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By M. Eraydin

Dewatering fine particles (e.g., flotation concentrates) is inefficient, energy intensive and often requires large capital and operating costs. To address these issues, a series of advanced dewatering technologies have been developed at Virginia Tech. These include novel dewatering aids and a hyperbaric centrifuge. Typically, the moistures obtained using these methods are 30% to 50% lower than those obtained using conventional methods, as demonstrated in laboratory and pilot-scale test programs. With another novel dewatering technology that has been tested in bench-scale tests, the moistures can be reduced to levels once believed to be attainable only through the use of thermal dryers. In this communication, test results obtained with these advanced dewatering technologies are presented and compared.

Jan 1, 2014

By Leopoldo Gutierrez

Eight oil sand ores with the bitumen content ranging between 3.6 and 15 wt.% and the fines content (-44 micrometers size fraction) between 9 and 69 vol.% were subjected to the standard alkali extraction test used to measure the degree of oxidation of metallurgical coals. The results showed that there is a strong correlation between the absorbance of extracted solutions at a wavelength of 520 nm and the ratio of the fines content to the bitumen content. The latter factor is directly relevant to assessing the extractability of bitumen from oil sand ores. Bitumen extraction tests showed that the bitumen recovery decreased from 90 % to 30 % when the absorbance at 520 nm increased from 0.23 to 0.64. A comparison of the UV/visible spectra of solutions obtained from the alkali extraction tests with solutions of Aldrich Humic Acids suggest that low bitumen/high fines oil sand ores release substantial amounts of organic matter very similar, if not identical, to humic acids. In contrast, high-bitumen and low-fines ores do not release as much of the organic matter, and UV spectra of these leached substances are quite different from those of humic acids. Overall, the results show that chemical composition of bitumen in the tested ores varies greatly with ore type and oxidation, and that the alkali extraction test is a promising technique to quickly assess the extractability of bitumen from a given ore type.

Sep 1, 2012

The objective of the paper is to develop a material balance calculation procedure for a production unit involving two plants separated by a pipeline. The case study is taken from the oil sands industry. The raw sands are first mixed with water in a conditioning plant, then transported through a pipeline to an oil extraction plant. The combination of pipeline dimensions and nominal throughput creates a significant variable time lag between the two plants. As usual, mass balance calculations required for the evaluation of plant performance indicators, such as bitumen recovery, are inaccurate due to measurement errors. In addition, in the present case study, the time lag of the pipe creates an additional source of uncertainty, which may lead to misinterpretations and wrong decisions. Raw data are usually reconciled through steady-state mass balancing, to correct for measurement errors. However, because of the significant pipeline dynamic lag, standard steady-state daily mass balance may fail at giving an appropriate picture of the operations. The proposed solution to the data reconciliation problem includes the use of a pipeline plug-flow model in the mass balance calculation. To fulfil the industrial constraint that current data reconciliation must not modify past reconciled values, while still satisfying dynamic constraints, a daily one-step method, i.e. a unitary filter-ing horizon, is recommended. The method is illustrated with simulation data, and the results com-pared to those of standard data reconciliation methods.

