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The Effect of Ionic Strength of Plant Water on Valuable Mineral and Gangue Recovery in a Platinum Bearing Ore from the Merensky Reef

Sep 13, 2010

By T Tran, F Lucien

Supercritical fluids (SCFs) have gained recognition as solvents for the extraction of a wide range of organic materials. Their principle advantages over conventional organic solvents are that they possess much more favourable transport properties and that such properties can be easily altered by adjusting the system temperature and/or pressure. More recently, SCF solvents have been employed in the extraction of metal ions. The direct extraction of metal ions using SCFs such as CO2 is normally not possible due to the charge neutralisation requirement for solubilisation. However, extraction can be achieved with a SCF solvent containing an organic complexing agent as a cosolvent (Laintz et al, 1992; Laintz and Tachikawa, 1994; Dehghani, 1996). The role of the SCF is therefore similar to the role of a diluent in conventional liquid-liquid or solvent extraction processes. In this regard, SC-CO2 is a particularly good diluent since it exhibits good solubility for many organic complexing agents. The extraction of metals with SCF solvents has been examined mainly in the analysis of environmental samples and the treatment of metal contaminated wastes. Nonetheless, some interesting results have been reported recently on the extraction of rare earth metals, which highlight the potential of SCF solvents in mineral processing applications (Laintz and Tachikawa, 1994; Dehghani, 1996).

Jan 1, 2000

The cleaning of copper containing fayalite slag using a CuFe alloy was studied under an oxygen pressure ranging from 10-7 to 5 X 10-11 atm at 1200º c. The reduction of copper from fayalite slags by Cu-Fe alloys was found to be very effective. For example, at a P 02 of 10-7 atm, the copper content in the slag was reduced from 4.1 to 0.402 wt. percent after 90 min. of reaction time using a Cu- 5.27 wt. percent Fe alloy. The copper reduction rates were found to be independent of P02 in the gas phase when using Cu-Fe alloys which exhibit an iron activity of greater than 0.4. A mechanism for slag c1eaning is proposed based on the concept that the Cu-Fe alloy lowers the oxygen potential of the slag according to Eq.1 1, fol1owed by the reduction of cuprous oxide by wustite as shown in Eq.2. Here X represents element X in the alloy phase while (X) represents the element in the slag phase. The copper and iron transfer behaviour obtained in this study are explained by a ?Stepwise equilibrium model.

Jan 1, 1985

By K Saito, M Hasegawa

Removing sulfur and phosphorus from molten iron can be expressed by the following reactions, respectively. [S]Fe + (O2-)slag = (S2-)slag + [O]Fe [P]Fe + (3/2) (O2-)slag + (5/2) (FeO)slag = (PO43-)slag + (5/2) Fe(liquid) These equations indicate that desulfurisation and dephosphorisation have opposite oxygen potential conditions. If a small amount of desulfurisation slag not removed is carried over to dephosphorisation process, the reaction of sulfur mentioned above proceeds toward left hand resulting in increasing sulfur content in molten iron. For better understanding of such re-sulfurisation reaction in hot metal pre-treatments, the present study aimed at evaluating the effect of iron oxide on the sulfur distribution ratio between slag and hot metal. To measure sulfide capacities and FeO activities simultaneously at temperatures below the melting point of pure iron, CaO-SiO2-FeO and CaO-Al2O3-FeO ternary molten slags were brought into equilibria with copper-iron-sulfur liquid alloys, and the equilibrium oxygen partial pressures were determined with an electrochemical technique involving the stabilised zirconia solid electrolyte. The experimental results showed that the sulfide capacity increased with an increase in FeO content, and this trend was consistent with the fact that FeO was basic. Although the addition of FeO raised the FeO activity and oxygen potential, the calculated value for sulfur distribution ratio between slag and hot metal increased with increasing FeO content.

