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Correlations of chemical properties of high-alkali solid fuels: A comparative study between Zhundong coal and biomass

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FUEL 2018年 211卷 629-637页

作者： Wang, Chang'an Zhu, Xin Liu, Xuan Lv, Qiang Zhao, Lei Che, Defu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China

The utilization of Zhundong coal has given rise to serious ash-related issues mainly because of its high-alkali characteristic, partly similar to biomass with high-potassium content. The chemical properties of such coals and biomass may have marked impacts on reactivity and ash fouling. However, the correlations of different chemical properties of high-alkali solid fuels have been seldom investigated, and then only on a few samples. Here, a comparative study of chemical properties of Zhundong coal and biomass was conducted based on a large database. Correlations between carbon content and ash yield and carbon content and fixed carbon were noted. The fuel ratios of nearly all types of agricultural biomass lay within a range of 0.15-0.30, approximately an order of magnitude lower than those of Zhundong coals, much lower than those of Zhundong coals. There were no significant associations between chemical property and wheat-growing region. In most cases, the ash composition, even for a single biomass type, showed considerable variation, with the K2O content of wheat and corn straw ash being particularly variable. Most Zhundong coals had medium and similar ash fusion temperatures regardless of the changing ash compositions. Contrary to biomass, the Na2O content in Zhundong coal ash was an order of magnitude higher than K2O content. The ash composition of a particular biomass type usually fell in a small region of the ternary diagram of acidic-alkali metal-alkaline earth metal oxide components.

关键词： High alkali Chemical property Zhundong coal Biomass Ternary distribution

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Study on thermal hydraulic characteristics under startup of SCWR

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PROGRESS IN NUCLEAR ENERGY 2020年 122卷 103266-103266页

作者： Wang, Laishun Yuan, Yuan Shan, Jianqiang Zhang, Xiaoying Sun Yat Sen Univ Sino French Inst Nucl Engn & Technol Zhuhai Guangdong Peoples R China Xi An Jiao Tong Univ Sch Nucl Sci & Technol State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

To investigate the startup characteristics of the supercritical pressure water-cooled reactor (SCWR) system, a complete startup system model of the SCWR was established with the analysis code SCTRAN, based on the high-performance light water reactor (HPLWR) steam cycle and SCWR circulation startup loop. The correctness of the model was verified in comparison with the steady-state parameters of the steam cycle of the HPLWR. A sliding pressure startup procedure with a circulation loop that employs a control system was analyzed, and the transient performances of the core, steam drum, turbine, reheaters, steam extraction and heaters at each stage were obtained. The calculation results showed that the startup sequence and startup thermal parameters could fully meet the expectations: the system starts up stably and the core remains in the single phase;the inlet steam of the turbine stays superheated;the core inlet temperature can reach 280 degrees C after the adoption of the high-pressure and low-pressure heaters;and the inlet pressure of the high-pressure turbine can be kept constant. During the startup process, the maximum cladding surface temperature (MCST) remains below the limit of 650 degrees C, suggesting that the entire startup procedure is safe and reliable.

关键词： Supercritical water reactor SCTRAN Recirculation pressure startup

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Nanoscale capillarity for mitigating gas bubble adhesion on arrayed photoelectrode during photoelectrochemical water splitting

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APPLIED PHYSICS LETTERS 2019年第23期114卷 231604-231604页

作者： Chen, Juanwen Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

One-dimensional (1D) arrayed photoelectrodes usually present superior performance in photoelectrochemical (PEC) water splitting. This superiority is known to be attributed to directional transport of photogenerated charge carriers. Herein, we show that in addition to this intrinsic charge transport property, a 1D arrayed structure introduces nanoscale capillary wetting, which is also believed to contribute to the improved PEC performance. Our theoretical model predicts that this morphology-dependent capillarity leads to the formation of a liquid film between the photoelectrode surface and the adhered bubble (the generated H-2/O-2 bubble), thus largely reducing the blockage of active sites at the bubble base. This prediction has been experimentally demonstrated by taking arrayed TiO2 nanorods as a model photoelectrode, with the observation of the PEC activity within the bubble base. This work extends our knowledge toward hydrodynamic functionality involved in morphology-controlled photoelectrodes for enhanced PEC performance.

