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Journal of Thermal Science 2019年第1期28卷 97-105页

作者： ZHANG Yawen LEI Fulin xiao yunhan Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) School of Chemical Engineering and Technology Tianjin University Key Laboratory of Advanced Energy and Power Institute of Engineering Thermophysics Chinese Academy of Sciences University of Chinese Academy of Sciences

The coal gasification behaviors in the pressurized high-density circulating fluidized bed under various solids circulation fluxes were studied with the CFD method, which combines the two-fluid model and coal gasification reactions represented by the chemical percolation devolatilization and the MGAS models. The numerical method was validated with two experimental cases, and detailed distributions of gas species and temperature in the riser were illustrated to understand the gasification process. To fully understand the influence of solids circulation flux on the gasification behavior, a series of cases were simulated with the solids flux varying gradually from 260 to 1010 kg/m^2 s, and the composition and quality of syngas were compared between various cases. The higher heating value of syngas firstly increased and then decreased with the increase of solids flux, and it reached the highest value around 480 kg/m^2 s. The influence of solids flux on gasification process was further analyzed through the contours of temperature, solids concentration, and gas composition in the riser.

关键词： CFD two-fluid model gasification high-density CFB

Synergistic Effect of Alkali Metals in Coal and Introduced CaO during Steam Gasification

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Journal of Thermal Science 2020年第6期29卷 1627-1637页

作者： LIU Yang YANG Xinfang LEI Fulin xiao yunhan Key Laboratory of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Research Center for Clean Energy and Power Chinese Academy of SciencesLianyungangJiangsu 222069China University of Chinese Academy of Sciences Beijing 100049China

The steam gasification kinetics of Zhundong raw coal and the washed coal by deionized water or hydrochloric acid with/without addition of CaO were tested by thermogravimetric analyzer(TGA)at medium temperatures(650℃ to 800℃).The cation contents of potassium and sodium in samples were determined by Inductively Coupled Plasma Optical Emission Spectrometer(ICP-OES).The Brunauer-Emmett-Teller(BET)surface area of the samples was tested by N2 adsorption,and the morphologies of the samples were characterized by scanning electron microscopy(SEM).Experimental results showed that the organic sodium was the main catalyst for the gasification of the pyrolysis char,and the gasification rate of the char could be enhanced further with the introduction of *** inherent alkali metals in coal and the introduced CaO showed a synergistic effect that occurred obviously above 735℃.The char conversion curves with or without CaO were fitted by the modified volumetric model(MVM).The calculated results indicated that the addition of CaO increased the pre-exponential factor obviously,but made little changes on the activation *** was proposed that the synergistic effect was resulted from the co-melting of the sodium and CaO,which facilitated the migration of the catalyst ions and the generation of C(O)intermediates for the gasification.

关键词： Zhundong coal alkali metals CaO synergistic effect steam gasification

Modeling and Experimental Validation on Pressure Drop in a Reverse-flow Cyclone Separator at High Inlet Solid Loading

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Journal of Thermal Science 2011年第4期20卷 343-348页

作者： Wu Xuezhi Liu Jie Xu Xiang xiao yunhan Key Laboratory of Advanced Energy and Power （Institute of Engineering Thermophysics） Chinese Academy of Sciences Beijing 100190 Graduate University of Chinese Academy of Sciences Beijing 100190

High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.

关键词： high inlet solid loading pressure drop reverse-flow cyclone modeling.

CFD simulation of smooth and T-abrupt exits in circulating fluidized bed risers

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Particuology 2010年第4期8卷 343-350页

作者： Xuezhi Wu Fan Jiang Xiang Xu yunhan xiao Key Laboratory of Advanced Energy and Power Institute of Engineering Thermophysics Chinese Academy ofSdences Beijing 100190 China Graduate University of the Chinese Academy ofSdences Beijing 100049 China

Gas-solid flow in circulating fluidized bed （CFB） risers depends not only on operating conditions but also on exit configurations. Few studies investigated the effects of exit configurations on flow structure using computational fluid dynamics （CFD）. This paper provides a 2D two-fluid model to simulate a cold bench-scale square cross-section riser with smooth and T-abrupt exits. The drag force between the gas and solid phases plays an important role in CFD. Since the drag force model based on homogeneous two- phase flow, such as the Wen-Yu correlation, could not capture the heterogeneous structures in gas-solid flow, the structure-dependent energy-minimization multi-scale （EMMS） drag force model （Wang, Ge, ＆ Li, 2008）, applicable for Geldart B particles （sand）, was integrated into the two-fluid model. The calculated axial solids hold-up profiles were respectively exponential curve for smooth exit and C-shaped curve for T-abrupt exit, both consistent with experimental data. This study once again proves the key role of drag force in CFD simulation and also shows the validity of CFD simulation （two-fluid model） to describe exit effects on ~as-solid flow in CFB risers.

关键词： T-abrupt exit Smooth exit Gas-solid flow CFBEMMS drag force model

Energy and Exergy Analysis of a Novel Efficient Combined Process by Hydrothermal Degradation and Superheated Steam Drying of Degradable Organic Wastes

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Journal of Thermal Science 2006年第3期15卷 274-280页

作者： Shuqing GUO yunhan xiao Wendong TIAN Zhedian ZHANG Zhongyuan University of Technology Zhengzhou City Henan Province 450007 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China

This paper considers the combination of hydrothermal degradation （HTD） and superheated steam （SHS） drying in disposal and processing of degradable organic wastes in municipal solid wastes （MSW）. In SHS drying, a fraction of dryer thermal energy input can be recovered and used to satisfy the heat requirement in maintaining the HTD operating temperature. Both energy and exergy analysis are applied to the combined process. The analysis covers ranges of dryer inlet temperatures of 202.38-234.19~C and feed water content of 32.5-65%. Thermal energy analysis shows that the combination of HTD and SHS drying can achieve thermal energy self-sufficiency （TES） by manipulating process variables. The exergy analysis indicates the location, type, and magnitude of the exergy losses during the whole process by applying the second law of thermodynamics.

关键词： hydrothermal degradation superheated steam drying energy analysis exergy analysis

Off-design performance of a chemical looping combustion (CLC) combined cycle:effects of ambient temperature

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Journal of Thermal Science 2010年第1期19卷 87-96页

作者： Jinling Chi Bo Wang Shijie Zhang yunhan xiao Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences (Institute of Engineering Thermophysics) P. O. Box 2706 Beijing 100190 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China

The present work investigates the influence of ambient temperature on the steady-state off-design thermodynamic performance of a chemical looping combustion(CLC) combined cycle.A sensitivity analysis of the CLC reactor system was conducted,which shows that the parameters that influence the temperatures of the CLC reactors most are the flow rate and temperature of air entering the air *** the ambient temperature variation,three off-design control strategies have been assumed and compared:1) without any Inlet Guide Vane(IGV) control,2) IGV control to maintain air reactor temperature and 3) IGV control to maintain constant fuel reactor temperature,aside from fuel flow rate *** indicate that,compared with the conventional combined cycle,due to the requirement of pressure balance at outlet of the two CLC reactors,CLC combined cycle shows completely different off-design thermodynamic characteristics regardless of the control strategy *** the first control strategy,temperatures of the two CLC reactors both rise obviously as ambient temperature *** control adopted by the second and the third strategy has the effect to maintain one of the two reactors' temperatures at design condition when ambient temperature is above design *** with the second strategy,the third would induce more severe decrease of efficiency and output power of the CLC combined cycle.

关键词： Chemical looping combustion Combined cycle Off-design performance Thermodynamic analysis Ambient temperature

Experimental Study of Falling-film Mode Transitions between Horizontal Tubes in CaCl_2/Water Absorber

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Journal of Thermal Science 2014年第4期23卷 338-345页

作者： XU Zhen SUN Wenqian LU Yuan xiao yunhan XIE Yingchun Key Laboratory of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of Sciences Research Center for Clean Energy and Power Chinese Academy of Sciences School of Engineering Ocean University of China

It is important to accurately predict the flow mode especially intertube falling-film mode of absorbent for its great impact on the heat and mass transfer in a horizontal tube absorber. In this paper, a test facility used to study falling-film outside horizontal tubes was built, and experiments were conducted to explore the intertube mode transi- tions with water-calcium chloride （CaC12/water） solution in quiescent surroundings. The correlations which are more suitable for predicting CaC1jwater solution intertube mode transitions were developed. In general, the transitional Re will decrease with the solution concentration increasing, and its effects increase with the transitions from droplet mode to sheet mode. Hysteresis exists in all the mode transitions, and it is more obvious for low concentration solutions. The results may be an important support for modeling, designing and operating of CaC12/water falling-film absorber.

