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  • 3051.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Energy consumption in fine crushing and dry rod grinding1992In: Minerals & metallurgical processing, ISSN 0747-9182, Vol. 9, no 2, 69-72 p.Article in journal (Refereed)
    Abstract [en]

    Fine crushing and rod grinding have been investigated using a laboratory-scale jaw crusher and a rod mill. The net energy consumption in both crushing and grinding was evaluated from torque measurements. An empirical relationship was established between energy consumption, particle size and operating parameters. When the mill feed size is reduced, through fine crushing, to about 80% passing 3 mm, the energy consumption will be minimized in a comminution chain of fine crushing and coarse rod grinding. The results in fine crushing were compared with a large-scale test.

  • 3052.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Monitoring grinding parameters by signal measurements for an industrial ball mill1993In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 40, no 1-2, 1-16 p.Article in journal (Refereed)
    Abstract [en]

    Mechanical grinding emits a high-intensity vibration signal that contains information on the mill operating state. Vibration signals from the mill are presented in the form of both mechanical vibration and acoustic pressure. To apply these source signals to monitoring of grinding parameters, industrial scale grinding tests were performed with an iron ore at LKAB, Malmberget. Three operating parameters were considered: the feed rate, the mill feed size and the pulp density of mill discharge. The measured response parameters were the ground product size, the power draw and the pulp temperature. The source signals of the time-domain waveforms were simultaneously sensed by accelerometer and microphone so as to obtain a "stereograph" of grinding. The signals were first stored on a DAT recorder and then converted into digital format by an oscilloscope. The digitised waveforms were transformed into frequency-domain spectra by power spectral estimation. The variations on the power spectra can be described by a few "latent" variables derived by principal component analysis. Finally, close relations were established between key grinding parameters and "latent" variables by multiple regression. Using signal measurements, an automatic and efficient strategy can be developed to monitor operating parameters for the control system in a ball grinding circuit.

  • 3053.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Monitoring grinding parameters by vibration signal measurement: a primary application1994In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 7, no 4, 495-501 p.Article in journal (Other academic)
    Abstract [en]

    Grinding plays an important role on energy consumption and subsequent separation stage in a mineral processing plant. To maintain higher grinding efficieny, the operating parameters must be continuously monitored and adjusted close to the setup of the optimal operating conditions. It is difficult and expensive to trace the frequent variations of the grinding parameters by traditional methods in commercial scale operation. Since mechanical grinding emits strong vibration signals, it can be picked up commercially available instrument in the form of time-domain waveform. The variations of the vibration signals were governed by the changes of the grinding state. A primary application was studied based on the industrial scale measurements, where the mechanical vibration was picked up by an accelerometer and acoustic pressure changes by a microphone. The digitised time-domain source signals were processed by digital signal processing technique. The variable grinding parameters were the power draw, the feed rate, the pulp density, and the particle sizes of the mill feed and the ground product. By principle component analysis and parameter identification, the variations of the grinding parameters were related to the changes of the source vibration signals. By vibration measurement, a new alternative could be developed for monitoring the operating parameters in grinding.

  • 3054.
    Zeng, Yigen
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Monitoring operation state by measuring vibration and acoustic signals in an industrial scale ball mill1994In: Konferens i mineralteknik: Luleå, 2-4 februari 1993 / [ed] Marianne Thomaeus; Eric Forssberg, MinFo , 1994, 159-170 p.Conference paper (Other academic)
  • 3055.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Multivariate statistical analysis of vibration signals from industrial scale ball grinding1995In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 8, no 4-5, 389-399 p.Article in journal (Refereed)
    Abstract [en]

    Multivariate statistical modelling based on vibration signal analysis was performed at commercial scale grinding. The source digital signals consist of three channels of mechanical vibrations obtained at the axial, horizontal and vertical directions. The feed rate, power draw, pulp temperature were collected automatically by the control system while samples of the feed material and ground product of the ball mill were manually taken to determine the particle size distributions and pulp densities. Using projection to the latent structure (PLS) and/or principle component regression (PCR), empirical models between grinding parameters of interests and the vibration signals were built based on the training data set collected in two weeks, thus the new grinding parameters could be automatically predicted whenever the vibration signals were known. The modelling results show that both the PCR and PLS model can be used to predict grinding parameters online.

  • 3056.
    Zeng, Yigen
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vibration characteristics in a large scale ball mill1993In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 22, no 5, 280-286 p.Article in journal (Refereed)
    Abstract [en]

    The vibration measurements were performed on an industrial scale ball mill located in LKAB, Malmberget, under commercial scale operation. After data acquisition and digital signal processing, it was found that the lower frequencies on the spectra were independent of the sensor location. The high frequencies were dependent on both the location and orientation of the sensor. Simple correlation analysis on all spectra data shows that the vibration signals are highly correlated from different sensor locations and orientations. Two vibration sensors should be situated at different orientations for each location. The first three factors from factor analysis account for 91.8% of variations of the original spectra. After rotation of the factor loading by equamax transform, three factors are mainly related to three orthogonal sensor orientations. It is therefore recommended to use three vibration sensors to map out the whole vibration signals from grinding.

  • 3057.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vibration signal emission from mono-size particle breakage1996In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 44-45, 59-69 p.Article in journal (Refereed)
    Abstract [en]

    A technique based on vibration measurement and analysis was used to study the breakage of mono-size dolomite on a hydraulic press. Up to a maximal pressure of 4 MPa, vibration signals during pressing and breakage of dolomite were picked up with two piezo-electric type accelerometers, which were screwed on to the breakage chamber and oriented in perpendicular directions. The source vibration signals were amplified and stored on a DAT recorder. A 'stereo' picture was built-up for describing the breakage events based on two-channel vibration signals. The saved time-domain waveforms were converted into digital format for the personal computer; thus, the breaking history may be replayed by plotting and zooming the waveforms, from which the frequency-domain power spectra were transformed. Primary studies showed that the most significant changes on the power spectra were on the frequency range of 500 to 2500 Hz, and were caused mainly by changes in the feed sizes to the crushing chamber. Relations between the vibration signal characteristics and the parameters in mono-size breakage events were derived by multiple regression based on principal component scores. It is shown that vibration signal measurement may provide additional information for studying single particle breakage events. Two examples are used to demonstrate the application of principal component analysis.

