Current status and development of copper beneficiation

Copper ore must pass the beneficiation, flotation is the primary method of copper ore not selected. With the continuous mining of copper ore, the grade of ore selected for it is reduced, the proportion of refractory composite ore and oxidized ore is increased, and the price increase of equipment and energy and the strict requirements of environmental protection are caused. The cost of mineral processing is increased and the difficulty of mineral processing is increased. . Therefore, how to reduce the cost of mineral processing and develop and utilize difficult-to-select low-grade copper ore is an important research topic in copper beneficiation.

First, the scale of the plant is expanded, the equipment is large, and the level of automation is high.

(1) The grade of ore is low, and the scale of the plant is expanded.

In recent decades, the world's copper ore mining grade has declined year by year. It was 1.88% in the 1950s, 1.33% in 1960, 1.1% in 1970, and 0.55% in 1980. Most of the large copper selection plants that the United States built from the 1970s were selected for lower grades. For example, the grade of copper ore selected by the West Yali Plant was only 0.32%, and the daily processing capacity was 90,000 tons.

Among the proven copper resources in China, the average grade is only 0.71%, and only 1/5 of the grade is greater than 1%. The grade of mine produced by Nonferrous Corporation is 0.69%, and the grade of copper mine still to be built is only 0.62%.

Mining of large low-grade porphyry copper deposits. According to preliminary statistics, porphyry copper deposits account for more than 60% of the world's proven copper resources; porphyry copper deposits in the United States and Chile account for 80% to 90% of the country's total reserves. Although the porphyry copper deposits are of low grade, the porphyry copper deposits are highly selectable and can be exploited on a large scale, with low mining and beneficiation costs, all of which are prerequisites for large-scale mining and expansion of the plant.

For example, the world's large open-pit copper mine Qiuji Mine is a very large porphyry copper mine with a daily processing capacity of 160,000 tons. According to preliminary statistics, there are currently more than 40 copper mines with a daily mining capacity of over 30,000 tons, most of which are porphyry copper mines, and also associated with gold , silver and molybdenum . Price component. China's Jiangxi Dexing Copper Mine is also a large-scale porphyry copper mine with a daily processing capacity of more than 90,000 tons. In addition to copper recovery, it also comprehensively recovers molybdenum and gold and silver, which greatly improves the comprehensive benefits of the plant.

(2) Large equipment

The expansion of the scale of the plant has led to the enlargement of equipment, especially the large-scale crushing and grinding equipment . Large-scale copper mines at home and abroad widely use self-grinding and semi-self-grinding, which can save capital investment due to self-grinding and semi-self-grinding. And production costs, have a good adaptability to the physical properties of the ore.

For example, in 1988, the United States Copton Copper Concentrator installed three Φ10.4m×4.6m semi- autogenous grinding machines . In 1992, the fourth grinding system was expanded to install one of the world's largest Φ10.97m×5.18m semi-self. The mill, Australia's Mount Aisa and other copper selection plants used two Φ8.13m×3.68m self-grinding machines to replace the fine crushing workshop, powder ore bin, rod mill and first ball mill in the reconstruction. Operating costs are reduced by 30%, and a feasibility study conducted in 1989 proved to save $9.8 million per year. This self-grinding-ball milling combined process reduces grinding fineness compared to the original process. China's Jiangxi Dexing Copper Mine Plant installed a Φ5.4m×6.0m ball mill, and each billiard mill and 8 Φ660mm cyclones constitute a closed circuit. The use of cyclones instead of classifiers is the development trend of grinding and grading in recent years.

The large-scale flotation equipment is also constantly developing, and large flotation machines have been widely used in copper selection plants. For example, the Finnish Outokumpu flotation machine, which was put into operation in September 1997, has a tank volume of 100 m ³ . The Maxwell MX-14 model used in the Opuska plant in Canada has a tank volume of 57 m ³ . The pontoon is in the shape of a drum, which is characterized by a power of 35% to 40% of the general flotation machine, a maintenance fee of 20% to 25%, and an area of ​​30% to 35% of the installation cost. China's Yunnan Yimen Muben Plant has invested more than 1 million yuan to change the rough sweeping to CHF-x14m ³ aerated agitation flotation machine; compared with the 6A flotation machine, the power consumption is 30% compared with 6A province, the water wheel The life of the cover is one and a half times longer than that of 6A, and the work efficiency is obviously improved.

