恒定的干燥条件。
  Drying test can determine the drying process of materials. Under the drying condition of the dryer, namely, the temperature, humidity, flow rate of the drying medium of the dryer and the contact amount with the material in the drying process are all set constant values. Observe the change of the moisture, temperature and drying speed of the drying material of the dryer in the drying process. If tested. The application of a certain temperature, humidity, wind speed of the hot air dryer to dry a small amount of wet materials is basically close to the constant drying conditions of the dryer.
  通过对物料在干燥过程中的变化(物料水分的变化和干燥速度随时间的变化)的测试得出的干燥速度曲线,可以将It本体物料的干燥过程分为以下几个阶段。
  The drying process of it bulk material can be divided into the following stages through the drying speed curve obtained from the test of the change of material in the drying process (the change of material moisture and the change of drying speed with time).
  1. 预热阶段
  1. preheating stage
  当物料与热风(干燥介质)接触时,热风将热量传递到物料表面。此时,由于单位时间内传递到材料表面的热量远远大于表面水分蒸发所需的热量,材料表面温度迅速升高。当热空气的湿球温度达到时,单位时间内传递到材料表面的热量等于表面水分蒸发所需的热量。这是处于平衡状态。在预热阶段,物料中的水分逐渐减少,表面温度逐渐升高。干燥机的干燥速度不断增加。预热时间短,不排除太多的水。
  When the material is in contact with hot air (drying medium), the hot air will transfer the heat to the material surface. At this time, because the heat transferred to the surface of the material in unit time is far greater than the heat required for evaporation of surface moisture, the surface temperature of the material rises rapidly. When the wet bulb temperature of the hot air reaches, the heat transferred to the surface of the material in unit time is equal to the heat required for the evaporation of the surface moisture. This is in balance. In the preheating stage, the moisture content in the material decreases and the surface temperature increases. The drying speed of dryer is increasing. The preheating time is short and too much water is not removed.
木屑烘干机厂家
  2. 干燥机的恒定干燥阶段
  2. Constant drying stage of dryer
  在干燥机干燥前释放,干燥机干燥速率恒定的物料干燥阶段称为恒定干燥阶段。在恒速干燥阶段的干燥,因为它的高含水物质,材料内部水分很容易扩散到表面,材料内部迁移率可以适应材料表面的水表面水的蒸发速度,使材料表面润湿结合水,传热速率和水蒸发速度维度保持不变。在这个阶段,干燥机的干燥速度与物料的粒度和盆内的初始湿度无关,而与干燥机的干燥温度、空气的湿度以及气流的速度和方向有关。它的特点是表面总是保持湿润。这种材料的温度不升高。
  The material drying stage which is released before drying and the drying rate of the dryer is constant is called constant drying stage. In the constant speed drying stage, because of its high water content material, the internal moisture of the material is easy to diffuse to the surface, the internal mobility of the material can adapt to the evaporation speed of the water surface on the surface of the material, so that the surface of the material is wetted with combined water, and the dimensions of heat transfer rate and water evaporation speed remain unchanged. In this stage, the drying speed of the dryer is not related to the particle size of the material and the initial humidity in the basin, but to the drying temperature of the dryer, the humidity of the air and the speed and direction of the air flow. Its characteristic is that the surface is always wet. The temperature of this material does not rise.
  3.干燥机的缓慢干燥阶段
  3. Slow drying stage of dryer
  当物料含水率降至临界含水率时,物料干燥速率随含水率的降低而降低
  When the moisture content of the material decreases to the critical moisture content, the drying rate of the material decreases with the decrease of the moisture content
  物料干燥机的干燥速率随着含水率的降低而减小,说明物料内部向表面的水分转移速率低于物料表面水分的蒸发速率。材料的表面,特别是突出部分会变得干燥,单位时间内的蒸发量会减少。因此,表面水分蒸发所需热量降低,物料表面温度逐渐升高,干燥机干燥速度降低。干燥机的干燥速度逐渐降低,后期下降较快。
  The drying rate of the material dryer decreases with the decrease of the moisture content, which indicates that the moisture transfer rate from the inside of the material to the surface is lower than the evaporation rate of the moisture on the surface of the material. The surface of the material, especially the protruding part, will become dry and the evaporation per unit time will be reduced. Therefore, the heat required for evaporation of surface moisture is reduced, the surface temperature of materials is gradually increased, and the drying speed of dryer is reduced. The drying speed of the dryer decreased gradually, and it decreased rapidly in the later stage.
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