Search Documents

By D. Silva-Galvan, R. D. Morales, S. Gonzáelez-López, A. Romero-Serrano, G. Plascencia-Barrera, F. Chavez-Alcala

This work is focussed on lead decopperising by two techniques: conventional top addition of sulfur and injection of sulfur powder. It is found that the first method proceeds under equilibrium conditions and the second one depends on kinetic considerations. Experiments were carried out using 15 kg lead baths at two temperatures, 340°C and 380°C. The carrying gas used for the injection trials was nitrogen at flow rates of 6.3 and 18.6 L min- 1• The results show that 'decopperising process is more efficient at temperatures close to the melting point of lead for the sulfur top addition process, whereas high temperatures produce better copper removal for the injection of sulfur powder. Besides, the sulfur injection with the higher nitrogen flow rate (18.6 L min-1) produced higher decopperising rates. Thermodynamic and kinetic models are used to simulate this lead refining process.

Jan 1, 2000

By Masaru Imaizumi, Hiroyuki Nomura, Mitsuharu Takita

"Cast iron possesses many superior characteristics caused from precipitated graphite structure, for example, castability, wear resistance, solid lubrication, damping capacity. But the more graphite hyper-eutectic cast iron contains, the lower its mechanical strength becomes, because graphite gives a negative effect to strength of cast iron. In addition, primary graphite tends to segregate during solidification, so uniform materials are difficult to be produced.In this study, authors introduced semi-solid processing in developing new and high quality cast iron. A series of semi-solid processing experiments were carried out to clarify the effect of stirring condition; solidification temperature and etc. on microstructures and characteristics of cast iron. In particular much attention is paid to the appearance of ternary eutectic zone at the final stage of solidification. As the results advanced hyper-eutectic cast iron was obtained with high quality of both the mechanical strength and wear resistance. As for the mechanical strength, 300MPa and 0.60% are obtained as the tensile strength and the elongation values, respectively, under the controlled stirring condition. This indicates that semi-solid processed hyper-eutectic cast iron is used prospectively without spheroidization.IntroductionCast iron has various good properties such as wear resistance, solid lubrication, damping capacity and machinability. The characteristics of cast iron are mainly decided by graphite structure, namely graphite shape and its distribution in the matrix. Mechanical strength of cast iron is large in the case of small quantity of graphite particles which are precipitated uniformly, however, it becomes small in the case of large quantity of graphite precipitated flakily."

Jan 1, 2000

By Sedef Pinar Basag, Onuralp Yucel, Ahmet Turan

Niederschlag process is commonly used to produce metallic antimony. The process is a metallothermic process which is conducted in one step for metallic antimony production. Using this method Sb2S3 is mixed with coal and metallic iron and subjected to reduction. During heating, antimony sulfide is decomposed and sulphur combines with iron to form the matte phase. Metallic antimony is collected at the bottom of the crucible. In this study, evaluation of Sb2S3 concentrate, extracted and obtained from West Anatolian Region of Turkey was investigated by using Niederschlag process. The reductant stoichiometry, reduction temperature and duration were carried out in the experiments. Chemical analysis methods by using atomic absorption spectrometry (AAS) and X-ray diffraction spectrometry (XRD) techniques were used for the characterization of the concentrate, metallic nuggets and matte phases.

Jan 1, 2016

By Halvor Dalaker, Pål Tetlie

The decomposition of methane has been studied experimentally in contact with various oxides at elevated temperatures. For each oxide, the temperature at which the cracking starts has been determined. No correlation was found to exist between the temperature for the onset of cracking for a given oxide and the affinity for carbon of the oxide's metallic component. In terms of potential for using methane as a reducing agent, calculations are presented that indicate that the suitability of an oxide for such reduction depends on the desired methane+oxide reaction being more energetically favourable than the methane+methane=ethylene/acetylene reactions.

