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By Peter Forschner

Classical Mixing Theory is based on applying many fundamental correlations to standard baffled dished bottomed vertical cylindrical vessels with high degrees of symmetry. Horizontal autoclaves operating at elevated temperatures and pressures have been used for more than two decades. All compartments and especially the first and last compartments are asymmetrical. To date no comparison of the effects of the asymmetric geometry on mixing system design and scale-up has been published. The results of investigating solids suspension, mixing time, momentum transfer from the impeller to feed slurry and feed inlet location in the first autoclave compartment are presented as influences on residence time distribution. CFD modeling was developed and verified with the test apparatus.

Jan 1, 2003

By Miguel Barron

Recently, a new lance design for BOF steelmaking has been proposed in the literature. This lance, in addition to six peripheral inclined supersonic nozzles, contains a vertical centered nozzle whose oxygen flow is independent from the main oxygen supply. The above authors affirm that their lance maximizes the droplet generation without causing spitting. In this work, the performance of a lance with four peripheral nozzles and one vertical centered nozzle is numerically modeled by means of Computational Fluid Dynamics software. Transient two dimensional computer simulations were carried out considering two phases, namely molten steel and gaseous oxygen. Numerical results confirm that bath agitation and droplet generation are enhanced as a result of the vertical centered nozzle, however a proper performance of this lance, related to a conventional one, strongly depends on the Mach number of the oxygen jets and the lance height.

Jan 1, 2008

By Thomas A. Post

The methodology of determining the optimum SX pumper-mixer system based on bench top, pilot, or small-scale solvent extraction systems, is demonstrated. The design of small-scale SX-plants is different than a full-scale plant. The difference is explained here. The use of dimensionless parameters Nh, Nq, and Np that describe the head, flow and power of the pumper is shown and how to use them for the scale-up. Additional data is required to determine the optimum operating range. Applications of this methodology were used to design well known currently operating SX plants. The emphasis on the optimization of hydraulic efficiency will be shown on examples, including how the hydraulic efficiency is affected when the throughput of the system goes beyond the design. Designs of all sizes of equipment will be shown which optimize the hydraulic efficiency.

Jan 1, 2003

By Yingtao Zhang, Shaofeng Du, Yiming Rong, Wenjun Zhao, Gang Wang

"20Cr2Ni4A steel is a kind of high quality steel mainly used for manufacturing high-duty gears in the world. The high-duty gear with good performance must have wear and fatigue resistance properties. In order to get the good properties, the high-duty gear needs a high hardness gear surface and a good hardness gradient along the depth direction. In this paper, the samples were designed and a vacuum carbonitriding process was put forward to improve the surface hardness of parts for 20Cr2Ni4A. The process contained carbonitriding, quenching, cryogenics, and tempering process. The surface hardness and hardness gradient of carbonitrided samples were measured and the good microstructure was gained. The surface hardness is 67.SHRC and the case depth is 1.2mm.IntroductionSteels are widely used in industry, but the fatigue strength and the wear resistance of steel is much low. So the heat treatment process is put forward to improve the mechanical properties of steel. It can be improved by high-energy heat treatment methods for medium-carbon and highcarbon steel. Those methods will not alter the chemistry of the base metal [ 1].For low-carbon steels, carburizing and quenching should be used to improve the steels' mechanical properties, especially the surface properties. Compared with the carburizing, carbonitriding has more advantages, such as a short production cycle, low temperature and small deformation of parts. Carbonitriding is a modified form of gas carburizing, rather than a form of nitriding. The modification consists of introducing ammonia into the gas carburizing atmosphere to add nitrogen to the carburized case as it is being produced. Nascent nitrogen forms at the work surface by the dissociation of ammonia in the furnace atmosphere; the nitrogen diffuses into the steel simultaneously with carbon. Typically, carbonitriding is carried out at a lower temperature and for a shorter time than is gas carburizing, producing a shallower case than is usual in production carburizing [2]. As a material surface strengthening technology, carbonitriding has been widely used in the production [3]. And vacuum carbonitriding process is better than carbonitriding, because the vacuum carbonitriding temperature can be higher than carbonitriding without surface oxidation."

