The comprehensive utilization and environment-friendliness of processes for recovering fresh water or valuable salt from seawater, salt-lakes, or mineral deposits are of utmost importance for sustainable development.One primitive sustainable process for recovering salt from sodium-sulfate-type brine in Yuncheng salt lake had been considered one of the greatest inventions of ancient China, however, the replaced process of mass extraction of single Na_2SO_4 in recent years, has reduced a large amount of residual brine.In this research, relying on the salt-forming diagram in the non-equilibrium state, the technical secrets of ancient salt processes were uncovered, and a new comprehensive utilization system was proposed and tested experimentally.The new system includes a vacuum salt-making process and a normal pressure kieserite process, which can gradually eliminate the existed waste liquid and aid in the sustainable development of the Yuncheng salt-lake.The continuous experiment of salt-making process running stably in the double salt region without double salt formation, which proves the feasibility of salt-forming diagram applied in industrial process.Thus salt-forming diagram would be extremely valuable to industry process design and control, especially, the treatment of concentrated brine.
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