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(1) The magnetic field of the ore screening magnetic field is weakened with the increase of the distance of the magnetic pole of the magnetic separator. When sorting wide-grain unfractionated ore, the magnetic forces acting on the coarse and fine particles are unequal, which reduces the sorting efficiency, hinders the sorting conditions and the selection of the magnetic separator sorting zone parameters. By sieving the material to make a particle size close to the upper and lower stone dressing, thereby improving the magnetic indicator.
The size of the mesh for ore screening is related to the type of magnetic separator used. For the upper feed type magnetic separator, the mesh size is related to the magnetic pole pitch or the pitch of the magnetic system and the ratio of the magnetic susceptibility of the selected components of the ore.
In the magnetic separation of -50 + 0 mm or -25 + 0 mm ferromagnetic ore, it is best to screen them into +6 mm and -6 mm, which will have a beneficial effect on the magnetic separation results. In general, the magnetic separation of less than 5 to 6 mm weak magnetic ore is rare. Screening fine ore is inefficient and costly and is therefore only used in individual cases. Such as a noble metal reprocessing ore concentrates.
(2) Ore dust removal and de-mud removal
In most cases, fine ore before demagnetization is dedusted or delimed. Magnetic separation indicators for dust removal or deliming before magnetic separation and no dust removal or mud removal.
(3) Premagnetization of ferromagnetic ore
Magnetic iron ore wet magnetic separation operation is often used premagnetisation and ground ore desliming job magnetic desliming slot machine or a hydraulic classifier. The pre-magnetized magnetite particles often form agglomerates, which settle faster than the non-magnetic particles, and the hydraulic grading method can take off the fine-grained gangue, thereby improving the subsequent magnetic separation operation.
(4) Demagnetization of ferromagnetic ore
The ferromagnetic particles form agglomerates after passing through a magnetic separator or a magnetizer. The presence of the agglomerates destroys the normal process of classification, which hinders dehydration during filtration and does not minimize the humidity of the filter cake. Therefore, in the fine-grained magnetite ore wet magnetic separation process, in order to destroy the agglomeration, the demagnetization operation is used before the classification of the grinding product or before the filtration of the fine concentrate.
(5) When the ore is dry and dry magnetically selected, as the ore humidity increases, the mutual adhesion of the ore particles increases, which deteriorates the magnetic separation process. This effect is particularly pronounced when the ore is fine-grained. For example, for mineral mixtures (dense magnetite ore), the particle size is -3 + 0 mm, the humidity should not exceed 0.5 to 1%; -6 + 0 mm, humidity is less than 1 to 1.5%; -12 + 0 mm, humidity is less than 2 ~ 2.5% and -25+0 mm humidity is less than 3 to 5%.
For porous limonite ore, the allowable humidity during dry selection is 6-10%.
New Technology of Magnetic Separation of Iron Ore---Ore Preparation before Magnetic Separation
The ore before magnetic separation is generally crushed and ground. The choice of other operations depends on the nature of the ore. These operations include: sieving, dust removal, deliming, pre-magnetic and demagnetization, drying and ore roasting.