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By Sunil Jayasekera

This paper describes the results of a study carried out to examine the feasibility of electrolytic recovery of silver from cyanide leach liquor generated from a Western Australian silver mine tailings using a novel high mass transfer electrowinning cell. The proposed circuit involves heap leaching and electrowinning in a closed loop. The filter-press-like closed electrode arrangement of the cell allowed much improved mass transfer of metal ions to the cathode surface, making direct electrowinning of metals from dilute solutions feasible. The tests were conducted both in the laboratory and at large scale using a prototype with ~1.0 m2 cathode area. The results showed that the recovery of silver from as low as 250 mg L-1tenor was feasible. The silver deposit produced with the prototype cell was non-adherent and powdery and could be readily removed from the closed cell. A system was developed so that silver powder was discharged continuously during the run.

Jan 1, 2003

By I. Sofia Fernandez del Rio

This paper describes a process for the treatment of the dusts generated during the operation of blast and reverberatory furnaces in the lead smelter, to remove zinc, cadmium, arsenic and halides from the circuit. The process consists of a Pefloles' developed leaching/purification stage and a solvent extraction process developed by Lurgi. The plant capacity is 5,000 tonnes Zn/year. The feed to solvent extraction contains 8 g/1 Zn. Impurities such as copper, iron, arsenic and cadmium are removed by conventional cementation processes. The cadmium product is 99.99 % pure. The solvent extraction process consists of two extraction stages, one washing stage and two stripping stages. D2EHPA is used as the extraction agent and 25% ammonia as the neutralizer. The rich-zinc solution is sent to the electrolytic zinc plant for zinc recovery. The raffinate produced, which is a mixture of ammonium sulfate and chloride, is used for agricultural applications.

Jan 1, 2000

By Zenjiro Asaki

The copper concentrate particles dissolve quickly into the molten matte in the smelting furnace of Mitsubishi Process, which indicates that the sulfide smelting is essentially a gas/liquid reaction. In this paper, theoretical calculation has been made on the rate of oxidation of FeS component in the matte to form FeO by rising gas bubbles using the penetration theory. The results showed that all the oxygen in the bubble of 1.2 cm in diameter, which is the maximum stable diameter, is consumed in 3 ms. This time required is sufficiently short, and it results in the actual operation of smelting furnace of 1100% oxygen-efficiency. These calculations indicate that most smelting reactions are completed just under the lance, except slag formation.

Jan 1, 2002

By Joachim Lemke

The stainless steel sheets of permanent cathodes at Norddeutsche Affinerie (NA) were damaged by corrosion after nearly 11 years in operation. The necessary raising of the strength for stripping the copper had increased the deformation of the stainless steel blades. Current efficiency declined. After investigating the possibilities, like buying new cathodes or treating the steel surface, i.e. by sliding, a repair process was developed whereby the stainless steel sheet was exchanged. Special laser technology for cutting used blades und welding new stainless steel sheets underneath the used hanger bar was applied because the energy input into steel is the lowest of all welding methods. The new stainless steel sheet was welded with the rolling line in a horizontal direction. The achieved flatness of the repaired cathode blades amounted to less than 4mm per meter. During 11 months NA repaired nearly 36,000 permanent cathodes and put them back into operation. Repair costs were much lower than the costs of buying new ones and current efficiency increased again to more than 96% with a current density of 340 A/m².

Jan 1, 2006

By Thomas Frost

In this time of market globalization, many industrial companies are including detailed arbitration clauses in their international contracts, in order to avoid the potential costs, delays, and uncertainties of litigation in foreign courts. Arbitration is less expensive and more flexible, procedurally, than court proceedings, and arbitral awards enjoy much greater international recognition than judgments of national courts. More than 134 countries have signed the 1958 United Nations Convention on the Recognition and Enforcement of Foreign Arbitral Awards, known as the "New York Convention", which facilitates the enforcement of arbitral awards internationally. There are several other similar arbitration conventions that provide for the enforcement of cross-border arbitral awards. Additionally, arbitral awards are not subject to appeal, whereas judgments of national courts are routinely subjected to a lengthy appeals process, and there are very few viable bases to challenge arbitral awards. This discussion will review key considerations in drafting arbitration clauses, including choice of law and choice of forum considerations; issues surrounding the selection of arbitrators; the discovery process; presentation of evidence; and enforcement of arbitral awards.

