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Ultrafine polycrystalline titania nanofibers for superior sodium storage

Journal of Energy Chemistry 2019年第11期28卷 153-161页

作者： Zhidan Diao Daming Zhao Chunxiao Lv Hongli Liu Dongjiang Yang Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049ShaanxiChina School of Environmental Science and Engineering Collaborative Innovation Centerfor Marine Biomass FibersMaterials and Textiles of Shandong ProvinceQingdao UniversityQingdao 266071ShandongChina

Sodium ion batteries have a huge potential for large-scale energy storage for the low cost and abundance of sodium resources. In this work, a novel structure of ultrafine polycrystalline TiO2 nanofibers is prepared on nickel foam/carbon cloth by a simple vapor deposition method. The as-prepared TiO2 nanofibers show excellent performance when used as anodes for sodium-ion batteries. Specifically, the TiO2 nanofibers@nickel foam electrode delivers a high reversible capacity of 263.2 m Ahg^-1 at 0.2 C and maintains a considerable capacity of 144.2 m Ahg^-1 at 10 C. The TiO2 nanofibers@carbon cloth electrode also shows excellent high-rate capability, sustaining a capacity of 148 m Ahg^-1 after 20 0 0 cycles at 10 C. It is believed that the novel nanofibrous structure increases the contact area with the electrolyte and greatly shortens the sodium ion diffusion distance, and meanwhile, the polycrystalline nature of nanofibers exposes more intercalation sites for sodium storage. Furthermore, the density functional theory calculations exhibit strong ionic interactions between the exposed TiO2(101) facets and sodium ions, leading to a preferable sodiation/desodiation process. The unique structural features endow the TiO2 nanofibers electrodes great advantages in rapid sodium storage with an outstanding high-rate capability.

关键词： Polycrystalline titania Nanofibers Sodium storage High-rate capability

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Unprofitability of small biogas plants without subsidies in the Brandenburg region

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ENVIRONMENTAL CHEMISTRY LETTERS 2021年第2期19卷 1823-1829页

作者： Gonzalez-Arias, Judith Baena-Moreno, Francisco M. Gonzalez-Castano, Miriam Arellano-Garcia, Harvey Lichtfouse, Eric Zhang, Zhien Univ Leon Nat Resources Inst IRENA Chem & Environm Bioproc Engn Grp Leon 24071 Spain Brandenburg Tech Univ Cottbus Senftenberg LS Prozess & Anlagentech D-03046 Cottbus Germany Univ Seville Chem & Environm Engn Dept Tech Sch Engn C Camino Descubrimientos S-N Seville 41092 Spain Aix Marseille Univ IRD CNRS INRAColl FranceCEREGE F-13100 Aix En Provence France Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Ohio State Univ William G Lowrie Dept Chem & Biomol Engn Columbus OH 43210 USA

The circular economy is calling for the rapid use of already-developed renewable energies. However, the successful implementation of those new fuels is limited by economic and political issues. For instance, in the Brandenburg region, Germany, biogas production from anaerobic digestion of biomass and wastes is a current alternative. However, the upgrading biogas to biomethane is still challenging and the economic viability is unknown. Therefore, we performed an economic analysis for biogas upgrading to biomethane in the Brandenburg region. Five biogas plant sizes were analyzed by the method of discounted cash flow. This method yields the net present value of the projects, thus revealing the profitability or non-profitability of the plants. Results indicate profitable outputs for medium and large plants, with net present values between 415 and 7009 keuro. However, the smallest plants have net present values from -4250 to -3389 keuro, thus needing further economic efforts or subsidies to reach profitability. Indeed, biomethane prices should range between 52.1 and 95.6 euro/MWh to make these projects profitable. Combinations of 50% of investment subsidized and 11.5 euro/MWh feed-in tariffs subsidies could make the projects reach profitability. These findings reveal that political actions such as green policies and subsidies are needed to implement green energy. This case study should serve as a potential tool for policy-makers toward a sustainable bioeconomy.

