Basic principle and application of heavy medium dressing
A medium having a density greater than water is generally referred to as a heavy medium. The beneficiation carried out in such a medium is referred to as heavy medium beneficiation, which is carried out according to the principle of Archimedes.
Any object will be subjected to buoyancy in the medium, and the size of the buoyancy F is equal to the weight of the same volume of medium that the object is arranged, ie
1. Types of heavy media
Heavy media is divided into heavy liquid and heavy suspension.
1 heavy liquid - heavy liquid is an aqueous solution of some high density organic liquid or inorganic salt. They are homogeneous liquids which can be formulated into different densities using organic solvents or water. The tribromo methane] or [CHBr3 tetrabromoethane (C2H4Br4] Densities of 2.9 ~ 3.0 g / cm3. With different amounts of benzene, toluene, or mixed with carbon tetrachloride, can change its density. Iodide mercuric iodide and potassium of 1: 1.24 ratio of the aqueous solution of the formulated, the highest density up to 3.2 g / cm3 CH2I2 diiodomethane [solution] densities of 3.2 g / cm3 thallium formate (CH3COOTl) and M propionic acid. The solution of é“Š[CH2(COOTl)2] has a density of up to 4.25 g/cm3. In addition, the aqueous solution of calcium chloride has a maximum density of 1.4 g/cm3; the aqueous solution of chlorinated front has a density of 1.8 to 2.0 g. /cm3; a solution of carbon tetrachloride and toluene, the density can reach 1.6g/cm3.
The common features of the above heavy liquids are limited sources, high prices, toxic, corrosive and difficult to recycle. It is almost never used as a medium in production and is used only for gravity analysis or separation of minerals in the laboratory.
The two-heavy suspension-one-heavy suspension is a heterogeneous two-phase medium composed of dense solid particles dispersed in water.
High-density solid particles act to increase the density of the medium, so it is called weighting. The weight of the weighted material is generally 200% to 80% of a 200 mesh, which can be uniformly dispersed in water. At this time, the larger ore particles placed therein are subjected to an increased buoyancy effect like a uniform medium. The ore particles with a density greater than the density of the resuspension can still sink, and vice versa. Because of its advantages of low cost and non-toxicity, heavy suspensions are widely used in industry. The heavy medium beneficiation currently referred to is actually re-suspension beneficiation.
2. Increase the quality of choice
The weighting used in the industry differs depending on the density of the resuspension required to be formulated, and the following are commonly used.
â‘ ferrosilicon silicon iron with a mineral containing Si in an amount of 13% to 18%, such as ferrosilicon density 6. 8 g / cm3., May be formulated density of 3.2 ~ 3.5 g / cm3 was resuspended. Ferrosilicon has the characteristics of oxidation resistance, hardness, and strong magnetic properties. It can be recycled and reused after screening and magnetic separation. According to different manufacturing methods, ferrosilicon is divided into ground ferrosilicon, sprayed ferrosilicon and electric furnace corundum waste (individual ferrosilicon), etc. The sprayed ferrosilicon has a spherical appearance and the viscosity of the suspension prepared at the same concentration is small. Easy to use.
â‘¡ galena eleven pure galena density of 7.5 0g / cm3, typically those used as a galena concentrate, Pb grade of 60%, a degree of dense suspension formulation 3.5 g / cm3. The galena suspension can be recovered and reused by flotation. However, its hardness is low and it is easy to mud. The prepared suspension has high viscosity and is easy to lose. Therefore, it has been gradually used less.
3 The density of pure magnetite of magnetite is about 5.0 g/cm3, and the density of suspension prepared with iron concentrate containing more than 60% of Fe is up to 2.5 g/cm3. Magnetite is not easily oxidized in water and can be recovered by weak magnetic separation.
In addition, by-products of the concentrator such as arsenic pyrite, pyrite, etc. can also be used for weighting.
From the point of view of mineral processing, the prepared resuspension should not only achieve the density required for sorting, but also have a small viscosity and good stability. For this reason, the selected weighting should have a sufficiently high density, and it is not easy to be muddled and oxidized during use, and the source is wide, the price is low, and the preparation and regeneration are convenient. These are factors that must be considered when selecting aggravation.
(III) Application of heavy medium mineral processing
From the principle point of view, heavy medium beneficiation is strictly selected according to density, regardless of the size and shape of the ore particles, the medium often exhibits higher viscosity, which seriously affects the sedimentation rate of the particles. If the ore size is large and the heavy minerals settle quickly, the influence on the stratification accuracy is not significant. However, if the ore size is small, the heavy mineral particles with a small part of the particle size will be settled to the bottom in the future. Out of the machine, which reduces sorting efficiency. Therefore, it is still necessary to pre-screen small ore particles before sorting.
The lower limit of the feed size heavy medium beneficiation of ore metal is 1.5 ~ 3mm, coal is 3 ~ 6mm, heavy medium cyclone may to 0.3 ~ 0.5mm; ore to a particle size upper limit, the metal ores is 50 ~ 150mm, The coal is 300 ~ 400mm. At present, it is generally considered that the suitable ore size range for sorting metal ore is 2 to 75 mm.
Due to the limitation of the density of the weighting itself, it is difficult for the suspension to reach a very high density, and it is usually only slightly higher than the density of the light mineral. Therefore, heavy medium ore dressing cannot obtain a high-grade final concentrate, but only a low-density single can be selected. The surrounding rock that is mixed with the gangue or mining process can therefore only be used as a pre-sorting operation. For coal, magnetite powder is often used as a weighting material. Because of its wide range of suspension densities, it is fully capable of sorting various coals and is easy to recycle. For non-ferrous metal ores, the most useful minerals for processing are aggregates or coarse-grained ores. After the ore is crushed, a large amount of monomeric gangue is produced, which is removed by the heavy medium beneficiation method, so that it no longer enters the grinding and sorting operation, thereby greatly reducing the production cost and improving the concentrating plant. Processing capacity. For underground mining of iron, manganese ore, the use of dense medium separation method can be pre-mixed in the surrounding rock removal, recovery geological grade. The heavy medium beneficiation method has been used to treat iron, manganese, tin , tungsten and other ores in China.
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