Huang Kaiguo Professor
Central South University, Changsha, CHINA
The Sidelight of Chinese Technology on Mineral Processing
Abstract: In this paper, the reverse-flotation of iron ore, bauxite, and carnallite, the collectorless flotation of copper sulphide ore, ingenious applications of sodium sulphide for flotation of sulphide ores, as well as table flotation of mix scraps of bronze and tin alloy was introduced respectively.
IntroductionChina has vast territory and abundant mineral resources. Due to its very large population, the average amount of mineral resource for a person is low. In addition, the mineral resource is poor, fine, and complex so that it is difficult to separate. China has always pay highly attention to resolve separating techniques of the above. Through many years’ strive, Chinese science and technology of mineral processing have achieved great progress. The fragment of the achievements is introduced in the article.
1. Reverse-flotation
The flotation process in which the useful minerals are concentrated in froth is called positive-flotation; the flotation process in which the useless minerals are concentrated in froth is called reverse-flotation.
1.1 The reverse-flotation of iron ore 〔1〕
The new technique of “cation reverse-flotation of iron concentrate with the flotation column” developed in tackling key problems of Chinese science and technology in the tenth five years has been successfully used in industry. This technique with international advanced level has improved the quality of iron concentrate. The grade of Fe concentrate obtained is as high as 68.8%, the content of SiO2 has reduced from 8% to 3.65%. The technique may simplify flotation flowsheet, lower the costs of electricity and reagents by 30% and raise economic benefit markedly.
1.2 The reverse-flotation of bauxite 〔2〕
Generally, the bauxite with the ratio of Al and Si more than 10 can be directly used for Al203 production. However, The majority of Chinese bauxite has a ratio of Al and Si lower than 10. In order to enlarge bauxite resource, China carried out tackled key problems on processing of the above bauxite and developed the unique technique--“selectively removing mud—removing Si by cation reverse-flotation”, in which, the surface potential of mineral particles was adjusted by adding dispersant, the mud was dispersed effectively and removed selectively, and by using suitable grinding methods and grinding medium, the selective grinding which is beneficial to the flotation can be achieved. The techniques obtained good results in the industrial test. For the crude ore with the ratio of Al and Si being 5.88, the ratio of Al and Si of concentrate ore is 10.12, the recovery is 82.4%.
The reagents used have abundant source and good water-solubility. The process can be carried out at room temperature.
Compared with the concentrate ore by positively flotation, the efficiency of pre-removing Si in the production of Al203 with the concentrate ore by reverse-flotation is higher. The feature of solubility is good, the pipeline shaping scabs is delayed, the settleability and compressibility of red mud is good, and the quality of the Al203 is also high.
The study on the complete utilization of bauxite with high Fe has got a success. Using combination of strongly magnetic separation and anion reverse-flotation developed a new technique. For the ore with Al203 more than 50% and the Fe203 more than 15%, the results obtained is as follows: the content of Al203 in Al concentrate ore is up 68%, the recovery of Al203 is up 74%, the grade of total Fe in Fe concentrate is up 57% (after subtracting crystallization water, the total Fe is up 61%), the recovery of Fe is as high as 56%. The technique develops a new approach to make full use of Chinese hydraulic bauxite resources with high Fe.
1.3 The reverse-flotation of Camallite 〔3〕
QingHai salt lake adopt the technique of Potassium Chloride reverse-flotation -cold crystallization which is developed independently, and set up major production base of potash fertilizer in China. This is carried out by the flotation of impurities such as calcium sulfate from camallite. The obtained pure camallite concentrate is used for the production of Potassium Chloride
2. Collectorless Flotation
As is well known, flotation needs collector, frother, regulating agent, but collectorless flotation doesn’t need collector. Utilizing or regulating the differential of chemical character of the mineral surfaces, and under the presence of frother and regulating agent, the separation flotation was achieved.
2.1 Collectorless flotation of copper sulphide ore〔4〕
In our work, the flotation of copper sulfide ores is achieved without using collectors. The results of the collectorless flotation tests are comparable to those obtained by using thiol collectors. The grade of the Cu concentrate obtained in the laboratory close-circuit tests is 26.15%Cu with a recovery of 95.3%, where a disseminated copper pre containing 1.88%Cu is used. The effects of some factors, such as redox potential, pH and the addition of sodium sulfide, lime and frother on the collectorless flotation of chalcopyrite are discussed.
The results of the collectorless flotation show that chalcopyrite can be floated better at high redox potential than at low redox potential, the increase of the redox potential of pulp is beneficial to the collectorless flotation of chalcopyrite.
It is fount that chalcopyrite can be floated better in acidic and basic pulp than in neutral conditions and that the optimum pH value for the flotation is about 10. When sodium sulfide is added, the copper recovery increases slightly, but the grade decrease, meanwhile the distribution of pyrite in copper concentrate increases. If the dosage of sodium sulfide is excessive, which is not suitable for the collectorless flotation of chalcopyrite.
