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By Ron Bernard

HW Process Technologies has successfully developed and commercialized various applications utilizing Engineered Membrane Separation (EMS?) systems for the processing of acidic copper hydrometallurgical solutions and wastewaters. Copper hydrometallurgical EMS? applications include water balance control and increased copper concentration in heap and dump copper leach operations, tankhouse bleed stream treatment to separate/recover copper and cobalt from iron, and removal of PLS/Electrolyte suspended solids/colloids to eliminate "crud" formation during copper SX/EW. Similar applications are underdevelopment to provide ionic separations in copper refinery bleed streams, copper smelter acid plant streams, as well as organic/LIX removal from aqueous electrolyte and raffinate streams. Copper mine wastewater EMS? applications include treatment of copper leach solution contaminated groundwaters for copper recovery and treatment of unwanted heap/dump drainage to provide enhanced precipitation, a smaller precipitation plant, improved operating costs and better quality discharge water, particularly in terms of TDS and sulfates. A discussion of the EMS? technology and general separation results on typical process solutions and wastewaters will be presented. HW Process Technologies, Inc. commercial installations treating copper pregnant solutions and leach solution contaminated groundwaters are in-place at an old Asarco smelter/refining operation, Mexicana de Cananea copper mine, and a major U.S. copper mine, with several additional installations pending. Several case studies, including results from a selection of these installations, will be included with detailed capital, operating cost, and system payback data.

Jan 1, 1999

By M. Vijayalakshmi, S. Saroja, C. Sudha, T. N. Prasanthi

"Ti-5Ta-2Nb alloy and 304L austenitic stainless steel were joined by explosive cladding process. Investigations on 'as received' explosive clad revealed high hardness very near the interface due to martensitic transformation of 304L steel base plate. To improve ductility, explosive clads were heat treated in the temperature range of 823 to 1073 K for 1 to 20 h. Consequent change in the microstructure and microchemistry of the clad interface was studied. No change in the interface microstructure was observed for heat treatment at 823 K. Increase in temperature lead to the formation of various reaction zones at the interface, their number and width increase with temperature and time of thermal exposure. Growth kinetics of the reaction zones was monitored and activation energy required for formation was calculated. From elemental redistribution profiles, effective inter-diffusivities of alloying elements were calculated as a function of concentration and activation energy required for inter-diffusion was evaluated.IntroductionFor engineering components exposed to highly oxidizing and corrosive environments, a titanium based alloy i.e Ti-5Ta-2Nb (Ti-Ta-Nb) is often chosen as a structural material [1,2]. For economic consideration, vessels and piping exposed to non-oxidizing conditions are fabricated from 304L austenitic stainless steel (304L SS). Hence, dissimilar joint of Ti-5Ta-2Nb alloy and austenitic stainless steel becomes unavoidable. Fusion welding processes are not suitable for joining Ti and Fe based alloys due to the propensity for the formation of intermetallic phases and subsequent reduction in the bond strength [3,4]. Hence, explosive cladding, a solid state welding technique, was used to achieve high integrity, corrosion resistant joints between the two alloys."

Jan 1, 2012

By Eduard Ouerra, Nuo Jin

"The use of polytetrafluoroethylene, PTFE, as a solid sorbent for elemental sulfur during pressure oxidation of chalcopyrite was investigated. The effects of agitation, PTFE particle size and lingin sulfonate addition were evaluated using leaching conditions that were otherwise similar to those employed in the CESL process. The effects of these factors and their interactions on chalcopyrite oxidation are explained in terms of interfacial forces and solid-solid interactions. Using relatively fine PTFE powder with vigorous agitation resulted in about 100% copper extraction in less than 90 minutes without the need for grinding of the flotation concentrate.IntroductionThe extraction of copper from sulfide ores has always been dominated by the conventional pyrometallurgical smelting process. Though much effort has been made to develop various hydrometallurgical processing routes, smelting remains as the dominant process, treating approximately 80% of the chalcopyrite concentrates worldwide [1]. However, some of recently emerged techniques for treating chalcopyrite through hydrometallurgical routes are showing results that are competitive with smelting in terms of economical feasibility. Representative methods include: Activox Process, CESL Process, Anglo/UBC Process, High Temperature Pressure Oxidation, and Bio-Oxidation. Among these, the CESL processes operate at a medium temperature range (typically 140-150GC) and oxygen pressure of 100 psi, with chloride as a catalyst, and reportedly achieve copper extractions of about 95% with a light regrinding of flotation concentrate to a p95 of 45 ìðé [2]. In spite of this satisfactory extraction result, the leach residues contain significant amounts of conglomerates which contain a small amount of unreacted concentrate [2], The conglomerations are formed because the elemental sulfur generated is liquid and sticky (melting point of sulfur being 119°C), and has a tendency to wet the sulfide mineral surface, a fact which inhibits the oxidation of the minerals. The overall process chemistry of the CESL process may be summarized as follows [3]:"

