I. Introduction
Gold Mine tailings ore beneficiation of gold or gold extraction process the recovery of other useful components of the waste solid powder, 0.15mm or less in diameter. Large-scale formal gold mine tailings are mostly disposed of by tailings stockpiling. However, with the expansion of the mine scale and the extension of mining history, the occupied land is expanding, and the cost of tailings pond construction and management is increasing. Small or medium-sized irregular mine tailings facilities are poor or no tailings ponds are built at all. Tailings are generally discharged into river trenches, river valleys or low-lying areas. Surface water pollution caused by accidents such as tailings leakage or direct efflux, tailings dust causes land desertification to cause farmland reduction, production and other incidents occur, which brings harm to people's lives and brings pollution to the ecological environment. Has been widely concerned by the whole society.
Gold mineral resources are non-renewable. Among China's gold resource reserves, refractory resource reserves account for 15% of the reserves of retained resources, while low-grade mines account for about 1/3 of the identified gold resources. According to statistics in 2006, there are 1757 gold mines in the country; 123 large gold mines, accounting for 1.3% of the total gold mines; 69 medium-sized gold mines, accounting for 3.93% of state-type gold mines, accounting for 35.23%; other small 1046 mines, accounting for 59.54%. With the increasing demand for gold, the massive development and utilization of mineral resources has made mineral resources increasingly scarce. The secondary development and utilization of tailings resources has the advantages of short construction period, low investment, quick effect, large-scale production, low cost, comprehensive recovery of various valuable elements and non-metallic elements, etc. Resources are getting more and more attention. “China’s Agenda 21†has included “the tailings disposal, management and resource demonstration project†as a priority plan in priority areas. The National Development and Reform Commission, the Ministry of Science and Technology and the Ministry of Environmental Protection have listed the comprehensive utilization of tailings resources as encouraged by the state. Resource conservation, comprehensive utilization and environmental protection technologies show that China has raised the development and utilization of tailings resources to a very important position. At present, China has done a lot of research on the recovery and utilization of secondary resources in tailings, and many of the results have been industrialized. With the continuous improvement and advancement of science and technology, vigorously developing gold tailings and fully recycling and utilizing secondary resources is of great significance for protecting and improving the ecological environment, improving the utilization of mineral resources and promoting the sustainable development of gold mines.
Second, gold, silver recycling
China's gold mines mainly use flotation-cyanide production processes. In the 1970s and 1980s, due to factors such as industrial policies, technical level, and smelting process, the comprehensive utilization of resources was generally low, and the waste was serious. The gold grade of tailings was too much above lg/t. Small mines with low technical level can reach 2~3g/t. For gold concentrates with high grade and difficult to be smelted, the gold grade of tailings is as high as 3~5g/t, some even higher. Therefore, it has a high recycling value. Due to the low production cost of secondary utilization of tailings resources, mining, crushing and grinding operations are no longer needed. At the same time, with the shortage of gold resources and the improvement of the level of metallurgical technology, these old tailings resources have been recycled. value.
Henan Jinyuan Gold Mining Co., Ltd. uses a re-election process to treat flotation tailings. Among them, the chute monthly production of gold concentrate 450t, grade 3.5g / t; shaker monthly production of gold concentrate 60t, grade 16g / t or more. After fine grinding, the gold concentrate is recovered by flotation, and the gold is recovered more than 2.5kg per month, with an annual profit of 1.53 million yuan. In November 2004, the company purchased four new spiral chutes and shaker equipment. In 2005, the company produced 1215.55t of shaker concentrate, grade 19.74g/t; 3551.1t of slippery concentrate, grade 2.18g/t, and accumulated profit of 2 million yuan. At present, the grade of tailings has dropped to 0.17g/t, and the total gold recovery rate has reached over 93%.
The Wuluo gold mine in Heilongjiang originally produced nearly 30,000 tons of cyanide tailings every year. For micro-fine gold tailings wrapped pyrite characteristics, the enrichment desliming cyclone, pressure filtration filter, dry ore roasting acid, cinder regrinding process for processing of iridium, cinder The gold leaching rate is about 65%, the annual recovery of gold is 91.8kg, the production of sulfuric acid is 18,000 tons, and the annual new profit is 7.466 million yuan, which brings considerable economic benefits to the enterprise.
