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By Jinsheng Wang, Xueming Lv, Wei Lv, Junyi Xiang, Xuewei Lv, Chenguang Bai

In this study, microwave heating was used to dry the nickel laterite which contains plenty of free water, crystal water and hydroxy water. The results showed that compared with the conventional drying process, the microwave drying greatly improved the drying efficiency of nickel laterite. The whole microwave drying process can be divided into three stages according to the drying rates, namely, the rising stage, stable stage and declining stage. The effects of microwave power output and particle size were also studied in the range of 0.8–2.0 KW microwave power and 3–6 cm of particle size. The results showed that the drying time significantly decreased with the increase of microwave power and decrease of particle size. The phases transition of the sample during the microwave drying process were also discussed.

Mar 1, 2018

By L. S. Montagna, R. M. C. Santana

"Since the industrial revolution, plastic products sector has growing bigly, however this fact presents as consequence the increase of municipal plastic waste (MPW).The aim of this work is to developmet polymer mixture from MPW with the adittion of rubber tire (TR) post use and to study the mechanical and morphologycal properties. The polymer mixtures Polypropylene/High impact polystyrene/TR (PP/HIPS/TR), where rate weight TR used was 10, 20 and 30 % and with three size particles (500, 710 e 1000 µm). The specimen tests were obtained by injection molding. Preliminary results of mechanical properties showed that the increase of TR influence in a reduction of the flexural and tensile resistance. Results by scanning electronic microscopy on the fracture surface of mixtures PP/HIPS/TR showed a better interaction of TR particle with HIPS than with PP. Also, the presence of microcavoids was observed, characteristic in PP/HIPS blends, favouring in the increase of its opacity.IntroductionOne great part of the municipal solid waste (MSW) is composed of polymer mixed since commodity plastics, blend to polymer composite. The processing of plastics mixtures for recycling has been attempted with some success, but poor mechanical properties and uncertain economic value limit their more versatile reuse. Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), poly(vinyl chloride) (PVC) and polystyrene (PS) are among the most common plastic waste, predominantly used in packaging food industry [1].One other problem that preoccupy to the society is the increase of rubber tire waste in the proportion of MSW. In Brazil, from 1999 to 2004, 39 % from 386 mil ton of tire post-use were destined to ciment Industry as source of energy [2]. However this destiny produces one other problem, environment pollution, due to gas mixture emitted.Recycling represents a valid alternative to the disposal of post-consumer plastics in common landfills if it is possible to obtain new materials with good final properties compatible with practical and, above all, by cheap methods [3]The reutilization of group tire rubber (TR) powder as a dispersed elastomeric phase in a thermoplastic matrix offers an opportunity to design second generation materials which would be recyclable due to the thermoplastic matrix and which potentially could present thermoplastic elastomer (TPE)-like mechanical behavior. [4]."

Jan 1, 2008

By C. Dupuis

Thiourea is a promising reagent for gold extraction especially from refractory ores that cannot be treated by traditional cyanidation route. In this study recovery of gold from thiourea leaching solutions was investigated by direct electrowinning. The electrolysis cell consisted of a carbon flow-through cathode and a lead anode. The anodic and cathodic compartments were separated by a membrane. Galvanostatic mode was chosen for operation of the cell. Factors affecting recovery efficiency such as cathode thickness, linear flowrate, current intensity, thiourea and gold concentrations were investigated. The influence of some species in solution on efficiency and selectivity of recovery was investigated. Gold recovery reached 99% but current efficiency was lower than 10%. The complex formed with ferric ion and formamidine disulfide are reduced before gold-thiourea complex. Thiourea consumption occurred during leaching mainly by oxidation and reaction with dissolved copper.

