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Study on Combustion Characteristics of Coals in High Temperature Water Vapor Atmospheres

Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2018年第12期52卷 84-92页

作者： Yao, Yashu Wen, Du Zhou, Qulan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

A scheme of adding high temperature water vapor to the combustion system to achieve low-nitrogen combustion is proposed to reduce NOx production during coal combustion, and its thermodynamic calculation and experimental research are carried out. Firstly, the possibility and limitation of the reactions in the volatile combustion process of coal after adding high temperature water vapor are examined by theoretical calculation based on the standard molar reaction Gibbs free energy change, the standard molar enthalpy and the equilibrium constant. Results of reaction path speculation show that in the high temperature water vapor atmosphere, the reactions of converting N element to N2 occur in the temperature range of coal combustion. Secondly, in reactions with various excess air coefficients, the equilibrium components after adding different concentrations of high temperature water vapor are calculated using the software HSC Chemistry. Results of the thermodynamic calculation show that the reaction of NOx precursor to N2 happens in a wide temperature range: when the temperature ranges from 700 to 800 and excess air coefficient lies between 0.6 and 0.8, the formation of NOx significantly reduces by adding high temperature water vapor;Reduction rate of NOx increases with the concentration of high temperature water vapor increasing. Eventually, the combustion characteristics of pulverized coal in water vapor and air atmosphere are tested in a pulverized coal fixed bed combustion experiment system. It shows that the formation of NOx is inhibited by adding high temperature water vapor and the effect is better that the result of the thermodynamic calculation, and the NOx reduction rate has a nonlinear relation with the water vapor concentration and the temperature. This study may provide an economical and efficient reference solution to low NOx combustion of coal. © 2018, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.

关键词： Coal combustion

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Mass Transfer and Kinetics of CO2 Absorption in Aqueous MDEA/DMSO Solutions

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2018年第8期39卷 1763-1768页

作者： Luo, Qin-Lan Fang, Bin Qiang, Lei Li, Na Zhou, Qu-Lan State key laboratory of multiphase flow in power engineering Xi'an Jiaotong University Xi'an710049 China

In this study, the CO2 absorption rates in aqueous MDEA/DMSO solutions at various temperatures of 293.15 K, 303.15 K, 313.15 K and 323.15 K and concentrations varied from 0.5 mol/L to 6.6 mol/K were measured by using a laboratory wetted-wall column reactor with an immobile gas-liquid interface. A simplified kinetic model of gas-liquid absorption was developed, the mass transfer and dynamic parameters, such as the absorption rate constant, the overall reaction rate constant, the second-order reaction rate constant and the enhancement factor, were evaluated. The relationship between second-order reaction rate constant and the reaction temperature was obtained, the effect of solution concentration on the enhancement factor was also assessed, and the activation energy was estimated at a value of 20.38 kJ/mol. © 2018, Science Press. All right reserved.

关键词： Kinetics

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Molecular sieving through a graphene nanopore： non-equilibrium molecular dynamics simulation

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Science Bulletin 2017年第8期62卷 554-562页

作者： Chengzhen Sun Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Two-dimensional graphene nanopores have shown great promise as ultra-permeable molecular sieves based on their size-sieving effects. We design a nitrogen/hydrogen modified graphene nanopore and conduct a transient non-equilibrium molecular dynamics simulation on its molecular sieving effects. The distinct time-varying molecular crossing numbers show that this special nanopore can efficiently sieve CO_2 and H_2S molecules from CH_4 molecules with high selectivity. By analyzing the molecular structure and pore functionalization-related molecular orientation and permeable zone in the nanopore, density distribution in the molecular adsorption layer on the graphene surface, as well as other features, the molecular sieving mechanisms of graphene nanopores are revealed. Finally, several implications on the design of highly-efficient graphene nanopores, especially for determining the porosity and chemical functionalization, as gas separation membranes are summarized based on the identified phenomena and mechanisms.

