Research and Practice of Dexing copper mine gold recovery
Wu Qiming Yin Qihua
(Dexing Copper Mine, Guixi, Jiangxi 334224)
Abstract This paper introduces the achievements of Dexing Copper Mine in improving gold recovery rate. The effects and shortcomings of various measures were analyzed, and the successful experience of improving the gold recovery rate was summarized.
Key words gold recovery, flotation, associated element, monomer, dissociation, low alkalinity, copper and sulfur separation
Dexing Copper Mine is a large-scale open-air porphyry copper mine. In addition to copper, there are many valuable elements associated with gold, silver , molybdenum and sulfur. The ore body contains 0.46% copper and 0.193g/t gold. The reserves are huge. During the beneficiation process, gold, silver and molybdenum are recovered in copper concentrate along with copper and recovered. For a long time, the mine has carried out more exploration and practice to strengthen the recovery of associated elements, especially the recovery of associated gold, and achieved good results, and the gold recovery rate has been gradually improved (Table 1). In particular, the recovery rate of gold recovery rate started in 2003, through the system, a large number of practices, has a deep understanding of how to strengthen the recovery of associated gold, summed up a series of production organization regulations and process technology standards, gold production organization and orderly The stability of the index is greatly improved. At present, the gold recovery rate is stable at around 66%, the associated gold production is 5300kg/a, and the output value is more than 500 million yuan, which has made an important contribution to improving the economic benefits of the mine.
Table 1 Recovery rate of gold in Dexing Copper Mine since the 6th Five-Year Plan
Time | 1981 | 1981~1985 | 1986~1990 | 1991~1995 | 1996~2000 | 2001~2005 |
Gold recovery rate /% | 40~50 | 50~60 | 62~66 | 62~68 | 65~68 |
1. Study on the occurrence and distribution of associated gold
Since the 1980s, it has cooperated with various research institutes. A lot of researches have been carried out on the associated gold (silver) geological resources, occurrence status and distribution law of the deposit, so that everyone has a systematic understanding of the status of gold (silver) resources, improve production organization, optimize processes and strengthen gold and silver in the future. Recycling provides an important basis.
1.1 Gold mineral type and embedding characteristics
Gold minerals are known in the ore as natural gold, silver gold, hoof gold and arsenic gold, with the most natural gold. According to its inlay characteristics, it can be divided into three categories: inclusion gold, intergranular gold and crack gold. From the comparison of the quantity of gold mineral inlays, the gold between the grains is the most, followed by the gold and fissure gold, but the weight of gold minerals in the form of inlays is the highest in the gold, and mainly in the metal sulfide minerals. packet body is present; most of the gold interparticle disseminated gold between natural mineral particles, in common between the metal sulfide minerals and gangue minerals; gOLD fissure microcracks present in the pyrite, quartz and carbonate minerals Filled and replaced, the shape is extremely irregular, and the particle size tends to be large.
1.2 Chemical phase analysis
Associated gold exists in ore minerals in various forms. Except for monomer gold and continuous metallographic phase, there are a certain amount of mineral gold and dispersed gold, and gold exists in the form of minerals (monomer gold + continuous body gold) + mineral gold) 90% and 86% in porphyry ore and phyllite ore, respectively, and dispersive gold is 10% and 14%, respectively. Under the condition that the ore grinding fineness meets the selected grain size requirement (-0.074mm accounts for 65%), the bare gold (monomer gold + continuous birth gold) in porphyry and phyllite ore accounts for 82% of the total gold and 73%, undissociated gold minerals are mainly found in sulfide minerals and silicate minerals, and mainly in the form of mineral gold.
1.3 Particle size characteristics of gold minerals
The gold mineral has a maximum particle size of 110 μm and a minimum of 0.6 μm, mostly in the range of 10 to 30 μm. In 1990, the research results of the Institute of Mineral Geology of the original color metal company showed that the distribution of gold minerals in different types of ore in different sections was very different. In 1997 and 1999, the Jiangxi Institute of Geology studied the occurrence and distribution of gold and silver associated with the main phyllite of the porphyry east and west porphyry in the Nanshan 0 line of the Tongchang mining area. The results show that the average size of gold minerals in the porphyry ore is 6 μm. , wherein the fine fraction (-10 μm) accounts for 64.08%, and the ultrafine fraction (-2 μm) is 33.98%; the average particle size of the gold mineral in the phyllite ore is 28.59 μm, wherein the fine fraction (-35 μm) is 68.75. %. The overall particle size distribution is shown in Table 2.
