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By Rolf R. von Oppenfeld

Onsite hazardous waste processors often find obtaining a Treatment Storage and Disposal (TSD) permit one of their first major challenges. Some processors may spend the time and money required by the permitting process, only to find out later that a permit was not necessary. This paper will present and analyze four strategies that processors may use to avoid obtaining a TSD permit. Some facilities will be able to remove their waste streams from RCRA's oversight by ensuring the material is not "hazardous" waste. Parties that treat waste while it is in process may be able to avoid generating "waste" altogether. Certain treatment facilities have been specifically exempted by EPA. Finally, treatment of waste while it is in generator storage tanks may be allowed without a RCRA TSD permit. Hazardous waste point of generation, an important determination relating to these strategies, will also be discussed. Generators and processors will find this paper useful when evaluating their permit exemption potential

Jan 1, 1996

By Supachai Surapunt

The distribution behavior of V A minor elements (As, Sb and Bi) in the smelting stage of the Mitsubishi process were evaluated thermodynamically based on thermodynamic data and operating data. The fractional distributions between the gas, slag and matte phases considered as the degree of vapor saturation of 1.0 are as follows: 53.8, 27.2 and 19% for As, 23.6, 56.6 and 19.8% for Sb, and 91.3, 1.1 and 7.6% for Bi, respectively. Arsenic is mostly distributed to the gas and slag phases. It is effectively eliminated by volatilizing and slagging. Antimony is mainly in the slag phase, which is suitably removed by slagging. Bismuth is easily vaporized to gas phase. The degree of vapor saturation has a large effeet on the distribution behaviors of the three elements between the three phases. The amount of a minor element in the charge has an effect on the distribution of As but no effect on the distributions of Sb and Bi. Increasing matte grade and temperature results in the change of distributions for As and Sb, significantly. The change in the distribution ratio between slag and matte phases also considerably affects the distributions of As and Sb. The distribution behavior of Bi is not significantly changed by the change in matte grade, temperature and distribution ratio.

Jan 1, 2003

By M. H. Staia

A Venezuelan ilmenite concentrate has been chlorinated at a temperature of 700" C by carbon tetrachloride. In the experimental rig, built at laboratory level, the direct chlorination process yielded a TiCI, recovery of approximately 85% after 280 minutes processing. The partial pressure of carbon tetrachloride was nearly atmospheric (0.94 atm). Product vapors from the reactor were fractionally condensed in a condenser which was maintained at a temperature of 250°C meanwhile TiCl, vapors were condensed in refrigerated coils at a temperature of -20°C. The concentrate used in this investigation was obtained by applying gravitational and magnetic concentration methods to the black sands. The experimental results have shown the need to asses the influence of the weight ratio of ilmenite to carbon tetrachloride on the resultant products. The equilibrium of the heterogeneous system has been calculated taking into account the initial experimental conditions.

Jan 1, 1995

By Edwin de Jesús Deveaux

After 32 years of operations beneficiating lateritic nickel ore in a fully integrated pyrometallurgical complex, Falconbridge Dominicana (FALCONDO), situated at Bonao and La Vega Provinces, Dominican Republic, has become profitable with one of the lowest nickel grade content processing plants in the world, and literally without any by-product (granulated slag, will be utilized in the future as a post-processing subproduct). To December 2002, mineral reserves were 64.1 million tonnes containing laterite grading as low as 1.15 % Ni when full dilution is applied. At a cut-off grade of 1.20% Ni, the reserves will provide 15-20 years of production. The mineralized thickness over the seven active deposits averages 6 m. Development of very selective and unique mining practices, together with improvements in the process plant, are key to achieving the production goal (30 kt Ni/yr) and to meet the quality standards for the ferronickel produced. Keywords: Laterites, grade control, mining methods, environment

