Search Documents

By Huimin Lu, Shi Zhou, Lisha Yang

"The Zeolitic imidazolate frameworks (ZIFs) were successfully synthesized by applying a combination of ionothermal synthesis and microwave energies for rapid synthesis. The synthesis was proceeded under various conditions including different raw materials, reaction temperature as well as microwave irradiation time. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are new type of porous materials formed by inerratic polyhedral in three-dimensional. They are the ideal crystalline substances for gas separation and storage. The assynthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and C02 adsorption test. Results illustrated that the synthesized samples had stable structure, high thermal stability (up to 530 °C) and C02 adsorption capacity (10.2 cm3/g at 0°C under ambient pressure). This novel method also showed great advantage with high energy efficiency, safe synthesis conditions, and rapid crystallization time (60 minutes).IntroductionNowadays, carbon dioxide capture has become imperative due to the global warming caused by the increase of C02 in the atmosphere, especially produced by the concentrated sources such as power plants [1]. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are ideal crystalline substances for gas separation and storage due to their structure diversity, high thermal and chemical stability [2-5]. They are formed by inerratic polyhedra in threedimensional with large cages and small apertures. Traditionally, ZIFs are synthesized by solvothermal method in a sealed autoclave under autogenous pressure [6-9]. However, in order to generate the products, the solvothermal temperature should not be lower than 100°C according to the sovlothermal mechanism. Moreover, at such a temperature, molecules with a low boiling point (such as water) may generate high pressure in reactor which might cause danger [9]. Thus the synthesis requires the equipment to possess resistance to autogenous pressure and corrosion. Further, conventional solvothermal methods need a long time to prepare products, usually a few days, which is a large energy consumption and inefficiency. So it is interesting to synthesis ZIFs through other ways under mild reaction condition with high energy efficiency."

Jan 1, 2012

By Xi Dai

The LiFe1-xNixPO4(x=0, 0.05, 0.10) cathode materials for Li-ion battery were synthesized with Fe1xNixC2O4?2H2O(x=0, 0.05, 0.10) as Fe sources by high temperature solid-state reaction method. The Fe1xNixC2O4?2H2O(x=0, 0.05, 0.10) materials were produced by liquid co-precipitation method and crystal structure and morphology of cathode materials were characterized by X-ray diffraction and scanning electron microscopy. The composition contents and charge-discharge performances were measured by chemistry analysis and charge-discharge apparatus. The XRD patterns showed that LiFe1-xNixPO4(x=0, 0.05, 0.10) cathode material samples were well-crystallized homogeneous olivine-type phase, with only tiny trivalent iron impurities according to chemistry analysis results. Charge-discharge test showed that cathode materials possessed excellent charge/discharge capacities, about 150mAh/g at 0.1C rate and more than 120mAh/g at 0.4C rate. The polarization of cathode in charge-discharge process can be restrained effectively, for the potential offset between oxidative peak and reductive peak of doped LiFePO4 material was only 0.079V, lower than pure LiFePO4 markedly.

Jan 1, 2006

By Robin D. Rogers

Room temperature ionic liquids (RTIL) can replace certain traditional organic solvents in liquid/liquid extraction of metal ions from aqueous systems. The very low vapor pressure and non-flammable nature of RTIL warrant consideration of these neoteric solvents for new processing technologies which will reduce pollution, Increase safety, and lower costs. Metal ion separations in RTIL, however, will typically require the use of an extractant and research is needed to identify suitable selective extractants which have appreciable solubility in the RTIL and low solubility In the aqueous phase. Choice of extractant should also take into account the toxicity, expense, and disposal of the ligand.

