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Numerical simulation on the multiphase flow and reoxidation of the molten steel in a two-strand tundish during ladle change

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1540-1553页

作者： Jingcheng Wang Zhentong Liu Wei Chen Hongliang Chen lifeng zhang School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Tianjin UniversityTianjin 300350China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

A 3D mathematical model was proposed to investigate the molten steel–slag–air multiphase flow in a two-strand slab continuous casting(CC)tundish during ladle change.The study focused on the exposure of the molten steel and the subsequent reoxidation occurrence.The exposure of the molten steel was calculated using the coupled realizable k–εmodel and volume of fluid(VOF)model.The diffusion of dissolved oxygen was determined by solving the user-defined scalar(UDS)equation.Moreover,the user-defined function(UDF)was used to describe the source term in the UDS equation and determine the oxidation rate and oxidation position.The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was also discussed.Increasing the refilling speed during ladle change reduced the refilling time and the exposure duration of the molten steel.However,the elevated refilling speed enlarged the slag eyes and increased the average dissolved oxygen content within the tundish,thereby exacerbating the reoxidation phenomenon.In addition,the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed.When the inlet speed was 3.0 m·s^(-1)during ladle change,the molten steel with a high dissolved oxygen content exited the outlet in a short period,reaching a maximum dissolved oxygen content of 0.000525wt%.Conversely,when the inlet speed was 1.8 m·s^(-1),the maximum dissolved oxygen content was 0.000382wt%.The refilling speed during the ladle change process must be appropriately decreased to minimize reoxidation effects and enhance the steel product quality.

关键词： tundish ladle change reoxidation multiphase flow numerical simulation

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Predictability of the 7·20 extreme rainstorm in Zhengzhou in stochastic kinetic-energy backscatter ensembles

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Science China Earth Sciences 2024年第7期67卷 2226-2241页

作者： Min YANG Peilong YU lifeng zhang Xiaobing PAN Quanjia ZHONG Yunying LI College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410073China Key Laboratory of High Impact Weather(Special) China Meteorological AdministrationChangsha 410073China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment ChangeNanjing University of Information Science and TechnologyNanjing 210044China Department of Ocean Science Hong Kong University of Science and TechnologyHong Kong 999077China

The scale-dependent predictability of the devastating 7·20 extreme rainstorm in Zhengzhou,China in 2021 was investigated via ensemble experiments,which were perturbed on different scales using the stochastic kinetic-energy backscatter(SKEB)scheme in the WRF model,with the innermost domain having a 3-km grid spacing.The daily rainfall(RAIN24h)and the cloudburst during 1600-1700 LST(RAIN1h)were considered.Results demonstrated that with larger perturbation scales,the ensemble spread for the rainfall maximum widens and rainfall forecasts become closer to the observations.In ensembles with mesoscale or convective-scale perturbations,RAIN1h loses predictability at scales smaller than 20 km and RAIN24h is predictable for all scales.Whereas in ensembles with synoptic-scale perturbations,the largest scale of predictability loss extends to 60 km for both RAIN1h and RAIN24h.Moreover,the average positional error in forecasting the heaviest rainfall for RAIN24h(RAIN1h)was 400 km(50-60)km.The southerly low-level jet near Zhengzhou was assumed to be directly responsible for the forecast uncertainty of RAIN1h.The rapid intensification in low-level cyclonic vorticity,mid-level divergence,and upward motion concomitant with the jet dynamically facilitated the cloudburst.Further analysis of the divergent,rotational and vertical kinetic spectra and the corresponding error spectra showed that the error kinetic energy at smaller scales grows faster than that at larger scales and saturates more quickly in all experiments.Larger-scale perturbations not only boost larger-scale error growth but are also conducive to error growth at all scales through a downscale cascade,which indicates that improving the accuracy of larger-scale flow forecast may discernibly contributes to the forecast of cloudburst intensity and position.

