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Comparison of feasibility,microstructure and performance of hybrid laser arc,activated flux tungsten inert GAS and friction stir welding for thick plate of innovative ultra-pure ferritic stainless steel

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Journal of Iron and Steel Research(International) 2022年第4期29卷 665-676页

作者： Jian Han Lian-meng Liu Xin-ya Chen Min-fang Chen Lei Cui Yang-chuan Cai Yin-bao Tian School of Materials Science and Engineering Tianjin University of TechnologyTianjin 300384China School of Materials Science and Engineering Tianjin UniversityTianjin 300072China

An innovative grade of ferritic stainless steel,ultra-pure 18Cr–2Mo thick plate,was designed and produced for special industrial application.In order to maintain its mechanical properties after joining,three advanced joining methods,hybrid laser arc welding,activated flux tungsten inert GAS welding and friction stir welding,were selected and conducted to connect the thick plates.The feasibility of three joining methods,the microstructure and mechanical properties were compared,and the results have demonstrated that the sound joint was successfully produced using the selected parameters through friction stir welding.The obtained hardness and impact toughness of the weld zone were satisfying.In terms of activated flux tungsten inert GAS welding,the crack will be created due to microstructural brittleness.And as for hybrid laser arc welding,the weld zone is narrow,and the addition of wire during welding for the top weld metal area leads to higher formation ratio of low-angle grain boundaries,which is beneficial to performance of the joint.However,there is still a weak area in the fusion line of the welded joint.The result has illustrated that the welding of innovative ultra-pure ferritic stainless steel thick plate by friction stir welding is feasible.

关键词： Ultra-pure ferritic stainless steel Hybrid welding Activated flux tungsten inert GAS Friction stir welding Microstructural evolution Mechanical property

Microwave irradiation-induced alterations in physicochemical properties and methane adsorption capability of coals: An experimental study using carbon molecular sieve

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CHINESE JOURNAL OF CHEMICAL ENGINEERING 2024年第4期68卷 165-180页

作者： Fu, Xuexiang Tang, Xing Xu, Yi Zhou, Xintao Zhang, Dengfeng Kunming Univ Sci & Technol Fac Chem Engn Kunming 650500 Peoples R China

In order to comprehend the applicability of microwave irradiation for recovering coalbed methane, it is necessary to evaluate the microwave irradiation -induced alterations in coals with varying levels of metamorphism. In this work, the carbon molecular sieve combined with KMnO4 oxidation was selected to fabricate carbon molecular sieve with diverse oxidation degrees, which can serve as model substances toward coals. Afterwards, the microwave irradiation dependences of pores, functional groups, and highpressure methane adsorption characteristics of model substances were studied. The results indicated that microwave irradiation causes rearrangement of oxygen -containing functional groups, which could block the micropores with a size of 0.40-0.60 nm in carbon molecular sieve; meanwhile, naphthalene and phenanthrene generated by macro -molecular structure pyrolysis due to microwave irradiation could block the micropores with a size of 0.70-0.90 nm. These alterations in micropore structure weaken the saturated methane adsorption capacity of oxidized carbon molecular sieve by 2.91%-23.28%, suggesting that microwave irradiation could promote methane desorption. Moreover, the increased mesopores found for oxidized carbon molecular sieve after microwave irradiation could benefit CH4 diffusion. In summary, the oxidized carbon molecular sieve can act as model substances toward coals with different ranks. Additionally, microwave irradiation is a promising technology to enhance coalbed methane recovery. (c) 2024 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

关键词： Microwave irradiation Physicochemical property Coal matrix Adsorption Carbon molecular sieve ONO-KONDO MODEL HIGH-PRESSURE ACTIVATED CARBONS LONGMAXI SHALE PORE CONNECTIVITY FUNCTIONAL-GROUPS GAS TEMPERATURE OXIDATION DIOXIDE

Cholesky GAS models for large time-varying covariance matrices

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Journal of Management Science and Engineering 2024年第1期9卷 115-142页

