Kim coal agglomeration (Coal Gold Agglomeration) referred CGA gold extraction process, which is based on the oil phase adhesion method, by the British oil and mining companies in 1983 to start the study. It is a process of adsorbing gold by using coal and oil and adding additives. It has strong selective adsorption to natural gold and its continuum, and has wide adaptability. It is fine and coarse for 5μm or less or 300μm or more. Gold particles can also be recycled efficiently. The process is simple, the process is short, the process is non-toxic, the selectivity is good, the adsorption rate is high, the aggregate load capacity is large, and the cycle can be used repeatedly. It not only ore of wide scope of application, but also recovery of silver and the platinum group metals and gold monomer was recovered at the same time with the living body. The process is non-filtration operation, equipment and plant investment is only one-third of the cyanide carbon slurry method, and the operation cost is also low, which has become a hot topic in the research of gold extraction technology at home and abroad in recent years.

Like the flotation, the CGA process first adds chemicals to the slurry to make the minerals such as gold hydrophobic, and then adds kerosene to agglomerate to form a kerosene gold agglomerate, which is separated during floating. The gold-bearing agglomerates produced can reach 1000 to 15000 g ∕t; the recovery rate of gold is 95%. The gold-bearing agglomerated ash is smelted into a merging gold by a fire method, and then treated by a wet method to separate gold and silver.

This process has been carried out in a semi-industrial test of a variety of raw materials from 1 to 5 t∕h. When the re-selected tailings containing gold not more than 1g∕t are continuously treated by a five-stage circulating adsorption tank, agglomerated concentrate containing 1000g∕t of gold can be obtained, and the recovery rate of gold is up to 75%. When used to treat oxidized ore containing more than 10g ∕t of gold, agglomerate concentrate containing 15000g ∕t of gold can be produced, and the recovery rate of gold is 95%. With the CCA process, as long as the fineness of the grinding is sufficient, the dissociation exposure of the gold particles is sufficient, and the recovery of the coarse and fine gold is extremely high regardless of the gold content of the raw material. Therefore, experts predict that the emergence of the CGA process will lead to a technological revolution in the fine metallurgy.

The Xinjiang Institute of Chemistry of the Chinese Academy of Sciences conducted research on the CGA process, progressed in 1990, and conducted small-scale experiments in 1991. Due to the large difference in density between the kerosene agglomerate and the slurry, in the commonly used overflow agitation tank, the agglomerates tend to float on the slurry and are not easily mixed uniformly, and a "dead zone" occurs, and the effect is not good. To this end, Lu Lizhu et al. designed a downflow agitation tank for the pilot test conducted in 1992. The characteristics of the tank are that the pumping performance of the impeller can be used to achieve uniform mixing of the two phases and the promotion of the mixed phase. Interstage transport, unlike the overflow adsorption tank, requires additional interstage lift equipment, and does not have to increase the interstage difference between the tanks.

The pilot work was carried out by the Institute of Chemical Metallurgy of the Chinese Academy of Sciences and the Xinjiang Institute of Chemistry. The scale of the experiment was 1t∕d. Before the test, the downflow agitating adsorption tank was compared with the current overflow straight impeller high-speed (1400r∕min) agitation tank and the self-priming pneumatic propeller-type impeller adsorption tank (Fig. 1).

Figure 1 Schematic diagram of adsorption tank for coal-gold agglomeration test

I-overflow type; II-self-priming inflatable type; III-downflow type;

A-pulp; B-kerosene agglomeration; C-air; D-mixed phase; E-baffle (4 pieces evenly distributed)

The test proves that the downflow agitating adsorption tank works well and has obvious superior performance, and the selected downflow agitating adsorption tank is a pilot plant with a scale of 1t/d.

Trial material is in quartz vein cyanide heap leach tailings oxide ores, natural or elemental gold was wrapped in pyrite and arsenopyrite, gold 4 ~ 6g / t. The tailings are ground to 85%-0.074mm (200 mesh), and the solid-liquid ratio is 1:3. The collector is added to the slurry to adjust the slurry, and then pumped to the stirred adsorption tank and the kerosene agglomerate. Stir the adsorption together. The adsorption operation is carried out by 2 to 4 grades respectively, and the slurry flows into the next tank through the interstage sieve, and the coal gold agglomerates are returned to the original adsorption tank to continue adsorption, and the adsorption time per tank is 1 to 3 hours. The recovery rate of gold is about 80%.

According to the results of the pilot test, the process flow developed by the Xinjiang Institute of Chemistry is shown in Figure 2. According to this process, the test of eleven mineral samples such as Shandong Zhaoyuan shows that the coal-gold agglomeration method is very suitable for oxidized ore, carbonate minerals, gold-bearing altered rock and so on, and single enrichment of agglomeration. The factors are mostly between 36 and 58 times, and the adsorption ratio can be further increased to increase the enrichment ratio. The adsorption recovery rate of gold is more than 94% except for individual raw materials, which is significantly higher than the cyanide leaching rate (see the table below). After the pilot test and the experimental study of various ores, the Xinjiang Institute of Chemistry established a 50t∕d industrial experiment and demonstration plant in Hami Gold Mine and Zhaoyuan Linglong Town in 1993 and 1994 respectively, in order to conduct more extensive research and Promote the industrial application of the coal-gold agglomeration process.

Figure 2 Coal gold agglomeration gold extraction process

Zhao Bing et al also studied the adverse effects of fine muddy oxidized ore on CGA process. Under normal conditions, fine muddy oxidized ore and iron cap type oxidized ore have adverse effects on beneficiation and cyanidation operations, as well as CGA processes. A gold mine is an oxidized ore containing S0.22% and Fe22.1%. Most of the gold particles are between 5 and 40 μm and are closely related to limonite. The ore is ground to produce a large amount of fine-grained slime. These fine slime have a large surface area, which will not only adsorb a large amount of chemicals from the pulp, but also increase the consumption of xanthate and black medicine, and also pollute the monomer and the continuum. On the surface, the adsorption recovery rate of kerosene agglomerates to gold is as low as about 60%. After the test, the iron oxide was removed by flotation desulfurization and dilute hydrochloric acid, and the kerosene agglomeration adsorption was carried out. The recovery rate of gold was increased to 80%, which was equivalent to the leaching index of the whole mud cyanide and liquid chlorination leaching gold. This is true, but the overall mud cyanidation and chlorination leaching costs are higher, and the CGA process is more economical and reasonable.

Table gold gold agglomeration process gold extraction test results

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