Picking is a beneficiation method that separates useful minerals from waste rock in ore by utilizing physical characteristics such as surface characteristics of the ore, conductivity, magnetism, radioactivity, and absorption and reflection of rays by the ore. The purpose of the selection is mainly to remove large pieces of waste rock or to pick up large pieces of rich ore, but sometimes it is also used as a selective operation (such as selected diamond mines). With the development of the theory and practice of sorting, in terms of utilization of resources, chosen also play a role (e.g., sorting and sodium feldspar, potassium feldspar, etc.).
Since the sorting operation can select large waste rock, eliminating the transportation, crushing, grinding and further mineral processing of these waste stones, the picking often has obvious economic benefits.
The picking operation has the following main advantages: (1) can partially replace the low-efficiency and high-cost selective mining method; (2) in the case of the same processing capacity of the main concentrator, due to the improved ore grade entering the concentrator , can improve the yield of metal; and (3) allows the outer table of some low grade ores as a useful resource, extended service life of the mine; (4) may be sorted out of the waste rock or building material for the filling material, substantially Cause environmental pollution. In addition, the picking operation process is simple, and its cost is only a fraction of the general beneficiation method, so picking operations are receiving increasing attention.
The sorting method treats the ore with an upper particle size limit of 250 to 300 mm and a lower limit of about 10 mm. For some precious minerals (such as diamond), the lower limit can be reduced to 0.5~1 mm.
Picking can be divided into three ways: split water selection (continuous selection), sorting (stack selection) and block selection. When the running water is selected, a certain thickness of the ore layer continuously passes through the detection zone. When sorting and block selection, one or a piece of ore passes through the detection zone alone. With the continuous improvement of the quality of the sorting equipment , the processing volume has been significantly increased by using the block sorting machine. At present, the industrial sorting machine is mainly based on block selection, and only the ore with very uneven mineralization is considered to adopt the flow water selection or sorting.
Block picking can be done in both manual and mechanical selection.
Hand selection is the sorting of ore and waste rock by hand based on the appearance characteristics (color, gloss, shape, etc.) between the ore and waste rock. In the past, the application of hand selection was extensive, especially for ore that was not well selected or guaranteed by some mechanical methods, such as asbestos and flaky mica , which were selected for long fibers. At present, due to the development of various mechanical sorting methods, the application range of hand selection has been gradually reduced.
The mechanical sorting method can not only select the nuggets with different appearances by means of instruments, but also make use of the difference in the reaction of the ore after being irradiated by visible light, γ-rays, γ-rays, etc., or using the difference in the natural radiation ability of the nuggets for beneficiation. In recent years, with the deepening of the selection process research, the improvement of equipment and the application of electronic computers, the selection of machinery has been improved. The expansion of the scope of picking applications and the improvement of the performance of the picking machine have greatly improved the selection and gradually formed a new pre-selected field.
Since the sorting equipment is widely controlled by electronic instruments, the name of "electronic sorting" has appeared, sometimes referred to as "radiation sorting", because it is necessary to use various radiation sources to illuminate the ore before sorting.
For ores containing non-ferrous, black, rare, radioactive, precious metals and non-metallic ores and building materials, the selection method has been widely used.ANSI Flange
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