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Numerical investigation of breakup process of molten blast furnace slag through air quenching dry granulation technique

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Journal of Iron and Steel Research International 2021年第1期28卷 10-18页

作者： Li-li Wang yu-zhu zhang yue Long College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063210HebeiChina

Molten slag is broken up by supersonic air into droplets through the air quenching dry slag granulation *** breakup process of blast furnace slag directly determines the droplet diameter and the waste heat *** order to gain deep insight into the granulation mechanism and visualize the breakup process,three-dimensional unsteady numerical simulation based on the k-x based shear stress transport turbulence model was conducted to simulate the transient breakup process of molten slag(k is the turbulent kinetic energy,and x is the specific dissipation rate).The coupled level-set and volume-of-fluid method was utilized to capture the sharp air–liquid *** results show that a flat film is formed firstly under the effects of air impingement,recirculation zone and pressure ***,the axial wave and the spanwise wave appear simultaneously and the film is broken up into ligaments owing to the generation of vortex and hole structure at the intersection of axial trough and spanwise ***,the ligaments are broken up into droplets owing to Rayleigh–Taylor instability at the air–liquid *** droplets smaller than 3.00 mm account for 80%,with the average diameter of 1.95 mm.

关键词： Breakup process Granulation mechanism Molten slag Air quenching Computational fluid dynamics

Crystallization behavior of blast-furnace slag by single hot thermocouple technique

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Journal of Iron and Steel Research International 2020年第3期27卷 259-265页

作者： Tie-lei Tian Shuang Cai yu-zhu zhang Hong-wei Xing College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063009HebeiChina College of Mechanical Engineering Yanshan UniversityQinhuangdao 066004HebeiChina

The crystallization behavior of blast-furnace slag under isothermal and continuous-cooling conditions was studied using the single hot thermocouple *** crystallization phases were obtained using FactSage software and X-ray *** crystallization kinetic parameters were calculated by combining these results with the Johnson-Mehl—Avrami *** isothermal conditions,the shortest crystallization incubation time was 24 and 18 s when the temperatures were 1300 and 1150℃,and the corresponding critical cooling rates were 4.5 and 14.3℃/s,*** 1270℃,the slag was difficult to crystallize and the fiber-forming rate *** the continuous-cooling rate was 6.5℃/s,the slag solidified into a glassy *** main crystallization phases,gehlenite,akermanite,anorthite,and melangite,were most easily *** growth factors of melangite and anorthite were approximately 1.63 and 1.68,respectively,which indicated that the crystals nucleated on the surface and grew in two dimensions.

关键词： Blast-furnace slag Cooling rate Crystallization Single hot thermocouple technique

Topological Stability and Entropy for Certain Set-valued Maps

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Acta Mathematica Sinica,English Series 2024年第4期40卷 962-984页

作者： yu zhang yu Jun zhu School of Mathematical Sciences Xiamen UniversityXiamen 361005P.R.China

In this paper,the dynamics(including shadowing property,expansiveness,topological stability and entropy)of several types of upper semi-continuous set-valued maps are mainly considered from differentiable dynamical systems points of *** is shown that(1)if f is a hyperbolic endomorphism then for eachε>0 there exists a C^(1)-neighborhood U of f such that the induced set-valued map F_(f,U)has theε-shadowing property,and moreover,if f is an expanding endomorphism then there exists a C^(1)-neighborhood U of f such that the induced set-valued map F_(f,U)has the Lipschitz shadowing property;(2)when a set-valued map F is generated by finite expanding endomorphisms,it has the shadowing property,and moreover,if the collection of the generators has no coincidence point then F is expansive and hence is topologically stable;(3)if f is an expanding endomorphism then for eachε>0 there exists a C^(1)-neighborhood U of f such that h(F_(f,U,ε))=h(f);(4)when F is generated by finite expanding endomorphisms with no coincidence point,the entropy formula of F is ***,the dynamics of the set-valued maps based on discontinuous maps on the interval are also considered.

