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Continuous hydrogen production by biomass gasification in supercritical water heated by molten salt flow: System development and reactor assessment

Continuous hydrogen production by biomass gasification in su...

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作者： Xiao, Peng Guo, Liejin Zhang, Ximin Zhu, Chao Ma, Shaohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 Shaan Xi Province China

Hydrogen production by biomass gasification using solar energy is a promising approach for overcoming the drawbacks of fossil fuel utilization, but the storage of discontinuous solar flux is a critical issue for continuous solar hydrogen production. A continuous hydrogen production system by biomass gasification in supercritical water using molten-salts-stored solar energy was proposed and constructed. A novel double tube helical heat exchanger was designed to be molten salts reactor for hydrogen production. Model compounds (glycerol/glucose) and real biomass (corn cob) were successfully gasified in this molten salts reactor for producing hydrogen-rich gas. The unique temperature profiles of biomass slurry in the reactor were observed and compared with that of conventional electrical heating and direct solar heating approaches. Product gases yield, gasification efficiency and exergy conversion efficiency of the reactor were analyzed. The results showed that the performances of reactor were determined by feedstock style, biomass concentration, residence time and biomass slurry temperature profiles. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Biomass

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Synthesis of CdS/CNTs photocatalysts and study of hydrogen production by photocatalytic water splitting

Synthesis of CdS/CNTs photocatalysts and study of hydrogen p...

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作者： Wang, Xixi Liu, Maochang Chen, Qingyun Zhang, Kai Chen, Jie Wang, Meng Guo, Penghui Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Shaanxi 710049 China

A series of CdS and CdS/CNTs photocatalysts were successfully prepared by hydrothermal method and they were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible optical absorption spectra (UV-Vis), etc. By studying their photocatalytic properties, it is found that, for CdS, photocatalysts prepared in appropriate alkaline environment presented higher hydrogen production activity, reaching 794.6 μmol h-1 g-1;the photocatalytic activity of CdS was obviously enhanced by combining it with CNTs via a special two-step hydrothermal method, and the corresponding hydrogen production rate reached 1.771 mmol h-1 g -1;the photocatalytic activity was further improved by loading co-catalyst NiS, achieving 12.13 mmol h-1 g-1. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Cadmium sulfide

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ZnS/ZnO heterojunction as photoelectrode: Type II band alignment towards enhanced photoelectrochemical performance

ZnS/ZnO heterojunction as photoelectrode: Type II band align...

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作者： Guo, Penghui Jiang, Jiangang Shen, Shaohua Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Shaanxi 710049 China

Heterojunction structures are attracting lots of attention for enhancing the electron injection across the interface. The ZnS/ZnO one-dimensional heterojunction film was firstly prepared via a chemical sulfidization following hydrothermal reaction. The heterostructure was characterized as ZnS(blende)/ZnO(wurtzite) shell-core nanorods via XRD, SEM and TEM. A type II band alignment structure of ZnS/ZnO composite was synthesized via a temperate condition proved by PLS and XPS. The values for valence band offset (VBO) and conduction band offset (CBO) were calculated to be 0.96 eV and 1.25 eV, respectively. The special electron structure in the heterojunction helped reduce the energy barrier height at the interface and enhance the separation of photo-generated carriers. Thus, the photoelectrochemical performance was highly improved, and a photocurrent density of 380 μA/cm2 at 0.9 V (vs. Ag/AgCl) was obtained. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Heterojunctions

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Fabricating CdS/BiVO4 and BiVO4/CdS heterostructured film photoelectrodes for photoelectrochemical applications

Fabricating CdS/BiVO4 and BiVO4/CdS heterostructured film ph...

