铜渣煤基直接还原过程中的铁物相转变

Phase transformation of iron in copper slag coal-based direct reduction

采用直接还原工艺回收铜冶炼渣中的铁,对不同温度下铁物相的转化以及金属铁颗粒的长大规律进行分析。通过对铜渣进行配料造球-煤基直接还原焙烧-弱磁选处理,得到了直接还原铁精矿指标随时间及温度的变化。结果表明,在焙烧温度1300℃,焙烧时间30 min的条件下得到了TFe质量分数为91.55%、金属化率为92.99%及回收率为82.99%的铁精矿。对不同还原温度下铁精矿分析表明:1050、1100、1150℃均生成了金属铁,但还原度及TFe含量较低。1200℃时发现有Fe2C5及SiC相的生成,形成的CaSiO3·FeSiO3液相影响了还原过程。1250℃时生成了Fe3C,但Fe2SiO4会与CaO形成低熔点矿物。1300℃时精矿中含有大量金属铁,但也形成了低熔点化合物,增加了后续处理的难度。金属铁颗粒首先出现在矿物颗粒失氧而产生的裂纹及孔洞的边缘,金属铁小颗粒被大颗粒吸收并聚结长大,金属铁经过斑点状-蠕虫状-仙人掌状的转变最后形成致密的金属铁层。

The direct reduction process was used to recover the iron in the copper smelting slag,and the transformation of iron phases and the growth rules of metallic iron particles at different temperatures were analyzed.The change of concentrate index with time and temperature was obtained through direct reduction roasting the pelletized copper slag with coal base and low-intensity magnetic separation.The results show that the concentrate with TFe content of 91.55 mass%,metallization rate of 92.99%and recovery rate of 82.99%could be obtained under the roasting temperature of 1300℃and roasting time of 30 min.The analysis of concentrate at different temperatures shows that iron-Fe is formed at 1050,1100 and 1150℃,but the degree of reduction and TFe content are low.The formation of Fe2C5 and SiC phases are found at 1200℃,and the liquid phase of CaSiO3·FeSiO3 affects the reduction process.And Fe3C is formed at 1250℃,but Fe2SiO4 and CaO will form low melting point minerals.At 1300℃,the concentrate contains a large amount of iron,but it forms a low-melting compounds,which increases difficulty in subsequent processing.Iron particles first appear at the edge of cracks and holes caused by oxygen loss of mineral particles,and small size of iron particles are absorbed and coalesced by large particles,after the transformation from speckled,vermicular and cactus palms,the metal iron finally forms a dense iron layer.