KCl is the important raw material for fertilizer production in China. The separation process synthesis for the salt-water systems with KCl has important theoretical significance and practical application value. With the example of NaCl-KCl-H2O system

this study has presented a synthesis method for the separation process synthesis of the disalt system with the same anionic. Based on the temperature affect and common-ion effect

this method was built by analyzing the solid-liquid equilibrium. The illustration method were used to determine the separation process form the phase diagram

the design process was very simple and practical. Two synthesis case of NaCl-KCl-H2O system and one of MgCl2-KCl-H2O system were given in the paper

respectively

and the corresponding technological processes were also given.