Jan 1, 1999

By Dao-Wu Yang, Ju-Lan Zeng, Li-Xian Sun, Yan Yao

"The hydration heat of the pure cement, the fly ash single-dopped cement, as well as the fly ash and fluorgypsum co-dopped cement were investigated by means of micro-calorimety with an eight-channel micro-calorimeter (TAM Air). The results showed that the hydration heat and the hydration rate could be reduced significantly by fly ash and fluorgypsum. However, the reduction was not proportional to the loading of dopant. The exothermic peak of the fly ash and fluorgypsum co-doped cement was appeared earlier than the fly ash single-doped cement. As the temperature decreased, the hydration heat and the hydration rate of the doped cement were reduced, and the exothermic peak appeared later. The effects of fly ash and fluorgypsum on the compressive strength of cement were also investigated. The results revealed that the early compressive strength of concrete made up of the co-doped cement was largely higher than that of the fly ash single-doped cement. Based on the experiment results obtained in this paper, we could conclude that fluorgypsum is a suitable additive for fly ash-doped cement.IntroductionFly ash and fluorgypsum are industrial waste. In 2008, nearly 400 million tons of fly ash has been produced by coal-burning power plants in China. And it is estimated that this number would exceed 500 million at the year of 2015. Besides, every year the fluoride salt factories in China discharge more than 100 million tons of fluorgypsum. Tremendous of fly ash and fluorgypsum occupy considerable land and contaminate air and water sources [1]. As a result, comprehensive utilization of this two industrial waste has draw great attention from all over the world.Cement is the most-used construction material on earth. But the production of cement consumes huge energy and destroys the environment. This problem might can be partly solved by applying fly ash and fluorgypsum as additive for cement [2-4]. During the last decade, some papers that focused on applying fly ash and fluorgypsum as additive for cement have been published [5, 6]. However, to the best of our knowledge, none of these papers investigated the hydration heat of the fly ash and fluorgypsum co-doped cement.The hydration of cement is an exothermic reaction, which can result in serious problem for mass concrete: The interior of the concrete could reach very high temperature as the hydration proceeded [7-9]. As a result, the great temperature difference between the interior and the outer of the concrete would exist and cause serious thermal stresses. Thus, the concrete would be destroyed by the cracks which in tum are resulted from the thermal stresses [10, 11]. The heat released by the cement hydration and the hydration rate is commonly regulated by adding mixed materials or transferring additive such as fly ash and fluorgypsum [12-14]."

Jan 1, 2011

By Masatsugu Morimitsu

"The novel smart anode, MSA ™, for electrowinning of non-ferrous metals such as copper, zinc, nickel, and cobalt has been developed by thermal decomposition. The smart anode consists of a titanium substrate coated with a catalytic oxide layer which comprises amorphous or less crystalline oxide coatings. The catalytic layer contains an iridium oxide-based mixture or a ruthenium oxide-based mixture. The smart anode provides a remarkable reduction in cell voltage compared to other anodes, e.g., commercially available coated titanium electrodes and lead alloy electrodes. The test data has demonstrated that a maximum voltage reduction by ca. 30% is possible compared to lead alloy anodes. The smart anode also gives some additional merits in suppressing unwanted deposits on the anode; i.e., deposition of MnOOH, Pb02, or CoOOH. The electrowinning with the smart anode is possible to be an environmentally friendly process with less energy consumption and less anode deposits.IntroductionA coated titanium electrode iridium oxide-based or ruthenium oxide-based catalytic layers is well known as an insoluble anode for oxygen or chlorine evolution in industrial electrolysis such as chloro-alkali electrolysis, electrogalvanizing or electrotinning of a steel, a thin film production by electrodeposition such as copper foil production (CFP), water electrolysis, and electrowinning of nonferrous metals. The anode is commercially produced by thermal decomposition of a precursor solution painted on a titanium substrate, and the decomposition is usually performed at 450 °C or more. The obtained catalytic oxide coating formed on the substrate contains crystalline oxide as an active component to oxygen or chlorine evolution. The author of this paper had met a problem of such a crystalline oxide coating in the application of copper foil production; the anode was unable to use for a long period because of a large amount of lead oxide (Pb02) deposited on the anode, and the cell voltage was seen to continuously increase and drastically rise by the accumulated Pb02. In this case, the voltage reduction by replacing a lead alloy anode with the dimensionally stable anode was initially observed, but was gradually lost and disappeared. Therefore, the author of this paper aimed and investigated to suppress the unwanted side reaction on the anode, and finally invented a new class of coating based on an amorphous iridium oxide mixture in 2003 [!]. The invented coating was obtained at a low temperature thermal decomposition, e.g., 360 °C, and the coating consisted of amorphous iridium oxide and amorphous tantalum oxide. This invention achieved that oxygen evolution potential shifted more negative so that the cell voltage was reduced, and no Pb02 was deposited in the electrolyte of CFP [2,3]."

Jan 1, 2012

By David G. Dixon

Although the kinetics of leaching processes are of paramount importance in the design and analysis of nearly all hydrometallurgical flowsheets, these concepts remain poorly understood and, as a result, are only rarely applied to mass and heat balance models. In this second of two papers, we demonstrate how simple yet powerful models of leaching kinetics and other rate processes may be added to mass and heat balance models, and apply these concepts using a spreadsheet model of a simplified pyrite autoclaving flowsheet. In particular, we focus on the interpretation and scale-up of batch leaching data, and on simple means for modeling other phenomena commonly associated with leaching, such as reagent depletion, gas-liquid mixing, and the precipitation of oxides and basic salts.

