Search Documents

By A. Golpaygan

Application of Computational Fluid Dynamics (CFD) modeling for simulation of fluid flow and combustion in industrial scale electric furnace is presented. Poor combustion efficiency, roof and/or side wall overheating, carry over to off-gas system and non-ideal radiative heat transfer to processes or cooling systems have been common limiting factors causing inadequate process performance of the furnace, operational problems, and safety hazards. This paper describes how CFD analysis can be used to obtain a better understanding of commonly observed problems associated with freeboard combustion. Examples are presented to describe using combustion CFD modeling to understand requirements to diagnose a problem with furnace design including required freeboard volume or possible roof/side wall overheating.

Jan 1, 2011

By Helena Byrdziak

KGHM Polska Miedz SA, in existence since nineteen seventies, operates three underground mines and three smelters with total production of over 400 000 mtpy of electrolytic copper. Its impact on the environment, very serious in the past, has been gradually reduced. While in general emissions into the air and water have been brought under control, attention recently has shifted to the disposal of wastes and residues. The main streams of wastes are flotation tailings, slags and dust captured from the dedusting systems. Much effort has already been expended and is still being spent to utilize this waste for by-products production or to dispose of it within the process by recycling. The most effective measures taken up thus far, as well as present activities directed at tailings disposal, are presented.

Jan 1, 1997

By David Yankovich, Geoff Hughes, David Haug, Jon Kaneshiro

"In March 2013, the Sanitation Districts of Los Angeles County began final design of the Joint Water Pollution Control Plant (JWPCP) Effluent Outfall Tunnel project. The new, approximately 7-mile, 18-ft internal diameter tunnel will provide additional capacity and redundancy for the existing 8- and 12-foot diameter tunnels, which were built in 1937 and 1958, respectively. Connections to an existing, active 14-foot arch force main and four existing ocean outfalls ranging from 5- to 10-foot diameter are required. This paper will present geological features for the project, and details of the proposed post-tensioned tunnel liner and associated structures. INTRODUCTION The Sanitation Districts of Los Angeles County (Sanitation Districts) are 23 independent special districts serving approximately 5.3 million residents in Los Angeles County. Seventeen of the districts that furnish sewerage services to the metropolitan Los Angeles area are signatory to a Joint Outfall Agreement that provides for a regional, interconnected system of facilities known as the Joint Outfall System (JOS). The JOS service area is shown in Figure 1. The JOS serves an area that encompasses 73 cities as well as unincorporated territory and parts of the City of Los Angeles. The JOS provides wastewater collection, treatment, reuse, and disposal for residential, commercial, and industrial users, and it includes seven treatment plants, the largest of which is the JWPCP, located in the City of Carson. Currently, secondary treated effluent is conveyed through two 6-mile long parallel tunnels, 8- and 12-feet in diameter, from the JWPCP to a manifold structure located at Royal Palms Beach, near White Point on the Palos Verdes (PV) Peninsula, from which four seafloor outfalls extend offshore. The two main outfalls, 90- and 120-inches in diameter, extend approximately 1.5 miles offshore and discharge at a depth of approximately 200 feet below sea level. The other two outfalls, 60- and 72-inches in diameter, are used for additional capacity during heavy rain events and extend a shorter distance offshore and discharge at shallower depths. A schematic of the existing system with the proposed tunnel and structures is shown in Figure 2, and the proposed 18-ft diameter tunnel alignment is shown in Figure 3. Both existing tunnels and main outfalls are required to be in service at all times."

Jan 1, 2016

By Jiakai Zhang

Many postconsumer electrical and electronic equipment wastes contain a considerable amount of rare earth elements (REEs); however, the current level of REE recycling from them is limited (<1%). Neodymium–iron–boron (NdFeB) magnets, used at both small- and large-scale, from computer hard disk drives and small tools to wind turbines and cars, are a good example of such waste materials that contain high content of neodymium (Nd) and dysprosium (Dy). These elements are considered critical metals because they are the main building block of emerging green technologies that will allow for GHG emission reductions. Because demand for these green products is increasing around the world, the demand for REEs is increasing quickly, putting their supply at risk in the near future. Thus, it is critical to develop efficient, robust, and cost-effective processes to recycle these elements from this class of electronic waste materials. Here, we performed a thorough characterization of a N52–NdFeB magnet to identify its composition, crystal structure, and morphology. Furthermore, we developed an efficient hydrometallurgical process to extract Nd and Dy with high efficiency (more than 95%).

