Search Documents

By Anne Kvithydl

Printed circuited boards contain considerable quantities of valuable metal, while also containing many environmental pollutants making them unsuitable for landfill. In this study the decomposition of common plastics used in printed circuit boards were studied. Polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyethylene (PE) were heated in both CO, and argon atmospheres using a thermo-gravimetric furnace (TG) coupled to a mass spectrometer (MS). Soda ash Na,C03 and baking soda NaHC03 were used as reactants. The degradation temperatures and evolved gases are presented for single plastics and mixtures. Mixed plastics are shown to behave as a sum of the individual plastics. The mass loss temperature is the same in CO, and argon. However, less residue is formed when heated in CO,.

Jan 1, 2008

By Norbert Steiner

For the desulfurization of weak SO2 gas streams, Degussa developed a process using dilute H2SO4 solution containing H2O, instead of conventional gas scrubbing with all solid absorbent medium (limestone, MgO). The process is based on fast reaction of H2O, with SO2 yielding H2SO4 up to 70% strength, depending on off-gas temperature. Compared to the conventional systems with typically < 95% efficiency, independent on the raw gas SO2 concentration, residual SO2 concentrations of less than 20 mg/Nm3 can be easily achieved, corresponding to nearly 100% removal. These features render the H2O, process a very attractive, low capital cost technology to retrofit existing conventional desulfurization plants.

Jan 1, 1996

By Rong Zhu, Guang-sheng Wei, Kai Dong, Ling-zhi Yang

As a shortage of information technology support, steel plant is unable to real-time tracking production cost of each working procedure, and can’t form the information feedback in time. Information integration technology for dynamic monitoring becomes a development trend of process control in advanced iron and steel enterprise. The paper based on the characteristics of EAF steelmaking process and requirements build the digital platform and process guidance model, which is designed to solve for smelting composition control, cost control, and optimizing guide in EAF steelmaking process. The model is including: data acquisition module, cost monitoring and calculation module, EAF endpoint carbon control module, alloy material optimization module, component monitoring and forecast module, process guidance module, data maintenance and query module.

Mar 1, 2018

By Fathi Habashi

Laboratory autoclaves for hydrometallurgical investigations are available in a variety of sizes, models, and materials of constructions. They vary in sizes from 25 mL to 2 liters for laboratory studies and 5 to 50 gallons for pilot plant work. They are essential tools for studying aqueous oxidation of sulfide concentrates, dissolution of oxide minerals at high temperature and pressure and hydrothermal precipitation reactions. The maximum pressure and temperature at which any pressure vessel can be used will depend upon the design of the vessel and the materials used in its construction. Since all materials lose strength at elevated temperatures, any pressure rating must be stated in terms of the temperature at which it applies. A review of existing models and their accessories will be given.

Jan 1, 2000

By M. K. Alam

Chemical Vapor Deposition (CVD) processes are currently attracting special attention in materials processing. CVD processes are now used to produce special materials in the form of thin films, coatings, composites, and optical fibers. This process produces material of high purity, in complex shapes, and in a variety of microstructures. It is a capital intensive process, involving use of high cost raw materials. Modeling simulations have the potential of reducing the time for CVD . process design, and the need for experimentation. Modeling would, therefore, appear to be an attractive option for producing a product of acceptable quality. At Ohio University, progress has been made in modeling of CVD processes, specially in the areas of optical fiber preform fabrication, and fiber coating.

Jan 1, 1990

By C. S. Ek

Tests have been performed to recover silver and lead from residues produced after a super-hot leaching in a zinc hydrometallurgical plant operating with jarosite precipitation. When this residue is leached in ammoniaammonium sulfate or in diethylenetriamine solutions, lead dissolution is not complete and its recovery from the aqueous solutions is either difficult, due to the operating conditions, either expensive due to the amount of added reagents. In both cases, silver is partly dissolved, partly left in a new residue still containing lead and baryum sulfates. The best treatment seems to include a selective flotation producing first a silver concentrate assaying about I % Ag, then a 50 % lead concentrate collecting the baryum salts, and a final quartz-gypsum tailing. Metal recoveries can reach 50 % and 80 %, respectively.

Jan 1, 1989

By Dianyuan Dang, Guihong Han, Wenjuan Wang, Tao Jiang, Yanfang Huang

In this study reduction kinetics and swelling behaviors in "two-step process” were investigated by weight-loss technique and visualizing physical changes of pellet. Results showed that reduction degree (r) increased with increasing temperature and time. According to the dynamic calculation, when reduction temperature was lower than 1000°C the reduction process was controlled by chemical reaction with apparent activation energy of 72.27 kJ/mol. When reduction temperature was higher than 1000 , the equation of t/[1-(1-r)1/3] against [1+2(1-r)-3(1-r)2/3]/[1-(1-r)1/3] followed straight lines, demonstrating that reduction was mixed-controlled. Swelling experiments indicated that the maximum swelling index increased with the increase of reduction temperature and CO content.