关键词： Interface dynamics Nanostructures Photoelectrochemical conversion Gas-solid interface Bubble dynamics Thin films Nanorods Capillarity Water-splitting Adhesion

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Heat-power decoupling technologies for coal-fired CHP plants: Operation flexibility and thermodynamic performance

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ENERGY 2019年 188卷 116074-000页

作者： Liu, Ming Wang, Shan Zhao, Yongliang Tang, Haiyu Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Heat-power decoupling is important for combined heat and power (CHP) plants because it improves their operational flexibility. In this study, off-design and thermodynamic analysis models are developed to examine and compare the operational flexibility improvement and thermodynamic performance of heat-power decoupling technologies. Quantitative analyses are then conducted on a 350 MW reference CHP plant. Results show that feasible operation domains are enlarged by heat- power decoupling technologies. Low-pressure turbine (LPT) renovations, such as zero output renovation and that with a bladeless shaft, have the most potential for reducing the feasible minimum power load, followed by electric boilers. Under a heating load of 300 MW, the feasible minimum power loads can be reduced by 71.6, 124.2, 42.4, and 157.7 MW with a heat pump, an electric boiler, a heat storage tank, and LPT renovations, respectively. However, the heating load of LPT renovations is completely coupled with power load, and its feasible operation domain is limited. Moreover, electric boilers decrease the energy and exergy efficiencies of CHP plants. Therefore, the heat storage tank decoupling technology is the preferable energy-saving option, followed by the heat pump decoupling technology. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Combined heat and power Operational flexibility Heat-power decoupling Thermodynamics Case study

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Size effect of one-dimensional nanostructures on bubble nucleation in water splitting

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APPLIED PHYSICS LETTERS 2019年第10期115卷 101602-101602页

作者： Chen, Juanwen Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

One-dimensional (1D) nanostructures have wide applications in photocatalysts for water splitting. Their surfaces may impact the gas bubble nucleation rate, thus influencing the efficiency of gas evolution. However, the effects of the 1D nanostructured surfaces on the bubble nucleation have not been studied to date. Herein, these effects are theoretically analyzed, based on the changes of free energy for a bubble nucleus forming inside/outside a nanotube. The results show that compared to flat surfaces, the inner tube wall favors the bubble nucleation, while the outer wall has an opposite effect. These differences become increasingly significant with tube radius R-t reducing when R-t<10r(*) (r(*)-bubble equilibrium radius). The size effect is further verified experimentally for bubble nucleation on TiO2 nanotube arrays. The sensitivity of bubble nucleation to nanostructure dimensions should be considered in designing high-efficient photocatalysts.

关键词： Nanotubes Nanostructures Supersaturation Water-splitting Bubble dynamics Free energy

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Experimental study of gas-liquid two-phase wavy stratified flow in horizontal pipe at high pressure

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2019年 143卷 118537-000页

作者： Wang, Yubo Liu, Zhigang Chang, Yingjie Zhao, Xiangyuan Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The regimes of gas-liquid two-phase flow in horizontal pipe at high pressure were experimentally investigated, and characteristics of wave stratified flow, such as wave length, wave height and propagation speed were calculated. The pressure drop was analyzed and friction factors, such as gas-wall, liquid wall and interfacial friction factors, were calculated and new correlations were deduced. Influence of interface wave on interfacial friction factor was studied, and characteristics of interface wave were included to deduce new correlation for it, and good accuracy was proved. For the gas-water two-phase flow at 2 MPa, transition from wave stratified to annular flow appears with smaller gas superficial velocity compared with that at atmosphere, and intermittent flow appears with greater liquid superficial velocity. Regime transition models are tested, for the gas-liquid two-phase flow at atmosphere the sheltering coefficient with value of 0.01 is appropriate. However, it is promoted to be 0.06 at 2 MPa, and good performance of regime transition model was reached. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： High pressure Wave stratified flow Regime transition model Interface wave Friction factor