关键词： Stochastic kinetic-energy backscatter(SKEB) Extreme rainfall Ensemble forecast Predictability

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An analysis of air pollution associated with the 2023 sand and dust storms over China:Aerosol properties and PM_(10) variability

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Geoscience Frontiers 2024年第2期15卷 155-168页

作者： Mikalai Filonchyk Michael P.Peterson lifeng zhang Haowen Yan Faculty of Geomatics Lanzhou Jiaotong UniversityLanzhou 730070China Gansu Provincial Engineering Laboratory for National Geographic State Monitoring Lanzhou 730070China Department of Geography/Geology University of Nebraska OmahaOmahaNE 68182USA

Every spring,a large part of China is confronted with sand and dust storms(SDS)–mainly originating in the Gobi(including Chinese and Mongolian Gobi)and Taklamakan deserts.In March-April 2023,most of northern,northwestern and northeastern China was struck by three sandstorms that affected an area with more than 500 million people.In this study,aerosol optical,microphysical and radiative properties were studied during these SDS events using an integrated approach that combines satellite,terrestrial and re-analysis data.The results showed that dusty conditions were observed in most areas north of the Yangtze River(Chang Jiang)with daily average PM_(10)concentrations exceeding 1000 lg/m^(3) in many cities.VIIRS aerosol optical depth(AOD)at 550 nm during three SDS events exceeded a value of 1 throughout nearly the entire northern part of the country.The AERONET data obtained from the AOE_Baotou site showed a significant increase in total AOD and a corresponding decrease in AE during the SDS.The single scattering albedo(SSA),asymmetry parameter(ASY),real refractive index(RRI)and imaginary refractive index(IRI)values indicate an abundance of scattering coarse-mode particles.Aerosol radiative forcing(ARF)at top of the atmosphere and at the earth’s surface was nearly always negative during the period and ranged from48.5 to+2.7 Wm^(-2)and from180.8 to66.6 Wm^(-2),resulting in high positive ARF values at ATM(from+63.8 to+132.3 Wm^(-2)).Each of these affects the heating of the atmosphere and cooling on the earth’s surface.The atmospheric heating rates ranged from 1.8 to 3.7 K day1.The formation of these SDS mainly resulted from the passage of cold fronts associated with low pressure systems in the Gobi and Taklamakan deserts,creating conditions for dust to rise into the atmosphere and move further downwind.

关键词： Dust storm PM_(10) Aerosol optical depth Radiative forcing VIIRS AERONET

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Targeting the Warburg effect:A revisited perspective from molecular mechanisms to traditional and innovative therapeutic strategies in cancer

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Acta Pharmaceutica Sinica B 2024年第3期14卷 953-1008页

作者： Minru Liao Dahong Yao lifeng Wu Chaodan Luo Zhiwen Wang Jin zhang Bo Liu Department of Biotherapy Cancer Center and State Key Laboratory of BiotherapyWest China HospitalSichuan UniversityChengdu 610041China School of Pharmaceutical Sciences Shenzhen Technology UniversityShenzhen 518118China School of Pharmacy Shenzhen University Medical SchoolShenzhen UniversityShenzhen 518055China Department of Psychology University of Southern CaliforniaLos AngelesCA 90089USA

Cancer reprogramming is an important facilitator of cancer development and survival,with tumor cells exhibiting a preference for aerobic glycolysis beyond oxidative phosphorylation,even under sufficient oxygen supply condition.This metabolic alteration,known as the Warburg effect,serves as a significant indicator of malignant tumor transformation.The Warburg effect primarily impacts cancer occurrence by influencing the aerobic glycolysis pathway in cancer cells.Key enzymes involved in this process include glucose transporters(GLUTs),HKs,PFKs,LDHs,and PKM2.Moreover,the expression of transcriptional regulatory factors and proteins,such as FOXM1,p53,NF-κB,HIF1a,and c-Myc,can also influence cancer progression.Furthermore,lncRNAs,miRNAs,and circular RNAs play a vital role in directly regulating the Warburg effect.Additionally,gene mutations,tumor microenvironment remodeling,and immune system interactions are closely associated with the Warburg effect.Notably,the development of drugs targeting the Warburg effect has exhibited promising potential in tumor treatment.This comprehensive review presents novel directions and approaches for the early diagnosis and treatment of cancer patients by conducting in-depth research and summarizing the bright prospects of targeting the Warburg effect in cancer.

