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By Yuanbo Zhang, Xiaoming Mao, Zhixiong You, Zhenyu Fan, Tao Jiang

"It is generally known that the formation of calcium ferrite is favorable during the iron ore sintering, which dominatingly contributes to the improvement of strength and reducibility of the finished sinters. In this study, effects of roasting temperature and 02 content of inlet gas on the sintering mineralization properties of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. The results showed the amount of calcium ferrite initially increased then decreased with the increase of the roasting temperature. The temperature of maximum calcium ferrite generation amount for different iron ores was determined as follows: hematite and limonite was 1275 °C, whereas specularite and magnetite was 1250 °C. Increasing 02 content of inlet gas was advantageous to the generation of calcium ferrite during the sintering. The sequence of 02 content affecting the mineralization properties of different iron ores was determined as follows: magnetite > hematite > specularite > limonite.IntroductionThe mineralization property of iron ore plays a significant role in the mineral composition and microstructure of finished sinters, which determine the quality and output of the sinters [1-2]. The mineralization process of sinters is composed of solid-phase reaction, formation of liquid-phase and crystallization. The formation and crystallization of liquid-phase is the foundation to the mineralization as the quality of the sinter is poor when concreted by solid-phase consolidation [3-4]. With respect to the iron ore sintering, liquid-phase regarded as bonding phase is generated between the iron ores and fluxes at high temperature [5]. Calcium ferrite is the most favorable liquid-phase among the bonding phases which dominatingly contributes to the improvement of strength and reducibility of the finished sinters [6-8]. Especially for high iron-low silicon sintering and high basicity sintering, making sure sufficient calcium ferrite quantity and reasonable distribution is crucial to the sinters [9-10]. Therefore, carrying out the researches on the high temperature reaction properties of iron ores is of great significance [11]."

Jan 1, 2013

By J. D. Scott

The counter-current jarosite acid wash circuit presently in operation in the zinc plant produces a combined jarosite plus Pb/Ag residue which is discarded. Extensive pilot-scale testwork, and some past in-plant operational experience, has shown that the zinc plant can be easily reconfigured to produce two residues during periods of high silver feeds and/or prices. Plant.optimized circuit configurations are available for silver recovery to a Pb/Ag residue and are in use for the prevention of Pb/Ag-jarosite formation in both the neutral and high-acid leaching circuits. Silver in the zinc plant undergoes several changes in state as it proceeds through these circuits. The roaster calcine is ~3:1 silver sulfate: silver metal, with metallic silver mainly as micro-Inclusions In an aluminosilicate phase. In neutral leach residue, the majority is as silver sulfide or Pb/Ag/Zn-sulfide coatings on unroasted sphalerite grains, with minor Pb/Ag-jarosite and some residual metallic silver in unreacted alumina-silicate grains. In high-acid leach residue, silver occurs as Se-rich silver sulfide particles in sulfur/jarosite ball aggregates, as silver sulfate impregnations in silica-gel masses and in solid solution in Pb/K/Zn~jarosite. Silver concentrations in solution range from 20 to 60 ppb.

Jan 1, 1990

By James B. Pfeiffer

TETRA Technologies, Inc., has applied its HDS? metals precipitation system to control a mine drainage problem. The effluent from the mine contains primarily zinc, manganese and iron, plus varying small amounts of cadmium, copper and lead. The flow from the mine averages 350 gpm, and varies considerably depending on season and weather conditions. The plant was designed to treat 1000 gpm of the water and generate a dense sludge suitable for recycling. The HDS? system contains a number of reactors, followed by post filtration and meets stringent metals discharge criteria as specified by New Source Performance Standards.

