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By D. Papazoglou

This work was undertaken to investigate the thermodynamic and kinetic feasibility of using hot sulfur dioxide bearing gases from smelting processes to selectively sulfate the nickel in nickel laterite ores for subsequent extraction in water. The environmental benefits ofthis approach, as opposed to releasing the gas to the atmosphere, and the economic benefit of directly utilizing the S02 rather than converting it to sulfuric acid are strong drivers for such a process. A thermodynamic analysis indicated that selective sulfation of the nickel could be feasible under appropriate conditions and these were explored through a series of laboratory scale experiments. Laterite samples were reacted at temperatures between 500 and 800°C with an equilibrated mixture of sulfur dioxide, oxygen and nitrogen in a fixed bed reactor. Tests were conducted on saprolitic ore from Bulong, Western Australia, limonitic ore from New Caledonia and garnieritic ore from Indonesia. Nickel extractions were highest from the limonite and relatively low from the other ores. The maximum selective extraction of nickel from the limonite in a single stage sulfation was 73%. Sulfation of other elements present in the laterites was also examined. A two-stage process was also identified which involved sulfation using a strong sulfation potential followed by weaker sulfation potential to attempt to convert ferric sulfate formed in the first stage to ferric oxide. This increased the extraction for the limonite ore to around 84% Ni, 95% Co and 2% Fe. Direct sulfation of laterite could be feasible in locations where sulfide smelting or roasting operations are relatively close to laterite deposits.

Jan 1, 2003

By K. A. Brunk

Newmont's research, operations, history and experience with pre-treatment of preg-robbing carbonaceous ores are described, with emphasis on the chemistry, physics and kinetics of chlorine treatment. Present operations, control strategy and projected changes are also described, including a summary of the adsorption of chlorine into pulps and off-gas scrubbing. Conditions of chlorination have been optimized by the use of Eh-pH diagrams of the gold-chlorine-water system, and have resulted in significant increases in gold recoveries and decreases in chlorine consumptions.

Jan 1, 1987

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off-gases from the copper and nickel flash smelting furnaces and converters in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are pre¬sented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By Wantae Kim, Jaechun Lee, Tatsuya Oki, Sungbaek Cho, Sangbae Kim

"Effect of attrition scrubbing on the recovery of platinum group metals(PGMs) from automotive catalytic converter was discussed. The attrition scrubbing as comminution and separation process was effective for the recovery of the catalyst layer, ?-alumina, from ceramic supporting matrix, cordierite, by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles less than 45µm by attrition scrubbing. The production of fine fraction less than 45µm increased as the residence time for attrition scrubbing increased. The fine fraction obtained at the residence time of 40min contained 19.25% CeO2, 1.93% ZrO2 and 418.8ppp PGMs. The recovery of ?-alumina in the fine fraction increased as the residence time increased. Simultaneously, the recoveries of CeO2, ZrO2 and PGMs increased and reached up to 82.9% CeO2, 78.7% ZrO2 and 78.9% PGMs at the attrition scrubbing time of 40min. The production of the fine fraction and recovery of ?- alumina increased when the solid concentration and initial feed size increased.IntroductionThe automobile catalytic converters contain appreciable amount of PGMs. Currently several million tons of used catalytic converters are disposed annually worldwide, each containing about 0.5-1g of platinum and 1-2g of all PGMs1). The recovery technologies of PGMs from spent catalytic converters have been thoroughly reviewed by numerous researchers since last decades. Two types of methods, wet and dry processes, have been commercially operated. In the wet process, the PGMs on the spent catalytic converters were dissolved mostly in the form of chlorocomplex, MCl6 2-, by contacting with aqueous solutions. Subsequently the resulting solutions are treated to concentrate and the precious metal ions are reduced by introducing metals such as Al, Fe and Zn in the concentrated system2). In the dry process, the spent catalytic converters are melted, in some case with CaO, at an elevated temperature to produce a low viscous slag. The PGMs in the melt are separated by allowing them to adsorb on Fe or Cu having high specific gravity7). Although highly pure precious metals could be obtainable, the recovery technologies of PGMs currently operated seem not to be cost-effective since PGMs embedded in these types of catalytic converters are present in very small quantities."

Jan 1, 2008

By L. A. Neumeier

The Bureau of Mines, U.S. Department of the Interior, is investigating the feasibility of partitioning complex sulfide minerals to simpler sulfide .phases by sulfldation reactions. Such partitioning can afford opportunity to improve selective extraction of mineral constituents of value. This report describes initial research involving sulfidation partitioning of chalcopyrite concentrates. Small chalcopyrite samples were sulfidized with elemental sulfur in glass capsules sealed after evacuating and backfilling with helium, by heating for 1 to 24 h at specific temperatures in the range of 250° to 500° C. which extends from below to above the boiling point of sulfur (-445° C). Above the boiling point of sulfur, the overall reaction with adequate sulfur (13.9 wt pct of CuFeS2) is 5CuFeS2 + 4S g ? Cu5FeS6 + 4FeS2.

