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By G. E. S. Lima, J. V. B. Lemes, F. G. D. Machado, J. Alexandre, L. G. Pedroti, L. A. F. Fioresi, W. E. H. Fernandes, R. C. S. S. Alvarenga

Cellulose fibers are extracted from renewable sources and have potential to be used in various fields. In this study, a type of Reactive Powder Concrete (RPC) was produced with the addition of Cellulose Nanofibers (CNF), a biopolymer extracted from lignocellulosic materials. Three different concrete compositions were produced, each with addition of 0.10, 0.20 and 0.25% of CNF in mass, proportionally to the cement’s mass. During the analysis were performed Scanning Electron Microscopic (SEM) tests, compressive strength and Young’s modulus tests after 1, 3, 7 and 28 days of production and shear and flexural strength after 28 days of production. The results showed that the addition of CNF in aqueous solution reduces the concrete’s workability and negatively affects mechanical properties.

Mar 1, 2017

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 I. A. H. Schneiderl

Eichhornia crassipes approaches being a scourge in many parts of the world, .choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This paper considers the possibility of using specific parts of the plant as an inexpensive adsorbent for the removal of heavy metals from contaminated chemical and mining industry waste waters. In particular the root of the plant was found to be an excellent accumulator of 'heavy metal ions including uranium from solution. It is. also suggested that dried roots of the plant ?might be placed in simple bags and used in a very low cost metal ion removal system.

Jan 1, 1995

By Yoshihiko Maeda

It is said that the 21st century will be an era of the remedy of the global environment. In order to reserve natural resources for the future and to avoid the dispersion of heavy metals after usage and to avoid pollution problems, it is extremely important to recycle heavy metals as much as possible by reasonable recovery procedures. The nonferrous metal industry is expected to play a important role in the recycling of heavy metals that are originally their products. From the depressed metal price experienced in Japan in 1980'h due to the sudden change in current exchange rate between US dollar and Japanese yen, one of major nonferrous metal company, Dowa Mining, has diversified its business area not only to the so-called down stream, but also to the environmental business including metal recycling, industrial waste treatment and soil remediation by utilizing technologis and facilities once used or still used for mining and smelting of copper, zinc, lead and precious metals. In this paper some of these applications will be presented.

Jan 1, 2003

By Toshihide Takenaka

The management of radioactivated stainless steel from a terminated nuclear reactor will become an important subject in the near future. The separation of the elements in stainless steel should be effective to reduce the management labor. In this study, the separation of the elements in stainless steel by an electrorefining tcchnique was investigated in an aqueous solution. The electrochemical reactions of the elements in stainless steel werc studied by voltammetry and potentio-static electrolysis was carried out. A stainless steel anode was dissolved electro-chcmically with good anodic current etliciency in a chloride solution. The residue, where Ni was concentrated, was found on the anode after electrolysis. The electrodeposit in a stainless steel cathode consisted mainly of Fe and Cr and the Ni content in it was less than 0.5wt% under suitable condition. It is concluded that an electrorefining technique is effective for the separation of the elements in stainless steel.

Jan 1, 2003

By Hüseyin Aydin

TWIP (Twinning-Induced Plasticity) steels have exceptionally good combinations of strength, ductility and damage tolerance which satisfy the recent requirements of automotive industries. Firstly, TWIP has the most beneficial effect on the work-hardening. It is believed that deformation twins increase the work-hardening rate by acting as obstacles against gliding dislocations. Moreover, TWIP steels have low to intermediate stacking fault energy and hence undergo extensive mechanical twinning during deformation, which in turn leads a good combination of both strength and ductility. To explain the mechanical characteristics and the mechanical behavior of the TWIP steels, we have been made some investigations and experiments that show the effects of microalloying elements and deformation mechanisms. In this study, three different compositions of TWIP steels have been produced. The microstructure and mechanical properties are characterized by using optical, electron microscopy and mechanical tests.

