悬浮焙烧过程中菱铁矿热解原位动力学、相变及产物特性研究

Siderite pyrolysis in suspension roasting:An in-situ study on kinetics,phase transformation,and product properties

菱铁矿是一种储量丰富的铁矿石,但其利用率较低,尚未得到高效开发利用。菱铁矿选择性转化为磁铁矿和CO是高效利用菱铁矿的关键。本文研究了悬浮磁化焙烧过程中菱铁矿的原位动力学和机理,丰富了菱铁矿作为还原剂的绿色悬浮磁化焙烧理论体系。气体产物分析表明,反应速率峰值随温度的升高而增大,且反应速率曲线呈现“早峰长尾”的特征。菱铁矿热解反应的机理模型为收缩球模型(R^(3)):f(α)=3(1-α)^(2/3),E_(α)为46.4653 k J/mol;A为0.5938 s^(-1);动力学方程为k=0.5938exp[-46.4653/(RT)]。原位HT-XRD结果表明,在N2气氛下菱铁矿的最终产物为磁铁矿和方铁矿,它们具有良好结晶度。在620℃时,固相产物的磁性达到峰值,其中饱和磁化强度(Ms)、剩磁磁化强度(Mr)和矫顽力(Hc)分别为53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g和12.40×10^(3)A/m。经过焙烧,菱铁矿颗粒的致密结构遭到破坏,转变为疏松多孔的结构,降低了颗粒的力学强度,有利于降低后续磨矿作业的能耗。

Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.