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By Toru Taniguchi

In the Mitsubishi smelting furnace, copper concentrate, silica sand and water granulated slag from the converting furnace are injected through the process lances, together with oxygen enriched air, into the melt. Because bath smelting is used, the rates of particles/melt and gas/melt reactions are high enough and therefore tine grinding of the solid materials is' not necessary. Among these reactions, the dissolution rate of silica sand is the slowest and limits the overall reactions in the smelting furnace. Information on the dissolution rate of silica sand plays an important role for design of a new furnace. Theoretical calculations of the dissolution rate .of silica particles have been reported elsewhere. The authors conducted cold model experiments and could verify the calculation. In this paper, the dependence of dissolution rates of particles on the gas blowing rate, particle size and solid penetration depth in the bath is discussed.

Jan 1, 2002

By H. Roberts, C. Hassall

The opening years of the new millennium will be characterised by the closure of many lead and zinc mines because of reserve depletion. However, weak commodity prices through the second half of the 1990s have slowed project evaluation and have made it difficult to raise finances for the development of new mines required to replace lost output and to meet increasing demand for metal in the future. Growth of lead and zinc demand will be determined by the pace of global economic activity, especially in the emerging economies. How rapidly demand grows will have a key bearing on the possible shortfall in mine output and the response of prices to the implied tightening of metal supplies early in the new millennium. These issues are the focus of a discussion of the critical lead and zinc supply developments which will unfold post 2000, taking into account project lead times and the role that recycled metal plays in meeting market demand.

Jan 1, 2000

By Shunichi Ajima

PT. Smelting Co. was established in February, 1996 to construct and operate the Gresik Smelter and Refinery. The construction work of first Copper Smelter and Refinery in Indonesia was completed in the end of August, 1998 and it was put into the integrated test operation in December, 1998. Gresik Smelter and Refinery is designed to produce 200,000 tpy of copper cathode from copper concentrate supplied from Grasberg Mine of PT. Freeport Indonesia Company in Irian Jaya, Indonesia. As by product 592,000 tpy of sulfuric acid, 382,000 tpy of slag, 31,000 tpy of gypsum and 480 tpy of slime will be produced in the full operation. Major processes applied at Gresik Smelter and Refinery are: Smelter: Mitsubishi Continuous Copper Smelting and Converting Process ( Mitsubishi Process ) Anode Casting: Continuous Casting of Copper Anodes with the Hazelett Twin Belt Caster Refinery: ISA Process Acid Plant: Lurgi Mitsubishi Double Contact Process

Jan 1, 1999

By M. Rosales

Using the k-e turbulence model, a mathematical fluid dynamics simulation of the flow characteristics in a Teniente converter has been conducted. Two cases were studied: - Transversal sections in the smelting-converting zone; and - A three-dimensional simulation that includes the walls of the reactor The calculations give the velocities field, the gravity waves amplitude, the splashing behaviour, the phase distribution and the shear stress distribution. The latter helps to explain the pattern of refractory lining wear. The calculation includes the approximate shape and dimensions, and the eventual coalescence of bubbles.

Jan 1, 1999

By G. St-Amant, V. Cloutier, E. Ghali, S. Jin, G. Houlachi

During the casting of lead-silver anodes, variations in cooling rates result in the formation of an uneven microstructure. The slowly cooled areas (SCA) have a coarser microstructure than that of the remaining part (called "the general zone"). The effect of anode microstructure on the electrochemical behavior was investigated using galvanostatic, potentiodynamic and electrochemical impedance techniques. The results show that the resistances for the two steps of the oxygen evolution reaction on the slowly cooled areas of Pb- Ag anodes are higher than that on the general zone. The double layer capacitance for the first step of the oxygen evolution reaction (OER) and the pseudocapacitance of the second step of OER on SCA are smaller than those on the general zone. The potentiodynamic results show that the amount of lead dioxide formed on the SCA is greater than that of the general zone of the anode. The potential decay curves after 30 minutes of galvanostatic polarization at 45 mA/cm2 show that the corrosion potential of the SCA is 200 mV lower than that of the general zone. This can lead to perforation because of the formation of a galvanic cell with a small anode and a large cathode.

