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By M. G. Silva-Valenzuela, H. Wiebeck, F. R. Valenzuela-Diaz, J. C. Arjona, S. H. Wang

Urea is the most used nitrogen fertilizer around the world being responsible for many environmental problems. Preparation of microcapsules from biodegradable polymer has been reported as a main system to sustain active substances, finding application in different areas. The objective of this work was to sustain urea in nanocomposite microcapsules of poly(3-hidroxybutyrate) (PHB) reinforced with a smectite Brazilian clay in its natural (MMT) and modified (OMMT) form. PHB/MMT and PHB/OMMT microcapsules were obtained by w/o/w emulsion. Characterization were performed by XRD and optical microscopy. Structural and morphological differences observed by XRD and optical microscopy shown that PHB/OMMT microcapsules are smaller than PHB/MMT microcapsules, with average size diameter ranging * 49 μm. Results indicate that PHB/OMMT microcapsules present more defects and fractures than PHB/MMT microcapsules.

Mar 1, 2018

By Yifei Zhang, Jianzhong Li, Wenhao Zhang

Eletrochemical behavior and corrosion properties of a Ti–6Al–4V alloy fabricated by selective laser melting in artificial seawater at temperature ranges from 20 to 40 °C were investigated using electrochemical techniques, including potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky measurement, etc. Equivalent circuits were simulated to investigate alloy surface and analytic effects of temperature on interface of alloy and solution. The results showed that corrosion potential increased with temperature rise, and the EIS presented a single capacitive resistance characteristics. When the temperature reached 35 °C or above, passive current increased, while the passivation phenomenon was not obvious and corresponding radiating arc radius reduced, indicating that the resistance decreased, conductivity of surface passivation film improved, and corrosion performance improved. According to the Mott-Schottky curves, alloys exhibited n-type semiconductor characteristics. With increasing temperature, conductivity of passivation film enhanced, and alloy corrosion resistance decreased. At 40 °C, alloy possessed the worst corrosion resistance.

Mar 1, 2018

By Manis Kumar Jha, D. D. Pathak, Archana Kumari

Treatment of secondary/waste to recover rare earth metals (REMs) is gaining importance due to its increasing global demand, lack of availability of high grade natural resources and huge generation of secondaries. Present paper reports the critical review on available processes for recovery of REMs from secondaries viz. manufacturing scraps, e-waste, industrial residues such as red mud, fly ash, waste water, etc. Hydrometallurgical processes with combination of Beneficiation/ Pyro-/Electro techniques are discussed to recover REMs effectively. The recommended processes require less energy to deliver high purity yield which is one step towards green environment. Salient findings on various methods are reported with recommendations which will be helpful to researchers working in the area of REMs extraction.

Mar 1, 2018

By Lixin Qian, Tiejun Chun, Yifan Wang, Huan Wang, Hongming Long, Zhengwei Yu

To solve the problem that the sintered liquid phase fluidity characteristic of low silica (w(SiO2) < 3 wt%) and high silica (w(SiO2) > 7 wt%)) iron ores were different from actual sintering production with using the common method based on w(CaO)/w(SiO2), a new improved method based on n(Fe2O3)/n(CaO) was proposed. The differences between two methods for iron ore fluidity detection were studied. The results show that when the common method is used to detect the liquid phase fluidity, as the content of SiO2 increased from 2.12 to 11.68 wt%, the amount of CaO addition augmented from 7.88 to 32.65 wt% and the corresponding fluidity index changed from 0 to 5.68. The fluidity index has a linearly positive correlation with the content of SiO2. The improved method could significantly reduce the effect of the change of CaO addition on the fluidity characteristic of iron ore which caused by the difference of SiO2.

Mar 1, 2018

By John Gordon

Rare earth elements (REE) required in modern technological products are found in shale rocks above and below coal seams. Often during the process of mining coal, shale rock adjacent to the seam inadvertently is removed then diverted to landfill sites. Ecologically sound and potentially economic methods of extracting the REEs from these landfills are proposed. Methods include utilizing geomemembrane barrier beneath the landfill site, ion exchanging with moderate pH, slightly acidic, sodium chloride solutions. Sodium hydroxide is utilized to precipitate the REE-hydroxides subsequently converted to REE-chlorides with suitable amount of hydrochloric acid. All acid and base streams are co-produced with efficient membrane/electrolysis technology. Concentrated-REE chlorides are transported tocentralized solventextraction facilities for isolation and purification. Solvent extraction processes also employ the methodology of using co-produced acid/base streams. This paper details minimization of environmental impacts and maximizing economics to produce valuable REEs while increasing the economics of coal mining.