Jan 1, 2002

By C. E. Hunt

Since the turn of the century, copper-nickel sulphide ores have been processed at the Sudbury, Ontario operations of INCO Limited, currently the largest integrated mining, milling, smelting and refining complex in the free world. Through the years operational, ecomomic, social and legislative changes have dictated the need for research and development directed at mitigating the impact of existing operations on the surrounding natural environment and also the reclamation of areas affected by earlier mining activities. Approximately one hundred years of mining history and the current annual processing of some 12 million tons of ore presents significant challenges with respect to waste disposal, liquid effluent treatment and land reclamation, particularly in light of rapidly evolving environmental regulations' and controls within the Province of Ontario.

Jan 1, 1992

By A. O. Apata, F. V. Adams

The use of rice husk ash as aggregate for foundry sand mould production has been studied. 5 –25wt% rice husk ash was added to the sand mixture. The chemical, physical and mechanical properties measured include: chemical analysis of the rice husk ash, particle size, density, permeability, compatibility mouldability, moisture content, green compression and shear strength, dry compression and shear strength. The result revealed that, addition of rice husk ash to River Niger Silica sand, increased the mouldability, compatibility, grain fineness number, both green and dry strength, slightly decreased the density, permeability and moisture content. The result shows that better properties is achievable by the addition of rice husk ash to River Niger silica sand and can be used to enhance the mould properties of foundry sand.

Mar 1, 2017

By James C. Foley

In-situ characterizations of green state part density and sintering state have long been desired in the powder metal community. Recent advances in non-contact electromagnetic acoustic transducer (EMAT) technology have enabled in-situ monitoring of acoustic amplitude and velocity as sintering proceeds. Samples were made from elemental powders of Al (99.99%), Al (99.7%), Ag, (99.99%), Cu (99.99%) and Fe (99.9%). The powders were pressed in a uniaxial die and examined with acoustic waves for changes in velocity and amplitude during sintering. The changes in acoustic properties were correlated with mechanical properties. Evolution of a series of reverberating echoes during sintering is shown to provide information on the state of sintering, changes in sintering kinetics as well as having the potential for detection of interior flaws.

Jan 1, 2001

By A. Lakschevitz

The Amazon region offers a large potential for gold extraction but its peculiar characteristics such as heavy rains, lacking of roads and general infra-structure, nature of the ore deposits, etc.. do require special care in plant design. REMETÁLICA has developed a know-how is designing leaching plants which have been demonstrated to be profitable under those tropical weather conditions. The solutions adopted are related to general process route, leach liquor distribution and flow pattern, conditioning of solids and effluent treatment. These plants, now operating in South America countries, demonstrate the success for the technology developed. A tipical plant with 800 t/day ore processing capacity, may require an investment of US$ 1.200.000,00, arid have? a pay back period of a few months, depending on ore grade.

Jan 1, 1989

By Wei Gao, Qing-cai Liu, Cun-fang Lu, Huimin Zheng, Jian Yang, Chun-ling Yao

"Mercury in flue gas of coal-fired plants was concerned as another serious pollution when sulfur dioxide pollution was controlled now. The adsorbent made from fly ash by thermal precipitation sulfur to remove mercury in fuel gas from coal combustion plant, SEM, BET, TGA and other measurement methods were used to characterize the effect on surface morphology, sulfur distribution and specific surface. High temperature deposition furnace was applied to increase sulfur content in fly ash based adsorbents produced in lab. The study found that sulfur attached to the adsorbent surface, mesopore and microporous structure, increasing its sulfur content of adsorbent. Sulfur was filled in interspace as small molecule S2, S5, increased their surface area and enhanced their adsorption capacity. The specific surface area increased by thermal precipitation sulfur, and specific surface area which increased with increasing temperature.1. IntroductionThe mercury emission caused by human activity has accounted for 10%-30% of total mercury emission all over the world[11, and the emission from coal-fired power plant have a huge proportion of these emission caused by human activity. Active carbon microstructure and surface morphology play an important role in its adsorption capability, which offers the potential for controlling environmental pollutant, such as sewage, fuel gas, atmosphere and et al [2,31, because it is a material with high specific surface area that long been considered as an excellent adsorbent. At present, include activated carbon, fly ash, calcium-based sorbents and other novel adsorbents. The adsorption capacity and production cost were very important in the process of mercury removal by adsorbents, so the mercury removal has focus on developing adsorbents of highly-efficient. In particular, the waste of metallurgical from coal combustion and the others have a significant advantage about the cost, and they have the highly-efficient in mercury removal after modified to enhance their adsorption capacity, such as fly ash of coal-fired. Apart from specific surface area, element content, pore structure, and surface morphology of activated carbon have great effect on its adsorption ability. Compared to adsorbents without modification, active carbon impregnated with other elements, such as chlorine, sulfur, bromine and et al. had more excellent characteristics to remove specific pollutants."

