Abstract: Investigations were conducted to purify crude Li₂CO₃ via direct carbonation with CO₂ at atmospheric pressure and pyrolysis with both water bath heating method and microwave heating method. The reaction kinetics of LiHCO₃ pyrolysis was studied and the effect of different operating conditions including initial concentration of LiHCO₃ solution, pyrolysis temperature and stirring speed on the purity of Li₂CO₃ was investigated to obtain the optimal operating conditions. Results showed that the effect law is similar in the two pyrolysis processes. The purity of the Li₂CO₃ increases firstly and then decreases with the increase of the initial concentration of LiHCO₃ solution and the stirring speed, while the purity of Li₂CO₃ first decreases and then increases with the increase of pyrolysis temperature. The product yield increases with the increase of initial concentration of LiHCO₃ solution and pyrolysis temperature and is essentially unaffected by the stirring speed. Under the optimal operating conditions, the purity of Li₂CO₃ can reach up to 99.86% and 99.81% in water bath heating and microwave heating process, respectively. In addition, the pyrolysis rate of microwave assisted pyrolysis is 6 times that of water bath heating process, indicating that the microwave heating technology can significantly improve pyrolysis efficiency and reduce energy consumption.

Key words: Lithium bicarbonate, Pyrolysis process, Traditional heating, Microwave heating, Product yield

摘要： Investigations were conducted to purify crude Li₂CO₃ via direct carbonation with CO₂ at atmospheric pressure and pyrolysis with both water bath heating method and microwave heating method. The reaction kinetics of LiHCO₃ pyrolysis was studied and the effect of different operating conditions including initial concentration of LiHCO₃ solution, pyrolysis temperature and stirring speed on the purity of Li₂CO₃ was investigated to obtain the optimal operating conditions. Results showed that the effect law is similar in the two pyrolysis processes. The purity of the Li₂CO₃ increases firstly and then decreases with the increase of the initial concentration of LiHCO₃ solution and the stirring speed, while the purity of Li₂CO₃ first decreases and then increases with the increase of pyrolysis temperature. The product yield increases with the increase of initial concentration of LiHCO₃ solution and pyrolysis temperature and is essentially unaffected by the stirring speed. Under the optimal operating conditions, the purity of Li₂CO₃ can reach up to 99.86% and 99.81% in water bath heating and microwave heating process, respectively. In addition, the pyrolysis rate of microwave assisted pyrolysis is 6 times that of water bath heating process, indicating that the microwave heating technology can significantly improve pyrolysis efficiency and reduce energy consumption.

关键词: Lithium bicarbonate, Pyrolysis process, Traditional heating, Microwave heating, Product yield