含硼铁精矿选择性还原综合利用基础研究

The resource of paigeite resource is rich in China, but conventional beneficiation process can preliminarily separate camsellite from paigeite only due to fine particle size, complicated composition, and intimate association of minerals. The boron-bearing iron concentrate with grade(B2O3) 4%~6% and recovery(B2O3) 20%~30% was obtained. Boron resource is hugely wasted in these conventional processes. In recent years, the further separation between boron and iron of boron-bearing iron concentrate become technical bottleneck for the development and utilization of paigeite resource. Therefore, the innovative technical development and fundamental research are significantly important to comprehensive utilization of boron-bearing iron concentrate..The project that combines the theories of mineral processing, ferrous metallurgy and other disciplines uses the selective reduction technology to reduce iron minerals to appropriate metallic iron particles for further separation and limit the reduction of boron minerals, then the iron power and boron-rich slag of high quality is to be obtained by magnetic separation,which will realize the comprehensive utilization of boron-bearing iron concentrate. The formation and change of major minerals, the growth mechanism and evaluation method of metallic iron particles, and controlling operation on distribution of boron and activity of boron-rich slag will be clarified by the investigation on mineralogy, reduction of iron minerals and growth of metallic iron particles, and the influence factors on composition and activity of boron-bearing phase in the selective reduction. Based on the achievement of this project, the fundamental theory and key technology will be proposed which will be an important theoretical support to comprehensive utilization of boron-bearing iron concentrate.

我国硼铁矿资源丰富，由于矿物结晶粒度细、组成复杂、共生关系密切等原因，常规选别方法仅能初步分离硼和铁，获得的含硼铁精矿中B2O3品位4%～6%，回收率20%～30%，造成硼资源的巨大浪费。含硼铁精矿中硼铁二次分离成为硼铁矿开发利用的技术瓶颈，研究该矿中硼铁分离创新性技术及其基础性科学问题具有重要的理论和实际意义。.本项目将矿物加工、冶金等多学科有机结合，采用选择性还原技术将含硼铁精矿中的铁矿物还原为适宜分选的铁颗粒，并控制硼矿物不被还原而进入渣相，再经分选获得铁粉和优质富硼渣，从而解决含硼铁精矿综合利用难题。通过研究不同还原阶段物料的工艺矿物学、铁矿物还原及铁颗粒生长规律、含硼相成分及活性影响因素，阐明选择性还原过程中主要矿物结构演变过程，形成铁颗粒粒度评价及控制体系，建立硼元素走向及富硼渣活性调控机制，解决选择性还原过程中的关键技术和基础性科学问题，为含硼铁精矿的综合利用提供理论支撑。

含硼铁精矿是硼铁矿选矿终端产品，其中含B2O3 4%～6%，占原矿硼总量的30%，含硼铁精矿中硼铁二次分离成为硼铁矿资源开发利用的技术瓶颈，因此，研究含硼铁精矿中硼、铁高效分离具有重要的理论与实际意义。.针对含硼铁精矿物料特性，突破了传统选矿理念，创造性提出“阶段选择性还原-高效分选”选冶联合新技术，即首先将含硼铁精矿中的铁氧化物充分还原为金属铁而硼氧化物不能被还原，然后在二段还原过程中促使金属铁晶粒长大到适宜分选的粒度，最后对还原熟料进行高效分选。.以还原熟料金属化率及分选指标为评价标准，系统地研究了还原温度、还原时间、升温速率、碳酸钠用量、氧化钙用量等因素对还原效果的影响。确定适宜的一段还原条件为还原温度1125℃，还原时间150min，升温速率5℃/min，碳酸钠添加量5%，氧化钙添加量5%。二段还原条件为还原温度1250 ℃，还原时间45 min。在此条件下制备出的还原熟料铁品位73.80%，金属化率为91.12%。经弱磁选获得TFe品位93.72%，回收率96.24%的铁粉及含B2O314.55%，硼回收率93.57%的富硼渣，富硼渣活性达81.23%。.应用光学显微镜、XRD、SEM、EDS等分析手段对不同阶段还原物料的化学组成、矿物组成、结晶粒度等特性进行了分析。研究结果表明，铁矿物以Fe3O4→FeO→Fe顺序被还原，其中以碳和铁氧化物的间接反应为主反应。硼镁石在阶段还原过程中失去结晶水变为遂安石(Mg2B2O5)，部分遂安石又与菱镁矿(MgCO3)分解产物氧化镁(MgO)结合形成小藤石（Mg3B2O6）。.利用热重分析技术，研究了含硼铁精矿选择性还原过程的动力学和动力学参数。等温法试验确定了配碳系数分别是1.0、1.5和2.0时含硼铁精矿选择性还原过程的活化能E分别是199.69KJ/mol、175.95KJ/mol和167.09KJ/mol ，指前因子A分别为3.89×104 min-1 、1.18×104 min-1和5.22×103 min-1。非等温法确定了配碳系数是2.0，升温速率是10℃/min时含硼铁精矿的活化能E为135.93KJ/mol，指前因子A为2.78×104 min-1。.本研究阐明了还原过程中主要矿物结构演变过程，建立了硼元素走向及富硼渣活性调控机制，获得了高品位铁粉和优质富硼渣，对含硼铁精矿的综合利用具有一定指导意义。