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By Javier Antoñanzas, Juan Carlos Múgica, Lourdes Yurramendi

The gasification of wastes containing an organic fraction is usually performed at low-medium temperature using different kind of catalysts. The off gas obtained is a mixture of carbon oxides, mainly carbon monoxide, and hydrogen and can be used for different energetic applications. The main problem is the production of tars in the off gas that has to be separated from the valuable gas flow and, finally, treated separately. An interesting alternative is the partial or total treatment of organics at high temperature. In this case, the off gas contains a higher content of hydrogen and elemental carbon as particulate matter. The energetic source to obtain a temperature in the range of 1,000 - 1,200 ºC is obtained by a plasma torch. In order to make de process attractive, an important issue to be considered is to commercialize the carbon obtained for different industrial applications.

Jan 1, 2008

By R. Chiarizia

Third phase formation, i.e., the splitting of the organic phase in two layers, is a common feature observed, under conditions of high loading, for many solvent extraction systems of both analytical and industrial interest. Although this phenomenon has been investigated in a large number of works, a structural and physico-chemical description is still lacking. In this work, small-angle neutron scattering (SANS) data for the tri-n-butylphosphate (TBP)-n-octane,Th(NO3)4-HNO3 solvent extraction system have been interpreted using the Baxter model for hard-spheres with surface adhesion. The increase in scattering intensity in the low Q range, observed when increasing amounts of HNO3 and/or Th(NO3)4 are introduced into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules plus solutes in their polar core. This intermicellar attraction, under appropriate conditions, leads to third phase formation.

Jan 1, 2003

By Rauf Hurman Eric

The high temperature liquid miscibility gap in the Ag-Ag2S pseudobinary portion of the Ag-S system has been redetermined by very carefully conducted equilibration-quenching experiments. Samples were contained in evacuated and sealed silica capsules. The stratified liquid phase compositions were obtained by chemical analysis. The miscibility gap extends from 14 to 32.3 atomic percent at the monotectic temperature of 906°C and closes at around 1320°C.Thermodynamic properties of the liquid solutions, including the limiting activity coefficient of sulfur in molten silver were expressed analytically by using the sub-regular solution model which proved to be in excellent agreement with the experimental findings.

Jan 1, 2006

By Sergio Demetrio

Over a period of nearly a hundred years throughout this century, the company direction and management of copper smelters in Chile has evolved from one characteristised by a paternalistic, autocratic style to one which empowers the local management team and people for running the smelter as a successful business. This paper discusses the evolution of the present style of management amidst changes in the Chilean Government, the mining industry and society since the beginning of this century.

Jan 1, 1999

By S. Subhawong

Following the startup of the zinc plant in Clarksville, Tennessee, in 1978, the original effluent treatment plant did not perform as designed. The sludge, produced in a conventional lime neutralization treatment, settled poorly and began to fill the permitted lined impoundment within two years, well short of the original design capacity. Another sludge pond had to be constructed. This led to a new process modification of the original design. Although the design is still based on the conventional lime precipitation of heavy metals, the current effluent treatment plant has evolved into a hydrometallurgical circuit, capable of producing good quality water without generating sludge. Undesirable elements are bled from the zinc circuit and are rejected through the effluent treatment operations. Wallboard grade gypsum is produced, instead of sludge, and all the gypsum is sold to cement and wallboard plants. This operation also recovers and returns more than 1,500 tonnes of zinc annually to the 105,000 tonne/y zinc plant.

Jan 1, 2000

By Z. S. Wronski

In rapidly solidified Fe-Nd-B permanent magnet alloys, the content and distribution of Nd-rich intermetallic and Fe-phases determine coercivity Hc and remanence Br. Consequently, microstructure plays a crucial role in deter- mining the (BH) max-product of permanent magnets fabricated from these alloys. A study has been initiated to investigate changes in microstructure and the effects on magnetic properties as the material is processed from arc-melted ingot to melt-spun flakes and finally to a product consolidated by hot-forming. Anisotropic magnetization behaviour has been observed in rapidly solidified flakes after low-temperature annealing.

Jan 1, 1989

By T. N. Chan

This paper provides some general discussions on the development of a new beneficiation process for the treatment of a highly complex monazite orebody located at Mt Weld, Laverton, Western Australia. The complexity of this rare earth ore and the associated problems encountered in ore preparation, desliming and flotation in beneficiation during the development study stage and the solutions to these problems are reviewed.