关键词： horizontal tube mode transitions water-calcium chloride solution correlations

Thermodynamic Performance Assessment of IGCC Power Plants with Various Syngas Cleanup Processes

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Journal of Thermal Science 2012年第5期21卷 391-403页

作者： yunhan xiao Zhen Li Bo Wang Lifeng Zhao Jinling Chi Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences(Institute of Engineering Thermo-physics) P. O. Box 2706 Beijing 100190 China Research Center for Cleaned Energy and Power Chinese Academy of Sciences University of the Chinese Academy of Sciences Beijing 100049 China

The present work explores how much IGCC can benefit from warm gas clean-up（WGCU）in comparison with conventional cold gas clean-up（CGCU） and what are the respective contributions of dry particulates removal and warm gas desulfurization （WGD） in a plant-wide point of view. Influences of key parameters of WGD on ther- modynamic performance of IGCC plant including desulfurization temperature, oxygen concentration in the re- generation stream, and H2S removal efficiency are discussed. It is obtained that the net efficiency of IGCC with full WGCU experiences an improvement of 1.77 percentage points compared with IGCC with full CGCU. Of which, dry particulates removal without water scrubber contributes about 1 percentage point. The influence of desulfurization temperature on thermodynamic performance of IGCC with WGD is weak especially when it is higher than about 350~C, which indicates that more focus should be put on investment cost, technical feasibility and sorbent stability for the selection of optimal operation temperature. Generally, 2%-3% of oxygen concentra- tion in the regeneration stream might be reasonable in a thermodynamic performance point of view. In addition, the improvement of 0.31 percentage points can be obtained by removal of H2S in the syngas from 27 ppm to 3 ppm.

关键词： IGCC Syngas clean-up Desulfurization ZnO sorbent Thermodynamic performance assessment

3D full-loop simulation and experimental verification of gas-solid flow hydrodynamics in a dense circulating fluidized bed

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Particuology 2014年第5期12卷 218-226页

作者： Xueyao Wang Xuezhi Wu Fulin Lei Jing Lei yunhan xiao Key Laboratory of Advanced Energy and Power Institute of Engineering Thermophysics Chinese Academy of Sdences Beijing 100190 China Research Center for Clean Energy and Power Chinese Academy of Sciences Lianyungang Jiangsu 222069 China School of Energy & Power Engineering North China Electric Power University Changping District Beijing 102206 China

Because of their advantages of high efficiency and low cost, numerical research methods for large-scale circulating fluidized bed （CFB） apparatus are gaining ever more importance. This article presents a numer- ical study of gas-solid flow dynamics using the Eulerian granular multiphase model with a drag coefficient correction based on the energy-minimization multi-scale （EMMS） model. A three-dimensional, full-loop, time-dependent simulation of the hydrodynamics of a dense CFB apparatus is performed. The process parameters （e.g., operating and initial conditions） are provided in accordance with the real experiment to enhance the accuracy of the simulation. The axial profiles of the averaged solid volume fractions and the solids flux at the outlet of the cyclone are in reasonable agreement with experimental data, thereby verifying the applicability of the mathematical and physical models. As a result, the streamline in the riser and standpipe as well as the solids distribution contours at the cross sections is analyzed. Computational fluid dynamics （CFD） serves as a basis for CFB modeling to help resolve certain issues long in dispute but difficult to address experimentally. The results of this study provide the basis of a general approach to describing dynamic simulations of gas-solid flows.

关键词： Gas-solid flow Circulating fluidized bed EMMS method 3D full-loop simulation

Experimental and Theoretical Study of an Internally Cooled Liquid Desiccant Dehumidifier

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Journal of Thermal Science 2023年第4期32卷 1684-1696页

作者： ZHENG Xin LU Yuan WANG Bo ZHAO Lifeng xiao yunhan Key Laboratory of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing100190China Research Center for Clean Energy and Power Chinese Academy of SciencesLianyungang222069China University of Chinese Academy of Sciences Beijing100049China

Liquid desiccant dehumidifiers are useful for simultaneously recovering heat and water from flue *** cooled dehumidifiers are generally superior to adiabatic dehumidifiers in terms of the consumption of the desiccant and the size of the equipment *** study examines the performance of a counter-flow dehumidifier through experiments and simulations under different operating conditions,and analyzes the moisture effectiveness and enthalpy effectiveness as performance *** applying correlations from the literature,the theoretical model can predict the performance of the dehumidifier within an acceptable range of *** to the experimental results,droplets were visible at a low desiccant flow rate when the velocity of the gas was above 4.88 m/***,a higher cooling ratio and a higher temperature of the solution enhanced the effectiveness of the dehumidification.A temperature cross occurred between the gas and the solution when the mass transfer was sufficiently high,which reflects better heat transfer performance than the conventional convective heat exchanger.

关键词： flue gas recovery water heat internal cooling calcium chloride