Grinding Parameters Optimization Technique For Meishan Iron Ore

Crushing and grinding is an important process of mineral processing in metal mine.The operating equipment investment,production costs,energy consumption and steel consumption in crushing and grinding is the largest proportion of Mineral Processing.So how to improve grinding efficiency,save energy,optimize grinding conditions is crucial.Meishan In Iron Concentrator grinding operation includes two stages of closed circuit mill,which is currently facing some problems.For example,the underflow of classsifiers is less than 5%;the ball size of 120mm and 80mm added into mill is too large resulting in over comminution;iron ore is easily enriched in underflow;high grade of-10?m products and high loss rate in overflow of secondary classification,and so on.This paper is concentrated on how to optimize the grinding parametres,to minimize over comminuted size fractions and to improve grinding efficiency.Based on the Meishan Iron ore mineralogy study,iron mainly occur in magnetite,martite,semi-martite,siderite,and a small amount occur in pyrite and iron silicate minerals.Total grade of iron is 47.62%,mainly valuable minerals for iron is magnetite,of which the iron distribution rate is 61.20%,followed by the hematite with distribution rate accounted for 18.26%.The sum of hematite and magnetite is 79.46%,the content of other iron minerals such as siderite is accounted for 17.38%,also it contains a small amount of iron sulfide iron and silicate iron.On this basis,a study of the factors affecting the first stage grinding process was carried out.According the content of new ?-74?m,?pass and ?-10?m,this paper determined the suitable range of grinding time,grinding concentration,mill speed,the production capacity of the mill and ball diameter.To further investigate the interaction between the different factors,this paper carried out grinding concentration,ball filling rate,grinding time as the main factor of the "three factors and five levels" orthogonal experiments to determine the grinding conditions:Grinding concentration 70%,filling rate 35%,grinding time 3min.For the secondary grinding,on the condition of the grinding media being steel forging,single steel balls and mixed balls,this paper studies the impact of grinding time,grinding concentration and filling rate and determine laboratory secondary grinding conditions:grinding time 3min,grinding concentration 75%.The secondary grinding media should adopt steel forging.Grinding test of mixed ball group as grinding media showed that a low filling rate of 35%-40%is priority with low speed.To examine the effect of different size fractions on magnetic separation recovery,magnetic separation were carried out for each size fraction and found that the recoveries of overall size fractions were above 90%,and that the coarser grain size,the higher recovery.Iron loss mainly occurred in-0.074mm products,suitable grinding fineness should take into account the large yield of qualified grain size,and the reduce of yield of over-communicated.In order to optimize the grinding effect and study the impact of the ball size,this paper adopted Duan ball diameter semi-theoretical formula to calculate each time the required ball mill diameter of each segment,For the practical grinding,the first ball mill of irregular lump ore required the maximum ball diameter is 80mm,the secondary mill required the maximum ball diameter is 50mm.After adopting optimized grinding on the conditions obtained in the orthogonal experiment,the grinding product compared with the overflow product of secondary classification,the yield of-0.074mm increased by 7.00%-10.00%;qualified grain yield increased by 3.21%?3.53%and particle size is more uniform;the recovery of qualified grain size increased by 0.34%?2.35%.Further separation of optimized grinding product was carried out,and concentrator products compared to overflow of secondary classification,the yield of iron concentrate raised 4.93%-10%,the recovery of TFe raised 5.74%-9.00%;due to the improvement of particle characteristics,the yield of magnetic separation tailings reduced 1.33%-5.00%,the recovery of TFe reduced 2.36%?4.17%in the loss,the recovery of S decreased 6.24%?11.67%in the loss.Compared with the overflow product of secondary classification,the yield of-10?m in tailings reduced 16.24%?30.08%.