Jan 1, 1992

By J. Murphy

The economics of microbial coal desulfurization are affected significantly by the proper selection of the plant site and by maintenance of variables at suitable levels. High sulfur coal particles below 200 mesh show sulfate production rates triple those with 150 mesh coal but grinding costs are greater. Slurry solids density increases from 5% to 20% reduced the rate constant by a factor of 10. Coal added to a batch reactor in the stationary phase resulted in a sudden second exponential sulfate production phase indicating feasibility of lower cost continuous operation. Successful operation in the absence of beef broth, yeast or added nutrients at non-sterile conditions enhanced projected economics. Finally, the need for adequate agitation and aeration was well established.

Jan 1, 1985

By M. Hashiuchi

In 1972, the tankhouse of the Tamano Smelter adopted a high current density electrolysis operation applying the PRC (Periodic Reverse Current) method. In 1994, the phase four production expansion project, which incorporated significant re-structuring of the organization, was completed and we have achieved an annual production capacity of 191,000 tons. The target of this project, the production capacity, was increased by 1'8% and labor productivity by 25%. After the expansion, some improvements in the starting sheet section and the verticality of the electrodes were carried out, and the efficiency of the operation was greatly enhanced, including the improvement of the quality of the electrolytic copper.

Jan 1, 1999

By Gavin K. W. Freeman

The efficient separation of cobalt from nickel is a fundamental objective in the refining of cobalt. Based on recent experience at the Corefco refinery in Fort Saskatchewan, the identification of a novel process for the selective precipitation of cobalt from aqueous ammonia leach liquors is described. The addition of calcium sulphate, CaSO4.2H2O (gypsum), to an aqueous solution containing cobalt(III) hexammine sulphate, [Co(NH3)6]2(SO4)3, will result in the precipitation of a sparingly soluble double salt having the stoichiometry, [Co(NH3)6]2(SO4)3.2CaSO4.xH2O, where x = 4 or 6. Leach residues, which may contain a significant quantity of cobalt associated with the cobalt calcium double salt, can be washed with process solutions that contain ammonium carbonate. After contact with ammonium carbonate, the cobalt is recovered into solution, while the calcium is re-precipitated as the insoluble carbonate. The simplicity of this elemental separation and its high selectivity for cobalt, as well as the demonstrated usefulness in improving cobalt recoveries, are the basis for the potential applications of this process.

Jan 1, 2003

By Thomas A. Post

The methodology of determining the optimum SX pumper-mixer system based on bench top, pilot, or small-scale solvent extraction systems, is demonstrated. The design of small-scale SX-plants is different than a full-scale plant. The difference is explained here. The use of dimensionless parameters Nh, Nq, and Np that describe the head, flow and power of the pumper is shown and how to use them for the scale-up. Additional data is required to determine the optimum operating range. Applications of this methodology were used to design well known currently operating SX plants. The emphasis on the optimization of hydraulic efficiency will be shown on examples, including how the hydraulic efficiency is affected when the throughput of the system goes beyond the design. Designs of all sizes of equipment will be shown which optimize the hydraulic efficiency.

Jan 1, 2003

By Hiroshi Nakazawa

An acid mine drainage in abandoned Horobetsu mine in Hokkaido, Japan, contains arsenic and iron ions; total arsenic ca.10ppm, As(III) ca. 8.5ppm, total iron 379ppm, ferrous iron 266ppm, pH1.8. Arsenic occurs mostly as arsenite (As (III)) or arsenate (As (V)) in natural water. As(III) is more difficult to be remove than As(V), and it is necessary to oxidize As(III) to As(V) for effective removal. 5mL of the mine drainage or its filtrate through the membrane filter (pore size 0.45m) were added to arsenite solutions (pH1.8) with the concentration of 5ppm. After the incubation of 30 days, As(III) was oxidized completely with the addition of the mine drainage while the oxidation did not occur with the addition of filtrate, indicating the microbial oxidation of As(III). In this paper, we have investigated the microbial oxidation of As(III) in acid water below pH2.0.

Jan 1, 2006

By Michael J. Nicol

One of the preferred methods for the recovery of gold from refractory gold ores and concentrates involves pressure oxidation in acidic solutions. The main refractory gold-containing minerals are pyrite and arsenopyrite and there is evidence that the presence of even small amounts of chloride can inhibit the oxidation of these minerals and also substantially reduce the recovery of gold. In this paper, the results of a study of the anodic (oxidation) and cathodic (reduction) behaviour of pyrite electrodes in acidic sulfate solutions containing ferric ions at different chloride concentrations and temperatures up to 200oC and pressures of 2000KPa are presented. The electrochemical studies have been complemented by pressure oxidation experiments on a refractory gold concentrate. Results have shown that, as the chloride concentration increases, the anodic reactivity of pyrite is largely unaffected but the rate of the cathodic reduction of iron(III) decreases. The rate of oxidation of a sulfide concentrate and the recovery of gold by cyanidation of the residues decreases at high concentrations of chloride.

