Search Documents

By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By Xiao Songwen

Based on the anion coordination polyhedron growth unit theory, the polymorph transformation mechanism of antimony white (Sb2O3) in hydro-process was investigated. The new findings had been verified in the commercial-scale test and it was shown that adding a small amount of tartrate ions was economical and effective for polymorph transformation of antimony white in hydro-process.

Jan 1, 2003

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for S02 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as El Teniente Converter and El Teniente Slag Cleaning Furnace.

Jan 1, 2003

By Jian Li

Corrosion resistance of materials is highly dependent on the microstructure of the specific material. Apart from general corrosion rate measurement using techniques like linear polarization and A.C. impedance, microstructural investigations are frequently needed to identify the root cause of corrosion. Advanced techniques, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have been well integrated into routine characterization studies. Other microscopy techniques, including electron probe micro-analyzer (EPMA), Auger, X-ray photon spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS), can provide detailed chemistry information on corrosion products. In recent years, focused-ion beam (FIB) microscopes have evolved into an important microstructural characterization instrument. In this study, corrosion of rebar encased in concrete was studied in great detail using advanced microscopy techniques. Corrosion product on the rebar surface was identified as ferrous oxide with relatively large crystal size. The morphology of this passive layer was thoroughly analyzed, and its formation mechanism is proposed.

Jan 1, 2009

By Guo Chen, Jin Chen, Jinhui Peng

In this paper, solving common problem of electrostatic precipitator (ESP), which was frequently ruptured of the cathode insulation in the production process were studied. The microwave heating airflow technology was introduced, which takes full advantage of its unique properties, solves the output problem of the high temperature air, achieves purpose of energy conservation, important economic significance and environmental significance. The mathematical models and designing of microwave high-temperature hot air system was calculated. The common forms of heat exchangers and comparative analysis were also introduced. The conditions found to be at the temperature of 240 °C. Under optimum conditions, the microwave heating power was 1482 W. Based on the mention results, this microwave heating method can be applied effectively and efficiently way for the production process of electrostatic precipitator.

Jan 1, 2015

By Patrick R. Taylor

Iron phosphate glasses are promising host matrices for vitrifying actinide rich nuclear wastes materials because of their high solubility of actinide oxides, high chemical durability, and relatively low melting temperatures. An iron phosphate waste form was developed at the University of Missouri-Rolla. The structure and property of the waste form were well characterized by materials techniques. However, to scale the process and advance it to commercial viability, it is necessary to understand the processing parameters, such as the partitioning of waste elements and the viscosity as a function of temperature. Viscosity of 40 Fe203 - 60 P205 mole % iron phosphate melts (prepared with phosphorous pentoxide and ferric oxide) at 1000-1200 C was measured by the rotating-spindle method. It was discovered that this fluid has non-Newtonian behavior. Experiments were performed to study flow properties following the Standard Test methods for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield) Viscometer (ASTM D 2196-86). Samples prepared using ammonium phosphate and ferric oxide showed Newtonian behavior and the temperature dependence of the viscosity was studied over the range of 1000 to 1200 degrees C. The difference in flow behavior between the two fluids was analyzed in terms of preparation conditions and variation in the final composition and phases. The partitioning behavior of waste elements in the iron phosphate glass was studied by melting in a high temperature furnace and JCP analysis. The experimental results show that the solubility of Ce and Sr in phosphate glasses is significantly higher than the solubility associated with borosilicate glasses. This strengthens the conclusion that iron phosphate may be a viable alternative to borosilicate glass for immobilization of high heavy-metal-content wastes and actinide rich wastes.

