有色金属(冶炼部分)

白云鄂博矿是一座大型多金属共生矿，以丰富的铁资源和稀土资源闻名于世。然而，由于矿石成分复杂，矿物嵌布粒度细等问题，铁和稀土的回收面临诸多困难。提高铁和稀土资源的综合回收对提高经济效益、保障国家战略资源安全和减少环境污染具有重要的现实意义。采用碳热还原熔分和强化结晶分离相结合的工艺，从白云鄂博矿中协同提取稀土和铁资源。碳热还原熔分试验表明，在最佳还原条件下(温度1 200℃、时间30 min、C/O=1.2)，还原铁的金属化率达到95.21%。在此基础上于1 550℃时，实现了渣铁高效的分离，得到了熔分铁和稀土品位为14.35%(质量分数)的稀土富渣。同时，还原30 min后，稀土矿物相完全转变为渣中硅酸盐(Ca_4.3Ce_5.7Si_6O_24.32F_1.68)结构。强化结晶分离试验表明，在1 200℃的冷却条件下，稀土相析出较完全。通过控制超重力分离参数(G=1 000)、保温时间(5 min)和温度(1 200℃)，实现了稀土相和渣相的高效分离，得到的人造稀土精矿中稀土品位显著提升至40.12%。该研究证实，将碳热还原熔分和强化结晶分离工艺相结合，可实现白云鄂博矿中铁和稀土的协同回收，同时避免了传统工艺回收率低的缺陷，为我国白云鄂博矿产资源的绿色高效开发提供了新的技术思路和实践依据。

Bayan Obo deposit is a polymetallic symbiotic ore primarily containing iron and rare earth elements(REEs). Currently, a combined beneficiation-metallurgy process is predominantly employed for recovering iron and REEs resources from the ore. However, the beneficiation process is significantly affected by ore characteristics, processing flowsheets, and technological levels, resulting in relatively low comprehensive recovery ratesonly 50%–70% for iron and just 10%–15% for REEs. In recent years, reduction-melting separation technology has garnered increasing attention in the research and application of Bayan Obo ore due to its low-carbon, highefficiency, and suitability for complex symbiotic ores. However, the resulting rare earth slag suffered from issues such as low rare earth content and complex elemental composition, which severely hindered the further recovery and utilization of rare earth elements. Current research on REEs recovery from the slag primarily focuses on two major approaches: hydrometallurgical leaching and mineral processing extraction of rare earth phases. In hydrometallurgy, direct leaching of rare earth slag faces challenges such as low REEs content, necessitating excessive chemical reagents to facilitate REEs dissolution. This not only consumes substantial resources but also generates large quantities of wastewater and residues. Regarding the separation of rare earth phases, conventional methods like natural sedimentation are employed. However, due to the intricate morphology of rare earth phases and their tight intergrowth with impurities, separation proves highly inefficient, resulting in extremely low REEs recovery rates. To explore efficient REEs recovery from slag and achieve synergistic extraction of iron and REEs, this study investigates the Bayan Obo ore using a reduction-melting separation-enhanced crystallization separation process. Thermodynamic analysis of carbothermal reduction reveals that the process involves phase transformations of both iron and rare earth minerals. According to the equilibrium diagram of iron oxide reduction, the initial reduction temperature for iron oxides in Bayan Obo ore has to exceed 701.32 ℃ to form metallic iron, with CO-mediated indirect reduction dominating at high temperatures. During reduction, rare earth minerals(monazite and bastnaesite) decompose into rare earth oxides. Gibbs free energy analysis of oxide formation indicates that within the temperature range of 800–1 800 ℃ and using coal powder as a reductant, the oxygen potential line of CO remains above that of rare earth oxides, suggesting their stability against reduction. These rare earth oxides will further react with calcium oxide and silicon dioxide in the rare earth slag, forming complex compounds. Experimental results demonstrate optimal parameters for iron oxide reduction: temperature of 1 200 ℃, duration of 30 min, and at C/O ratio of 1.2, achieving a metallization rate of 95.21%. Concurrently, REEs transitions completely from their original REPO₄ and REFCO₃ structures to silicate phase, exhibiting a homogeneous dispersion without localized enrichment. The optimal reduction product was held at 1 550 ℃ for 60 min to conduct the slag-iron separation experiment, yielding rare earth slag with an REEs grade of 14.35 wt.%. Further investigation into the crystallization behavior of REEs in the slag reveals that at 1 400 ℃, REEs remain uniformly dispersed without phase precipitation, sporadic white precipitates emerges at 1 300 ℃, significant growth and crystallization occurres at 1 200 ℃, and equilibrium is reached at 1 100 ℃ with no further notable size increase. The separation experiment was conducted under optimal crystallization temperature, a separation time of 10 min, and G=1 000, supergravity separation experiments demonstrate that supergravity effectively overcame interfacial tension between rare earth phases and the slag matrix, producing an artificial rare earth concentrate with an REEs grade of 40.12%(mass fraction), The research outcomes not only achieve synergistic recovery of rare earth elements and iron, but also provide a novel technological perspective for the comprehensive utilization of Bayan Obo ore resources.