摘要
Roasting bastnaesite concentrates is a crucial process in extracting rare earths.This study explored an efficient suspension roasting technology and investigated the bastnaesite pyrolysis and cerium(Ce)oxidation.Relevant analytical tests were applied to evaluate the phase and surface property variations of bastnaesite,and isothermal kinetic analysis of bastnaesite pyrolysis and Ce oxidation was performed.The results revealed that bastnaesite decomposed rapidly and accompanied by Ce oxidation,and the gas-solid products were identified as CO_(2),Ce_(7)O_(12),La_(2)O_(3),CeF_(3) and LaF_(3),with Ce oxidation restricted by bastnaesite pyrolysis.As roasting time prolonged,cracks and pores appeared on bastnaesite surface;the BET specific surface and pore diameter increased.In later roasting period,the pore diameter continued to increase but the specific surface decreased,assigned to particle fusion agglomeration and pore consolidation.Additionally,the surface C content reduced and Ce(Ⅳ)content increased gradually as roasting progressed.The reaction kinetics all followed Avrami-Erofeev equations,the reaction orders of bastnaesite pyrolysis and Ce oxidation decreased with decreasing reaction temperature.The calculated activation energies at lower temperatures were higher than those calculated at higher temperatures.This study analyzed the bastnaesite reaction mechanism to supply a reference for the application of suspension roasting technology in bastnaesite smelting.
氟碳铈矿氧化焙烧是提取稀土元素的关键工艺。本文采用一种清洁高效的悬浮焙烧技术研究了氟碳铈矿热解和铈氧化过程。通过相关分析测试,探讨了氟碳铈矿在焙烧过程中的相变和表面性质演变,并对热解和铈氧化进行了等温动力学分析。结果表明,氟碳铈矿焙烧的气固产物为CO_(2)、Ce_(7)O_(12)、La_(2)O_(3)、CeF_(3)和LaF_(3),氟碳铈矿迅速分解并伴随铈的氧化。随着焙烧时间的延长,氟碳铈矿表面出现裂纹和孔隙,BET比表面积和孔径增大。在焙烧后期,孔径继续增大,但比表面积减小,这与颗粒熔融团聚和孔隙闭合有关。此外,随着焙烧的进行,表面碳含量逐渐减少,而Ce(Ⅳ)含量逐渐增加。氟碳铈矿热解和铈氧化反应动力学均符合随机成核与生长模型,但反应级数随温度的降低而减少。低温条件下的活化能高于高温条件下的。本研究分析了氟碳铈矿的反应机理,可为悬浮焙烧技术在氟碳铈矿冶炼中的应用提供参考。
基金
Projects(2022YFC2905800,2021YFC2901000)supported by the National Key R&D Program of China
Project(52174242)supported by the National Science and Technology of China
Project(52130406)supported by the National Science and Technology Major Project of China。
作者简介
Corresponding author:LI Wen-bo,PhD,Professor,E-mail:liwenbo@mail.neu.edu.cn,ORCID:https://orcid.org/0000-0002-4988-9766。