Jan 1, 1989

By Thomas Buenger

The Hamburg smelter of Norddeutsche Affinerie AG is situated near the city of Hamburg’s downtown and is therefore particularly subjected to fulfill environmental requirements according to the German legal regulations. Thus, investments related to increasing concentrate throughput are always linked to packages to enhance the emission status of the smelter. This connection between environmental protection and productivity enhancement should be explained by the example of the Peirce-Smith converter plant of the Hamburg smelter. Such outstanding investments can be demonstrated by the transition from scrap charging via boat from the front side to a fully automatic and completely sucked scrap charging system.

Jan 1, 2009

By U. Kammer

The reduction of the lead content in the separator fraction produced during the mechanical processing of spent lead-acid batteries is an important environmental and economical issues. The reduction of lead down to less than 1 percent is very difficult using hydroseparators that are common in battery recycling facilities. Very promising results were achieved performing experiments on a test rig using a new technology in battery treatment: a discharge-type jigging unit. The materials is fed onto the jigging bed and transported through the machine. Due to the intensive movement of the feed, an additional washing effect is also obtained in addition to separation of the lead and plastic fractions. The knowledge gained from this development work at UVR-FIA GmbH in Freiberg, Germany, led to a patent application. This paper focuses on the results of the development work and the start-up and one year's operation of the industrial-scale application at Harz-Metall GmbH in Goslar, Gennany.

Jan 1, 2000

By Stefan Mutl

By the term sorting one understands the separation of a material mixture into two or several products according to different material characteristics in the preparation technology. The oldest sorting procedure, the handpicking, is less and less used to separate different material mixtures because of the considerable personnel expenditure and the strict hygienic regulations at the workplaces in Europe. In general, the manual assortment is able to solve separation tasks, which could not be solved by machines so far. The picking is one of the most selective processing methods. However, the progress in the computer and sensor engineering today makes the creation of automatic picking devices possible, whose efficiency goes far beyond the possibilities of handpicking. Therefore in the future automatic picking will not only be applied to already common applications like the waste glass assortment by colour, but also to the assortment of complex composed material mixtures e.g. old shreddered cars. Thus, the automatic picking, supported by high performance computer systems and new sensor technology, gains more and more significance within many applications of waste processing. However, in order to apply automatic sorting procedures for different material streams within recycling processes, a substantial research and development need still is existing. The desire of the users is to sort more extensively in order to achieve products with bigger material varieties, In addition, the requirement of the accuracy of recognizing and sorting out of single grains rises, This lecture illustrates the procedure of the hand picking before it was employed in waste processing. Thus, a renaissance of a long forgotten method is happening in terms of today's state of the art procedure "automatic picking". Possible technologies, fields of application and future potentials of this technology are pointed out.

Jan 1, 2003

By C. S. Ek

Tests have been performed to recover silver and lead from residues produced after a super-hot leaching in a zinc hydrometallurgical plant operating with jarosite precipitation. When this residue is leached in ammoniaammonium sulfate or in diethylenetriamine solutions, lead dissolution is not complete and its recovery from the aqueous solutions is either difficult, due to the operating conditions, either expensive due to the amount of added reagents. In both cases, silver is partly dissolved, partly left in a new residue still containing lead and baryum sulfates. The best treatment seems to include a selective flotation producing first a silver concentrate assaying about I % Ag, then a 50 % lead concentrate collecting the baryum salts, and a final quartz-gypsum tailing. Metal recoveries can reach 50 % and 80 %, respectively.

Jan 1, 1989

By KAGAN BENZESIK, Onuralp Yücel, Mehmet Bugdaycı, Ahmet Turan

ZrB2 and B4C are one of the most significant advanced ceramics. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, Carbon black, B2O3 were used as starting material to produce ZrB2-B4C powders by SHS. Also Mg powder was used as the reductant. The reaction mixtures (approximately 100 g) were mixed thoroughly 15 minutes in a turbula mixer and charged into Cu crucible and compacted. W (tungsten) wire was placed at the top of copper crucible and the reaction realized by passing current through the wire. After initiation, a highly exothermic reaction became in a self-sustaining mode and propagated throughout the SHS mixture. The samples were characterized by using AAS and X-Ray Diffraction.

