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By Richard D. Hangi

Process mineralogy techniques are uniquely applicable to industrial problems related to the extractive metallurgy of nickel, cobalt, and associated metals. Reflected 1ight microscopy, together with selected determinations by scanning electron microscopy-energy dispersive spectrographic analysis and electron probe microanalysis, provides the means to identify the ore minerals cobalt and nickel ores, determine the abundance of each ore mineral, assess the extent of intergrowth between the cobalt and nickel minerals and other ore and gangue minerals in the ores and concentrates, and predict the potential success of cobalt and nickel extraction by grinding, flotation, pyrometallurgical, and hydrometallurgical treatments. In addition, the extent of locking of the cobalt and nickel minerals with each other and with the gangue minerals can be directly observed by reflected light microscopy. Where ores have been treated by hydrometallurgical procedures, reflected light microscopy can serve to determine the causes of excessive leach consumption. Finally, the partitioning of cobalt and nickel between high-temperature synthetic phases produced by pyrometallurgical treatment can be precisely determined by process mineralogy techniques. Case histories from cobalt and nickel deposits illustrate the value of applied mineralogical techniques in the study of cobalt and nickel ores, beneficiation, hydrometallurgial, and pyrometallurgical products.

Jan 1, 1993

By V. Jiricny

There is a growing need to process galvanized steel scrap from automobiles, etc., in order to remove the zinc coating that otherwise causes problems in remelting of the scrap in electric arc furnaces. One approach that has moved to the pilot plant stage is that of Metal Recovery Technologies, Inc., of East Chicago (MRI). That company leaches the zinc fiom the scrap with a sodium hydroxide solution. The leached and washed scrap can then be returned to the steel industry. What is left is a sodium hydroxidelzincate solution which must be processed to recover the zinc and the NaOH. Presently, this is done by MRI using electrodeposition on planar electrodes at moderate current density and the resulting zinc is in the form of fine powder which is hard to process into, say, zinc for galvanizing. MRI has supported an investigation of a novel electrode, the spouted bed electrode (SBE), for zinc electrodeposition. In laboratory cells, zinc particles with low porosity have been grown up to 3mm in size. Microanalysis of the deposited zinc showed low level of impurities. DC energy consumption values were usually in the range of 2-2.5 kWg which is well below the energy consumption of the existing cells (and of present-day cells for electrowinning from acid sulfate electrolytes). These results were achieved at current densities (few thousand A/m2) that are much higher than possible with conventional electrodes. Discussion is provided of the scale-up of the cell to a commercial scale.

Jan 1, 1998

By Min Chen, Lei Xu, Weijun Huang, Shuai Zhang

For the purpose of extending the service life of MgO-C bricks used as linings of vanadium-extraction converters, the effect of Fe addition on properties of MgO-C bricks was investigated. The results showed the addition of Fe could effectively improve the sinterability of the oxidized layer of the MgO-C refractory at 1400°C due to the effect of FeO (formed by oxidation of Fe) on formation of MgO-FeOss and modification of the microstructure, and excellent corrosion resistance against vanadium containing slag was also obtained due to the increase of compactness of the oxidized layer and concentration of FeO in the oxidized layer. Consequently, it is considered that MgO-C brick by introducing the new phase of Fe is a favorable substitute of MgO-C refractory to be used as linings of vanadium-extraction converters.