Jan 1, 2012

By Hanlu Xie, Liang Yu, Ping Wang, Yuanchi Dong

"The leaching process is the first step when recycling BF slag as raw material for some other products. While studying the kinetics of the BF slag leaching process, a fractal phenomenon was found, which indicated some interesting mechanism in the process. The result suggested a new understanding of the leaching process in detail which useful for the industrial applicationIntroductionTypical composition (wt. %) of blast furnace slag varied in a pretty wide range: SiO2 30–40, Al2O3 10–20, CaO 30–40, MgO 5–10.The ground granulated slag is commonly used as base of roadway (mixed with natural inert for paving, soil stabilization, etc.) or one of the resources of Portland cements because of its good hydraulic activity [1]. To recycle the slag economically, the selective recovery of some components of the slag may be considered. As main components exist in the slag, silica [2, 3 and 4] and alumina [4] recovery was first considered.While recovering of silica from the slag, silica gels are recovered selectively from the leaching solution deriving from the treatment of the slag with waste sulfuric acid. After separation of the exhausted solid of leaching, the silica gel is precipitated from the solution at pH 3.2. Although the silica gels obtained by this procedure contain many impurities and need some more work afterward, it is the first and important step for the process.In the prior work [5], silica extraction using blast furnace slag had been investigated, focused on the pH value of selectively silica extraction. In the present work, kinetics of the leaching process was focused. It is important to design an economical process.ExperimentalThe composition of the slag and the calcined gels has been determined by a LINK860 (Oxford Instruments, Oak Ridge, TN) energy dispersive spectrometer (EDS) in conjunction with a CAMBRIDGE S250-M2 (Cambridge Instrument Ltd., Cambridge, U.K.) scanning electron microscope(SEM). The leaching of slag and the precipitation of silica gels have been conducted at atmospheric pressure in a stirred reactor placed at temperature controlled by a heated water bath."

Jan 1, 2008

By Abhishek Lahiri

Titanium dioxide is extracted from titaniferous ores by chloride and sulfate processes. These two processes produce wastes in the forms of iron chloride, iron sulfate and rare earth oxides gangue, each of which has to go through a further treatment before it can be disposed safely, which may be expensive. The shortage of high-grade ores is also making the two conventional processes less efficient. In view of the above mentioned problems, an alternate beneficiation process of roasting titaniferous ores with soda ash is discussed. The advantage of this process is that, there is no production of wastes. The impurities present in the ore can be selectively separated after the roasting process. The roasting of titaniferous ores with soda ash was carried out between temperatures of 873K and1173K for several hours. The roasting process resulted in the formation of complex alkali compounds and various sodium titanate compounds, depending on the Na2CO3to ore ratio. The phases formed after roasting were characterized using the X-ray powder diffraction (XRD), X-ray florescence (XRF) and scanning electron microscopy (SEM) techniques. The phase equilibria in the Na-Ti-O system are evaluated and compared with the phases obtained after the roasting process. The effects of temperature and the proportion of sodium carbonate on titaniferous ores are also discussed. From the experimental data, the overall reaction kinetics and phases formed were analyzed to ascertain the mechanism of overall reaction and the rate-limiting steps.