Jan 1, 2016

By Y. Maeda

Non-ferrous smelting furnaces generally install a gas cooling system for treatment of waste gas containing SO2,. From the point of view of corrosion resistance and recovery of waste heat, the high pressure boiler system is the best way to cool gas, however this system requires high initial investment and relatively higher operating costs. Because the feasibility of this boiler system greatly depends on the smelting process and scale, other lower temperature systems, e.g. water-cooled jacket system, are more suitable if the smelting process does not produce enough steam nor generate enough electricity to compensate operating cost. In additton, the water-cooled jacket system is simple in structure and easy to operate. For those reasons, it is applied widely. A new smelting furnace was planned in our factory and it was necessary to install waste gas cooling equipment. In our case, a water-cooled jacket system was more feasible because of the low gas volume and high dust content. It was also expected to operate without maintenance for ten years. On the other hand, some leakage problems with the water-cooled jacket had been experienced in the past. That is because SO2 In the waste gas changed into sulfuric acid which corroded the jacket material. As the first step, several data from actual' usage were reviewed to throw light on the corrosion process, and an appropriate procedure to determine the operating temperature of cooling water was obtained. For the basis of this study, a water-cooled jacket system was newly designed and tested for three months in a pilot plant. After this system's performance was confirmed, it was installed in a new furnace as a commercial plant. After one year of operation, the initial thickness of carbon steel jacket remains almost the same.

Jan 1, 1992

By D. W. Collins

Several organic and inorganic substances are widely used to control deposit structure and morphology during the electroprocessing of copper. Methods for monitoring the levels of thiourea, glue and guar gum during electrorefining and electrowinning have been successfully developed under the trade names of Reatrol and CollaMat. Other instrumental methods have been developed for additives and decomposition products associated with the electroplating of copper and other metals. Generally, these methods have been found to be either insufficiently sensitive or lacking in the desired selectivity for some or all of the additives. These procedures have mostly employed DC techniques; i.e., cyclic voltammetry, Tafel analysis, etc. In this work, chronopotentiometry (CP) and AC voltammetry were used to examine the interaction of glue, guar gum, thiourea and chloride during the electroplating of copper onto a platinum electrode. In addition, the interactions between the additives have been explored. It was found that glue in pure electrolyte (H2S04 and CuS04 only) had no effect on the chronopotentiogram. Glue was only active if chloride ions were present. The addition of thiourea resulted in several different chronopotentiograms depending on the presence of either chloride or chloride and glue. Thiourea used in conjunction with glue and chloride showed a significant increase in the polarization during copper deposition when compared to the electrolyte containing only glue and chloride. The use of a modified channel electrode further increased the sensitivity of CP. The use of AC voltammetry was explored as a technique to monitor some of the additives. AC voltammograms have more spectral detail then their DC counterparts and it is possible to monitor some of the additives at very low concentrations with AC techniques.

Jan 1, 1999

By M. Vijayalakshmi, S. Saroja, C. Sudha, T. N. Prasanthi

"Ti-5Ta-2Nb alloy and 304L austenitic stainless steel were joined by explosive cladding process. Investigations on 'as received' explosive clad revealed high hardness very near the interface due to martensitic transformation of 304L steel base plate. To improve ductility, explosive clads were heat treated in the temperature range of 823 to 1073 K for 1 to 20 h. Consequent change in the microstructure and microchemistry of the clad interface was studied. No change in the interface microstructure was observed for heat treatment at 823 K. Increase in temperature lead to the formation of various reaction zones at the interface, their number and width increase with temperature and time of thermal exposure. Growth kinetics of the reaction zones was monitored and activation energy required for formation was calculated. From elemental redistribution profiles, effective inter-diffusivities of alloying elements were calculated as a function of concentration and activation energy required for inter-diffusion was evaluated.IntroductionFor engineering components exposed to highly oxidizing and corrosive environments, a titanium based alloy i.e Ti-5Ta-2Nb (Ti-Ta-Nb) is often chosen as a structural material [1,2]. For economic consideration, vessels and piping exposed to non-oxidizing conditions are fabricated from 304L austenitic stainless steel (304L SS). Hence, dissimilar joint of Ti-5Ta-2Nb alloy and austenitic stainless steel becomes unavoidable. Fusion welding processes are not suitable for joining Ti and Fe based alloys due to the propensity for the formation of intermetallic phases and subsequent reduction in the bond strength [3,4]. Hence, explosive cladding, a solid state welding technique, was used to achieve high integrity, corrosion resistant joints between the two alloys."

