Research On New Technology And Mechanism Of Comprehensive Recovery Of Tin And Iron From Oxidized Vein Tin Tailings

The primary tin ore resources of China list top position in the world and will be gradually exhausted with the increase of mining exploitation scale and speed, the beneficiation feed grade is becoming poorer day by day, which all severely restrict the sustainable development of tin mining industry. The complex properties of tin ores and the easy overgrinding of cassiterite result in the lower recovery of tin (about50%-70%). Meanwhile, the more than one hundred years of tin mining activity in China, has left millions of tonnages of tin tailings. The more than250million tons tin tailings in "Capital of Tin"-Gejiu with about0.19%Sn and18%Fe respectively, about400000tons tin metal and40million tons iron metal and many other associated metals have a great of comprehensive utilization value, its potential value has more than100million Yuan. Due to its leanness in valuable minerals and insufficient technologies available to handle such low-grade tailings, the economical efficiency and large-scale utilization of such tin tailings are still disappointedly scarce until today. Therefore, the theoretical and applied research of comprehensively utilizing valuable metals in tin tailings from YUNNAN TIN GROUP (YTG) is of typicalness and great significance.The oxidized vein tin tailings from YTG has some characteristics that the dissemination particle size of cassiterite is fine, cassiterite is intimately associated with iron minerals, it is difficult to separate tin from iron and the content of carbonate minerals is high ect. Applying the conventional beneficiation technology, a obtained concentrate assaying about2%-3%Sn with the recovery of about40%-50%respectively was low, the grade and recovery of tin and iron in the reconcetration tailing were high and the resources such as iron ect were not recovered from the tailing. Under the background, an oxidized vein tin tailings was selected as the research object by the support of the Joint Foundation between the National Natural Science Foundation Committee of China and Yunnan Provincial Government (Grant No. U0937602). The process mineralogy of sample is studied by the means of XRD and SEM-EDS etc. Aiming at material characteristic,we put forward a new method for recovering tin and iron by the cohesion roasting-magnetic separation technology, and the effects of cohesion roasting on the recovery of tin and iron from coarse and fine particle materials are explored, a new process, i.e. a cohesion roasting-magnetizing separation process and its key parameters are obtained, which realizes, the comprehensive recovery of tin and iron; The thermodynamic analysis provides a theory support for the new technology; Through the flotation experiments of pure minerals such as cassiterite, hematite and calcite, the separation experiments of cassiterite and hematite or cassiterite and calcite in the binary system and the study on the adsorption mechanism of cassiterite and reagents, the basis is provided for the recovery of micro-fine particle cassiterite from tin tailing slime.Basing on the process mineralogy research of coarse and fine particle and a fresh fine particle tin tailing, a cohesion roasting and magnetic separation technology with the synchronization recovery of tin and iron is firstly applied to an oxidation vein tin tailing. A iron concentrate assaying62.17%-66.58%Fe with the recovery of84.65%-87.47%and a tin-rich middling assaying4.0%1-4.56%Sn with the tin recovery of61.93-63.55%are obtained from the feed assaying0.15%-0.20%Sn and8.87%-22.42%Fe, and the reprocessing tailings contains less than0.02%Sn and1.00%Fe, which are better than the indexes obtained by the concentrational process. The process realizes the highly efficient separation of tin and iron minerals with gangue minerals, and the comprehensive recovery of cassiterite and iron minerals. The technology characteristics are of short process, simple and feasible.Through the thermodynamic analysis of the possible reactions in the cohesion roasting, and the XRD and SEM-EDS analysis of calcine comparing to raw material, the mechanism of high efficient separation of tin and iron minerals from gangue minerals, and the separation and synchronous recovery of tin and iron minerals are revealed, namely,the fine particle limonite and hematite could be cohesively reduced into the coarse particle magnetite, the formed liquid cassiterite may generate cohesion and gangue minerals such as carbonate would not change, which are the key of high efficient separation of tin and iron minerals from gangue minerals; it is easy to the liberation of cassiterite and magnetite because of the formation porosities and cracks in the mineral phase interface, which create the conditions of cassiterite and magnetite.The flotation results of single minerals show that the floatability of cassiterite is better than that of hematite and calcite; Pine oil has collecting function for cassiterite, hematite and calcite, the the adsorption form is the physical adsorption between pure minerals with reagents; Benzohydroxamic acid has better collecting ability for the cassiterite, its action mechanism is that the C-O and N-O bond in the structure of benzohydroxamic acid is absorbed to the surface of cassiterite by chemistry absorption; Pb2+has activation effect for cassiterite and is help to the recovery of cassiterite; the depressants have the different inhibitory action for cassiterite flotation in these experiments. The experimental results of artificial mixed minerals are consistent with the separation results of the actual tin tailing slime and show that it is difficult to realize the separation of cassiterite with hematite or calcite in these tests.According to the research results of tin mud properties and pure minerals flotation tests, a new process, i.e. a no-depressant-dispersant and undesliming flotation is determined. Through the process, under the conditions of500g/t benzohydroxamic acid,600g/t lead nitrate and120g/t pine oil in the roughing flotation etc, a tin-rich middling assaying3.50%Sn with the tin recovery of74.60%are obtained from the feed assaying0.15%Sn by one roughing, one scavenging and four cleaning, the micro-fine cassiterite could be efficient recovered from a tin slime. The separation experiments of the binary system and the study on the adsorption mechanism of minerals and reagents ect. explain the conclusions of a full-slime flotation without depressants and depressants.