Search Documents

By Min Chen, Lei Xu, Weijun Huang, Shuai Zhang

For the purpose of extending the service life of MgO-C bricks used as linings of vanadium-extraction converters, the effect of Fe addition on properties of MgO-C bricks was investigated. The results showed the addition of Fe could effectively improve the sinterability of the oxidized layer of the MgO-C refractory at 1400°C due to the effect of FeO (formed by oxidation of Fe) on formation of MgO-FeOss and modification of the microstructure, and excellent corrosion resistance against vanadium containing slag was also obtained due to the increase of compactness of the oxidized layer and concentration of FeO in the oxidized layer. Consequently, it is considered that MgO-C brick by introducing the new phase of Fe is a favorable substitute of MgO-C refractory to be used as linings of vanadium-extraction converters.

Jan 1, 2015

By Arthur G. Hunt

Smelting using the direct-to-blister process commenced at Olympic Dam on 31 July 1988. The unique nature of the Olympic Dam ore body led to the selection of the direct to blister smelting process. Significant improvement in the design of the furnace and the understanding of the fundamentals of the process and its operation has occurred in the 10 years of operation. The paper will discuss the operation of the #1 Smelter and the design, preparation for start up and early operating experience of the #2 Smelter.

Jan 1, 1999

By J. Lui

The 15m high Inco flash furnace uptake was designed as a reaction chamber with the objective of destroying the H2S contained in the furnace off-gas by combustion with oxygen at about 1300?C. Until recently, the oxygen required for this purpose was injected through afterburners located at the bottom of the uptake. An undesirable side effect of this practice was the formation of build up accretions on the inside walls of the uptake. This buildup had a negative impact on both the furnace on line time and the control of the flash smelting process. In late 200 I, the afterburners were relocated to the roof of the uptake. As a result, about 80% of the uptake accretion buildup disappeared with obvious beneficial effects for the operation of the furnace. This paper discusses key flash smelting aspects that affect the operation of the flash furnace uptake such as the dusting rate, the formation of H2S in the freeboard of the furnace, and the impact of using coke to supply some of the heat required by the process. The mechanism of buildup formation and its dependence on uptake afterburners location are also examined. Prof. Yazawa's sulfide smelting thermodynamic relationships proved instrumental in understanding the conditions that influence the formation and the elimination ofH2S and uptake buildup.

Jan 1, 2003

By John A. Herbst

Plantwide control of mineral processing operations has long been sought for its potential benefits. These benefits include minute-to-minute optimization, reacting to disturbances in ore characteristics and equipment status as they happen and the coordination of all unit operations in pursuit of the highest performance level. However several difficult challenges have kept us from fully realizing those benefits. One of these challenges has been to provide fairly complete quantitative descriptions of Unit operations to account for critical interactions within and 'between unit operations. In some cases we understand the physics and chemistry very well and can incorporate that 'knowledge into phenomenological models. In other cases our knowledge is incomplete, so we must rely on other forms of knowledge such as fuzzy logic or neural nets. Another challenge to be met has been to simultaneously compute a large number of manipulated variables. In the past this challenge was met by optimizing only unit-by-unit, rather than on a global basis to significantly reduce the number of variables. In this paper, a procedure that globally optimizes one or two important variables is outlined. This procedure comes much closer to true plantwide optimizing control while remaining computationally feasible. Finally, another major challenge is to choose a meaningful global objective that can be calculated With the models and can be effectively optimized. Financial goals seems to be the objectives of choice. This paper discusses recent progress In overcoming the challenges and illustrates a promising approach which is being pursued at :Mexicana de Cobre's 'La Caridad copper ore concentrator. At M de C, advanced ,control strategies have been 'installed one at a time in the crushing, grinding and flotation sections. During this period, the throughput of La Caridad, Mexico's largest copper concentrator, 'increased from 76;000 tpd to 90,000 tpd. Plantwide integration is expected' to gain an additional 3% improvement in profitability.

