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An improved EMMS model for turbulent flow in pipe and its solution

Particuology 2023年第5期76卷 1-12页

作者： Lin Zhang Wen Lai Huang Jianhua Chen State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing100190China

Based on the existing energy-minimization multi-scale(EMMS)model for turbulent flow in pipe,an improved version is proposed,in which not only a new radial velocity distribution is introduced but also the quantification of total dissipation over the cross-section of pipe is improved for the dominant mechanism of fully turbulent flow in *** four dynamic equality constraints and some other constraints are constructed but there are five parameters involved,leading to one free variable *** the compromise in competition between dominant mechanisms for laminar and fully turbulent flow in pipe respectively,the above four constructed dynamic equality constraints can be ***,the cases for turbulent flow in pipe with low,moderate and high Reynolds number are simulated by the improved EMMS *** numerical results show that the model can obtain reasonable results which agree well with the data computed by the direct numerical simulation and those obtained by *** illustrates that the improved EMMS model for turbulent flow in pipe is reasonable and the compromise in competition between dominant mechanisms is indeed a universal governing principle hidden in complex ***,one more EMMS model for a complex system is offered,pro-moting the further development of mesoscience.

关键词： Mesoscience EMMS Compromise in competition Dominant mechanism Turbulent flow in pipe

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3D coarse-grained DPM simulation of the MIP reaction-regeneration loop

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Particuology 2024年第6期89卷 57-66页

作者： Yanhao Ye Shuai Zhang Ji Xu Wei Ge State Key Laboratory of Mesoscience and Engineering(formerly State Key Laboratory of Multiphase Complex Systems) Institute of Process EngineeringChinese Academy of SciencesBeijing100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing100049China

The reactor-regenerator loop is the core facility of the maximizing iso-paraffin(MIP)*** the discrete particle method(DPM)simulation can provide detailed information at the particle scale,it has been unable to simulate such a complex loop system due to limitations of coarse-grained(CG)models,computing software,and *** this study,a newly proposed soft-shell CG-DPM model with a CG ratio of up to 800 is used to simulate a 3.5 Mt/a industrial-scale MIP reactor-regenerator *** solid fraction distribution obtained is found to agree well with in-situ *** properties including the distribution of solid fraction,gas and solid velocity,standard derivation of solid fraction with time,temporal distribution of the flow field,and particle residence time distribution are measured in the simulation,which are meaningful to better design and operate such systems in the future.

关键词： Discrete particle method Coarse-grain Maximizing iso-paraffins Full-loop Reaction-regeneration system

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Deposition of thin TiO_(2)films on fluorophlogopite particle surface by CVD in fluidized bed reactor to prepare silver pearlescent pigments

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Particuology 2024年第6期89卷 88-98页

作者： Ming Liu Guoqiang Shao Pengpeng Lv Jun Li Qingshan Zhu State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Two critical parameters:Glossiness and chromaticity space of pearlescent pigments were evaluated based on crystallinity and grain *** the roughness and the vertical distance evolution along the surface of deposited TiO_(2)film are affected by the *** optimal crystallinity of TiO_(2)was deposited at the temperature of 350℃.The TiCl4 concentration effectively changed the grain ***,the high flow rate of fluidizing gas and optimal gas–solid ratio(<0.11 m^(3)/(kg h))restricted the change of TiCl_(4)concentrations in fluidized bed *** this case,the grain size of the deposited TiO_(2)film was about 55 *** on the grain size,the color of pearlescent pigments was adjusted by controlling the film thickness based on TiO_(2)***,the silver pearlescent pigment with high glossiness was prepared by chemical vapor deposition method in a fluidized bed reactor.

关键词： Fluidized bed chemical vapor deposition TiO_(2)film deposition Pearlescent pigment Free powder restrain Crystal growth

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Effect of methanol on the pyrolysis behaviour of kerogen by ReaxFF molecular dynamics simulations

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MOLECULAR SIMULATION 2024年第1期50卷 43-54页

作者： Yu, Mingyue Zhan, Jin-Hui Li, Xiang He, Wen Liu, Xiaoxing Shenyang Univ Chem Technol Coll Chem Technol Shenyang Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China

A series of molecular dynamics simulations were performed using the ReaxFF reactive force field to investigate the pyrolysis of Longkou oil shale kerogen in the presence of methanol. The roles of methanol in kerogen pyrolysis were deeply explored to reveal the microscopic mechanism of methanolysis by analyzing the distribution of products, the consumption of methanol, and the formation processes of typical products at different temperatures. The results demonstrate that the yield of shale oil in the presence of methanol is consistently higher than that of kerogen direct pyrolysis at the same temperature, which is consistent with the trend of oil yield with temperature reported by previous methanolysis experiments. Methanol supplies a large number of small radicals under the pyrolysis condition, which can facilitate the breakage of weak bonds and take part in the formation of products through combining with the radical fragments generated by the pyrolysis of kerogen. This study will provide theoretical guidance for understanding the methanolysis process of oil shale.

