The vacuum belt dryer can dry two kinds of materials: one is pure extract type raw materials (including water extraction, alcohol extraction, water purification alcohol, etc.), and the other is water powder mixed type raw materials (including particle mixing). However, both raw materials must have good fluidity, especially the gouache mixed raw materials should not be thoroughly mixed and need to be kept warm and stirred to prevent the materials from solidifying after cooling.
In vacuum belt drying, the original specific gravity and solid content of the material are two key parameters.
Since most of the raw materials are concentrated extracts, the specific gravity is generally around 1.20, and for the drying effect of the vacuum belt dryer, the specific gravity of the extract is in the range of 1.27 to 1.35; The solid content requirement of the paste can theoretically range from 30% to 75%, but if the yield is to be increased, the most effective extract solid content should be kept at 45% to 75%. Because the extract with too low solid content is prone to the following two problems during the drying process, one is that the extract is difficult to fix the flow on the carrier conveyor belt; the second is that the extract lacks the skeleton support when the extract evaporates and cannot be dried on the conveyor belt. Afterwards, it is completely peeled off from the conveyor belt.
Another parameter to consider during vacuum belt drying is the viscosity of the extract, as most of the extracts have a large viscosity, which is the most annoying problem with conventional spray drying and vacuum dryers. The vacuum belt dryer has a unique advantage in this respect. Under normal circumstances, if the conveyor belt is properly selected and the heating and cooling temperature parameters are reasonable, the materials with a viscosity below 14000 mm/s can be well dried in the equipment.