Jan 1, 1994

By Chengxian Lui

Detailed mineralogical and metallurgical investigations were carried out on a phosphorous-bearing manganese carbonate ore from the Huayuan manganese mine, Hunan, China. Microprobe analyses indicate that the Manganese occurs mainly in calc-rhodochrosite and in rhodochrosite. The cOll'pOsitional range of these manganese carbonate minerals is 50 -80 % MnOJ3, 0 -35 % CaOJ3, 5-35 % MgC03 and 0 -15 F~. The manganese carbonate minerals are very fine grained, IOOSt are between 4.6 and 9.4 1m in diameter. The small grains are clustered into aggregates that form bands 0.5 to 10 rnn wide. The phosphorous-bearing mineral in the ore is fluorapatite and is in grains that are generally smaller than 6 1m in diameter. Metallurgical tests show that it is possible to concentrate the aggregates of manganese carbonate minerals by high intensity magnetic separation, and to reduce the phosphorous content by rpasting the concentrate to convert the manganese carl::x>nates to insoluble hausmannite, and then leaching the roast product with HCI to dissolve the fluorapatite.

Jan 1, 1989

By Hongbo Zhao, Jun Wang, Wenqing Qin, Guanzhou Qiu

Jan 1, 2015

By Guohui Zheng

The ever increasing quantities of solid wastes generated by various industries are at the source of the growing need for proper waste disposal methods. Thermal treatment of combustible wastes is a proven technology which permits the reduction of hazardous material having to be landfilled. However, this method is not universally applicable to waste disposal. For example, the transferal of heavy toxic metals into the thermal remediation products is a major issue of public concern. This paper focuses on the analysis of morphology changes from solid sludge to ash which is a product of the sludge combustion. The morphological parameters analyzed were particle size and external surface. They were determined using Jeol 840 Super Probe. The experiments were conducted in a computer-controlled high-temperature combustion system consisting of the thermogravimetric furnace coupled with Fourier transform infrared spectrometer (TGA-FTIR). Sludge particles were made of complex fibers trapped in the aluminosilicate matrix. At low temperatures, up to 680 K, the solid residue looked similar to the initial sludge. Between 680 K and 1180 K the sludge underwent intensive burning and steadily changed into powdered ash. At the temperature of 1050 K the ash was composed of separate, flat flakes with sizes ranging from 5 to 20 um. At 1470 K the flakes aggregated into large particles. The surface observed at 1670 K was a mixture of mullite crystals. Such structure could result from the solidification of the ash material after its melting. Morphological changes influenced the distribution of metals in the solid residue. For example, Cr was concentrated in small aggregates. Such distribution should allow for recovery of valuable metals from the solid waste residue.

Jan 1, 1996

By D. A. Robbins

The Resource Conservation and Recovery Act. of 1976 (RCRA) requires testing of waste materials as part of the determination of whether these materials are classified and managed as hazardous wastes. The adoption of one standard testing procedure and its application to all types of waste materials has stirred much controversy. In the center of this controversy is the appropriateness of this testing procedure in characterizing non-ferrous metal intermediates and slags. The authors have evaluated the relative availability of metals in several types of copper and lead slags as defined by various testing protocols. Also discussed is the relationship between the chemical character of the slag and the availability of metals to leaching and certain metallurgical practices that can influence metals availability.

Jan 1, 1983

By Robert Vidal

The performance of a laboratory-scale cell for the electrolysis of an aqueous chrome alum solution was studied. Electrode potentials, pH, and Eh were recorded. An optimum catholyte pH of about 2.5, consistent with information from the literature was observed. Values exceeding this range resulted in a precipitate formation and are detected by wavering cathode potentials. The role of anodically produced dichromate ions was investigated by chemical analysis. It was found that the steady state concentration of dichromate ions varies inversely with fluid flow from catholyte to anolyte. This concentration was also reduced with the use of precious metal coated titanium anodes.

Jan 1, 1994

By Yuanbo Zhang, Daoyuan Zhang, Youlian Zhou, Guanghui Li, Tao Jiang

"Modified humic acid (MHA) has been developed by Central South University (CSU) and authorized in China. It has been reported that MHA is an effective binder for oxidized pellets prepared from specularite concentrates. In this research, effects of MHA binder on roasting behaviors of the specularite pellets are studied. MHA is an organic binder, containing much carbon, hydrogen, oxygen, etc. During the roasting, MHA can provide some heat because of combustion of hydrocarbon, which is beneficial for the recrystallization of Fe2O3 in the specularite pellets at high temperature. Simultaneously, part of hematite particles within the pellets are firstly reduced to magnetite, then, magnetite is oxidized into secondary hematite, which obviously improves the roasting performance of specularite pellets.IntroductionOxidized pellets have been widely used in steel production as a kind of high quality burden for blast furnace ironmaking [1]. In recent years, production of oxidized pellets is developing very fast. Therefore, the supply of high quality magnetite concentrates, which is the most suitable for pellet production, becomes scarce. It is imperative to pursue new alternative materials for oxidized pellet production [2]. Specularite concentrates have attracted widespread attention due to the advantages of high total Fe grade and low impurity content. However, due to the poor ballability and firing performance, specularite has not yet been widely applied into pellet production [3, 4]."

