Introduction and characteristics of vacuum disc dryer:
(1) when the water is vaporized, the pressure is proportional to the temperature, thus drying under low pressure can be dried at low temperature. It is very suitable for the heat sensitive materials to prevent the material from overheating and denaturing.
(2) the heat and mass transfer direction of the convective drying is opposite, the mass transfer resistance is large, the hard shell is easy to appear on the surface of the material, the direction of the heat and mass transfer of the vacuum conduction drying is the same, and the internal and external pressure difference of the material is great, the mass transfer resistance is small, and the hard shell will not appear.
(3) dry in a closed and anoxic environment, suitable for oxidizing materials, and also beneficial to kill some bacteria. It is beneficial to the drying of food materials and is also suitable for materials that are not allowed to pollute during the drying process.
(4) dry under closed and low pressure. The gas in the system is very small. It is suitable for solvent recovery process with high recovery rate.
(5) the dry environment is isolated from the atmosphere and is suitable for drying inflammable and explosive materials in the air.
(6) Some materials with color and fragrance are easier to maintain their original characteristics when they are dried at low temperature and airtight, which is impossible for convective drying.
(7) vacuum drying equipment is a kind of external pressure vessel, which has complex structure, consumes more steel and has high cost.
(8) the sealing of the equipment is complex and the maintenance cost is high.
(9) the cost and operating cost of the vacuum maintenance system are all higher than that of the atmospheric drying method.
(10) drying under low pressure has adverse effects on heat transfer. When the evaporation temperature is too low, the steam pressure inside the material is low, the mass transfer power is insufficient, and the drying rate is affected.