Jan 1, 1989

By Jorge Gibson, P. Chris Pistorius, Megha Jampani

Increased utilization of natural gas in blast furnace ironmaking can decrease both the cost and the carbon intensity of ironmaking, given current US natural gas prices. In this paper, three ways to utilize natural gas are compared: tuyère injection, prereduction of iron ore, and shaft injection. The basis for comparison includes coke replacement ratios, carbon intensity and furnace productivity. These were calculated using relevant mass and energy balances, a blast furnace productivity correlation based on the bosh gas flow rate, and measured and modeled prereduction kinetics. Of the natural gas utilization methods, prereduction has the highest effective coke replacement ratio (and hence the largest advantage in raw material cost), but is likely to have the highest capital requirement.

Mar 1, 2017

By Christiana Mystrioti

Greece is the only EU country with extensive nickel laterite deposits. Since the 1960s, the Greek laterites are treated for ferronickel production via a pyrometallurgical route, which involves pre-reduction of the ore in rotary kilns and reduction smelting in electric arc furnaces. Due to the rising cost of energy and the decreasing grade of mined laterites, the pyrometallurgical treatment is economically marginal. For this reason, alternative treatment processes are currently under investigation. Potential applicability of hydrometallurgical treatment, using either H2SO4 or HCl, under atmospheric pressure conditions, for Ni and Co extraction from two low grade laterite ores, was examined in the present work. The two samples were selected to represent the different mineralogical composition of the saprolitic and limonitic ore deposits of the Greek laterites. The investigated parameters were temperature (65–90 °C), acid concentration (1–4 N) and solid to liquid ratio (10–30% w/v). The results indicated that HCl was more efficient than H2SO4 for the treatment of the saprolitic ore; Ni and Co extractions were very high for both elements, up to 98% and 96% respectively, while H2SO4 could leach efficiently Ni, up to 100%, but extracted only 34% of Co. Hydrochloric acid was also more efficient for the treatment of the limonitic ore, with Ni and Co extractions up to 98.3% and 87.6% respectively. With H2SO4 the maximum extractions were 71.3% for Ni and 52.1% for Co.

By Tianzu Yang, Weifeng Liu, Lin Chen, Wei Chen, DUCHAO ZHANG

Ni-M (Metal=Cu, Fe, Co, Mn, Zn, Cr) aerogel catalysts were tested for CH4 oxy-CO2 reforming. It was found that the Ni-Co bimetallic aerogel catalyst had the highest activity and stability in methane oxy-CO2 reforming among all the Ni-M aerogel catalysts. It exhibited a steady activity of 79 % (in terms of CH4 conversion) at 750 oC, which is the highest activity under a similar reaction condition as compared with those published in literature. Characterizations for the reduced catalysts indicated the formation of Ni-Co alloy, while other transition metals separated from Ni during the reduction process. Therefore, the active species in the Ni-Co bimetallic catalyst showed a stronger interaction than those in other Ni-M catalysts, which might be one of the main reasons for the better catalytic performance of the catalyst.

Jan 1, 2016

By Carvalho A. Felipe de

The search for environmentally friendly and cost-effective methods for gold extraction has been undertaken in order to provide alternatives to the use of cyanide leaching in the gold industry. Among such alternative reagents is the combination of chloride and hypochlorite ions due to their oxidation of metallic gold and its complexation. Therefore, the current work aims at investigating gold leaching from an oxidized material by means of a solution comprising calcium hypochlorite and sodium chlorite. The sample used in the current research contained 66.1% Fe2O3, 20.4%SiO2, and 35.7 g/t of Au. In addition, XRD and SEM-EDS analysis revealed iron oxide, quartz and muscovite as the main crystalline phases in the sample. For comparison purposes, cyanidation of the oxidized material resulted in 90% gold extraction in 24 h. The reference conditions for the leaching tests with the chlorite-hypochlorite system were: particle size −37 μm, solid/liquid ratio of 10% (w/v), 10 g/L NaCl, 10 g/L Ca (OCl)2, pH 5–6, 3 h of leaching. The effects of the: (i) Ca(OCl)2 concentration, (ii) NaCl concentration, (iii) pHrange and (iv) the effect of pulp density in the extraction of gold were assessed. In addition, the stability of the hypochlorite solutions (OCl−) was investigated. The ideal concentrations of Ca(OCl)2 and NaCl were determined as 25 g/L and 15 g/L, respectively, whereas the optimal pH range was 4–6. Under these conditions, the final gold extraction reached approximately 84%. By varying the solids content of the pulp (10%, 20% and 30%), it was observed that the lower solids value resulted in greater gold extraction (84%). The degradation of the hypochlorite solution and the possible catalytic effect of the presence of the solid were evidenced. To sumup, in the experiment, high gold extractions were achieved in shorter periods of time (3 h), as compared to the cyanidation of the same sample. On the other hand, itwas necessary to use significant amounts of the reagent due to hypochlorite instability at the pH conditions recommended for high gold extractions.

