Study On The Separation Of Jinchuan Nickel Ore Using A Shortened Column Flotation

Nickel, also called"Vitamin for Industry,"is a very important nonferrous metal for China's national economic and high-tech development. In recent years, with the development of China's minerals industry, the exploration of nickel resources has been gradually enhanced, however, easy-to-separate ores have been decreasing year by year while the proportion of poor quality and difficult-to-separate nickel ores is rising steadily. The laregest nickel reserve in China is called Jinchuan nickel sulfide ore, and cell-type flotation technology has been used for nickel separation at Jinchuan. Due to the inherent inefficiencies associated with traditional flotation machines including the single mineralized separation and low mineralization efficiency, the separation technology of nickel sulfide using flotation machine has its problems such as complex process and high processing cost. Compared with flotation machine, flotation column has many advantages including simple structure, energy saving, high efficiency, and efficient separation of micro-fine mineral, etc. Thus, it is applied in cleaning flotation to improve the concentrate grade in nickel sulfide ore dressing plants; however it has been rarely used in hard-to-separate ores, rough and scavenging operations due to the lack of an intensified separation mechanism in most present flotation columns, which cannot guarantee high efficient recovery rate. Consequently, using highly efficient separation methods, equipment and technologies to explore nickel sulfide ores and improve their recovery rate and separation efficiency is a very urgent and important research project in nickel separating industry.In order to achieve the highly efficient separation of nickel sulfide ores, the basic theory and flotation characteristics of nickel sulfide ores were systematically investigated in this dissertation, combined with the mineralogical characterization of Jinchuan nickel ores. The reasons of poor floatability of this ultra-fine nickel ores were analyzed and an improved separation process was designed. Mineralogical analysis indicated that the Jinchuan nickel sulfide ores consist of mostly pentlandite and violarite and the particle size of some pentlandite is quite small; in addition, there is also little pentlandite inlayed in gangue minerals in the form of fine particles or nervation. In the two parts the small size of pentlandite makes dissociation difficult in grinding, which results in some nickel residues in pyrrhotite and veinstone minerals and this directly affects the mineral separation performance. Violarite has high volatility and is easy to be oxidized and overgrinded, so its floation nature is quite complicated. The inlaid degree of all kinds of sulfide minerals in ores forms irregularly. After grinding the whole grade size and distribution of nickel and copper are in the form of"dumbbell-shaped"and the separation is difficult. The Jinchuan nickel ores contain large amount of ophiolite which has great effects on separation and mainly leads to the above-norm level of magnesium oxide in flotation concentrate. In addition, ophiolite is a kind of veinstone mineral containing of low hardness and density magnesium; it is easy to break down into fine clay particles and hard to settle down; ophiolite slime also can easily adhere to air bubbles and enter into froth pulp. In the same time, ophiolite has greater superficial free ability, and easily adheres to the bubble generator in flotation; the existence of ophiolite slime affects the viscosity of ore pulp, packs the fine grain sulfide ores and forms strong cover of slime to the surface of rough grain sulfide ores, which in turn adversely affect the selectivity of flotation process.Base on the technological mineralogy characteristics of Jinchuan nickel sulfide ores, the flotation characteristics of nickel sulfide ores were studied in this dissertation. The bubble mineralization of Jinchuan nickel ores and the separation of mineralized floccules under centrifugal force field enviroment were investigated. And it has found that the centrifugal force field separation does not separate with the particles and density of ores but with the density of mineralized air floccules. In order to obtain better separation efficiency, based on previous studies this dissertation in further forms grade composition in the form of"dumbbell-shaped"and ores separation theory of metal distribution--fineness controlled optimized floatation theory of the hard-to-separate nickel ores. In this theory, it uses fine grinding to improve the grade composition and metal distribution. The floating grade composition and the distribution should be closer to the grade composition and metal distribution of concentrate not tailing, which is useful to the flotation recovery of nickel concentrate. After fine grinding, the grade distribution transmits to fine grade distribution, so highly efficient fine floatation and separation methods shall be employed to realize the effective recovery of fine particle. Highly efficient separation equipment and technology shall be used to improve the overall separation performance and based on the research put forward matched highly efficient floatation grade distribution curve and recovery rate curve. Aiming at the hard separation characteristics of fine grade nickel ores and analysis of the floatation process of nickel sulfide ores, this dissertation studied column separation theory in details. Using cyclonic static micro-bubble flotation column multi-mineralization separation method to strengthen and create suitable fluid separation environment for separation process of the fine grade hard-to-separate nickel ores to strengthen the bubble collision and mineralization of the fine poor nickel ores and the selective floation of mineralized bubbles.The dissertation studied and demonstrated that micro-bubble, centrifugal force field and the pipe flow mineralized turbulence degree have significant effects of on fine particle separation. Based on detailed research, this dissertation reasonably demonstrates some parameters which affect nickel ore separation such as strengthening means of micro-bubble, circular separation pressure, and the height of flotation column and theoretical model.The existing problems of the separation of Jinchuan nickel ores were identified. To efficiently separate the difficult-to-separate Jinchuan nickel sulfide ores, nickel tailing re-separation column separation and the second-stage highly efficient column separation and two-stages united Column separation was developed. Under fortified separation condition, through proper technological adjustments, separation performance indicators such as recovery rate and concentrate grade, etc. have been measurably increased compared with floatation machine separation. And that justifies the application of column separation equipment and technology in the separation of fine grade hard-to-separate nickel ores. Comparison and optimized different technology finally demonstrate the most proper the second-stage column flotation column under optimized fine grinding condition, which lays a fundamental base to the highly efficient exploration and utilization of fine grade hard-to-separate poor nickel ores.Through technological development and pilot-scale testing, a combined process using fine grinding + flotation machine + column flotation has increased 3% of concentrate grade compared with original process, and the recovery rate has also increased 3%. This new process strengthened the gathering and recovery of micro-fine pentlandite, effectively controlled the floatation of magnesium silicate gangue, and measurably improved the mineral separation efficiency of Jinchuan nickel ores. Based on pilot testing, industrial-scale flotation columns were designed, and the application results indicate that column separation technology of fine grade hard-to-separate nickel ore can greatly simplify the separation process circuit, reduce energy consumption and save processing cost.The column separation equipment and technology proposed in this research for fine hard-to-separate nickel ores treatment overcomes the shortcomings of conventional flotation equipment including single means of bubble mineralization and the lack of intense separation mechanism. Application of the proposed technology also resulted in simplified flotation process, lower processing cost, and improved the flotation efficiency, which lays a strong base for our country's highly efficient exploration and utilization of finely sized hard-to-separate ores.