Gold mine heap leaching drip operation system
I. Introduction
Gold deposits are distributed in all provinces of the country, but industrial-scale gold deposits are mainly distributed in the central, western and northern regions of China, as well as newly discovered metallogenic belts in recent years. Of the proven gold reserves, 30% are refractory gold mines. According to incomplete statistics mechanism, the vision of refractory gold reserves of 1,000 tons, have proven reserves containing 700 tons of arsenic, sulfur is difficult to directly gold cyanide, there are at least 40 to 100 reserves 1 The ton of refractory gold mines cannot be exploited due to environmental problems. The treatment of these difficult to use "staying mines" has become one of the main "bottleneck" issues affecting the sustainable development of China's gold industry. With the large-scale exploitation of easy mining, the development and utilization of refractory gold resources has become an important task for gold mining. In terms of pretreatment technology for refractory gold resources, it is urgent and urgent to accelerate the introduction of advanced technologies such as new method pretreatment technology and heating oxidation method to accelerate the introduction and secondary development of gold mine technology related equipment.
The state is paying more and more attention to environmental protection issues. In view of the large impact of the backward processes of gold smelting technology on the water environment and the atmospheric environment, advanced processes should be used instead of the old ones. In order to reduce the cost of environmental governance, protect the human living environment and achieve sustainable development of gold production.
After joining the World Trade Organization, the challenges facing China's gold industry mainly have two aspects: First, the issue of opening up the gold market. According to the World Trade Organization market access principle, the Chinese gold market will be open to the international community; the second is the issue of corporate competitiveness. Compared with the international advanced level, our enterprises have a large gap in terms of scale, capital, technology and cost, and their competitiveness is relatively poor. To this end, we propose to introduce the international advanced, efficient and environmentally friendly gold drip operation system in China's gold production, and promote it as soon as possible through necessary experimental research and engineering demonstration to improve the production efficiency and environmental protection of refractory gold mines.
(1) Cyanide gold extraction process
Heap leaching is an important technical means for gold extraction in gold mines. In order to achieve full contact between gold ore particles and Na 2 CN, it has become very important to adopt advanced technical means in the selection and smelting technology. In addition to finding new high-efficiency or non-toxic immersion gold solvents and pressurized oxidation processes, bacterial oxidation processes, chemical oxidation processes, and chlorination and sulfur-containing reagent oxidation methods, we should also improve the immersion gold technology methods, such as: A method of adding cyanide through a pipe by spraying or dripping.
(II) Key technologies of heap leaching treatment process
In order to solve the problems in the process, the corresponding immersion gold solvent is uniformly and reliably distributed and evenly distributed in the gold ore powder, and it is necessary to adopt advanced technology. At present, many gold mines have adopted spray methods to achieve this goal. However, some spraying methods are not easy to control the amount of immersion gold solvent, and it is difficult to increase the leaching rate. At the same time, the tiny water droplets containing cyanide sprayed into the air are easily diffused, causing damage and pollution to the human body and the environment. In order to better solve environmental problems, reduce energy consumption, optimize the ratio of immersion gold solution, increase the leaching rate, and reduce the amount of immersion gold solution, the heap-leaching method in the wet processing technology should be improved.
Figure 1 Schematic diagram of gold mine production process
(3) Environmental protection requirements
Cyanide contained in the immersion gold solvent during spraying can seriously pollute the atmosphere and water environment. Excessive use of cyanide can lead to cost of sewage treatment and environmental treatment in the mining area, and even increase production costs. With the continuous reduction of easy-leaching gold ore resources and the increasingly urgent requirements for environmental protection worldwide, the technology of mixing with the process is becoming more and more important. Therefore, the spray process will be subject to drip heap leaching. Process challenges.
The dripping method used in the heap leaching process has also been developed in developed countries, and the United States has adopted this technology in many mining areas. The environment has been greatly improved with this technology, and the drip method has contributed to the US gold production and environmental protection of the mining area.