Jan 1, 2012

By Guo Chen, Xuefeng Liao, Tu Hu, Shengzhou Zhang, Hongying Xia, Jinhui Peng, Libo Zhang

Pine nut shell is as raw material for preparation of high surface area activated carbon (HSAAC) by microwave induced KOH activation. The effects of microwave power, activation duration and KOH/C mass rate (R) on the iodine adsorption capability and activated carbon yield were investigated. Additionally the surface characteristics of HSAAC were characterized by nitrogen adsorption isotherms and SEM. The operating variables were optimized utilizing the response surface methodology and were identified microwave power 738W, activation duration 17 min, and R 4, corresponding to a yield of 46.28 % and an iodine number of 2154 mg/g. The key pore structure parameters of HSAAC such as the Brunauer–Emmett–Teller (BET) surface area and total pore volume were estimated to be 3819 m2/g and 2.09 mL/g, respectively. The findings strongly support the feasibility of microwave heating for preparation of HSAAC from spent pine nut shell by microwave induced KOH activation.

Jan 1, 2016

By Zhihe Dou

SHS reaction system has advantages of heat flux density, energy concentration and reaction speed, with sufficient conditions in thermodynamic and kinetic reaction. This paper invented a new technology of SHS metallurgy of preparing melting point alloys and refractory compounds using its own chemical energy. SHS-leaching process for preparing nano boron powder or ultrafine boride powder and SHS-casting process for preparing titanium-based alloy and immiscible alloy were studied. The results indicate that highly active boron powder of greater than purity of 93%, particle size less than 100nm and purity greater than 98.5%, particle size less than 400nm REB6 can be prepared. With SHS-Casting process, the oxygen content of less than 0.59% ferrotitanium, oxygen content of less than 0.5% titanium alloy and ?40-80*100mm large size of CuCr, Cu-Fe alloy ingots were prepared. This technology has greatly enhanced the thermal reduction method added values of preparing metallurgical products and its competitiveness.

Jan 1, 2014

By Muhlis Nezihi Saridede, Burak Birol

"The scraps of high quality steels generally contain expensive alloying elements such as chromium, vanadium, nickel, etc. These scraps are melted in an induction or an electric arc furnace and refined in ESR (Electroslag Remelting) purification process. A significant amount of alloying elements are lost during these processes. In order to avoid these losses, scraps can be utilized directly in ESR by skipping the melting step. In this study, 316L stainless steel scraps were refined in ESR with selected synthetic slags. The products were analyzed by optic emission spectrometry and the effects of slag compositions on the alloying element losses were examined. According to the analysis of the scrap and the products, generally chromium, nickel and manganese losses were encountered. It was determined that the alloying element losses has no connection with electrical conductivity. The slag containing CaF2, Al2O3, and FeO gives the optimum Cr and Ni losses.IntroductionElectroslag remelting (ESR), which is the consumable electrode refining process, finds a wide range of utilization for the production of high quality, low inclusion alloys. This process is based on melting a consumable electrode under a molten synthetic slag containing CaF2, Al2O3, CaO etc. The synthetic slag provides the chemical refining and insulation of molten metal from air which leads to a higher purity and an inclusion-free product. [ 1,2] A schematic diagram of ESR system is shown in Figure 1."

