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By Georg Unland, Thomas Wegner

"Impact crushers are widely used in different industries to crush materials which can vary from soft to hard and from ductile to brittle. However, the sizing of impact crushers is still based rather on empirical than on scientific approaches. Therefore, a test rotor was developed in order to investigate the principles of comminution by impact. Rocks of diabase with different diameters were used to gain the crushing properties with the following results:RESISTANCE AGAINST CRUSHINGLikelihood of BreakageThe likelihood of breakage is a function of the impact velocity and the particle diameter. The likelihood increases with higher velocities and larger diameters. Maximum Crushing ForceThe crushing force is related to the area of projection of the rock. The smaller the particles and the higher the velocities the larger are the maximum related contact forces.Contact TimeThe contact time increases with the rock diameter whereas the influence of the impact velocity is neglectable.Mass Specific Crushing WorkThe mass specific crushing work decreases with the particle diameter and increases with the impact velocity."

Jan 1, 2003

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 A. Boulton

Low molecular weight synthetic polymers substituted with hydroxyl, carboxyl or sulfonate functional groups were used to improve the flotation separation of zinc or copper sulfide minerals from iron sulfide gangue minerals in three massive sulfide ores of different mineral composition. These polymers produced significant improvements in zinc or copper grades as a result of a selective depression of iron sulfide minerals. These results are significant considering the differences in ore type, proportion and type of iron sulfide minerals present, and grinding medium used in this study.

Jan 1, 2003

By C. Abbruzzese, F. Vegliò, S. Ubaldini, R. Massidda

The aim of this paper was to study the influence of different water/organic solvent mixtures (isopropyl alcohol, ethanol and ethylene glycol) on the gold desorption process. The experimental work was carried out on laboratory scale, using activated coconut carbon with different temperatures and extraction times, without adding cyanide. Best results have been obtained in this order: isopropyl alcohol > ethylene glycol > ethanol. Starting from gold concentration of about 5 g Au per kg of carbon, best kinetics resulted in 97-100% of gold extraction, after 8 hours of desorption, at a temperature of 80ºC.

Jan 1, 2003

By Jussi Liipo, Pertti Lamberg

Image analysis of process samples gives precise data on particles and their composition. The results presented as liberation tables and maximum grade-recovery curves are informative and good for comparing different feed materials, but basing on them it is impossible to predict the results of the mineral separation process (flotation, magnetic separation, gravity separation) in details. The exact and extensive particle data has remained large unused, because there has not been a model nor a modeling program to include particle information in mineral separation processes. This study introduces a method, which incorporates the particle data in the kinetic model of flotation. Similar approach can be used in modeling other separation processes, too.

Jan 1, 2003

By Peter Ay, Matthias Schmidt, Christian Stollberg

"The aim of the study is the development of a seamless reprocessing procedure for plastics from automotive parts which are to be recycled (figure 1). Before automatic sorting can be performed, the materials first have to be identified by a near and middle infrared (NIR/MIR) system.Materials reprocessing basically includes research on size reduction, decoating, and roughening of the materials. Variants of the necessary technologies such as different shredders and mills and physico-chemical or mechanical decoating and roughening procedures together with the fundamental approaches underlying these methods are investigated and benchmarked. This allows the theoretical determination of the impact of each method not only on the overall process but also on the result achieved within the identification and sorting procedures."

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 Willis Forsling, Prabhakar Swarna, Hanumantha Rao Kota

"The solubility of wollastonite and its Hallimond flotation behavior as a function of dodecylamine concentration and pH are examined. The flotation response is characterized by adsorption and surface energy in the presence of amine. The methods of UV-Visible and FT-IR spectroscopy for adsorption and sessile-drop contact angle for surface energy estimation are employed.The results of wollastonite dissolution clearly showed its non uniform dissolution. The surfaces are depleted with calcium ions and became rich in silicon within 10 min of flotation time. Maximum flotation of wollastonite corresponds to a half monolayer coverage of amine, which is substantiated by the surface energy parameters as shown in figure 1."

Jan 1, 2003

By Rainer M. Lotzien, Michael J. G. Battersby, Jan Kleefeld, Julian V. Brown, Rainer M. Imhof

A new flotation system has been developed to improve the generally slow separating differentials of fine bubbles and fine particle suspensions. The new technology is based on established pneumatic flotation designs called Imhoflot which use intensive in-line pre-aeration to aerate the flotation pulp prior to its introduction to the separating cell. In the new system (see figure 1) this separation is speeded up dramatically by the introduction of centrifugal motivation in the separating vessel, without the use of internal moving parts. The design focuses on providing increased differential forces on buoyant mineralised bubbles and hydrophilic fines. The commercial benefit to industry is much reduced residence time, less than 30 seconds, which offers considerable cost savings in equipment and infrastructure.

