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By Ken-ichiro Uemura

"The DIOS process has been developed for eight years since 1988. The research project was started with the element studies carried out by each of the five integrated steel making companies in Japan, the final two and half years were spent for the pilot plant studies. Operation were conducted in the entirely closed and pressurized system successfully as planned. From the result, the DIOS process was proved to be viable as a future iron-making process substitutable for the conventional blast furnace. In addition, a lot of findings were obtained. Hot metal productivity was primarily determined by a oxygen flow rate, and a coal consumption varied depending on the productivity. The post combustion ratio was a little lower than expected from the result of the element study. It was supposed to relate the gas-reforming with coal or volatile matter in the free space of the furnace. Hot metal carbon content seemed to depend on the char content in slag.INTRODUCTIONThe JISF's DIOS pilot plant (DIOS=Direct Iron Ore Smelting Reduction Process) has finished its last campaign of the operations in January 1996. The project was started in 1988 as a joint research of the Center for Coal Utilization, Japan and the Japan Iron and Steel Federation (JISF) with a subsidy for promoting coal productions and utilization technologies from the Agency of National Resources and Energy, the Ministry of International Trade and Industry(MITI). Throughout the pilot plant test, a total of over 20,000 tons of hot metal was produced for more than 2,000 hours of the operation. Recorded production rate was 538 ton/day for 3 days at a specific coal consumption of approx. 1,000kg/hmt. Long-term operation was carried out in the fifth campaign for 18 days, which has proved that the entirely closed and pressurized DIOS process works well as planned. In Figure 1 is shown the representative operational performance obtained in the first five campaigns. The project is going to be finished by the end of March this year after investigating the technical viability and economic potential of the process, and completing the conceptual design of the DIOS commercial plant. In this paper, the system and facilities of the DIOS process are first introduced and some of the results of the pilot plant test are detailed later."

Jan 1, 1996

By K. D. Peaslee, V. L. Richards, C. H. Rawlins, S. N. Lekakh

"Steel-making processes generate carbon dioxide air emissions and a slag co-product. The aim of this project was to develop a functional sequestration system using steelmaking slag to permanently capture carbon dioxide emitted in steelmaking offgas. A possible parallel benefit of this process would be rapid chemical stabilization of the slag minerals with reducing swelling or leaching.This paper summarizes the original results of the project, including mineralogical and structural features of carbon sequestration with steel making slag, mathematical modeling of reaction phenomena using a modified shrinking core model, METSIM modeling of several possible industrial applications, a thermo-gravimetrical study of the reaction between slags and different gases, and design and testing for a lab scale apparatus consisted of two reactors.1. IntroductionThe U.S. produces 9-14 Mt of steelmaking slag annually, which represents approximately 10-15 wt. % of crude steel output.1,2 Primary uses for steelmaking slag include high quality mineral aggregate, Portland cement, unconfined fill, soil conditioning, and pH neutralization of abandoned mine drainage.3,4 The key factor prescribing slag use is the alkaline-earth metal (e.g. Ca and Mg) oxides content, which contribute to overall basicity and cementitious strength. However, as-produced steelmaking slag is chemically unstable. Calcium and magnesium oxides readily form hydroxides and carbonates through reaction with atmospheric gases. Both hydroxide and carbonate formation produce substantial mechanical swelling leading to heave failure in confined construction applications, thus many states dictate stockpile aging for 3-6 months prior to commercial use.5,6 Sequestration of carbon dioxide is a natural corollary to forced carbonation. The conversion of CaO/MgO to carbonates serves both to stabilize the slag, and permanently capture and store the CO2."