Jan 1, 2009

By Jianhong Dong, Min Chen, Cuihuan Huang, Bo Li, Nan Wang

"Scale layer can be formed on the slab surface in the areas of secondary cooling and strand discharge during continuous casting process. From 1000 °C -1200 °C, the influence of steel composition on the stable oxide phases inside scale layer, particularly the types of alloying elements including aluminum, silicon and chromium, is investigated under different partial pressures of water vapor by the calculated predominance diagrams of iron oxide as well as its intermediate compounds formed with other metal oxides, and the stable oxide phase composition within scale layer under the working condition of secondary cooling is discussed. At lower partial pressure of water vapor, only a iron spinel (or ferrosilicate) phase is the stable phase with any alloying element contents in steel composition, whereas the stable phases are FeO and iron spine! (or ferrosilicate) inside the scale layer at higher partial pressures of water vapor .IntroductionOxide scale formation on the surface of cast and rolled products because of oxidation by the surrounding oxidizing atmosphere is a significant disturbance factor in steelmaking. The yield loss of iron because of scale formation is considerable during continuous casting and hot rolling process. Surface quality more often is impaired by scale property, which increasing the difficulty of quality assurance, dimensional accuracy and performance control. Furthermore, a potential source for subsequent surface cracking (hot shortness) can be caused by the enrichment of scrap residuals (Cu, As and Sn) at the steel substrate surface as a result of steel oxidation [1-2]. In flat products manufacture via thin slab casting technologies, these phenomena are particularly pronounced and require enhanced development efforts in descaling efficiency [3].Compared with the scale formation in continuous casting, the quantity of scale formed during hot rolling and reheating in the rolling mill is larger, and control of scale formation and descaling is a long-established task in hot rolling. Therefore, extensive research and development work have been carried out, including the effects of heating and rolling temperature on the thickness and microstructure of scale layer, heating time and furnace atmosphere, cooling mode, and steel composition on the scale formation, more attention has been given to the control of scale formation during reheating and hot-rolling process. On the other hand, hardly any specific efforts and countermeasures are taken in continuous casting, and very less research has been done despite the network-type crack on the as-cast strand surface caused by the subscale enrichment of scrap residuals [ 4-7]."

Jan 1, 2014

By J. Pérez

A lead smelter slag with high copper, lead, arsenic and silver contents was treated at laboratory scale for arsenic removal. The slag was first leached at atmospberic pressure with sulfuric acid and oxygen. According to arsenic contents leaching of most of the arsenic was achieved in either one or two stages, producing a lead-silver rich residue and a solution high in copper and arsenic concentrations. Alternative routes were considered to treat the resulting solution. Firstly, solvent extraction of arsenic with a mixture of TBP and 2-etbyl-bexanol was tested and extractions of over 95 percent of arsenic were achieved. Secondly, a copper arsenate precipitation treatment was done to eliminate arsenic and copper from solution.

Jan 1, 1996

By Shuqiang Guo, Gonghui Yang, Xingxing Zhang, Yuyang Bian, Song Chen, Weizhong Ding, Yinhe Liu, Lan Jiang

One of the most promising refractory materials for application is zirconia in melting superalloy. In this work, the properties and phase composition of magnesia partially stabilized zirconia ceramics (MgO-PSZ) under different sintering temperatures were systematically investigated. Commercial magnesia partially stabilized zirconia (MgO-PSZ) powders were selected as the starting materials. The magnesia partially stabilized zirconia phase composition was measured by X-ray diffraction (XRD), the density of sintered samples was tested by vacuum density instrument, the thermal expansion were obtained by thermal dilatometer from ambient temperature up to 1450°C, and the microstructures of MgO-PSZ were characterised by scanning electron microscope (SEM). The results indicated that the properties of thermal expansion, densification, microstructures and phase composition were significantly affected by sintering temperature. Densification was consistent with SEM micrographs of MgO-PSZ at different sintering temperatures.

Jan 1, 2015

By Marcio Toshio Tanaka, Marcelo Breda Mourao, Cyro Takano, Cesar Yuji Narita

"The concerns in questions related to the environmental impact in the steelmaking industries caused mainly on the gas emissions such as the dioxide carbon are due to its raw material such as the coal, a fossil and non renewable resource. The purpose of this paper is to replace from 10% to 50% of the coal used in cokemaking by mixing it with a renewable source (wood charcoal). The powder (- 325 mesh) from both raw materials (coal and wood charcoal) were mixed in order to obtain a briquette that was then heat treated at 1100°C to obtain the biocoke. Results of usual analysis (coke reactivity index, coke strength after reaction and cold crushing strength test) were employed to compare to regular coke briquettes. It was found that biocoke with different amounts of wood charcoal present features enabling it to be used in some ore reductionprocesses.1. IntroductionThe iron and steelmaking industry is a heavy emitter of carbon dioxide; according to the World Steel Association, 6.5% of global emissions of this greenhouse gas is due to the production of ferrous materials [ 1]. This is due to the fact that the fuel and reductant employed in the blast furnace is metallurgical coke, obtained from fossil coal. There are some projects aiming to reduce or even eliminate the emission of fossil GHG in the iron and steelmaking process [2]. Most of them propose the capture and storage of the gas (CCS) [3], a technology not yet proven. Other studies point out that the coke consumption in the blast furnace could be reduced by using high reactivity coke; this could lead to lower temperatures in the thermal reserve zone of the blast furnace and consequently less fuel rate in the furnace.The use of biomass in the iron ore reduction process is known as an environmentally accepted solution, as biomass does not release already fossilized carbon."