Jan 1, 2014

Most of the Indian coking coals are medium coking and of very high ash content. Beneficiation of these coals is a must for their utilisation in coke making. During washing while the ash content of the coal is reduced, the same is expected to affect the reactive-inert ratio and the proportion of various petrographic constituents in the clean coal. This will affect the coking behaviour, including the expansion characteristics, of such coal. An increase in expansion behaviour of coal increases the wall pressure and may damage the battery wall. Therefore, close monitoring of coking properties along with drop in ash is necessary for smooth use of the coal in coke ovens. An effort is, therefore, essential to understand the impact of washing on its coking properties. The studies were carried out with captive coals of Tata Steel, India. Three medium coking coal samples namely, VII A, VI A and XI SEB seam coals of West Bokaro Colliery were used for the study. The coal samples after washing to different ash levels were subjected to the following analysis: proximate, crucible swelling number (CSN), LT GK test, dilatometer and plastometer tests and petrography. The experimental data were then analysed to assess the relationship of various coking properties of the coal with its ash content. The studies clearly show that there is a strong impact of beneficiation of the coal on its coking behaviour. The impacts are more at lower level of ash in the clean coal. In general, the coking properties increase with a decrease in ash. This is primarily due to an enrichment of vitrinte materials in the clean coal and an increase in the reactive-inert ratio in the coals. However, the most important impact of the lowering ash is on the increase in the swelling nature of the coal. The coals with lower ash become highly expanding in nature. This may be very critical from operations of coke ovens point of view, especially stamp charged coke ovens. Necessary precaution should be taken in selecting the other coal blend constituents when these coals are beneficiated to a very low level of ash content.

Jan 1, 2014

By D. Z. Wei

Amine collectors with different structures and length of carbon-chain have been widely used in oxide minerals flotation. In this paper, we synthesized one kind of binary amine, N-dodecylethyl- enediamine, and studied its flotation performance. From the results, we can see N-dodecylethylenediamine which has excellent frothability, is a new type of chelating surfactants. And it also has fine catchability to quartz and hematite. The recoveries of quartz and hematite increase with the augment of N-dodecylethylenediamine concentration. When the dosage of collector reaches 100g/t, the recoveries of quartz and hematite achieve 95.30% and 87.89% respectively. Meanwhile, the influence of pH on the flotation recovery of hematite is studied and test results showed that, as pH increases, the flotation recovery rises until pH=9. And the recovery reaches its maximum in alkalescence. The collector has better flotation capability to quartz than to hematite. And the maximum recovery of quartz is gained in alkaline media, which reaches 97.87%. Finally, the flotation mechanism of N-dodecylethylenediamine is discussed through the measurement of infrared spectroscopy.

Jan 1, 2014

Cyanide is reactive to copper minerals and is not suitable to extract the gold from the copper bearing ores. Ammoniacal thiosulfate is considered an excellent alternative lixiviant for leaching copper bearing gold ores. Unfortunately the results of high reagent consumption and poor gold ex-traction were found by thiosulfate leaching of synthetic gold ores containing chalcopyrite, chalcocite or bornite and a mild refractory copper-bearing sulfidic gold ore. In this investigation, several processes have been applied to reduce the impacts of these minerals on gold leaching. The process included: the pre-oxidation of copper sulphide minerals in water or ammonia solution, the reduction of dissolved oxygen in the lixiviant (0.3 ppm DO or 0.7% oxygen), adding phosphate anion in the leach or pre-leach stage, and the addition of a strong copper ligand (e.g., EDA and DETA). The results indicated that the gold extraction could be improved to 93% with the thiosulfate consumption being reduced to less than 8 kg/t. The dissolution of copper minerals was found to be the major reason for increased consumption of thiosulfate and the highly reductive leached surfaces are responsible for the reduced gold extractions.

Jan 1, 2014

By Ralph J. Holmes, Victor Sharp, Steven J. Spencer, Kevin J. Davey, Jonathan J. Campbell, Peter L. Phillips, David G. Barker

"Improved measurement tools for monitoring and control of AG/SAG mill performance have a high level of interest in industry. Historically, acoustic emission monitoring has been widely used on SAG/AG/ball mills and hydrocyclones to provide new information on the conditions inside these devices affecting their performance. The current work was focused on a new technique using surface vibration monitoring of a number of pilot-scale and production-scale AG/SAG mills to yield insights into the events occurring in the mills. The development of relationships between signal analysis outputs and mill operating conditions can be used for soft-sensor measurement of mill process variables. The technique used an array of accelerometers mounted on the mill lifter bolts linked to a fast data acquisition system which monitored the surface waves generated during operation. Details of the system are presented. Mill operating variables were adjusted systematically to provide a wide range of operating conditions for surface vibration signal collection. The experimental approach is discussed.The signals acquired during the experiments were analysed using a range of techniques. The results show that strong relationships exist between measured vibration power (both total power and within certain frequency bands) and mill load level/power and mill speed. A new method for extraction of power spectral density and band power information on features of interest in a mill rotation cycle is also presented.These results show that single sensor analysis information from the surface vibration system can be used as soft sensor inputs for monitoring process variables such as mill load that until now, have not been reliably measured. System outputs also show considerable promise in the area of condition monitoring. An example of the signal analysis output is presented showing elevated vibration levels in an area with higher resultant wear. Eventually, it is considered that outputs from this system for process variable and wear condition monitoring will be key new inputs to an online AG/SAG mill monitoring and control system."

