| The grinding workshop section is an important part of the mineral processing. It determines the mineral separation plant's disposal capability, and its investment expenditure of capital construction and management expenditure occupy most of the total plant's financing. Moreover, the quality of the grinding products gravely affects the economic and technological targets of ore processing.The grinding process is complicated and changeful, and the ball mill's parameters are various. In many plants, the grinding efficiency of the ball mill is very low, that is, the percent of the grinding products, whose size is smaller than 0.074mm, is few, the circulation burthen is too big or too small, the classification efficiency is too low, and the mineral separation targets always descend. The reason is that either the size of the ball, which has been loaded in the mill, is too big, or the characteristic of the ball charge in the mill is fallacious, by adding a kind of big ball. This dissertation introduces the method of accurate loading and adding balls. This method will improve the equality of the grinding products and increase the separation targets by determining the exact size of the balls, which will be loaded in the mill, and by adopting a reasonable method of adding balls.The method of accurate loading and adding balls consists of several steps. Firstly, the mechanical character of the ore should be measured. Secondly, the grain composition characteristic of the feed to the mill ought to be analyzed detailedly and the grain ought to be divided into 4 or 5 groups in sequence. Thirdly, by adopting the Duan's semi-theory formula (Formula 3.3), we will work out the exact ball size corresponding to every grain group. Then, we will carry through the grinding experiments in the laboratory to validate the calculating results. Finally, the scientific method of adding ball should be ascertained, by drawing the accumulative ball charge curve of the original loading balls and the accumulative ball chargecurve of the adding balls in the coordinate chart.Several ore processing plants, whose grinding operation has been improved by adopting the method of accurate loading and adding balls, show the results as follows: (1) The mill's productivity has augmented 10%~15% in the case of the same grain size distribution of the mill's feed and discharge. (2) The monomer decomposing degree of mineral has increased 5%~6% in the case that the size distribution of the grinding products have not changed. (3) The recovery has increased 1%~3% and the concentrate grade also has advanced, in the same separation condition. (4) In the case that the ball material has not changed, the consumptions of ball have fallen 10%~20%. (5) The power of mill has fallen 3%~5% with the same system of loading ball. (6) The mill's noise has descend more than 5dB. (7) The longevity of mill's scaleboard has prolonged.After adopting the method of accurate loading and adding balls, Dahongshan Plant show the results as follows: (1) In the classifier's overflow of the first grind, the percent of products, whose size is smaller than 0.074mm, reached 74.30% and increased 14.12%, the monomer decomposing degree of mineral increased 9.76% and the monomer metal's percent increased 8.13%, in comparison with the per cent that was measured in May when the second project had just been put into production. And the circulation burthen increased 119%, the quality classification efficiency reached 39.37%, i.e., it enhanced 110%, and the quantity classification efficiency reached 50.06%, i.e., it enhanced 3.34%. (2) In the classifier's overflow of the second grind, the percent of products, whose size is smaller than 0.074mm, reached 94.49% and increased 13.83% and the monomer decomposing degree of mineral increased 8.43%, in comparison with the percent that was measured in May when the second project had just been put into production. The metal percent in the products whose size is smaller than - 19um fell 1.53% (from 3.99% to 2.46%), that is to say, by adopting adding iron se... |
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