Jan 1, 2004

By Kurt A. M. Westerlund

The basic function of primary gas handling downstream non-ferrous pyro-metallurgical processes is cooling hot sticky gases to treatable temperature levels (e.g. entering ESP). That means managing efficient the critical gaseous components from a molten via a sticky to a solid phase. The article outlines the modem gas cooling methods combined with efficient heat recovery. Examples of the alternative use of recovered steam energy are outlined; as e.g. drying of concentrate and power generation. The heat transfer impact of the insulating dust is called fouling and circumstances causing fouling are described. Modem cooling surface design and cleaning techniques to keep fouling in reasonable limits are described. Leakage- and false air ingress into the gas handling lines often limits smelting capacity. The objective is generally to minimize the infiltration of air but it still takes place at open interfaces (e.g. at reactor hood, feed port). Leakage air at furnace roofs for example can be reduced to a minimum by adopting the pressure gas sealing used at present In-Bath-Lance furnaces. Modernization and optimization methods to de-bottleneck existing waste heat boiler gas cooling capacity by highly efficient surface cleaning systems and false air avoiding (e.g. bundle roof boxes, dust discharge) are detailed described.

Jan 1, 1999

By Andre L. De Vegt

Hydrogen sulfide is an expensive chemical used in nickel, zinc and copper mining and metallurgical operations for selective recovery and concentration of metals, from leach water streams, acid plant blow down streams, refinery electrolyte bleeds and precious metal, plant bleeds. Hydrogen sulfide is either produced on site by catalytic reduction of elemental sulfur or transported to the site as liquefied hydrogen sulfide (H2S) or as a sodium sulfide solution (NaHS) Biologically produced hydrogen sulfide has economically very interesting, application possibilities in the mining and metallurgical industry. Converting sulfates from waste streams into usable hydrogen sulfide by biological reduction results in operational cost savings in existing lime treatment systems. H2S can be produced biologically for less-than $500/ton S. For the past ten years Paques has been engaged in the development and installation of treatment systems based on biotechnological processes to remove sulfur compounds from water, air and gaseous streams. Paques has designed and installed a groundwater treatment system for the Budelco zinc refinery in the Netherlands to remove sulfate and heavy metals. The hydrogen sulfide produced is used for recovery of metals,, mainly zinc, from the ground water stream. The system has been operating since May 1992 treating a flow of 5000 m3/d. At Kennecott's Bingham Canyon Utah copper mine, a pilot plant started operation in November 1995 to develop the process for selective recovery of copper from leach water using biologically produced hydrogen sulfide from sulfate containing groundwater. Other pilot plants are operated at DOE's Pittsburgh Research Center and at Cominco Research focusing on selective recovery of metals.

Jan 1, 1998

By A. V. Tarasov

The proposed process is based on creating a controlled frothed layer of molten slag, in which fine particles of carbonaceous reductant and raw material to be processed are mixed with emulsified iron. Frothing of the slag layer without external blowing occurs as a result of intensive evolution of gaseous reduction products. The froth reaction process is maintained due to the heat of an electric arc in the slag layer. When the metal bath is heated by the arc to 1400- 1 500°C, the low temperature of the slag surface of about 1200-1 300°C is maintained due to low thermal conductivity of slag froth preventing heat loss. In order to maintain the required slag froth level and control the process temperature, air tuyeres are installed above the slag bath; blowing air serves also for oxidation of zinc in fumes and for its transportation. High adsorption and thermal insulating properties of slag froth ensure virtually complete elimination of dust and mist entrainment along with low heat losses. The main macrokinetic regularities of the carbon thermal reduction of zinc-containing slag melts have been studied under frothing conditions. The mechanism of formation of gas-slag emulsion has been identified under the conditions of reaction [C]+[O]=CO occurring locally at the slag-metal interface. It has been demonstrated that under the froth reduction conditions the zinc removal rate from the melt increases on the average by 3 to 5 times. Based on the physical and chemical data obtained, basic principles of the dezincing technology have been developed for different intermediate oxide iron-containing products produced in the process of ferrous and non-ferrous metals production.