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Stability and activity maintenance of sol-gel Ni-MxOy (M = Ti, Zr, Ta) catalysts during continuous gasification of glycerol in supercritical water

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JOURNAL OF SUPERCRITICAL FLUIDS 2019年 148卷 137-147页

作者： Li, Sha Savage, Phillip E. Guo, Liejin Nanjing Univ Sci & Technol Sch Energy & Power Engn Nanjing 210094 Jiangsu Peoples R China Univ Michigan Dept Chem Engn Ann Arbor MI 48109 USA Penn State Univ Dept Chem Engn University Pk PA 16802 USA Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The long-term stability of activities and physicochemical properties for nickel nanoparticles supported on TiO2, ZrO(2 )and Ta2O5 prepared by sol-gel methods, was evaluated for continuous supercritical water gasification (SCWG) of 3 wt.% glycerol at 425 degrees C and 25.2 MPa. The Ni/TiO2 catalyst bed gradually deactivated while the Ni/ZrO2 and Ni/Ta2O5 catalyst beds showed persistent and high carbon gasification efficiency for 80 h operation. Characterization results verified that property stabilization of the sol-gel Ni/ZrO(2 )and Ni/Ta2O5 catalysts occurred in the long-term SCWG flow, indicating a "catalyst in-situ activation" effect that enhanced the activity and coking resistance of the as-prepared sol-gel catalysts for continuous SCWG. Results also indicate that sintering of Ni with the supports to form new phases and metal leaching of the catalyst materials in the SCW flow may be key deactivation factors of the catalyst beds.

关键词： Supercritical water gasification Supercritical water Nickel catalyst Stability Glycerol

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A Sustainable Multipurpose Separator Directed Against the Shuttle Effect of Polysulfides for High-Performance Lithium-Sulfur Batteries

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ADVANCED ENERGY MATERIALS 2022年第19期12卷 2200160-2200160页

作者： Wang, Wei Xi, Kai Li, Bowen Li, Haojie Liu, Sheng Wang, Jianan Zhao, Hongyang Li, Huanglong Abdelkader, Amor M. Gao, Xueping Li, Guoran Nankai Univ Renewable Energy Convers & Storage Ctr Inst New Energy Mat Chem Sch Mat Sci & Engn Tianjin 300350 Peoples R China Xi An Jiao Tong Univ Sch Chem Xian Key Lab Sustainable Energy Mat Chem Xian 710049 Peoples R China Tsinghua Univ Ctr Brain Inspired Comp Res Dept Precis Instrument Beijing 100190 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Dept Environm Sci & Engn Xian 710049 Peoples R China Chinese Inst Brain Res Beijing 102206 Peoples R China Bournemouth Univ Fac Sci & Technol Talbot Campus Poole BH12 5BB Dorset England

The success of lithium-sulfur batteries will reduce the expected Co, Ni resource challenges from the wide adoption of lithium-ion batteries. Unfortunately, the shuttle effect of soluble polysulfides brings many problems. Anchoring or blocking polysulfides on the cathode side using functional separators is the dominant strategy for addressing this. However, the blocked polysulfides gradually aggregate on the separator to form the so-called "dead sulfur" and withdraw from cycling. Herein, a multipurpose separator is proposed that enables catalytic activation of the blocked polysulfides to prevent the formation of "dead sulfur", and contribute to capacity. The multifunctionality is supported by montmorillonite (MMT) that provides sufficient channels for lithium-ion transport, and selenium-doped sulfurized-polyacrylonitrile (Se(0.06)SPAN) that catalyzes conversion of "dead sulfur" and simultaneously contributes capacity. The theoretical calculations reveal Se(0.06)SPAN/MMT has a low migration barrier for Li+ and a low decomposition barrier for Li2S, facilitating the conversion and minimizing "dead sulfur". Consequently, the Li-S battery with the Se(0.06)SPAN/MMT@PP (polypropylene) separator shows a low fading rate of 0.034% during 1000 cycles and achieves a super-high areal capacity (33.07 mAh cm(-2)) under high sulfur loading (26.75 mg cm(-2)) and lean electrolyte conditions (4.5 mu L mg(-1)). Moreover, the multipurpose separator has encouraging performance in stability, flexibility, and sustainability.