Jan 1, 1996

By Mohamad Omarei, S. M. Sadrameli

"The aim of this research work was to produce biodiesel (fatty acid methyl esters, FAME) from canola oil using KOH loaded on y-Al203 support as a heterogeneous catalyst. Different parameters such as effects of the molar ratio of methanol to oil, catalyst amount and reaction time on the yield were investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used for characterization of the catalysts. A biodiesel yield of 86.67% was obtained under catalyst preparation and transesterification conditions of calcinations temperature of 773 K, 4 h of reaction time at 338 K, and using 3.5 wt% catalysts and molar ratio of methanol/oil of 15:1. The leaching of potassium species in the spent catalyst was observed.1. IntroductionBiodiesel is an eco-friendly and alternative energy source for diesel engines that can be synthesized by transesterfication of vegetable oil or animal fat with alcohols [1 ]. There are four principal approaches to the synthesis of biodiesel involving the transesterification of the triglycerides of the plant oils and animal fats: base catalysis [2], acid catalysis [3-5], employing supercritical alcohol conditions [6] and enzyme catalysis [7]. The commonly used homogeneous catalysts are NaOH, KOH and their alkoxides. Homogeneous alkali-catalyzed transesterification is much faster than acidcatalyzed transesterfication [8]. However, a large amount of water is required to transfer the catalysts from the organic phase to a water phase after the reaction. Therefore, it is considerably more costly to separate the catalyst from the produced solution [9]. These disadvantages could be removed by use of a heterogeneous catalyst [10]. The use of heterogeneous catalysts eliminates the neutralization step, hence it results much easier to separate from liquid products. Also, they can be designed to give a higher activity and selectivity and to have longer catalyst lifetimes [11]. A large number of different heterogeneous catalysts have been synthesized for biodiesel production. For example, calcined Mg-Al hydrotalcites [12], zeolite and metal catalysts [13], metal oxides such as calcium oxide (CaO) [14], magnesium oxide (MgO) [15], zirconium oxide (Zr02) [16], and supported catalysts [17] have been investigated as heterogeneous catalysts. CaO and MgO are most frequently used heterogeneous catalysts for biodiesel production [18]. In this present work, we aimed at developing an efficient catalyst for transesterification of canola oil. We have prepared KOH/ Al203 by impregnation and applied to determine the optimum conditions for biodiesel production. Three different variables including reaction time , alcohol to oil molar ratio and catalyst loading with may influence the quality of the produced biodiesel were optimized. Moreover, SEM (scan electron microscope), XRD (X-ray diffraction) and XRF were used for characterization of the catalysts."

Jan 1, 2012

By R. W. Lawrence

A high rate biological reduction technology has been developed to provide low cost hydrogen sulphide for various uses in water treatment and metallurgical processes. Commercial operations produce sulphide safely at a fraction of the cost of chemical sulphide. The biologically produced H2S is used for treatment of acid wastewater and selective metal recovery whereby metals present in wastewater streams are recovered in high grade metal sulphide concentrates that are sold to smelters. The combination of biological H2S production and selective metal recovery is currently marketed under the process name BioSulphide-Thiopaq. The process can be applied on a stand-alone basis or in conjunction with a conventional lime water treatment. Process advantages include: reduced lime treatment costs, reduced volume of waste sludge free of toxic metals leading to reduced long term environmental liabilities, selective recovery of metals and, in some cases, net profit from water treatment achieved through the sale of metal concentrates. Three case studies are presented to provide examples water treatment and metal recovery: the Caribou Mine, New Brunswick; the Phelps Dodge Bisbee operations, Arizona; and Falconbridge?s Raglan nickel mine in Quebec. A fourth case study is presented to highlight environmental control for treatment of ARD in the Leadville mining district of Colorado. Process flowsheets, capital and operating costs are presented for the four case studies

Jan 1, 2003

By James P. Bennett

The U.S. Bureau of Mines, Tuscaloosa Research Center, is conducting a review of the usage of different types of refractories, the current industrial practices to recycle/dispose of spent refractories, and the concerns associated with these practices. This information will serve as the technical basis for initiating a research program to recycle or find alternate uses for spent refractory materials. Approximately 1.6 million metric tons of clay based and 1.2 million metric tons of non-clay based refractory materials were manufactured in the United States in 1992 alone, representing a value of almost 2 billion dollars. Landfill has been and remains the disposal means of choice. Issues such as environmental regulations, concerns over landfill disposal, future liability, and product stewardship programs have brought about increased emphasis for recycling or alternate material use. Information on refractory consumption and the issues associated with recycling or disposing of used materials will be discussed, including current recycling practices.

Jan 1, 1995

By Mingming Zhang, Mallikharjuna R. Bogala, Ramana G. Reddy

Steelmaking desulfurization slag samples were characterized using chemical, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) methods. The objective of this work is to investigate the occurrence of sulfur and phosphorus components in the slag samples and to identify their origin and associations with the iron phases. Thermodynamic calculations results confirm the presence of phosphorus and sulfur components in the slag sample at high temperatures (1400 to 1800oC). The main constituents of slag include Ca3SiO5 (28.1%), MgO (9.31%), Ca3(PO4)2 (9.18%), CaS (8.39%) and CaO (5.68%). The major phosphorus and sulfur components of the slag are Ca3PO4 (99.2%) and CaS (79.3%) respectively. Characterization studies indicate the presence of microparticles of different sizes and shapes in the slag sample. Elemental analysis of these particles confirm the presence of major elements (O, Mg, Al, Si, S, Ca and Fe) in the slag sample.