Jan 1, 2006

By C. Allen

A series of zinc chloride electrowinning tests was carried out in a laboratory scale cell to evaluate the effect of temperature, current density, electrolyte composition, gas sparging and additives on the performance of the cell with respect to current efficiency, voltage, specific energy consumption and deposit morphology. The anode material was DSA for chlorine evolution and the cathode was made of aluminum. At 400 A/m2 current density, a current efficiency of 90.9%, a voltage of 3.4 V and an energy consumption of 2.78 kWh/kg were observed. Air sparging was found beneficial but was not pursued for health and safety reasons. Various additives in the same chemical family as tetrabutyl ammonium chloride (TBAC1) were tested. Both TBAC1 and tetrabutyl ammonium bromide were found to be equally effective. Attempts to carry out the electrolysis at 1200 A/m2 were not as successful.

Jan 1, 2000

By Hirokazu Narita

The extractability for Pd(II) using MOTDA and DHS and their durability against a mixed solution of HNO3 and HCl was investigated by solvent extraction and FT-IR measurements. Both MOTDA and DHS selectively extracted Pd(II) over Pt(IV) from 0.75 M HNO32.25 M HCl solutions. The extraction rate of Pd(II) with MOTDA was much greater than that with DHS. In the durability test, the extraction percentage of Pd(II) and the FT-IR spectra were measured using MOTDA and DHS after stirring with 0.75 M HNO32.25 M HCl solutions. The extraction percentage of Pd(II) with MOTDA hardly changed during the two-month stirring; however, that with DHS decreased with an increase in the stirring time. The FT-IR spectra showed the sulfoxide formation by the oxidation of the sulfide in DHS, but not in MOTDA. Consequently, it was found that MOTDA is more durable than DHS.

Jan 1, 2006

By H. Y. Cho

LS-Nikko Copper Inc, has been operating its Onsan copper smelter since 1979. The smelter began its operation with a designed capacity of 80,000 tpa of copper from concentrates and its smelting capacity was increased to 140,000 tpa of copper by modifying the existing line in 1988. The Mitsubishi Continuous Smelting and Converting Process has been operating since 1998 at the initial capacity of 160,000 tpa of copper. In 2002, the smelting capacity of the Onsan smelter has been increased to 426,000 tpa of copper from concentrate. Now the Onsan smelter has plans to increase its smelting capacity to 500,000 tpa of copper from concentrates by 2010. During the expansion work, the modernization of facilities will be accompanied by an increase in smelting capacity, via the Outokumpu process. This paper reviews the brief history of smelting capacity increase in Onsan smelter and its Outokumpu process modernization plans.

Jan 1, 2006

By G. Roy Chaudhury

Adsorption techniques are comparatively low cost and effective for treatment of arsenic contaminated drinking water. Various adsorbents such as alumina, ferrihydrite and manganese ores have been used, but there has been little investigation of modifying the structure of ferrihydrite to improve its adsorptive efficiency of As(III) and As(V). In the present study the incorporation of manganese oxide into the ferrihydrite structure was carried out and the prepared materials used in arsenic adsorption experiments. The compounds were X-ray amorphous, but TGA/DTA and FTIR analysis showed some structural characteristics. Sorption studies reported in this paper indicate the excellent arsenic removal properties of the manganese/iron compounds with a loading capacity of 0.3 mmol/g. Adsorption follows first order kinetics and the results fitted to adsorption and mass transfer models. Arsenic levels in water containing 1 mg/L As(V) were reduced by 50% in 20 minutes and 90% in 60 minutes using 1 g/L manganic ferric oxyhydroxide.