Jan 1, 2002

By Richard D. Hagni

An enhanced Interest in pyrometallurgical dusts has recently emerged due to increased world-wide environmental concerns. Mineralogical study of dusts samples from lead sinter plants. lead smelters, and secondary steel mill electric arc furnaces has shown that they can be readily studied by reflected light microscopy. These dusts typically are composed of small particles sufficiently large that their mineralogical identification and characterization can be conducted under the reflecting light microscope. Scanning electron microscope-energy dispersive spectroscopic analysis (SEM-EDS) has been used to confirm optical identifications and chemical compositions. The sinter and blast furnace dusts at the Doe Run Smelter at Herculaneum, Missouri are commonly about 20-150 11m. They consist predominantly of galena, chalcopyrite, sinter. slag. coke. and particles. Dusts from remote sampling sites 112-1 mile from the lead smelter are composed of similar particles and abundant fine-grained particles, less than 10 um. of locally derived calcium-aluminum silicates. Electric arc furnace (EAF) dusts are mostly spherical and less than 10 11m. They consist predominantly of iron oxides (magnetite. franklinite. jacobsite and solid solutions of these spinels), zincite. and calcium-iron silicate glass, together with smaller amounts of hematite. sylvite. coke and metallic iron. Reflected light microscopy is rapid provides mineralogical data on individual grains within dust particles. and allows direct observations of textural intergrowths in pyrometallurgical dust particles.

Jan 1, 1991

By Hiromichi Ohta

Precise thermal properties of molten materials are essentially required for analyzing the metal production process. These properties are also important as a clue to consider the dynamic structure of liquid materials. However, it is difficult to obtain the precise thermal diffusivity values of molten oxides at high temperature because of the experimental uncertainties arising from the bubble formation or the severe separation of radiative and conductive heat components. Recently a novel laser flash method has also developed for measuring thermal diffusivity of molten oxides at high temperature. In this new technique, the sample is melted in a metal crucible and heated to the desired temperature. A single laser pulse is flashed on the bottom of the metal crucible and the infrared ray irradiated from the same bottom surface is measured for obtaining the temperature decay, from which the thermal diffusivity of the liquid sample can be estimated. The usefulness and validity of this new laser flash technique have been confirmed by obtaining the thermal diffusivity values of silicate melts in the wide temperature range between 773 and 1673 K.

Jan 1, 2003

By Dae Jin Ha

Sticking phenomenon occurring during hot rolling of two STS 430JlL ferritic stainless steels was analyzed by hot-rolling simulation tests. The sticking started from the initial nucleation stage in which the rolled materials were stuck onto the roll specimen surface, proceeded to the growth stage in which stuck fragments grew further, and reached the saturation stage. The modified 430JlL steel had a smaller number of sticking nucleation sites and slower growth rate than the conventional 430JlL steel because of higher high temperature hardness, thereby leading to less serious sticking. When the simulation test was conducted at 1070 °c, Cr oxides were formed on the surface of the rolled materials, and thus the sticking was drastically reduced because of the increased surface hardness of the rolled materials. In order to prevent the sticking, high-temperature properties of the rolled materials should be enhanced when rolled at 900°C or 1000 °C, and rolling conditions and alloying compositions, under which the oxide formation was promoted, were more important than high-temperature properties when rolled at higher temperatures than 1000 oC.

Jan 1, 2008

By Xu Weimin

The existing copper electrorefining tankhouse of Jinchuan Nonferrous Metals Complex (JNC) was commissioned in 1986 for refining blister copper anodes. Blister copper is produced by reverberating chalcocite separated from converter high grade nickel-copper matter by means of flotation. Special chemical analysis of the anodes shows, a composition of 93.02 - 95.72 % copper, 3.0 - 4.96 % nickel and 0.5 - 1.23 % sulfur. The wide range of composition makes the electrorefining process fairly different from others throughout the world. The initial nickel content of 20 ppm and sulfur 40 ppm or more in copper cathodes are reduced to 8.5 ppm and 11 ppm respectively. Since 1986 the tankhouse has undergone significant evolutionary modifications and implementations to ameliorate cathodes quality desirably. The important fact is that the N-additive was utilized through many studies and pilot and field trials successfully. While our primary purpose is to improve chemical quality of the cathodes, tankhouse capacity is increased considerably and the process is perfected satisfactorily. The tankhouse is described with special emphasis on JINCHUAN PROCESS. The upgrading of our product by the utilization of the N-additive is highlighted. The other aspects of the tankhouse including spent electrolyte treatment and by product nickel sulfate manufacturing are briefed as well. Key words: JINCHUAN PROCESS, anode, cathode, electrolyte, electrorefining, N-additive.

