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The U.S. Bureau of Mines investigated CaF2-assisted H2SO4 leaching to extract Mn from domestic silicate manganese resources. A pyroxmangite ((Mn,Fe)Sio3) ore containing, in pct, 34 Mn, 23 Si, 3 Ca, and 1 Fe was leached at 90° C for 3 h in a solution containing, in g/L, 12 Mn, 140 H2SO4, 130 (NH4)2SO4, and 5 CaFz. Manganese extraction of 92 pct was achieved. Manganese of greater than 99 pct purity was prepared by electrolyzing the purified pregnant solution at a current density of 50 mA/cm2. The current efficiency was 65 pct.

Jan 1, 1991

By Jilai Xue, Jun Zhu, Baisong Li

"TiB2-C/C Function Gradient Materials (FGM) is used in cathode materials to improve aluminum wettability and melt penetration in aluminum electrolysis. In this investigation, FGM was tested for use as part of the cathode materials, where a 10 mm thick TiB2-rich layer was on the top as an Al-wettable surface, the TiB2-C layers in the middle as a gradient layer and the carbon on the bottom as a base. Electrical resistances ofFGM were determined in the temperature range of25- 9600C in argon atmosphere. The results show that the present of TiB2-C gradient layer can reduce the open porosity and the electrical resistance of the cathodes materials at elevated temperatures. The cathode samples after aluminum electrolysis usually demonstrates an increase in electrical resistance, but the application of FGM layer can compensate such an increase for certain extend due to less variation in porosity and lower the level of melts penetration.IntroductionCarbon is still used for aluminum reduction cathodes dominantly, but it has a poor wetting properties by liquid aluminum and the anode-cathode distance has to be kept about 4-5cm with an additional 1.3-2.0 V voltage drop [l]. TiB2 has better wettability by liquid aluminum with higher electrical conductivity and stronger chemical resistance to the electrolyte attack. And the wettability ofTiB2-C composites cathode on liquid aluminum can be also improved, while liquid aluminum can completely wet the cathode surface ifTiB2 content exceeds 27% [2-4]. However, during the process of TiB2-C composites cathodes preparation and aluminum electrolysis, the deformation by temperature variation or sodium penetration are great disparity between TiB2 and carbon due to their physical properties difference. This will accelerate the cathodes cracking and deterioration."

Jan 1, 2013

By Zhucheng Huang, Ronghai ZHONG, Tao Jiang, Jun ZOU

The method of reduction roasting and magnetic separation of low-grade, micro- fine disseminated refractory iron ore following granulation with coal produced unexpected success. Pellets of iron ore with diameter between 3 and 8mm were granulated with coal, bentonite and water. The raw pellets and reduction products were analyzed by scanning electron microscopy and x-ray diffraction. Results show uniformly distributed coal powders inside the pellets improved the kinetics of the reduction process and accelerated the reduction rate. Reduction time was higher at temperatures below 890℃, which resulted in the formation of substantial amounts of fayalite. When temperature was increased, micro- fine hematite was then quickly reduced to iron metal and the amount of fayalite decreased sharply. When pellets were reduced at 950℃ for 25min, reduction products with 56.73% metallization rate were obtained. After grinding and magnetic separation, a concentrate with 72.18% Fetot was obtained.

Jan 1, 2015

By Alan P. Prosser

The heap leaching of gold ores by cyanide solution was simulated by computer program. The program uses only basic m1neralogical and chemical data; no process testwork data, such as column leach results, are required. The simulation can be used to forecast the consequences of various changes before and during the testwork, design and operation stages of a particular ore-process system. Also, data about the state of different parts of the heap at various times help create an understanding of what is happening. The effects of mineralogical and process variables on the overall performance of the ?heap leaching process are illustrated. Comparisons are made to column leach tests and production data. The potential of the simulation strategy is discussed for making better use of operating experience and for suggesting specific research objectives. It has become clear that more attention should be paid to other metals that dissolve in the solution.