Jan 1, 2011

By Chen Wen, Li Zhao-jia, Zhao Qiang, Ning Shun-ming, Tang Sanchuan, Wang Hong-qiang

"The carbon-burdened and cold-bonded pelletizing-electrosmelting process is used to dispose low-grade manganese, and the qualified rich-manganese slag is obtained. On the condition that reduction roasting temperature was 1000?, reduction time was 45min, particle-size was -1mm, reductant dosage was 1.6%, basicity was 0.3, smelting temperature was 1410?, smelting time was 60min, it had a good effect on the melting between slag and metallographic phase, the manganese content was 32.58%, manganese recovery was 92.16% in the slag; while the iron content was 94.40%, iron recovery was 95.32% in the metallographic phase. It was proved by the demonstration tests.IntroductionManganese is an important raw material for steelmaking, which is extensively utilized in modern industry, the consumption of manganese for iron and steel industry accounts for 90% to 95%. After mining over 30 years, the high-grade manganese resources drop markedly, especially with the hypergrowth of steel industry, the domestic manganese is far from the requirement, as a result, we have to buy significant quantities of manganese overseas. Besides, the property of imported manganese is more and more complex, and the high-grade and lump manganese decrease year by year, while the fines and high-crystal water manganese are on the increase. Therefore, how to make effective use of domestic low-grade manganese and intensify the manganese’s smelting is an effective approach to reduce the cost of manganese series ferroalloy and improves market competitiveness[1-4]. It has important practical meaning."

Jan 1, 2012

By De-qing Geng, Guang-liang Wu

The waste slag generated by the LF refining process of Q345B low alloy hot-rolled steel, still has some refining capabilities. If recycled, it can reduce environmental pollution, and save the economic costs. A research on melting Characteristics of Q345B steel LF refining waste slag was investigated by using orthogonal experimental method, and the effect laws of composition on that were analyzed. Through variance analysis and significance criterion, it is concluded that the optimum ingredient of the regenerated LF refining slag is 25%A12O3, 12%CaF2, 7%MgO and R= (CaO)/ (SiO2) =2.5. And the regression analysis is carried out by using SPSS software, to get the mathematical relationship between ingredient with high reliability and melting temperature of refining slag T=1451.3-6.25CaF2+2.36 R.

Jan 1, 2016

By Jilai Xue, Jun Zhu, Germain Kouma Ndong, Qiaochu Liu, Luxing Feng

"High-temperature oxidation and corrosion behaviors of Ni-Fe-Cr alloy as inert anodes for aluminum electrolysis have been studied in oxygen and molten electrolyte. The oxidation and corrosion scales on the anodes tested were analyzed using XRD and SEM-EDS. The oxidation rate is found to increase with increasing temperature from 700 °C to 950 °C, which can be approximately described by an inverse power rate function. The oxidation scales at 750 °C, 920 °C and 950 °C contain Cr-rich phase along with FeCr204 and (Feo.6Cro4)203. The corrosion extent of Ni-Fe-Cr anodes in electrolyte is dominated by temperature, which can make the scales thickness double from 700 °C to 750 °C or from 920 °C to 950 °C. Cr and Fe in the scales on the anode in electrolysis corrode preferentially into the molten electrolyte, while the nickel oxides could better sustain the corrosive environment in electrolysis. The results can be useful for developing inert anode material for potential application in aluminum electrolysis.IntroductionThe development of an inert anode for aluminum electrolysis has been a long term goal for aluminum industry. The present process for primary aluminum production involves the reduction of alumina with carbon anodes, forming carbon dioxide:"

Jan 1, 2013

By Zhanjun Wang, Yongqi Sun, Mei Zhang, Zuotai Zhang, Min Guo

The role of fluorine on the viscous and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-(CaF2) slags were explored using the rotating cylinder method, non-isothermal differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the viscosity slightly decreased with increasing CaF2 content. It was also found that CaF2 addition can promote the primary phase transformed from MgFe2O4 spinel to Ca3(PO4)F, which was beneficial to the enrichment of phosphorus. Additionally, the structure of the slags explained by X-ray photoelectron spectroscopy (XPS) and magic angular spinning nuclear magnetic resonance (MAS-NMR) were further analyzed, which was well in accordance with the above analysis.