Jan 1, 2008

By Y. K. Rao

Relatively pure crystalline lead sulfate (PbSO4) can be produced by chemical vapor transport from an impure source such as the lead-acid battery paste or the roast-ore-leach-residue from a hy¬drometallurgical process-route. In a closed-reactor, transport of matter is induced by a tempera¬ture-gradient and the steady-state transfer rate can be calculated using the data on the standard free energies of formation for the species present and the pertinent binary diffusion coefficients. The present work focusses on chemical vapor transport in a tubular reactor (1.4-cm inner diameter x 10-cm long) with the source- and deposition-ends held at 850°C (T,) and 750°C (Td), respectively; PbC12(g) is the 'solvent' or 'transport agent' and NiSO4(s) placed in the source-zone -serves to maintain a sufficiently high S0,-potential such that the stability of the lead sulfate species is ensured. For the purposes of analysis, the gas-phase in the reactor is assumed to consist of eight species: H2O, PbC12, SO3, SO2. O2 HO, C12, and PbC14. The reaction between C12(g) and PbSO4(s) in the high-temperature source-zone produces PbCl2, SO2, and 02; four more reaction-equilibria in the same zone yield other species. In the low-temperature deposition-zone, reaction equilibrium involving PbC12, H2O, and SO, leads to the nucleation and growth of PbSO4 crystals; three other reaction-equilibria occur in this zone. By employing the virtual equilibrium state for the end-zones and coupling it to the Stefan-Maxwell diffusion equations for each of the gas species, the respective partial pressures for these, in the source- and deposition-zones, are computed at steady-state. From these data, the molar fluxes of PbCl2. PbCl4, and so forth, are determined. Allowing for the transport-enhancing effects of thermal convection, the net transport rate of lead (or PbSO4) is duly calculated for specified initial conditions. The predicted rates show very good agreement with measured rate data reported in the literature [ V. Plies, T. Kohlmann and R. Gruehn: Z. anorg. allg. Chem, 568, 62 (1989)

Jan 1, 1995

By E. Fregeau-Wu

The major obstacle in recycling steelmaking slags to the blast furnace is their phosphorus content. Removal of the phosphorus, which is primarily associated with the silicate and phosphate phases, would allow for greater recycle of these slags for their iron, manganese, and lime contents. Calculations show that separation of the silicates from the oxide phases would remove nearly 90% of the phosphorus from the slag. The variable grain size of the as-received slag made liberation by fine grinding difficult. Therefore, slow-cooling experiments were undertaken to improve the grain size distribution. The grain size distributions were determined using in-situ image analysis. The samples were ground to their apparent liberation size and high gradient magnetic separation was used to separate the magnetic oxides from the nonmagnetic silicates and phosphates. Liberation analysis and modeling was performed on selected separation products for discussion of benefication characteristics.

Jan 1, 1995

By E. O. Ávila-Davila, F. R. Barrientos-Hernández, I. A. Lira -Hernández, Miguel Pérez-Labra, M. Reyes-Pérez, J. Antonio Romero-Serrano

Slag from smelting reduction processes were characterized by chemical analysis, XRD, SEM-EDS and XRF. The results revealed Ag concentrations of 362 g/t of slag, the slag mineralogical characterization by XRD and SEM-EDS showed mineralogical species oxidized complex containing Pb, Zn, Ca, Si, Fe, As, S in its structure, silver was found in globules associated lead in the slag and the furutobeite specie. The leaching study was conducted to evaluate process variables such as NaCN concentration: from 7.8x10-3M - 1.26x10-1M, temperature: 25-50°C, particle size: +140 mesh to -400 mesh, stirring speed of 750 rpm - 900 rpm. All studies were performed with a NaOH concentration of 0.2 M. The optimal values of silver recovery encountered in conditions of 7.8x10-3M NaCN, agitation rate of 750 rpm, temperature of 35°C and with a treatment time of 240 min. We also observed that a particle size -400 mesh will have optimum recoveries compared to +140 mesh, +200, +270 and +325.

Jan 1, 2015

By Marcos Aurélio S. Costa, Nilton F. Nagem, Andreia B. Henriques, Herman S. Mansur, Alexandra A. P. Mansur, Antonio E. C. Peres, Valeria G. Silva

The superfine material generated in the Bayer process was used in one innovatively way as a precursor to geopolymerization techniques because of the presence of Gibbsite. Gibbsite can play a role in system adjustment because of the SiO2/Al2O3 ratio. Furthermore in the geopolymeric system it was studied the influenceof the additives such as kaolin, metakaolin and sodium trisilicate in an alkaline media. Others conditions to form the geopolymer were also evaluated such as solid/liquid ratio, SiO2/Al2O3 ratio and total alkaline. The raw materials and geopolymeric products were characterized by several techniques e.g. XRD, DSC, FTIR and SEM. Through the FTIR technique it was observed an increase in intensity and bandwidth in the region centered at 1010 cm-1, which is related to the asymmetric vibration Si(Al)-O, this is an indicating of the possible geopolymer formation This broadening of the band promotes a relative disappearance (overlapping) peaks at 965 and 935 cm-1 associated with raw material (ESPDust).

