New tailings harmless treatment process and practice

Lingbao Jinyuan Mining Co., Ltd. actively implements the development strategy of “gold-based, comprehensive development and utilization”. In June 2006, a new comprehensive technology for the comprehensive utilization of small Qinling quartz vein gold-molybdenum polymetallic ore resources was independently developed for the gold- molybdenum polymetallic ore resources in the Xiaoqinling North ore belt, and gold, silver , molybdenum, copper , lead and sulfur were comprehensively recovered. On the basis of the original 350t/d whole mud cyanide carbon pulp plant (referred to as carbon pulp plant), a multi-metal comprehensive recovery ore dressing plant with a scale of 1000t/d (referred to as a thousand tons of plant) was expanded. After the expansion, the tailings discharge is more than three times. Since there is no new tailings pond, the original tailings storage capacity is rapidly shrinking. The problem ahead is that the tailings are not safely stored. At the same time, the production water consumption has increased by 3 More than one, and after nearly 30 years of mining in the Xiaoqinling area, the amount of water in the mine dropped sharply. Although the water was multiplied, the water volume still had a large gap. Although the amount of tailings water is large, the tailing water reuse rate is less than 40%, and it is often forced to stop due to lack of water. Jinyuan Company conducted in-depth research on the safe storage of tailings and the reuse of tailings water, and independently developed a new harmless treatment process for tailings.

1. New tailings harmless treatment process

(1) Brief description of tailings properties

1. The properties of tailings in 1,000 tons of plant

The thousand-tonne plant is selected from low-grade quartz vein gold-molybdenum polymetallic ore. The process includes mixed flotation, cyanide gold extraction, flotation of molybdenum, lead and copper, and comprehensive recovery of gold, molybdenum, lead and copper. The tailings components are mainly quartz, calcium carbonate and other minerals, the tailings yield is 99%, the tailings specific gravity is 2.9t/m ³ , the tailings pulp concentration is 26% to 29%, and the ore type pH is 6-7, -200 mesh. The grade accounts for 60%-65%, but the -400 mesh fraction accounts for 38.68%, and the particle size composition is very uneven. The particle size composition of tailings is shown in Table 1.

Table 1 Results of sieve size analysis of tailings in 1,000 tons of plant

2, carbon slurry plant tailings properties

In order to improve the recovery rate of gold, the carbon pulp mill adopts the closed-stage fine grinding process of the ore section; its tailings particle size is -200 mesh, 90% to 93%, pulp concentration is 45%-48%, and tailings quantity is 350t/d. The tailings water contains 0.05% sodium cyanide.

(2) Tailings harmless treatment process

The new tailings harmless treatment process refers to the tailings after dewatering by concentration-filtration and second-stage dewatering, and the tailings dry slag and backwater are obtained. The tailings dry slag is directly stored in the tailings yard, and the return water is recycled. There is no need to build a tailings pond for the tailings yard. The process of harmless treatment of tailings is shown in Figure 1.

Figure 1 Process of harmless treatment of tailings

The 1,000 tons of tailings from the plant to the deep cone thickener for concentration and dehydration, the concentration of the slurry is increased from 26% to 29% to 62% to 65%, and then the concentrated bottom slurry is pumped to the ceramic filter to filter and dehydrate. The tailings dry residue contains less than 13% water. The tailings dry slag is transported to the tailings yard by belt conveyor. It is paved by loader, layer-by-layer rolling, tamping and covering the soil to restore vegetation or reclamation; thickener overflow water and ceramic filter filtrate water are collectively called Backwater, the return water is purified by the backwater treatment system and reused for the production cycle.

The tailings of the carbon slurry plant flows to the agitation tank. The agitation tank acts as a buffer and agitator. It is pumped directly to the ceramic filter for filtration. The filter residue and the 1,000 tons of tailings filter cake are transported to the tail with the same belt conveyor. At the mine yard, the filtrate water is reused in the carbon pulp plant.