Xinjiang a Gold Process flotation tailings, with sodium carbonate as a pH adjusting agent, sulfuric acid as the activator of copper, gold flotation rate of 69%, the processing l million t of gold tailings recycled 3kg, significant economic benefits.
The ore type of Wulong Gold Mine in Liaoning is mainly composed of secondary sulfide minerals. The size of gold inlay is fine. The beneficiation process used at that time is flotation process. Due to the limitation of process flow and ore dressing conditions, the grade of tailings is high, and the gold grade is about O.9g/t. In the past 50 years of production, the tailings stockpiles have been about 1.2 million tons. The mine has established a carbon pulp plant with a treatment capacity of 800t/d. The tailings are directly cyanidated and gold extracted. The leaching rate of gold is over 70%, and the annual economic benefit is more than 2 million yuan.
The Hunan Xiangxi Gold Mine has successfully recovered the valuable elements in the old tailings. Under the conditions of tailings grades Au2.18g/t and Sb0.71%, the recovery rates of the metallurgical preparations Au67.22% and Sbl4 were obtained respectively. The % indicator has an annual profit tax of 2.528 million yuan.
The secondary utilization of tailings resources plays a decisive role in alleviating resource tensions and extending the service life of mines for resource-poor gold mines.
Third, associated mineral recovery
Most of China's gold mineral resources are common (concomitant) ores. Many gold mine tailings contain a variety of associated elemental components for comprehensive recovery, especially in the initial stage of the mine. A large number of associated valuable components are associated with the tailings. Loss. Because some associated minerals will also be enriched to some extent during the flotation process, tailings generally have a higher grade. According to the survey, some plants using flotation-gold concentrate cyanidation process, the content of valuable elements in the leaching residue is generally higher than the minimum industrial grade, and some even more than twice the minimum industrial grade. For example, gold ore is often associated with copper, zinc , lead , iron, sulfur, etc. There are a considerable number of tailings with lead grades >1%, sulfur grades >8%, copper grades >0.2%, and iron grades >10%. Therefore, it has a certain value of recycling.
(1) Copper recycling
The copper cyanide tailings of Laojiaoshan Gold Mine in Heilongjiang Province is 0.305% copper, 2.08% arsenic and particle size-O.074mm, accounting for 95%. Adopting the more advanced flotation process directly from the cyanide tailings slurry to suppress arsenic floating copper, obtaining copper concentrates with 18.32% copper, 9.69g/t gold, 99.2g/t silver , 33.6% sulfur and 0.07% arsenic. The copper recovery rate is 89%.
(2) Lead recycling
The cyanide residue, lead and arsenic content produced during the beneficiation process of the Sanshandao gold deposit in Shandong Province is relatively high. In order to recover the metal and improve the quality of by-product sulfur concentrate, the mine invested 3 million yuan to build a lead-selecting plant. The grade of lead concentrate recovered is 55%, the recovery rate is over 80%, and it can process 30,000 per year. Residual t cyanide residue. This not only solves the problem of long-term storage of cyanide slag and pollutes the environment, but also increases economic benefits.
(3) Iron recovery
According to the characteristics of tailings, Henan Ankang Gold Mine uses a magnetic separation and re-election process to re-select tailings. First two-stage dry magnetic separation process is selected from magnetite, hematite, garnet and a titanium ore and tailings from carved, shaker and then sorting the gold tailings. Each year, 1700 tons of iron concentrate can be recovered from the tailings, and the recovered gold is 2.187kg. The annual output value is 441,200 yuan.
The Hengkou Gold Mine in southern Shaanxi uses a single φ600mm×600mm permanent magnet single-roller dry sorter to sort iron concentrate from tailings with a yield of 31.2% and an iron concentrate grade of 65% to 68%. Mine 1100t, with the help of a shaker, the gold can be 1.53kg, creating a production value of nearly 300,000 yuan. According to the nature of tailings, Shaanxi Hanyin Gold Mine uses a wet magnetic separator to sort iron concentrate from tailings. After the iron ore concentrate is sorted, the ilmenite and garnet are separated by a roasting-magnetic separation process. According to preliminary estimates, the annual output of ilmenite 360t, garnet 468t, and 216t of magnetite not selected during the iron selection, the fine gold chips 1.218kg, the total output value can reach 1.7 million yuan.
