Discussion on the removal method of nickel, copper and selenium in Jinchuan copper anode mud

Copper anode mud is rich in valuable elements heavy non-ferrous metals, precious metals, rare metals, it has always been much attention. From the recovery of these valuable elements, the world has made a large number of process test research and development and equipment installation improvement, and various experimental research and industrial applications have made significant progress in the 1970s and 1980s. In the past 30 years, China has made great progress in various experimental research and industrial application of copper anode mud treatment. Especially in the research of wet process, great progress has been made in recovering elements such as gold and silver .

Jinchuan Company's current method of processing copper anode mud is similar to other manufacturers in the same industry in China, and it is treated by sulphation roasting-leaching method. Since the actual production using coal-fired heating device and is aging, there is an operation difficult to accurately control the harsh production environment, low metal recovery, many disadvantages of higher production costs. Moreover, during the “Tenth Five-Year Plan” period of Jinchuan Company, the copper production capacity was greatly improved, showing that the copper anode mud treatment capacity is seriously insufficient, so it is necessary to improve the technical transformation and operation technical conditions of the current production.

Second, the characteristics and causes of Jinchuan copper anode mud

(1) Chemical composition and phase composition

Copper anode mud is generally divided into three categories: copper sulfide ore electrolytic anode mud, copper- nickel sulfide ore electrolytic anode mud and copper mixed anode mud. Jinchuan copper anode mud is a copper-nickel sulfide ore electrolytic anode mud, the color is black and gray, the particle size is between 100 and 200 mesh, and mixed with a small amount of sand and other debris. The chemical composition and phase composition are shown in Tables 1 and 2.

Table 1 Jinchuan copper anode mud chemical composition %

Table 2 Composition of main elements of Jinchuan copper anode mud

(2) Features

From Table 1 and Table 2 it can be seen Jinchuan copper anode slime significant features: (1) a nickel-containing particularly high content of selenium with respect to the amount of silver is concerned, are much higher, and with a certain amount of a platinum group Metal; (2) Nickel phase composition is particularly complex, mainly NiO, and a certain amount of high-valence oxide phase; (3) less silver content relative to selenium, part of selenium combined with copper to form Cu ₂ Se, CuAgSe, etc. phase.

(III) Analysis of causes

The Jinchuan copper-nickel sulfide deposit is not only rich in nickel and copper, but also rich in sulfur, cobalt , platinum, palladium , gold, silver and selenium. Table 3 lists the content of associated metal elements in Jinchuan ore.

Table 3 Associated element content in Jinchuan ore g/t

In the nickel fire smelting process, only a certain amount of selenium is lost in the flue gas during roasting, smelting, etc., and the other elements are enriched in nickel-copper sorghum. When sorghum is ground, about 10% of gold, platinum group elements and almost all of silver and selenium enter the copper system. In the process of copper smelting, except for the small loss of selenium in these elements, almost all other elements enter the copper anode mud, which forms the characteristics of the platinum anode metal and the high content of selenium in the copper anode mud.

Now the copper anode mud contains high nickel content, and the phase composition is complicated. It also needs to be analyzed from the sorghum grinding and floating. The copper concentrate produced by sorghum grinding and floating contains 65%~70% copper and contains nickel. % to 5%. After smelting and refining in a reverberatory furnace, the nickel in the obtained copper anode plate is mainly in the form of Ni ₃ S ₂ , Ni ^[9] . During the electrolysis of copper, nickel mainly enters the electrolyte, and a small amount of nickel enters in the form of NiO and NiS. Copper anode mud, copper anode mud contains 10% to 15% of nickel and 50% to 60% of copper. Since 1988, the copper system has gradually adopted self-heating furnace smelting and Caldo furnace blowing. Nickel has a strong oxidizing atmosphere during the blowing process, mainly in the presence of NiO phase, which leads to nickel in the copper anode slime with NiO and (Ni , Fe) ₃ O ₄ and other forms exist, these phases do not enter the electrolyte during copper electrolysis, but directly or further oxidized into high-valent oxides into the copper anode mud, and a small part of the copper in the anode plate enters the copper anode mud This formed the Jinchuan copper anode mud with a particularly high nickel content and complex phase composition.

Third, Jinchuan copper anode mud current production process

Jinchuan Company has been producing copper anode mud since 1971. For the treatment of this material, many domestic research institutes have carried out various experimental research work. In 1987, the process of processing secondary copper anode mud was put into production. The original design scale was The 40t secondary anode mud is treated annually. After several years of production operation, it is considered that the loss of silver and selenium is greatly lost in the process of melting and electrolyzing the secondary anode mud, and it adds a burden to the production of the main process. Thus, in 1990, the anode mud was directly treated with a small kiln. With the change of anode mud composition and the commissioning of the new system in the copper electrolysis workshop, in 1996, the expansion and transformation were carried out, so that the copper anode slime can be calcined at a rate of 500t/a, because the anode mud needs to be re-fired twice or even three times. The actual processing capacity of the anode mud can only reach 300t/a. At present, the process flow of copper anode mud treatment is shown in Figure 1.