Jan 1, 2013

By Xuling Chen, Yi Wang, Xiaohui Fan

"The current control method of grate-kiln iron ore oxide pellet production is lack of accuracy and normalization due to the limited detection conditions. Therefore, mathematical models of grate-kiln temperature field are presented. With calculation of gas-particle heat transfer as well as enthalpy changes of moisture evaporation and magnetite oxidation, the thermal history of pellets throughout grate-kiln process can be acquired and used for production status estimation. Taking the calculated results as well as detected data in production as inputs, process parameters such as running speed, fan opening and coal injection rate as adjusting objects, expert system for grate-kiln pellet production is outlined. And the preheating section dominated control strategy is explained. Results of production application show that the stability rate of gas temperature in gas hood of preheating section is increased from 91.0% to 94.2%, compressive strength and first grade rate of pellet are increased by 3.62% and 2.36%, respectively, while FeO content is 18.18% lower. Control guidance of this expert system can solve production anomalies effectively, stabilize grate-kiln iron ore oxide pellet production and improve pellet quality.IntroductionSteel industry in China has developed rapidly in recent years. China’s crude steel production in 2010 is nearly 627 million, which is 44.2% of the world total production. Burden with higher quality is demanded by enlargement and modernization of blast furnaces. And oxide pellet production has become a growing concern. In 2010, the total production of pellet in China is 110 million, and about 60% is produced by grate-kiln process."

Jan 1, 2012

By Isıl Kerti, Sibel Daglılar, Sinem Yıldırım

In this study, effect of rolling and coiling temperature in thermo mechanical controlled process (TMCP), on the microstructure and mechanical properties of dual phase (DP) steel according to martensite volume fraction (MVF) rate was investigated. By using various finishing mill exit temperature and cooling conditions that is controlled laminar cooling system, the microstructural evolution of coil improves the mechanical properties with lower costs and higher productivities, in comparison to the heat treatment after rolling. The main part of the paper contains the result of tensile, yield and microstructure properties of DP600 steel produced on hot strip rolling plant and run- out table line. The results show that a higher MVF and an increasing cooling rate after the last deformation raised strength of the DP600 steel. The yield strength and ultimate tensile strength increase by decreasing coiling temperature.

Jan 1, 2015

By Petrus Christiaan Pistorius, Ming Tang

Magnetite concentrate is pelletized and then hardened by elevated-temperature oxidation to hematite, to produce pellets for ironmaking. Previous work showed that the rate of oxidation is under mixed control of gaseous mass transfer of molecular oxygen through the pellet pores, and solid-state diffusion into the oxidizing grains. Because of the partially limiting role of solid-state diffusion, concentrate size distribution strongly affects pellet oxidation. Previously, a simple mixed-control model was formulated to describe isothermal oxidation. In that model, the main effect of concentrate size distribution was on the plateau level of oxidation which is reached at a given temperature. However, the extent of plateau oxidation increases with increased temperature, requiring a more complex model for non-isothermal oxidation. In this paper, predictions of the non-isothermal model confirm the strong effects of concentrate size distribution and oxygen enrichment. In particular, a greater fraction of coarse magnetite particles would be beneficial, decreasing the size of the macroscopic unoxidized pellet core.

Jan 1, 2015

By John E. Litz

The Denver Process is a chemical/metallurgical process for treating radioactive or mixed wastes by extraction and concentration of the radioactive and/or hazardous component(s). The process was developed at bench scale, evaluated at pilot scale, and will be implemented at full scale to remediate a low-level radioactive sludge. Six unit operations comprise the process: feed handling, leaching, solvent extraction, electrodeposition, precipitation, and tailing preparation. Unit operation design may be modified to tailor the process for varying feed stock composition. Radioactive or mixed waste is reacted with aggressive reagents in an aqueous phase, solubilizing targeted components. These components are then selectively extracted and concentrated in subsequent steps. Waste solids and solution exit the process as non-hazardous non¬radioactive waste. Dehydration of aqueous waste by submerged combustion eliminates aqueous discharge.