Since the 1980s, flotation columns have made great progress in the application of copper selection plants at home and abroad, especially the flotation column has been successfully applied in the selected area of ​​the flotation circuit. Since the flotation column can produce high-grade final concentrate, reduce the number of selections, simplify the selection of circuits, simplify and improve the process control of the selected circuit, and low operating and maintenance costs, it can successfully replace the machinery in the selection operation. Stirring flotation machine.

(III) Improvement of the automation level of the factory

Due to the size of the plant and the large size of the equipment, the automation requirements are also getting higher and higher. Automation generally increases the capacity of the plant to 10% to 15%, labor productivity by 20% to 50%, and production costs by 3% to 5%. Therefore, in the newly-built or old factory renovation, most of them use the automatic control of the unit or production section and even the centralized control of the whole plant. Since the 1980s, computer control has been widely used in developed countries such as the United States, the United Kingdom, Canada, and Australia. For example, the Australia Mount Isa No. 4 copper selection plant uses the HP2116G computer to control the grinding circuit to maximize the throughput with the same particle size; and to use closed-circuit television to monitor the grinding operation.

The level of factory automation in China is also gradually increasing. How to use the constant feeding and ball mill concentration automatic control instrument in the North Copper Concentrator, the silver smelting plant developed and adopted BYF slurry current-carrying X-fluorescence analyzer for on-line detection.

Tongling Nonferrous Metals Co., Ltd. Fenghuangshan Concentrator is one of the factories with high mechanization and automation level in China. The plant has a general control room. All equipments such as crushing, grinding, flotation and dewatering are operated by the general control room. The power meter can also be used to understand the production situation of the whole plant. The grinding operation uses an r-ray concentration meter to control the concentration of the ore discharge of the rod mill and the ball mill. Not only can the measurement be made, but also the high-speed slurry concentration can be used to increase the flotation index. The automatic control of flotation pH is composed of pHG-2IA industrial acidity meter and pHGF-B submersible cleaning acidity transmitter, supporting application; the flotation process stabilization control adopts Curry-300 slurry current X - Fluorescence analyzer.

Second, research and development of new flotation process

(1) Application of branch stream flotation process

The establishment and promotion of the new branch flotation flotation process attracted great attention at home and abroad. Through the industrial test of this process, Dexing Copper Mine improved the grade of copper concentrate by 2.74% and the recovery rate by 0.7%. At the same time, it reduced one. In selected operations, the consumption of flotation reagents decreased significantly. After the branch flotation of Baoshan Copper Mine, the copper-molybdenum mixed concentrate can enter the copper-molybdenum separation system without centralized selection. The grade of the copper concentrate of the final product is increased from 33.18% to 73.37%. The first-grade product rate of minerals increased from 48.48% to 85.14%.

In June 1993, Dongchuan Mining Bureau fell snow flotation plant to reduce the number of flotation machines in No. 3 system by branch flow flotation, and selected 2 mixing tanks, saving electricity costs of about 15.57 million yuan; saving sodium sulfide The cost of Dinghuang and No. 2 oil totaled 323,200 yuan; the economic benefit of increasing silver recovery was 645,800 yuan.

(II) Electrochemical method for slurry research and application

In recent years, the electrochemical process of pulping has carried out a lot of research work at home and abroad, and has made great progress, and is considered to be a promising method for strengthening the flotation process.

