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Pre-reduction of WO_(3)-Co_(3)O_(4)by H_(2)-C_(2)H_4 in a fluidized bed

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Chinese Journal of Chemical Engineering 2024年第2期66卷 273-284页

作者： Huijun Shang Hengli li weijun li Feng Pan Zhan Du State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences(CAS)Beijing 100190China College of Chemical Engineering Nanjing Technology UniversityNanjing 211816China School of Chemistry and Chemical Engineering Shihezi UniversityShihezi 832003China College of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Chinalco Environmental Protection and Energy Conservation Group Co. Ltd.Xiong’an 071700China

In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been *** study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon *** results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are *** pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)

关键词： Fluidization WO_(3)-Co_(3)O_(4) Reduction Carbon deposition Rate equation

Integration of HAZOP and Bayesian network in city gas explosion emergency response processes

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Emergency Management Science and Technology 2022年第1期2卷 167-175页

作者： Peng Gao weijun li College of Safety and Environmental Engineering Shandong University of Science and TechnologyQingdao 266590ShandongChina

City gas explosion accidents have occurred frequently in recent years,leading to major injuries and *** effective emergency response process is necessary to deal with city gas accidents by preventing them from expanding and reducing ***,emergency response is a complex process that includes many contributing factors,such as personnel,departments,and *** one or more of these factors fails,it will affect the implementation of the emergency ***,more efforts should be made on the systematic procedures and methods addressing risks in emergency response *** the view of Process Hazard Analysis(PHA),the emergency response process can be seen as a work process with many operation *** this sense,PHA methods such as HAZOP can be used for the risk analysis of the emergency response ***,the emergency response process of a city gas explosion accident is broken down into procedure-based *** HAZOP is used to comprehensively review the process and obtain deviations,causes,and consequences,which are considered as risk ***,Bayesian networks are used to characterize the inter relationships of various factors and quantify the risk of the emergency response ***,the most critical events can be identified based on the sensitivity *** results show that firefighters'operations,management of the emergency command center,and environmental conditions on site are critical factors during city gas explosion *** method proposed can help identify potential risks of the emergency response process systematically and prevent accident expansion.

关键词： operations HAZOP explosion

Mineralogical characteristics of airborne particles collected in Beijing during a severe Asian dust storm period in spring 2002

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Science China Earth Sciences 2007年第6期50卷 953-959页

作者： SHAO LongYi li weijun YANG ShuShen SHI ZongBo LÜ Senlin The State Key Laboratory of Coal Resources and Safety Mining China University of Mining and TechnologyBeijing 100083China Department of Resources and Earth Sciences China University of Mining and TechnologyBeijing 100083China Faculty of Environmental and Symbiotic Sciences Prefectural University of KumamotoKumamoto 862-8502Japan

Asian dust storm (ADS) samples were collected on March 20,2002 in Beijing,China. High-resolution field emission scanning electron microscopy with energy dispersive X-ray detector (FESEM-EDX) and X-ray diffraction (XRD) were used to study the morphology,chemical compositions,number-size dis-tributions and mineralogical compositions of ADS particles. The mineral particles were major compo-nents in the ADS samples,accounting for 94% by number. The XRD analysis indicated that the dust particles were dominated by clay (40.3%),and quartz (19.5%),followed by plagioclase (8.4%),calcite (7.5%),K-feldspar (1.5%),hematite (0.9%),pyrite (0.9%),hornblende (0.4%) and gypsum (0.3%),with a certain amount of noncrystalline materials (20.3%). Clay minerals were mainly illite/smectite mixed lay-ers (78%),followed by illite (9%),kaolinite (6%),and chlorite (7%). In addition to these main minerals,FESEM-EDX also detected some trace minerals,such as dolomite,pyrite,thenardite,as well as heavy minerals represented by rutile,ilmenite and apatite. The mineralogical compositions of the 2002-03-20 Asian dust storm and the Saharan dust plumes were similar but the clay mineralogy showed a great distinction,with the illite/smectite mixed layers being common in the Asian dust storm but illite being common in the Saharan dust plumes.