Jan 1, 2003

By Martin Brueggemann

The Tyrone copper solution extraction and electrowinning plant was the first such facility built by Phelps Dodge Mining Company in 1984. Over the next 20 years, the aqueous flow rate capacity of the plant has been expanded from the original design of 12,000 gallons per minute (gpm) to 34,000 gpm to meet production goals in the face of declining copper grades in the leach solutions. The ability to process higher aqueous flow rates through existing equipment comes at the expense of increased organic loss through entrainment to raffinate. These losses of organic (diluent and extraction reagents) can account for up to 10 percent of the plant?s total operating costs. With the recent dramatic price increase of petroleum-based products, these operating costs due to losses are sure to increase. This paper will discuss recent improvements at the Tyrone SXEW plant that have resulted in a 40 percent reduction of organic losses. These improvements include picket fence modifications, new fence materials, organic recovery systems, and operational practices within the solution extraction process.

Jan 1, 2006

By O. I. Platonov

The experience that has been gained by MMC ?Norilsk Nickel? at its Trans-Polar Division (PD) operations since 1981 in the field of recovery of elemental sulfur from off-gas generated by the Vanyukov and flash smelting through its reduction by natural gas is briefly outlined in the present paper. The key challenge the operators treating off-gas originated from autogenous smelting are usually faced with is the presence of sulphur trioxide in it. Furthermore, air inflows along the entire gas flue increase oxygen concentration in off-gas, thus leading to over-consumption of the reducer (natural gas). Another issue attached to the methane technology is a low yield of hydrogen sulphide largely preventing efficient downstream Claus conversion of the gas. The new flowsheet for treatment of autogenous smelting off-gases including dry dust-cleaning followed by the gas reduction in homogenous reactor developed by OAO Gipronickel Institute on the basis of industrial-scale production of elemental sulfur in Norilsk is presented.

Jan 1, 2006

By Ian M. Ritchie

Right across the universities of the developed world, the traditional disciplines of physics and chemistry are losing ground. Extractive metallurgy, which depends so heavily on chemistry, is also contracting despite a clear need for people with this kind of training in the mining industry. Reasons for this loss of popularity are discussed in this paper. High on the list is one of image. The extraction of metals is widely seen as a dirty, polluting, sunset industry which involves working in remote and uncomfortable corners of the earth for inadequate compensation. Ways in which the image problem can be overcome are considered. It is concluded that a concerted effort needs to be made by the universities and industry to redress this situation. The importance of extractive metallurgy, both now and in the future, when a greater emphasis will be placed on sustainability and recycling, needs to be stressed. In addition, courses need to incorporate training for a career path that leads on beyond extractive metallurgy.

Jan 1, 2003

By Brian Lightfoot

Ausmelt Technology uses a furnace/slag/lance system in a way analogous to the way a chemical engineer would use a mixed reactor. The technology is sufficiently versatile to treat materials under a very wide range of temperature and chemical conditions. At one extreme the system has been operated at temperatures high enough and oxygen potentials low enough to make iron. At the other extreme it has been operated of temperatures as low as 800°C and oxygen potentials high enough to cupel lead from silver. This versatility permits the treatment of a great variety of wastes including asbestos, mixed organic\heavy metal wastes, incinerator ash smelter residues, waste water treatment sludges, organochlorine compounds and many others.

Jan 1, 1994

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 K. A. Natarajan

Microbe-mineral interactions in the leaching of complex sulfides are discussed with respect to (a) role of galvanic interactions in selective dissolution, (b) bacterial attachment to sulfide mineral substrates and (c) the utility of specially adapted metal tolerant bacterial strains. Experimental results obtained in the leaching of two types of complex sulfides, namely, a lead-zinc-copper sulfide and a copper-nickel sulfide are illustrated.

