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Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation-low-temperature reduction

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International Journal of Minerals,Metallurgy and Materials 2023年第6期30卷 1057-1066页

作者： Haoyan Sun zheng zou Meiju Zhang Dong Yan Innovation Academy for Green Manufacture Chinese Academy of SciencesBeijing 100190China Institute of Process Engineering Chinese Academy of SciencesState Key Laboratory of Multiphase Complex SystemsBeijing 100190China University of Chinese Academy of Sciences School of Chemical EngineeringBeijing 100049China

Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ***,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic *** systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for *** found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low *** optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 *** roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.

关键词： magnetization roasting fluidization siderite preoxdization low-temperature reduction

A new drag model for TFM simulation of gas-solid bubbling fluidized beds with Geldart-B particles

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Particuology 2014年第4期12卷 151-159页

作者： Yingce Wang zheng zou Hongzhong Li Qingshan Zhu State Key Laboratory of Multi-phase Complex Systems Institute of Process EngineeringChinese Academy of Sciences Graduate School of Chinese Academy of Science

In this work, a new drag model for TFM simulation in gas-solid bubbling fluidized beds was proposed, and a set of equations was derived to determine the meso-scale structural parameters to calculate the drag characteristics of Geldart-B particles under low gas velocities. In the new model, the meso-scale structure was characterized while accounting for the bubble and meso-scale structure effects on the drag coefficient. The Fluent software, incorporating the new drag model, was used to simulate the fluidization behavior. Experiments were performed in a Plexiglas cylindrical fluidized bed consisting of quartz sand as the solid phase and ambient air as the gas phase. Comparisons based on the solids hold-up inside the fluidized bed at different superficial gas velocities, were made between the 2D Cartesian simulations, and the experimental data, showing that the results of the new drag model reached much better agreement with exoerimental data than those of the Gidasoow dra~ model did.

关键词： Fluidization Bubbling fluidized bed CFD Geldart-B particles Drag model

Simulation with a structure-based mass-transfer model for turbulent fluidized beds

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Particuology 2018年第4期16卷 40-47页

作者： Dong Yan Hongzhong Li zheng zou Qingshan Zhu State Key Laboratory of Multi-phase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P.O. Box 353 Beijing 100190 PR China University of Chinese Academy of Sciences Beijing 100049 PR China

A structure-based mass-transfer model for turbulent fluidized beds （TFBs） was established according to mass conservation and the balance of mass transfer and reaction. Unlike the traditional method, which assumes a homogeneous structure, this model considered the presence of voids and particle clusters in TFBs and built correlations for each phase. The flow parameters were solved based on a previously proposed structure-based drag model. The catalytic combustion of methane at three temperatures and ozone decomposition at various gas velocities were used to validate the model. The TFB reactions com- prised intrinsic reaction kinetics, internal diffusion, and external diffusion. The simulation results, which compared favorably with experimental data and were better than those based on the average method, demonstrated that methane was primarily consumed at the bottom of the bed and the methane concentration was closely related to the presence of the catalyst. The flow and diffusion had an important effect on the methane concentration. This model also predicted the outlet concentrations for ozone decomposition, which increased with increasing gas velocity, lnterphase mass transfer was presented as the limiting step for this system. This structure-based mass-transfer model is important for the industrial application of TFBs.

关键词： Mass transfer Simulation Turbulent fluidized bed Structure-based

A hydrodynamic model of loop seal with a fluidized standpipe for a circulating fluidized bed

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Particuology 2018年第1期16卷 50-58页

作者： Changjin Li zheng zou Hongzhong Li Qingshan Zhu State Key Laboratory of Multi-phase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Loop seals are among the most common non-mechanical valves used in circulating fluidized bed sys- tems. In the present work. a fundamental study is conducted of a fluidized loop seal, which consists of a fluidized standpipe, a fluidized supply chamber, and a fluidized recycling chamber. Based on the princi- ples of momentum, mass. and energy conservation, a hydrodynamic model for a loop seal is established, consisting of 13 equations. The effects of operating conditions such as the bottom aeration rate, total solid inventory, and fluidizing gas velocity in the riser on the solids flow rate and the performance of the loop seal are studied by a combination of model analysis and experiments. The experiments are carried out in a circulating fluidized bed with silica gel particles （Geldart group A）. The model predictions show good agreement with the experimental data.

关键词： Circulating fluidized bed Loop seal Hydrodynamic model

Detection time analysis for the multiple-user cooperative spectrum sensing scheme in cognitive radio networks

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Science in China(Series F) 2009年第10期52卷 1915-1925页

作者： ZHU Jia zheng BaoYu zou YuLong Institute of Signal Processing and Transmission Nanjing University of Posts and Telecomm Nanjing 210003 China

In this paper, a novel multiple-user cooperative spectrum sensing （MCSS） scheme is proposed to achieve the spatial diversity gains for cognitive radio （CR） networks, where only the best relay, selected among all the candidate relays in accordance with the quality of channel conditions, is utilized to cooperatively detect the primary user. Closed-form expressions of detection time for the traditional non-cooperative and the proposed MCSS schemes are derived over Rayleigh fading channels. In addition, numerical experimentations are conducted to make a performance comparison between the noncooperative sensing and our scheme. The result shows that by exploiting the multiple-user cooperation, the detection time is reduced greatly and moreover, diversity gains obtained by the MCSS scheme increase with a rise in the number of candidate relays.

关键词： cognitive radio networks multiple-user cooperation spectrum sensing cooperative diversity

Hydrodynamic behavior of magnetized fluidized beds with admixtures of Geldart-B magnetizable and nonmagnetizable particles

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Particuology 2016年第6期14卷 86-94页

作者： Quanhong Zhu Hongzhong Li Qingshan Zhu Jun Li zheng zou State Key Laboratory of Multi-phase Complex Systems Institute of Process Engineering Chinese Academy of Sciences. P.O. Box 353 Beijing 100190 China University of Chinese Academy ofSdences Beijing 100049 China

This work focuses on the hydrodynamic behavior of admixtures of Geldart-B magnetizable and non- magnetizable particles in a magnetized fluidized bed. The applied magnetic field was axial, uniform, and steady. In operating the beds, the magnetization-LAST mode was adopted under which four distinct flow regimes exist： fixed, magnetized-bubbling, partial segregation-bubbling, and total segregation-bubbling, The operational phase diagram was drawn to display the transitions between flow regimes in an intuitive manner. Only in the magnetized-bubbling regime could the magnetic field reduce the bubble size and improve fluidization quality. In the segregation-bubbling regimes, fluidization quality deteriorated as segregation developed. The segregation of the binary mixture was quantitatively studied by observing pressure drops in the local bed. Reasons for the improvement in fluidization quality as well as the occur- rence of segregation were analyzed. Furthermore. the flow regime transition under magnetization-LAST operation mode was different from that under magnetization-FIRST mode. The magnetically stabilized bed （MSB） flow regime, which could be easily created under magnetization-FIRST mode, could no longer be achieved under magnetization-LAST mode. With the admixture, the MSB was proved to be a metastable equilibrium state. Under the magnetization-LAST mode, the admixture bed reached directly the stable equilibrium state-bubbling with segregation.

关键词： Magnetized fluidized bed Admixture Magnetization-LAST Flow regime Hydrodynamic Segregation

GPU-based discrete element simulation on flow stability of flat-bottomed hopper

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Chinese Journal of Chemical Engineering 2018年第1期26卷 43-52页

作者： Li Peng zheng zou Libo Zhang Qingshan Zhu Hongzhong Li State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChineseAcademy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

In this study, the flow stability of the flat-bottomed hopper was investigated via GPU-based discrete element method(DEM) simulation. With the material height inside the hopper reducing, the fluctuation of the flow rate indicates an unstable discharge. The flow regions of the unstable discharge were compared with that of the stable discharge, a key transformation zone, where the voidage showed the largest difference between unstable and stable discharge, was revealed. To identify the relevance of the key transformation zone and the hopper flow stability, the voidage variation of the key transformation zone with material height reducing was studied.A sharp increase in the voidage in the key transformation zone was considered to be the standard for judging the unstable hopper flow, and the ‘Top–Bottom effect' of the hopper was defined, which indicated the hopper flow was unstable when the hopper only had the top area and the bottom area, because the voidage of particles in the top area and the bottom area were both variables.