Jan 1, 2016

By M. Bugdayci, Onuralp Yucel, K. C. Tasyurek

This paper is a contribution to the theory and quantitative understanding of the processes for the production of magnesium, calcium and strontium metals by metallothermic process. In the present study, effect of reductant type was investigated. Thermodynamic simulation of system was made by Fact Sage 6.4 program. In order to produce magnesium metal, effects of reductants “FeSi, Al, Si and CaC2” were investigated. To understand Calcium-oxide reduction system, effects of Al and CaF2 addition were investigated for different temperatures. In the last simulations, SrO reduction parameters were simulated. Al used as main reductant and BaO, CaO, CaC2 were added to green mixture as a functional additive. Finally probable phases and minimum reduction temperatures are determined.

Mar 1, 2018

By Ronald J. McGregor

An overview or precious metals project development and start-up, which emphasizes the process decision. Logic which determines process flowsheet, project economics, and training required to train new operators for start-up. The process decision required to successfully develop a precious metals project requires a blending of test data, environmental considerations and operations experience. Decisions to use Merrill-Crowe or carbon adsorption/ electrowinning/replating, fixed pad or multi-use pad {in heap leach) are dependent not only on technology but also on ability to train new operators. The market for experienced operators is acutely depleted and almost all new operators will have to be "home grown". Experience from the Brewer project in South Carolina as well as other projects put together in the West will be discussed.

Jan 1, 1989

By Qingsheng Liu

A new method of recycling aluminum dross for preparation Al-Si-Ti alloy was studied in this paper. This was carried out in two processes. first the aluminum doss was pretreated by leaching and calcining process, the fine purity and phase of the intermediate oxide powder up to electrolysis demands, then, could be obtained when aluminum dross after washing have been leached for 2h at 100? in 20% hydrochloric acid and calcined for 2h at 1200?, which was treated by cryoite-based molten salt electrolysis. Finally, the Al-Si-Ti alloy was successfully obtained through electrochemical co-deposition in the cathode shows a typical as-cast microstructure. This new recycling method can produce high quality alloy and may bring remarkable economic and social benefits.

Jan 1, 2010

By Li Chen

A new process, i.e. Ball milling--Neural leaching--Oxidation calcinations--Chloridizing distillation--Hydrolysis, was designed to recover germanium from the vacuum furnace slag produced in Shaoguan smelter. The suitable process and operational parameters were determined for the practical production.

Jan 1, 2005

By J. A. Eisele

There is currently much interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using alkaline cyanide solution. Agitation leaching tests were performed by the Bureau of Mines on 14 precious metal ores using sodium cyanide (?NaCN) and thiourea [(NH2)2CS) as extractants. The objective was to compare the results of the two extractants. NaCN was used at a concentration of 2 g/L with and without H202 as an oxidant. (NH2)2CS was used at concentrations of 2 and 20 gjL, and the solution potential was controlled at 390 to 420 mV standard hydrogen electrode (Eh) with Fe2(S04)3. With both reagents a.t 2 g/L extractant levels, NaCN extracted more gold and silver than (NH2liCS from all of the ores. At 20 g/L (NH2)2CS compared with 2 g/L NaCN, (NH2)2CS extracted more gold than NaCN from two ores, the same amount from one ore, and more silver from one ore. NaCN extracted more gold than (NH2 )2CS from 10 ores and more silver from 4 ores.

Jan 1, 1989

By Iain B. Mackenzie

In 1997, a thin layer of Microtherm Microporous Insulation was used to replace fireclay brick behind the magnesia/chrome working lining in #5 refining furnace at BHP?s San Manuel AZ smelter. A 23°C reduction in shell temperature was obtained, together with a large increase in the working capacity of the vessel. There was no sign of metal penetration as a result of the increased insulation. Following these highly favorable results, BHP have introduced this product into all of their refining furnaces.