Jan 1, 2003

By G. Belardi

This paper presents the preliminary results of a research programme conducted to assess the feasibility of a flotation technique in the remediation of soils severely affected by heavy metal contamination. The use of flotation in soil remediation is a recent practice. The main difficulties are given by the variety and peculiarity of the heavy metal containing species, and also by the grain size. Most of the studies reported in the literature concern the use of conventional collectors, such as xanthates, after a preliminary chemical modification of the metal bearing species through sulphidization. On the basis of the minera-petrographic characterization and of speciation, some classes of reagents have been selected, capable of acting both on metal-bearing species and all metallic cations to be separated. The design of the synthetic molecules has been based on the coordinative properties of the metallic centres and functionalized in order to act as collectors for a wide range of metals independently on their surrounding atoms. In laboratory experiments a sample of stream sediment has been utilized, whose contamination is caused by the runoff from Sardinia mine waste dumps and overflow from the settling ponds. The material showed contamination mainly from Zn, Pb and Cu and to a lesser extent from Cr, Ni, Cd, and Sb associated in mixed particles of Fe and Mn. Flotation tests on a laboratory scale have been performed on grain sizes less than 355 µm in laboratory cell Minerais & Metaux. The effects of the structure of collectors (functional group, chain configuration) as well as of the principal flotation parameters (such as pH, concentration of reagent) on the grade and recovery of heavy metals in the concentrate and in the tailings (remediated soil) have been investigated. The results of the laboratory tests substantially confirm the theoretical premises, and the most effecive reagents found belong to the classes ATP, MBT, MBO, fat acids and phosphates.

Jan 1, 2014

By Carlos Rabanal, Levi Guzmán

"The concern regarding grinding media consumption rates is as old as the invention of the tumbling mill. Over the years many materials and grinding media shapes have been tested. Through all this, steel grinding balls have proved to be the most effective media for comminution in tumbling mills. There have been several approaches to be able to the wear of the ball charge in any given mill, all of them based on limited empirical evidence. The mining industry still utilizes the Bond Abrasion test that was developed in the 1960´s. As shown later in this publication, this approach shows error greater than 60%. More recently, in 2007, Radziszewski from Mc Gill University has proposed a different total grinding media wear model; this model is based on decoupling the effects of the abrasion, corrosion and impact wear mechanisms. Also in 2007, Benavente, at the time with Moly-Cop Peru, presented an empirical model relating both ore properties and operational conditions that would affect the wear performance of the grinding media. For the database referred in this article, Benavente’s model shows an average error of ± 12% which represents a higher degree of improvement in comparison with previous approaches. The current paper presents recent research conducted by Moly-Cop Peru to further improve the capability of the empirical model originally developed by Benavente to estimate grinding media wear rates. The work performed included extensive determinations of the Bond Abrasion Index for different types of ores, collected at industrial grinding applications where the corresponding operational information was made available. The results of the research enabled us to build a more robust and confident model for estimating the grinding media wear rate. The average error of this new model is in the order of ± 9% which is a significant improvement over the models previously described."