Jan 1, 2014

By Junji Shibata

Zeolite synthesized from coal fly ash has many intelligent properties such as cation exchange, adsorption, catalyst and so on. The suitable use of the zeolite, however, is not established in an actual commercial scale yet. From the viewpoints of an effective usage of coal fly ash and the zeolite obtained from coal fly ash, we propose the new concept for environmentally friendly usage of zeolite, in which coal fly ash safely returns to the soil with growing plants and purifying wastewater. This method can make great contribution to recycle of coal fly ash, to purification of high nutritious water and to tree planting.

Jan 1, 2002

By S. q. Honingh, G. Van Weert

Currently produced zinc-enriched blast furnace dust is stored on site at CORUS IJmuiden. To end this practise, a research program was started in 1996. Four technologies were studied: oxidative autoclave leaching in a chloride medium, fluid bed pyrohydrochloridisation (pyrohydrolysis) to yield lead-zinc-free (hematite) calcine, EAF (plasma) smelting/zinc fuming, and incorporation of the dust in 'iron foundry cupola charges. All aim to remove zinc and lead, recycle the iron residue internally, and produce a saleable zinc-lead product.

Jan 1, 2000

By Tatsuro Ariyama, Michitaka Sato, Atsushi Sakai, Sumiyuki Kishimoto, Ryota Murai

"In order to achieve high pulverized coal injection operation in a blast furnace, optimization of the injection lance arrangement was carried out using an experimental furnace and mathematical models. To increase the injection rate of pulverized coal, it is required to raise the combustion efficiency of pulverized coal. It became clear that multi-point injection and the lance arrangement to avoid interference among the coal streams injected were so effective in increasing combustion efficiency. With these findings, the eccentric double lance arrangement has been newly developed.At NKK, Fukuyama No.4 Blast Furnace, after the improvement of the lance arrangement, the maximum injection rate reached up to 230 kg/thm and an average monthly record of 218 kg/thm was successfully achieved.IntroductionFrom the viewpoints of reducing the production cost of pig iron and prolonging coke oven life, high pulverized coal injection over 200 kglthm is actively pursued by ironmaking industries[1-2].Coal particles injected into the blast furnace are consumed by combustion in the raceway and also in-furnace reaction like solution-loss reaction (C + CO2 = 2CO). The amount of coal consumed by the latter process is determined by the carbon balance in the blast furnace and there is a limit. Therefore, to increase the injection rate, it is desirable to improve the combustion efficiency in the raceway. For these purposes, the optimization of the lance arrangement was examined by a hot model and mathematical models."

Jan 1, 1996

By T. Shoji

"The human history is characterized by social development based on mineral and energy resources, and many conflicts to take the resources by power. This is shown by not only world wars but also many local conflicts as well as international supremacy.IntroductionThe world population after B. C. 10000, which is summarized in several papers, is approximated by four straight lines on a semilogarithmic diagram as shown in Figure 1 [l]. The annual rates of increasing are 0.0041, 0.071, 0.53, and 1.85 % from the old and young periods. The boundaries among four periods are approximately B. C. 4600, AD. 1670, and 1930. The start of the second period seems to correspond to the beginning of agriculture and cattle breeding. Precisely speaking, the usage of natural energy resources such as woods and domestic animals already began, but is inferred to have become common after the age. The third and fourth periods are characterized by the common usage of coal and oil, respectivety. Not only energy resources but also mineral resources including gold, copper, iron and others are also important for the human history.Mineral and energy resources have supported the development of the .human civilization, and have caused many conflicts because of this reason. Every day newspapers report conflicts, such as Chechnya, East Timor and Ache. We can easily point out the facts that the conflicts closely relate to mineral and energy resources. Groznyj, Capital of Chechnya, is located on the western margin of Caspian oil field. Many mineral deposits occur in Kavkaz Mountains running south of Chechnya. Subsea oil fields occur in Timor Gap located between East Timor and Australia. Ache is also one of oil fields in Indonesia. It is very difficult to state present conflicts independently of a political view of point. For this reason let us try to historically review the relation between mineral and energy resources and international domination and conflicts [2] based on many papers [3]."

