China Nonferrous Metallurgy

Abstract:Taking copper smelting industry as an example, this paper focuses on the relationship between energy consumption and carbon emission. Firstly, the relevant accounting standards, accounting boundaries and accounting methods of copper smelting energy consumption and carbon emission are sorted out; Secondly, the difference and correlation between copper smelting energy consumption and carbon emission are analyzed. The difference is mainly reflected in the boundary range, such as energy-consumed medium and process emission, and the correlation is mainly reflected in the linear relationship between carbon emission and energy consumption value; Thirdly, based on typical copper smelting process cases and Chinese industry statistical data, the comprehensive energy consumption and carbon emission are estimated, and the near linear correlation between them is verified. The ratio of carbon emission calculated based on national grid emission factor to comprehensive energy consumption calculated by equal value is about 2.0; Finally, suggestions on standard revision are put forward from the aspects of accounting boundary, power conversion coefficient and emission factor value, for reference by the staff of relevant departments.

Abstract:Waste PCBs contain a large number of harmful substances such as heavy metals, polyvinyl chloride and brominated flame retardants. There is still no appropriate technology for treating the uneconomic glass fiber and epoxy resin therein, resulting in secondary pollution. In this paper, a self-designed rotary pyrolysis furnace was used for low-temperature anaerobic pyrolysis of waste PCBs in inert atmosphere. The effects of final pyrolysis temperature, holding time, heating rate and material size on the pyrolysis rate of waste PCBs and pyrolysis product yield were investigated. The experimental results show that the waste PCBs can be fully pyrolyzed under the conditions of pyrolysis temperature of 600℃, pyrolysis time of 45min, heating rate of 10℃/min and particle size of 50mm×50mm. The pyrolysis products are as follows: pyrolysis oil, which can be used as fuel after dehalogenation treatment; pyrolysis residue, a good smelting raw material; and pyrolysis gas, an excellent clean energy after impurity removal treatment.

Abstract:Electrolytic copper foils serve as crucial raw materials of CCL, PCB and lithium ion batteries, and ultra-thin copper foils will become the leading product in the market. By adjusting process parameters of electrolytic copper foil and controlling the proportion of additives, high purity and double shiny ultra-thin copper foils with uniform structure, great performance and a thickness of 4.5μm are produced, and its structure, appearance and performance are analyzed by using XRD, SEM, roughness meter and universal testing machine. Results show that ultra-thin copper foils are of high purity (99.98% Cu) and have an extremely low content of impurities (＜0.001%). They have uniform surface density and thickness with a fluctuation within 1%. The (111) texture that affects their tensile strength is preferred orientation and the coefficient is 58.8; the (220) texture coefficient that affects their elongation is relatively low. The matte surface of double shiny ultra-thin copper foil is evenly distributed by small particles of hilly structure, and the horizontal and vertical roughness fluctuates within a reasonable range. Ultra-thin copper foils boast excellent mechanical properties, with tensile strength of 671.54±20MPa and elongation at break of 5.81%±3.2%, which are remarkably better than those of 6μm and 8μm copper foils in the market. Besides, ultra-thin copper foils can acquire high-temperature oxidation resistance after passivation.

Abstract:In view of the issues existing in the treatment of acidic heavy metal-bearing effluent produced in the process of lead-zinc smelting by lime neutralization, sulfidization process and their combined processes, the method combining sustained-release sulfidization process with staged neutralization is proposed in this paper, and a new sustained-release sulfidizing agent is used to carry out the purification and heavy metal removal test of acidic effluent from lead-zinc smelting, and the following conclusions are drawn: under the conditions that the dosage of sustained-release sulfidizing agent is twice the theoretical demand, the solution acidity is 60g/L, the sulfidization reaction time is 40min, and the stirring speed is 300r/min, as well as under normal temperature and pressure, the removal rate of heavy metal ions As, Tl, Cd in the acidic effluent can reach more than 99% and Hg removal rate is above 90%. The solution resulting from neutralization meets the discharge limit requirements in the Emission Standard of Pollutants for Lead, Zinc Industry (GB 25466—2010), and the produced gypsum residue reaches the level of recycling.

