Development trend of mining technology, technology and equipment in foreign mines

While deepening the construction of green mines, China is also facing a more severe test of the technical level. With economic development, China has proven high-quality mineral resources nearly depleted, the total supply of raw materials shortages, complex low-grade ore resources or secondary resources will gradually become the main raw material for traditional geological, mining, mineral processing, metallurgy, Science, technology, materials, processing, and environment have presented great challenges. At the same time, with the development of science and technology and the gradual consumption of shallow ore bodies, many mining companies have increased the depth of exploitation, and the inherent high stress and high ground pressure of deep deposits are Features such as high ground temperature are gradually revealed.

I. Introduction to the development of mine filling technology

The development of mine filling technology has gone through many stages. At the beginning of the 20th century, many mines first adopted the water sand filling process, which is prone to safety accidents and blockage problems. Then there is a wall-type filling mining method, but the method is controlled by Excessive depletion caused by waste rock falling along with the veins; returning to traditional wood support in the 1940s and 1950s; in the late 1960s and early 1970s, casualties caused by rock bursts became major The problem, the filling method has re-emerged, people have established various mathematical models to predict the energy release rate, and fill the design; in 1973, the filling process adopted by Il Engol, the excavated waste rock was crushed in the stope. The machine is broken to below 25mm, and then the waste rock and water are blown to the built-in box of the stope by the pressure booster; the cemented dewatered tailings cement filling system is built and used in 1977, but this method exists in the centrifugal dewatering machine. There are many practical problems, and in some cases, a large amount of dust generated by compressed air is harmful to health; in the early 1980s, many mines began to use graded tailings as the basic filling aggregate. This system is economical and simple and suitable for narrow and deep stopes. The advantage of using graded tailings in deep mines is that all preparation work can be carried out on the surface, with minimal impact on existing mine infrastructure. Moreover, the filling and filling of the filling material does not require dewatering or mechanical dewatering facilities in the pit, and the filling body can control the pressure of the mining site, support the surrounding rock of the upper and lower plates, reduce, delay and prevent the destruction and movement of the surrounding rock in the post-harvest area, and As a workbench that continues to be harvested, or after the mine is mined, it is filled once and then to support the ore around the upper and lower plates, so that the adjacent pillars can be smoothly recovered. At present, the cement filling system for pipeline self-flow transportation has been widely used in metal mines.

2. Cementing and filling mining technology, technology and equipment used in mining and mining

The cement filling and filling method has the dual functions of environmental protection and improving the recovery rate of ore in the case of ensuring safety. The filling process involves the safety and economic benefits of the mine. Therefore, it has attracted extensive attention from the mining industry at home and abroad, and has been obtained in mines such as nonferrous metals and gold. More and more applications have achieved a lot of research results.

The main problem of cement filling is that the filling cost is too high. In the cost of cementing filling materials, cement costs account for nearly 60%-80%. Therefore, an important way to reduce the cost of cementing filling is to find cement substitutes to reduce cement consumption. Research and application of domestic and international practice shows that the smelter water granulated slag, powder coal ash thermal power plant, aluminum plant red mud, are the good performance of cement substitute. In particular, fly ash, in addition to partially replacing cement to reduce the filling cost, can also improve the slurry flow performance and improve the slurry suspensibility, so it is more widely used.

The new process test is carried out by filling the high tailings with full tailings cement, using high water quick setting material and mixing with the whole tail mortar to make a filling slurry with a mass concentration of 30%-70%. After charging into the stope, no dehydration is required. 8h can be used for equipment work. Despite the shortcomings of the high-aluminum high-water quick-setting material used, the material basically solves the technical problems of tailings grading de-sludge, underground de-watering, and stope roofing, in order to better utilize the full tailings filling. It has opened up a whole new field and laid the foundation for the development of new high-speed quick-setting materials with wide source of materials, low cost and better performance.

