Material Properties
1) The viscosity of the material in the double cone rotary vacuum dryer The viscosity of the material changes with its moisture content. The viscosity can make the material agglomerate into lumps and stick to the wall of the cylinder. After drying, it is easy to stick to the dust collector and the wall of the pipe. Pneumatic vibrating and crushing devices can be used.
2) The allowable temperature of the material. The allowable temperature is the maximum temperature that the material can withstand. Exceeding this temperature will result in a change in material potency, decomposition damage or discoloration.
3) Bulk density of material The mass of material per unit volume is called bulk density. Since the material is a mixture of absolutely dry material and moisture, the absolutely dry material is often granular, powdery or solid block material, and the gap between the absolutely dry material particles varies with the different moisture content in the material. The bulk density of the original wet material and the material in the drying process is very different, and attention should be paid when choosing a dryer.
4) The slip angle of the material When stacking granular or powdery materials, when the angle between the inclined surface and the bottom surface of the material stack increases to a certain angle, the side material will slide down. The angle between the slope where the material slips and the bottom surface is called the slip angle of the material. The slip angle is related to material composition, moisture content, particle size and viscosity. When choosing a double cone dryer, you can choose the angle of the cone with reference to the slip angle of the material.
Drying Temperature
Depending on the physical properties of the material, an appropriate temperature can be selected. Usually, the variable temperature drying method can be used. The temperature is low at the initial stage of drying, and the temperature is gradually increased to increase the drying rate.
When vacuuming and heating, the drying speed is slow. When the material is heated to above the vaporization temperature of water, the drying speed will suddenly increase. The material is heated to the vaporization temperature under the corresponding pressure within the allowable temperature range and vaporizes a lot. The temperature remains unchanged, the added heat is used for the heat of vaporization and various heat losses, and the vacuum system continuously discharges the vaporized steam to maintain the pressure difference between the evaporation surface and the space, so that the drying continues. The moisture content of the material is reduced to a certain extent, and the moisture evaporated from the material is reduced. Under the condition of the same heating amount, the temperature of the material begins to rise, the pressure difference between the evaporation surface and the space decreases, and the drying enters the deceleration stage. The drying rate gradually decreases until it reaches zero.
Working Vacuum
Usually 103~10?Pa is used. The vacuum degree is high, the moisture vaporization temperature in the material is low, and the drying speed is fast. But the vacuum is too high, which leads to an increase in the cost of the air extraction system and an increase in the price of the dried material, which is not economical.
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