In Russia, the electrification treatment (cathode current 70-90A/m ² , energization time 7-10min) can enhance the activation of cyanite by sodium sulfide, and increase its floatability from 56.1% to 81.2%. Electrochemical treatment of xanthate or black drug at a current intensity of 248-320 A/m ² can increase the recovery of copper and nickel by 6.54% and 1.65%, respectively, and the iron content of the concentrate by 4.95%. In the United States, the separation of molybdenum and chalcopyrite was carried out under external control potential. The external control potential was -1.2V, the molybdenum ore was floatable, and the chalcopyrite was not floating. When the potential rose to +0.3V, the molybdenum ore was difficult to float, yellow. The copper mine can be floated. The lime test in the industrial test of Hubei Copper Mountain Copper Mine is adjusted to pH 10-11, the slurry potential is adjusted to 142-189 mV, the copper sulfide mine has no collector, and the less collector (45 g/t) floats. The flotation index similar to the conventional flotation (collector 113.8 g/t) can be obtained.

In addition, the electrochemical treatment of the float water and the return water can not only obtain the float water of the desired composition, but also realize the closed loop of the float water selection, and can reduce the amount of the flotation agent and increase the flotation index.

(III) Application of Inflatable Mixing Process

Ore contains large amounts of pyrite and pyrrhotite ore less copper and copper nickel zinc ore, iron ore by oxidation inflatable vulcanization accelerator, reinforcing the sorting process, to improve the Russian containing a large amount (50% to 60%) pyrrhotite The copper preferential flotation index of high-copper nickel ore in iron ore is aerated for 20min. The copper recovery rate is increased by 4.1%~4.7%, the copper grade is increased by 1%~1.4%, and the dosage of butyl is reduced. 19 to 25 g/t is reduced to 12 to 17 g/t, and the foaming agent is lowered from 20 g/t to 5 to 8 g/t. The Norland Company Concentrator in Canada processes copper, zinc, pyrite and pyrrhotite ore. In addition to the aeration of the slurry in the grinding operation, it also inflates the pulp before the copper-zinc flotation, effectively suppressing the yellow iron. Mine and pyrrhotite increase copper recovery by 4%.

(4) Refining of coarse concentrate or medium mine

Re-grinding coarse concentrates or medium mines is also one of the ways to improve the selection criteria. The Hujiatun Concentrator of Zhongtiaoshan Copper Mine adopts the process of refining the coarse concentrate after re-grinding, and the grade of copper concentrate is increased by more than 4%. In order to obtain superior grade copper concentrate and silver concentrate, Jinduicheng No. 1 Plant has two sections of re-grinding in the selected section. The second section has a fineness of -500 mesh and 82%.

Third, the comprehensive recovery of associated metals

In order to improve economic efficiency and make full use of mineral resources, copper mines at home and abroad attach great importance to the comprehensive recovery of associated elements, especially the recovery of precious metals such as gold and silver.

Dexing Copper Mine used Y-89 yellow medicine developed by Guangzhou Nonferrous Metal Research Institute to replace Dinghuang Medicine, and carried out industrial tests in Zhangzhou Constituency. The results showed that copper concentrate was not reduced under the premise of copper index. The recovery rate has increased by 5.17%. After the third-phase project is put into operation, it will process 90,000 tons of ore per day, increase production of gold by 283.6kg/a, and increase revenue by more than 20 million yuan/a. Hubei Daye Iron Mine adopts a new collector SLS-1, which can effectively improve the recovery rate of copper and gold in mixed flotation operation. Compared with the use of ethyl ketone, the recovery rates of copper and gold increased by 3.75% and 8.16%, respectively.

Flash flotation is one of the effective ways to improve the recovery of gold and silver in copper mines. Flash flotation is the underflow of cyclone classification after grinding. The gold and silver grades in the underflow are higher than the ore and the coarser grain size is recycled. This part of gold and silver can reduce the loss of over-grinding. Two SK-240 flash flotation machines were installed at the Lidwell Copper Concentrator in Indonesia, which increased the recovery rate of gold and silver by 19% and 1.5% respectively. Inflatable pulping of ore containing a large amount of pyrite and pyrrhotite can enhance the flotation of copper and gold; the Saranda plant adopts an aerated pulping process to increase the recovery rate of gold by 15%.

In addition, adjusting the process structure, increasing the fineness of grinding, lowering the pH value and using a combination of agents can also improve the recovery rate of gold and silver in copper ore.