Abstract:Complex arsenic-containing gold-copper concentrate is treated by pyrometallurgical technologies such as oxygen-enriched bottom-blowing smelting technology and oxygen-enriched side-blowing smelting technology which are more conductive to removal of impurities by oxidation due to a high oxygen potential of these two technologies. However, the oxygen-enriched bottom-blowing smelting technology has such shortcomings as large air leakage, high-content sulfur trioxide in off-gas and incapability of cooling subsequent off-gas directly by spraying water for arsenic recovery. This paper introduces a company s production practice of complex arsenic-containing gold-copper concentrate processed by oxygen-enriched side-blowing smelting technology from four aspects, namely composition of raw materials, process flow, main equipment and production operation. And the practice proves that the oxygen-enriched side-blowing smelting technology boasts technical advantages, including capability of handling gold-copper concentrate with a high arsenic content, high direct metal recovery rate and high-grade arsenic recovered from off-gas. Good production effects have been obtained after optimization and improvement of issues in the practice such as large slag output, short service life of the top of copper bath and slag bath, production of foaming slag and inadequate monitoring of furnace body expansion. This practice sets an example of complex arsenic-containing gold-copper concentrate processed by oxygen-enriched side-blowing smelting technology for the same industry.

Abstract:The copper to sulfuric acid ratio is a key index to affect normal production of copper electrolysis. The imbalance of copper to sulfuric acid ratio can easily intensify the polarization of concentration, enhance the concentration of impurity ions and thereby affect the cathode copper quality. This paper tracks and investigates the trend in the variation of copper ion concentration, sulfuric acid concentration and concentration of As5+, Sb3+, Bi3+ and Ni2+ in different areas and at different time during the copper electrolysis process as well as corresponding cathode copper quality, analyzes the impact mechanism of copper to sulfuric acid proportion on cathode copper quality, and draws the conclusion as follows. Imbalance of copper to sulfuric acid ratio will intensity the enrichment of impurity ions and facilitate formation of granules on the surface of the cathode copper. A proper ratio of copper to sulfuric acid can improve the appearance quality of cathode copper; insufficient volume of purified electrolyte will accelerate the hydrolysis of various salts in the electrolyte and cause imbalance of copper to sulfuric acid ratio, while increasing the volume of purified electrolyte is beneficial for maintaining normal copper to sulfuric acid ratio. The fine property of electrolyte and uniformity of ion concentration can be improved by the means of enhanced electrolyte convection, which prevents the imbalance of copper to sulfuric acid ratio in the electrolyte; when the size of impurity ions in the electrolyte is large, the copper to sulfuric acid ratio shall maintain in the range from 0.25 to 0.3.

Abstract:The increasingly high impurity content in raw materials for copper smelting has resulted in more than more impurities contained in copper anode plates. The conventional electrolytic technology for treating high-impurity anode plates has problems of low yield rate of Grade-A copper, low production capacity and high energy consumption, etc. Although the ultra-high current density electrolysis technology developed in recent years has basically solved the problems in the electrorefining of high-impurity anode plates, it’s still trapped by the liable blockage of electrolyte feeding device, high cell voltage and DC power consumption, among other problems. Based on the existing high current density electrolysis technology, Xiangguang Copper Co., Ltd has made innovative modification to the electrolysis device, electrolyte circulation system and electrolyte filtration system, updated and optimized the technology in actual practice, developed standard operating procedures and finally realized the ideal production goals, i.e., stable operation at the current density of 420~580A/m², Grade-A copper yield rate of 100%, spent anode ratio of less than 13%, and standard coal consumption of 51.91kg per ton of copper.

