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By Petre Stelian Nita

In small steelmaking shops, in foundries and forging plants, there are not too many option to recycle the basic slags, which are not suitable for many purposes of recycling, because of their low chemical and structural stability. A solution of an adequate recycling is a direct recycling in EAF. Several quality requirements, physico-chemical properties and proportions of slags must be analysed. The progress in this fields permites to establish an adequate proportion of recycled slag, based on enough exact computation of the related property. For oxydizing slag, obtained during melting and in the first part of decarburization operation, the problem of phosphoms contents can be analysed using the phosphate capacity (C PO34-). For reducing periods, during deoxidization operation, desulphurization also occurs and the problem of the sulphur contents can be analysed using the sulphur and sulphide capacities ( Cs / Cs) Between this two complex thermodynamic indicators of the slags. a direct relation is established, using thermodynamic aspects, resulting from the equilibrium constants for dephosphorization and desulphurization process and also, using the optical basicity of slags, computable from the chemical analysis of the slags. On this basis starting from the steel quality requirements. adequate strategies can be established in order to obtain high rates of recycling (between 50-80%) of steelmaking slags. Important cost savings are obtained through this procedure, based on the correct amounts of the fresh lime, iron ore and fluidizers. Keywords: Slag, Properties, Recycling

Jan 1, 2003

By Gretel Parker

In situ Raman spectroscopic investigations of copper iron sulfides in leach solutions have been undertaken. Coupling potentiodynamic techniques to Raman spectroscopy produces a powerful tool for studying mineral surface response to changing conditions, while ESEM and high-vacuum techniques provide complementary ex-situ information on surface structure and composition. Oxidative acid leaching of chalcopyrite at ambient temperature yielded a product with S-S bonds that were shifted from those seen with covellite, with little evidence of elemental sulfur formation. Leaching of chalcopyrite led to non-homogeneous product distribution. Raman spectroscopy was able to identify the products formed on the mineral surfacein situ while leaching was occurring. Raman mapping and imaging demonstrated a surface distribution of the products which can be related to composition and structure changes of the mineral surface. The surface formed on chalcopyrite after anodic oxidation at 0.570 V vs. Ag/AgCl in 0.1 mol dm-3 HCl undergoes laser-induced transformation.

Jan 1, 2003

By Caisa Samuelsson, Taishi Matsushita, Hannes Holmgren, Sina Mostaghel

"Rönnskär Smelter of Boliden Mineral AB, Sweden, is a large end-processor of secondary raw materials and waste, including electronic scrap. Electronic scrap may introduce various impurities to the smelter's flow-sheet, among which alumina is a common and significant one. This article summarizes the results of an ongoing research at Luleä University of Technology, Sweden, to study the influences of alumina on different properties of slag from the zinc fuming process at Rönnskär smelter. A combination of different experimental techniques and thermodynamic calculations have been used to investigate properties such as density, surface tension, effective thermal diffusivity, viscosity, and melting/leaching behaviors. Results show that the addition of alumina to this slag increases the degree of polymerization of the melt, and physical properties vary correspondingly. Mineralogy of the semi-rapidly solidified samples is also changed due to alumina addition. A correlation between mineralogy and leaching behavior can be observed.IntroductionBoliden's Rönnskär Smelter is a base- and precious-metals producer located in north of Sweden. Its main products are copper, zinc clinker, lead, gold, and silver. Sulphuric acid, liquid sulphuric dioxide and iron sand (granulated slag) are some of its main by-products. In order to optimize the overall outcome of the process, different refining units are integrated in the smelter's flow-sheet (Figure 1). Copper concentrates and fluxing materials (mainly silica sand) are charged to the process. The produced matte is sent to the converter and the generated slag is charged to the fuming furnace, where it is treated by reducing gases to produce zinc clinker. The converter's slag is charged to the electric furnace, while the fumed slag is tapped into the settling furnace for further cleaning, where matte, slag and speiss (residual metals) are separated. The matte from the settling furnace is also sent to the converters; its speiss is sold to external customers; and its slag is water granulated and sold as construction material, which is known as iron sand."

