The leading products of evaporators are wastewater evaporators, three-effect evaporators, double-effect evaporators, falling film evaporators, external circulation evaporators, forced circulation evaporators, salt-containing transpiration crystallizers, MVR transpiration crystallizers; the leading products of concentrators are Extraction and concentration equipment, vacuum concentration tank, double-effect concentrator, single-effect concentrator, low-temperature concentrator and other equipment. Generally, the following factors should be considered when selecting a model:
1. The viscosity of the solution
The scale of the change of solution viscosity during the transpiration process is the primary consideration in the selection. The range of solution viscosity applicable to various evaporators is shown in the table.
2. The thermal stability of the solution
When the solution that is easy to decompose, polymerize and scale when heated for a long time is evaporated, the evaporator with less stagnant material and short residence time should be selected.
3. Solution with crystals separated
For solutions with crystals separated during transpiration, an external heating evaporator or forced circulation evaporator should be used.
4. Foaming solution
The solution that is easy to foam will generate a large number of layers of heavy and unbreakable foam when it evaporates. After filling the entire separation chamber, it will be discharged with the secondary steam. It will not only lose the material, but also pollute the condenser. To evaporate this solution, an external heating evaporator, a forced circulation evaporator or a rising film evaporator should be used. If the design of the central circulating tube evaporator and the hanging basket evaporator is larger, it can also be used for the transpiration of this solution.
5. Corrosive solutions
When evaporating corrosive solutions, the heating tube should be made of special materials, or the inner wall should be lined with corrosion-resistant materials. If the solution is not afraid of contamination, a direct contact evaporator can also be used.
6. Easy scaling solution
No matter what kind of solution is transpired. After the evaporator is used for a long time, there will always be dirt on the heat transfer surface. The thermal conductivity of the scale layer is very small, so for the solution that is easy to scale, it should be considered to choose an evaporator that is easy to dry and clean and has a high circulation rate of the solution.
7. The processing capacity of the solution
The processing capacity of the solution is also an element that should be considered in the selection type. When the heat transfer area is required to be greater than 10m2, it is not suitable to use a scraper stirring thin film evaporator. When the heat transfer area is required to be more than 20m2, it is advisable to use multi-effect transpiration operation.
In a word, it should depend on its physical condition. Choose a suitable evaporator, and some functions of common evaporators can be listed according to the list.