For gold companies, energy consumption has been an important indicator of business assessment index. As a resource-based industry, to a certain extent, gold mines are industries that use energy for resources. Therefore, reducing energy consumption has always been the goal of gold companies and their tireless pursuit.
During the "Twelfth Five-Year Plan" period, the Ministry of Science and Technology set up a special project to study the technology and equipment for reducing the energy consumption of grinding and floating in gold mines. The major gold mining enterprises also responded positively and carried out technological innovation and equipment research and development. Although the work has achieved certain results, it is regrettable that the effect is not significant, and the energy consumption of the grinding and floating section of the gold mine has always remained high.
Status: Most of the beneficiation plant did not meet
The concentrating plant is the main production unit and an important component of the mining enterprise. It uses various mineral processing methods and technological processes to obtain concentrates with higher grades from the ore. From a functional point of view, the concentrator mainly undertakes operations such as crushing, grinding, flotation and tailings transportation of ore.
Grinding operations are extremely important production links for mineral separation and are the most energy-intensive operations in the concentrator. According to statistics, grinding energy consumption accounts for 40% to 60% of the total energy consumption of the concentrator, while flotation accounts for 10% to 20% of the total energy consumption of the concentrator. It can be said that grinding and flotation are the cost of the concentrator. Can be "big family."
“In the grinding operation, the largest power consumption is the ball mill used for grinding. Others like slurry pump, vibrating screen, flotation machine, blower, etc. are also high-power consumption equipment.†Henan Jinyuan Gold Mining Co., Ltd. Wang Ruixiang, chairman of the responsible company, said.
According to the "China Gold News" reporter, the total power consumption of Henan Jinyuan Company from January to July 2016 was 34.531 million kWh. Among them, the concentrating plant consumes 22.644 million kWh, accounting for 65% of the company's total consumption; the grinding operation consumes 12.60 million kWh, the flotation operation consumes 455.37 million kWh, and the total grinding and floating is 1715.95 million kWh, accounting for ore dressing. 76% of the plant's consumption, accounting for 49.7% of the company's electricity consumption.
From the point of view of the power consumption and consumption index, Henan Jinyuan Company's concentrating plant has a power consumption of 18.48 kWh/ton and a flotation operation power consumption of 6.68 kWh/ton, which together account for 25.16 kWh/ton. The power consumption of the concentrator is 76% of the 32.94 kWh/ton, accounting for 49.7% of the company's power consumption of 50.63 kWh/ton.
“According to the grinding fineness of more than 85% of -200 mesh (less than 0.074 mm), if the energy consumption of traditional crushing grinding is about 24.5 kWh/ton to 33 kWh/ton, if semi-self-grinding + ball milling is used Process, grinding energy consumption is about 27 kWh / ton to 41 kWh / ton; flotation energy consumption is about 7.5 kWh / ton to 10 kWh / ton." Senior Engineer, Metallurgical Selected Mine, Beijing Research Institute of Mining and Metallurgy He Guohua introduced.
"According to the latest energy consumption limit standards for gold mining and smelting units, the requirements for comprehensive energy consumption for new and rebuilt gold ore smelting units are not included in the established concentrating plants. More than 5%, most of them did not meet the admission criteria. In other words, if these enterprises are new enterprises, they are basically unable to approve the establishment of the factory. However, these enterprises are still continuing to produce based on various factors. Zhang Qingbo, chief engineer of the Changchun Gold Research Institute, said with emotion.
A ball miller in the Sanxin Moufu section of Hubei added steel balls to ensure that the "4261" ball mill current reached 140A or more, improving grinding efficiency.
Reason: low power utilization
Grinding is the fine ore that is ground into a powder by a ball mill. The working process of the ball mill is that the material enters the cylinder through the hollow shaft of the feed end cover. When the cylinder rotates, centrifugal force and friction force are generated to make the medium (steel When the ball and the ore rise to a certain height with the wall of the cylinder, the parabola falls or falls down by its own weight. The grinding of the ore is mainly achieved by the impact force when the crushing medium falls and the grinding action during the movement. The movement of ore is achieved by constant pressure on the ore.
“What is really useful is the energy of the grinding medium. Most of the energy is used for lifting. In addition, the ball mill is rolling and grinding, only point-to-point contact with each other, and the utilization rate is low. These two aspects lead to true grinding. Mines have less electrical energy, and most of them are wasted in the grinding process. According to statistics, the utilization rate of grinding energy is only 30% to 40%." Zhang Qingbo said.