Jan 1, 1989

By D. Donald Downey

Pilot Testing Ion Exchange Resin (IEX) can go from very simple beaker testing to complicated column testing. Space velocities, regenerant quantities, loading capacities, ion leakage, are all terms that get accumulated together to prove or disprove a resin’s (or resins’) ability to load a single ion (or specific set of ions). Not getting all the resin’s operating parameters correct will disqualify (or at least skew) the results. Laboratory tests for capacity, moisture content, bead size, metals fouling, etc.—what does it all mean? At last count, there were over twenty-five separate ion exchange resin tests (analyses) that were available to end users. Standard testing procedures identify the resin properties but more specific procedures can be used to identify problems with equipment operation. Then, there are the costs to consider; simple cation resin testing (moisture content, total capacity and bead integrity) is in the $200/sample range. However, add to this Chatillon, Russian Ball Mill Test, HIAC particle size, metals and % regeneration test procedures and the lab work can increase to over $1000/sample. In this paper, the author will explain the “must-do” pilot and test procedures and why they are important and the key to understanding how resin performs ion exchange.

By Christopher M. Moore

DK Recycling und Rohelsen GmbH converts 380 000 annual tonnes of iron containing waste materials Into pig Iron. Zinc Is the main reason that these materials are classified as waste. The materials are processed In the conventional way by making sinter which is then smelted in a blast furnace to foundry grade pig iron. The trick lies not in the unit operations which are quite standard but rather In the modifications made to the plant and operating procedures to cope with the much higher levels of tramp elements.

Jan 1, 1995

By S. W. Marcuson

Smelting of nickel-copper sulfide ores at Vale Inco’s Sudbury operations commenced in 1888 and the first converting plant went into operation in 1892. As the demand for nickel grew, the smelting operations expanded and by the 1960’s the Copper Cliff Smelter featured the longest converter aisle in the world with space for nineteen Peirce-Smith converters. During this long period, different converting techniques and vessels were employed. The evolution of converting is reviewed with special emphasis on the modifications made to the Peirce-Smith vessel to accommodate the metallurgical and process needs of the changing times.

Jan 1, 2009

By Wei Yu, Tiejun Chun, Jian Pan, Deqing Zhu

In this paper, improving the pelletization of Brazilian hematite by adding a boron bearing additive was carried out, and the pelletization parameters were also optimized. The mechanism of boron bearing additive was revealed in the kinetics of crystal grain growth by using LEICA microscopy and its software to measure hematite grain growth. Good qualities of green balls are manufactured with drop numbers above 5.7 times/0.5m, compressive strength higher than 13 N/pellet and thermal shock temperature over 620? under the following conditions: 1.2wt% bentonite, 0.4wt% boron bearing additive, 7wt% moisture and pelletizing in disc for 15 min. When the green balls were preheated at 1000? for 8 min and fired at 1280? for 15 min, the compressive strength of the fired pellets containing boron bearing additive is about 3096 N/pellet, which is far beyond the standard requirement for good quality pellets. Compared to the fired pellets without adding any boron bearing additives, the compressive strength of fired pellets containing boron bearing additive is increased by 1225 N/pellet. It is revealed that adding boron additive into the hematite pellets help to form more liquid phases, lower the activation energy of the hematite grain growth by 135.2 kJ/mol and increase grain growth rate by 33.6%, leading to higher strength of fired pellets due to forming more coarse and dense recrystallized hematite and energy saving by firing at lower temperatures for shorten time.

Jan 1, 2011

By May Nyman

Due to the vast diversity of chemical media in which metal separations are executed, a wide range of ion separation materials are employed, This ,results in an ongoing effort to discover new phases with novel ion exchange properties. We present here the synthesis of a novel class at, thermally and chemically stable microporous, niobate-based materials. Ion exchange studies show these new phases are highly selective for Sr2+ and other bivalent metals.

Jan 1, 1999

By James T. Skoch

With the ongoing pressure on the secondary aluminum business to limit the amount of waste generated from processing aluminum dross, it becomes very advantageous to preprocess the dross to reduce waste. The advantage of preprocessing is that it significantly reduces the oxides and salt cake generated when melted. Various products can be produced from the oxides for the steel industry. The following paper will demonstrate that removal of oxide fines before melting will result in large volumes of material not being landfilled. We will show that the end result of this technology is to significantly reduce the amount of salt cake sent to a landfill while maximizing the recyclability of the aluminum dross.