By Norbert Hort, Karl Ulrich Kainer, Carsten Blawert, Daniel Fechner

"With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap and the changing legislation will force car manufacturers to take magnesium recycling into consideration. So far post consumer scrap has not been used for magnesium alloy production. Quite a reasonable amount of automotive scrap is likely to end up in a mixed light metal shredder fraction. The separation of mixed magnesium scrap according to several alloys is complex. Therefore secondary magnesium alloys made from blended post consumer scrap would be useful. For this work a matrix of potential recycling alloys was prepared by chill casting and high pressure die casting. The materials were investigated for their microstructure, mechanical properties, heat resistance and corrosion properties. The results will be presented in this paper.IntroductionWithin the last ten to fifteen years several heavy magnesium parts have been assembled in passenger cars, such as gear box housings and crank cases [1, 2]. Reasons are the lately developed new heat resistant alloys and the increasing responsibility of automotive manufacturers to reduce the vehicles weight and thereby CO2 emissions. The latter is pushed by international legislation [3, 4]. The rising quantity of magnesium in automobiles will result in an increasing amount of so called post consumer scrap at the end of the vehicles life.So far magnesium recycling was done only for clean scrap that is free from impurities, contaminations and sorted according to a chemical composition or a single alloy respectively [5- 15]. The latter is also called class 1 scrap and mainly consists of sprues and runners from magnesium die casters [15, 16]. For the upcoming automotive post consumer scrap the materials quality strongly depends on the way end of life vehicles are treated. By proper dismantling of old cars, the bigger magnesium components could be collected and possibly treated similar to class 1 scrap [15]. Up to date automotive manufacturers have no uniform recycling system for end of live vehicles. Most probably a considerable quantity of old cars will be shredded. The resulting light metal shredder fraction will contain aluminium and magnesium scrap, both from several alloys. A separation of mixed magnesium and aluminium scrap is feasible according to [17]. Other authors claimed that the grade of separation of magnesium from aluminium is still not sufficient for a proper industrial recycling process of magnesium post consumer scrap [15, 16]. If an automatic sorting is possible it will probably be very expensive [18]. Therefore, so far the main use of post consumer scrap has been the steel desulphurisation and aluminium production [15]. The use of post consumer scrap for magnesium alloy production has been considered already by [15] and [16] but some problems have to be approached."

