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By Fernando Aracati Botelho, Jose Antonio Silva Souza, Luis Alves Venancio, Emanuel Negrão Macedo

"1 AbstractThe production of alumina from bauxite using the Bayer process generates 0.7 to 2.0 ton of the residue known as red mud and about 800 kg of CO2 per ton of alumina. The direct use of exhaust gases to react and neutralize the bauxite residue may allow a double gain: open a wide range of new applications for bauxite residue reducing its reactivity and sequester from 3 8 to 107 kg of CO2 per ton of alumina. This paper shows a pilot scale reaction of a suspension of bauxite residue-water with flue gas produced from direct burning oil, similar to the exhaust gases of a refinery. Two different types of reactors are used, a spray tower and a packed column. The inlet and exhaust gases are analyzed using electrochemical cells and non-dispersive infrared sensors. The pH of the suspension is monitored during the reaction and after to evaluate the buffer effect. 2 IntroductionThe production of millions of tons per year of alumina around the world generates from 0. 7 to 2.0 ton of the residue known as red mud (RM) per ton of alumina. The vast majority of the red mud is stored in large sealed lakes. Due to the high reactivity this material is considered dangerous and currently there is no operating process capable of reusing all the material produced at any refinery. These lakes after filled of solid material eventually have the surface revegetated [4]. In any case they will remain as an environmental passive and needs monitoring for decades. The search of a industrial process that combines the reduction of the CO2 emission and the reduction the pH of the red mud opening the possibility of large scale and economically viable ways is the main objective of this work.The use of the exhaust gases of the refmeries to neutralize the bauxite residue may allow a double gain: Open a large array of new applications for the residue with the reduction of its reactivity and sequester millions of tones ofCO2 plus other gases like SO2 [7] and NOx. This project studies the reaction of the exhaust gases from a boiler burning diesel with RM in different reactor types and conditions in order to obtain parameters to design equipment capable of process this reaction on a larger scale. With these objective compositions of red mud were processed with flue gas at concentration similar to the exhaust gases of the calcination process and boilers of the refmeries."

Jan 1, 2012

By Hongmin Zhu, Suning Liu, Kai Huang

"Recovery of silicon particles from the cutting slurry for the manufacturing of solar grade silicon is very important to recycle this kind of special resource. The challenge is to separate the silicon particles from the mixed abrasive particles which contain SiC. Various methods such as sedimentation, centrifugation, and flotation have been conducted, while in present work, a simple and effective novel method was proposed to study the separation of Si and coexisting SiC particles in the cutting slurry. The new process is based on the size difference between the two kinds of microparticles. And the membranes with the different pore sizes of 1µm, 2µm, 3µm and 5µm were used to test the pass ratio and separation efficiency of the suspension. Results shows that the effective separation of Si and SiC microparticles was obtained under the optimal conditions, and indicating great potential of practical enrichment of Si from the coexisting abrasive particles.IntroductionWith the development of the world economy, energy shortage and environment problem is becoming more and more seriously. Solar energy, which is regarded as one of the most important new energy in the word, has received much attention and interest from the scientists [1, 2]. More than 80% solar cells are manufactured by the high purity polysilicon as the raw material. The main process of producing silicon wafer is by multi-wire slicing. In this slice processing, large amount of slurry is produced. The slurry contains more than 30% wt silicon powder, silicon carbide powder as the abrasive, scraps of metal chips, as well as cutting abrasive suspension polyethylene glycol (PEG). The high-purified silicon powders are worth recycling and reusing as the materials for preparing solar-grade silicon though it is a big challenge [3].Most of the current studies were focusing on the recycling of the silicon carbide and PEG, while work on the recycling of the high-purified silicon is not so been focused since there is lacking of very effective separation and recovery technologies till up now. Nishijima utilized the method of superconducting magnetic to recycle the abrasive [4]. Wang applied a combinational process of chemical treatment, high-gravity centrifugation, high-temperature precipitation technique and directional solidification to enrich the silicon [5]. And other purification methods, such as centrifugation [6], froth flotation technologies [7], electrical filed separation [8] and phase-transfer process [9] have been employed. The disadvantages such as using poisonous media or complex equipments decrease the feasibility and efficiency of the above mentioned techniques."

