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By Nolberto Moreno Borjas

This paper outlines the detrimental impact that unblended ore can have on the Ni and Co recoveries and the ore slurry density with real data from the Caron low-pressure ammonia leaching process for the Punta Gorda ore. The author briefly discusses the reason for the decrease in slurry density that the process experiences. The lower metal recoveries in the process that are caused by the unblended ore chemical characteristics and variations are shown with a data base statistical analysis drawn from the results obtained from a pilot test, designed with different ore bypassed from the normal process flow and a similar ore from a similar metallurgical treatment. Keywords: Ni-Co Laterite, Caron Process, Ore Blending, Slurry Density, Metal Recovery

Jan 1, 2004

By Gaballah I.

Elimination of arsenic, mercury and zinc from synthetic solutions containing H;\A.sD4. HgCI2 and ZnCI2 using modified barks was investigated. The pH range was varied from ?1 to 10. The initial concentrations of individual element were 10,100 and 1000 ppm. More than 99 % of mercury and 65 % of zinc cations were removed by the modified bark .. In this case, the modified bark reacts as a cation exchanger leading to the release of ' two protons for every HgII or ZnII fixed by this material. About 30 % of arsenic was eliminated from the solution. This 'low efficiency could be attributed to? the presence of arsenic ,as. anion. Decontamination of a treated industrial effluent containing 4 ppm of ion? metals was performed on a pilot plant scale by the modified bll(k. More than 70'% of these ion metals were eliminated.

Jan 1, 1995

By R. C. Nascimento

It was investigated the effect of the addition of bentonite on the physical propertiesof pellets produced from fines of manganese ores. Cold-bonded pellets were produced. Pellets bearing up to 1 wt% of bentonite were submitted to strength compression resistance tests, fatigue of pellets to impact and maximum height of fall tests. A correlation of resistance of the pellets and time for curing were stablished. The produced pellets match the conditions for raw materials used in electric smelting hrnaces to produce manganese based ferro-alloys.

Jan 1, 1995

By P. N. Anyalebechi

The effects of a cross-hatched grooved mold surface topography, casting speed, and superheat on the morphology of solidifying shells of aluminum alloy 3003 have been characterized by a series of immersion tests. The cross-hatched grooves were 0.232 mm deep with wavelength or spacing between 1 mm and 15 mm. The shells solidified at casting speed of less than 10 mm/s on the 1 mm spaced cross-hatched grooved mold surface were fairly uniform with little or no localized variations in thickness. However, the propensity for non-uniform shell growth morphology was exacerbated by an increase in casting speed, melt superheat, and the wavelength of the cross-hatched grooves. This is provisionally attributed to their effects on interfacial heat transfer and wetting of the mold surface by the molten metal.

Jan 1, 2008

By Hsing Kuang Lin

Ferric chloride leaching w.as applied to a complex sulfide ore from Tok, Alaska to dissolve zinc, lead, silver and copper. Gold in the leaching residue, as well as in the ore, is found to be refractory to the conventional cyanidation process. Roasting, pressure oxidation and elemental sulfur removal followed by cyanidation were tested to improve gold dissolution. Also tested were thiourea leaching and high-pressure cyanidation. The readsorption of dissolved gold by carbonaceous matter in the chloride leaching residue was analyzed. Based on the experimental results, factors causing difficulty of gold dissolution from the leaching residue are discussed.

Jan 1, 1989

By Theodore Ineich

The “BIOMOre” project aims to prove the technical feasibility of indirect in situ bioleaching of sulfide minerals contained in a deep underground deposit, by bringing together the disciplines required to make a success. The underground location in Poland was provided by project partner KGHM inside an operating copper mine. Key components of this project were the design and construction of a pilot plant, and its operation in an underground environment. This project also included a ∼250 t (100 m3) fragmented rock reactor hydraulically connected to the pilot plant. The pilot plant consisted of several tanks and pumps, a fluidised bed ferric iron generating bioreactor containing immobilised acidophilic iron oxidation biomass, and all the required instrumentation and utilities. Before the bioleaching phase could start, the rock reactor had to be flushed continuously firstly with water to remove chloride salts that are corrosive and also harmful for the bacteria used in the bioreactor, and secondly, with sulfuric acid solution to react with the carbonates present in the ore matrix. This paper summarizes the design, construction, commissioning, and operation of the pilot plant.

