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By Wenbo Luo, Kang Liu, Fusheng Mao, Jilai Xue, Jun Zhu, Chunlei Yang

Extracting alumina from coal fly ash (CFA) is of great interest for both environmental protection and recycling valuable alumina content. In this study, ultrasonic aided leaching process as an effective method was investigated to enhance extracting Al2O3 from CFA via concentrated sulfuric acid sintering. The influence of ultrasonic power and processing time were tested under the conditions as the same as those without ultrasound. It is found that the alumina extraction rate can reach 90.5 % with ultrasound assistance, while the ultrasonic treatment can reduce almost 15 ~ 30 min in leaching time and 5 ~ 10 oC in leaching temperature than those without ultrasonic operation at the same Al2O3 extraction rate. In addition, the ultrasonic can reduce calcium content by 6 ~ 8 % dissolved into the leaching liquid. SEM analysis also shows that the residue particle size with ultrasound is smaller than that without ultrasonic treatment.

Jan 1, 2015

By Mary Cunningham

The EPA and DOE have collaborated on a series of studies to evaluate the effectiveness of treatment technologies at stabilizing bulk elemental mercury and wastes containing high concentrations (i.e., with greater than 260 mglkg total mercury) and multiple forms of mercury. The data from these treatment demonstrations are intended to help EPA to determine if regulatory revisions to allow a stabilization alternative for high-mercury subcategory wastes are warranted. In addition to mercury-contaminated wastes, the disposal of bulk elemental mercury is of concern because of the excess quantity of mercury in the Defense Logistics Agency (DLA) stockpile, as well as other potential sources of excess elemental mercury. The studies evaluated the effectiveness of several technologies at: I) stabilization of mercury in a "hard-to-treat" matrix; and 2) conversion of elemental mercury into a stable waste form for disposal. A surrogate waste was designed for the study on high-mercury wastes, which included an organic form of mercury, elemental mercury, and several mercury salts in an inorganic matrix. The surrogate waste and the bulk elemental mercury were treated by the vendors, and the treated waste forms evaluated for mercury Icachability, using both the TCLP and an automated, constant-pH leaching protocol. Constant pH leaching was conducted at pH 2,4,6,8 10 and 12 for 14 days at each pH. The leaching data demonstrate that the stability of the mercury in three treated waste forms varies widely across the pH range tested. Clearly, the stability of mercury in these treated waste forms will be highly dependant on the disposal conditions. The combination of site-specific disposal conditions and appropriate treatment technology must be considered as decisions are made about disposal of high-mercury wastes.

Jan 1, 2003

By Dengfu Chen, Yunwei Huang, Mujun Long, Kui Lv, Pei Xu, Lin Bai

The surface temperature of continuous casting slab in the secondary cooling zone is a key parameter of production control. However, the accuracy of radiation temperature measurement of high temperature casting slab is greatly affected by the environmental factors, such as water vapor, spray, water film and other participational medias during continuous casting process. In this paper, the radiation characteristics of water vapor and its influences to radiation temperature measurement of continuous casting slab were investigated. Based on the database HITRAN 2004 and the measuring principle of monochrome thermometer & colorimetric thermometer, the measuring errors under different operating infrared spectral wavelength were compared. Results showed that spectral region with wavelength nearby 1.0μm or 1.6μm would be the optimum for high temperature infrared thermometer used under the conditions with moist steam, water spray and water film at the secondary cooling zone in steel continuous casting.

Jan 1, 2016

By Alan Branham

The Mike deposit is a large, low grade, oxide, gold-copper system found at the intersection of two major faults that bound the Carlin Window, Eureka County, Nevada. Disseminated gold occurs within metamorphosed and hydrothermally altered silty limestone (Silurian-Devonian Roberts Mountains Formation), beneath 182 m (600 feet) of barren Tertiary sediments and tuffs. A supergene copper oxide blanket occurs beneath and locally overlaps the lower portion of the gold zone. Decalcification argillization, silicification, and brecciation are superimposed on earlier calcsilicate hornfels and marbles. Altered dikes and sills intrude the gold zone and are locally auriferous.