Jan 1, 2015

By Richard D. Hagni

The techniques of reflected light microscopy and cathodoluminescence microscopy are uniquely suited to the study of the products from many important industrial problems. Ref1 ected 1 ight microscopy provides the means to rapidly identify the mineralogy of an industrial sample, determine the abundance of each phase, and examine the mineral intergrowths or textures. Cathodoluminescence microscopy is a relatively new instrument that provides the means to cause many minerals to cathodoluminescence under the microscopy. The cathodoluminescence of a mineral allows it to be readily distinguished from other phases that differ in cathodoluminescence but are similar in optical properties. Cathodoluminescence microscopy is especially useful to detect cathodoluminescence minerals that are present in only small quantities. Reflected 1ight microscopy and cathodoluminescence microscopy have been successfully applied in studies of beneficiation products, prediction of beneficiation and leaching problems, phosphatic iron ores and mill products, pyrometallurgical products, roasted refractory gold-bearing sulfides, ceramic build-ups, electric arc furnace and smelter dusts, and other industrial products.

Jan 1, 1993

By V. A. Luganov

The behavior of arsenopyrite under heating has been studied by many scientists. It has been already established that under heating at more than 650°C and without air access the arsenopyrite dissociates with the formation of one atom arsenic. Under vacuum the dissociation process begins at 550 DC with the formation of elemental arsenic. The residue of dissociation process contains pyrrhotite and throilitc. In the presence of pyrite, arsenopyrite dissociates under lower temperature and with a higher velocity than without it. The industrial realization of fool scale processing of arsenic bearing raw materials is possible only by the use of standard equipment and oxygen containing blast In this view the paper presents the results of the study on the effect of oxygen in the gaseous phase and its addition into the charge of pyrite in the process of arsenopyrite decomposition. Thermodynamic analyses showed that under thermal processing of arsenopyrite in the presence of pyrite and limited quantities of oxygen in the gaseous phase the formation of arsenic sulfides is possible according to the following reactions:

Jan 1, 2003

By Ryosuke O. Suzuki

A combined process of electrolysis of CaO in the molten CaCl2 and of calciothermic reduction, so-called OS process, was applied to prepare metallic vanadium directly from V2O3. The fine metallic powder containing 1860 mass ppm oxygen was obtained using 0.5mol%CaO-CaCl2 melt for 10.8 ks at 1173 K. The oxygen level did not decrease further even when twice electricity was applied. Because the metallic vanadium could be electrochemically deoxidized to the level of 10 ppm oxygen from 1.48 %, the large amount of by-product, CaO, due to reduction and the large surface area of the fine particles are the reasons of high oxygen content in the reduced powder.

Jan 1, 2006

By Ulrich Kerney

In 1996, bath smelting technology for lead recovery from concentrates and secondary materials was introduced in Nordenham to replace the common sinter plant/shaft furnace operation. Since start-up, a continuous improvement of equipment and operation lead to a steady increase of capacity and plant availability. The decision to skip the reduction stage for slag treatment now allows the treatment of 200000 t/a feed materials with a secondary fraction of up to 70 %. The main feed source for the furnace is automotive battery recycling, which offers oxide paste and metallics to be molten under oxidizing conditions in the lance fired furnace. The lead bullion is transferred to the refinery, where copper, silver and other impurities are removed. Silver is recovered as doré quality. All loopings are recycled to the BSF. Inert feed material is collected in a so-called lead concentrate of metallurgical origin, the primary slag, which is sold. It is rather a valuable feed material for further processing than a slag The off-gas is cooled in a flux-flow system, entering then an electrostatic dust precipitator. Having passed a further washing and cooling system, SO2 is oxidized and collected and sold as concentrated sulphuric acid. The presentation will cover a review of the start-up phase, the development of significant production parameters over the last years and actual production routes and figures. A comparison of environmental data between new and old applied technology is made.