关键词： Warburg effect Cancer Regulatory factor LncRNAs miRNAs Traditional Chinese medicine Small-molecule drug Drug resistance

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Effect of oxide inclusions on MnS precipitates and tensile mechanical property of high-strength low-alloy steel

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Journal of Iron and Steel Research(International) 2024年第5期31卷 1210-1220页

作者： Xiao-yong Gao Hong Wei Li-feng zhang School of Mechanical Engineering Yanshan UniversityQinhuangdao066004HebeiChina School of Materials Science and Engineering Yanshan UniversityQinhuangdao066004HebeiChina School of Mechanical and Materials Engineering North China University of TechnologyBeijing100144China

The key role of oxide inclusions on the microstructure and mechanical property of a high-strength low-alloy steel was investigated.The field emission scanning electron microscope equipped with energy-dispersive spectrometry was used to characterize MnS precipitates.Oxide inclusions play an important role in the shape control of MnS precipitates.More oxides fovored to decrease the size and the aspect ratio of MnS precipitates.With less oxide inclusions in the steel,approximately over 16.7%MnS precipitates were with aspect ratio a>5 and pure MnS precipitates accounted for 75.9%in number.However,with more oxide inclusions in the steel,only 7.4%MnS precipitates were with a>5 and pure MnS precipitates accounted for 60.1%in number.Refinement of MnS by oxide inclusions improved the strength and inhibited the anisotropy.More oxide inclusions in the steel increased the yield strength and tensile strength of the steel in both longitudinal and transverse directions,and lowered the anisotropy of the mechanical property.

关键词： High-strength low-alloy steel MnS Oxide inclusion Mechanical property Anisotropy

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Mechanistic investigation on Ag-Cu_(2)O in electrocatalytic CO_(2) to CH_(4) by in situ/operando spectroscopic and theoretical analysis

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Journal of Energy Chemistry 2024年第1期88卷 521-531,I0012页

作者： Min Sun Luxiao zhang Fuli Tian Jiaxin Li Yanqiu Lei Heng zhang lifeng Han Zhihua Guo Yonghui Gao Fenrong Liu Yan Wang Luhui Wang Shanghong Zeng School of Chemistry and Chemical Engineering Inner Mongolia UniversityHohhot 010021Inner MongoliaChina Key Laboratory of Medicinal and Edible Plants Resources of Hainan Province Hainan Vocational University of Science and TechnologyHaikou 571126HainanChina State Key Laboratory of Baiyunobo Rare Earth Resource Research and Comprehensive Utilization Baotou Research Institute of Rare EarthsBaotou 014030Inner MongoliaChina Zhejiang Key Laboratory of Petrochemical Environmental Pollution Control Zhejiang Ocean UniversityZhoushan 316022ZhejiangChina

Silver-copper electrocatalysts have demonstrated effectively catalytic performance in electroreduction CO_(2) toward CH_(4),yet a revealing insight into the reaction pathway and mechanism has remained elusive.Herein,we construct chemically bonded Ag-Cu_(2)O boundaries,in which the complete reduction of Cu_(2)O to Cu has been strongly impeded owing to the presence of surface Ag shell.The interfacial confinement effect helps to maintain Cu^(+)sites at the Ag-Cu_(2)O boundaries.Using in situ/operando spectroscopy and theoretical simulations,it is revealed that CO_(2) is enriched at the Ag-Cu_(2)O boundaries due to the enhanced physisorption and chemisorption to CO_(2),activating CO_(2) to form the stable intermediate^(*)CO.The boundaries between Ag shell and the Cu_(2)O mediate local^(*)CO coverage and promote^(*)CHO intermediate formation,consequently facilitating CO_(2)-to-CH_(4) conversion.This work not only reveals the structure-activity relationships but also offers insights into the reaction mechanism on Ag-Cu catalysts for efficient electrocatalytic CO_(2) reduction.

