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A study on free radical behaviors and reactions in supercritical water using quantum chemical simulation

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Journal of Molecular Liquids 2025年 419卷

作者： Ding, Weijing Takahashi, Osamu Wang, Junying Jin, Hui School of Transportation and Vehicle Engineering Shandong University of Technology Shandong Zi'bo255000 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China of Advanced Science and Engineering Hiroshima University Higashi-Hiroshima739-8526 Japan

Supercritical water (SCW) gasification is one of clean and efficient utilization way of biomass, other organic matters or coal for hydrogen production, in which radical reactions studies in SCW are limited but crucial. Density-functional tight-binding (DFTB) molecular simulation is one of efficient and convenient approaches to investigate these microscopic processes. Therefore, free radical reactions in severe SCW environment were investigated via DFTB calculations in this work. The results showed that the order of the free radicals containing bond cleavages reacted in SCW environment was ·OH, ·CH, ·CH2, ·HO2, ·CH3 and ·C6H5 under the same conditions. The reaction processes of different radicals in SCW were obtained. ·H was the most active free radical of reactions. This work is expected to understand the properties of free radicals in SCW better and explore intrinsic reaction mechanisms, which may provide a theoretical support for accomplishing efficient and low-carbon complete SCW gasification for hydrogen production. © 2024 Elsevier B.V.

关键词： Free radical Gasification Hydrogen production Reaction Supercritical Water (SCW)

Development of a Two-Phase flow Solver with Drift-Flux Model Based on Openfoam: Validation Against Single/Two-Phase and Boiling flow

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SSRN 2024年

作者： Wu, Wenqiang Zhang, Dalin Huang, Tao Du, Peng Zhou, Lei Wang, Bo Deng, Jian Qiu, Zhifang Tian, Wenxi Qiu, Suizheng Su, Guanghui State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Nuclear Power Institute of China 328 Changshun Avenue Chengdu610213 China

Based on the open-source platform OpenFOAM, this paper implements a two-phase flow solver for drift flux models with realistic closure relations. The solver inherits the numerical method from the OpenFOAM framework, adopts the PIMPLE algorithm, and follows its discrete and matrix-solving criteria, focusing on developing a two-phase flow model and constitutive models. The drift velocity model is based on Ishii and his collaborators’ work. The remaining models, such as wall friction, wall heat transfer, interfacial heat and mass transfer, are taken from TRACE Theory Manual. To fulfill the condition of conjugate heat transfer between fluid and solid, a virtual solid heat transfer function is developed under the premise of a single-domain solver. Extensive and successful validation has been conducted involving single-phase, two-phase, and boiling flow heat transfer phenomena by comparing with experimental data or typical system codes, and the two-phase flow solver's success has been demonstrated in several aspects. © 2024, The Authors. All rights reserved.

关键词： Two phase flow

Characteristics and Prediction Model of Co-Pyrolysis of Sewage Sludge and Camellia Seed Shell

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SSRN 2022年

作者： Wang, Bo Liu, Yinhe Guan, Yu Feng, Yiwei Pan, Hejitian State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi’an710049 China

Tar is an undesired product in the process of sewage sludge pyrolysis, which affects the normal operation of the equipment. In this paper, the characteristics of co-pyrolysis of sewage sludge and camellia seed shell for tar reduction and syngas production were explored. The content and composition of tar and pyrolysis gas co-pyrolyzed with different proportions of sewage sludge (JAS) and camellia seed shell samples (CSS) were studied. The weight loss characteristics of the samples were studied by thermogravimetric experiment, and the synergistic effects of different stages were analyzed. The performances of back propagation (BP) neural network and particle swarm optimization-back propagation neural network (PSO-BP) in reflecting the nonlinear relationship between temperature, mixing ratio, heating rate and remaining weight were compared. The results show that the tar yield was the lowest when 40JAS60CSS was pyrolyzed, which could alleviate the serious problems caused by the tar. Compared with the JAS single pyrolysis, the co-pyrolysis of JAS and CSS improved the content of PAHs and reduced the content of aliphatic hydrocarbons in the tar. The inhibition and promotion effects of co-pyrolysis would be transformed into each other with the progress of the pyrolysis, and the transformations were concentrated in the S 2 stage where the weight loss of the sample is the largest. The constructed PSO-BP-30 model contained two hidden layers, each with 12 neurons, which accurately reflected the nonlinear relationship between the temperature, mixing ratio, heating rate and residual weight. © 2022, The Authors. All rights reserved.

关键词： Pyrolysis

Integrated Co2 Capture and Conversion by Three-Step Chemical Looping Dry Reforming of Methane

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SSRN 2025年

作者： Liu, Yunlian Liu, Mingkai Shen, Yuanhui Li, Yang Gai, Zhongrui Zhang, Ruqi Pan, Ying Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The integrated CO2 capture and conversion (ICCC) has emerged as a promising and cost-effective pathway for achieving carbon neutrality. However, limited energy-efficient pathways and durable materials for ICCC systems remains challenging. This study proposes a novel approach that synergistically integrates CO2 capture and conversion through a unified chemical framework. The method employs Li-based sorbents for CO2 capture, coupled with CH4-driven sorbent regeneration that is seamlessly integrated with chemical looping dry reforming of methane (CLDRM), enabling in-situ CO2 conversion. By coupling sorbent regeneration with CLDRM, this system enhances decarbonation kinetics through Le Chatelier's principle via continuous CO2 conversion. One-step calcination synthesized Li-based sorbents particles exhibit stable CO2 capture capacity of 5.25 mmol·g-1 within 15 min per cycle, maintaining 7.5-15% operational efficiency over 40 cycles at 600 ℃. In CLDRM, hydrogen radicals from CH4 dissociation promote the conversion of CO2 to intermediates, lowering the apparent activation energy of sorbents regeneration by 29.2%. Through systematic optimization in a fixed-bed reactor, we achieved 90% CO2 uptake and 85% CH4 conversion, with syngas production rates reaching 13.71 mL·min-1·g-1. Notably, the H2/CO molar ratio in syngas stabilizes ~1.6, aligns with iron-based Fischer-Tropsch and methanol synthesis to produce valuable fuels. This integrated system maintains >80% syngas purity with © 2025, The Authors. All rights reserved.

关键词： Activation energy

Load Forecasting of District Heating System Based on Improved Fb-Prophet Model

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SSRN 2022年

作者： Shakeel, Asim Chong, Daotong Wang, Jinshi State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi'An710049 China

Accurate load forecasting of district heating networks (DHN) is an essential guide to guaranteeing effective energy production, distribution, and rational utilization. Artificial neural networks have been extensively applied to heating energy prediction in DHN. An improved FB-Prophet model with additional positional encoding layers has been developed to forecast the DHN heat consumption. The accuracy of univariate and multivariate FB-prophet models is evaluated;this paper also investigates how training data affects the accuracy and robustness of improved FB-prophet model. Results revealed that the accuracy of the improved FB-Prophet model increases as the amount of training data increases;it is also observed that there exists a turning point after which robustness starts to decrease. To explore the performance of the improved FB-Prophet model in heating load forecasting tasks, another seven machine learning models, namely FB-Prophet, DeepVAR, long-short term memory (LSTM), extreme gradient boosting (XGBoost), multilayer perceptron (MLP), recurrent neural network (RNN), and support vector regression (SVR) are used for comparison. The historical heating load, outside temperature, relative humidity, speed of wind, direction of wind, and weather type (sunny, overcast, rainy) of a DHN in Serbia are utilized as the key parameters to extensively investigate the effectiveness of the improved FB-Prophet model. The prediction outcomes of all the models were analyzed thoroughly. The results indicated that the improved FB-Prophet model can generate the most precise and consistent predictions and it showed better results for sparse and noisy data of DHN. The prediction curve is fitted to the trend of hourly DHN consumption change, which can play an effective guiding function in the distribution of heat. © 2022, The Authors. All rights reserved.

关键词： Forecasting

Enhanced catalytic activity for simultaneous removal of PCDD/Fs and NO over carbon nanotubes modified MnO_(x)-CeO_(2)/TiO_(2)catalyst at low temperatu

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Waste Disposal and Sustainable Energy 2021年第1期3卷 63-71页

作者： Qiulin Wang Zhuping Jiang Jianjian Zhou Jin Jing School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Henan Diesel Engine Industry Co LtdLuoyang 471000China

Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO ***-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was *** comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen *** addition improves the catalytic activity for their simultaneous *** optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed *** results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO ***,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen *** the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simulta

关键词： o-DCBz catalytic oxidation Simultaneous removal MnO_(x)-CeO_(2)catalyst Composite carrier Carbon nanotube

Experimental Study on Non-Isothermal Mixing Characteristics of Water in T-Junction

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Experimental Study on Non-Isothermal Mixing Characteristics ...

China Instrument and Control Society (ACCIS), Academic Conference of

作者： Shuhan Liu Wencang Guo Xianliang Lei Zhaojun Yuan Shuqi Meng Desheng Jin State Key Laboratory of Multiphase Flow Engineering Xi'an Jiaotong University Xian China China Nuclear Power Technology Research Institute Co. Ltd. Shen Zhen Guangdong China

ISBN: (数字)9798350350326

ISBN: (纸本)9798350350333

T-junction is an essential component in piping system of various thermal systems. When hot and cold fluid mixing in the T-junction, several compound mechanisms (like turbulent mixing, turbulent penetration, fluid stratification) make the mixing characteristics more complex. To clearly reveal such mixing mechanism with non-isothermal fluids, an experimental study was conducted with Ultrasound Doppler Velocimetry (UDV) and fast-response thermocouples bundle. The results show that the local velocity uncertainty of the UDV is within 10%, the uncertainty of the thermocouple bundle is 0.5°C, and the response time is 66.7 ms. After verification, the mixing characteristics between the main and branch pipe under different momentum ratios and temperature differences were discussed. It is shown that as the momentum ratio decreases, the location of the most intense radial temperature fluctuations and velocity fluctuations shifts towards the lower wall. At the same time, the peak flow rate in the cross-section increases by 35.7% and the main branch fluid mixing is more homogeneous. As the temperature difference increases, the thermal stratification is more pronounced and the velocity fluctuation peak moves towards the upper wall of the pipe.

关键词： Temperature measurement Temperature distribution Fluctuations Fluids Uncertainty Measurement uncertainty Thermocouples Distance measurement Velocity measurement Voltage control

A Gpu-Accelerated Multi-Resolution Lsmps Method for multiphase flows Simulation with Gas-Liquid Phase Transition

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SSRN 2024年

作者： Cao, Sheng Ren, Qianyong Wang, Wenpeng Zhang, Bin Shan, Jianqiang School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

The meshless Lagrangian method (particle method) demonstrates significant advantages in simulating multiphase flows with highly dynamic phase interfaces and has been widely applied in research areas such as ocean engineering, nuclear engineering, and aerospace engineering. The least squares moving particle semi-implicit (LSMPS) method theoretically attains high-order accuracy, significantly enhancing the precision and stability of simulations. However, compared to traditional Eulerian methods, its numerical discretization is more complex and computationally intensive, which limits its applicability in large-scale simulations. To mitigate these challenges, a multi-resolution particle model is implemented to reduce computational costs, and algorithmic improvements and optimizations enable GPU-based parallel processing, significantly boosting computational efficiency. Building on this foundation, a high-precision surface particle detection algorithm and a stable gas-liquid phase transition model are developed. The phase transition model integrates the volume change resulting from phase transition as a source term in the pressure Poisson equation. Benchmark tests of single bubble rising in liquid, Rayleigh-Taylor instability, and two-dimensional horizontal film boiling were conducted to validate the accuracy and efficiency of the GPU- accelerated multi-resolution LSMPS method for simulating multiphase flows, thereby promoting the application of the LSMPS method in both scientific research and practical engineering. © 2024, The Authors. All rights reserved.

关键词： Poisson equation

An Experimental Study on Ash Deposition Problem of Low-Low Temperature Flue Gas System 9th

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An Experimental Study on Ash Deposition Problem of Low-Low T...

9th International Symposium on Coal Combustion, ISCC 2019

作者： Yan, Yu Jiang, Jiahao Guo, Jin Li, Yuesheng Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Guangdong Institue of Special Equipment Inspection and Research Foshan528251 China Guangdong Institue of Special Equipment Inspection and Research Shunde Institue of Inspection Foshan528300 China

ISBN: (纸本)9789811616563

In order to achieve the ultra-clean emission standards, many power plants in China have completed the installation of low-low temperature flue gas system. However, during the operation of this system, many problems have emerged, such as the ash deposition problem in the heat exchanger and dry ESP (electrostatic precipitator). In this paper, the fixed adsorption system and entrained flow experimental system were built to study the ash deposition characteristics in low-low temperature flue gas system under different temperatures and particle sizes. The repose angle was measured to evaluate the flowability and adhesion capacity of ash particles. The results show that as the increase of adsorption time, the particle size increased gradually, and the agglomeration effect is attenuated after the particles have reached adsorption saturation. The time at which the ash particles began to agglomerate with each other was defined as the agglomeration threshold. As the adsorption temperature decreased, the particle size growth rate increased. The smaller the size of ash particles, the more significant the agglomeration effect. Large particles were easy to adsorb small particles, but the agglomeration effect between large particles was weak. In addition, in the initial stage of particle agglomeration, it was mainly included the adhesion between smaller particles and the adhesion of smaller particles on the surface of large particles. The followability of the ash particles was greatly reduced after the adsorption and agglomeration process. The repose angle of the ash particles increased as the temperature of the flue gas decreased. The smaller the particle size, the larger the repose angle changes, and the more pronounced the repose angle is influenced by the adsorption temperature. The flue gas temperature cannot be blindly dropped in pursuit of high sulfur oxide removal efficiency and dust removal efficiency. © 2022, Tsinghua University Press.

关键词： Particle size