关键词： Graphene nanopore Molecular sieve Molecular dynamics Gas separation membrane

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Fully resolved simulations of a stationary finite-sized particle in wall turbulence over a rough bed

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Physical Review Fluids 2019年第9期4卷 094302-094302页

作者： Xing Li S. Balachandar Hyungoo Lee Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Mechanical & Aerospace Engineering University of Florida Gainesville Florida 32608 USA Power Reactor Development Division Korea Atomic Energy Research Institute Daedeok-daero 989 Yuseong-gu Daejeon 305–353 Republic of Korea

Understanding the force on a finite-sized particle immersed in a turbulent boundary layer close to a rough wall is of fundamental importance in predicting particle motion in a variety of industrial and environmental applications. Here we perform fully resolved direct numerical simulations with an immersed boundary method to investigate the forces on a stationary finite-sized particle in wall turbulence over a rough bed. Results show that for the particle sitting on the rough bed, lift is the main contributor to wall-normal force and can be well predicted with proper application of existing force models. The higher lift force is mainly due to the sweep events which temporarily increase the relative velocity as well as local shear magnitude. In contrast, for a particle located slightly away from the rough bed, the wall-normal force is mainly due to the wall-normal component of drag, so ejections and outward interactions are responsible for the increase in the wall-normal force. The standard drag law with near-wall correction can reasonably predict this wall-normal force on the particle, except for the large fluctuations due to self-induced vortex shedding.

关键词： Fluid-particle interactions Sediment transport

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The application of dual-mesh coupled heat transfer porous media model on the numerical simulation of a shell-tube heat exchanger

The application of dual-mesh coupled heat transfer porous me...

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International Topical Meeting on Advances in Thermal Hydraulics 2018, ATH 2018 - Held in conjunction with the 2018 American Nuclear Society (ANS) Winter Meeting

作者： Song, Guangdong Yang, Qingchuan Qiu, Binbin Yang, Hongyi Yu, Huajin Liu, Mengmeng China Institute of Atomic Energy Beijing102413 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

It is an urgent demand to find an alternative model to replace the actual tube bundles area when using numerical simulation to study the Intermediate Heat Exchanger(IHX) of a Sodium-cooled Fast Reactor. An appropriate alternative model can be a substitute for the actual model of IHX in terms of heat transfer and fluid flow. Dual-mesh coupled heat transfer is used based on the porous media model in FLUENT to simulate the flow field of a simple shell-tube heat exchanger and get temperature, velocity and pressure field data of the primary and the secondary fluid simultaneously. The result meets well with that acquired from the calculation of an actual model which proves that the method in this paper is reliable and is able to reduce the modeling and meshing work. © 2018 International Topical Meeting on Advances in Thermal Hydraulics, ATH 2018 - Embedded Topical Meeting. All rights reserved.

关键词： Mesh generation

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Deciphering Ligand Controlled Structural Evolution of Prussian Blue Analogues and Their Electrochemical Activation during Alkaline Water Oxidation

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Angewandte Chemie 2022年第49期134卷

作者： Baghendra Singh Pandian Mannu Yu-Cheng Huang Ravi Prakash Shaohua Shen Chung-Li Dong Arindam Indra Department of Chemistry IIT(BHU) Varanasi UP-221005 India Department of Physics Tamkang University New Taipei City Taiwan School of Material Science and Technology IIT(BHU) Varanasi UP-221005 India International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi An Shi Xi'an 710049 China

Herein, we have demonstrated the control over the structure of precatalysts to tune the properties of the active catalysts and their water oxidation activity. The reaction of K 3 [Fe(CN) 6 ] and Na 2 [Fe(CN) 5 (NO)] with Co(OH) 2 @CC produced precatalysts PC-1 and PC-2, respectively, with distinct structural and electronic features. The replacement of the −CN group with strong π-acceptor −NO modulates the electronic and atomic structure of PC-2. As a result, a facile electrochemical transformation of PC-2 into active catalyst Fe−Co(OH) 2 -Co(O)OH (AC-2) has been attained only in 15 CV cycles while 600 CV cycles are required for the electrochemical activation of PC-1 into AC-1. The X-ray absorption studies reveal the contraction of the Co−O and Fe−O bond in AC-2 because of the presence of a higher amount of Co 3+ and Fe 3+ than in AC-1. The high valent Co 3+ and Fe 3+ modulates the electronic properties of AC-2 and assists in the O−O bond formation, leading to the improved water oxidation activity.

