Mineral Processing Plant Alkaline Anionic-Cationic Method for Mica Production

During the mica process development work, it was determined that the platy shape of the mica could be utilized to preconcentrate the ore prior to flotation. Humphreys spirals were effectively used to remove a large part of the quartz, along with the limonite and other heavy minerals in the ore. Normally, 50 to 55 percent of the ore was rejected in the preconcentration step with only a minor loss of mica. Thus the flotation feed was upgraded from about 16 percent mica to over 35 percent mica. The preconcentration step permitted the size of the flotation section to be scaled down, reduced reagent requirements, and reduced overall costs for processing mica.

Continuous treatment of the ore using the alkaline anionic-cationic method included grinding, trommel screening, preconcentration, classification, conditioning, and flotation. The flowsheet for the process is shown in figure 2.

The ore was ground in a rodmill with sodium hydroxide to aid in dispersing and removing clay slimes. The grinding was adjusted until the 20-mesh trommel oversize consisted of almost pure mica, which was removed as a separate oversize mica concentrate. The minus 20-mesh trommel undersize passed to a Humphreys spiral to concentrate the mica partially and to remove a large part of the quartz, limonite, and heavy minerals. The spiral rejected about 55 percent of the total weight of the ore with a loss of only 3 percent of the total mica. The rougher concentrate was partly deslimed in a bowl-rake classifier to remove clay slimes, which were essentially all minus 325 mesh. The ore contained about 20 percent minus 200 mesh after grinding, preconcentration, and desliming. The pulp then passed to conditioners, where the reagents for pH control and quartz depression and the fatty acid mica collector were added. The pulp from the conditioners flowed to a bank of rougher flotation cells, where the amine collector was added to the first cell. A rougher froth was recovered and cleaned three times to produce a finished mica concentrate. The continuous pilot plant test accounted for a recovery of 91.9 percent of the mica in the feed in a product containing 98.6 percent mica. The test results are summarized in tables 6 and 7.