The effects of lime on collectorless flotation were investigated. The experimental results show that disseminated copper sulphide ore can be floated well with varying addition of lime, and that the potential of the pulp slightly reduced by the addition of lime, but still ranged within that of collectorless flotation, In addition, the flotation of pyrite can be strongly suppressed by the addition of lime, which improves the grade of copper concentrate.
The performance of a frother in the collectorless flotation system is greatly different from that in the conventional flotation system. In collectorless flotation system, a frother can be adsorbed alone. Because of the semiconductivity of chalcopyrite, a frother may be also be adsorbed physically on the surface of sulphide minerals. The adsorption of the frother increases with the raising of the redox potential of the pulp.
Comparison between the collectorless flotation and the conventional flotation. The collectorless flotation of chalcopyrite is almost as efficient as the flotation with collectors. However, the distribution of pyrite in copper concentrate is lower by the collectorless flotation than by the conventional flotation. In addition, the flotation rate of chalcopyrite is higher than that of pyrite during the collectorless flotation. Thus, it is found that the collectorless flotation can separate chalcopyrite from pyrite more efficiently.
2.2 Ingenious applications of sodium sulphide for flotation of sulphide ores〔5〕
For a Cu-pyrite ore, collectorless differential of copper sulphide could be achieved experimentally without Na2S, and collectorless bulk flotation of copper and pyrite could be conducted successfully with appropriate addition of Na2S. For a pyrite ore, collectorless flotation of pyrite was achieved by inducing Na2S. Our studies also revealed that the conventional flotation process of a Mo-Bi-pyrite ore could be modified and simplified significantly by using Na2S ingeniously, thus producing three high final Mo, Bi, and pyrite concentrates with only eight stages of flotation.
We applied Na2S ingeniously to modify a conventional flotation process of Mo-Bi-pyrite ores. Under the influence of Na2S, both molybdenite and pyrite were floated collectorlessly, while the bismuthinite was depressed. The obtained Mo-pyrite bulk concentrate was then sent to a flotation separation stage, where the pyrite was depressed using additional Na2S, thus producing the Mo and pyrite concentration. The depressed bismuthinite was activated with sulphuric acid or oxidants, and then floated with xanthates, thereby producing the Bi concentrate. The procedures, reagent scheme and flowsheet of the new process were very simple, and three final Mo, Bi, and pyrite concentrates of quality were obtained with only eight stages of flotation, thereby greatly simplifying and improving the separation process.
3. Table flotation of mix scraps of bronze and tin alloy 〔6〕
In locomotive, ship building work and other manufacturing industries, a large amount of metal scraps consisting of bronze and tin alloy filings are formed during the machining of bush axle. For quite a long time these metal scraps could not be utilized due to the difficulties to separate and regenerate the scraps into two marketable products of bronze and tin alloy.
We applied a novel separation technique which separates successfully a mix of bronze and tin alloy filings of minus 5 min in size into two high quality products of bronze and tin alloy, with good yields. Comparing the standard bronze and tin alloy, the content of different element of bronze filing and tin alloy filing is very close to each. Having melted and optimized in group, it can fit in with standard entirely.
The main feature of this novel separation technique is based on a unique combination of a classification and table flotation processing technology coupled with the use of effective reagents for table flotation.
References
〔1〕Xin Lang Cai Jing Zong Heng, hyyp://finance.sina.com.cn 2005-10-19;
An Gang Qian Hua Wang, http://www.qianhuaweb.com 2002-11-19
〔2〕Zhong Guo You Se Jin Shu Ke Ji Xin Xi Wang, www.cnitdc.com 2005-6-13;
Zhong Guo Chan Ye Jing Ji, Xin Xi Wang, www.cinic.org.cn 2006-1-27
〔3〕Wanfang Data (Chinainfo), Sea-Lake Salt and Chemical Industry 2002 Vol.31 No.3
〔4〕Huang kaiguo, wang dianzuo, Collectorless flotation of copper sulphide ores, At the Sym. of Extractive Metallurgy and Materials Science Organized, Changsha, China, Sept. 21-24,1987; In Journal of Central-South Institute of Mining and Metallurgy, China, No.4, 1988
〔5〕Huang kaiguo, Ling jinghong, Ingenious applications of sodium sulphide for flotation of sulphide ores, At 4th UBC-McGill Int. Sym. On Fundamentals of Mineral Processing at the 40th annual Conference of Metallurgists in Toronto, Canada, August 26-29, 2001
〔6〕 Huang kaiguo, Xu wenxion, Chen jin, The separation of mixture scraps of bronze and tin alloy, The 2nd Int. Sym. On East Asian Resources Recycling Tech., Seoul, October 14-16 1993
本文发表于2006.5.乌克兰 克里沃罗格（Kryvyi Rih）‘矿冶工业长远发展’国际科技研讨会 ☺
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