Jan 1, 2008

By Bin Xu, Qian Li, Yong-bin Yang, Xiao-liang Liu, Tao Jiang, Yan Zhang

Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

Jan 1, 2015

By Sen-xiang Yang, Xin-teng Liang, Gui-jun Li, Jian-hua Zeng, Yong Chen

"This research is based on PANSTEEL 120t steelmaking converter technology to have the quantitative description of the time needed in uniform mixing of molten steel in the converter with the computer. In present work, the numerical simulation approach is used to analyze oxygen lance nozzle, the flow condition of oxygen and flow status of molten steel in the converter. The various oxygen jet flows that come out from different angles and the flow status of all kinds of jet flows in the converter have also been simulated. All of the simulation parameters are based on the specifically practical conditions according to the physical conditions of PANSTEEL 120 t steelmaking converter. Through numerical simulation, the angle parameter of the oxygen lance nozzle is 16 °. The optimized oxygen lance 536-16 has a good performance in industrial application. This kind of phenomenon shows that the ways and processes of numerical simulation in this research are right.IntroductionThe oxygen lance system is the significant process in semi-steel making converter. It's related to whether the converter or even the whole system can function well. While in actual production, many problems emerge in the process of using the former oxygen lance, such as re-drying, slopping, high lance position, dead burning and even blowing out. In continuous fast-paced process, the unstableness of oxygen lance will lead to speed droop or even stop pouring. Analysis shows that all these problems are not only related to the raw materials but also the design of oxygen lance. Bad oxygen lance's scorification kinetics condition and low content of FeOn in early slag are the direct factors that we cannot easily control in steelmaking at present [l]. Therefore, the good scorification kinetics condition which is related to nozzle has good influence on BOF steel making."

Jan 1, 2013

By James Vaughan

Australia is a major miner of ore that requires hydrometallurgical processing. According to the 2016 US Geological Survey Minerals Commodities Summaries, the country is 1st for aluminium (bauxite) and lithium, 2nd for gold, zinc and cobalt, 4th for nickel and silver, and 6th for copper mining, not to mention its wealth in coal and iron ore. In this paper, examples of recent Australian hydrometallurgical activities are summarised. Then, selected research projects from the University of Queensland hydrometallurgy research group are profiled. The projects profiled are related to fundamental aspects of processing bauxite with organics and reactive silica as well as the development of a synergistic hydro- and pyrometallurgical process for copper. The process context and motivation for the research is introduced, key results are highlighted with the associated relevant references.

By Alexander V. Derevyanko, Victor P. Popov, Alexander I. Raitchenko

"If an electric current flows along some electroconductive suspension in columnar form the solid particles are 'experienced thermal, mechanical, and electromagnetic influences.The objects were suspension Sn (liquid) - Ni-Cr-Mo-W alloy (solid particles). This is refractory alloy on the Ni base. The direct constant current (with density -106 A/m2 ) flowed through the named suspension during 180+300 sec. At the beginning of experiments samples were ones containing particles suspended uniformly in volume. Although density of solid particles was ~9x103 kg/m3 , i. e. higher than density of liquid Sn (-6.8x103 kg/m3 ), after end of this processing, the non-uniform distribution of particles in volume of samples was observed: concentration of Ni-alloy particles in lower part was smaller than their concentration in upper part of samples, and simultaneously their concentration is increased near outer surface. There was probably the natural convection of Benard-Rayleigh type which had carried, so lid particles upwards, and, in same time, there was the action of spatial Lorentz-forces directed to center forcing the radial movement.The knowledge of named phenomena can be useful for elaboration of technology of gradient dispersed materials and development of some materials science fields.IntroductionThe liquid metal with the electric current or under the alternating magnetic field is experienced compression. This action causes the pressure within metal and the change of the surface of the metal column (see, for example, [1-4]). One of results of such an electromagnetic compression is extraction of the foreign solid particles from a cylindrical liquid sample to surface in the radial directions. However, more complicated paths of the inclusions are observed under some conditions of electric treatment."

Jan 1, 1999

By K. D. Mondale

The chemical and physical properties of samples from ten sedimentary zeolite deposits. (representing chabazite, clinoptilolite, erionite and mordenite types), have been determined as a prelude to the development of a wet beneficiation process. The mineralogical composition of each deposit and such properties as morphology, size, apparent density, surface area, pore volume, relative hardness and zeta potential in solution have been determined. Some of these properties, especially apparent density and relative hardness, were found to differ significantly from textbook values. Based on differences in properties between the zeolites and their associated gangue minerals, a wet beneficiation process has been developed which makes use of selective grinding, sizing, sorting and gravity concentration. Additionally, an alternative upgrading process using flotation has been developed for one of the deposits.