Jan 1, 2015

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By A. Kiziltas, D. J. Gardner, C. W. Mcllwraith, J. W. Bridge, M. L. Peterson

"Dynamic mechanical thermal analysis (DMTA) tests were conducted on high-oil content, paraffin-based wax used in wax-coated granular composites. These composites make up the surface of synthetic Thoroughbred horse racetracks used in North America. The modulus and damping response from the DMTA tests were correlated with the dynamic triaxial shear strength response of the bulk track material taken at two different operational temperatures and at four strain rates. The purpose of these tests is to understand the mechanisms of shear strengthening of the bulk track material as the wax is heated through the first crystalline solid to liquid nominal transition temperature. Previous work using differential scanning calorimetry confirmed that under common operational surface temperatures, the wax coatings undergo distinct thermal transitions. The resulting increase in triaxial shear strength values affects the consistency of the racetrack which, in turn, can potentially affect Thoroughbred racing performance and safety of the track surface.IntroductionSynthetic granular composite materials are being used in nine Thoroughbred horse racetracks in the United States as well as in other tracks around the world. In one case, their use was mandated by the state of California in 2007 due to testimony that these tracks were significantly safer than traditional dirt tracks [1]. Several synthetic tracks have shown substantial reductions in injuries since switching to synthetics; one California track showed a 75% reduction in catastrophic horse injuries during the first year as compared to the previous year racing on a dirt track [2]. The composition of the tracks in the U.S. generally consist of silica sand (>70%), polymer fibers (<5%), and rubber particles (0-15%) all coated with a paraffin-based, high oil content wax [3, 4]. In a recent study of several synthetic racetracks, to include the track location in this study, the oil content ranged from 34 to over 44% by mass [5]."

Jan 1, 2011

By R. L. Nyirenda

An investigation of the reducibility of a cassiterite concentrate with charcoal was made in the temperature range of 1123-1373 K. The course of the reaction was monitored by a combination of sample weight loss measurements, product gas analysis, and chemical analysis of the reaction product. It was found that the cassiterite could be best reduced by a combination? of high temperature, reasonably high charcoal proportions, high charge poroslty, and the addition of a small percentage of lime. Analysis of kinetic data obtained from isothermal experiments using theory from the oxidation of carbon by carbon dioxide gave an activation energy value of 255 lci/mole for the consumption of carbon by reaction with cassiterite.

Jan 1, 1990

By A. J. Davidson

A novel sensor is described for the measurement of the copper content of copper matte. Due to the high copper concentrations found in matte, potentiometric sensors are not sufficiently sensitive. A highly sensitive sensor has been developed based on a modification of the amperometric technique using a copper ion conductor, Cusicon. The results correlate closely with the theoretical predictions.

Jan 1, 1998

By Shadia J. Ikhmayies

In this work the equilibrium temperature-composition phase diagrams of the Si-O2 system were calculated using Thermo-Calc software in the temperature range 500–3000 K. Constituents of stable phases were obtained, and the amounts of certain phases where investigated with the variations in the composition of oxygen and temperature. It is found that quartz with silicon represent a stable phase in the temperature range 500–1150 K, while tridymite with silicon represent a stable phase in the temperature range 1150–1700 K. A liquid phase is found besides tridymite in the temperature range 1700–1750 K, and a stable phase of cristobalite with liquid appears in the temperature range 1750–2000. The maximum amounts of quartz, tridymite, and cristobalite are found at oxygen mole percent of 67.7%.

Mar 1, 2017

By R. W. Smith

Living and killed organisms, particularly microorganisms, and extracellular products derived from the organisms are increasingly finding use in minerals engineering. Goals include both enhancement of mineral processing/11.ydrometallurgica,l operations and remediation of mineral industry wastes. Some of the applications, such as biologically assisted leaching of ?sulfide ores and bioxidation of refractory gold ores, are well established commercial ?processes used around the world. Others, such as the use. of organisms for the removal of heavy metal ions from dilute aqueous streams, are nearing commercial application. Many other uses of microorganisms and. their derivatives are potentially possible. These include use of microorganisms in flocculation or flotation of minerals., remediation of organics potentially discharged from mineral engineering operations, degradation of cyanide, the recovery of bitumen from heavy oil reservoirs and tar sands and the solubilisation of lignites and low rank coals. In order to fully exploit these many possible uses of organisms and their derivatives, extensive fundamental .and .applied research work exploring the fundamentals, potential and practicality of the various possible uses of microorganisms in mineral engineering should be vigorously pursued. ?