  • 3058. Zeng, Yigen
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vibration signal measurement: An alternative for describing mechanical grinding process1994In: Particulate Science and Technology, ISSN 0272-6351, E-ISSN 1548-0046, Vol. 12, no 3, 223-233 p.Article in journal (Refereed)
  • 3059.
    Zeng, Yigen
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Zum Einfluss der Arbeitsparameter eines Labor-Backenbrechers auf die Produktfeinheit und den Energiebedarf1991In: Aufbereitungstechnik - Mineral processing, ISSN 0004-783X, Vol. 32, no 10, 527-527 p.Article in journal (Other academic)
  • 3060.
    Zeng, Yigen
    et al.
    Luleå tekniska universitet.
    Zheng, Min
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Monitoring jaw crushing parameters via vibration signal measurement1993In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 39, no 3, 199-208 p.Article in journal (Refereed)
    Abstract [en]

    Fine crushing tests were performed on a laboratory scale jaw crusher with dry, monosize dolomite. The source vibration signal was picked up by an accelerometer, the acceleration signal was amplified by a vibrometer, and then stored on a DAT recorder during whole testing period. For each crushing test, three vibration signal samples were taken and converted into an IBM PC accessible data format using a digital oscilloscope. The digitized vibration signal was analyzed with the aid of digital signal processing technique. Through spectral inspection and principal component analysis, it was found that two major frequency bands, 250-400 and 700-900 Hz, were strongly related with the variation of the operating parameters. The first four principal components account for 91% of the total variation of the vibration signal. It was found that the inter-particle collision and attrition without breakage mainly affects the energy of the 250-400 Hz frequency band, and the variation of the frequency band of 700-900 Hz characterizes the breakage events of dolomite. With the aid of the multivariate data analysis, the relationship was established between the power spectral density and the operating parameters such as the feed rate to the crusher, the close side crusher setting and the charge volume of dolomite in the crusher chamber. The product size distribution described by Gaudin equation was also related to the vibration signal. Thus, an alternative method for monitoring the operating state can therefore be developed through measuring and processing the vibration signal from crushing.

  • 3061.
    Zhai, Hongxin
    Luleå tekniska universitet.
    Parameters in wet grinding: the influence of process variables on autogenous and conventional grinding1985Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The effects of autogenous and conventional grinding on the liberation of particles have been studied on the laboratory, pilot and industrial scales. It appears that autogenous grinding, down to flotation fineness, results in a higher degree of liberation and smoother particle surface for flotation, than is obtained with conventional grinding. An energy-liberation model is derived which provides a rapid analysis technique for determination of the optimum net energy consumption. It reveals the importance of ore characteristics in liberation. The relative importance of the effects of charge volume, feed rate, feed size or classification efficiency, mill speed and pulp density on fineness, net energy consumption and mean residence time have been studied using a multiple parameter approach. Computer-based response surfaces delineate all aspects of the comprehensive effects of the process variables on conventional grinding. The work described here also includes a study of the transport behaviour of particles flowing through conventional mills. A new RTD-model is established and confirmed under practical conditions. The implication of the mean residence time in net energy consumption and grinding fineness is investigated. On the other hand, the relations between fineness and net energy consumption are also modelled. Here, the importance of classi fication on efficiency in continuous grinding is demonstrated.

  • 3062.
    Zhai, Hongxin
    Luleå tekniska universitet.
    The influence of autogenous grinding on the liberation of particles1984Licentiate thesis, comprehensive summary (Other academic)
  • 3063. Zhang, H.
    et al.
    Gandin, C. -A
    He, J.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of solidification path and carbide precipitation in Fe-C-V-Cr-Mo-W high speed steels2012In: MCWASP XIII: International Conference On Modeling Of Casting, Welding And Advanced Solidification Processes, Institute of Physics (IOP), 2012, no 1, 012061- p.Conference paper (Refereed)
    Abstract [en]

    The solidification path and precipitation of carbides in the Fe-C-V-Cr-Mo-W high speed steel system are predicted with the help of thermodynamic equilibrium calculations. The Partial Equilibrium (PE) approximation is favoured. According to experimental data for high speed steel samples, the precipitating solidification sequence of carbides, including nature, composition and amount are discussed as a function of the nominal composition of C and V. The results show that the solidification path can be reasonably predicted by the Partial Equilibrium approximation for cooling rate lower than 10 K min -1. The experimental results suffer from the sensitivity limitation of the characterization methods used when the phase fraction becomes too small.

  • 3064. Zhang, H. -W
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Wang, E. -G
    He, J. -C
    Simulation of macrosegregation and solidification microstructure evolution for Al-Si alloy by coupled cellular automaton-finite volume model2012In: Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals, ISSN 1004-0609, Vol. 22, no 7, 1883-1896 p.Article in journal (Refereed)
    Abstract [en]

    A coupled cellular automaton-finite volume (CA-FV) model for macroscopic fluid flow, heat transfer, solute transport and microscopic nucleation and grain growth procedure was developed and applied in an Al-Si binary alloy solidification process. The model reflects the dendrite growth kinetics in the presence of fluid flow, the nucleation and growth in CA scale due to the increase of undercooling, and the feedback of solid fraction and temperature to FV nodes due to the nucleation and growth. The coupled CA-FV model can predict the recalescence and the intergranular segregation during alloy solidification process, which shows great advantages compared with the results by FV model and CA-FV model without fluid flow. The effects of fluid flow on the solute distribution and the solidification morphologies, as well as the influence of ingot size on the solidification structures, were discussed with the CA-FV model.

  • 3065. Zhang, Hongwei
    et al.
    Gandin, Charles-Andre
    Ben Hamouda, Haithem
    Tourret, Damien
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Jicheng
    Prediction of Solidification Paths for Fe-C-Cr Alloys by a Multiphase Segregation Model Coupled to Thermodynamic Equilibrium Calculations2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, 1859-1866 p.Article in journal (Refereed)
    Abstract [en]

    A microsegregation model for the solidification of multicomponent alloys is developed It couples the volume-averaged conservation equations for total mass solute mass and energy assuming a uniform temperature The diffusion in the liquid and solid phases the growth kinetics of the solidifying microstructures and the velocity of the solid/liquid and solid/solid phase interfaces are considered in the model Equilibrium between phases is taken into account and computed using dedicated thermodynamic software The thermodynamic properties and their evolutions during solidification are directly retrieved from a database Illustration is provided by the solidification of a Fe-C-Cr alloy The occurrence of the recalescence due to the growth of the microstructure and the progress of solidification are predicted The solidification behavior near to recalescence is evaluated By adjusting the cooling intensity and the solute diffusivities extreme approximations are retrieved The model shows potentials to be coupled with a macrosegregation model for application to the solidification of multicomponent alloys

  • 3066. Zhang, Hongwei
    et al.
    Liu, Qiang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Shibata, Hiroyuki
    Wang, Qiang
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Jicheng
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Partial Equilibrium Prediction of Solidification and Carbide Precipitation in Ti-added High Cr Cast Irons2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 2, 374-383 p.Article in journal (Refereed)
    Abstract [en]