Abstract:Copper electrolyte flow field is of great importance to the ion concentration, temperature distribution and anode slime settling in electrolytic cells. In this paper, Fluent-based numerical simulation has been conducted on a domestic copper electrolytic cell in terms of three different feeding modes of electrolyte, i.e., one-side parallel flow, bidirectional parallel flow and new-type parallel flow. The simulation results show that in the one-side parallel flow feeding mode, the electrolyte flows from bottom to top, which is easy to stir up the anode slime settled in the cell, causing low-purity of cathode copper and unfavorable for the reasonable recovery of anode slime; in the bidirectional parallel flow feeding mode, the electrolyte flows from top to bottom, the flow velocity at the inlet is high, the velocity difference in the flow field may cause backflow, unfavorable for anode slime settling; the new-type parallel flow is an upgrade of the bidirectional parallel flow, in this feeding mode, the number of feeding and discharge ports is reduced, the inlets on two sides is different in height, which makes most of electrolyte enter between plates and reduces the flow velocity at the cell bottom. It boasts the advantages of uniform and stable velocity at flow field, short electrolysis cycle and convenience in maintenance.

Abstract:The high-pressure acid leaching process used to treat laterite-nickel ore with low content of magnesium oxide. The Ni can be precipitated with the hydroxides or sulfides from the leaching solution after Fe&Al removing. This paper proposes to use calcium hydroxide as a precipitant, combined with alkali activation controlling technology, under the appropriate calcium hydroxide dosage coefficient, to study the properties of the precipitation products, nickel cobalt hydroxide and calcium sulfate, under different activation times. Finally, it is determined that the best activation time is 3~4min. At this time, the precipitation rate of nickel can reach more than 80%, and the physical properties of calcium sulfate are also suitable for the subsequent separation process.

Abstract:Raw materials for zinc smelting used by Bayannaoer Zijin Nonferrous Metal Co., Ltd. are characterized by a high content of Fe, Co and S and a low content of Zn. Supernatant produced from neutral leaching contains a high content of cobalt up to 50~100mg/L. In order to control the cost, the company makes an exploration of the cobalt removal process by antimony salt, β-naphthol and new reagent and draws a conclusion as follows. During the practical production, cobalt removal and purification process by antimony salt is characterized by a frequent fluctuation of cobalt content, unstable cobalt removal, larger consumption of zinc powder and great difficulty in on-site operation. Hence it is suitable for zinc sulfate purification process with a low cobalt content Cobalt removal and purification process with naphthol shows a good effect, with stable system and simple on-site operation, but it only works for cobalt removal rather than other impurity elements. When impurity elements such as Fe, Ni, As and Ge in the zinc sulfate solution are at a high content, it is still necessary to take other measures for removal. Cobalt removal process with new reagent can remove miscellaneous impurities, which not only yields a good cobalt removal result but also works well for other impurity elements in the zinc sulfate solution with simple on-site operation and continuous and steady production. Among three purification processes, the last one features the minimum unit consumption (cathode zinc per ton) of zinc powder and processing cost.

Abstract:Secondary Zn is mainly concentrated in smelting dust and slag, featuring a low grade of Zn and other complex composition. Utilization of secondary Zn refers to recovering valuable metals from it as much as possible. The process of secondary Zn recovery comprises phase restructuring of raw materials and slag and comprehensive hydrometallurgical recovery. The former includes rotary kiln process and fuming furnace process while the latter includes conventional processes, F and Cl removal process, extraction process in chloride salt system and process in alkaline system. This paper elaborates on all relevant processes, analyzes their pros and cons, and points out that phase restructuring only provides favorable conditions for valuable metal recovery and should be coupled with the hydrometallurgical recovery process to realize valuable metal recovery. F and Cl are still main factors affecting hydrometallurgical recovery process of secondary Zn. One single method cannot achieve economical and complete removal of F and Cl, and thus various methods should be integrated and reasonably designed for process optimization.

