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By Hidenori Okamoto, Katuto Itoh

"Nippon Mining & Metals' Hitachi Refinery refines 40% of the anodes produced at its Saganoseki Smelter & Refinery. Its current annual production stands at 180,000tons.The refinery always endeavors to increase productivity. One of the outcomes of its efforts is an originally developed automatic short-circuit detector used to inspect short-circuits between anode and cathode. The detector is designed to inspect the 56 pairs of anode and cathode in a cell by fluxgate sensors at once. It inspects 564 cells, automatically and un-manned, and gathers data to be put into a computer. The development of the detector led to a reduction of man-power and achieved a detection accuracy superior to that of a hand-held gauss-meter. In addition, statistical and historical processing of the data enabled early detection and early recovery of the cells with poor efficiency.The new system also contributed to raising the refining capacity and reducing the unit steam consumption, because it is possible to inspect even the cells covered with thermal insulation sheets.IntroductionInspection of cells is an important component of the operation management of a tank-house. At the Hitachi Plant, it used to be carried out by two workers who walked on and checked all the cells of its tank-house once a day to find out any short-circuits in the cells, using hand-held gauss-meters. They inspected about 33 thousand pairs of cathodes and anodes a day and removed nodules by hammers. This method had following problems:it needed much manpower.the walk on the cells sometimes deranged electrodes positions.there was radiation-loss connected with the inspection due tothe fact that the workers were obliged to uncover thermal insulation sheets on the cells while inspecting."

Jan 1, 2000

By Andrew Campbell, Michael Reed

"WorleyParsons has used Discrete Event Simulation methods in conjunction with more traditional process models to assess the performance of copper smelting operations. This work was performed to determine the plant capacities and suitability of proposed debottlenecking options including accounting for the planned and unplanned (breakdowns) shutdowns in the various parts of the plant and supply chain. This paper outlines the methods used along with demonstrating the benefits of selecting a feasible option and minimizing capital and operating costs.IntroductionTraditionally for de bottlenecking studies of smelters and other process plants, a mass balance is performed based on continuous operating rates and expected operating hours. Smelters have several points of failure that will restrict, if not take the entire plant offline. By using a more detailed model, validated against plant experience, bottlenecks can be demonstrated and strategies to remove them to increase plant availability and economic.The modeling simulates the plant performance in real time, and by performing enough simulation the expected long run performance of the plant can be estimated. The models have been built using ExtendSim which is a powerful Discrete Event Simulation software package that is ideally suited to the batch and semi-batch processes and events that occur within smelter operating environments. The value of performing this work is that the operational performance of the plant can be assessed ensuring production targets are met, without using excessive capital outlay."

Jan 1, 2013

By Peter A. Spencer

Bacterial oxidation technology has the ability to selectively attack sulphide minerals. Selectivity allows oxidation of more reactive minerals and the extraction of valuable metals while leaving the bulk of the sulphide component unreacted. Partial oxidation can be used on arsenopyrite to recover gold and for the leaching of base metals, such as copper and nickel, from pyritic ore and concentrate without generation of large quantities of acidic iron solution, which must be neutralized. Thus, rejection of pyrite during the oxidation process can considerably reduce treatment costs. Acid generation in tailings dams would be minimal, compared with most Thiobacillus cultures, as the optimum growth temperature of Bactechts culture is above ambient.

Jan 1, 1992

By Munetaka Iwasaki

Nitrogen strongly affects mechanical properties of steel and therefore we may sometimes modify the various processes for its content. Numerous studies based on the results of chemical analysis of quenched samples were reported with a few exceptions of Hot Sievert method. The technique always poses a risk of uncertainty whether the true content of nitrogen in liquid metal is measured or not. In this study vacuum remelting under relatively low pressure was done to enhance gas phase mass transfer. Total pressure of the melt chamber was about 10-3 pa and electron beam heating was used. Mass spectroscopy was used for the direct observation of the rate of denitrization. Nitrogen molecules or atoms were detected by a mass spectrometer set above the melt. Continuous monitoring of the intensity of the fixed mass number may reflect the transfer of nitrogen from the melt to the vacuum. The results of the new and conventional techniques agree, both technique can be verified.