Jan 1, 2006

By Elizabeth M. Ho

Oxidants are added in uranium leaching in acid media to convert iron(II) in solution to iron(III). Iron(III) has an important role in the leaching of uranium by acting as an electron transfer agent for the oxidation of uranium(IV) to uranium(VI). The oxidation of iron(II) to iron(III) in sulfate solutions using sulfur dioxide/oxygen (SO2/O2) was carried out under typical uranium leaching conditions (pH 1-2, 20-50°C) to confirm literature trends and this work was then extended to the use of SO2/O2 in the leaching of uranium ore. The oxidation rate was found to be dependent on the initial SO2/O2 volumetric ratio and the oxygen mass transfer rate, but was independent of the initial iron(III) concentration above about 200 ppm at pH 2. The presence of 55 ppm organic extractant (Alamine 336) decreased the reaction rate. The oxygen mass transfer coefficient (kLa) for the mixing tank system was measured and was found to decrease with increasing solids density in a 1 g L-1 MgSO4.7H2O solution.

Jan 1, 2003

By I. Ohnaka

Although many works have been reported on the semisolid casting, the mold filling behavior of semi-solid alloys has not been so well understood. This paper compares the physical and numerical simulation results on the mold filling behavior. Physical simulation was performed by using solid-water mixture. The numerical simulation was made under the assumption of one phase flow with an effective viscosity. It was found that the solid particles stabilize the flow greatly if the kaction solid exceeds about 0.4, because viscosity increases greatly. The overall flow behavior can be estimated by the numerical simulation. Interesting flow behavior was also found which can not be observed in the case of one phase flow and which is difficult to simulate by the one phase flow assumption.

Jan 1, 1997

By Feng Gao

A general unsteady- state model, based on a cracked substrate, has been developed to account for reaction and diffusion within porous substrate during oxidation of Carbon Fiber Reinforced Carbon matrix (CIC) composites. The effects of several parameters, such as diffusion and reaction rate ratio, oxygen concentration, and composite density, on oxidation process are explored. Also, theoretical results for a set of parameter values of the CIC composites are compared with experimental data. It shows that the model predicted values agreed well with the experimental data in weight loss. Based on this model, quantitative predictions of oxidation of a composite with cracked substrate can be made.

Jan 1, 1993

By Juan H. Rojas C.

The Chuquicamata mining and metallurgical complex is the main Division belonging to Corporation Nacional del Cobre de Chile (CODELCO-CHILE) and it accounts for 50% of the 1.4 Mt of fine copper output of the Corporation. It has been producing copper since 1915. The paper refers to the challenges that Chuquicamata has to solve in the near future. These challenges are: the increasing operation costs associated to a 800 m depth pit with low prices in an overstocked copper market; the increasing people's sensitivity to environmental preservation; and, the transformation needed for achieving high levels of organizational effectiveness. According to Corporate policy, Chuquicamata is making efforts to switch from a management style focused on supply to a management style focused on demand side of the industry. In this direction is tempting to establish strategic alliances to develop both new copper products and uses, to rise the metal demand. In more than 80 years of operation, Chuquicamata had exploited just one third of its geological resources. The exploitation of the remaining two third is a huge engineering challenge, taking into account the depth of the deposit, the impurities content, the decreasing ore grades and the transportation distances for waste dumping. All those factors are relevant in the economical process of transforming geological resources into ore reserves. Chuquicamata has other limitations. First, a 20,000 people town just aside the pit that limits the mining rates because of dust generation; second the scarceness of water in the desert area where Chuquicamata deposit is located; and, finally, the new tailing pond is a problem which solution will demand huge engineering efforts and investments. People are the principal factor associated to a company success. In this field, Chuquicamata have been progressing, but much more efforts from people will be necessary to reduce production costs for being successful as any other price-taker within the copper industry. Chuquicamata must develop the skills of its Supervisors to transform them into leaders and entrepreneurs, who additionally have the challenge of passing on their knowledge to non-professional workers. It is an ethic commitment to assure personal and professional growth of workers, as the only sustainable way to get real and integral success.

Jan 1, 1999

By Hector M. Henao

To provide thermodynamic data for converting nickel matte to liquid nickel at high temperature, an experimental study was conducted on the phase equilibrium between the Ni-S alloy and the FeOX-SiO2, FeOx-CaO, and CaO-A12O3 base slag in a magnesia crucible and the CaO-Al2O3-MgO slag in an alumina crucible. All experiments were carried out at 1773 K under controlled pso2 of 0.1 atm and po2 in a range between 5x10- and 10-5 atm by using CO-CO2-SO2 gas mixtures. The dissolution of nickel in the slag was found to be minimum for the CaO-Al203¬-MgO slag with a molar ratio of NCaO/NA1203=1.7. The solubility of nickel in this slag at p02 of 6x10 atm (just before the precipitation of solid NiO) was 4 mass%. This result suggests that a CaO-A12O3 base slag could be used in converting Ni-S melt to nickel while minimizing nickel losses to the slag.