Jan 1, 1993

By Jesse White, Tyler Salisbury

Research projects contain many stages of development from the conception of an idea to a fullscale commercial operation. The transition from laboratory-scale research to bench-scale roasting can represent a significant increase in complexity and cost, depending on how many variables are being evaluated. Thermogravimetric analysis (TGA) can simulate roasting conditions and produce a small sample for chemical analysis or materials characterization. A simultaneous thermogravimetric and differential scanning calorimetry (TG–DSC) can identify endothermic and exothermic reaction temperatures. Using thermal analysis, some of the process variables can be tested and eliminated such as ore and reagent blends, retention times, operating temperatures, and some atmospheres.

Jan 1, 2015

By J. M. Khodadadi

"A computational study of the effect of thermocapillary convection on melting of a droplet under the influence of an incident uniform heat flux is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the time-dependent continuity, momentum and energy equations in the spherical coordinate system are solved. During the early periods of the melting process, conduction mode of heat transfer is dominant. As the thermocapillary convection is strengthened due to the growth of the melt zone, melting on the side of the droplet is observed to be much faster in comparison to the conduction-only case. Due to the skewedness of the temperature field, a new recirculating vortex is created which promotes melting within the droplet. The effects of the change in the sign of the surface-tension temperature coefficient on the melting pattern are also investigated.1. IntroductionMelting and solidification of materials are important processes which are encountered in nature and numerous industrial applications. Due to the recent upsurge of interest in such processes as spray casting, space radiators, rapid solidification, purification of materials, containerless processing, etc., there is a need to analyze the transport phenomena of melting and solidification in spherical configurations. Specifically, the effect of thermocapillary convection on the melting of metallic droplets has not been addressed at all. Only a few authors have studied the transport phenomena without phase change in spherical droplets. Oliver and DeWitt [l] worked out a series solution for the thermal and surface-tension-driven flow fields for a droplet experiencing an irradiant energy flux in the microgravity environment. Kudo et al. [2] solved the coupled momentum and energy equations numerically for the same problem without dropping the convective terms. Due to the nonexistence of any previous work on transport phenomena during the thermocapillary-assisted melting of metal droplets, this study was initiated to elucidate the features of the phenomenon."

Jan 1, 1999

By Kang-In Rhee

A series of processes to recover the gold from electronic scrap which contains initially about 200-600 ppm Au have been developed. First, mechanical beneficiation including shredding, crushing and screening was employed. Results showed that 99 percent of gold component leaves in the fraction of under 1 mm of crushed scrap and its concentration was enriched to about 800 ppm without incineration. The scrap was leached in 50% aqua regia solution and gold was dissolved completely at 60°C within 2 hours. Other valuable metals such as silver, copper, nickel and iron were also dissolved. This resulting solution was boiled to remove nitrous compounds in the leachate. Finally, a newly designed electrolyzer was tested to recover the gold metal. More than 99% of gold and silver were recovered within an hour in electrowinning process.

Jan 1, 1995

By Shigeatsu Nakazawa

Activities of Bi and In in the Bi-In liquid alloy were measured over the whole range of eomposition at the temperatures from 850K to 1050K. An alloy was vaeuum-sealed in a quartz cell and heated at the temperature of interest. The absorption for 307nm radiation from Bi lamp was measured for Bi atom vapor in the cell. By heating a pure metal as a standard and measuring the absorbance as a function of the temperature, an analytical curve for Bi atom vapor was constructed and used for conversion of the absorbance to the vapor density. Bi activity was determined as the ratio of the Bi atom vapor density over the alloy to that over a pure metal. The same procedure was applied to the In 304nm radiation from In lamp and In activity was determined independently of Bi. Results showed that the liquid Bi-In system behaves like a regular solution.

Jan 1, 2003

By A. Dadgar

Extraction of gold and silver from two refractory concentrates using cyanide and bromine reagents was reported at the 12th International Precious Metal Conference (1). The objective of this paper is to present the gold extraction, recovery, and economics for two refractory concentrates using cyanide and bromine reagents. Gold extractions for cyanide leaching (24- 48 hours) and bromine leaching (6 hours) were the same and ranged from 94% to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods, were better than 99.9%. A preliminary economic analysis indicates that chemical costs? for cyanidation and bromine process are $9.50 and $10.50, respectively per ton of calcine processed.