Jan 1, 1999

Environmental and public concerns and the banned use of cyanide for the recovery of gold in some parts of the world have heightened the search for an alternative lixiviant to cyanide. Thiosulfate appears to be the most promising alternative to cyanide due to thiosulfate being non-toxic, relatively cheap compared to cyanide and generally gold recoveries are similar to those of cyanide. The most widely researched thiosulfate process is one where copper ions and ammonia are added to the solution. This paper reviews the leaching of gold in thiosulfate solutions and the contributions of the research at Monash University to the understanding of the gold oxidation reaction in thiosulfate solutions, the solution chemistry when copper ions, ammonia and oxygen are present, the influence of the changing solution chemistry on the gold leach kinetics, and the application of thiosulfate in the leaching of gold from ores. It is clearly shown that the gold oxidation rate is hindered in thiosulfate solutions. In the presence of copper ions the gold oxidation rate though is significantly enhanced and thus is why copper(II) is more effective than other oxidants in the thiosulfate leach system. The copper-ammonia-thiosulfate leach solution chemistry is shown to be very complex, especially in the presence of oxygen as the rate of thiosulfate oxidation increases and the majority of the copper ions are not maintained in the copper(II) oxidation state. The thiosulfate oxidation rate must also be maintained low as an intermediate thiosulfate oxidation product hinders gold leaching. In optimising the recovery of gold from ores with copper-ammonia-thiosulfate leach solutions it is important to evaluate and minimise any negative effect an ore may have on the leach solution chemistry and hence gold leaching.

Jan 1, 2003

By Andreas Dietrich

Laser off-gas measurement of CO, O2 and temperature has been carried online in EAFs. A visualization screen shows the values of CO and Oxygen and temperature for the entire heat, and includes the status of furnace equipment. The historical data of the heats are stored such that the furnace performance can be evaluated and optimized. A short comparison between laser based and conventional systems has been carried out related to speed, influence of dust, water, pressure, protection for bag house explosions. A high water and/or dust content in the sample does not represent a problem for this type of system. The measurement method works without interruption even under worst conditions such as dirty scrap, carbon injection etc. The installation was developed in conjunction with Marienhuette, Graz. They are 100% scrap based with a tap to tap time of ca. 46 min. Keywords: Laser Measurement, Off Gas, CO, O2, Temperature

Jan 1, 2003

By C. M. Iheagwara

This paper has addressed the issues that constitute major obstacles to the cost- effective and efficient operation of metallurgical vessels from the refractory standpoint. Refractories generally withstand severe conditions of high temperature reactions as well as physical loading/impingement and hence degenerate and need replacement. Scarcity of some refractory materials especially high alumina and magnesite ores in some places, the prohibitive cost and the frequency of replacement of damaged refractories threaten the continued support for metallurgical operations. Some of the causes, prevention and cure for refractory wear have been discussed and rational strategies (short and long term) have been recommended which if implemented should go a long way towards arresting the perennial problems they portend.

Jan 1, 1991

By Anestis Vlyssides, Elli Maria Barampouti, Sofia Mai, ?postolos Vlyssides

"A new anaerobic reactor variation, the UASB/CO2-stripper reactor was conceived. It consisted of a conventional UASB reactor that recirculated the biogas produced. The sludge characteristics of this system were examined when treating high strength wastewater. From the data collected, it was obvious that the UASB/CO2-stripper system can satisfactorily operate at higher loading rates (25 g COD·L-1·d-1). A pronounced effect on the quality of the granular sludge was observed. The VSS/TSS ratio decreased sharply. A considerable decrease in the mean granule diameter was observed, while the specific gravity of the granules increased. The sludge bed porosity increased significantly leading to a considerable expansion of the sludge bed. These changes in the sludge properties led to a gradual shift of the system towards a fluidized bed process as far as its hydraulic characteristics were concerned.IntroductionIn recent years energy considerations and environmental concerns have increased the interest in direct anaerobic treatment of industrial wastes. The anaerobic method of waste treatment offers, under the present circumstances, a number of significant advantages with trivial or more serious drawbacks over other treatment methods. The major obstacle to the application of the process for this specific purpose is perhaps the difficulty of extending it to a stable and simple operational form. A number of reactor configurations has been developed leading to high biomass concentrations, e.g. the contact process, the filter reactor, the UASB reactor, and the fluidized bed systems, but the process stability problem still remains [1].A prime objective in the operation of anaerobic waste treatment process is the maintenance of a proper pH range. Thus, a possible solution to the process stability problem could be obtained by increasing alkalinity in the anaerobic systems. Therefore, the main objective of this paper is to present and evaluate the results of a system (UASB/ CO2-stripper) with increased alkalinity concentrations."