Jan 1, 1985

By Habib Saridikmen

In this experimental study the effects of slag composition on the phosphide capacities of the slag as well as on the phosphorus distribution ratios between the slag and metal phases encountered in ferromanganese smelting have been determined at 1500°C under carbon monoxide atmosphere. The distribution results were employed to calculate the phosphide capacities of the SiO2-Al2O3-CaO-MgO-MnO slags in equilibrium with the Mn-Fe-Si-Csatd.metal phase. The classical gas-slag-metal equilibrium-quenching technique was employed using CO gas atmosphere and graphite crucibles to saturate the metal phase with respect to carbon. The phosphorus distribution ratio increased from 0.045 to 0.375 when the slag basicity increased from 0.72 to 1.39. As expected, the distribution ratio decreased from 0.375 to 0.105 when silica increased from 37 % to 45.8% in the slag phase. The phosphide capacity values were calculated by using the results of experiments. Empirical relationships were developed to express the phosphorus distribution ratios and phosphide capacities of the above slags.

Jan 1, 2006

By K. A. Elbarawy

Processing of Egyptian barite ore with a composition of 85.5% BaSO4; 2.75%SiO2;1.56%Fe2O3 and 5.1% Al2O3 was performed with the aim to prepare pure barium salts. The process took place through pelletization-solid state reduction and leaching steps. Each of these steps was optimized. Pure barium sulphate (99% < 0.82µm) and carbonate (99%<0.75µm )were the final products. This article deals with the reduction process that occur whn coal was added to the ore during pelletization in the ratio of 5:1 stoichiometry. Optimum reduction of pellets of 8-12mm in diameter was achieved after 60 minutes at 1050oC and under a rate of 5 lmin-1 of nitrogen atmosphere, where 87.79% of the ore was reduced. The kinetic studies showed that the reduction process could be modeled according to the core mechanism of diffusion control in which the effective diffusivity is based on the surface area of unreacted ore. The activation energy calculated was 92.7 kJmol-1.

Jan 1, 2006

By Kurt Westerlund

The design of the economically most profitable and technically most feasible smelter process gas handing and treatment as an integrated part of the total metallurgical process is discussed and exemplified, with alternative flow sheets including material and energy balances, investment and operating costs. Retrofitting and de-bottlenecking of existing gas handling lines wil1 be described and exemplified. Methods of increasing total gas handling line availability will be described.

Jan 1, 1992

By A. H. -J. Siegmund

Since the last survey of lead smelters in 1987, the lead industry has experienced many changes. Technological innovations, in combination with a dramatic shift in the market structure as well as more stringent government regulations, caused major upheavals in many different areas. Therefore, a new survey was performed to review the progress in the technology of lead recovery over the least decade. The newly conducted survey reflects all current phases of the world's primary lead production, from charge preparation to refined metal shipment. It was prepared by sending questionnaires to individual companies, and the detailed statistical data of this survey are presented. In considering the data developed from the survey, it should be recognized that the primary lead industry is at a crossroad where novel technologies will gradually substitute the sinter machine - blast furnace operation in the new millennium.

Jan 1, 2000

By Jeaneth S. Benedetto

The physical and chemical processes developed for recovery of uranium and phosphor from phosphoro-uraniferous ore bodies consists of three basic steps: concentration of the phosphate bearing uranium by flotation, chemical dissolution of the concentrate by wet phosphoric acid and extraction of uranium by solvent. In this process two products are obtained: 1) uranium and 2) phosphoric acid. The purpose of this work was to develop technological know-how of phosphoric acid purification though an extraction of P2O5 by solvents. It was investigated by two lines of research. In the first one the uranium was extracted before the phosphoric acid purification. In the second, the phosphoric acid was extracted before uranium recovery. The comparison of the two processes is shown in this paper. Experimental work was developed on a laboratory scale to select and optimize the process variables. After the laboratory study, the research of extraction and stripping was continued on a pilot scale in pulsed perforated-plate columns in order to investigate the main operational and process conditions. The first phosphoric acid extraction experiments showed good results using a raffinate sample obtained from the uranium extraction process. It was possible to obtain a high purity phosphoric acid.

Jan 1, 2003