As the main direction of research and development of difficult metallurgical technology in the future, from the perspective of technological development trends at home and abroad, the pretreatment technology for environmentally-friendly refractory gold ore will become an important development and application in the future. aims.
Second, the immersion gold solution distribution technology
The leaching gold solution distribution shower technology is the key technology of the heap leaching method. This paper focuses on the comparison and analysis of the two technologies of spraying and dripping.
In the case of conventional spraying for heaping, at the beginning, since the spraying intensity does not exceed the infiltration capacity of the ore powder, the surface of the ore powder will not form a water layer, and the infiltration in this case is called free infiltration. The infiltration rate of the mineral powder is equal to the rainfall intensity. With the high spraying intensity and the increase of spraying time, the surface of the ore powder quickly forms a water-bearing layer, and the formation of the infiltration process becomes pressurized infiltration, and the efficiency of the leaching decreases.
Using the drip infiltration method, the solution acts directly on the surface of the ore powder pile. The surface of the ore powder will not form a water layer, the infiltration rate is fast, and it can fully contact with the gold immersion solvent and wash the surface of the ore powder, which will precipitate the gold powder very much. favorable.
Modern drip equipment has pressure compensation, anti-clogging device, uniform outflow and can use the optimal drip strength and immersion gold solution concentration according to the ore composition, grade and degree of fracture.
(1) Dipping method of immersion gold solution
Overview of dripping methods
The method of applying the dripping technology to the immersion gold solution and uniformly spraying the immersion gold solution on the ore powder has been widely used abroad. According to the summary of foreign manufacturers, drip has the following advantages:
1. High performance and high reliability, easy to install;
2, can reduce production costs;
3. Eliminate the effects of the wind;
4, can run all year round;
5. Reduce the damage of chemical substances by the sun's ultraviolet rays;
6. Reduce the discharge and loss of the immersion gold solution;
7. Saving construction costs of liquid storage tanks and water diversion channels;
8, automatic cleaning and anti-blocking of the dripper;
9. Reducing the impact on operators, the surrounding environment and land is conducive to environmental protection.
Drip can increase the air content in the solution, which means increasing the oxygen content of the chemical reaction and participating in the precipitation of gold deposits; the drip system can precisely control the concentration of cyanide solution and reduce the loss of sodium cyanide in the air. The drip system is easy to increase the temperature control equipment to achieve the purpose of increasing the temperature of the heap immersion chemical reaction. The drip system has high automation, easy operation, high production efficiency, high reliability, less impact on the environment, and relatively low production cost.
Figure 2 Schematic diagram of the drip system process
Figure 3 Drip system floor plan
(B) the characteristics of the dripping method
In order to solve the refractory gold ore smelting, roasting is the oldest and traditional pretreatment method for processing gold ore. The advantage of the roasting process is that it has relatively strong adaptability (can handle gold-bearing refractory gold ore), operation The cost is relatively low. The disadvantage of this process is that it is sensitive to changes in operating parameters and feedstock composition, and it is easy to cause over-burning or under-burning. In the case of under-burning, the sulfur-containing and arsenic-containing minerals in the ore are not fully decomposed, and the partial burning of the calcined sand during overburning causes The pores of the calcine are closed to find a secondary coating of the particles, resulting in a decrease in the leaching rate of gold. In addition, sulfur dioxide and arsenic trioxide will be produced during roasting, and when the comprehensive recovery is unfavorable, the atmosphere and the environment will be seriously polluted. From the current point of view, as environmental protection requirements become more stringent, the cost of flue gas treatment associated with the process will be greatly improved.
At the same time of establishing the drip system, we will consider adding heating equipment through the drip system, which will make the dripping method have been improved and developed. In recent years, foreign research institutions are developing and researching more effective heating wet technology. Although it is still in the experimental research stage, it has shown good industrial application prospects like the heating wet technology process.
2, can accurately control the delivery of gold immersion liquid
The drip pipe network pressure is much lower than that of the spray, and the solution composition loss is small, and the application amount to the quarry pile can be accurately calculated and controlled, especially after the automatic control system is adopted, the solution concentration and flow rate control are more accurate.
