Microbubble Column에 의한 휘수연석의 부유선별에 관한 연구

Abstract

Abstract

Flotation of Molybdenite by Microbubble Column

Kang Hyun Ho Advisor : Prof. Han, Oh-hyung, Ph.D. Dept. of Energy & Resources Engineering Graduate School of Chosun University

Molybdenite, commercially the most important ore mineral of molybdeum (not produced as metal in nature), is relatively abundant in compared to other metallic minerals in Korea. But, as the grade of raw ore from the domestic mines is too low (below Mo 0.5 %), it is required to develop a new separation technique, suitable for domestic mines, for the efficient separation of low grade molybdenite. Therefore, in this study, the results below were acquired by conducting a microbubble column flotation on 6 molybdenite samples changing conditions such as the kind of reagent and its amount, the amount of wash-water and air flow rate to confirm the flotation, the efficient depression of gangue mineral and the possibility of improving the flotation efficiency through an establishment of appropriate reagent and its optimal amount and elementary technology.

41.4 % Mo was obtained with 84.75 % recovery by conducting a batch flotation on the raw ore of Shin-Yeomi mine molybdenite(Mo 0.4 %). But, in the result of conducting microbubble column flotation, the efficiency of flotation was low due to the low grade of molybdenite ore(0.4 %) and fine particles of impurity. Also, 52.5 % Mo was obtained with 62.28 % recovery by conducting a column flotation on a batch flotation concentrate (Mo 28.1 %).

The product with 53.5 % Mo and Cu(impurity) contents of 0.86 % was obtained by making an experiment to improve the grade (of Mo) and depressing Cu on the first concentrate of KMC(Mo 21.8 %). However, as the recovery was low, marking 33.88 %, and contents of Cu was over 0.5 %. it is considered that the additional experiment to improve the recovery and depressing Cu should be made.

By employing microbubble column separation technique on the imported concentrate of KAF(Mo 48.7 %), a fine particle separation technique, able to recover high quality concentrate(over Mo 57 %) more than 90 % without cleaning was established. Also, as a result of separate SEM & mapping of each element on feed concentrate and tailing, in the case of Cu(impurity), limit on complete separation was identified due to the bond between Cu ultra fine particle under 6.62 ㎛ and Mo.

As a result of performing XRD and composite analysis on the first concentrate of Dong-Won NMC(Mo 17.4 %), quartz, grossular and hedenbergite existed as gangue minerals. Also, when an experiment was made without separate grinding process to confirm the possibility of microbubble column's continuous flotation process, there was a limit to improving the grade up to over Mo 36 %. Therefore, after 5 minutes grinding time, Mo 54.8 % was obtained with 88.26% recovery at a condition of DF 250 as frother (3 L/ton), sodium silicate as depressant (1 kg/ton), Lime (1 kg/ton), ATCC (10 mL), wash water of 450 mL/min. and air flow rate of 830 mL/min.

The first concentrate of Dong-Won NMC added with the flocculant in the precipitating and dewatering process of tailings in order to recycle circulation water showed Mo grade 20.4 % and had no difference with the fourth sample concerning components. However, unlike the fourth sample, on microbubble column flotation, the efficiency of flotation was low marking Mo 45.2 % and the recovery 27.46 %. Also, in the result of conducting a batch flotation on a same sample in KIGAM (by Jeon and Park), for improving the grade and recovery, it was confirmed that the amount of pH needs to be adjusted to the range of pH 5 ～ 6 (which is subacid).

It was confirmed that a final concentrate of Dong-Won NMC(Mo 50.4 %) was formed with high grade over 57 % Mo in relative coarse particle range of 60 × 140 mesh. Also, an experiment was made to confirm the possibilities of increasing the grade and recovery of Dong-Won NMC`s final concentrate. As a result, Mo 58.6 % (MoS2 97.83 %) was obtained with 87.47 % recovery at a condition of 15 minutes grinding time, kerosene as collector 0.1 L/ton, AF 65 as frother 7.2 L/ton, wash water of 630 mL/min and air flow rate of 1,197 mL/min.

In this study, it was confirmed that a microbubble column flotation needs a separate re-grinding process and a large amount of frother to maintain stable bubble layer compared to a batch flotation. However, about 50 % Mo was obtained with about 80 % recovery from 5 ～ 6 times of cleaning stage in a batch flotation, whereas more than 54 % Mo was obtained with over 85 % recovery from only 1 time of flotation in a microbubble column flotation. Also, as the raw ore with low grade of 0.4 % showed low flotation efficiency due to accompanied floating fine particles of gangue mineral compared to that in a batch flotation, it was confirmed that it is more efficient to conduct a microbubble column flotation on the 1st concentrate of batch flotation.