Search Documents

By Hanlu Xie, Liang Yu, Ping Wang, Yuanchi Dong

"The leaching process is the first step when recycling BF slag as raw material for some other products. While studying the kinetics of the BF slag leaching process, a fractal phenomenon was found, which indicated some interesting mechanism in the process. The result suggested a new understanding of the leaching process in detail which useful for the industrial applicationIntroductionTypical composition (wt. %) of blast furnace slag varied in a pretty wide range: SiO2 30–40, Al2O3 10–20, CaO 30–40, MgO 5–10.The ground granulated slag is commonly used as base of roadway (mixed with natural inert for paving, soil stabilization, etc.) or one of the resources of Portland cements because of its good hydraulic activity [1]. To recycle the slag economically, the selective recovery of some components of the slag may be considered. As main components exist in the slag, silica [2, 3 and 4] and alumina [4] recovery was first considered.While recovering of silica from the slag, silica gels are recovered selectively from the leaching solution deriving from the treatment of the slag with waste sulfuric acid. After separation of the exhausted solid of leaching, the silica gel is precipitated from the solution at pH 3.2. Although the silica gels obtained by this procedure contain many impurities and need some more work afterward, it is the first and important step for the process.In the prior work [5], silica extraction using blast furnace slag had been investigated, focused on the pH value of selectively silica extraction. In the present work, kinetics of the leaching process was focused. It is important to design an economical process.ExperimentalThe composition of the slag and the calcined gels has been determined by a LINK860 (Oxford Instruments, Oak Ridge, TN) energy dispersive spectrometer (EDS) in conjunction with a CAMBRIDGE S250-M2 (Cambridge Instrument Ltd., Cambridge, U.K.) scanning electron microscope(SEM). The leaching of slag and the precipitation of silica gels have been conducted at atmospheric pressure in a stirred reactor placed at temperature controlled by a heated water bath."

Jan 1, 2008

By Laurentiu Nastac

"An advanced casting simulation-based optimization approach was applied in this study to assist in the improvement of the mold design of aerospace components made of A3 56 alloy. By using this approach, mold filling and solidification related defects (including macro-shrinkage and shrinkage porosity) were significantly minimized and hence it helped in cost reduction, performance enhancement and quality assurance of complex A3 56 cast parts.An experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and shrinkage porosities were performed using A3 5 6 plates cast in fiiran-silica sand molds using the Prometal's Rapid Casting Technology (RCT) - mold printing technology. Correlations between Niyama values and the pore percentage were also developed. Thus, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macro-shrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A3 56 casting components.IntroductionThis paper describes the process modeling approach used in the development of the mold design technology used to produce assist in the improvement of the mold design of aerospace components made of A356 alloy. Nova Flow&Solid™ software [3] was applied in this study. This casting simulation software was previously validated for several alloys including Ti, steel and superalloys [1-4]. The objective of this paper is to calibrate and validate the simulation software for A356 alloy sand mold castings. For this purpose, an experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and microshrinkage (e.g., shrinkage porosities) were performed using A356 plates cast in fiiran-silica sand molds using the Prometal Rapid Casting Technology (RCT) mold printing technology. The details of the RCT technology are shown in Fig. 1 [5]. Prometal's RCT technology is used for rapid production of sand molds and cores directly from CAD files. The RCT technology relies upon ink jet printer technology to selectively bind the grains of sand to create three-dimensional sand molds and cores. Mold filling and solidification modeling as well as stress analysis are typically performed to properly design the casting and the rig system of each prototype component."