Jan 1, 2014

By Jian Li, S. Penttilä, P. Liu, W. Zheng, C. Bibby

"The materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. The current Canadian pressure-tube supercritical water (SCW) concept design requires core outlet temperature of 650 °C at 25 MPa with peak cladding temperature reaching as high as 850 °C. Aside from oilier challenges, there is currently very limited data on candidate stainless steels' corrosion resistance under this operating condition. Austenite stainless steels that include 316L, 304H, AL6XN and 3 l0S that cover a wide range of Cr contents are promising candidates for either direct in core applications or as base coating materials. However, their corrosion resistance has not been tested systematically under this stringent condition. In this study, these types of stainless steels are tested, and their corrosion resistances are compared.IntroductionThe Canadian pressure-tube supercritical water (SCW) concept will operate at a core outlet temperature of 650 °C at a pressure of 25 MPa, with potential peak cladding temperature reaching as high as 850 °C. High-temperature corrosion resistance is one of the key design requirements for fuel cladding components. As summarized by Allen [1 ], most testing to date has been carried out at temperatures below 730 °C. To date, SCW corrosion data above 600 °C is very limited. Even at relatively low temperature exposure to SCW (e.g. 500 °C), F/M steels develop a thick oxide layer rapidly, while some austenitic stainless steels develop thinner surface oxide. Ni based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of intermetallic precipitates [2-5]. Dissolution of major alloying components from all of these alloys could also pose significant problems for downstream piping [6]. Kaneda et al. [7] suggested some modified stainless steels provide better SCW general corrosion resistance, with no sign of SCC under the slow-strain rate test.Cho [8] suggested that as the Cr content increase, general corrosion resistance improved at 510 °C and 25 MPa. However, similar to Cho's work, most of the SCW corrosion resistance assessments were based on weight change measurement. This can be unreliable due to potential exfoliation of thick oxide film. Besides, there have been no systematic SCW corrosion resistance tests for candidate stainless steels under higher temperatures. SCW corrosion rate increase dramatically for alloys tested at 600 °C [1]. It is also important to understand the role of major alloying elements under this stringent operating condition, not only for fuel cladding components' materials selection, but also for coating materials development."

Jan 1, 2013

By Walter E. Dean

Twenty six samples of carbonaceous gold ores and associated rocks from outcrop and mine localities in northcentral Nevada were analyzed for concentrations of major. minor, and trace elements, total sulfur, and organic carbon. Q-mode factor analysis was used to define six distinctive carbonate, organic, and detrital associations of elements, and to group samples based on these associations. The trace metals that have clearly enriched the organic-carbon-rich samples are V, Zn, Ni, Cu, Cr, and Mo, although few of the samples could be considered "metal-rich" when compared to other organic-carbon-rich black shales. Rock-Eval pyrolysis was used to evaluate thermal maturity and hydrocarbon yield of the samples. Unfortunately, most samples were too thermally altered to be suitable for routine organic geochemical characterization of organic matter. The 813C values of organic carbon in rocks from different deposits have a trimodal distribution, but there is no clear distinction between the three groups of deposits that can be related to age, thermal history, or depositional environment.

