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Combustion and heat transfer characteristics of a 300 MW pulverized-coal boiler retrofitted with biogas co-combustion

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Thermal Science and engineering Progress 2025年

作者： Fengxia An Fanhui Shen Zhaoping Zhong Yunan Chen Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and Environment Southeast University Nanjing 210096 China China Energy Science and Technology Research Institute Co. Ltd. Nanjing 210023 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Biomass co-combustion is an important measure to reduce the carbon dioxide emissions for pulverized-coal boilers. However, little work has been done to reveal the change in the heat transfer performance of retrofitted boilers. In this paper, the heat transfer process of furnace heating surfaces in a 300 MW pulverized-coal boiler with biogas co-combustion is invested by numerical simulation which combines the three-dimensional (3D) CFD model for combustion and heat transfer process of flue gas and the one-dimensional (1D) analytical model for the working fluid. The following conclusions can be drawn: the completeness of fuel combustion will be improved when biogas is injected into the furnace, and the peak concentration of carbon monoxide (CO) in the primary combustion zone decreases from 2.5 % to 0.93 % when the biogas co-combustion ratio increases from 0 % to 30 %, indicating that the risk of high-temperature corrosion on the water wall can be reduced. The 30 % biogas co-firing scheme with the biogas injection positions being both SA-1 and SOFA-3 is best in all cases studied in this work, because the temperature in the furnace and the heat transfer between the flue gas and the working fluid are most uniform, which contributes to the high boiler efficiency, low thermal NO x formation and good flexibility. Co-combusting 30 % biogas can increase the outlet working fluid dryness from 0.39 to 0.53 at the outlet of waterwalls, leading to an increase in the heat absorption in the furnace and a decrease in heat absorption at the tail convective heating surfaces, which should be considered carefully in the operation of the biogas co-combustion boilers. The research findings of this paper will provide technical support for the operation and control of pulverized-coal boilers co-firing biogas.

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Insight into carbon corrosion of different carbon supports for Pt-based electrocatalysts using accelerated stress tests in polymer electrolyte fuel cells

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JOURNAL OF power SOURCES 2022年 551卷

作者： Qi, Yongzhen Huang, Ying Gao, Ziliang Chen, Celine H. Perego, Andrea Yildirim, Hakan Odgaard, Madeleine Asset, Tristan Atanassov, Plamen V. Zenyuk, Iryna Univ Calif Irvine Dept Mech & Aerosp Engn Irvine CA 92697 USA Univ Calif Irvine Dept Mat Sci & Engn Irvine CA USA Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Univ Calif Irvine Natl Fuel Cell Res Ctr Dept Chem & Biomol Engn Irvine CA USA IRD Fuel Cells LLC 8500 Washington St NE Albuquerque NM 87113 USA

Carbon-based catalyst support and Pt catalysts are commonly used in polymer electrolyte fuel cells (PEFCs). During cell start-up and shutdown processes, carbon support oxidation occurs, which leads to losses of electrochemical performance. In this work, carbon corrosion accelerated stress tests (ASTs) were performed and lifetimes of high surface area carbon (HSAC) and graphitized carbon (GrC) supports were investigated. 1000 AST cycles were conducted on Pt/HSAC while 10000 AST cycles were conducted on Pt/GrC due to different carbon corrosion rates, and both Pt/HSAC and Pt/GrC showed rapid decrease of performance at end of life (EOL). Detailed comparisons of electrochemical characterizations were also conducted between Pt/HSAC and Pt/GrC. Electrochemical surface area (ECSA) loss in different levels was found for both Pt/HSAC and Pt/GrC due to Pt loss, Pt detachment and particles coalescence, which also resulted in reduction of SO3 group coverage and more tortuous H+ transportation, leading to decreased catalyst layer ionic conductivity. For Pt/HSAC after 1000 AST cycles, more than 2 times higher ECSA loss but with only 50% greater particle size growth and similar Pt loss strongly suggested that a greater Pt detachment occurred on HSAC support during the AST cycles. Apart from that, it was found that after 1000 AST cycles, graphitized carbon support was much more robust compared to HSAC support, and it showed 2 times less ECSA reduction, 2.5 times less catalyst layer ionic conductivity reduction and 4 times less SO3 group coverage reduction. Double layer capacitances increased for both carbon supports after AST at their EOLs, as more disordered carbon contacts were formed, which created more contacts between solid and ionic materials. This study shows a possibility of Pt/GrC catalysts to meet the Department of Energy (DOE) target of 5000 AST carbon cycles, as the Pt/GrC cell met the target of <= 40% ECSA loss of initial area.

