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With the increasing attention of environmental pollution and tailing treatment, tailing processing has become one of the important links in current mineral processing production.
The tailings are one of the products of separation operation in mineral processing. Due to the low content of its useful components, the tailings cannot be further separated under the current mineral processing technology and economic conditions. After the ore is ground into the very fine pulp, the ore powder less than 0.075mm generally accounts for 50%-70%, and some of them are even finer, the pulp concentration is generally around 15%-40%. If it is discharged into a tailings pond, there will be a large amount of water in addition to the ore, basically equivalent to a reservoir. The accumulation of tailings can not only cause environmental pollution, but also easily lead to tailings dam break, bringing hidden safety risks. Therefore, how to discharge and stockpile the tailings has become an important problem.
Use the table of contents below to navigate through the guide:
In terms of tailings discharge methods, there are two main tailings processing methods: tailings wet discharging and tailings dry stacking.
Tailings wet discharging is a kind of traditional tailings wet stacking method. The tailings slurry directly through the pipe into the tailings without any treatment. Through the plain sedimentation, the upper water of the tailings pond is recycled. And the tailings pond is closed when the tailings pond meets the requirements of the load elevation, then the soil and water conservation, vegetation restoration and land reclamation can be carried out above the tailings pond. The traditional tailings wet discharging and storage exist the hidden danger, the dam construction, use, maintenance, management need a lot of manpower, material resources and financial resources. Any slight negligence will lead to a major safety accident and property loss. Therefore, the initial investment in the tailings pond is very higher.
The tailings dry stacking is a new tailings processing method in recent years. After the multistage concentrating, the tailings pulp is sent to a series of high-efficient dewatering equipment, and slag with low water content, easy to curing and stored is formed. The slag can be used as the building materials, or transferred to the fixed location for dry storage. The tailings dry stacking technology can relieve the capacity pressure of tailings pond storage, reduce the safety hidden danger of tailings pond and increase the means of tailings reprocessing, which is a kind of tailings processing technology to realize the green mine.
In general, the tailings dry stacking technology is mainly composed of slurry pump, hydrocyclone, efficient improved thickener, high-frequency dewatering screen, chamber filter press and slurry conveying device.
The tailings are transported to the hydrocyclone for concentration and classification by the slurry pump, the sand setting of the hydrocyclone enters into the high-frequency dewatering screen for dehydration, and the overflow enters into the efficient improved thickener for concentration. The coarse tailings treated by the high-frequency dewatering screen are transported to the material yard for stockpiling by the belt conveyor. Among them, the tailings after concentrated by the efficient improved thickener are transported to the filter press by slurry pump for filtration, and the filter cake of the filter press is self-discharged to the belt conveyor, and the fine tailings are transported to the material yard for storage.
The hydrocyclone is mainly composed of cylinder, cone, overflow port, bottom flow port and feed port. The hydrocyclone is used for the tailing's concentration, dehydration and separation, which is featured with simple structure, high efficiency and low investment. In the tailings dry stacking, the hydrocyclone used in the classification of tailings pulp can effectively improve the sand settling rate, improve the classifying efficiency and ensure the sand settling concentration.
The structure of high-frequency dewatering screen includes the vibration motor, screen, dewatering screen frame, support and rubber spring. The high-frequency dewatering screen is new and highly efficient dewatering equipment with a simple structure, easier maintenance and simple operation. It can not only meet the dewatering and classification requirements of fine minerals, but also be widely used in the dewatering operation of fine tailings because of its large handling capacity and good dewatering effect. In the tailings dry stacking, the high-frequency dewatering screen adopts the unique sieve plate and the motor with high-frequency vibration, which not only makes the pulp particles not easy to pass through the sieve hole, but also obtain the higher dehydration efficiency. Finally, the water content of dry pile tailings are less than 15%.
The efficient improved thickener is mainly composed of a circular concentrator and rake mud scraper. It is suitable for fine and ultra-fine materials, and its processing capacity is much higher than that of conventional thickener. In the tailings dry stacking, adopting the flocculant concentration technology can greatly increase the settling velocity and solid flux of the fine tailings, finally, obtain a higher underflow concentration.
The chamber filter press is mainly composed of five parts: the rack, automatic drawing board, the filtration, the hydraulic pressure and the electrical control. The chamber filter press is widely used in tailings dry stacking by relying on its positive pressure, high pressure, strong dehydration, the low water content of filter cake and low energy consumption. The filtrate of tailings treated with the chamber filter press is clear and transparent, which can meet the requirements of direct discharging of environmental wastewater, and the moisture content of dry slag after filtration can reach below 8%, which greatly reduces the transportation cost of tailings and the risk of the dry heap of tailings.
In the tailings dry stacking, the slurry pump is an essential conveying equipment of tailings slurry, which is used to transport the slurry to hydrocyclone and chamber filter press. The liner of the slurry pump adopts wear-resisting rubber, which not only enhances its wear-resisting performance, but also ensures that cyclone and filter press are in a good working state and prolong the service life of the slurry pump.
The tailings dry stacking can not only save the construction cost and routine maintenance cost of the traditional tailings pond, but also make full use of the backwater, greatly save the occupied area and the reclamation treatment cost after the tailings pond is closed.
The tailings dry stacking avoids the risks of a dam break, overflow and collapse in tailings ponds, eliminates the hidden safety hazards, save the safety input and reduces environmental pollution.
In general, the production cost of tailings dry stacking is higher 3% - 10% than the tailing's wet discharging, but tailings dry stacking saves more than 30％ in the early stage of the tailings storage facility on the construction costs. In addition, during the comprehensive recovery and utilization of tailings in the later stage, the dry heap tailings are easier to be mined and utilized than the tailings slurry in the tailings pond, which is in line with the current national policies on tailings discharge.
With the release of the national "green mine" standard, the tailings dry stacking has shown great advantages in economy, environment and safety, which has become an important choice for tailings processing in the future. In the practice, it is suggested to choose the suitable tailings dry stacking technology according to the tailings scale, investment, and customize the equipment used in the tailings dry stacking.