(1) crushing and grinding
According to the investigation, jaw crushers are mostly used for coarse crushing, standard cone crushers are used for medium crushing, and short-headed cone crushers and roller crushers are used for fine crushing. Most small and medium-sized gold concentrator adopts two-stage and one-closed circuit ore crushing process, while large gold concentrator adopts three-stage and one-closed circuit ore crushing process.
In order to improve the mineral processing capacity and tap the potential of equipment, the ore crushing process was reformed, and the utilization coefficient of the mill was improved. The main measures taken are more crushing and less grinding to reduce the grinding particle size.
(2) Re-election
Gravity separation is widely used in rock gold mines, mostly as an auxiliary process for recovering coarse gold in grinding circuit, which creates favorable conditions for flotation and cyanidation processes, improves mineral processing indexes, improves the total recovery rate of gold, and plays a positive role in increasing production and reducing costs. More than 0/0 gold concentrator in Shandong province have adopted gravity separation technology, and the average total recovery rate can be increased by 2% ~ 3%, which has good economic benefits. According to incomplete statistics, millions of yuan can be earned every year. Henan, Hunan, Inner Mongolia and other provinces (regions) have also achieved good results, and the main equipment used is chute, vibrating screen, jig and short cone cyclone. From the point of view of most gold mines in China, the combined flotation-gravity separation process (gravity separation of flotation tailings) is suitable, and the stage grinding and stage separation process should be vigorously promoted in the future, and the principle of early harvest should be advocated.
(3) Flotation
According to the investigation, about 80% of rock gold mines in China use flotation to select gold, and most of the concentrates produced are sent to non-ferrous smelters for treatment. Due to the increasing development of cyanide gold extraction and the efforts of enterprises to improve economic benefits and reduce concentrate transportation losses, the product structure has changed greatly in recent years, and more on-site treatment has been adopted (of course, due to the contradiction between dressing and metallurgy and pricing problems, mines are forced to treat themselves on the spot), which has promoted the great development of flotation technology and occupied a very important position in gold production. There are usually two processes: preferential flotation and mixed flotation. In recent years, new progress has been made in technological process transformation and reagent addition system, and the flotation recovery rate has also been significantly improved. According to the investigation results of flotation process indexes of more than 40 gold concentrator in China, the flotation recovery rate of sulfide ore is 90%, and a few of them are as high as 95% ~ 97%. The recovery rate of oxidized ore is about 75%; Individual reached 80% ~ 85%. In recent years, there are many innovations and scientific research achievements in flotation process, and the effect is obvious. At present, stage grinding-flotation process and gravity flotation combined process are the main trends of flotation technology development in China. For example, Xiangxi Gold Mine adopts the combined process of gravity and flotation, carries out stage grinding and stage separation, and obtains good indexes, and the recovery rate is improved by more than 6%; Jiaojia Gold Mine, Wulong Gold Mine, Wenyu Gold Mine and Dongchuang Gold Mine have also made certain achievements. Another example is Xincheng Gold Mine. The original process is direct flotation of raw ore. Due to the high mud content (high mud content of ore itself, insufficient cemented filling strength of mining tailings, which brings some mud and sand), the mineral processing index is declining continuously. After investigation and experiment, the recovery rate was increased from 93.05% to 95.0 1% and the concentrate grade was increased from 135g/t to 140g/t by using the mud-sand separation process, which stabilized the production. Because the grade of raw ore in Jinchangyu Gold Mine is decreasing year by year, the flotation index is decreasing. Through the experimental study with Shenyang Gold Research Institute and other units, the branch flotation process was adopted to improve the flotation index and concentrate grade. This scientific research achievement (passed the technical appraisal in June 1988 and June 1) has gained new enlightenment for the transformation of flotation process. Of course, flotation, like other methods, is not omnipotent and cannot be effective for all gold-bearing ores. When selecting the technological process, we should mainly consider the properties of ore and carry out various demonstrations and tests.
In recent years, in order to improve the separation effect, many improvements and studies have been made on the dosing system and mixed medication while the process has been continuously improved, and the automatic control of dosing has also made new progress.
(4) Chemical beneficiation-Shui Ye gold extraction process.
1. Gold extraction by mixed mercury method
The process of extracting gold from mixed mercury is an ancient process, simple and economical, and suitable for the recovery of crude monomer gold. Many gold mines in China still use this method. With the development of gold production and the progress of science and technology, the process of extracting gold with mixed mercury has been continuously improved and perfected. Due to more and more stringent environmental protection requirements, some mines canceled the mercury mixing operation and replaced it with gravity separation, flotation and cyanidation to extract gold.
