Research On Magnetic Roasting-Magnetic Separation Technology Of New Caledonia Chromite

The ironmaking cost continued to rise with high dependence on import ore resources, which makes the utilization of low-grade iron ore resources for ironmaking process is particularly necessary, especially for some corporations far from the seaport. New Caledonia chrome ore, which contains TFe 32.58% and the content of Cr2O3 is 29.46%, is neither suitable for BF ironmaking nor smelting process of Fe Cr, and the magnetic susceptibility of it is so low that it’s difficult to improve its grade by mineral processing, leading to most of which have not been effectively utilized. This paper takes the New Caledonia chrome ore as the research object, systematical studying the pelletizing process, roasting process and the technology for improving the magnetic susceptibility for the purpose of providing the theory support for the use of New Caledonia chrome ore.The study on the chrome ore with XRD and optical microscope finds that the primary composition of New Caledonia chrome ore is chromite, and particles of that shows granular distribution, with good crystallization degree, compact structure, coarse grain and less pore. The Cr3+ in the chromite is often replaced by Fe3+ and Al3+ and becomes isomorphism structure, and Fe2+ is often replaced by Mg2+, forming magnesium chromiteand iron eskolaite, which leads to separation difficulty.The result of pelletizing test shows that: only when bentonite ratio is about 2%, can the quality of green ball meet the demand of transportation and roasting process; the appropriate parameters of New Caledonia chrome raw ore pelletizing process are following: 2% bentonite, 2% pulverized coal, the proportion that the mineral powder granularity less than 200 mesh control in 80%, 9.5% moisture of green ball; the suitable drying parameters of New Caledonia chrome raw ore pellets are: the particle size of pellet is 8~15mm;the suthickness of pellet is about 200mm; drying air velocity is 1m/s with 300℃drying temperature and 10 min drying time.Basket of magnetic roasting is not suitable for magnetic roasting process of chrome raw ore pellet. New Caledonia chrome raw ore pellets are magnetize roasted 40 minutes with high temperature reaction tube under 800℃ isolated from air atmosphere using primary grinding, primary magnetic separation and one concentrating process, which can obtain iron concentrate with 58.67% TFe and chromium concentrate with 46.96% Cr2O3. The recovery of TFe and Cr2O3 reached 77.06% and 84.75% respectively and the yield of iron concentrate and chromium concentrate are 46.23% and 53.77% respectively.