Jan 1, 2006

By F. Leclerc, V. Rebeyrolle, M. Revil-Baudard, A. Jardy, M. Založnik, H. Combeau

"Since the quality of Vacuum Arc Remelted ingots is linked to their chemical homogeneity and metallurgical structure, a modeling study of the solidification during VAR has been undertaken. It is based on the solution of the coupled transient heat, momentum and solute transport equations during the remelting of a cylindrical ingot. Solidification mechanisms implemented in the model include a full coupling between energy and solute transport in the mushy zone, and accounting for nucleation and finite diffusion of solutes at the microscopic scale, in both solid and liquid phases. This modeling can be applied to actual multi-component alloys. In this paper, the macrosegregation in Zircaloy 4 ingots is investigated. To validate the model, one single melt of a homogeneous electrode has been specifically performed. The comparison between the predicted macrosegregation and the experimental results shows the importance of accounting for solutal convection to forecast properly the macrosegregation in remelted ingots.IntroductionVacuum Arc Remelting of zirconium alloy ingots is a key step in the manufacturing process of fuel assembly components in nuclear reactors. The control of the chemical homogeneity is indeed fundamental to ensure the quality and the in-reactor performance of the final products. Despite the use of electromagnetic stirring to homogenize the liquid melt composition, chemical heterogeneities develop in the mushy zone during the solidification stage. One of the main challenges for zirconium producers, as well as titanium producers, is to master the VAR process in order to control the macrosegregation in remelted ingots. Macrosegregation results from the association of microsegregation and transport phenomena. The latter are primarily due to the flow in the liquid and mushy parts. It is now well established [1-4] that the hydrodynamics of the melt pool in a VAR ingot depends on the combined action of the followings: thermal and solutal buoyancy, self-induced electromagnetic force and the periodic centrifugal force caused by the angular movement generated by the stirring. However, for zirconium alloy ingots, the effects of thermal and solutal buoyancy forces on macrosegregation through their influence on the flow in the mushy zone have not been clearly identified."

Jan 1, 2012

By Ricardo Badilla-Ohlbaum

Copper has been used by man for a very long time and unlike certain other metals, it is an essential element for life. Its toxicity arises both from a deficit and excess copper exposure/intake. The focus of the current discussions in countries of the European Union (EU) and in some USA States, is based on the concerns, independent of the scientific facts and the economic status of these claims, of the negative influence of copper and other metals on health and the environment. These discussions have influenced the new regulations of copper in drinking water, and the approach to regulate the appropriate levels of copper in surface water, soils and sediments. To illustrate the challenges ahead for copper, the evidence by which the current US Environmental Protection Agency (USEPA), the World Health Organization (WHO) and EU recommendation and regulations regarding copper in drinking water have been derived is presented and discussed. The gaps between the demands for new standards of health and the environment and the practical scientific tools to achieve these goals are presented, and the need to develop new regulating paradigms is also illustrated. The introduction of methodologies for the regulation of essential elements and acute inorganic substances in drinking water is discussed, as well as the status of the present approach contained in the International Program of Chemical Safety Environmental Health Criteria, (EHC) N° 170. The impact of the possible restrictions on the use of copper in the EU because of health and environmental concerns in terms of the world market for copper is discussed.

Jan 1, 1999

By M. Somerville

In 1989 CSIRO Minerals initiated investigations into continuous converting of copper matte into low sulphur blister in Sirosmelt type reactors. Following the successful piloting of this processing route, some effort was directed towards a single stage copper making process where copper metal is made in one step from concentrate. The aim of the project is to develop a continuous process, which offers considerable environmental and economic benefits over conventional copper making processes, which use Pierce-Smith converters. In the selection of the optimum flowsheet a number of slag treatment options have been considered and tested. These unit operations include: leaching and electrowinning, flotation-leaching-electrowinning and flotation with recycling of recovered copper through the smelting vessel. In this paper the suitability of these process options are evaluated using the available information and recently measured copper recoveries from our testwork at CSIRO. The operating and capital costs of the various options have been estimated using Aspen Plus simulation procedures. The most attractive flowsheet in terms of capital and operating costs is the treatment of slag using mineral processing techniques and the recycle of a copper slag concentrate to the smelting vessel. It has been found that the chemistry of the slag being treated has a large bearing on the recovery of copper in flotation and hence on the economics of the process.