By Zhao Hengxian

We studied the phase diagram of Na3AlFe-ZrO system, reduction of ZrO2 by aluminium and electrochemical behaviours of ZrO2 in the system. The results show that Na3ALF6-ZrO2 system is a simle eutectic one, that the velocity of reduction of ZrO2 in the system is rapid al 960'C and that the Zr content in the alloy abtained can reach as high as 2.5wt%. Potential scanning shows that there exist new current peaks on the potential scanning plats except for the cuurent peaks corresponding to the oxidation of aluminium. The method of making Al-Zr alloy in our paper has advantages over the traditional method of mixing metals.

Jan 1, 1992

By C. Lupi

"The energy consumption of copper production by electrowinning, generally represents more than 1/4 of the total energy requirement in hydrometallurgical traditional process (roasting, leaching, purification and electrowinning). The considerable saving can be achieved just in this step that requires about 2.2 kWhlkg of the produced copper. To save energy the cell voltage, or more appropriately its anodic component, can be reduced: that is because the anodic voltage represents the main component of cell voltage and so it is largely responsible for the excessive energy consumption in copper sulphate electrowinning.In this work some ways are studied to lower the anodic voltage. First the cobalt ions were added to the sulphate solution in order to study the catalytic effect on oxygen discharge. Then lead alloys anodes (Pb-Ag, Pb-Sb-Ag and Pb-Ca) were used to promote a better oxygen evolution as a result of a different anodic surface. Their behaviour was compared with the PbSb traditional ones. Finally, as already pointed out by several authors for zinc electrowinning, ethylene glycol was employed as anodic depolariser in order to verify its effectiveness in the case of copper electrowinning. By combining all the above-mentioned ways, energy saving ranging from 20% to 27% is achieved.All the tests were carried out on a laboratory pilot-plant for long time to simulate the industrial conditions. The obtained copper deposits were observed by SEM to highlight their morphology."

Jan 1, 1997

By John R. Goode

Barrick Gold Corporation operates gold mines in the United States, Chile, 'Peru, Canada, and in the near future, in l1anzania. Barrick meets environmental requirements and limits the potentially adverse effect of cyanide discharge to the environment using various cyanide destruction techniques. Barrick operations use, or have used, natural degradation, ferrous sulphate, hydrogen peroxide, Caro's acid, alkaline chlorination, and the SO/Air process for cyanide destruction. This paper presents a general discussion of the options for controlling cyanide in plant effluent and provides details of Barrick's operating experience including general notes on costs.

Jan 1, 1998

By George P. Demopoulos

In this paper the production and stability of crystalline scorodite (FeAsO4·2H2O) is discussed both on the basis of previously published work as well as recent work performed in our laboratory. The production of scorodite, especially from arsenic-rich and iron-deficient sulphate solutions offers a number of operational advantages such as high arsenic content, stoichiometriciron demand, and excellent dewatering characteristics. In addition to hydrothermal production of scorodite the work done over the last 10 years in our laboratory has determined that it is feasible to produce scorodite by step-wise lime neutralization at 90°C. The atmospheric scorodite possesses the same structural and solubility characteristics with the hydrothermally produced scorodite. Long term equilibration tests (up to 66 weeks) in the pH range 5 to 9 and temperatures from 22 °C to 75 °C revealed scorodite to undergo slow incongruent dissolutionyielding a highly metastable nano-sized 2-line ferrihydrite phase. The equilibrium arsenic concentration with this phase was 0.35, 0.96 and 5.87 mg/L at pH 5, 6, and 7 respectively at 22°C. In the presence of gypsum slightly lower concentrations were measured, this being more pronounced at pH>7. It was tentatively deduced that a Fe-Ca-AsO4 association (in the form of a phase resembling the mineral yukonite) contributes to the lowering of As concentration. Finally thermodynamic calculations determined that scorodite is stable in the presence of ferrihydriteunder oxic conditions up to pH 6.75 at 22 °C or higher pH at lower temperature and gypsum-saturated solutions. Keywords: Scorodite, Crystallization, Arsenic, Solubility, Stability, Precipitation, Disposal, Extraction, Processing, Metals, and Environment.