关键词： Polyelectrolytes

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Existing DNB-type CHF mechanistic models and relations with visualized experiments in forced convective flow boiling: A review

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PROGRESS IN NUCLEAR ENERGY 2022年 148卷 1页

作者： Liu, Yang Liu, Wei Gu, Long Shan, Jianqiang Zhang, Lu Su, Xingkang Lanzhou Univ Sch Nucl Sci & Technol Lanzhou 730000 Gansu Peoples R China China Huaneng Grp CO LTD Huaneng Nucl Energy Technol Inst Shanghai 200126 Peoples R China Chinese Acad Sci Inst Modern Phys Lanzhou 730000 Gansu Peoples R China Univ Chinese Acad Sci Sch Nucl Sci & Technol Beijing 100864 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

This paper reviews in detail the existing visualized experiments and mechanistic models of DNB-type CHF in forced convective flow boiling. And summarizes and reviews the existing CHF mechanistic models from the perspective of whether the NVG (Net Vapor Generation) point is established or not, from both the micro and macro aspects, and the relationship between the visualized phenomenon and the CHF models has been explained. In addition, a visualized experiment within the geometry and parameters of the PWRs was launched with R-134a fluid to explore the similarities and differences between the existing visualized phenomena under tube, annulus, and rectangular channels, especially in the influence of grid. Finally, the possible development direction of the DNB-type CHF mechanistic model and the problems to be solved are clarified.

关键词： CHF DNB Visualized experiment Mechanistic model Trigger mechanism Bubble behavior Grid PWRs

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Numerical investigation on bubble dynamics during pool nucleate boiling in presence of a non-uniform electric field by LBM

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APPLIED THERMAL engineering 2019年 155卷 637-649页

作者： Feng, Yuan Li, Huixiong Guo, Kaikai Lei, Xianliang Zhao, Jianfu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Chinese Acad Sci Inst Mech CAS Key Lab Micrograv Beijing 100190 Peoples R China Univ Chinese Acad Sci Sch Engn Sci Beijing 100049 Peoples R China

Previous experimental studies proved that an external electric field could accelerate the detachment of vapor bubble. However, it was difficult to investigate the influencing mechanism of an electric field on bubble dynamics because of the limit of experimental technical methods. To solve this problem, a two-dimensional lattice Boltzmann model was developed in this paper to simulate the pool boiling in presence of an external electric field by coupling the pseudopotential model with phase-change model and electric field model. The growth and detachment of a single bubble on a horizontal wall during pool nucleate boiling with a non-uniform electric field was simulated. The influence of gravitational acceleration and electric field intensity on bubble dynamics was investigated in detail, and the influencing mechanism of an external electric field on bubble dynamics during pool nucleate boiling was analyzed. The numerical results showed that increasing electric filed intensity could decrease both bubble departure diameter and bubble release period. Decreasing gravitational acceleration could strengthen the influence of electric field intensity on bubble departure diameter and bubble release frequency. In other words, the non-uniform electric field established at present study could effectively reduce the possibility of heat transfer deterioration under microgravity.

关键词： Lattice Boltzmann method Electrohydrodynamics Bubble departure diameter Bubble release frequency

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Optimization and Techno-Economic analysis of catalytic gasification of wheat straw biomass using ASPEN PLUS model

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ARABIAN JOURNAL OF CHEMISTRY 2024年第7期17卷

作者： Hasnain, Muhammad Faheem Ul Ali, Hassan Osaf Aziz, Shahid Kouotou, Patrick Mountapmbeme Waqas, Muhammad Naqvi, Syed Murawat Abbas Athar, Muhammad Hassaan Ammar, Muhammad Shah, Imran Jung, Dong-Won Xi An Jiao Tong Univ Sch Energy & Power Engn Xian Key Lab Solid Waste Recycling & Resource Reco Xian 710049 Peoples R China Hiroshima Univ Dept Mech Engn Combust Engn Lab Hiroshima 7398527 Japan Jeju Natl Univ Dept Mech Engn 102 Jejudaehak Ro Jeju Si 63243 South Korea Univ Maroua Natl Adv Sch Engn POB 46 Maroua Cameroon Univ Ebolowa Adv Sch Agr Forestry Water Resources & Environm POB 118 Ebolowa Cameroon Univ Sargodha Coll Engn & Technol Dept Mech Ind & Energy Syst Sargodha 40100 Pakistan NFC Inst Engn & Fertilizer Res Dept Mech Engn Faisalabad 38000 Pakistan Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Govt Coll Univ Dept Chem Engn Technol Faisalabad 38000 Pakistan Air Univ Dept Mechatron Engn Islamabad 44000 Pakistan Jeju Natl Univ Fac Appl Energy Syst Major Mech Engn 102 Jejudaehak Ro Jeju Si 63243 South Korea

