Mercury mixing process (2)

Usually added in an amount of mercury 9 times amount of gold-containing material, but with the grinding particle size and gold content (Table 4). Mercury can be added to the amalgamation cartridge at the same time as the material, but practice has shown that adding mercury to the cartridge after grinding for a certain period of time can increase the efficiency of mercury mixing and reduce the consumption of mercury.

The rotation speed of the amalgamation cylinder can be adjusted. Generally, the rotation speed of the grinding stage without mercury is 30-35r/min, and the rotation speed of the mercury mixing stage after adding mercury is generally 20-25r/min. The rotation time depends on the nature of the material. For 1-2h, it is determined by common test methods.
Mercury in the amalgamation cylinder is intermittent operation. The process consists of charging, running and unloading. The products of the amalgamation cylinder are treated with mercury traps, suede chutes or amalgamation plates to obtain mercury paste and heavy minerals.
When dealing with clean gold materials with a clean surface, a light-mixed mercury-mixing cylinder is used, which has a low rotation speed (20-22r/min) and a small ball loading capacity (10-20kg). Heavy-duty amalgamation cartridges are used when dealing with materials containing a large number of gold-linked organisms and heavily contaminated gold surfaces. The steel ball is added into the cylinder to grind the material, so that the gold is sufficiently dissociated from the monomer, and the surface oxide film of the gold particle is removed. In the production practice, most of the materials to be mixed with mercury are placed in the amalgamation cylinder of the steel ball. The grinding is not carried out for 3-8 hours, and the rotation speed is 30-35r/min, so that the material particle size reaches 0.1-0.05mm. At this time, the solid concentration in the slurry is 50%-70%, and the appropriate amount of lime is added (the alkali content should be about 0.0015%), then the mercury is added, and the mercury mixing tube is operated at a lower rotation speed (20-25r/min). 1-3h. After the amalgamation is completed, water and mercury are added to the mercury-mixing cylinder, and then rotated for half an hour to start discharging. The time of grinding and amalgamation varies depending on the nature of the material and is usually determined experimentally. After the slurry and mercury paste after the internal amalgamation are discharged from the internal amalgamation equipment, the tailings and the mercury paste are separated by a trap, a chute, a classifier, and the like.
The internal amalgamation method is only suitable for the treatment of gold , copper , lead and zinc -free gold deposits, or for the separation of gold from other heavy sands. Internal amalgamation is a common method of gold selection in China's gold mines. It is mainly used to extract gold from heavy sand concentrates and separate gold from other heavy minerals. A small number of rock gold mines use a radon mining machine for the recovery of coarse-grained monomer gold. [next]
The main disadvantage of the internal amalgamation method is the "powdering" of mercury. In the grinding process, mercury is also pulverized into particles, which are wrapped and covered by the oxide film of the base metal, the lubricating oil film and the slime particles, and lose the ability to combine with each other to cause pulverization of mercury. Mercury is difficult to separate from the ore being processed, most of the mercury is lost, and it can also carry gold. Especially when the siliceous finely ground ore containing arsenic, antimony ore when, mercury powder phenomenon is most serious, also the largest loss of mercury. In the case of internal amalgamation, the loss of mercury per ton of ore fluctuates between 2-15g. The lost powdered mercury often contains 3%-15% of gold, which reduces the recovery rate of gold.
3) Ball mill is a simple method of mixing mercury with a ball mill. The mercury is added to the ball mill at a rate of 4-5 times the gold content of the ore every 15-20 minutes. The bottom of the ball mill is placed at the bottom of the ore tank and installed in the lower part of the classifier overflow weir. Chute to capture mercury paste. Production practice shows that 60%-70% of the mercury paste is deposited in the ball mill bin, 10%-15% of the mercury paste is deposited on the banquet in the sump, and 5%-10% of the mercury paste is deposited on the grading. The machine overflows on the chute. Clean the mercury paste every 2-3d. Due to the serious loss of mercury paste, the recovery rate of gold is only 60%-70%. When processing quartz veins containing gold ore, the mercury consumption is 4-8 g/t. This method of amalgamation is simple to operate, but the loss of mercury paste is severe and has been used less in industrial production.