By R. H. Hanewald

INMETCO, a subsidiary of Inco Limited, is the only facility in North America that provides High Temperature Metals Recovery for nickel-, chromium-, and iron-bearing wastes. Since 1978, this process has prevented more than 775,000 tons of materials from becoming part of the nation&apos;s waste stream. The paper describes Inco&apos;s experience in metals recovery, traces the development and explains the operation of the High Temperature Metals Recovery Process, and examines the procedures and criteria used to determine whether spent catalysts meet process feed specifications. An overview of the current requirements for transporting spent catalysts is provided. The paper concludes with brief case histories of catalysts users employing High Temperature Recovery to manage spent catalyst.

Jan 1, 1995

By Frank D. Lamb, Lloyg H. Baning

"The crushed-stone industry has long been troubled with the problem of producing a more or less cubical product for use as concrete aggregate. Its seriousness varies widely for each producer, depending upon the character of the rock employed for raw material and the ultimate use of the crushed stone. For many construction uses, such as the macadam or bituminous-concrete- type road, flat pieces are not objectionable and may even be preferable to more cubical rock. However, most specifications for concrete require that the stone must be reasonably free from flat and elongated pieces.The rigid specifications set by many contractors have resulted in the rejection of coarse aggregate that, except for the presence of an excessive amount of flat and elongated pieces, would be entirely acceptable. In many instances, if an efficient, economical method of removing flat and elongated pieces were available, local producers could meet the requirements of the contractor and thus eliminate the necessity for importing more cubical material.A brief investigation of the problem of removal of flat and elongated pieces from crushed aggregate, carried out at the Eastern Experiment Station of the Bureau of Mines, indicated that it is mechanically possible to remove flat pieces from crushed rock.TEST EQUIPMENTA number of mechanical devices are used by the coal industry for separating slate from coal; these depend upon the difference in shape of the crushed slate as compared with the coal. Such devices as shutter screens, spiral separators, and the Norman picker would be suitable for removing flat pieces from crushed rock in the same manner as they are used by the coal industry. None of these devices was immediately available for testing purposes, so an attempt was made to construct a simple device that could be used in commercial operations."

Sep 1, 1944

By T Sasaoka, H Shimada

Mined-out limestone/aggregate quarries in Japan contain many high and enormous pit walls. Many precious resources are abandoned in these final pit walls. In addition, there are many mines which are located in or near populated areas in Japan. Utilisationof the potentially useful under- ground space at mined-out sites is a topic relevant to the practice of surface mining. This paper describes and discusses the concept of underground space utilisation and tunnelling systems, referring specifically to geotechnical/ tunnelling parameters.

Jan 1, 2008

By J. A. Venter

Mineralogical studies indicate the Pt-Pd-Bi-Te class to react poorly on the flotation stimuli and indications are that these minerals are slow floaters. However, recent studies performed on a number of minerals from this class indicated strong interactions with potassium ethyl xanthate resulting in the formation of dixanthogen (only one of several xanthate species). The poor flotation response is not a result of poor interaction of xanthate with the surface. It is proposed that the oxidation products of sulfides in the process water interact with the PGM surface. To test this, the effect of thiosulfate (an important oxidation product of sulfides) was investigated by employing electrochemical measurements and FTIR spectroscopy. The electrochemical investigations indicate no strong effect of thiosulfate on the interaction of xanthate with the minerals surface as well as the reduction of oxygenthiosulfate is likely not responsible for the poor flotation response of these minerals in industrial plants.