Jan 1, 1999

By W. E. Wallace

Rare earth elements combine with most, of the metallic elements. As early as 1971 over a thousand intermetallics had been identified and described(1) From a magnetics viewpoint, systems involving. the d-transition metals Fe, Co and Ni are particularly interesting. In these systems there are at least four significant interactions: R-R exchange (R - a rare earth), R-T exchange (T = a transition metal), R-R exchange and the crystal field interaction acting upon the. rare earth ion. There is complex interplay between these interactions leading to bewildering variety in their magnetic behavior., Because of this and in view of the commercial significance of some rare earth intermetallics, studies of these systems has been an unusually active area of inquiry for the past two or three decades. The large magnetic moment of many of the rare earths, viz., 10 µB per atom for Dy and Ho, 9 1B for Tb and Er, etc., attracted, attention many years ago to the rare earths as potential ingredients for alloys to be used in permanent magnet fabrication. The utility of a permanent magnet in high perform¬ance devices (travelling wave tubes, voice coil motors, brushless motors, etc.) is in large measure determined by its maximum energy product, (BH)max. [(BH)max is the maximum value of B (magnetic induction) and H in the 2nd quadrant of the hysteresis loop.] Enhanced atomic moment in princple can lead to increased B and a large maximum energy product. Until about 1970 the largest (BH)max value known was about 5 MGOe(mega-gauss Oersted). This was for A1NiCo - an alloy involving Al, Ni and Co. It was recognized that the rare-earths had the potential for much higher energy product; in the case of Dy the theoretical energy product is about 35.0 MGOe., 70 times that of Alnico. (Needless to say, this theoretical value has never been achieved.) Large-scale efforts began about 30 years ago to synthesize magnetic materials containing rare earths and which would be suitable for permanent magnet fabrication. It was recognized by Strnat(2) et al. that a material to, be useful in high energy magnet fabrication would have to satisfy three. criteria:

Jan 1, 1992

By Jiu-ju Cai, Wen-caho Liu, Fei Liu

"With the northern cities of China as study objects, and to confirm Ground-source heat pump system of the environmental benefit and the developing direction. In this paper LCA was applied to the environmental benefit Ground-source heat pump System from raw materials acquisition to system production, utilization and disposal. The conclusion shows that Ground-source heat pump system of the environmental benefit in the northern cities of China. The result showed that Ground-source heat pump system had remarkable environmental benefit. 1. Introduction Life cycle assessment Originate in the sixties of last century, what it paid close attention to is to obtain processing from products raw materials, the processing of products produces, products transportation, products use and maintain to the influence to environment of course. It is a products -oriented environmental management style, it is the environmental management mode of meeting the needs of sustainable development strategy [1]. The research object was in the city and lie in the North of China, would undertake Beijing Olympic Games some football matches in the second half of 08, in order to improve the local environment, adjust the energy structure, reduce the heating consumption of urban coal in the centre, eliminate the coal-burning boiler under 10 tons, since 2005, the local government promotes and utilizes actively the heat pump technology in the source substitute the heating of coal-burning boiler. At present, this area is adopted the technological heating area of heat pump of source reach 20 million square meters, account for this area heat 11.2% of area always, it is estimated, by 2010, adopt the technological heating area of heat pump of source will reach 65 million square meters, the proportion of the area rises to about 30% to account for this area and always heat [2 ]. Study to the whole lifespan of heating system of heat pump of ground source of this area on the basis of LCA method, obtain the products impact on environment of different stages and environmental benefit, find out and reduce or dispel the measure of the influence, improve the environmental benefit of the ground source heat pump heating system.2. MethodologyThe research approach used in this research is the Life cycle assessment, the frame of the research approach is goal and scope definition, the inventory analysis, impact assessment, interpretation.[3][4][5]"