Jan 1, 1988

By Isabela Leao Amaral da Silva, Felipe Perisse Duarte Lopes, Alice Barreto Bevitori, Sergio Neves Monteiro

"Jute fibers have in the past decades being investigated as possible reinforcement of polymer composites. However, information is still needed on the fiber interaction with a polymeric matrix for a complete evaluation of the capacity of load transference inside the composite. The present work investigated the interaction of jute fibers with polyester matrix by means of the critical length assessment through pullout tests. Tensile tests of polyester sockets embedded with different fiber lengths allowed the critical length to be determined and then the interface shear stress to be calculated. A relatively low interfacial strength was found, which indicates a weak adhesion between the ramie fiber and the polyester matrix. The SEM analysis of pulled out fibers corroborates this result.Introduction Natural fiber, mainly those lignocellulosic extracted from plants, have, in the past few decades, attracted the attention not only of scientists but also of industrial technologists of our society interested in their engineering applications. As it is well known, uses of natural fiber in clothes carpets, baskets, ropes and low cost construction roofing has existed from the beginning of our civilization. Today environmental and energy saving issues are motivating research works on new uses of lignocellulosic fibers in polymer composites [1-6]. Moreover, industrial application of lignocellulosic fiber composites are already in technological sectors such the automobile industry, packing and civil construction [7-9].In addition to environmental, economical and social benefits, some lignocellulosic fibers present specific properties that are comparable to those of other synthetic fiber used for polymer composite reinforcement. For instance, the specific strength (GPa.cm3/g) of curaua (1.31), sisal (0.92) and ramie (0.93) fibers, from results obtained with very thin diameters [10] are relatively closer to that of glass fiber E (1.33). Therefore, in principle, it would be technically justified to replace glass fiber, which is more expensive, toxic and represents a problem to the environment [ll], by a strong lignocellulosic fiber. However, serious drawbacks such non-uniform dimensions and heterogeneous properties [6] as well as the tendency to form aggregates during processing and incompatibility with a hydrophobic polymer matrix, reduce the potential of lignocellulosic fiber to be used as composite reinforcement [1-6]. In particular, a low interfacial strength causes a weak adhesion between the hydrophilic fiber and the polymer matrix."

Jan 1, 2011

By lonkion M. Font

Due to the known disadvantages of the use of iron silicate slag in the nickel converting stage, i.e., high metal losses, high magnetite content, and low fixation of impurities in the slag, the development of the new proposed "ferrous calcium silicate slag" for smelting and converting processes of nickel is very promising. Hence, considering the successful experimental results of using CaO base slag for the nickel smelting process, a study based on a detailed comparison for the phase equilibrium, and the minor elements distribution between the NilS2-FeS matte with either FeOx-CaO or FeOx-Si02 base slag was investigated. The main results are summarized as: no difference in the nickel losses between both slags was found at high nickel content in the matte, and the fractional distribution analysis for arsenic and antimony pointed out their preferential fixation in the calcium ferrite slag rather than in the iron silicate slag. Considering the energy and pollution issues, the technical feasibility of using calcium ferrite slag in a converting process of the Bessemer matte will have a prominent future for the nickel industry.

Jan 1, 2003

By Kazuyuki Kakegawa

"Sintered body of lead zirconate titanate (PZT) was prepared through the spark plasma sintering (SPS) technique. When the mixture of raw materials was calcined at 800°C and sintered at 900°C for 10 min. with SPS technique, the sintered body had almost theoretical density but was a mixture of lead titanate (PT) and PZT. When a calcining temperature of 1100°C was employed, sintered body had a single PZT phase but a lower density. High dielectric constant was obtained for a sample calcined at 800°C, sintered with SPS tecbriique and fired again in the air at 1100°C.IntroductionSpark plasma sintering (SPS) is a recently developed technique for sintering metals and ceramics1. The scheme of SPS is shown in Fig. 1. Sample is put in a graphite die in a vacuum chamber. It is pressed and pulse voltage is applied. The electric current heats the die. It is said that the pulse causes a spark-plasma between particles in the sample. Because of the spark- plasma, sample can be sintered at temperatures lower than that in the ordinary sintering by several hundred degrees of Celsius. The sintering period is also very short2Low sintering temperature and short sintering period in SPS technique cause low reaction rate. It is both disadvantage and advantage. In some cases, the reaction cannot be completed under the SPS conditions. If a mixture of several compositions having different properties can be sintered without a compositional change by the diffusion during the sintering, combination of properties, and therefore a design of property will be possible3. The low reaction rate of SPS may enable such combination."

