Search Documents

By Edward Rosenberg

The synthesis and characterization of silica polyamine composites modified with a variety of sulfur containing ligands is described. The two most successful ligands in terms of sulfur in-corporation and mercury capture are ethylene sulfide and carbon disulfide. The ethylene sulfide forms either an amino mercaptane or a polysulfide upon reaction with amino groups on the composite. The carbon disulfide undoubtedly forms a dithiocarbamate functional group upon reaction of the amino group under basic conditions. Both materials posses excellent capture kinetics and capacities for mercury, Once captured, the mercury is extremely difficult to remove from the composite materials, even with concentrated acids, and they easily pass the TCLP test. The materials are compared with related thioether modified silica polyamine composites and appropriate potential applications are discussed.

Jan 1, 2003

By R. C. Nascimento

It was investigated the effect of the addition of bentonite on the physical propertiesof pellets produced from fines of manganese ores. Cold-bonded pellets were produced. Pellets bearing up to 1 wt% of bentonite were submitted to strength compression resistance tests, fatigue of pellets to impact and maximum height of fall tests. A correlation of resistance of the pellets and time for curing were stablished. The produced pellets match the conditions for raw materials used in electric smelting hrnaces to produce manganese based ferro-alloys.

Jan 1, 1995

By B. R. Davis, Neale R. Neelameggham, R. E. Brown

The element Calcium element has a unique place in the production of etals, intermetallics and other compounds. The unusualness arises from the fact that we have several possible reductants – metallic calcium, calcium carbide, calcium cyanamide and calcium hydride. A review of how metallic calcium is manufactured and utilized is presented. The difficulties involved in producing the metal in large quantities and price implications are noted. . Fundamental thermodynamics of how these act as reductants are shown, along with the historic application of these in metal production during the past century and a half. Alternate applications as to how to control the cost of the reductant is indicated, such as the numerous attempts in making low cost titanium utilizing direct or indirect calcium reductant.

Jan 1, 2014

By Robert C. Laudon

Spectral reflectance data for 335 minerals, including 228 minimum-maximum combinations for anisotropic minerals giving a total of 563 data sets, have been collected from the literature and combined into a single database. Quantitative color values for x, y, Y, Ad , and Pe referred to ICI standard i11uminant C have been calculated from the spectral reflectance data and are included in the database. The programs plot spectral reflectance curves together with all quantitative color data for each mineral in the database. The plots and data can be directed to a dot-matrix printer such that a databook of quantitative color and spectral reflectance having one mineral per page can be generated for the ore microscopy laboratory. In addition, by sorting the database and grouping the minerals, groups or individual minerals can be plotted on the chromaticity diagram, and this plot can also be sent to a dot-matrix printer. The programs are written in compiled BASICA for an IBM-PC with graphics capabilities and at least 128KB random access memory (RAM). The databases are accessible either through the BASIC programs or through any commercial database system capable of loading and writing to an ASCII format sequential file. The programs and database are available by sending a blank diskette and self addressed, stamped envelope to the authors.

Jan 1, 1987

By Takeshi Ohgai, Hisaaki Fukushima, Tetsuya Akiyama, Joon-Seo Ki

"Recently, an intensive attention has been paid to the electrodeposition of Zn-Cr alloy in the field of the production of super-highly corrosion-resistant alloy plated steel sheets for the next generation. In this study the electrodeposition of Zn-Cr alloys from the sulfate baths was conducted to investigate the codeposition mechanism of Cr with Zn. As a result, Cr was codeposited with Zn at higher current densities in both polyethyleneglycol(PEG)-free and PEG- containing baths. However, PEG made it possible to reduce Cr+ to the metallic state and Cr existed in the form of Cr(III) hydroxide in the deposits obtained from PEG-free bath. The measurements of the partial polarization curve of Zn and the pH in the cathode layer revealed that PEG acted as a polarizer to shift the cathode potential to the reduction potential of the composited hydroxides of Zn and Cr formed due to the pH rise in the cathode layer.1. IntroductionRecently, much attention has been paid to the electrodeposition of Zn-Cr alloys because of its application to the production of super-highly corrosion-resistant alloy plated steel sheets for the next generation1Hl_ Some researches have already tried to commercialize this type of steel sheet. High corrosion-resistance of this steel sheet is brought about by codeposited Cr in the alloys. According to Piontelli's classification5l concerned with metal deposition from aqueous solution, Cr belong; to an inert metal and its deposition is associated with a large amount of hydrogen evolution. Therefore the current efficiency for Cr deposition is extremely poor. It has been also reported that Cr is unable to codeposit in the electrodeposited Zn film in the absence of a certain additive in the solution. 0-compounds group colloids7l, ether group organic compounds8), 9>, peptide based compounds10l, etc., have been found to be effective additives to induce the codeposition of Cr with Zn. However, few studies have been made on the codeposition mechanism of Cr with Zn. In this research, the fundamental electrodeposition behavior of Zn-Cr alloys from sulfate baths was investigated to clarify the codeposition mechanism."