Jan 1, 2008

By T. A. Chepushtanova, B. Mishra, E. O. Kilibayev, V. A. Luganov

"The paper contains the results of studying about modification of pyrite and arsenopyrite specific surface and porosity at their thermal decomposition. The studying of specific surface was carry out by B.E.T. – adsorption of nitrogen at his boiling-point. In our work were using the electron-microscopical, X-ray structure analysis and chemical analysis. There was established that the decomposition of pyrite and arsenopyrite accompany by increasing of pores volume from 0.303 · 10-3 to 1.23 · 10-3 at increasing of pyrite degree of decomposition about 41 % and then decrease about 0.131 · 10-3 m3/g at degree of decomposition near 100 %. The surface area of pores increase from 0.31 to 1.085 m2/g with following lowering due to enlargement and confluence of minor, small pores. Increasing of porosity accompany with increasing of particles windage that appear the result of heightened dust-furnace partially decomposing pyrite and arsenopyrite particles by air flow from furnace reaction zone. This explains heightened contention of sulfide sulfur in roast dust of sulfide concentrate. 1. INTRODUCTION As a result of ore base exhaustion of ferrous and nonferrous metallurgy at metallurgical treatment are involving more complicated and less qualitative ores. Magnetiting ores content considerable quantity of pyrite complicative the technology of iron extraction. At the same time the pyrite concentrates wining at dressing content different nonferrous metals in industrial quantities. Extracting ores of nonferrous metals are contenting considerable quantity of arsenic at the present time. Extraction of base metals from complicated raw materials demands new technologies. Arsenic contenting in ores is necessary to utilize (waste burial) in more ecological compatible form. Arsenic on acting metallurgical and chemical enterprises from technological cycle is withdrawing in the form of arsenate – arsenite cakes, burial of their may lead to seriously ecological problems as times goes by. In Kazakh National Technical University is carry out the cycle of researching by pyrite, arsenopyrite and arsenate – arsenite cakes treatment with the object of arsenic withdrawal in sulfide form – in more ecological and safe form and with the object of preparation of initial ore raw materials to following pyro- and hydrometallurgical treatment. As a result of sulfidizing of arsenate – arsenite cakes by pyrite are forming the volatile arsenic forms and pyrrhotite of variable structure."

Jan 1, 2008

By Daniel Kim, Justin McAllister, Shijie Wang

"At the Kennecott Utah Copper Refinery, impurities in the electrolyte are being precipitated in the circulation system and form a hard scale in the piping. This scale must be removed periodically for proper electrolyte flow. Distinct layers of differing composition form as the operating conditions of the tank house change. Scale samples from the inlet and outlet pipes were analyzed to discover the nature of the precipitates. Each sample was sectioned and examined under optical microscopy and SEM. The composition of the scale was analyzed using ICP, XRD, and SEM/EDX mapping. The rate of deposition was determined by measuring the amount deposited on new pipes after elapsed time intervals. In order to determine how to minimize the formation of the scale, the mechanism was studied and the results are presented in this paper.IntroductionIn copper electrorefining, impure copper anodes are refined into pure copper cathodes. The impurities from the anodes are either insoluble and report to the slimes or soluble and dissolve concentrating in the electrolyte. These impurities are controlled by bleeding electrolyte from the system. Over time, the impurities combine to precipitate a hard scale on the surfaces contacted by the electrolyte. The scale causes problems with tank house circulation systems. In order for the refinery to operate properly, the scale must be removed periodically from the walls of the pipes. The first step to control the buildup of scale on the pipes is to understand the composition and the phases that are present in the scale."

Jan 1, 2012

By Maria Margarida Lima, Maria Lucelinda Cunha, Dora Algarvio

"The main goal of the present work is the quality improvement of the recycled aggregates produced by a construction and demolition waste (C&DW) recycling facility located in Montemor-o-Novo, Portugal. The recycling process was developed on a pilot plant scale with 50 t/h of capacity. Process operations are the hammer mill comminution, magnetic separation and screening.In order to improve the knowledge on the C&DW, a characterization procedure was implemented by hand-sorting, magnetic and density separation on representative samples. On the other hand, to improve the quality of the produced aggregates, the bar screen size fractions were analysed, according to the Portuguese Standard (NP EN 933-1 2000).Wood was identified as the critical contaminant, representing 17% by weight of the total contaminants. Sieving results showed that about 97%, 76%, 56%, 98% and 57% were on the correct size range, which lower results are probably due to the type of screens and/or the material characteristics of the recycled aggregates.IntroductionThe construction and demolition waste problemConstruction and demolition waste (C&DW) is generated by the construction activity, resulting from both, buildings or other structures construction and old structures demolition. As a reference, it can be told that C&DW comprises about 40 to 50% of rubbish (concrete, asphalt, bricks, blocks and dirt), 20 to 30% of wood and related products and 20 to 30% of miscellaneous wastes [1]. In Portugal, C&DW is classified in the LER (Portuguese nick name for the European Waste List), Chapter 17, and includes a diversity of wastes, like concrete, bricks, ceramics, bricks, wood, glass, plaster, copper, zinc, lead, iron, steel, as well as insulation and roofing materials. C&DW stream has several characteristics which make it particularly difficult to deal with and are summarized in the following five items.(1) Lack of information on quantities generated: In Portugal, the C&DW sector has been neglected over the past years, which meant that there are not consistent information concerning the quantities and composition of these wastes yet. Several estimates, based in different assumptions, indicate different results, which may vary from 219 Mt to 10 931 Mt [2]."