Shandong Longtouwang Gold Mine has recovered iron from tailings since 1990, and annually recovers 1076 tons of iron concentrate with a grade of 60%.
(4) Sulfur recovery
The type of ore in the Qibaoshan gold deposit in Shandong Province is gold, copper and sulfur symbiotic ore. The metal sulfide is mainly pyrite, and there are a small amount of chalcopyrite and porphyrite. Since 1995, the sulfur concentrate has been recovered from the gold tailings. The sulfur recovery method was used to recover sulfur. However, due to the high cost, the cyclone pretreatment process was adopted in the second half of 1996, which reduced the cost of sulfur selection. 45%, achieved very good results. The obtained grade of sulfur concentrate is 37.6%, the recovery rate is 82.46%, and the concentrate contains less mud, which is easy to precipitate and dehydrate, and the annual benefit can be increased by about 1.2 million yuan.
The Wushan Copper Mine in Jiangxi Province re-selected and recovered sulfur from the tailings, and the grade of sulfur concentrate obtained was 36.83%, the recovery rate was 89.42%, and the annual processing of tailings reached 3.5 million tons. The annual profit reached 2.83 million yuan.
(5) Comprehensive recovery
Shandong Sanshandao Gold Mine recovers 28,300 tons of sulfur concentrate and more than 2,100 tons of lead per year from tailings. The Henan Ankang Gold Mine adopts a three-stage dry magnetic separation-shaker selection process. Each year, the iron concentrate is sorted from the tailings by l700t, and the recovered gold is 2.187kg. The annual output value is 441,200 yuan. The magnetic separation in the Hengkou gold mine in southern Shaanxi can be used to sort out iron ore concentrates with a grade of 65% to 68% from the tailings, and use a shaker to recover 1.53kg of gold, with an annual output value of 300,000 yuan.
Henan Lingbao Gold Co., Ltd. continuously researches the production process according to the ore characteristics of Xiaoqinling Gold Mine, and realizes comprehensive recovery of various elements such as silver, copper, sulfur and lead. At present, the daily gold concentrate has increased from 700t to 900t, forming a production capacity of 10t smelting gold, 30t silver, nearly 10,000 tons of electrolytic copper and 160,000 tons of industrial sulfuric acid. By-products such as electrolytic copper, sulfuric acid, and silver account for nearly 30% of sales revenue. The produced electrolytic copper is the main raw material of a local copper foil factory. Industrial sulfuric acid provides raw material guarantee for chemical enterprises in the local and surrounding areas.
Since 1999, Shandong Jinhua Group Daye Gold Mine has studied the comprehensive recovery technology of tailings, and has invested 2.25 million yuan in research funding to complete the research on tailings recovery technology, technology and application. Sericite mine tailings recycling plant, the annual handling tailings 320,000 t, sericite an annual output of 66 000 t, sulfur concentrate 2570t, gold 125kg.
Shandong Penglai Gold Smelter has an annual output of 30,000 tons of cyanide tailings. According to estimates, the annual output of the plant's tailings contains about 0.13t of gold, 2.1t of silver and a large amount of iron. In order to utilize these resources, Penglai Gold Group Co., Ltd. invested 102 million yuan to establish Penglai Jinye Nano Material Co., Ltd., implemented gold smelting cyanide tailings in addition to cyanide gold and comprehensive utilization projects, effectively preventing cyanide and mercury , Environmental pollution caused by heavy metal ions such as lead. At present, the first phase of the project has been completed and put into operation. It can recover 0.12t of gold, 1.89t of silver, 15,000 tons of nanometer iron oxide red, and 30,000 tons of industrial ammonium sulfate.
Fourth, tailings utilization
It is a well-established fact that solid waste is often referred to as “the raw material placed in the wrong placeâ€. From the perspective of the law of material immortality and human development and utilization, all solid waste can be reused to participate in the next material cycle. From this point of view, the tailings themselves have obvious resource characteristics.