Jan 1, 2002

Hazardous waste has often very complicated chemical compositions in a variety of physical forms and is normally processed in rotary kiln incinerators. Due to large variations in waste types and difficulties in feed characterization, the complex transport processes within the incinerator are not well understood, and the incineration process meets challenges in a smooth operation, and expects various uncertainties in the process chemistry and emission control. For better understanding of the incineration process, simulation was carried out by using Computational Fluid-dynamics (CFD) to characterize temperature and species distribution in the incinerator. In order to catch certain aspects of thermal and chemical behavior, a novel approach is proposed to represent approximately the waste streams and the subsequent combustion process. Hazardous waste in various forms from an industrial-rotary-kiln waste incinerator is firstly converted to a hydrocarbon-based virtual fuel mixture with approximately the same HIC molar ratio and calorific value. The simulation of the combustion process of the simplified hazardous waste was proceeded with a combustion model. The distribution of temperature and chemical species especially the remaining CO in the system is preliminarily investigated. Distribution of CO concentration, as a good indicator of emission level for the incineration process, could be used to evaluate the emission control. The predicted temperature distribution has been compared with available measurement data from an operating rotary kiln waste incinerator at AVR-Chieme, in the Netherlands. Reasonable agreement has been reached between the measured and predicted temperature data. In the next step, measurement of species distribution in the system is planned to further validate the combustion model.

Jan 1, 2003

By M. C. Ruiz

The leaching behavior of chalcopyrite concentrate in acidic CuC12-NaCI-O2 solutions was investigated. Experiments were conducted under continuos flow of oxygen at atmospheric pressures. The results indicated that among the variables temperature has the largest influence on the dissolution of chalcopyrite in this medium, and high copper extraction can only be obtained at temperatures near the boiling point of the solution. It was also found that the stirring speed did not influence appreciably the dissolution of chalcopyrite. An increase in the oxygen flow rate up to 0.1 1/min increased the copper extraction. The total chloride concentration affects the dissolution of chalcopyrite up to about 4 M. Copper extraction of 93 % was obtained in leaching chalcopyrite of size fraction -400 # Tyler at 105 OC in 2 hours.

Jan 1, 1997

By T. Inami

The chlorine leach of the anode slime was studied in order to improve the treatment process at the Niihama Nickel Refinery. The anode slime originates from the nickel matte electrorefining and, contains 3-5% of nickel as sulfides. A comparative study has been conducted on the filter cake resulting from the sulfur filtration of the molten anode slime. The kinetic factors of the chlorine leach such as temperature, grain size were defined. Under the optimized condition, 70-80% of the nickel is recovered from the slime or filter cake. On the basis of these results, the chlorine leach process for the treatment of anode slime has been established. The leaching plant has been installed and successfully operated since 1986.

Jan 1, 1988

By Jun Zhu, Jilai Xuel, Tao Li

"Coal gangue is industrial waste containing Al2O3 and SiO2 with great recycling and reuse values. This work is aimed at extracting Al2O3 content in the coal gangue by a process of carbonthermal reduction - alkaline leaching. The Al2O3 and SiO2 contents first became a mixture of SiC and Al2O3 in the process of carbonthermal reduction, and then Al2O3 was separated by leaching in NaOH solution, thus producing the sodium aluminate solution for Al(OH)3 precipitation. The products generated at various stages in the process were inspected using XRD and chemical analysis. The effects of parameters such as reduction temperature, carbon ratio, NaOH concentration, leaching time, leaching temperature, stirring speed, etc were investigated in details.IntroductionCoal gangue is an industrial residue resulted from the process of coal mining and washing, accounting for 100 - 150 kg with 1 ton raw coal mined. The existence of coal gangue in large quantities has become a serious problem for environment pollution. On the other hand, the chemical compositions of coal gangue are Si02 and Ah03 primarily. In China, the accumulation storage capacity of Ah03 in coal gangue is not less than 600 million ton at a rough estimate, which should be considered as an abundant second resource [1]. If the alumina can be recycling and reused effectively from coal gangue, it will not only reduce the imperilments caused by coal gangue, but also yield good economic returns.Generally, the processes of extracting Al2O3 from coal gangue can be divided into acid leaching (vitriol or hydrochloric acid) and alkaline leaching (mostly NaOH) [2]. The acid leaching processes have many problems, such as lower leaching ratio, corroding the equipments, recycling the spent acid hardly, etc. The primary matter of alkaline leaching process is silica dissolving with alumina, which brings perplexing desilication process, alumina loss seriously and higher energy consumption."

