Abstract: Pyrolysis rate of witherite seriously affects the barium hydroxide yield.Preparation process conditions of barium hydroxide by high-temperature pyrolysis of witherite and hot water leaching were studied.Effects of temperature，pressure，particle size，additives，and atmosphere on pyrolysis rate were also investigated.Results showed that when the particle size of witherite was small，it could reduce the temperature of pyrolysis；when the particle size was under 150 μm，the ideal pyrolysis temperature was 1 373.15 K；adding graphite or some other carbon additives could greatly improve the pyrolysis rate of barium carbonate； adding argon inert gas to change the gas composition in the furnace and to reduce the concentration of CO and CO₂ produced in the reaction had little influence on improving pyrolysis rate of witherite；when argon gas flow was 0.5 m3/h，the pyrolysis rate increased only by 2.55%；calcining barium ore in vacuum sintering furnace（absolute pressure 5 Pa） could greatly improve the pyrolysis rate and reduce the pyrolysis temperature；the best pyrolysis temperature was 1 273.15 K and barium conversion rate was 82.3%；and the lower pressure and less CO2 could improve the pyrolysis rate of witherite.

Key words: barium ore；witherite；barium hydroxide；pyrolysis