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By Hongli Wen, Guangkun Shen, Qiong Deng, Shoujian Huang, Min Gan, Xiaohui Fan

"Due to the low iron grade and high sulfur content, pyrite cinder is difficult to be directly used for iron-making. In this paper, technology of magnetic roasting -grinding and magnetic separation -acid leaching was put forward for reclamation of pyrite cinder. For pyrite cinder of TFe53.51%, S2.20 %, studies showed that good magnetic effect can be achieved at roasting temperature 650~7000, reducing atmosphere CO/(CO + C02) 10~20% and roasting time 10~30 minutes. In separation conditions of grinding size -0.045mm accounting for 96.09% and magnetic field intensity of 1240 GS, iron concentrate of TFe64.81 %, S0.18% and iron recovery rate 91.44% was achieved. Acid leaching was studied to strengthen desulfurization. Results showed that high-quality iron ore concentrate of TFe66.3 l %, S0.10% was obtained under the conditions of hydrochloric acid mass fraction of 5%, pulp density of30%, leaching temperature of70? and leaching time of2 hours.IntroductionPyrite cinder is produced as a by-product of sulfuric acid industry [1] Domestic production is more than 12 million tons every year and occupied area is over 10 million square meters [2,3]. The pyrite cinder outdoor not only pollutes air but also damages surrounding surface [4] It after treatment used for iron-making is an ideal reclamation approach for its rich iron which is commonly 40-60% [5]. But pyrite cinder gets low utilization for its low iron grade and high sulfur content in China [6]. Therefore, comprehensive utilization of pyrite cinder has profound significance to environmental protection and the development of domestic iron and steel industry."

Jan 1, 2013

By Marco Zurco, Claudia M. Mendez, Alicia E. Ares, Carlos E. Schvezov, Carlos M. Rodriguez

"Zinc-Tin alloys were solidified in horizontal form and the obtained results were analyzed. During solidification the distribution of temperatures were measured by using thermocouples located strategically along the length of the samples. From the measured temperatures the following parameters were derived; the local temperature gradient, the cooling rate and the velocities of the liquid and solids fronts. Comparing the structure of the samples and the values of these parameters it was found that the temperature gradient reaches minimum values of as low as - 0.6 °C/cm, and velocities of the fronts of around 0.1 cm/s. In addition, the grain size was measured along the samples. The results are presented and discussed in the frame of the results previously obtained for other alloys.IntroductionGenerally solidification leads to two types of grain morphologies: columnar and equiaxed. The origin of each one has been the subject of numerous theoretical and experimental researches in the field of metallurgy for many years [1-7]. The columnar-to-equiaxed transition, CET, is considered as an object of high technological relevance with respect to the directional solidification of metallic alloys. This structure transition may be sharp or gradual and it has been reported to be dependent on thermal conditions associated with the casting process, including melt convection, heat transfer coefficients at the metal-mold interface, growth rates, thermal gradients, cooling rates, transport of solute, alloy composition, melt superheat, mold temperature, mold design, casting size, casting geometry, and the concentration of nucleating particles. As a consequence, it is critical for industrial applications to understand the physical mechanisms which control this transition during solidification. Many studies highlight the importance of the relative growth of the equiaxed and columnar grains and develop expressions or numerical procedures to describe a criterion for the CET. A number of experimental investigations reported in the literature suggest that the CET occurs when GL in the melt reaches a minimum critical value [5-7]."

Jan 1, 2012

By C. Lupi

Zinc impure solutions as spent electrolytes, leach liquors coming from aqueous treatment of both minerals and solid waste, need to be purified before undergoing the treatment to obtain the final product. Solvent extraction is one of the most selective operations particularly when many metallic ions are present in solution. Zinc pure solutions are frequently obtained using DZEHPA as extractant. In this work an investigation on zinc extraction effectiveness of naftenic acid was carried out. After determining the best diluent and the optimal extractant concentration, the partition coefficient was determined as a function of temperature, equilibrium pH and zinc concentration. Finally same batch tests to determine the equilibrium curves at room temperature on exhausted electrolyte coming from zinc cell were carried out by using naftenic acid, D2EHPA and TBP. The pH giving, for each extractant, the best extraction yield was selected in order to compare the equilibrium curves. Experimental results show that all the examined extractants are very effective in zinc extraction if the process conditions are appropriately selected. In order to avoid an impure solution pre- treatment and to obtain the maximum ertraction yield the appropriate solvent can be chosen.

Jan 1, 1998

By Peter G. Mason

Over the last 15 years numerous Pressure Oxidation and Pressure Leach plants have been installed throughout the world. The technology is no longer regarded with awe and trepidation as plants designed to treat a wide range of feedstocks continue to be successfully brought on line. Important aspects of the design of such plants include feed preparation, slurry pumping, heating and heat recovery, pressure control and let-down, vessel design, safety and provision of associated services.

Jan 1, 1999

By Hai-Xing Fang, Bing Xie, Hong-Yi Li

"In the duplex melting process, chromium forms chromium spinels, the study of which will help to exploit the Hongge ores (rich in chromium) in the Panzhihua-Xichang area in China. Mimicked chromium slag was synthesized. The oxidation and decomposition mechanism of the Fe-Cr spinels contained was studied in a sodium roasting process. The effects of temperature, roasting time, amount of soda added and filling reagents were investigated. The leaching-reduction-precipitation-calcination procedure to extract Cr2CO3 was optimized. The results showed that the optimized roasting temperature was 1000~1020°C with a stoichiometric Na2CO3 addition and without any filling reagents. Roasted materials were leached with distilled water and were filtered to obtain a chromium-containing solution, which was adjusted to pH 1.60-1.80. A reducing reagent, NaHSO3, was added in a stoichiometric ratio and the solution was then adjusted to pH 7.25~8.25. Maximum Cr2O3 precipitation was obtained and the precipitate was calcined at 1050°C for 2h to obtain Cr2Ü3 with recovery rate over 96%.IntroductionChromium is widely applied in the metallurgical industry, in refractory materials and in the chemical industry with its particular properties of hardness, wear-resistance, high temperature resistance and corrosion resistance [1]. There is no free state of chromium in nature and chromite is the main chromium containing mineral [2], China is poor in chromium resources, despite its large demand, and there are few deposits of high grade of chromite ores except in some regions in Tibet and Xinjiang province [1, 4]. Hongge, one of largest titanomagnetite mines in Panzhihua-Xichang area, is a polymetallic deposit mainly containing iron and titanium; it is also associated with various beneficial elements such as chromium, copper, nickel, etc. [3]. As investigated in Reference 3, the chromium reserves of Hongge ores are so large that it is of great importance to study how to extract the chromium from them."

Jan 1, 2012

By Mikiya Tanaka, Mikio Kobayashi, Mansour A. S. A1Ghamdi, Kenji Tatsumi, Yukinori Saiki, Hirotaka Senba

"In order to recover nickel ion in a spent electroless nickel - phosphorus alloy plating bath and, at the same time, to remove impurities such as iron and zinc, the applicability of solvent extraction with LlX84I as the extractant has been investigated using actual spent solution. Although the extraction efficiency of nickel from the spent solution is considerably lower than that from the nickel sulfate-nitrate solution, nickel in the spent solution is selectively extracted with high efficiency at the pH of 6 - 7. The extracted nickel is effectively stripped by sulfuric acid at a pH of less .than· 3. On the basis of these results, a· flowsheet for recovering nickel from the spent solution is proposed Chemical equilibrium calculations of the spent solution has shown that the complex formations of nickel with anions such as lactate and phosphonate ions become predominant in the pH range between 2 and 6. This results in the depression of nickel extraction efficiency from the spent solution as compared with that from the .nickel sulfate-nitrate solution. By combining these aqueous equilibrium calculations with the· extraction model considering the extraction stoichiometry and the aggregation of the extractant in the organic phase, the extraction behavior of nickel is quantitatively predicted.IntroductionElectroless plating is indispensable for the recent advanced industries such as the electronic and mechanical industries. Electroless plating baths are repeatedly used by supplying the metal salts; however, the accumulation of the counter anions of the metal ions, the components formed by the oxidation of the reducing reagents in the plating baths, and the metal ions as impurities dissolved from the surface of the objective materials degrades the· quality of the plating. Thus, the baths are finally treated by a precipitation method to form a large amount of metal sludge, which is disposed in dumping sites. Therefore, from the standpoints of environmental protection and resource preservation, it is highly desired to establish a recycling process of the plating baths with minimum emission. Solvent extraction seems to be one of the 'suitable methods to recover metals from the spent electroless plating baths, because the concentration of the metal ion in the baths is relatively high, which is advantageous to solvent extraction as compared with the ion-exchange and adsorption methods. Some studies about the application of solvent extraction have already been carried out using simulated spe11t electroless plating baths [1-3]."

Jan 1, 2000

By Guo Chen, Xuefeng Liao, Tu Hu, Shengzhou Zhang, Hongying Xia, Jinhui Peng, Libo Zhang

Pine nut shell is as raw material for preparation of high surface area activated carbon (HSAAC) by microwave induced KOH activation. The effects of microwave power, activation duration and KOH/C mass rate (R) on the iodine adsorption capability and activated carbon yield were investigated. Additionally the surface characteristics of HSAAC were characterized by nitrogen adsorption isotherms and SEM. The operating variables were optimized utilizing the response surface methodology and were identified microwave power 738W, activation duration 17 min, and R 4, corresponding to a yield of 46.28 % and an iodine number of 2154 mg/g. The key pore structure parameters of HSAAC such as the Brunauer–Emmett–Teller (BET) surface area and total pore volume were estimated to be 3819 m2/g and 2.09 mL/g, respectively. The findings strongly support the feasibility of microwave heating for preparation of HSAAC from spent pine nut shell by microwave induced KOH activation.

Jan 1, 2016

Physical and chemical methods were investigated to tower thorium levels in Eneabba Ilmenite from the natural levels of 180-500 ppm to give Becher Process synthetic rutile with less than 100 ppm thorium. Chemlcal treatments, but not physical separations were successful. A pilot plant trial of a sodium hydroxide leach (25M NaOH at 75°C and 40 wt% solids for Ih) followed by a sulphuric acid leach (3M H2S04 at 90°C and 60 wt% solids for 211) confirmed that thorium could be removed to below 100 ppm. However, the activity of the ilmenite was not lowered to the same extent

Jan 1, 1996

By Filipe de Menezes Torres, Augusto Pereira de Sa, Itavahn Alves da Silva, Eliana Ferreira Rodrigues, Carlos Antonio da Silva, Varadarajan Seshadri

Top slag eye opening which happens as a result of gas injection is a function of the gas flow rate in addition to other factors such as ladle geometry, porous plug location as well as slag properties. Slag eye opening leads to entrapment of atmospheric nitrogen, oxygen by the steel melt affecting adversely the steel quality. In this work aspects of mixing and eye formation in steel making ladles with inert gas injection have been analyzed through physical and mathematical modeling techniques. Influence of ladle, gas flow rate and distribution and slag properties has been assessed. A correlation for estimating eye opening has been developed. Results from PIV measurements and images of eye opening obtained using a camera have been utilized to validate results from CFD simulation.

Jan 1, 2015

By Minjun Tang, Jianfeng Zhou, Feng Chen, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"Reduction swellability index (Rsn and low temperature reduction disintegration index (RDI) of vanadium-titanium magnetite oxidized pellets are harmful to the processing of ironmaking, for example, causing serious gas permeability, decreased yield, higher coke ratio and more furnace dust. Thus, the improvements of RSI and RDI of vanadium-titanium magnetite oxidized pellets were investigated in this paper, including the pretreatment of raw material, additives of dolomite or boric acid, pellets treated in chloride solution and so on. The results showed that damp milling as pretreatment and boric acid added in pelletizing were conducive to the RSI which decreased 5% and 7% respectively, while they were not efficient enough in improving RDI. Dolomite was efficient in improving RSI, but had negative effect on RDI. There was no evidence to show that RSI and RDI would be improved when pellets were treated in chloride solution. Pursuing this further, the mechanism of those improvements were investigated.IntroductionIn the world, vanadium-titanium magnetite utilization is investigated around how to recover iron, titanium, vanadium, and divided into blast-furnace method and non-blast-furnace method according to respective characteristics. Blast furnace method [1, 2] can recover iron and vanadium effectively, but Ti02 cannot be recycled. Non-blast-furnace methods include rotary kiln-electric furnace method, pre-reduction electric furnace method, reduction- grinding method and sodium vanadium-rotary kiln-electric furnace method and so on. [3-7]Comparing to the Non-blast-furnace method, the method of blast furnace smelting has been put into industrial applications. And it has the following advantages: First of all, effective recycling iron and vanadium; Second, technical problems of high titanium slag in blast furnace smelting; Third, it has mature technology in blast furnace smelting."