In gold production, the process of extracting gold with mixed mercury still occupies an important position, and there are application examples at home and abroad. At present, the process has been applied in Zhangjiakou, Hebei, Erdaogou, Liaoning, Jiapigou, Jilin, Yinan, Shandong and other gold mines. Erdaogou gold mine in Liaoning Province was originally a single flotation process, and it was changed into a combined flotation process with mixed mercury according to the ore properties. The total recovery rate increased by 7.8 1% (the recovery rate of mixed mercury reached 64.6%), and the tailings grade decreased from 0.74g/t to 0.32g/t, with an annual benefit of 1.58 million yuan. The key to gold extraction by mixed mercury method is how to take protective measures to eliminate mercury pollution.
2. Cyanide gold extraction process
Cyanidation is the main method to extract gold from ore or concentrate in modern times. The cyanide gold extraction process includes several basic processes, such as cyanide leaching, washing and filtering of leached pulp, extracting gold from cyanide solution or cyanide pulp and smelting of finished products. There are basically two gold extraction processes in the existing gold cyanide plants in China. One is the so-called conventional cyanidation process (CCD method and CCF method) which uses a thickener for continuous countercurrent washing, and the other is the filterless cyanidation carbon pulp process (CIP method and CIL method) which directly absorbs and recovers gold from cyanidation pulp without filtration washing.
Conventional cyanidation processes can be divided into two types according to the different materials to be treated: one is cyanidation plants that treat flotation gold concentrates or mixed mercury and gravity separation tailings. This technology is mostly used in large state-owned mines. Such as Jinchangyu, Hebei; Wulong, Liaoning, Yangzhaiyu, Henan; Zhaoyuan, Xincheng, Jiaojia and Sanshandao gold mines in Shandong Province. The other is a gold concentrator, which deals with argillaceous oxidized ore and adopts all-mud stirring cyanidation method. Such as Jilin trench; Tuanjiegou, Heilongjiang; Anhui Xinqiao gold and silver mine and other mines.
As early as 1930s, China began to extract gold by cyanidation. During the period of 1936 ~ 1938, Taiwan Province Jinguashi gold mine used cyanide-zinc powder replacement process to extract gold, with an annual output of152,000.
After 1960s, in order to adapt to the development of national economy and vigorously develop mineral gold production, some mines adopted intermittent mechanical agitation cyanidation process and continuous agitation cyanidation process instead of percolation cyanidation process. 1967 realized the continuous mechanical agitation cyanidation process for the first time in the concentrator of Lingshan and Linglong gold mines in Zhaoyuan Gold Mine, Shandong Province, and the cyanidation gold extraction increased from 70% to 93.23%. Since then, continuous mechanical agitation cyanidation process has been rapidly popularized in major gold mines in China. 1970 jinchangyu gold mine and 1977 Wulong gold mine cyanidation plants were built and put into operation one after another, and then a number of domestic mechanical agitation cyanidation plants were built and put into operation one after another, and the cyanidation process of gold extraction entered a new development stage.
Since 1980s, with the continuous development of gold production and the rapid development of gold resources, a large number of gold-bearing oxide ores with high argillaceous content have appeared. The research on all-slime cyanidation and agitation leaching of this kind of ore was carried out, and a cyanidation plant with a daily processing capacity of 500t ore was built in Tuanjiegou Gold Mine of Heilongjiang Province, which was put into operation on 1983. Since then, the whole mud cyanidation process has been widely used to extract gold in Henan, Jilin, Hebei, Shaanxi, Inner Mongolia and other places. At the same time, in order to solve the difficulty of solid-liquid separation in dense filtration of argillaceous oxidized ore, Changchun Gold Research Institute began to extract gold from Tuanjiegou gold mine by carbon slurry method in June 5438+0979165438+10. The experimental study lasted for two years and was successful. On this basis, in August of 1984, the first gold extraction plant with a daily processing capacity of 50t was designed and built in Linghu Gold Mine, Henan Province. The cyanide gold extraction process in China has taken a big step forward. Gold extraction from carbon slurry has become one of the important methods to treat argillaceous oxidized ore. Since then, gold extraction plants have been built in Jilin, Henan, Inner Mongolia, Shaanxi and other places. At the end of 1984, the Gold Bureau of the Ministry of Metallurgy established a 250t (Xitongyu) gold mine in Shaanxi Province and a 450t (Zhangjiakou) gold leaching plant in Zhangjiakou, Hebei Province, respectively, in order to popularize the application of carbon slurry gold extraction technology in China and transplant and digest foreign advanced technology and equipment. According to the investigation, the recovery rate of Zhangjiakou Gold Mine is 93.54% (the recovery rate of1988 carbon slurry is 90.25%).