Jan 1, 2014

By Himaki Nakano, Kenji Hara, Toshiaki Tsuru, Shunsuke Kawano, Takeshi Ohgai, Hisaaki Fukushima, Shigeo Kobayashi, Tetsuya Akiyama

"Electrodeposition of Fe-Ni and Zn-Ni alloys from aqueous solutions is one of the well-known examples of anomalous codeposition in which less noble metal deposits preferentially. In this paper, the electrodeposition behavior of these alloy systems was compared between the methanol and aqueous baths. In Fe-Ni system, the significant suppression of the deposition rate of more noble Ni was observed over a wide range of electrolysis conditions in both methanol and aqueous baths. However, the electrodeposition of Zn-Ni alloys showed the typical feature of normal type codeposition in the methanol baths, which was completely different from that in aqueous sulfate baths. The difference in the electrodeposition mechanism between Fe-Ni and Zn-Ni alloys was discussed on the basis of the alloy deposition behavior in the baths in which the activity of water was varied:INTRODUCTION'It has been well known that Fe-Ni alloys show an excellent soft magnetic property. Therefore, thin films of this alloy have been used to fabricate the'-various magnetic devices. For the production of Fe-Ni thin films, dry processes such as sputtering, PVD and CVD are 'employed frequently and the resulting films showed a preferable property as a magnetic material. Electrolyses as a production technique of thin films, on the other hand, has the advantage over other processes in its cheaper production cost due to the simplicity of the production unit The Zn-iron-group metal alloys such as Zn-Ni and Zn-Fe electrodeposited on a steel sheet ale known to exhibit excellent corrosion resistance and therefore the electrodeposition of these, alloys has been applied to the production of surface treated steel sheets mainly for automotive body panels.According to Brenner (1), the electrodeposition behavior of Fe-Ni and Zn-Ni alloys was' classified into the' 'anomalous type. In this type of codeposition, less noble metal, i.e. Fe for Fe-Ni and Zn for Zn-Ni system, deposits preferentially and the change in -the alloy composition- with the variation of electrolysis conditions was unpredictable because of their obscure deposition mechanism. Since most properties of the alloys mainly depend on their composition, the composition of the deposited' alloys must be controlled strictly. Therefore, it is neces5al)' to clarify the mechanism of anomalous codepasition in Fe-Ni and Zn-Ni systems: Several mechanisms have been proposed so fur, and among them the hydroxide .suppression mechanism (2), (3) has been regarded most plauslble depend on their composition, the composition of the deposited' alloys must be controlled strictly. Therefore, it is necessary to clarify the mechanism of anomalous codeposition in Fe-Ni and Zn-Ni systems: Several mechanisms have been proposed so far, and among them the hydroxide suppression mechanism (2), (3) has been regarded most plausible. According to this mechanism, it can be predicted that the codeposition behavior depends greatly on the characteristic of water solvent in this study, using methanol as a solvent, the electrodeposition behavior of the anomalous codeposition was investigated to discuss the validity of the hydroxide suppression mechanism."

Jan 1, 2000

By S. Boisvert

Risk-based Inspection (RBI) addresses the challenges associated with ageing plants by focusing the inspection effort on the process equipments with the highest risk, thereby improving plant safety and reducing inspection costs. The RBI methodology is commonly used in the oil industry through the API 581 standard. Since no such standard exists in the mining and metals industry, BPR-Bechtel has developed one using inspection data from process equipments in CEZinc. Models were developed for various damage mechanisms, such as uniform corrosion and stress corrosion cracking. The equations were organized into a user friendly software that facilitates the implementation process.

Jan 1, 2010

By Werner Wenzel

Methods to increase the gas penetration through sinter layers. In the field of agglomeration, sintering has gained importance, specially in Europe; in Best-Europe this trend will continue till the year 1980, since it is quite probable that in the blast furnace burdens with 50-60 sinter, 10-20 % pellets and 20-25 % ore lumps will be employed. In order to meet this demand for sinter, new sinter bands with reaction areas between 300-400 m2 will be constructed. Chemical and physical phenomena during the Suction-Draught-sinter process. Iron ore sintering is generally considered as a burning process where the material contains 90-95 % ash i.e. non-combustible ingredients. Sintering represents a heterogeneous exothermic reaction in which the chemical phenomena as combustion, calcination, hydration, reduction and oxydation are superposed by physical phenomena. The physical phenomena are devided into material transport and simultaniously occurring heat transport processes. The velocity of these combined physico-chemical reactions i.e. the change in the reaction site per unit time determine the efficiency of the sinter process. The gas permeability as an important criterion of heat transport during the Suction-Draught sinter process.

