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Click to add WeChatWith the rapid development of the international community, the demand for gold continues to rise and the price continues to rise. In order to meet market demand, we need not only to actively explore and develop new gold resources, but also to improve the utilization rate of existing gold resources, which requires the improvement of mineral processing technology, especially the key indicator of gold recovery rate. For different types of gold ores in nature, appropriate gold extraction processes need to be adopted. Commonly used gold extraction methods include gravity separation, flotation and cyanidation.
Gravity separation is one of the commonly used methods in gold ore dressing. Based on the difference in mineral density and particle size, mechanical force is used to achieve layered separation in the fluid medium to effectively recover coarse free gold. This method has the advantages of environmental protection and low cost. It is widely used in the treatment of placer gold mines. At the same time, it is used as an auxiliary means of rock gold ore dressing to recover coarse gold in the grinding circuit.
Common equipment includes chutes, jigs and shaking tables. Jigging gold selection is suitable for sorting coarse mineral particles, with a particle size range from 50mm to 0.007mm. Chute gold selection is suitable for low-grade placer gold mines, processing fine-grained materials with low mud content. The material particle size range is 0.6~0.03mm and the recovery rate can reach 60%-90%. It has the characteristics of simple structure, large processing capacity and low cost. Shaking table gold selection is suitable for finer-grained materials, with a particle size range of 3~0.019mm. The gold selection process is stable and reliable, with a high rich ore ratio and easy management. In vein gold mines, gravity separation is often used in combination with other processes to improve the overall mineral processing efficiency and gold recovery rate.
Flotation is widely used in gold ore dressing, especially for gold-bearing ores containing highly floatable sulfide minerals. Since gold is hydrophobic and has good floatability, xanthate and black medicine are used as collectors, combined with inhibitors such as lime, cyanide and sodium sulfide, to effectively enrich gold and sulfide minerals into concentrates. Flotation can not only efficiently recover gold, but also realize the comprehensive utilization of multiple metals, such as enriching gold into copper and lead concentrates for further extraction.
For gold ores with uniform and coarse particle size, a grinding and flotation process is usually used. For difficult-to-treat ores, flotation is often used as part of a combined process to effectively improve the gold recovery rate. However, since gold is usually enriched in sulfide concentrates, flotation usually needs to be used in conjunction with other processes, such as cyanide leaching, roasting or high acid washing, to achieve effective gold recovery.
As the main process for efficient gold recovery, cyanide is particularly suitable for treating gold-containing oxidized ores with high ore mud content. Cyanide leaching is performed on the crushed and ground ore, and cyanide ions react with gold to form a complex that dissolves in the solution, and then is adsorbed on activated carbon, electrolyzed or replaced with zinc powder, and then smelted to extract gold.
Carbon Ink Pulp Process (CIP) is a process in which activated carbon is put into cyanide slurry to adsorb dissolved gold on the activated carbon and then extract gold from the activated carbon. The main steps include preparation of leaching raw materials, stirring leaching and countercurrent carbon adsorption, gold-loaded carbon desorption, electrolysis, smelting ingots and carbon regeneration. CIP is suitable for amalgam tailings, gravity separation tailings or muddy oxidized ores, with a recovery rate of up to 90%. Carbon Ink Pulp Process (CIP) has the advantages of high recovery rate and simple operation, and is particularly suitable for processing gold mines with high mud content. However, the process also has high investment and operating costs, operational complexity, and potential impacts on the environment and safety.
Carbon leaching (CIL) combines the adsorption and extraction processes on the basis of carbon slurry. Activated carbon is added to the leaching tank, and leaching and adsorption are carried out simultaneously, that is, leaching and adsorption, and then the gold-loaded carbon is desorbed and electrolyzed. The advantage of carbon leaching (CIL) is that it reduces the number of leaching tanks and shortens the process, thereby reducing infrastructure investment and production costs; leaching and adsorption improve the dissolution kinetics of gold, which is conducive to gold leaching and adsorption.
Pool leaching is suitable for low-grade gold and silver mines and gold mines with less clay content, with a recovery rate of 50% to 70%. The design of the percolation tank is diverse, and the material can be wood, iron or cement. The bottom is laid with a false bottom and filter cloth to support the ore and promote the penetration of the leachate. The ore is placed in the leaching tank, and the circulating pump pumps the leachate prepared in the lean liquid tank into the tank, and the precious liquid is then replaced. Compared with the CIL and CIP methods, the pool leaching method has a lower cost, can improve the economic benefits of low-grade gold mines, is easy to operate and has low labor costs. However, the initial construction investment of the pool leaching method is large, the leaching cycle is long, and the leaching efficiency is easily affected by factors such as the solvent dissolution rate, penetration rate and material characteristics.
Heap leaching gold is an economical and efficient gold extraction process, especially suitable for processing low-grade ores and tailings of 0.5-3g/t. The ore is crushed to an appropriate particle size, piled on the bottom pad, and the ore pile is sprayed with sodium cyanide solution to dissolve gold and silver in the solution. Then activated carbon adsorption, zinc replacement or electrolytic deposition are used to recover gold. Heap leaching has the advantages of simple process, low investment, quick effect and low cost. The gold recovery rate can reach 50-90%, so that the ore with no economic value can be recycled. The tailings are discharged after disinfection, realizing the economic recovery and utilization of resources.
In the gold ore selection process, the ore dressing plant should first conduct ore dressing tests, analyze the ore properties in detail, and formulate an optimized ore dressing plan based on the actual situation, investment and other factors of the gold ore dressing plant, so as to achieve efficient selection of concentrate and improvement of ore dressing recovery rate, and achieve an ideal return on investment.
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