Second, the characteristics of the process

(1) “Zero” emission tailings treatment process for water saving and bad protection

Tailings water usually contains various mineral processing chemicals, metal ions, and even highly toxic substances, which cannot be directly discharged. The process uses the adsorption method to re-purify the recycled water for repeated use, which not only saves water resources, but also avoids environmental pollution caused by waste water discharge. The backwater is purified by the adsorption method, which can recover the trace amount of gold in the water, improve the comprehensive utilization rate of the minerals, and remove the harmful substances such as oil and medicine in the water, and avoid the accumulation of oil and medicine in the water to affect the production technical indicators. For the simple mineral processing water of the pharmaceutical system, it can be directly reused without adsorption and purification, such as single metal beneficiation and full mud cyanidation. The reuse rate of backwater in the 1,000-tonne plant has reached 92.6%. It is ahead of the technical requirements of the Ministry of Environmental Protection, the Ministry of Land and Resources and the Ministry of Health on the technical requirements for mine ecological environmental protection and pollution prevention. The reuse rate should reach the target of 75%. Although the tailings dry slag contains 13% to 15% of water and traces of toxic and harmful substances, it has been completely enclosed in the yard to avoid extravasation and diffusion. After long-term open-air exposure and natural degradation, the environment is basically eliminated. Hazard. Therefore, the process is called the “zero” emission tailings treatment process for water saving and environmental protection.

(2) Safe and economic tailings treatment

The stability of the tailings yard depends mainly on the compaction of the tailings. The key to ensuring the degree of compaction is to control the moisture content of the tailings. The moisture content of the tailings slag of the process is less than 13% to 15%, and the direct dry storage can only build the tailings pile without the need to build a tailings pond. The water content of the filter tailings is generally between 18% and 25%. It needs to be naturally dried and dehydrated in the transfer yard before being transported to the permanent yard. It cannot be directly stored. The tailings dry slag of the process is directly paved with a loader, and at the same time, crushing and compacting are carried out, and then the soil can be restored to restore vegetation or reclamation. The compaction degree of the tailings can reach above 0.95, and the tailing mine has good safety performance. Restoring vegetation in time can prevent dust from flying and polluting the atmosphere, preventing rainwater from scouring the slope of the yard, affecting the stability of the yard, and simplifying the tailings treatment process. Under normal circumstances, the tailings yard is waterless, and the capital investment of the tailings management tailings warehouse generally accounts for more than 10% of the total investment in mine construction, accounting for about 20% of the investment in the plant. The operating cost of the tailings facility accounts for the plant. More than 30% of production costs, obviously, the construction of tailings ponds can reduce mine investment and operating costs. See Table 2 for comparison of tailings concentrated straight tailings pond and harmless treatment.

Table 2 Comparison of tailings concentrated straight tailings pond and harmless treatment

(3) Efficient automated tailings processing equipment

1. Efficient tailings concentration and dewatering equipment

Concentrated dehydration is an important part of tailings treatment. The process adopts the national patent high-efficiency concentrating equipment -deep cone thickener (patent number ZL200720093039.8), which obtains high concentration underflow and low solid content overflow. The deep cone thickener consists of a deep cone, a feeding device, a stirring device, a control box, etc. The slurry first enters the feeding device, and the large particles that are easy to settle quickly settle to the taper, and the fine particles are dispersed from the lower part of the feeding device to the dense phase deposition. The layer is further settled, the clarified overflow water is discharged from the upper overflow weir, and the lower cone bottom discharges a high concentration of the underflow. Compared with the commonly used thickener, the deep cone thickener has a high profile in the shape, and its height to diameter ratio is 2.1 to 2.40. Practice shows that the deep cone thickener processes the multi-metal gold-molybdenum ore flotation tailings. The underflow slurry concentration can reach more than 65%. High-concentration pulp creates good conditions for reducing the moisture content of the filter cake and increasing the productivity of the filter. The suspended matter content in the overflow is less than 160×10 ^-6 , which can be used as production water. According to the data, the concentration concentration of the tailings is only 45% to 50% by the series concentration process of the hydrocyclone and thickener. Other high-efficiency gravity sedimentation dewatering equipments, although optimized for the structure of the thickener equipment, need to add flocculant to assist dehydration in order to have a better concentration effect. The patented device can achieve high concentration of concentrated pulp and clear overflow without adding flocculant and without cyclone.

