Screen Performance Optimization : Part 28: Derrick Corporation

Abstract

The Derrick Corporation participated in this project in a slig~1tly different way. Rather than ship machines to the Coleraine Minerals Research Laboratory pilot plant, two drums of each sample were shipped to the Derrick Corporation laboratory in Buffalo, New York. In addition, Derrick requested that two machines be tested rather than one, so that a previous technology could be compared with the new. Both changes in protocol were approved by the Minnesota Department of Natural Resources, for which acknowledgment and thanks are certainly due. Using the feed samples, Derrick staff optimized the separations in an initial series of tests. From these tests, the optimum solids, panel sizes, and other relevant operating conditions were selected before formal test sequences began. The scope of work for this project follows the pattern set in Part 1, in which five tests were completed on each of two feed samples, one from Hibbing Taconite, and one from Northshore Mining. In this case, the number of tests is doubled again to apply to two different screening machines. Part 2 also includes silica and magnetic iron assays on head samples as well as on each size fraction. The separation criteria for these tests was to achieve a split near 100 microns for the Hibbing Taconite material, and an undersize grade close to 90% -325 mesh for the Northshore Mining material. After the panels were selected and other operating issues were decided, the formal test sequence involved using two values for feed rate and two values of feed solids that were just higher and just lower than in the initial tests. The idea was to bracket the optimum separation and measure the variation in screen performance as these two parameters varied. For each machine sample combination, the four tests were completed in a 2x2 pattern, and a fifth test was a repetition of one of the first four in order to measure experimental error.