Jan 1, 2014

By P. C. A. Maia, J Alexandre, F. A. J. Saboya, A. R. G. Azevedo, G. C. Xavier

"This work shows the characterization of clay and the granite waste by-product from the sawing process of the granitic blocks, used as raw material for brick ceramic. Besides, shows the degradation of the ceramic material obtained with different by-product contents in the waste after lab test degradation, is investigated. The clay is obtained from mine use areas of ceramic industry in Campos-RI and the waste is originating from of the area of Cachoeiro-ES, an important center of decorative stone in Brazil. The mixes were made by the addition of 0% up to 10% of the waste in the raw material. After drying and firing up to 900°C, obtained prismatic pieces were considered intact. Physico-mechanical properties were obtained from wet and drying tests in laboratory considering 50 and 150 cycles. The results showed that the use of powder byproduct has a considerably influence on the weathering and strength of the material.IntroductionThe ornamental rocks and coating defines the most promising areas of business in the mineral sector [l]. In this context, the Espirito Santo appears as the main Brazilian state in production and export of ornamental rocks, representing 47% of national production [2] which in tum is one of the economic sectors most representative of this State, due of its transport logistics and port vocation that facilitates the export of such products.It is estimated that the state of Espirito Santo there are approximately 1,200 companies dedicated to the activities of ornamental rock by providing 20,000 direct jobs [ 1]. These mobilize support activities, such as companies that provide machinery, equipment and supplies for industries, including service providers for maintenance.However, the production of rocks produces about 15,000 tons of granite waste/month [3] only in the municipality of Cachoeiro ltapemirim-ES. This is justified by the presence of more than 500 extraction industries, cutting and processing of stone, with about 900 looms, waste generators.According to [4], there is great potential for the use of granite waste in red ceramics introduced for the manufacture of bricks, blocks structural ceramics. and other ceramic products, especially when evaluated on exposure to weathering."

Jan 1, 2014

By Peng ZANG, Qihang Liu

Experimental work was conducted to determine the relationships of coal char conversion with temperature and heat absorption. The results show that at an earlier stage of the coke forming process, lump coal would absorb large amounts of heat but the increase of high temperature strength of lump coal was not significant. Contrarily, the lump coal’s high temperature strength was greatly improved at later stage of coke forming process. A number of residual coal was found in most tuyere coke samples illustrating that the lump coals added in the melter gasifier were not completely transformed into coke when they arrived at the tuyere region. The results indicate that the improvement of lump coal’s high temperature performance is limited in the melting gasifier by the low coke forming rate which could become the core factor of fines generation of lump coal in the melting gasifier.

Jan 1, 2016

By Arvind Thekdi, Cynthia Belt2

"Waste heat from industrial operations in metals industry represents 20% to 50% of the total energy used in most manufacturing plants. Reduction and recovery of waste heat offers the most attractive and cost effective method of reducing energy intensity for an industrial plant to meet corporate energy saving goals. It is possible to reduce or recover 30% to 60% of the available waste heat by using conventional and readily available technologies. Projects to reduce or recovery waste heat may offer less than 3 years payback to as short as a few months. This paper presents information on most commonly used methods for waste heat reduction and recovery in the metals industry operations. It describes the methods and use of analysis tools that would allow a user to estimate energy savings, CO2 or GHG reduction potential, and economic benefit and includes appropriate case histories.Waste Heat SourcesSources of waste heat abound with the metals industry. While the overall quantity of energy is high, the sources are distributed throughout a plant. The largest source within the metals industry is within furnace exhaust / flue gases. This includes the high temperature gases from burners in process heating such melting, calcining, and sintering operations. It also includes lower temperature gases from heat treat, dryers, and heaters. Lower temperatures are also found after post processed hot gases. This could include heat left after heat exchangers, regenerative systems, thermal oxidizers, and emission control systems. Other hot gases include air used in direct and indirect cooling.While waste heat in form of exhaust gases is readily recognized, waste heat can also be found within liquids and solids. Waste heat within liquids includes things such as cooling water, heated wash water, and blow down water. Solids can be hot product at discharge after processing or reactions are complete. Indeed, not only is energy wasted in the hot metal that slowly air-cools, but additional energy may be used in providing air or water-cooling to increase the speed of cooling. Other waste heat sources are not as apparent and include things like hot surfaces, steam leaks, boiler blow down water, etc. Table 1 and Figure 1 show several major sources along with the temperature range and characteristics of the source."

Jan 1, 2011

By W. G. Davenport

Chapter 13 evaluated the %02 in blast, industrial oxygen and oil requirements for smelting FeSrCuFeS2 concentrates~ This chapter examines high eu grade CU2S-CuFeS2 concentrates the same way.

Jan 1, 2001

By Gerardo H. Achurra

During the last years, the Caletones Smelter, like others copper smelters in the world, has evolved from the conventional, inefficient, pollutant and expensive technologies, to modern, environmentally friendly and efficient ones. For this reason' as well as to improve its competitive position this Smelter shut down the reverberatory furnace, started up two big acid plants and has developed some pyrometallurgical technologies. The main facilities of the Caletones Smelting and Converting Process, in the present and the future, are the Teniente Converters, the reactors with a high operational availability that have reached concentrate top process capacities near to 2,400 tpd. These reactors operate in most of Chilean smelters as well as in other smelters in the world such as in Zambia, Peru and Mexico. Since 2000, the Caletones Smelting and Converting Process, has been adapted in two Teniente Converters, four Slag Cleaning Furnaces and four Pierce -Smith Converters. These facilities, together with the operation of two Fluidized Bed Dryers and two Oxygen Plants have allowed to reach concentrate smelting capacities and copper productions of 1,250 ktpy and 380 kfipy, respectively. Associated to EI Teniente Division Expansion Plan, Caletones Smelter, in the first stage, will increase its capacity to 1,440 ktpy in 2004. In the long term, Caletones has different options, such as the processing of 1,600 to 2,000 ktpy of concentrate, producing anodes, white metal or a mixture of them. These options are connected with CODELCO's Smelters & Refineries Strategic Plan, including Mejillones Project. The main challenges of Caletones Smelter are associated to the development and the consolidation of the Continuous and Environmental Friendly Processes, automation and control of different processes and to the improvement of its leadership between other Copper Smelters in the world.

Jan 1, 2003

By Robert W. Bartlett

"Bioheap pretreatment of sulfidic refractory gold ore prior to cyanide leaching is a promising new technology, especially for low-grade ores that cannot afford to be oxidized by pressure leaching or roasting. When an ore contains both refractory and non-refractory (oxidized) gold, an economic decision must be made whether, or not, to pretreat before cyanide leaching. This choice is more complex than the familiar ore/waste cut-off grade decision. Pretreatment usually increases recovery but delays receiving revenue. Based on choosing the processing route that maximizes the present value of the ore, an equation is developed that computes a ""critical cyanide leachable gold grade"" for determining whether pretreating will be profitable. If the ore's actual cyanide leachable grade, without pretreatment, is above this ""critical grade,"" it will not pay to pretreat. The waste/ore cut-off grade, pretreatment yield (leachable grade after pretreatment), total gold grade, pretreatment operating cost and the project's financial discount rate are parameters in the equation. Results of example calculations are provided. This equation can be used for mine development planning and, when bioheap pretreatment is an available option, for daily operating decisions on individual ore blocks.IntroductionOres that are refractory because of sulfide mineral encapsulation of microscopic gold are becoming important. These ores must be pretreated to oxidize the sulfides to liberate the gold prior to cyanide leaching. The conventional pretreatment process technologies are pressure leaching with oxygen and two-stage fluid bed roasting. However, low-grade refractory ores cannot afford the high operating costs of these processes. And, small mines with limited reserves cannot justify the high capital costs of these processes."

Jan 1, 1997

By Nicola Baldo, Marco Pasetto

"The paper discusses the results of a laboratory study, aimed to evaluate the suitability of the bottom ash from Municipal Solid Waste Incineration (MSWI), obtained from different Italian plants, to be recycled in the lithic skeleton of bituminous mixtures, for base layers of road and airport pavements. The research involved a preliminary study of the physical and geotechnical properties of the bottom ash by itself; it was followed by a mechanical characterization of the bituminous concretes. The traditional Marshall methodology was used to identify the optimum bitumen content; the mixtures were also mechanically checked by means of the stiffness modulus test, repeated load axial test and fatigue test. Because the requisites for acceptance in the Italian Specifications and Standards have been satisfied and given the positive mechanical performances, it has been verified that the MSWI bottom ash can be used as substitution of the lithic materials in the road bases, also with very high contents (up to 81% on the weight of the aggregate). Introduction The incineration of Municipal Solid Wastes (MSWs) provides for by-products which can be mainly classified as bottom ash and fly ash. The first one, corresponding to the 25% on the weight of the wastes to be incinerated, so resulting the principal product of the process, is mainly composed by Silica (Si), Iron (Fe), Calcium (Ca), Aluminium (Al), Sodium (Na) and Potassium (K) oxides, so presenting a composition similar to that of different natural materials. Its metallic fraction can be recovered; the remaining part is usually stocked in dumping or, less frequently, recycled. Bottom ash can be re-utilised in the construction of new infrastructures, especially in bitumen bounded mixtures, because of the inert properties of the binder which covers the grains with a subtle film, that prevents the release of heavy metals. The paper describes a study aimed to design new bituminous mixes for flexible road and airport pavements, realised with the highest content of 4 types of bottom ashes, deriving from different MSWI plants of the Northern Italy. The ashes will be named as BA1, BA2, BA3, BA4 respectively (the origin cannot be specified)."

Jan 1, 2008

By Andre Krzysik

"Fluidized bed technology has been used in the industry for almost 100 years. To fully understand the process hundreds if not thousands of researchers were and are involved in finding the way to predict the behavior of the solids when subjected to the flow of media through them and the conditions of the solids in the fluidized state. The difficulties in predicting the behavior of solids in the fluidized state stem from the complexity and abnormality of the parameters related to the solid particles. Theoretical calculations can in some degree account for some of them. Particle size distribution, their shape, density, moisture content and physical and chemical reaction that may exist in the fluidized bed reactor play an extremely important role and influence the behavior of the fluidized bed. This paper focuses on the practical examples of the fluid bed equipment and the use of different conditions to process various products.IntroductionEach process application has its own unique requirements and the designers of the equipment must take into consideration specific process requirements, specific properties of the material to be processed (both physical and chemical), and physical and chemical reactions/changes that are taking place in the reactor (heat and mass exchange, chemical reactions, isomorphic change etc.). Each individual piece of equipment must also satisfy specific requirements/ preferences of the client that will operate and maintain the equipment. Those often represent greater challenges than the process on its own, and are equally important to the satisfactory operation of the plant. That includes aspects like location of the equipment, environmental effects, and expected life of the equipment, process control, access, maintenance, and many others.Over the period of time a great deal of research, both theoretical and practical have been carried out and the results of that work are available for equipment designers. For the simple applications that information is usually sufficient and the selection of a suitable solution is relatively simple. In many instances, the available information is not sufficient, and often specialized test work needs to be conducted to obtain additional data. In many cases a pilot installation is built in which the required process is tested. Only then the commercial equipment is designed. The following deal with specific installations that were designed to satisfy specific requirements. In some instances, additional problems were discovered during the commissioning of the equipment that required on site modification. The continuous monitoring of the equipment that was supplied to the various clients allowed us to further develop and improve our designs."

Jan 1, 2014

By Luis Velazquez, Andrea Zavala, Nora Munguia

"This paper is aimed at describing the evolutive strategy in which the University of Sonora is following for optimizing the organic and inorganic material life cycle in the products used on campus. The institutional strategy has be oriented towards new patterns of behaviors in order to integrate the principles of sustainability as a guideline for preventing, eliminating, and/or reducing the negative environmental and occupational impacts generated when performing university substantive functions of teaching, research, and outreaching and partnership as well as its management operation tasks.IntroductionThe University of Sonora is the largest and most important university among several other universities in both the city and the state. It is a public university with a 29,792 students in three campuses in the state. The main campus of the University of Sonora is located in the capital city of Hermosillo, which has a population of more than 609,829, in the state of Sonora in the northwestern region of Mexico [1].Despite the fact that in the University of Sonora there were, in the eighties, some projects dealing with environmental issues, there was not until 1992 that the sustainability efforts were really initiated. It happened when the Sustainable Development Group was created in the Department of Industrial and Systems Engineering as a response to the need for adapting the industrial engineering curricula to the challenge of sustainable development [2]. In order to promote sustainability, it has been necessary to cope and break with several university paradigms. For this reason, the strategy for becoming a sustainable university has continuously evolved throughout the years from a simple structure composed by individual and isolated projects to a systematic and integrative Sustainability Management System. Thanks to this evolution, the University of Sonora has won a respectable reputation in the greater community and it is seen in the region as an icon of sustainability promoter. In this sense, the substantives functions of education, research, and outreach and partnership, which are considered supportive and integrative, have also evolved to play a key role for the success of sustainability initiatives.The institution has followed four avenues for becoming a sustainable university; education, research, outreaching and partnership and greening the campus [3]."

