Abstract: The effects of leaching conditions on chromium extraction rate were investigated in the oxidative pressure leaching process of chromite ore with sodium hydroxide solution, including particle size, stirring speed, NaOH-to-ore ratio and temperature. The results showed that the extraction rate of Cr reached above 98% after 300 min at 250℃ with NaOH concentration of 60%(w), oxygen partial pressure of 3.2 MPa, particle size below 50 mm, stirring speed of 650 r/min and mass ratio of NaOH to ore 4.0:1. And the chromium extraction rate increased with the decrease of ore particle size and the increase of stirring speed, mass ratio of NaOH to ore and temperature. The macro-kinetic investigation revealed that the leaching process was controlled by reactant diffusion in the solid product layer and described by 1-2/3X-(1-X)2/3=kt with apparent activation energy of 54.5 kJ/mol and pre-exponential factor of 328.4 min-1.

Key words: chromite ore, sodium chromate, elevated pressure, alkali leaching, kinetics, oxygen

摘要： 研究了铬铁矿加压碱浸氧化反应的动力学过程，考察了铬铁矿粒度、搅拌、碱矿质量比和反应温度等对铬浸出率的影响. 结果表明，反应温度250℃、碱浓度60%(w)、氧分压3.2 MPa、铬铁矿粒度小于50 mm、搅拌转速650 r/min、碱矿质量比4.0:1、反应时间240 min的条件下，铬铁矿中铬的浸出率达98%以上，且随铬铁矿粒径减小、搅拌转速增加、碱矿质量比增加和反应温度升高而提高. 反应产物为MgFe2O4和Mg(OH)2，浸出时呈固态包裹在未反应颗粒外层. 宏观动力学研究结果表明，铬铁矿加压碱浸氧化反应过程受反应物在固体产物层中的扩散控制，可用方程1-2/3X-(1-X)2/3=kt描述，该反应的表观活化能E=54.5 kJ/mol，指前因子A=328.4 min-1.

关键词: 铬铁矿, 铬酸钠, 加压, 碱浸, 动力学, 氧气