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mining tailings, some mud and sand are brought in, the beneficiation indexes continuously decrease. Through investigation and test, the process flow of mud sand separation is adopted, the recovery rate is increased from 93.05% to 95.01%, the concentrate grade is increased from 135g / T to 140g / T, and the proction is stable. Because the grade of raw ore in Jinchangyu Gold Mine is decreasing year by year, the flotation index is reced. Through the cooperation with Shenyang Gold Institute and other units, the branch flotation process is adopted, and the flotation index and concentrate grade are improved. This scientific research achievement (passed the technical appraisal in January 1988) provides new enlightenment for the reform of flotation process. Of course, like other methods, flotation method is not omnipotent, and it is impossible to be effective for all gold bearing ores. The ore properties should be mainly considered. When selecting the technological process, it is necessary to carry out various demonstrations and tests

in recent years, in order to improve the separation effect, many improvements and researches have been made on the reagent addition system and mixed medication, and new progress has been made in the automatic control of dosing< (4) chemical separation hydrometallurgical gold extraction process

1. Mixed mercury gold extraction process

is an ancient gold extraction process, which is simple, economical and suitable for the recovery of coarse monomer gold. This method is still used in many gold mines in China. With the development of gold proction and the progress of science and technology, the process of extracting gold by mixed mercury method has been improved and perfected. Due to the increasingly stringent requirements of environmental protection, some mines have cancelled the mercury mixing operation and replaced it by gravity separation, flotation and cyanidation

in the proction of gold, the process of extracting gold by mixed mercury method still plays an important role, and has been applied at home and abroad. At present, this technology has been applied in many gold mines, such as Zhangjiakou, Hebei, Ergou, Liaoning, Jiapigou, Jilin and Yinan, Shandong. Liaoning Ergou gold mine was originally a single flotation process. According to the ore properties, it was changed into a combined process of mixed mercury and flotation. The total recovery was increased by 7.81% (the recovery of mixed mercury was 64.6%), the tailings grade was reced from 0.74g/t to 0.32g/t, and the annual benefit was 1.58 million yuan. The key to the process of gold extraction by mixed mercury method is how to take protective measures to eliminate mercury pollution< Cyanidation is the main method of extracting gold from ore or concentrate. The process of gold extraction by cyanidation includes: cyanidation leaching, washing and filtration of leaching pulp, extraction of gold from cyanidation solution or cyanidation pulp and smelting of finished procts. There are two kinds of gold extraction processes in the existing cyanidation plants of gold mines in China. One is the so-called conventional cyanidation process (CCD method and CCF method) in which the thickener is used for continuous countercurrent washing and zinc powder is used to replace the precipitation to recover gold. The other is that there is no need for filtration and washing, CIP process and CIL process were used to recover gold from cyanide pulp directly by activated carbon adsorption
the conventional cyanidation process can be divided into two types according to different materials: one is cyanidation plant which processes flotation gold concentrate or mixed mercury and gravity tailings. Most of them are large state-owned mines. For example, Jinchangyu in Hebei Province; Wulong, Liaoning, Yangzhaiyu, Henan; Zhaoyuan, Xincheng, Jiaojia and Sanshan gold mines in Shandong Province. The other is a gold extraction plant which processes argillaceous oxide ore and uses whole slime stirring cyanidation. Such as Jilin trench; Tuanjiegou, Heilongjiang Province; Xinqiao gold and silver mine in Anhui Province

the cyanidation process has been used in China since 1930s. During 1936-1938, Jinguashi gold mine in Taiwan used cyanidation zinc powder replacement process to extract gold with an annual output of 150000 taels< After entering the 1960s, in order to adapt to the development of national economy and vigorously develop the proction of mineral gold, the intermittent mechanical agitation cyanidation process and continuous agitation cyanidation process were successively adopted in some mines to replace the percolation cyanidation process. In 1967, the continuous mechanical agitation cyanidation process was first realized in Lingshan and Linglong gold concentrators of Zhaoyuan gold mine, Shandong Province. The cyanidation rate increased from 70% to 93.23%. Since then, the continuous mechanical agitation cyanidation process has been rapidly promoted in major gold mines in China. The cyanidation plants of Changyu gold mine in 1970 and Wulong gold mine in 1977 were successively built and put into operation. Since then, a number of mechanical stirring cyanidation plants have been built and put into operation in China. The cyanidation process has entered a new stage of development