Jan 1, 2011

By Claudio Toro, Alex Moyano, Rodrigo Díaz, Hugo Jara, Carlos Caballero, Pedro Morales, Leandro Guzmán

"During 2007, Codelco-Chile carried out industrial tests to validate the Continuous Converting Process in the Teniente Converter of the Codelco Norte smelter.For planning and starting up the tests, a predictive, analytical and dynamic model was developed to support operational decisions. The dynamic model was developed using the METSIM® platform and dynamic data exchange (DDE) to operate smoothly with MS Excel®. The main feature of this real-time model was the on/off-line ability to work and gather data from either the smelter’s PI system® or database, and simulate the operation with or without scheduled events and controls.The main model development aspects, which include thermodynamics, metallurgical and kinetic considerations, slag-type and on-line mass and heat balances of the process, as well as the successful validation of the model, are presented and discussed in the present paper."

Jan 1, 2009

By Dengfu Chen, Yunwei Huang, Mujun Long, Kui Lv, Pei Xu, Lin Bai

The surface temperature of continuous casting slab in the secondary cooling zone is a key parameter of production control. However, the accuracy of radiation temperature measurement of high temperature casting slab is greatly affected by the environmental factors, such as water vapor, spray, water film and other participational medias during continuous casting process. In this paper, the radiation characteristics of water vapor and its influences to radiation temperature measurement of continuous casting slab were investigated. Based on the database HITRAN 2004 and the measuring principle of monochrome thermometer & colorimetric thermometer, the measuring errors under different operating infrared spectral wavelength were compared. Results showed that spectral region with wavelength nearby 1.0μm or 1.6μm would be the optimum for high temperature infrared thermometer used under the conditions with moist steam, water spray and water film at the secondary cooling zone in steel continuous casting.

Jan 1, 2016

By Barry J. Welch

The production of primary aluminium can potentially lead to metal that, with minimum treatment, meets a high purity standard. Smelters that can achieve a significant proportion of their production in this manner have a competitive edge which is of growing importance as the use grows for such items as compact discs and the like. Superimposed on the desire to produce high quality metal are stringent environmental requirements that the industry must adhere to. The environmental 'legislation focuses on fluoride emissions and the approach adopted is towards a zero waste management philosophy. The fluoride recycling process does, however, result in volatile impurities being captured and recycled to the cell. Aluminium has an extremely high reduction potential and this results in a significant proportion of the recycled impurities being reduced at the electrolyte metal interface and thus contaminating the metal. This paper reviews sources of impurities and the impact of the operating procedures adopted on metal treatment.

Jan 1, 1996

By Baozhong Ma, Chengyan Wang, Yongqiang Chen, Peng Xing

This paper introduces an oxygen-enriched flash smelting (OFS) process for lead smelting. Compared with the bath smelting, OFS has many advantages, including wide adaptability, high yield, low energy consumption, little uncontrolled emission, and considerable metals recoveries. Test results showed that increasing CaO could effectively reduce lead content in the slag, and the appropriate mass ratios of FeO-to-SiO2 and CaO-to-SiO2 were 1.15 and 0.6, respectively. The testing and commissioning indicated when OFS was used to treat material containing 30% of lead, the residual lead in slag could decrease to 4–10%. Furthermore, after zinc volatilization using an ore-smelting electric furnace, contents of lead, zinc, silver, gold and copper in the final slag were below 2%, 2%, 6 g/L, 0.1 g/L and 1%, respectively. The total recoveries of lead, zinc, silver, gold, copper and sulfur were above 98, 90, 99.5, 99.5, 85 and 98%, respectively.