The new technology of block cement filling has been promoted and applied. The process means that the waste rock is not excavated in the underground, and is directly filled into the goaf or the stope. The waste rock and the cement mortar are alternately cut, and the block cement filling body is naturally mixed. Since the block stone and the mortar are separately transported, the mortar is used. The penetrating consolidation stone does not need to be stirred, and its filling body strength is close to the concrete cementing filling strength. Compared with the concrete cementing filling, the filling efficiency is improved, the process is simpler, the labor intensity of the worker is greatly reduced, and a good technical economy is obtained. effect.

The filling process technology for applying hydraulic conveying of graded tailings pipeline has been quite mature. In order to solve the problem of difficulty in stacking silt after dewatering of tailings and complex tailings classification process, many mines have recently promoted full tailings cementing filling technology, but the process requires mechanical methods for concentration and filtration, and the process is complicated and the cost is relatively high. high. In recent years, the full tailings paste pumping and cementing filling process has promoted the advancement of the full tailings cementing filling technology, providing a successful example for mines with low tailings yield and insufficient filling sources.

The addition of chemical admixtures is an effective way to improve fluid flow performance and is widely used in concrete engineering. Adding a small amount of admixture can improve the workability of concrete and improve the physical and mechanical properties and durability of hardened concrete.

Pipeline self-flow is a typical solid-liquid two-phase flow. The design of the pipeline self-flow conveying system requires quantitative analysis and calculation of the flow performance of the slurry and the resistance loss (hydraulic gradient) of the pipeline. In order to meet the actual needs of production, the theory of two-phase flow has been studied in-depth at home and abroad. According to different material properties and conveying conditions, various empirical formulas for hydraulic gradient calculation are proposed. The famous ones such as Euphen's formula, Newitt's formula, Kars' formula, etc.; according to the suspension state of the slurry in the pipeline For the influence of slurry transport performance, the ways to improve the flow characteristics of the slurry are proposed. The critical pipe diameter, critical slurry flow rate and conveying capacity required for the design of the filling system have relatively reliable calculation methods.

3. Research and development trend of mine filling and mining technology, technology and equipment

1 filling material

The latest results of the study Nugget plaster Filling the Australian Mount Isa, the design principles stone paste filling. Through several large-scale agitation tests and free fall tests, it was shown that the block gypsum filling can form a uniform filling body. The block gypsum filler is composed of a graded tailings cement slurry and a proportion of block stones, which exhibit similar bond paste characteristics. The compressive strength exceeds 1 Mpa under the condition of an average addition of 1.5% to 2% of cement.

The Williams mine in Canada uses a stabilizer called DELVO, which is used in the block cementing process. As a result, DELVO stabilizers help to reduce pipe blockage and increase strength. After using this stabilizer, the number of cleaning of the surface mixing tank was also reduced by 45%.

The Savuka mine in South Africa uses BF98 plasticizer, which contains gypsum, which acts to increase the filler concentration and reduce the loss of water and fine particles. Plasticizers also ensure increased flow rates at high concentrations and reduce pipe wear and maintenance costs.

Hecla Corporation of the United States has studied the use of Pozzlith 344N blending agent to reduce the amount of filler gelling agent and improve the fluidity of the filler. The result is a 20% reduction in the amount of cement that does not affect the filling strength and fluidity.

2 Filling mechanics

The University of Montreal in Canada has studied a new method for testing stress and strain in on-site fillings. The traditional approach is to combine borehole sampling with indoor model testing. The new method is to use a new set of equipment, which can drill holes by itself, install stress and strain sensors inside the drill bit, the signal is transmitted back to the working surface through the cable, and there is a protective layer between the drill tool and the sensor to prevent the sensor from being generated during the drilling process. interference. The average drilling speed is 0.1 m/min. Calculated by 8 hours per shift, 7 sets of data can be measured per shift. The advantage of this method is that it does not affect mining operations.