Jan 1, 2015

By K. J. Murphy, A. R. Smith, A. P. Odorski

"The need for large quantities of oxygen for use in metallurgical processes was a major driving force in the commercialization of tonnage air separation plants. Oxygen, nitrogen and argon impact the quality, energy efficiency and environmental aspects of metals production. Cryogenic air separation processes have been used to supply most industrial requirements, however, newer technologies are available or under development to meet the needs of today's and tomorrow's metallurgical processes. This paper reviews the technical features and state of development of adsorption, chemical, cryogenic and membrane technologies. The technologies are compared in terms of plant size, oxygen purity and pressure, nitrogen and argon co-production, product use pattern and back-up requirements. Computer control systems are described that optimize operation over varying load patterns and ambient conditions; substantially lowering energy consumption. IntroductionOxygen production totalled 390 billion cubic feet in 1987. Although current production is lower than the peak of 455 billion cubic feet reached in 1979, oxygen remains the fifth leading chemical product manufactured in the u.s. (1) Metals manufacturing and fabrication accounts for sixty percent of the oxygen consumed in the u.s. Oxygen use in the steel industry consists of air enrichment for conversion of iron ore, purification of the iron in basic oxygen or other furnaces, and for cutting and welding the finished steel product. Nonferrous ores are smelted in oxygen enriched atmospheres to reduce energy consumption and increase capture of sulfur compounds to meet environmental requirements. In the future oxygen usage is expected to become even more important in metals production as energy costs increase, environmental standards become more stringent, and as new coal based processes become commercialized. Oxygen usage per ton of metal in the new direct reduction processes can be up to ten times higher than traditional steel making."

Jan 1, 1988

By Jack S. McPartland

The recent developments on the concentration and recovery of gold from leached gold thiosulfate solutions by solvent extraction, reduction-precipitation, and electrochemical deposition are reviewed in this paper. Alkyl phosphorus esters have been found to extract gold only in alkaline thiosulfate solutions, The recovery of gold increases with thiosulfate concentration in the aqueous phase and with alkyl phosphorus esters concentration in the organic phase with aliphatic hydrocarbon diluents. The addition of ammonia improves the extraction. The extraction of gold with amines in either aliphatic or aromatic diluent decreased in the following order: primary>secondary>tertiary amines. Increase in the extractant concentration at high pH increased the extraction of gold. At pH < 9, the primary amine, RR&apos;CHNH2 with 1&apos;9-23 carbon atoms is the main extractant with TBP as the synergistic reagent and at pH >9, the primary amine shows a synergistic effect on the extraction of gold&apos; with TBP. TheAu(I) ions in thiosulfate solution are reduced by sodium borohydride (SBH) to metallic gold, with particles in the sub micron range, At an SBH/ Au ratio of 6.25, pH = 6, and at room temperature, the I e ppm Au(I) in a solution of ] 0 gil thiosulfate was completely reduced to metallic gold in about 60 minutes.

Jan 1, 1999

By Ji-He Wei

The ESR of Cu-Cr-Zr alloy has been experimentally investigated. The remelting experiments have been carried out with different slag fluxes in the Cal, + Nal, CaF2 + ZrO2 and CaF2 + NaF + ZrO2 systems on an ESR furnace of 25kg capacity; using a water-cooled copper mould of 96.5 mm diameter, with the forged square bar electrodes of 50x50 mm2. The slag amount was taken to be 1.5 kg. The remelting current and voltage used were 1600-1800A and !5-25K, respectively. The influence of the slag composition on the stability of the remelting process and the losses of alloying elements (2r and Cr) has been considered and examined. The technologies of hot working and heat treatment of the ES ingot have been described and discussed. Some physical properties of the slag in a CuF2 + NaF + ZrO2 system and the remelted Cu-Cr-Zr alloy have been determined. The results indicated that with the slag flux of CaF2 + NaF + l0 mass % ZrO2 and the other operation parameters employed, a high quality ingot of Cu-Cr-Zr alloy may be obtained at the considerably high yields of Zr and Cr by means of ESR. For the remelted Cu-Cr-Zr alloy with a specified composition of 0.5 mass % Cr and 0.1 mass % Zr, the appropriate electrical conductivity, hardness and softening temperature are as high as 45-46S/m, HRB 82-84 and 550°C. respectively. The properties of the Cu-Cr-Zr alloy products are in accordance with and superior to the requirements and specifications of ISO5l82-l99l(E).