Jan 1, 2014

By M. A. C. Goes

Over the last twenty years CETEM has been involved in the preparation and certification of reference material from ores, concentrates and related materials for use in analytical laboratories associated with mining, metallurgy and earth sciences. CETEM provides reference materials from mineral samples, not available from the existing sources, to meet the needs of the mining and mineral industry. CBPA-1 and CBPA-2 respectively are samples of copper sulphide ore and flotation concentrate, both originated from Sossego Mine, located in Pará State, Brazil. The batch characterization was carried out by a collaborative measurement program with participation of 20 industrial, commercial and government laboratories from South America, North America, Europe, Asia and Africa. The certificates and report were issued in December 2007 (http://www.cetem.gov.br/ mrc/ing). The objective of this paper was to describe the procedures for material preparation and the collaborative approach involving a collaborative interlaboratory measurement program to certify CBPA-1 and CBPA-2.

Jan 1, 2014

By M. Barsky, E. Barsky

It is generally accepted that the optimal flow velocity for gravity classification is the final particle settling velocity or, which is the same, the particle spin velocity. However, we have found differences between the settling velocities and the spin velocities of the very same particles. Here we present the results of experiments in a cascading gravitational classifier comprising eleven stages. The feed material was introduced at each stage successively, from the first to the eleventh. The optimal flow velocity was determined for each case. From these experiments it follows that the value of the optimal flow velocity depends to a greater extent on the point of introduction of the feed (i.e., on the design of the device) than it does on the interaction between the solid phase and the flow.

Jan 1, 2003

By X. Q. Chen

According to the different characters of the middle-low grade bauxite, based on the normal flotation & reverse flotation technology, the author innovates the new technology which is named bi-flotation, it integrates the advantages of normal flotation & reverse flotation, while avoids their disadvantages. Take Henan middle-low grade bauxite as research object, according to the pilot experiment of bi-flotation technology, the concentrate A/S is 9.37 and the recovery of alumina is 80.18% by flotation separate the raw ore which A/S is only 4.19.

Jan 1, 2014

By C. Dorfling

Experimental work was performed using a bench scale autoclave to evaluate the effects that leaching temperature, pressure, initial acid concentration, and the solid to liquid ratio have on the behaviour of base metals and platinum group metals in a high-pressure sulphuric acid oxygen leaching system. The concentrations of metals in the leach solution were measured over time at different leaching conditions. At the conditions investigated, the initial acid concentration had the largest influence on the copper leaching kinetics, while the leaching rates of the other precious metals (OPMs: rhodium, ruthenium, and iridium) were highly dependent on the leaching temperature. A set of chemical reactions that can be used to describe the leaching chemistry was proposed, and the associated reaction kinetics were quantified. As a first estimation, the rate expressions were considered first order, and the rate constants were determined using the method of least squares, considering the experimental and predicted concentrations obtained for the different leaching conditions. Of the OPM compounds, the sulphides showed the fastest dissolution rate, followed by OPM alloys, and finally the OPM oxides. During the initial leaching stages, base metals and OPMs competed for the available dissolved oxygen, with oxygen being preferentially used for copper leaching. Precipitation of OPMs during the initial leaching stages can be ascribed to copper and nickel dissolution according to exchange reactions between dissolved OPMs and copper present as digenite or nickel present as polydymite. Control of the autoclave residence time is of particular importance to enhance the selectivity of this leaching step, given the dependence of the PGM leaching rates on the extent of copper dissolution.