作者： Tingguo Zheng Shiqi Ye Department of Statistics and Data Science School of EconomicsXiamen UniversityXiamen361005China Wang Yanan Institute for Studies in Economics Xiamen UniversityXiamen361005China Paula and Gregory Chow Institute for Studies in Economics Xiamen UniversityXiamen361005China

This paper develops a new class of multivariate models for large-dimensional time-varying covariance matrices,called Cholesky generalized autoregressive score(GAS)models,which are based on the Cholesky decomposition of the covariance matrix and assume that the parameters are score-driven.Specifically,two types of score-driven updates are considered:one is closer to the GARCH family,and the other is inspired by the stochastic volatility model.We demonstrate that the models can be estimated equation-wise and are computationally feasible for high-dimensional cases.Moreover,we design an equationwise dynamic model averaging or selection algorithm which simultaneously extracts model and parameter uncertainties,equipped with dynamically estimated model parameters.The simulation results illustrate the superiority of the proposed models.Finally,using a sizeable daily return dataset that includes 124 sectors in the Chinese stock market,two empirical studies with a small sample and a full sample are conducted to verify the advantages of our models.The full sample analysis by a dynamic correlation network documents significant structural changes in the Chinese stock market before and after COVID-19.

关键词： Cholesky decomposition GAS Dynamic conditional correlations Dynamic model averaging

Differences and identification on multi-time hydrocarbon generation of carboniferous-permian coaly source rocks in the Huanghua Depression, Bohai Bay Basin

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PETROLEUM SCIENCE 2024年第2期21卷 765-776页

作者： Xu, Jin-Jun Cheng, Xian-Gang Peng, Shu-Nan Jiang, Jun-Cai Wu, Qi-Long Lou, Da Cheng, Fu-Qi Lin, La-Mei China Univ Petr East China Natl Key Lab Deep Oil & Gas Qingdao 266580 Shandong Peoples R China PetroChina Dagang Oilfield Co Tianjin 300280 Peoples R China

Coal is a solid combustible mineral, and coal-bearing strata have important hydrocarbon generation potential and contribute to more than 12% of the global hydrocarbon resources. However, the deposition and hydrocarbon evolution process of ancient coal-bearing strata is characterized by multiple geological times, leading to obvious distinctions in their hydrocarbon generation potential, geological processes, and production, which affect the evaluation and exploration of hydrocarbon resources derived from coaly source rocks worldwide. This study aimed to identify the differences on oil-generated parent macerals and the production of oil generated from different coaly source rocks and through different oil generation processes. Integrating with the analysis of previous tectonic burial history and hydrocarbon generation history, high-temperature and high-pressure thermal simulation experiments, organic geochemistry, and organic petrology were performed on the Carboniferous-Permian (C-P) coaly source rocks in the Huanghua Depression, Bohai Bay Basin. The oil-generated parent macerals of coal's secondary oil generation process (SOGP) were mainly hydrogen-rich collotelinite, collodetrinite, sporinite, and cutinite, while the oil-generated parent macerals of tertiary oil generation process (TOGP) were the remaining small amount of hydrogen-rich collotelinite, sporinite, and cutinite, as well as dispersed soluble organic matter and unexhausted residual hydrocarbons. Compared with coal, the oil-generated parent macerals of coaly shale SOGP were mostly sporinite and cutinite. And part of hydrogen-poor vitrinite, lacking hydrocarbon-rich macerals, and macerals of the TOGP, in addition to some remaining cutinite and a small amount of crude oil and bitumen from SOGP contributed to the oil yield. The results indicated that the changes in oil yield had a good junction between SOGP and TOGP, both coal and coaly shale had higher SOGP aborted oil yield than TOGP starting yield, and coaly shale TOGP peak oil yield was lower than SOG

关键词： Thermal simulation Multi -time oil generation processes Coaly source rock Carboniferous-permian Huanghua Depression AROMATIC-HYDROCARBONS THERMAL EVOLUTION BEARING STRATA SOLID BITUMEN OIL-FIELD MATURITY MARINE ORIGIN CHINA GAS

Highly selective separation of propylene/propane mixture on cost-effectively four-carbon linkers based metal-organic frameworks

