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中南大学学报(自然科学版)

Journal of Central South University

第39卷    第2期    总第180期    2008年4月

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文章编号:1672-7207(2008)02−0311−06
铵光卤石热脱水及热分解动力学
周宁波1,肖 华1,陈白珍2,侯朝辉1

(1. 湖南理工学院 化学化工系,湖南 岳阳,414000;2. 中南大学 冶金科学与工程学院,湖南 长沙,410083)

摘 要: 将盐湖水氯镁石溶液和氨法沉镁过滤后的氯化铵溶液混合,在一定条件下制得铵光卤石,研究铵光卤石在热空气中脱水为低水铵光卤石的最佳工艺条件,同时对铵光卤石进行热重差热分析(TG-DTA)。研究结果表明:铵光卤石在热空气中脱水是分步进行的,包括脱水、水解、热分解等化学反应;在110~180 ℃控制脱水时间可得低水合铵光卤石不水解,超过此温度范围时铵光卤石在脱水的同时会部分发生水解。且铵光卤石于160 ℃脱水4 h可得到含结晶水为0.5~1的低水合铵光卤石,其可用作生产无水氯化镁的原料。用Freeman-Carroll法计算的动力学参数表明,铵光卤石在各温度范围内的脱水反应均不是基元反应,而是由多个不同级数的基元反应所  控制。

 

关键字: 铵光卤石;热脱水;热分解;动力学

Dehydration and thermal decomposition kinetics on ammonium carnallite in flowing air condition
ZHOU Ning-bo1, XIAO Hua1, CHEN Bai-zhen2, HOU Zhao-hui1

1. Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414000, China;2. School of Metallurgical Science and Technology, Central South University, Changsha 410083, China

Abstract:The optimum dehydration technology in hot air atmosphere and thermogravimetry-differential thermal analysis (TG-DTA) curves of ammonium carnallite, which was synthesized using the saline lake bischofite and filtrate stock of deposit magnesium by ammonia as raw materials were studied. The results show that ammonium carnallite will change to dehydrated ammonium carnallite by heating from 110 ℃ to 180 ℃ for controlling dehydration time. But the hydrolysis takes place when temperature is higher than the above temperature. Dehydration process includes dehydration, hydrolysis and thermal decomposition. Dehydrated ammonium carnallite (MgCl2•NH4Cl•nH2O, n=0.5−1) is obtained at 160 ℃ for 4 h, suitable for preparation of anhydrous magnesium chloride. Kinetic parameters calculated by Freeman-Carroll method show that the dehydration of ammonium carnallite is not an elementary reaction, but controlled by a series of elementary reactions in different temperature ranges.

 

Key words: ammonium carnallite; dehydration; thermal decomposition; kinetics

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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