关键词： electrocatalysis lithium-sulfur batteries montmorillonite polyacrylonitrile separators

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Ash deposition and sodium migration behaviors during combustion of Zhundong coals in a drop tube furnace

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JOURNAL OF THE ENERGY INSTITUTE 2018年第2期91卷 251-261页

作者： Wang, Chang'an Li, Guangyu Du, Yongbo Yan, Yu Li, Hao Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Zhundong coalfield is one super-large coalfield recently discovered in China. However, the utilization of Zhundong coal in power plants has caused serious ash-related issues mainly due to its high-sodium feature. The ash deposition problem on convection heat exchanger surfaces is still particularly difficult to resolve and its mechanism has yet to be fully understood. This study deals with the ash deposition and alkali metal migration behaviors on convection heat exchanger surfaces between 400 and 800 degrees C during combustion of Zhundong coal using a lab-scale drop tube reactor. Experimental results show that the sodium content in ash deposit of Zhundong coals increases obviously as the deposition temperature decreases from 800 to 600 degrees C, while it is almost unchanged below 600 degrees C. The contents of iron and calcium in ash deposits exhibit nonmonotonic variations as the deposit probe temperature varies between 400 and 800 degrees C. Quartz and calcium sulfate are main crystalline phases in ash deposit of Zhundong coals. Calcium is inclined to present as calcite and lime at low deposition temperature, while high temperature facilitates calcium sulfation. Sodium of crystalline phase is found as albite and sodium sulfate at low deposition temperature. Both condensation of gaseous alkali metals and formation of low melting minerals were responsible for the ash deposition phenomenon on convection heat exchanger surfaces involved in combustion of Zhundong coal. The sodium content in ash deposit decreases considerably with the increasing combustion temperature while the case of iron variation is opposite due to its low-volatility. In addition, the Na content in ash deposits increases obviously with the access air ratio reduced from 1.2 to 1.05, but the local weakly reducing atmosphere leads to less iron within ash deposits. Clarification of sodium migration and evaluation of ash deposition behaviors during combustion of Zhundong coal is helpful for a better e

关键词： Zhundong coalfield High-sodium coal Ash deposit Transition behavior Deposition temperature

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Transformation and release of potassium during fixed-bed pyrolysis of biomass

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JOURNAL OF THE ENERGY INSTITUTE 2018年第4期91卷 630-637页

作者： Deng, Lei Ye, Jiaming Jin, Xi Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

To study the release and transformation of fuel K during rapid pyrolysis of biomass, wheat straw, corn stalk and rice hull are pyrolyzed in a fixed-bed reactor system during 400-1000 degrees C, and weight measurement, elemental composition analysis, and chemical fractionation analysis are performed. The effects of fuel type, pyrolysis temperature, co-pyrolysis of different fuels, and water washing pretreatment are discussed. The results show that for all biomass fuels, the released K is far less than the water-soluble K and a sudden increase occurs in the fraction of ion-exchangeable K at 400 degrees C, whereas a significant increase happens in the fraction of insoluble K above 800 degrees C. Wheat straw releases less than 5% of K at 400 and 500 degrees C. As temperature rises, the K release increases abruptly and around 40% of K enters the gas phase at 1000 degrees C. Rice hull has a slow and linear K release with increasing pyrolysis temperature. Corn stalk has the lowest K release during 400-800 degrees C. Co-pyrolysis of wheat straw and rice hull reduce the K release at 1000 degrees C, and the biggest decrement is 0.76 mg g(-1). Water washing removes all the water-soluble K of corn stalk and part of ion-exchangeable K enters the gas phase during pyrolysis of the washed sample. Water washing decreases the K release from 2.77 to 0.18 mg g(-1) at 1000 degrees C. (C) 2017 Energy Institute. Published by Elsevier Ltd. All rights reserved.

关键词： Potassium release Transformation Biomass pyrolysis Co-pyrolysis Water washing

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