Jan 1, 2013

By Atinuke Oladoye, David Esezobor

"Particulate Copper Silicon carbide (Cu-SiCp) composites find application as wear and heat resistant materials in electrical sliding contacts such as in homopolar machines, railway overhead current collector systems where high electrical/thermal conductivity combined with good wear properties is required. However, challenges occur during machining due to the presence of hard reinforcement in the matrix. This may lead to high turnover of tool wear and poor surface finish. The adoption of near-net shape technology to produce such hard-to-machine metal matrix composites and subsequent finish machining with its attendant cost has reported limited success. This paper critically appraises the challenges and opportunities in the improvement of tribological characteristics of particulate Cu-SiC composites and identifies low cost reinforcement material that could be used to improve its tribological characteristics.IntroductionTribology consideration is increasingly becoming a decisive factor in the design and selection of materials for applications involving interacting surfaces in relative motion. The consideration is mainly on the combined effects of friction and lubrication on material's wear integrity and performance amongst other. Annual losses due to tribology in the US industries are estimated at between 1-2% of the Gross National Income [1], in Russia it is about 1-4% of the GDP [2]. Thus, the attributes of tribology has become imperative in modem machinery especially those applications involving sliding and rolling surfaces, and electrical contacts [3- 8].These are readily found in homopolar machines, internal combustion engines, aircraft engines, gears, cams, seals and railway overhead current collector systems [9-12]. In these systems, the dissipation of frictional heat arising from the interacting surfaces as quickly as possible imposes constraints on the choice of materials for such application to prevent softening, plastic and shear flow and the transfer of metal as wear debris onto the interacting surfaces. If these possibilities occur, system performance is compromised and premature failure may result. Materials for these systems are expected to possess high electrical and thermal conductivities, low coefficient of thermal expansion, good corrosion resistance and high melting point [3-8, 13]."

Jan 1, 2011

By Carl C. Nesbitt

A study was conducted to examine the treatment of metal-bearing effluents by precipitating the metals as sulfides and simultaneously collecting the particles by flotation. The precipitant was hydrogen sulfide gas which was introduced into a bench-scale column cell with air. The study included experiments of various flotation reagents and column configurations in treating solutions containing dissolved copper, lead, mercury, iron, zinc and cadmium. An acidic laboratory waste from a local copper operation was used to test the column with a solution containing several metals and arsenic. Precipitates were observed to form at the gas/liquid interface when the gas mixtures were rich in H2S. Copper, mercury, lead, and cadmium were precipitated from solution as sulfides to concentrations near detection limits. The flotation of these precipitates was enhanced with small amounts of S-7151 promoter from American Cyanamide Company and Dowfroth 1263 mixed with the feed. The recovery of the precipitates in this manner produced a smaller volume slurry which was easier to dewatering than a slurry produced by conventional precipitation techniques. The low pH and high oxidation-reduction potential in the cell from H2S addition was not conducive to form precipitates of iron, zinc or arsenic. However, these ions were precipitated as sulfides by raising the pH of the column discharge.

Jan 1, 1994

By Kurt A. M. Westerlund

The basic function of primary gas handling downstream non-ferrous pyro-metallurgical processes is cooling hot sticky gases to treatable temperature levels (e.g. entering ESP). That means managing efficient the critical gaseous components from a molten via a sticky to a solid phase. The article outlines the modem gas cooling methods combined with efficient heat recovery. Examples of the alternative use of recovered steam energy are outlined; as e.g. drying of concentrate and power generation. The heat transfer impact of the insulating dust is called fouling and circumstances causing fouling are described. Modem cooling surface design and cleaning techniques to keep fouling in reasonable limits are described. Leakage- and false air ingress into the gas handling lines often limits smelting capacity. The objective is generally to minimize the infiltration of air but it still takes place at open interfaces (e.g. at reactor hood, feed port). Leakage air at furnace roofs for example can be reduced to a minimum by adopting the pressure gas sealing used at present In-Bath-Lance furnaces. Modernization and optimization methods to de-bottleneck existing waste heat boiler gas cooling capacity by highly efficient surface cleaning systems and false air avoiding (e.g. bundle roof boxes, dust discharge) are detailed described.

