Study On The Floatation Behaviour For Donganshan Carbonate-containing Iron Ore

In recent year, the iron ore market of China shows a serious shortage situation and the imports of iron ore increase substantially because of the rapid development of iron and steel industry and the continuous rise of iron and steel production. In the period of Tenth Five-Year, the imports of iron ore of China were increased from 92.31Mt in 2001 to 275Mt in 2005, which increased 180Mt. The imports of iron ore of China were reached 383Mt in 2007 and 416Mt in 2008 respectively, which accounted for more than 50% of iron ore consumption of our country. In order to ensure the health and sustainable development of iron and steel industry of China, it is necessary to supply high quality iron ore with stability and enough. For this reason, it has been proposed clearly in the Eleventh Five-Year Planning that the low-grade iron ore resources should be used actively. It is also imminent to use the refractory iron ore. So, it is significant to explore and utilize the complex-refractory iron ore.The iron ore of Donganshan is classical refractory hematite in our country with the characteristics of low-grade, fine disseminated granularity and complex composition and structure. To study the technique of separating this type of iron ore is always regarded as the grand research project of our country and/or Metallurgical Department since Sixth Five-Year. Looking upon the flowsheet evolution which is changed from two-stage grinding, single direct floatation to two-stage grinding, middlings regrinding, gravity separation-magnetic separation-anionic reverse floatation which is running now, we can see that high ferrooxidans ore is utilized effectively and the concentrate grade is increased from 60% to 64.8%. But the problem of poor adaptability for separating the carbonate-containing iron ore has not been solved until now. Especially for separating the carbonate-containing iron ore which content is over 10%, the index of floatation is deteriorated rapidly, evenly, no separation is achieved. So, it is necessary to solve the separation problem of Donganshan iron ore floatation according to the floatation behaviour of carbonate-containing iron ore.The technical mineralogy characteristics, main minerals floatability, floatation separation characteristics, floatation separation mechanism and floatation technology and process of Donganshan carbonate-containing iron ore are studied systematically in this study.Studying of main minerals floatability shows that, using the combination of starch and CaCl2 as regulators in the floatation system of anionic collector, when pH is 5 to 7, the floatability of siderite is better and the floatability of magnetite, hematite or quartz is worse, but when pH is higher than 11, the floatability of quartz is better and the floatability of magnetite or hematite is worse. In different pH extent, an obvious floatation difference is appeared between different minerals.Studying of floatation separation characteristics and its mechanism shows that, in the floatation system of anionic collector, the iron minerals and quartz can be separated from each other by direct floatation in the strong acid or neutral condition, hematite and quartz can be separated from each other by reverse floatation. The existing of siderite creates a fatal impact on the floatation separation result of iron mineral. The enrichment ratio of concentrate and collective index are decreasing with the content of siderite increasing.Because siderite is adsorbed and covered on the surface of quartz and hematite, the surface properties of quartz and hematite is similar as the surface property of siderite, which leads to the similar floatability between these two minerals and siderite. So, a new flowsheet, step-floatation, is explored to separate siderite, hematite and quartz from each other, that is, siderite is separated firstly under neutral condition, so the influence of siderite can be eliminated, then, quartz is separated by floatation under strong alkaline condition.Studying on the floatation process shows that, using step-floatation to treat the mixed magnetic concentrate of Donganshan beneficiation plant, the result of the laboratory closed-circuit experiment can be obtained with concentrate grade 67.84%, recovery 69.47%, and tailings grade 19.15%, recovery 19.14%. The result of continuous floatation experiment can be obtained with concentrate grade 66.37%, recovery 62.93%, and tailings grade 22.67%, recovery 22.96%. By first step floatation, about 54.34% siderite in raw material is concentrated to the rougher concentrate which grade is about 38%. The rougher concentrate is treated by roasting-magnetic separation and the final concentrate with grade 57.80% and recovery 49.53% can be obtained. Thus, the final concentrate of siderite can be utilized further.In this study, a new flowsheet, step-floatation, to process Donganshan carbonate-containing iron ore is explored firstly, and a good separation result can be obtained using this new flowsheet, which has obvious innovation and practice. This research result has a great guiding significance for the exploitation and utilization of Donganshan carbonate-containing iron ore.