First, the classification of dehydration process
According to the use of dehydrated products, the main processes of solid-liquid separation of wet beneficiation products are as follows:
(1) Concentrate dehydration. For the purpose of recovering concentrate, it is also possible to recover clean water containing almost no solids. Used to treat flotation or fine-grain re-concentration concentrates. The flow shown in Figure 1 is generally used. The wet concentrate obtained by vacuum filtration needs to be dried in order to meet the requirements of the raw materials for the subsequent operation, or to prevent the concentrate from freezing in the severe cold area.
(2) Dewatering of tailings. For the purpose of recovering clean water (containing very low solids), the excess water in the tailings is removed from the ore dressing plant for recycling. At the same time, increase the concentration of tailings, reduce the amount of tailings transport, save energy and improve the economic benefits of mineral processing. In the dry run of the tailings, the dry heap of the concentrator, the tailings slurry must be concentrated and filtered. The dehydration process of coarse and fine tailings is shown in Fig. 2 and Fig. 3.
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(3) Dehydration of medium ore. The purpose is to increase the concentration of medium ore or low grade coarse ore concentrate and provide a suitable concentration of slurry for the next operation. It is also possible to recover the separated water at the same time for recycling. The process is shown in Figure 4.
(4) Grading desalination. For the purpose of separating the fine-grained grade or slime in the slurry, provide suitable slurry for the next sorting operation, or recycle the coarse-grained washing product, or separate or discard the indiscriminate stream. The deliming process is shown in Figure 4.
Second, the dehydration process selection
The selection of the dehydration process of the ore dressing product is mainly determined according to the moisture or concentration requirements of the material after dewatering, the difference in the particle size of the material, and the combined state of the material and water. Generally consider the combination of equipment selection.
The ideal liquid-solid separation process should be to completely separate the liquid and solid. There is actually no such device. Under normal circumstances, there will always be fine solid materials remaining in the liquid, and some of the liquid will remain in the solids. The form of moisture in the wet concentrate can be divided into crystal water, accumulated water, surface water, and capillary. Water and gravity water. The crystal water is removed in the mineral lattice only when it is calcined; the accumulated water is the water accumulated by the adsorption force on the surface of the mineral, usually the amount of water is small; the surface water is due to the molecular gravitation between the ore and the water. Exist, and in the form of accumulated water, a thick water film surrounds the ore particles; the capillary water is present by capillary suction, and the size of the ore particles affects the partial or full filling of the pores, and moves due to capillary attraction; Gravity water fills all the pores of the ore and moves the ore under the action of gravity. Therefore, the choice of dewatering method is closely related to the particle size of the dewatered material. The dewatering of coarse and medium concentrates is usually carried out by natural dehydration or mechanical dehydration. The equipment is simple, the dehydration efficiency is high, and most of the gravity water can be removed. Dehydrated Shield Concentrate contains about 5-10% water; fine-grain concentrate (such as flotation product) is dehydrated, generally using two steps of concentration and filtration. Most of the gravity water can be removed by concentration. The concentrated product contains about 40-60% water; the remaining gravity water and most of the capillary water can be removed by filtration. The water content of the filter cake is generally 8-15%. In the cold area, the concentrate is transported. When the distance is very long or there are special requirements for the water content of the concentrate, it should generally be dried to reduce the moisture to a few percent or a few thousandths to prevent freezing and save freight.
In the concentration and filtration of fine concentrate, in order to make the fine particles settle faster, sometimes a dielectric, a hydrophobic agent or a polymer flocculant is added to the slurry to promote the aggregation of the fine solids into a mass, which increases the sedimentation and filtration. speed. For fine-grained magnetic concentrates, a relatively inexpensive magnetic agglomeration (pre-magnetic) method can be used to promote a total settlement.
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