Jan 1, 1999

By H. Itou, J. M. Toguri, T. Takasu

"Marangoni convection has a large effect on materials processing since it remarkably enhances heat and mass transport near a free interface. To have a better understanding of the behavior of Marangoni convection in molten salts, observation and calculation of the thermal convection in a column held between a pair of Pt disks (2mm in diameter) fixed to hot thermocouples, were carried out.Calculated flow patterns and absolute values of fluid velocity agreed well with the observed results. When the temperatures of both disks were set equal and the height of liquid column was 2.4mm, four vortexes were generated on the longitudinal plane with a typical velocity of 15mm/s . From the calculated isothermal lines, the behavior of the enhanced heat transport was obvious; fluid heated at the disks was conveyed to the free surface and the cooled fluid at the surface was conveyed to the inner region. Increase in the height of column and/or increase in the absolute value of applied temperature difference lead to increase in fluid velocity lineally in this calculation range.IntroductionIn the processing of many materials, fluid flow of melts has a large effect on refining capabilities and on the characteristics of the produced material. Marangoni convection is generated when a spatial gradient of interfacial tension exists on the free interface due to differences in temperature and/or concentration. This promotes heat and mass transfer locally near the interface.For example, Marangoni convection which are created following the dissolution of interfacially active materials, increases the local corrosion rate of refractories (1-3). In absorption and discharge of oxygen and/or nitrogen in a molten metal, the effective reaction rate of the gas components through the gas-liquid interface increases (4-7). Also in crystal growth, the distribution of defects and impurities in the crystal is affected and this can alter its quality (8-11 ). The temperature distribution is also affected and can greatly change the productivity. For these reasons, the effectiveness of Marangoni convection in refining should be quantitatively clarified and its control should be better understood."

Jan 1, 1997

By Claudia Gasparrini

Uranium occurs in a variety of minerals, the more common primary ones of which are uraninite-pitchblende, coffinite and a group known as the complex multiple oxides. Identification and description of the uranium-bearing and associated minerals in ore samples may give a preliminary indication of the potential economic importance of the deposit and may also suggest initial approaches to metal extraction. The present paper reviews the common uranium minerals, describes their manner of occurrence and compares the types of deposits with which they are associated. Methods and techniques for their identification are described and their leaching characteristics discussed.

Jan 1, 1981

By A. R. Laplante

Recent developments in gold metallurgy are used to illustrate how the interface between gravity recovery and hydrometallurgy has evolved in recent years. Of particular interest is the use of gravity recovery to produce high-grade concentrates that can be subjected to intensive cyanidation. It is expected that a growing proportion of gold production, possibly close to 50% in certain countries, will follow this route. Other examples of the interaction between gravity recovery and cyanidation are also provided. Implications for new and renewed research directions are discussed.

Jan 1, 2003

By W. Riekehof

The paper explains required practice and equipment for capturing airborne fumes and particulates in hot-dip zinc galvanizing plants. An economic and technical comparison of enclosure and tank rim suction options is presented. The paper also compares the performance of various filter media in filtering fumes, to determine the effect of changes in flux as well as changes in filter finishlcoating methods. This includes a recommendation for how to achieve the best result with respect to pressure loss and cleaning behavior of the filter.

Jan 1, 1992

By D. G. Hattingh, A Els-Botes

"Considerable information is available on the factors influencing the iron-zinc reaction rate at 450° C of low carbon steels, in comparison there is a scarcity _of similar fundamental information of spheroidal graphite irons. This can be attributed to the more complex microstructure and ferrous alloy chemical analysis of spheroidal graphite irons. Hot-dip galvanizers have identified the complexity in controlling and predicting the thickness of the galvanized coating formed on commercial cast irons, which has serious financial implications for both the galvanizer and customer.Commercial hot-dip galvanizing has been in use for over 160 years and yet an elementary understanding of the dynamics associated with the hot-dip galvanizing of spheroidal graphite cast iron is still insufficient. To allow the. process to become a modem surface engineering technology, the fundamental aspects of the process must be thoroughly understood.When a clean iron or steel article is dipped into the molten zinc, zinc initially solidifies around the steel or iron. As heat is transferred to the article form the bath, this initial solidified zinc layer remelts and a series of iron-zinc alloy is formed by the reaction of the zinc with the surface of the article; on removal from the bath, some of the molten zinc is taken out on top of the alloy layers. At normal galvanizing temperature (450 °C), the reaction between iron and zinc is usually parabolic with time. The rate of reaction is rapid at first but then slows down and the coating thickness does not increase greatly if the article is immersed in the bath for longer times(1)."