Jan 1, 2000

By José García-Antón, Valentín Pérez-Herranz, José Luís Guiñón, Henry Reyes

"The majority of chromium electroplating operations employ Cr(VI)-based baths. During these processes, Cr(VI) is reduced to Cr(III). Besides Cr(III) other undesirable impurities are present such as iron, copper and nickel. The build-up of the impurities limits the lifetime of the plating solutions. Since the disposal of spent chromic acid baths is expensive and can cause significant environmental degradation, there is increasing interest in finding ways to regenerate waste chromium liquors.In this work, an electrolytic cell separated by microporous ceramic diaphragms was used to regenerate chromium plating solutions. The effect of the ceramic diaphragm structure parameters, such as porosity and pore size, on the performance indicators of the electrochemical reactor (fractional conversion, current efficiency, product yield, specific energy consumption) was investigated.The fractional conversion, the product yield and the current efficiency increased and the specific energy consumption decreased with the decrease in porosity.IntroductionChromic acid is widely used in industrial applications such as steel manufacture, metal finishing industries, aluminium anodising, pasivation of cadmium, magnesium, and zinc, etching of plastics and another industrial operations related with processing ferrous and no ferrous metals [1]. These processes employ baths with high concentrations in chromic acid, about 180 and 350 g/L, where hexavalent chromium is reduced to Cr(III):"

Jan 1, 2008

By Sundarrajm Suresh, Hrushikesh G. Pimpalgaonkar, Thiyagarajan Paramadayalan

In this paper, a model of a fuel cell system has been proposed to account for the membrane physics at the micro level which is coupled with the macroscopic flow and mass transport phenomena occurring in a single channel of a Polymer Electrode Membrane Fuel Cell (PEMFC) system. We have developed a novel approach to model the catalyst layer electrochemical processes in a Membrane Electrode Assembly (MEA) and coupled it with mass transport and fluid flow calculations at the channel level using STAR-CD commercial software. The predicted values of the cell voltage from this micro-macro model are validated with experimental data available in the literature. A sensitivity analysis has been carried out to study the effect of the design and operating parameters such as catalyst loading and initial temperature on the overall performance of the PEMFC. The results indicate that the cell voltage increases at higher platinum catalyst loading and is also independent of the choice of initial cell temperature.

Jan 1, 2012

By Karl A. Gschneidner

Magnetic refrigeration was first used in the mid-1920's and new developments seem to have taken place about every 20 years, and this is especially true for the mid-1990's. The active magnetic regenerator magnetic refrigerator has the promise to become the first practical machine utilizing the magnetocaloric effect for cooling (and also heating). The basic principles are briefly discussed. Since the temperature lift for the magnetocaloric effect spans about 50 K, one will need to utilize several ferromagnets with different magnetic ordering temperatures in order to reach temperatures below ~250 K. The basic properties, behaviors, limitations, and new phenomena and knowledge are discussed.

Jan 1, 1997

By Hector M. Lizama

A new technology, known as the HydroZinc? process, is described for the recovery of zinc from sulphide ores that includes heap leaching, neutralization, solvent extraction and electrowinning. Unit operations were scaled up from bench-scale to a 1-t/d zinc cathode demonstration plant. Bench-scale studies defined the process chemistry and a process flowsheet. Column tests were used to design full-scale heaps for zinc bioleaching, and mini-pilot equipment was used to design a solvent extraction circuit. The characteristics of the process required development of a bleed circuit for water and impurities. The complete integrated process was tested on a demonstration plant scale for two years, with about 10 000 t of zinc sulphide ore being bioleached in two 6-m-tall test heaps. In addition to 1 t/d of zinc cathode, iron hydroxide and gypsum residues were produced. The process also generated a small effluent bleed. Over the course of the two-year demonstration test, a number of technical hurdles were overcome and several improvements were made. Some of the more significant ones are presented along with process descriptions and experimental and demonstration plant data. Some engineering aspects and economic evaluations of the new process are also discussed.

Jan 1, 2003

By Jason Graetz

Aluminum hydride is a covalent, binary hydride that has been known for more than 60 years and is an attractive medium for on-board automotive hydrogen storage, since it contains 10.1 % by wt. hydrogen with a density of 1.48 g/ml. There are at least 7 non-solvated AlH3 phases, namely a, a', a, ?, d, e and ?. The properties of a-AlH3, obtained from the Dow Chemical Co. in 1980, have been previously reported. Here we present a description of the thermodynamic and kinetic properties of freshly prepared a, 0 and y phases of AlH3. In all cases the decomposition kinetics are appreciable below 100" C and all will meet the DOE 2010 gravimetric and volumetric vehicular system targets (6 wt% H2 and 0.045 kg/L). However, further research will be required to develop an efficient and economical process to regenerate AlH3 from the spent A1 powder.