Jan 1, 2012

By A. Pagliero

The coulombimetric reduction method has been used as an evaluation technique for Pb-Ca-Sn anode corrosion in the LIX-SX-EW process. The proposed methodology involves three consecutive steps, i.e., cleaning, oxidation and reduction. They are carried out in the same experimental unit, in solutions containing 180 g/L H2S04 with and without the addition of cobalt. The authors have worked in a wide range of oxidation current densities, from 150 to 500 A/m2 for in a period from 0.5 to 120 hours. It can be concluded from the results that there would be a linear relationship between the applied electrical charge I*T (Coulomb) and the anode corrosion expressed as transformed Pb mass (mg), for solutions with or without the addition of cobalt. The exception is that for the last one the corrosion rate is 5 times faster, which was observed for every layer. From the evaluation of different corrosion layers, one can point out that its composition is mainly in the form of sulphate. In the presence of cobalt, about 67% of Pb would be as sulphate (PbSO4), about 27% as a basic oxide (PbO) and only 6% as oxide PbO2 on the surface. From this result, it appears that great transformations occurred in the metal/sulphate interface. Without the addition of cobalt, the proportion of oxide Pb02 on the surface increased up to 11.5%. According to the previous statement and considering that Pb was found mainly as sulphate, the authors recommend its determination be used as quality selection criterion. Its evaluation should be performed in the acid solutions with 200 ppm cobalt addition at an oxidation current density of 300 A/m2 for a period of 24 hours.

Jan 1, 1999

By Erwin Flender, Preben N. Hansen, Peter R. Sahm

"Until now FDM-Techniques have been widely used for Modeling Solidification Processes in Castings. Often a rigid, regular type of enmeshment (cubes, , --) have been used. This has the advantage of low CPU-costs, but the disadvantage of a zig-zag presentation of the interface between the casting and the mold. The last point is the reason why FEM-Techniques, giving the possibility of a true presentation of the shape in the enmeshment, are increasingly used. The disadvantage is the high CPU-costs. In this paper, a technique is presented, which uses the FDM-Mesh with the zig-zag presentation of shape and ADI-Algorithms to calculate temperatures and gradients. The new idea is that the calculated parameters are not presented related to the mesh in which they are calculated, but displayed using the true shape of the casting. Such an advantage of both low CPU-costs and shape correct presentation of the calculated results are achieved. IntroductionThe main reason for using a regular type of enmeshment is that it gives the possibility, via ADI-Algorithms, of obtaining a very fast FDM-Technique. The technique presented by P.R. Sahm and P. N. Hansen (1984), and also used by E. Flender (1985), is numerically so stable that average time steps, at least 200 times larger than the limit given by the explicit FDM-Technique, can be applied. To obtain reasonably good results, average time steps in the range of 20 to 50 times the explicit limit seems to be applicable. It should be pointed out,however, that FDM-Techniques can be used on arbitrary nets, the disadvantages being the same as for the FEM-Techniques. This has, among others, been discussed by P.R. Sahm and P.N. Hansen (1984)."

Jan 1, 1986

By Jan G. H. du Preez, C. Viviers, B. J. A. M. van Brecht, H. E. Rohwer, Nicole M. Sumter

"At the basis of metal ion separation lies some particularly metal ion specific chemical property which lends itself towards exploitation. This could be in the form of an anionic complex or a neutral chelate complex. In the former a cationic centre with a particularly high affinity for the complex will have to be designed. In the latter case a stereospecific chelate ligand containing the correct symmetry and type of donor atoms will have to be designed. In both above cases the ""active centre"" can be entered in a from that it can function in different media of hydrophobicity, eg a precipitant, a resin or a solvent extractant. Recent results obtained in this laboratory will be used to illustrate how the above variables can be exploited to develop improved processes for the separation of base metal and platinum group metals.IntroductionThe separation of metal ions in hydrometallurgy can be performed broadly speaking with two major aims. Firstly the separation/removal of a certain group of metal ions, either as a means of preconcentration or as a removal from effluent as part of a purification process and, secondly the removal of a specific metal ion from an industrial stream in order to produce a specific metal in a pure form. This latter operation is by far the most difficult of the two and is becoming more so in the light of the fact that the world is moving in the direction of lower grade ores and increasing pollution. Such a process can be divided into three essential parts, firstly the molecular one in which an active centre is required to obtain specificity, secondly a matrix within which this active centre must function, i.e. as part of a resin or solvent extractant and thirdly the design of the total system to optimize the realization of the operation."

