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Mechanisms of strengthening energy and mass transfer in microbial conversion of flue-gas-derived CO_(2) to biodiesel and biogas fuels

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碳中和(英文) 2022年第1期1卷 479-490页

作者： Jun Cheng kefa cen State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China

The goals of national energy security and sustainable development necessitate the role of renewable energy,of which biomass energy is an essential choice for realizing the strategic energy diversification and building a lowcarbon energy *** conversion of flue-gas-derived CO_(2) for producing biodiesel and biogas has been considered a significant technology in new energy *** carbon sequestration is a hot research direction for ***,three fundamental problems relating to energy/mass transfer and conversion remain as follows:(1)contradictory relationship between high resistance of cell membrane micropores and high flux of flue-gas-derived CO_(2) limits mass transfer rate of CO_(2) molecules across cell membrane;(2)low biocatalytic activity of intracellular enzymes with high-concentration CO_(2) results in difficulties in directional carbon/hydrogen conversion;(3)competition between multiple intracellular reaction pathways and high energy barriers of target products hinder the desirable cascade energy ***,key scientific issues of microbial energy conversion lie in the understanding on directional carbon/hydrogen conversion and desirable cascade energy *** researches have established a theoretical foundation of microbial energy conversion which strengthens energy/mass transfer in microbial *** innovative results in previous studies have been obtained as follows:(1)Reveal mass transfer mechanism of vortex flow across cell membrane micropores.(2)Propose a strategy that directionally regulates enzyme activity.(3)Establish chain reaction pathways coupled with step changes.

关键词： Microalgal conversion Energy and mass transfer Flue gas CO_(2) Biodiesel Biogas fuels

Influence of coke rate on thermal treatment of waste selective catalytic reduction(SCR)catalyst during iron ore sintering

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Chinese Journal of Chemical Engineering 2022年第2期35卷 415-423页

作者： Pengnan Ma Jiankang Wang Hanxiao Meng Laiquan Lv Hao Fang kefa cen Hao Zhou State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou 310027China

Waste selective catalytic reduction(SCR)catalyst as a hazardous waste has a significant impact on the environment and human *** present study,a novel technology for thermal treatment of waste SCR catalyst was proposed by adding it to sinter mix for iron ore *** influences of coke rate on the flame front propagation,sinter microstructure,and sinter quality during sintering co-processing the waste SCR catalyst process were *** situ tests results indicated the maximum sintering bed temperature increased at higher coke rate,indicating more liquid phase generated and higher airflow *** sintering time was longer and the calculated flame front speed dropped at higher coke *** microstructure results found the coalescence and reshaping of bubbles were more fully with increasing coke *** porosity dropped from 35.28%to 25.66%,the pore average diameter of large pores decreased from 383.76μm to 311.43μ*** increasing coke rate,the sinter indexes of tumbler index,productivity,and yield,increased from 33.2%,9.2 t·m^(-2)·d^(-1),28.9%to 58.0%,36.0 t·m^(-2)·d^(-1),68.9%,***,a comprehensive index was introduced to systematically assess the influence of coke rate on sinter quality,which rose from 100 to 200 when coke rate was increased from 3.5%(mass)to 5.5%(mass).

关键词： Flame front Waste selective catalytic reduction(SCR) catalyst Thermal treatment Iron ore sintering

Analysis of Flowing and Heat Transfer of Commercial Molten Nitrate in Porous Foundation Material

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Journal of Thermal Science 2023年第4期32卷 1455-1465页

作者： SHI Hua ZHOU Hao MENG Hanxiao LV Laiquan LIU Tianxiao ZUO Yuhang cen kefa State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou310027China

The leakage accident of molten salt in the thermal storage tank will cause the shutdown and enormous economic losses of Concentrated Solar Power *** study investigates the heat transfer and flow characteristic of commercial molten nitrates leaking in the thermal state porous foundation *** migration width and depth of three molten nitrates,Solar Salt(60 wt%NaNO_(3)-40 wt%KNO_(3)),Hitec XL(7 wt%NaNO_(3)-45 wt%KNO_(3)-48 wt%Ca(NO_(3))_(2))and Hitec(7 wt%NaNO_(3)-53 wt%KNO_(3)-40 wt%NaNO_(2)),are obtained at different operating *** results indicate that the temperature rising rate of foundation material in the nitrate leaking process has a trend of first increasing rapidly and then decreasing,and then it increases slightly as the depth *** temperature rising rate increases obviously with increasing operating temperature of the molten *** the increase of the operating temperature,the distances from the storage tank bottom to solid salt in foundation and the total migration depths both increase obviously,while the average migrating widths change *** the same operating temperature,the temperature rising rate of the foundation material where Hitec XL and Hitec salt leak is significantly greater than that with Solar Salt,which is closely related to the melting points of molten *** migration depth of Hitec is 95.03%greater than that of Solar Salt and 19.11%larger than that of Hitec XL at the operating temperature of 300℃.Compared with Hitec XL,the leakage of Hitec with a smaller viscosity has a larger temperature rising rate and a wider and deeper transporting range during the leakage *** work could guide the installation locations of the leak detection devices for high temperature storage tank and the environmental treatment of leaking accident.