4. Progress in flotation separation technology of copper sulfide ore

(1) Copper sulfide sulfide

Pyrite is often found in copper sulfide ore, both of which have good electrical conductivity and floatability. Ge Baoliang et al. discuss the floatability of chalcopyrite and pyrite and its flotation separation method from the aspects of ore structure, semiconducting properties and electrochemistry. Sulfur Nitrogen No. 9 is used as a collector. At pH=11, The thermodynamic potential of flotation of two minerals is quite different, and it is expected to achieve flotation separation. Self-induced flotation and sulfur-induced flotation can overcome the non-selective adsorption of collector flotation, which is a promising method for separation of copper and sulfur. The Guangxi Rongxian copper mine uses a combination of humic acid and lime to inhibit pyrite. When the copper recovery rate is similar to that of lime alone, the copper concentrate grade is increased from 14% to 18%.

Shi Daomin and other copper mines in the Tongshan copper mine of Daye, using a coarse two-sweep mixed flotation, mixed with alkaline pulp (Ding Huang Yao: Ethyl sulfide = 4:1) to obtain coarse concentrate, and then fine Grinding 96% -200 mesh, the copper and sulfur are fully dissociated, and the sulfur concentrate with sulfur content of 35.95% is obtained, and the low-grade pyrite is comprehensively recovered. Alvarez et al. studied the surface tension of minerals with methanol and studied the flotation separation of a chalcopyrite and pyrite. It was found that a volume fraction of 1% methanol and a small amount of S-701 collector were added to the slurry. With satisfactory results, this process can replace the conventional method of inhibiting pyrite by lime. At the same time, the use of methanol is advantageous for fine flotation, which provides another flotation process for muddy and over-pulverized chalcopyrite.

(2) Copper sulfide molybdenum ore

Nitrogen instead of air medium separation Copper molybdenum is widely used in the world copper and molybdenum plant. Nitrogen can prevent the oxidation of chemicals, especially Na2S, thus reducing the amount of Na2S. The Canadian Gibraltar Copper and Molybdenum Plant uses nitrogen medium to eliminate steaming. To reduce the amount of Na2S from 8kg/t to 2kg/t. Russia used non-polar collector HNOTPNH-3 instead of spindle oil to treat copper-molybdenum ore. As a result, the recovery rate of copper and molybdenum increased by 1% and 0.5%, respectively.

U.S. Patent describes a more complex secondary phosphate and a thio-bis xanthate acetate mixture, copper-molybdenum can increase the separation effect. Also introduced a copper-molybdenum ore preferential copper flotation process, adding sulfite ion and caustic starch to adjust the pH value of 5.2 ~ 6.2, after adding slurry to add alkyl dithio phosphite float copper, copper tailings plus coal oil is selected from molybdenum.

The research and application of organic inhibitors has also achieved great progress. Common low-molecular organic inhibitor consisting of alkanes (short chain), affinity group and a hydrophilic group composed of a solid, such as thioglycolic acid (sodium), mercaptoethanol, thio-uracil tetramethyl pilips oil and introduced to the Austrian side (ORFOM ) D series products for commercial brands. Due to the high price of such agents, large-scale industrial applications are still difficult.

(3) Copper sulfide nickel ore

Canada International Nickel's copper sulphur uses diphenyl hydrazine as a collector for chalcopyrite, and dextrin is used as an inhibitor of pentlandite for preferential flotation, which greatly improves selectivity. Nickel removal rate is less than that under the same conditions. The dextrin blank test was 50% higher.

Russia's Northern Nickel Company successfully applied electrochemical methods to treat high-ice nickel slurry, thereby improving the selectivity of copper-nickel flotation separation. Industrial test results show that the electrochemical treatment method can increase the production efficiency by 15% to 20%, and also reduce the nickel content of the copper concentrate and the copper content in the nickel concentrate.

V. Research and development of joint metallurgical process or chemical beneficiation process

In order to improve the comprehensive utilization level of copper ore, the application of the combined metallurgy process or chemical beneficiation method is an important development trend.

