Graduation tower

Structure used in the production of salt

A graduation tower is a structure, used in the production of salt, that removes water from a saline solution by evaporation, increasing its concentration of mineral salts. The tower consists of a wooden wall-like frame stuffed with bundles of brushwood that have to be changed every five to ten years, as they become encrusted with mineral deposits over time. The salt water runs down the tower and partly evaporates. At the same time, some minerals from the solution are left behind on the brushwood twigs.

This keyword could refer to multiple things. Here are some suggestions: