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By Jeong-Hwan Kim

The liquid-liquid reactive process (solution process) is often adopted as a synthetic method for precipitated calcium carbonate (PCC) in laboratory studies for its simplicity in operation or ease in controlling process variables. Still, PCC are produced commercially by passing carbon dioxide through a milk of lime, i.e., by a gas-liquid reacting method (carbonation process). Few studies on the carbonation process have been conducted, since the process variables are interrelated and difficult to control compared to the solution process. In this study, both carbonation and solution processes were employed to study the polymorphs of calcium carbonate and growth rate of PCC crystals. The effects of the characteristics of limestone ores as a raw material in the synthetic system of PCC on the synthetic characteristics of PCC were also investigated. To control the nucleation rate in the synthetic systems, the shape factor was considered most important. Single-phase aragonite PCC could be synthesized under a variety of controlled experimental conditions such as ionic strength, solution composition, concentrations of additive ions, and temperature.

Jan 1, 2006

By J. A. Jensen

In-situ composites were produced in both Ti matrix (Ti-20Y) and Mg matrix (Mg-20Ti, Mg- 20Nb, Mg-20Fe, and Mg-8Li) alloys. In Ti-20Y, a < 1010 > fiber texture formed in both the Ti and Y phases, and UTS increased from 240 MPa, (as-cast) to 950 MPa after deformation processing to a true strain of 7.3. Deformation processing produced smaller UTS increases in the Mg-matrix composites, but they showed exceptional resistance to weakening from exposure to elevated temperatures. The Mg-20Fe, Mg-20Nb. and Mg-20Ti composites tolerated 6-hour exposure to 400°C with no reduction in their 250 to 300 MPa room temperature UTS. All composites studied had excellent ductility and machinability.

Jan 1, 1995

By Kongfang Feng, Fei Ruan, Zhiyu Liu, Jieyu Zhang, Xin Hong, Shaobo Zheng, Jixu Wang, Jinyin Xie

"Mixing phenomena in smelting reduction furnaces with asymmetric side blowing were studied in this paper. Mixing phenomena in a smelting reduction furnace was represented as the mixing time by electrical conductivity measurements. Experiments were performed in a water model under various operating conditions to determine the effects of horizontal angle, radial angle, inserting depth, flow rate of the upper and the lower side nozzle, the included angle between the upper side nozzle, and the lower side nozzle on mixing phenomena in smelting reduction furnace. Comparing mixing time and mixing phenomena, the optimal conditions were obtained for an asymmetric side blowing process.IntroductionIn recent years, many countries have put forward development strategies for saving resources and environment-friendly, the development of various industries had to face its influence for resources and the environment .As we all know, the steel industry is a pillar industry of the global economy, in which ironmaking is an important part of it. In the modern ironmaking process, the blast furnace is regarded as the most important equipment and tool. But with the increasing scarcity of metallurgical coke resources and considering the environmental impact of such processes, metallurgists proposed the concept of smelting reduction. Smelting reduction processes to produce hot metal from iron ore and coal were being developed as a possible alternative to the traditional blast furnace. At present, a number of smelting reduction processes had been developed all over the world, they were mainly included COREX, HISMELT, FINEX, DIOS, etc."

Jan 1, 2012

By Dirk Verhulst

The Altair Hydrochloride Pigment Process is a new ?third route?, besides the established high-temperature chloride process and the older sulfate process, to manufacture TiO2 pigment from ilmenite ore. It has been tested at a scale of 5 t/day feed. The ore concentrate is digested in high-acid, high total chloride solution (+/- 39% Cl). Titanium and iron both go into solution. Iron is separated as FeCl2 crystals after reduction and cooling. Titanium is transferred by solvent extraction into a purified, high-Ti stream. It is spray-hydrolyzed to produce a TiO2 hydrate and further calcined with additives into high-quality pigment. HCl solutions generated by pyrohydrolysis and spray hydrolysis are treated by pressure-swing distillation to regenerate HCl gas for re-injection into the digestion reactor. All chloride streams are recycled. Recent work has concentrated on optimization, particularly in 3 areas: - Solvent extraction: a new organic mixture, including a new diluent, makes it possible to work at room temperature, to avoid TiO2 hydrolysis problems and to improve phase disengagement and impurity separation. - Pigment finishing: a systematic study of the parameters involved, followed by long runs in the best conditions confirm pigment quality. - Flow sheet optimization: innovative modifications of the conditions of spray hydrolysis and pyrohydrolysis, combined with re-routing of streams achieve significant energy savings. A 100 t/year pilot plant including these features as well as other process improvements is under construction.