Jan 1, 2003

By R. Peter King, Claudio L. Schneider, Reiner Neumann

Predicting the liberation spectra that is produced from breakage of two-phase ores under the random fracture assumption can be accomplished by measuring the conditional, on length, linear grade distribution directly from images obtained from a representative sample of the unbroken texture. The technique tremendously simplifies the prediction problem by avoiding the multiple convolutions that arise from the traditional method based on a description of texture from a measurement of the chord length distributions associated with each phase in the unbroken texture. For a 3-phase system, the phase transition probabilities associated with the textural information make the traditional calculation an almost insurmountable mathematical problem. The direct measurement procedure on the other hand can be expanded to three phases comparatively easily.

Jan 1, 2003

By S. Kelebek, A. Khan, J. Caceres, D. Beckett

"Pyrrhotite in nickel-copper sulphide ores is nickeliferrous and intimately associated with pentlandite. Due to its low nickel content, pyrrhotite rejection is an important step in processing of these ores. In our laboratory, various reagents were investigated for their effect on pyrrhotite depression. Among these, a combined use of triethylenetetramine and sodium metabisulphite was found highly promising.The work described in this paper has two parts. The firs part is a summary of results obtained on process samples from the pyrrhotite rejection circuit at Falconbridge’s Strathcona Mill. The second part involves simulation of the circuit performance based on the reagent conditions used in the experimental work and the concept of split factors.Two sets of reagent conditions were evaluated. The first one involved baseline conditions, simulating the current reagent performance. The second one simulated the impact these new reagents can have on the circuit performance.The simulation results obtained under baseline conditions indicated a good agreement with the current circuit performance (Figure 1). The simulation results suggest that at practically the same pentlandite recovery and tailing grades, the circuit concentrate nickel grade can be doubled through effective pyrrhotite rejection by these new reagents (Figure 2)."

Jan 1, 2003

By Andrey V. Tarasov

"An environmentally clean and virtually waste-less technology for treatment of domestic and industrial solid waste (HGIW) including other toxic chloride-containing materials has been developed and proven on a full scale by the Gintsvetmet Institute in cooperation with some other Russian organizations.The essence of the process is that the HGIW are decomposing in the liquid base in air-bed slag melted layer under the temperature of 1350-1400°C.HGIW is considered as fuel heat-producing energy of 1500-1800 kCal/kg with 51,7%.Processing of municipal and industrial solid waste in molten slag is carried out autogenously without additional fuel, the blowing is enriched by oxygen up to 50-70%.The complex makes it possible to treat the furnace charge without preliminary drying and sorting with big differences in chemical and morphological composition due to the versatile firing chamber.The proposed process resolves the acute and globally significant problem of dioxin formation.The purpose of the proposed technology is to ensure such destruction of the structural lattice that would guarantee irreversible transformation of the resultant substances to prevent formation of dioxins. It was established the required preconditions to achieve this purpose."

Jan 1, 2003

By Sashnee Raja, Mehdi Nemati, Ashley Sissing, Susan T. L. Harrison

"Extreme thermophiles, operating at 65 - 90°C, are finding increasing application in biohydrometallurgy. These micro-organisms have the advantage of exhibiting better oxidation kinetics in terms of reaction rate and extent of mineral solubilisation (Duarte et al., 1993; Norris and Barr, 1988; Konishi et al., 1995). These extreme thermophilic Archae, characterised by a different cell envelope structure (König and Stetter 1986, König 1988, Michel et al. 1980) perceived to provide reduced structural strength in comparison to bacterial envelopes, and customised metabolic pathwaysThe active tank bioleaching process, used for high rate leaching, is conducted in a slurry bioreactor. Here sufficient energy dissipation is required to ensure suspension of the mineral phase as well as to sustain high rates of gas liquid mass transfer. It is well known that subjection to hydrodynamic stress of sufficient magnitude may alter the physiological state of a range of micro-organisms through changed viability (ability of the microbes to grow), metabolic activity and integrity. While limited study on the influence of the solids phase on thermophilic leaching performance is reported, initial reports suggest that the thermophiles used for bio-oxidation appear to be sensitive to hydrodynamic conditions (Jordan et al 1993, Clark and Norris, 1996) and the presence of solids (Norris and Bar 1988, Le Roux and Wakerley, 1988, Escobar et al. 1993, Torres et al. 1995, Nemati and Harrison, 2000)."