The wet treatment oxidation process widely used abroad is basically a leaching-extraction-electrowinning method (ie, Sx-Ew method). Due to the investment in Sx-Ew method, the process flow is simple, the cost of electric copper is low, and the secondary resources can be fully utilized (the mined areas, the oxidized zone, the exfoliated surface ore, the beneficiation tailings, etc. that cannot be utilized by conventional beneficiation methods) . As a result, the copper production produced by the law has increased year by year, especially in the United States and Chile; currently, copper produced by this method accounts for about 10% of the copper production in Western countries. See Table 1.

Table 1 Copper production in the Western countries Sx-Ew method

With the growth of technology in China and the increasing demand for copper, the wet copper extraction technology has also made rapid progress in recent years. For example, the process of heap-leaching-precipitation-replacement of sponge-copper ore and leaching-extraction-electrowinning in Yunnan Province has achieved good results for many small-scale copper oxide mines. According to incomplete statistics, Yunnan The electricity produced by this method is about 6000t/a. The high-grade copper oxide ore in the southern ore belt of Wushan Copper Mine in Jiangxi Province has a copper grade of 1.29% and an oxidation rate of 72%. The heap leaching-extraction-electrowinning process is used to recover copper. The effective area of ​​the heap leaching field is about 2700m2, and the slope of the heap is generally 35°~40°. The bottom pad of the heap leaching field is made of medium-fine tailings plus plastic film interlayer and coarse tailings three-layer structure. Dikes and excavation drainage flood control ditches are built around the dumping site. According to several years of production practice experience, the height of each layer is generally controlled at 1~1.5m. After the copper leaching of the next layer reaches a certain level, a new layer of ore is pushed. The leaching solution is sent to the sump and pressurized by the pump and precipitated in the two pools. Then it enters the extraction system and is treated by the “two extractions and one reverse” process. The copper-rich liquid is removed into the electrowinning production by the sand filter to remove the organic matter and some impurities. copper. However, due to the late start of the industrial technology of wet copper smelting technology in China, there are still some problems in the process (exposure agent expensive, high consumption, low copper extraction rate and environmental pollution, etc.), which needs further research and resolution in the future.

The Dongchuan Mining Bureau Research Institute has developed a new process for the combined process of hydrothermal vulcanization-flotation and ammonia leaching-sulfurization-flotation. According to the industrial test results of Dongchuan Tangdan copper oxide ore, the concentrate grade and recovery rate of conventional sulfide flotation are 10.09% and 73.09%, respectively. The concentrate grade and recovery rate of hydrothermal vulcanization flotation method can reach 18.97%. And 86.89%, while the ammonia leaching - sulfide precipitation - flotation method of concentrate grade and recovery rate as high as 25.45% and 90.36%.

The hydrothermal vulcanization-flotation process is essentially a development of conventional vulcanization flotation. The principle is to chemically react sulfur with copper oxide mineral under hot pressing conditions to form a stable and easy-to-select artificial copper sulfide mineral, and recover it by using floatation copper sulfide in warm water. Ammonia leaching - sulphide precipitation - flotation method is the addition of elemental sulphur (sulfur powder) during the pressure leaching process. Immediately after the copper oxide mineral is dissolved by NH3 to CO2, it is precipitated into copper sulphide. Pulp directly without solid-liquid separation and distillation, after the recovery of NH3 and CO2, the precipitated "artificial copper sulfide" any original ore and natural copper sulfide flotation recovery together, although the two processes good sorting results However, due to the heating and pressurization conditions, this affects its promotion and application in actual production.

Separation-flotation method is one of the effective processes for the treatment of difficult-to-oxidize copper ore. So far, no copper oxide minerals that can not be treated by this method have been found, but this method has high energy consumption and high cost, so the actual production There are still difficulties in wide application.

In summary, although the mining grade of copper ore has decreased year by year, the grade and recovery rate of copper concentrate has increased year by year with the development of mineral processing technology and technological progress.

The expansion of the scale of the plant will inevitably lead to the enlargement of equipment and the improvement of automation. The development and research of new flotation reagents is an important measure to improve the selection of refractory copper oxide ore. The application of the combined metallurgical process or chemical beneficiation process, especially the leaching-extraction-electrowinning method, is widely used in the production of copper minerals that cannot be solved by conventional flotation.