Sep 1, 2012

By Tracy Shimmield, Philip Samar

"Metals have been mined as ores since pre-history but metal production has increased dramatically in modern times driven by expanding Global GDP. Metal ore mining produces large amounts of waste rock and mine tailings. Mine tailings are the wastes produced after extracting the desired metal from the ore. There are several ways of dealing with this waste, and Ritcey (2005) identifies the following possibilities, land-based storage, backfill to the mine, deep lake disposal and marine disposal. In Papua New Guinea (PNG), both Misima and Lihir Mines adopted the marine disposal option, releasing tailings through a submerged pipe onto the sea floor. This special case is referred to as Deep Sea Tailings Placement (DSTP) in which the tailings deposition is sufficiently deep as to be below the euphotic zone. The most important aspect of deep sea tailings placement is that the tailings are deposited at great depth where exchanges between the seabed and the surface layers are small. The first quantitative multidisciplinary study of tailings impact on the deep sea was carried out from 2006 to 2010 in Papua New Guinea. The physical, chemical and biological work carried out has placed PNG at the forefront of research into the assessment and management of deep-sea environmental impacts related to mining in PNG. The study has provided data which has led to a better understanding of the ecological and geochemical processes in deep water that accompany DSTP in PNG and provided baseline data on deep-sea ecosystems in a scientifically poorly known tropical ocean. Additionally, guidelines on best practice for DSTP have been developed Here we present geochemical data obtained from sediment samples from the marine environment surrounding Lihir and Misima Islands."

Jan 1, 2014

By Wei Sun, Chengwei Li, Zhiyong Gao, Yuehua Hu

"Grinding for mineral liberation is a prerequisite for a successful flotation separation. Different grinding media produce mineral particles with different morphologies and surface properties. In this study, the surface physicochemical properties of fluorite particles produced by ball and rod mills were systematically investigated through single mineral flotation experiment, wettability measurement, X-ray diffraction (XRD) test and scanning electron microscopy (SEM) observations. The XRD observations reveal that the surface exposure degree for both mill particles follows the order {111} > {110} > {100}. The difference lies in that the rod mill ones have a higher exposure of more reactive {110} and {100} surfaces, leading to a stronger interaction with the collector. The difference also leads to their higher elongation and lower roundness values of rod mill particles which are beneficial for the particle-bubble attachment by shorting the induction time. The wettability and flotation results show that the rod mill ones have a lower critical surface tension and a greater hydrophobicity when treated with the collector solution and accordingly perform a higher flotation recovery. This work, for the first time, revealed the importance of the exposure of crystal surfaces in determine the shape factors and reactivity of the mineral particles and will help provide guidance for optimizing flotation separation and particle surface modification. INTRODUCTIONFluorite (CaF2) is the most important source mineral for producing F-based chemicals and materials which are widely used in industrial, environmental, and medical fields [1, 2]. In ore deposit, there are two kinds of occurrence forms of fluorite mineral. Firstly, the fluorite mainly coexisted with the gangue minerals like calcite (CaCO3) and quartz (SiO2). Because of their similar density and fine-grained dissemination in ore deposit, ball mill grinding before flotation separation has been widely applied to produce relatively fine particles [3]. Secondly, the fluorite is often associated with other valuable minerals with higher relative density such as scheelite (CaWO4) and cassiterite (SnO2). Due to their obvious density differences and coarsely grained distribution in ore deposit, rod mill grinding before gravity separation has been usually used to produce more uniform particles and avoid over-grinding [4-6]. After the gravity separation, a flotation separation is also employed to beneficiate the fluorite [7]."

Jan 1, 2018

The relative abundance of coal in India compared to other fossil fuels makes it a natural choice as the primary source of fuel, be it for steel making, power generation or for other uses. The wide variations in nature and type of Indian coals formed during lower Gondawana period and categorized as difficult-to-wash due to its typical mineral matter association with the organic matrix call for suitable beneficiation techniques as the preferred option for quality upgradation. The good quality coking coals of the upper seams are fast depleting leaving behind the inferior quality lower seam coal. The lower seam coals presently being mined are mostly low volatile coking coal (LVC). They constitute about 50% of the total coking coal reserves in India. The beneficiation of Low Volatile Coking coals pose a major challenge and detailed R & D studies was taken up to study the beneficiation characteristics of these coals. The studies revealed that the liberation characteristics at coarser sizes are very poor and the coal is to be ground to finer sizes for liberation. The most important factor that determines coal cleaning efficiency is liberation of organic matter from mineral matter. To achieve liberation grinding is necessary as a result range amount of ultra fines (-0.063 mm) coal is generated. Presence of these large amount of ultrafine in the coal fines, often impose severe technical constraints affecting not only its floatability but also in the downstream treatment of the products like dewatering and cake formation particularly when it is beneficiating through froth flotation. In the present paper optimization of ultra fines (-0.063 mm) has been tried for a LVC coal of Jharia coal field for the better liberation and beneficiation of the above coal fines. It is observed that by optimized, combination of size and number of balls generation of fines can be controlled with liberation. Keywords: coking coal, liberation, floatability, dewatering