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Chinese Journal of Chemical Engineering 2022年第11期51卷 126-134页

作者： Daofei Lv Junhao Xu Pingjun Zhou Shi Tu Feng Xu Jian Yan Hongxia Xi Zewei Liu Wenbing Yuan Qiang Fu Xin Chen Qibin Xia School of Environmental and Chemical Engineering Foshan UniversityFoshan 528000China School of Chemistry and Chemical Engineering South China University of TechnologyGuangzhou 510641China Sichuan Jinyuansheng New Energy Technology Co. LtdMeishan 620010China

The separation of propylene and propane is an important but challenging process,primarily achieved through energy-intensive distillation technology in the petrochemical industry.Here,we reported two natural C4linkers based metal–organic frameworks(MIP-202 and MIP-203)for C_(3)H_(6)/C_(3)H_(8)separation.Adsorption isotherms and selectivity calculations were performed to study the adsorption performance for C_(3)H_(6)/C_(3)H_(8)separation.Results show that C_(3)H_(6)/C_(3)H_(8)uptake ratios(298 K,100 kPa)for MIP-202 and MIP-203 are 2.34 and 7.4,respectively.C_(3)H_(6)/C_(3)H_(8)uptake ratio(303 K,100 k Pa)for MIP-203 is up to50.0.The mechanism for enhanced separation performance of C_(3)H_(6)/C_(3)H_(8)on MIP-203 at higher temperature(303 K)was revealed by the in situ PXRD characterization.The adsorption selectivities of C_(3)H_(6)/C_(3)H_(8)on MIP-202 and MIP-203(298 K,100 k Pa)are 8.8 and 551.4,respectively.The mechanism for the preferential adsorption of C_(3)H_(6)over C_(3)H_(8)in MIP-202 and MIP-203 was revealed by the Monte Carlo simulation.The cost of organic ligands for MIP-202 and MIP-203 was lower than that of organic ligands for those top-performance MOFs.Our work sets a new benchmark for C_(3)H_(6)sorbents with high adsorption selectivities.

关键词： Propylene Propane Separation GAS Adsorption Metal-organic frameworks

Influence of longwall mining on the stability of GAS wells in chain pillars

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International Journal of Mining Science and Technology 2020年第1期30卷 3-9页

作者： Peter Zhang Heather Dougherty Daniel Su Jack Trackemas Berk Tulu CDC NIOSH Pittsburgh Mining Research Division(PMRD)PittsburghPA 15236USA Department of Mining Engineering West Virginia UniversityMorgantownWV 26505USA

Longwall mining has a significant influence on GAS wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in GAS well casings.If the GAS well casings are compromised or ruptured,natural GAS could migrate into the mine workings,potentially causing a fire or explosion.By the current safety regulations,the GAS wells in the chain pillars have to be either plugged or protected by adequate coal pillars.The current regulations for GAS well pillar design are based on the 1957 Pennsylvania GAS well pillar study.The study provided guidelines for GAS well pillars by considering their support area and overburden depth as well as the location of the GAS wells within the pillars.As the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep cover.GAS well casing of failures have occurred even though the chain pillars for the GAS wells met the requirements by the 1957 study.This study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional GAS wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam.The study results indicate that overburden depth and pillar size are not the only determining factors for GAS well stability.The other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of GAS wells.Numerical modeling was used to model abutment pressure,subsurface deformations,and the response of GAS well casings.The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of GAS well failures,thereby providing a more quantifiable approach to assess the stability of the GAS wells in longwall chain pillars.

