| Nickel is a kind of nonferrous metal with many excellent properties which has a wide range of uses and a huge market demand. Jinchuan, in China, is the world’s famous copper-nickel ore producing area and the nickel metal reserves of 5.5 million t, the third in similar ore deposits in the world. But after years of mining, the nickel ore resources is more and more "lean, fine, miscellaneous ", Jinchuan nickel mine now mostly is lean ore (nickel containing0.3-1.0%), accounting for about 74%. Low grade, fine-grain disseminated and combined with complex patterns of "difficult separation ore" and some of the intermediate products in the smelting process also is the mineral resources can be used again. Therefore, the separation research for the valuable metals in this kind of complex refractory ores has important theory significance and practical value.Jinchuan copper-nickel ore dressing mainly exist the following technical difficulties:(1) copper-nickel ore mostly is lean intergrowth, complex dissemination and fine-grain disseminated, so copper-nickel and gangue can’t achieve effective separation; (2) the mud content of middling is big and the ore grain size is very fine, the -0.074mm (200 mesh) accounted for more than 95%,-0.025mm (500 mesh) accounted for more than 34%,0.010mm (1340 mesh) accounted for more than 18%; (3) alteration become serious and serpentine, tremolite, such as high content of magnesium silicate, MgO style content as high as 20% above, such magnesium silicate easily with nickel pyrite occur " heterocoagulation phenomenon" seriously in the pulp seriously interference separation process of pentlandite.This paper take the middling from Jinchuan copper- nickel ore dressing as the research object and study the properties of the sample ore by chemical element analysis, XRD diffraction analysis, scanning electron microscopy (SEM) and X-ray spectrometry (SEM-EDS) analysis, phase analysis and granularity analysis process mineralogy examination method. Based on the systematic process mineralogy, the method of "selective acid leaching out of magnesium and activated flotation slag" is proposed. The single factor experiment method is used to carry out the acid leaching out of magnesium condition test and the slag flotation test, and the following main results are obtained:(1) Find out the composition of the ore sample and the mineralogical characteristics of the main minerals. The main component of the dressing middling from Jinchuan copper-nickel ore is serpentine, talc, orpiment iron ore, chlorite, magnesium oxide and tremolite etc. The Valuable metals of the ore sample are copper and nickel and their content are 1.37% and 1.32% respectively. The copper mainly exists in the form of copper sulfide. Copper and nickel minerals are fine or micro fine grained inclusions embedded throughout in the iron ore and magnesia silicate minerals and mostly are the lean intergrowth. The main gangue mineral of the flotation dressing middling from Jinchuan copper-nickel ore is serpentine, talc, orpiment iron ore, chlorite, magnesium oxide and tremolite etc. The harmful impurity MgO content, up to 20.87%, mainly existed in the form of serpentine; the sulfur content is higher, mainly exists in the form of pyrite and orpiment iron ore and it has certain influence on flotation.(2) The optimum leaching conditions were obtained by selective acid leaching out of magnesium test:sulphuric acid concentration is 14.5%, leaching temperature is 75℃, leaching time is 4 hours, liquid-solid ratio of 5:1, stirring intensity is 300 r/min and the grinding fineness-0.037mm is 80%. Under these conditions, the leaching rate of MgO is 83.27%, and the loss rate of copper and nickel is 5.73% and 4.23% respectively. Acid leaching out of magnesium is greatly limit the removal of MgO of the dressing middling from copper-nickel ore and the loss rate of nickel and copper is low, in addition, copper and nickel minerals in the leaching slag have a good enrichment; it eliminating the" heterogeneous condensation " phenomenon between serpentine and nickel pyrite and also improving the intensity of the role of the collector; Cleaning the oxide film on the surface of the nickel pyrite and activating the nickel pyrite, etc.(3)The suitable flotation condition were obtained by he leaching slag flotation condition test:grinding fineness -0.037mm 80% sodium hexametaphosphate and sodium silicate (2:1) as adjusting agent and the comprehensive usage is 600 g/t; Butyl xanthate as a collector and the dosage is 120 g/t; J-622 as the foaming agent and the dosage is 60 g/t. Under this condition the closed-circuit test is carried out and obtained the tenth level of nickel concentrate and the grade and recovery rate are 3.17%, 95.46%. The nickel concentrate containing copper 2.83% and copper operation recovery rate is 91.78%; the concentrate containing MgO is 4.97%(industrial standard is 6.5%) and the effect is good. The flotation process only has two times of rough selection operations with short, easy to operate, strong industrial and other advantages.(4) The test results using pure mineral show that the serpentine with noremoving magnesium has a huge effect on the flotation of pyrite is huge. Under the condition of pH is 8.6, add 10% of the serpentine and the recovery rate of pyrite down from 92.17% to 10.98%; after the serpentine carrying out the acid leaching out of magnesium it can significantly eliminate "heterocoagulation phenomenon" between pyrite and serpentine and make the mineral particles dispersed and bring the befit to the flotation of copper-nickel ore. The main mechanism is that the Mg2+ on the surface of Serpentine was dissolved in the acid solution and the negative shift of Zeta potential eliminates the positive charge on the surface of the serpentine. |
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