According to the experimental research of scientific and technological innovation, the technical level of gold production in China has been greatly improved. For example, the replacement of gold mud with zinc powder instead of zinc wire was successful in Jinchangyu Gold Mine, so that the replacement rate reached 99.89%, the gold grade of gold mud was obviously improved, the zinc consumption was reduced from 2.2kg/t to 0.6kg/t, and the production cost was greatly reduced. Subsequently, it was popularized and applied in Zhaoyuan, Jiaojia, Xincheng, Wulong and other mines, and achieved remarkable results. The heap leaching technology of low-grade oxidized ore was successfully tested in Hushan Gold Mine in Dandong, and has been popularized and applied in Henan, Hebei, Liaoning, Yunnan, Hubei, Inner Mongolia, Heilongjiang, Jilin, Shaanxi and other provinces, with obvious economic effects, which opened the way for the development and utilization of low-grade oxidized ore. According to incomplete statistics, the annual output of heap leaching gold in China is more than 22,000 (only 65,438+3,000 in Henan Province), but compared with developed countries, the scale of heap leaching in China is relatively small, generally1×103 ~ 3×1003t/heap.
Introduce and digest foreign advanced technology and equipment (such as American high-efficiency thickener, double-helix stirring leaching tank, Japanese Mars pump, belt filter, etc.). ) further improved the equipment level and technical level of China's gold production, and also promoted the development of China's gold beneficiation equipment in the direction of high efficiency, energy saving, large-scale and automation. In recent years, the research of new technologies such as thiourea extraction, thiosulfate extraction, pre-oxidation bacterial leaching, pressure catalytic leaching and resin adsorption has also made new progress. 1979 The experiment of thiourea gold extraction in Changchun Gold Research Institute was successful. 1984 A thiourea gold extraction workshop was built in Guangxi Longshui Mine, with a daily processing capacity of10 ~ 20t (1987 passed the ministerial appraisal). Although other processes are in the experimental research stage, ready to build a factory and put into production, it is enough to show that the gold extraction technology in China has developed to a new level.
(5) Gold smelting and recovery
Gold smelting is the last process of gold production, and its product is finished gold. Smelting can be divided into rough refining and refining. After finishing and rough machining, the products are all alloy (commonly known as alloy gold), and most of the real estate gold mines in China are alloy gold, which are sold directly to banks. Gold-rich ore blocks and various gold concentrates are transported to non-ferrous smelters for processing and refining finished gold (commonly known as content gold). Over the past 40 years since the founding of the People's Republic of China, gold smelting and comprehensive recovery have developed rapidly, the level of smelting technology and process equipment has been continuously improved, and the smelting cost has been reduced day by day, which has promoted the development of gold production.
1. In-situ melting of gold in gold mines
Before 1970s, gold production was in the primary stage of development. Except for a few mines, cyanidation is used to extract gold. The main gold in the mine is the smelting of natural gold and placer gravity concentrate, and the mercury paste produced by the mixed mercury extraction process is used as the raw material for local smelting. The amount of local gold only accounts for 30% of the total output, and 70% is recovered by Jinyi Nonferrous Smelter.
After 1970, gold production developed gradually, cyanide process was widely used, and the gold output of mines increased day by day. 1985, the output of finished gold in mines accounts for 70% of the national gold output, and most of the concentrate products produced by concentrator adopt in-situ cyanide smelting.
In-situ smelting in mines mostly adopts the traditional crucible method, and the gold content of the alloy gold produced is different due to the different production technology and the properties of the treated materials. Due to the low gold content of direct selling banks or the non-pricing of silver, some mines adopt chemical impurity removal and remelting or electrolytic separation and refining of gold and silver to improve quality and economic benefits. Shui Ye's new process was adopted in Jiaojia Gold Mine 1984. The cyanide gold mud was removed by electrochlorination (gold was extracted by aqueous solution chlorination and silver was extracted by ammonia leaching), and the finished gold with 99.9% gold grade and silver ingot with 99.9% silver were obtained. At the same time, copper and lead in gold mud are also recovered (wet treatment of gold mud has a tendency to be popularized). Zhaoyuan Gold Mine successfully developed a φ 1.5× 1.8m converter to smelt gold slime, which replaced the past crucible smelting, reduced the cost and improved the working conditions. This method has been widely used in Shandong Xincheng Gold Mine and other mines, and the effect is good.