Jan 1, 1995

By Sergey Komarov, Manuela Diaz, Sano. Masamichi

"Mixing time, bubble behavior and absorption rate of gas injected into a liquid bath through rotary L-shaped lances have been studied by cold models with an effort to improve refining characteristics of metallurgical processes. Two kinds of the rotary lances were tested, namely the single-hole lance and the multi-hole lance. The effects of gas flow rate, bath depth and rotation speed were examined.It is found that when gas is injected through the rotary lances, the mixing intensity and the gas absorption rate are larger than that for the gas injection through stationary lances. The effect of rotation speed decreases as the bath depth and the gas flow rate increase.The multi-hole lance produces much smaller bubbles, which lead to an increase in the volumetric mass transfer coefficient by 3-4 times as compared with the single-hole lance. However, the effect of rotation speed is smaller for the multi-hole lance. The obtained results are explained in terms of the bubble coalescence and fragmentation, the rate of which depends on the departure bubble size and the power supplied to the liquid bath.IntroductionIn recent years, there has been a growing interest in the development of gas injector for metallurgical processes. The majority of the previous work was focused on modification to the injector design to improve mixing and to increase the of chemical reaction rate. These two goals can not be necessarily achieved by the same way. Bottom nozzles and stationary immersed top lances, which have been widely applied to steelmaking processes, are effective for the bath mixing, but have a limit to decrease in the bubble size. This results from a vigorous coalescence occurring between the bubbles when they rise in the molten bath as a bubble swarm.One of the ways to ensure the small bubble size and the effective bath stirring is the gas purging through rotary injectors. A number of studies have been undertaken to improve the refining characteristics by using rotary injectors. All of them are related to aluminum refining. The SNIF equipment (The Spinning Nozzle Inert Flotation) has significantly improved the quality of aluminum products at National Luxemburg Aluminum [1]. Rotary injectors made in the form of a disc have been applied to the Alcoa 622 [2] and the GBF processes [3]. A study of the gas injection by a rotary impeller has been carried out by C. Leroy and G. Pignacelt [4]. All researchers note the significant improvement in removal of sodium, calcium, hydrogen and non-metallic inclusion."

Jan 1, 1996

By Tracey Brommer, Britt Elin Gihleengen, Elsa Olivetti, Randolph Kirchain

"Increased demand resulting from the economic and environmental advantages of recycling secondary materials has constrained secondary material supply. As a result of constrained supply, the conventional strategy to maximize recycled content in an individual aluminum alloy must be expanded to maximizing total recycled content in a given production period. This work compares the performance over a two week period of an actual remelter for two strategies; a sequential charge-by-charge optimization framework and an integrated approach that explicitly incorporates the production schedule. Optimizing across the entire two week production is found to increase recycled content and minimize primary and alloying material additions. It is expected that as the scrap material market continues to be constrained by high demand, longer term batch planning strategies that can optimize material allocation will deliver improved performance.IntroductionIntensifying economic and environmental pressure to incorporate secondary aluminum into products is pushing remelters to explore additional strategies and tools to increase recycled content. Aluminum remelters are exploring alternative sources of secondary materials because of constrained secondary material supply and relatively high primary and secondary material cost [1]. Computational models, such as blending models are a tool that could help industrial remelters mitigate supply and cost challenges and thereby increase recycled content. In particular, computational tools can help manage the incorporation of new raw materials of variable quality. Blending models find many industrial applications and have been explored for over sixty years originating with the classic nut-mix problem dating back to 1950’s [2]. Blending models optimize the raw material input to make a desired product subject to a series of constraints such as product specifications and material availability. Deterministic and linear blending model formulations are presently implemented in some industrial aluminum remelters [3]. The primary reluctance of aluminum remelters against computational model implementation is the incapability of their blending models to reflect the intricacy of industrial remelting conditions [4]. For example, to reduce calculation time, industrial aluminum blending models usually optimize a batch plan for a single alloy and are not formulated to optimize several products simultaneously. Since such a model does not include knowledge of subsequent charges in the optimized batch plan, the resulting batch plans tend to deplete the “cleanest” secondary materials leaving the more uncertain and compositionally challenging materials for later charges. As a result, a remelter may override the calculated batch plan or leave certain scrap materials out of the material input to conserve these materials for alternative products scheduled for later production. This work explores an alternative aluminum charge planning tool that can optimize across an extended production schedule and compares it to a heuristic sequential optimization strategy reflecting an industrial remelter."

Jan 1, 2012

By Germán Richter a

To comply with the chilean air quality regulation requirements, the Hernan Videla Lira Smelter which is a custom smelter having to cope with a wide variety of concentrates, has developed a two-step modernization plan. The main steps are: - A second acid plant of 80,000 Nm3/hr to be operating at the end of 1996. This will increase the sulphur capture from 43% to 701/o in association with the replacement of the Hoboken converter by a second PS-converter to reduce the operation problems resulting from the treating of high garde matte. - Oxygen enrichment, is going to be incorporated in 1998 in the Teniente Converter and PS-converters in association with tuyere injection of dry concentrates, increasing the sulphur capture to 90 - 93% of sulphur inputs. By this program, sulphur emissions will be decreased from 40,000 tpy today to less than 8,000 tpy and in this way to carry out the environmental regulations.

