Abstract:

Chromium ore processing residue (COPR) from roasting chromite without calcium is characterized systematically.The detoxification of COPR by SO₂ reduction is investigated. The detoxification process combining mechanical activation with SO₂ reduction is proposed. The results show that the main phases of the COPR are (Fe, Mg) (Cr,Fe) ₂O₄ and MgAlFeO₄. The content of Cr₂O₃ in the CPR is 12.23%. The smaller the particle size of COPR, the lower the content of the total Cr(Ⅵ), water-soluble Cr(Ⅵ) and insoluble Cr(Ⅵ). In the detoxification process of COPR by SO₂ reduction, stirring can promote the process of external diffusion effectively and increasing liquid solid ratio is beneficial to the leaching of Cr(Ⅵ) in the COPR. With the increase of temperature, the leaching of Cr(Ⅵ) in COPR increases first, then decreases sharply. The pressure of reaction system has little influence on the detoxification of the COPR. Under the optimized experimental conditions:the pressure 0.1 MPa, the temperature 60℃, the stirring speed 500 r·min^-1, and the reaction time 60 min, the removal rate of Cr(Ⅵ) in COPR was 90%, while the removal rate of Cr(Ⅵ) in COPR was 98.1%, and Cr(Ⅵ) content falls below 25 mg·kg^-1, meeting the national discharge standard after 90 min of mechanical activation to the COPR.

Key words: chromite processing residue, reductive detoxification, leaching, mechanical activation

摘要：

系统地对铬铁矿无钙焙烧渣进行了表征，并研究了SO₂还原解毒铬渣，提出了机械活化与SO₂还原相结合的解毒工艺。结果表明，该铬渣主要物相组成是（Fe，Mg）（Cr，Fe）₂O₄和MgAlFeO₄，铬渣中Cr₂O₃含量为12.23%，铬渣粒径越小，含有的总Cr（Ⅵ）、水溶性Cr（Ⅵ）、难溶性Cr（Ⅵ）量越小。SO₂还原解毒铬渣工艺过程中搅拌能有效强化外扩散过程，液固比增大有利于铬渣中Cr（Ⅵ）的浸出，铬渣中Cr（Ⅵ）的浸出随温度升高先增加后急剧降低，反应体系中压力变化对铬渣还原解毒效果影响不大。优化的SO₂还原解毒铬渣条件为：压力0.1 MPa、温度60℃、搅拌速度500 r·min^-1、反应时间60 min，此时铬渣中Cr（Ⅵ）的去除率达90%；机械活化90 min的铬渣进行SO₂还原解毒60 min后，渣中的Cr（Ⅵ）去除率达到98.1%，含量降至25 mg·kg^-1以下，达到国家排放标准。

关键词: 无钙焙烧铬渣, 还原解毒, 浸取, 机械活化