Jun 19, 2024

By A. Ghahremaninezhad, E. Jorjani, A. Riahi, Islamic Azad University, B. Nazari, H. Hani, Z. Manafi

The presence of a high iron concentration, 9.1 g/L, in the raffinate of the Sarcheshmeh copper heap bioleach process led to the formation of various types of jarosite, (K,Na,NH4,H3O)Fe3(SO4)2(OH)6, on the heap mineral surfaces. This study probes iron removal from the raffinate using a bio-oxidation process based on A. ferrooxidans bacteria in the presence and absence of jarosite seed. The jarosite seed was biologically synthesized using A. ferrooxidans bacteria. The effect of solution pH (1.5 to 2.5) and jarosite seed dosage (0 to 15 wt.%) on iron removal was examined. It was demonstrated that the concentration of iron ions present in the raffinate decreased from 9.1 g/L to 2.5 g/L with the addition of 10 wt.% jarosite seed at pH 2 and 130 rpm mixing rate at 32°C. Three different types of raffinate including (1) native raffinate containing 9.1, 3.4, 5.7 g/L of total, ferric and ferrous iron, respectively, (2) bio-oxidized raffinate in the absence of the jarosite seed containing 8.5 g/L total iron (mainly ferric with negligible ferrous), (3) bio-oxidized raffinate in the presence of jarosite seed containing 2.55 g/L total iron (mainly ferric with negligible ferrous) were used in mesophilic, moderate thermophilic and thermophilic bioleaching processes. The results of the flask tests showed that the highest copper bioleaching recoveries of 9.4, 49.4 and 90.8 % were achieved using raffinate (3) with mesophilic, moderate thermophilic and thermophilic bioleaching processes, respectively.

Jan 1, 2016

By Leslie C. Taylor, Scott A. Yamada, William L. Fourney

Previous studies have shown that the pressure load on a target by a buried explosive charge is not smoothly distributed. The effort reported here was undertaken to explore the mechanisms believed to cause this uneven pressure distribution: jets from the surface originating in instabilities caused by the explosive shockwave interacting with surface irregularities. Small-scale tests using conical, hemispherical, and cylindrical indentations in the sand surface above a buried charge were conducted to identify trends in the velocity and form of the resulting jets. In these tests, the most important factor affecting the resulting jets was the distance between the bottom of the indentation and the top of the charge. Cylindrical indentations resulted in higher jet velocities than those from comparable hemispherical and conical indentations.

Jan 1, 2012

By Sepulvedam Jaime E., Levi Guzmán Rivera

"Grinding media consumption rates and their dependence on key operating conditions in semiautogenous grinding mills is analyzed on the basis of a detailed mathematical model recently developed by Moly-Cop´s specialists which describes and takes into account the three primary media consumption mechanisms, namely: abrasion/corrosion, surface spalling and impact ball breakage. The influence of key mill operating conditions – such as ball filling, discharge grate opening, mill speed, lifter profile, and ball quality – on their corresponding grinding media consumption rates is explored via a variety of model simulations, discussing in every case the independent contribution of each of the indicated consumption mechanisms to the estimated total ball consumption rate.INTRODUCTIONA thorough understanding of the independent contribution of each grinding media wear mechanism is extremely important, especially in semi-autogenous grinding (SAG) operations where macrowear (spalling) and ball breakage cannot be ignored or neglected. The high impact conditions imposed in modern SAG milling environments has created serious challenges for grinding media manufacturers since their products must be able to perform with minimal breakage and surface spalling.GRINDING MEDIA WEAR MECHANISMFor SAG milling operations, at least 3 different mechanisms have been identified as the main contributors to the observed overall grinding media consumption, here referred to as: abrasion / corrosion, ball breakage and surface spalling.Wear by Abrasion/CorrosionThe abrasive/corrosive wear mechanism has been discussed in depth in previous publications (Benavente Hector, 2007; Guzman Levi, 2014; Sepulveda and Morrow, 2014). The most widely accepted approach to mathematically characterize the consumption (wear) kinetics of grinding media in rotary tumbling mills is known as the Linear Wear Theory (Prentice, 1943; Norquist, 1950; Sepulveda, 2004) which claims that—at each instant 't' after a grinding body enters the mill load—the rate at which the body loses weight is directly proportional to its surface area exposed."