Jan 1, 1991

By V. A. Shumsky, I. P. Polyakov, N. M. Ospanov, M. A. Lyamina, N. N. Ushakov

Studies on the kinetics of the competitive processes of PbS volatilization and PbS oxidation, as applied to the heat and mass transfer conditions in the flame of the Kivcet furnace, revealed that the rate-determining factor is the supply of heat. Therefore, low yields of fume in the autogenous flash smelting of lead sulphide feeds are noted despite the high volatility of PbS at 1,300-1,400°C. Dust formation in the autogenous flash smelting of Kivcet-smelters does not exceed 5-7%, of which fumes amount to ~ 80%. Using extra fuel during autogenous smelting involves the mismatch of the sulphide oxidation rate and the release of heat in the flame, and increases the fume yield. This is a major cause of the high dust formation in pilot plant trials. The analysis of dust formation in the Kivcet smelting of oxidized lead feeds in an industrialscale smelter shows an overall increase of dust formation (up to 10% of the feed), with fumes constituting ~ 80% of the dust. A pronounced increase of the zinc component of the fumes is also noted. Lead

Jan 1, 2000

By A. Broussaud

An original methodology has been developed for steady state simulation of selective grinding and mineral liberation in rod and ball mills. Three fundamental aspects of the methodology are presented successively : modeling ore texture, modeling grinding and its selectivity, and modeling mineral liberation. The methodology for modeling ore texture includes the conversion of 2D data into 3D reconstructed information and the use of the BILCO coherent material balance software. The models for grinding Simulation are classified into three levels, corresponding to three levels of available experimental data. All models account for grinding selectivity and for variations of engineering para-meters and operating conditions. An algorithm has been introduced to forecast mineral liberation, compatible with accurate simulation of selective grinding, which generates reasonable results.

Jan 1, 1987

By N. Can

Kinetics and mechanism of the chemical interactions between Si3N4 and TiC were investigated by isothermally reacting samples under nitrogen and argon atmospheres at temperatures between 1600°C and 1700°C? The initial composition of the powder compact contained 20, 30 and 40 volume per cent TiC? Kinetic analysis were performed by measuring mass losses and composition of the titanium carbonitride (TiC1-xNx) at predetermined time intervals? It was found that in the Si3N4-TiC system the degree and rate of the reactions increased with increasing temperature and content of TiC in both nitrogen and argon atmospheres? Si3N4 in the presence of TiC was stable in nitrogen atmosphere and the reactions were confined to Si3N4/TiC and TiC/N2 interfaces? At both interfaces interchange reaction occurs by simultaneous diffusion of nitrogen towards the centre of the particle and desoprtion of carbon in the opposite direction resulting in formation of titanium carbonitrides with various compositions? Reaction products under nitrogen atmosphere were B-SiC, TiCl1-xNx and N2? The maximum "x" value in TiC1-xNx was found to be 0?67 under nitrogen atmosphere? Si3N4 was found to be unstable in argon atmosphere in the presence of TiC and dissociated into liquid silicon and nitrogen gas within approximately four hours of reaction time, depending on temperature? The reaction mechanism in the initial stages of the interaction between Si3N4 and TiC under argon atmosphere proceeds similar to reactions under nitrogen atmosphere? However, considerable amount of Si3N4 dissociates within the first half hour? Liquid silicon aggressively attack both TiC1-xNx and unreacted or partially reacted TiC particles through cracks and pores and diffuses into interier part of the particle forming liquid solutions? After this stage, reactions under argon atmosphere proceeded according to Si-Ti-C ternary system?

Jan 1, 1999

By Guihong Han, Duo Zhang, Yanfang Huang

Ni2SiO4 was prepared by chemical precipitation process as a novel anode material for lithium-ion batteries. The structure and morphology of further annealed Ni2SiO4 samples were characterized by XRD and SEM analysis. The electrochemical performance including cyclic voltammetric curves (CV), electrochemical impedance spectra (EIS), charge/discharge curves and cycling performances were also determined. The results demonstrated that the crystal structure of the samples is orthorhombic having space group Pmn21. The morphological structure of materials exhibited cubic particles with sizes in the range of 50–80 nm. The first cycle charge capacity of the pure Ni2SiO4 particles reached to 753 mAh g−1 with the coulombic efficiency of 63.8%. The charge capacity remained 305 mAh g−1 at a current density of 100 mA g−1 even after 50 cycles, which is nearly 208% higher than those of the Ni2SiO4 with SiO2 impurity. Ni2SiO4 can be a promising alternative anode material.

