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By Charles H. Rawlins

Reported is work done on processing of steel mill effluents in the areas of dewatering and separation. Much of the waste from these operations is in the form of sludges from scrubbers, in which the primary constituent is iron oxide. Recycling of the sludge&apos;s magnetic fraction has become economically attractive in order to reduce the overall volume placed in landfills. The objective of this research is to determine the effectiveness of combining magnetic and cyclonic forces, to recover iron oxide particles from waste water stream, while decreasing the volume to be disposed. Three different size hydrocyclones, operating within the field of a quadripole magnet, were tested using varying feed pulp densities of magnetite, magnetite/dolomite, blast furnace (BF), and basic oxygen furnace (BOF) slurries. In the first three cases, the percentage of magnetics recovered increased to greater than 95%. The limiting operational factors are; high pulp density for small cyclones, which can cause flow blockage within the magnet field, and extremely fine particle sizes (<2 microns), which cannot be recovered. The results indicate this technique can remove virtually all the magnetic particles from some steel effluents to a 40-50% weight percent solids pulp, on an in line continuous basis.

Jan 1, 1994

By Yotamu Hara, Animesh Jha

"High Curie temperature and large magnetic anisotropy make cobalt an important magnetic material for power engineering applications of magnets operating above ambient. It is also an essential constituent of modem lithium - cobalt oxide batteries, without which modem electronic gadgets will be functionless. Both these applications of cobalt save energy and reduce C02 emission. Ironically, however the production of cobalt from copper and nickel smelting in the world remains one of the least energy efficient process. The paper analyzes the energy balance, material and process chemistry of overall cobalt recovery and the waste generated, which entail the process limitations. We discuss a novel approach for the reduction of sulphide minerals with CaS04, permitting better separation of metals from slag and generating higher concentrations of S02. Such an approach may seem to be an alternative energy efficient option for processing and further purification of cobalt in metallic form. The results are discussed in the context of process thermodynamics and reaction kinetics for Coalloy production.IntroductionCopper sulphides bearing minerals are predominantly associated with iron and cobalt sulphides minerals. Carrollite (CuC02S4) is a mineral that has both copper and cobalt sulphides [1,2], which may also contain FeS, by substituting either Cu2+ or Co2+ ions in mineral lattice. On smelting copper - cobalt - iron sulphide concentrates, some parts of the cobalt often partition to matte at preferentially low oxygen potential by forming eventually an alloy phase with copper, however a significant fraction is often lost into an oxide slag rich in iron and silica. The slag heaps accumulated in the Copperbelt region in Zambia from last 60 years of mineral processing and metal extraction is reported to be 0.3 to 2.6 wt% of cobalt element, which is high [3]. Cobalt is also available in smaller concentrations in the copper smelting and converter slag, as reported in the investigations on the recycling of such slag materials using leaching with ammonium salt [4], iron chloride [5], and sulphuric acid [6], and solvent extraction [7].The recovery of cobalt from slag, irrespective of the techniques researched so far, does not seem energy efficient because the molten slag at 1300°C is quenched by losing thermal and chemical energy. The quenched slag is again reheated to above room temperature for leaching and above liquidus for carbothermic reduction of residual cobalt oxide. For example, in Mintek DC arc smelting [3], 80% of cobalt and 95% nickel are recovered by expending 600 kW per tonne. Assuming that the mineral carrollite is the starting phase, the univariant calculations for the Co-Ca-Si-S-0, Fe-Ca-Si-S-0, and Co-C-Si-S-0 systems are shown in Figure la, lb, and le, respectively at 1573 K."

Jan 1, 2012

By Roberto Parra

The classic criteria of the preparation of the charge for the smelting of copper concentrates in at flash furnace considers the mass and energy balance from the chemical and mineralogy composition of the concentrates. The operation parameters fixed with this method don&apos;t assure the stability of the operation and the critical problems of the slag quality and dust formation occurs very often. This paper presents the results of a laboratory test that allows the prediction of the behavior of concentrates blends in the view of the minimization of the dust formation and the magnetite control in the slag. The combustion of different copper concentrates and blends were done in a drop tube furnace The results show that the magnetite and dust formation don&apos;t have a linear behavior with the weight proportion of the blend and some optimal blends of 2 or 3 types of concentrates can be identified. From the reasonable hypothesis that the qualitative behavior of blends in the drop tube represents the real behavior in the burner, the preparation of the charge with this approach could help to solve those operational problems.

Jan 1, 2003

By Ivan Imris

The iron production has generated many tonnes of very fine residues with high concentration of iron. In addition, during the recycling of galvanised steel scrap in the steel making processes the zinc and lead are largely concentrated in the dust. These kinds of dusts are usually dumped beside the metallurgical plants and cause environmental problems. Therefore the metal recovery from the metallurgical residues has become a major interest not only from the viewpoint of metals recycling but mainly from the viewpoint of environmental land protection. The thermodynamic analyses and laboratory experiments suggested that the metals could be recovered from metallurgical wastes by reduction roasting and by plasma smelting processes. The iron rich pellets with very high metallization may be obtained from metallurgical wastes by the reduction roasting and the inert slag and pig iron could be produced by plasma smelting processes. In both cases the iron rich products are suitable for the steel production. During the reduction roasting or plasma smelting the high volatile zinc and lead metals were removed and enriched as a secondary dust, Zn-Pb concentrate, which is suitable for processing in zinc and lead smelters. Suggested processes are commercially feasible and environmentally friendly without any solid or liquid waste.

Jan 1, 2003

By Mostafa O. El-Bealy

"To estimate the interdendritic cracking tendency in casting processes, a new model for interdendritic cracking criteria has been proposed. The model combines a concept of the alloying element effect on the interdendritic strain generation and therefore on the susceptibility of interdendritic cracking phenomena. A susceptibility of interdendritic cracking is modeled by using El-Bealy's interdendritic cracking susceptibility function ""BJCSF' and the opening displacement between the dendrites ""EIA "". These concepts are modeled based on the previous experimental observations and ElBealy' approach. The model is implemented numerically for a one-dimensional model problem with some similarities to the casting of steel. The variation of some key parameters that are known to influence the frequency and severity of the interdendritic cracking is then studied.I. INTRODUCTIONInterdendritic cracking ""hot tearing"" commonly encountered in both ferrous and nonferrous castings (1,2]. It is generally believed that interdendritic cracks start to nucleate and develop in the interdendritic strain region within the mushy zone [l-5]. The interdendritic strain region is then definitely coherent, but continuous films of liquid still exit (4,5]. This distinguishes interdendritic cracks from cold cracks forming during the casting process after complete solidification (6,7].Much effort has been put into the understanding of the interdendritic cracking phenomena, and several theories have been proposed. Fellini [8] stated that interdendritic crack ""hot tear"" will result if the material is subjected to too high of accumulated strain within so called vulnerable part of the solidification interval. Kinosita et. al. [9] and Campbell (10] also emphasized the role of tensile stresses in the forming of interdendritic cracks. Most interdendritic cracks criteria simply consider the size of solidification interval, stating that solidification range is associated with a lager interdendritic cracking susceptibility than a short range. Clyne and Davies (11] formulated a more refined such criteria based upon the time spent in different regimes of the solidification interval. They defined a vulnerable region in which thin continuous films of interdendritic liquid exist, and the permeability is low. When thermal strains are induced in this region, the film is not able to sustain the stresses, and an interdendritic crack will form."

Jan 1, 2001

By Lixin Qian, Tiejun Chun, Yifan Wang, Huan Wang, Hongming Long, Zhengwei Yu

To solve the problem that the sintered liquid phase fluidity characteristic of low silica (w(SiO2) < 3 wt%) and high silica (w(SiO2) > 7 wt%)) iron ores were different from actual sintering production with using the common method based on w(CaO)/w(SiO2), a new improved method based on n(Fe2O3)/n(CaO) was proposed. The differences between two methods for iron ore fluidity detection were studied. The results show that when the common method is used to detect the liquid phase fluidity, as the content of SiO2 increased from 2.12 to 11.68 wt%, the amount of CaO addition augmented from 7.88 to 32.65 wt% and the corresponding fluidity index changed from 0 to 5.68. The fluidity index has a linearly positive correlation with the content of SiO2. The improved method could significantly reduce the effect of the change of CaO addition on the fluidity characteristic of iron ore which caused by the difference of SiO2.

Mar 1, 2018

By Bin Xu, Qian Li, Xiaoliang Liu, Yongbin Yang, Hongwei Li, Tao Jiang, Yan Zhang

The direct cyanide leaching rate of gold from a gold calcine was only 71.33%, due to 19.51% of gold being encapsulated in the iron oxides. To enhance the cyanide leaching of gold, the calcine was pretreated with acid or alkali washing. The mechanisms by which acid and alkali pretreatment improve gold leaching from calcine are investigated through chemical analysis, XRD, and SEM-EDS characterization.

Mar 1, 2017

By Sebastian Schmuck, Petrico von Schweinichen, Dieter Senk, Mohammad Peymandar

"At Department of Ferrous Metallurgy of the RWTH Aachen University in Germany steels in the system Fe-Mn-C(-Al) are investigated and produced in the framework of the SFB 761 ""steel-ab initio"". A new world of steel grades leads to special challenges regarding the production and recycling at the end-of-life cycle of product. In order to recycle high manganese steel alloys the EAF has to be chosen preferentially. A good slag practice is necessary avoiding loss of manganese content during melting in the EAF. This paper investigates on the reaction kinetics at the interface of slag and steel containing Mn (17-22 wt.-%) and up to 3 wt.-% Al. The effect of changes in the composition of slag and steel on the interfacial reaction kinetics is studied. The thermodynamic software FactSage™ is utilized to calculate the composition of slag and steel at equilibrium.IntroductionTRIP and TWIP steels are highly alloyed steels which show superior strength and ductility when compared to standard carbon steel and stainless steel alloys. These TRIP- and TWIPsteel grades contain typically 15-30 wt.-% manganese, 0-4 wt.-% silicon and aluminum, and up to 1 wt.-% carbon. Steels containing 18-28 wt.-% manganese and 0.7-1.2 wt.-% carbon together with aluminum addition from 3 to 12 wt. -% and without silicon refer to TRIPLEX high manganese steel alloys. These alloys combine high strength at even large ductility [ 1-4]. At the Department of Ferrous Metallurgy (IEHK) of the RWTH Aachen University in Germany, steels in the system Fe-Mn-C(-Al) is under investigation at the collaborative research center, SFB 761 ""Steel-ab initio"". In this project, high manganese alloyed TRIP and TWIP steels are in the focus.The mechanical properties such as high strength and high ductility make this kind of steels perfect candidates for impact absorption applications in auto body such as vehicle doors and bumpers [2, 5]. With increasing the use of TRIP-, TWIP- and TRIPLEX-steels more high manganese steel scraps will be available at the end of life cycle of products, which need to develop the technologies and metallurgical processes to recovery of high manganese steel. A new steel grade brings new challenges in recycling. In order to recycle high manganese steel scraps the electric arc furnaces (EAF) have to be chosen preferentially [1]. Nevertheless it's not easy to prevent the manganese loss during the process in EAF. During the oxygen refining of high manganese molten steel in EAF the manganese content decreases strongly by oxidation and vaporization, which is affected by slag composition, slag properties such as basicity and viscosity, slag weight as well as melt temperature [6-8]."

Jan 1, 2014

By Onuralp Yucel, Ahmet Turan, Murat Alkan, Hasan Ozer

SHS (Self-propagating High-temperature Synthesis) is one of the important methods to synthesize B4C powders. The process contains the reaction of boron oxide powders (B2O3) with magnesium reducing agent and carbon black carburizer. SHS products are leached in HCl media to purify synthesized B4C powders in the following step. In the present study, effects of various functional additives (KClO3, KHSO4, MgSO4.7H2O, NaCl, MgO and Na2SO4) in the SHS stage were carried out. Various proportions of the additives were mixed with the initial SHS charge mixtures. Two different molar ratios were employed in the initial SHS mixtures as 1:3:0.8 B2O3:Mg:C and 1:2.5:0.8 B2O3:Mg:C. After the SHS step, HCl leaching process was applied to the SHS products. Filter cakes were dried and characterized by using X-Ray Diffraction Spectroscopy, BET and chemical analysis techniques.

Jan 1, 2015

By Jr. Robison

"Aluminothermic (""thermite"") smelting became commercial with the development of tonnage aluminum, and prospered producing metals and alloys with higher cleanliness, consistency and elemental control than competing technologies. We explore the scope of thermite smelting, and metallothermic smelting in general; the thermochemistry of the process; and its advantages and limitations as applied to industrial production. We review currently-produced products of thermite smelting in several forms and a wide range of heat sizes. As these products serve several industries, we relate the demands of those industries to the requirements imposed on the thermite process, leading to process dynamics and mechanisms to control/alter those dynamics. We review ways to lower the process costs by altering process stoichiometry, using other energy sources and utilizing less costly materials while considering effects on product quality and customer requirements. Finally, we examine overall emissions control and waste disposal.IntroductionAluminothermic smelting is the reduction of various oxides by aluminum to produce metals or alloys with varying levels of residual aluminum. One of the earliest uses of the process was the production of liquid iron to weld railroad rails, later modified in ""thermite grenades"" used to ""spike"" artillery pieces in World War II. Then during the 50's, 60's and 70's the growth of jet aircraft created a demand for new superalloys and titanium alloys, both requiring master alloys for efficient production. Aluminothermic smelting grew with the aerospace industry and with the expansion of microalloyed steels. It is very much a niche industry, dependent on the specialized demands of the specialty steel, superalloy and titanium industries. In this paper we introduce the characteristics of aluminothermic smelting, the scope of smelting operations, the markets served, and the environmental aspects of the process, as seen through the eyes of a company using aluminothermic smelting for over fifty years"

Jan 1, 2012

By Ivo André

Sorption of copper ions from aqueous solutions by dried biomass of the aquatic plant Potamogeton luscens was studied at laboratory scale. The aquatic plant was collected in water resources in Brazil, washed, dried at 60°C and ground in a bladed mixer. Sorption experiments were conducted in agitated flasks and in a packed bed column. Maximum copper removal was obtained between pH 5.0 and 6.6 when copper was present in the ionic form Cu&apos;. Sorption followed the Langmuir isotherm with saturation attained at 35 mg/g. Free energy of sorption was found, to be of the order of -25 kJ/mol. Sorption kinetics data were better described by a second order reaction and rate constants were calculated in 0.030 1/(min.mg) for - 4.0 mm particles and 0.081 1/(min.mg) for - 0.59 mm particles. Removal of metal ions in a packed bed column showed that Potamogeton luscens biomass can be used in several sorption/dessorption cycles. After sorbent saturation, copper ions can be recovered from the loaded biomass by elution-with H2SO4, solution. Main mechanism responsible for heavy metal uptake was found to be ion exchange. Results are discussed in terms of the surface properties of the biomaterial, solution chemistry of copper ions and thermodynamics parameters.

Jan 1, 1995

By R. E. Brewer

Pilot scale flotation tests were conducted with a l?ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pet of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated. The tailings were first water leached at approximately 60? C, and the water-leached tailings, containing approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH&apos; and sodium sulfide addition on gold flotation recovery and redox potentials were examined. Maximum gold flotation recovery, 36 pct, was achieved at pH 8,5 with a sodium sulfide addition of 0.18 Ib/st. Overall gold recovery by leaching and flotation was in the range of 70 to 80 pet.

Jan 1, 1989

The effect of change in slag composition upon metal losses to the slag and the relationship between slag composition and slag matte separation was investigated at 1400°C. The synthetic slags containing CaO, MgO, SiO2,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Precious Group Metals) from the Merensky Reef of South Africa. The matte with a grade of 9.3% Cu and 16.0% Ni was a typical electric furnace product. The results indicated that the Cu and Ni solubility in the slag increases with the increase of the basicity ratio and CaO and MgO contents of the slag. At constant CaO/MgO ratios the rise in basicity decreases the metal losses. When FeO and SiO2 contents of the slag are kept constant, the substitution of MgO with CaO decreases the metal losses. The relationship between slag composition and matte-slag separation was found to depend primarily on the basicity ratio and the FeO content of the slag. The net effect comes from a strong interaction of the two in such a way that increasing basicity and decreasing FeO contents deteriorate the clean separation of the two phases.

Jan 1, 1994

By Natasa Mitevska

In order to ensure the minimal copper concentration in the reverb furnace slag, the graphical optimization method is used and the optimal slag composition of the reverberatory furnaces No.1 and No.2 in the RTB BOR, Copper Smelter and Refinery (Serbia) is obtained: (Si02) .. 38.0%; (FeO) .. 40.0%; (Fe3O4) = 5.0%; (CaO) = 5.0%; (Al2O3) .. 6.0%. Keywords: Optimization, Reverb Furnace Slag, Graphical Method

Jan 1, 2003

By Stephen R. Brown

Current conditions in the copper market demand that mine and plant operators make budgeted production targets at the lowest possible unit costs. For those companies bringing new production capacity on-line, achieving budgeted production levels as quickly as possible after start-up is vitally important to minimize unit costs and to begin a positive cash flow. Whether the objective is to simply improve unit costs or successfully start-up a new, complex plant, success will be strongly influenced by .the skill levels of the operators :and supervisors. The only way to assure return on plant investment, and to survive during depressed metal prices, is to ensure that plant operators have the knowledge to effectively run the plant. Technology available in computer-based, multimedia training systems, including: interactive animation, videos, voice-overs, schematics, and text can now be used to train operators at their own pace using plant-specific information. Additionally, it has been shown that learning through multimedia provides a higher degree of long term retention than more traditional learning methods.

Jan 1, 1999

By Runsheng Xu, Haiyang Wang, Pengcheng Zhang, Tengfei Song

Semi coke, a byproduct in the chemical industry, is a new fuel for blast furnace injection in China. In this study, semi coke and bitumite were milled into different size, ranged from 0.147mm to under 0.074mm. The content of volatile matter and ash, which affect the combustibility of semi coke, were measured using muffle furnace. The mixture, in which the proportion of coal in different sizes changed, was blend by semi coke and bitumite with different size. Activation energy calculation and the comprehensive combustion characteristic index of all kinds of blends was also discussed. The result obtained by Thermogravimetry –Derivative Thermogravimetry curves indicates that the smaller the size of mixture is, the lower for the characteristic temperature, and the better for its combustibility, Semi coke can be a substitute for anthracite in blast furnace injection.

Jan 1, 2015

By Taegong Ryu

The thermal plasma process has been applied to the preparation of nanosized tungsten carbide (WC1-x). The reduction and carburization of the vaporized chloride by methane-hydrogen mixtures produced nanosized WC1-x powder, with a small amount of WC or W2C phase. The products were characterized using XRD, carbon analyzer, and TEM. The effects of plasma torch power, the flow rate of primary plasma gas (Ar) to generate plasma flame, and the addition of secondary plasma gas (H2) on the product composition were investigated. The tungsten carbide (WC1-x) powder had a particle size less than 30 nm. The powder was treated under hydrogen atmosphere to fully carburize the WC1-x, and W2C phases to WC as well as remove excess carbon in the product. Finally, WC powder with a grain size less than 40 nm was obtained.

Jan 1, 2008

By Larry G. Twidwell, Jannette L. Chorney, Bryce D. Ruffier, Katelyn M. Lyons, Daniel W. Gaede, Ryan J. Foy, Jerome P. Downey

The Army Research Laboratory (ARL) has an interest in the recovery and processing of rare earth elements. At Montana Tech, elevated temperature chlorination of rare earth oxides is presently being investigated as a potential methods leading to the selective separation and recovery of rare earth elements from mineral ores and concentrates. After preliminary evaluation, ytterbium oxide was selected as a representative surrogate material for more extensive chlorination studies. Methods used to determine the conversion and recovery include X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis. These data have been used to establish and confirm process conditions that consistently yield high conversion efficiencies. Based on the promising results, further experimentation is underway to ascertain the metallurgical response of other rare earth oxides and carbonates to the roasting process. The end goal is to create a robust process for industrial application that has greater efficiency and reduced costs as compared to current practice.

Jan 1, 2015

By Chaoying Ni, Dimitry Sediako, Prashant Karandikar, Sean Fudger

Neutron diffraction measurements were performed on steel encapsulated metal matrix composites (MMCs) in order to quantify bulk residual stresses. A coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of several macro hybridized materials systems. Systems consisting of an A36, 304 stainless steel, or Nitronic® 50 stainless steel shell filled with an Al-SiC or Al-Al2O3 metal matrix composite are evaluated in this work. Upon cooling from processing temperatures residual strains are generated due to a CTE mismatch between each of the phases: steel, aluminum, and reinforcement. The analysis shows variation in the measured strain and stress results due to outer steel thickness, difference in CTE between materials, and relative position within the composite.

Mar 1, 2017

By S. A. Davis

In July of 1996, the Kroll process began production again at TIMET&apos;s Henderson, NV, manufacturing facility. This, after being shut down for several years due to low market demand for titanium. Faced with limited pond capacity and increasing costs for water and wastewater disposal and storage; process changes were made to recycle water used to wash Kroll titanium sponge back into the sponge leaching process. This idea was revisited from 1992-93, when three consecutive attempts to recycle water for this application were unsuccessful due to early pump failure. Since it was uncertain why previous attempts failed, a complete understanding of the existing system was first sought. This included reviewing piping and flow diagrams; taking field measurements for all the piping, valves, and fittings; analyzing the wastewater composition; and modeling the fluid dynamics and control of the system. The fluid dynamics of the system were modeled by breaking the piping network up into nodes and applying the Bernoulli equation to each segment. The fluid flowrate control valves were modeled for this purpose also and the models were used to help specify the required processing equipment and control ranges and tolerances. Once the project was completed, an operating procedure was prepared for operation, startup, and shutdown of the washer water recycle system.

Jan 1, 1999