Jan 1, 2005

By B. Mishra

The major waste product of the alkaline extraction of alumina from bauxite [Bayer Process] is known as red-mud. Approximately, a ton of red-mud is produced for every two tons of bauxite that is mined. The red-mud produced from Jamaican bauxite is rich in hematite, alumina and titanium oxide. It has been shown that over 90 wt. pct. alumina can be recovered from red-mud by soda-ash sintering and caustic leaching. Hematite can be carbothermically reduced with a degree of metallization of over 94 pct. At this stage, the product could be charged through the tuyeres in an iron blast furnace or smelted to produce pig iron. The mineralogical characteristics of the reduced product are not amenable to magnetic separation for iron recovery. The problems associated with the use of reduced red-mud as an alternative to direct-reduced iron [DRI] has also been discussed. Special attention has been paid to lower the alkali content of the reduced material. If smelted, the concentration of titanium oxide in the slag will be significantly high justifying its recovery by an acid-leach process. This paper describes the successful efforts of iron and alumina recovery.

Jan 1, 2000

By Carlos Mauricio Fontes Vieira, Sergio Neves Monteiro, Thiago Samarão Motta

This work has as its objective to characterize ceramic bodies formulated with ornamental rock waste and two different clays to produce ceramic paver. Specimens were made by uniaxial press-molding at 20 MPa and then fired at 950 and 1050oC respectively. The determined technological properties were: plasticity, dry bulk density, linear shrinkage, water absorption and flexural rupture strength. The results showed that the type of the clay has strong influence on the properties of interest for heavy clay ceramics. The investigated waste must be incorporated in small amounts to avoid increasing in the porosity of the ceramics.

Jan 1, 2015

By Adam Powell, Salvador Barriga, Matthew Earlam

"The inert anode is a key enabling technology for dramatic energy and emissions reduction in extractive metallurgy. In molten salts, the materials challenge is nearly insurmountable: the anode must conduct electrons at high temperature in a pure oxygen and molten salt environment. A solid electrolyte, e.g. zirconia, between the salt and anode removes the molten salt stability constraint, and can act as a container for a liquid metal anode. This can be liquid silver for oxygen-generating inert anodes, or several metals for natural gas-fueled anodes; it is possible to switch between these modes. The solid electrolyte brings several other benefits: it eliminates molten salt contamination of the anode gas, creates a reducing environment enabling low-cost steel vessels, increases current efficiency, and eliminates carbon contamination of the product. New developments presented here, including current collector and low-cost anode designs, amplify these benefits for producing aluminum, magnesium, rare-earths, and other metals.IntroductionReactive metals such as magnesium, aluminum and rare-earths play increasing roles in efficient transportation and clean energy. In response to new fuel economy standards, automotive OEMs are planning large increases in use of aluminum and magnesium to reduce vehicle weight. Rareearth permanent magnet motors and generators exhibit better power-to-weight and efficiency than induction motors and other designs, making this today's primary motor technology for hybrid and electric vehicles, and for wind turbines. Nickel metal hydride (NiMH) batteries with lanthanum are dominant in hybrids. In 2011, transportation comprised 28.6 out of 103.1 EJ of US energy consumption [1] and 1,845 out of 5,471 million metric tonnes (MMT = 109 kg) CO2e of US greenhouse gas (GHG) emissions [1], creating big targets for economy-wide reductions.Unfortunately processes for making reactive metals for these applications are very inefficient and heavily-polluting. In primary aluminum production, Hall-Heroult cell electricity use [2] is more than double the reaction enthalpy due to heat losses through frozen cryolite side-walls and anode gases, graphite anode plants add significant energy use and GHG emissions [2] (see Table 1). Magnesium is even worse: silicothermic reduction by the Pidgeon process in China produces about 85% of the world's magnesium using coal or coke gas [3]. Chloride electrolysis begins with high-purity MgO and requires carbochlorination or hydrochlorination and costly chloride dehydration [4]—rendered unnecessary for aluminum by the Hall-Heroult cell. Production of neodymium and lanthanum with graphite anodes leads to inconsistent carbon content: small cells make 1 kg batches for analysis, sorting and sale by carbon content, with very high labor and analysis costs. And vertical electrodes give no incentive to reduce anode effect: some reports indicate that China's rare-earth metal industry emits more CF4 and C2F6—with global warming potential (GWP) 6500 and 9200 times CO2 respectively—than China's aluminum industry [5]."

