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By Ronel du Plessis, John C. Davidtz, Jan D. Miller

Xanthates (dithiocarbonates) have been the collector of choice for the flotation of sulfide minerals ever since the flotation process was developed and have been studied quite extensively. Recently, trithiocarbonates have been shown to be very effective in bulk sulfide bench-scale flotation. Fundamental analysis using electrochemical techniques have supported these bench-scale results, illustrating that the trithiocarbonate (TTC) collectors are more readily oxidized to their corresponding dithiolates, than the dithiocarbonate (DTC) collectors, as is shown in Figure 1.

Jan 1, 2003

By O. N. Mohanty, S. Mohan Rao, N. D. Rao, T. Mukherjee, P. V. T. Rao

"Chromite ore is an indispensable raw material in the manufacture of ferro-chrome and charge-chrome, which are used for the production of stainless and other alloy steels. The demand for chromite ore is ever increasing because of increasing consumption of these steels. Keeping this in view, Tata Steel is keen to recover values from fines and wastes, and also to produce value added products from their captive chromite mines and its processing plants.Tata Steel has its captive chromite resources at Sukinda, Orissa. They contain two ore types, i.e. (i) Ferruginous and (ii) Siliceous. The generation of off-grade ores is an increasing trend and simultaneously customer quality requirements are becoming ever more stringent. The ferruginous type ore also contains a considerable quantity of in-situ fines (~20% particles below 0.5 mm) that compound the beneficiation problem.In many places, in India and abroad, mined non-marketable off-grade and low grade chromite ores are upgraded by using either simple classification techniques like screw classification, hydrosizing, hydrocycloning or conventional gravity concentration processes such as Heavy media separation, Jigging, Spiraling, Tabling etc.At Tata Steel, the ferruginous type ores are treated in Chrome Ore Beneficiation (COB) Plant that comprises: a crushing and grinding circuit; a classification circuit using hydrocyclones; and a beneficiation circuit using 4 stage spirals in the coarse circuit (-0.5+0.1 mm) and 3 stage spirals & tables in the fine circuit (-0.1+0.038 mm). In this process, 3 types of tailings are being generated and together analyses about 17 % Cr2O3, which is high. From the present operation the chromite recovery is around 70% and could not produce coarse concentrates (+0.5 mm size). Whereas the siliceous type ore is treated in the Lumpy Ore Processing (LOP) plant, consisting of crushing-washing & classification-hand sorting operations, to produce marketable grade lumpy ore and –10 mm de-slimed fines. These fines are intermittently treated in the COB plant. The higher silica content (greater than 1%) and low Cr/Fe ratio (less than 2.8) are the problems with these concentrates."

Jan 1, 2003

By Dingwu Feng, Jannie S. J. van Deventer

"The effect of ultrasonication on reactions at solid/liquid interfaces was investigated by using an ultrasonic probe in two slurry systems, i.e. cyanidation of a refractory sulphide ore and geopolymerisation of metakaolinite. The surfactant dithiophosphate was used to render the gold bearing sulphide particles hydrophobic, in an attempt to induce the formation of cavitation bubbles directly at the desired surfaces. Oxygen was injected into the cyanidation system to improve the attachment of oxygen bubbles to the hydrophobic sulphide surfaces. Geopolymerisation occurs in highly alkaline solution with waste aluminosilicate oxides and silicates as the reactants. The process of geopolymerisation is believed to involve dissolution of Al-Si oxides from solid particles, diffusion of dissolved Al-Si complex from the solid surface into the gel phase, condensation of gel phase and hardening of the gel phase. It has never been investigated how ultrasonication affects the above steps in synthesising geopolymers, despite a number of papers dealing with sonochemical synthesis of materials. The introduction of power ultrasound into such slurry systems is expected to result in advanced geopolymer materials.In the cyanidation of the pyrite concentrate, the kinetics of gold extraction were significantly enhanced in the presence of ultrasound, due to the prevention of passivation and the enhanced dissolution of sulphides. Cyanide consumption was significantly reduced with ultrasonication, owing to the oxidation of soluble sulphides to sulphate, minimising the cyanide consumption by sulphides. With oxygen injection, ultrasound significantly enhanced the leaching of gold from the pyrite concentrate, as oxygen could enhance the formation of the oxidation radicals by ultrasonic cavitation. In the presence of dithiophosphate, ultrasound further improved gold leaching in the oxygen-aerated system. Dithiophosphate could selectively adsorb at gold host sulphide surfaces, and make the surfaces hydrophobic. As a result, the ultrasonication effectiveness could be enhanced through forming cavitation bubbles directly at the interfaces."