Jan 1, 1995

By Douglas J. Harvey, Chi-Mou Ni

"This paper presents an analysis technique for the solidification of metal castings. This method, based on a modified finite difference scheme with an irregular mesh, is capable of dealing with the complex geometries of castings. The nonlinearities in material properties of specific heat and thermal conductivity, arising from the phase change during solidification, are accounted for in the step-by-step calculations. Two solidification problems are solved with this analysis technique and the calculated results compare satisfactorily with experimental data. IntroductionCasting process design engineers are often faced with the difficult problem of designing castings to be produced porosity-free. Since the solidification of metal is affected by many interacting variables such as the thermal conductivity, density, and specific heat of both the molten metal and the mold, it is easily seen why this is a difficult task.Typically, casting tooling design is an intuitive process which builds on past successful methods. After processing equipment is constructed, trial castings are made and examined for dimensions and integrity. Changes in the tooling are generally required to improve casting soundness or to reduce cycle time. In the permanent mold process, tooling is complex and difficult to alter after initial construction. The water-cooled steel molds are part of the complete automated system. Associated holding furnaces, pouring ladles, casting conveyers, and utility connections all make other than minor adjustments a costly and time consuming task. An analytical method for using the principles of heat transfer for predicting solidification patterns would be of great value in the permanent mold process by minimizing costly changes."

Jan 1, 1986

By John L. Sundstrom

Complete systems were designed -and are in operation to recycle the effluent streams and to remove impurities from tankhouse. electrolyte, Heavy em¬phasis was placed on making usable products from as many streams as poss¬ible at minimum capital and operating costs. Almost complete recycling: and reuse of water and sulfuric acid were paramount. Techniques used in-clude solvent extraction - electrowinning, evaporation - crystallization and filtration.

Jan 1, 1992

By Gudrun A. Saevarsdotti

For decades tile aluminium industry has been practicing gas treatment of aluminium melts. This treatment is of great importance because of its influence on 'impurity" and inclusion removal from the melt. The gas-melt interaction is greatly influenced by the gas composition, melt temperature etc. This paper gives an overview of the interaction between argon-chlorine gas mixtures and the aluminium melt. It covers the thermodynamics of the reaction between the chlorine and a number of different elements commonly found in liquid aluminium, and discusses the behaviour of reaction products in the melt. The paper reports an experimental study of the behaviour of the chlorine-molten aluminium interface, using sodium contaminated aluminium melt with and without the addition of grain refiner.

Jan 1, 1996

By Stephen Chryssoulis, Stamen Dimov

Detection and quantification of precious metals (Au, Pd, Pt, and Rh) in spinels and silicate minerals is important for establishing the maximum attainable recovery by sulphide flotation. To achieve this goal subpart per billion (ppb) detection limits are required plus the ability to quantify results. Existing quantitative microbeam techniques (EPMA, PIXE, SIMS, TOFLIMS) have limits of detection in the O. l-200ppm range. Time-of-flight resonance ionization mass spectrometry (TOF-RIMS) is a microbeam analytical technique that allows for the identification and quantification of atomic species in very small quantities. It utilizes a tunable laser source for resonant excitation and ionization of a particular element of interest and has some unique features: elemental selectivity, linear response over a large dynamic range and very high sensitivity. The analysis consist of three steps: (i) the solid sample is vaporized by laser ablation to form a plume containing neutral atoms, (ii) the neutral atoms of a specific atomic element in the plume are resonantly excited and ionized by another tunable laser, and finally (iii) the ions created are mass analyzed in a time-of-flight mass spectrometer. A TOF-RIMS mass spectrometer was developed at AMTEL for trace element analysis of Au, Pd, and Rh in minerals. The spectrometer was calibrated using homogeneous CANMET and NIST reference samples covering three orders of magnitude in concentration. Attained minimum detection limits (MDL=2cr of the background) are in the low ppb range.