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作者： Jiang, Jiangang Wang, Meng Li, Rong Ma, Lijing Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering International Research Center of Renewable Energy Xi'An Jiaotong University Shaanxi 710049 China

The photoelectrochemical (PEC) properties of heterostructured CdS/BiVO 4 and BiVO4/CdS film electrodes on conducting glass for hydrogen production under visible light were investigated. These two types heterostructured film electrodes were prepared using spin coating method and ultrasonic spray pyrolysis method. The structural analyses of the prepared films were determined by using XRD, SEM, EDX and UV-vis. Photoelectrochemical measurements were carried out in a convenient three electrodes cell with 0.5 M Na2SO3 aqueous solution. In order to investigate band gap influence of electrode PEC property, a series ITO/Cd1-xZn xS/BiVO4 and ITO/BiVO4/Cd1-xZn xS (x = 0 ∼ 1) film electrodes were also synthesized. After PEC test, a maximum photocurrent density from ITO/CdS/BiVO4 film electrode was confirmed. The maximum photocurrent density, 3 times and 113 times as that of single CdS film electrode and single BiVO4 film electrode, respectively. Incident photon to current conversion (IPCE) of as prepared film electrodes were measured and the value were 65% (ITO/CdS/BiVO 4), 22% (single CdS film) and 10% (ITO/BiVO4/CdS) at 480 nm with 0.3 V external bias. Comparison with ITO/BiVO4/CdS electrode and single Cd1-xZnxS electrodes, the heterostructured ITO/CdS/BiVO4 electrode can effectively suppress photogenerated electron-hole recombination and enhance light harvesting. Therefore, the ITO/CdS/BiVO4 electrode gave the maximum photocurrent density and IPCE value. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Bismuth compounds

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Synthesis of uniform ZnO/ZnS/CdS nanorod films with ion-exchange approach and photoelectrochemical performances

Synthesis of uniform ZnO/ZnS/CdS nanorod films with ion-exch...

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作者： Jiang, Jiangang Wang, Meng Ma, Lijing Chen, Qingyun Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering International Research Center of Renewable Energy Xi'An Jiaotong University Shaanxi 710049 China

The uniform ZnO/ZnS/CdS core-shell nanorod film was synthesized by a two-step ion-exchange method. The crystal structure, morphology, composition and optical property of as-prepared films were characterized by X-ray diffraction (XRD), Raman, Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy dispersive X-ray Detector (EDX) and UV-vis techniques. The results showed that the ZnO nanorod arrays can be used as sacrificial templates to synthesize uniform ZnS layer and further transform into CdS by simple ion-exchange approach. The CdS content in the films can be adjusted easily by changing the reaction temperature. The intimate contact between core and shell can be observed by high-resolution TEM image, which decrease the crystal boundary potential barrier and then facilitate the photogenerated charges transfer between the different phases. In this experiment, the ZnO/ZnS/CdS nanorod films were used in the photoelectrochemical (PEC) hydrogen production. And it is found that the film prepared at 70 C (first step) and 100 C (second step) gives a maximum photocurrent density and photo conversion efficiency. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Cadmium sulfide

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Experimental study on loop heat pipe with flat evaporator at different tilt angles

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Hsi-An Chiao Tung Ta Hsueh/Journal of Xi'an Jiaotong University 2013年第5期47卷 38-43页

作者： Long, Yan Wei, Jinjia Lü, Xiao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

To realize highly efficient heat dissipation of electronics, a loop heat pipe (LHP) with a flat evaporator was designed to study its operation characteristics at the tilt angles of 0°, 30°, 45°, 60°, 90° with an improved evaporator structure and a well arranged pipes which can reduce heat loss due to back conduction and improve inner flow performance. The results show that the LHP with inclination has a lower power to start up than the horizontal one, and at the same heat load, the operation temperature of the evaporator is much lower and the system is easier to reach a steady state with less temperature oscillations. However, there is slight difference in operating performance for the LHP at different title angles. The thermal resistance decreases with an increase in the heat load and a steady state occurs at last. The thermal resistance is larger for the horizontal case than that for the inclination case at the same heat load. The thermal resistances are very different at different tilt angles at low heat load, but the difference is small at high heat load.

关键词： Thermal load

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Simulation of hemodynamics in portal vein hypertension using CFD

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医用生物力学 2013年第S1期28卷 99-101页

作者： Xiao Li Yansong Pu Peng Nie Zongfang Li Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Second Affiliated Hospital Xi'an Jiaotong University Department of Radiology Huaihe Hospital of Henan University

Introduction Liver cirrhosis generally occurs with the hemodynamic changes during the portal vein hypertension and finally leads to the atrophy of the right lobe of the liver and hepatic failure^[1].According to the hemodynamic changes,a hypothesis has been proposed that the liver volume is related to the istribution of blood from the splenic vein（SV）that involves nutrition from spleen and pancreas^[2,3].The objective of the present paper is to simulate the blood flow in real models of portal vein hypertension and validate the hypothesis using computational fluid dynamics（CFD）*** This study includes 2 patients with liver cirrhosis and a set of 4 normal subjects.