Jan 1, 2006

By Raymond PoIick

The Demag Electric Slag Cleaning Furnace installed at the Asarco Smelter in Hayden Arizona is one of the few rectangular electric furnaces now operating. The long transition times from charge to tap allow exceptionally clean skims (high recovery); however, the furnace design is complex. Additional Asarco requirements for rapid installation and commissioning further complicated the design. When operating and wear effects accumulated after two years of use, steps were taken to rebuild the furnace with enhanced durability based on the design parameters experience in actual use.

Jan 1, 1993

By Y. W. Miao

Along the south-west coast of Taiwan is about 550,000 metric tons of heavy sand deposit containing about 10 % black monazite. The Institute has developed a separation process to recover the individual rare earths and the developed process has been commercialized by a local private company. The decomposition of the local black monazite by sodium hydroxide through hydrothermal and fusion methods has been investigated. In the hydrothermal process 4.5 wt. % of aqueous alkali solution was used in an autoclave. In the fusion process, caustic soda (9.8% NaOH) was employed in am open cylindrical reactor. The same product of hydrous rare earth oxides were obtained and then dissolved by hydrochloric acid and the p-H adjusted in order to separate the thorium from the rare earths. After filtration, the filtrate contained rare earth chloride and the cake contained mainly the silica and thorium hydroxide. Both methods give a yield of 90 % with respect to the rare earths recovery. A detailed description of operation and comparison of the two methods are given.

Jan 1, 1989

By M. Ramprecht, M. Wu, A. Kharicha, A. Ludwig, H. Holzgruber

"The influence of the frequency of AC power supply on the magneto-hydrodynamic during the electroslag remelting process is studied. The focus is on the electrodynamic field and its resulting mechanical effects on the flow and liquid interfaces. The possible influence of the electrochemistry on the droplet formation is qualitatively discussed.IntroductionThe electroslag remelting (ESR) process is a secondary melting technique which can be used for a variety of metals and alloys, provided appropriate fluxes (slags) and melting parameters are employed. The ESR process is presently operating mostly with AC current of about 50 Hz. However for reasons primarily of inductive losses in the electric circuit, furnaces for ingots larger than 1 m, use or are projected to use current of very low frequency (< 5 Hz). Effects of lower frequencies (2.5-5Hz) on macrostructure and non-metallic inclusions were recently studied by Chang [1]. Most of investigations were performed either with DC power or with AC of 50-60 Hz [2-4]."

Jan 1, 2012

By Hector M. Henao

There is an increasing trend in the copper smelters to recycle electronic materials, which contain relatively high concentration of precious metals. As a consequence, the amount of precious metals lost in the slag phase is increasing. To determine the portion of the precious metals chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. Thus, an experimental study was carried out to determine the distribution of precious metals (Au, Pt, Pd, Rh, Ru) between the equilibrated copper matte and iron-silicate slag phases. The experiments were made in a magnesia crucible at 1573 K and a fixed partial pressure of SO2 of 0.1 atm for the matte grades between 40 and 70 mass% of copper. It was found that the distribution ratios (defined as mass% X in slag/mass% X in matte, where X represents the precious metal) are around 10-2 for Ru, 10-3 for Au, Pt and Pd and 10-4 for Rh. The distribution ratios show a tendency to increase when the grade of matte is increased.

Jan 1, 2006

By Li Fangi

This paper describes the characteristics and regularities of a process to recover rare earth minerals from Baotou Ore with H-205 collector. H-205 is a kind of hydroxamic acid with amide as a polar group and poly-cycle aromatic hydrocarbon as a non-polar group, having strong ability to capture RE minerals (bastnasite, monazite). When adding a certain dosage of water glass and some other modifying agents, and maintaining pH value between 8.5 and 9.5, RE minerals can be effectively separated from calcium and barium minerals, such as fluorite and barite, etc. Under normal flotation temperature and concentration, when using H-205 to float RE minerals, it needs a bit longer conditioning time (a few minutes longer than that for the conventional collectors). It is also shown that the reagent has the property of resistance to hard water. The laboratory scale and pilot scale tests of the process have been carried out on bulk froth containing RE minerals and fluorite taken from Ore Dressing Plant of Baotou Iron and Steel Company, in both cases, high grade RE concentrates were obtained and the recovery increased remarkably. Therefore, the process has a great practical value.

