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By K. G. Tshilombo

It should be possible to use an oxygen probe to follow iron removal during converting, if local equilibrium is established between iron in the matte and the iron oxides in the fayalitic slag. The oxygen activity is expected to increase strongly as the iron content of the matte decreases (and the iron activity in the matte drops) while the iron oxide activity in the slag remains constant. To test this idea, oxygen activities were measured in synthetic mattes (made up of mixture of Cu2S, FeS and Ni3S2) when in contact with silica saturated SiO2-FeO slags, and silica and (initially) magnetite saturated SiO2-FeO-Fe3O4slags. The measurements were performed on laboratory scale at 1250°C, using an oxygen probe consisting of a stabilized zirconia electrolyte and Fe/FeO reference, and containing the sample in a silica crucible. Electrical contact to the matte was by means of a platinum wire. The measured oxygen activity was sensitive to the iron content of the matte, and insensitive to the composition of the gas atmosphere over the melt. The measured oxygen activity was generally close to that predicted by Fact Sage calculations. This indicates that such oxygen activity measurements could be useful to monitor iron removal during converting of nickel-copper-iron mattes.

Jan 1, 2006

By K. G. Tshilombo

It should be possible to use an oxygen probe to follow iron removal during converting, if local equilibrium is established between iron in the matte and the iron oxides in the fayalitic slag. The oxygen activity is expected to increase strongly as the iron content of the matte decreases (and the iron activity in the matte drops) while the iron oxide activity in the slag remains constant. To test this idea, oxygen activities were measured in synthetic mattes (made up of mixtures of Cu2S, FeS and Ni3S2) when in contact with silica saturated SiO2-FeO slags, and silica and (initially) magnetite saturated SiO2-FeO-Fe3O4slags. The measurements were performed on laboratory scale at 1250°C, using an oxygen probe consisting of an MgO-stabilized zirconia electrolyte and Fe/FeO reference, and containing the sample in a silica crucible. Electrical contact to the matte was by means of a platinum wire. The measured oxygen activity was sensitive to the iron content of the matte, and insensitive to the composition of the gas atmosphere over the melt. The measured oxygen activity was generally close to that predicted by Fact Sage calculations. This indicates that such oxygen activity measurements could be useful to monitor iron removal during converting of nickel-copper-iron mattes.

Jan 1, 2007

Quartz, adularia and clay minerals from low-sulfidation epithermal veins at Hishikari were analyzed for their oxygen and hydrogen stable isotope compositions to establish the source of paleohydrothermal waters. Positive correlation between Au-Ag and adularia: quartz ratio, the presence of quartz pseudomorphs of bladed calcite, and Au-bearing smectite and vermiculite is indicative, but not definitive, evidence for the control of boiling on ore mineralization. Oxygen isotope equilibrium temperatures between quartz and adularia are about 220¦C and average homogenization temperatures of fluid inclusions vary between 190 to 210¦C. The calculated d18OH2O and dDH2O values (from quartz, adularia and early smectite) are consistent with paleohydrothermal fluids that were a mixture of magmatic and meteoric waters, or alternatively, the values could derive from heated meteoric water which had undergone isotope exchange during circulation through basement rock. Overall, d18Oqtz values in veins increase toward the north, most likely reflecting palaeo-fluid flow (source).

Jan 1, 2001

By Stanislaus Skowronski

THE melting of cathode copper, usually containing 99.98+ per cent. Cu, would appear to be a simple matter. Owing to the well known affinity of copper for sulphur, however, so much sulphur is absorbed by the copper during the operation that a long and expensive refining process is required to remove it, and the final product is inferior in purity and lower in electrical conductivity than the original cathode copper. The furnace operation, as now conducted, includes the following stages: 1. Charging the cathodes into the furnace. 2. Melting the cathodes. 3. Oxidizing period-saturating the copper with cuprous sub-oxide and bringing the metal to the condition known as "set copper;" this is now done by blowing air into the molten bath of metal. 4. Reduction period, otherwise known as "poling," whereby the oxygen previously added is removed by covering the molten bath completely with coke or charcoal and introducing large poles of green wood; this reduces the cuprous sub-oxide, bringing the copper to the "tough pitch" stage ready for casting. 5. Casting Period. Many experiments have been made to obviate the long periods of oxidation and subsequent reduction, with no success. While the copper first, cast will be good, as indicated by the set surface of the bars, it is impossible to hold it to the "tough pitch" condition, and long before the whole charge has been poured the copper will become "overpoled," entailing numerous difficulties. Sulphur has always been blamed by the furnace men as the reason why this refining process is necessary, yet the literature on the subject does not sufficiently emphasize how small a proportion of sulphur will ruin copper for practical purposes.