Jan 1, 2008

By Djalma Souza, Rubén Sánchez, Regina Maria Pinheiro, Carlos Maurício Fontes Vieira, Sergio Neves Monteiro

"This work has for objectives to characterize a waste generated in the form of sludge during the treatment of the effluent of a paper making industry and to evaluate the effect of its incorporation up to 10 wt.% on the properties of a clayey body used for brick production. For the characterization of the waste the following techniques were used: X-ray diffraction, X-ray fluorescence, differential thermal analysis and termogravimetric analysis with mass spectrometry. Specimens were prepared by uniaxial pressing at 20 MPa before firing at 750 °C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The results showed that, in agreement with the characteristics of the waste, its recycling into red ceramic can contribute to decrease the consumption of fuel during the firing stage. However, the waste changes the physical and mechanical properties, generating a deleterious effect on the water absorption and flexural rupture strength of the ceramic.IntroductionAccording to the Brazilian Association of Pulp and Paper, in the last 10 years, the global production of paper grew 35%. Brazil produced 8,2 million tons of paper in 2004 and held the position of the seventh largest world manufacturer of pulp, with about 9,4 million tons per year [1]. The pulp and paper industry generates effluents that present problems related to their disposal, even after the treatment. Among the solid wastes generated by this industry, the main waste is the primary sludge from the effluent treatment plant (ETP).After the initial treatment the decanted solids go through a dewatering stage, generating the solid form denominated primary sludge. This sludge resembles a paper paste of dark gray color when humid, and clear gray color when dry. This primary waste is composed basically of kaolin, pulp, traces of chemical substances and water. This waste generated in the pulp and paper industry depends on the characteristics of the process and of the employed techniques. It can vary significantly from one industrial unit to another, even in the case that the final products are similar. Its composition is approximately 60% of kaolin and 40% of pulp, and these percentages can vary in some moments as a function of the process [2,3]."

Jan 1, 2008

By R. E. Molnar

A number of flowsheets have been designed and operated, or are currently being considered, to extract copper from leach solutions having much more copper than the 4 g/L levels typically found in heap leach liquors. Dealing with these solutions has required that the envelope for ?normal? copper solvent extraction be pushed beyond the usually considered limits. Others have published information on flowsheets to recover copper from leach liquors containing over 25 g/L copper. Secondary solvent extraction circuits are often required to attain satisfactory overall recoveries. This paper reviews some of the issues faced in three pilot plant circuits that were operated by SGS Lakefield Research to produce cathode copper from solutions containing 8 to 20 g/L Cu. The primary objective was to maximize copper extraction using one solvent extraction circuit. The role of feed acidity and the disposition of impurities such as iron and chloride are considered. The challenges of running short SX piloting campaigns are discussed.

Jan 1, 2003

By Graeme Miller

The geotechnical characteristics of the ore are important in understanding the kinetics of a copper heap leach. These characteristics can indicate potential problems and can be used to determine the semi-quantitative changes in field kinetics as compared with column kinetics. The application of this approach allows a more rigorously based determination of ?scale up factors? than has been the case the date. The shrinking core model has been shown to be a poor predictor of leach kinetics based on the crushed ore size distribution. However the model itself is a very useful tool to analyse commercial heap data. Significant geotechnical parameters such as: bulk density / stress characteristic, limit moisture capacity and particle density are used to determine the effect of changes on the diffusion controlled leach rate. By consideration of the geotechnical reaction of the ore mass the leach rate changes are related to changes in these variables. Analysis of commercial heap data has indicated effective diffusion lengths of up to ten times the largest particle size.