Jan 1, 2000

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Charles W. Kenney

Mercury contamination of soil at an old chemical plant surrounded by a residential community and adjacent to a river has provided unique challenges for the current owner. Inorganic and organic mercury compounds had accumulated over the past 50 years to levels that require remediation. Hazen Research, Inc. conducted a multi-phased program to characterize contaminants and their occurrences, evaluate various treatment technologies, and demonstrate the selected technology at bench and pilot scales. A combined physical cleaning and chemical treatment was demonstrated to meet treatment goals for the site. This paper discusses the methods of process selection and results of the bench-and pilot-scale testing.

Jan 1, 2003

By Devon A. Hannan

Thermodynamic modeling calculations were undertaken for the recovery of mercury from HgTe using a vacuum retort reactor. However, discrepancies were noted in the available thermodynamic data which introduced uncertainty in the model results. Consequently, a series of transpiration experiments were first undertaken on the thermal decomposition of HgTe into an inert carrier gas stream according to the following reaction: HgTe(s) Hg(g) + Te(s) From the measured weight loss of the HgTe samples, the Gibhs free energy change for the above volatilization reaction was determined as a function of temperature. The experimentally determined Gibbs free energy values were found to be approximately 30% larger (more posi-tive) than the values available in databases such as HSC Chemistry. By conducting a second-law analysis on the experimental data, the heat of formation of HgTe at 298.15 K and the en-tropyat 298.15 K were determined, which then formed the basis for a new database for the modeling calculations. The results of this study showed that HgTe was more stable at elevated temperatures than was generally indicated in the literature. The new database is given in a for-mat for direct insertion in HSC Chemistry. Using the new database, modeling calculations were conducted to examine the effects of the re-tort pressure and the molar ratio of purge gas to HgTe on the volatilization of mercury from HgTe. A diagram is presented that shows the minimum temperature for 100% volatilization of mercury from HgTe as a function of retort pressure for different molar ratios of purge gas (N2) to HgTe. For example, it was found that the minimum temperature for 100% volatilization could be decreased by 175 K, at a retort pressure of 0.05 bar, if the molar ratio ofN2 to HgTe is increased from 1.0: 1 to 100.0: I.

Jan 1, 2003

By P. C. Chaubal

The overall kinetics of oxidation of single partic1es of chalcopyrite have been studied for temperatures up to 1273 K. The experiments were conducted in a stationary bed reactor using a non-isothermal technique. Any mass and heat transfer effects on the kinetics of oxidation were eliminated by using a high-enough gas flowrate. Up to temperatures of 873 K, pore-bl1ocking kinetics were applicable, whereas above 873 K, power-law kinetics gave a satisfactory fit of the data. The activation energy was 215 kJ/mol below 754 Kand 23.7 kJ/mol above 1,060 K. Predominance area diagrams were constructed at various temperatures and used in conjunction with X-ray analyses of partially oxidized samples to determine the intermediate phases formed during the reaction. The analysi1s also provides a justification for the kinetic models used. The results indicate that the reaction rate is first order with respect to oxygen concentration and inversely proportional to the square of the particle size throughout the ranges of temperature studied.

Jan 1, 1985

By L. I. Rosato

A novel hydrometallurgical process for the recovery of silver and gold from neutral leach residue that is based upon leaching with thiourea, is described. Laboratory and pilot plant studies have shown that 80-90% of the silver and 60-70% of the gold can be recovered by:? ( i) leaching zinc calcine with &apos;Spent electrolyte at pH 2.0-3.0 to generate a precious metal-bearing zinc ferrite residue, (ii) leaching of the thickened zinc ferrite with 3-5 g/L thiourea in a six stage carbon-in-pulp circuit, (iii) elution of silver and gold from the loaded carbon with a thiourea- butanol solution, (iv) thermal regeneration of the stripped carbon and (v) recovery of the precious metals from the pregnant eluate by cementation with zinc dust. The reasons for adopting the thiourea CIP leach and the preferred operating parameters for each process step are presented. The requirements for the destruction of any thiourea transferred to the zinc circuit are outlined, and the results of an integrated one tonne/day pilot plant operation at Canadian Electrolytic Zinc are given.

