Process technology of mica
Process
The beneficiation of mica ore is the enrichment process of raw mica. Raw mica refers to mica crystals of any thickness with a contour area greater than or equal to 4 cm2 in the raw ore. The amount of raw mica content in the raw ore is called the raw mica ore content, which is usually expressed by the weight of raw mica per unit ore volume (kg/m3). The ratio of the total weight of raw mica in the concentrate obtained by beneficiation to the total weight of raw mica contained in the raw ore is called the recovery rate.
In industry, it is mainly directly processed from mica natural crystals into the desired product. The larger the mica crystal without defects, the higher its economic value, so in the process of mica ore beneficiation, it is necessary to protect the natural crystal of mica as much as possible from destruction.
At present, for the beneficiation of mica pieces with a crystal contour area greater than 4cm, it is mainly carried out according to the difference in shape and friction coefficient between mica crystal and gangue, and the commonly used methods include hand selection, friction selection, and shape selection. For the fragmented mica with a crystal contour area of less than 4cm, it is mainly sorted according to the difference between its physical and chemical properties and the gangue surface, and the method used is flotation.
(1) Mica beneficiation method and its process
a. Hand selection
Workers pick mica that have been separated from each other on the mining face or pit mouth ore pile; The conjoined bodies of mica and gangue are crushed with a hand hammer, and the mica is selected.
b. Frictional beneficiation
According to the difference between the sliding friction coefficient of the lamella mica crystal and the rolling friction coefficient of the round gangue, the mica crystal and the gangue are separated. One of the equipment used is the inclined plate sorter. The machine is composed of a set of metal inclined plates, each inclined plate is 1350mm long and 1000mm wide, and the inclination angle of the next inclined plate is greater than the inclination angle of the previous inclined plate. The lower end of each oblique plate leaves a gap for collecting mica crystals, and its width decreases in the order of the oblique plates. The leading edge of the gap is equipped with triangular weir plates. During the sorting process, large ganguestones roll down to the pile; Mica and smaller veined stones are blocked by weir plates and fall through a gap to a diagonal plate. The above process is repeated sequentially on the inclined plate to gradually separate the mica from the gangue. At present, the friction beneficiation process and equipment are not perfect, so the method has not been widely used in mica ore beneficiation.
C. Shape beneficiation
According to the different shapes of mica crystals and gangue, the ability to pass through the sieve slits and sieve holes of the sieve in the sieve is different, so that the mica and gangue are separated. When selecting, a sieve with more than two layers of different sieve surface structure is used, and the first layer of sieve screen is generally strip-shaped; The second screen screen is square. When the raw ore enters the sieve surface, due to vibration or rolling, flake mica and small pieces of gangue can leak from the strip sieve slit to the second sieve surface; Because the second layer is a lattice sieve, it can be sifted to remove gangue and leave flaky mica. The shape beneficiation method has the advantages of simple process, less equipment, high productivity and good sorting effect, so it has been widely used in mica mines.
The process of mica
a. Flotation
Sorting is carried out according to the different surface physical and chemical properties of mica and gangue. The ore is crushed and milled to dissociate the mica monomer, and under the action of the agent, the mica becomes a foam product and separates from the gangue. Mica flotation can be performed in acidic or alkaline slurries, and cations of amines with long carbon chains and anions of fatty acids are the collectors of mica. In the mica flotation process, three stages of rough selection and three stages of selection are required to obtain mica concentrate. Therefore, mica ore floats are selected to recover mica and fine-grained mica below 14 mesh in pegmatites and mica schists. In China, mica ore flotation has not yet been produced and applied.
B. Winnowing
Mica winnowing is mostly achieved through special equipment. The process is generally as follows: crushing→ screening and grading→ winnowing. After the ore is crushed, mica basically forms flakes, while gangue minerals feldspar, quartz and other lumpy particles. According to this, the selected materials are pre-divided into narrow particle levels by multi-level grading, and special winnowing equipment is used to sort according to the difference in their suspension speed in the air flow. The winnowing method is suitable for areas with a lack of water sources and has been used in actual production.