    Carbide precipitation and eutectic phase transformation during solidification of Fe-C-Cr-Ti-Mn-Mo-Ni-Si Ti-added high-chromium cast irons (HCCIs) were studied numerically and experimentally by the help of Partial Equilibrium approximation, DSC thermal analyses and EDX analyses. The main carbides formed during the solidification are distinguished as MC, primary M7C3 and eutectic M7C3 from their distinguished constitution, while other researchers didn't distinguish the primary and eutectic M7C3 carbide. Through comparing the prediction of Partial Equilibrium approximation with DSC thermal analysis measurement, the precipitation sequence of the eutectic structure in HCCIs is clarified to follow the sequence of FCC prior to the eutectic M7C3, although they were usually expected to precipitate simultaneously. The hardness index of the HCCIs is evaluated quantatively by summation of the contributions of the Vickers hardness of MC, primary M7C3 and eutectic M7C3 carbides with predicted precipitation amount and composition / constitution. The effects of C, Ti and Cr contents on the precipitation sequence, the amount and the composition of carbides as well as the hardness of the HCCIs are discussed deeply. Finally, the validity of Partial Equilibrium approximation is shown in prediction of the solidification in multicomponent system with large amount of precipitated carbides.

  • 3067. Zhang, Hongwei
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Gandin, Charles-Andre
    He, Jicheng
    Prediction of Carbide Precipitation Using Partial Equilibrium Approximation in Fe-C-V-W-Cr-Mo High Speed Steels2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 3, 493-501 p.Article in journal (Refereed)
    Abstract [en]

    In Fe-C-V-W-Cr-Mo high speed steels, the nature of carbides during the solidification are discussed as a function of C, V and W content by the help of Partial Equilibrium (PE) approximation and thermodynamic calculations. The results show that the solidification path and carbide precipitation can be reasonably predicted by the Partial Equilibrium approximation for cooling rate lower than 10-13 K min(-1). From the viewpoint of hardness control by carbides, it is found that among the main carbides MC, M6C and M7C3, the increase of C favours the formation of MC, M7C3 but decreases the hardness of M7C3 by increasing the Fe content in it. Meanwhile, the increase of V only increases the amount of MC and V content therein, and the increase of W largely increases the amount of M6C and W content in it. As a result, the addition of V and W improves the hardness of MC and M6C carbides.

  • 3068. Zhang, Hongwei
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Lei, Hong
    He, Jicheng
    Restrictions of Physical Properties on Solidification Microstructures of Al-based Binary Alloys by Cellular Automaton2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, 1835-1842 p.Article in journal (Refereed)
    Abstract [en]

    The solidification microstructure evolution and the Columnar to Equiaxed Transition (CET) during Al-Si and Al-Cu binary alloy solidification processes are analyzed by the help of Cellular Automaton-Finite Difference (CA-FD) model The effects of the physical properties except the effects of the nucleation parameters and the operation parameters on the cooling curves the dendrite growth the solidification morphologies and the CET of the Al-Si and Al-Cu binary alloys are emphatically discussed Results show that the solidification morphologies are internally influenced by the physical properties related to the dendrite tip growth kinetics Besides the solute diffusivity in liquid D-L and the growth restriction parameter Q=mC(o)(k(S/L)-1) the Gibbs-Thomson coefficient Gamma shows a great effect on dendrite tip growth rate Their effects on the dendrite tip kinetics are ordered as m(k(S/L)-1)>Gamma>D-L The growth rate can be predicted efficiently by the present simplified expression based on GGAN model combining several physical parameters and the local under-cooling which clearly shows the physical meaning of the constant coefficients in the simplified expression based on KGT model The equiaxed ratio related to the solidification morphologies can also be evaluated as a function of those physical properties

  • 3069. Zhang, Hongwei
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Wu, Rangqiong
    Wang, Qiang
    He, Jicheng
    Prediction of Solidification Microstructure and Columnar-to-equiaxed Transition of Al-Si Alloy by Two-dimensional Cellular Automaton with "Decentred Square" Growth Algorithm2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, 1000-1009 p.Article in journal (Refereed)
    Abstract [en]

    A Cellular Automaton (CA)-Finite Difference (FD) coupling model was developed to analyze the evolution of solidification microstructure and the columnar-to-equiaxed transition (CET) in AI-Si alloy. Kobayashi's microsegregation equation was adopted to describe the solute diffusion in solid phase, and a "decentred square" growth algorithm with coordinate transformation was performed to describe the grain growth and the entrapment of neighbor cells. Through the examination on the effects of operation parameters and nucleation parameters on solidification morphologies, it was found that the length of columnar grains is controlled by the dendrite tip growth kinetics, and that the width of columnar grains is controlled by the implicit relationship between nucleation density and cooling rate at ingot surface. It was also found that the size of equiaxed grains is controlled by the competition of the nucleation and the grain growth. With the controllability of nucleation density in the bulk of liquid for equiaxed grain size, the nucleant and the nucleation density in actual AI-Si alloy were estimated. Both of the CET criteria based on the solidification path by CA-FD coupling model and the one based on the curves of critical temperature gradient conditions by Hunt's model were strongly dependent on nucleation undercooling and Si concentration. A good agreement was obtained between these two.

  • 3070. Zhang, Hongwei
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Xing, Wei
    Wang, Aili
    He, Jicheng
    Influences of Flow Intensity, Cooling Rate and Nucleation Density at Ingot Surface on Deflective Growth of Dendrites for Al-based Alloy2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, 1010-1018 p.Article in journal (Refereed)
    Abstract [en]

    The dendrite tip growth kinetics in the flow field and the decentred quadrilateral growth algorithm for describing the evolution of grain growth are combined in Cellular Automaton model to predict the deflective growth of dendrites inclined toward upstream direction. The influences of flow intensity, cooling rate (or solidification rate), nucleation density at ingot surface on the deflective growth of dendrites are discussed. The increase of flow intensity dominantly forces the dendrites to grow in upstream direction; on the contrary, the increases of nucleation density at ingot surface and cooling rate suppress slightly this deflective growth. The relations predicted among deflection angle, flow intensity and solidification rate for AI-Si alloy and Al-Cu alloy show the same tendency as that in Okano et al.'s empirical expression deduced from experiments on steel. The deflection angle predicted for Al-Cu alloy fits well with previous experimental results.

  • 3071.
    Zhang, Hui-ning
    et al.
    School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou.
    Li, Jian-li
    Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan.
    Xu, An-jun
    Metallurgical and Ecological Engineering School, University of Science and Technology, Beijing.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    He, Dong-feng
    Metallurgical and Ecological Engineering School, University of Science and Technology, Beijing.
    Tian, Nai-yuan
    Metallurgical and Ecological Engineering School, University of Science and Technology, Beijing.
    Carbothermic Reduction of Zinc and Iron Oxides in Electric Arc Furnace Dust2014In: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 21, no 4, 427-432 p.Article in journal (Refereed)
    Abstract [en]

    The reduction of zinc and iron oxides from electric arc furnace dust (EAFD) by carbon was investigated at temperatures between 800 and 1300 °C. The analytic technique employed includes chemical analysis, X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) equipped with X-ray energy dispersive spectrometry (EDS), and thermodynamic database FactSage 6. 2. It was found that the reduction of zinc and iron oxides depends largely on Boudouad reaction. At 900 °C, zinc exists in tested samples as ZnO, which is reduced in the temperature range of 1000 — 1100 °C. At 1100 °C, 99. 11% of the zinc is evaporated. The metallization ratio of Fe is 79. 19% at 1300 °C, as the content of Fe2+ is still 9. 40%. A higher temperature is thus required for a higher reduction degree of Fe oxides by solid or gaseous carbon

  • 3072. Zhang, R.
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software AB, Sweden.
    Taskinen, P.
    Phase equilibria study and thermodynamic description of the BaO-CaO-Al2O3 system2017In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 100, no 6, 2722-2731 p.Article in journal (Refereed)
    Abstract [en]

    A combined experimental investigation and thermodynamic assessment was performed for the BaO-CaO-Al2O3 system. By using a high-temperature equilibration/quenching technique and scanning electron microscopy, electron probe microanalysis, and X-ray powder diffraction analysis, the phase equilibria at 1500°C and phase stability of BaCa2Al8O15 phase were determined. An extensive literature survey was conducted for the experimental and thermodynamic modeling data of the BaO-CaO-Al2O3 system. According to the literature data and the present measurements, a thermodynamic assessment was made in order to obtain a set of self-consistent thermodynamic parameters to describe the BaO-CaO-Al2O3 system. Based on the thermodynamic parameters acquired in this work, isothermal sections at 1100°C, 1250°C, 1400°C, 1475°C, and 1500°C and the BaO·Al2O3-CaO·Al2O3 and BaO·6Al2O3-CaO·6Al2O3 joints were calculated and compared with the available experimental data.

  • 3073. Zhang, Rui
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Taskinen, Pekka
    Thermodynamic descriptions of the BaO-CaO, BaO-SrO, BaO-SiO2 and SrO-SiO2 systems2016In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 54, 107-116 p.Article in journal (Refereed)
    Abstract [en]

    In order to provide an adequate basis for extrapolation into higher order oxide systems, a thermodynamic assessment was performed on the BaO-CaO, BaO-SrO, BaO-SiO2 and SrO-SiO2 binary systems by critically evaluating the available experimental data and Previous thermodynamic modeling. Associate solution model was applied to describe the molten phase in the BaO-SiO2 and SrO-SiO2 systems. Two associates, Ba2SiO4 and BaSiO3, were tested and compared with the previous assessment with only one associate Ba2SiO4. A set of self-consistent thermodynamic parameters for the descriptions of each oxide system is presented. The phase diagrams, thermodynamic properties including activities, standard enthalpies of formation at 298.15 K and enthalpy increments were calculated according to the thermodynamic parameters acquired in the present work. For the BaO-SiO2 and SrO-SiO2 systems, the site fractions of species in the liquid were calculated to illustrate the chemical short-range order tendency of the compound(s) in the liquid phase.

  • 3074. Zhang, Shang-Zhou
    et al.
    Cui, Hao
    Li, Ming-Man
    Yu, Hui
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yang, Rui
    Hu, Qing-Miao
    First-principles study of phase stability and elastic properties of binary Ti-xTM (TM = V,Cr,Nb,Mo) and ternary Ti-15TH-yAl alloys2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 110, 80-89 p.Article in journal (Refereed)
    Abstract [en]

    The phase stability and elastic property of binary Ti-chi TM (TM=V, Cr, Nb, Mo) and ternary Ti-15TH-yAl alloys are investigated systematically by using a first-principles method. The coherent potential approximation is employed to describe the random distribution of the alloying atoms in the alloys. We show that the transition metal (TM) elements V, Cr, Nb, Mo increase the elastic stability of the beta phase but decreases that of the a phase. The polycrystalline bulk modulus of the a phase increases with the concentration of the TM alloying elements whereas the Young's modulus and shear modulus are weakened. For the beta phase, all the polycrystalline elastic moduli hardens with the addition of the TM alloying elements. The influence of the simple metal (SM) element Al on the elastic properties is much weaker than the TM ones. The TM alloying elements increase the stability of the beta relative to the alpha and omega phases. Al stabilizes significantly the beta phase over the omega phase. Our calculations suggest that the d electron density dominates the elastic modulus but not the relative phase stability. The interaction between the TM and SM alloying elements in titanium alloys matters to the relative stability.

  • 3075.
    Zhang, Shunli
    Luleå tekniska universitet.
    Materials recycling of electronic scrap by physical separation1997Licentiate thesis, comprehensive summary (Other academic)
  • 3076.
    Zhang, Shunli
    Luleå tekniska universitet.
    Recycling and processing of end-of-life electric and electronic equipment: fundamentals and applications1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a concept of scrapology of end-of-life electric and electronic equipment (EOL EEE) as a basis on which to develop effective recycling techniques. Various study approaches associated with this concept are detailed in this thesis. In addition, the present work investigates materials separation techniques, in particular eddy current separation (ECS) technology. Based on our research work, a number of novel design alternatives for further developing ECS have been proposed. Major challenges encountered in processing and recycling of EOL EEE are discussed. The main results obtained in this study should be helpful in designing, implementing and improving a recycling system for EOL EEE.

  • 3077.
    Zhang, Shunli
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Cable and wire scrap recycling by physical separation technologies1998In: Environmental & Waste Management, ISSN 1460-5147, Vol. 1, no 3, 189-202 p.Article in journal (Refereed)
    Abstract [en]

    For cable and wire scrap recycling, physical separation technologies can offer a solution that is both environmentally friendly and economically viable. It is clear that such toxic emissions as hydrogen chloride and chlorine gases resulting from burning polyvinyl chloride (PVC) can be avoided, and that both metals and plastics can be recovered and reused. In this paper, physical separation techniques employed in the cable and wire scrap recycling industry throughout the world are described. A critical comparison of various separation techniques has been made. It appears that density-based separation techniques, in particular, air tables have been implemented extensively in this specific recycling industry world-wide. However, many other separation techniques capable of recycling cable and wire scrap have also been developed with a view towards improving separation selectivity (product quality), while maintaining a sufficient level of materials recovery. Of these, it seems that electrodynamic or high tension separation techniques remain to be developed by designing new electrode systems

  • 3078.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Intelligent liberation and classification of electronic scrap1999In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 105, no 1, 295-301 p.Article in journal (Refereed)
    Abstract [en]

    Mechanical recycling of electronic scrap oriented towards overall materials recovery from obsolete electronics is being implemented worldwide. The main reason is that the amount of electronic scrap is increasing and that the content of the precious metals present is decreasing. In this context, an effective liberation of various materials like metals and plastics is a crucial step towards mechanical separation. In addition, classification of electronic scrap is also important to be able to provide an appropriate feed material for the subsequent separation process. In the present study, liberation and its impact on the separation of personal computer (PC) scrap and printed circuit board (PCB) scrap has been investigated in detail. A special equipment functioning as a shape separator and an aspirator was used for the classification of electronic scrap.

  • 3079. Zhang, Shunli
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanical recycling of electronics scrap: the current status and prospects1998In: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 16, no 2, 119-128 p.Article in journal (Refereed)
    Abstract [en]

    Of the various mechanical metal recycling techniques employed in electronic scrap processing, air table separation, magnetic separation and eddy current separation technolo gies have proved to be the most commercially successful. In addition, it is very important, even indispensable, that, prior to the physical processing of electronic scrap, selective dis mantling and identification (if necessary) be employed. It is, however, recognized that problems such as process optimiza tion and organics handling remain and that in-depth charac terization of electronic scrap will be essential in this context.

  • 3080.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanical separation-oriented characterization of electronic scrap1997In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 21, no 4, 247-269 p.Article in journal (Refereed)
    Abstract [en]

    The ever-increasing amount of electronic scrap and the steadily-decreasing contents of the precious metals used in electronics, as well as the ever-growing environmental awareness, challenges such conventional precious-metal-oriented recycling techniques as pyrometallurgy. Separation and beneficiation of various materials encountered in electronic scrap might provide a correct solution ahead. In this context, mechanical separation-oriented characterization of electronic scrap was conducted in an attempt to evaluate the amenability of mechanical separation processes. Liberation degrees of various metals from the non-metals, which are crucial for mechanical separation, were analyzed by means of a grain counting approach. It is found that the metallic particles below 2 mm achieve almost complete liberation. Particle shapes were also quantified through an image processing system. The results obtained show that the shapes of the particles, as a result of shredding, turn out to be heterogeneous, thereby complicating mechanical separation processes. In addition, separability of various materials was ascertained by a sink–float analysis. It has been shown that density-based separation techniques shall be viable in separating metals from plastics, light plastics (ABS, PS and PVC, etc.) from glass fiber reinforced resins and aluminum from heavy metals. Specifically, a high quality copper concentrate can be expected by density-based separation techniques. Moreover, FT-IR spectra of plastics pieces from the light fractions after the sink–float testing show that PC scrap primarily contains ABS, PS and PVC plastics with the density range of +1.0–1.5 g/cm3, whereas PCB scrap mainly contains glass fiber reinforced epoxy resins plastics with the density range of +1.5–2.0 g/cm3.

  • 3081.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Optimization of electrodynamic separation for metals recovery from electronic scrap1998In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 22, no 3-4, 143-162 p.Article in journal (Refereed)
    Abstract [en]

    The performance of an electrodynamic separator has been optimized in the present study for metals recovery from electronic scrap. Eight variables involved in the system was investigated by a 2IV8-4 fractional factorial design in an attempt to determine the significant variables. The effects of those variables were detailed with glass, polyvinyl chloride (PVC) as a representative of plastics, copper wires, copper and aluminum granulates. For various binary mixtures of copper wires and glass or PVC plastic, the electrodynamic separator is able to produce copper products with the grade ranging from 93 to 99%, and recovery from 95 to 99%, respectively, under the optimized conditions. Further, one sample which is a middling fraction resulting from air table separation was also tested. For a single pass, copper and aluminum was upgraded approximately from 11 and 7% to 34 and 22%, while maintaining the corresponding recovery of 87 and 99%, respectively.

  • 3082.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Arvidson, Bo
    Moss, William
    Investigation of the parameters of rotating drum type eddy current separators1998In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 27, no 6, 253-260 p.Article in journal (Refereed)
    Abstract [en]

    Rotating eddy current separators are increasingly used in waste processing industries, particularly in the automobile and electric scrap recycling, for recovery of non-ferrous metals. If misused, however, a substantial loss of the metal values can incur. A deeper understanding of the influences of a large number of parameters involved in the eddy current separation system is of great help in optimizing the performance of an eddy current separator. In the present study, a rotating drum-type High-Force eddy current separator, has been investigated extensively with a wide range of materials including aluminum, copper, brass, zinc, lead and polyvinyl chloride (PVC). The results obtained show that the material-related variables like particle size and shape play a critical role in maximizing the deflections of the metal particles, implying that an effective liberation of the materials to be recovered is crucial. Further, the machine-related variables like rotational frequency and positioning of the magnetic field are of great importance. It appears that, for a given conductor, the deflection is proportional to the rotational frequency of the magnetic field.

  • 3083.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Arvidson, Bo R.
    Current status of eddy current separation1998In: Erzmetall, ISSN 0044-2658, Vol. 51, no 12, 829-836 p.Article in journal (Refereed)
    Abstract [en]

    he three-stage evolution of eddy current separation with the equipment and applications is critically analyzed in this paper, with the third stage of development highlighted. It can be concluded that the eddy current separators of generation III are associated with the development of the magnetic roll system design which includes the magnet configuration in a magnetic roll, the magnetic roll configuration in a separator, and the eddy current induction regimes. With a continuing improvement of the magnetic roll system design, it is expected that the eddy current separators of the next generation will be widely applied in the recycling industry.

  • 3084.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Arvidson, Bo R.
    International Process Systems, Inc., Golden, CO.
    Moss, William
    International Process Systems, Inc., Golden, CO.
    Aluminum recovery from electronic scrap by High-Force R eddy-current separators1998In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 23, no 4, 225-241 p.Article in journal (Refereed)
    Abstract [en]

    The amount of electronic scrap which contains a substantial portion of non-ferrous metals, primarily copper and aluminum, has been growing. The present study is directed toward aluminum recovery by a newly developed eddy current separator. The investigation on shredded personal computer and printed circuit board scrap demonstrates that the High-Force® eddy-current separator will be applicable for this purpose. It has been shown that, by a single pass of the materials on the High-Force® eddy-current separator, an aluminum concentrate out of personal computer scrap can be obtained with a purity of 85%, while maintaining a recovery in excess of 90%, with the feed rate being up to 0.3 kg/min.