Jan 1, 2012

By Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"In this paper, we describe the current status and research progress on the utilization of typical industrial solid wastes in China. We propose a creative method called “eco-utilizing wastes” with an aim of both integration and increment but without second-time waste and pollution, in terms of the characteristics of typical industrial solid wastes, such as titanium-bearing blast furnace slag, high-silicon iron tailing and boron-enriched slag as well as oil shale.Situation of Typical Industrial Solid Wastes in ChinaThough mineral resources in China are abundant, most of these are low grade ores. Moreover, the distribution of mineral resources is asymmetric, which causes the increase of cost and decrease of the economic benefit. Over-exploitation of mineral resources results in a large number of solid wastes. The accumulation of solid wastes not only means the waste of valuable resources, but also causes environment deterioration. There exist some problems in the current practice of the disposal of industrial solid waste, such as only emphasizing the final results and causing new pollution and waste [1]. So the research and development of a high value-added method has a high practical relevance to our nation. Based on the present status and research progress of industrial solid wastes in China, a creative new idea and method for eco-utilization of solid wastes is proposed in this paper."

Jan 1, 2012

By Kouichi Nakano

Austenitic stainless steel, which includes nickel for stabilizing austenitic structure, is used for various purposes, for example, for structural material, corrosion-resistant material, biomaterial etc. Nickel is set as one of the rare metals and economizing on nickel as the natural resources is required. On the other hand, nickel is one of the metals that cause metallic allergy frequently. Therefore, high nitrogen stainless steel, where nitrogen stabilizes austenitic structure instead of nickel, has been developed in Japan and some of the foreign countries for the above reason. When high nitrogen stainless steel is fused and bonded, dissolved nitrogen is released to the atmospheric area, and some of the material properties will change. In this study, we bonded high nitrogen stainless steel by stud welding process, which is able to bond at short time, and we evaluate joint performance. We have got some interesting results from the other tests and examinations.

Jan 1, 2016

By K. Sanjay

Factorial optimisation technique has been used to develop regression equations at different time intervals for extraction of manganese from precipitated manganese oxide/hydroxide in sulphuric acid using charcoal as the reductant. The three parameters chosen for a 23 full factorial design were : acid concentration, amount of carbon and temperature. The regression equations were used to predict >> 90% extractions as well as kinetic data.

Jan 1, 1996

By H. Y. Sohn, M. K. McCarter, Bradley C. Paul

"A computer model was constructed for bacterial leaching of the major sulfides found in porphyry deposits, including bornite, chalcocite, chalcopyrite, covellite, cubanite, enargite, native copper, pyrite, and pyrrhotite. The model incorporates equations for the sulfide minerals dispersed in the rock matrix. Leaching occurs by reactions with ferric ion diffusing into the rock fragment: Ferrous ion is resenerated to ferric with oxygen by bacteria at a temperature dependent rate. The model keeps track of the net acid generated, oxygen consumed by the bacterial oxidation of ferrous ion, heat generated, jarosite and hematite precipitated, and copper leached. The model was used to predict the rate of copper recovery, heat generation and oxygen demand for a variety of run-of-mine sized porphyry ores. These results were used in the design of a ventilation system and the economic analysis of a modified in situ extraction method that may be cost competitive with conventional copper production involving open pit mining.IntroductionA study was undertaken at the University of Utah to evaluate the technological and economic feasibility of mining copper by a method referred to as Flood Drain Leach Cell (FDLC) mining. Cells 60 by 75 meters in plan and 70 meters in height are created throughout the ore body by a modified Vertical Retreat Mining technique that includes the removal of 25% swell material. The swell material is leached in finger dumps on the surface while the cells underground are bulkheaded, flooded, drained, and artificially aerated to promote bacterial ferric sulfate leaching. Solutions are cycled through several cells to reach pregnant grade of 1 gram copper per liter of solution. These solutions are then fed to an underground solvent extraction plant and then a surface electrowinning tankhouse."

Jan 1, 1988

By D. E. Larson

The U. S. Bureau of Mines has developed a image analysis methodology to correlate the energy consumed during the grinding of an ore to the mineral liberation achieved. Energy consumption values are obtained using a laboratory-scale ball mill equipped with a torque sensor, and an automated image analyzer is used to determine the liberation present in ground products. By combining liberation information with energy consumption data an appraisal can be made of the energy required to liberate the mineral(s) of interest. Results of tests performed on a complex sulfide material determined the effects of grind duration on the liberation achieved and the energy efficiency.

Jan 1, 1995

By A. A. Trickett

In the treatment of gases from pyrometallurgical processes prior to acid manufacture, volatile components, sulphur trioxide and particulates ,are removed in wet gas cleantng systems. In the process a weak acid stream is generated, typically less than 10% H2S04, contaminated with volatiles such as arsenic, fluoride and chloride', plus metallic particulates. This effluent stream has, in the past, been disposed of in a variety of different ways. As a result of changing environmental legislation, smelters are having to review alternative solutions for treating this effluent stream. This paper' will describe a process developed by Chemetics which treats this effluent stream, generating a small dry metal sulphate stream plus a clean acid stream which is suitable for recycling to the smelter acid plant.