The main problems in the current production process are the elimination of silver and selenium, and the low nickel leaching rate. The reasons are mainly analyzed: (1) the temperature control of the two roastings is inaccurate, the time is high and the time is low, mainly because the temperature is low, which leads to the incomplete removal of selenium; (2) the raw material is added during the acid leaching process ( The uncalcined copper anode mud sinks silver, which makes the phase composition of the secondary calcined material more complicated, and the purpose of high selenium removal rate and high nickel leaching rate cannot be achieved.

Fourth, the process of processing similar materials

There are very few copper anode slime similar to Jinchuan in China. The copper anode slime of the foreign Finland Outokumpu and the former Soviet Moscow copper plant is similar to the Jinchuan composition ^[1] . Its chemical composition is shown in Table 4.

Table 4 Foreign copper anode mud chemical composition %

The Moscow copper plant used the flotation method to separate the precious metal from the nickel-copper selenium element in the copper anode mud, and later studied the method of hot-press leaching copper anode mud. According to another data, the copper anode slime expansion test containing (%): Ni8.21, Cu16.8, Pb19.5, Sb9.8, Ag11.4, Se2.3, Te1.5 is processed at T=437K. Po ₂ =0.2MPa, C _{sulfuric acid} = 125g / L, Ï„ = 120min, can achieve a high leaching rate: η _Ni = 98%, η _Cu = 98%, Ni, Cu content in the leaching residue is 1 %the following.

Outokumpu's handling of copper anode mud also began large-scale process improvement and equipment improvement research in the early 1980s, and was put into industrial application. In the next 20 years, the technology and its technology will be widely promoted to the world. Equipment (including automation control, etc.). Outokumpu copper anode mud treatment methods have been used in some or all of the manufacturers in many countries.

The Outokumpu copper anode mud treatment method is oxidized acid leaching copper, pressurized acid leaching nickel and sulfurous acid roasting. Because of the high gold and silver content of the raw materials and the high efficiency of copper oxidizing acid leaching, Outokumpu has adopted this cost-effective method to remove copper from copper anode slime.

The nickel removal process was carried out by hot sulphuric acid leaching method before 1985. The temperature was 150-200 ° C for 8 h. After the reaction was completed, it was placed in a water leaching tank to dilute and filter to obtain leaching slag containing less than 1% nickel and copper. . The nickel is subjected to pressurized acid leaching, and the technical conditions are a temperature of 150 to 180 ° C, a pressure of 0.7 to 0.8 MPa, and a time of 2 to 4 hours. After nickel removal, the slag contains nickel below 1%. The process has the following advantages: (1) reduced acid consumption; (2) reduced volume of evaporation and concentration; (3) reduced energy consumption; (4) reduced corrosion of equipment; (5) high metal recovery rate The production cost is low.

Selenium was distilled off process prior to its improvements are sulfuric acid roasting steaming selenium, i.e. the slurry of concentrated sulfuric acid copper anode mud, and then into the roasting furnace fed cast iron plate, the firing temperature 600 ℃, time 24 ~ 48h. This method has a large number of SO ₂ emissions due to severe corrosion and roasting, resulting in many equipment failures and serious environmental pollution. To this end, the company focused on the development of a sulfite roasting de-selenization method, which is to add the anode mud to the roasting tray, stack it in the roaster, and pass the heated SO ₂ gas and air (or oxygen). The mixed gas, and the flue gas is forcedly circulated in the furnace to transfer the heat of the flue gas to the charge, the heat efficiency is high, the gas generated by the reaction is absorbed by the dilute sulfuric acid circulating through the ejector, and after the ejector, the selenium is in the vertical reaction tube and the circulation Separation in the tank, regular filtration, washing, and drying, can produce selenium powder with purity ≥99.5. The detoxification process of Outokumpu copper anode mud is shown in Figure 2.

The advantages of this method are significant: reduced flue gas volume, reduced waste acid, improved working environment, and reduced corrosion, reducing maintenance and operating costs. This Outokumpu roaster has been used in Chile, India, Sweden, the United States, the former Yugoslavia, Zambia and other countries. Updated improvements in the application of Chilean state-owned mining companies: improved selenium precipitation system, reduced suspended solids in circulating fluids, reduced pipe crusting, reduced pump wear; modified circulation piping system, reduced roasting furnace shutdown time, improved Processing capacity. The flow chart of the improved recycling equipment is shown in Figure 3.