Jan 1, 2012

By P. L. Sibrell

The U.S. Bureau of Mines has tested cyanide leaching for recovery of palladium (Pd) from spent petroleum processing catalysts. Three different catalyst samples were supplied by a spent-catalyst processor. These catalysts consisted of a zeolite base and contained 0.4 to 0.7 pct Pd. During alkaline cyanide leaching, the catalysts exhibited ion-exchange properties due to their zeolite matrices. Hydrogen ions were released from the zeolite in exchange for sodium ions in solution, resulting in a significant decrease in solution pH. This could present a safety hazard because of the potential for release of toxic hydrogen cyanide gas. A pretreatment .step where the catalysts were contacted with a 1.0M sodium hydroxide solution was found to prevent the pH shift from occurring. Following the sodium hydroxide pretreatment, two stages of leaching at 160 °C with solution containing 1 pct sodium cyanide and 0.1M sodium hydroxide gave at least 75 and up to 95 pct Pd recovery. The Pd was quantitatively recovered from the leach solution by thermal decomposition in an autoclave at 250 °C for 1 h. The Pd content of the precipitate was over 50 pct. Thermal decomposition also decreased the total cyanide content of the barren solution to less than 0.2 mg/L. The catalyst leach residues passed the Federal Toxicity Characteristic Leaching Procedure and the California Waste Extraction Test, indicating that landfill disposal of the leach residues would be acceptable.

Jan 1, 1995

By Michael A. Eamon

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

Jan 1, 1991

By J. K. Brimacombe, I. V. Samarasekera, B. G. Thomas

"Mathematical models have been developed for the processing of static cast steel ingots and are app1ied to investigate the mechanisms for the formation of panel cracks. Panel cracking is an intermittent but persistent defect that causes affected steel ingots to be scrapped. A two-dimensional, finite-element, heat-transfer model was formulated and employed to calculate the temperature distribution in both large and small steel ingots during the various processing stages from initial casting to the start of rolling, including solidification, cooling in the mold and in air, reheating in the soaking pit, and subsequent air cooling. The stress state in the ingot arising from the calculated temperature variations was then determined. This involved the development of a transient, elasto-visco-plastic, finite element, thermal stress model, including the effects of phase transformation volume changes and kinetics creep, and temperature-dependent, mechanical properties. The results of the mathematical model predictions of temperature and stress were then used to determine the mechanisms and to suggest solutions for two different types of panel crack formation. Mid-face panel cracks apparently form during air cooling when the mid-face surface temperature is between the Arl and 500~C. Off-corner panel cracks appear to initiate internally during the early stages of reheating but do not propagate to the surface until much later. IntroductionPanel crack formation in static-cast steel ingots is a defect that has been plaguing the steel industry for several decades. Although the problem is intermittent, it is also serious since affected ingots must be scrapped. Panel cracks are manifested as two distinct types of cracking problems. ""Mid-face"" panel cracks are found exclusively in small, 2 to 6 ton, medium carbon steel (0.3 to 0.7% C) ingots and usually exhibit a single, continuous, longitudinal crack down the center of one of the ingot faces as shown in Fig. l (l). ""Off-corner"" panel cracks often form roughly oval, discontinuous crack patterns on the wide faces of large, 20 to 30 ton ingots as seen in Fig. 2 (2). They affect only low carbon steels (0. l to 0.2% C) with high manganese content. Both defects affect only aluminum-treated steels and are caused by a combination of intermediate temperature ductility loss involving aluminum-nitride precipitation and thermal stress generation. The ductility problem has received a good deal of attention which was the subject of a recent review (3). The present study was undertaken to investigate the thermal stress aspects of the problem through the development of mathematical models of heat transfer and stress generation in static-cast steel ingots. The ultimate objective was to elucidate the mechanisms of formation for both types of panel crack and to evaluate possible solutions to the problem."

Jan 1, 1986

By Gabriel A. Torma

This paper provides infonnation on selected technologies available for remediation of metal contaminated soils and industrial effluent solutions. Because some of the industrial sites are contaminated with organics (solvents, gasolines and oils), an effort has been made to introduce the most frequently used cost-effective cleanup methods, such as "bioventing" and "composting." The microorganisms involved in these processes are capable of degrading organic soil contaminants to environmentally harmless compounds: water and carbon dioxide. Heavy metals and radionuclides contaminated mining and industrial sites can be remediated by using adapted heap and dump leaching technologies, which can be chemical in nature or bio-assisted. The importance of volume reduction by physical separation is discussed. A special attention is devoted to the remediation of soils by leaching (soil washing) to remove heavy metal contaminants, such as chromium, lead, nickel and cadmium. Furthermore, the applicability of biosorption technology in the remediation of heavy metals and radionuclides contaminated industrial waste waters and acidic mining effluent solutions was indicated.