Jan 3, 1918

GWILLIAM H. CLAMER* (Philadelphia, Pa.).-Sulphur is not so detrimental in its effect if oxygen is also present, so that in sulphur-carrying bronzes and brasses, it is advantageous to maintain a certain percentage of oxygen. As a matter of fact, it would be possible sometimes to correct difficulties by actually adding oxygen. If the cathodes were charged directly into an electric furnace in a neutral or reducing atmosphere, a very high grade of copper would result by a simple melting operation. This would very largely eliminate the loss occasioned by melting in a reverberatory furnace. In such a furnace a large amount of slag is produced during the oxidizing stage of refining. Notwithstanding the fact that melting in an electric furnace might be somewhat more expensive than melting in a fuel furnace, the ultimate result would be a saving and the production of a very high grade of copper.

Jan 1, 1919

By Michael J. Sapko, Eric S. Weiss

The U.S. Bureau of Mines has been conducting research on the secondary explosion hazards associated with the mining of oil shale under gassy mine conditions. Explosive incendivity tests have been conducted in a 28 m~3 (1000 ft~3) gallery to evaluate the relative incendivity of experimental emulsion-ANFO blends. The incendivity was measured by determining the minimum inert stemming requirements for preventing the ignition of a methane-air atmosphere by the discharge of hot detonation products from a 5.7 cm (2.25 in) diameter borehole.

Jan 1, 1990

By Daniel B. Brimhall

The research presented here was initiated to investigate the role of atmospheric oxygen in the leaching of copper waste dumps. The problem of increasing the recovery rate of copper from these dumps is or great importance considering there are by conservative estimate in excess of fifteen billion pounds of copper located in dumps in the western United States. At this time, there is an increased interest in recovering copper from these dumps on a large scale. Large tonnages of low-grade material are being placed on the waste dumps of most copper mining operations in the western United States each day. The size of these dumps ranges from 5.5 million tons at Mineral Park, Arizona, to 4 billion tons at Kennecott's Utah operation (1). Leach solutions are recycled and contain ferrous and ferric sulfates. Large quantities of dissolved aluminum, magnesium and calcium salts may also be present. To this solution make up water is added to maintain the solution inventory and sulfuric acid is added for pH adjustment. Iron is introduced into the leach solution by the dissolution of the iron-containing sulfide and oxidized minerals present in the ore deposit. In addition to the iron from dump leaching, iron is also introduced during the precipitation process when the pregnant solution is passed over metallic scrap iron if cementation is used to reduce the copper in solution.

Jan 1, 1972

By Milton E. Wadsworth, Daniel B. Brimhall

Column leach studies of a low-grade porphyry copper ore were made. The technique used involved alternating oxygen absorption and copper leach cycles. The leach solution was displayed from the column with oxygen. The volume of oxygen reacting with the ore was measured with a gas burette. The copper released as a result of exposure to oxygen was correlated with the oxygen uptake. The oxidation rate was found to be dependent on the pH of the solution wetting the particles and was markedly increased by increasing the temperature of the system. Decreasing the particle size of the sample increased the oxidation rate. A material balance on the system indicated 1 mole of oxygen yielded in excess of 1 mole of copper in solution. A discussion of the important parameters is presented and the results are related to dump leaching in general.

Jan 1, 1974

By E. Asselin

Electrochemical polarization experiments were conducted on alloy 625 in ammonia solution between 25 and 225°C and the results were compared with those of an oxygen solubility model. Results confirm that corrosion is under oxygen control, Normalized corrosion rates are determined based on the rate of oxygen diffusion to the corroding surface, and the corrosion rate at 200°C (-9.7 µA.cm-2) is roughly 24 times higher than the corrosion rate at 25°C (0.4 nA,cm-2), An oxygen-solubility model for Supercritical Water Oxidation (SCWO) conditions was generated using the Redlich¬Kwong-Soave (RKS) equation of state, Results of the model confirm many of the experimental observations from SCWO reactors which suggest that corrosion is at a maximum at temperatures just short of the critical point, The RKS/oxygen diffusion model predicts that the corrosion rate at 365° C is ?85 times higher than the corrosion rate at 25' C. Given that a normalized corrosion rate is obtained, this type of model could be useful for selection of SCWO reactor materials.