Jan 1, 1992

By Oleg Ostrovski

Industrial pyrometallurgical processes in ferrous metallurgy are based on carbothermal reduction of metal oxides. Carbothermal reduction of stable oxides requires high temperatures. Lowtemperature reduction can be implemented by using methane-containing gas with high carbon activity, or by carbothermal reduction under reduced CO partial pressure. Under standard conditions, methane is thermodynamically unstable above 550 °C and decomposes to solid carbon and hydrogen. At appropriate CH4/H2 ratio and temperature, carbon activity in the methane-containing gas phase can be well above unity relative to graphite, which provides favorable thermodynamic conditions for reduction. To maintain these conditions, the rate of reduction/carburisation should be higher than the rate of solid carbon deposition. The paper discusses reduction of pure manganese and chromium oxides at relatively low temperatures, and constraints in reduction of manganese and chromium ores. Reduction of metal oxides by carbon in hydrogen as an alternative use of natural gas is also discussed.

Jan 1, 2014

By L. J. Davies

Refractories usage in furnaces for the extraction of nickel from both sulphides and lateritic ores is reviewed. Recent changes in raw materials and basic brick qualities developed to meet the increasing demands of existing and new processes are outlined. Examples of used brick examinations to establish mechanisms of wear are given. The importance of physical and chemical properties are discussed. The use of simulative laboratory testing to aid in refractories development and selection is described.

Jan 1, 1988

By Albert F. S. Seboukens

A 5;6 MVA pyrometallurgical demonstration-scale pilot plant was commissioned at Mintek, South Africa, in 1994, using lead blast-furnace slag and coke as raw materials. The plant included a.d.c. power. supply, two plasma-arc furnaces' and an ISP lead-splash condenser. Slags containing typically 12 per cent zinc oxide and 3 per cent lead oxide are produced as a waste during the smelting of lead in a blast furnace. These slags are a potential: resource for the recovery of lead and zinc. During 1994, about 600 t of lead blast-furnace, slag was proceced through the pilot plant using the Enviroplas process. Zinc and lead oxides were reduced to their respective metals, volatilized, and collected in an. ISP lead splash condenser. Prime Western grade zinc and slags disposable in accordance with current US legislation, were produced. Zinc condensation efficiencies of about 80 per cent were achieved.

Jan 1, 1995

By Xuefeng She, Qingguo Xue, Jingsong Wang, Guang Wang

Iron nugget could be got at high temperature using carbon composite pellet, which were made by the mixture of ludwigite and reducing agent. In order to reduce sulfur content in the nugget, effects of additives on the desulfurization was investigated. The sulfur content could be dramatically reduced if the CaO was introduced into the pellet and the sulfur content was as low as 0.046wt.% when the addition amount of CaO was 5wt.%. However, the melting separation of pellet became increasingly difficult and the yield of iron decreased when CaO content in the pellet gradually increased. Na2CO3 could also reduce the sulfur content in the iron nugget and made the iron and slag separate difficultly as well. When 6wt.% Na2CO3 was added into the pellet, the pellet was too difficult to melt separation and the sulfur content in the nugget was 0.084wt.%, which didn’t meet the need of steel making.

Jan 1, 2015

By J. P. Bellot

During the non-ferrous metal processing, the melting step under vacuum or under rarefied gas leads to volatile metal losses. It is the case of the metallurgical processing of the nickel-based, titanium-based or zirconium-based alloys where the evaporation losses don't allow a sufficient control of the alloy chemical composition. A theoretical approach has been carried out involving both a continuum description in the liquid phase and a molecular approach in the rarefied gas phase. The finite volume method is used in order to solve the coupled transport equationsin the liquid, whereas the Boltzmann equation is modelled by using a Monte Carlo method. At the liquid metal and metallic vapor interface, the volatilization and recondensation fluxes link up the two calculations. Simulation results are given for the melting and refining of reactive metals such as titanium alloys where the control of the chemical composition remains a major difficulty. The validity of the kinetic Langmuir's law is discussed for different operating conditions.

