Concentration is mainly done for removing water (generally coming from an acid or water remaining after reaction) inside the solution and get the required concentration for the next step (granulation, prilling, direct selling, etc.)
A falling film evaporator is a special type of heat exchanger used to concentrate solutions. In a falling film evaporator, evaporation takes place inside vertical tubes through which the process fluid to be evaporated flows downwards by gravity as a continuous film. Steam or process steam can be used as the heating medium is placed on the outside of the tubes.
The air swept concentrator is a special type of heat exchanger used to get very high concentrated solutions (up to 99.9% of ANSOL). The steam used in the falling film part evaporates the major part of the water in the feed solution while the hot air bubbling in the bottom box helps to get rid of the last percent of water.