Jan 1, 2005

By Yoji Imai, Akio Watanabe, Masakazu Mukaida

"To clarify the feasibility of alkoxides and acetylacetonates as precursors for laser CVD of metal oxides, vapors of tantalum or titanium alkoxides and zirconium acetylacetonate were irradiated by KrF excimer laser and deposits were characterized by XRD and XPS measurements. As for tantalum and titanium, non-stoichiometric crystalline oxides grew nearly phototropically, however, zirconium oxides deposited showed only halo-pattern by XRD measurements. Electric conductivity measurements of tantalum oxides implied the improvement of the insulating properties by the addition of activated oxygen to the ambient.IntroductionThere has been renewed increasing attention to the metallic oxide thin films because ofits promising usefulness in many applications, such as high-Tc superconductors and ferroelectric devices. A variety of thin film preparation techniques have been studied such as sputtering, chemical liquid deposition (sol-gel and metalorganic decomposition), pulsed laser deposition and chemical vapor deposition (CVD). Among them, we think CVD is the most promising method because it offers a high controllability of morphology and good step coverage at relatively high growth rate. Preparation of oxide films by CVD can be achieved using a precursor containing metallic element and oxygen containing gas such as N20 at the same time. However, metalorganic (MO) compounds which contain both metallic element and oxygen, directly bonded to metallic element, seems to be more favorable because some of MO has a good properties for CVD such as a rather high vapor pressure, stability in ambient and low toxicity."

Jan 1, 1998

By Massimiliano Zanin, William Skinner, Owusu Clement, Jonas Addai-Mensah, Daniel Fornasiero

This paper highlights the importance of pulp aeration in the selective separation of chalcopyrite from chalcopyrite/pyrite mixtures of varying pyrite content (20-80 wt.%). Laboratory batch flotation studies and oxygen demand tests were performed to predict the optimum amount of air required for the selective separation of chalcopyrite from pyrite. The pulp oxygen demand was shown to increase with increasing pyrite content but decrease with time as more air is introduced into the system. Complementary batch flotation tests showed significant improvement in chalcopyrite flotation under moderate pre-aeration of the pulp. However, a continuous decrease of chalcopyrite flotation was observed under highly aerated conditions. The amount of air required to achieve maximum chalcopyrite flotation recovery correlated positively with the mass fraction of pyrite in the pulps. The greater the wt.% of pyrite in the chalcopyrite/pyrite pulp, the longer the aeration time required. The optimum aeration time was established as the time before which the oxygen consumption rate constant reaches a bottom plateau. Surface analysis (XPS) indicated that the continuous decrease in pyrite recovery observed with increasing aeration time was due to the formation of more iron oxy/hydroxide on its surfaces, the same species accounting for the decrease in Cp recovery after prolonged aeration.

Jan 1, 2014

By S Brown

With oxygen conditioning routinely used in both the lead and zinc circuits at Pasminco Elura Mine a more sophisticated method of determining oxygen demand was required. It is known that different ore types have different oxygen consumption rates, however oxygen is added at a fixed rate regardless of ore type in the plant. Therefore, a simple laboratory test was devised to measure the oxygen demand of ores. The paper describes the technique employed, and provides an interpretation of the results. These data, together with pulp chemical measurements (Eh, pH and EDTA extraction data) were correlated against laboratory flotation performance to establish the relationship between oxygen demand and the position of the grade/recovery curve.