Jan 1, 2006

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade.

Jan 1, 2006

By Ricardo Ponce

In recent years, ENAMI implemented modernisation plans at its two smelters in order to meet the government&apos;s environmental regulations introduced in the early 1990s. The modernisation plans defined the new SO2 and particulates emission targets, deadlines for compliance, and the revised treatment capacities of the smelters. At Las Ventanas smelter, the principal process change consisted of eliminating the reverberatory furnace. All the smelter feed is currently processed in a 4m diameter, 14m long Teniente Converter, using up to 34% oxygen enriched air. Dry concentrate is injected into the bath through tuyeres. A fuel oil burner compensates for any process heat deficiency. The Teniente Converter high copper content slag is cleaned in an electric furnace. This furnace is also used to melt internal reverts. This paper will discuss the successful operation of the slag cleaning electric furnace.

Jan 1, 1999

By K. Knuutila

The behaviour of thiourea, animal glue and chloride ions in the electro¬lysis of copper has been investigated by various different electrochemical experiments, i.e. polarization curves with stationary copper electrodes, long-time galvanostatic electrolyses and Hull cell experiments. Polarization curves with stationary copper electrodes show that animal glue has a polarizative effect on the deposition potential. Small thiourea contents affect depolarizatively when high concentrations retard the copper deposition. The microstructures of the deposited copper after the long-time electrolyses show that animal glue favours a basis oriented deposition structure. With thiourea the field orientated structure was evident. It was also observed that the deposited structure depended much on the grain structure of the starter sheet. The chloride ion concentration has a drastic effect on. the crystal size of the deposited copper as it was found out in Hull cell tests. Chloride ions flattened the the crystals and the deposition became smoother when the chloride ions were added. The cathode copper quality is discussed according to the literature. Special attention is paid on the codeposition of thiourea and the origin of sulphur impurities in copper cathodes.

Jan 1, 1987

By Jonathan M. Berkoe

Design engineers and metallurgists have long recognized the need for better methods to calculate a wide range of fluid dynamic effects in smelters and hydro- metallurgical facilities. Examples can range from the capture of fume in the secondary hoods of a copper converter, to controlling the thermal effects of heat transfer resulting from metal and slag flows within a furnace. With the advent of relatively low-cost, high- speed computers and user-friendly, commercially available computerized fluid dynamic (CFD) programs, these calculations can now be made. Use of CFD increased the understanding of both hot gas and molten flows in smelter facilities and has already led to design improvements in converter fume control hoods as well as improved management of heat transfer in electric furnaces. This paper will present two representative CFD applications to metals industry facilities. To date, Bechtel has implemented CFD results on four continents.

Jan 1, 1999

By Bogidar V. Mihaylov

Bacterial oxidation of a low-grade sulfide gold ore was investigated in order to enhance leaching of gold. The experiments were carried out in columns using mixed cultures of Thiobacillus ferrooxidansisolated from the ore. Fractions with different screen analyses were oxidized in two regimes - one pass of the solution and circulating, solution. Constant temperature and flow-rate of the percolating solution were maintained during the experiments. A correlation between the concentrations of copper and iron in the solution leaving the columns and pH and Eh values was observed. The effect of bacterial activity was proved by means of thiourea and cyanide leaching of the oxidized ore.