with the continuous development of gold proction and the rapid development of gold resources, a large number of argillaceous high gold bearing oxide ores have been increased since the 1980s. The research on the whole slime cyanidation agitation leaching of this kind of ores has been carried out, and a cyanidation plant with a daily treatment capacity of 500 tons has been built in Tuanjiegou gold mine, Heilongjiang Province, which was put into proction in 1983. Since then, the whole slime cyanidation process has been widely used 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 use the non filtration carbon slurry process to extract gold from the ore of Tuanjiegou gold mine in November 1979. The experimental research lasted for two years and was successful. On this basis, in August 1984, China's first gold extraction plant with 50 tons of ore per day was designed and built in Linghu gold mine, Henan Province. It is a great step forward in the cyanidation process of gold extraction in China. The technology of extracting gold by carbon slurry has become one of the most important methods to treat argillaceous oxidized ore in rock gold mines. Since then, gold extraction plants have been established in Jilin, Henan, Inner Mongolia, Shaanxi and other places. At the end of 1984, the gold Bureau of the Ministry of metallurgical instry, in order to promote the application of carbon slurry process in China, transplanted and digested foreign advanced technology and equipment, cooperated with David McKee company of the United States, and established a 250t / D (xitongyu) and 450t / D (Zhangjiakou) carbon leaching gold extraction plant in xitongyu gold mine of Shaanxi Province and Zhangjiakou gold mine of Hebei Province, respectively. According to the investigation, the recovery rate of Zhangjiakou gold mine is 93.54% (the recovery rate of carbon slurry was 90.25% in 1988)

relying on science and technology, the experimental research of technological innovation has greatly improved the level of gold proction technology in China. For example, Jinchangyu Gold Mine successfully used zinc powder instead of zinc wire to replace gold mud, the replacement rate reached 99.89%, the gold grade of gold mud was significantly improved, the zinc consumption was reced from 2.2kg/t to 0.6kg/t, and the proction cost was greatly reced. Then, the application in Zhaoyuan, Jiaojia, Xincheng, Wulong and other mines also achieved obvious results. The heap leaching process of low-grade oxidized ore has been applied in Henan, Hebei, Liaoning, Yunnan, Hubei, Inner Mongolia, Heilongjiang, Jilin, Shaanxi and other provinces after the successful test in Dandong Hushan gold mine. The economic effect is obvious, which opens a way for the development and utilization of low-grade oxidized ore. According to incomplete statistics, the annual output of gold proced by heap leaching in China is more than 10000 taels (only 13000 taels of gold proced by heap leaching in Henan Province), but compared with developed countries, the scale of heap leaching in China is smaller, generally 1 × 103~3 × 103t / heap, 10000 t / heap is less, and there is a big gap in technology. In 1988, Shuangwang gold mine in Tai County, Shaanxi province put into operation, and achieved gratifying results (ore grade 1.5g/t)

the introction and digestion of foreign advanced technology and equipment (such as high-efficiency thickener in the United States, double screw stirring leaching tank, Mars pump in Japan, belt filter, etc.) has further improved the equipment level and technical level of China's gold proction, and promoted the development of China's gold proction equipment in the direction of high efficiency, energy saving, large-scale and automation. In recent years, new progress has been made in the research of new technologies such as thiourea extraction, thiosulfate extraction, preoxidation bacterial leaching, pressure catalytic leaching and resin adsorption. In 1979, Changchun Gold Research Institute successfully carried out the experiment of extracting gold with thiourea, and in 1984, a daily processing gold flotation plant was built in Guangxi Longshui mine