Mar 1, 2018

By Gregory A. Knapp

Treatment of industrial wastewaters generally advances with specific chemical concentration and mass-flow targets, established by National Pollutant Discharge Elimination System (NPDES) permits. Treated discharges must also address toxicity to test and receiving water organisms. Various parameters might need consideration during treatment design and planning, such as the known toxicants, hardness, alkalinity, solids, nutrients, metals in both the dissolved and particulate state, and even flow. Since toxicity is used as a "catch all" regulatory monitoring tool, design of treatment systems should focus on the various factors contributing to toxicity.

Jan 1, 1996

By P. N. Anyalebechi

The effects of Si (0.19-0.52 wI. %), Fe (0.20 wI. %-0.44 wI. %), and Cr (0-0.10 wI.%) on the response of ingots of aluminum alloy 3004 solidified at different rates (O.IO°C/s to 30°C/s), to homogenization heat treatment have been investigated. Response to homogenization was determined by quantifying the following microstructural parameters: (i) amount of Mn retained in solid solution; (ii) types, relative amounts, sizes, size distributions, shapes, and chemical compositions of second phases; (iii) extent of the alpha-transformation (i.e., AI6(Fe,Mn) --7 (XAI12( Fe,MnhSi) reaction; (iv) dispersoid formation; and (v) alleviation of dendritic microsegregation. Of the three alloying elements investigated, Si had the greatest effect on the response of aluminum alloy 3004 to heat treatment. Increase in Si content, fineness of cast microstructure, and homogenization temperature facilitated alpha-transformation reaction, dissolution of Mg2Si, loss of Mn supersaturation, and formation of AldFe,Mn)3Si and Mg2Si dispersoids.

Jan 1, 2008

By Xinzhong Deng, Naixiang Feng, Kejia Liu, Jianping Peng, Yaowu Wang, Yi Zhang, Yuezhong Di

Low-carbon Ti2O3 was prepared by carbonthermal reduction of the mixture of titanium dioxide and activated carbon at vacuum condition. The kinetics and phase evolution of Ti2O3 formation process were investigated through X-ray diffraction and gravimetric analysis. The only intermediate phase detected is Ti3O5. The reduction time was reduced sharply to 4 h when temperature was raised to 1300 °C. The best molar ratio of activated carbon and TiO2 is 0.6–1. At this condition, the content of Ti2O3 in slag is up to 95.63% and the content of the carbon element is below 0.004%, which meets the requirements for the further preparation of metal Ti by FFC Cambridge process. At the same time, the microstructure of Ti2O3 generated presented porosity, which would promote the electro-deoxidation process extremely.

Mar 1, 2017

By Peter K. Liaw, Charlie R. Brooks, David C. Joy, Wei Zhao

In this paper, effects of oxidation, porosity and fiber-fabric stacking sequence on flexural strength of a continuous silicon carbide fiber (SiCr) fabric-reinforced SiC ceramic-matrix composite (CFCC) were studied. The failure mechanisms were correlated with flexural strengths of CFCC samples, both before and after oxidation. Microstructures and fractography were investigated using scanning electron microscopy (SEM). The chemical change after oxidation, such as Si, C, and 0, and their distributions, were detected by the SEM energy-dispersive X-ray spectroscopy (EDXS) line-scan chemical analysis technique. These effects on the strength of the CFCC can be attributed to following reasons: (i) The decrease in the flexural strength after oxidation is mainly due to degradation of the strength of Nicalon fibers and the damage of fiber/matrix interface both caused by high-temperature chemical reactions, (ii) Porosity is not too important in affecting the strength of the CFCC, when the bonding of the forced flow chemical vapor infiltration (FCVI)-SiC matrix is stronger than that of the fiber/matrix interface. However, a higher porosity content will be harmful, because higher porosity will both decrease the effective elastic modulus of the FCVI-SiC and make pore-linkage easier to occur, which is more likely to cause premature failure, (iii) The variation in the lamina stacking sequence of the CFCC changes the elastic stress distributions along the thickness direction of specimens, the magnitude of ceramic matrix-cracking stress, the effective elastic moduli of the laminate, and different crack initiation sites as well as different failure modes, and thus, leading to the scatter in the flexural strength of the CFCC.

Jan 1, 1998