Jan 1, 1998

By M. Wallin

Millions of tons of sludge from different metallurgical processes are produced worldwide annually, and the environmental impact of landfilling these often hazardous sludges stresses the need to understand their role as valuable resources. The current work explores the potential of producing a saleable low-phosphorous ferromanganese alloy by utilizing sludge from the silicomanganese industry together with an iron source. The aim of the project is to explore the feasibility and practical challenges related to reduction and dissolution of manganese and silicon from the sludge to liquid metal and slag. Parameters such as ratio of input material as well as the effect of adding limestone and coke to the mixture were explored by thermodynamic calculations and adapted experimentally. Results show that a ferromanganese alloy, in fact, can be formed, while silicon and calcium forms a complex slag that captures a significant amount of impurities.

By Yasuo Ojima

The mainstream of copper smelting processes in the world today is a combination of Outokumpu type Flash smelting and PS (Pierse Smith) converting process. Presently it can be estimated that about 50% of the worldwide copper production is produced by the Flash smelting process and 80% by the PS converting process. PS converting process due to its operational flexibility and despite its batch character of operation has been widely used in many smelters for more than 100 years. However, an environmental issue has been pointed out related to this process because of the difficulty of handling the fugitive gases. Recently several copper smelters in the world have been newly construeted and others have executed major modification and modernization. The continuous converting process has been applied in many of them instead of PS converting process. This paper compares PS to the emerging continuous converting process and makes a prospect of the future of the copper converting process.

Jan 1, 2003

By John H. Schloen

Copper refineries are constantly looking for methods to upgrade their plants to reduce refining costs and to improve the purity of their electrolytic cathodes at the same time that the purity of the anodes they refine is being lowered by the rehabilitation of reverberatory furnace smelters to one of the direct smelting processes. The comments given below are based on the answers to the questionnaire returned bf the 36 copper refineries that represent 66% of the western world s refining capacity. Eleven refineries employ some form of uniform weight anade casting, e.g., Outokumpu, Contilanode, Mitsubishi, Lurgi, or Hazelett. This type of anode casting presents the best possibility for improving cathode purity. The cathode press of Phelps Dadge can improve current efficiencies and cathode quality. The press is used on first-run cathodes, after 48-60 hours, on half-cells at a time without interruption of the cell current. One refinery interrupts current for sever.al hours to allow the anode slime to settle before the, cathode pressing. The cathode press is now used at eight refineries. Apart from periodic reverse current (PRC), it is not expected that current densities will be increased. Thirty refineries, using direct current, average 231 amps/M, with a low of 178 and a high of 350. Five refineries use PRC at an average of 338 amps/M, with a low of 290 and a high of 380. Current efficiencies are good at an average of 94%, with a low of 88% and a high of 99% for the 34 refineries that reported. It must be remembered that the cycle efficiency with PRC is about 93%., so that the effective current efficiency with PRC would be only .94 X .93 or 87% However, PRC should be considered seriously for refinery expansions because it can save about 25% on capital costs.