Jan 1, 1987

By Lloyd R. Nelson

The feasibility of producing low carbon (LC) ferromanganese (FeMn) by lime-'ore' melt refining of high-grade ferromanganese silicon (FeMnSi) was investigated. Thermodynamic simulations demonstrated significant benefits in moving from a single-stage ladle operation to a two-stage counter-current reladling operation (to emulate the commercial Penin Process). The theoretical alloy silicon content was predicted to be refined from 1.57 to 0.005 per cent silicon, at a 6.2 per cent higher manganese yield (yield predicted to increase from 82.3 to 88.5 per cent). Extension of this counter-current refining principle, to a multistage Counter-Current Reaction Launder (CCRL) was investigated using the Slag Metal And Gas Klnetics (SMAK) software to model the mass transfer kinetics of the multicomponent coupled reaction system. Simulation results suggested that commercial production of 50 000 tonnes per annum (tpa) of refined LC FeMn, containing less than 0.5 per cent silicon, at manganese yields of up to 90 per cent, should be feasible in a compact CCRL (7 m long by 0.7 m wide).

Jan 1, 1994

By C. P. Broadbent

The process metallurgy of many nickel laterite smelting operations is controlled largely by the physical chemistry of the slag system. Consequently, accurate phase diagram information and physicochemical property data are essential to interpret and predict the behaviour and optimisation of the overall process. The system (SiO2 - MgO - FeO) first described by Bowen et al. between 1914 and 1935 and the system (SiO2 - MgO - FeO - Fe2O3) determined by Muan and Osborne in 1956 are of particular relevance to the study of nickel laterite smelting slags as these systems form a reasonable approximation of many industrial slags. This paper will review the literature for these (and other relevant) phase systems. In addition data available from the ternary and (quasi)ternary phase diagrams will be compared with data obtained from industrial slags. The physico-chemical properties under consideration will include; melting and crystallisation behaviour (solidus and liquidus temperatures), viscosity - temperature relationships, heat flux considerations, electrical conductivity, surface and interfacial tension.

Jan 1, 1993

By M. K. Ghosh, B. C. Tripathy, A. Baral

Present work is focused on the recovery of Mn as a value added product from the leach liquor of scrap lithium-ion batteries (LIBs) of mobile phones by the method of precipitation. The LIBs were crushed and bene ficiated by wet scrubbing method to separate cathodic material, plastic and metallic parts. The cathodic material was found to contain 11.3% Mn, 10% Co, 2.4% Cu and 2.4% Li. The cathodic material was processed for leaching under the optimized condition developed by our group at CSIR-NML. Solvent extraction method was used to extract acid using organic extractant Tris(2-ethylhexyl)amine (TEHA) in order to reduce the consumption of alkali required during precipitation studies. The acid free leach liquor was subjected to puri fication for removal of Fe, Li, Cu and Co as precipitate at different pH. Systematic precipitation studies were carried in batch and continuous mode to recover Mn as Mn(OH) 2 at pH *10 which was further roasted at 450 °C for 4 h to get pure Mn 3O4.

Mar 1, 2018

By George Kachaniwsky

Until mid-1982 the Mines Gaspe copper smelter consisted of a fluid bed roaster, a reverberatory furnace, two Peirce-Smith converters of which only one was blowing at any one time, anode casting facilities, and a single contact sulphuric acid plant treating both roaster and converter gases. Reduced concentrate supplies have led to the shutdown of the roaster and, as a result, it was necessary to adapt the converter and acid plant operation to the new operating mode: green concentrate smelting with resulting lower matte grades and acid plant treatment of off-gases from only one blowing converter. Therefore, modifications were carried out to existing equipment and methods of operation and control. This paper describes the result of work done to obtain steady, maximum strength, converter off-gas flow and an efficient acid plant operation. Topics covered include: optimization of converter operation, tightness of hood and off-gas ducting, improvements in acid plant/converter communications and modifications of acid plant operation and control to cope with the fluctuations in converter gas flowrates and strengths.

