beneficiationThe part of the product of intermediate separation operation that has low content of useful target components and cannot be used for production is called tailings.Tailings are a treasure to be tapped.Experts believe that the current task of China's mining circular economy is to develop and utilize a large number of tailings that have been shelved for a long time.
One of the products of separation operation in mineral processing, the part with the lowest content of useful target component is called tailings.Under the current technical and economic conditions, it is no longer suitable for further separation.However, with the development of production science and technology, useful target components may have further economic value for recycling.Tailings are not completely useless wastes, and often contain components that can be used for other purposes, which can be comprehensively utilized.The realization of waste free discharge is the need for the full utilization of mineral resources and the protection of the ecological environment.
Different types and structures of ores require different beneficiation processes. Tailings produced by different beneficiation processes often have certain differences in process properties, especially in particle shape and particle grading. According to the beneficiation process, tailings can be divided into the following types: manual tailings, gravity tailings, magnetic tailings, flotation tailingsTailings from chemical beneficiation, electric separation and photoelectric separation.It can also be classified according to the combination and collocation of the main constituent minerals in the tailings.
2. Problems caused by tailings
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With the economic development, the demand for mineral products has increased significantly, and the mining development scale has increased accordingly, and the number of beneficiation tailings will continue to increase;In addition, the grade of many available metal ores is decreasing day by day. In order to meet the growing demand for mineral products, the scale of beneficiation is becoming larger and larger, so the number of beneficiation tailings produced will also increase significantly, and a large number of stockpiled tailings will cause many problems for mining, environment and economy.
(1) The cost of mineral resources is serious.Because the tailings not only contain useful components such as metallic ore and non-metallic ore that can be re selected, but also the final tailings that cannot be re selected have many uses, the amount of useful components wasted in the tailings is considerable.
(2) The stockpiling of tailings occupies a large amount of land, and the stockpiling investment is huge.The treatment of tailings at home and abroad, regardless of whether the useful minerals in the tailings have recovery value, is mostly stockpiled on the ground.The stockpiling of tailings not only occupies a large amount of cultivated land, but also easily causes environmental pollution, water and soil loss, vegetation damage, etc. in the mining area.
(3) Impact of tailings on natural ecological environment.The impact of tailings on the natural ecological environment is shown in the following aspects: ① tailings are easy to flow and collapse during stockpiling, causing vegetation damage and injury accidents, especially collapse and landslide in rainy season.The dam body of tailings pond is relatively high, and there are hidden dangers. ②The composition of tailings and residual beneficiation reagents have seriously damaged the ecological environment, especially the tailings containing heavy metals, in which sulfide produces acidic water to further leach heavy metals, and its loss will cause harm to the entire ecological environment.
3 Recovery of tailings
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(1) Value of tailings
For example, there are 61 tailings ponds in the tin polymetallic mine in Nandan, Guangxi. Among the total 25.22 million tons of tailings, there are a large number of non-ferrous metals, such as tin, antimony, lead, zinc, silver, gold, indium, cadmium, and non-metallic minerals, such as arsenic and sulfur. The grade is above the national industrial grade index, and some have reached the large or extra large scale. The preliminary scale estimates that there are 3 billion yuan of resources.With the new development of mineral processing technology, the recovery of these metals is no less than the establishment of a new mine.The tailings of Panzhihua Iron Mine in Sichuan Province contain more than ten beneficial components such as copper, nickel, titanium and vanadium, which is equivalent to a large nonferrous metal mine.Non metallic minerals, such as coal gangue and other surrounding rocks in coal mines, are also useful materials, which have been excavated to the ground and piled together.
(2) Tailings development and utilization measures
In order to further improve the development and utilization of tailings resources, the following measures are recommended:
First, formulate and implement relevant policies to support enterprises to carry out technological breakthroughs and technological transformation;At the same time, we will implement preferential policies such as reduction and exemption of resource taxes, and guide and encourage the society and enterprises to invest in the utilization of resources such as tailings.
Second, we should strengthen technological innovation in the comprehensive utilization of tailings, research and develop advanced technology, advanced equipment, and advanced processes, and accelerate the transformation of research results.
Third, make good use of the central financial funds, focus on supporting the utilization of resources in tailings and "waste residue" of large enterprises and large mining areas, and play a leading and exemplary role.
Fourth, strengthen the management of development access, formulate and improve the standards for the access and supervision of mining development enterprises, promote the restructuring of enterprises, and strengthen and expand mining enterprises.
The fifth is to strengthen the safety production management in the development and utilization of tailings to prevent safety production accidents.
(3) Development prospect of mine tailings recovery
China is in the stage of accelerated industrialization and urbanization, with large consumption of mineral resources and high dependence on foreign countries.However, the global price of mineral products continues to rise, increasing the production costs of mineral product demand enterprises, and at the same time increasing the pressure on resource security.
Under the situation of tight supply of global mineral resources, the developed countries found that the residue and tailings left after the processing and utilization of mineral resources contain business opportunities for secondary utilization.China is a big mining country, and the development and utilization of a large amount of tailings accumulated for a long time can not only "turn waste into treasure", but also effectively alleviate the pressure on resources and environment.
Tailings are the "waste" discharged by mining enterprises under certain technical and economic conditions, but they are also potential secondary resources. When technical and economic conditions permit, they can be effectively developed again.
After ore separation and comprehensive utilization, its main useful components are enriched into concentrate, while other residual substances are called tailings.The content of main useful components in tailings is called tailings grade.It is an important parameter for selecting economic and reasonable beneficiation scheme and evaluating ore washability.