关键词： Electrochemical Reconstruction Oxygen Evolution Reaction Prussian Blue Analogue Ultrathin Nanosheets XAS Studies

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Adsorption and Diffusion of Gas Molecules on Graphite Surface

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2018年第1期39卷 110-113页

作者： Sun, Cheng-Zhen Bai, Bo-Feng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The adsorption and diffusion characteristics of gas molecules on graphite surface are investigated by molecular dynamics simulations. The results show that the adsorption intensity of gas molecules on graphite surface is related to the atomic interactions between gas molecules and carbon atoms in graphite;different gas molecules present distinct adsorption intensities on graphite surface. The adsorption characteristics can be described by the Langmuir isothermal adsorption model, where the molecular number density in the adsorption layer increases with increasing gas pressure. From the decreasing diffusion coefficients with increasing gas pressure and the normal probability distribution of molecular moving distance in a certain time period, it is concluded that the gas diffusion on graphite surface is mainly controlled by the molecular collisions and approaches the bulk diffusion phenomenon. Accordingly, the molecular number density in the adsorption layer has a great effect on the surface diffusion coefficients, resulting in the obviously lower diffusion coefficients of CO2 and H2S molecules with stronger adsorption intensities than those of CH4 and N2 molecules with weaker adsorption intensities. © 2018, Science Press. All right reserved.

关键词： Adsorption

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Life cycle assessment of a 1000 MW supercritical pulverized coal power plant under partial loads 31

Life cycle assessment of a 1000 MW supercritical pulverized ...

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31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2018

作者： Han, Xiaoqu Chen, Nana Karellas, Sotirios Liu, Ming Liu, Jiping Yan, Junjie Kakaras, Emmanuel State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China Laboratory of Steam Boilers and Thermal Plants National Technical University of Athens Athens Greece

ISBN: (纸本)9789729959646

With increasing share of renewable energy sources, pulverized coal (PC) power plants have to participate in peak load regulations frequently and operate in partial loads regularly. The energy efficiency and eco-efficiency are both affected significantly in this manner. Therefore, an overall concept for the estimation of environmental impacts from PC plants under nominal and partial loads should be established in life cycle assessment (LCA) methodology. In the present work, a 1000 MW supercritical coal-fired unit, which is the main force for power supply in China, was modeled using commercial simulation tools (GSE and SimaPro). The aim is to investigate the environmental impacts under different working conditions from the perspective of LCA. Moreover, a partial load feedwater heating system with ejector in a coal-fired power unit was proposed and investigated. Model validation and LCA analysis under nominal load show that GWP and PCOP are the main environmental impacts of PC plants. But AP and EP are also serious concerns. Under partial loads, the AP and EP increase significantly, resulted from the reduction in NOx removal efficiency. It is thereby concluded that the mechanisms of formation, migration, and removal of different kinds of pollutant emissions influence the LCA results significantly. Therefore, operation optimization was carried out based on the guidelines of the LCA framework, to reduce the environmental impacts of PC power plants under partial loads. It is indicated that through the integration of an ejector, the NOx removal efficiency at extremely low load (30%) can be maintained at a high level. The environment impact potentials can thus be reduced effectively. © 2018 University of Minho. All rights reserved.