Mar 1, 2018

By Patrik Yrjas, Daniel Lindberg, Emil Vainio

Recovery of trace elements from different industrial waste streams is important in realizing the goals of the circular economy. Ash streams from waste combustion can contain high levels of both toxic and valuable trace elements. These elements can be separated during the combustion process based on volatilization and condensation, as well as being separated in post-combustion processes, through thermal or leaching treatment. In this study, an overview is given of the thermal methods for recovery of valuable elements from ash fractions derived from waste incineration. In addition, a case study is presented of the behaviour of ash-forming elements in combustion of MSW and demolition wood, with special focus on the elements Co, Cu, and Sb. In conclusion, it is shown that thermodynamic modeling of high temperature processes can be a useful tool to predict ash behavior both during combustion and in the post combustion treatment of the ash.

Mar 1, 2018

By Zhihe Dou, Jiang Liu, Ting-an ZHANG, Yukun Huang

The paper aimed to propose that mixed rare earth concentrate was decomposed by pressurized calcification where mechanical milling was applied simultaneously (also known as mechanochemical calcification). The bastnaesite and monazite were both decomposed by OH−, where released rare earth formed RE (OH)3, released fluorine and phosphorus formed CaF2 and Ca2P2O7. Then, the calcified slag was leached by diluted hydrochloric acid to extract rare earth and both recover fluorine and phosphorus. The phase transformation regularity, the behavioral trends of rare earth, fluorine and phosphorus were investigated. Results showed under the optimal conditions of ball to material weight 80:1, the calcification temperature 250 °C, the liquid-solid ratio 5:1, the leaching yield of rare earth reached to 92.16%, Ce was 86.47%, La was 97.58%, Nd was 99.99% and the mass fraction of F, P entering into calcified liquor were 8.27, 0.21% respectively. The micromorphology of the mineral has a transition from dense to fluffy, and then became dense again.

Mar 1, 2018

By Rajashekhar Marti, York R. Smith

Lithium is anticipated to be a key, strategic material in the clean technology economy. The majority of lithium reserves are contained in continental brines and sea water (>60%). Currently the most economical approach to recover lithium from such resources is through selective adsorption. Spinel type lithium manganese oxide and lithium titanium oxide have demonstrated to be excellent candidate materials (after de-lithiation). However, due to the small size of the powders, they have limited industrial application and require immobilization. In this work, we examine the application of novel manganese oxide nanowire composites for the extraction of lithium from dilute solutions. Manganese oxide nanowires were synthesized and simultaneously immobilized on diatomaceous earth via hydrothermal method. Lithium manganese oxide were then formed by solid-state reaction, de-lithiated and tested for lithium ion adsorption.

Mar 1, 2018

By Maryam Ghodrat, Bijan Samali

Disposal of waste syringes in a safe and eco-friendly way has been an issue of considerable scale for decades. The generated amount of waste syringes has escalated with the rapid growth in population and wide acceptance towards single-use medical devices. Some hospitals have their own on-site incinerators ,but recent tightening of air quality regulations and landfill levies led to the closure of manyon-site incinerators. The solution to this problem implicates the development of an environmentally-sound method that would employ these waste materials. This work investigates a thermodynamic modelling approach for incineration treatment of waste plastic syringes in Electric Arc Furnace (EAF) steelmaking. Mass balance was obtained from HSC Chemistry thermochemical package. The results indicate that the rate of iron oxide reduction in the slag is higher when coke is partially replaced by waste plastic syringes. Furthermore, the amount of dust and stack gas emission was reduced by around 0.4% and 1.25% respectively by replacing 20%-weight of pure coke with waste plastic syringes. The study demonstrates part of the coke can be successfully replaced by waste plastic syringes in electric arc furnace to provide additional energy from combustion without affecting the main process.

Mar 1, 2018

By Yuri Hovanski, Jingyi Zhang, David P. Field, Piyush Upadhyay

Friction stir welding has gained wide interest in industry and drawn large research attention due to its high level of automation and superior joint performance. In this study we further expand the welding parameters to be of magnitudes higher than those previously reported to lower the cost and enable high volume joint production. Sound butt-joints were produced with aluminum alloy 6111-T4 blanks with welding speeds up to 6000 mm/min. Tensile tests of the joint pieces show >97% joint efficiency in terms of ultimate tensile strength. The T4 natural aging and grain refinement is found to contribute to the superior joint properties. Electron backscatter diffraction (EBSD) analysis is used to qualitatively study the local shear texture inside the nugget zones of the welds. The shear texture result is a good indicator of the material flow directions in the nugget zones. The flow directions behind the rotation tool are found to be flattened towards the top surface of the workpiece when the welding speed is increased, suggesting intense material mixing and transportation along the longitudinal welding direction (WD).