Sep 1, 2012

By Dmitriy Makarov

The paper presents the modeling and analysis of oxidation of pyrite copper-zinc ore samples from the Letnee, Yaman-Kasy and Valentorskoye deposits. It is found, that the oxidized samples contain copper and zinc sulfates that are leached under the sample and water contact. It is shown, that sulfide floatability is decreased by the longer-term oxidation.We advise to improve nonferrous metals recovery by joint leaching and ultrasonic treatment of oxidized compounds. Study of the geotechnological processes of non-ferrous metal extraction, on the basis of two copper-zinc ore deposits shows, that heap leaching is of little use for the ores of the Letnee deposit. Leaching results for the Yaman-Kasy ore showed more promise.

Sep 1, 2012

By J. Y. Tian

In view of the fact that many domestic iron ore-dressing plant applying flotation cells in the re-verse flotation, to improve the technical level of magnetite reverse flotation, we apply such a technological process of one stage rougher and two stages scavenger flotation column respectively. The middling from the two stage scavenger process are returned to magnetic separation for condensing. By contrast, the technological process of one stage rougher and one stage cleaning flotation cells is made up of by multi-magnetic separation and magnetic middling regrinding separations. It has been proved that the flotation column we offer can simplify the technological process structure, obtain advanced technical indexes, run the system smoothly, reduce energy consumption, and be environ-mental friendly.

Jan 1, 2014

By S. Narra

Converting biomass into valuable fuel requires various preprocessing of the raw materials. Biomass densification is one of the conversion processes for its utilization. The aim of densification is to produce biomass pellets, which can withstand regular handling stresses and exhibit high densities with uniform size and shape. Physical properties, such as the particle size distribution after comminution is of highest importance for the binding mechanisms in the pelletisation process. Durability and strength of the pellets play an important role indicating the ability to withstand handling stresses. Particle size distributions of the cereal straws (Rye and Wheat) after specific comminution and liberation processes have been carried out with the help of three different image analysis (Microscope, Camsizer and Fibreshape). The durability of the pellets have been investigated as specified in the standards (ASAE standard S269.4) with a quadratic crate and the strength of the pellets with compression and tension testing machine (Zwick Roell type: ZMART.PRO). The particles size results showed differences in both length and width after different comminution processing. An exact comparison between the particle size analyses with the three different image analyses was not possible. The particle size distribution and the different comminution processes displayed influences on the durability and strength of the produced pellets. The particle size distribution displayed approximately 40 % of fines and 60 % of fibers. The particle size distribution displayed a direct relation to the durability of the pellets. Further durability and strength of the pellets displayed a good correlation.

Sep 1, 2012

By D. Whittles, S. Kingman, S. Bradshaw, N. Miles

The influence of microwave energy at high electric field strength on ore strength has been investigated. Two ores of varying mineralogy were treated in both multimode and single mode microwave cavities. After treatment, any change in strength relative to untreated ore was established. It was shown that in the multimode cavity reduction in strength was related to the applied power level. Results of tests carried out in the single mode cavities showed that, for both ores, reductions in ore strength > 50% could be achieved in very short periods (<1 second). Thermal stress analysis showed that the mechanism of microwave induced failure was the development of tangential stresses at the grain boundaries. It was concluded that operation at 915 MHz with high power and short residence times gives feasible scale-up possibilities.

Jan 1, 2003