V. Process selection of Jinchuan copper anode mud treatment

(1) Principles of process selection

The general principle of selecting the process flow is advanced and reliable technology and economical and reasonable. The specific aspects can be as follows: (1) The process is simple, the process is advanced, and the comprehensive utilization rate is high; (2) The technical and economic indicators are high, and the materials and energy consumption are low; (3) The equipment is easy to manufacture, convenient for maintenance and maintenance, (4) good working conditions and environmental protection; (5) the relationship between investment and economic benefits.

(2) Jinchuan copper anode mud treatment available for selection

According to the high nickel content of Jinchuan copper anode mud, there are only two processes that can be selected and successfully applied in industry: one is traditional sulphation roasting de-selenium, acid leaching de-copper nickel; the other is Pressurization leaching removes copper and nickel, and sulfite roasts to remove selenium. Because the copper anode mud of Jinchuan Company is very high relative to silver, the blasting acid leaching pretreatment can not achieve good copper removal effect, and experimental research has also proved this point ^[8] . Therefore, whether using sulphation roasting or pressurized acid leaching, the de-nickel de-nickel should be completed in the same process. The principle flow chart of the two processes for treating Jinchuan copper anode mud is shown in Figure 4 and Figure 5, respectively.

(3) Comparison of the two processes (see Table 5)

Table 5 Comparison of characteristics of Jinchuan copper anode mud treated by two kinds of processes

(IV) Application of sulphate roasting and leaching process of Jinchuan copper anode slime

Jinchuan has used sulfation roasting and leaching processes to treat copper anode slime for more than ten years of production practice and experience, and the pressure leaching process has achieved industrial production in Jinchuan. Sulfite roasting and de-selenization has not been done in Jinchuan. Therefore, on the basis of the original production, it is a very stable and reliable process choice to properly optimize the technical conditions, strengthen the production process, increase the metal recovery rate, and reduce the production cost.

(5) Development direction of Jinchuan copper anode mud treatment process

It can be seen from the comparison of the two processes in Table 5 above that the treatment of copper anode slime by pressure leaching process is a technologically advanced and economically significant process, and Jinchuan Company is currently conducting an industrial test of nickel concentrate ore leaching, this test The success will drive the development of the Jinchuan pressure leaching process; sulfite roasting can be carried out for small experimental studies or direct introduction of technology. In summary, the development direction of Jinchuan copper anode mud treatment should be the comprehensive recovery process of pressure leaching and sulfiting roasting.

Conclusion

(1) Jinchuan copper anode mud has the characteristics of high nickel content, complex phase composition, high selenium content and high silver content, and difficulty in removing copper. Therefore, the treatment process is also complicated;

(2) The treatment of Jinchuan copper anode mud by two roasting and two leaching processes is safe and reliable, but it must bear heavy pressures such as environmental protection and equipment loss, and should look for new technologies with environmental protection standards and comprehensive recovery;

(3) The use of pressurized acid leaching and sulfiting roasting can solve environmental problems, improve the operating environment, and reduce energy consumption and acid consumption in the production process. It should be the development direction of Jinchuan copper anode mud treatment.

references

1. O.Hyrarinen, Outokumpu's Poly Refinery recovers selenium and precious metals from copper anode mud, Jinchuan Translation Collection, June 1982

2, Kato Kazuo, etc., copper anode mud roasting process improvement, non-ferrous smelting, 1989 (2)

3, heavy non-ferrous smelting Design Manual. Precious metals mercury, tin and antimony volume, Metallurgical Industry Press, November 1996

4, Sun Guoxiong, roasting-sulfuric acid, nitric acid leaching process for the treatment of nickel-containing copper anode mud, the first national nickel-cobalt conference proceedings, September 1987

5. Yang Rong, Production Practice of Oxygen-Enriched Smelting Process of Nickel-Containing Copper Concentrate, Jinchuan Science and Technology, 1992(4)

6. To Tianlong, an industrial test to improve the current density of Jinchuan copper electrolysis and its economic benefits, Jinchuan Science and Technology, 1997 (4)

7. Copper electrolysis anode mud autoclave sulfuric acid leaching test, non-ferrous smelting, 1992 (3)

8. O. Hyrarinen et al., Selenium is recovered from the anode mud of a copper refinery. Nonferrous smelting, 1991(1)

9, Outokumpu's anode mud treatment, non-ferrous smelting. 1993(1)

10. Xu Chuanhua, Outokumpu's smelting technology. Nonferrous smelting, 2000(5)

11. Separation of Selenium, Tellurium , Platinum and Palladium in the Precious Metals Workshop of the State-owned Mining Company of Chile, Nonferrous Metals, 1993(5)

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