Mar 1, 2018

By Yuya Nakai, Kuniaki Murase, Kazuhiro Fukami, Atsushi Kitada, Ken Adachi

Concerning nodulation in copper electrore fining, it has been reported that short circuits caused by nodulation have the largest impact on the current efficiency. Therefore, to improve the current efficiency, it is important to prevent nodulation. In this research, the nodulation growth was investigated by replicating nodulation in the laboratory. The experiments were conducted by cathodic electrodeposition on copper plates attached to copper sticks of various heights. The nodulation was analyzed in terms of growth rates versus the initial heights.

Mar 1, 2018

By Ming-Feng Ye, Guang-liang Wu

The microstructure and mechanical strength variations of chromite pellets preheated and roasted in air were studied systematically. The results show that the chromite (Fe,Mg)(Cr,Fe,Al)2O4 is oxidized to magnesium-rich (Mg,Fe)(Cr,Fe, Al)2O4 and ferrochromium complex oxide (Cr,Fe,Al)2O3 in the preheating process over 500 °C. When the temperature is higher than 1000 °C, the new phase (Cr,Fe, Al)2O3 is formed, which is mainly distributed in the outer layer of a single chromite particle. Inner the particles there are acicular (Cr,Fe,Al)2O3 and unoxidized (Fe,Mg) (Cr,Fe,Al)2O4, which forming an interwoven structure together. The oxidation rates of pellets can reach to superior limits in 20 min. With the temperature increasing from 950 to 1300 °C, the mechanical strength and oxidized rates increase to varying degrees correspondingly.

Mar 1, 2018

By Shengli Wu, Binbin Du, Mingyin Kou, Laixin Wang, Kai Gu, Shun Yao, Heng Zhou

Coke plays an important role on the actual blast furnace production (BF), and its quality significantly influences the BF ironmaking process. In this study, the effects of physical properties, chemical composition and high-temperature properties of coke on main technical indexes of blast furnace were investigated. Some coke indexes were defined to evaluate the coke quality. The main technical indexes of BF include production, quality of HM, and fuel consumption. The quantitative relationship between coke quality and main technical indexes of BF were obtained after a series of statistical analysis. What’s more, the effect of these coke quality indexes on blast furnace smelting process was also explored, and all the relationships obtained from the analysis will provide a theoretical basis for the appropriate use of coke in blast furnace. The most reasonable range of coke quality indexes can be determined combining with the actual production as well.

Mar 1, 2018

By Djalma Souza, Jean Igor Margem, Sergio N. Monteiro, Frederico M. Margem

Synthetic fibers have been used for many years to attend the demands required by the technologica lfields. However, the use of them has been questioned due to the impact on the environment. In this way, the natural fibers have received extensive attention, in particular hybrid fabrics of natural fibers to reinforce environmentally friendly polymer matrix composites. Thus, the present work has the objective of evaluating and comparing the mechanical properties of composites formed by hybrid fabric with 70% Malva—30% Jute in epoxy polymer matrix. The tests carried out are the Charpy and Izod Impact Tests, with specimens of 10, 20 and 30% in volume of hybrid fabric environmentally friendly into polymer matrix composites at room temperature. The 30% samples had the best results, functioning as an efficient reinforcement.

Mar 1, 2018

By Monica M. Jimenez Correa, Jorge A. Soares Tenorio, Denise Crocce Romano Espinosa, Paula Aliprandini

The surface zone of nickel laterite ore is generally considered as residue. However, because of the depletion of ore sources and the increase in demand, this previously discarded zone may now be processed economically for nickel and cobalt. After leaching and removal of the impurities, the solution contains cobalt, magnesium, manganese and nickel. Solvent extraction is a hydrometallurgical technique used in the separation of metals from aqueous solutions. Cyanex 272 and D2EHPA are extractants used to separate nickel from cobalt. The mixture of extractants can change the performance during the metals extraction. This work aims to evaluate the solvent extraction of nickel and cobalt when Cyanex 272 and D2EHPA are mixed. The results showed that the increased concentration of D2EHPA in the organic phase increased the extraction of nickel and magnesium. However, cobalt extraction was reduced and the manganese extraction was not altered.

Mar 1, 2018

By Mike Johnson, Greg Andrews, Niels Verbaan, Ernesto Bourricaudy, David Dreisinger

Search Minerals has developed a Direct Extraction Process for recovery of rare earths from the Foxtrot and Deep Fox deposits in Labrador Canada. The process includes crushing, acid treatment, water leaching, impurity removal, precipitation of an intermediate rare earth product and finally re fining of the intermediate product to produce a high purity mixed rare earth oxide (*99% total rare each oxides). The Direct Extraction Process has been validated in an extensive demonstration pilot plant program at SGS Minerals. A total of 3 tonnes of material was processed to produce final mixed rare earth product. The results of the demonstration pilot plant program are reported.

