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By He Zhi-jun, Ning Zhe, Pang Qing-hai, Zhang Jun-hong, Zhan Wen-long

In this study, Raman spectroscopy was utilized to investigate the evolution of char structure in pulverized coal (PC) during microwave irradiation. The results indicated that though microwave treatment was carried out at low powers of 132W or 264W, significant variation in char structure was still observed. Char structure turned out to be more irregular firstly under microwave irradiation. However, char structure of superior regularity was obtained with the extension of irradiation time. It can be conclude that short time microwave treatment may facilitate the chemical activity of coal, while long time microwave irradiation on PC may deteriorate its combustion or pyrolysis property.

Jan 1, 2016

By Biserka Lucheva, Tzonio Tzonev

"Recycling of aluminum scrap and dross is significant in the economic and energy saving, as well as in the environmental protection. Recovery of metal aluminum depends on many factors. The aim of this work is to investigate experimentally the metal recovery under different conditions. The processing of aluminum dross was carried out in DC electric arc rotary furnace. The optimal technological parameters are determined. It is turned out that the presence of crushing refractory bodies during the processing of the aluminum dross in the rotary furnace increases the degree of aluminum recovery with about 10 %.IntroductionCompact and granular aluminum dross are used for the fulfillment of the experiments, which were obtained by salt free melting of aluminum scrap. The only preliminary preparation of the compact dross is crushing them into proper size, in compliance with the size of the opening for furnace charging and removing of fraction – 1 mm. The granular dross is subjected to sieving also with the purpose to remove the fraction – 1 mm. In these conditions the content of the metal phase in the compact dross is 72 %, and in the granular – 77 %. The processing of aluminum dross was carried out in DC electric arc rotary furnace (Figure 1).The purpose of this research is to investigate experimentally the metal recovery under different conditions and to establish the dominant factors, which need to be controlled."

Jan 1, 2008

By A. Kapilashrami

Slag foaming proves to be both blessing and curse for the process productivity, depending on where in the process it occurs. In pyrometallurgical processes, slag foaming is often a result of chemical reactions taking place in the slag. As the slag composition and reaction rates are changing, foaming occurs under dynamic conditions. In the present work, slag foaming was studied with XRF. The foam displayed a fluctuating behaviour, unaccountable by existing models. The concept of foaming index was found not to be satisfactory in describing the foam, resulting in the need for alternative theories. The rate of fluctuations was seen to be related to the difference between rate of gas generation and rate of gas escape from the system (Ug-Ue) as well as the bubble sizes. Thus, model development of dynamic foaming phenomenon has to take the effective chemical reaction rate as well as the bubble sizes into consideration. The first step in obtaining foam is to form bubbles. In the present work, gas bubbles were generated through chemical reaction at interface between two immiscible liquids and the bubble formation was studied optically. The gas bubble size was seen to be uninfluenced by the reaction rate. However, bubble formation was seen to take place in one of the phases and since the bubbles consequently traversed the interface under the influence of buoyancy, the viscosity of the first phase was found to influence the final bubble size where increased viscosity would yield a larger bubble size.

Jan 1, 2006

By Peter Schwartz

This paper presents GBN's "Global Scenarios" for the first decade of the 21st century. We describe a set of key scenario actors and develop 6 driving forces in demography, technology, climate change, macroeconomic change, globalization, and geopolitics. We argue that a set of majorchallenges to world systems of commerce and politics will coalesce in the next several years. We develop four scenarios which differ according to how these challenges are handled, and which scenario actors play the key roles in managing the transition.

Jan 1, 1999

By Robert W. Hyers

Electromagnetic levitation has proven important in a wide range of experiments, all affected by fluid flow. For some experiments such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress, or shear strain rate are required. In most cases it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, opaque, reactive, high-temperature, metastable, or all of these. Furthermore, recirculating flow limits the utility of tracking surface particles, since they collect in stagnation points ratherthan following the flow. Most research groups have chosen mathematical modeling to assess the internal flow in levitated droplets. A variety of analytical and numerical methods have been applied, including both laminar flow and various turbulence models. A number of these models are reviewed and their impact on different containerless experiments is assessed. Much of the research reviewed here was performed by alumni of Professor Julian Szekely, and by others using similar methods.