关键词： Set-valued map orbit space hyperbolic endomorphism perturbation shadowing expansiveness topological stability entropy

近20年中医药治疗功能性便秘研究现况可视化分析

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世界中西医结合杂志 2024年第1期19卷 60-67,71页

作者：曹巍巍李鹏朱煜璋郭修田上海中医药大学附属市中医医院肛肠科上海200071

目的了解近20年中医药治疗功能性便秘(Functional constipation,FC)的研究现状、前沿、趋势。方法计算机检索中国知识资源总库(CNKI)、中国学术期刊数据库(万方数据)2000年1月1日—2021年12月31日期间治疗FC文献。采用VOSviewer 1.6.18... 详细信息

目的了解近20年中医药治疗功能性便秘(Functional constipation,FC)的研究现状、前沿、趋势。方法计算机检索中国知识资源总库(CNKI)、中国学术期刊数据库(万方数据)2000年1月1日—2021年12月31日期间治疗FC文献。采用VOSviewer 1.6.18软件行作者合作网络和关键词共现分析;使用CiteSpace 5.8.R3行关键词聚类、时间线图和突现分析,了解该领域研究热点和趋势。结果共检索到2986篇相关文献,人工筛选,剔除重复文献1098篇,共纳入1888篇文献,共得出3569位作者,2037个关键词,设置作者及关键词出现频率的阈值为5,共有167个结果高于阈值,利用CiteSpace软件对关键词进行聚类。要求每个聚类至少有10个以上节点,共得到9个聚类。结论过去20年,中医药领域的FC文献年发文量总体呈上升—波动—下降的变化趋势。2000—2010年这10年中,关于FC研究的文献呈快速增长的趋势。肠道菌群、血清P物质(Substance p,SP)、血管活性肠肽(Vasoactive intestinal peptide,VIP)、一氧化氮(Nitric oxide,NO)、针灸推拿、儿童FC等是最近5年研究的趋势热点。

关键词：功能性便秘中医药可视化分析 VOSviewer CiteSpace

Microstructure Variation of Pellets Containing Ferrous Dust during Carbonation Consolidation

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Journal of Iron and Steel Research International 2015年第2期22卷 128-134页

作者： Yan SHI Shi-meng LIU Chang-qing HU yu-zhu zhang College of Material and Metallurgy Northeastern University Hebei Key Laboratory of Modern Metallurgy Technology Hebei United University

The carbonation and microstructure characteristics of pellets containing ferrous dusts were investigated during carbonation consolidation at differem reaction temperatures and CO2 partial pressures. The results indicated that green pellets had loose and network supporting structure with initial strength, and large cracks and pores existed in the pellets. The carbonation reaction was controlled by interracial chemical reaction at the initial fast stage, which limited diffusion and thus caused the reaction rate to decrease. With increasing reaction temperature and CO2 partial pressure, the conversion rates of CaO and the number of microcrystalline CaCO3 particles increased, and the volume expansion of CaCO3 led to a decrease in the open porosity, average pore size and specific surface area of the pellets. Micro pores were occluded, and the number of smaller pores （diameter less than 50 nm） increased, thereby resulting in the more compact and uniform structure of carbonated pellets. Simuhaneously, the dense structure prevented CO2 diffusion into the product layer, affecting the increase in carbonation conversion rate.

关键词： ferrous dust microstructure CaO conversion rate carbonated pellet green pellet

Properties of ten-year-aged argon oxygen decarburization stainless steel slag

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Journal of Iron and Steel Research International 2021年第10期28卷 1233-1242页

作者： Ya-jun Wang Ya-nan Zeng Jun-guo Li yu-zhu zhang Wei Wang College of Metallurgy and Energy North China University of Science and TechnologyTangshan063210HebeiChina School of Metallurgy Northeastern UniversityShenyang110819LiaoningChina

The characteristics of argon oxygen decarburization slag(AODS)for smelting stainless steel that has been aged for 10 years were *** types of AODSs distributed at three positions in a slag heap were sampled for comparison *** analysis,mineral phase identification,thermogravimetric analysis,and micromorphology analysis were used to study the element migration trends and carbonation behavior of AODS after long-term *** leaching tests were performed to study the chromium leachability of the aged *** results show that during the long-term aging process,the AODS heap had undergone oxidation and carbonation,accompanied by element migration and mineralogical *** surface slag had the highest degree of carbonation but the weakest chromium *** chemical composition of the middle slag was the closest to that of the original *** the bottom steel slag,in addition to magnesium,certain depositions of other elements were *** matrix phases in the aged slag were dicalcium silicate and merwinite,and the chromium was mainly wrapped in these matrix phases in the form of oxides,spinels,or *** the combined effects of carbonation and oxidation,the leaching characteristics of the chromium in the aged slag varied greatly depending on the *** bottom slag had the strongest chromium leachability,and the hexavalent chromium had long-term continuous leachability.