Jan 1, 2003

By Valery V. Kostjuk, Victor. N. Bredikhin, Alexander I. Shevelev, Evgeny A. Kazban

"The investigations to improve the process data have been done in order to stabilize the functioning of drying units. The scheme of turnings preparation with centrifuging and subsequent thermal degreasing (tandem) is proposed. To improve the efficiency of the process the scheme of reclamation of the centrifuge fugate is developed with production of oil and service circulating water. Empirical dependences of the turnings temperature influence on the lubricant-coolants content in centrifuging are gained. When the turnings temperature is increased to 80 C the residual content of LC is decreased by 1.5%. The investigations aimed to improve the preparation of non-ferrous turnings have allowed to decrease the melting loss by 15-20%; to stabilize the process of thermal drying of turnings; to decrease sharply (by 60- 70%) the volume of LC combustion products; to reclaim the centrifuge fugate and produce oil and servicecirculating water.Non-ferrous turning and primarily aluminum and copper alloys turning is a stable source of secondary raw materials for metallurgical works.Direct by lubricant-coolants (LC) of various types: synthetic, semi synthetic, oily and emulsions.On the base of investigations concerning various methods of the non-ferrous turning processing the favorable one has been selected taking in to consideration the economy, ecology and quality of the finished product (alloy). Two-stage process is developed. The main idea of the process is the elimination of the lubricant-coolants (LC) to the limit specified in advance. The applied method is centrifuging with subsequent final elimination of LC by thermal method.Constant value of LC content at the inlet of the thermal unit excludes practically the oxidation of metal and as a consequence increases the output by 10 –15 % in metallurgical processing."

Jan 1, 2003

By Slobodan B. Vujic

"Some twenty years ago, during construction of flotation in the “Veliki Krivelj” copper and non-metallic mine Bor, a computer supported system for remote controle of technological process was installed. Nowadays, the major part of equipment of this system is worn-out and technically old-fashioned. Having this in mind a decision was made to design a new computer supported information-management system for Flotation. The paper presents a concept and features of project solutions.For the requirements of remote monitoring and management of technological process in Flotation of “Veliki Krivelj”, Copper and non-metallic minerals mine in Bor, Yugoslavia (hereinafter: CNM Bor), a measuring-regulation equipment was implemented and a computer control system, adjusted for that time, built some twenty years ago. The major part of this equipment is today worn out and technically out of date.Having estimated that production and business activities could hardly be more efficient, operative and successful on one hand, and available mineral and other resources rationally exploited, the CNM Bor made a decision in 1999 to improve information-management function of Flotation. The idea was that the set task be realized through development and introduction into practice up-to-date integrated and computer-supported production-business information-management system. The first logic step in completion of this task refers to engineering-creative determination of information management system (hereinafter: IMS), namely to project elaboration.When considering the real system from technical, technological, organization, monitoring-management, logistic and business aspects, the Project on IMS of Flotation, should provide a rational, modern and, for the real system conditions, complete solution. The Project solutions should be based on the most recent knowledge from computer and measuring-regulation technics as well as from CIM concept (Computer Integrated Manufacturing)."

Jan 1, 2003

By Bronwynne K. Williams

"In deriving flotation kinetic models, the froth phase was, until recently, either ignored or treated entirely empirically. The behaviour of the froth is now known to be usually important and sometimes dominant in determining flotation performance. Hence numerous methods have been developed for sampling the flotation froths and models incorporating the effects of the froth behaviour have been derived.Such models will assist in determining more accurate estimations of the kinetic parameters utilised in the designing of industrial scale plants thus reducing the incurred costs of over designing. In particular, improved models for batch tests may lead to more effective use of batch testwork for prediction of continuous plant behaviour. A more detailed model is thus proposed which allows for a more realistic approach to the flow distribution in the froth phase.PROPOSED MODELThe batch flotation process is split into two stages in time, namely before the froth begins to overflow and after. The assumptions made, and hence the calculations, are different for each stage.The air enters the slurry at t=0 and generates froth. The superficial velocity of the air through the cell is given by go. It is assumed that the rate of froth breakage (gb) is constant during the first stage. The froth rises with a uniform net velocity throughout the cell and no mixing is assumed to occur.After the froth begins to overflow, the velocity distribution of the gas is modeled by segmenting the froth phase as shown in Figure 1. A model for bubble breakage rate or measurements of froth velocity allows one to obtain the volumetric rate of concentrate froth production. The entrained water and associated particles and a drop-back mechanism are also allowed for in the model."