The use of tailings is the most effective way to achieve small tail or no tailing process in mines. It is the most promising development direction for mines to realize tailings resource and harmlessness. It can not only make full use of mineral resources, but also solve the problem of ecological environment pollution. It can also produce considerable economic benefits.
(1) Tailings filling
When mining resources are opened, a large number of goafs are formed underground. The existence of goaf causes the stress of the rock mass to be redistributed, causing stress concentration around the goaf, which will cause deformation, damage and movement of the roof, surrounding rock and pillar of the goaf, and even the roof caving and surface. Collapse. Geological disasters and safety accidents such as ground collapse, landslides, and subsidence induced by mining have become common and are a major hidden danger in safe production. When filling mining method, the goaf is filled with the mining of ore, which is the technical support to protect the surrounding rock from collapsing and realize the coordinated development of mining safety production and environment.
The mine using the filling method needs to backfill 0.25-0.4 m 3 or more of filler for every 1 t of ore mined. Tailings is a kind of better filling material, which can be used for local materials and waste utilization, which saves the cost of collecting, crushing, transporting and other production waste rock, and is conducive to protecting the ecological environment. Under normal circumstances, the use of tailings as a filling, the filling cost is only 1/4 to 1/10 of the cost of crushing stone.
China's current tailings filling technology is a way to fill the underground goaf with graded tailings as filling material, but there are widespread equipment investment, high raw material cost, slow dehydration speed, slow cement condensation, low early strength, and Defects such as low top rate. At present, the more advanced filling technology is produced by co-grinding early-strength fast-hardening cement clinker or plain silicon clinker with active mixed materials or inactive mixed materials, quick-setting admixtures, expansion materials, plasticizing materials and water-retaining materials. Low-grade cement. Although the performance of this type of cement material has been improved, there are also disadvantages such as large amount of clinker, low strength, and high production cost, and it is impossible to produce low-cost 32.5 MPa cement. When the full tailings are filled, the amount of cement gel material often exceeds 15% or even 25%, which makes it difficult to reduce the filling cost.
The full tailings active filling technology mainly uses a small amount of cement and a high-concentration non-grading full-grain tailings as a filling method to fill the underground goaf. Its core technology is to greatly reduce the cost of cement production and adjust the filling technology requirements. The cement with a capacity of 32.5 MPa per ton can be reduced by 30-100 yuan compared with the same grade of cement in the market. The flexural strength of 3d, 7d and 28d exceeds the national ordinary silicate. 32.5MPa cement standard, and improved filling performance, reducing equipment investment.
After the flotation of the Sanshandao Gold Mine in Shandong Province is classified by a cyclone, the fine-grained grade enters the tailings pond, and the coarse-grained grade is filled into the sand silo for underground filling. The tailings can be used for about 250,000 tons per year. The Jiaojia Gold Mine in Shandong uses tailings as a filling area for filling in the underground. The tailings are used for 3 million tons per year, and the tailings utilization rate is over 50%.
(2) Production of building materials
At present, the use of tailings brick making technology is becoming more and more mature, and there are many varieties, such as making ceramic tiles, burning bricks, non-burning bricks, wall tiles, paving bricks, hollow bricks, aerated concrete blocks, and the like. The production of sintered brick tailings is large, and the production efficiency is high. It can be used for wall materials. Generally, it is extruded, dried, and sintered at about 1000 °C. The compressive strength is >15MPa, and the pass rate is 87%-95%. 240mm × 115mm × 53mm burnt brick, the production cost is only O.10 ~ 0.15 yuan / block, and the use of tailings 70% ~ 80%. It is necessary to add 6% to 12% of cement, 10% to 15% of modified tailings, and 30% to 85% of original tailings for making burn-free bricks. Generally, it is pressed and formed. After 28 days of natural curing, the specification is 240mm×115mm. The strength of the non-burned brick of ×53mm is 14.2MPa, and the strength of the porous brick of the specification of 240mm×115mm×90mm is 5.7～13MPa.