Jan 1, 2003

By Markus A. Reuter, Antoinette van Schaik

"INTRODUCTIONGoods and products, such as passenger vehicles, are manufactured by using a wide spectrum of different raw materials to meet highest consumer requirements during use. Due to the time-varying composition and complexity of multi-component products such as cars, recycling is complicated. It involves a network of interconnected processes and material and energy flows. Improving the efficiency of the material cycle of the car to comply with the recycling targets as imposed by EU legislation, requires insight into all aspects influencing the closing of the material cycle (dynamics, technology, economy, legislation, etc.) and their mutual relation. In order to define the link between recycling end-of-life products, their changing composition and design a dynamic model was developed for the resource cycle of cars. The model integrates the optimisation of the material cycle with the dynamic behaviour of recycling systems."

Jan 1, 2003

By M. Ghiani, R. Peretti, S. di Giovanni, G. Zonnedda, A. Serci

"An interesting occurrence of gold bearing ores of economic interest has recently been discovered in the Serrenti- Furtei district, central-southern Sardinia (Italy). The upper part of the orebodies are leaner and fairly porous, and are undergoing intense oxidation processes. In the lower parts sulphide ores predominate, chiefly enargite-luzonite and pyrite and these have a more compact structure. The passage from the oxidized to the sulphide zones, is rather irregular and difficult to delineate. The gold, generally occurring in its native form, is found in small grains. Mineral reserves in the area concerned were originally estimated to total 2.77 Mt: 0.63 Mt of oxide minerals with average gold content of 2.75 g/t and 2.14 Mt of sulphide ores with average gold grade of 3.18 g/t.Recovery of the valuable metals is a complex problem.The effectiveness of a variety of gold extraction techniques has been evaluated conducting tests on batches of ore representative of the different orebody depths obtained from core samples.The techniques investigated were: heap and vat leaching; flotation and flotation followed by leaching of the flotation tailings. The findings indicate that:• the gold contained in the ores in the upper oxidized zones of the deposit can be efficiently recovered by direct cyanidation via heap or vat leaching;• the sulphide ores in the deeper portions, that are not amenable to direct cyanidation but contain enargite concentrations of potential economic interest can be processed by means of flotation to produce a gold/copper bulk concentrate;• beneficiation of the difficult-to-treat minerals contained in the transition zone requires some knowledge of their intrinsic properties. A distinction should be made between the ores containing minor amounts of enargite which appear to be amenable to vat leaching and those with relatively higher enargite content which are processed using bulk flotation of the gold and copper minerals followed by vat leaching of the resultant tailings."

Jan 1, 2003

By Susanna A. C. Stadler, Chris Aldrich, Jacques J. Eksteen

"Slag foaming occurs in several pyrometallurgical processes. These processes include steelmaking in basic oxygen steelmaking furnaces and electric arc furnaces as well as various non-ferrous operations like sulphide smelting/converting and base metal slag cleaning. Although slag foaming in steelmaking processes has been extensively researched, little attention has been given to slag foaming in non-ferrous operations. Slag foaming phenomena are complex because often the system consists of three or more phases. With this in mind, factors previously identified as influencing slag foaming were investigated. These include the slag basicity, physical properties of the slag, namely viscosity, surface tension and density, the formation of particles due to undercooling of the slag and the FexO concentration in the slag.Slag foaming was investigated in a vertical tube furnace. The different slags were contained in alumina crucibles and bubbling argon gas through the molten slag induced foaming. The foam height was measured by using stainless steel probes and a voltmeter. The conductivity of the slags made it possible to measure the foam height from the position of the probes when the electrical circuit was completed. Slags were foamed at different temperatures to investigate the effect of solid precipitates.The effect of increasing FexO concentration was found to decrease the foam index due to lower viscosities, but higher surface tension depression appears to have led to increased foam index values at high FexO concentrations."

Jan 1, 2003

By Masakazu Niinae, Kenji Aoki

"Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble substances. At a higher pH, the soil particles sorb more heavy metals than at a lower pH and the precipitation of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering cleanup more difficult and electrokinetic extraction inefficient.In this study, the effectiveness of introducing a complexing agent to enhance the removal of cadmium from kaolinite in the region of neutral pH by ionic migration is examined. The complexing agent selected was ethylenediaminetetraacetic acid (EDTA). The investigation was carried out in a laboratory-scale column containing kaolinite contaminated with cadmium. As the results of the study, cadmium migrates toward the anode without accumulation of cadmium and is successfully removed at the anode reservoir."