Table 2 Gold mineral particle size distribution
Size/μm | +70 | -70+60 | -60-+50 | -50-+40 | -40-+30 | -30-+20 | -20-+10 | -10 |
content/% | 2.4 | 1.3 | 3.5 | 6.7 | 5.7 | 26.4 | 31.7 | 22.3 |
1.4 Gold distribution in ore
Whether it is porphyry ore or phyllite ore, chalcopyrite is the main carrier mineral of gold, followed by pyrite, and gold is relatively low in gangue minerals. See Table 3 for the geological distribution and process distribution of gold.
Table 3 Gold geological distribution and process allocation
Ore type | Distribution | Gold share /% | |||
Monomer gold and continuous gold | Chalcopyrite | Pyrite | Gangue stone | ||
porphyry | Geological distribution | - | 40~58 | 15~30 | 30~35 |
Process distribution | 69.86 | 7.91 | 14.53 | 7.70 | |
Thousands of rocks | Geological distribution | - | 58~68 | 13~18 | 20~25 |
Process distribution | 66.41 | 14.54 | 9.37 | 9.68 | |
It can be seen from the process balance of ore gold that the main carrier mineral of gold is chalcopyrite and pyrite, plus monomer gold and continuous gold, the ideal recovery rate of gold is the highest expected value of 78%~81%, the second expectation value. It is 73%~76%. [next]
2 , mineral processing technology research
2.1 Crude concentrate re-grinding copper and sulfur separation process
Before 1978, a grinding process was used, one grinding and one flotation. The dissociation degree of useful minerals was only about 48%, and the copper concentrate grade and copper and gold recovery rate were very low. The crude concentrate re-grinding copper-sulfur separation process is economically solved by the implementation of coarse ore re-grinding, and the problem of low dissociation of useful mineral monomers is solved economically. The successful application of this process has increased the copper concentrate grade from about 12% to over 24%, the copper recovery rate from 80% to about 84%, and the gold recovery rate from about 55% to about 60%. This process has been used until now, creating great economic benefits for the company. The process flow before and after the improvement is shown in Figures 1 and 2.
Figure 1 Process before 1978
Figure 2 Process flow of re-grinding copper and sulfur in coarse concentrate
2.2 Low alkalinity copper and sulfur separation process
The low-alkalinity copper-sulfur separation process was carried out for the high pH value of copper-sulfur separation operation and the serious loss of associated elements. In 1995, it began to promote its application in production and continuously improved in practice, effectively reducing the amount of lime (Figure 3), improving the stability of the index, and reducing the loss of associated elements such as gold in the process of copper and sulfur separation. A new breakthrough in the recycling of associated elements.
Figure 3 Lime consumption of Dexing Copper Mine from 1991 to 2005
2.2.1 Replace the lime with a CTP part
CTP is a small molecule inhibitor that can selectively inhibit pyrite at a lower pH (10~11), but has no inhibitory effect on copper minerals, thus achieving lower alkalinity conditions. The separation of copper and sulfur greatly reduces the consumption of lime and facilitates the recovery of associated elements such as gold. Industrial tests have achieved good results: the gold and silver recovery rates are 3.38% and 2.56% higher, respectively, compared to the pure lime process in the Pazhou plant. After the application of CTP in Dashan Concentrator in 1995, the lime consumption was rapidly reduced from the original 8 kg/t to below 5 kg/t, and the production index was stable. It was promoted and applied in the whole mine in 1998. [next]
2.2.2 Application of K202 auxiliary inhibitor
K202 is also a copper-sulfur separation auxiliary inhibitor, which can achieve copper-sulfur separation at a lower pH (10~12), which can greatly reduce the amount of copper and sulfur separated lime (only 29% of pure lime process). It indicates that the copper, gold and silver indexes are better than the lime process. However, in the practical application of the product, the agent is more susceptible to oxidation and the index fluctuates greatly, so it cannot be promoted and applied.