Jan 1, 1971

By Fred H. Lippold, Wm. H. Wolf

Methods of fair payment for excavating, supporting, and concrete lining tunnels have been sought by various owners for years. Tunneling techniques have changed with the development of equipment-from the hand-mucking operation to the machine mucker and, most recently, to machine-boring; from tunnel supports using timber sets to steel sets to rock bolts and, most recently, to shotcrete support; and from hand-placing the concrete lining using wooden forms to pumping or pneumatic placing using steel forms. As tunnel construction techniques advanced, so did methods for payment for the work performed. The recent development of tunnel-boring machines, or "moles," is precipitating another change. These changes have led to some difficulty in providing proper payment for the various items of work for different types of tunnels. As a major construction agency engaged in water-resources development in the western states, the U.S. Bureau of Reclamation has long been aware of the need for clarification of payment provisions in tunnel construction. The Bureau has some 150 miles of tunnels completed on its projects and about 50 miles of tunnels under construction. In this construction, the Bureau has benefited by the advance made by contractors in improving the techniques of tunnel excavation. To assure that the Bureau has an up-to-date approach to payment provisions, the Chief Engineer recently established a "standard" method of payment for all types of tunnels. It is believed that this new method of payment will be equitable for all contractors bidding on various types of tunnels using the diversity of methods of excavation now available to them. These payment provisions provide for different quantities for excavated tunnels using the blasting technique or using machine-boring techniques. In this way, the contractors have a choice in excavation methods and an equal opportunity to be low in their bids. We believe this will be an incentive to all contractors to be as progressive as the development of new equipment economically allows.

Jan 1, 1970

By Robert D. Pehlke

"The evolution of oxygen steelmaking is reviewed and new operating processes are described. The developments which could impact this technology are summarized. Staged and continuous steelmaking are considered in the light of new technologies. The future opportunities for oxygen steelmaking processes are overviewed. IntroductionThe use of oxygen in steelmaking was originally brought on the scene by the development of pneumatic steelmaking. Sir Henry Bessemer in England originally conceptualized the use of gaseous oxygen in steelmaking, and then he and William Kelly in Eddyville, Kentucky independently developed the original pneumatic process which involved blowing air through a bath of molten pig iron to oxidize the carbon and silicon and produce steel. This process and many following processes, including those which would use pure oxygen gas, have been proposed.Beginning with the first commercial oxygen steelmaking vessels at Linz, Austria in 1952, the world steelmaking industry has adopted this style of processing. In general, the process has involved the use of steel scrap in amounts from 20 to 35% of the metallic charge with molten pig iron produced in blast furnaces making up the remainder. The impurities in the charge are oxidized through the use of oxygen gas injected into the steelmaking vessel.However, currently being adopted into commerical practice and on the horizon are a number of advances in this process which include the use of iron ores as a source of iron and oxygen, the use of an all scrap charge, incorporation of pre-reduced iron, the use of auxillary fuels to change the balance of cold and liquid iron-base charge materials and numerous refining techniques."

Jan 1, 1988

By C. Martinez, S. Helle, M. Pincheira

We studied the feasibility of automated mineralogy to discriminate between tennantite and enargite, the main sulfosalts found in the Rio Blanco deposit, Codelco-Chile, in order to predict the content of minor elements (As, Sb, Ag, Pb, Zn) that impact on the process and concentrate prices. The identification of these minerals is feasible using traditional microscopy, however not possible by automated mineralogy. This drawback prevents comparing the databases generated in the past by means of conventional microscopy with the information obtained at present by QEMSCAN. To differentiate enargite from tennantite the mineral composition of both sulfosalts was studied by electron microprobe. The presence of associated minor element contents of about 8% zinc in tennantites and not exceeding 0.07% in enargites were used to modify the SIP database of QEMSCAN to enable the quantification of these phases in samples of head, residue and concentrate coming from As-bearing domains of the deposits. Detection limits allowed to determine the mineral species in the head, concentrate and residues. The integration of methodologies such as automated mineralogy and microprobe can be used successfully to quantify the presence of some ore forming solid solution.