关键词： cirrhosis hemodynamic nutrition pancreas splenic atrophy hypothesis validate finally spleen

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Study on ignition delay times of dimethyl ether/propane/O2/Ar mixtures at elevated pressures

Study on ignition delay times of dimethyl ether/propane/O2/A...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Hu, Erjiang Pan, Lun Zhang, Zihang Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an Shaanxi 710049 China

Ignition delay times of dimethyl ether (DME) and propane blends were measured in a shock tube at varied DME blending ratios (0%, 20%, 50%, 80%, 100%), equivalence ratios (0.5, 1.0, 2.0), temperatures (1100-1500 K) and pressures of 20 atm. Mechanism validations were conducted using different chemical kinetic models. A new C5 chemical model with DME sub-model was developed and it can well predict experimental ignition delay times of pure propane, DME and their blends. Experimental and numerical results show that with the decrease of temperature, the ignition delay times increase and the activation energy decreases slightly. With the increase of equivalence ratio, ignition delay times increase for propane and decrease for DME in this study. Ignition delay times decrease with the increase of DME blending ratio and the decrease rates become larger with the increase of equivalence ratio. The peak values of H and OH mole fraction increase with increasing the DME blending ratio, and they promote the ignition of DME/propane blends. Sensitivity analysis shows that the reaction rates of R1 and R353 increase with the increase of DME blending ratio and induces the decrease of the ignition delay time of DME/propane blends.

关键词： Ethers

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A study of auto-ignition of H2/CO/O2/Ar mixtures at elevated pressure and moderate temperature using shock tube

A study of auto-ignition of H2/CO/O2/Ar mixtures at elevated...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Thi, Luong Dinh Zhang, Yingjia Fu, Jin Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an Shaanxi710049 China

Ignition delays of stoichiometric syngas mixtures (H2/CO/O 2) diluted with argon were measured behind the reflected shock wave at pressures of 0.2, 1.0 and 2.0 MPa, temperature from 896 to 1264 K, equivalence ratios of 0.3, 1.0 and 1.5. The effect of non-ideal conditions on ignition delays, determined by pressure trace behind the reflected shock wave (pressure rise rate is approximately 4.22%/ms), was used to calculate. Six available mechanisms were selected to simulate the ignition delays of syngas mixtures, the predicted results were compared with the measured ones. These results indicated that there is no mechanism can calculate accurately ignition delays over all testing conditions. The ignition delays predicted with three mechanisms (Davis 2005, USC ver 2.0, NUI nc5-49) are close to the measured ones. Using the Davis mechanism to analyse reaction kinetics, the achieved results showed that the reaction R1 dominates the ignition process of syngas. The reaction R31 plays an important promoted role in ignition process of syngas mixtures.

关键词： Shock tubes

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Modeling the evolution of aeolian sand transport in a wind tunnel

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AIP Conference Proceedings 2013年第1期1547卷 758-765页

作者： Fengjun Xiao Liejin Guo Debiao Li Yueshe Wang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

An Eulerian-Lagrangian numerical simulation is performed to study aeolian sand transport in a wind tunnel. The evolutions of three parameters, sand mass flux, decay rate of sand mass flux profile and sand particle mean horizontal velocity with time, are investigated. The results show that: Sand mass flux takes more time to reach the saturated state than the last two parameters. First, we prove the evolution with time in the simulation is similar to the evolution in the length direction in a wind tunnel and then the experimental data from unsaturated wind tunnel can be used in the quantitative comparison with simulated saturated results. Second, detailed comparison is carried out. The tendency of sand mass flux is consistent with the experimental data. Decay rate of sand mass flux profile and sand particle mean horizontal velocity fit the experimental data well especially for cases of small free stream wind velocity, and the deviation is getting larger with the increasing of free stream wind velocity.

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