Relationship between ore size and leaching rate

Whether heap leaching requires ore crushing, depending on the structure of the ore, the primary state, that is disseminated metals and extent wrapped; secondly on the level of the main metal ore grade.

As far as the ore structure is concerned, this property varies greatly for different ores. For example, the ore-type calcareous sandstone in Sharbrak, Xinjiang, is broken to -40mm, and the leaching rate is 90%. The breccia of the Shuangwang gold deposit in Shaanxi is broken to -15mm, and the leaching rate can only reach 75%. Many gold mines in the Yanshan Mountains (such as Hebei Zhangjiakou Gold Mine, Jinchangyu Gold Mine, Liaoning Redstone Gold Mine, etc.) are all oxidized quartz veins containing gold ore, with low levels of harmful impurities, but the packaged gold content is more than 50%. For this type of ore, even if it is broken to -15mm, the heap leaching rate is only 50% to 65%, but once the ore is broken to -200 mesh, 90% or more, the gold is dissociated, so the ore is all mud. The leaching rate of cyanidation exceeds 90%. In the middle and lower reaches of the Yangtze River, Hubei, Hunan, Jiangxi, and especially Anhui provinces, there are many iron cap-type gold mines. Although the degree of oxidation is high and the ore is porous, the amount of gold is also large. The ore is generally broken to -12mm. The leaching rate of heap leaching can reach 80%.

The produced ore is directly broken into the yard without being broken, and is usually called the original ore heap leaching. Foreign gold mines have some ore of very low grade ore heap leaching, and no such examples have been found in China. However, the ore heap leaching of uranium mines is available, such as the Huangfengling uranium deposit in Jiangxi and the Zoujiashan uranium deposit, with a leaching rate of 90%. The uranium minerals in these ores have been fully oxidized, the ore fissures have developed, and uranium has been adsorbed. Most uranium ore is not suitable for heap leaching. The characteristics of these ores are that the uranium minerals are small, scattered and easily surrounded by gangue, and the ore itself is dense and hard, without being broken, the minerals cannot be dissociated from the inclusions and cannot be contacted with the leaching solution. Therefore, the degree of fragmentation of these ores is an important condition for determining the leaching rate. Such as rhyolite ore, its hardness is very large and very dense. When the ore is ground to -200 mesh and 80% is stirred and leached, the leaching rate can reach 94%. The relationship between the leaching rate of heap leaching and the ore particle size is shown in Table 1.

Table 1 Relationship between leaching rate of rhyolite ore and ore particle size

* Sulfuric acid consumption refers to the amount of sulfuric acid consumed as a percentage of the ore.

The above-mentioned heap leaching tail slag was sieved, and various fine-grained ore of different sizes were separated for chemical analysis, and the correlation between the leaching rate and the ore size was determined by the least squares method as shown in Table 2.

Table 2 Correlation between leaching rate and ore size

Note: Y-leaching rate; D-ore size (mm).

Plot the relevant formulas of the table column to obtain a straight line as shown in Figure 1. The leaching rate is a function of the ore size. Guangdong cotton pit uranium deposits, the Department of granite Dongkeng uranium deposit, ore leaching rate and grain size relationship is very close, ore finer grain size, the higher the rate of leaching, leaching faster. It can be seen that for most heap leaching fields, crushing is an important process and often becomes a major factor affecting the leaching rate. Table 3 shows the relationship between ore particle size and leaching rate of a gold deposit in China.

Figure 1 Relationship between leaching rate and ore particle size

The three lines in the figure indicate different shower/stop ratios:

1-14/82; 2-14/58; 3-14/34

Table 3 Relationship between ore particle size and leaching rate of a gold deposit

Leaching temperature: 25 ° C.

The finer the ore is broken, the better the leaching rate, but it may cause some unfavorable factors for the whole heap leaching. For example, energy consumption, material consumption (mainly leaching agent) is too high, and harmful impurities in the leaching solution are more. The subsequent processing steps are complicated and should be fully considered in practical work.

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