Jan 1, 2014

By P. T. Velu, R. G. Reddy

"The use of emf measurements to derive classical thermochemical data has been in use for many years. The reaction associated with electrochemical process is harnessed in a galvanic cell and energy involved measured in terms of electromotive force. The property requirements of sensor electrodes used differ for various aqueous, molten salt and solid electrolyte systems. The electrodes for molten salt electrolytes need special care for construction. This paper describes the studies carried out using an Ag/ AgCI reference electrode. This electrode was used to measure the solubility of compounds in molten salt electrolytes. The results obtained using this electrode are in excellent agreement with the values from chemical analysis method.I. IntroductionThe technique of obtaining a metal from its oxides by electrolysis is more than a century old process now. In these processes, it has been well established that for halide electrolytes, only the dissolved oxides are available for the dissociation at the electrode to release the metal during electrolysis. Therefore, the solubility of metallic oxides in the molten salt electrolytes is an important parameter which determines the economical and technical viability of these processes. The widely used molten salts systems in halides are fluorides and chlorides. The fluoride electrolyte system is used in our present study.The viability of obtaining aluminum alloys by in-situ electrochemical processing has been outlined in our earlier publications[1-8]. Studies on the solubility of various alloying element compounds is a part of our ongoing research efforts for the direct production of Al-Li alloys. As mentioned above, the solubility of lithium oxide and lithium carbonate compounds in molten fluoride electrolyte system have studied using EMF technique. The change in potential of the molten electrolyte was measured by a working electrode against the reference electrode with the addition of lithium compound."

Jan 1, 1997

By E. I. Robinsky

"In light of the recurring spills and failures of conventional tailings disposal pond dams, a brief review of the Thickened Tailings Disposal (TTD) system is presented. It is shown that by the process of thickening the tailings to a heavy slurry prior to disposal, it is possible to create a self-supporting deposit of tailings and to eliminate the typical superimposed settling pond. These features, together with the ability to reclaim the disposal area even as mining continues, preclude an ecological disaster. IntroductionMine tailings spills are really not such rare occurrences. They have been happening on many continents, in many countries. Neither Canada nor the United States have been spared. In Ontario, the most recent spill occurred at a closed-down tailings disposal area in Matachewan, in 1991.Such continuing disasters could be avoided if a different approach were taken to the disposal of tailings wastes. The recent failures at the Los Frailes mine in Spain, the Omai mine in Guyana, and the Marcopper mine in the Philippines, will hopefully shake up the industry to consider other methods of disposal. The reason why the failure of a conventional tailings disposal dam is so environmentally disastrous is not the dam itself, but the fact that the dam retains a mass of very loose unconsolidated tailings and a great deal of water, or process fluid1. If the dam fails, the contents liquefy completely as they flow through the breach. In this liquid state, they can flow many miles downstream. If the dam itself were built of tailings material, as is often the case, it too would liquefy and join the flow.The reason the material is so loose in the first place is that it has been discharged into a pond filled with water. The tailings particles drift down through the water, their weight reduced by 50% due to buoyancy, to form a loose structure, like a “house of cards,” or lakebottom mud. It doesn’t take much of a shock to collapse the material into a liquefied state."

Jan 1, 1999

By Honggang Zhong, Tan Yi, Qijie Zhai, Zhao Dan, Xinping Mao, Huigai Li

"The influence of superheat degree on the distribution and volume content of inclusions were studied in 65Mn thin slab produced by compact strip production(CSP) in Zhujiang Steel in China, The results showed that the diameters of inclusions are mainly less than 5µm. Most of the inclusions gathered at the 1/4 thickness direction for the thin slab of 27? superheat degree, compared with the center position for that of 37?. There are more inclusions larger than 50µm in the low superheat samples, which is caused by the short floating time. In addition, the inclusions were observed and analyzed by metallurgical microscope, SEM and EDS in order to ensure their composition, type and further find their source. It was find that the types of these inclusions mainly are Al2O3, SiO2,CaO and their composites, a few of them are TiN and MnS.IntroductionIt is well known that inclusions have a great impact on the strength, plasticity, fracture toughness, cutting performance, fatigue property and corrosion resistance of steels. Especially, with the demand for thinner slab, the cleanness is increasingly becoming more significant as a quality criterion[1]. High manganese and carbon steels not only demonstrate high strength but also proper plasticity. There are many problems unsolved for 65Mn steel as a result of the low solidification rate, bad thermal strength, crack sensitivity and low casting temperature[2,3].The superheat of the molten steel has a great impact on the erosion of refractory lining, molten steel fluidity and non-metallic inclusion behavior[4]. The serious erosion situation of ladle lining, nozzle and casting tundish will give rise to more inclusions at a high superheat. Meantime higher superheat will make second dendrite arm spacing coursing and element segregation which lead to inclusion, bubble formation and shrinkage cavity. On the contrary, it is hard for non-metallic inclusions to float up with a low superheat value. Inclusions of 65Mn steel, which produced in different superheat condition by CSP, were studied for the sake of higher slab properties including statistics and EDS analysis."