Jan 1, 2014

By Ravi S. Bellur-Ramaswamy, Daniel A. Tortorelli, Robert Haber, Nahil A. Sobh

We optimize continuous quench process parameters to produce functionally graded aluminum alloy extrudates. To perform this task, an optimization problem is defined and solved using a standard nonlinear programming algorithm. Ingredients of this algorithm include 1) the process parameters to be optimized, 2) a cost function: the weighted average of the precipitate number density distribution, 3) constraint functions to limit the temperature gradient (and hence distortion and residual stress) and exit temperature, and 4) their sensitivities with respect to the process parameters. The cost and constraint functions are dependent on the temperature and precipitate size which are obtained by balancing energy to determine the temperature distribution and by using a reaction-rate theory to determine the precipitate particle sizes and their distributions. Both the temperature and the precipitate models are solved via the discontinuous Galerkin finite element method. The energy balance incorporates nonlinear boundary conditions and material properties. The temperature field is then used in the reaction rate model which has as many as 105 degrees of- freedom per finite element node. After computing the temperature and precipitate size distributions we must compute their sensitivities. This seemingly intractable computational task is resolved thanks to the discontinuous Galerkin finite element formulation and the direct differentiation sensitivity method. A three-dimension example is provided to demonstrate the algorithm.

Jan 1, 2001

By Xuan Cheng

The electrochemistry of sulfide mineral flotation is reviewed with particular emphasis on galvanic interaction among minerals and grinding media, and its relevance to flotation of complex sulfide ores is discussed. Surface alteration due to galvanic interactions among chalcopyrite, pyrrhotite and mild steel is analyzed in terms of voltammetric and chronoamperometric studies on individual minerals and through galvanic current measurements in 2- and 3- electrode combinations. The results are related to laboratory flotation behaviors of chalcopyrite-pyrrhotite mixtures simulating copper-nickel bearing Duluth gabbro.

Jan 1, 1993

By Jorge Alberto Soares Tenório, Flávia Paulucci Cianga Silvas, Bianca Medeiros, Denise Crocce Romano Espinosa, Ivo André Homrich Schneider, Daniella Cardoso Buzzi, José Roberto de Oliveira

"AMD is one of the main problems associated with mining activities and the techniques used in their treatment may be the biosorption. The aim of this work was to study the rice husk as a biosorbent for the AMD treatment keeping constant: pH (2.6), biomass concentration (1g.L-1), temperature (25°C) and agitation (175rpm). And varying the contact time of 5, 20, 60 and 240 minutes. Rice husk samples will be characterized before and after the biosorptives tests through analysis of SEM and IR. The micrographs indicate the occurrence of micro-precipitation and changes in biomass physical structure. Since the infrared spectra indicate changes in functional groups present in the biomass before and after the biosorptives tests. AMD synthetic solutions will be analyzed by ICP in order to quantify the metals concentration captured by biomassIntroductionThe preoccupation for the environment has led the industry in general, to treat their waste. As the only industrial activity is increasing, the pollutants generated must undergo treatment processes aimed at reducing pollution, and therefore, less aggression ecosystems.In mining there is waste water with accumulation of heavy metals, and these are harmful to health of living beings, thus being one of those industries responsible for some pollution of the environment. These wastewater in contact with oxygen to generate an acidic water is called acid mine drainage (AMD). This aqueous solution has a pH below 3 and varieties of dissolved metals. When this solution comes in contact with water, generates a series of environmental problems, so there is a need to recover the metals present in the DAM."