Grinding is the material preparation process for flotation, and crushing is closely linked to grinding. Before grinding, it is necessary to crush the ore to achieve the proper ore size. When determining the optimum particle size of the ball mill (ie, the final crushed product size), the total technical and economic effects of crushing and grinding should be considered. The larger the particle size of the crushed product, the higher the crusher 's production capacity and the lower the power consumption of the crusher; however, the production capacity of the mill will be reduced, and the electrical energy consumption of the mill will increase. On the contrary, the smaller the particle size of the crushed ore, the smaller the production capacity of the crusher, and the higher the electric energy consumption of the crushed ore; but the production capacity of the grinding machine will increase, and the electric energy consumption of the grinding can be reduced.
However, in actual production, due to the difference in equipment, different grinding equipment has different mineral grain size requirements for ore, which is one of the reasons why it is impossible to maximize production efficiency and reduce energy consumption.
Solution: research and development of advanced equipment and processes
For gold companies, reducing energy consumption means lowering costs, so the major gold groups have invested heavily in research to reduce the energy consumption of grinding and floating. “There is currently no equipment or technology to replace the ball mill.†Zhang Qingbo said, “The old-fashioned ball mill is commonly used in China, and the ultra-fine grinding like Germany has been able to grind coarse ore into fine ore with a diameter of more than ten microns. We need to introduce and develop advanced equipment and technology."
Many domestic concentrators are unable to effectively reduce energy consumption due to equipment limitations, and some companies still use some old equipment. “The 7 billiard mills in Jinshan Gold Mine are all equipments in the 1990s. There are no excavation space for more grinding and less grinding, and optimization processes. Replacing more advanced equipment is the only way to reduce energy consumption and reduce costs. Yuan Zhenyong, deputy general manager of Jiangxi Jinshan Mining Co., Ltd. said, “At present, our ore dressing cost has reached 60-70 yuan/ton. If equipment is replaced, the cost of mineral processing can be reduced by nearly 20 yuan/ton.â€
Zhang Qingbo also stressed: "The advanced level of equipment will greatly help the improvement of grinding efficiency, which can effectively reduce energy consumption and cost."
Flotation is also a high-energy-consuming section. According to Zhang Qingbo, the small-scale flotation machine is still widely used, with high energy consumption and low efficiency. Therefore, flotation also needs to be innovated in equipment and processes. At present, the development trend of flotation is the flotation machine size and flotation column. “Flotation machine is large-scale, one flotation can handle more pulp, which can improve flotation efficiency; while flotation column can achieve separation flotation without strong agitation, and can reduce flotation energy consumption by several times. ."He said.
Equipment levels are a key factor in determining energy consumption, and optimizing equipment accessories can also reduce energy consumption. Henan Jinyuan Gold Mine plans to replace the cast steel lining used now with a rubber lining. The quality of the rubber lining is small, which can effectively reduce the quality of the cylinder, thus reducing the load on the motor, saving power consumption, and making it easier to replace. , greatly reducing downtime and improving the efficiency of business operations. Meanwhile, the use of special rubber liner formulation, vulcanized by high pressure, a substantial increase in wear resistance, rubber elasticity buffer further own unique intense impact is greatly reduced, effectively extending the life expected life of up to 1.5 times the manganese steel backing Up to 2 times.
“Using the energy-saving compensator can save up to 15% energy.†Zhang Qingbo said, “Because the ball mill is pulsed, it is not rotating at a constant speed, but it is fast and slow. The energy-saving compensator stores excess energy and releases it when needed. come out."
In addition, energy consumption can be reduced by improving the grinding process. After decades of practical experience, we have gradually formed a process concept of combining crushing and grinding with multiple crushing and grinding. The crusher destroys the internal structure of the ore, reduces the strength of the ore and the size of the ore, and then grinds it with a mill to improve the overall grinding efficiency.
Henan Jinyuan Company completed its reconstruction and expansion in 2008, the production process has been very stable, and the grinding and floating operation section is regarded as the most important mineral processing section, and its process and equipment have been very stable. Wang Ruixiang said: "With the guarantee of normal daily processing capacity and equipment operating rate, the power consumption of each equipment in Jinyuan Gold Mine Concentrator has been basically stable and it is difficult to effectively reduce it in the short term."
Therefore, Henan Jinyuan Company considered to save energy through appropriate small reform measures. “We can enhance daily management and promote energy conservation through management. When equipment maintenance needs to be shut down, guide operators to make correct shutdown sequence, especially flotation section. By timely discharging and timely closing high pressure fans, it can effectively prevent There is equipment idling, resulting in waste of energy.†Wang Ruixiang said, “Improve the production organization, through reasonable distribution of minerals, evenly feeding the mine, can improve the efficiency of the ball mill, prevent the ball mill from idling, resulting in energy waste.â€
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