Jan 1, 2012

Datun Concentrator currently processes complex sulfide ores in Gejiu Municipality, Yunnan Province, China. The ore contains much higher arsenic than other ores. The run of mine ore is fed to the concentrator to recover copper and tin by bulk flotation and gravity concentration, and then the other sulphides, such as pyrite, arsenopyrite, etc. didn?t get utilized and are discarded as tailings due to the high arsenic content. In order to utilize the pyrites in the tailings, a series of tests have been conducted for finding the solution of arsenic removal from high arsenic-bearing pyrite concentrates through simple flotation process. By means of orthogonal experimental design, the optimized levels and main factors have been found out for the roughing stage. Through selection of the effective in-organic depressants for the arsenic-bearing minerals, the arsenic in the pyrite concentrate can be removed to meet the requirement of sulfuric acid plant (As%=0.5%) by the open flotation process, i.e., one-time roughing and two-time cleaning.

Jan 1, 2014

By F. K. Letowski

Leaching in froth is a particular case of a three phase (liquid-solid-gaseous) process which combines flotation with leaching by using a reactive gaseous reagent as a flotation carrier and a leaching solution as the reactive liquid medium to fonn the foam (froth) in&apos; which the solid particles are suspended. Some physico-chemical and engineering aspects of leaching in froth are discussed and illustrated by its application for cleaning the mineral graphite. Leaching of the graphite concentrate containing 4L4% of the elemental carbon and 3.16% of the sulphidic &apos;sulphur was canied out in the froth fonned by: (a) a concentrated chloride solution, with a small addition of nitric acid, in the foam state; (b) a mixture of gaseous O2, NO., and H20 encapsulated in the foam; and (c) notable particles of graphite suspended in the foam. The laboratory experiments werecanied out in a "flotation column"-type reactor ala temperature from 80 to !08°C and under total pressure of 100 to 200kPa. In the 3-stage leaching-flotation process, the non-flotable fraction of particles was separated three times from the notable fraction. The concentration of carbon and elemental sulphur in the final flotable fraction was 96% C and 0.38% S respectively. The expected advantages and possible application in hydrometallurgy are suggested.

Jan 1, 1995

By J. E. Dutrizac, J. B. Sunstrum

"Lead was among the first metals known to man, and there are indications that lead was produced by the reductive smelting of galena in the mountains surrounding the Black Sea as early as 3000 B. C .(1). The early metallurgists soon discovered that silver could be recovered from lead bullion by cupellation techniques, and that the litharge product of the cupellation process could be reduced to give silver-free lead metal. By the Graeco-Roman era, lead-silver ores were being extensively exploited for both their silver and lead contents. Although silver was always of prime concern, a number of industrial uses existed for lead that included piping and sheeting. Subsequently, lead metallurgical practice developed steadily in different parts of the world, and was a relatively mature technology by the time of the European colonization of North America. In the United States, lead was produced on a small scale as early as 1720, and by 1800, the extensive Pb-Zn deposits of Missouri-Kansas and the upper Mississippi Valley were being developed(2). Many of the early American lead ores were low in silver, and seemed to have been worked primarily for their lead contents. Major uses of lead at the time included bullets, pipe and sheeting. During the period 1860-1890, the silver-rich galena ores of the western United States were exploited, and a number of lead smelters were operated. Although all the smelters produced lead metal, the recuperation of the associated silver and gold values was generally of prime concern. In Canada, lead deposits are abundant, and galenarich outcrops frequently attracted the attention of the early explorers and prospectors. In fact, the first record of a Canadian ore deposit seems to have been the observation of an argentiferous galena vein near Lake Temiscamingue in 17 41(3). The presence of silver-bearing lead deposits naturally attracted the attention of the mining community, and many outcrops were worked throughout the country. Because of the problems associated with transporting lead concentrates to existing American or overseas smelters, attention soon shifted to the establishment of local lead smelting facilities. The purpose of this article is to examine those early smelting efforts and to try to identify the first ""successful"" Canadian lead smelter."

Jan 1, 1999