  • 3085.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Arvidsson, Bo R.
    International Process Systems, Inc., Golden, CO.
    Moss, William
    International Process Systems, Inc., Golden, CO.
    Separation mechanisms and criteria of a rotating eddy-current separator operation1999In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 25, no 3, 215-232 p.Article in journal (Refereed)
    Abstract [en]

    Much work has so far been done for modelling the magnetic deflecting (repulsive) force of eddy current separators. However, selective separation of various materials by eddy current separation depends not only on magnetic deflecting forces but also on competing forces like the gravitational force and the centrifugal force. Co-acting forces on a particle leaving the external drum are analyzed and evaluated in this study. Separation mechanisms of metal/non-metal and metal/metal separation systems have been investigated by a newly-developed High-Force® eddy-current separator. Further, a separation model governing an effective separation among various materials is presented. Based on this separation model, four practical separation criteria for metal/metal separation systems are put forward and have been substantiated experimentally.

  • 3086.
    Zhang, Shunli
    et al.
    Luleå tekniska universitet.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Houwelingen, Jan van
    Delft University of Technology.
    Rem, Peter
    Department of Raw Materials Technology, Delft University of Technology.
    Wei, Liuying
    Luleå tekniska universitet.
    End-of-life electric and electronic equipment management towards the 21st century2000In: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 18, no 1, 73-85 p.Article in journal (Refereed)
    Abstract [en]

    With the rapid growth of the electronics industry and an evergrowing environmental awareness worldwide, an environmentally sound and economically viable management system for endoflife (EOL) electric and electronic equipment (EEE) is of great importance for sustainable development. Traditional recycling and processing of EOL electronics directed towards the recovery of copper and precious metals, will be faced with many challenges in the future. It has been recognized by the EOL EEE recycling industry that a new strategy for EOL EEE must be developed. In this paper, current status and future trends in EOL EEE management are presented. Selective dismantling of valuable and hazardous components is evaluated in terms of a graderecovery (GR) concept. It is concluded that selective dismantling and mechanical processing must be coordinated in such a way as to produce suitable materials for subsequent handling at the lowest cost. Furthermore, new developments in mechanical and thermal processing of EOL EEE are also discussed, which involve water table and eddy current separation techniques and reduction of dioxins and furans during combustion of the plastics containing halogenated flame retardants. In addition, the challenges and perspectives associated with EOL management of plastics and cathode ray tubes (CRTs) encountered in EOL EEE are highlighted in this paper. It is predicted that EEE, being designed for recycling in the 21st century, will be processed and recycled economically and ecologically on becoming obsolete.

  • 3087.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Rem, Peter C
    Delft University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Investigation of separability of particles smaller than 5 mm by eddy current separation technology. Part I: Rotating type eddy current separators1999In: Magnetic and Electrical Separation, ISSN 1055-6915, E-ISSN 1029-0303, Vol. 9, no 4, 233-251 p.Article in journal (Refereed)
    Abstract [en]

    Owing to the growing emergence of the end-of-life electrical and electronic products with complex material structures and an ever-diminishing particle size of the valuable metals involved, development of eddy current separators (ECS) has been targeting selective separation of small non-ferrous metal particles smaller than 5 mm. Separability of various materials smaller than 5 mm, including fine copper wires, has been investigated using ECS with various design concepts. The present research work is divided into two parts, with Part I focusing on the rotating type ECS which are today common in practice, and with Part II dedicated to the ECS with novel concepts such as wet ECS technology. In Part I, three rotating belted-drum ECS were employed, which are manufactured by Bakker Magnetics, the Netherlands, Huron Valley Steel Co., US, and Eriez Magnetics, UK respectively. It is found that the belted-drum ECS are effective for separating materials below 5 mm if the magnetic drum rotates in opposite direction to the conveyor belt. The separation principle, particularly the 'backward phenomenon' of the rotating type ECS for small particles has been unravelled in the present study. Moreover, separation of Al from the 0-10 mm fraction of electronic scrap has been conducted. The results obtained demonstrate that the belted-drum ECS with appropriate design may be applicable for separation of small aluminum particles from electronic scrap.

  • 3088.
    Zhang, Shunli
    et al.
    Luleå University of Technology.
    Rem, Peter C
    Delft University of Technology.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Particle trajectory simulation of two-drum eddy current separators1999In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 26, no 2, 71-90 p.Article in journal (Refereed)
    Abstract [en]

    Particle trajectories of the newly-developed two-drum eddy current separators are simulated by the ECSIM software package. The simulation results have been substantiated by measuring the horizontal displacements of the particles to be investigated under the same conditions. It is shown that the simulation results are in good agreement with the experimental ones. Further, on the basis of the simulation results obtained, the potential for improving the design of two-drum eddy current separators is discussed. It appears that the performance of two-drum eddy current separators, when processing small particles, may be enhanced by strengthening the magnetic field intensity and simultaneously increasing the maximum drum speed.

  • 3089.
    Zhang, Xian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Atmospheric corrosion of Galfan coatings on steel in chloride-rich environments2013In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 73, 62-71 p.Article in journal (Refereed)
    Abstract [en]

    Galfan coatings on steel in laboratory exposures with predeposited NaCl and cyclic wet/dry conditions exhibit nearly the same corrosion products as after 5 years of marine exposure. A general scenario for corrosion product evolution on Galfan in chloride-rich atmospheres is proposed. It includes the initial formation of ZnO, ZnAl2O4 and Al2O3 and subsequent formation of Zn6Al2(OH)(16)CO3 center dot 4H(2)O, and Zn2Al(OH)(6)Cl center dot 2H(2)O and/or Zn5Cl2(OH)(8)center dot H2O. An important phase is Zn6Al2(OH)(16)CO3 center dot 4H(2)O, which largely governs the reduced long-term zinc runoff from Galfan. A clear influence of microstructure could be observed on corrosion initiation in the slightly zinc-richer eta-Zn phase adjacent to the beta-Al phase.