Jan 1, 2016

By A. A. Nourbakhsha

During the last few years, low cement castable refractories found more application in industry, because of good low and high temperature mechanical properties.In the case of alumina based castables ,usually fume silica or reactive alumina are used as superfines in the matrix to form mullite at high temperature which depends to source of alumina . Mullite network formation improves the hot mechanical properties and thermal shock resistance of bodies. The mullitisation of andalusite (so called primary mullite) also produces a certain amount of rich silica glass, part of it being expelled out of the grain. This phenomenon restrict the application of andalusite low cement castable in pig iron ladle. In this research, firstly 8 pig iron ladles from ESC(esfahan Steel company) with different conditions selected and monitored during usage to determine of main factors affecting on corrosion of refractories. Results showed that tap to tap time and undischarged pig iron are the main ones.Therefore monolithic refractories such as castables which increase thermal shock resistance could be substituted. Regarding to ternary phase diagram of Al2O3-SiO2-CaO ,fumed silica was selected as fine particle.After optimization of particle size distribution by using of modified andreasen equation and rehological properties ,different mixture were composed with andalusite ,fume silica, reactive alumina,secar 71 ,SiC and kyanite.All aggregates system components were mixed dry for 1 min in hobart mixer .After water addition wet mixing was continued until getting flowing about 4 min.The ready mixes were poured in the moulds of of 25mm X 25mm X 140mm with vibrations .After demoulding the samples were cured for 24 hrs and dried at 110OC/18hrsand then fired at 1100-1500OC. Physical ,mechanical ,phase analysis(XRD) and microstructure studies (SEM)were carried out according to ASTM standards. Results showed that by addition of kyanite ,more mullite phase formed through the matrix but,because of expansion occured during this phase transformoration, some cracks formed and mechanical properties decreased.By SiC addition the silica film on the surface of SiC lead to improvement of mechanical properties at high temperature

Oct 1, 2011

A large lab apparatus was designed using a scale-down methodology based on the design legacy of the current FLSmidth commercial forced air flotation machines. This new apparatus, along with a new test methodology, was used to evaluate new rapid prototype concepts. The apparatus was designed to monitor bubble size, power, pumping capacity, Jg, velocity profiles, froth character, and tip speed. The methodology developed follows a sequence that goes from hydrodynamic tests and solids suspension tests to a flotation kinetic test. This methodology has been demonstrated to be a good tool to determine the effect of machine design changes on flotation.

Jan 1, 2012

By Norman Pilling

The effects of lead and tin up to maximum contents of about 0.1 per cent. each, in the presence of oxygen between 0.04 and 0.30 per cent., have been studied. Tin is retained efficiently in the oxidized condition, whereas lead is not. An approximate relation between the lead-oxygen and tin-oxygen contents is deduced which, if observed, permits the presence of these elements without detrimental effect. Excess of lead beyond this limit affects ductility and rolling properties adversely and an excess of tin correspondingly diminishes the conductivity. It is shown that copper carrying a combined lead and tin content of several hundredths per cent., yet fully equal in quality to electrolytic wirebar, may be produced under commercial conditions. TIN is not normally found in more than bare traces in current grades of American electrolytic copper, and lead is rarely found to more than a few thousandths per cent. In the electrolytic refining of copper these metals do not present great difficulty in separation and their presence in any considerable amount in copper that has been refined by this method need not be tolerated. On the other hand, the effect of these elements is not entirely academic, as a considerable tonnage of scrap copper liberally contaminated with them has been reclaimed by the fire-refining process into metal with a residual lead and tin content of several hundredths per cent., yet having excellent working properties and fully equal in quality to current grades of electrolytic wirebar. Such copper has been found entirely suitable for use in the manufacture of electrical apparatus. In the absence of oxygen, tin is known to depress the conductivity rapidly, and lead to impair ductility and the rolling properties, yet the effects of these metals on commercial grades of copper-i. e., copper containing from 0.03 to 0.10 per cent. of oxygen-apparently has not received systematic attention. Occasional reference is made to the fact that in the presence of oxygen lead may be tolerated, yet Addicks says,1 in regard to overpoling: "The unstable condition can be controlled by adding certain substances, notably lead, in small quantities, but as mere

