Study On Gas Bubble Assisted High Gradient Magnetic Separation And Process Experiments Of Iron Tailling Containing Rare Earths

High gradient magnetic separation (HGMS) is a known universal mean to separate weakly fine magnetic minerals, but it easily subject to gangue inclusion and magnetic medium jam. In this paper, we design a gas-mixing assisted HGMS (g-HGMS) by use of introducing gas bubbles in the separation space of HGMS, then conduct element and process separation tests for one iron tailing containing rare earths, in order to enhance the separation efficiency of common HGMS.Element separation test shows that the introduction of gas-mixing can restrain gangue inclusion in magnetic separation, thus increase iron grade in concentrate for HGMS. The further first g-HGMS - second g-HGMS process tests show, when magnetic field of 0.8T/0.6T~0.4T first/second separation, magnetic medium filling rate of 3.89%, and a gas flow rate of 0.16m3/h are used as the experimental parameters, a iron concentrate of grade of 48.2% and a recovery of 53.39% was obtained from the original tailing of TFe=17.8%. In contrast to free gas-mixing, the grade increases by about 3% and recovery decreases by about 1%. The analysis of fluid mechanics suggests there are two reasons responsible for the improvement of iron grade due to gas mixing. Firstly, the rising bubbles activize periodic pressure waves along their trajectorie, loosen and dejoin the aggregates suspended in mineral slurry, reducing the gangue inclusion; secondly, due to contact and collision of rising bubbles encountered with magnetic medium arranged in the separation zone, some bubbles random break, the resultant local negative pressure can laniate the agglomerates adsorbed in magnetic medium, and clean out the concentrate.The centrifugal saparation- g-HGMS– inverse floatation process tests show, in the optimization routine, an iron concentrate of grade of 53.6% and a recovery of 42.5% and a rare earth middle concentrate of grade of 20.38% and a recovery of 42.5% were obtained respectively form the original tailing of TFe=17.8% and REO=6.36%. In contrast to free gas-mixing, the iron concentrate increases in grade by about 3~4% and decreases in recovery by about 1~2%.