Jan 1, 2008

By Honorio Oliveros Gómez, Oscar Jaime B. Restrepo

"Colombia produces nine tons of electronic waste per year and there are approximately 60 tons accumulation generated in the last nine years. This work aims to establish a general methodology in the laboratory to recover gold, silver and platinum group present in electronic waste, also explore other forms of recovery of metals contained in electronic waste. We selected seven types of electronic cards present in the computers, which have their parent desoldering electronic components. Initially, we characterized the components of the cards through X-ray diffraction and SEM, to identify the metal species and composition. Tests were conducted laboratory hydrometallurgical recovery of metals. This paper proposes a methodology for laboratory-scale work.INTRODUCTIONColombia produces nine tonnes of electronic waste per year and build there in about 60 tons generated in the last 9 years [1], Computers, TVs, audio equipment, monitors, cell phones, remote controls, printers and operated toys battery, among others are part of this inventory, which mostly comes to landfills, because the lack of legislation to control the final destination of waste electrical and electronic equipment, and lack of efficient technologies to recover materials [2]. Under these circumstances which have environmental implications, technological and economic recovery is essential metals present in the electronic cards of computers, by hydrometallurgical with subsequent base metal electrodeposition [3]. Pyrometallurgical route is discarded by major implications for economic and environmental [4]. Recovery From this perspective, the determination of the metal fraction and the relationship between the different metals, using the SEM characterization techniques - BSE and XRD is indispensable [5] It follows with electrolytic dissociation processes in the leaching and electrodeposition [6], and unit operations in the laboratory to carry out successfully these processes on a larger scale. Were randomly selected computer twenty-four postcards for nine types of cards have different functions in the computer, which, through the absorption desoldering technique, they broke the resistance (thermal, surface, photoresist, power), capacitors (ceramic, electrolytic), diodes (silicon, germanium, high frequency), transistor (NPN, PNP), processors, integrated (high, medium and low frequency), the RAM card and pin parallel port serial"

Jan 1, 2011

By Wankun Wang, Shixing Wang, Jinhui Peng, Zebiao Zhang

"Germanium leaching from germanium dust and fume was carried out using sulphuric acid. Response surface methodology (RSM), based on a five level, four variable central composite design (CCD), was employed to obtain the best possible combination of liquid/solid ratio (Xi: 2-10), leaching time (X2: 1-5 h), sulphuric acid concentration (X3:3.15-15.75mol/L) and leaching temperature (X4:50-90 *C) for germanium leaching. The obtained experimental data were fit to a one-order polynomial equation using multiple regression analysis and also analyzed by analysis of variance (ANOVA). The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The optimum extraction conditions were: liquid/solid ratio of 10, leaching time of 1 h, sulphuric acid concentration of 15.75 mol/L, and leaching temperature of 87.8 'C. Under these conditions, the germanium leaching extent was 65.14%, which is in close agreement with the value predicted by the model. The samples were characterized before and after leaching using X-ray diffraction (XRD).IntroductionResponse surface methodology (RSM) is one of the relevant multivariate techniques which can deal with multivariant experimental design strategy, statistical modeling and process optimization [1-15]. It is used to examine the relationship between one or more response variables and a set of quantitative experimental variables or factors. This method is often employed after the vital controllable factors are identified. It is also used to find the factor settings that optimize the response. Designs of this type are usually chosen when a curvature in the response surface is suspected [6], The process optimization of the sulphuric acid leaching of germanium from germanium dust and fume has not been reported in the literature. Hence the present work intends to assess the effects of variables such as liquid/solid ratio, leaching time, sulphuric acid concentration and leaching temperature and to identify the optimum conditions using RSM. The characteristics of sample before and after leaching are assessed using the advanced analytical instruments such as X-ray diffraction (XRD)."