Jan 1, 1989

By Ximena Massone

Chile is the most important copper producer in the world and the mining sector plays a key value in its economy. However, at present the country does not have a satisfactory set of regulations about closure and restoration of mining operations. In our country many mining operations will, in the near future, shut down their activities, therefore, it is of utmost importance to elaborate and enforce a set of regulations to prevent risks and to protect the environment. The present study is focused on reviewing and analyzing the existing national regulations about the closure of mining operations and preparing a comparative analysis with other international regulations of countries with mining experience. The final results of the study will be a legal proposal to regulate the closure of mining operations in Chile, aiming at minimizing the potential environmental adverse impact, internalizing the social costs by the relevant operators and defining all aspects of liability for the environmental damage.

Jan 1, 1999

By R. A. Cockerell

This paper is concerned with the application of Advanced Process Control (APC) to copper smelting processes. A number of key issues relating to the application of APC, such as modelling for control, process dynamics and time delays, instrumentation and sampling, are discussed. A general methodology for the application of APC is then presented. Finally, three case studies are presented to demonstrate the benefits and efficacy of applying APC.

Jan 1, 1999

By V. A. Bryukvin

It has been found that by superimposing symmetric alternating current over the process, the rate of nickel and cobalt leaching from metallized products with copper sulfate solutions increases by a factor of 1.5 to 2.0 and the apparent activation energy of the process investigated is reduced from 12 down to 6.6 kcal/mole. It appears especially attractive to use alternating current for anodic dissolution (oxidation) of metallic scrap of refractory metals and their alloys in ammonia electrolytes permits production of high-grade commercial products in the form of respective ammonium salts using a short and virtually reagent-free process flowsheet. Similar approaches can be applied also for electrochemical processing of nickel and copper scrap in sulfuric acid media with subsequent recovery of pure sulfate salts or electrolytic processing. Electrochemical technology for recycling of tungsten-cobalt (WC 15) and tungsten-rhenium (WR 20) alloys has been also investigated. In the former case, anodic oxidation of carbide alloy was carried out in nitric acid electrolyte with production of pure tungstic acid. The research conducted has indicated that the physicochemical effect of alternating current results in a lower activation energy of electrode reactions due to changes in the mechanisms of the electrode reactions themselves.

Jan 1, 2006

By Maria de Campos

The pre-reduction behaviour of chromite particles in methane-argon and methane-hydrogen gas mixtures was investigated between 1050°C and 1250°C. Loose bed of chromite particles were reacted in a vertical tube furnace under a pre-set gas mixture predetermined time intervals. Metallization results were obtained for the Cr and Fe components by chemically analyzing the reaction products. SEM-EDAX techniques and X-ray diffraction were employed to elucidate the reduction mechanism. It was found that higher reduction kinetics and higher Cr:Fe ratios in the metal phase would be achieved when hydrocarbon gas was used in comparison to classical carbothermic reduction at a given temperature. The reduction rate was generally bulk gas mass transfer controlled to the reaction site for initial stages which then was followed by ionic diffusion rate control. It is proposed that methane did not partake directly in the reduction but cracked, presenting the reaction site with hydrogen gas and atomic carbon, which was able to immediately react at the immediate area of reduction regeneration CO and H2 and thus maintaining a low partial pressure of oxygen at the reaction site.

Jan 1, 2006

By W. L. Cornell

The processing of lead tailings for removal of the heavy metals produces concentrates upgraded in Co and Ni values. Reflected light microscopy, scanning electron microscopy, image analysis, and Vickers hardness measurements were used to identify mineral species, associations, degree of liberation, and distributions to the test products. Siegenite and bravoite were the most common species encountered, but violarite and enriched pyrite and marcasite phases were also identified. Liberation for the Co and Ni minerals contained in the tailings was 20 micrometers or less.

Jan 1, 1993