Jan 1, 2016

By Larry Twidwell, Ed Rosenberg, Courtney Young, Sean Dudley, William Gleason, Maureen Chorney

Experimental and industrially produced polystyrene and silica resins are tested for recovery capabilities of Rare Earth Elements (REE). Testing regimes being used are typical of resin analysis. Inductively Coupled Plasma-AES results indicate that preferential separation and recovery is possible in the adjusted pH range of2 to 10, solution conditions, and resin type. Testing conditions are resulting in structure modification of the composite resin as indicated by X-Ray Diffraction, Differential Scanning Calorimetry, Scanning Electron Microscopy, Mercury Porisometry, and density analysis. Resin modification indicates both surface and internal structure alteration outside of reported standard behavior of resins. Structural changes have ramification for both Rare Earth Recovery RER and traditional resin operations. Analysis shows that the resin uptake of REE can be manipulated for concentration. Further analysis with SEM work indicates that widespread surface and interior modification is taking place as resins load with REE. This modification is leading to pore rupture and particle breakage. Further investigation is being performed to determine the mode of breakage.

Jan 1, 2015

By Edward Peters

Scandium (Sc) has unique properties and is one of the more valuable elements in the periodic table. Scandium can be used in solid oxide fuel cells and to produce high strength aluminium alloys of value, for example, in the aerospace industry. Scandium is often grouped together with the rare earth elements (REE). Amongst others, scandium can be found in bauxite residues, so called red mud. It is possible to extract and enrich scandium from red mud by leaching and solvent extraction. Scandium can then be recovered from the pregnant strip liquor by crystallization. The strip liquor will however still contain certain impurity elements. In the present work, a method for obtaining a pure scandium solid phase by direct crystallization from the strip liquor is evaluated. It was found that Fe and Ti co-precipitate with Sc under the conditions employed.

By M. Demuth, B. Holleis, M. Potesser, D. Spoljaric

"In 2005, Messer Group established a technology competence centre for metallurgy in Gumpoldskirchen (Austria), with the aim to develop oxygen burners which satisfy today's and upcoming standards of legislation as well as customer requirements. With the assistance of the Development Sponsorship Fund (FFF) of Austria, cooperation with the University of Leoben was agreed on. With the long term experience of the Gas-Warme-Institut ""GWI"" in Essen (Germany) and the University of Leoben, different new burners have been developed.The efficiency of industrial combustion processes can be increased in two ways (which can be seen in Figure 1 ), either by preheating the fuel and combustion air or by adding oxygen. Due to the high 79 % Nz ballast in air combustion, only low flame temperatures can be reached. This results in high heat loss in the exhaust gas, caused by the low combustion efficiency. Oxygen can be introduced into the combustion chamber using different techniques:• Oxygen fuel burners• Direct oxygen injection into the fuel air flame• Underlaying of the fuel air flame• Enrichment of the combustion airIn Figure 2, the theoretical flame temperature for the stoichiometrical combustion of natural gas is plotted as a function of oxygen enrichment. Therefore, it can be concluded that even low enrichment values produce higher flame temperatures and result in higher combustion efficiency."

Jan 1, 2012

By Huimin Lu, Lian Zhou, Qiang Li

"A three-dimensional mathematical model is developed for the regenerative rotary hearth furnace with 40 meters medium diameter. The influence of combustion switchover and outlet pressure on the fluctuation and distribution of temperature and pressure is studied with numerical simulation method. The results showed that the temperature field and flow field is suitable for requirement of industrial production; the fluctuation of the temperature field and pressure is acceptable; the influence of outlet pressure on the furnace pressure is great.IntroduceRotary hearth furnace which is originally utilized as heat treating and reheating industrial furnace, now is also used for carbon based DRl production. With the need of market and the concern of resource recycling and environmental issues, the DRl production from ore or from waste material by rotary hearth furnace attracts more and more attentions from steel industry [1,2].When rotary hearth furnace works, the feed pellets are charged on the hearth and rotate within an annular furnace chamber with the process of reduction. For the sake of rapid reduction, usually the depth of the pellet is one or two layers, accounting for less than 90% of the volume of furnace. As result, the exhaust gases carry away a lot of heat, so that energy utilization efficient is low [3]. Currently, in order to reduce the consumption of energy and improve the production efficiency, many methods have been adopted. The regenerative combustion technology is one of the most promising."

Jan 1, 2013