Article
Engineering, Chemical
Kwangbyol Jang, Yali Feng, Haoran Li
Summary: The behavior of gas bubbles in a gas-solid fluidized bed was studied through computational fluid dynamics simulation. Gas bubble size and rise velocity increased with gas velocity. The design of the gas distributor significantly influenced bubble behavior, along with factors such as static bed height and superficial gas velocity.
CHEMICAL ENGINEERING & TECHNOLOGY
(2021)
Article
Engineering, Chemical
Shijie Yu, Xiaoxiao Yang, Jie Xiang, Hui Zhou, Qinghai Li, Yanguo Zhang
Summary: This study statistically analyzed the effects of bed size on voidage in gas-solid bubbling fluidized beds. Results showed that with increasing bed size, voidage and its dispersion degree decreased, while asymmetry and steepness degree increased. Bed size had a stronger impact on voidage at lower axial positions.
Article
Engineering, Chemical
Kaiqiao Wu, Shuxian Jiang, Victor Francia, Marc-Olivier Coppens
Summary: In rectangular and cylindrical annular fluidized beds, pulsating gas flow can create regular bubble patterns, overcoming challenges seen in conventional units. This study provides new opportunities for modularization of fluidized bed operations.
Article
Engineering, Chemical
Tingting Dong, Yongli Ma, Mingyan Liu
Summary: This paper investigates the gas-liquid mass transfer characteristics in a gas-liquid-solid mini fluidized bed (GLSMFB). The study finds that the liquid volumetric mass transfer coefficient and gas-liquid interfacial area increase with the increase of the superficial gas velocity within the experimental parameter range. Additionally, the liquid volumetric mass transfer coefficient increases with the increase of the superficial liquid velocity at the same ratio of superficial gas to liquid velocity.
Review
Engineering, Chemical
Pierre Sauriol, Javad Vahabzadeh Pasikhani, Jaber Shabanian, Jamal Chaouki
Summary: The high velocity injection of gas in a particulate system leads to the formation of a gas-solid structure characterized by enhanced momentum, mass, and heat transfers. This review focuses on the empirical correlations developed to predict the jet penetration length and half-angle at various operating conditions in different bed configurations in gas-solid fluidized beds. It also discusses the advances in modeling efforts, scale-up issues, and proposes an iterative approach for designing and scaling up injection systems in a gas-solid fluidized bed.
Article
Engineering, Chemical
Soo Youp Park, Pil -Sang Youn, Dong Hun Lee, Daewook Kim, Yooseob Won, Jeong-Hoo Choi, Ji Bong Joo, Sung-Ho Jo, Ho-Jung Ryu
Summary: This study investigates particle attrition induced by bubbles in a bubbling fluidized bed using CO2 adsorbent particles. The relationship between the rate of attrition by gas jets and the rate of attrition by bubbles is revealed, showing that the rate constant of attrition by bubbles is the product of the rate constant of attrition by gas jets and dimensionless particle diameter. The results show that the rate of attrition by bubbles is proportional to the energy given to the bed solids by bubbles, and the size of the fine particles formed by attrition increases with bed mass and gas velocity.
ADVANCED POWDER TECHNOLOGY
(2022)
Article
Engineering, Environmental
Xiangnan Li, Yan Hao, Peng Zhao, Mengfan Fan, Shili Song
Summary: The study conducted hydrodynamic simulations of gas-liquid-solid mini-fluidized beds using the VOF-DEM coupling model, achieving steady state flow and obtaining axial and radial profiles of phase holdups. The simulation proved effective in predicting phase holdups and explaining hydrodynamic mechanisms.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Engineering, Environmental
Daoye Yang, Zhangyou Wu, Guihuan Yao, Chenxiao Zhang, Qitao Bian
Summary: The study utilized a 32-electrode ECVT system to investigate the axial dispersion of gas-solid flow in a CFB riser, demonstrating the system's effectiveness in collecting flow details and revealing flow characteristics.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Engineering, Environmental
Zhao-Quan Wen, Xi-Bao Zhang, Zheng-Hong Luo
Summary: A new model was developed to simulate the bubble size distribution in gas-solid bubbling fluidized bed, considering the collisions and wake entrainment of bubbles. The coalescence efficiency of colliding bubbles was developed based on the liquid film drainage process in a gas-liquid system. The model results effectively predicted the bubble size distribution and showed good agreement with experimental data.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Engineering, Chemical
Chao Wang, Zhennan Han, Haolong Bai, Liangliang Fu, Mengjuan Zhang, Guangwen Xu, Dingrong Bai, Guoqing Guan
Summary: This work presents a theoretical analysis of the near-plug gas flow conditions in micro gas-solid fluidized beds using a simple one-dimensional dispersion model. The analysis is validated by comparing it with experimental results. The study improves the criterion for near-plug gas flow in micro fluidized beds and has important implications for further research and design of micro fluidized beds.
Article
Engineering, Environmental
Zeneng Sun, Jesse Zhu
Summary: The hydrodynamics and reactor performance in a recently proposed gas-solids circulating turbulent fluidized bed (CTFB) were compared with conventional fluidized beds and a high-density circulating fluidized bed (HDCFB) riser. The study found that the CTFB exhibits characteristics similar to both a conventional fluidized bed and an HDCFB, depending on the G(s)/U-g ratio. The CTFB also showed a larger number of smaller bubbles compared to other bed types, resulting in superior reactor performance in terms of effective reaction rate, mass transfer rates, and solids backmixing.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Mechanics
Fernando D. Cunez, Erick M. Franklin
Summary: Fluidized beds are commonly used in industry for their high rates of mass and heat transfers. This paper reports experiments with a mm-scale gas-solid fluidized bed and finds that alternating high-and low-compactness regions appear in the bed, significantly reducing the agitation and transfer rates. Increasing the flow velocity can mitigate the problem but does not eliminate it completely. The results provide insights for chemical and pharmaceutical processes involving powders.
MECHANICS RESEARCH COMMUNICATIONS
(2023)
Article
Engineering, Chemical
Shijiao Li, Peng Zhao, Ji Xu, Li Zhang, Junwu Wang
Summary: This study investigates the fluidization of polydisperse particles in bubbling micro-fluidized beds using CFD-DEM. The study validates the method by comparing it with experimental measurements and then performs a detailed analysis of bed hydrodynamics. The results show that particle size distribution enhances fluidization quality and that significant axial segregation is observed only in the case of wide PSD. The study provides insights into the role of PSD in gas fluidization and the similarities and differences between micro and large fluidized beds.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Engineering, Chemical
Mojtaba Rasteh, Goodarz Ahmadi, S. H. Hosseini
Summary: This study investigated the effect of Gaussian distribution width, average particle diameter, particle loading, and the tapered angle on minimum fluidization velocity in tapered fluidized beds through extensive experiments. The results showed an increase in minimum fluidization velocity with increasing average particle diameter, particle loading, and tapered angle. There was also a nonmonotonic behavior of minimum fluidization velocity as the Gaussian distribution width increased. The proposed correlation for predicting minimum fluidization velocity in tapered beds showed good agreement with experimental data and was compared with three earlier models.
Article
Engineering, Chemical
Salma Benzarti, Hatem Mhiri, Philippe Bournot
Summary: Fluidized beds have been crucial in processing industries for almost a century. However, their scaling up has been hindered by complex hydrodynamic behavior and diverse solids handling. This study simulated the hydrodynamic behavior of a 2D circulating fluidized bed under different superficial gas velocities and found that the gas/solid feeding configuration significantly affects the flow structure.
Article
Engineering, Chemical
Elham Heidari, Salman Movahedirad, Mohammad Amin Sobati
Summary: This study investigates binder evaporation as a significant microscale phenomenon in fluidized bed wet granulation. It models the evaporation of a single droplet, a sessile droplet, and a liquid bridge, taking into account the effects of operational conditions and liquid/particle properties. The results show that higher relative velocity and smaller equilibrium contact angle increase the evaporation rate, while increasing the length of the binder bridge reduces the rupture time.
CANADIAN JOURNAL OF CHEMICAL ENGINEERING
(2023)
Article
Engineering, Chemical
Ahmad Mortezaee, Salman Movahedirad, Mohammad Amin Sobati
Summary: Oxidative desulphurization of heavy fuel oil faces challenges such as gum formation and waste hydrocarbons. Gum formation increases as the hydrogen/carbon ratio of the diluting solvents decreases. It is caused by polymer formation reactions induced by peroxide radicals. A simple and efficient extractive desulphurization method using dimethylformamide as the solvent is proposed, achieving a high desulphurization rate.
CANADIAN JOURNAL OF CHEMICAL ENGINEERING
(2023)
Article
Engineering, Chemical
Rahul Subburaj, Yali Tang, Niels G. Deen
Summary: The objective of this work is to establish a lift model that considers the variation in the bubble spreading mechanism with different column aspect ratios. A strategic approach has been developed to explore the dependency of the lift variation with local flow variables. Numerical simulations using Computational Fluid Dynamics - Discrete Particle Method (CFD-DPM) coupled with Volume of Fluid (VOF) method in the open-source framework OpenFOAM are performed. It is found that the local gas fraction and the vorticity are strongly correlated with the lift coefficient. However, using one of these two variables alone cannot describe the lift variation within the bubble columns. A unified lift model is established that depends on both local gas fraction and vorticity. Euler-Lagrange simulations using this lift model demonstrate excellent agreement on the bubbly dynamics with experiments of homogeneous bubbly flows and bubble swarms.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Engineering, Chemical
Saeed Ghasemzade Bariki, Movahedirad Salman, Majid Ghojavand
Summary: Polycaprolactone nanoparticles (NPs) were produced using a co-flow glass capillary device, with sizes of 990 nm at a continuous phase velocity of 0.05m and 426 nm at a continuous phase velocity of 0.2m/s. The droplet formation process in the co-flow microchannel was simulated using computational fluid dynamics (CFD). A cut-off value of 0.81 for the dispersed phase volume fraction was proposed to determine droplet size. A scenario for NP formation from micro-droplets was expressed. Additionally, a dimensionless exponential form correlation for droplet size estimation was proposed based on 27 CFD simulations. The results showed that increasing the continuous phase velocity led to the formation of more small NPs, and the ratio of micro-droplets to NPs size was between 735 and 755.
CANADIAN JOURNAL OF CHEMICAL ENGINEERING
(2023)
Article
Engineering, Chemical
X. Liu, X. Zhang, J. Li, Q. Zhu, N. G. Deen, Y. Tang
Summary: Direct reduction of combusted iron powders using renewable energy is crucial for a carbon-neutral iron fuel cycle. Lab-scale reduction experiments show that a temperature of 500 degrees C achieves a reduction degree higher than 90%, while higher temperatures result in particle sintering and lower reduction degree due to quick defluidization. The study highlights the significance of temperature on sintering and reduction behavior, with negligible impact from gas velocity. The findings offer insights for the design of hydrogen-based iron fuel regeneration processes.
Article
Engineering, Chemical
X. Liu, X. Zhang, J. Li, Q. Zhu, N. G. Deen, Y. Tang
Summary: Hydrogen-based direct reduction of iron oxide powder in gas-fluidized beds is a developing technology, but the agglomeration of fine powder at high temperatures is a key issue. This study experimentally investigates the (de-)fluidization behavior of micron-sized combusted iron particles to understand the high-temperature agglomeration mechanism. The effects of various operating and material variables on the fluidization and agglomeration behavior are examined, and a theoretical model is developed to predict the boundaries of fluidization regimes. The obtained knowledge is then applied for experimental design of the hydrogen-based iron direct reduction process.