Jan 1, 2006

By Michael J. Virnig

The formation of crud is a normal part of operating a solvent extraction circuit for the recovery of copper. It periodically must be removed from the circuit. This results in significant costs in terms of manpower, downtime, and loss of circuit organic. Field studies have been carried out that show that the presence of a thermodynamic modifier in the organic phase contributes to crud formation. In an effort to better understand what factors contribute to crud formation, laboratory studies involving competitive adsorption studies with model solids have been carried out. The results of these laboratory studies will be integrated with the results of the field studies to present a better understanding of crud formation.

Jan 1, 1999

By D. Valic

In 1997, 9.2 million tonnes of mined, recoverable copper was produced, of which, 1.8 million tonnes or 19.4% was produced by leaching, solvent extraction and electrowinning. The amount of copper produced by this method grew faster than those attained from concentrate smelting, signifying the growing importance of this low-cost production method. Statistical experimental design, unlike traditional approaches, allows for proper distribution of experiments within the boundaries of factors being studied such that the number of experiments required to develop a sound relationship between the factors and a response is minimized. In the past, very little use has been made of statistical experimental design in copper electrowinning studies. Traditional one- variable-at-a-time approaches are widely employed for this purpose. The present study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A/m2), copper concentration (25 and 65 gL), and temperature (40 and 60 °C). Pure synthetic electrolyte with a constant acid concentration of 180 g/L was used throughout the study. The designed study produced a linear relationship where the independent variables of current density, copper concentration, and temperature, and their interactions, were found statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to be incorporated into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.

Jan 1, 1999

By Mariola Saternus

The quality of the liquid metal has the biggest influence on the quality of the final products. In the metallurgical industry, and especially in aluminium production the refining process is the important technological stage. Today the most popular are refining reactors with impellers like URO ? 200, which can generate small gas bubbles. A rotary impeller also makes the metal bath to be stirred well. There are two basic hydrodynamic parameters: the flow rate of refining gas and the mixing of refining gas (impeller rotation) that influence metal stirring and generating small gas bubbles. The paper presents the influence of the flow rate of refining gas on the hydrogen removal process from aluminium (final hydrogen concentration), taking into consideration the refining process of AlSi7Mg alloy and using URO - 200. The mathematical model of this process is also presented. The equation needed for calculation of the final hydrogen concentration as a function of the equivalent bubble diameter is shown. Basing on this equation the calculations of bubble diameter and optimal refining time are done. This paper presents the physical model (the water one) of aluminium refining process and the gas dispersion taking into account the fact that the gas flow rate is changing from 2,5 to 17,5 l/min and the impeller speed is changing from 0 to 400 rpm. Schemes of gas dispersion in liquid metal in comparison with the model data are shown and the optimal values of the gas flow rate and the impeller speed are chosen.

Jan 1, 2006

By V. A. Bryukvin

A hydroelectrochemical technology has been proposed and experimentally proven for processing metallic gold- and silver-containing concentrates on the basis of copper and copper alloys obtained as a result of preliminary physico-mechanical upgrading of electronic scrap. The proposed technology is based on hydroelectrochemical leaching of scrap using reversible electric current and diluted nitric acid solutions, containing complexing agents, permitting complete separation of gold from the nonferrous matrix without involving gold in the process, and dissolving copper, zinc, lead and tin virtually without any emission of nitrose gases.

Jan 1, 2006

By Luiz R. P. De Andrade Lima

This paper presents a mathematical model for the oxide copper ore heap leaching process. The data used in the model include physical-chemical, .geometrical and operational data, as: leachable metals ore contents, .flow rate and acid concentration, parameters of passivity, ore size distribution, the average residence time of the solution in the heap, height, irrigated area and weight of ore in the heap. In this model the heap is divided into horizontal and plane layers of constant area. The flow of the liquid in the heap is considered unidirectional and the solid-fluid reaction model is considered under diffusive control. The average residence time of the solution into the heap and the apparent effective diffusivity of the acid through the ore particles have .a significant influence on the rate of the copper extraction and its concentration in the pregnant solution; therefore these parameters are used in the model calibration. When this algorithm was applied to a laboratory test, the results showed that the model is adequate to predict the process performance.