Jan 1, 2012

By Philip L. Sibrell

A new process utilizing pulsed fluidized limestone beds was tested for the remediation of acid mine drainage at the Friendship Hill National Historic Site, in southwestern Pennsylvania. A 230 liter-per-minute treatment system was constructed and operated over a fourteen-month period from June 2000 through September 2001. Over this period of time, 50,000 metric tons of limestone were used to treat 50 million liters of water. The influent water pH was 2.5 and acidity was 1000 mg/L as CaCO3. Despite the high potential for armoring at the site, effluent pH during normal plant operation ranged from 5.7 to 7.8 and averaged 6.8. As a result of the high influent acidity, sufficient CO2 was generated and recycled to provide a net alkaline discharge with about 50 mg/L as CaCO3 alkalinity. Additions of commercial CO2 increased effluent alkalinity to as high as 300 mg/L, and could be a useful process management tool for transient high flows or acidities. Metal removal rates were 95% for aluminum (60 mg/L in influent), 50 to 90% for iron (Fe), depending on the ratio of ferrous to ferric iron, which varied seasonally (200 mg/L in influent), and <10% of manganese (Mn) (10 mg/L in influent). Ferrous iron and Mn removal was incomplete because of the high pH required for precipitation of these species. Iron removal could be improved by increased aeration following neutralization, and Mn removal could be effected by a post treatment passive settling/oxidation pond. Metal hydroxide sludges were settled in settling tanks, and then hauled from the site for aesthetic purposes. Over 450 metric tons of sludge were removed from the water over the life of the project. The dried sludge was tested by the Toxicity Characteristics Leaching Protocol (TCLP) and was found to be non-hazardous. Treatment costs were $43,000 per year and $1.08 per m3, but could be decreased to $22,000 and $0.51 per m3 by decreasing labor use and by on-site sludge handling. These results confirm the utility of the new process in treatment of acid impaired waters that were previously not amenable to low cost limestone treatment.

Jan 1, 2003

By Rumen Markov, Lubomir Kuzev

"The treatment technologies for municipal solid waste (MSW) are effective mainly for components sized over 40 – 50 mm. This fraction is separated by screening in the beginning of the process. Usually the undersized product is deposited without additional treatment. Its quantity is variable from several up to 30 – 40 % of the total MSW. Both oversized and undersized fractions are formed by all types of primary matter. Adapted technologies from mineral processing will provide a suitable technology for treatment of MSW under 40 – 50 mm. The MSW content depends on the geographical location, the degree of urbanization and other factors. The methods can be applied for separations of different components suitable for recycling or other utilization are: • Separation by density; • Separation in thin liquid layer; • Selective grinding and screening; • Flotation, etc. Introduction Municipal solid waste (MSW) represents an integral part of public urbanization. However, there are some drawbacks stemming from MSW, in regard to its collection, transport and elimination. Different approaches exits worldwide for tackling the problems arising from MSW. For a short period of time, the attitude towards MSW has evolved in several levels, each further level being characterized by higher percentage of utilization of MSW components. Thus, the bottom line has been shifted from safety storage towards processing that includes recycling and maximal utilization of MSW components. Technologic processes applied for treatment of MSW have a common feature – that the fine components, having sizes under 20 mm, 30 mm, 40 mm, or 50 mm are excluded from treatment process trough screening, and in most cases diverted without any additional treatment to preliminary prepared storage sites. MSW in Sofia – current situation The amount of MSW collected daily in Sofia as around 1000 t/24 h. It is stored or baled. Baling is a spare alternative of storage, since baling insures only temporal keeping of MSW, till the building of suitable storage site where the bales will be transported and buried. The morphologic composition of MSW in Sofia has been determined several times at different time intervals, from some Bulgarian organizations as well as from the Japanese organization JICA. So far, however, there is still a lack of enough systematical and comprehensive study. Generalized results from the studies on the MSW components, as well as some important parameters are given in Table 1."