Jan 1, 1990

By T. Ueno

Naoshima Smelter & Refinery of Mitsubishi Materials Crop. commissioned a new Mitsubishi continuous copper smelter in May 1991. Process offgas volume of the conventional reverberatory furnace line, one of the previous smelters having been shut down, was very large and thus two acid plants had been operated. It was expected that the offgas volume would, be reduced at the new smelter to about a half of the sum of those from previous two smelters and the sulfur dioxide strength would be increased. So various alternatives were studied to minimize the operation cost. And it was decided to utilize both of the plants with minor modifications by diluting the gas either with air or with dilute gases. The acid plants now receive off gases from the new copper smelter, a sintering machine of a lead smelter and a decomposer of waste acid. The paper discusses plant design, operation, improvements and modifications realized in relation with the retrofitting of the copper smelter.

Jan 1, 1992

By A. Tsubouchi, F. Noguchi, T. Takasu

"A high current density operation is desired to improve the productivity in copper electrorefining. However, a lot of problems still remain such as passivation at anode, dendritic deposition at cathode and impurity behavior during the electro refining.Effects of the current densitY on the morphology of copper deposition on the cathode, and passivation at the anode were investigated at various fluid velocity of electrolyte in the present study.Although a granular appearance of the copper deposition was obtained with increasing high current density, it was depressed by an increase of the fluid velocity of the electrolyte. A uniform deposition on the cathode was also observed when the fluid velocity of the electrolyte become higher. It was ascertained that passivation at the anode was suppressed by circulating electrolyte during electrolysis. INTRODUCTIONIt is desirable to operate at high current density in copper electrorefining in order to improve plant productivity without enlarging the size of electrodes(1). However, there are many problems in copper electrorefining at high current density with the usual commercial practice, for example, anode passivation, dendritic deposition and an increase of impurities in the cathode.In general, it is effective to agitate the electrolyte in order to suppress these problems(2). Smith et a1.(3) have performed electro refining experiments at various current densities in the range of 8 to 32 Aldm2 and at electrolyte fluid velocities in the range of 40 to 120 mlmin, and they obtained well consolidated, void free copper even at high current density in a high electrolyte velocity. However, they did not discuss the recovery ratio and the passivation behaviour at the anode. Walsh et a1.(4)(5)(6) experimented with the rotating cylinder electrode, and ascertained that electrolysis can be carried out at high current densities under the condition of pure electrolyte.With regards to anode passivation, there are several papers by previous workers(7)(8). Our group ascertained the process of producing anode slime during electrolysis(9). However, these experiments were carried out without forced circulation of electrolyte. Therefore, in the present study, to solve these problems, we electrolyzed at current densities in the range of 4 to 50 Aldm2 with circulating electrolyte in the range of 0 to 48 mlrnin. The effect of electrolyte fluid velocity on the surface morphology of deposited copper at cathode and passivation at anode were investigated when electrolysis were carried out with circulating electrolyte at high fluid velocity and at high current density."

Jan 1, 1997

By D. W. Collins

The uptake of gold from halide solutions by activated carbon has been investigated using various techniques. Halide systems typically exhibit combined adsorption-reduction type behavior. In an attempt to gain more information about the nature of these processes, samples of synthetic highly-oriented pyrolytic graphite (HOPG) were contacted with aqueous solutions of gold-iodide. HOPG represents a model structure for activated carbon comprising of basal- plane sites, edge sites, and various defect sites. Two basic instrumental methods were used to examine the uptake of gold by HOPG. The first was standard X-ray photoelectron spectroscopy (XPS). The other involved several scanning probe techniques. XPS clearly indicated a preferred uptake of gold at edge sites. However, iodine appeared to be distributed on both basal-plane and edge sites. At low iodine additions, tapping mode AFM showed that clusters were concentrated along steps and surface defects. At high iodine concentrations, the HOPG surface was uniformly covered by iodine.