关键词： Biomethane production Biogas upgrading Green energy Brandenburg development Waste valorization Energy independence

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Syngas Characteristics From Catalytic Gasification of Polystyrene and Pinewood in CO2 Atmosphere

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JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME 2021年第5期143卷 052304页

作者： Liu, Xuan Burra, Kiran Raj G. Wang, Zhiwei Li, Jinhu Che, Defu Gupta, Ashwani K. Univ Maryland Dept Mech Engn Combust Lab College Pk MD 20742 USA Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Henan Univ Technol Coll Environm Engn Zhengzhou 450001 Peoples R China China Univ Min & Technol Sch Safety Engn Xuzhou 221116 Jiangsu Peoples R China

Syngas production from catalytic gasification of polystyrene and pinewood in CO2 atmosphere was investigated over Ni-Mg/Al2O3 catalyst in a fixed-bed reactor at 900 degrees C. A quasi in situ method was adopted for catalytic gasification wherein the catalyst placed downstream of the feedstock in the same reactor was used for enhanced syngas production. The effect of catalyst on evolutionary behavior, cumulative syngas yield, syngas composition, and cold gas efficiency was systematically analyzed. The results showed that addition of catalyst for polystyrene gasification resulted in enhanced yields of 63% H-2, 20% CO, 119% CH4, and 85% C-2-C-3 yields. Enhanced H-2 and light hydrocarbon yields were mainly from enhanced cracking of pyrolytic vapors from polystyrene degradation, while the CO yield was attributed to CO2-assisted reforming of benzene derivatives from primary cracking and polycyclic aromatic hydrocarbons (PAHs) from secondary gas phase condensations. The yields of H-2, CO, CH4, and C-2-C-3 from pinewood gasification in the presence of catalyst was also enhanced by 150%, 14%, 39%, and 16%, respectively, indicating that Ni-Mg/Al2O3 catalyst can efficiently enhance syngas production in CO2-assisted gasification. A comparison of syngas composition between non-catalytic and catalytic conditions revealed improved syngas quality in catalytic gasification with increased H-2 mole fraction but decreased CO mole fraction. Furthermore, cold gas efficiency enhanced from 44% to 57% in catalytic polystyrene gasification, and from 75% to 94% in catalytic pinewood gasification. The results suggest that catalytic CO2 gasification offers a promising pathway for efficient energy production from wastes plastics and biomass while simultaneously using CO2.

关键词： Ni-catalyst CO2 gasification plastic wastes syngas production energy efficiency alternative energy sources energy conversion systems energy from biomass hydrogen energy

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Density Data of Two (H2 + CO2) Mixtures and a (H2 + CO2 + CH4) Mixture by a Modified Burnett Method at Temperature 673 K and Pressures up to 25 MPa

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JOURNAL OF CHEMICAL AND engineering DATA 2019年第4期64卷 1693-1704页

作者： Cheng, Siyuan Shang, Fei Ma, Weigang Jin, Hui Sakoda, Naoya Zhang, Xing Guo, Liejin Tsinghua Univ Dept Engn Mech Key Lab Thermal Sci & Power Engn Minist Educ Beijing 100084 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power & Engn Xian 710049 Shaanxi Peoples R China Kyushu Univ Dept Mech Engn Fukuoka Fukuoka 8190395 Japan

The PVT properties of the (H-2 + CO2) mixtures and the (H-2 + CO2 + CH4) mixtures in the supercritical region of water are significant for making full use of the gas mixtures in the coal and supercritical water gasification. We report PVT measurements of the (0.6005 H-2 + 0.3995 CO2), (0.6992 H-2 + 0.3008 CO2), and (0.6026 H-2 + 0.1948 CO2 + 0.2026 CH4) mixtures (all in mole fractions) at temperature 673 K and pressures of (0.5 to 25) MPa, measured by a modified Burnett method. The upper bounds of the expanded uncertainties at 95% confidence are 0.2 K for temperature, *** for pressure, and *** for density. The density data were compared with those predicted using the GERG-2008 equation of state. The deviations between the calculated and experimental data are not more than ***. Furthermore, the densities were found in accordance with the weighted average of the components' existing equations of state using their mole fractions within *** for all of the mixtures in this work. The second and third virial coefficients were determined at temperature 673 K for hydrogen and all of the mixtures investigated.

关键词： Hydrogen Theoretical and computational chemistry Chromatography Mixtures Compressibility

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Experimental study on natural convection heat transfer in a two-layer corium pool based on COPRA facility

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NUCLEAR engineering AND DESIGN 2019年 349卷 136-143页

作者： Zhou, Yukun Zhang, Yapei Zhang, Kui Wu, Shihao Yu, Zhiyu Tian, Wenxi Qiu, Suizheng Su, G. H. Xi An Jiao Tong Univ Sch Nucl Sci & Technol Shaanxi Engn Res Ctr Adv Nucl Energy State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