Jan 1, 1989

By K. Sarveswara Rao

The present paper firstly describes some recent trends from literature on energy management via process intensification to arrive at sustainable technologies for aqueous processing of minerals, metals and materials. Secondly, the energy saving measures practiced in leaching, solid-solution separation, solution purification, metal and material winning and environmental aspects have been discussed. The emerging importance of interdisciplinary nature of hydrometallurgy for practical applications is also highlighted. With the above background, the present paper describes an overview of energy conservation and autoclave processes with a special reference to hydrometallurgical research activities of our Laboratory.

Jan 1, 2008

By René Winand

Due to chemical and electrochemical behavior of the most common additives in copper electrorefining i.e. gelatine, thiourea and chloride ions, it is essential to simulate as far as possible true industrial practice while performing laboratory experiments. The three additives must be studied simultaneously, and added continuously to the electrorefining cell. Ratio electrolyte volume to cathode area; ratio bleed flow to cathode area; hydrodynamic conditions; residence time of electrolyte in the cell; current density; electrolyte and soluble anode must be as near as possible to industrial ones. Experiments performed in the author's laboratory show that under these conditions, reproducible results can be obtained at normal industrial current density and at high current density as well. Problems are however still encountered when developing a sensor for additives monitoring, due to electrolyte redox potential and to substrate influenced thin layer deposition.

Jan 1, 1995

By Hiromichi Ohla

Precise thermal properties of molten materials are essentially required for analyzing the metal production process. These properties are also important as a clue to consider the dynamic structure of liquid materials. However, it is difficult to obtain the precise thermal diffusivity values of molten oxides at high temperature because of the experimental uncertainties arising from the bubble formation or the severe separation of radiative and conductive heat components. Recently a novel laser flash method has also developed for measuring thernnal diffusivity of molten oxides at high temperature. In this new technique, the sample is melted in a metal crucible and heated to the desired temperature. A single laser pulse is flashed on the bottom of the metal crucible and the infrared ray irradiated from the same bottom surface is measured for obtaining the temperature decay, from which the thennal diffusivity of the liquid sample can be estimated. The usefulness and validity of this new laser flash technique have been confirmed by obtaining the thermal diffusivity values of silicate melts in the wide temperature range between 773 and 1673 K.

Jan 1, 2003

By Mostafa O. El-Bealy

"To estimate the interdendritic cracking tendency in casting processes, a new model for interdendritic cracking criteria has been proposed. The model combines a concept of the alloying element effect on the interdendritic strain generation and therefore on the susceptibility of interdendritic cracking phenomena. A susceptibility of interdendritic cracking is modeled by using El-Bealy's interdendritic cracking susceptibility function ""BJCSF' and the opening displacement between the dendrites ""EIA "". These concepts are modeled based on the previous experimental observations and ElBealy' approach. The model is implemented numerically for a one-dimensional model problem with some similarities to the casting of steel. The variation of some key parameters that are known to influence the frequency and severity of the interdendritic cracking is then studied.I. INTRODUCTIONInterdendritic cracking ""hot tearing"" commonly encountered in both ferrous and nonferrous castings (1,2]. It is generally believed that interdendritic cracks start to nucleate and develop in the interdendritic strain region within the mushy zone [l-5]. The interdendritic strain region is then definitely coherent, but continuous films of liquid still exit (4,5]. This distinguishes interdendritic cracks from cold cracks forming during the casting process after complete solidification (6,7].Much effort has been put into the understanding of the interdendritic cracking phenomena, and several theories have been proposed. Fellini [8] stated that interdendritic crack ""hot tear"" will result if the material is subjected to too high of accumulated strain within so called vulnerable part of the solidification interval. Kinosita et. al. [9] and Campbell (10] also emphasized the role of tensile stresses in the forming of interdendritic cracks. Most interdendritic cracks criteria simply consider the size of solidification interval, stating that solidification range is associated with a lager interdendritic cracking susceptibility than a short range. Clyne and Davies (11] formulated a more refined such criteria based upon the time spent in different regimes of the solidification interval. They defined a vulnerable region in which thin continuous films of interdendritic liquid exist, and the permeability is low. When thermal strains are induced in this region, the film is not able to sustain the stresses, and an interdendritic crack will form."

Jan 1, 2001