Ceiling Fan With Light,Dc Ceiling Fan,Decorative Ceiling Fan 3 Balde,Durable Ceiling Fan Lamp Guangdong Shunde Liangci Electric CO.,LTD , https://www.marckeez.com
The impact on tailings discharge planning is not only the natural nature of the tailings and the engineering properties of the site, but also the choice of appropriate emission methods. Surface emissions are currently the most commonly used emission method and still play an important role in tailings management. However, due to the development of economic conditions, technical conditions and management conditions, more practical and innovative emission methods will be produced.
First, the surface emissions
According to the general concept, the surface discharge of tailings is a tailings reservoir that uses some type of dam to form a block, accommodate tailings and ore dressing wastewater, so that the tailings are precipitated from the suspended state to form a stable sedimentary layer, so that the wastewater is clarified and returned to the plant. use. Due to the concentration of tailings discharge and the corresponding dam type, surface discharge methods may include dams, ascending dams, ring dams and dry disposal.
(I) dams The dams used for tailings discharge are dams constructed at full height one time before they are discharged to the tailings pond. Dam materials usually use a variety of natural soils. The retaining dam includes an impervious core wall, a drainage belt, a percolation layer and an upstream rockfill. The percolation layer, internal seepage control and slope design can be carried out according to the common earth dam technology. However, since the upstream slope of the tailings dam does not experience a steep water level drop, it can be steeper than the upstream slope of the ordinary storage dam.
The retaining dam is suitable for tailings reservoirs with high water storage requirements, such as a tailings reservoir with a large amount of storm runoff, or where the tailings wastewater is recycled due to the constraints of the beneficiation process, or a large storage volume for tailings precipitation. In the case of evaporation area, or in the case of controlling the tailwater wastewater to contaminate the local water system.
The retaining dam can be divided into valley dams and ring dams due to the different construction sites. The valley dam is built at the beginning of the valley discharge area and spans the valley to build a dam. Usually, the dam is provided with an impervious core wall, and the bottom of the reservoir is impervious. The structure of the annular dam is similar to that of the valley dam. The outer dam is provided with an impervious core wall, and the bottom of the reservoir is impervious to the water cushion. The annular dam is built in a flat section, so it is not as tightly constrained as the valley dam in the terrain. It is more flexible and suitable for site selection close to the stope and plant selection, so as to make use of waste rock to build dams and reduce tailings transportation costs. However, due to the length of the dam, a large amount of dam material is needed, and the possibility of wind erosion and the risk of dam damage are also increased.
From the engineering point of view, the retaining dam is suitable for any type and graded tailings. It is suitable for any discharge method, and has good seismic performance. The dam body is built once, without the limitation of increasing speed, and the anti-seepage performance is high. The cost of damming is high.
(2) Ascending dam surface The most common use of tailings ponds is the ascending dam, which, unlike the retaining dam, is a dam constructed in phases during the entire service period of the tailings pond. First, the initial dam is constructed. The initial design of the dam and dam is generally considered to be the tail mine output of the first 2 to 3 years of the tailings pond and the appropriate flood flow. Subsequently, according to the predetermined tailings rise, the allowable flood accumulation in the reservoir is increased in steps. The ascending dam uses a wide range of building materials, including natural soil, open-pit and underground mining waste rock, hydraulic sedimentation or swirling tailings.
The advantages of the ascending dam are obvious: 1 Due to the allocation of construction costs during the entire service period of the tailings pond, the initial project cost is low, which is only the necessary cost for the initial dam construction. In a long time interval spending will total discounted costs and achieve greater cash flow benefit. 2 Since it is not necessary to prepare the dam material at the initial stage of dam construction, there is great flexibility in the choice of dam material. If the dam rises in sync with its productivity during the mining process, the mining waste rock or tailings can provide the ideal dam material. In some occasions where suitable natural soil cannot be obtained, it may be necessary to use the waste rock to build a dam, not to mention that even if suitable natural soil is available, the waste rock should be disposed of, except in the case where the transportation distance is not too long, except In addition to a certain amount of compaction fees, the materials are provided "free of charge".
The ascending dam can be divided into three types: upstream dam, downstream dam and central line dam according to the moving direction of the dam crest line relative to the initial dam position during the ascent of the dam. China and South Africa mainly use upstream dams.
(3) The design of the ring dam tailings dam is different from that of ordinary dams. The core lies in the difference in storage medium and function. For tailings dams only, it focuses on distinguishing tailings reservoir function and determining dam type in tailings slurry concentration, state and discharge pattern. Includes high concentration central discharge and semi-dry spray discharge.
(4) Dry disposal The tailings are dried in solid form. Before the tailings are settled, the water is discharged from the belt filter to form dry tailings, thereby reducing leakage of tailings wastewater.
Belt filtration has been widely used in France and South Africa and has since become part of the uranium ore dressing process in Europe. The belt filter works in a simple manner. As the tailings moves on the filter braid of the synthetic rubber support, a vacuum device is used to extract the liquid from the tailings, thereby reducing the water content of the tailings from about 50% to 20% to 30%. Processed into a "dry cake" like stacking.
There is great controversy about the economic effects and feasibility of tailings belt filtration. Factors such as grinding process and gypsum content all affect the filtration effect, and high clay content ore cannot be used at all. The capital and operating costs of belt filtration are high and only reasonable as part of the beneficiation operation, rather than an additional dewatering process.
Since the tailings are disposed of in a substantially solid form, land recovery can be carried out simultaneously with tailings disposal, which has great advantages. However, the 20 % to 30 % water content of the solid tailings can nearly saturate the tailings under the in-situ porosity. Compared with the tailings reservoir discharged from the common slurry, the reduction of the leakage is largely determined by the base material. Permeability, in the absence of a cushion or low permeability base material, the leakage of saturated tailings will still be large.
Second, underground emissions
Although the surface tailings pond is the most widely used tailings discharge method, underground mining has long used tailings sand to fill the empty area to support the rock formation, which also plays a second role objectively, namely reducing the surface treatment capacity of the tailings. . In recent years, due to the increase in the cost of surface emissions and the pressure on environmental management regulations, underground emissions have been increasingly recognized as regular emission options. Especially in the case where the discharged tailings are inert and not potentially dangerous, underground discharge has outstanding advantages. As a result, underground emissions are solely for the purpose of disposal of tailings, including underground mine filling, open pit discharge and special pit discharge.
Third, deep water discharge
Most of the world's tailings are deposited on land, and the tailings pond is abandoned before land restoration. However, people always pay attention to the long-term effects of tailings reservoir pollutants seepage into the environment, groundwater and water sources. Another method is to pump the tailings to the deep lake or offshore, but it has not been widely used due to controversy over environmental and ecological issues. The main feature of deep lake and offshore discharge is that the water level above the tailings forms an ideal oxygen barrier, which inhibits the formation of acid reactions of sulfides; reduces the appearance of bacteria, helps prevent oxidation; saves the cost of expensive tailings construction If such emissions are allowed in the environment, deep lakes or offshore emissions will occupy less land, which has the advantage of beautifying the environment.
Tailings discharge method
The tailings discharge methods mainly include surface discharge, underground discharge and deep water discharge. In addition, at present, some mining areas actively use tailings to make harm to profit, and use tailings as bulk fillers or raw materials, which is actually the most active tailings treatment.