Jan 1, 2002

By Margarete Kalin

Mine abandonment is associated with the securing of access to underground workings, shafts, raises and adits. Waste rock piles and tailings are generally contoured and revegetated. When the waste materials contain pyritic material seepages can often emerge long after the physical reclamation work has been carried out. Their extent and origin has to be delineated to facilitate remedial measures. The depth to which the seepages extended can be determined with an electromagnetic (EM) survey. This paper reports on the experience gained using a winter and a summer EM survey correlated with measurements of specific conductivity at the sediment water interface. Lake sediments and ponds which represent a homogenous background material are good media, where specific conductivity and electromagnetic conductivity can be correlated. The origin of the seepage within the recontoured mine site requires detailed site knowledge, as many anomalies in heterogenous materials such as represented by a mine site are evident.

Jan 1, 1994

By Luciano B. Oliveira, Luis G. C. Marques, Sergio N. Monteiro, Marcos V. M. Fagundes

"Biodiesel production is normally associated with large plantations of oily vegetables such as soybean and colza, in large rural areas. However, in the municipal limits of the city of Rio de Janeiro, southeast of Brazil, biodiesel is being produced from wastes commonly generated by typical urban activities such as sewage sludge, discarded fat from meat markets and post-used cooking oils. In the present work, the experience of producing biodiesel from urban wastes in Rio de Janeiro is assessed. The type of precursor materials, equipments and logistics are presented. The environmental and economical advantages as well as the drawbacks are discussed.IntroductionThe interest for a liquid fuel that could substitute those obtained from petroleum started more than one hundred years ago when Rudolph Diesel tested his no-spark internal combustion engine, impelled by compression, with peanut oil. By that time, petroleum was beginning to be extracted in large scale and no one was concerned with the future environmental problems and its eventual depletion. In the last century, the successful association of petroleum based fuels with the automotive industry was an almost insurmountable obstacle to any attempt to use nonmineral oils [1]. In addition to the greater efficiency and, by then, lower price of the diesel from petroleum, the use of plain vegetable oils introduced undesirable carbon deposits and reduced the engine lifetime. Today, the situation is reverse. The continuous increase in the price of petroleum and, above all, its contribution to climate changes are strongly motivating the use of biofuels to replace those obtained from fossil fuels such as petroleum, natural gas and coal [2].In the case of the common petroleum derived diesel, many countries are now engaged in large scale substitution programs. The USA should produce more than 700 million litters of biodiesel, while the European Community is expected too produce around 6.5 billion litters in 2008. In Brazil, the federal biodiesel program imposed a minimum of 2% addition to the common diesel. This would demand a production of 800 million litters in 2008 [3]. The Brazilian biodiesel is made from a diversified source of vegetables mainly castor bean, African palm and soybean. The main producers are agrobusiness firms located in large rural areas of the Brazilian hinterland [4]."

Jan 1, 2008

By John Petersen

Heap bioleaching technology has become well established for the exploitation of copper sulfide ores. Still, in many operations the rate of copper extraction is rather slow, often taking two years or more to recover 80% of the copper. Chalcocite, the most common secondary copper sulfide, leaches by a two-stage mechanism. The first stage is rapid, whereas the second stage has a high activation energy and proceeds slowly at ambient temperatures. Nonetheless, this rate is still considerably faster than what is typically realized in a full-scale heap. A comprehensive column bioleaching study of a chalcocite ore has shown that the chalcocite columns are leached in a zone-wise fashion. The first zone corresponds to the first stage of chalcocite leaching, where all ferric produced by the bacteria is immediately consumed and all acid entering with the feed solution is consumed within a relatively narrow band. The second stage of chalcocite leaching proceeds much more slowly in the wake of the first stage, within a zone that grows gradually over the entire length of the column. The overall rate of leaching is thus determined by the rate of acid supply into the column rather than by mineral or bacterial kinetics, at least until the entire column is engaged in second-stage chalcocite leaching. In full scale heaps, there is evidence to suggest that solution distribution favours channelling between relatively large clusters of material which are exposed only to stagnant solution. Reagents have to migrate into such clusters by diffusion, which retards the delivery of acid dramatically. Thus, we believe that the rate of chalcocite oxidation in heaps is governed by sideways diffusion rather than downward migration. Column experimental results have been reproduced with a comprehensive heap-modelling tool. The model predicts that by simply changing the length of the average diffusion channel from column conditions (a few cm) to heap conditions (tens of cm), extraction times can change from weeks to years under otherwise identical conditions.

Jan 1, 2003