Jan 1, 1996

By C. M. Acuna

Scarcity of high grade copper low impurity content ores is a reality and processing of low grade dirty concentrates is a need. In spite of this fact, innovative strategies have to be looked at to comply with day to day more stringent environmental regulations. From this perspective the production of matte grades over 70% in copper presents several merits, but it must be contrasted with the fractional distribution of impurities reporting to the condensed phases. Converting of white metal high in arsenic content results in moderate fraction of arsenic to gas, but high deportment to blister. Therefore, production of anode copper, as required by the electrolytic refinery, may result in several operational difficulties. Furthermore, by recycling the flue dust and slag produced in the smelting-fire refining cycle, the arsenic content in the feed to smelting increases and so does in the resulting anode copper. The Teniente Converter, as a smelting unity, has probed suitable for production of high matte grade near white metal composition but regarding distribution behaviour of impurities there is lack of reliable data, specially when processing concentrates over 1% in arsenic content. In the new scenario, i.e. low grade copper high arsenic content concentrates, to fully asses the merits of this technology the effect of matte grade, secondary materials recycling and arsenic in feed upon the distribution coefficient of arsenic between slag and matte, mainly, must be evaluated both from a theoretical approach and by use of industrial data. Based on available data correlations of distribution coefficient, matte grade and matte/slag ratios with arsenic in feed and copper content in slag are worked out. Based on these results suggestions as to matte grades facilitating to deal more efficiently with the handling of smelting byproducts are proposed.

Jan 1, 2006

By Mary Cunningham

The EPA and DOE have collaborated on a series of studies to evaluate the effectiveness of treatment technologies at stabilizing bulk elemental mercury and wastes containing high concentrations (i.e., with greater than 260 mglkg total mercury) and multiple forms of mercury. The data from these treatment demonstrations are intended to help EPA to determine if regulatory revisions to allow a stabilization alternative for high-mercury subcategory wastes are warranted. In addition to mercury-contaminated wastes, the disposal of bulk elemental mercury is of concern because of the excess quantity of mercury in the Defense Logistics Agency (DLA) stockpile, as well as other potential sources of excess elemental mercury. The studies evaluated the effectiveness of several technologies at: I) stabilization of mercury in a "hard-to-treat" matrix; and 2) conversion of elemental mercury into a stable waste form for disposal. A surrogate waste was designed for the study on high-mercury wastes, which included an organic form of mercury, elemental mercury, and several mercury salts in an inorganic matrix. The surrogate waste and the bulk elemental mercury were treated by the vendors, and the treated waste forms evaluated for mercury Icachability, using both the TCLP and an automated, constant-pH leaching protocol. Constant pH leaching was conducted at pH 2,4,6,8 10 and 12 for 14 days at each pH. The leaching data demonstrate that the stability of the mercury in three treated waste forms varies widely across the pH range tested. Clearly, the stability of mercury in these treated waste forms will be highly dependant on the disposal conditions. The combination of site-specific disposal conditions and appropriate treatment technology must be considered as decisions are made about disposal of high-mercury wastes.

Jan 1, 2003

By Murray Hughes, Neil Brown, John Carran

"A control system architecture has been developed using the Ward-Mellor structured analysis techniques for real-time applications. This approach has produced several advantages over traditional control system implementation methods including:•,partitioning of the control system into discrete control functions.•,easy identification of the interaction between individual control functions and the rest of the system including the impact of changes at the control system boundary (i.e. additional inputs or outputs).•,simplified control software testing.•,a closed loop design, implementation and documentation process.This paper describes a generic control application in which the process specification and control system design are logically linked. Both components are used by process engineers for on-going development.IntroductionAluminium is reduced from alumina in multiple electrochemical semi-batch reactors. Raw material additions and molten metal withdrawal are made at discrete intervals ranging from seconds to days. The electrolytic reduction process is continuous, despite the semi-batch nature of the material inputs and outputs. The chemical and physical processes that occur within each reactor are complex and interdependent, therefore simple methods used for the control of many chemical processes are impractical. The process control system is required to optimise operating efficiencies within the safe operating zone.The process control of aluminium reduction cells is heavily biased towards calculation of process variables with relatively few measured sensors. Each cell is controlled independently of the other cells, although changes to process conditions and raw material . quality will affect all cells. The process responds relatively slowly and with significant time lags. Measurements and process variable calculations occur each second, however the accuracy and precision of actuator response and sensor sampling are measured 111 milliseconds. Time-based scheduling is a significant component of reduction cell control."

Jan 1, 1994

By James C. Sever

Two green field magnesium reduction plants are under consideration using dolomite as the raw material. The Calix calciner was independently selected for both plants. The unique design of this calciner is detailed and the advantages defined for the specific application. The low carbon foot print of this unit combined with the ability to capture food grade carbon dioxide makes this an environmentally proactive approach to carboniferous ore calcination.

Jan 1, 2015