Jan 1, 2000

By Mike Dry

Conventionally, lithium-bearing brines are processed via solar evaporation, chemical purification, and either electrolysis to lithium hydroxide or precipitation of lithium carbonate. Lithium-ion battery technology and electric vehicles are forecast to greatly increase the demand for lithium, but not all lithium-bearing brines are amenable to the conventional extraction process and new approaches are being developed. The chemistry associated with conventional lithium extraction is outlined and two new approaches are discussed.

By G. E. S. Lima, I. K. R. Andrade, N. G. Viana, R. O. G. Martins, L. M. Sathler, L. G. Pedroti, C. M. M. E. Torres, W. E. H. Fernandes, C. M. Silva, M. A. Caetano

In Brazil, kraft pulp mills are rapidly expanding and industrial waste generation is increasing. Technical feasibility of using solid wastes from kraft pulp mills as raw material in other industries may be an interesting approach to manage environmental and economic aspects of the industry. This paper proposes the incorporation, in different proportions (0, 2.5, 5 and 7.5%), of alkaline solid wastes from pulp mills, namely dregs and grits, to clinker in the Portland cement industry. The research was carried out in two steps: (i) characterization of dregs, grits and clinker; (ii) laboratory testing (determination of soundness by the Le Chatelier method, determination of setting times, determination of water content of the paste with normal consistency, determination of compressive strength and static modulus of elasticity). The results showed that the addition of dregs and grits to the clinker up to 2.5% were feasible according to the Portland cement Brazilian standards.

Mar 1, 2017

By Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"In this paper, we describe the current status and research progress on the utilization of typical industrial solid wastes in China. We propose a creative method called “eco-utilizing wastes” with an aim of both integration and increment but without second-time waste and pollution, in terms of the characteristics of typical industrial solid wastes, such as titanium-bearing blast furnace slag, high-silicon iron tailing and boron-enriched slag as well as oil shale.Situation of Typical Industrial Solid Wastes in ChinaThough mineral resources in China are abundant, most of these are low grade ores. Moreover, the distribution of mineral resources is asymmetric, which causes the increase of cost and decrease of the economic benefit. Over-exploitation of mineral resources results in a large number of solid wastes. The accumulation of solid wastes not only means the waste of valuable resources, but also causes environment deterioration. There exist some problems in the current practice of the disposal of industrial solid waste, such as only emphasizing the final results and causing new pollution and waste [1]. So the research and development of a high value-added method has a high practical relevance to our nation. Based on the present status and research progress of industrial solid wastes in China, a creative new idea and method for eco-utilization of solid wastes is proposed in this paper."

Jan 1, 2012

By A. Block-Bolten

Copper concentrates from northern Peru contain large amounts of arsenic and antimony in the form of sulfosalts like enargite, tennantite and tetrahedrite. These impurities affect up to 30% of Peruvian copper production. Under the sponsorship of the Instituto Geologico Minero y Metalurgico in Lima a project to separate copper from arsenic without pollution of the environment is being carried out at the National University of Trujillo in Peru. The U.N.T. process is unique in the respect of using .low melting salts as solvents, and sulfides of metals with high cation potential as destructors of the complex sulfosalt molecules. Laboratory scale experiments have given encouraging results but interesting and difficult problems developed on scale-up. The process is pyro-hydrometal-lurgical and under certain circumstances its economics are promising.

Jan 1, 1981