Jan 2, 1926

By E. Ghali, W. Zhang, C. Su, N. Sorour, G. Houlachi

"Zinc electrowinning process is sensitive to the presence of metallic impurities such as lead ions that could substantially and negatively affect the power consumption and surface morphology. Effect of various concentrations of manganese ions and traces of lead ions up to 2.5 mg L-1 added to the electrolyte during electrowinning have been investigated by electrochemical polarization techniques such as galvanostatic, cyclic voltammetry and potentiodynamic. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to examine the surface morphology and crystallographic orientation, respectively. Microwave plasma-atomic emission spectrometry has been used to determine the lead content in the deposit and in the electrolyte after electrodeposition. It was found that lead ions added to the zinc electrolyte led to the increase of cathodic overpotential and current efficiencies of zinc deposit. However, addition of Mn2+ into the zinc electrolyte resulted in the decrease of cathodic potential and current efficiency of zinc deposit. It can be stated as example that galvanostatic polarisation at 40?C and 52.5 mA cm-2 in presence of lead up to 0.1-0.2 mg L-1 in the electrolyte and 8-12 g L-1 Mn could be better considered as practical working parameters for electrowinning process.INTRODUCTIONApproximately 85% of the global production of zinc metal is produced by electrolytic process (Sinclair, 2005). The main goal of the zinc plant is to obtain pure zinc deposits with high current efficiencies. Smooth and pure deposits with high current efficiency (CE) are always obtained from pure electrolytes (Alfantazi & Dreisinger, 2001). The presence of metallic impurities in the zinc sulphate electrolyte is a major problem for the zinc electrowinning industry, since decreases in current efficiency, changes in deposit morphology and cathodic polarization are observed for electrolytes containing small concentrations of impurities (Ault & Frazer, 1988; Muresan, Maurin, Oniciu & Gaga, 1996). Low level concentrations as parts per million of these impurities are reported to influence negatively the zinc electrodeposition (Beshore, Flori, Schade & O'Keefe, 1987)."

Jan 1, 2016

By W. E. Wallace, V. Castranova, F. Saus, D. Bates, C. A. Hill, V. Vallyathan, M. J. Keane

"Two in vitro systems are being developed to model initial stages in the interaction of respired dusts with the acinar region of the lung. Incubation of quartz and kaolin with dipalmitoyl glycerophosphorylcholine, a major component of pulmonary surfactant, suppresses the prompt C)1otoxicity of both dusts as measured by in vitro enzyme release from pulmonary macrophages or assay by erythrocyte hemolysis. Additional data is presented to quantitate the detoxification of quartz and kaolin by dipalmitoyl lecithin. Subsequent incubation of lecithin treated dusts with phospholipase enzymes results in partial to complete restoration of the assayed cytotoxic potentials, dependent on the lipase activity applied, the incubation time, and the mineral. Restored cytotoxic potential is due to removal of the prophylactic lecithin surface coating and/or due to residual lysolecithin which is produced by the partial enzymatic digestion of lecithin. Data is presented on the contribution of each mechanism to the restored toxicity. Again, this is dependent on the mineral used, the lipase activity applied, and digestion time. Additionally, a system is under development to challenge pulmonary macrophages in culture with native and surfactant treated dusts. A preliminary test of the dipalmitoyl lecithin - quartz rabbit pulmonary macrophage system is presented to illustrate the method.IntroductionRespirable quartz dust exposure is known to cause librotic lung disease; respirable clay dust exposure is less likely to do so as indicated by epidemiologic data on occupational exposures and by animal model studiesP·7) The hypothesis that damage to pulmonary macrophages in the acinar region of the lung by respired dusts is an early event in the disease process requires consideration because kaolin clay and quartz dusts are comparably cytotoxic to pulmonary macrophages in vitro.(3•9)"