Abstract:Cobalt removal is a key step in the purification process of zinc hydrometallurgy. With a rising content of impurities in zinc sulfate solution, issues will emerge, such as lowered qualified rate of purified solution, difficulty in pressure filtration of purified residue, high unit consumption of zinc powder and unstable electrowinning process. A smelting enterprise uses cobalt removal process by antimony salt to purify zinc sulfate solution. In order to address the above issues, a comparative test on atomized zinc powder and EF zinc powder used in the purification process is carried out. A conclusion is drawn that the atomized zincpowder of high purity can be applied to stage-1 purification process to remove copper and cadmium in the liquid and alleviate the impact of impurities in zincpowderon the grade of sponge cadmium and sponge copper; EF zincpowder with 1%-4% lead can realize in-depth cobalt removal within a short time; the concentration of Zn2+ and Ca in zinc sulfate solution is controlled to be not larger than 155g/L and 0.4g/L respectively, which can ensure smooth operation of cobalt removal. When cobalt is removed from zinc sulfate solution, EF zinc powder as the leading reagent is coupled with atomized zinc powder to maintain a high cobalt removal rate and avoid cobalt re-dissolution resulting from prolonged pressure filtration. Besides, improvement of zinc powder quality and reasonable control of process parameters for cobalt removal are significant measures to lower unit consumption of zinc powder, enhance qualified rate of purified solution and ensure steady production of zinc electrowinning.

Abstract:The hydrolysis process for Fe removal exists such problems as large fluctuation of Fe2+ concentration in resulting solution, high Zn loss rate, high unit consumption of hydrogen peroxide and calcium carbonate, etc. Under this background, the continuous and intermittent combined goethite Fe removal process is proposed, while considering the actual production conditions and site conditions. In this process, oxygen is used to replace hydrogen peroxide, the dosing method of hydrogen peroxide is optimized, dross is used as neutralizer to replace calcium carbonate, by these methods the Fe2+ in the resulting solution is reduced below 25mg/L, Zn concentration in the resulting solution improved from 110g/L~120g/L to 130g/L~140g/L, Zn loss reduced from 6%~8% to 2%~3%, the unit consumption of hydrogen peroxide reduced by more than 70%, and no calcium carbonate is used.

Abstract:Given that SnO is volatile and rotary kiln is suitable for handling solid materials, tests are conducted to explore the reduction volatilization process of refractory low-grade tin in rotary kiln, including melting point determination test, comparison test between pelletizing and not pelletizing, feed pelletizing orthogonal test and continuous feeding and discharging test. Conclusions drawn from these tests are that according to theoretical analysis and melting point determination test, the proper temperature of reduction volatilization should be controlled at 900~1100℃, and the adhesive CaO is beneficial to increasing the melting point of low-grade tin middlings and reduction volatilization of tin. And this process can realize effective separation of tin from other impurities and a volatilization rate of over 88.85%.

Abstract:As the product of wolframite concentrate acidolysis, crude tungstic acid can be used as the raw material to produce ammonium paratungstate and tungsten trioxide. Orthogonal tests are conducted on such processes of crude tungstic acid as dissolution in aqueous ammonia, alkaline leaching of dissolution residue, evaporation and crystallization. Comprehensive tests are carried out on the basis of better orthogonal tests and conclusions are drawn as follow: recommended process flow only adopts dissolution in aqueous ammonia once and that residual tungsten in dissolution residue is recovered by alkaline leaching. The crude tungstic acid produced from wolframite concentrate acidolysis by hydrochloric acid is directly subject to the process flow of dissolution in aqueous ammonia, evaporation and crystallization so as to obtain ammonium paratungstate with 88.46%~88.75% WO₃. The purity of WO₃ can exceed 99.9% after roasting. The residue after dissolution in aqueous ammonia undergoes alkaline leaching to fully recover tungsten. The dissolution rate of WO₃ in aqueous ammonia can exceed 89% and that in alkaline solution can be over 10%. The total recovery rate of WO₃ is over 99% and the direct recovery rate surpasses 75%. After crude tungstic acid is subject to dissolution in aqueous ammonia and alkaline leaching, tantalum, niobium and tin are concentrated in caustic dross that can be used as the raw material to recover tantalum and niobium.