煅烧菱镁矿在氯化铵乙二醇溶液中的浸取动力学

Leaching Kinetics of Calcined Magnesite from Glycol Solution Dissolved with Ammonium Chloride

系统地研究了菱镁矿的煅烧条件以及煅烧粉在氯化铵乙二醇溶液中的浸取动力学.菱镁矿在750℃下煅烧2h左右能使MgCO3分解完全而CaCO3不分解,过烧会使晶粒长大,从而降低浸取速率.在消除外扩散影响的前提下,浸取过程在反应物(NH4Cl与MgO)以化学计量比反应、氯化铵的初始浓度为0～1.23mol/L时符合未反应收缩核模型(Unreacted shrinking coremodel),且浓度为1.23mol/L时浸取速率达到最大;浸取速率受表面化学反应控制,活化能为44.74kJ/mol.

The calcination conditions of magnesite and the leaching kinetics of calcined powder in glycol solution dissolved with ammonium chloride were systematically studied. It was found that MgCO3 was decomposed completely under 750 ℃ for 2 h, but CaCO3 was not. Over calcination of magnesite could obviously lower down the leaching rate of calcined powder due to the growth of its particles. Without the effect of outer diffusion, the leaching process accorded with unreacted shrinking core model at the stoichiometric proportion of NH4Cl-MgO and initial concentration of NH4Cl between 0-1.23 mol/L. Furthermore, the leaching rate reached the maximum value with 1.23 mol/L initial concentration of NH4Cl. It was concluded that the leaching rate was controlled by surface chemical reaction. The activation energy was calculated as 44.74 kJ/mol by the model on the basis of experimental data.