The Shuangqishan Gold Mine in Fujian Province has an annual output of nearly 80,000 tons of tailings, which not only occupies forest resources, but also brings great harm to the surrounding ecological environment. The mine's scientific and technical personnel conducted extensive experimental research on the use of mine tailings, and developed and produced ceramic glaze materials ranging from brown to black. According to the relevant experts' evaluation, the project is a preferred project in the current environmental protection field. It has made new breakthroughs in the process of manufacturing dark series ceramic color glaze. It has obtained national patents and is suitable for high-end furnishings art porcelain and daily-use porcelain. The project uses the effective mineral components selected from the gold tailings as the main raw material, and adds appropriate amount of color-developing minerals for preparation, and based on this, produces tailings ceramic products. According to the introduction of professionals, compared with the existing production technology of color glaze ceramics, the use of this technology does not require the addition of a large amount of frit and chemical raw materials in the production process, and the utilization rate of tailings is 60%.
The “Comprehensive Utilization of Porcelain Clay Tailings and Gold Tailings Preparation of Aerated Concrete Blocks†project jointly completed by Fujian Normal University, Fujian Province Modified Plastics Technology Development Base and Fujian Wanqi Non-Metallic Materials Co., Ltd. successfully passed the Fujian Identification of the organization of the Provincial Construction Department. The project comprehensively utilizes the three leading products of Wanqi Company to burn the industrial waste residue such as gold tailings, porcelain tailings (waste residue) and low-grade limestone produced in the production process and light-weight concrete blocks, thus establishing the mine. The circular economy park has a strong novelty. The total planned scale of the project is 500,000 m 3 of aerated concrete blocks per year. The project is planned to be carried out in three phases. The first production line with an annual output of 100,000 m 3 aerated concrete block was put into operation in early 2007, with a total investment of 11.827 million yuan, of which construction investment was 9,883,700 yuan. Calculated at the price of 200 yuan / m 3 , the annual output value can reach 20 million yuan, the annual total profit of 3,295,500 yuan, the tax paid 1,075,600 yuan, net profit of 2,183,900 yuan, has a good economic prospects. At the same time, as an industrial chain project of “resources, products, wastes and renewable resourcesâ€, the production of aerated concrete can save energy, protect the environment and cultivate land, and reduce pollution. It is a demonstration project for the development of circular economy. It will promote the steady and rapid development of the economy of the same industry and the construction of regional cities and counties, and it has very good social benefits.
Shandong Jiaojia Gold Mine invested 2 million yuan in 1996, introduced foreign “double-free†brick production technology, built 4 production lines, and can use 60,000 tons of tailings per year. Shandong Penglai Jinzheng Building Materials, Jiaojia Gold Mine, etc. took the lead in the use of tailings to produce wall panels, concrete blocks, concrete standard bricks and other energy-saving and environmentally-friendly building materials, filling the gap in Shandong Province, using more than 300,000 tons of tailings per year, saving 20% ​​of land. Million m 2 . Shandong Institute of Building Materials used the Jiaojia gold mine tailings and a small amount of local cheap clay to develop ceramic tiles and floor tiles in line with national standards. At present, the mine is jointly carrying out technical research with universities and colleges to prepare for the extraction of silica and alumina from tailings. If industrial production is realized, the economic benefits will be very optimistic, and the tailings produced by the mine can be effectively utilized.
The Tailiuhang Gold Mine tailings reservoir in Penglai City, Shandong Province has an inventory of about 2 million tons of tailings and produces more than 200,000 tons of tailings per year. In addition, companies around the Daliuhang Gold Mine also have a large amount of tailings resources. In order to solve the problems of tailings heap storage and pollution, Daliuhang Gold Mine and Penglai Zhengye Development Co., Ltd. jointly established Penglai Zhengye Building Materials Co., Ltd., using gold tailings to produce hollow bricks, colored tiles and other environmentally friendly greens. Building materials products have realized the comprehensive utilization of tailings resources. The total investment of the project is 12 million yuan. The design capacity is 100,000 tons of tailings. The annual output value is expected to reach 50 million yuan and the annual profit will reach 10 million yuan. The implementation of the project can significantly improve the ecological environment of the Daliuhang mining area and its surrounding areas, reduce environmental pollution and energy consumption, and save a lot of land. The economic, social and ecological benefits are considerable.