Jan 1, 1983

By Fuming Wang, Changrong Li, Dan Wu, Wei Shen, Yaxu Zheng

In order to improve the oxidation resistance of Cr–Mo–V steel for high-speed railway brake discs, a higher Cr was added to the steel. Effect of temperature on the oxidation behavior of brake disc steel with different Cr contents was studied by OM, SEM and XRD. The results show that the oxidation curves at 500 °C obey a linear oxidation law in 0–2 h and 2–20 h, respectively. The oxide layer is thin and the oxidation products are Fe2O3 and Fe3O4. The oxidation curve at 700 °C follows a linear law within 2 h. With the oxidation time extending, the oxidation curves follow a parabolic law and the oxide layer becomes thicker. Moreover, the oxide layer is divided into two layers. The outer oxide layer is loose and is mainly Fe2O3, while the inner layer is denser and consists of FeO and FeCr2O4. The oxide layer thickness reduces and the oxidation resistance of the steel is improved with Cr content is increased.

Mar 1, 2018

By Yan Zeng

Lithium metal silicates (Li2MSiO4, M = Fe or Mn) composed of abundant and non-toxic elements are important cathode materials for Li-ion batteries (LIB). In contrast to solid-state or sol-gel methods, hydrothermal synthesis conducted in pressure reactors is a favorable processing route as it provides the potential for scalable production and is environmentally benign. However, the key is to control the precipitation reaction to obtain powders with desired properties to meet battery specifications. Through a systematic study, we have found that Li2MSiO4 with tunable size from 300 nm to 1.5 μm can be produced by adjusting precursor concentrations, temperature, and reaction time. Under optimum conditions, high purity Li2MSiO4 with minimum defects were successfully produced and examined as an LIB cathode. The use of complexing agents promoted the formation of unique hollow particles via the self-assembling of elongated crystals. A four-step formation mechanism is proposed based on extensive characterizations with XRD, HR-TEM, SEM, and Mössbauer spectroscopy.

By Marcio B. Fonseca

Nickel-cobalt laterite deposits have become the focus of attention for hydrometallurgical processing. Following the lessons of the second generation high pressure acid leach (HPAL) projects in Western Australia other Ni-Co laterite projects are now evaluating potential HPAL projects with a rigorous integrated approach that begins with geological modeling, resource estimation and metallurgical studies. The Vermelho nickel-cobalt laterite deposit has been under exploration and study for several years with investigations of various metallurgical processes. Recent HPAL studies have indicated that the nickel and cobalt laterite at this deposit is amenable to upgrading by silica rejection followed by pressure leaching. These studies have required a detailed geological investigation to generate a new resource model. The recent development of a sophisticated geological model integrated with a multi-element resource estimation for this complex tropical nickel laterite deposit in northern Brazil provides an example of the contribution of geology at the critical project stage where process technology decisions are made on relatively small samples of the total resource.\ Keywords: Ni Laterite, Geological Modeling, Resource Estimation

Jan 1, 2004

By E. Açma

Sivas-Divrigi flotation plant has a capacity of 90,000 tpy. Beneficiation of the tailings of iron ore magnetic separator seems to be attractive, because of its Cu, Co, and Ni contents. In the experimental work, sulfidic flotation concentrate is produced from these tailings. A roasting-leaching-H2S precipitation procedure is used to treat this concentrate, containing 0.55% Cu, 0.51% Co, 0.74% Ni, and 0.027% Zn. Sulfatizing roasting is carried out in a rotary furnace at 690°C. Roasted product is leached with 10 gpl HzSOl at 70°C and 30% pulp density. For the precipitation of desired metal, H2S is bubbled through the concentrated solution of repeated leaching, under controlled temperature and pH. Final metal recoveries of 91% Cu, 91% Co, and 50% Ni, and 92% Zn are attained. Roasting gases with their 13% SO2 content are suitable for H2SO4 production and the leach residues can be integrated with the iron ore processing plant as they contain 57.4% Fe and very low non-ferrous metals.

Jan 1, 1993

By John Pilling

The concept of microstructure, its evolution through materials processing and its effect on the properties of the material is, perhaps, the foundation upon which the science of materials is built. PHAUST, a computer aided learning program, attempts to provide instruction in establishing the relationships between phase diagrams, thermal processing and microstructure. Using phase diagrams derived from a database or created by the user, the evolution of microstructure during processing is quantified using the lever rule and/or the Scheil equation and tracked through a doubly linked list (a form of binary tree). Microstructures, in the form of full colour cartoons are then drawn using the quantitative and logical information contained within the linked list using bitmapped templates and logigal operators such as NOT. AND, OR and XOR, giving the student a view of the structure as it would be seen under the optical microscope. The software provides complete diagnostics of student answers, locates errors and misconceptions as well as providing tutoring towards the correct solution method and answer.

Jan 1, 1991

By L. I. Rosato

A novel hydrometallurgical process for the recovery of silver and gold from neutral leach residue that is based upon leaching with thiourea, is described. Laboratory and pilot plant studies have shown that 80-90% of the silver and 60-70% of the gold can be recovered by:? ( i) leaching zinc calcine with 'Spent electrolyte at pH 2.0-3.0 to generate a precious metal-bearing zinc ferrite residue, (ii) leaching of the thickened zinc ferrite with 3-5 g/L thiourea in a six stage carbon-in-pulp circuit, (iii) elution of silver and gold from the loaded carbon with a thiourea- butanol solution, (iv) thermal regeneration of the stripped carbon and (v) recovery of the precious metals from the pregnant eluate by cementation with zinc dust. The reasons for adopting the thiourea CIP leach and the preferred operating parameters for each process step are presented. The requirements for the destruction of any thiourea transferred to the zinc circuit are outlined, and the results of an integrated one tonne/day pilot plant operation at Canadian Electrolytic Zinc are given.

Jan 1, 1990

By Mao Chen, Tim Evans, Zhixing Zhao, Weidong Zhang, Baojun Zhao, Dongqing Wang

High temperature softening behaviours of iron blast furnace feeds (sinter, lump and pellet) have been determined under conditions simulated to the blast furnace. The industrial samples were packed with sandwich structure (coke / ore / coke) in graphite crucibles and 30 CO / 70 Ar gas mixture was blowing directly through the bottom of the crucibles. The displacement and temperature were continuously recorded simultaneously to construct the softening curves. Separated quenching experiments were also carried out at selected temperatures under the same gas atmosphere. The temperatures were selected corresponding to the turning points of the softening curves. The phase assemblages and composition of each phase in quenched samples were analysed by Electron Probe X-ray Microanalysis (EPMA). The proportion of the liquid formed at temperature was obtained from the backscattered electron images. The deformation characteristics of these complex multi-phase materials are shown to be related directly to the phase assemblages of the samples and the microstructures. FactSage was also used to assist the predictions of liquid / solid fractions and their compositions.

Jan 1, 2015

By Yuuki Yoshida

Electrolytic manganese dioxide, EMD, is the positive electrode material of primary batteries and the raw material of LMC used as the positive mass of lithium ion batteries and is currently produced by anodic deposition on and harvesting from a titanium anode in acidic manganese sulfate solutions prepared by dissolving high purity of manganese sulfate into sulfuric acid solutions. This paper presents an alternative method of EMD production using a novel anode, Mn2O3 coated titanium, at lower operating temperature than the current process to explore a possibility of manganese recovery from zinc electrowinning solutions. The Mn2O3/ Ti anode prepared by thermal decomposition of a precursor solution containing Mn (II) showed the anodic deposition of MnO2 by constant current electrolysis and the current efficiency was 95% in maximum, while the current efficiency and the crystallographic structure of deposited MnO2 depended on the current density, the electrolysis time, the bath temperature, and the concentration of Mn(II). The deposited MnO2 was successfully harvested from the anode and the recovery rate was 98%.