关键词： Asian dust storm (ADS) inhalable particle (PM10) X-ray diffraction (XRD) individual particles analysis Beijing

Size,composition,and mixing state of individual aerosol particles in a South China coastal city

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Journal of Environmental Sciences 2010年第4期22卷 561-569页

作者： weijun li Longyi Shao Zhishi Wang Rongrong Shen Shusheng Yang Uwa Tang State Key Laboratory of Coal Resources and Safe Mining College of Geoscience and Surveying Engineering China University of Mining and Technology (Beijing) Beijing 100083 China. Faculty of Science and Technology University of Macao Macao China Environment Research Institute Shandong University Shandong 250100 China

Aerosol samples were collected in summer in Macao, a coastal city of the Pearl River Delta Region in China. Morphology, size, elemental composition, and mixing state of individual aerosol particles were determined by scanning electron microscopy coupled energy dispersive X-ray （SEM/EDX） and transmission electron microscopy （TEM）. Based on the morphologies of 5711 aerosol particles, they consist of soot （32%）, mineral （17%）, secondary-（22%）, and unknown fine particles （29%）. The sizes of these particles were mostly distributed between 0.1 and 0.4 μm. Compositions of 202 mineral particles were obtained by SEM/EDX. Mineral particles were mainly classified into three types： Si-rich, Ca-rich, and Na-rich. The compositions of typical mineral particles can indicate their sources in sampling location. For example, mineral particles, collected along the main street, were associated with trace amounts of heavy metals, such as Zn, Ti, Mn, Ba, Pb, and As. TEM observations indicate that most Na-rich particles were aged sea salt particles （e.g., Na2SO4 and NaNO3） which formed through heterogeneous chemical reactions between sea salt and acidic gases. Additionally, aging time of soot was short in Macao due to high humidity, high temperature, and high levels of sunlight in Macao. Most of soot and fine mineral dust particles were internally mixed with secondary particles.

关键词： individual aerosol particles soot heterogeneous reaction sea salt

Trace metals in atmospheric fine particles in one industrial urban city: Spatial variations, sources, and health implications

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Journal of Environmental Sciences 2014年第1期26卷 205-213页

作者： Shengzhen Zhou Qi Yuan weijun li Yaling Lu Yangmei Zhang Wenxing Wang Environment Research Institute Shandong University State Key Laboratory of Coal Resources and Safe Mining China University of Mining & Technology Chinese Academy of Meteorological Sciences China Meteorological Administration

Trace metals in PM2.5 were measured at one industrial site and one urban site during September, 2010 in Ji＇nan, eastern China. Individual aerosol particles and PM2.5 samples were collected concurrently at both sites. Mass concentrations of eleven trace metals （i.e., Al, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, and Pb） and one metalloid （i.e., As） were measured by inductively coupled plasma atomic emission spectroscopy （ICP-AES）. The result shows that mass concentrations of PM2.5 （130μg/m3） and trace metals （4.03 μg/m3） at the industrial site were 1.3 times and 1.7 times higher than those at the urban site, respectively, indicating that industrial activities nearby the city can emit trace metals into the surrounding atmosphere. Fe concentrations were the highest among all the measured trace metals at both sites, with concentrations of 1.04 ixg/m 3 at the urban site and 2.41 Itg/m3 at the industrial site, respectively. In addition, Pb showed the highest enrichment factors at both sites, suggesting the emissions from anthropogenic activities existed around the city. Correlation coefficient analysis and principal component analysis revealed that Cu, Fe, Mn, Pb, and Zn were originated from vehicular traffic and industrial emissions at both sites; As, Cr, and part of Pb from coal-fired power plant; Ba and Ti from natural soil. Based on the transmission electron microscopy analysis, we found that most of the trace metals were internally mixed with secondary sulfate/organic particles. These internally mixed trace metals in the urban air may have different toxic abilities compared with externally mixed trace metals.

关键词： trace metals PM2.5 enrichment factors principal component analysis (PCA) industrial sources

High-performance supercapacitors based on free-standing SiC@PEDOT nanowires with robust cycling stability

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Journal of Energy Chemistry 2022年第3期31卷 30-37,I0002页

作者： Wenna liu Xiaoxiao li weijun li Yumin Ye Hong Wang Peipei Su Weiyou Yang Ya Yang Ningbo Key Laboratory of Specialty Polymers School of Materials Science and Chemical EngineeringNingbo UniversityNingbo 315211ZhejiangChina Institute of Materials Ningbo University of TechnologyNingbo 315016ZhejiangChina CAS Center for Excellence in Nanoscience Beijing Key Laboratory of Micro-nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 101400China

Conductive polymers as one of the candidate materials with pseudocapacitor behavior have inspired wide attentions,because of their high conductivity,fexibility,low cost and excellent ***,the intrinsically poor cycling stability induced by the volume change over the doping/dedoping redox process limits their practical ***,we report the exploration of electrodes with robust cycling capacity for supercapacitors(SCs),which are rationally designed by coating conductive poly(3,4-ethylenedioxythiophene)(PEDOT)around free-standing SiC nanowires using an all-dry oxidative chemical vaper deposition(oCVD)*** as-constructed SiC@PEDOT nanowire architecture enables a specific capacitance of 26.53 m F/cm^(2)at 0.2 m A/cm^(2),which is~370%to that of SiC nanowire counterpart(7.04 m F/cm^(2)).Moreover,their aqueous-based SCs exhibit robust cycling stability with104%capacity retention after 10000 cycles,which is among the highest values achieved for PEDOTbased SCs.