Jan 1, 1996

By Wenying Liu

The effect of aeration on chalcocite heap leaching was studied by analyzing the historical data from two chalcocite heap leach pads located in Chile, one with aeration and the other without aeration. The data showed that the copper leaching kinetics of the aerated heap was greater than that of the unaerated heap within a certain leaching period, after which there was no effect of aeration on the copper leaching kinetics. The total acid consumption per ton of ore processed was higher in the case of aeration, which was supported by the higher pH of the PLS. But the net acid consumption per ton of copper produced was the same in the two cases. Approximately 5% of the total iron added to the unaerated heap was precipitated inside the heap. In contrast, there was no net iron precipitation or generation inside the aerated heap. Bacteria activities were thought to occur even in the unaerated heap, but the extent was much less than in the aerated heap. Given the importance of forced aeration in chalcocite heap bioleaching, mathematical modelling will be applied in the future work to assist the optimization of the aeration system design.

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011

By Thomas Niehoff

Many industrial processes require energy. Energy is required for melting or heating purposes. The heat can be generated by electrical heating or combustion/oxidation of hydrocarbons. Oxygen supports the combustion process. Oxygen is naturally contained in air with about 21 vol.-percent. The use of technical oxygen will allow an increase to the natural oxygen concentration of combustion air. Altering the combustion process by increasing the oxygen content has various effects. These effects are described and analyzed with regard to heat transfer, emissions and energy consumption. Industrial processes requiring oxyfuel are described and discussed regarding energy aspects.

Jan 1, 2008

By Ko-ichiro Ohno

It is recently recognized that the iron reduction and melting as well as the slag separation of a composite of granular iron ore and coal are completed in a very short period of about IO minutes when the composite is rapidly heated up to approximately 1673K. These phenomena are expected to be applied to a new iron-making process. The mechanism of iron ore reduction and iron-slag separation during rapid heating has not yet been revealed and the fundamental research has just started. Carburization of the reduced iron is regarded as one of the most important steps in this process. In the present work, the composite was prepared from four kinds of coal or graphite as a carbon source and electrolytic iron powder as a completely reduced iron ore. The temperature at which the liquid formation and iron carburization occurred was monitored. Direct observation of smelting reduction behavior was made by a confocal laser-scanning microscope combined with the infrared image-heating furnace to clarify the effect of molten ash on iron carburization. It was found that the meltdown temperature of composite became lower as the melting temperature of coal ash decreased. From the observed result, it was presumed that the liquid slag would act as an important media for the carbon transfer from coal to iron. The carburization mechanism during the smelting reduction was estimated as follows. When slag containing iron oxide melted down and contacted carbon, iron oxide in the slag was reduced and the formation of the metallic iron particle as well as the its carburization occurred simultaneously at the slag-carbon interface. Carburized iron particle was carried from slag- carbon to slag-iron interfaces due to the slag convection flow caused by the difference of the interfacial tension between the carbon-slag and iron-slag interfaces. Carburization of reduced iron could proceed with a repeat of the above-mentioned process.

Jan 1, 2003

By Carla Lupi, Alessandro Pescetelli

"Spent lead battery recycling still shows few weak points in the achievement of a 100% recycling of different waste matters and by- products arising from the recycling process. Some of said problems are dealing with aqueous streams outgoing the recycling plant, and more particularly, a) the waste waters discarded from the breaking and separation unit, b) purification of the spent electrolyte drained from waste batteries and upgrade to a quality compatible with full re-use by the batteries’ manufacturers, c) purification of the mother liquors discarded in the sodium sulfate crystallization process so to produce a salt of commercial grade. All of the above listed problems have been satisfactorily overcome applying an electrochemical process that, through different process conditions and parameters, is able to remove the harmful impurities that hinder the successful commercialization of such by products, or, at least, that can avoid heavy and expensive treatment plant and operation.IntroductionAlmost 100% of commercial lead and lead alloys produced by secondary lead plants is recycled to the new lead accumulators manufacture. The other by-products and residues produced through the lead recycling process may be classified into two groups:a) matters reusable in the new accumulators production processb) matters produced as a result of various reagents and additives used in the recycling process, to be sold to different market sectorsQuality and saleability of by-products are significant points for the economics of the secondary lead plant operation, because, if said by-products are not saleable, they are just wastes, so offsetting potential revenues, and, at the same time, adding a heavy burden to operating cost, like disposal cost [1]. When looking at a typical, modern lead scrap batteries recovery cycle, it is quite evident that we are still rather far from dealing with a waste-less technology (fig.1).The group a) includes 3 by-products produced through the breaking process: among those matters the polypropylene only usually reaches a standard quality suitable for sale to lead manufacturing sector or to other sectors as well. The other two by-products, electrolyte and separators, do not still reach, through a viable and effective regeneration process, a quality standard sufficient for their re-use in the lead batteries sector ."