(4) Tailings recovery equipment
① Tailings reclaimer
It is an energy saving and efficient beneficiation equipment used for recovering tailings in the magnetite process flow without loss of ore powder and making full use of effective resources.With the development of production technology in the society's mineral processing equipment industry, the slogan of "green, efficient and energy saving" is about to come out, and green, environmental protection and energy saving are imperative.Therefore, the function of tailings reclaimer is particularly important.High efficiency tailings reclaimer can not only effectively curb pollution behavior, but also greatly reduce production costs and improve production efficiency. It has the characteristics of low input and high output.
② Tailings sludge dehydrator
The best choice for tailings dewatering - belt sludge dehydrator, with large processing capacity, low energy consumption and labor saving, sludge dewatering of tailings becomes a necessary work for the next step of tailings work.
Tailings recovery equipment is the latest type of machinery used for tailings production and recovery in China's recent ore dressing (iron) industry.Its production mode: it is mainly to re clean and recycle the waste from mineral processing of mining equipment. The recovery rate has reached a new level. It is produced by single machine in a unique way, which (can also be used with mill, roller and other equipment) saves the national mineral resources to the maximum extent.The equipment has the characteristics of excellent materials, reasonable design structure, convenient operation and high economic return rate.
4 Tailings treatment
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Tailings treatment technology
The waste slag and slag discharged by mining enterprises after beneficiation are mostly discharged in the form of slurry, which accumulates over time to form tailings pond.How to deal with tailings?
At present, the treatment method of tailings is generally used as the filling material of underground mining goaf, that is, water sand filling material or cemented filling aggregate;Or some of them directly cover the tailings dump with soil for farmland, plant crops or plant trees for afforestation.In fact, the most economic treatment method of tailings is to make sand from tailings and use them as raw materials for building materials. For example, the treated tailings can be used as raw materials for cement, tile, aerated concrete, permeable brick, refractory, fire insulation material, glass, ceramsite, concrete aggregate, etc. Tailings sand can replace part of machine-made sand to make concrete, build roadsPavement materials, etc[1]。
The comprehensive utilization of tailings resources at home and abroad can be summarized as follows:
(1) First of all, comprehensive recovery and utilization of useful components of tailings resources should be done as far as possible. Advanced technology and reasonable process should be used to reselect tailings to maximize the recovery of useful components in tailings, which can further reduce the number of tailings.Some concentrators are developing towards tailing free.
(2) Tailings are used as filling materials for mined out areas of underground mining, that is, water sand filling materials or cemented filling aggregates.Tailings are used as filling materials in the mined out area. The most ideal filling process is the full tailings filling process, but it is still in the experimental research stage.In production, the coarse part of tailings is used as the filling material in the goaf.The tailings of the beneficiation (belt conveyor) plant are discharged and sent to the tailings preparation section for grading, and the coarse sand is sent to the underground goaf, while the fine particles are sent to the tailings pond for stockpiling.This tailings treatment method has been applied at home and abroad.
(3) Tailings are used as raw materials for building materials: cement, silicate tailings brick, tile, aerated concrete, cast stone, refractory, glass, ceramsite, concrete aggregate, glass ceramics, slag tiles, foam glass and foam materials.
(4) Tailings are used to build roads, pavement materials, anti-skid materials, coastal farmland, etc.
(5) The tailings dump shall be covered with soil for farmland, planted with crops or planted with trees for afforestation.
(6) The tailings are stacked in a specially built tailings pond, which is the most widely used tailings treatment method in most concentrators at present.
Water treatment technology of tailings pond
Water treatment technology: Tailings pond is a large volume sedimentation storage pond, which can be set up on valley, slope, beach or flat land by using the terrain and surrounded by dams.Drainage wells and pipes are set in the pond, or drainage ditches are set along the edge. Tailings water will overflow after clarification and purification in the pond.Suspended solids in tailings water are deposited at the bottom of the pond.Waste water shall stay in the pool for at least one day and night.This method can effectively remove suspended solids in wastewater, and the content of heavy metals and flotation reagents is also reduced.The longer the residence time, the better the treatment effect.The overflow water of tailings pond can be recycled.Gravity separation, magnetic separation and simple flotation of single metal ore do not require high water quality, and the water recycling utilization rate can reach 80%, or there is no drainage at all.When the tailings particles are extremely fine and some of them are colloidal, coagulants can be added to the tailings water to speed up the clarification process and improve the treatment effect.If lime is added to tailings water, 60~70% of xanthate and black powder can be removed.
If the supernatant of tailings pond fails to meet the discharge standard, it shall be further treated.
Common treatment methods include: ① lime neutralization method and calcined dolomite adsorption method can be used to remove heavy metals.0.81 mg of lime is required to remove 1 mg of copper, 0.88 mg of lime is required to remove 1 mg of nickel, and the pH is required to be controlled above 8.5.Copper and lead ions can be removed by adsorption of calcined dolomite with particle size less than 0.1 mm.25 mg dolomite is needed to remove 1 mg copper and 2.5 mg dolomite is needed to remove 1 mg lead. ②Ore adsorption method is used to remove flotation agent. Lead zinc ore adsorbable organic flotation agent is used, and 200 mg lead zinc ore is required to remove 1 mg organic flotation agent.Activated carbon adsorption is more effective, but it is expensive. ③Cyanide containing wastewater mainly adopts chemical oxidation method, such as bleaching powder oxidation method;Ferrous sulfate lime method and lead zinc ore method can also be used to remove cyanide. Adding 200g ore per gram of cyanide can remove about 90% of simple cyanide or about 70% of complex cyanide.Sodium cyanide can be recovered from high concentration cyanide containing wastewater[2]。