During core meltdown accidents, the heat flux distribution along the wall of lower plenum was closely related to the potential of vessel failure. Concerning with the natural convection heat transfer behavior in stratified corium pools, several two-layer tests were performed on COPRA facility recently. The test vessel (a 1/4 circular slice with an inner radius of 2.2 m and a width of 0.2 m) is divided into two parts by a plate made of 304 stainless steel. The lower part, heated by 18 electrical heating rods, is applied to simulate the oxide pool. The upper part without heat generation is assumed to be a metallic layer. During the experiment, different heating powers and boundary conditions were employed to obtain the temperature distributions of oxide pool and metal layer, as well as the heat flux through the vessel wall. Prototypic Ra' range, varied from 1.88 x 10(16) to 5.39 x 10(16), was successfully achieved in the oxide pool. Despite the smaller downward Nu(dn) numbers, the upward Nu(up) numbers within this study were well in accordance with the reported data. It should be mentioned that the results of water are unrepresentative for the reactor situation since no crust was formed in the bottom and top of oxide pool. However, the current study will still attract interest by the qualitative analysis of top cooling influence on natural convection phenomenon and provide valuable information to other researchers who concern with the crust formation and focusing effect on stratified corium pools behavior.

关键词： Severe accident Two-layer corium pool Natural convection COPRA

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Numerical simulation of high temperature gas cooled reactors on less of coolant accident 18

Numerical simulation of high temperature gas cooled reactors...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Zhang, Shuangbao Li, Liangxing Xie, Wei Wang, Kailin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xianning West Road 28# Xi’an city710049 China

The high temperature gas-cooled reactor (HTR) is well known for its prominent inherent safety, high efficiency and low carbon environmental protection, which has been identified as one of the candidates for the Generation IV nuclear energy system technology. Accurate and reliable thermal hydraulic analysis is of great significance to the system design and safe operation of HTR. Based on the coolant flow and heat transfer process in the core of HTR, this study establishes a three-dimensional model by using CFD (Computational Fluid Dynamics) software firstly, and the flow and heat transfer process of helium coolant is simulate in the core. The temperature distribution of HTR is calculated at steady state, and the calculation results were compared with the related published results for validation and verification. After that, the models are employed to study the thermal hydraulic characteristics under the loss of coolant accident of HTR. The results show that as the coolant passes through the core from top to bottom, helium is continuously heated, and the temperature increases from top to bottom. The temperature reached a maximum at the core exit position of 1032.75 K. It stated that the model can be employed to simulate the thermal hydraulic analysis for HTR. The calculation results of the loss-of-coolant, indicates t as the flow rate decreases, the coolant temperature rises gradually. When the coolant is completely lost, the temperature reaches a maximum of 1723.19 K, and it is still lower than the design limit of 1893.15 K. © 2019 American Nuclear Society. All rights reserved.

关键词： Coolants

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The theoretical and numerical analysis on a multi-blade liquid lead pump 27

The theoretical and numerical analysis on a multi-blade liqu...

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27th International Conference on Nuclear engineering: Nuclear power Saves the World!, ICONE 2019

作者： Wang, Kailin Li, Liangxing Xie, Wei Zhang, Shuangbao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xianning West Road 28# Xi'an city710049 China

ISBN: (纸本)9784888983051

Lead or lead-alloy cooled fast reactors (LFRs) have been proved to be the most promising Generation IV reactors with high performance in neutronics, thermal hydraulics and security features. Small forced circulation modular LFRs is one of the potential candidates for LFRs development which has attracted particular attention in recent years. When lead-bismuth eutectic (LBE) is used as coolant, the primary LBE pump is a key conveying equipment, and therefore the hydraulic performance of LBE pump is great important to the safety of LFR. Motivated by improving the hydraulics performance of LBE pump, this paper presents a theoretical and computational analysis on an axial flow pump. The guide blades are set at the outlet of the impeller to eliminate the rotational motion of the liquid LBE and transform the kinetic energy of the rotational motion into pressure energy. The rotation angle of the blade is optimized based on the theoretical analysis to reduce the vortex and raise efficiency. As well, the outlet speed and pressure parameters of each part in the pump are calculated. After that, a three-dimensional model of the modified pump is established by using CFD software and the flow characteristics of LBE in the pump are simulated. Albeit the high velocity liquid LBE alloy still exists in the side of pump shroud, some erosion-related issues remain to be fully addressed. The results of the study show that the axial LBE pump could be used as a viable solution for the design of the new generation of small module reactor primary pump from a thermo-fluid dynamic point of view. © 2018-2019 by JSME

关键词： Pumps

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Influence of Char Intermediates on Synergistic Effects During Co-Pyrolysis of Pinewood and Polycarbonate

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JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME 2021年第5期143卷 052107页