关键词： Argon oxygen decarburization slag Aging Chromium Leaching Mineral phase

Preparation and Metallurgical Analysis of High Activity Burnt Lime for Steelmaking

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Journal of Iron and Steel Research International 2016年第9期23卷 884-890页

作者： Hua-qiang HAO yu-zhu zhang Su-ju HAO Chao-fa zhang Wu-feng JIANG Peng-hui CUI College of Metallurgy Northeastern University Department of Long Product Tangshan Iron and Steel CompanyHebei Iron and Steel Group College of Metallurgy & Energy Key Laboratory of the Ministry of Education for Modern Metallurgy TechnologyNorth China University of Science and Technology

Burnt lime is an important material in steelmaking and its activity degree is a key factor for liquid steel quality. The burnt lime was made by the calcination of limestone in a high pressure electric furnace. The burnt lime mineralogical phases and micro-morphologies were characterized by X-ray diffraction （XRD） and field emission scan- ning electron microscopy （FE-SEM）. The burnt lime activity degree was determined by acid-base titration, the burnt lime pore distribution was measured by mercury intrusion porosimetry （MIP）, and the thermal effect of a mixture of burnt lime and slag was measured by differential scanning calorimetry （DSC）. The results showed that the CaO grain size and pore size of burnt lime made under high pressure were larger than those of burnt lime made under atmos- pheric pressure. The CaO grain size and pore size increased and the laminate phenomenon also occurred clearly under high pressure. The activity degree of burnt lime made under high pressure was greater than that made under atmos- pheric pressure. The maximum activity degree was 437 mL for burnt lime made under a pressure of 0.4 MPa. For the same ratio of CaO to SiOz, the melting temperature, hemisphere temperature and fluidity temperature of slag decreased with increasing burnt lime activity degree. The higher the activity degree the burnt lime had, the better the slag forming occurred. It was advantageous for -2CaO · SiO2 and 3CaO · SiO2 forming at lower temperatures if the burnt lime activity degree was increased.

关键词： burnt lime high pressure calcination activity degree physical property slag performance

Cascade model for continuous prediction of silicon content of molten iron with coupled state variable nodes

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Journal of Iron and Steel Research International 2023年第5期30卷 897-914页

作者： Yang Han Ze-qian Cui Li-jing Wang Jie Li Ai-min Yang yu-zhu zhang Hebei Engineering Research Center for the Intelligentization of Iron Ore Optimization and Ironmaking Raw Materials Preparation Processes North China University of Science and TechnologyTangshan 063210HebeiChina College of Metallurgy and Energy North China University of Science and TechnologyTangshan 063210HebeiChina

With the goal of achieving advanced and multi-step prediction of silicon content of molten iron in the blast furnace ironmaking process,a path adaptive optimization seeking strategy coupled with simulated annealing algorithm and genetic algorithm was proposed from the perspective of innovative intelligent algorithm *** was further coupled with wavelet neural network algorithm to deeply explore the nonlinear and strong coupling relationship between the information of big data samples and construct a cascade model for continuous prediction of silicon content of molten iron with the intelligent research results of state variables such as permeability index as the node and silicon content forecast as the *** the model construction process,the 3r criterion was used for non-anomaly estimation of abnormal data to build a time-aligned sample set for multi-step forecasting of iron content,the normalization method was used to eliminate the influence of dimensionality of sample information,and the spearman correlation analysis algorithm was used to eliminate the time delay between state variables,control variables,and silicon content of molten iron in the blast furnace smelting *** results show that permeability and theoretical combustion temperature as the key state variable nodes have real-time correlation with the silicon content of molten iron,and there are accurate forecasting results on the optimal path with the endpoint of molten iron silicon content *** path finding based on the improved genetic algorithm of simulated annealing has good effect on the downscaling and depth characterization of sample data and improves the data ecology for the application of wavelet neural network *** accuracy of the real-time continuous forecasting model for the silicon content of molten iron reaches 95.24%;the hit rate of continuous forecasting one step ahead reaches 91.16%,and the hit rate of continuous forecasting five steps ahead is 87.41

关键词： Silicon content Molten iron Optimal path State variable node Wavelet neural network Step-by-step prediction

Influence of Cohesive Zone Shape on Solid Flow in COREX Melter Gasifier by Discrete Element Method

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Journal of Iron and Steel Research International 2015年第4期22卷 304-310页

作者： Li-hao HAN Zhi-guo LUO Heng ZHOU Zong-shu ZOU yu-zhu zhang School of Materials and Metallurgy Northeastern University College of Metallurgy and Energy Hebei United University

Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the co- hesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main re- gions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increa- ses. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.

关键词： COREX melter gasifier discrete element method porosity distribution cohesive zone shape solid flow