Jan 1, 2000

By P. Lussiez

Precipitates consisting of amorphous ferrihydrite and crystalline goethite have been prepared by aging hydrolyzed Fe (III) solutions at room temperature. The precipitates have been characterized by x-ray diffraction and differential thermal analysis. The amorphous ferrihydrite transforms to goethite with time. The ferrihydrite to goethite transformation is affected by the presence of small amounts of copper or nickel coprecipitated with the iron. .The addition of copper decreases the amount of goethite at a given aging time and increases the amount of coprecipitate which is initially dissolved in sulfuric acid, but it does not seem to affect the dissolution of the crystalline part'. It is proposed that adsorption of copper hydroxo species on goethite nuclei delays the ferrihydrite to goethite transformation. The effect of nickel is less dramatic than that of copper. Apparently a portion of the added nickel is adsorbed on the goethite crystallite surface rather than incorporated into the goethite lattice.

Jan 1, 1981

By Adam C. Powell

A new Cahn-Hilliard phase field model of transport-limited electrochemistry describes phase boundary motion due to oxidation and reduction reactions at metal-electrolyte interfaces. Benchmarks demonstrating the accuracy of the method include open circuit voltage and closed circuit current in metallothermic reduction, and linear stability theory in metal electrolysis, including a new stability criterion for reduction of liquid metal from liquid electrolyte. The model is applied here to understanding cathode interface stability in titanium electrolysis e.g. in the SOM process developed with Uday Pal, and to structure evolution in subhalide reduction of titanium dichloride by magnesium developed by Toru Okabe. Potential for application to new fuel cell and battery systems is also discussed.

Jan 1, 2006

By Stein Tore Johansen

The flow of a liquid through a large grain filter has been considered. An improved form of the fluid dynamic equations describing flows through porous media is proposed. The theory is applicable to all Reynolds numbers. Particulate inclusions are described by passive scalar fields where only very simple mechanisms for particle removal are included. However, the deposition of particles are allowed to change the "porosity" of the filter. Hence, the flow pattern through the filter will change as the filter ages. The theory is employed to the filtration of aluminum in an industrial grain filter. The model shows that the filter is not effectively designed and there is room for considerable improvement. The dynamic "aging" process of the filter is shown to change the filtration from bed filtration to cake filtration. Finally, the predicted inclusion collection efficiencies are compared to efficiencies measured in an industrial filter. The predicted initial efficiencies are in very good agreement with experimental results.

Jan 1, 1990

By Jose Antonio Silva Souza, Emanuel Negrao Macedo, Iara Ferreira Santos, Otacilio Dias, Luis C. A. Venancio

"The Bayer process alumina production generates 0.7 to 2.0 ton of bauxite residue (BR) and an average of 1.0 ton of C02 per ton of alumina produced. The direct reaction of exhaust gases to reduce the alkalinity of the BR may allow a triple gain: improve the storage conditions, open a range of new applications for BR and sequester from 16 to 102 kg of C02 per ton of alumina. This paper shows the measurement of C02 captured during a pilot scale reaction of a suspension of BR in water with flue gas, produced from direct oil burning. Three different types of reactors were used: one spray tower and two packed columns. The inlet and exhaust gases were analyzed using electrochemical and non dispersive infrared sensors. The pH of the suspension was monitored during and after the reaction to evaluate the buffer effect.IntroductionAlumina is mainly produced from refining bauxite using the Bayer process. This process consists of extracting the aluminum oxide through its dissolution in caustic soda and the separation of insoluble residues. The remaining bauxite residue (BR) although not particularly toxic, poses risks to the environment due to the large volume and its reactivity. According to the latest technology it is stacked on sealed deposits specially constructed. To date the vast majority of the bauxite residue that has been produced was stored and were not incorporated into any existing production processes to significant amount with exception to some extent of the sintering process residue at Russia and China [l]. On the other hand, a strategic goal was set in 2010 by the Bauxite and Alumina Committee of the International Aluminium Institute (formed by the majority of the industries) to reuse 20% of BR in 2025 [2]. China has established the same objective for 2015[1].This paper is a sequel of two others presented at TMS 2010/2012 [3-4] and describes:• A pilot plant assembled for testing the carbonation process of BR with gaseous effluents similar of the refining process.• The methodology used to measure the amount of C02 captured during the carbonation process.• The results of the carbonation process, the C02 capture and the buffering effect of the pH.This process is studied in order to consume minimal power and use the effluent as efficiently as possible in different reactors from low cost to ultra high performance. The process is designed for minimizing the power consumption and equipment investment."