Jan 1, 1999

By Carlos M. Fontes Vieira, Ruben J. Sanchez Rodriguez, Carlos E. Gomes Ribeiro

"In this study we attempted to model a response surface for the apparent dry density of ternary blends of calcitic marble particles. The crushed marble was divided into three granulometric ranges. Simplex network methodology was used to determine the mathematical relation between granulometric ranges and apparent dry density (ADD) of particle mixtures. A highly significant regression was obtained and the simplex network methodology proved to be able to predict high packing particle compositions.IntroductionProblems with packing and expected porosity of particles are common and widely recognized to be important in terms of both fundamental physics and engineering applications. For example, densification of a powder mass is important in the shaping of solids in ceramics, powder metallurgy or composite synthesis; chemical processes such as solid-liquid separation (sedimentation, thickening and filtration), raw material handling (stockpiling, blending, drying, storage and transportation) and pyrometallurgical processes (agglomeration, coke making, ore sintering, blast furnace iron making and new iron making processes) [1,2].Many factors can affect particle packing, but in practice, there are three main factors: (dimensionless) particle size distribution, particle shape and absolute particle size [2].Geometrical and practical methods were developed to predict properties in mixtures. Zou, Gan and Yu [2] present a paper treating a prediction of the porosity of multi-component mixtures of cohesive (fine) and non-cohesive (coarse) particles. Bahiense et al. [3,4] used a simplex network to determine a mathematical model for obtain the optimal compositions between aggregates to a greater packing of a ternary particles mixture. Despite these techniques for predicting particle packing, some studies in particulate composites production don't present clear criteria for choice of particle distribution [5,6]. As the best particle packaging depends on the size, distribution and shape of these particles, individual models can be constructed for specific combinations of these factors."

Jan 1, 2014

By Hiroshi Ono

"By newly developed ICP method, trace amounts of As(III), As(V) .,Sb(III) and Sb(V) were precisely determined within accuracy of sub ng/ml. As(III) and Sb(III) were separated from As(V) and Sb(V) by extracting into ·xylene as diethyldithiocarbamate complexes using diethylammonium diethyldithiocarbamate (DDDC), and then back-extracted into nitric acid for a quantitative determiruition by ICP-AES equipped with hydridegeneration system The recoveries of As(III) and Sb(III) were satisfactory throughout the extraction with 0.04mol/l DDDC in xylene from lmol/l hydrochloric acid solution and the back-extraction with 7 mol/l nitric acid. As(V) and Sb(V) were reduced to As(III) and Sb(III) by ascorbic acid and potassium iodide, and their quantities were determined as mentioned above. The detection limits were found to be 0.58ng/ml for As(III), 0.63ng/ml for Sb(III) using 50ml of a sample. The proposed method was applied to analysis of the real sample.Introduction In drain, arsenic(AS) concentration is prescribed below 0.lmg/l, so As must be removed. As is existed at .the form of As(III) or As(V) in solution. For t1Jeir difference of chemic;µ property, it is not easy to remove As in solution. So it is an urgent necessity to develop for determining concentration of As(III) and As(V). Antimony( Sb) has resemblance .chemical property to As. So Sb was experimented the same as As.The separation and determination of As(III) and As(V) have been carried out using several methods, such as ICP after copreclpitating separation, HPLC, direct hydride generation atomic absorption. However these methods have some problems. One of main problems is that HPLC and direct hydride generation atomic absorption methods are influenced by coexisting elements."

Jan 1, 2000

By Jin-Chun Kim

Nanosized W based powders (W, WC, WC-Co) were produced by chemical vapor condensation (CVC) process. Two different solid W(CO)6 and Co2(CO)8 metal-organic materials were used as precursors. CVC experiment was conducted in the temperature range of 400-1100. As-CVC WC1-x powder which had non-stoichiometric composition was carburized by using of the CH4-H2 mixed gas in temperature range of 750-850. The CVC W and WC1-x powders showed loosely agglomeration structure, and the Co powder had intricate long stand structure because of intrinsic magnetic properties of Co phase. Carbon content of the CVC powders controlled by gas-phase carburization was well matched with theoretical WC stoichiometry (6.13wt%).

Jan 1, 2006

By Anthony C. Mulligan

Metals have historically been used in mining since they offer an excellent combination of hardness, toughness and cost and can be fabricated to form a variety of shapes. However, for many applications the metals used today have limited performance in the environments in which they are needed. This is particularly true for geothermal environments where the brines are highly siliceous causing corrosion and accelerated wear of many components. Geothermal sources are increasingly being explored for their high thermal value as well as possible sources for future minerals. While advanced ceramics have historically been expensive to produce in comparison with metals, they offer significantly greater corrosion resistance and hardness and can improve the overall performance when used in selected ?problem? areas. One of the major drawbacks in the use of ceramics in high impact areas has been their brittle nature and propensity to fracture and spall (fail) when loaded. Recent advances in the fabrication of ceramics have combined hard (strong) ceramics with more ductile ceramics in a architecturally designed microstructure, thus allowing ceramics to perform well in these high impact regions. Additionally, ceramics are significantly more inert to corrosion from either alkaline or acidic environments and can typically be used for significantly longer periods in these environments than their metallic counterparts.