Mar 1, 1989

By K. Oraee

Proven and probable coal reserves in Iran are estimated to be in excess of 5 Billion tons while the annual coal production is a mere 2 Million tons. Underdevelopment of the industry has proved higher production levels to be impossible, despite growing demand for energy supplies. The existences of numerous legislation are thought to have a detrimental effect on coal mining activities to the extent that some business entities have become uneconomical in many areas. This paper provides an analysis of the prevailing mining laws, policy making, legal frameworks and obstacles. It also outlines some other obstacles enshrined in the law and also highlights areas where foreign direct investment should be encouraged. The costs of lost opportunities are then estimated. The paper concludes by demonstrating that deregulations, amendments and in some cases complete abolishment of the incumbent legislations governing the coal mining industry will greatly enhance development of the industry. The analysis provided in this paper together with the results obtained, can prove useful to macro-economic policy makers both at local and national levels.

Feb 27, 2013

By Peck RC

The ore body at Elura contains fine grained galena and sphalerite in a matrix which is mostly pyrite. A differential flotation circuit concentrates lead and silver in the first section and zinc in the second. The lead section, shown in figure 1, was sampled in detail previously and the metallurgical performance assessed on a size by size basis. That assessment took no account of liberation and given the fine grained nature of the ore body, this could lead to an incomplete picture of the flotation performance. Liberation measurements were made using the QEM*SEM system on four size fractions of samples taken from seven different streams in the lead section. Using the mineral flows obtained from the mass balance around the lead section an excellent liberation balance was obtained which enabled the effect of liberation on the flotation performance to be assessed. The measurements indicated that only 17 per cent of the galena and 28 per cent of the sphalerite in the flotation feed was liberated. On the other hand 31 per cent of the gangue iron sulphides were liberated. The final concentrate was largely composed of locked galena and locked iron sulphides with 85 per cent of the product being locked. There was a small but significant fraction of liberated pyrite.

Jan 1, 1991

By Mark Sherman, M. Dennis, Raj Rajamani

"The two Alumbrera 36ft (10.97m)dia. SAG mills were sized, using the FDW ""Grindpower 'I program, to treat an average of 1852 tph each. This paper describes how modelling of the shell lifter design, using the Millsoft program, identified milling inefficiencies caused by poor charge motion. This explained the ""as built"" circuit's inability to achieve the throughput rates predcted by the circuit's designer. Use of the Millsoft program to design a new, dramatically different lifter configuration, in conjunction with a different approach to variable speed drive utilization, has resulted in an improved charge motion and a 30% increase in hard ore milling rates. The new lifter design has allowed the designer's predicted average throughput rates to be achieved.IntroductionThe Alumbrera project grinding circuit consists of two 36ft dia. X 17ft EGL, 13 500 kW, variable speed, gearless drive SAG mills coupled to four 20ft dia. X 30ft EGL, 6 000 kW fixed speed, gear driven, ball mills. The circuit is configured as two identical grinding aisles, each consisting of one SAG mill and two ball mills. No pebble crushing circuit was installed due to the expected absence of a critical size fraction in the first years of production. However, the grinding circuit layout does incorporate space for a pebble crushing retrofit. At present, only about 5% - 10% of the new mill feed reports as trommel oversize and is recycled back to each SAG mill using a water cannon.The circuit was designed to be ball mill limited and to treat the four major Alumbrera ore types at rates varying between 68 000 tpd, and 89 750 tpd, depending on ore hardness. Average throughput rate, and hence nominal design rate, for the grinding circuit was 80 000 tpd (1 852tph per line at 90% availability)."