Jan 1, 2000

By Antoine Allanore, Luis A. Ortiz, Donald R. Sadoway

"The steelmaking industry has drastically reduced its energy consumption in the last fifty years, and today’s technologies are considered to operate at their optimal efficiency with respect to energy needs. To cope with new constraints related to greenhouse gas (GHG) emissions, a change of paradigm is necessary. One of the promising technologies that could be deployed to help reach CO2 mitigation targets relies on the intensive use of electricity: molten oxide electrolysis (MOE). This paper presents the key process parameters that need to be tuned to address the practical needs for both high productivity in a steelmaking reactor and for an energy efficient process. Herein we show that contrary to common perception, the electrolysis process for ironmaking requires less energy than today’s chemical reduction route. Furthermore, we prove that most of the energy that must be provided to operate the electrolytic iron production cell is thermal energy which is readily generated by joule heating during electrolysis due to large currents being passed through the electrolyte. The energy consumption of the electrolysis cell is therefore shown to be highly dependent on the cell configuration and the chemistry of the electrolyte. As a consequence, the CO2-impact of the technology strongly depends on both the power production mode and the technological choices for design of the process, including cell configuration. Surprisingly enough, even when the electricity generation is not carbon-free, MOE still appears to be viable from the perspective of reducing GHG emissions providing sound reactor design considerations are made.IntroductionIn the context of greenhouse gas (GHG) emissions mitigation, the steelmaking industry is considering several techniques that could sustain the efforts and progress achieved by this sector in the last decades [1]. A recent report [2] on potential routes for low-CO2 steelmaking highlighted for all techniques both the strong dependency of CO2 emissions on electric power production mode and the need for a decrease in energy consumption per tonne of steel. Incited to innovate with respect to this last criterion, the steel industry considers electrolysis to be a promising technological solution, and in particular the molten oxide electrolysis (MOE) process. This process conducts electrolysis in a mixture of oxides that dissolve the iron oxide feed, which by the action of electric current is decomposed into liquid iron and oxygen gas. The opportunity for reduction in energy consumption during steelmaking by MOE is commonly attributed to the “direct” pathway from iron oxide to liquid metal offered by the use of a molten oxide melt and operation at a temperature above the melting point of iron, ideally 1600°C, to provide enough superheat for tapping the molten iron product:"

Jan 1, 2011

By Tiejun Chun, Jian Pan, Deqing Zhu, Zhiyong Ruan

"In this paper, the desulfuration of pyrite cinder pellets was carried out. Phase analysis shows that most sulfur of pyrite cinder exists in the form of elementary sulfur. Most sulfur was removed in preheating stage. 81.25% sulfur was removed and the average SO2 concentration of exhaust gas was 1365ppm when the pellets were preheated at 950oC for 9 min. The final product, assaying 62.42wt%Fe and 0.02wt%S content at 96.88% desulfuration was achieved under the conditions of preheating at 950? for 9 min and roasting at 1200? for 15 min, which can be used as the burden for blast furnace.IntroductionPyrite cinder, as a subsidiary product of sulfuric acid production by roasting of pyrite ores, was solid waste in sulfuric acid enterprises. According to the statistics, the annual production of pyrite cinder is about 15 million tons in China. Besides, there is lots of pyrite cinder deposited for many years [1-3]. The pyrite cinder consumed in the cement and other industries as auxiliary additives only accounts for less 30% of its total discharge and the left is stored in waste pond, occupying much land and polluting environment in China [4-5]. Moreover, pyrite cinder contains iron between 30-63% which can be utilized as a cheap raw material for ironmaking by sintering or pelletizing processes, which can not only prevent pollution but also provide cheap raw materials for ironmaking [6-7]. However, compared to traditional iron ore concentrate, pyrite cinder possesses higher sulfur content."

Jan 1, 2012