2.2.3 Implement lime dispersion addition and optimize addition ratio
In order to avoid local saturation of lime, the recovery of associated elements is affected. According to the process requirements, there should be three added points for the separation of lime and sulfur from work: rough selection, fine one and fine two, and the requirements for the addition ratio are clearly defined. However, because the lime milk addition pipeline is easy to scale, the cleaning workload is large, and the flow rate of each operation point is roughly distributed manually, which makes it difficult to achieve normal and accurate dispersion addition. The site is often only added in the second, which causes the process local lime to be severely saturated, which greatly affects The recovery of associated elements such as gold. Through continuous exploration and practice, the flow rate of lime milk is increased by increasing the height difference, the open channel transportation, reducing the curve, etc., and the fouling time is delayed, and the observation and cleaning are facilitated, the stability of the lime milk addition is improved, and the dispersion addition is initially realized. After that, the automatic addition and transformation were carried out to realize the accurate control of the total addition amount and the flow rate of each point, and gradually explored the optimization and addition ratio to finally determine the rough selection: Jingyi: Jing 2 = 2:1:1 distribution ratio was further realized. The convenient, reasonable and accurate addition of lime milk is beneficial to reduce the unit consumption of lime, avoid the adverse effects of partial saturation of lime on the recovery of associated elements such as gold, and further improve the stability of the separation index of copper and sulfur.
2.2.4 Add a small amount of selective collector (butylamine black drug, AP ) in the second stage
In order to increase the difference in floatability of copper and sulfur minerals, it is difficult to reduce the separation of copper and sulfur. By adding a selective collector, the copper concentrate grade and the recovery of associated elements such as gold and silver are taken into account. When the copper concentrate grade is similar, the recovery rate of the second-stage gold is increased by about 1.5%.
2.3 Asynchronous mixed flotation process
The advantage of the asynchronous mixed flotation process for the copper-sulfur mixed flotation process is that different collectors are used in stages, and different coarse concentrates are obtained and treated separately to achieve “easy harvest and early harvestâ€, and copper and gold are improved. Comprehensive index of silver and molybdenum: The first step is to use a selective collector XF-3 to obtain a one-step coarse concentrate with a copper recovery rate of 80%. The second step is still to use yellow medicinal enhanced flotation to recover poor floatability and solution. Insufficient copper, gold and other minerals, get a two-step coarse concentrate. The two parts of coarse concentrate are treated separately, and the one-step coarse concentrate can realize the separation of copper and sulfur under the condition of low alkalinity, which is very beneficial to the recovery of associated elements. The process flow is shown in Figure 4. The asynchronous mixed flotation process has achieved good indexes in both industrial tests, especially in improving the recovery of associated elements. The recovery rate of gold and molybdenum increased by 2.21% compared with the original process. 17.65%, but the process is more complicated, the foam is sticky, the two-step coarse concentrate is too large, and the operation control is difficult, and further improvement is needed.
Figure 4 Asynchronous hybrid flotation process flow chart
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2.4 step-by-step priority flotation new process
The new step-by-step flotation process (Fig. 5) has the same idea as the asynchronous mixed flotation process. It also uses different collectors in stages to obtain different coarse concentrates and treat them separately to achieve “easy harvest and early harvestâ€. However, there are significant differences with the former, mainly including: 1) One step of coarse grinding is no longer ground, avoiding over-grinding of dissociated copper minerals, and is conducive to the recovery of associated elements such as copper and gold. 2) One step and one tailings are all returned to the two-step re-grinding to further dissociate the copper-gold minerals, while avoiding the circulation of the continuous body in one step. The principle of “easy to accept and early harvest†is more thorough, which is beneficial to copper and gold. Recycling of associated elements and obtaining a one-step concentrate with a higher grade. The one-step copper concentrate grade in the step-by-step process is easily more than 28%, which is higher than 25.33% of the asynchronous mixed flotation process. 3) The crude concentrate yield is 7%~8%, which is equivalent to the mixed flotation process. The asynchronous mixed flotation process is high, reaching 9.63%, and the separation pressure of copper and sulfur is very large. 4) Step-by-step priority flotation process One-step two-stage occupation of equipment is rarely asynchronous hybrid flotation process. The number of devices used in the second and second stages is the same as the two-step process. 5) The step-by-step priority flotation process is simpler and more conducive to on-site implementation. The process achieved good results in small-scale experiments. Compared with the mixed flotation process, the copper concentrate grade increased by 1.83%, and the copper and gold recovery rates increased by 0.11% and 2.75%, respectively. Since the application of this process in Dashan in September 2001, it has not only solved the problem that the grade of Dashan copper concentrate is difficult to improve, but also improved the copper concentrate grade from 24% to over 25%, and the enrichment ratio and recovery rate of molybdenum The molybdenum enrichment ratio is increased from about 30 times to 45 times or more, and the molybdenum recovery rate is increased from 50% to 60% to 65%. However, due to the constraints of Dashan flotation equipment configuration, this process has not been fully reflected in improving the recovery rate of copper and gold.