Jan 1, 2003

By Sylvie C. Bouffard

The need for a better understanding of the heap biooxidation pretreatment of pyritic refractory gold ores has prompted us to develop a rigorous mathematical model of the process. The hydrological structure of the model takes the form of lateral stagnant pores in contact with a uniformly distributed gas stream and connected to vertical plug flow channels, as suggested by the results of an independent study of column hydrology. A model of pyrite oxidation kinetics was derived based on electrochemical leaching theory and the results of potentiostatic stirred tank and column tests. The growth rates of attached and planktonic iron- and sulfur-oxidizing cells are modeled with separate Monod expressions over three separate temperature ranges corresponding to mesophiles, moderate thermophiles, and extreme thermophiles. Isothermal column tests validate the model simulations. Excellent fits of several leaching indicators (potential, extent of sulfide oxidation, iron concentration, cell numbers) reveal the rate-limiting step to shift from particle kinetics to oxygen gas/liquid mass transfer with increasing temperatures and pyrite head grades. Competition for oxygen between sulfur- and iron-oxidizing microorganisms lowers potentials and slows down pyrite oxidation. This modeling tool may assist engineers in the design and operation of heaps to give more complete gold liberation in a shorter time.

Jan 1, 2003

By Varadajan Seshadri

Torpedo cars have been extensively used for pig iron desulfurization although its geometry is not considered to be ideal as far as mixing and mass transfer are concerned. Complications arise from scaffolds formed through aggregation of flux, slag and pig iron during operation. Following industry demand a 1:6 torpedo car physical model was operated to assess the optimum refining conditions for pig iron desulfurization. Similarity between the model and prototype were established through Froude and turbulent Reynolds criteria. Mixing times were evaluated by pulse tracer addition and the kinetics of metal/slag interactions were assessed from experiments investigating iodine transfer from kerosene to water. The influence of parameters such as level of metal, gas flow rate, lance penetration, lance orientation, presence of scaffold were evaluated. Mixing times were found to be shorter than regular desulfurization time and also not very sensitive to scaffold presence. Scaffold contributes to the reduction of the useful volume only. Mass transfer at the permanent reactor is more effective when the torpedo is operated at its full capacity. The experiments also highlight the dominance of the transitory reactor as compared with the permanent reactor.

Jan 1, 2006

By Simon Lekakh

Direct reduction of Cu,Ni,W,VandMo oxides from various industrial wastes the melting of iron and steel in different furnaces was studied by thermodynamic computation and experimental methods. Thermodynamics was used to compute the final partition of the alloying additions between iron-carbon melts and oxides contained in the slag. It was shown that the sequence of the reduction reactions depended on the melt composition as well as temperature. Kinetic factors limited recovery in induction melting, while experimentally measured final partition coefficients were close to equilibrium during EAF melting. The possibility of the partial substitution of expensive ferroalloys, by different industrial wastes containing nonferrous oxides, was evaluated in foundry and mini-mill conditions.

Jan 1, 2006

By G. Hanko, A. Lebleu, M. Sibony, J. Lecadet

The New Jersey distillation process is today the most important pyrometallurgical method for the production of zinc of very high purity. The flexibility of the pyrometallurgical zinc production process, especially its ability for recycling, makes it competitive, although it is energy intensive. A deeper knowledge of the New Jersey process is necessary to further increase its technical performance by ensuring its global safety. A project, integrated in the European research program EUREKA, has been started in order to define the process chemistry of distillation. Experimental measurements have been carried out with a column at the laboratory scale, and the results, linked with industrial measurements, support the development of a model based on material and thermal balances. The first conclusions indicate that the key parameters for process optimization are the column geometry and the distribution of the thermal losses.

