Abstract: The cooling crystallization process of ammonium chloride by the double decomposition reaction between ammonium nitrate and potassium chloride was studied.The effects of the cooling rate，agitation rate，and adding amount of crystal seed etc.on the purity and the particle size distribution of ammonium chloride product were investigated.Results showed that the particle size of ammonium chloride and separation efficiency could be improved effectively，with proper cooling rate，stirring rate，and crystal seed adding amount.The optimum operation conditions were as follows: cooling rate was 0.3 K/min，agitation rate was 350 r/min，particle size of crystal seed was 150~180 μm，and quantity of crystal seed was 1.88%.Under these conditions，the ammonium chloride crystals will get bigger and evener particle size.

Key words: ammonium chloride, cooling crystallization, ammonium nitrate, potassium chloride, double decomposition reaction