Jan 1, 1998

By John M. Gaines

Lead concentrates from the Viburnum Trend in the Southeast Missouri Lead district are sintered prior to smelting to bind the particles together homogenize the feed, and reduce the sulfur content. Good sinter forms competent masses about 4 to 6 inches across, that hal!e about 15% porosity and good mechanical strength to withstand transport and the weight of the overlying load in the smelter. Bad sinter has poor mechanical strength and forms fine fragments that retard the circulation of reducing gases in the furnace and lengthen the time required for reduction. The productivity of the lead smelter depends on good sinter feed. Because some lead sinter plants produce bad sinter about 20% of the time, this applied mineralogy study has been undertaken to determine the mineralogical and microtextural differences between good and bad sinter. A reflected light microscopic study of 130 polished sections has shown that good and bad sinters differ distinctly in their mineralogy, tex1ure. and character of, porosity. Good sinter consists of hardystonite, franklinite. lead-zinc-bearing magnesium-calcium silicate, lead silicate matrix, and large crystals of calcium-magnesium-iron silicate, together with minor amounts of lead oxides, lead-zinc silicate, metallic lead, specular hematite, magnetite, lead-iron-bearing zincite and zinc-Iead-magnesium-bearing wustite in a tightly intergrown mesh of crystals and with an evenly distributed porosity of 15% to 20%. Electron microprobe analyses show that the principal phases contain lead (or zinc): hardystonite (4-20% Pb) franklinite (2-14% Pb) and lead silicate matrix (65-74% Pb). Bad sinter differs from good sinter in the greater abundance of lead silicate matrix, galena metallic lead, and lead oxides and the lesser abundance of hardystonite, franklinite and calcium-magnesium-iron silicate. Bad Sinter is characterized by a lack of an intimate intergrowth of the constituent phases. Its porosity is much lower commonly 0 to 5% and those pores are concentrated in local areas rather than distributed evenly throughout the sinter.

Jan 1, 1991

By M. Tangstad, H. Mølnäs, J. D. Steenkamp

"Temperature affects several aspects of pyrometallurgical systems, including thermodynamics and reaction kinetics. Reliability of temperature measurements in laboratory and plant applications is thus important from process, safety and financial perspectives. This case study briefly introduces different techniques utilized for temperature validation, and demonstrates temperature validation on laboratory scale utilizing the wire-bridge method. Pt/Ptl3Rh thermocouple hot junctions were constructed by mechanically connecting thermocouple wires through a pure metal bridge consisting of copper, gold, nickel or palladium wire. When heating the wire-bridge thermocouple alongside a regular Pt/Ptl3Rh thermocouple, temperature offsets were quantified as the wirebridge thermocouple short-circuited at the melting points of the pure metals. At the melting points of gold (1064°C) and palladium (1555°C), average measured temperature offsets were -2.1°C ± 2.3°C and 0.2°C ± 0.4°C, respectively. Results from the copper and nickel wire-bridges were inconclusive. The paper concludes with a discussion on the potential industrial applications of the technique.IntroductionThermocouples are probably the simplest of all temperature sensors, but are widely utilized due to simplicity, versatility and ability to handle a variety of experimental conditions and industrial applications. Additionally, thermocouples are often the only option in research laboratories requiring high temperature measurements, and a high level of reliability is usually required from thermodynamic, kinetic as well as safety points of view.The study presented here originated from a test program where the compatibility between different types of carbon-based refractory materials and industrial slag produced in silicomanganese furnaces were investigated on a laboratory scale utilizing the static crucible test[l]. Due to the nature of the silicomanganese production process, the compatibility tests were to be conducted at 1600CC[2]. Details of the experimental set-up utilized for the compatibility tests are discussed in the Experimental Set-up and Method Statement section later in this paper."