Review
Engineering, Environmental
Faezeh Mirshafiee, Salman Movahedirad, Mohammad Amin Sobati, Reyhaneh Alaee, Sasan Zarei, Hamed Sargazi
Summary: Desulfurization is crucial in oil refining to mitigate the harmful effects of sulfur compounds. Naphtha, a key middle distillate, is extensively used as a fuel for automotive, engine, and jet-B applications. Hydrodesulfurization (HDS) is the conventional method employed to remove sulfur, but oxidative desulfurization (ODS) is gaining attention due to its mild reaction conditions and absence of hydrogen requirement. While ODS of diesel has been extensively investigated, limited studies have focused on ODS of naphtha. Understanding the challenges and optimizing ODS for naphtha, particularly in mini-refinery applications, is essential. This study comprehensively examines naphtha cuts, ODS mechanism, classification and comparative analysis of different ODS methods, various oxidants/catalysts, and kinetics of ODS reaction. Additionally, the impact of temperature, pH, catalyst content, and oxidation time on desulfurization efficiency is investigated, along with discussion on research gaps and suggestions for future studies in the field of ODS of naphtha.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2023)
Article
Engineering, Chemical
Faeze Khalighi, Niels G. Deen, Yali Tang, Albertus W. Vreman
Summary: Enhancing the efficiency of industrial water electrolysis for hydrogen production is crucial for the energy transition. This study investigates the growth of a single hydrogen bubble on a vertical cathode in a 30 wt% KOH solution, and examines the effects of flow rate and operation pressure on bubble growth behavior, species concentrations, potential, and current density. The results show that increasing flow velocity slightly improves efficiency, while increasing operation pressure slows down bubble growth and slightly decreases efficiency.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Energy & Fuels
C. J. M. Hessels, D. W. J. Lelivelt, N. C. Stevens, Y. Tang, N. G. Deen, G. Finotello
Summary: In this study, the fluidization and reduction behavior of micron-sized iron oxide powder produced by iron combustion were investigated in a lab-scale cylindrical fluidized bed. The minimum fluidization velocity (umf) was found to stabilize above a normalized static bed height of 0.5 H/D. Experimental results deviated from the Ergun correlation at temperatures above 560 K, prompting the proposal of a new correlation that takes cohesive inter-particle solid bridge force into account. Reduction experiments revealed gradual defluidization at temperatures exceeding 800 K, with a maximum reduction degree of 61% achieved at 807 K and 100 vol% H2.
Article
Engineering, Chemical
Chih-Chia Huang, Jeroen A. van Oijen, Niels G. Deen, Yali Tang
Summary: In Euler-Lagrange models, the information exchange in particulate systems is often smoothed from particles' location to nearby computational cells. However, the current constant diffusivity approach fails to consider the variation in particle sizes in polydisperse systems. This paper proposes a particle-size dependent smoothing scheme called non-constant diffusivity approach.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Electrochemistry
Akmal Irfan Majid, Niels van Graefschepe, Giulia Finotello, John van der Schaaf, Niels G. Deen, Yali Tang
Summary: Sustainable iron production requires reducing energy consumption and emissions. The electroreduction of iron oxide at low temperatures offers a promising solution as it utilizes electrical energy with competitive energy consumption. Experimental studies show that electrochemical reduction in alkaline electrolytes achieves higher current efficiency, lower energy consumption, and higher purity of the iron product.
ELECTROCHIMICA ACTA
(2023)
Article
Energy & Fuels
X. Liu, C. J. M. Hessels, N. G. Deen, Y. Tang
Summary: In this study, the (de-)fluidization behavior of micron-sized iron oxide particles in a 3-D fluidized bed was investigated using Computational Fluid Dynamics coupled with a coarse-grained Discrete Element Method. The effects of temperature on various parameters such as bed pressure drop, void fraction distribution, particle velocity distribution, and agglomerate size were studied. The developed model demonstrated the ability to predict particle agglomeration behavior, providing insight for the design of the DRI process in high-temperature fluidized beds.
Article
Engineering, Chemical
C. J. M. Hessels, A. H. J. Smeets, G. Finotello, N. G. Deen, Y. Tang
Summary: The sintering behavior of micron-sized combusted iron powder was investigated in a packed bed reactor under inert and reducing conditions. Compression tests were conducted to measure the degree of sintering. A sintering model based on solid state surface diffusion of iron atoms was developed and matched the experimental results. Sintering of combusted iron occurred at temperatures ≥ 575 degrees C and increased exponentially with temperature. The observed decrease in reduction rate at high temperatures was attributed to the formation of wustite as an intermediate species.
Article
Electrochemistry
A. M. Meulenbroek, B. W. J. Bernts, N. G. Deen, A. W. Vreman
Summary: This work develops and validates a numerical model for Marangoni flow around a growing hydrogen bubble on a microelectrode. The model accurately predicts the evolution of the bubble radius, the temperature profile around the bubble, and the profile of the Marangoni velocity. Different models are recommended for different stages of the bubble evolution.
ELECTROCHIMICA ACTA
(2023)
Article
Engineering, Chemical
Rahul Subburaj, Yali Tang, Niels G. Deen
Summary: This study investigates the effect of wire mesh on bubbles in a microstructured bubble column reactor and develops a closure model to predict bubble behavior. The validated model accurately predicts reactor performance and aids in the design of wire meshes to increase bubble interfacial area.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2023)
