I. Heavy (zhong) selection of gold extraction process
Re-election is the most traditional method of gold withdrawal. Because of its simple process and low cost, it is effective for trapping monomer renting gold. Therefore, the process still dominates the gold extraction of sand mines. However, in recent years. The re-election process is very rapid for the gold extraction of rock gold mines. Several large or new large-scale rock gold mines in foreign countries have used re-election method to extract monomer gold in the grinding circuit. Some rock gold mines in China also have applications, and all have received good results.
Improvements and innovations in re-election equipment have driven the development of re-election gold extraction processes. Such as the successful development of the movable chute, the round jig, the Nielsen concentrator using the centrifugal force field, and the successful agitating chute and STL type water jacket centrifuge developed in China, the recovery rate of re-election is further improved, and it has received obvious effect.
Second, flotation gold extraction process
From the 1950s to the 1970s, in addition to gold, China's gold production basically uses the flotation method to produce concentrates, and then sends them to the smelting plant to produce finished gold. This method is still the most economical and rational process for sulfide ore containing metals such as gold, copper , lead , zinc, etc. It can realize the comprehensive utilization of polymetallics. After the 1980s, the flotation gold extraction process has developed greatly and has entered a new level.
(1) Flotation of new equipment and new pharmacy
In recent years, due to the emergence of new flotation equipment and new flotation reagents, the flotation recovery index (grade and recovery rate) has been continuously improved. For example, the flotation column has been applied in developed countries, which has brought the flotation process to a new level. China has improved the old-fashioned A-type flotation machine, and developed high-efficiency flotation machines such as SF type, BS-K4 type, JJF type, QF type and CHF-Y type, which make the concentrate grade and recovery rate different. The degree of improvement. For example, after a BS-K4 flotation machine was used in a gold mine in Henan, the concentrate grade was increased from the original 17.44 g/ton to 24 g/ton, and the tailings grade was reduced from 0.55 g/ton to 0.3 g/ton.
The use of new flotation reagents and combination medications has greatly improved flotation conditions and enhanced harvesting capacity, thereby increasing flotation recovery and reducing drug consumption. For example, a copper mine in Jiangxi used the advanced xanthate collector Y-89, which effectively improved the selection of copper, silver and sulfur, especially the recovery rate of associated gold increased by 2.5%. And the total amount of the agent was reduced by 46 g/t. A copper mine in Hubei uses P-60 mixed with isobutyl xanthate to use flotation sulfide ore. The gold recovery rate was increased by 5.77%.
(2) Flotation combined process
The single flotation process has not adapted to the increasingly complex ore properties, and the development of the beneficiation and gold extraction process technology has formed a trend toward the development of joint process. Such as re-election-flotation process, flotation-cyanide process (concentrate or tailings cyanidation), cyanidation-flotation and re-election (flotation)-carbon leaching processes are widely used in gold mines at home and abroad. For example, the re-election-flotation process can overcome the shortcomings of the difficulty in collecting and collecting the rented grain. A gold mine in Hebei belongs to a gold-bearing polymetallic deposit with a daily treatment capacity of 300 tons/day. The process adopted is a flotation-concentrate cyanide-leaching separation process, which achieves the purpose of comprehensive recovery of polymetallics.
In view of the ever-changing nature and increasing complexity of the ore, the use of the combined beneficiation process can indeed maximize the recovery index. This is a very beneficial way for China's gold mines, especially the old mines that have been in operation for many years, to tap the potential for comprehensive recovery. .
Third, cyanide gold extraction process
At the beginning of the 20th century, cyanide gold was promoted and applied in industry. About 80% of the world's new gold mines are currently raised by cyanidation. How to shorten the leaching time, further increase the leaching rate and reduce the consumption of cyanide is a subject that people are constantly researching and exploring. Therefore, the current development of the process has reached a fairly high level internationally.
(I) Improvement of cyanide gold extraction process
1. Use an oxidant (pure oxygen or oxide) in the leaching process and extend the oxygen absorbing process, such as oxygen resin leaching. The benefits of using auxiliary oxidants: one is to effectively increase the leaching rate of gold and silver; the second is to speed up the leaching speed and shorten the leaching time; the third is to reduce the consumption of cyanide and reduce the amount of lead nitrate. The leaching rate of the Longtoushan gold mine in Guangxi was increased by 4.31%. The use of auxiliary oxidants has been widely promoted throughout the world as the best technology for optimizing the cyanidation process.
2. The copper-gold ore was leached by ammonia-cyanide system. In 1986, it was successfully operated in a small tailings treatment plant abroad. In China's experimental study to improve the copper-bearing gold concentrate in Hunchun, the ammonia-cyanide system was used to leaching, which significantly increased the gold leaching rate to 38.98%. For cyanide leaching of gold-copper ore and copper-bearing concentrates, this technology will show strong vitality.
3, edge grinding and immersion process can enhance the leaching effect. For example, the 216 geological team of Shanxi Geological Survey Bureau recently used TW type tower grinder to immerse and immerse arsenic refractory gold concentrate in the side grinding, the treatment volume is 30 tons/day, and the grinding fineness is 95%-98%. Under the 400 mesh condition, the gold leaching rate increased by 8%. If the tower grinding machine is used to implement the edge grinding and immersion process in gold mines, it will be a major innovation in the cyanide gold extraction process.
(II) Development of gold recovery process from cyanide leachate
Gold is recovered from cyanide leachate (or pulp), and the three major processes of industrial production are mature, namely zinc powder replacement process; activated carbon adsorption process and ion exchange resin process. The activated carbon adsorption process is more economical and effective, and the ion exchange resin process has become a latecomer with its superior physical and chemical properties, and has been rapidly developed. Nevertheless, the zinc powder replacement process is very beneficial in the treatment of silver-containing ores and gold-containing solutions.