Jan 1, 2011

By S. P. Jupp

A 2-D coupled thermo-mechanical model was developed to simulate hot tandem rolling of AA5056 aluminum alloy using the commercial finite element software package, ABAQUS The model was used to predict the temperature, strain rate and strain distribution in the strip at any position in the roll bite and was verified through comparisons with literature results in terms of both temperature and strain predictions at the roll bite exit. A sensitivity analysis indicated that model predictions of temperature and strain at the roll bite exit were sensitive to the friction coefficient and moderately sensitive to the heat transfer coefficient for the conditions studied. Microstructure equations taken from the literature were used to make predictions at various positions in the strip. The temperature, strain rate and strain vary dramatically through the thickness of the strip in the roll bite. The sensitivity of the microstructure predictions to these parameters was assessed and it was found that using average values of temperature and strain rate in the roll bite versus exit values significantly influenced the resulting microstructure predictions.

Jan 1, 2001

Acid generation from reactive sulphide mineral tailings has become a major environmental problem in the mining industry. Initiation of chemical and biochemical oxidation reactions of the sulphide mineral leads to acid generation. A novel concept of safe disposal and utilization of reactive fine mill tailings is presented in this paper. The paper also presents the results of a preliminary laboratory experimental .study of the concept. The tailings are agglomerated using portland cement as a binder. The cold bonded agglomerates are encapsulated with other chemical additives to act as acid neutralizers, oxygen and ironoxidizing bactericides., The primary. factors influencing the choice of bacterfoides to inhibit the acid generating bacteria are their costs, toxicity and environmental friendliness. The paper discusses the utilization of agglomerated' products as aggregates for underground backfill, or as gravel for surface land cover.

Jan 1, 1991

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 Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade.

Jan 1, 2006

By Yang Wang, Xiancong Zhao, Hao Bai, Qi Shi, Zhancheng Guo

Linz-Donawitz converter gas (LDG) or basic oxygen steelmaking gas (BOSG) is one of the most important secondary energy sources in iron and steel industry, whose effective use plays a vital role in energy saving and emission reduction. However, the generation of LDG suffers from great fluctuation with respect to the production status of steel making. Therefore, a long term prediction model of LDG generation would be essential in gas system balancing and optimization. In this paper, a long term prediction model for the generation volume of LDG was proposed based on the steelmaking production estimation from Gantt chart and k-means clustering algorithm. Compared with the previous model, this model considered the influence of different steel type on LDG generation. The experimental results of a steel plant demonstrate that the proposed model exhibits high accuracy and can provide an effective guidance for balancing and scheduling of byproduct gases.

Jan 1, 2016

By Mark William Kennedy

"Electric furnaces containing high quantities of slag are applied in many areas of pyrometallurgy, often for smelting or slag cleaning. A variety of ratios or rules of thumb have been employed in the industry for the dimensioning of these vessels, in most cases with no clear technical basis.In this paper, several design guidelines are presented (electrode size, spacing, vessel dimensions, energy intensity, etc.) as an attempt to provide some technical basis for optimal dimensioning.Furnace heat generation is related to side wall copper cooler heat losses, in an attempt to establish a methodical design strategy particularly for minimum electrode to wall spacing for modern furnaces with cooled linings.Issues regarding the true nature of heat production in a slag furnace are discussed with regards to the possible impact on accurate modeling and design.IntroductionSlag furnaces have passed through a number of design 'generations' characterized by increasing energy intensities, improved electrode technologies and advancing development in their physical structure or 'furnace integrity' as shown in Table I f 1]. A 3rd generation furnace using ultra-high-power (UHP) graphite electrodes is shown in Figure 1, as a generic example of the types of physical structures present in modern slag furnace designs [1]."