Jan 1, 2012

By S. Seetharaman

In the processing of molten metals, it is extremely important to monitor continuously the concentration levels of various minor elements, In the production of common metals like copper, iron and aluminium electrochemical sensors involving solid, as well as liquid electrolytes are being increasingly used to measure the concentrations of minor elements The present paper deals with the electrochemical principles underlying these measurements and the possible errors involved. One of the major difficulties in the case of the solid electrolytes is to correct for the consequences oldie electronic contribution to the conduction of the electrolyte. The application of the electrochemical sensors for molten metals processing involves designing of these probes to withstand the industrial operating conditions. In this respect, significant achievements have been made with respect to the design of oxygen probes for liquid metals in general and liquid copper in particular. Some of the salient design features are discussed in the paper, The application of auxiliary electrodes for impurities in molten metals like phosphorus in copper and silicon in iron are taken up. The development of oxygen sensors for slags is given special attention. Recent developments' in the field of sensor technology, as applied to metals processing are highlighted.

Jan 1, 1996

By G. G. Krishna Murthy

Several experiments were carried out to simulate the bath smelting reactions where iron oxide particles were dropped on to an iron-carbon bath containing molten CaO-SiO2-Al2O3 slag layer on its surface. The composition of the slags used in the experiments was %CaO:46.1; %SiO2:41.7; and %A1203:12.2. Experiments were con¬ducted with carbon saturated iron melts contained in either a pure graphite crucible whose walls were covered with a pure alumina tube, or a pure flat bottom alumina crucible, at 1723-1823 K. Degree of reduction of a pure iron oxide particle was linear with time in the initial stages (up to about 20% oxygen of the original pellet was reduced). The rate of reduction of smaller oxide pellets was smaller than that of a bigger pellet - the time for complete reduction of a 5.6 g wustite pellet was smaller than that for a 1.2 g wustite pellet. It was also established that the interaction rates obtained by adding a molten pure oxide particle of given weight to the system were lower than that determined by using a solid oxide particle of same weight. The overall rates of reduction decreased with decreasing the bath temperature. The experimentally determined rates of reduction based on the time for 70% reduction were influenced substantially by addition of slag up to about 50 g on to a bath of 78.8 mm in diameter, and remained constant when slag present on the bath surface was between 50 g and 200 g.

Jan 1, 1993

By Marcelo B. Mourao

Interactions of carbonaceous materials with liquid Fe-C melts have been investigated experimentally by determining the volatile yield due to rapid devolatilization (Flash Pyrolysis) and rates of dissolution at temperatures ranging from 1623 to 1873 K. The volatile yield increased with increasing the temperature. The comparison of results of different types of carbonaceous materials was possible by expressing the volatile yield in terms of Enhancement Factor, fE. The rates of dissolution of spectroscopic graphite and an industrial coke seemed to obey the correlation for natural convection under turbulent conditions. The experimental data for the graphite suggested that the rate of dissolution was controlled by the mass-transfer in the liquid boundary layer adjacent to the solid sample. The value for the empirical parameter correlating the dissolution coefficient and the operating variables was found to be 0.19 which was close to that reported in the literature. The comparison of the results obtained for the coke samples with those for the graphite revealed that the impurities and the porosity of the samples can effect the dissolution rates.

Jan 1, 1992

By Tang Chaoho

Laboratory research on the reducing and matte smelting of Jamesonite concentrate has been carried out. The influence of the process conditions such as the smelting temperature, the amount of pyrite cinder (the agent of fixed sulfur) and the amount of additives on the smelting process have been studied. Under the optimum condition the direct recovery ratios of antimony and lead are 83.26% and 68.50% respectively. The ratio of fixed sulfur is 98.97% but more than 15% lead and 30% silver remained in the ferrous matte. The key problem to be solved of this new process is how economical and effective is the recovery of silver and lead in ferrous matte.

Jan 1, 2003