Jan 1, 1999

By K. Kavouridis

The competitiveness of power production from lignite depends on the ability of coal industry to meet CO2 emissions limits, as specified by the Kyoto protocol. According to the National Allocation plan issued by EC, power plants should reduce CO2 emissions to a certain level, other-wise they will be obliged to cover the difference buying CO2 certificates through the Emission Trading Scheme. These charges will increase the operating cost of current units, as well as the investment cost for new units. To predict the increase in the marginal cost of electric power produced from the current plants of Western Macedonia, an emissions factor (CO2 t/MWh) for various units has been computed. Based on the algorithm used, this factor depends on the calorific value of the lignite, the efficiency of the power plant and the oxidation factor of the unit. For lignite plants with efficiency ~37%, CO2 emissions factor ranged from 1.19 t/MWh to 1.32 t/MWh. The increase in the marginal cost of kWh, as compared to the values of CO2 certificates, is higher in units fed with low quality lignite and worsens if the efficiency of the unit is low too. Also the presence of calcareous minerals in lignite increases the CO2 emissions and consequently the cost of power generation.

Jan 1, 2006

By H. A. Kortmann

For the commercial production of iron ore pellets from hematite ores, as it is practiced in various pellet plants, the addition of lime has shown to be an efficient means with a view to improving cold compression and abrasive strength of the indurated pellets considerably. Unfortunately, it has also been shown at the same time, that the metallurgical properties as, for instance, swelling behavior, softening during reduction under load and disintegration of the grain, can be adversely affected to a high degree. In the course of smelting tests carried out by renowned steelworks, blast furnace operation was heavily disturbed by the swelling and early softening of the pellets, also by their disintegration in the low-temperature range, which altogether led to a considerable lowering of the smelting rate (1, 2, 3).

Jan 1, 1972

By J. A. L. Napier, J. S. Kuijpers

SYNOPSIS This paper demonstrates that the horizontal stresses induced by the creation of a tabular scope in a single mining step are always tensile at the centre of the stope span, but that compressive stresses are actively generated in hangingwalls and footwalls during sequential mining. A stress-distribution mechanism is introduced, and is used to explain the results for elastic behaviour, and for inelastic behaviour both during a single mining step and during multiple mining steps.

Jan 1, 1991

By Glenn A. Hazen

Longwall mining is the preferred method for removing underground coal since a larger amount of coal can be removed faster and with less waste when compared to the room-and pillar type mining. Thus, the coal tonnage removed each year by longwall mining methods has increased dramatically. However, a high extraction rate results in surface subsidence which has adverse effects on the environment and on surface structures. Predictions of structural damage are dependent on the magnitude of the expected horizontal strains. Three methods for predicting subsidence characteristics are considered in this paper: the graphical method, the profile method, and the finite element method. All three methods can be used to predict ground movements and horizontal strains. However, the finite element method, which takes into account the structural properties of the stratigraphy and equilibrium of the overburden, is theoretically the more logical choice for use in subsidence prediction.

Jan 1, 1987

By Rob Farnfield, Mike Kelly, Toby White

There are a variety of sources of dynamic stress which can affect a building and give rise to cracking. A two-storey house, situated in the middle of a surface coal mine was monitored for a period of 30 months to attempt to identify the major causes of cracking. The factors described as environmental include internal and external temperature, humidity, wind speed and direction, rainfall and water table level. These were monitored using a weather station and piezometer and recorded every 20 minutes. The other factors are vibratory and include normal household movement (walking, shutting doors etc.), vehicle vibration and blast vibration. All the significant vibrations in the house were recorded using four sets of velocity transducers and accelerometers.

Jan 1, 1993