Jan 1, 2008

By E. N. Mounsey

Ausmelt Technology was selected by Bindura Nickel Corporation (BNC) as the basis for a new copper circuit to process nickel plant copper leach residue to blister, anode and finally cathode copper and recover PGM values at the Bindura Smelter Refinery (BSR). The process selected, based on Ausmelt Technology to smelt and convert the residue to matte and blister copper and produce a discard slag, is novel incorporating smelting, converting and slag reduction process steps in a single Ausmelt vessel. The process demands a high quality blister copper product with low levels of arsenic and nickel. This paper reviews the project and the initial operational results to the end of 1997 of the Ausmelt Top Submerged Lancing (TSL) smelter and discusses the implications for the wider TSL converter market.

Jan 1, 1998

By Alexandre Chagnes

The extraction properties of two synthesized cationic exchangers, i.e. bis (1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBoPP) and bis(1,3-diisobutoxypropan- 2-yl) phosphoric acid (IPA), have been studied for the liquid-liquid extraction of Co(II), Ni(II) and Mn(II) contained in 1 M HCl. A comparison of the extraction properties of these extractants diluted in kerosene with Cyanex® 272 shows BiDiBoPP and IPA extract advantageously at lower pH than Cyanex® 272 and a better Co(II)-Mn(II) separation is achieved using BiDiBoPP or IPA than with Cyanex® 272.

By Suman Das, Justin J. Gambone, Rohan Bansal, Ranadip Acharya, Paul Cilino

"This paper focuses on generating a quantitative microstructure prediction model for Scanning Laser Epitaxy (SLE) process based on coupled flow-thermal modeling using Finite Volume method. SLE is a laser-based additive manufacturing process for the deposition of equiaxed, directionally solidified and single-crystal nickel superalloys through the melting of alloy powders onto superalloy substrates. In the current work, the detailed effects of natural and Marangoni convection on the flow field are studied and the results are analyzed in terms of the temperature gradient, vorticity parameter, melt pool dimensions and mushy region extent. The detailed property data of the processed superalloy and the laser scan path are incorporated in the model to predict the microstructure in realistic scenario. An optimization study is carried out to evaluate the critical parameter values at which the columnar-to-equiaxed and the oriented-tomisoriented transition take place. This work is sponsored by the Office of Naval Research through grant N00014-11-1-0670.IntroductionSLE is a laser-based additive manufacturing process for the creation of structures in equiaxed, directionally solidified and single-crystal nickel superalloys through the selective melting and resolidification of superalloy powders. In SLE, a tightly focused laser beam is guided by a highspeed galvanometer scanners allowing for tight control of the amount of energy being applied to the top of the powder bed, as well as the speed at which the melt pool moves across the substrate. Under the proper operating conditions and with sufficient substrate meltback, the solidification microstructure follows the morphology of the underlying substrate, allowing for directional and even SX growth.Several reports on the modeling aspects of laser cladding-based additive manufacturing approaches can be found in the literature. Approaches based on Finite Element Methods (FEM) and Finite Volume Methods (FVM) are employed for the thermal modeling of the system [1, 2]. Gaumann coupled the Columnar to Equiaxed Transition (CET) modeling with the Rosenthal solution in earlier work based on laser cladding [3]. Rappaz et. al. provided a detailed modeling of the microstructure/columnar orientation based on the solidification velocity and crystalline orientation [4]. This approach is based on the selection of the growth direction that closely follows the melt pool normal direction. Later on, substrate orientation is also taken into account [5, 6]."

Jan 1, 2013

By J. T. Stanley

The identification of crystal phases and crystal chemistry can be critical to understanding the mechanisms of waste material interaction with native soils. Understanding these mechanisms can suggest correct methods for remediation and treatment. A program is outlined and examples are given of the development of effective techniques for rapid phase identification of environmental samples using electron microscopy. The program concentrates on the development of integrated object oriented software to aid rapid searching of online databases and rapid simulation of potential crystal diffraction patterns. Examples come from dried sludge taken from a former hard-chrome plating facility.