Jan 1, 2000

By Stephen R. Grano, Jon Glatthaar, Philippe Steinier, Christopher J. Greet

"The importance of the oxygen content of sulphide mineral pulps in determining which reactions occur, and their subsequent influence on flotation behaviour is grossly underestimated in most operating concentrators. While pH is routinely monitored, Eh and dissolved oxygen measurements are obtained infrequently. However, dissolved oxygen measurements in conjunction with other pulp chemical parameters (i.e. pH, Eh, and EDTA extractable metal ion analysis), can provide valuable insight into where and what type of reactions are occurring within a circuit. Unfortunately, these readings yield “instantaneous” measurements of the pulp chemical parameters.What is needed is a means of establishing how reactive a pulp is, and how this reactivity changes as components of the system are manipulated. Oxygen demand provides an opportunity to do this. Several attempts at measuring the oxygen demand of a pulp have been made in the past with varying degrees of success. Most notable among these are Noranda and BOC Gases.Learning from these experiences, Magotteaux have developed the MagO2 ® demand vessel to measure the oxygen demand of mineral pulps. This paper described the apparatus, and through a case study on Broken Hill lead/zinc ore demonstrates how the MagO2 ® demand vessel is used.INTRODUCTIONThe role of oxygen in flotation is complex. While a considerable body of work exists demonstrating the strong involvement of oxygen in the interactions between sulphide minerals and collector (Gaudin and Finkelstein, 1965; Gaudin, 1974; Woods, 1984; Laajalehto, Nowak and Suoninen, 1993), the presence of oxygen can also affect the oxidation state of sulphide and non-sulphide minerals, which can impact on their flotation behaviour. Further, sulphide mineral oxidation is related to their oxygen demand (Spira and Rosenblum, 1994)."

Jan 1, 2004

By Robert W. Bartlett, Keith A. Prisbrey

"Natural biooxidation of shallow, refractory ore heaps, relying on gaseous oxygen diffusion from the heap surface is attractive because of its simplicity and potential low cost, especially without using a lined pad, which is possible if percolation of leachate through the heap is avoided. In this case, the excess oxidation enthalpy must be removed by water evaporation from within the wet ore heap, and the rising water vapor flux within it will impede the downward oxygen flux. An analysis of this process shows that for typical values of pyrite grades and limited temperature increases in the ore heap, the oxidation rate and penetration into the heap is reduced to values between about 30 percent and 50 percent of those obtained when leachate percolation occurs and water evaporation is not a significant mechanism of heat removal.IntroductionHeap biooxidation of refractory gold ores, needed as a pretreatment step to liberate the gold for subsequent extraction by leaching, requires large amounts of oxygen for the normal amounts of sulfide minerals that are typically present, one to two percent pyrite and/or arsenopyrite.The importance and potential limitations of oxygen transport into commercial ore heaps, which are much larger than encountered with column tests of ore and with pilot heaps, has been recognized111 • Commercial ore heaps using radial stacking conveyors are typically about nine meters high and may be 100 meters or more in lateral dimension. Three oxygen transport mechanisms have been identified and analyzed: ( 1) natural convection, which arises from an increase in buoyancy caused by the temperature rise and gas composition changes associated with the exothermic oxidation of the sulfide minerals within the ore heap, (2) forced air ventilation, using low pressure fans and air distribution pipes within the heap, and (3) diffusion of oxygen in the gas-filled void spaces within the ore heap driven by the oxygen concentration gradient from the surface of the heap to the mineral oxidation loci within it."