2. Automatic energy-saving nylon mine filtration equipment

The key to whether the tailings can be directly stored is the water content of the tailings. The tailings filtration is the final step to control the moisture content of the tailings. The filter equipment mainly includes a filter press, a belt filter, a cartridge filter and the like. The process selects a new type of high-efficiency, energy-saving and environmentally-friendly solid-liquid separation equipment-ceramic filter to filter tailings, which is a micro-porous ceramic, ultrasonic technology and automatic control, instead of the traditional filter press. The working cycle of the ceramic filter consists of five parts: slurry to the human, filter cake formation, filter cake drying, filter cake discharge and backwashing. It is characterized by high efficiency and simple operation. It can realize 100% complete treatment of tailings. The moisture content of filter residue is 13%-15%. The looseness is good. It can be directly stored, transported and compacted without drying with a dryer. The filtrate water is generally recyclable like tap water. The results of tailings ceramic filtration and tailings pressure filtration are shown in Table 3. The filter press is mainly used for the dehydration of gold products with large viscosity and fine particle size, concentrate dewatering of concentrates, gold cyanide washing, etc., and is rarely used in tailings treatment.

Table 3 Comparison of tailings ceramic filtration and tailings pressure filtration

Third, the scope of application of the process

(1) Applicable to tailings treatment of new and old mining enterprises

The new concentrating plant of the mining enterprise chooses this process, and only the tailings yard is built without the need to build a tailings pond. It can reduce the capital investment, speed up the construction, avoid investing a large amount of funds for land acquisition, agriculture, forestry, and young crop compensation, and ensure the safe heap of tailings. Save. This process can be used for the expansion of the old mining enterprise ore dressing plant, which can extend the service life of the tailings warehouse in the active service. The tailings dry slag can be directly stored in the dry type, and can also be used for dam construction. The coefficient can be from 1.O to 1.4 or higher.

(2) Applicable to tailings treatment of mining enterprises in arid and water-deficient areas

For the arid and water-deficient areas in the north, the tailings water can be recycled and the return water utilization rate is high, which not only saves water resources, but also avoids pollution of groundwater resources, and fundamentally solves the problem of environmental pollution. It is also possible to comprehensively recover valuable elements from tailings water.

Fourth, the implementation effect

The re-use of the tailings water of the 1,000-tonne plant can recover the fine-grained gold, save various kinds of ore dressing pharmacy fees, and the water supply cost is about 1.2 million yuan/a. By the end of 2009, the accumulated water saving was about 3.17 million tons, and the landfill was about 16.49 mu. The reuse rate of the return water cycle reached 92.6%, which fundamentally solved the production water consumption of the thousand tons of plants.

The repeated recycling of the carbon water plant backwater can reduce the cyanide-containing wastewater by 120,000 m ³ per year, and the cyanide ion and alkali in the recycled water can be recycled, which can save sodium cyanide 45t/a and lime 30t/a. There is no need to build another sewage treatment facility, which can reduce the treatment cost of cyanide-containing wastewater by 180,000 yuan/a, and eliminate the water pollution caused by cyanide-containing wastewater.

The tailings are directly stored in the tailings yard, no need to build a tailings pond, and the tailings management personnel are 10 fewer than the tailings pond. According to the calculation of 10 years, the labor cost can be reduced by 2 million yuan; according to the 10-year service life, the tailings yard is 4.597 million yuan less than the tailings investment; the tailings are layered to ensure the safe storage of tailings.

V. Conclusion

The tailings harmless treatment process is a new type of tailings storage method. The new process equipment technology is used to control the water content of the tailings to be below 13%~15%. The tailings are stored in the tailings yard, and only the tailings yard is built. There is no need to build a tailings pond, which realizes the organic combination and unification of water saving, environmental protection, safety and efficiency, and promotes the sustainable and harmonious development of people and nature.

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