Jan 1, 1993

By Philippe Henry

"Hydrometal provides an adequate technology to reintroduce otherwise lost metal units into the industrial cycle, thereby saving resources and energy, while keeping the environment cleaner. Two case studies at an integrated hydrometallurgical recycling facility (Hydrométal) in Belgium are discussed: (I) Residual low quality acid and caustic are used in the processing of zinc industry cements to produce copper, nickel, cobalt and zinc concentrates by several consecutive selective leach - precipitation processes.(II) Copper anode slimes are treated and their precious metal contents are recovered. Depending on the composition of the slimes, separate or combined concentrates of copper, bismuth, tellurium/selenium and silver/precious metals can be produced."

Jan 1, 2008

By E. S. Geskin, W. L. Chen, A. Vora

"This paper is concerned with the application of an abrasive waterjet for metal shaping. The waterjet cutting technology uses water compressed to the pressure up to 55,000 psia which is accelerated in a cylindric nozzle. Abrasive particles are then supplied into the water stream and accelerated by the water. Cutting occurs via the interaction between the water-particles stream and a workpiece that causes material erosion at the impingement zone. The mechanism of this interaction enables shaping of practically any material with a minimal effect on the metallurgy of subsurface. The motion of the jet penetrating through a material body is guided by a robotic arm. A waterjet cutter is becoming one of the principal tools for shaping titanium, super-alloys and other hard-to-machine metals and composites. The shaping, resulting from the waterjet cutter, is very similar to laser beam cutting. However, unlike laser processing, there is no damage to the subsurface structure.The presented work discusses the experimental study of cutting of titanium plates. The results of these experiments demonstrate the potential of the abrasive waterjet as a shaping tool. IntroductionOne of the main avenues in the development of metal shaping is the use of high energy beams as cutting tools (1,2). There are a number of advanced beam oriented material removal technologies, such as laser, electron beam, plasma and abrasive waterjet (AWJ) cutting. The advantages of AWJ cutting are well understood and documented (3-14). This technology has the potential of becoming the principal tool for netshaping and netsurfacing of parts. However, the use of AWJ is currently limited to cutting of hard-to-machine materials such as titanium, superalloys, glass, composites, etc. The cost of A W J cutting is much higher and the productivity is much lower than those of the thermal cutting. At the same time abrasive waterjet can be used for shaping any existing technological material from fabrics, plastics, aluminum to glass, composites, and diamonds. The material losses during AWJ shaping are minimal. The roughness and waveness of the surfaces generated during AWJ cutting are substantially less than those of the thermal cutting. Due to the size of the jet cross-section total force exerted by the jet on a workpiece does not exceed 30-50 newtons. This terminates the need in the use of complex fixture for material holding. Low applied forces and low surface temperature prevent the damage of metal subsurface in the course of cutting. The small size of the impingement area will determine the limited width of the kerf. Due to the size of kerf and unidirectional character of the water jet the formation of practically any metal contour is possible."

Jan 1, 1988

By T. Tamagawa

Vaporization of zinc and mixing of zinc vapor with CO-CO2 mixtures were studied experimentally to prepare Zn(g)-CO-CO2-Ar mixtures with desired composition for investigating the condensation behavior and efficiency of zinc vapor. The vaporization rate of zinc was generally constant under given conditions, and could be increased by raising the flow rate of the carrier gas, temperature and vaporization area. The Zn(g)-CO-CO,,-Ar mixtures were quenched by a water-cooling sampling tube for measuring the actual composition of the mixtures in the reactor. The oxidation extent of the zinc vapor in the CO-CO2 mixtures had relation to the CO2/CO ratios and the temperatures. Under current conditions, it was necessary to employ the CO2/CO ratio below 0.125 for mixing the zinc vapor with CO-CO2 mixtures without oxidation. In addition, the appearances and zinc contents of the condensed zinc on the sampling tube were also examined.

Jan 1, 2001

By Stephen C. Britten

An in-situ amperometric slag sensor for measuring the concentration of easily dissociable oxides in slags at temperatures between 1200-1600°C is being developed. The sensor provides the same information as potentiometric sensors while also providing data on the concentration of the transition metal species and the diffision kinetics within the slag. The electrochemical technique utilized in the sensor is similar to methods utilized in aqueous voltammetry.

Jan 1, 1998