Jan 1, 2003

By P. J. Moor

Britannia Refined Metals Ltd. was built in 1931 to refine the lead bullion produced at the Mt. Isa mine in Queensland, Australia. Several periods of expansion and development have taken place over the intervening years, leading to major increases in the refining capacity for both lead and silver. A plant for treating recycled lead-acid batteries was added in 1976. This was redeveloped in the early 1990's to utilise Isasmelt technology for the smelting operations. Most recently the No. 2 refinery kettle floor was extended to enable it to process lead bullion produced from two Imperial Smelting Furnaces (ISF), at Britannia Zinc Ltd. in Avonmouth, England and at MIM Hüttenwerke in Duisburg, Germany. This expansion included the provision of a plant for the hygienic handling of drosses and skims. This paper briefly describes the present primary refining operations and gives an update on the most recent developments in the process metallurgy and operating practices that have taken place.

Jan 1, 2000

By P. Ruz

A melt transfer ladle was 3D modeled by means of a mathematical fluid dynamics and heat transfer program. Internal temperature profiles were calculated as a time function for a normal ladle and for a pre-heated refractory lined ladle. It was shown that in a normal ladle the molten metal cools down quickly forming accretions. By using an inner lining there are practically no accretions build up within a typical time of operation. Therefore, by applying a refractory lining to a melt transfer ladle and keeping it at a moderate to high temperature it is possible to reduce cold dope circulation in the smelter.

Jan 1, 1999

By C. Anderson

Most applications of copper metallurgy are geared towards primary production. However, as recycling of materials is a growing industry, one future facility will rely on copper metallurgy as a means of processing precious metals. This paper will discuss the derivation of the proposed copper pyrometallurgical and electrometallurgical unit operations to be utilized in industrial recycling of secondary precious metals.

Jan 1, 1999

By Alex Mezei

Experimental rheology data are needed to produce design criteria for mass and energy transfer processes. Large throughput plants operate under continuous flow mode. The capital cost is determined by the accuracy of the rheology data used for design. The operating cost is dictated by the energy required to sustain the flowing conditions of various process slurries. Typically, rheology investigations are carried out during the final stages of metallurgical testwork, which is too late to set the design criteria for the pilot plant. This leads to increased testwork cost, and sometimes lowers confidence in the quality of the data produced. In addition, the engineering and feasibility studies are often delayed because of the lack of pertinent rheology data. One of the objectives of this paper is to emphasize the importance of timely planning and execution of the rheology study, which is shown to be a critical component of the overall testwork program. Various applications are discussed, including elaboration of process and equipment design criteria. In this paper, the emphasis is placed on gold and nickel laterite hydrometallurgy applications.

Jan 1, 2003

By J. Tang

The major problem with the Nd-Fe-B magnet is its low operating temperature, i.e., the coercivity decreases so rapidly with increasing temperature that the practical maximum operating temperature-is only 100 °C. Meanwhile, it has been reported that nitrogen addition can drastically increase the Curie temperature of both R2Fe17 and RTiFe11 (R = rare earths). A reasonable question is, then, can one see a similar effect in Nd-Fe-B system? Experiments have been conducted to examine how magnetic properties of Nd-Fe-B magnet are affected by the nitrogen addition. Our results show that part of Nd2Fe14B maintains its original crystal structure and no substantial change in To, due to such N2 treatment is found. However, part of the sample decomposes into a-Fe and, possibly, Nd nitride as a result of nitrogen treatment.

Jan 1, 1992

By Frédéric Pineau, Guillaume D'Amours

Semisolid metal processing of metallic alloys takes advantage of the thixotropic behavior of material with non-dendritic microstructure to produce near-net-shape components with improved mechanical properties. The much higher apparent viscosity of the semisolid billet limits the risk of oxide formed on the free surfaces to become incorporated into the easting during the process. But, the external-skin on the periphery of the billet, which is often partially solidified and contaminated with lubricants, should not be included into the casting as this can be a cause of reject for most structural parts. In this paper, a preliminary model is set-up using the LS-DYNA SPH formulation to follow the paths of the skin. Calculations carried out show that this approach appears to be very promising to predict the paths of contaminated skins into semisolid castings. It can then be utilized to design suitable molds and gating systems.

Jan 1, 2012

By J. A. Sanhueza

The environmental regulations and terms issued by the Chilean Government for all copper concentrate smelters have been a very important reason for permitting project developments that drastically decrease the sulfur emissions due to the pirometallurgycal copper process. A remarkable case of the Hernan Videla Lira Copper smelter, located on the Copiapó Valley and very near some housing-sets of a city of high development, are described. Results of this project's implementation of the control and reduction of off gas emissions, the control and monitoring system, the community conflicts, and the strategy to comply with the demands established by the state environmental institutions, are presented.

Jan 1, 1999