Jan 1, 2006

By E. J. Peuraniemi

Recently commissioned Kennecott-Outokumpu flash converting was developed to replace the approved but environmentally outdated Peirce-Smith -converting to satisfy the globally tightening emission regulations. In the present study, dust formation and reaction mechanisms of two copper mattes with different experimental parameters were studied in lean suspension conditions. Both mattes had very high copper content of approximately 75 wt% and low iron content of 4.5 wt% and 1.2 wt% Fe. A laboratory scale, vertical laminar-flow furnace with a low feeding rate was used to simulate the phenomena taking place in the reaction shaft of a flash converter. Experimental conditions included temperature of 1300 °C with reaction gas oxygen contents of 20 vol%, 50 vol%, and 75 vol%. In the experiments, sieved particle fractions were fed to the furnace and sampled after short reaction time intervals by quenching them into a water film. Collected particles were analysed chemically for their main elements to define their removal rates. Also, optical and scanning electron microscopy with EDS-analyser were applied to determine phenomena occurring during reactions. Kinetics of oxidation as well as ignition of particles are discussed. Changes in particle morphology, size, and composition are reviewed to describe dust formation and reaction mechanisms.

Jan 1, 1999

By Ning Wang, Bing Xie, Hong-Yi Li

"Compared to traditional sodium roasting, calcified roast inhibits chlorine pollution. A vanadium extraction technique based on a calcified roast is especially suitable for vanadium slag with high calcium content. In this report, V205was extracted from vanadium slag by calcified roast followed by acid leaching and hydrolysis precipitation. In optimized conditions, the high silicon low vanadium slag was roasted at 850'C for 2 hours without CaO addition. The roasted materials were leached with 35 % H2SO4 in liquid/solid ratio of 5:1 (mL/g) at 95OC for 4 hours. The extraction of vanadium was as high as 97.66 %. These results are instructive to V2O5 production in industry.IntroductionVanadium slag is produced in converter, sodium salt roasting is the commonly used technique to extract vanadium. In sodium salt roasting, vanadium slag is roasted with sodium salts including sodium chloride and soda as additives, followed by leaching with acidic or basic solution [1]. However, in this process chloride reacts to produce corrosive gases including HC1 andCl2- SO2 and SO3 can also corrode equipment severely and are also an environmental contaminant. The low melting point of sodium salts leads to fusion agglomeration, which blocks vanadium oxidation and thus decreases the extraction rate of vanadium. A large amount of sodium salts consumed as roasting additives increases the production cost. Moreover, sodium salt roasting requires low CaO content in vanadium slag. When the CaO content increases to 1%, V2O5 extraction can amount to 4.7%-9% [2]. For vanadium slag with high CaO content, the sodium salt roasting technique leads to low vanadium extraction rate."

Jan 1, 2012

By Yavuz Ali Topkaya, Aydin Rusen

"In this study, zinc and lead recovery from zinc plant leach residue obtained from Çinkur using hydrometallurgical methods have been investigated by laboratory scale experiments. Considering more than one million tons leach residue (LR) rich in Zn (12.43%) and Pb (15.51%) in the stockyard and environmentally hazardous, it is essentially necessary to process Çinkur LR. Zinc and lead have been recovered in two main stages. As a first step, Çinkur LR was releached by using hot sulphuric acid for zinc recovery. About 72 % Zn was recovered by using 150 g/l H2SO4 at 95 oC in 2 hours with a pulp density of 200 g/l. Secondly, for lead recovery brine (NaCl) leaching tests were performed on the secondary Çinkur LR obtained after acid leaching process. In brine leaching while lead recoveries up to 95 % could be attained at a low pulp density, the maximum recovery obtained was 84.9 % at a high pulp density (200 g/l) with 300 g/l NaCl concentration in 10 minutes at 95 oC. Introduction Zinc and lead have been known and used by humans since ancient times and also they are important nonferrous metals [1]. Zinc and lead have different properties thus they are used in various application areas, ranging from automobiles to construction, from batteries to textile. Zinc and lead deposits are widely distributed in the Earth’s crust. The principal ore mineral for zinc is zinc sulfide, Sphalerite (ZnS), and lead sulphide, Galena (PbS), is the main source of lead in the world [2].Although zinc is generally produced from sulphidic ores (ZnS) or concentrates by Roast – Leach – Electrowinning (RLE) in the world, in Turkey, zinc production is based on zinc carbonate ores (ZnCO3), and at the Çinkur plant zinc was produced from zinc carbonate from its establishment to 1997 due to high reserves of zinc carbonate in that region. Çinkur is the only plant in Turkey that produces Zn from primary ore containing ZnCO3 by Waelz – Leach - Electrowinning route [3]. However, due to depletion of local high grade ores, oxidized ore concentrates were imported from Iran after 1997, until this plant was shut down. Therefore, there are two different leach residues (LR) which are Turkish LR (TLR) and Iranian LR (ILR) in Çinkur stockpiles. It has been estimated that the total amount of leach residue is more than one million tons of which the major part is Turkish leach residue (TLR)."

Jan 1, 2008