Jan 1, 1999

By Bruce W. Downing

MagPower has developed methods to control the detrimental formation of hydrogen that occurs in electrochemical reactions in numerous commercial applications such as the Magnesium-Air Fuel Cell, electrowinning, zinc alkaline batteries, hydrogen embrittlement, waste water/ metal recycling and coolants. The company?s approach to an alternative energy source is the development of an environmentally friendly non-toxic alternative power source that generates electricity through a combination of magnesium, oxygen and a saltwater electrolyte with MagPower?s patent pending hydrogen inhibitors. The magnesium-air technology has never reached the commercial stage due to its limiting power output caused by hydrogen generation. MagPowerhas solved this problem and has patents pending on its intellectual property; the Hydrogen Inhibitors and has developed several consumer power units for a variety of applications through licensing agreements. The company has also shown that the inhibitors have an impact on zinc electrowinning through laboratory test work where current efficiency was improved. This will significantly reduce power consumption and increase the efficiency of the electrowinning process, as well as reduce the potential acid mist hazards associated with electrowinning.

Jan 1, 2003

By Leonard J. Friedman

The contact process for the production of sulfuric acid has been used commercially since before the turn of the century (1880?s), and rapidly replaced the chamber process after the development of vanadium catalysts in the early 1900's (1910's - 1920's). Plant size has increased from a few tons per week to single train units in excess of 4,000 tons per day. Much of the history of the contact process is in the minds of the few remaining early process pioneers that started in the industry in the 1920's and 1930?s, and in sulfuric acid industry books published in 1921, 1925, 1936, and the last Deucker and West in 1959. Since those not familiar with history are doomed to repeat the failures and mistakes of the past, this paper includes a brief history of the contact process along with the history and development of equipment and materials in each equipment area of the process. The main focus of the paper is to present the development and analysis of equipment and materials in the contact section of the sulfuric acid plant - from the dry tower to stack.

Jan 1, 1999

By Marcelo R. Esquivel

A MmNi5 alloy is synthesized by a combination of mechanical milling and low temperature heating processes. Synthesis time is 40 h for powders milled in a low energy ball mill at room temperature. A reduction in milling time is obtained if massive sample is mechanically milled at shorter times (2 h to 10 h) and heated at temperatures lower (600 ºC) than the usual temperatures used in equilibrium methods (>800 ºC). The alloy formation is detected even at a combination of temperatures as low as 200 ºC and milling times as short as 5 h. The temporal evolution of mechanical milling process was followed by both X-ray diffraction (XRD) and scanning electron microscopy (SEM) to detect the main stages of milling. Four stages were detected: Initial, Intermediate, Final and Completion. These stages were correlated to an enhancement of the synthesis method by combination of times of milling shorter than 10 h and temperatures of heating lower than 600 ºC.

Jan 1, 2006

Iron, chloride and manganese are the three major impurities transferred to copper electrowinning tankhouses via chemical and/or physical entrainment. The control of these impurities via bleeding of tankhouse electrolyte is costly. Recently, Eichrom Industries have developed an improved iron control process and tested this process in a pilot study at the Girilambone Copper Company (GCC). The patented process utilizes a fixed bed ion exchange reactor filled with Eichrom's Diphonix® resin. Iron is loaded on the resin and subsequently eluted by a cuprous sulfate eluant. The control of chloride and manganese has been studied using different chemical techniques. The removal of chloride from electrowinning electrolytes was tested using precipitation of chloride as cuprous chloride. Copper wire cuttings are used to produce cuprous ions. Chloride levels are reduced to around 30 ppm in electrolyte at 40°C. The removal of manganese using a precipitation process practiced in zinc electrowinning purification has been tested for implementation. The process involves reacting manganous ions in solution with permanganate ions. The reaction produces an insoluble manganese dioxide reaction product. The bench scale and pilot plant results from testing of these purification processes are reported.

Jan 1, 1999

By M. C. Nielson

The paper describes the design and operation of pulsed columns as replacements for conventional mixer/settlers. The advantages, which the columns offer, include a reduction in real estate for the plant, elimination of diluent evaporation, containment of noxious vapors and reduced crud formation. In addition to the description of operation, the paper presents the findings of laboratory tests of pulsed columns extracting copper from pregnant leach solutions and also delineates potential advantages of the pulsed column in copper solvent extraction.