关键词： nitrate foundation material leaking flow heat transfer

Pore-structure regulation and heteroatom doping of activated carbon for supercapacitors with excellent rate performance and power density

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Waste Disposal and Sustainable Energy 2023年第3期5卷 417-426页

作者： Jian Zhang Huachao Yang Zhesong Huang HuiHui Zhang Xinchao Lu Jianhua Yan kefa cen Zheng Bo State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringCollege of Energy EngineeringZhejiang UniversityHangzhou310027ZhejiangChina

Activated carbon(AC)has attracted tremendous research interest as an electrode material for supercapacitors owing to its high specific surface area,high porosity,and low ***,AC-based supercapacitors suffer from limited rate performance and low power density,which mainly arise from their inherently low electrical conductivity and sluggish ion dynamics in the ***,we propose a simple yet effective strategy to address the aforementioned issue by nitrogen/fluorine doping and enlarging the micropore *** the treatment,the decomposition products of NH4F react with the carbon atoms to dope the AC with nitrogen/fluorine and simultaneously enlarge the pores by *** treated AC shows a higher specific surface area of 1826 m2 g^(−1)(by~15%),more micropores with a diameter around 0.93 nm(by~33%),better wettability(contact angle decreased from 120°to 45°),and excellent electrical conductivity(96 S m^(−1))compared with untreated AC(39 S m^(−1)).The as-fabricated supercapacitors demonstrate excellent specific capacitance(26 F g^(−1)at 1 A g^(−1)),significantly reduced electrical resistance(by~50%),and improved rate performance(from 46.21 to 64.39%at current densities of 1 to 20 A g^(−1)).Moreover,the treated AC-based supercapacitor achieves a maximum energy density of 25 Wh kg^(−1)at 1000 W kg^(−1)and a maximum power density of 10,875 W kg^(−1)at 15 Wh kg^(−1),which clearly outperforms pristine AC-based *** synergistic treatment strategy provides an effective way to improve the rate performance and power density of AC-based supercapacitors.

关键词： Activated carbon Heteroatom doping Pore-size modification Rate performance Supercapacitors

Direct Numerical Simulation of Particle Dispersion in the Flow Around a Circular Cylinder

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Journal of Thermal Science 2004年第4期13卷 344-349页

作者： Lan Liu Feng Ji Jianren Fan kefa cen Inst. of Thermal Power Eng. Zhejiang Univ. Hangzhou 310027 China

The major objective of the paper is to use direct numerical simulation method to get the dispersion patterns of different Stokes number particles in cylinder wake at low Reynolds numbers. The gas fluid structure is simulated by a spectral-element method with third-order accuracy. Non-reflecting boundary condition is specified for the outlet downstream boundary. Lagrangian approach is used to trace particle trajectory. The simulation results show factors to be considered to characterize the particle dispersion and find different particle dispersion pattern in a circular cylinder wake and in a plane wake.

关键词： direct numerical simulation wake particle dispersion gas-solid fluid.

Transitional phenomenon of particle dispersion in gas-solid two-phase flows

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Chinese Science Bulletin 2007年第3期52卷 408-417页

作者： LUO Kun FAN JianRen cen kefa State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou 310027 China

Without using any turbulent model, direct numerical simulation of a three-dimensional gas-solid two-phase turbulent jet was performed by finite volume method. The effects on dispersion of particles with different Stokes numbers by the transitional behavior of turbulent structures were investigated. To produce high-resolution results and reduce the computation and storage, the fractional-step projection algorithm was used to solve the governing equations of gas phase fluid. The low-storage, three-order Runge-Kutta scheme was used for time integration. The governing equations of particles were solved in the Lagrangian framework. These numerical schemes were validated by the good agreement be-tween the statistical results of flow field and the related experimental data. In the study of particle dis-persion, it was found that the effects on particle dispersion by the spanwise vortex structures were prominent. The new behaviors of particle dispersion were also observed during the evolution of the flow field, i.e. the transitional phenomenon of particle dispersion occurs for the particles with small and intermediate Stokes numbers.