关键词： Kerogen methanolysis mechanism molecular dynamics ReaxFF

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Construction of multifunctional lanthanum manganese mixed nanoparticles mediated by ionic liquids for selective aerobic oxidation of cyclohexane

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Rare Metals 2024年第5期43卷 2205-2221页

作者： Hao Li Rui-Rui Zhang Ke-Xin Li Shuang Wei Yu-Mei Liu Rui-Xia Liu Beijing Key Laboratory of Ionic Liquids Clean Process CAS Key Laboratory of Green Process and EngineeringState Key Laboratory of Multiphase Complex SystemsInstitute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Selective oxidation of alkanes to produce highvalue chemicals is an essential strategy and means to realize efficient utilization of *** this work,a strategy of lanthanum manganese mixed metal oxides(LMMO)regulated via a facile ionic liquid(IL)-assisted hydrothermal method was proposed to construct the multifunctional catalysts,which exhibited excellent catalytic performance in the selective aerobic oxidation of *** 8.9%cyclohexane conversion with 90%KA oi(cyclohexanol and cyclohexanone)selectivity was achieved over the optimal LMMO catalyst under mild *** effects of anion type,carbon chain length and concentration of ILs on the structure and properties of catalysts were investigated through various characterizations,indicating the structure-directing and template effect of ILs on the multifunctional *** formation of self-assembled spherical nanoparticles followed the"dissolution-nucleation-proliferation"mechanism with the introduction of 1-butyl-3-methylimidazolium hydrogen sulfate,ascribing the synergistic effect between the microenvironment of ILs and the hydrothermal ***,the high reactive oxygen concentration redox capacity,and suitable basic sites of LMMO catalysts mediated by ILs enhance the activation of C-H bonds and molecular oxygen,simultaneously influencing the adsorption and desorption of the substrate.A comprehensive understanding of the high KA oil selectivity and radical reaction mechanism was elucidated based on in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and radical trapping *** recycling and regeneration experiments further illuminated that the removal of adsorbed cyclohexanone acting on the LMMO catalyst was the key to achieve high KA oil selectivity.

关键词： Ionic liquids Nanoparticle Multifunctional catalyst Cyclohexane oxidation

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Exploring multiple phases and first-order phase transitions in Kármán Vortex Street

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Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 47-54页

作者： Xu Li Xing Xiang Tingting Xue Limin Wang Xiaosong Chen School of Systems Science and Institute of Nonequilibrium Systems Beijing Normal UniversityBeijing 100875China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy ofSciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Kármán Vortex Street, a fascinating phenomenon of fluid dynamics, has intrigued the scientific community for a long time. Many researchers have dedicated their efforts to unraveling the essence of this intriguing flow pattern. Here, we apply the lattice Boltzmann method with curved boundary conditions to simulate flows around a circular cylinder and study the emergence of Kármán Vortex Street using the eigen microstate approach, which can identify phase transition and its order-parameter. At low Reynolds number, there is only one dominant eigen microstate W_(1) of laminar flow. At Re_(c)^(1)= 53.6, there is a phase transition with the emergence of an eigen microstate pair W^(2,3) of pressure and velocity fields. Further at Re_(c)^(2)= 56, there is another phase transition with the emergence of two eigen microstate pairs W^(4,5) and W^(6,7). Using the renormalization group theory of eigen microstate,both phase transitions are determined to be first-order. The two-dimensional energy spectrum of eigen microstate for W^(1), W^(2,3) after Re_(c)^(1), W^(4-7) after Re_(c)^(2) exhibit-5/3 power-law behavior of Kolnogorov's K41 theory. These results reveal the complexity and provide an analysis of the Kármán Vortex Street from the perspective of phase transitions.

关键词： Kármán Vortex Street first-order phase transition eigen microstate approach renormalization group theory of eigen microstate

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Optimization of decoupling combustion characteristics of coal briquettes and biomass pellets in household stoves

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Chinese Journal of Chemical Engineering 2023年第7期59卷 182-192页

作者： Jian Han Xinhua Liu Shanwei Hu Nan Zhang Jingjing Wang Bin Liang State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Burning coal briquettes or biomass pellets in household decoupling stoves is of significance to the reduction of residential pollutant emissions such as NO and CO. In order to make full use of the superiority of decoupling combustion technology, the household stoves should be specially designed and optimized to adapt to fuel types and combustion characteristics. Using numerical simulation and experimental validation, this study quantitatively clarified that the reducibility of devolatilization char plays an important role in the suppression of NO emission in the decoupling combustion of coal, while the reducibility of pyrolysis gases has a dominant effect on the reduction of NO in the decoupling combustion of biomass. An optimal parameter combination of throat height and grate angle was obtained for the simultaneous suppression of NO and CO emissions in the household decoupling stove burning coal briquettes. Two types of decoupling stoves were developed to enable the clean combustion of biomass pellets. The A-type biomass stove with a multi-pass smoke tunnel shows a better comprehensive NO and CO reduction effectiveness than the B-type biomass stove consisting of a two-stage grate structure and an S-shaped pyrolysis chamber. The optimal structural parameters provided references for the design and manufacture of commercial decoupling coal and biomass stoves.