Jan 1, 2003

By Williams Calderon, César Arredondo, Gonzalo Montes-Atenas

The quality of final concentrate in froth flotation circuits is largely dictated by the correct implementation of the froth washing operation in flotation cleaning stages, which are commonly installed in column flotation cells. In flotation plants, this aspect has been largely overlooked and the froth washing is restricted to the use of perforated piping through which process water flows producing a similar effect to that observed in "fountains": jet created with low energy crosses the froth phase washing out entrained particles as well as particles weakly attached to bubbles. The aim of this research study is to assess the efficiency of traditional froth washing systems theoretically and experimentally. A theoretical model was implemented using Fluent® software where a jet of variable speed was introduced in a continuous soft matter phase with physical properties similar to those observed in a froth phase in wet and dry conditions. In addition, a simple experimental protocol was designed to validate the model. It was found that the water process jet-like flow influences the behavior of 2 to 3 times the equivalent volume in the froth phase. Such influence zone is dramatically reduced as the froth phase becomes drier. These results were confirmed by the experimental findings indicating that a better froth washing technologies must be assessed and implemented. Some aspects of the ideal froth washing system are derived and discussed in details.

Jan 1, 2014

By Cheng Gan, Gui Xiahui, Li Shulei, Cao Yijun, Liu Jiongtian, Wu Lun

Flotation rate constant is an essential parameter in the flotation process. The fine coal sample utilized in this investigation is anthracite from the Shenhuo mine in eastern China. Fine coal flotation rate tests were conducted to compare the flotation rate constant at constant power input with that at gradually increasing power input. Results indicate that the flotation rate constant decreases with the flotation process and increases as the flotation energy is increased. In addition, the flotation rate constant is close to the maximum value. The increasing trend of the flotation rate constant gradually slows down as the flotation energy input increases.

Jan 1, 2014

By Wu Tao, Lu Shijie, Xia Xiaoou, Zhang Ming

The impeller and stator are the most important components that can significantly influence the performance of flotation cells directly. The performance of the impeller and stator of KYF flotation cell is revealed by CFD (Computational Fluid Dynamic) simulation in this paper. A method of obtaining the circulation volume is proposed. The circulation volume is proportional to third power of impeller diameter. And the circulation volume increases linearly with the increasing of the speed. CFD simulation can draw the conclusions that there is a proportional relationship between power consumption, third power of speed and fifth power of impeller diameter. CFD prediction results agree with the theoretical formula. The difference between the forward and backward impeller is analysed in the paper. The circulation volume of the backward impeller is obviously larger than that of the forward impeller under the same condition, but power consumption of the backward impeller is lower. It is demonstrated that the impeller and stator system of KYF flotation cell is an efficient and reasonable stirring mechanism. CFD simulation could be reliably used in flotation cell design and optimization.

Jan 1, 2014

By Xiong Dahe

"SLon vertical ring and pulsating high gradient magnetic separator utilizes the combined force field of magnetism, pulsating fluid and gravity to beneficiate weakly magnetic minerals with the advantages of large beneficial ratio, high recovery, matrix not easy to be blocked and excellent performance.We have developed SLon-750; SLon-1000; SLon-1250; SLon-1500; SLon-1750 and SLon-2000 VP HGMS. Now more than 200 of them have been successfully applied in China.Application in Qi Dashan Mineral processing Plant of Anshan Iron and Steel Company: The iron ore consists of magnetite and hematite. In 2001, six SLon-1750 magnetic separators are applied to control the tails grade of fine hematite. The results of flowsheet is: feed grade 30.15%Fe, concentrate grade 67.00%Fe, iron recovery 75.86%. The results set up the historic high record of this plant and the processing coast is greatly reduced.Application in Gushan Iron Mine of Ma Anshan Iron and steel Company: There are 6 SLon-1750 and 4 SLon-1500 magnetic separators applied in this mine to treat refractory hematite ore. The feeding grade is about 45%Fe. The final iron concentrate grade is about 60%Fe and the iron recovery is about 76%. The results are much better than the previous gravity flowsheet.Application in Meishan Iron Mine of Shanghai Baoshan Iron and Steel Company: The mined ore consists of magnetite, hematite and siderite. Because of a relatively high content of phosphorus, the iron concentrate could not meet the market requirements. Now 18 SLon-1500 magnetic separators are applied to reduce phosphorus, which is reduced from about 0.4%P to 0.246%P. The quality of iron concentrate is greatly upgraded.Application in Panzhihua Ilmenite Processing Plant: In the past, the -0.045mm ilmenite fraction was discarded in to the tails because of lack of high efficient equipment. In 2001, the plant built up a magneticflotation flowsheet to recover the fine ilmenite from the -0.045mm fraction with 6 SLon-1500 magnetic separators. The total results are: feed grade 11%TiO2, concentrate grade=47% TiO2, recovery 44%. Each year the flowsheet recovers 60,000t fine ilmenite concentrate."

Jan 1, 2003