关键词：气固两相流颗粒分散瞬变现象湍流模型直接数值模拟

Conversions of fuel-N, volatile-N, and char-N to NO and N_2O during combustion of a single coal particle in O_2/N_2 and O_2/H_2O at low temperature

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Chinese Journal of Chemical Engineering 2018年第9期26卷 1967-1977页

作者： Yuan Li Hao Zhou Ning Li Runchao Qiu kefa cen State Key Laboratory of Clean Energy Utilization Institute for Thermal Power Engineering Zhejiang University

Oxy-steam combustion is a promising next-generation combustion *** of fuel-N,volatile-N,and char-N to NO and N_2O during combustion of a single coal particle in O_2/N_2and O_2/H_2O were studied in a tube reactor at low *** O_2/N_2,NO reaches the maximum value in the devolatilization stage and N_2O reaches the maximum value in the char combustion *** O_2/H_2O,both NO and N_2O reach the maximum values in the char combustion *** total conversion ratios of fuel-N to NO and N_2O in O_2/N_2are obviously higher than those in O_2/H_2O,due to the reduction of H_2O on NO and N_*** changes the trade-off between NO and N_*** O_2/N_2and O_2/H_2O,the conversion ratios of fuel-N,volatile-N,and char-N to NO increase with increasing temperature,and those to N_2O show the opposite *** conversion ratios of fuel-N,volatile-N,and char-N to NO reach the maximum values at b O_2N=30 vol%in O_2/N_*** O_2/H_2O,the conversion ratios of fuel-N and char-N to NO reach the maximum values at b O_2N=30 vol%,and the conversion ratio of volatile-N to NO shows a slightly increasing trend with increasing oxygen *** conversion ratios of fuel-N,volatile-N,and char-N to N_2O decrease with increasing oxygen concentration in both atmospheres.A higher coal rank has higher conversion ratios of fuel-N to NO and N_*** coal exhibits the highest conversion ratios of fuel-N,volatile-N,and char-N to NO and N_2O in both *** work is to develop efficient ways to understand and control NO and N_2O emissions for a clean and sustainable atmosphere.

关键词： N2O 燃烧粒子低温度煤液化作用活动范围反应堆

Frequency comparative study of coal-fired fly ash acoustic agglomeration

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Journal of Environmental Sciences 2011年第11期23卷 1845-1851页

作者： Jianzhong Liu Jie Wang Guangxue Zhang Junhu Zhou kefa cen State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China Institute for Energy Engineering China Jiliang UniversityHangzhou 310018China

Particulate pollution is main kind of atmospheric *** fine particles are seriously harmful to human health and *** agglomeration is considered as a promising pretreatment technology for fine particle *** mechanisms of acoustic agglomeration are very complex and the agglomeration efficiency is affected by many *** most important and controversial factor is *** studies between high-frequency and low-frequency sound source to agglomerate coal- fired fly ash were carried out to investigate the influence of frequency on agglomeration *** agglomeration theoretical analysis,experimental particle size distributions （PSDs） and orthogonal design were *** results showed that the 20 kHz high-frequency sound source was not suitable to agglomerate coal-fired fly *** within the size ranging from 0.2 to 0.25 μm the particles agglomerated to adhere together,and the agglomerated particles were smaller than 2.5 μ*** application of low-frequency （1000–1800 Hz） sound source was proved as an advisable pretreatment with the highest agglomeration efficiency of 75.3%,and all the number concentrations within the measuring range *** design L16 （4） 3 was introduced to determine the optimum frequency and optimize acoustic agglomeration *** to the results of orthogonal analysis,frequency was the dominant factor of coal-fired fly ash acoustic agglomeration and the optimum frequency was 1400 Hz.

关键词： coal-fired fly ash acoustic agglomeration frequency agglomeration kernel orthogonal design

Rotation speed measurement of moving particles in a CFB riser

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Particuology 2009年第4期7卷 238-244页

作者： Xuecheng Wu Qinhui Wang Zhongyang Luo Mengxiang Fang kefa cen State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou Zhejiang 310027 China

This paper presents a study on measuring rotation speed of moving glass beads with an average diameter of 500 p.m in a pilot-scale circulating fluidized bed （CFB） riser with a high-speed digital imaging system. Two methods have been developed to calculate particle rotation speed from the particle images. The first method consists of a fully automated algorithm based on cross-correlation of gray distribution of particle images for particles whose rotation axes are （nearly） perpendicular to the imaging plane, and the second method calculates the speed of particle rotation by identifying its rotation axis using two or more characteristic points on its surface. The reliability of the two methods is verified by using a small sphere with known speed and direction of rotation. The first method is shown to be capable of measuring accurately the rotation speed for the particle with a rotation axis （nearly） perpendicular to the imaging plane and filtering off other particles using an appropriate threshold of correlation coefficient. The second method is shown to be capable of yielding both the speed and direction of particle rotation, with a measurement error of less than 10%. Results of both methods on real glass beads in a CFB riser are compared against each other.

关键词： Rotation speed measurement Moving particles Gas-solid flow Circulating fluidized bed (CFB)