Jan 1, 2013

By Michael A. Eamon

Magma Copper Company has operated its San Manuel SX-EW Plant facilities since 1986. The original plant facilities have a design capacity of 25,000 tons per year of electrowon copper cathode produced by processing pregnant leach solutions from an open pit/heap leach operation. In 1988, the plant was expanded to 50,000 tons per year to incorporate processing leach solutions from an insitu leaching operation. This paper presents a general overview of plant practices with particular emphasis on process innovations developed and implemented by Magma during construction and operation.

Jan 1, 1991

The oxidation of zinc vapour plays a very important part in the operation of the Imperial Smelting Process. The kinetics of the reoxidation of zinc vapour by carbon dioxide and water vapour onto quartz and zinc oxide substrates is qualitatively understood and this pertains to the conditions found as the gases are being transferred from the furnace to the splash condenser. However, re-oxidation also occurs in the shaft of the furnace where the solid substrates are sinter and metallurgical coke. It was found that there was a threefold increase in the rate of oxidation on sinter, compared to quartz and a 30 to 300 increase in rate on the coke. This was attributed to the high surface area offered by these materials.

Jan 1, 2003

By M Philip Schwarz

"This paper reviews the status of computational modelling of a variety of common metals reduction processes, namely the blast furnace, rotary kiln and fluidised bed, and one new process not yet commercialised, namely smelting-reduction as in the HIsmelt Process. In each case, the last decade has seen the emergence of the capability to simulate the processes using multi-phase reacting computational fluid dynamics techniques. In some cases this capability is still in the process of being developed, and the next few years will see the maturing of the modelling techniques. As they become established, it will be possible to apply them to further refine the older technologies such as blast furnaces and rotary kilns, and assist in the optimisation, commercialisation and acceptance of the newer technologies such as fluidised bed and molten bath reduction. The development of a computational fluid dynamic model of bath smelting-reduction is described in some detail to illustrate how a large number of complex and interacting phenomena can be successfully simulated within a CFD framework. IntroductionPyrometallurgical reduction processes, such as the iron blast furnace, have become increasing more sophisticated through the centuries, so that today they are often highly efficient. There are continuing pressures, however, to refine existing processes and develop new ones. The imperatives are often economic, given that the long-term trend in the price of metals is always downward. In recent times, there has been the additional need to improve the environmental impact of metal production. Given that they almost inevitably require the use of carbon, metal reduction processes are large sources of greenhouse gases, and even a relatively small improvement in efficiency can be valuable in reducing CO2 production. Local environmental issues, such as the need to control of particulate emissions, are also driving incremental improvements in equipment.In addition to the economic and environmental drivers mentioned above, new process development is also being driven by the need to process new ores, and the need to produce unrefined metal in a form more compatible with alternative routes for downstream processing. An example of the latter is the production of DR! (Direct Reduced Iron) as a feed for EAF Electric Arc Furnace) in mini-mills.Further improvement of processes that have already been honed by continual plant experimentation over many years is not an easy task. To deliver further gains in efficiency, throughput, or product quality requires a highly sophisticated tool: one such tool· is computational modelling."

Jan 1, 2001

By O. A. Ogunseitan

The contamination of aquatic ecosystems by mercury wastes is one of the most serious forms of environmental pollution associated with the metal mining and electrochemical industries. The transformation of inorganic mercury to alkylated species is a reversible bacterially-mediated process. The production of methylated mercury is of ?major public health and eco-toxicological concern because these forms of mercury are highly toxic ?and they bioaccumulate in aquatic organisms. We determined the response of the genetic determinants of mei:cury transrormation by Pseudomonas species (that predominate in contaminated soils and sediments), to the concentration and species? or available mercurfiations. By combining selective isolation and gene. ?probe techniques, the intrinsic genetic potential for mercury detoxification in a contaminated environment ?can be estimated. We determined that genetic units required for mericury volatilization (merA ?for mercuric reductase) are naturally amplified in response to mercury. Mercury-resistant bacteria that tolerate up to 100 ug Hg(Il)/ml of medium contain about 10 times more DNA fragments encoding merA than in unadapted bacteria. The exposure of bacteria to methylated.Hg (10 ug/ml lake water) produced increases (up to 10 times) in .genetic units, and higher levels of genetic expression (up to 50 times) per ml of lake water for the mercury reductase system, than on-induced lake water. The findings suggest that in environments where methylated Hg may accumulate as a result of bacterial activity, the reverse reaction which leads to the removal of mercury through volatilization from the system, may be achieved by inducing genetic ?amplification and expression of the mercuric reductase gene system.