Jan 1, 1987

By Vladimiros G. Papangelakis

During the past five years, chemical modelling work at the University of Toronto has elucidated the role of soluble magnesium on the autoclave acidity and has demonstrated why feeds rich in magnesium, and other divalent metals, require more than the stoichiometric requirements in acid to produce a leaching performance comparable to that of low magnesium feeds. This understanding has allowed the calculation of acid additions to the pressure acid leach (PAL) on a less empirical basis. Optimizing acid additions to the PAL confers savings in neutralization costs, ensures high productivity and minimises corrosion problems. Hence, our picture of the solution chemistry inside the autoclave during the PAL process has been substantially improved and is reviewed here. Experimental techniques based on solubility and direct acidity measurements that support the theoretical predictions are presented. Concepts of chemical modelling of electrolyte systems at high temperature and software issues are also discussed. Finally, a better understanding of the solution chemistry at temperature has led to better kinetics models because all metal dissolution and precipitation reactions are acid driven and controlled. . Therefore, reactor modelling efforts by our group are also presented and a reactor model with very good performance, as compared to pilot-plant data, is also made here. Finally, in spite of the above success in PAL solution chemistry and reactor modelling, significant challenges lie ahead in theoretical data gaps and instrumentation; these are also discussed in this paper. Keywords: Laterites, process modelling, pressure acid leach, solution chemistry, chemical modelling, reactor simulation

Jan 1, 2004

By Pengfu Tan

NiModel, a thermodynamic model, database and computer program, has been developed to predict the distribution behavior of Ni, Cu, Co, Fe, S, O, As, Sb and Bi, and heat balance in the nickel pyrometallurgical processes such as Outokumpu flash smelting, Outokumpu direct high-grade matte smelting, INCO flash smelting, and Peirce-Smith converting processes. In this model, as much as 16 elements (Ni, Cu, Co, Fe, As, Sb, Bi, S, O, Al, Ca, Mg, Si, N, C and H) are considered. The compositions of matte, slag and gaseous phases, and heat balance are calculated using the thermodynamic data and the activity coefficients of the components derived from the experimental data. The model predictions were compared with the known industrial data from Kalgoorlie Nickel Smelter in Australia, Outokumpu Harjavalta Nickel Smelter in Finland and INCO Metals Company in Canada, and an excellent agreement was obtained. In this paper, the applications of NiModel in the nickel pyrometallurgical industries have been presented. NiModel has been used by Jinchuan Group Limited in China.

Jan 1, 2004

By Ram V. Ramachandran

As an industry with major potential impacts (both good and bad) on water resources and due to the rising costs of process water, the mining and metallurgical processing industry has a key responsibility to contribute to the overall goal of preserving both the quantity and quality of water available within the watersheds they operate in. As we plan for new and existing mining and metallurgical projects, we need to consider a hierarchy of options to minimize our impact within the watersheds we operate; keeping clean water clean by diverting around our operations; reduction in the amount of water we use; reuse of water wherever possible, and improvements to water quality for recycling and/or release to environment. Technology is needed to treat water to improve its quality for reuse or release to the original watershed. While lime precipitation followed by sulfide polishing is effective for removal of most of the metals, it does little or nothing to remove ammonium ions and anions such as chloride, nitrate, molybdate, arsenate and selenite/selenite. Regulations on sulfate limits in treated discharge water has drawn close attention to the treatment of acid mine drainage (AMD). Management of brine and salt disposal is also posing a problem due to strict regulations and cost of disposal. This paper will: (a) address issues associated with managing water with the objective of maintaining water sheds—status quo-during and after operation (b) discuss potential technologies for advanced water treatment plants.