Jan 1, 1996

By Rey B. Marquez

This paper introduces and outlines the implementation of Reliability Centered Maintenance (RCM) at Phelps Dodge Hidalgo Inc. By using a disciplined approach to the everyday maintenance functions, a proactive strategy is being developed which "raises the bar" for plant maintenance. The main objectives are: integration of Operations and Maintenance partnerships, transformation of maintenance practices from a reactive to proactive mode through the introduction of a progressive Predictive/Preventive Maintenance program (PDM/PM) paradigm changes, increased management support of maintenance functions, introduction of new indices and root cause analysis, updated; training, and definition of RCM components. RCM is the vehicle being utilized to reach the higher level of equipment availability and utilization. However, the ultimate goal is to venture beyond RCM and into the new frontier of Total Maintenance Management (TMM).

Jan 1, 1998

By G. T. Lapidus

One of Society’s major concerns with hydrometallurgical processing is the large amount of water that is quintessential to its nature. This is especially troubling in arid areas, where the population struggles to procure potable water for their daily needs. For that reason, it has become our responsibility to conceive, design and implement processing schemes that not only use as little water as possible, but recycle streams within the plant itself and minimize waste that exits its perimeter. With this in mind, the conference will center on the importance of selecting the appropriate chemical systems and integrating material balances to avoid reagent overkill and to detect impurity accumulation. The three “R’s” (reuse, recycle and recovery) of aqueous solutions within the processes are emphasized. Examples of processes for the recovery of lead, copper, precious and PG metals from minerals and waste materials will be presented.

By U. M. Mutnti

In order to meet the stringent market requirements for high purity cobalt, ZCCM commissioned the VIR plant in December 1982. The plant comprises a 4.1 tonne/heat vacuum induction furnace with a rated annual capacity of 2,500 MT of barstock. In the VIR furnace, molten cobalt is held under vacuum at 1600°C resulting in the removal of more volatile impurity elements by distillation. Operations todate have demonstrated that Pb, Zn and Cd have good distillation rates in excess of 95%, leading to cobalt containing 1 ppm or less of the above elements. Removal of other impurities such as Se, Bi is about 65% with the finished product still assaying around 1 ppm of each of these elements. Vacuum refining of cobalt offers an economic route for producing higher grades of cobalt from the type of concentrates and treatment processes available within ZCCM. The consistency of VIR cobalt quality has been confirmed by ZCCM and some of its alloy customers.

Jan 1, 1988

By I. S. Blair

The Mufulira smelter (1, 2,' 3, 4,) is one of three smelters situated on the Zambian Copperbelt to treat concentrates and other intermediate products produced in the area. Two mining companies, Roan Consolidated Mines Limited (RCM) and Nchanga Consolidated Copper Mines Limited (NCCM) each have 51% Zambia Government participation. RCM operates two smelters, one at its Mufulira Division and the other at its Luanshya Dl vision. NCCM operates one smelter at its Rokana Division (5). The Mufulira smelter was commissioned in 1937 with two reverberatory furnaces and four converters. The final product, blister copper, was cast from a holding furnace. In 1952 two anode furnaces and a common casting wheel were installed to feed a new and adjacent electrolytic refinery. In 1956 the smelter was extended to accommodate increasing production from the new Chibuluma mine and expansion at Mufulira mine. A third reverberatory furnace, a fifth converter and duplicate anode processing and casting facility were added. The Copperbelt smelters suffered a loss of production potential when higher ash content coals were used in reverberatory smelting furnaces from 1966 onwards. This, and the planned production increases from Mufulira and other RCM mines, indicated a smelting shortfall of 55,000 tonnes of copper a year in the combined capacity of the RCM smelters.

Jan 1, 1976

By R. S. Krarner

Fly ash, a by-product of coal burning power plants, poses a major problem for the utility industry since most fly ash must be landfilled. These quantities may represent as much as 20% of the total material going into landfills. A major problem with fly ash utilization is that although the ash consists of useable components, ash composition can vary depending on the types of coal burned and plant operating conditions. Ash is first characterized using SEM, image analysis, and chemical methods. Processing techniques were developed to separate ash into various components including cenospheres, magnetic spheres, carbon, and clean ash. These products are again evaluated for various utilizations before being used to produce valuable products such as mullite, activated carbon, fillers in plastics, and concrete.