Jan 1, 2008

By Yongxiang Yang, Yanping Xiao, Robert G. Harskamp

"Stricter environmental regulations demand for safer treatment and disposal of incineratior fly ashes. So far no sound technology and processes are available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the MSW (Municipal Solid Waste) incinerator residues. The objective of the current research is to better understand the behaviour of the environmental harmful elements during low or high temperature treatment, and to find an optimum route for an efficient processing of the incineration fly ash. In the present study, the fly ashes including boiler ash and ESP (Electrostatic Precipitator) ash sampled from a MSW incinerator were washed with warm water, and the residues were dried and sintered or vitrified at high temperatures. The solutions from ash washing were analysed, and will be treated for salt extraction and purification. The ash residues before and after thermal treatment were also analysed. The results of vitrification and thermal behaviour were compared with those from the ashes without pre-washing. It was found that water pre-washing is an efficient way to remove certain water-dissolvable volatile salts such as chlorides, and thus the secondary emissions during vitrification could be reduced. INTRODUCTION The air pollution control residues from MSW incineration are classified as harzardous waste, including boiler ash, ESP ash and filter cake. The boiler ash is the firstly settled flue dust in the dust-collecting equipment under the boiler, the ESP ash is collected by an electrostatic precipitator in the second step, finally the flue-gas is further cleaned by the wet-scrubbers and residues are accumulated in the filter cake. Both the boiler ash and ESP ash are classified as hazardous materials, harmful to the environment due to the high concentrations of environmental hazardous elements. However, due to the different locations of the ash collection, the boiler ash has different compositions compared to the ESP ash, and is considered less toxic. Fly ash is generally toxic and with low bulk density, and has to be treated before final disposal. The current industrial practice is normally the landfilling after partial detoxification such as cement solidification."

Jan 1, 2008

By Takashi Yoshida

"This paper will discuss the recent situation and future of the zinc industry from the technical point of view. It includes recent problems faced by the zinc industry and technological developments. One of the biggest problems of the zinc industry is raw materials. Traditional zinc concentrate becomes much complicated with respect to its chemical and physical properties. Thus, each process faced various problems. Also, secondary resources, generating so called recycling processes, become much more important. Recycling is, of course, a very important aspect for sustainable development of society. Secondary raw material also includes a great variety of impurities not included or very low levels in traditional zinc concentrate. Some problems are caused by these impurities. To overcome these problems some technological challenges have been taking place. Details will be discussed in the symposium.IntroductionZinc is a very useful metal based on its elechtro-chemical, chemical and physical properties. The most important usage is galvernizing of steel which is used for automobile, construction and a very wide range of other indutries. Also, zinc is used for dicasting and other alloys such as brass. Smelting of zinc is different from other metal because of its electro-chemical properties. Many parameters should be controled compared with other metals such as iron and copper. Typical zinc smelting processes are the Imperial Smelting Process (ISP) and the electlolytic process. The ISP process is a pyro-metallurgical process using a blast furnace. The electrolytic process is a hydrometallurgical process. Both processes are energy intensive, and the smelting process cost is increasing because of higher energy costs. The situation of the ISP is very severe because of higher coke prices. Recently, many ISP plants have been shut down because of economic reasons"

Jan 1, 2012

By B. Boryczko, J. Norwisz, Jose Escobedo Bocardo, Z. Kolenda, A. Holda

"Classical thermodynamic analysis of any thermal and chemical process is usually based on the first law of thermodynamics. Such an approach is not sufficient when deeper understanding of the nature of each elementary process is required. The use of the first and second law of thermodynamics together is necessary to solve practical process more effectively. Enthalpy and exergy balances allow to enhance our understanding of thermal processes especially when cumulative consumption of energy and exergy is calculated. To ensure reliability of such an analysis the least squares method for adjustment of mass balances of principal chemical elements has been applied and described in detail. Numerical analysis has been carried out to compare two different processes of copper production – shaft furnace and flash smelting.IntroductionClassical thermodynamic analysis of any technological process is usually based on the First Law of Thermodynamics in the form of energy (enthalpy) balances. Such an approach is useful in engineering practice as it makes analysis easier in the global scale neglecting modeling of the elementary processes, allows calculation of the thermal efficiency and makes possible to control quality of the measurement results. Additionally, graphical presentation of the energy balance is simple in the form of Sankey diagram.In the case of aluminum electrolysis process, design of the new electrolyzer or its modernization is always based on the enthalpy balance.However, deeper thermodynamic analysis leads to the conclusion that such an approach is not sufficient. The First Law of Thermodynamics guarantees the exact equivalence of the various forms of energy (allowing all forms to be measured in the common unit such as joules) but it does not guarantee interconversibility. Thermal energy (heat) is in a peculiar and unique position, for whereas all other forms can be completely converted into thermal energy, the reverse process id impossible, only a portion of the heat can be converted into mechanical energy. Explanation comes from application of exergy balances. As we know exergy expresses the amount of mechanical work necessary to produce a material in its specified state from components common in the natural environment, in a reversible way, heat being exchanged only with environment [1]. Consumption of exergy connected with the fabrication of some considered product appears not only in the plant manufacturing the product, but also in all plants delivering raw materials for the final production process"

Jan 1, 2008