Jan 1, 2003

By Shuji Owada, Mayumi Ito, Idemitsu Kosan Co. Ltd., Takehiko Nishimu, Sadayuki Shinozaki, Takashi Ando, Tomoe Ota

"fElectrical disintegration (ED) by high voltage electrical pulse is a relatively new technique which was demonstrated by Tomsk and Mekhanobr in the 1960’s and has been investigated in detail by Andres in the 1990’s. In the ED, the electrodes should contact to the targeted material and the energy of high voltage pulse is charged directly to the material. It has been reported that the ED is quite efficient to improve liberation of composite materials, because electrical current passes often through the conductive part and/or along the phase boundaries. Theoretically, the energy required in the ED should be lower than in the other mechanical breakage methods, because breakage occurs basically by tensile strength in the ED while in the other mechanical methods it does mainly by compressive strength which is generally ten times or higher than tensile strength.Coal, involving many kinds of mineral matters, is considered to be one of the targets for the ED to apply to. In Japan, national “Hyper-Coal Project” is now running, in which ultra-clean coal (less than 200ppm of ash, 0.5ppm of Na and K, and 2ppm of Ca) is planned to produce by combining advanced coal preparation and liquefaction technologies for the purpose of direct injection of coal combustion gas to turbine. The ED is one of the major techniques to be developed in this project, since mineral matters must be liberated before introducing to the following advanced separation processes. Liberation is important also for the utilization of middling coals generated from usual coal preparation plants. The application of the ED to the middling coals is considered effective for upgrading these coals with higher liberation degree and less energy input."

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 P. M. Solozhenkin

"Galvanochemical process (GChP)) cleaning of sewages is realized in the field of shortcirquited galvanic elements from the mixture current the materials place in purification’s solution and form multitude galvanopairs without external electric field in presence oxygen of the air. The galvanochemical process is electrochemical process utilizing galvanic pairs: coke - iron, iron - copper and others and process does not require chemical reagents.The effect of basic parameters of the cleaning effectiveness have been studied depending on oxidizing of galvanopairs. Adjusting nature, type of galvanic pairs and forming three component system possible to enlarge emf circuits to 2.378 V.The role of ?2, as basic agent, for generation of hydrogen peroxide and hydroxyl ions.It was stated, that removing of metal ions from solutions occur mainly on account of sorption and hydrolytic sedimentation of iron oxihydrates.Determined separate stages of the process: coagulation, sorptions of admixtures on freshly formed ferric oxides and oxidizing destruction of organic components of effluents in presence of ?2 ? ?2?2. Shown efficiency of the method for removing of Cu, Cr, Ni, Zn, As ions, as well as fluoride, phosphate and cyanide anions and oil products, surface-active and flotation reagents. Cleaned water can be recycled for some processes non-critical toward residual concentration of admixtures, as total salt contents is lowered on 60-75 % and reaching limits of concentration for toxic components.The concept of high power unit creation was developed, and galvanochemical pulsator is presented. The pulsator is not expensive, and exploitation expences are low, as well as servise is simple with high effectiveness, and capacity. The galvanoflotation process is developing, combining galvanochemistry and flotation of hydrofobic admixtures (oil, surface-active agents).The galvanochemical flotators are presented."

Jan 1, 2003

By Stefan Mutz, Thomas Pretz, Jörg Julius, Frank Hilbk-Kortenbruck, Aachen, Hartmut Harbeck

"The annual global production of primary aluminium was about 22 million tons in the year 2000. This represents the second largest production rate in the world market after steel. Experts are predicting that the global demand for aluminium will rise in the near future.In contrast to other metals such as copper, the recycling of aluminium is considered relatively difficult. There are two main alloying groups, namely cast and wrought. In the case of aluminium it is important that the constituents within the scrap aluminium to be smelted are clearly identified. Within the secondary remelting process alloying does take place, but a removal of unwanted metal constituents is problematic. Therefore mixed aluminium scrap (not genuine in-house collected material) can only be used to produce cast aluminium. Thus, in other words a down-cycling of wrought (extrusions and rolled) products occurs. However, in spite of these difficulties there is an increasing trend to produce aluminium from secondary scrap (approx. 35% in Germany). Similar trends have been identified in the USA and other industrialised countries. This development is mainly caused by the high energy consumption for the production of aluminium from bauxite. Producing aluminium from scrap is saving about 95 % of the energy in comparison to the processing of primary raw materials.An improvement in sorting technology is necessary to separate wrought and cast alloys of aluminium as the absolute amount of recovery from old scrap is higher than the demand for cast.This contribution presents some alternative methods, utilizing automatic picking technologies, which will be used to separate secondary aluminium in the future. During the recent years, some major progresses have been made in automatic picking technologies for different applications in the processing of primary and secondary materials.For the sorting of aluminium scrap a special additional sensor will be necessary. The best detection will ultimately be based on online elemental analysis of single particles. First investigations in the field of laser based systems for these applications have already been performed several years ago. One of the laser based techniques is the laserinduced breakdown spectrometry (LIBS)."

Jan 1, 2003