Jan 1, 1994

By Sandra M. Stash

An integrated copper production complex includes mining, milling and smelting facilities which are usually at or near a common site, and sized to complement one another in capacity. There may also be an electrolytic retlnery serving the complex, but not always totally dedicated to its production. Mines and mills without co-owned smelters are not usually considered integrated. The first marketable product of an integrated complex is blister, or in some cases electrolytically refined copper. The nature of integrated operation brings together all of the environmental issues associated with copper production, but currently operating and newly planned facilities are required to anticipate these issues and meet stringent regulations. Older complexes, however, may have legacies of 50 or more years of operation unencumbered by current levels of environmental strictures: nevertheless, they must be remediated. Using examples from closure and remediation of the mining and mineral processing facilities in the Upper Clark Fork River Basin of Montana, the authors review some of the problems encountered since CERCLA's1 enactment in 1980, and the solutions to those problems, bearing in mind that not all of the problems and solutions were technical. Much has been written about the mines of Butte -the "Richest Hill on Earth" as it was known in its day and the mills, smelters and refineries they spawned. These facilities comprised an archetype of the integrated copper complex: from ore to metal in facilities serving and depending on one another. Many great stories of technological innovations and business triumphs have been told about Butte and Anaconda's mining history and the place The Anaconda Company occupies in that history. However, relatively little has been written about the final days: 25 years during which the once-great complex was closed, and the remnants of past glories were remediated after nearly a century of operation. This paper offers some insights from the real world affecting similar complexes still operating, and, hopefully, lessons for others just starting down the path to final closure.

Jan 1, 2003

By Zhanjun Wang, Yongqi Sun, Mei Zhang, Zuotai Zhang, Min Guo

The role of fluorine on the viscous and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-(CaF2) slags were explored using the rotating cylinder method, non-isothermal differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the viscosity slightly decreased with increasing CaF2 content. It was also found that CaF2 addition can promote the primary phase transformed from MgFe2O4 spinel to Ca3(PO4)F, which was beneficial to the enrichment of phosphorus. Additionally, the structure of the slags explained by X-ray photoelectron spectroscopy (XPS) and magic angular spinning nuclear magnetic resonance (MAS-NMR) were further analyzed, which was well in accordance with the above analysis.

Jan 1, 2016

By Jiangtao Li, Zhongwei Zhao, Xingyu Chen, Xuheng Liu

The method of ultrasonic-assisted leaching was used to extract vanadium from the stone coal, with alkali as leaching reagent. The effects of ultrasonic power, concentration of alkali, reaction temperature, liquid-solid ratio and reaction time were investigated, respectively. The optimal ultrasonic leaching condition for vanadium extraction is as follows: ultrasonic power 230W, concentration of alkali 5%, liquid-solid ratio 3:1, reaction temperature 90℃ and reaction time 1h. The leaching rate of vanadium reaches 76.4% under the optimal condition, which is 12.2% higher than that of non-ultrasonic leaching. The reason on enhancing the leaching rate of vanadium by ultrasonic leaching was discussed. It is indicated that the ultrasonic cavitation can increase the surface area of mineral, which is beneficial to facilitate the reaction rate. Keywords: stone coal; vanadium; alkaline leaching; ultrasonic

Jan 1, 2014

By H. Kamarudin

The behaviour of cassiterite-sulphosuccinamate flotation system was examined in the light of zeta potentials measured by micro-electrophoresis method. It was observed that sulphosuccinamate substantially affects the zeta potentials of cassiterite, lowering its i.e.p. to pH 2.5 and indicating a specific adsorption and/or chemical interaction. The optimum concentration for flotation, as seen in micro-flotation tests, was found to be associated with the most effective lowering of the zeta potentials, the optimum pH being 3.0. The effect of cations in the pulp was examined for the presence of ferrous, ferric, aluminium and lead ions. The ions ferric and aluminium were observed to create an intense effect of increasing the potentials to positive side, possibly due to adsorption of cation hydroxy complexes, as indicated by their respective species distribution diagrams.