Biomass gasification efficiently produces heat, electricity, and power. However, removing harmful contaminants from raw syngas is crucial. Tar production is a challenge due to blockage, plugging, and corrosion. Tar steam reforming (TSR) is the most promising technique, converting high molecular weight hydrocarbons into CO, CO 2 , H 2 , and CH 4 . In this study, a model of biomass gasification using wheat straw as biomass feedstock has been developed using Aspen Plus. The gasification flow sheet encompasses gasification, catalytic filter candle, gas cleaning, impurity removal reactor, separator, and subsequent sorbent reactors. Ni-based catalysts with Ni ratios (5%, 10%, and 15%) are used to simulate TSR reactions. Results show that the 15% Ni-Co-Al 2 O 3 catalyst outperforms the 10% and 5% Ni-Co-Al 2 O 3 catalysts. This study explores the impact of temperature, catalyst loadings, and steam-to-carbon (S/C) ratios on toluene conversion and hydrogen yield in catalytic steam reforming, along with temperature, steam-to-biomass ratios, and equivalence ratio on syngas fraction in gasification. It includes a techno-economic analysis of wheat straw gasification to improve syngas energy through efficient tar conversion.

关键词： Biomass gasification Tar removal Catalytic steam reforming Aspen plus Techno-economic analysis

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Numerical Investigation of the Effects of Swirl-Vane Angle and Particle Size on Combustion and flow Characteristics in a Vertical Cyclone Barrel

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JOURNAL OF ENERGY engineering 2020年第4期146卷

作者： Tang, Chunli Zhu, Tao Hu, Yueyi Wang, Limin Che, Defu Liu, Yanhua Xi An Jiao Tong Univ Sch Human Settlements & Civil Engn Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The cyclone-fired boiler has become a very competitive boiler type for utilizing coal with a low ash melting point and high alkali. Because of the higher combustion intensity in the cyclone barrel, good flow and combustion performances are of great significance to the safe and efficient operation of the cyclone-fired boiler. The flow and combustion characteristics in a vertical cyclone barrel were numerically investigated, which has never been done before to the author's knowledge. The results showed that the pulverized coal particles are spun forward in the cyclone barrel driven by the tangentially rotating airflow, and the maximum velocity in the cyclone barrel is in the annular zone near the barrel wall. With the decrease in the swirl-vane angle of the primary air inlet or the increase in the particle diameter, the location where the particles collided with the barrel wall moves up along the axial direction of the cyclone barrel and the colliding chance increases. For the vertical cyclone barrel, the optimum particle diameter range is 70-110 mu m, so the capture ratio of particles is greater than 99.4%.

关键词： Cyclone barrel flow and combustion characteristics Swirl-vane angle Particle size High-alkali coal

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Floating flexible microbial fuel cells for electricity generation and municipal wastewater treatment

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SEPARATION AND PURIFICATION TECHNOLOGY 2022年 300卷

作者： Pu, Kai-Bo Li, Teng-Teng Gao, Jia-Yao Chen, Qing-Yun Guo, Kun Zhou, Min Wang, Chin-Tsan Wang, Yun-Hai Xi An Jiao Tong Univ Dept Environm Sci & Engn Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Int Res Ctr Renewable Energy Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Peoples R China Pengan Ecol Environm Monitoring Stn Nanchong 637800 Peoples R China Natl Ilan Univ Dept Mech & Electro Mech Engn Ilan City Taipei Taiwan

A new design of floating flexible microbial fuel cell (FMFC) was constructed by combining the carbon nanoparticles modified titanium foil anode (CNPs/ TF), insulating cloth, and air-cathode loaded with Pt/ C catalyst. This FMFC can float on wastewater and generate a maximum power density of over 250 mW m- 2 whose power performance is higher than other reported floating MFCs. After 21 days of operating on municipal wastewater, the results showed that the chemical oxygen demand (COD) undertaken by this FMFC would decrease from 3845 mg L-1 to 308 mg L-1. It showed that the COD removal efficiency was 92.1% and it was better than a control without FMFC and whose COD removal efficiency was 61.5%. In addition, the cost of the FMFC is much lower than those traditional and common MFCs due to their membrane-free structure. Finally, it was also found that Geoalkalibacter was dominant exoelectrogens in anodic biofilm and benefited the power generation performance of FMFC. This study showed that this novel FMFC could polish the performance of municipal wastewater treatment and also produce electric power in future.