关键词： Ag shell Interfacial confinement effect Cu~+ Local*CO coverage CO_(2)reduction

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Influence of substituting B_(2)O_(3) with Li_(2)O on the viscosity,structure and crystalline phase of low-reactivity mold flux

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International Journal of Minerals,Metallurgy and Materials 2023年第7期30卷 1320-1328页

作者： Rongzhen Mo Xubin zhang Ying Ren Junjie Hu lifeng zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Lecture at College of Materials Science and Engineering Chongqing UniversityChongqing 400030China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

The low-reactivity mold flux with low SiO_(2)content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO_(2)in mold flux.However,the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency.In this study,the co-addition of Li_(2)O and B_(2)O_(3)in CaO–Al_(2)O_(3)–10wt%Si O_(2)based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel,and the effect of Li_(2)O replacing B_(2)O_(3)on properties of mold flux was investigated.The viscosity of the mold flux with 2wt%Li_(2)O and 6wt%B_(2)O_(3)reached a minimum value of 0.07 Pa·s.The break temperature and melting point showed a similar trend with the viscosity.Besides,the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity.It demonstrated that with increasing Li_(2)O content in the mold flux from 0 to 6 wt%,the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li+released by Li_(2)O,indicating the added Li_(2)O was preferentially associated with Al^(3+)as a charge compensator.The precipitation of LiAlO_(2)crystalline phase gradually increased with the replacement of B_(2)O_(3)by Li_(2)O.Therefore,Li_(2)O content should be controlled below 2wt%to avoid LiAlO_(2)precipitation,which was harmful to the continuous casting of highaluminum steels.

关键词： low-reactivity mold flux viscosity structure crystalline phase

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Mathematical simulation of hot metal desulfurization during KR process coupled with an unreacted core model

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International Journal of Minerals,Metallurgy and Materials 2022年第4期29卷 758-766页

作者： Yanyu Zhao Wei Chen Shusen Cheng lifeng zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

A three-dimensional mathematical model was established to predict the multiphase flow,motion and dispersion of desulfurizer particles,and desulfurization of hot metal during the Kanbara reactor(KR)process.The turbulent kinetic energy-turbulent dissipation rate(k-ε)turbulence model,volume-of-fluid multiphase model,discrete-phase model,and unreacted core model for the reaction between the hot metal and particles were coupled.The measured sulfur content of the hot metal with time during the actual KR process was employed to validate the current mathematical model.The distance from the lowest point of the liquid level to the bottom of the ladle decreased from 3170 to2191 mm when the rotation speed increased from 30 to 110 r/min,which had a great effect on the dispersion of desulfurizer particles.The critical rotation speed for the vortex to reach the upper edge of the stirring impeller was 70 r/min when the immersion depth was 1500 mm.The desulfurization rate increased with the increase in the impeller rotation speed,whereas the influence of the immersion depth was relatively small.Formulas for different rotation parameters on the desulfurization rate constant and turbulent energy dissipation rate were proposed to evaluate the variation in sulfur content over time.

关键词： desulfurization unreacted core model desulfurizer dispersion KR process fluid flow

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In situ observation of the dissolution kinetics of Al_(2)O_(3) particles in CaO–Al_(2)O_(3)–SiO_(2) slags using laser confocal scanning microscopy

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International Journal of Minerals,Metallurgy and Materials 2023年第2期30卷 345-353页

作者： Changyu Ren Caide Huang lifeng zhang Ying Ren School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004China Shougang Jingtang United Iron and Steel Co. Ltd.Tangshan 063200China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.

关键词： inclusion dissolution kinetics confocal scanning laser microscope refining slag

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Precise control of Pt encapsulation in zeolite-based catalysts for a stable low-temperature CO oxidation reaction

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Science China Chemistry 2022年第10期65卷 2015-2022页

作者： Yatian Liu lifeng zhang Zejian Dong Langli Luo Institute of Molecular Plus Tianjin UniversityTianjin 300072China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China

Metal–zeolite catalysts are vital in chemical and fuel production for their great stability,stereo-selectivity,and atom economy.When metal species keep shrinking their sizes to the subnanometer region,their spatial distribution in the zeolite framework/channels could have a great impact on their catalytic performance.Here,we precisely control the Pt species loaded on a silicalite-1 zeolite and characterize their structural status to the catalytic performance for CO oxidation.We find that Pt species exits as few-atom clusters encapsulated in the channels and destructively embedded Pt nanoparticles in the framework,besides the conventional surface-supported Pt.By utilizing effective Pt sites and limiting their sizes in the zeolite,we can maximize the catalytic CO oxidation performance of 1 at.% Pt-loaded zeolite catalysts to achieve a T100 as low as 90 ℃ and a stable reaction above 216 h.

关键词： zeolites encapsulation CO oxidation Pt atomic scale

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