The dryer is one of the washing machines and is generally used to remove moisture from the material after the water has been eluted. Most dryers include a rotating drum that is driven by a belt with hot air around the drum to evaporate moisture. The drying cylinders all adopt the principle of positive and negative rotation of the drum to achieve the non-winding effect of the dried articles. Due to the same drying method, the heat energy consumed by drying and dehydrating one kilogram is basically the same, and the capacity of the heat source (hot air stove, steam radiator, etc.) of the dryer is also certain, so the main technical index of the dryer - drying capacity It is often based on the amount of dewatering per hour (or the maximum amount of dewatering). This indicator is measured under certain conditions, such as wet material type, initial moisture content, ultimate moisture content, hot air temperature, ambient temperature and humidity, and the like. As long as one of the conditions changes, the production capacity of the dryer equipment will have an impact, sometimes the impact is still large. The following are explained separately:
First, the type of wet materials
Wet material type refers here to the combination of material and moisture. The wet material can be divided into 1 capillary porous material, and the moisture is mainly combined with the capillary force, such as sand, silica, activated carbon, ceramics, etc., the bonding strength between water and material is small, drying is relatively easy; 2 colloid The combination of materials, moisture and materials is dominant, such as glue and flour dough. The material generally exhibits high viscosity, and the combined strength of moisture and material is large, and drying is difficult. 3 Capillary porous colloid materials have more than The nature of the two types of materials, such as peat, clay, wood, fabric, grain, leather, etc., is the most diverse, but the form of water combination between such materials is also different, which determines the difficulty of dehydration under the same conditions. Are not the same.
The shape of the material also has a great influence on the drying, such as granular materials, the particles are much harder to dry than the particles, and the bulk material is smaller in thickness than the thick one and is easy to dry.
Second, moisture content of wet materials
Moisture content (wet content) is the percentage of moisture in the total weight of the wet material.
The initial moisture content refers to the moisture content of the wet material before entering the dryer. Usually, the wet material can work in the dryer. The higher the initial moisture content, the more the dewatering capacity exhibited by the dryer is. . Conversely, the higher the initial moisture content and the higher the final moisture content, the more the dryer equipment can reach the maximum dewatering capacity, but the dry material yield decreases.
Third, the ultimate moisture content
Generally, the drying section is in the slow-drying stage. The lower the final moisture content is, the more difficult the drying is. The longer the drying time is required, the lower the thermal efficiency, and therefore the yield.
Fourth, hot air temperature
Hot air temperature, or drying medium temperature, is one of the most sensitive conditions in drying. The higher the hot air temperature, the more heat energy is contained, and the lower the relative humidity of the hot air, the stronger the ability to absorb water and carry moisture, which is very favorable for drying, and the drying heat efficiency is also high. In many drying equipment, when the other conditions are unchanged, the dewatering capacity of the dryer is basically proportional to the change of the hot air temperature. When selecting the drying equipment, it is necessary to have sufficient data for the ultimate temperature of the damaged material. In the case of material approval, try to select the high temperature medium. It should be noted that there are many drying methods, especially rapid drying. The temperature of the dried material is much lower than the drying medium temperature. For example, the hot air temperature of the air dryer is as high as 250 ° C or higher, and the discharge temperature is generally 60 ° C. the following. Dryer equipment
5. Environmental temperature and humidity
Here mainly refers to the influence of weather changes on the drying. Generally, the dryer equipment is heated by the atmosphere as the drying medium. The higher the temperature of the atmosphere, the lower the humidity, the more favorable it is to dry, while the southern spring and summer, the rain Humidity, high humidity, is not conducive to the performance of drying capacity, affecting production.
China has a vast territory, and the air humidity in the south and the south varies greatly. In some parts of the south, the humidity in winter is only 0.008 kg water / kg dry air, and in spring and summer, the atmospheric humidity is as high as 0.025 kg water / kg dry air, more than three times the former, therefore, in the comparison The hot air drying under low exhaust gas temperature (<90 °C), the atmospheric humidity increases in spring and summer, the drying rate will inevitably decrease, and the time required will rise. Due to the increase in atmospheric humidity, the equilibrium water content of the material will inevitably rise. These factors will reduce the dry yield and, in some cases, reduce the yield by more than 50%.