Jan 1, 1991

By Paul B. Queneau

U.S. plants solely devoted to recovering values from metal-rich wastes have established market niches based on one or more competitive advantages: superior process technology, access to key feedstocks, unique equipment, special knowledge of markets, and an appropriate exit for outfall water. Plant methodology, competitiveness, environmental factors, and economics are examined, with particular attention to feedstocks, technologies, products, and outputs.

Jan 1, 2003

By G. M. Bond

Reduction of the emissions of greenhouse gases, such as CO,, is currently the subject of extensive research. A novel strategy is put forward here, based on a biomimetic approach providing accelerated deposition into carbonate form for long-term sequestration. It offers the advantages of a process that: does not require concentration of CO, from flue gases; could potentially be used in an on-site scrubber to provide a plant-by-plant solution to reducing CO, emissions; is an environmentally benign procss with an environmentally benign product; and is based on readily available, low-cost reagents (except perhaps the catalyst).

Jan 1, 1999

By James W. Evans, Brian R. Wildey

"Carbon has been the principal reducing agent in producing metals for centuries. Carbon is an inexpensive reducing agent, but also an effective one, as any undergraduate who knows her Ellingham diagrams is aware. Even in the production of aluminum, an electrolytic process, carbon consumed at the anodes serves to reduce the voltage of the Hall-Héroult cell. The interest in reducing the amount of anthropogenic CO2 has led to this examination of whether a switch to hydrogen as a major reductant is feasible and economic. The main source of hydrogen is natural gas and its production entails the generation of CO2; however, that CO2 is more easily captured than, say, the CO2 leaving an iron blast furnace. Calculations and speculations lead to conclusions about whether there is significant benefit to be obtained from such a radical change in our way of producing metals and the approximate cost of such change.IntroductionThe 1991 paper by Forrest and Szekely1 was one of the first to examine the impact of CO2 emissions from the primary metals industries on global climate change. These authors compared data from 1968 and 1985 and reported a drop in carbon emissions from 115.8 million tons to 65.6Mt over this period, the latter figure representing approximately 1% of the world’s greenhouse gas emissions. Much of this reduction was due to a drop in steel output (with carbon emissions increasing within the aluminum and copper industries in this period) but some were due to technological changes such as increased use of continuous casting. A more recent paper on CO2 emissions, focused on the steel industry in Japan, is that of Ariyama and Sato2. These authors report CO2 emissions of 182.4Mt from the Japanese steel, industry in 2003, down from 194.8Mt in 1990. The former represents 14% of the GHG emissions for Japan in 2003. Much of this emission is from ironmaking and the authors break these emissions down into"

Jan 1, 2008

By J. A. Bakken

Thermal plasmas are interesting for a wide range of metallurgical and chemical processing applications. The 300 kW experimental reactor PRESS, which has been in use since 1987, is operated in the transferred arc mode with three or one plasma torches . Tests include remelting of silicon fines and production of ultrafine silica. Work on a novel three stage process for production of silicon metal is under way. A 1:1 model of the plasma reactor is used to measure the wall heat flux distribution calorimetrically. The cold walls of this model are divided into several water-cooled sections. The same plasma torches as in the real hot-wall reactor are used. In parallel to the experiments and calorimetric measurements theoretical work is done on numerical modelling of one and three transferred arcs. A modified version of the flow simulation program FLUENT from Creare Ltd. is used.

Jan 1, 1991