Jan 1, 1991

By G. Gomathi, K. Asokan, K. Subramanian

An electrochemical reactor with anode and cathode chambers separated by a composite perfluoro polymer cation exchange membrane was designed, fabricated and used for the reduction of dissolved carbon dioxide under ambient conditions to formate. The flow reactor enhanced the mass transfer of carbon dioxide compared to the batch reactor. Experiments were conducted using two different perfluoro polymer membranes - Nafion 961. Efficacy of CO2 reduction on various cathode materials (Cd, Pb, Sn and Zn plated stainless steel woven mesh) were determined. Optimum values of flow rate and current density were evaluated for the energy efficient formation of formate in aqueous KHCO3 (pH 7.5-8.5) buffer solutions.

Jan 1, 2008

By Vladimir Mindin

Simulation of complex equilibria is usually done in the P-T-X coordinates, where "Xu is the amount of individual chemical components in the system. This approach is not productive in some very important cases: (i) investigation of "open" systems, (ii) determination of coordinates (trajectories) of mono-variant points, among others. To solve these and some other problems, we use the idea of chemical potentials of elements (CPE) of the system. A system of different coordinates axes (CPE-axes ) leads to a new strategy of simulation, observing the results of the simulation, and to efficient technology of compressing and storage the data of the simulation.

Jan 1, 1994

By D. E. Roberts

Over 425 million used automotive oil filters are discarded in the United States each year. Estimates prior to this research claim that 10% are recycled with the remainder typically being landfillcd. Surveys conducted with ferrous scrap users and oil filter processors as part of this research reveal that at least 15% are currently being recycled as ferrous scrap. Oil filter scrap is not being used by many operations because of concerns with scrap consistency and quality. These concerns stem from trials conducted in the infancy of the oil filter recycling movement. Consistent scrap quality depends both on the content of the used oil filters and the processing technique used to produce the scrap. Technology has advanced since the first recycling trials were conducted by steelmakers. Several different types of scrap are available, including pucks, bricks, cubes, and shred. This research conducted at the University of Missouri-Rolla investigated the content of used oil filters and compares the recyclability of different oil filter sizes and designs. Filters vary by application and vary between manufacturers for a particular application. An understanding of the scrap itself as well as the concerns and problems of both oil filter recyclers and oil filter processors is necessary to increase the number of used oil filters being recycled.

Jan 1, 1996

By Levent Özmen

Colemanite is a mineral containing varying amount of boron that is found in abundance in Turkey. It has a good possibility to be used as a flux in iron and steel industry. In this study a review of the use of colemanite, as a flux agent in steel production has been carried out and various related aspects such as its influence in metal-slag reactions, solubility of lime and magnesia in the slag are discussed along its performance in several points of views including its technical and environmental usage characteristics. Positive and negative factors of using this material as a flux are also underlined.

Jan 1, 2006

By Finn Olesen, Melina Garcia, Mark William Kennedy

"Furnace resistance is a function of the complex interrelationship between many factors including: operating practice, slag conductivity, temperature, power intensity, and geometry (electrode shape, diameter, spacing, immersion, slag depth, etc.).Accurate prediction of resistance is critical for success of the overall furnace design. The sizing of electrodes, columns, bus-bars, and transformers are all impacted. Estimation of minimum and maximum resistance or maximum operational current, as well as the maximum operating voltage are of fundamental importance.Various mathematical tools have been developed to assist designers with the selection of furnace dimensions and the prediction of resistance. Elkem found the methods of Downing and Urban 1965 and Westly 1975, to be particularly useful.In the current paper, comparisons are drawn between data from spent aluminum pot lining (SPL) demonstration testing at Elkem Bjolvefossen and predictions based on these classical tools and 3D finite element modeling (FEM) with COMSOL.®"

Jan 1, 2012

At the present time, cyanide is the most widely used reagent to extract gold from its ores and concentrates. However, its use in mining has become the focus of intense attack by various groups throughout the world; as a consequence, a renewed effort has been launched to find suitable alternative lixiviants to recover gold. Chlorination was the most popular process to extract gold, before it was rendered obsolete with the advent of the cyanidation process at the turn of the last century, not least because it required the use of potentially hazardous and costly chlorine to oxidize/complex the gold. The PLASTOL® process, originally designed to recover the platinum group metals (PGM?s) from their ores and concentrates, provides an alternative to cyanide for gold ores. The process generates oxidizing conditions in the autoclave capable of forming the AuIII ion, and gold chloro-complexes result from the addition of small quantities (~5-10 g/L) of sodium chloride to the autoclave. The principles of the PLASTOL® process are briefly described, and several applications of the process to gold concentrates are presented. Various options available to recover gold from PLASTOL® leach solutions are also discussed.

