Natural evaporation: refers to the evaporation of a solution at a temperature lower than the boiling point, such as when salt is exposed to seawater. In this case, due to the solvent only vaporizing on the surface of the solution, the solvent vaporization rate is low.

The indirect heat source heats the walls of the container and transfers it to the evaporated solution. The heat transfer process carried out in a wall type heat exchanger.

The steam generated in the heating chamber contains a large amount of liquid foam, which can be separated from the steam through self condensation or the action of a defoamer when it reaches a larger evaporation chamber. Usually, the defoamer is located at the top of the evaporation chamber. Boiling evaporation: Heating a solution to its boiling point to evaporate in a boiling state. The evaporation operations in industry are basically of this type.