  • 3090.
    Zhang, Xian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mechanistic studies of corrosion product flaking on copper and copper-based alloys in marine environments2014In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 85, 15-25 p.Article in journal (Refereed)
    Abstract [en]

    The mechanism of corrosion product flaking on bare copper sheet and three copper-based alloys in chloride rich environments has been explored through field and laboratory exposures. The tendency for flaking is much more pronounced on Cu and Cu-4 wt%Sn than on Cu-15 wt%Zn and Cu-5 wt%Al-5 wt%Zn. This difference is explained by the initial formation of zinc and zinc-aluminum hydroxycarbonates on Cu15Zn and Cu5Al5Zn, which delays the formation of CuCl, a precursor of Cu-2(OH)(3)Cl. As a result, the observed volume expansion during transformation of CuCl to Cu-2(OH)(3)Cl, and concomitant corrosion product flaking, is less severe on Cu15Zn and Cu5Al5Zn than on Cu and Cu4Sn.

  • 3091.
    Zhang, Zhi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of flow fields during filling of a sampler2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized.

    The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.

  • 3092.
    Zhang, Zhi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    On the Study of a Liquid Steel Sampling Process2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The liquid steel sampling method is one of the commonly used procedures in monitoring the steelmaking process. Besides it can be used for analyzing the dissolved alloys, hydrogen content and oxygen content, it can be also employed to monitor the inclusion characteristics at the steelmakings. Here, a crucial point is that the steel sampler should be filled and the metal solidifies without changing the inclusion characteristics. Therefore, the objective of this work is to fundamentally understand the liquid steel sampling process by means of analyzing and modeling the two-phase flow during the sampler filling process, and verifying the mathematical model by using the experimental data.

    The present dissertation presents an experimental and theoretical study of the filling process of both the lollipop-shaped sampler and the rectangular-shaped sampler. Firstly, a physical modeling by using a water model has been carried out to fundamentally investigate the flow pattern inside the sampler vessels during its filling. The flow patterns were obtained by a PIV system. Then, a mathematical model has been built to theoretically understand the phenomena. The commercial CFD code was used. Here, different turbulence model have been compared between the realizable k-ε turbulence model and Wilcox k-ω turbulence model. It concludes that the Wilcox k-ω turbulence model agrees well with the PIV measurements.HH

    Thus, the preferred it was further employed to predict the turbulent flow inside the production lollipop-shaped sampler fillings. It is important to find that the average collision volume in the production steel sampler without solidification at filling is about 30 times higher than that in a ladle furnace.

    In the end, the whole sampling system was modeled. The initial solidification during the filling was taken into account. Focus was on the influence of the initial solidification on the inclusion concentrations. A discrete phase model was used to simulate the movement of inclusions in the liquid steel. Some selected different sized primary inclusions that exist in the ladles at a steelmaking process were simulated.

    The same method of studying the filling procedure of the lollipop-shaped sampler was further applied to comprehensively investigate the rectangular-shaped sampler.

  • 3093.
    Zhang, Zhi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Iguchi, Manabu
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Physical modeling of a sampler filling for molten steel2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 10, 1522-1529 p.Article in journal (Refereed)
    Abstract [en]

    In recent years, much attention has been paid to determining not only the composition, but also the inclusion characteristics from liquid steel samples extracted from a ladle or a tundish. Here, a crucial point is that the steel sampler is filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process. In this paper, this is done using physical modeling of a lollipop-shaped sampler. More specifically, particle image velocimetry was employed to capture the flow field and calculate the velocity vectors during the entire experiment. The filling rate at the pin part of the sampler was varied during the experiments. It was found that due to the geometry change at the transition from the inlet pin to the body part of the sampler, the flow is very chaotic at the initial filling stage. Furthermore, vortexes are formed in the water sampler vessel during all the fillings and the height of the vortex center varies with the filling rate. Overall, it was found that the flow patterns in the lollipop-shaped sampler vessel can be characterized into three distinct flow regions: the upper vortexes region, the lower horizontal flow region and the middle nozzle flow region.

  • 3094.
    Zhang, Zhi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Iguchi, Manabu
    Pär, Jönsson
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An Experimental and Numerical Study of theFilling of a Steel SamplerManuscript (preprint) (Other academic)
    Abstract [en]

    During the steelmaking process, it is important to understand the origin, types and nature ofinclusions. After an initial period of heating, mixing and chemical reactions in an electric arcfurnace and some crucial processes in a ladle, taking liquid steel samples in the ladle is a criticalstep in monitoring the inclusion population. This paper presents a study of filling of a steelsampler process as well as the primary inclusion dispersions inside a steel sample. To betterunderstand the influence of filling on the inclusion populations, physical modelings of waterfilling in a rectangular-shaped vessel have been carried out to study flow fields. The flow fieldswere obtained by a Particle Image Velocimetry. Thereafter, simulation of water samplers havebeen done to mathematically study the flow fields. The physical modeling data were used forverification of the model predictions, including the selection of the most appropriate turbulencemodel. Finally, simulations of the filling of liquid steel were carried out for a rectangular-shapedsampler, which is used in the laboratory.

  • 3095.
    Zhang, Zhi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical Modelling of Water Sampler Filling2010In: Steel Research International, ISSN 1611-3683, Vol. 81, no 2, 112-122 p.Article in journal (Refereed)
    Abstract [en]

    Steel samples taken from ladles or tundishes during the steel making process can be of significant importance when monitoring the inclusion size and distribution. In order to preserve the original size and distributions of inclusions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Thus, it is necessary to investigate the flow during a sampling process to make sure that this is minimized. In addition, it is important to study the turbulence characteristics, since it is known to influence the inclusion growth. This study presents mathematical modelling of sampler filling using water as a media and experimental results for verification. The study focuses on a lollipop-shaped sampler since it is one of the most common in the industry. The sampler is filled from an inlet pin located at the bottom centre of the main body. In addition, two different turbulence models, the realizable k-ε model and Wilcox k-ω model, were used to study the flow pattern in the sampler. The predictions were compared to experimental results obtained by Particle Image Velocimetry (PIV) measurements. It was found that the flow field predictions using the Wilcox k-ω model agreed best with the flow field obtained by PIV measurements. Furthermore, it was illustrated that the Wilcox k-ω model can be used for predictions of the different flow regions as well as the positions of the centres of vortexes which are located near the free surface. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.