Combined use of plastic and biomass wastes offers promising pathway for simultaneous energy production and waste disposal. In this article, the co-pyrolysis of pinewood and polycarbonate (PC) was performed in a fixed bed reactor to quantify their synergistic interaction on the product output and determine the effect of char intermediates on the synergistic effects. The extent of synergistic effects was obtained via a direct comparison of results from co-pyrolysis of pinewood-polycarbonate mixture with the weighted average values from pyrolysis of individual components. The observed synergistic effects were further examined from the influence of char intermediates using tailored feedstock configurations to gain more insights into the synergistic mechanism. The results showed co-pyrolysis resulted in enhancement by 33% in H-2, 26% in CO, and 19% in total syngas yields compared to their weighted values from individual pyrolysis. Co-pyrolysis also exhibited superiority in energy recovery with the overall energy efficiency promoted from 42.9% to 48.6%. Deconvolution of synergistic effects revealed that pinewood char catalytically enhanced PC degradation, while the effect of PC char on pinewood pyrolysis was minimal. This article provides results on deconvolved understanding of synergistic effects in co-pyrolysis of lignocellulosic biomass and PC wastes, which is very helpful in designing clean and efficient energy recovery systems from these waste resources.

关键词： lignocellulosic biomass waste polycarbonate co-pyrolysis synergistic effects feedstock configuration alternative energy sources energy conversion systems energy extraction of energy from its natural resource energy from biomass

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Towards enhanced understanding of synergistic effects in co-pyrolysis of pinewood and polycarbonate

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APPLIED ENERGY 2021年 289卷 116662-116662页

Utilization of biomass and plastic wastes has drawn growing attention in recent years as it offers promising pathway for simultaneous energy production and waste disposal. In this paper, the co-pyrolysis of pinewood and polycarbonate was performed in a fixed bed reactor with focus on determining the extent of synergistic effects and unraveling the underlying synergistic mechanism. The extent of synergistic effects was quantified via direct comparison of the results from co-pyrolysis of pinewood-polycarbonate mixture with the weighted average values from individual components pyrolysis. The observed synergistic effects were further deconvolved into different component interactions (such as volatiles-volatiles interactions, volatiles-feedstocks interaction, and catalytic effects of chars) using tailored feedstock configurations to gain more insights into the synergistic mechanism. The results showed that co-pyrolysis enhancedH(2) by 33%, CO by 26%, and total syngas yields by 19% as compared to their weighted values from individual pyrolysis. Co-pyrolysis also exhibited superiority in energy recovery as the overall energy efficiency was noticeably promoted from 42.9% to 48.6%. Deconvolution of synergistic effects revealed that volatiles-volatiles interactions were the primary contributor for the enhancement of H-2 and CO. Examination of volatiles-feedstock interactions indicated that the highly reactive pinewood volatiles facilitated polycarbonate degradation, while polycarbonate volatiles were relatively stable and unable to promote pinewood decomposition. Furthermore, pinewood char catalytically enhanced poly carbonate degradation. This paper provides a deconvolved understanding of synergistic effects in co-pyrolysis of lignocellulosic biomass and polycarbonate wastes, which is very helpful in designing clean and efficient energy recovery systems from these waste resources.

关键词： Lignocellulosic biomass Waste polycarbonate Co-pyrolysis Synergistic effects Feedstock configuration

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Strengthened spatial charge separation over Z-scheme heterojunction photocatalyst for efficient photocatalytic H2 evolution

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APPLIED SURFACE SCIENCE 2019年 475卷 453-461页

作者： Luo, Bing Song, Rui Geng, Jiafeng Jing, Dengwei Huang, Zhenxiong Xi An Jiao Tong Univ Int Res Ctr Renewable Energy Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Graphitic carbon nitride (g-C3N4) is a very promising earth abundant and visible light response photocatalyst for H-2 production. Fabricating novel nanostructure or combining with other semiconductors have been attempted to further enhance its activity. alpha-FeOOH, due to its structures greatly facilitating electrolyte transport, has been widely used as an excellent OER cocatalyst assisting the PEC water splitting process. However, to the best of our knowledge, it has not been attempted in photocatalytic H-2 generation. Herein, g-C3N4 modified with beta-FeOOH was designed for the first time for photocatalytic H-2 production. It showed H-2 production rate as 2.02 mmol.h(-1).g(-1), which was almost 6 times of pure g-C3N4. The significantly promoted catalytic activity was ascribed to the greatly enhanced charge separation efficiency by forming spatial separated reservoirs of photo activated electrons and holes in the Z-scheme heterojunction, corresponding to the conduction band of g-C3N4 and the valence band of beta-FeOOH, respectively. Our work should be valuable for fabricating visible-light response heterojunction based photocatalysts with better photocatalytic performance.

关键词： beta-FeOOH Graphitic carbon nitride Heterojunction Hydrogen evolution Photocatalysis

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