Jan 1, 1996

By Na Wang, Chao Du, Yao Zhang Shuqiang Jiao, Hongmin Zhu

"Na2NbAlO5 was synthesized using Nb2O5 and NaAlO2 as raw materials in molten NaCl-CaCl2 by a solid reaction. With an addition of sodium into the melts, Na2NbAlO5 was subsequently reduced to form NbAl3 intermetallic compound with a particle size of 50-300nm.IntroductionThe intermetallic compounds of niobium aluminides have been a subject of research interests as high temperature materials because of their properties such as high melting temperature, large specific strength at elevated temperature, good resistance to high temperature oxidation, low density and large ductility [1,2]. They are applicable for turbine blades in aircraft engines and stationary gas turbines [3,4].In recent years, the methods of powder synthesis have been widely discussed. There are many methods to synthesis intermetallic compounds such as conventional melting and solidification [5], powder metallurgy [6,7], reaction sintering [8] and reaction sintering with prior mechanical activation [9,10]. There is a prominent weakness in such methods that they use metal to produce intermetallic compounds by the means of diffusion reaction. Although the metal can diffusion sufficiently, it is still hard to avoid maldistribution of the constituents which impairs the properties of the materials."

Jan 1, 2012

By John R. FitzPatrick

The separation and purification of uranium from either nitric acid or hydrochloric acid media tan be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated' to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps. We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (100-gram) flow experiments using depleted uranium, were done after the small-scale evaluation Of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments' involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and' amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process. Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail.

Jan 1, 1996

By C. E. Dodson

Conventionally hydrometallurgical recovery processes from sulphide concentrates include roasting, leaching, precipitation, impurity removal and zinc electrowinning. The use of the novel (yet commercially proven in other mineral and metallurgical industries) TORBED process reactor for the flash roasting of sulphides will be proposed. The potential advantages in its application will be discussed including very fine particle processing capability, lower cost smaller roasters, waste minimization, improved leaching efficiency and overall process simplification.

Jan 1, 1999

By H. K. Fouad, L. A. Guirguis

The starting mill strip solution· for this study· is an ammonium uranyl tricarbonate solution of pH 8.2 containing 20g uranium/liter, after a DEPA/TOPO extraction process from sulfuric acid leaching liquor. To the first portion of the concentrated acidified strip solution, hydrofuoric acid is added at 95°C in reduced condition to obtain uranium tetrafluoride. The second portion of the uranyl carbonate strip is subjected to a precipitation step by admixing 0.3 volume of non-solvent precipitating agent such as acetone per volume of uranium. ·Uranium oxide (U30 8) is obtained from this precipitate by calcination for half an hour at 800°C in air. The third portion of the strip solution is neutralized to a pH 6.5 with sulfuric acid to precipitate iron and other contaminants. The solution is further acidified to a pH 1.85 with continuous air bubbling to remove CO2, followed by H2Ch precipitation at pH 3.5 to obtain uranyl peroxide. The latter is reduced by stannous chloride to obtain uranium trioxide dihydrate UO3. 2H20. Identifications, characterization· and purity of these products are carried out by complete chemical analyses, Scanning electron microscope study, tap density determination, X-ray diffraction and infrared spectroscopic investigations. The achieved results agreed well with that of the published data for these nuclear grade purity products.

Jan 1, 2000

By P. Louis

Although cobalt is known and used for its hardness and wear resistance, ductile cobalt can be obtained by electrolysis in chloride solutions, under the following conditions : pH : 1.5 - 2, Co++ : 30 - 60 g/l, current density : 100 - 500 A/m2, temperature 40 - 70°C. No explanation was found for the ductility of the deposit under these conditions. Indeed the ductile P (FCC) cobalt and the hydrogen contents in the cobalt deposits are nearly the same as those obtained in a sulfate media, which gives brittle depo¬sits under equivalent electrolysis conditions. Malleable cobalt sheets can be easily obtained under the proposed conditions which could lead to new applications for cobalt.

Jan 1, 1988

By Thenepalli Thriveni, Ch. Ramakrishna, Yujin Jegal, Ji Whan Ahn, Jyothi Rajesh Kumar

In alumina production or alumina refining, bauxite is converted to alumina (aluminium oxide) The rare-earth elements (REEs) are a group of 17 chemically similar metallic elements (15 lanthanides, including scandium and yttrium). Rare earth elements play a key role in many industrial applications, petroleum refining, clean energy, automobile, electronics, and defense applications. These rare earths are essential to the success of green technologies. China today controls more than 95 percent of the rare-earth supplies and nearly all rare-earth refining and after 2009 year rare earths crisis raises due to China’s export restrictions and growing internal demand for rare earth elements. The extraction of gallium and yttrium from Korean red mud (KC red mud) by selective acid leaching was explored. The recovery of gallium and yttrium from a leach solution of the Korean red mud using solvent extraction was studied. A number of extractants were investigated for the extraction of those mentioned two rare earth elements and also we proposed a flow sheet of rare earth elements respectively. The toxic heavy metals presented in KC red mud were removed by CO2 stabilization.

Jan 1, 2015