关键词： Floating flexible microbial fuel cell CNPs TF anodes power generation COD removal Microbial community Geoalkalibacter

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A Model to Improve Granular Temperature in CFD-DEM Simulations

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ENERGIES 2020年第18期13卷 4730页

作者： Yu, Yaxiong Zhao, Li Li, Yu Zhou, Qiang Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

CFD-DEM (computational fluid dynamic-discrete element method) is a promising approach for simulating fluid-solid flows in fluidized beds. This approach generally under-predicts the granular temperature due to the use of drag models for the average drag force. This work develops a simple model to improve the granular temperature through increasing the drag force fluctuations on the particles. The increased drag force fluctuations are designed to match those obtained from PR-DNSs (particle-resolved direct numerical simulations). The impacts of the present model on the granular temperatures are demonstrated by posteriori tests. The posteriori tests of tri-periodic gas-solid flows show that simulations with the present model can obtain transient as well as steady-state granular temperature correctly. Moreover, the posteriori tests of fluidized beds indicated that the present model could significantly improve the granular temperature for the homogenous or slightly inhomogeneous systems, while it showed negligible improvement on the granular temperature for the significantly inhomogeneous systems.

关键词： CFD-DEM fluidized beds granular temperature drag force

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Diffusion of High-Temperature and High-Pressure CH₄ Gas in SiO₂ Nanochannels

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FRONTIERS IN ENERGY RESEARCH 2021年 9卷

作者： Cui, Shuheng Fu, Jianfeng Guo, Minling Zhao, Zhixiang Sun, Chengzhen Wang, Yujun CNOOC EnerTech Drilling & Prod Co CNOOC Energy Technol & Serv Ltd Tianjin Peoples R China CNOOC Ltd Zhanjiang Branch Zhanjiang Peoples R China Xian Polytech Univ Sch Urban Planning & Municipal Engn Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China

Fundamental understandings of nanoconfined methane (CH4) are crucial to improving the exploitation of tight gas. In this study, diffusivity, one of the key transport properties of high-temperature and high-pressure methane gas, is examined under confinement in the silica nanochannels by using molecular dynamics simulations by employing Einstein diffusion equation. It was found that the diffusivity of nanoconfined methane is obviously anisotropic, namely, the perpendicular diffusion coefficient is lower than that in the longitudinal direction. The anisotropic diffusivity of nanoconfined methane is attributed to the restricted effect of potential interactions from the atoms of walls, which is verified by analyzing the diffusivity of methane molecules in the potential wells with Lagrangian dynamics. The diffusion coefficients of nanoconfined methane decrease with the increase of atomic potentials in the wall, which can be explained by the density distributions of methane in the nanochannels. Furthermore, we reveal the dependence of the diffusivity of nanoconfined methane on the channel height and confining effect of the wall on the diffusivity of methane molecules. The obtained results can provide a molecular insight into the transport properties of methane confined in nanospace and a theoretical guidance for the efficient extraction of tight gas.

关键词： diffusivity SiO2 nanochannels nanoconfined fluid tight gas molecular dynamics

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Suppression of magnetism and Seebeck effect in Na0.875CoO2 induced by SbCo dopants

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MATERIALS FOR RENEWABLE AND SUSTAINABLE ENERGY 2020年第1期9卷 1-8页

作者： Assadi, M. H. N. Mele, Paolo Fronzi, Marco Univ New South Wales Sch Mat Sci & Engn Sydney NSW 2052 Australia Shibaura Inst Technol SIT Res Labs Koto Ku 3-7-5 Toyosu Tokyo 1358548 Japan Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Univ Technol Sydney Sch Math & Phys Sci Sydney NSW 2007 Australia

We examined the electronic property of Sb-doped Na0.785CoO2 using density functional calculations based on GGA+U formalism. We demonstrated that Sb dopants were the most stable when replacing Co ions within the complex Na0.875CoO2 lattice structure. We also showed that the Sb-Co dopants adopted the + 5 oxidation state introducing two electrons into the host Na0.875CoO2 compound. The newly introduced electrons recombined with holes that were borne on Co4+ sites that had been created by sodium vacancies. The elimination of Co4+ species, in turn, rendered Na-0.875(Co0.9375Sb0.0625)O-2 non-magnetic and diminished the compound's thermoelectric effect. Furthermore, the Sb-Co dopants tended to aggregate with the Na vacancies keeping a minimum distance. The conclusions drawn here can be generalised to other highly oxidised dopants in NaxCoO2 that replace a Co.

关键词： Sodium cobaltate Sb dopant Thermoelectric effect Magnetism Density functional theory

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