The American Institute for Occupational Safety and Health studied the relative displacement of the surrounding rock from the lucky Friday mine to the stope, the interaction between the cementation load and the steel bar. Eight stratified data were collected showing that the displacement of the surrounding rock caused the deformation of the filling body, thereby applying a load to the vertical anchor in the filling. The results analysis shows that the backing support system with steel anchors is effective.

Russia's Sergey N. Zhurin conducted a pore pressure control test for tailings discharged tailings. The test experiment was done in Gubkin iron ore, more than 80% of the tail water is pumped to the two mortar test stope observed distribution hole filling pressure zone plate, while the hole filling body also analyzed by FEM model numbers Pressure distribution. The results of the on-site investigation revealed that there is no correlation between the pore pressures in the adjacent stope, and the water pressure of the filling retaining wall mainly depends on the speed of the filter passing through the retaining wall.

South Africa has proposed new filling design standards for existing filling design standards for ultra-deep well mining research, suggesting that 60% to 70% of the goaf should be filled.

3 paste filling

The Australian Mount Isa Mine uses two simple, cost-effective test methods to study paste characteristics when developing paste filling techniques, to help paste filling design, ie flow cone test and small slump cone test. Through these tests, the flow characteristics of the paste can be predicted. The flow cone consists of a cone and a section of outlet tube with a cone angle of 14° and a volume of 2 L. The outlet tube has an inner diameter of 30 mm and a length of 150 mm and is connected to the cone. The small slump cone test is based on the standard slump test of the building. The data shows that the typical slump of the paste is 150-250 mm, the slump of the concrete is 30-60 mm, and the slump of the pumped concrete is 100-125 mm.

The Clinton Mine Paste Filling System in Australia was not operating properly during the first 18 months of operation. Most of the problems were related to pipe wear. Later, ceramic and rubber gaskets were used in the wearable areas to reduce wear. Greatly reduce downtime. At the beginning of the filling, two batches of slurry without added cement are prepared and filled into the pipeline for the purpose of wetting the pipe and then adding cement. At the end of the operation, 2 to 3 batches of cement-free slurry are also charged, and then the pipeline is cleaned with water and air. An air pressure gauge is installed on the surface to determine if the pipe is clean. At the beginning of the air supply, the pressure reached 700 kPa due to the slurry and water in the pipe, and the pressure gradually decreased to 200 kPa, at which time the slurry and water in the pipe were cleaned. If the paste has not yet entered the pipeline within 20 minutes, the pipeline will be cleaned manually or automatically. Since the paste is fed into the pipeline in batches, high dynamic loads are generated in the downhole pipeline. During the first 18 months of operation, due to the dynamic load, the joints of the pipeline are often damaged. To this end, the following measures are taken: The knife-gate (gate knife) type valve is used to limit the flow rate to ensure the semi-continuous flow of the paste in the pipeline; the flange is used to replace the tongue-and-groove tube at the position susceptible to high dynamic load; and the slump is reduced; Install the double flange tube in the appropriate place. The Clinton Mine has established a standard that when the paste has a yield stress of 800 Pa (approximately 85% solids concentration), the paste can be successfully filled. The mine is the first mine in Australia to apply paste filling technology and has achieved many successful experiences.

The Neves Corvo mine in Portugal studied the strength of the paste filling mine and the relationship between laboratory test values ​​and field values. The liquefaction of the paste in the second step of the mine was also studied. The results of laboratory tests and field tests showed that adding 2% cement, the possibility of liquefaction of the paste filling is small, and when adding 0.5% cement, Liquefaction is highly likely, so it is common to add 1% cement to avoid liquefaction. When minimizing the risk of liquefaction, the 28-day uniaxial compressive strength should reach 172 kPa, the cement addition at this time is about 1.5%, and the filling body can reach 10 m.