Mar 1, 2018

By Jose Carlos D'Abreu, Edelink Efrain Tinoco Falero, Mauricio Marcos Otaviano

The production and consumption of Direct Reduced Iron (DRI) are continuously increasing, as a consequence of the impact of shale gas extraction technology on the Natural Gas (NG) market. Considering this context, DRI may improve the Blast Furnace (BF), Electric arc Furnace (EAF) and LD converter ’s productivities and consequently their competitiveness. In this work the results of a cooperative research conducted by PUC-Rio University and a Brazilian mining company are presented. Laboratory-scale simulation tests, using DR commercial pellets and typical industrial operational parameters of a benchmarked DR shaft furnace, were conducted and planned using statistical and factorial analysis. In the simulated experiments, the following three regions of the DR shaft furnace were considered: Reduction Zone (RZ), Transition Zone (TZ) and Cooling Zone (CZ). Three stages were considered in the research development: (i) the reactions and equations concerning pellet metallization and Carbon precipitation were analyzed; (ii) experiments focused on the de finition of the carburization kinetic equations occurring in the Transition and Cooling zones, and finally, (iii) aimed to develop the “METCARB” model, a computational program conceived to simulate mathe- matically the metallization and carbonization reactions along the height of the furnace. In conclusion, a comparison is made with industrial results in order to validate the resulting “METCARB” model.

Mar 1, 2018

By S. N. Monteiro, L. G. Pedroti, D. P. Santos, M. S. Peixoto, G. C. Xavier

The Baixada Campista is a region located in the municipality of Campos dos Goytacazes and is known as an important pole producing ceramic artifacts in Brazil. The clay used in this production is usually extracted from different layers of the region itself undergoing a pretreatment process. The objective of this work was to characterize the different soils (A, B and C), from different layers of the reservoir, in order to characterize the different physical and chemical characteristics (granulometry, determination of Atterberg limits, moisture and chemical analysis). To optimize, using the simplex methodology, properties such as mechanical strength, porosity and linear retraction. The results pointed to an optimum proportion of the clays studied so that the properties meet the Brazilian technical norms, being the proportion of 30% of soil A, 30% of soil B and 40% of soil C well.

Mar 1, 2018

By Zhucheng Huang, Zhikai Liang, Ronghai ZHONG, Lingyun Yi

In this work, research of reduction process was studied by means of rotary kiln (u1.5 m /C215 m) process anatomy in order to provide fine guidance to large-scale operation. It was shown that the average reduction degree of 89.96% and metallization ratio of 85.15% were obtained at the highest temperature of 977°C and total residence time of 90 min. The generation amount of metallic iron in section of temperature higher than 900°C and lower than 900°C was 34.15 and 56.38%, respectively. The section of lower temperature of 830–900 °C played an important role in formation of metallic iron, making it possible for mini-pellet to reduce quickly at lower temperature. Two main tasks were completed for mini-pellets in rotary kiln: the reduction of iron oxides in the range of 15.0–4.5 m as well as migration and bene ficiation of metallic iron, facilitating the subsequent separation of iron and gangue minerals.

Mar 1, 2018

By Maria S. Gudjonsdottir, Miao Yu, Gudrun Saevarsdottir, Pall Valdimarsson

Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30–45% of the total waste heat is carried away by the exhaust gas from the smelter and is the most easily accessible waste heat stream. Alcoa Fjarðaál in east Iceland produces 350 000 tons annually, emitting the 110 °C exhaust gas with 88.1 MW of heat, which contains 13.39 MW exergy. In this study, three scenarios, including organic Rankine cycle (ORC) system, heat supply system and combined heat and power (CHP) system, were proposed to recover waste heat from the exhaust gas. The electric power generation potential is estimated by ORC models. The maximum power output was found to be 2.57 MW for an evaporation temperature of 61.22 °C and R-123 as working fluid. 42.34 MW can be produced by the heat supply system with the same temperature drop of the exhaust gas in the ORC system. The heat requirement for local district heating can be fulfilled by the heat supply system, and there is a potential opportunity for agriculture, snow melting and other industrial applications. The CHP system is more comprehensive. 1.156 MW power and 23.55 MW heating capacity can be produced by CHP system. The highest energy efficiency is achieved by the heat supply system and the maximum power output can be obtained with the ORC system. The efficiency of energy utilization in aluminum production can be effectively improved by waste heat recovery as studied in this paper.

Mar 1, 2018