关键词： PEDOT SiC nanowires Supercapacitor Energy storage Cycling stability

Introduction to the special issue on “COVID-19”

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Geoscience Frontiers 2022年第6期13卷 208-209页

作者： Luis F.O.Silva weijun li Teresa Moreno Department of Civil and Environmental Universidad de la CostaCUC Department of Atmospheric Sciences School of Earth SciencesZhejiang University Institute for Environmental Assessment and Water Research Consejo Superior de Investigaciones Científicas

COVID-19 pandemic is wreaking havoc and bringing the whole world into a standstill in an unprecedented fashion. Joint efforts from multiple sectors to address the various aspects of environment and public health through usage of green technologies have become essential. The application of cleaner and effective technologies can be expanded to management and control, pollution mitigation and valorization of waste. In this Special Issue of Geoscience Frontiers, we present contributions addressing the interactions of COVID-19 in relation to environment and human health.

关键词： bringing expanded COV

Learning to represent 2D human face with mathematical model

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CAAI Transactions on Intelligence Technology 2024年第1期9卷 54-68页

作者： liping Zhang weijun li linjun Sun lina Yu Xin Ning Xiaoli Dong AnnLab Institute of SemiconductorsChinese Academy of SciencesBeijingChina Center of Materials Science and Optoelectronics Engineering School of Integrated CircuitsUniversity of Chinese Academy of SciencesBeijingChina Beijing Key Laboratory of Semiconductor Neural Network Intelligent Sensing and Computing Technology BeijingChina

How to represent a human face pattern?While it is presented in a continuous way in human visual system,computers often store and process it in a discrete manner with 2D arrays of *** authors attempt to learn a continuous surface representation for face image with explicit ***,an explicit model(EmFace)for human face representation is pro-posed in the form of a finite sum of mathematical terms,where each term is an analytic function ***,to estimate the unknown parameters of EmFace,a novel neural network,EmNet,is designed with an encoder-decoder structure and trained from massive face images,where the encoder is defined by a deep convolutional neural network and the decoder is an explicit mathematical expression of *** authors demonstrate that our EmFace represents face image more accurate than the comparison method,with an average mean square error of 0.000888,0.000936,0.000953 on LFW,IARPA Janus Benchmark-B,and IJB-C *** results show that,EmFace has a higher representation performance on faces with various expressions,postures,and other ***,EmFace achieves reasonable performance on several face image processing tasks,including face image restoration,denoising,and transformation.

关键词： artificial neural networks face analysis image processing mathematics computing

Multi-objective optimization of methane production system from biomass through anaerobic digestion

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Chinese Journal of Chemical Engineering 2018年第10期26卷 2084-2092页

作者： weijun li Jakob Kj?bsted Huusom Zhimao Zhou Yi Nie Yajing Xu Xiangping Zhang Beijing Key Laboratory of Ionic liquids Clean Process State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Sino-Danish Center for Education and Research University of Chinese Academy of Sciences Department of Chemical & Biochemical Engineering Technical University of Denmark

This work addressed the multi-objective optimization of a biogas production system considering both environmental and economic criteria. A mixed integer non-linear programming(MINLP) model was established and solved with non-dominated sorting genetic algorithm Ⅱ, from which the Pareto fronts, the optimal technology combinations and operation conditions were obtained and analyzed. It's found that the system is feasible in both environmental and economic considerations after optimization. The most expensive processing section is decarbonization; the most expensive equipment is anaerobic digester; the most power-consuming processing section is digestion, followed by decarbonization and waste management. The positive green degree value on the process is attributed to processing section of digestion and waste management. 3:1 chicken feces and corn straw, solar energy, pressure swing adsorption and 3:1 chicken feces and rice straw, solar energy, pressure swing adsorption are turned out to be two robust technology combinations under different prices of methane and electricity by sensitivity analysis. The optimization results provide support for optimal design and operation of biogas production system considering environmental and economic objectives.

关键词： Biogas production system MINLP Multi-objective optimization Non-dominated sorting genetic algorithm Ⅱ Green degree value