Figure 5 Step-by-step priority flotation process flow chart
2.5 Y-89 application
Sulfide ore is the main carrier mineral of gold. In the existing process, strengthening a portion of sulfide minerals is critical to improving gold recovery, and the use of high-efficiency collectors is one of the effective ways. Dexing Copper Mine has carried out a large number of research and test work in this area, among which the new drug Y-89 has been promoted and applied. Y-89 is a long-chain high-grade xanthate developed by the Guangzhou Institute of Nonferrous Metals in the early 1990s. It has strong absorption power for copper-gold minerals. The results of industrial tests showed that the gold recovery rate was improved by about 5% compared with the ethyl butyl xanthate in the 1:1 ratio of butyl xanthate and ethyl xanthate. Y-89 has been used in Dexing Copper Mine for many years, which has effectively promoted the improvement of gold recovery rate. However, due to its strong harvesting power, it has a certain impact on the separation of copper and sulfur, which is not conducive to the further improvement of copper concentrate grade and its use.
3 Correlation between copper and gold flotation indicators
As an important companion element, gold has a close relationship with copper and sulfur minerals. The study of gold occurrence status shows that gold and copper have a close positive correlation. Through statistical analysis of a large number of experimental data and production data, it is found that there is a clear correlation between copper and gold flotation indicators. It can be seen from Fig. 6, Fig. 7 and Fig. 8 that, regardless of the test data (feeding -0.074 mm accounted for 97.8%, different copper concentrates were obtained by controlling the lime addition amount to adjust the pH value of the slurry and appropriately increasing the number of selections. Grade) is also the production data. As the grade of copper concentrate increases, the gold recovery rate decreases gradually. There is a significant negative linear correlation between the two, while the recovery rates of copper and sulfur and gold recovery are more obvious. The positive correlation, and the positive correlation of copper-gold recovery rate is higher than the sulfur-gold recovery rate correlation, which is consistent with the results of gold occurrence research. Within a certain range, these correlation analysis have certain guiding significance for production. In fact, it has been verified and applied well in the production process in recent years.
Figure 6 Relationship between concentrate recovery rate and copper grade
A-test data; b-production data
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Figure 7 Relationship between concentrate recovery rate and copper recovery rate
Figure 8 Relationship between concentrate recovery rate and sulfur recovery rate
4 Conclusion
1) The gold minerals in the Dexing copper ore body have fine grain size, and increasing the dissociation degree of mineral monomers is a prerequisite for obtaining better indicators. The crude concentrate re-grinding copper-sulfur separation process economically solves the problem that the ore is under-grinded and the dissociation degree of useful mineral monomers is low by implementing coarse re-grinding. Increase gold recovery from 55% to 60%.
2) The implementation of low alkalinity copper and sulfur separation process, the lime unit consumption is gradually reduced from 7 kg/t or more to the current 3 kg/t, which greatly improves the second stage flotation environment and reduces gold and molybdenum. The loss of associated elements in the copper-sulfur separation process is a new breakthrough in the recovery of associated elements such as gold.
3) Asynchronous mixed flotation process and step-wise preferential flotation process By adopting different collectors in stages, different ways of processing the coarse concentrates are obtained, which realizes “easy to accept early harvest†and can significantly improve gold and molybdenum recovery. rate.
4) The gold recovery rate has a significant positive correlation with the recovery rate of copper and sulfur. The use of high-efficiency collectors to enhance the recovery of a section of sulfide minerals is an effective means to increase the recovery rate of copper and gold.
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