The Homestake Gold Exchange in the United States adds 14-17g/t of mercury to the ball mill. It is equipped with a Clark Todo mercury trap at the ball discharge end of the ball mill, followed by a mercury-mixed plate. The equipment can recover about 15g of mercury paste from each ton of ore. The ore contains gold 10.7g/(t·h), the recovery rate of gold is 71.6%, the cyanide tailings are cyanide, and the cyanide is gold. The recovery rate is 25.4%, so the total recovery rate of the plant gold can reach 97%.
2. External Mercury Method The externally mixed mercury equipment used in China's gold mines is mainly flat amalgamation board, as well as other amalgamation machinery and feed tanks and mercury traps that cooperate with amalgamation boards. Suitable for processing gold-containing polymetallic ores. Mostly used as an auxiliary equipment before flotation or cyanidation, installed in the discharge port of the ball mill or the overflow of the classifier, recovering the coarse free gold or cooperating with the shaker and chute to recover the monomer gold in the sand mine. . Rarely used alone, often in combination with flotation, re-election and cyanidation.
The amalgam plate is divided into a fixed amalgam plate and a vibrating amalgam plate. Making three mercury plate material, copper plates, silver and silver-plated copper plate. China's production practice shows that silver-plated copper plate has the best mercury-mixing effect, and the recovery rate of gold is 3%-5% higher than that of copper plate. After the silver plate is plated with silver, it can prevent the formation of black spots caused by the green copper hydroxide stain and the decomposition of sulfide on the surface of the plate, which is conducive to the amalgamation operation. It reduces the surface tension of mercury and improves the infiltration of mercury into gold. Moreover, since mercury forms a silver mercury paste on the silver plate, the mercury surface has greater toughness and wear resistance. In addition, the silver-mercury paste has a greater resistance to the amalgamation of the acid and sulfide in the pulp than the pure mercury. Therefore, silver-plated copper plates are commonly used in production as a mercury-mixing plate. [next]
1) Types of amalgamation plates Mercury amalgamation plates can be classified into two types: fixed amalgam plates and vibrating amalgam plates.
1 fixed mercury plate. The fixed amalgam plate consists of three parts: the bracket, the bed surface and the mercury plate. The bracket and the bed surface can be made of wood or steel, but the bed surface must not leak pulp. The bed is covered with silver-plated copper plate (mercury plate), thickness 3-5mm, width 400-600mm, length 800-1000mm. The bracket and the bed surface can be made of wood or steel, and the fixed amalgam plate has three forms: flat, stepped and with an intermediate trap. China's gold production mines mainly use flat fixed mercury amalgamation plates (as shown in Figure 3). Fixed mercury amalgamation plates with intermediate trapping grooves are commonly used abroad (as shown in Figure 4). The intermediate trapping groove can capture coarse-grained free gold, but the ore will be deposited in the trapping ditch, affecting normal operation. The stepped fixed amalgam plate used abroad uses a height difference of 30-50mm as a step to form a multi-stage stepped amalgamation plate. The slurry can be evenly mixed to avoid the stratification of the slurry and promote the free gold to sink into the bottom layer. In order to make the gold particles in good contact with the mercury plate. The mercury plate is attached to the bed surface one by one according to the oblique direction of the bracket, as shown in FIG. The area of ​​mercury plate depends mainly on the amount of ore processed, the nature of the ore and the role of amalgamation in the gold selection process.

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The area of ​​mercury plate is related to the treatment volume, the nature of the ore and the position of the amalgamation process in the process. In normal operation, the thickness of the slurry flow on the surface of the mercury plate is 5-8mm, the flow rate is 0.5-0.7m/s, production practice The mercury plate area required for the treatment of 1t ore is 0.05-0.5m ² /d. When the amalgam operation is based on the recovery of coarse free gold before cyanidation or flotation, the mercury plate can be set at 0.1-0.2m. ² / (t·d). The production quotas for mercury plates are listed in Table 5, depending on the nature of the ore and the position of the amalgamation process in the process.