Jan 1, 2012

By Shuqiang Guo, Dingsheng Tan, Weizhong Ding, Zunyu Hu

"The mixture of hydrochloric acid and magnesium chloride is a good lixiviant for leaching of laterite. The solution can enhance the leaching ability because of the proton activity deviated positively from ideal. Otherwise, the existence of magnesium chloride in the lixiviant affects the dissolution behavior of magnesia, which may be an advantage of the process with less hydrochloric acid consumption. An investigation of magnesia particle dissolved in strong hydrochloric acid solution has been conducted. Influences of concentration of the magnesium chloride and hydrochloric acid and temperature on magnesia dissolution were studied. The dissolution mechanism was also discussed in this paper.IntroductionThere has recently been much interest in the use of hydrochloric acid leaching processes for recovering metal from ores or secondary resources [l-41_ Compared with sulfuric acid, the use of hydrochloric acid as lixiviant offers significant advantages including faster leaching kinetics even at atmospheric conditions, higher leaching rate and greater solubility for most metal chlorides [5-61 .With the gradual decline of the nickel sulfide supply, the extraction of nickel from laterites has become increasingly attractive [7-s1. Nickel may be co=ercially recovered from laterites both by pyrometallurgical and hydrometallurgical processes. The drawbacks of pyrometallurgical processes include the requirement of high grade ores, substantial energy input and loss of cobalt bound within ores. The extraction of Ni from lower grade nickel laterites ores is suited by hydrometallurgical routes, which play an increasingly important role with depletion of higher grade deposits."

Jan 1, 2014

By S. Mondon

Hibi Smelter which is a Copper Smelter lining a blast furnace, produces 2,700 metric tons of anode copper per month. Generally, in a copper refinery, arsenic and antimony are considerably troublesome impurities. With regard to the elimination of antimony, Hibi Smelter has two handicaps described as follows. (1) Smelting under the slightly oxidizing atmosphere in the blast furnace. (2) Recycling the converter slag to the blast furnace after cooling. Therefore antimony and arsenic, mainly antimony, elimination tests, in which the alkaline flux was injected through the two tuyeres in the blowing stage, were carried out in the rotary anode furnace. Antimony and arsenic were respectively removed more than 90 96 from the molten copper, and their high eliminations are discussed by application of the transitory and permanent reaction model with the flux injection, which was presented by T. Lehner.

Jan 1, 1983

By Fang-Qui Zu

Understanding the nature of liquid structures and properties remains an open problem for many fundamental and applied fields such as materials sciences and processing. And as well known, there is no other defined phase line above liquidus (TL ) in phase diagrams of ordinary binary systems. However, via different experimental resorts, our research results on over 30 metallic melts including alloys and elements show a novel physical image: temperature induced liquid-liquid structure transition (TI-LLST) can occur hundreds of degrees over TL. On the other hand, the solidification behaviors and structures out of the melts experienced TI-LLST are distinct from those out of the melts before TI-LLST. In this presentation, some characteristic aspects of the TI-LLST and the effects on solidification behaviors and structures are briefly summarized, and the pertinent rules and mechanism are also analyzed.

Jan 1, 2009

By Yang Tian-zu

The separation of precious metals from base metals containing in gold-antimony alloys by selective chlorination leaching under controlling potential was studied in this work. The effects of the consumption of hydrogen peroxide, the concentration of hydrochloric acid, the concentration of sulfuric acid, leaching temperature, leaching time and the liquid-solid ratio in hydrochloric acid system on the leaching efficiencies of the base metals have been investigated. The optimal leaching conditions of the gold-antimony alloys are as follows: hydrochloric acid concentration 4.0mol?L-1, sulfuric acid concentration 1.2mol?L-1, liquid-solid ratio L:S=7.5:1, the leaching temperature 80 0C, leaching time 2h, and the oxidation potential of the leaching system 400±20mV( vs SCE).The leaching efficiencies of copper, nickel and antimony are more than 99% and the gold leaching efficiency is about 0.042% under the above leaching conditions. The base metals containing in the gold-antimony alloy are separated from the precious metals thoroughly.

Jan 1, 2006