By Xie Zhang, Chongyang Zhao, Qingyun Huang, Bing Xie, Xiaopeng Zhen

"Extracting vanadium from vanadium containing hot metal into vanadium slag by BOF is the main vanadium production process in China. In this paper, the influence of Si content in hot metal on the quality of vanadium slag is analyzed. Synthetic vanadium slag with different SiO2 content were melted at 1673 K and then cooled to 303K at the cooling rate of 3?/min. Optical microscopy, SEM, EDS and XRD were used to analyze the mineralogical phases and crystallization behavior of vanadium slag. The results show that vanadium slag mainly contains spinel phase and silicate phase; V is enriched in the spinel phases while Si is concentrated in Fe2SiO4 CaFeSi2O6 and (Fe,Mn)2SiO4 as silicate phase. The melting point of slag increases gradually with the addition of SiO2; whereas viscosity decreases with an addition of 15~19% SiO2 and increases with an addition of 19~27% SiO2.IntroductionVanadium is an important element which is used almost exclusively in ferrous and non-ferrous alloys. The major vanadium products include FeV, V2O5, V2O3, VN and Al-V-Ti alloy. Furthermore, vanadium slags are mostly produced by oxidizing the elements in V-containing hot metal during a duplex refining process. Therefore, the process of removing vanadium from hot metal has its significance on the subsequent process[1].The extraction of vanadium is greatly affected by the mineralogical composition of vanadium slag[2], the distribution of the elements between the spinel and silicate phases and its physic-chemical properties. These characteristics of vanadium slag have been studied in some details. It has been reported that Si mainly exists mainly in the form of silicate which wraps the spinel crystals while small amount of Si stands as phosphorus quartz or diopside[2]. Chen et al.[3, 4] points out, when SiO2 content in vanadium slag increased every 1%, V2O5 decreased 1.48%. Moreover, silicate phases would embarrass the oxidation of V-containing spinels through decreasing the exposing probability[5]. Meanwhile, melting point and viscosity of vanadium slag has been greatly influenced by the SiO2 content. Therefore, this work attempts to analyze the above-mentioned questions systematically."

Jan 1, 2012

By Minna Rämä

Iron containing leach residues like jarosite and goethite from electrolytic zinc production contain many valuable metals and harmful substances. These metals and substances should be removed in order to obtain an acceptable, stable and reusable product, and maximize economic feasibility as well as minimize environmental footprint. In this work, the processing of jarosite leach residue was studied in laboratory scale experiments under oxidizing and reducing conditions at high temperatures. First, the pretreated material was melted and oxidized to produce a melt of metal oxides. Second, the oxide melt was reduced in CO–CO2 atmosphere. Target after the reduction step was to obtain a clean slag and a liquid metal or speiss phase that collects the valuable metals, such as silver. The kinetics of the thermal processing were studied for determining optimal times and conditions for the aforementioned process steps. The preliminary results show that the process is thermodynamically feasible, and the desired phases can be obtained in the experimental conditions investigated.

By C. Coetzee

Additives are commonly used in copper electrowinning to improve cathode morphology. Polysaccharides such as guar are generally favoured as additives due to their compatibility with solvent extraction. Polyacrylamides are, however, being considered as possible alternatives. Understanding the influence of the structural chemistry of additives on electrowinning performance is critical to utilise them efficiently. This paper investigated polyacrylamide additives which are structurally different; their effects on copper electrodeposition were characterized and compared to that of guar. Electrochemical impedance spectroscopy (EIS) were used to characterize the effects of molecular weight and ionic charge of the polyacrylamides on electrodeposition. The findings were compared against results obtained with an industrially used guar product. Equivalent circuit modelling of EIS data indicated that an increase in polyacrylamide concentration and a decrease in additive molecular weight increased the overall system resistance.

By Rina Kim

There are many factors which affect the gold cyanidation mechanism— mineral composition, free cyanide and dissolved oxygen (DO) concentrations, heavy metal additions, etc. This study combines electrochemistry and surface analysis methods to examine the effectiveness of the above factors on gold cyanidation process. Three gold ore samples were used in this study. Sample 1 was a pyrite concentrate, contained mercury and silver. Sample 2 also contained sulfide minerals, including galena. Sample 3 contained pyrite with sphalerite and galena. In the case of samples 1 and 2, the presence of heavy metals enhanced gold cyanidation kinetics, though the addition of higher DO was not effective on improving the kinetics. Sample 3 showed an opposite behavior: the kinetics was not enhanced by galena, because of its relatively small amount, however, the use of higher DO made improvement in the gold leaching kinetics, likely caused by iron species generated by pyrite oxidation.

By Thomas E. P. Wechsler

The limiting factor for most pyro-metallurgical processes in secondary cop- per melting is the time required to heat and melt the product. American Combustion's proprietary PYRETRON variable £uel/air/oxygen combustion system improves the throughput of existing scrap melting and heating furnaces for copper and copper alloy production by increasing the rate of heat transfer from the flame to the product. The increased productivity and energy savings obtained from this technology can result in sizable reductions in operating costs for smelting operations.