Mar 1, 2018

By Keith Axler

The high reactivity of plutonium metal presents safety concerns related to material containment during fire scenarios. Plutonium metal is liquid at temperatures achieved under selected fire scenarios. The appearance of liquid plutonium challenges the corrosion resistance of the containment materials. However, by the in situ formation of intermetallic compounds, the plutonium metal can be stabilized as solid and the integrity of the containment vessels preserved. Studies have been conducted to demonstrate candidate materials, including lead, which can be introduced to the liquid-plutonium system and bind the corrosive liquid metal through the formation of intermetallic phases. The results of these investigations will be presented along with a discussion of the experimentally determined phase behavior for the plutonium-lead system.

Jan 1, 1995

By J. Antrekowitsch

Keywords: residues, fluorides, chlorides, zinc, steel mill dust The recyclability of various nonferrous metal wastes often suffers from a relatively high fluorine and chlorine content. Both are inserted in most cases by the use of plastic contaminated scrap and a wide variety of different coatings. These halogens lead to poor product qualities and off gas contamination. Especially the history of zinc recovery from steel mill dusts shows, that the today common hydrometallurgical options are on their limit and therefore are not sufficient in most cases. This thermochemical study should give more information about different pyrometallurgical options, that offer both a chlorine and fluorine reduction and efficient zinc recovery, preferably in one process step. Selective evaporation in different atmospheres and conversion with the use of hydrogen are the main parts in this study. The results combined with the relatively small information available from literature should provide a basis for further investigations in this field.

Jan 1, 2005

By Uday Pal

In direct reduction processes for iron and steel making, significant amounts of Fe-C alloy droplets are generated and these remain suspended in relatively low FeO (around 5%) containing slags. Earlier workers have found that when the FeO content in the slag is <5%, the decarburization reaction becomes extremely slow (virtually ceases to occur) even though the alloy droplet contains a significant amount of carbons (2-3%). Understanding this rate controlling kinetic phenomena is crucial to designing an&apos; optimum direct steel making process. We studied decarburization of Fe-C particles by low FeO (<5%) containing CaO-SiO2A12O3 slags and found that by putting both the droplet and the slag in direct contact with an inert electronically conductive member that extends deep inside the slag bulk were able to quickly and completely decarburize the droplets. A detailed description and an explanation of the process will be presented.

Jan 1, 1995

By K. Koike, N. Masuko, Y. Takasaki

At the Zinc & Lead'95 symposium, one of the authors presented several modifications of Pb-Ag-Ca alloy anodes for the zinc electrowinning process, and also, the behavior of some organic additives in the electrolyte. In this study, the mechanical properties of the electrode materials composed by Pb-0.5 wt% Ag-(0~0.8) wt% Ca were studied by the tensile and Vickers hardness methods. Furthermore, experimental research on the influence of rolling and annealing treatments on the electrolytic behavior and mechanical properties of these alloys was carried out. The tensile strengths of the annealed Pb-0.5 wt% Ag-(0.1-0.8) wt% Ca alloys were the same or higher than those of the as-cast Pb-0.9 wt% Ag alloy. The anode potential using the as-cast Pb-0.5 wt% Ag-0.6 wt% Ca alloy decreased compared to the as-cast Pb-0.9 wt% Ag alloy. Moreover, the annealed Pb-0.5 wt% Ag - 0.6 wt% Ca anode after rolling showed a lower anode potential than the as-cast Pb-0.5 wt% Ag - 0.6 wt% Ca anode.

Jan 1, 2000

At the present time, cyanide is the most widely used reagent to extract gold from its ores and concentrates. However, its use in mining has become the focus of intense attack by various groups throughout the world; as a consequence, a renewed effort has been launched to find suitable alternative lixiviants to recover gold. Chlorination was the most popular process to extract gold, before it was rendered obsolete with the advent of the cyanidation process at the turn of the last century, not least because it required the use of potentially hazardous and costly chlorine to oxidize/complex the gold. The PLASTOL® process, originally designed to recover the platinum group metals (PGM?s) from their ores and concentrates, provides an alternative to cyanide for gold ores. The process generates oxidizing conditions in the autoclave capable of forming the AuIII ion, and gold chloro-complexes result from the addition of small quantities (~5-10 g/L) of sodium chloride to the autoclave. The principles of the PLASTOL® process are briefly described, and several applications of the process to gold concentrates are presented. Various options available to recover gold from PLASTOL® leach solutions are also discussed.

Jan 1, 2003