By Alaina Mallard, Jannette Chorney, David Hutchins, Grant C. Wallace, Jerome P. Downey

Current commercial processes for producing ceramic carbides require temperatures of 1400–2000 °C and often use extensive milling operations to produce a powder product. A process that could reduce the energy requirements of commercial carbide production could allow for these materials to be implemented in a greater number of applications. In this study, tungstate (WO4 2−) and silicate (SiO3 2−) anions were adsorbed onto activated carbon and converted into silicon carbide (SiC) whiskers and a mixture of tungsten and tungsten carbide (W/WC) crystals via carbothermal reduction using inert and reducing gas atmospheres at temperatures much lower than what is required by current commercial processes (950 °C for W/WC/W2C and 1200 °C for SiC). The adsorption process was statistically-optimized via a central composite response surface analysis using DesignExpert 9. Inductive coupled plasma optical emission spectroscopy (ICP-OES) was used to measure, and optimize, adsorption efficiency while the carburization products were characterized using X-ray diffraction and scanning electron microscopy.

Mar 1, 2017

By Xueming Lv

The rotary kiln-electric furnace (RKEF) process is the main method for producing ferronickel from nickel laterite ore. However, this process is energy intensive as it involves several high temperature steps. Therefore, a novel process is proposed to directly produce ferronickel from nickel laterite ore by semi-molten reduction, which is expected to be realized in a rotary hearth furnace (RHF). The RHF process is able to shorten the flow sheet, decrease the reaction temperature as well as reduce energy consumption. In this study, the influence of basicity on reduction of nickel laterite ore was investigated. The results showed that it is possible to produce the ferronickel nugget directly at 1400 °C when the quaternary basicity [(mCaO + mMgO)/(mSiO2 + mAl2O3)] was fixed at 0.60. Under this experimental condition, the grade and the recovery ratio of nickel reached 11.53% and 98.59%, and the grade and recovery ratio of Fe were 84.16% and 68.72%, respectively.

By Shaohua Ju

Siderite ore is abundant around the world, due to its inert properties of low grade, mudding when milling and low magnetic, and it is very hard to be beneficiated. Nowadays, decomposition by roasting becomes the main process for utilization of the siderite ore. The methods of energy input for roasting are normally electrical heating, coal or gas combustion. Because traditional roasting methods owns some disadvantiges, such as low energy utilization, high cost and/or large exhaust pollution, only about 10% of the siderite ores in China were used as iron concentrate. In this work, the possibility of roasting siderite ore with microwave energy is studied by both laboratory and pilot experiments. The result of laboratory experiments showed that the optimized condition is roasting for 20 min with a power density of 3 W/g, and the Fe content of the final sample obtained is about 59.12%. The pilot experiments result showed that the decomposition is thoroughly, and the main phases of the roasted material are magnetite and wustite, and the energy consumption of the roasting process is 695.8 KWh/t.

Jan 1, 2014

By A. Arenas-Flores, Pandiyan Thangarasu, J. P. Hernández-Lara, F. R. Barrientos-Hernández, J. A. Romero-Serrano, A. Hernández-Ramírez, M. Pérez-Labra

BaTiO3 doped with Gd3+, was synthesized from BaCO3, TiO2, and Gd2O3 as powders using the solid state reaction method (Ba1-xGdxTi1-x/4O3). The milling of the precursors was performed in an agate mortar with acetone as control means and compositions x = 0.001, 0.005, 0.05, 0.15, 0.25, 0.35 Gd3+ (wt%). Firstly, the powder mixture was decarbonated at 900 °C for 8 h, after it was sintered at 1400 °C for 5 h. Tetragonality of synthesized BaTiO3 doped with Gd3+ was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy (RS). Subsequently, the powders sintered were uniaxially compacted cold until to obtain pellets of about 10 mm in diameter; which again were sintered at 1400 °C for 4 h. XRD patterns and Raman spectra results revealed that the crystal phase of the obtained particles was predominately tetragonal BaTiO3.

Mar 1, 2017