Jan 1, 2000

By R. Menge, N. Basin, M. Sibony, J. Lecadet, S. Schmidt

In 1996, Metaleurop replaced its conventional sintering and blast furnace lead smelting activity in Nordenham, Germany by Sirosmelt/Ausmelt technology. Following some alterations to the process and the equipment, the bath smelting plant reached its design capacity for the treatment of lead concentrates, lead sulphate paste from spent batteries, secondaries and internal by-products. A reliable metallurgical process has been established, and thus higher process stability has been achieved, increasing simultaneously the refractory life. Nevertheless, improvements are needed to control the process with a better automation system and reliable expert-systems, because of the intensity of the smelting process. The introduction of the Sirosmelt process for the pyrometallurgical production of lead instead of the prior conventional process has also demonstrated the following advantages: reduced emissions of heavy metals and gaseous compounds, reduction of the specific energy consumption, minimization of residues and a reduction of staff and maintenance costs. The environmental performance of the plant meets the requirements of the German regulations.

Jan 1, 2000

By Elli Nurminen

Fouling of heat recovery process equipment may significantly decrease their heat transfer efficiency. In Copper Flash Smelting process flue dust tends to form build-ups on the heat recovery boiler walls. Thermal transportation properties of copper flash smelting flue dust and its components have been studied. The effects of porosity and temperature on thermal transportation properties have also been determined. The results indicate that dust and its components are effective thermal insulators and build-up layers on the boiler walls are likely to decrease greatly the heat transfer efficiency of the boiler. Decreasing dust layer porosity has a strong increasing effect on thermal conductivity and increasing temperature has a slight decreasing effect on thermal conductivity. The results may be used in CFD-modelling and optimisation of the process.

Jan 1, 2006

By Bernhard J. Ralph

In refractory gold ores much of the gold occurs in sub-microscopic form in sulfide minerals, most commonly pyrite and arsenopyrite Bacterial leaching is being developed as a pretreatment for these minerals to aid the liberation of gold and a variety of extracting reagents. This paper reviews the nature of the principal micro-organisms involved, the effects of various physico-chemical factors on the rate and extent of extraction, and likely mechanisms involved.

Jan 1, 1989

By P. K. Jha, M. M. Mahapatra, H. K. Mohanty, Pradeep Kumar

"During friction stir welding, the tool geometries affect the weld together with the process parameters like welding speed, vertical pressure and tool rotational speed. The present investigation deals with the three dimensional computational fluid dynamics modeling of friction stir welding process considering material flow around the tool, welding speed with respect to tool geometries. Friction stir welding tools with different tool geometries were used for the experiments to achieve acceptable aluminum welds. The temperatures near the welds for each tool were experimentally observed. A 3-D computational fluid dynamics (CFD) model was developed. Temperature-dependent material properties of the aluminum alloy were used in the CFD model. Thermal analysis was carried out considering rotational speed, vertical pressure and traverse speed for the tool geometries. The numerically predicted stirring patterns and temperature profiles closely matched with the experimental ones. IntroductionThe friction stir welding (FSW) is a solid state welding process where generally the metallic materials are joined by the combined action of frictional heating and weld zone stirring by a rotating tool [1]. The heat generated in the process is much below the requirement of melting the plates; hence the FSW process is devoid of harmful effects those are observed during arc welding. The FSW process utilizes a tool which has a shoulder and a protruding pin known as the probe. The shoulder is responsible for frictional heating while the pin probe facilitates stirring of the joint material. A schematic of FSW process is shown in Fig. 1."

Jan 1, 2012

By Manuel Pérez-Tello

A mathematical model to represent the expansion and fragmentation of copper matte particles oxidized under flash converting conditions is presented. The model assumes the particles to be initially nonporous, have a constant mass prior to fragmentation, and travel at a constant velocity throughout the reaction chamber. The model requires the specification of five parameters: the particle expansion rate, a fragmentation diameter factor, a fragmentation size distribution parameter, and the fractions of the finest and the coarsest particles in the feed that undergo fragmentation. The model predictions show good agreement with experimental data collected in a laboratory flash converting furnace over a wide range of experimental conditions. The evolution of the size distribution of the particles along the reactor length was computed, and the model parameters were correlated with the experimental operating variables. Model predictions indicate that particle residence time is an important factor in the generation of dust. The presence of two maxima in the particle density function may be attributed to turbulent conditions prevailing in the furnace, which cause particles to follow very different trajectories within the furnace even if they are injected at the same location.

Jan 1, 2006