关键词： Decoupling combustion Coal Biomass Numerical simulation Nitrogen oxide Carbon monoxide

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Effect of high stirring speed on the agglomerate behaviors for cohesive SiO_(2) powders in gas fluidization

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Particuology 2023年第9期80卷 192-201页

作者： Fan Liu Zhan Du Qingshan Zhu Xiaojun Guo Hebang Shi Pengpeng Lv Hongzhong Li School of Chemical Engineering University of Chinese Academy of SciencesBeijing100049China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChina Academy of SciencesBeijing100190China

The effects of superficial gas velocity and mechanical stirring speed on the precise regulation of flow regimes for cohesive SiO2 powders(mean diameter is 16μm)were experimentally investigated in a stirring-assisted fluidized *** results showed that compared with the agglomerates formed in the non-assisted fluidization of cohesive SiO2 powders,the introduction of mechanical stirring could effectively reduce the size of agglomerates and well disperse the agglomerates during *** best regulation range of agglomerate particulate fluidization can be achieved at 600 rpm when agglomerate sizes were reduced to below 200μ*** investigation based on the operational phase diagram revealed that transformations of flow regimes were dominated by both stirring speed and gas *** stirring applied enlarges the operational range of agglomerate particulate fluidization(APF)with a delayed onset of bubbling for cohesive ***,the exorbitant speed increases the collision velocity and contact area between small agglomerates,which results in the formation of unstable agglomerates and the whirlpool of powder.

关键词： Cohesive powders Stirring-assisted fluidized bed Agglomerate size Agglomerate particulate fluidization

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Numerical investigation of honeycomb channel design: Effect of rounded corners on selective catalytic reduction of NO

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CHEMICAL ENGINEERING SCIENCE 2024年 285卷

作者： Chen, Hao Shi, Yao Liu, Xiangkun Sui, Yanan He, Yijian Yu, Jian Xu, Guangwen Zhou, Xinggui Duan, Xuezhi East China Univ Sci & Technol State Key Lab Chem Engn 130 Meilong Rd Shanghai 200237 Peoples R China Chinese Acad Sci Inst Proc Engn State Key Lab Multiphase Complex Syst Beijing 100190 Peoples R China

In this work, single-channel models are established to investigate the effect of rounded corners on overall performance of honeycomb catalyst with various channel geometries and cell densities (Ncell). As channel shape factor (gamma) increases, pressure drops all rise slowly at low gamma (0 similar to 0.5) and increases dramatically when gamma > 0.5, aligning with monolith voidage and hydraulic diameter variations. Hexagon-channel catalysts with open corners exhibit the smallest pressure drop increase (17.3 %), while triangle-channel catalysts with acute corners show the highest rise (100.1 %). The increase in Ncell leads to a similar rise (43 %) in pressure drop. NO conversions decrease with gamma due to reduced external surface area, with maximum conversions observed for triangle-channels (low gamma) and hexagon-channels (high gamma). Increasing Ncell enhances NO removal and mitigate rounded-corner effect on conversion (4.5 % to 1.2 % reduction). Based on that, a design strategy suggesting gamma = 0.5 is proposed to eliminate ash accumulation and maintain acceptable catalyst performance.

关键词： Honeycomb monolithic catalysts Selective catalytic reduction Rounded corners

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Fluidization thermal decomposition of sodium fluosilicate

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Chinese Journal of Chemical Engineering 2023年第5期57卷 329-337页

作者： Feng Pan Sugang Ma Yu Ge Chuanlin Fan Qingshan Zhu State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences(CAS)Beijing 100190China College of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

To break through the thermodynamic limitation that sodium fluosilicate only can be completely decomposed at high temperature,the technology of pre-decomposition under SiF_(4) atmosphere and deep decomposition under air condition at lower temperature was *** hydrolysis reaction of sodium fluosilicate can be effectively restrained when drying under vacuum or low *** decomposition results of sodium fluosilicate indicate that temperature has a very significant effect on its *** decomposition ratio can reach 79.4%at 600℃ for 1 h,and 99.6% at 700℃ for 1 h under air condition,*** velocity and the type of inert gas have no significant effect on its *** particles affect its decomposition performance due to agglomeration,while coarse particles have good thermal decomposition performance without significant *** decomposition reaction process in fluidized bed satisfies the classical Avrami Erofe'EV model,with the reaction order of 1.5 and the activation energy of 61.35 kJ·mol^(-1).

关键词： Sodium hexafluorosilicate Preparation Silicon tetrafluoride Absorption Fluidized bed

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