Dandong City Building Materials Research Institute uses gold tail slag to add plastic material with good plasticity and color. After sintering, it is a new type of building decoration material-waste slag facing brick with a density of 2.19g/cm 3 and a water absorption rate of 6.07%. The flexural strength is 26.85 MPa, and the frost resistance, rapid cooling resistance, and aging resistance all meet the prescribed standards.
Shandong Longtouwang Gold Mine divides the tailings into three parts. The large slag is used as paving material, the fine mud is sold as a by-product, and the other tailings are used as brick materials. In 1991, a brick factory with an annual output of 17 million bricks was built.
In addition, tailings can be used to make concrete products. The modified tailings can be used to make concrete products, which can replace 30% to 60% of cement gel materials, and replace 30% to 50% of fine aggregates. The produced concrete products have stable performance, good quality and low cost. And other advantages, suitable for the production of prefabricated components such as roadside stone, retaining stone, culvert, road board, cement board, cement pipe.
V. Development of tailings utilization
(1) Production of dry powder mortar
Dry mortar is a granular or powdery mixture of fine aggregates and inorganic binders, water-retaining thickening materials, mineral admixtures and additives in a certain ratio. In layman's terms, mainly sand, cement, water retention thickeners, additives and pulverized coal ash composition. Among them, the yellow sand should screen a certain particle size and dry the water. The cement can be made of ordinary Portland cement. The water-retaining thickening material accounts for 2% to 3% of the total amount, and the mixed fly ash can account for about 10% of the total. . In addition, additives such as early strength agents and quick-drying agents can be added according to the requirements of the variety.
Dry mortar has become the fastest growing new product in the world's building materials industry. It has been widely used in some developed countries in Europe and America, and has basically replaced traditional technology. At present, there are large-scale dry mortar production plants in Korea, Japan, Singapore and other countries, and the types of dry mortar on the market are also very rich. The application of domestic dry mortar is in its infancy, and the Ministry of Construction has recognized the prospects and value of dry mortar in the future Chinese market, and listed it as one of the key development and encouragement projects.
The whole tailings dry mortar is a granular or powdery mixture of tailings (fine aggregate) and cementitious materials, water-retaining thickening materials and additives in a certain proportion. It mainly consists of tailings, cement and admixtures. Among them, dry tailings account for 60% to 85%, cement accounts for 5% to 20%, and water retention thickeners account for 2% to 3%. Admixtures such as early strength agents and quick-drying agents can be added according to the requirements of the variety.
(2) Production of Portland cement
Tailings as a batching agent for the production of Portland cement technology is becoming more and more mature. It can be directly applied to the production of rotary kiln, shaft kiln cement and cement mill station without changing the traditional production process, especially suitable for vertical kiln cement clinker. Production. According to the nature of tailings and cement production process, the tailings can be used in an amount of 20% to 50%. The physical indexes of cement products fully meet and exceed the standard requirements of 32.5MPa Portland cement, and they are easy to grind. Improve stability, shorten safety, improve early strength, maintain late strength, and improve setting time. Taking an annual output of 100,000 tons of cement production enterprises as an example, 20% to 50% of tailings are used in cement ingredients, and the annual net profit can be increased by 100 to 1.5 million yuan, which not only has significant economic benefits, but also brings mining and cement enterprises. Significant social and environmental benefits.
Conclusion
Today, with the depletion of mineral resources, the increasing use of geological resources and the increasing environmental awareness, the development and utilization of secondary resources is particularly important. The recovery and utilization of tailings resources has become an inevitable choice for the sustainable development of gold mines. Relying on scientific and technological progress, starting from the characteristics of mines and tailings, recycling and utilization of tailings resources on the principle of resource, harmless and circular economy, it will play an important role in alleviating the shortage of gold resources and extending the service life of gold mines. effect. Gold mining enterprises fully exploit and use tailings to maximize the realization of gold tailings resources, which will achieve the goal of harmony between human beings, environment and resources, and achieve sustainable development of environmental, economic and social benefits.
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