A medium having a density greater than water is generally referred to as a heavy medium, and beneficiation in such a medium is referred to as heavy medium beneficiation.
The basic principle of heavy medium dressing is the Archimedes principle. Any object in the medium is subject to the buoyancy of the medium, the buoyancy is equal to the weight of the same volume discharged by the object, ie P = VΔg
Where P is the buoyancy of the medium to the object;
V——the volume of the medium from which the object is discharged;
Δ - medium density;
g - the acceleration of gravity.
It can be seen that the magnitude of the buoyancy P of the object increases as the density Δ of the medium used increases. because
Therefore, for a given ore in heavy media beneficiation, its gravity G 0 and gravitational acceleration g 0 in the medium will decrease as the density of the medium used increases. However, for two ore particles with different densities, according to the formula g 02 — g 01 = ( 1 / δ 1 — 1 / δ 2 ) Δg, it can be seen that ( g 02 — g 01 ) is proportional to Δ, that is, with the points When the media density Δ value is increased, the difference of the gravitational acceleration of the two different mineral particles moving in the medium ( g 02 — g 01 ) will increase accordingly, making it easier to sort the two in the medium. . In this sense, beneficiation in a denser medium is advantageous for gravity beneficiation by density sorting.
In heavy medium dressing, the behavior of each ore in the medium is determined by the relationship between the absolute weight G of the ore in vacuum and the buoyancy P in the medium, when the density of the particles is δ 1 and δ 2 At certain times, the motion of the particles is determined by the density of the medium Δ.
For any ore particle with δ> Δ, G>P, g0 is a positive value, consistent with the direction of g, such a mineral particle sinks to the bottom in the medium;
Any granule of δ< Δ, G
For granules with δ = Δ, G = P, g = 0, the ore particles are suspended in the medium. If the dielectric layer is thick, the media density of the upper and lower layers is uneven (such as resuspension), and the medium ore particles with different densities are suspended in the dielectric layer of the same density as their own.
It can be seen from the above three cases that the sorting effect is best when the sorting medium is between the light and heavy ore density, that is, δ 1 < Δ < δ 2 . Because the direction of the light and heavy ore particles g0 is exactly the opposite, according to the Archimedes principle, the two will move in both directions of floating and sinking in the medium.
In actual production, as the ore is continuously fed, the floating and sinking ore particles in the sorting medium are increasing. If appropriate measures are taken, the separated light and heavy ore particles are discharged from the sorting equipment in a timely and accurate manner. Light and heavy products can be obtained separately, so that the production can be carried out continuously.
From the principle of sorting, heavy medium beneficiation is a process of strictly sorting by density. Due to the small influence of the shape and particle size of the ore particles, its sorting precision is very high, and even minerals with a density difference of about 0.1~0.05 can be effectively sorted. Therefore, the effect is more significant when dealing with "difficult-selected ore", and the range of the selected material can also be wide, but the granular particles with too small particle size, especially when the density is close to the density of the medium, the sedimentation speed is small, which will cause the separation process. It is carried out very slowly, which reduces the accuracy of the separation. Currently in dense medium separation metal ore particle size limit of 2 to 3 mm in the control, the upper limit of selected particle size is determined primarily by the material disseminated ore particle size and equipment, generally 50 to 150 mm.
Heavy medium beneficiation is suitable for the treatment of coarse-grained and fine-grained aggregates. After the ore is crushed or broken, a large amount of gangue can be dissociated, and useful minerals appear as monomers and continuum. At this time, a large amount of gangue can be discarded by heavy medium beneficiation, thereby greatly reducing the amount of ore processed in the next step, which can save the ore dressing cost and expand the processing of the original ore amount of the plant.
Since the dense medium separation material can be sorted wide level, and the processing capacity is relatively large, and therefore may be used to sorting iron ore, coal, non-ferrous metals, rare metals and non-metallic ore.
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