  • 3096.
    Zhang, Zhi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Simulation of the Filling of a Liquid Steel Sampler2010In: Steel Research International, ISSN 1611-3683, Vol. 81, no 9, 749-758 p.Article in journal (Refereed)
    Abstract [en]

    Steel samples extracted from the ladle furnace in liquid state are vital to monitor the steel making process in the iron & steel industries. The main function of the steel sample is to exam whether the steel is at the aimed composition for elements that dissolve in steel. In addition, more interest is arising to determine the inclusion characteristics in steel samples, in order to monitor the development throughout the process. However, the molten steel sampling is a process involving multi-phenomena such as a high temperature, a fast solidification, reoxidation of steel and a highly turbulent flow pattern. Therefore, mathematical simulations have been carried out to fundamentally study the sampler filling process. The Wilcox k-ω turbulence model was employed to predict the turbulent flow. The calculated results show that flow patterns inside the sampler can be classified into three distinct flow regions: the vortex flow region close to the free surface, the lower horizontal flow region and the middle vertical flow region. From the flow and turbulence data, the inclusion particle collision volume rate was calculated to study the influence of turbulent flow on the inclusion growth in the sampler during fillings. It is shown that the collision volume in the sampler is much higher than that found in the ladle furnace, where the steel sampling normally takes place. This is due to the high turbulence energy dissipation rate in the samplers compared to the ladles.

  • 3097.
    Zhang, Zhi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Yokoya, Shinichiro
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Numerical Study of Swirl Blade Effects in Uphill Teeming Casting2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, 1756-1762 p.Article in journal (Refereed)
    Abstract [en]

    The initial filling period during ingot casting was studied theoretically The motivation was that it is crucial to achieve a preferred flow pattern which can lead to a smooth filling condition particularly during the initial teeming stage In this study a twist-tape swirl blade was applied in a mathematical model to create a swirl flow in the inlet of the mold The swirl blade was set vertically lust beneath the inlet which was made of a gradually divergent cross section area The results showed that combinations of the inlet swirl flow and mold with gradually divergent bottom contributes to 0 Inlet flow passes along the wall of the mold ii) the formation of a very uniform velocity distribution within only 6s after the molten steel filled into the mold and 10 No formation of a hump on the free surface of the mold during the entire filling times These phenomena will ensure that the mold flux is spread onto the surface of liquid steel evenly Besides the stable surface also prevents the mold flux from being dispersed into the molten steel

  • 3098.
    Zhang, Zongyin
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sandström, Rolf
    KTH, Superseded Departments, Materials Science and Engineering.
    Fe-Mn-Si master alloy steel by powder metallurgy processing2004In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 363, no 02-jan, 194-202 p.Article in journal (Refereed)
    Abstract [en]

    Fe-Mn-Si master alloy powders were produced by three methods: milling, atomising, and a combination of atomisation and milling. The effects of sintering temperature, time and atmosphere on the properties of sintered steels with these Fe-Mn-Si master alloy powders were studied. The density of the compacts increases with sintering temperature and time. The ultimate tensile strength and hardness increases with sintering temperature and time mainly due to increasing amounts of bainite and martensite after cooling. Elongation is initially raised with sintering temperature and time probably due to improved bonding between powder particles. The compacts with the milled and atomised-milled master alloy showed about the same mechanical properties. On the other hand, the steel with the atomised powder gave lower strength and elongation in both hydrogen and argon-5% hydrogen. Small dimensional changes have been obtained in the steels with milled and atomised-milled Fe-Mn-Si master alloys sintered at 1200degreesC. It was shown that transient liquid phase sintering accelerates the sintering process, which leads to improved mechanical properties.

  • 3099.
    Zhang, Zuotai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Synthesis and Characterization of MgA1ON-BN refractories2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In order to meet the need of metallurgical industry in the world, a new MgAlON-BN composite which can be used for example in special refractory nozzles, tubes and break rings for the continuous casting of steel was studied in the present thesis. The aim was to understand the mechanism of synthesis and their physicochemical properties during the application. Thus, the thermodynamic properties, synthesis process, mechanical properties, thermal shock behaviour, thermal diffusivity/conductivity as well as corrosion resistance to molten iron containing oxygen and molten slag of MgAlON and MgAlON-BN composites have been investigated.

    The Gibbs energy of formation of MgAlON was estimated using the method proposed by Kaufman. The phase stability diagram of Mg-Al-O-N-B was investigated, and consequently the synthesis parameters were determined. MgAlON and MgAlON-BN composites were fabricated by hot-pressing method. The composites obtained this way were characterized by XRD, SEM, TEM and HREM analyses. A Matrix-flushing method was employed in the quantitative XRD analysis for the multi-component samples to understand the mechanism of synthesis.

    The relationship between mechanical properties and microstructure of the composites was investigated. The experimental results indicated that BN addition has significant influence on the mechanical properties of the composites. These can be explained by the fact that BN has low Young’s modulus, density and non-reactive nature as well as considerable anisotropy of many properties such as thermal expansion, thermal diffusivity/conductivity. Thus, the addition of BN in MgAlON is likely to lead to the presence of microcracks caused by the mismatch of thermal expansion coefficient. The microcracks result in the enhancement of the strength at elevated temperature and thermal shock durability of the composites.

    Effective thermal conductivities were evaluated from the present experimental results of thermal diffusivities, heat capacity and density. A model suitable for present composites has been derived based on Luo’s model. The predicted lines calculated by the model were in good agreement with experimental results.

    The reactions between the composites and molten iron as well as the slag were investigated by ‘‘finger’’ experiments and sessile drop experiments. Both experimental results indicated that the BN addition has positive influence on the corrosion resistance. These are attributed to the excellent corrosion resistance of BN to molten iron and slag, such as the higher contact angle between BN substrate and liquid iron and molten slag compared with that obtained for pure MgAlON.

  • 3100.
    Zhang, Zuotai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, Wenchao
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermal diffusivity/conductivity of MgAlON-BN Composites2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, 615-621 p.Article in journal (Refereed)
    Abstract [en]

    Thermal diffusivity and heat capacity of MgAlON and MgAlON-BN composites were measured in the temperature range of 25 degrees C to 1300 degrees C using a laser flash technique and a differential scanning calorimeter (DSC) technique, respectively. Based on these measurements, effective thermal conductivity of the composites was calculated using the values measured earlier in the same substance. The experimental effective thermal conductivity results of the composites containing different BN contents were found to show the similar trend, which decreased rapidly with increasing temperature below 900 degrees C followed by a slow decrease with further increasing temperature. This can be explained by the fact that thermal conduction in both components, MgAlON and BN, was dominated by phonons. The phonon mean free path decreased with increasing temperature, limited by the characteristic length between two neighboring atoms. The BN addition has significant influence on the effective thermal conductivity. The effective thermal conductivity of the composites containing BN exhibited a small degree of anisotropy with respect to preferred orientation of the BN phase. The degree of anisotropy of the composites increased with increasing BN content, which is particularly pronounced at the higher BN additions. An equation suitable for the present composites has been derived based on Luo's model. The model was slightly modified in the present article. The predicted values calculated by the model were in good agreement with experimental results.

596061626364 3051 - 3100 of 3180
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