Jan 1, 2008

By Shunli Zhang

Metals recovery from electronic scrap by physical separation may provide an alternative to the current recycling approach, through which halogenated flame retardants can result in hazardous dibenzo-p-dioxins and dibenzo-furans. On the basis of a complete sink-float analysis of personal computer and printed circuit board scrap, and in view of the advantages of dry processes for electronic scrap recycling by mechanical separation, air table separation is prioritized in an attempt to separate metals from plastics and glass involved. In the present paper, theoretical and practical considerations of air table separation have been detailed. It has been shown that air table separation is effective for recovering copper and precious metals from this specific waste stream. With the feed rate of 60 kg per hour, the combined grade and recovery of copper, gold, and silver attainable for the two heavy products produced by the air table used in the present study was shown in the following table:

Jan 1, 1998

By R. Padilla, I. Gonzalez, M. C. Ruiz, J. Salgado

The mining companies in Chile are increasingly using chloride salts and/or sea water in the sulfuric acid leaching of copper minerals. For this reason, the effect of chloride ions on the solvent extraction equilibria was investigated. Copper extraction isotherms were determined at 25 and 35 °C for aqueous solutions containing 6 g/l of Cu, 7 g/l of Fe, chloride ion concentrations of 0, 60 and 110 g/l, and a pH of 2.0. The organic phases were 20% v/v solutions of a ketoxime (LIX 84-IC) or a salicylaldoxime (LIX 860 N-IC). It was determined that the presence of chloride in the aqueous solution had a large negative effect on the extraction equilibria for both extractants, particularly the ketoxime. Therefore, as the chloride ion concentration increases, an efficient use of the extractant would become more difficult. An increase in the temperature from 25 to 35 °C positively affected the extraction equilibria for these extractants.

Mar 1, 2017

By Fjeldstad Karin Jusnes

Two quartz types used in the silicon and ferrosilicon industry were heated to temperatures of 1600 and 1700 °C. The parameters varied were the temperature and the holding time at maximum temperature. The amount of quartz, cristobalite and intermediate amorphous phase were measured using XRD and the internal standard method. Type P showed a much larger ability to transform to cristobalite at lower temperatures than type A. Type P had a larger amount of alkali and alkaline earth impurities. This could have enhanced the transformation to cristobalite. For quartz type A the amount of cristobalite was larger at 1600 °C than 1700 °C. This can also be seen for some of the samples of type P at shorter holding times.

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 Lakshman D. Jayaweera

Today's rapidly developing and changing technologies and industrial products and practices frequently carry with them the increased generation of materials that, if improperly dealt with, can threaten both public health and the environment. Mercury is an element that poses great problems in the many forms in which it is to be found in the mineral processing industry. These forms are often contained in hazardous wastes and residues which may be unstable, and in which the contained mercury has value. This paper presents some of the stabilisation and recovery methods which are based on hydrometallurgical techniques and thermodynamic stability considerations.

Jan 1, 1994

By Guo Chen, Jin Chen, Jinhui Peng

In this study, the influences of the green evaluation variables on the characterization of microwave shaft furnaces were systematically investigated. These variables include: resource consumption, environment impact, production cost, processing time and quality of microwave shaft furnaces. A greenness evaluation index, evaluation system and evaluation model of microwave shaft furnaces were established. The analytic hierarchy process and fuzzy comprehensive evaluation were applied to the evaluation process. Resource consumption and environment impact had a statistically significant effect on the green evaluation of microwave shaft furnaces. The results indicated that green evaluation techniques can be applied effectively and efficiently to the process manufacturing of microwave shaft furnaces.

Jan 1, 2015

By Pedro Lobarinhas

In the present work a two dimensional computational model is derived for the description of the time dependent heap leaching process. The flow inside the heap is calculated using the diffusion equations for the flow in porous media. The soil conductivity is also estimated assuming a close packed structure for the grain packing inside the heap. These equations, with appropriate boundary conditions, are solved using a time step splitting scheme. From this calculation the amount of leaching reagent in contact with the ore at any position inside the heap can be calculated and, once coupled with appropriate reaction equations, the amount of metals extracted can be computed and leaching agent concentration updated. The model is tested with available experimental data and the results have shown to be in a very good agreement. The model predicts all the transient features of the data.

Jan 1, 1999