Jan 1, 1999

By J. A. Sanhueza

The environmental regulations and terms issued by the Chilean Government for all copper concentrate smelters have been a very important reason for permitting project developments that drastically decrease the sulfur emissions due to the pirometallurgycal copper process. A remarkable case of the Hernan Videla Lira Copper smelter, located on the Copiapó Valley and very near some housing-sets of a city of high development, are described. Results of this project's implementation of the control and reduction of off gas emissions, the control and monitoring system, the community conflicts, and the strategy to comply with the demands established by the state environmental institutions, are presented.

Jan 1, 1999

By P. Stantke

In recent years the CollaMat process has been used successfully worldwide in a number of copper electrorefining tankhouses as an instrument for measuring the glue concentration and optimizing cathode quality. Owing to its measuring principles the CollaMat can be used not just for measuring the concentration of active glue but also the activity of other substances, which have an impact similar to glue on the copper deposition. In SX-EW plants guar is frequently used instead of glue as a levelling additive. In our laboratory the effect (activity) and the decomposition rate of guar in copper electrolyte was examined. As expected, the results show that guar has an effect similar to glue on the copper deposition. However, at the same temperature, a greater quantity of guar is required to achieve the same results. As with glue, the decomposition rate (due to hydrolysis) of guar is strongly dependent on the temperature. Therefore, in practice, its on-line monitoring is necessary to guarantee the same guar activity at any time.

Jan 1, 1999

By Ahmet Geveci

[Generally accepted formula related to sulfur slag-metal distribution ratio is given by the following equation: [ ] According to the above equation it can be deduced that sulfur distribution between slag and metal is governed mainly by metal composition (?s term), slag composition (slag basicity and in turn sulfide capacity), oxygen potential of the system (ao¬¬ term) and temperature(related to equilibrium constant, K). In this study, the results of ladle furnace operations conducted in Erdemir-Iron and Steel Works Co. (Turkey) in relation to sulfur removal, have been given. Typical ladle furnace slag analyses of 4937K quality steel have been presented. Activity coefficient of FetO,?FetO, have been calculated with the relation obtained fromthe literature. Activity calculations have been performed with the program written in Mathcad. The changes in activity of aFetO in the slag phase,, have also been studied in relation to the sulfur removal: The relation between % Decrease aFetO and %DeS (measured)have been investigated for 4937K runs and someother types of steel produced in the Erdemir Plant. Related to ladle operations %desulfurization defined as [(%Sinitial-%Sfinal)/S%initial]*100 values have been presented for different steel qualities.]

Jan 1, 2006

By Dhanesh Chandra

Long term stability studies were conducted on four variants of LaNi5; 10,000 hydriding/dehydriding cycles were used to evaluate their suitability for a metal hydride cooling system. Thermodynamic and structural studies were conducted to determine changes in these materials during cycling test period. The hydrogen sorption properties of LaNi5.2, and Lao 9Gd0.1Ni5 and LaNi4.75In0.27 were seriously degraded during the tests but the LaNi4.8Sn0.22 hydride was virtually unaffected. Hydride isotherms were measured at the beginning and at intervals through out the test period to observe the nature and extent of damage degradation in the sorption properties. X-ray diffraction studies of the alloys (LaNi5.2, LaO.9Gd0.1Ni5 LaNi4 8Sn0.22) and their respective hydride, before and after test, provided insight with regards to the observed changes in the hydride properties. Electron microscopic studies were also conducted to evaluate the changes in particle sizes.

Jan 1, 1989

By C. Camurri

Results from the Metallurgical Department of Universidad de Conception showed that fire-refined copper could be rolled without previous remelting for deoxidation. The goal of this work is to determine the rheology of fire-refined copper from tensile tests at different temperatures and strain rates, and Ford plane compression tests. All that in order to simulate and calculate rolling process variables. For rheology hardness coefficients, n variables between 0.28 at 600°C and 0.46 at ambient temperature are obtained. The sensibility coefficient for strain rate m varies between 0.056 at 600°C and 0.006 at ambient temperature. The activation energy for plastic flow Q in the considered temperature range is 1436 cal/mol.

Jan 1, 1999