It is used to low grade magnetite. Due to the strong magnetic and easy to grind, one stage grinding is adopted for magnetite with coarse particle distribution, conversely the multi stages grinding. At present the fine grinding technology promoted by Xinhai improves the concentrate grate from 61% to 67%.
Weak magnetic mineral could use the strong magnetic mineral separation process after the magnetizing and roasting.
In two stages grinding, stages separation, single weak magnetic flow, fine grinding means adding fine screen regrinding process to separate fine minerals timely and reduce the over-grinding. It improves the capacity of ball mill and concentrate grade by 2%.
A magnetite in Inner Mongolia, the main mental mineral was magnetite with disseminated structure and fine particle distribution. The iron content was about 12-16%. This plant adopted the grinding-weak magnetic process and obtained 65% concentrate grade and 90% recovery rate, but the operation cost is too high after a long time running. It authorized Xinhai to reform the process. Xinhai did not only keep the original indexes, but also reduce the operation costs. Indexes comparison as follow
|Comparison of Reformation||Process||Iron Concentrate Grade|
|Iron Concentrate Recovery Rate|
|Before Reformation||Three stages grinding, Three stages magnetic separation||65.58||90.15|
|After Reformation||Stages grinding, stages separation||67.81||92.69|
Due to the low grade of the iron ore, the stages grinding and stages separation could reduce energy consumption. Cost saving is the key of developing the mine. The fine grinding process has guide significance for similar iron ore