Patent EA-000208-B1 (EA)
Title: Method for grinding of granular material and grinding equipment
Inventor: HINTIKKA VAINO VILJO HEIKKI
IPC: B02C17/04
Filed: 1996-03-07
Abstract: 1. A method for grinding granular material, particularly ore material, wherein the employed feed is precomminuted ore material or corresponding solids and water, which are fed into a mill serving as the grinding apparatus, comprising a grinding chamber provided with a grinder charge, in which grinding chamber the solids are ground, and from the grinding chamber there is obtained a mill product with a determined grain size distribution, characterized in that the solids content, i.e. slurry density, in the feed is adjusted to be such that it is of the order 45 % by weight or less, in which case the solids content of the slurry to be treated in the grinding chamber is set at such a steady-state pulp density which is higher than the feed slurry density, advantageously within the range of 45-65 % by weight, and that the excess water is made to flow through the grinding chamber at a faster average rate than the solids. 2. A method according to Claim 1, characterized in that the feed slurry density is adjusted to be such that its solids content is advantageously within the range of 25-45 % by weight, even below 25 % by weight. 3. A method according to Claim 1 or 2, characterized in that in the outlet of the grinding chamber, the mill product is classified so that the coarse element is returned to grinding, whereas the fine element falling below a determined grain size is let out of the grinding chamber along with the excess water. 4. A method according to Claim 1, 2 or 3, characterized in that the size of the grinder charge is defined so that in the curve of the solids maximum feed all charge, there is obtained a point of change where the maximum angle coefficient turns smaller, or where the capacity maximum is located (figures 4, 5. 6 and 7). 5. A method according to any of the preceding Claims, characterized in that in order to improve the classification of the product obtained from the grinding chamber, the product is shifted through a screen with a predetermined screen opening size. 6. A method according to any of the preceding Claims, characterized in that the feed slurry density is adjusted to be suitable by continuously measuring, for instance by weighing, the volume of the solids and water fed to the grinding process and by defining the weight ratio thereof. 7. A grinding apparatus comprising a mill (1) provided with a grinding chamber (2) and a grinder charge (3) contained therein for realizing the grinding proper, said mill including feed and discharge openings (4, 5), feed members for supplying the feed composed of preground ore material or similar solids and water to the mill (1) through the feed opening (5) and discharge means for letting the mill product out of the mill (1), said mill product having a determined grain size distribution, characterized in that the feed members comprise an adjusting device for adjusting the feed slurry density. 8. A grinding apparatus according to Claim 7, characterized in that the feed members comprise means for administering solids and water, a measuring and controlling unit (42) for determining slurry density and for adjusting the feed of solids and water. 9. A grinding apparatus according to Claim 7 or 8, characterized in that the discharge means comprise a classifier (14), which is arranged in connection with the grinding chamber (2) prior to the discharge opening (5), by means of which classifier (14) the coarse solids surpassing the predetermined grain size are returned to the grinding chamber. 10. A grinding apparatus according to Claim 9, characterized in that the classifier ('14) includes a screen (15). 11. A grinding apparatus according to any of the Claims 7-10, characterized in that the ratio of the diameter of the grinding chamber (2) to the length thereof is one or more, advantageously of the order two. 12. A grinding apparatus according to any of the preceding Claims 7-10, characterized in that the efficiency of the mill is measured by means of torque measuring devices, such as a strain gauge detector, from the rotating axis of the rotating device.