关键词： Emission control

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Decrypting the Controlled Product Selectivity over Ag−Cu Bimetallic Surface Alloys for Electrochemical CO2Reduction

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Angewandte Chemie 2023年第19期135卷

作者： Daixing Wei Yiqing Wang Prof. Chung-Li Dong Zhengqi Zhang Xinyu Wang Dr. Yu-Cheng Huang Yuchuan Shi Xiaoli Zhao Jialin Wang Prof. Ran Long Prof. Yujie Xiong Prof. Fan Dong Prof. Mingtao Li Prof. Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Physics Tamkang University New Taipei City 25137 Taiwan Hefei National Laboratory for Physical Sciences at the Microscale Frontiers Science Center for Planetary Exploration and Emerging Technologies School of Chemistry and Materials Science and National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230026 China Research Center for Environmental and Energy Catalysis Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu 611731 China

Electrochemical CO 2 reduction reaction (ECO 2 RR) with controlled product selectivity is realized on Ag−Cu bimetallic surface alloys, with high selectivity towards C2 hydrocarbons/alcohols (≈60 % faradaic efficiency, FE), C1 hydrocarbons/alcohols (≈41 % FE) and CO (≈74 % FE) achieved by tuning surface compositions and applied potentials. In situ spectral investigations and theoretical calculations reveal that surface-composition-dependent d-band center could tune *CO binding strengths, regulating the *CO subsequent reaction pathways and then the product selectivity. Further adjusting the applied potentials will alter the energy of participated electrons, which leads to controlled ECO 2 RR selectivity towards desired products. A predominant region map, with an indicator proposed to evaluate the thermodynamic predominance of the *CO subsequent reactions, is then provided as a reliable theoretical guidance for the controllable ECO 2 RR product selectivity over bimetallic alloys.

关键词： Alloys CO2 Reduction Controlled Product Selectivity Electrochemistry

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Carbon-Confined Indium Oxides for Efficient Carbon Dioxide Reduction in a Solid-State Electrolyte flow Cell

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Angewandte Chemie 2022年第21期134卷

作者： Zhitong Wang Yansong Zhou Dongyu Liu Ruijuan Qi Chenfeng Xia Prof. Mingtao Li Prof. Bo You Prof. Bao Yu Xia School of Chemistry and Chemical Engineering Key Laboratory of Material Chemistry for Energy Conversion and Storage Ministry of Education) Hubei Key Laboratory of Material Chemistry and Service Failure Hubei Engineering Research Center for Biomaterials and Medical Protective Materials Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology (HUST) 1037 Luoyu Rd Wuhan 430074 China International Research Center for Renewable Energy (IRCRE) State Key Laboratory of Multiphase Flow in Power Engineering (MFPE) Xi'an Jiaotong University (XJTU) 28 Xianning West Road Xi'an 710049 China HSE University 101000 Moscow Russia Key Laboratory of Polar Materials and Devices (MOE) Department of Electronics School of Physics and Electronic Science East China Normal University Shanghai 200241 China

Developing robust electrocatalysts and advanced devices is important for electrochemical carbon dioxide (CO 2 ) reduction toward the generation of valuable chemicals. We present herein a carbon-confined indium oxide electrocatalyst for stable and efficient CO 2 reduction. The reductive corrosion of oxidative indium to the metallic state during electrolysis could be prevented by carbon protection, and the applied carbon layer also optimizes the reaction intermediate adsorption, which enables both high selectivity and activity for CO 2 reduction. In a liquid-phase flow cell, the formate selectivity exceeds 90 % in a wide potential window from −0.8 V to −1.3 V vs. RHE. The continuous production of ca. 0.12 M pure formic acid solution is further demonstrated at a current density of 30 mA cm −2 in a solid-state electrolyte mediated reactor. This work provides significant concepts in the parallel development of electrocatalysts and devices for carbon-neutral technologies.

关键词： Carbon Dioxide Reduction Corrosion-Resistant Electrocatalyst Indium Oxide Solid-State Electrolyte

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