Jan 1, 1999

By Robert R. Beebe

On the night of August 1'9-20, 1995, seepage was seen at the toe of the Omai tailings dam in Guyana. The mill was immediately shut down, and within two hours the flow, then mostly water, was diverted into an inactive mining pit nearby. At about the same time a second more serious break occurred at a point where water and solids could flow directly into the Omai River. By the time Ii coffer dam could be completed in the early morning of August 24, some 4.2 million cubic meters of tailings water and solids had escaped from the dam, of which nearly2.9 million cubic meters had reached the Omai River. This paper outlines some initial Process considerations and operational decisions which might have contributed to the dam's failure, describes how the Government of Guyana and the operator, Omai Gold Mines Limited, cooperated in dealing with immediate problems and shows how the Government set about investigating the accident. In particular, the paper details the work of a Process Review Committee comprising Guyanese and foreign experts convened to assess the gold processing and effluent management systems at Omai, and to recommend actions where appropriate.

Jan 1, 1998

By M. Misra

The removal of lead and other heavy metals present in an active US Army small arms firing range soil was evaluated in a pilot scale test program at Ft. Polk, Louisiana. Two different acid based extraction processes in conjunction with conventional physical separation methods were used. Physical separation processes consisting of screening and gravity operations removed most of the coarse lead particulates and slugs. Hydrochloric acid leaching followed by precipitation of lead as hydroxide recycled clean soil containing less than 500 mg/L. total lead and less than 5 mg/L TCLP lead. Lead extraction efficiency with hydrochloric acid was 96 percent. The results of lead removal by physical separation in conjunction with acetic acid leaching were not consistent over the whole test period and the total soil processed.

Jan 1, 1998

By R. Cheng

The kinetics of the solvent extraction of ythium from HCl solution with mono-2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (HEHEHP) have been studied using a rotating diffusion cell (RDC). The effects of rotation speed, pH, ymium and extractant concentrations and temperature on the rate of extraction were examined. The rate of extraction of ythium appears to be controlled by an interfacial reaction of metal ion and extractant. The concentration of the latter is determined mainly by diffusion through the membrane. The contributions of the rates of diffusion in the diffusion layer, diffusion in the membrane and chemical reaction at the interface to the overall rate have been calculated on the basis of a kinetic model.

Jan 1, 1992

By C. W. Vierrether

Mineralogical analysis contributes directly to the selection of applicable beneficiation techniques for a given site. Tentative remediation methods for use on the Sharon Steel tailings in Midvale, Salt lake County, UT, were determined in part by mineralogical characterization. A systematic characterization scheme was employed to identify mineral species, mineral associations, and grain size. This paper presents the mineral content and distribution data collected for site characterization. This data was used to determine areas that were representative of the total tailings at the Sharon Steel site. Although this was the main focus of characterization, other useful information was obtained. The approximate location of "old jig tails" was identified and insight on possible arsenic, mobility through the pile was also obtained from the mineralogical study.

Jan 1, 1991

By A. S. Block-Bolten

Two innovations in nickel-arsenic separation have been studied on a laboratory scale. The first requires only a nitric acid atmospheric leach without preliminary roasting and leads to favorable final conditions for precipitation of arsenic as highly stable FeAsO4, The second is an NaOH-H2O2 pressure leach which is an alternative to the known NaOH-O2 pressure leach. Either method offers the possibility of rapid and efficient separation of nickel from arsenic and is applicable, for example to the high grade niccolite deposits in the Great Slave Lake area of northern Canada.

Jan 1, 1982

By Jan Petter Maehlen

Solid H-absorbing materials are in focus of ongoing R&D to offer viable solutions for the hydrogen storage and supply systems aimed on use of hydrogen as energy carrier for automotive transportation. Low operating pressures, combined with high gravimetric and volumetric efficiencies, together with fast kinetics of hydrogen release at ambient temperatures (providing conditions for a low energy loss due to decomposition), are the most important features of the ?ideal? H storage material. Hydrides of the light elements are the only possible candidates to build systems with an overall efficiency similar to those accommodating liquid or compressed (700 bar) hydrogen. One promising material from this point of view is aluminium trihydride, alane AlH3 with a gravimetric storage capacity of 10 wt.% H. This work was focused on studies of the crystal structure and thermal decomposition of alane by application of powder synchrotron X-Ray diffraction.

Jan 1, 2006