粉砕ボールの磨耗とミル内ボールの平衡負荷
1974 年 90 巻 1039 号 p. 601-606
詳細
1974 年 90 巻 1039 号 p. 601-606
The size of make-up balls is one of the most important factors affecting capacity and grinding efficiency of ball mills. However, the size distribution of seasoned ball load which performs actual grinding work is establis hed by the relationship between ball size x and the rate of wear as well. Employing the thickness of film removed by wear per hour h(x) as the wear rate at size x, the author has derived eq.(1) which states that the distribution of number of balls in an equilibrium ball load is determined by h(x).
Previous studies which appear in references indicate that h(x) follows eq.(4).From eqs.(1) and (4) the distribution of the number of balls n(x) is n(x) =nf/2kxm (5) where nf is the number of make-up balls fed per hour, k and m are constants.
Eq.(9) derived from eq.(5) shows the size distribution of equilibrium ball load is determined by the wear film index m.And the value can be obtained when the size distribution of equilibrium ball load in an operating mill is measured. The index m in Yaguki No.3 mill with make-up balls rationed is found approximately zero by using eq.(17)(fig.1).This means equal film wear in equal grinding time.
Additional, equations on the equilibrium ball load for practical applications are also presented as follows. And it is expected that the control of ball mill operation will have more scientific means when the wear film indices are measured in mariy operating mills.
1) The procedure to calculate the start-up media is described (eqs.9 and 17 and fig.1).
2) Specific surface area is given.in eqs.(21) or (23).
3) Actual wear rate is obtained by eqs.(24) to (27).It was 4.2×10-4cm/h in Yaguki No.3 mill.
4) Size of the individual ball reduces as indicated in eqs.(30) or (31), and the time required to reach equilibrium is given in eqs.(33) or (34).
5) After the condition of make-up balls is changed, the portion of remaining balls previously fed decreases as stated in eqs.(35) and (36) corresponding to weight and surface area respectively (fig.2).
6) Loss of weight of remaining balls per hour is given in eq.(37).
