Leaching process (1)

(1) The leaching method generally consists of two types: leaching leaching and stirring leaching. The leaching leaching can be divided into three types: tank immersion, heap leaching and in-situ immersion. When the tank is immersed, the ore must be crushed to less than 10 mm for the lean ore with less porosity. Heap leaching is used for ore that has been mined or broken to a certain size, such as a waste rock with a large porosity, an off-surface mine and a lean ore. In-situ leaching is mainly used for the recovery of the target components contained in underground mines or mined-out areas of mines or pillars. Therefore, the infiltration is only suitable for some materials with large porosity and coarse grain size, which are usually produced by intermittent operation.
Stirring is suitable for various mineral raw materials, and can be carried out under normal temperature and normal pressure or hot pressing conditions, and can be intermittent or continuous operation.
According to the relative movement mode of the immersed material and the leaching agent, it can be divided into three types: downstream leaching, countercurrent leaching and cross-flow leaching. If the direction of flow of the immersed material and the leaching agent is the same, it is leaching in the downstream direction; if the flow direction is opposite, it is leaching in the countercurrent; if the flow direction is staggered, it is leached in the cross flow. When leaching in the downstream, the content of the target component in the immersion liquid is high, and the consumption of the leaching agent is small, but the leaching speed is small and the leaching time is long. The cross-flow leaching speed is large, and the leaching rate is high, but the immersion liquid volume is large, the component content is low, and the leaching agent consumption is large. Countercurrent leaching can make full use of the remaining leaching agent in the immersion liquid. The content of the target component in the immersion liquid is higher, but the leaching speed is smaller than that of the cross flow. The percolation tank immersion can be carried out by any of the above three methods, and the heap leaching and the in-situ leaching are generally carried out by a downstream circulation leaching method. Continuous soaking is commonly used in downstream leaching. If cross-flow or counter-current leaching is used, solid-liquid separation operations need to be added between the stages, and the operation is complicated. Intermittent impregnation is generally a single tank downstream leaching.
In order to reduce reagent consumption, increase leaching rate and create favorable operating conditions for subsequent operations, different leaching methods can be used in production, such as leaching of mixed ore, leaching of mineral ore (sediment or mineral), and leaching of liquid. And multi-stage leaching, etc., if the subsequent operation is electrowinning, the oxidizing immersion liquid can be further reduced and leached, and the reduced immersion liquid product can reduce the power consumption.
(2) Leaching equipment

The structure of the percolation tank (pool) is shown in Figure 1. The outer casing can be made of wood, brick, concrete, etc., and is lined with an acid-proof layer (tile, plastic, epoxy resin, etc.). The percolation tank should be able to withstand pressure, Leakage and corrosion resistance. The main operating parameters are reagent concentration, discharge rate, component content of the immersion liquid, and residual concentration of the leaching agent. When the residual concentration of the leaching agent is high, it should be returned to the leaching. Usually, multiple tanks are operated at the same time, and the immersion liquid is mixed to ensure that the immersion liquid component is relatively stable.
The heap leaching field for heap leaching can be located on hillsides, valleys or flat land. The grounding should be treated with anti-seepage treatment. The anti-seepage layer can withstand the pressure of the heap in addition to anti-penetration and corrosion resistance. In order to protect the ply, it is often coated with fine-grained waste rock and coarse-grained waste stone of 0.5-2.0 m thick. The liquid distribution method is determined according to factors such as climatic conditions, heap height, surface area of ​​the heap, porosity, operation period, mineral composition and particle size composition. Use a cloth, a cloth or a vertical tube. The immersion liquid is generally circulated by a pump to increase the concentration of the target component in the immersion liquid and to reduce the reagent consumption. At the end of the leaching, the immersed ore is transported to the tailings mine by car or mine car.
In-situ immersion is generally performed on the surface of the surveyed mining site (subjecting holes, recovery holes, etc.), the leaching agent is injected into the ore body from the injection hole, and the immersion liquid is pumped from the recovery hole to the ground for treatment. Therefore, expensive well construction, mining, transportation, crushing, grinding and solid-liquid separation processes can be eliminated, which can reduce environmental pollution and improve working conditions. However, in-situ leaching requires good permeability of the ore body, and there is a corresponding impervious layer around the ore body, the bedrock is stable, and the groundwater level is low, so as to prevent the loss of the immersion liquid and facilitate the recovery of the immersion liquid. At present, in-situ leaching is mainly used to recover copper and uranium from goaf. It can be used as leaching agent in clear water, acid liquid or acid-containing water. It can be used to discharge liquid in the surface or roadway. Leachate.
There are two types of stirring and leaching: atmospheric pressure and hot pressing. Common pressure stirring tanks, compressed air agitation tanks (towers) and fluidized leaching towers are used for hot pressure leaching. Device).

The structure of the mechanical stirring leaching tank is shown in Fig. 2. There are multiple oars and single oars. The agitator has paddle type, propeller type, anchor type and turbine type. A paddle or propeller type agitator is often used for leaching. The material of the agitation tank varies depending on the leaching medium. When the acid is immersed, the tank body may be lined with carbon steel, rubber brick or plastic, or stainless steel tank and enamel tank. An ordinary carbon steel tank can be used for alkali leaching. The agitating paddle is generally carbon steel lining, lined with glass reinforced plastic or made of stainless steel. The tank body is cylindrical, the bottom of the tank is round or flat, and there is a circulating cylinder in the center. The leaching temperature can be controlled by electric heating, jacket heating or direct steam heating. The volume of the agitation tank depends on the scale and is often used in smaller factories and mines. [next]

The common compressed air agitation tank is a Boqiuke tank (tower). Its structure is shown in Fig. 3. It is a tall cylinder with a central circulation cylinder in the middle. The compressed air tube is directly connected to the lower part of the central circulation cylinder to adjust the compressed air pressure and The flow rate controls the agitation intensity of the slurry. Compressed air agitation tanks are often used in larger factories and mines.

In the past ten years, the fluidization technology has been greatly developed. Figure 4 is the structural diagram of the fluidized countercurrent leaching tower. The slurry enters the tower stably and evenly through the feed pipe, in the middle of the tower (leaching section). The leaching agent is added to the upper and lower portions for countercurrent leaching, and the washing water is added to the lower portion (washing section) of the column for countercurrent washing. The washed coarse sand is discharged through the bottom discharge port, and the leaching slurry containing fine ore particles flows out from the overflow port. In the production, hot water of 50 to 60 ° C can be used as washing water to increase the leaching temperature.

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