3. Effective use of gold leaching cyanide and reducing energy consumption
The drip system avoids the dissipation loss during the solution distribution process, and can accurately quantitatively transport the immersion gold solution into the ore powder pile, thereby reducing the amount of solution used and reducing the energy consumed by the circulation system.
4, no knots and stagnant water
The drip leaching technology can completely eliminate the phenomenon of squashing on the surface of the slag powder pile, and eliminate the problem of water accumulation and infiltration in the slag powder, and improve the gold extraction rate.
Third, gold mine drip operation and management system
The drip system uses the international advanced drip system and control system. It consists of the following devices:
Computer control system (wired or wireless)
Gold mine powder pile control and solution ratio control system based on pH value and NaCN concentration level
Drip dispensing system with dropper for Mine-TraXX or Drip In for Heap Leach mining systems
The system has great flexibility in expansion and can be applied to a heap leaching operation or to a large heap leaching operation composed of multiple stacks.
Figure 4 Example of dripping system
(1) Computer Control System
The modular computer stacking control system is a modular structure. Each control unit can be composed of 3 or 5 input/output modules. The communication between the system and the control center can be via cable or wireless.
Figure 5 system control box
With the expansion of production scale, computer control systems can be developed into a large-scale network management system integrated with the Internet in the future, as shown in the following figure:
Figure 6 network system block diagram
(2) Solution ratio control system
The control system is a computer controlled programmatic solution ratio control system. Operated by self-developed software, it has great flexibility and can be customized according to the specific requirements of users. The system allows the user to accurately monitor and control the drip environment using any type of digital/analog sensor or device.
The drip control system and the solution ratio control system can be used independently of each other or combined as one or more drip control systems. Through the friendly software interface or the respective display panel of the control unit. Display the status of the system, adjust system parameters, statistically analyze the activities of the production process and system technical indicators to form a comprehensive report.
The system is capable of detecting drip and heating device failures or large monitoring deviations by telephone, pager or other communication device.
Figure 7 solution ratio control system
Authorized users can remotely monitor drip and heating conditions and control the system via a computer modem.
(3) Drip pipe network system
This project adopts mining special drip tube or labyrinth drip tube produced by Israel or American drip products company. The product adopts wide-channel technology with dripper, double inlet technology for dripper, and high-concentration immersion gold chemicals. Drip operation technology. Has the following advantages:
Wide flow channel for water sources with high levels of immersion gold compounds.
The flow passage inlet has a large filtering area, and the built-in filter screen area is 10 times larger than similar products. This project uses a dripper flow rate of 7.0 l/h.
The labyrinth structure has strong eddy currents and impurities do not block the flow path.
The dripper is automatically cleaned at the start and end of irrigation.
Available in a variety of sizes, pipe diameters, dripper spacing and wall thickness.
Figure 8 Drip tube
The drip system saves the performance of the immersion gold solution, and the utilization rate of the immersion gold solution reaches 98%.
Fourth, promote the application
In the Tenth Five-Year Plan, it has been proposed that the main objective of the technical equipment transformation of China's gold production is that the technological equipment and major technical and economic indicators of large enterprises are close to or reach the international advanced level. It is difficult to tackle the difficulties of gold mining and smelting technology, realize industrialization, and utilize 300 tons of refractory gold resources; solve special technical problems such as geotechnical exploration, mining and environmental protection of mining enterprises, and reduce the resource consumption ratio from 1:1.7 to 1 : 1.5. Increase research on water-saving and energy-saving process equipment to reduce energy consumption and consumption of mines.
In environmental protection, we must raise awareness of environmental protection, actively promote clean production processes, and do a good job in comprehensive utilization. The “three wastes†emissions of enterprises must meet national or local standards. Conditional large and medium-sized gold enterprises actively create “garden-style enterprises†and “zero-emission mines†to create a more beautiful production environment.
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