Gravity separation is a long-standing beneficiation method. Due to its simplicity, low cost, and growing development, the gravity separation method is still the main beneficiation method for tungsten tin ore and coal. It has also been widely used in the selection of certain non-ferrous metals, ferrous metals, precious metals and non-metallic ores.
The gravity separation method sorts minerals according to the difference in mineral relative density (usually called specific gravity). Mineral with different densities are subjected to fluid dynamics and various mechanical forces in the moving medium (water, air, and rerolling), resulting in suitable loose delamination and separation conditions, so that mineral particles of different densities are separated. Mineral particles and shape will affect the accuracy of sorting by density.
Due to the difference in density of various mixed ore particles, the settling speed in moving media (such as water, heavy media with a density greater than water, and air) is different, and the degree of movement is also different, so as to achieve the separation of minerals. The process is based on the law of sedimentation of ore particles in other media.
The common characteristics of the various gravity separation processes are:
① There must be a difference in density (or particle size) between the ore particles;
②The sorting process is carried out in the moving medium;
③ Under the combined action of gravity, fluid dynamics and other mechanical forces, the ore group is loose and layered by density (or particle size);
④ The materials in good layers are separated under the transportation of moving media, and different final products are obtained.
The flotation method is based on the difference in the physical and chemical properties of the mineral surface, processed by the flotation agent, and the mineral is selectively attached to the bubbles to achieve the purpose of separation. Non-ferrous metal ores, such as copper, lead, zinc, sulfur, and molybdenum, are mainly treated by flotation. Some ferrous metals, rare metals, and some non-metallic ores, such as graphite ore and apatite, are also selected by flotation.
In the flotation process, flotation agents are added to the ore pulp to improve and adjust the floatability of the minerals. Many minerals without natural floatability are changed from non-floatable to floatable after the action of flotation agent, or vice versa. In order to artificially control the floatability of minerals. So some people say that flotation reagents are the mainstay of flotation technology, which makes sense. The development of flotation agent is inseparable from the development of flotation process. The production practice of flotation has promoted the research of flotation agent, and the development of flotation agent has promoted the development of flotation technology.
Magnetic separation is a mineral separation method that uses the difference in magnetic properties of various minerals to perform separation in the magnetic field of a magnetic separator. When the ore particles with different magnetic properties pass through the magnetic field of the magnetic separator, they must be subjected to magnetic and mechanical forces. Due to the different magnetic force on the ores with stronger magnetism and the ores with weaker magnetism, different movement trajectories are generated, so that the ores are classified into two or more separate beneficiation products according to their different magnetic properties.
Magnetic separation is widely used in the selection of ferrous metal ores, the selection of non-ferrous and rare metal ores, the recovery of media in heavy media beneficiation, the removal of iron-containing impurities from non-metallic mineral raw materials, the discharge of iron objects to protect the crusher, and the smelting The steel slag produced recovers scrap steel and removes pollutants from production and domestic sewage.
In recent years, due to the development of high field strength and high gradient magnetic separators, the field of application of magnetic separation methods is still expanding, such as the removal of paramagnetic particulate impurities in chemicals and drugs.
Types of magnetic separator
At present, there are many types of magnetic separators used at home and abroad, and the classification methods are different. According to different characteristics, there are the following classification methods.
(1) According to the magnetic source of magnetic separator, it can be divided into permanent magnetic separator and electromagnetic magnetic separator.
(2) According to the strength of the magnetic field, it can be divided into:
① Weak magnetic field magnetic separator, the magnetic field intensity on the surface of the magnetic pole Ho = 72 ~ 136 kA/m, and the magnetic field force HgradH = (2. 5 ~ 5.0) × 1011 A2/m3;
②Medium magnetic separator, the magnetic field intensity on the surface of the magnetic pole Ho =160~480 kA/m;
③ Magnetic separator with strong magnetic field, the magnetic field intensity on the surface of the magnetic pole Ho = 480~1600 kA/m, and the magnetic field force HgradH=(1.5~6.0) × 1013 A2/m3.
(3) According to the selection process, the medium can be divided into dry magnetic separator and wet magnetic separator.
(4) According to the type of magnetic field, it can be divided into constant magnetic field, pulsating magnetic field and alternating magnetic field magnetic separator.
(5) According to the shape and structure of the machine body, it is divided into belt magnetic separator, drum magnetic separator, roller magnetic separator, disc magnetic separator, ring magnetic separator, cage magnetic separator and pulley magnetic separator .
Among them, it is mainly distinguished by the strength of the magnetic field and the structure type of the selected medium.
The weak magnetic separator is mainly used to sort strong magnetic minerals, such as magnetite, titanomagnetite, ferrosilicon. In the past, most of the industries were electromagnetic magnetic systems, and the shape of the body was mostly cylindrical and belt. At present, most of them are permanent magnetic systems and cylindrical shapes, and the wet type is widely used.
In the past, in the field of strong magnetic field magnetic separators at home and abroad, dry magnetic separators with coarser particle size were mainly used to select non-ferrous metals and rare metal minerals. In the past ten years, in order to select low-grade, fine-grained weak magnetic For minerals, various types of wet strong magnetic separators have been developed, such as ring type, cage type, and disc type.
The medium magnetic field magnetic separator is mainly used to sort the locally oxidized strong magnetic ore.
According to the different conductivity of ore minerals and gangue mineral particles, the method of sorting in high voltage electric field.
The electrical properties of minerals are the basis for electrical separation. The electrical properties of the two minerals are different, so that electrical separation is possible. The parameters representing the electrical properties of minerals mainly include the dielectric constant, electrical conductivity and relative resistance, electrothermal property, specific conductivity and rectification of minerals.
The dielectric constant is represented by the symbol ε. The larger the ε, the better the conductivity of the mineral, and vice versa. In general, those with ε>10~12 or more belong to conductors, which can be separated by the usual high-voltage electrical separation, while those below this value are difficult to sort by conventional electrical separation methods.
Generally, the mineral resistance in electrical selection is the resistance when the particle size of the mineral is d=1 mm, that is, the ohm value. When the mineral resistance is less than 106Ω, it indicates that its conductivity is better. If the resistance is greater than 106Ω and less than 107Ω, the conductivity is medium. If the resistance is greater than 107Ω, the conductivity is poor, and conventional electrical separation cannot be used.
The specific electrical conductivity of a mineral is the amount of electrons flowing out of or flowing out of the ore particles. It is often expressed by the ratio of the lowest voltage of the electron flow on the ore particles to the lowest voltage of the electron flow on the graphite. The higher the outgoing voltage, the worse the conductivity.