关键词： Stability Discrete element method(DEM) Granular flow Top-Bottom effect Flow regions

Effect of antibacterial photodynamic therapy on Streptococcus mutans plaque biofilm in vitro

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Journal of Innovative Optical Health Sciences 2020年第6期3卷 36-46页

作者： Xiaoyue Liang Zhaohui zou zheng zou Changyi Li Xiaoxi Dong Huijuan Yin Guohui Yan Department of Endodontics Tianjin Medical University Stomatology Hospital Tianjin 300070 P.R.China Department of Prosthodontics Tianjin Medical University Stomatology Hospital Tianjin 300070 P.R.China Institute of Biomedical Engineering Chinese Academy of Medical Sciences&Peking Union Medical College Tianjin 300192 P.R.China

The main objective of this study is to evaluate the antibacterial effect of antibacterial pho-todynamic therapy(aPDT)on Streptococcus mutans(***)biofilm model in *** selection of photosensitizers is the key step for the efficacy of photodynamic therapy(PDT).However,no studies have been conducted in the oral field to compare the functional char-acteristics and application effects of PDT mediated by various *** this re-search,the antibacterial effect of Methylene blue(MB)/650 nm laser and Hematoporphyrin monomethyl ether(HMME)/532 nm laser on *** biofilm was compared under different energy densities to provide experimental reference for the clinical application of the two *** yield of lactic acid was analyzed by Colony forming unit(CFU)and spectrophotometry,and the complete biofilm activity was measured by Confocal Laser Scanning Microscopy(CLSM)to evaluate the bactericidal effect on each *** on the results of CFU,the bacterial colonies formed by 30.4J/cm^(2)532nm MB-aPDT group and 30.4J/cm^(2)532nm HMME-aPDT group were significantly less than those in other groups,and the bacterial colonies in HMME-aPDT group were less than those in HMME-aPDT *** acid production in all treatment groups except the photosensitizer group was statistically lower than that in the normal saline control *** activity of bacterial plaque biofilm was significantly decreased in the two groups treated with 30.4 J/cm^(2) ***,aPDT suitable for energy measurement can kill *** plaque biofilm,and MB-aPDT is better than HMME-aPDT.

关键词： Caries Methylene blue(MB) Hematoporyrin monomethyl Ether(HMME) laser antimicrobial photodynamic therapy(aPDT)

CFD simulation for reduction of pyrolusite in fluidized beds

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Particuology 2023年第8期79卷 109-120页

作者： Jingyi Zhu Qi Liu zheng zou Qingshan Zhu Hongzhong Li Haoran Li State Key Laboratory of Multi-phase Complex Systems Institute of Processing EngineeringChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China State Key Laboratory of Biochemical Engineering Institute of Processing EngineeringChinese Academy of SciencesBeijing100190China

In this study,a CFD model coupled with heterogeneous flow structure,mass transfer equations,and chemical reaction kinetics is established to forecast the pyrolusite reduction reaction *** with the previous studies which ignore the volume change of solids phase,the influence of volume shrinkage on reaction and flow behavior is explored in this *** shrinkage of pyrolusite is proved to be non-negligible in predicting the conversion *** negligence of volume shrinkage leads to the overestimation of conversion rate for its inaccurate estimation of surface area for ***,the influence of volume shrinkage on the reaction is found smaller in the scaled-up reactor.

关键词： Heterogeneous flow structure Chemical reaction kinetics CFD Bubbling fluidized bed Pyrolusite reduction reaction