关键词： Longwall mining GAS well Chain pillar Casing stability

GAS Sensors Based on Chemi?Resistive Hybrid Functional Nanomaterials

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Nano-Micro Letters 2020年第6期12卷 27-69页

作者： Yingying Jian Wenwen Hu Zhenhuan Zhao Pengfei Cheng Hossam Haick Mingshui Yao Weiwei Wu School of Advanced Materials and Nanotechnology Interdisciplinary Research Center of Smart SensorsXidian UniversityXi’an 710071People’s Republic of China School of Aerospace Science and Technology Xidian UniversityXi’an 710071People’s Republic of China Department of Chemical Engineering Russell Berrie Nanotechnology InstituteTechnion-Israel Institute of Technology3200003 HaifaIsrael Institute for Integrated Cell-Material Sciences(WPI-iCeMS) Kyoto University Institute for Advanced StudyKyoto UniversityYoshida Ushinomiya-choSakyo-kuKyoto 606-8501Japan

Chemi-resistive sensors based on hybrid functional materials are promising candidates for GAS sensing with high responsivity,good selectivity,fast response/recovery,great stability/repeatability,room-working temperature,low cost,and easy-to-fabricate,for versatile applications.This progress report reviews the advantages and advances of these sensing structures compared with the single constituent,according to five main sensing forms:manipulating/constructing heterojunctions,catalytic reaction,charge transfer,charge carrier transport,molecular binding/sieving,and their combinations.Promises and challenges of the advances of each form are presented and discussed.Critical thinking and ideas regarding the orientation of the development of hybrid material-based GAS sensor in the future are discussed.

关键词： GAS sensor Hybrid Chemi-resistor Functional nanomaterials

Hierarchical Ag-SiO_2@Fe_3O_4magnetic composites for elemental mercury removal from non-ferrous metal smelting flue GAS

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Journal of Environmental Sciences 2019年第5期31卷 111-120页

作者： Yongpeng Ma Bailong Mu Xiaojing Zhang Hongzhong Zhang Haomiao Xu Zan Qu Li Gao Henan Collaborative Innovation Center of Environmental Pollution Control and Ecological Restoration School of Material and Chemical Engineering Zhengzhou University of Light Industry School of Environmental Science and Engineering Shanghai Jiao Tong University College of Resources and Environmental Science Ningxia University

Hierarchical Ag-SiO_2@Fe_3O_4 magnetic composites were selected for elemental mercury(Hg^0) removal from non-ferrous metal smelting flue GAS in this study. Results showed that the hierarchical Ag-SiO_2@Fe_3O_4 magnetic composites had favorable Hg^0 removal ability at low temperature. Moreover, the adsorption capacity of hierarchical magnetic composite is much larger than that of pure Fe_3O_4 and SiO_2@Fe_3O_4. The Hg^0 removal efficiency reached the highest value as approximately 92% under the reaction temperature of 150°C, while the removal efficiency sharply reduced in the absence of O_2. The characterization results indicated that Ag nanoparticles grew on the surface of SiO_2@Fe_3O_4 support. The large surface area of SiO_2 supplied efficient reaction room for Hg and Ag atoms. Ag–Hg amalgam is generated on the surface of the composites. In addition, this magnetic material could be easily separated from fly ashes when adopted for treating real flue GAS, and the spent materials could be regenerated using a simple thermal-desorption method.

关键词： Elemental mercury Silver nanoparticles Magnetic composites Non-ferrous metal Flue GAS

Effect of wet flue GAS desulfurization(WFGD) on fine particle(PM_(2.5)) emission from coal-fired boilers

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Journal of Environmental Sciences 2019年第3期31卷 32-42页

作者： Sen Yao Shuiyuan Cheng Jianbing Li Hanyu Zhang Jia Jia Xiaowei Sun Key Laboratory of Beijing on Regional Air Pollution Control Beijing University of Technology Environmental Engineering Program University of Northern British Columbia

In this study, the characteristics of fine particles before and after wet flue GAS desulfurization(WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%–56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094–0.946 μm was observed. The watersoluble ion content accounted for a very large proportion of PM_(2.5) mass, and its proportion in PM_(2.5) increased from 28.39%–41.08% to 48.96%–61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component(Ca^(2+) for unit A, Mg^(2+) for unit B, and Na+for unit C) and the proportion of SO_4^(2-) in PM_(2.5), and it increased the CE/AE values of PM_(2.5) from 0.82–0.98 to 0.93–1.27 for the three study units.

关键词： PM2.5 Wet flue GAS desulfurization Size distribution Number concentration