Abstract: Thermodynamic calculation and analysis were made for the reaction system of preparing NH₃ by using thermal decomposition of NH₄Cl and Mg(OH)₂.Process conditions of the preparation of NH₃ were investigated with reaction temperature,amount-of-substance ratio, and reaction time as the variables and with nitrogen content of solid product,chlorine yield,and NH₃ yield as evaluation indexes.Results showed the chlorine yield and NH₃ yield both could reach more than 90% and the decomposition of Mg(OH)₂ and NH₄Cl could directly produce NH₃ without inletting water steam into the reactor when the reaction temperature was 375 ℃,reaction time was 50 min,and amount -of-substance ratio of Mg(OH)₂ to NH₄Cl was 1∶0.75.

Key words: magnesium hydroxide, ammonium chloride, thermal decomposition