In developed countries, in the pulp system, the development trend of activated carbon adsorption is carbon leaching. High-strength, wear-resistant coconut shell charcoal is commonly used in carbon. The carbon analysis is widely used in the Zade process. In recent years, the application of the heating and pressure analysis process and the cyanide-free analysis process have been promoted. China's Laojiaoshan gold mine in Heilongjiang Province successfully adopted a cyanide-free analytical process, which can save 33 tons of solid sodium cyanide, worth 530,000 yuan.
The ion exchange resin process is widely used in Eastern European countries. The development and application of new resins has become the core of the forward development of resin pulp technology. The use of new anion exchange resins and chelating resins greatly improves the resin adsorption properties.
Xinjiang Axi Gold Mine is the first large-scale gold mine in China to introduce resin gold extraction technology, with a production scale of 750 tons/day. The production practice proves that the resin has high mechanical strength and low wear, and the resin consumption is only 25 g/ton; the adsorption capacity of the resin is high and the adsorption speed is fast; the concentration of the adsorbed pulp is 5% to 7% higher than that of the carbon slurry method. This also shows that the resin slurry method is superior to the carbon slurry method in many aspects, and it is worthy of being promoted and applied in China.
(c) Cyanide dissolves gold, which is highly undesirable because it is highly toxic. For many years, attempts have been made to replace it with other less toxic leaching agents. In recent years, great progress has been made in this area. The leaching agents developed include thiourea, chlorine, bromine , iodine , nitrogen, thiocyanate, and thiosulfate, which are more industrially significant. It is a thiourea and bromine.
Thiourea immersion gold has a lot of research results at home and abroad, sulfur gland leaching gold is fast, non-toxic, not sensitive to harmful elements such as copper and arsenic, it may become the most promising solution for industrial production except cyanide. Gold pharmacy.
The problem that hinders the industrial application of thiourea is the high consumption of chemicals; the leaching pulp is acidic, and the leaching equipment needs to be preserved; the lack of an excellent method for effectively recovering gold and silver from thiourea solution has no economic advantage compared with cyanide gold extraction. . Therefore, it is currently limited to small-scale industrial applications (processing high-grade gold concentrates). Recently, Minmet of Ireland has developed a new process for immersion gold with thiourea. The process has undergone significant improvements in adsorption, recovery and solution recycling. Thereby reducing the loss of thiourea and improving the leaching and precipitation efficiency. The process is suitable for ore of various grades, and has lower power consumption and less reagent usage than the cyanidation method. Save on environmental governance costs. Suitable for small-scale mining applications.
Brominated gold extraction is likely to be the most promising leaching process to replace cyanide gold. Great Lake Chemical Company, in order to evaluate the effect of bromine and cyanide leaching, systematically studied the bromination gold extraction process. The results show that bromine is superior to cyanide as a gold leaching agent. Mainly in the following aspects:
1, the price is cheap.
2. High leaching rate. The same leaching rate (90% to 95%) as that of cyanide leaching gold can be achieved.
3. The leaching speed is fast. Leaching with 4 h was equivalent to leaching with cyanide for 24 h to 48 h.
4. It is non-toxic and non-corrosive at low concentrations.
5, the drug can be recycled.
6. It is convenient to recover gold from the solution, and the recycling process of cyanidation method can be adopted. In order to fill the gap in bromination and gold extraction technology, the company has been conducting research work. Although the application of bromine is still at a relatively early stage, as time goes by, the Australian gold extraction process will gradually be recognized and accepted by people. The advantages of the process will also be verified by industrial production.
Fourth, heap leaching gold extraction process
The heap leaching gold extraction process is currently considered to be the most economical gold extraction method. Production practice shows that the infrastructure investment of the heap leaching production mine is about 25% of the construction plant. Production costs are only 35%-40% of the cost required compared to the more economical carbon slurry process. A large part of the increase in gold production in the world's major gold producing countries in recent years comes from heap leaching. At present, the production scale of heap leaching has been enlarged, and the heap leaching technology has also developed in depth.
(1) The scale of production is continuously expanding, and the grade of impregnation is gradually reduced.
At present, the international large-scale heap leaching plants include the Yanacocha gold mine heap leaching plant in Peru and the RoundMountain gold mine leaching plant in the United States. The Yanacocha gold mine heap leaching plant processes 1.36 million tons of ore per month with an average gold grade of 1.4 g/t. The Round Mountain gold heap leaching plant has a daily processing capacity of 45,000 tons and an average gold grade of 1.1 grams/ton. The largest heap leaching plant in China is the Zijinshan Gold Mine in Fujian Province. The annual processing of ore is 2.6 million tons, and the grade of human immersion ore is 1.4g/ton-1.7g/ton, and the leaching rate is 70%.
(II) Improvement of mineral granulation technology
The application of granulation technology has brought the heap leaching and gold extraction process to a new level. By using granulation technology, heap leaching and gold extraction can be carried out for ore with poor permeability, argillaceous minerals and abandoned tailings. In addition, cyanide is added during the granulation process to make the cyanide and the ore more evenly contacted to enhance the leaching effect, which is also an innovation of granulation technology.
(3) Adding auxiliary agents to increase the leaching rate. Shorten leaching time
(1) Pure oxygen and calcium peroxide will be used in the heap leaching process. The results of column immersion test show that the process can improve the heap leaching recovery rate, shorten the leaching period, and reduce the oxide consumption and water consumption.
(2) Adding a surfactant to significantly improve the leaching effect. The addition of this surfactant, the leaching test of the broken siliceous oxidized ore, the leaching rate increased by 24%; the leaching rate of the argillaceous ore was increased by 4%.
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