Jan 1, 1994

By Rubén J. Sánchez Rodriguez, Carlos M. Fontes Vieira, Carlos E. Gomes Ribeiro

Ornamental compound stone are produced by industry for decades, however, few published studies describe these materials. Brazil has many deposits of stone wastes and a big potential to produce these materials. This work aims to evaluate the chemical resistance of ornamental compound stones produced with marble waste and unsaturated polyester. An adaptation of Annex H of ABNT NBR 13818:97 standard, with reagents commonly used in household products, was used. The results were compared with those obtained for natural stone used in composite production.

Jan 1, 2015

By Pengcheng Li, Wei-Tong Du, Yu Wang, Gang Wen

Carbon dioxide could be utilized as a weak oxidant and a kind of coolant to oxidize elements, meanwhile, helping control the temperature during the converter vanadium extraction process. However, the optimum content of CO2 and the cooling effect of CO2 at low content have not been reported. In this study, experimental research based on the influence of different CO2 contents from 0% to 25% injected to the vanadium-containing hot metal was carried out, as well as contrast experiments of O2-N2 mixed blowing. The results indicated that the optimum content of CO2 was 15%. Under the optimum condition, the oxidation of [C] was the lowest and the oxidation rate of [V] was 96.9%, while the temperature was also lower than the O2-N2 mixed blowing. This paper provide a potential property for utilizing CO2 during the converter vanadium extraction process.

Jan 1, 2016

By Jianhua Xin, Min Chen, Lei Xu, Haohua Deng, Nan Wang

A mathematical model of converter slagging and steelmaking process by replacing part of lime with limestone is established. The rate equations of oxidation reactions and lime dissolution in converter under the limestone substitution proportion increasing from 25 to 50% can be obtained and the effects of limestone substitution proportion on the variations of the composition of hot metal, slag and converter gas during the steelmaking process are investigated. In the process of converter slagging and steelmaking by replacing part of lime with limestone, increasing the hot metal temperature and the lance height could be favor to increase the content of FeO in the slag and accelerate the limestone decomposition and dissolution. With the limestone substitution proportion increasing from 25 to 50%, the maximum of oxygen supply ratio increases from 10.7 to 19.7% and the temperature drop of converter bath is 8–60 °C.

Mar 1, 2018

By M. Ide, K. Takemura, S. Taenaka, K. Shinzawa

"The laser characteristic is strongry dependent upon the stoichometry of forsterite (Mg2Si04) and YSO (Y2Si05) single crystals, because of change in the valency and occupied sites of doped Cr in the lattice so that mole ratios of Mg0/Si02 and Y203/Si02 in the above single crystals must be precisely analyzed. In this study ICP-AES was applied for analyzing the mole ratios. Emission intensities corresponding to Si and Mg or Si and Y were measured at the same time with internal standard method. Preparation of sample solutions, measurement conditions of ICP-AES and interferences by coexisting components were discussed, resulting in excellently precise detennination of stoichometry of the above single crystals.IntroductionIn conventional stoichiometric analysis of single crystals, the stoichiometry is detennined by analyzing each component separately with titrimetry and gravimetry techniques. On the other hand, by stoichiometric analyses using ICP-AES, emission intensities corresponding to components are measured at the same time with internal standard method. Consequently erros caused by variation of analytical condition are canceled out.Cr-doped Mg2Si04 and Y2Si05 syngle crystals are known as laser materials. The change of valency and occupied sites of doped Cr affect the characteristic of single crystal as aleser materials. The change of state of doped Cr.Stoichometric composition of Mg2Si04 is constructed by 2mole of MgO and 1mole of Si02, and Y2Si05 is constructed by 1mole of Y203 and 1mole of Si02. In this study, required analytical precision in component mole ratio is within an error of 0.0010 for Mg2Si04 (CV=0.05wt%), and within an error of 0.0030 for Y2Si05 (CV=0.05wt%) (Table I )."

Jan 1, 1998

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 Shigeru Ueda, Shin-ya Kitamura, Dong Jun Shin, Xu Gao

Steelmaking slag contains useful elements such as P and Mn. Generally, in the carbothermic reduction of slag, not only P but also Mn are reduced and a Fe–P–Mn alloy is formed. In this study, the possibility of the separation of Mn and P was investigated. A mixture of synthesized slag and graphite was heated at 1773 K, and the compositions of the separated slag and metal were analyzed. The results showed that with a decrease in basicity, the reduction of P was enhanced but that of Mn was suppressed. Thus, under an optimum condition, steelmaking slag was separated into a Fe–P alloy and a high MnO-containing slag. Although further investigation is necessary, the formed alloy and slag could be used as raw materials for fertilizers and Fe–Mn alloys, respectively. This paper elucidates the concept of this process and the results of the fundamental experiments.

Mar 1, 2018