硅镁型红土镍矿脱羟基相变过程动力学研究

Kinetic Study of the Dehydroxylation Phase Transition Process in Silica-Magnesium Laterite Nickel Ores

镍具有优良的物理化学性质,应用领域广泛,镍资源主要存在于硫化镍矿和红土镍矿中,目前红土镍矿正逐渐成为主要的镍提取原料,由于红土镍矿含水量大,在冶炼过程中通常要对矿石进行高温预处理,目的是去除矿石晶格里的羟基水以及预先还原部分金属,但这部分羟基水的脱除需要消耗大量能量,并且产生物相变化,对预还原及浸出都会产生影响,因此探究红土镍矿脱羟基过程的物相变化及动力学条件,对后续加工作业具有重要的研究意义。利用热力学分析软件模拟计算了红土镍矿加热过程中可能发生的化学反应,并采用热重-差热分析及XRD分析研究了硅镁型红土镍矿加热过程的物相变化,从室温到1400℃范围内进行了5种升温速率的非等温动力学实验,在256.8、582.8和823.0℃处有三个特征峰,分别对应褐铁矿脱羟基、蛇纹石脱羟基以及硅酸盐矿物的相变。采用非等温动力学模型求解来确定反应的表观活化能及指前因子,使用Flynn-Wall-Ozawa法和Kissinger-Akahira-Sunose法计算了蛇纹石脱羟基过程的活化能,并利用Satava-Sestak法对常用的30种机理函数进行拟合,保留符合条件的机理函数,确定Avrami-Erofeev方程的A1/3函数符合脱羟基过程,其积分形式为G(α)=[-ln(1-α)]3,求得蛇纹石脱羟基反应的活化能为258.71kJ/mol,lnA为28.94,平均线性相关系数为0.9951,蛇纹石脱羟基过程符合随机成核及随后生长模型。

Nickel has excellent physicochemical properties and a wide range of applications,nickel resources are mainly found in nickel sulfide ores and nickel laterite ores,and nickel laterite ores are gradually becoming the main raw materials for nickel extraction.Due to the high water-content of nickel laterite ores,high temperature pre-treatment of the ores is usually required in the smelting process to remove hydroxylated water in the lattice of the ores and to pre-reduction of part of the metal,but this part of the hydroxylated water removal needs to consume a lot of energy and produce physical phase changes,which will affect the pre-reduction and leaching.However,the removal of this part of hydroxyl water needs to consume a large amount of energy,and produces physical phase changes,which will have an impact on the pre-reduction and leaching,so it is important to investigate the physical phase changes and kinetic conditions of the dehydroxylation process of nickel laterite ores for the subsequent processing operations.In this paper,the possible chemical reactions during the heating process of nickel laterite ore were simulated and calculated using thermodynamic analysis software,and the physical phase changes during the heating process of nickel laterite ore of silica-magnesium type were investigated using thermogravimetric-differential thermal analysis and XRD analysis,and non-isothermal kinetic experiments were carried out at five heatingrates from room temperature to 1400℃.Three characteristic peaks were observed at 256.8,582.8and 823.0℃,corresponding to the fuselage dehydroxylation process.The three characteristic peaks corresponding to the dehydroxylation of limonite,dehydroxylation of serpentine,and phase transformation of silicate minerals respectively.A non-isothermal kinetic model solution was used to determine the apparent activation energy and the finger front factor of the reaction.The activation energy of the serpentine dehydroxylation process was calculated by using the Flynn-Wall-Ozawa method and the Kissinger-Akahira-Sunose method,and 30commonly used mechanistic functions were fitted by using the Satava-Sestak method,and the eligible mechanistic functions were retained.The A1/3function of the Avrami-Erofeev equation was determined to be consistent with the dehydroxylation process,and its integral form was G(α)=[-ln(1-α)]3,which yielded the activation energy of the serpentine dehydroxylation reaction to be 258.71kJ/mol,lnA being 28.94,and the average linear correlation coefficient of 0.9951.The serpentine dehydroxylation process is consistent with stochastic nucleation and subsequent growth of serpentines.The process is consistent with the stochastic nucleation and subsequent growth model.