It is well known that in order for the heap leaching to proceed smoothly and achieve the desired results, the ore heap must have good permeability and uniformity of penetration of the entire heap. If the ore contains high amounts of mud, or too much powder ore, especially argillaceous ore, the permeability of the heap is poor, the leaching solution cannot penetrate into the inside of the heap, and the mineral cannot contact the leaching solution, so it is impossible to talk about heap leaching. If the ore has too much ore or high mud content, it will also affect the uniformity of penetration of the whole ore heap.

Due to the influence of gravity, the coarse and fine materials in the pile will be naturally graded and concentrated in a certain area of ​​the pile. Coarse ore is concentrated in the bottom and periphery, while fine ore (especially ore and fine) is concentrated in the center and upper part of the pile. The segregation phenomenon of coarse ore is shown in Fig. 1. As a result of segregation of coarse ore, the pores in various parts of the heap are obviously different. Their respective capillary pressures and saturations are different. When the leaching solution passes, the leaching solution Rapid flow through the coarse ore zone, while in fine ore and slime areas, the solution may only wet the surface of the heap, or only penetrate into the area very close to the surface, from the side (around the heap), or high The area of ​​porosity runs away. The leachate is not exposed to the lower ore of these areas, forming an unreacted zone in the heap leach, or referred to as a "dead zone." As a result, the leaching rate of the entire heap is greatly affected.

Figure 1 Segregation of coarse ore in the process of pile-up

Although copper heap leaching has a history of more than a thousand years, uranium ore heap leaching has more than 30 years of experience, but until the 1980s, experts believed that argillaceous ore could not be treated by heap leaching, too much powder ore could not be used. Heap leaching method. However, from the viewpoint of chemical reaction kinetics, it is desirable that the finer ore particles are as fine as possible to increase the area of ​​the reaction; from the standpoint of process mineralogy, in order to dissociate the minerals from the inclusions, the ore must be made as small as possible. Good; from the geological point of view, the ore exposed or close to the surface, due to weathering, mostly oxidized ore, high mud, loose and porous, mineral exposure is relatively full, mostly in a free state. In an example gold ore, or near the surface of the exposed oxide ore, the free gold, the golden ratio is often even more than 80%, and deeply buried primary gold ores, the gold is most pyrite, arsenopyrite Wrapped in iron ore, quartz and other gangues. As a result, caused by the intense weathering of argillaceous ore, long-term accumulation table outside the mine, crushed size fractions fine powder ore, beneficiation plant a large number of tailings (flotation very effective because the primary ore, while the effect of oxidized ore Poor, a large amount of oxidized ore in tailings) is the main target of heap leaching, and it is also a mineral raw material that is especially suitable for heap leaching. However, due to poor permeability, it has been considered as unsuitable for heap leaching. As a result, the application of heap leaching technology has been limited to coarse-grained ore for a long time, so the long leaching period and low leaching rate are mistaken as a symbol of heap leaching. After long-term research, the American Renault Metallurgical Institute pioneered the industrial trial of granulation heap leaching and achieved success. This patented technology is quickly and widely used in gold mine heap leaching production. Most of the gold heap leaching in the United States uses granulation heap leaching technology, which shortens the leaching period and increases the leaching rate. The leaching rate of gold mines using granulated heap leaching is generally 80%, and individual up to 90%. According to a survey in the United States, 73% of the heap leaching ore in the United States is open-pit mining, and 23% of the heap leaching ore is a long-term accumulation of off-balance sheet or smelting tailings. Only 4% of the heap leaching ore comes from underground mining. This fully reflects the use of granulated heap leaching to make muddy ore, tailings and off-balance mines.

Granulation causes the fine mud or fine-grained ore to agglomerate into uniform larger particles (5 to 10 mm), so that the permeability of the heap can be increased by more than 1000 times. In addition, the size of the ore particles after granulation is narrow, which avoids the common segregation phenomenon in the pile-up process, so the uniformity of the entire heap is guaranteed. Granulation is a pretreatment step before ore leaching. In this process, a leaching agent (such as uranium, copper ore, acid pre-cyanation, gold ore pre-cyanide) may be added in advance, thereby shortening the leaching period.

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Cleaning agents are a large category, including inorganic cleaning and organic cleaning. The difference between organic cleaning agents and inorganic cleaning agents Simply put, organic cleaning agents are cleaning agents made of carbon-containing compounds, and inorganic cleaning agents are cleaning agents made of carbon-free compounds, so they are inorganic. We are usually divided into three categories: water-based, semi-aqueous, and non-aqueous cleaning agents.

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