Abstract
For the purpose of using laterite ores as raw materials of iron production, it is necessary to remove nickel and chromium minerals from the ores. In the previous paper, denickelizing of laterite ores was investigated by means of sufuric acid leaching after the selective reduction.
The present paper is concerned with the removal of chromium mineral from laterite ores by means of selective grinding followed by classification and magnetic roasting followed by magnetic separation.
The results obtained are as follows.
1) Chromium mineral contained in laterite ores is chromite replaced by aluminum ion for chromium ion and is insoluble in hot solution of concentrated hydrochloric acid. 70 to 80 percent of its particles is in the size range of 35 to 200 mesh.
2) For the preferential size reduction mineral of iron mineral particles to that of chromite particles, an attrition machine is more effective than a ball mill. When the ores ground by attrition machine are sized by a sieve of 200 mesh, about 80 percent of iron is recovered into a fine size fraction and about 50 percent of chromium is removed into a coarse size fraction.
3) The magnetization of the magnetic roasted samples of laterite ores is lower than those of goethite and limonite. This low magnetization may be due to the solid solution replacement of impurity such as aluminum ion.
4) In the magnetic separation of the magnetic roasted samples of laterite ores, using a ferrogum magnetic separator, 90 to 95 percent of iron is recovered into magnetic product and 40 to 45 percent of cromium is removed into nonmagnetic product. This unsatisfactory results are explained by the fact that the magnetization of the magnetic roasted samples of laterite ores is low.
