Mineral picking - hand selection
Hand picking is an ancient method of picking dressing stone. When there are more waste stones in the ore mining, and the ore and waste rock have obvious differences in color, shape and transparency, hand selection is often used. It can select waste rock when the ore has a large particle size, and avoid the transportation, crushing, grinding and further mineral processing of the waste rock. Although the selection of mechanical picking has been greatly reduced due to the development of science and technology, the application range of hand selection has been significantly reduced. However, due to its simplicity and economy, it has been playing a certain role in the practice of mineral processing at home and abroad.
1 Hand-selected ore processing granularity
Since the particle size of the nugget is too large or too small, it is not suitable for manual hand selection. Therefore, the commonly used particle size range is 400~250mm, 250~150mm, 150~75mm, 75~40mm, 40~25mm. Of course, each mine will be based on it. The specific conditions are to be applied; in the case of determining the color and gloss of ore and waste rock, the larger the ore particle size, the higher the hand selection rate; if the ore particle size is -50mm +30mm, the hand selection is 0.75 ~ 1.0t/ (Ban·People); and at 30~15mm, the hand selection efficiency is 0.3 ~ 0.4t / (class · person).
2 waste rock selection rate
Can the use of hand-selected and their work can elect how much waste rock have a great relationship, it generally takes a certain amount of representative ore, election after handling the job, according to their chosen amount of waste rock and the metal (of useful elements) of Loss rate, after technical and economic accounting, it is determined whether to use hand-selection operations; it is also possible to simply make a preliminary estimate, such as 30% to 40% of waste rock for undesired ore with a particle size of less than 100mm without sieving. Or for the easy-selected ore that has been sieved and has a particle size larger than 100mm, 40% to 60% of waste rock can be selected, and the application of hand-selection is more likely.
3 hand selection equipment
Commonly used hand-selecting equipment is a hand-selected belt and a hand-selected table. The hand-selected belt conveyor is similar to the belt conveyor, but the belt idler needs to be flat, the belt speed is in the range of 0.2 to 0.4 m/s, the belt width is not more than 1.2 m, and the belt has a light source, which can be ordinary as needed. The illumination source can also be a fluorescent lamp or the like. The height of the lighting is about 2m from the ground. The area of ​​the hand-selected platform is determined according to the number of people who participate in the selection; for example, the area of ​​the hand-selected platform for four people is about 3.2 square meters.
4 hand selection application examples
Although mechanical picking has made great progress both at home and abroad, the hand selection has not been completely replaced at home and abroad. It still has some applications when selecting metal and non-metal mines.
(1) Application of hand selection in tungsten ore dressing
Since most of the tungsten deposits are low-grade ore, many mines have clear boundaries between the ore-bearing gangue and the surrounding rock, and the color is clearly defined. After the ore is washed and classified, the artificial hand can be used to discard a large amount of waste rock, so many tungsten in China. The mineral processing plant, such as the Dajishan tungsten ore dressing plant in Jiangxi, the Xihuashan tungsten ore dressing plant, the Pangushan tungsten ore dressing plant, the Yankeng tungsten ore dressing plant, and the Hunan Yaogangxian tungsten ore dressing plant, etc. Hand selection. Hand-selected waste rock rate is generally up to 50%, and high is up to 70%. Another example is the tungsten mine of Yunnan Pubei Tungsten Co., Ltd. When the ore particle size is 400~300mm, it can be disposed of 10%~20% tailings by hand selection (fluorescent lamp on the hand-selected belt), and the particle size is 60~20mm. In the ore, 60% to 70% of waste rock can be discarded by hand. The mine has considered the use of photoelectric sorting machines instead of hand-selection. In 2006, it sent samples to Australia's UltraSort. After testing, it can be effectively sorted. The processing capacity of sorting machines can be as high as tens to 200 tons per hour. However, the sorting machine is priced at $900,000, and the sorting machine needs some auxiliary equipment to match it. After accounting, it is not economical, so it is not purchased. The hand selection operation is still on the scene.
(2) Application of hand selection in diamond ore dressing
The ore dressing process of diamond ore is generally complicated, including ointment beneficiation, flotation, re-election, magnetic separation, electro-election, and chemical beneficiation. Different from the general ore beneficiation method, the surface of the diamond will emit fluorescence under X-ray irradiation, and most of the gangue does not have this characteristic, so the diamond ore process often has X-ray sorting (hand selection or mechanical picking). For example, in the process of Shandong Mengyin Diamond Mine, the main diamond mining area in China, there is still a hand-selection. The factory has installed an X-ray sorting machine (GXJ-II type) to treat the ore particle size of 20~9mm, but the effect not ideal. In 2005, its partners proposed to use the X-ray picker produced in South Africa (optional particle size lower limit is 1mm, processing capacity is about 20t/h), and the price is US$478,000. The factory has not adopted it after consideration. Therefore, in the process of the factory, the ore of the grain size of -50mm+40mm, -5mm+3mm, -3mm + 1mm is still retained.
Part of the content is selected from the "Selection Engineer Handbook"
Workers hand pick ore in the workshop
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