Zhaoyuan Smelter is the first gold smelter independently developed, designed and built in China. It specializes in processing polymetallic sulfide gold concentrate, mainly extracting gold and recovering silver, copper, lead and sulfur at the same time. Is a new enterprise integrating comprehensive smelting and chemical industry. The completion and commissioning of Zhaoyuan Smelter has filled a technical gap in China's gold production and smelting process. The combined process of roasting-acid leaching-(salt leaching)-cyanide leaching was adopted, which solved the long-standing contradiction in mining, dressing and smelting production, and solved the problems of long-distance transportation loss (annual loss rate of 2% ~ 3%), heavy transportation pressure and comprehensive utilization of gold concentrate.
The production process design of this factory absorbs advanced experience at home and abroad, adopts vacuum belt filter as leaching residue washing and filtering equipment, and adopts axial flow cyanidation leaching tank for tertiary leaching, tertiary solid-liquid separation and leaching residue washing, with advanced process flow.
2. Recovery of associated gold from nonferrous smelters
In gold production, the recovery of associated gold from polymetallic ores occupies a considerable position. Gold is selected into concentrate together with non-ferrous metals such as copper and lead, and gold and silver are recovered in copper and lead smelting. In order to increase the output of gold, some nonferrous smelters in China have successively built comprehensive recovery workshops for precious metals. By the end of 1985, there were more than 20 workshops in China, including Zhuzhou, Shanghai, Yunnan, Chongqing, Wuhan, Fuchunjiang, Tianjin and Taiyuan electrolytic copper plants. Among them, the associated gold output of Shenyang, Shanghai and Zhuzhou smelters accounts for more than 90% of the total associated gold output in China, which is an important force in China's gold production. The recovery of associated gold by these enterprises is based on the fact that gold and silver are enriched in crude copper and crude lead during copper-lead smelting, and gold and silver are precipitated in electrolytic anode mud during electrolytic refining of crude copper and crude lead. Therefore, extracting gold and silver from anode mud is the main way to recover associated gold and silver.
The treatment process of copper anode slime has developed rapidly. Through continuous reform and innovation, the traditional pyrometallurgical production process is more mature and perfect. Semi-wet combined process and all-wet new process have been successfully tested and put into production, which greatly improves the level of smelting technology and equipment in China. Such as improvement of pyrometallurgical copper removal process, comprehensive recovery of valuable elements, improvement of furnace body and perfection of dust removal system. The transformation of electrolytic cell and the popularization and application of intermediate frequency furnace make pyrometallurgical process mature and perfect gradually, and the technical and economic indexes are improved. Pyrolysis technology has the advantages of stable technical conditions, mature technology, high comprehensive utilization rate, strong adaptability of raw materials, large capacity and low cost, and is still widely used in smelters such as Shenyang, Zhuzhou and Shangye. Fuchunjiang Smelter, Wuhan Smelter and Chongqing Smelter have successively adopted the new all-wet process and achieved remarkable results. Yunnan Smelter and Tianjin Electrolytic Copper Factory successfully adopted the combined flowsheet of beneficiation and metallurgy and put it into production, which also achieved remarkable economic benefits. The success and application of gold extraction process from sulfuric acid residue has also opened up a new way for gold production and full utilization of resources in China.
(6) heap leaching production process
In China's gold resources, the number of low-grade oxide ores accounts for a certain proportion. It is not economical to treat this kind of ore by conventional cyanidation process, but the heap leaching production process still has economic benefits. Further expansion of heap leaching production scale in the future is one of the ways to increase gold production in China. At the end of 1970s, China began to study the heap leaching process of low-grade gold-bearing oxide ore. After the small-scale production of Hushan Gold Mine in Dandong, Liaoning Province was successful, it was popularized and applied in some mines in Linghu, Yindongpo, Mojiang, Hebei Chongli and Chifeng, Inner Mongolia, and achieved satisfactory economic benefits, which opened the way for the development and utilization of low-grade gold-bearing oxide ore. Because the heap leaching gold extraction process is simple, easy to operate, less investment, good benefit and fast start-up, the heap leaching gold extraction process has developed rapidly. In recent years, the State Council and Gold Corporation attached great importance to it, and the heap leaching production technology has made new development, the scale and quantity of heap leaching have increased, and the production technology has been continuously improved and improved. Granulation technology, the application of activated carbon adsorption column and the development of gold-loaded carbon desorption electrodeposition process have added new vitality to the popularization and application of heap leaching gold extraction process.