Jan 1, 2012

By Richard L. Summers

The shaped charge has proven in various military and industrial applications to be an effective penetrator of materials. Upon initiation a detonation wave traverses the explosive billet, collapsing a metallic liner and creating a jetting process. From multiple non-simultaneous flash radiographs of the jet in free flight, the observer can study the collapse, formation, and growth of a shaped charge jet. Digitization of a particulated jet's position and shape from the radiograph into electronic storage files provides the experimentalist with an efficient basis for data reduction. With the aid of a simple personal computer, one can in a matter of minutes generate a wealth of information concerning jet formation after initiation and thus gain insight into the quality of its manufacture, design, and assembly. This paper will in detail explain the methods in place for fully automated data reduction of radiographic films. Methods of computer aided digitization of particulated jets and analysis of physical jet characteristics and performance will be discussed.

Jan 1, 1992

By Steven C. Torma

The present article reviews some of the technologies available for recycling high-energy yield explosives loaded projectiles. These activities lead to reduction of military ammunition stockpiles and their conversion into commercial and industrial applications. The recycling technologies involve dismantling and separation of ammunition components into recyclable metals, plastics, paper and explosive materials. The metal 1 ic components will be sent to smelters, where they will be converted to products that can be used in a variety of industries, such as construction, automotive, housing and so on. Plastics and paper will be recycled and reused. Explosives will be recycled to be used for industrial purposes in the mining industry. Propellants (ammonium nitrate and ammonium perchlorate) can be ground to small particle size and treated to be used in the agricultural industry as fertilizer. In addition, some of the excess explosive material recovered in the demilitarization process may be incinerated to produce energy for steam production for heating purposes, or for production of electricity. Furthermore, this article reviews the developments in the bioremediation of explosive contaminated soils and industrial effluents.

Jan 1, 1994

By V. Gornitz

The Orphan mine uranium deposit, Grand Canyon, Arizona, is a cylindrical collapse-breccia pipe, 70 to 150 m in diameter and 500 m deep. Pipe fill was derived from the Supai Group, Hermit Shale, and the Coconino Sandstone. Uraninite, with Cu, Fe, Pb, Zn and Ni-Co sulfides is concentrated along the pipe boundary ring fracture (annular ring) and within the central porous sandstone matrix. There is some suggestion of vertical and lateral zonation of U with respect to Cu. Reduction of ferric oxide cement from red beds and recrystallization of carbonate, with formation of kaolinite preceded major ore deposition. Early Ni sulfides, arsenides and disseminated pyrite were followed by massive pyrite, and botryoidal uraninite, which in turn was suc-ceeded by Cu, Zn and Pb sulfides. A second, later generation of uraninite was closely intergrown with hematite and base metal sulfides. Oxidation of primary minerals may have been associated with Tertiary regional uplift. The paragenetic sequence closely resembles that of other Grand Canyon breccia pipes, except for the extensive development of the distinctive uraninite-hematite association. Mineral assemblages at the Orphan suggest possible mixing of the metal-bearing solution(s) with a more oxidized fluid, containing soluble uranyl complexes. Homogenization temperatures of fluid inclusions in calcite (GO-lIO?C) at the Orphan fall within the lower end of the range observed at other breccia pipes.

Jan 1, 1987

By Zuoren Huang

The flowsheet of the hyd.rametallurgical zinc plant which is in use at Zhuzhou Smelters is described. The principal features of the process are fluid bed roasting, continuous calcine leaching, solution purification, zinc electrolysis, electrolyte cooling, and finally, the melting and casting of zinc forms. The Zhuzhou process for the flotation of silver from the leach residue collected on the Moor filters is described. The technical details of the process are outlined and the operating data are analyzed. The flotation facilities are described in detail and concentrate grades and recoveries are presented. The waelz process is used to concentrate In, Ge and Ga remaining in the leach residue after silver flotation. These elements subsequently are recovered by selective leaching in sulphuric acid, and details of this operation also are presented.

Jan 1, 1990