The Brunswick mine in Canada decided to build a paste filling system in July 1997. Prior to this, the tailings test, loop transport test and pre-feasibility study were completed. The entire system invested $24.1 million. The filling station is controlled by a programmable logic controller (PLCS) hybrid computer system and a Fisher Provox Distributed Control System (DCS). The PLCS processes the digital information, turns on the sequence of the motor and valve, and the DCS processes the analog information to provide an interface for the operator. A processing information system (PI) is used as a database and provides sensor orientation for analysis by filling station operators and technicians. Install 5 mobile cameras at the outlet of the filling pipe to monitor the filling. The video signal is sent to the surface filling station via a set of (Leaky feeder) communication systems and fiber optics. If the filling is drilled into the stop, install an ultrasonic flow meter as close as possible to the outlet to monitor the filling. In the downhole pipeline, 18 sensors are installed to continuously monitor the pressure in the pipeline. The pressure signal is monitored by the downhole PLCS and then transmitted back to the surface filling station via a data cable and fiber optic network. The system also has a Leaky feeder radio communication system for voice communication. The paste mixing at the Brunswick mine uses a blade mixer for continuous operation, unlike traditional batch mixing. Practice has proved that the blade mixer works reliably. Cement is added wet.

In the feasibility study stage, the test results are: solid weight content of 81% to 83%, corresponding slump 178 ~ 254 mm, suitable for preparation and transport. In actual production, the solid weight concentration is 78% to 80%. According to the current change of the mixer, cement can be accurately added and the slump is maintained between 140 and 165 mm.

Japan introduced the Toyoha mine plan to introduce paste filling technology, the main purpose is to prevent heat flow from the goaf and improve the downhole climate. The underground temperature is 10 to 20 times the average temperature of the Japanese islands, and the highest temperature measured in the borehole reaches 242 °C. The mine only completed the surface loop test and the second test was planned downhole.

A mine in Canada studied the compatibility between the rheological properties of the paste and the filling pipe network. The conclusion of the study is that the problem of paste filling comes from one or more of the following aspects: pipe network design, aggregate level With design, water-cement ratio or production process. These issues can be minimized during the design phase. When the rheological properties of the paste are incompatible with the pipe network, a large number of failures will occur. In the pipe network design phase, the pipe diameter, aggregate grading and water-cement ratio determine the operating state of the system, so the system's adaptability should be considered during the design phase. Strength and rheological properties tests should be performed at the same time, not only to meet the strength requirements, but also to ensure that the rheological properties are compatible with the pipe network. The basic principle of design and what must be done is to ensure that the pipe network is compatible with the rheology of the paste.

4 filling equipment and operation

A typical example is the optimization of filling equipment for high concentration filling of the Stratoni mine in Greece. The mine is located in northeast Greece, lead zinc ore mining to the approach adopted under the filling method. Due to the difficulty in conveying, the filling body beam is often damaged. Therefore, relying on the addition of cement to solve, resulting in increased filling costs, and the construction of a new filling station, economically unreasonable. The solution is to optimize and retrofit existing filling systems, with an investment of only $35,000. Cement consumption accounts for a considerable proportion of operating costs, saving 1% of cement, and the mine can save $50,000 per year. Optimization measures included changing the diameter of the shaft to 100 mm and changing the diameter of the shaft to 125 mm to prevent precipitation of particles in the pipeline. In addition, in order to improve the filling consistency, a control facility is added in the filling station, and the program consistency logic (PLC) is installed on the filling system by controlling the current consistency of the slurry by the metering disc mixer.

Germany has studied advanced filling equipment to reduce or eliminate wear and corrosion methods in filling equipment. The filling pipeline mainly uses basalt- lined steel pipes, which are pressure-resistant and the pipes are flanged. The lining prevents wear and corrosion and provides an almost polished surface.

Australia's Olympic Dam mine uses a deep-hole empty field method, with empty gravel cement filling and stone filling. The filling material enters the top of the stope through the borehole from the surface. Due to the adverse effects of the dust and humid air in the stope, the filling process cannot be observed by the naked eye. To this end, a millimeter-wave radar is developed. Using this radar to observe the filling process and obtain real-time data of the relative positions of different filling bodies is an effective means to control the filling of the stope.

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