Jan 1, 1991

By A. Shemi

Tungsten carbide scrap (WC–Co) is material generated from the tungsten carbide manufacturing process and worn out or used carbide parts from industry. Tungsten (W) ores contain about 3 wt% WO3 and their W concentrates about 10– 75 wt% WO3. Tungsten carbide scrap typically contains 40–95 wt% W. The high intrinsic value of W and the fact that the least valuable scrap contains more W than the average tungsten ore makes tungsten carbide scrap a worthy material for re-use. This study has investigated the selective dissolution of the cobalt (Co) binder phase, and recovery of tungsten monocarbide (WC) and Co using an acid leach process. The Co component was selectively leached leaving the WC solid particles intact. Further investigation using a complexing agent-aided acid leach process that takes advantage of organic chelating agents that form a soluble tungsten complex in place of the passive insoluble tungsten oxide is envisaged. The optimal dissolution of the Co binder phase using an inorganic acid in conjunction with an organic complexing agent is a novel approach with the potential of reduced leaching times and possibility of regenerating the unreacted organic acid.

By W. G. Davenport

A flash furnace can be run many different ways. It can, for example, be operated with: (a) highly 02"enriched, ambient temperature blast and no fossil fuel (b) considerable fossil fuel and hot, slightly Or enriched blast. It can also produce different grades of matte. With all these possibilities, the flash furnace operator can benefit from any technique that will indicate the 'best' way to operate his furnace. One such technique is Excel's 'Solver'optimizationroutine#. This chapter shows how our matrices and Excers optimization.abllity can be used to optimize a flash furnace operation. The chapter sets three optimization goals: (a) minimum industrial oxygen + oil cost, $ per tonne of concentrate (b) maximum smelting rate, tonnes of concentrate per hour (c) maximum profit, $ per hour.

Jan 1, 2001

By S. N. Monteiro, C. M. F. Vieira, A. P. N. M. de Sa, J. P. D. Vitorino

"This work has as its objective to characterize an ash waste and to evaluate its incorporation into a clay to produce bricks and roofing tiles. The waste is a type of fly-ash resulting from the incineration of a selected part of urban garbage, which is basically constituted of organic matter and plastics. The waste was submitted to mineralogical and chemical characterization. Compositions were prepared with incorporation of the waste in amounts of up to 20wt.% into athe clay. Rectangular specimens were prepared by extrusion and fired in a laboratory furnace at 900°C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The results showed that the waste is predominantly composed of quartz and calcium compounds. The incorporation of the ash was deleterious to the evaluated properties of the clay. It is suggested that the incorporation should be made in amounts below 5wt. % to avoid deleterious effect in the mechanical strength and water absorption of the clayey ceramic.IntroductionThe world attention has turned to a subject of great concern today, the production and disposal of large amounts of industrial wastes as well as wastes of various sources. When deposed in an unsuitable place, these wastes can cause considerable harm to human health and to the environment. Our planet suffers with air pollution, groundwater and soil contamination as well as silting of rivers and lakes with the growing amounts of our society wastes.The recycling of waste materials is of great interest to the industries, mainly due to the environmental agencies legislation. One of the practices for correct disposal of these wastes being investigated is to incorporate into red ceramics, such as bricks and roofing tiles. The natural variability of the characteristics of the clays associated with the relatively simple processing techniques and also the low performance required for the products allow the presence of relatively high levels of impurities in clayey ceramics."

Jan 1, 2011

By Aureo D. V. Machado

An experimental study to obtain zirconia powders (ZrOz) from carboxylate zirconium solutions followed by hydrogen peroxide stripping and precipitation, has been carried out. Zirconium carboxylate was prepared by solvent extraction from a chloride aqueous phase using magnesium carboxylate as organic phase. The variables examined in the precipitation reaction were: Temperature: 25 - 90 ?C ? H202= concentration: 0.3 - 5% wt/wt - pH: 1 ? 9 Organic/Aqueous ratio (1/1) and reaction time (30 minutes) were maintained at constant levels. The optimum results (98% precipitation) were achieved at 25 °C, 5 % wt/wt H202=, and pH = 5. The precipitates were composed of large amorphous aggregates (<I00 micrometers). After calcination for 1 hour at 1000 OC, monoclinic ZrO2 with a large variation in particle size (1 -100 micrometers) was obtained.

Jan 1, 1991