Jan 1, 1994

By S. Ferlay

"The main purpose of the ZIMA VAL project (Label EUREKA EU1367 and LIFE ENV/F/000278) is to demonstrate industrial scale recovery and recycling of the main components of used dry batteries (zinc, manganese dioxide, mercury, and stainless steel) into high added value products. The originality of the ZIMA VAL process resides in:1- the use of hydrometallurgy2- alkaline treatment implementation (highly selective) for zinc and mercury3- electrochemical recovery of high quality products.4- the recycling of all the battery components (zinc, mercury, manganese dioxide, stainless steel) ·5- low operating and investment costs.The process consists of physical classification, mechanical dismantling, hydrometallurgy and electrochemistry. The purpose of the demonstration plant in FALAISE (Calvados - France) is to define the technical and technological parameters of an industrial unit for the treatment of 2400 tonnes per year of used batteries."

Jan 1, 2000

By Jens Kristen Laursen

In 1999, Molymex S.A. de C.V. (Molymex), Mexico. (a company wholly owned by Molibdenos y Metales S.A. (Molymet), Chile) decided to install the Haldor Topsrae Wet gas Sulphuric Aicd (WSA) process for cleaning of the 4-5% SO2 off-gas from their molybdenum sulphide master in Cumpas, Mexico to produce sulphuric acid. The decision to install a WSA plant was based on the successful operation of a WSA plant at Molymet's molybdenum sulphide roaster in Santiago, Chile since 1993. This paper describes the process layout of the Cumpas plant, the operating experience of the Santiago plant, and the, differences in. process design between the two plants. It will furthermore summarise the applications of the WSA process for other roasting plants and smelters within the non-ferrous. metals industry producing metals such as copper, lead, and molybdenum.

Jan 1, 2002

By Jong-Oh Jo1

Thermodynamics of Ti, N and O in liquid iron was studied in order to establish a data base for the prediction of TiN and TiOx formation in liquid stainless steels containing various alloying elements including Cr, Ni and Si as a function of temperature. The interaction parameters of these elements on Ti and N were determined using the metal-nitride-gas equilibration technique. The TiN stability diagram for a commercial stainless steel grade was constructed from the measured thermodynamic parameters, and its validity was confirmed experimentally. The interaction parameters between Ti and O, and the equilibrium constants for Ti deoxidation reactions for the formation of Ti2O3 and Ti3O5 were also determined by the equilibration of the melts with those oxides identified by the XRD and the EPMA analyses.

Jan 1, 2006

By Fatma Arslan

Alada (Kayseri-Turkey) lead-zinc sulfide-oxide ores contain 10.17% Pb, 10.98 %Zn, 164 g/t Cd and 57 g/t Ag. During the laboratory scale flotation tests of these ores, it was found that almost all zinc was remained in the tailings that contain 12.31% Zn, 1.35%Pb, 198.3 g/t Cd, and 22.3%Fe. Three different methods were studied such as basic (NaOH) leaching, roasting+acidic (H2SO4) leaching and direct acidic (H2SO4) leaching for recovering metals that these tailings contain. In the direct acidic leaching, which gave the best results, dissolution efficiencies of 91.5% zinc, 78.2% cadmium, and 14.3% iron were reached at the optimum leaching conditions while Pb remained in the leach residues and the acid consumption was 422.3 kg/ton of tailings.

Jan 1, 2006

By A. Mejias, M. A. Garcia, G. Diaz

During 1997 and 1998 two successful zinc feasibility studies, Skorpion and Sanyati, were carried out by Tecnicas Reunidas based on the modified ZINCEX® technology. The technical viability of each project was proved during more than 600 h of continuous running in a pilot plant. The Skorpion zinc project would recover 150,000 t SHG Zn/y from an oxidized zinc ore of a Namibian mine. The economical study showed that the plant would have the lowest production costs in the world. The Sanyati zinc project would treat a bleed from an existing copper refinery in Zimbabwe to recover 5,000 t SHG Zn/y. In the first case the electrowinning cellhouse was supplied by Union Miniere and in the second by Tecnicas Reunidas. This article highlights the pilot plant results and the advantages of the proposed process over conventional zinc production practices.

Jan 1, 2000