Jan 1, 1997

By N. S. Dalal, B. Jafarl, M. M. Suryan, V. Vallyathan

"The biologic events leading to coal workers' pneumoconiosis (C'WP) are not yet fully understood. There is no good correlation between toxicity studies or animal models with human epidemiologic and pathologic data. Several studies have shown that the severity and prevalence of the CWP in miners correlate strongly with the rank and type of the coal mined. However this has not been found to be the case with laboratory animal models or in vitro studies. In 1980 Russian scientists Artemov and Resnik suggested that the discrepancy may be related to the excessive amount of short-lived free radicals present in freshly generated coal mine dust. Because of their short life, such free radicals would be absent in the ""stale"" coal dust used in most animal experiments. To test this hypothesis we have undertaken a systematic study of the generation, reactivity with oxygen and biological significance of free radicals in coal dust.Electron spin resonance (ESR) was used as a technique for the direct detection of radical production and kinetics of decay. ESR signals from the newly generated radicals decreased with time on exposure to oxygen or when stored in biological buffers at a rapid rate. In vitro biological tests were carried out which suggest that the reaction between the newly generated radicals and oxygen plays a significant role in the sample's cytotoxicity.Materials and MethodsESR measurements were made at X-band (~9.7 GHz) using a computer-controlled Bruker ER200D ESR spectrometer. 11te two coals studied in detail were obtained from the Pennsylvania State University Coal Depository. These were, a bituminous sample, PSOC-1172 (72% carbon) and an anthracite sample, PSOC 867 (95% carbon). Coal particles of several millimeter (mm) dimensions were evacuated to a pressure of ~10-3 mm Hg typically overnight. Without exposure to air, these particles were ground in an agate mortar with an agate pestle for about 30 minutes and then sieved through a 20 \1111 mesh filter before ESR measurements or cytotoxicity studies. As an index of cytotoxicity, hemolysis was measured according to the method of Harrington, with minor modifications. Sheep erythrocytes (2%) were incubated with test samples at 37°C for one hour, and the hemoglobin released was quantitatively estimated photometrically. Additionally, release of alveolar macrophage enzyme lactate dehydrogenase (LOH) was estimated after incubation of the macrophages with the coal particles at different time intervals after the grinding. Enzyme activity was assayed according to the method of Wrobleski and LaDue and expressed as percent of enzyme released in 2 hours per million cells with 1 mg of coal."

Jan 1, 1989

By W. Hoecker, S. Watson

The use of oxygen (Goldox™) in gold leaching has emerged as a significant modification in the past nine years. The Goldox™ process was ori gi na 11 y developed by Afrox Ltd ( part of the BOC Group) and is currently used in South Africa, Australia, Canada and the United States. Although a variety of benefits have been observed with oxygen, this paper out 1 i nes the main ones with reference to Australian plant data. The case studies were categorised into the ore type: Oxide, blends and primary ore.

Jan 1, 1992

By David J. Krichten

A method of retrofitting air-fuel burners with oxy-fuel capability overcomes the potential problems associated with oxygen combustion in aluminum melting furnaces. The retrofit burner uses the existing combustion air connection, burner housing, and burner tile and replaces the gas tube with an oxy-gas burner. Maintaining a portion of the air flow to the burner reduces the potential for localized overheating. Proper design of the burner reduces NOx emissions by moderating the flame temperature with furnace gas recirculation. Economic analysis of using oxygen shows the benefits are increased productivity and reduced overall unit cost of melting. In practice, the melt rate in rotary furnaces increases by up to 50% and by up to 35% in reverberatory furnaces. Oxygen utilization reduces total melting cost by 112-314 cents per pound of aluminum melted.

Jan 1, 1997

By M. Cloete, C. MacLagan, A. Newall

This paper initially gives a brief overview of Zinc Corporation of South Africa Limited (Zincor). The original design parameters of the Zincor roasters are compared to the current operation, and the requirements for efficient roasting are listed. Roaster operational problems experienced during the early to mid 1990's are outlined. A description of the investigation and the outcome to increase overall roaster availability are given. The history and the development of the use of oxygen at the Zincor roaster operation, with an account of the associated operational experiences, are explained.

Jan 1, 2000

By J. E. Forbes

Oxygen enrichment of the converter air at Rustenburg Platinum Mines by J. E. FORBES (Associate Member)* An account is given of the adoption of oxygen enrichment to accelerate converting operations and so permit the handling of larger quantities of feed materials. In addition to achieving its object, the use of oxygen-enriched air (6 per cent oxygen by volume) results in an increase in the concentration of sulphur dioxide in the converter off-gas. The slags have the same composition as those produced without oxygen enrichment, and the operation of the converters is easily controlled.

Jan 1, 1977

By G. S. Victorovich

Technical progress in primary smelting has changed the face of the copper industry in the years since the Second World War. Much of this change has resulted from a wide acceptance of flash smelting technology. In addition, research has been directed toward devising converting processes to replace conventional Peirce-Smith converting technology. One major thrust has involved a revival of the old " ", idea of oxygen flash converting of comminuted mattes. This paper reviews the 60-year history of flash converting. Particular attention is paid to Inco's investigations into the processing of white metal containing significant amounts of nickel and, in some cases, iron. Thermodynamic analysis and laboratory experimental results are presented which throw light on the behaviour of nickel and other salient features of flash converting. The possible role of oxygen flash converting in the copper pyrometallurgy of the future is briefly discussed vis-a-vis direct production of copper.

Jan 1, 1993