Jan 1, 2003

By N. Moelans

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NiINiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at 1100 and 1200°C and pO2 values between 10-3 and 10.12 bar were obtained. The measurements were evaluated with? thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By Takeshi Azakami

By combining the iron reduction process with the usual rotary kiln process, the direct production of metallic zinc from EAF dust is proposed. After thermodynamic estimation and desk-top experiments it is confirmed that the process is hopeful under suitable conditions. In order to get some practical test data the enlargement of the process scale was planned and the bench scale tests were carried on successfully. In these experiments a zinc ingot of PW grade was produced from EAF dust.

Jan 1, 2003

By Matthew C. Binsfield

The simultaneous electro winning of zinc and manganese from waste water treatment plant sludge was studied as a part of the overall research program, which was conducted to develop the methods for removal of environmentally hazardous metals from the Bunker Hill Superfund Site. This paper discusses the electrolytic method for recovery of zinc and manganese from the solution produced by leaching of sludge with S02 + H2S04. After three stage purification of the leaching solution, zinc and manganese were electro won simultaneously in an undivided electrolytic cell. Zinc was deposited on an aluminum cathode, while manganese was simultaneously produced (as Mn02) on a lead silver anode. The electrowinning parameters studied were the effects of: temperature, current density, electrode material, spacing of electrodes, composition of electrolyte, and electrolyte additives. Anodic and cathodic efficiencies were 30 and 91%, respectively. In light of the process design parameters discussed in the paper, which are affecting the electrowinning, these efficiencies were found as acceptable with regard to the quality and marketability of the products.

Jan 1, 1996

By Norbert L. Piret

From the copper smelter operation a various outputs are to exert negative impacts on the environment. Particularly, emissions like SO2 and dusts, solid wastes like contaminated gypsum and arsenic sludge, effluents and heated cooling water are generated. Most countries have sitipulated an environmental legislation to provide the framework for an efficient environmental management. As part of the planning activities for x major greenfield copper smelter, the Following elaborations are required and were drawn up. -The Environmental Impact Assessment which is the first step of environmental management and mandatory for every new project. - The Environmental Monitoring Plan, which describes the monitoring procedures for the main impacts identified and assessed. -The Environmental Management Plan, which deals with the minimization of environmental impacts, and the methods of its implementation.

Jan 1, 1996

By Yu-ichi Kanbe

It becomes more important to control the composition of inclusions with increasing the demand for quality of products in terms of cleanliness. Along with the development of refining technology to make inclusions harmless, a study was made to develop how to predict the quality of final products. At first, observations of a number of defects revealed that the defects were caused by inclusions larger than 100 m in diameter. Therefore it is required to detect relatively large inclusions in steel, whose existence is quite rare, to identify the quality. In order to estimate the maximum size of inclusions in a given sample, the method with statistics of extreme values has been applied for continuously cast (CC) slabs, hot-rolled coils and cold-rolled coils of type 304 stainless steel. For the CC slabs the diameter of inclusions, which were analyzed to be mostly silicate with globular shape, in the specimens was measured. For the coils, the width of inclusions was measured at the unit section perpendicular to rolling direction because it corresponds to the diameter assuming that the width of globular inclusions does not vary with rolled. Then maximum inclusion diameter in a specimen was calculated. As a result, the obtained values in the rolled coils are larger than in the slabs. This may imply that the measurement with the coils gives the values closer to the truth. Besides, the measurement with the coils is even faster than with the slabs due to its simplicity of preparation of the specimens.

Jan 1, 2006