Hydrodynamics and heat transfer of gas–solid two-phase mixtures flowing through packed beds – a review
TL;DR: In this paper, a review of the recent development in the field including both hydrodynamics and heat transfer of gas-solid two-phase mixtures flowing through packed beds is presented.
Abstract: Flow of a gas–solid two-phase mixture through a packed bed is relevant to a number of industrial processes such as heat recovery and filtration of dusty flue gases, iron making in shaft reactors, gas purification, and sorption enhanced reaction processes. In spite of the industrial relevance, little work has been reported in the literature. The limited amount of research work has mainly addressed the macroscopic hydrodynamics in terms of pressure drop and solids hold-ups at the ambient temperature. Very little is done, until fairly recent, on solids motion at the single particle level, hydrodynamics at elevated temperatures and heat transfer. This paper reviews the recent development in the field including both the hydrodynamics and heat transfer of gas–solid two-phase mixtures flowing through packed beds, which is believed to represent the state-of-the-art in the field. The review is not aimed to be exhaustive but rather focused on our own work carried out over the past few years in the Institute of Particle Science & Engineering at the University of Leeds. And some of our results are compared with that of other groups.
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TL;DR: In this article, three devolatilization schemes for biomass fast pyrolysis were tested and validated in a numerical model that considered the multiphase hydrodynamics and chemical reactions of biomass fast pyrrithm.
Abstract: Three devolatilization schemes to simulate biomass fast pyrolysis were tested and validated in this study. Fast pyrolysis is an attractive process in converting lignocellulosic biomass to valued products. Accurate numerical models can help understand the conversion process and be used for reactor design and optimization. This study used a numerical model that considered the multiphase hydrodynamics and chemical reactions of biomass fast pyrolysis. The gas and solid phases were simulated by using a multifluid model that considered multiple species in each phase. Three devolatilization schemes for biomass fast pyrolysis were incorporated into the model to simulate the tempo-spatial evolutions of all phases and species. The predicted product yields were compared and validated using experimental data. It was found that the best predictions were given by a scheme that used three components to represent biomass and also considered organic liquid cracking into gas. Under the reactor conditions studied, all three devolatilization schemes predicted relatively fast decomposition of biomass and the reactor hydrodynamics was not significantly affected by the specifics of the devolatilization schemes. Overall, an accurate devolatilization scheme to simulate the chemical changes of biomass particles is essential to predicting the product yield of biomass fast pyrolysis at the reactor scale. © 2014 American Institute of Chemical Engineers Environ Prog,, 33: 756–761, 2014
46 citations
Cites background from "Hydrodynamics and heat transfer of ..."
...The effects of different physical models, such as interphase coefficients for momentum [8, 9] and heat transfer [10], have gained considerable attention in multiphase CFD simulation [11]....
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TL;DR: In this paper, the authors investigated the heat storage and heat transfer behavior of supercritical air flowing through a rock bed with the working temperature and pressure ranging up to 120°C and 6.55 MPa, respectively.
30 citations
TL;DR: In this article, a new process has been proposed and investigated for low temperature hydrogen production from hydrocarbons with simultaneous CO2 abatement, based on a concept involving simultaneous hydrogen production and CO2 removal, which uses a stationary catalyst phase and a continuously moving adsorbent phase for in situ removal of CO2 and ex situ regeneration of adsorbents.
Abstract: A new process has recently been proposed and investigated for low temperature hydrogen production from hydrocarbons with simultaneous CO2 abatement. It is based on a concept involving simultaneous hydrogen production and CO2 removal, which uses a stationary catalyst phase and a continuously moving adsorbent phase for in situ removal of CO2 and ex situ regeneration of adsorbent. This paper summaries the recent developments in the technology using methane (main composition of natual gas) and glycerol (main by-product of biofuels) as the model feedstocks and microsized hydrotalcite as the CO2 adsorbent. The paper consists of an overview of the new technology, associated fundamental studies including dynamics of adsorption, hydrodynamics, solid hold-up and heat transfer, and chemical reactions. Challenges for further development of the technology and process optimisation are also briefly discussed.
25 citations
TL;DR: The basic mechanisms of sublimation two-phase flows are reviewed and several representative refrigeration systems are introduced and compared in this review study, which may give useful indications for future innovations.
Abstract: Sublimation is one phase change mechanism which usually happens under low-to-moderate temperatures and at the same time large amounts of latent heat can be utilized. Low temperature sublimation has been proposed in a lot of applications as one useful cooling/refrigeration mechanisms, such as medical cooling, food engineering, chemical synthesis, domestic cooling and many industrial sectors. In this review study, the basic mechanisms of sublimation two-phase flows are firstly reviewed. In earlier years, theoretical studies focused on and analyzed surface crystal structure effect. Later, the focus was on recent developments in numerical modeling and experimental verifications. Numerical modeling studies were mainly focused on the sublimation parameter behaviors under various ambient situation and container geometries. In recent years, it is also found that multi-scale modeling has become one of the most promising topics in this field. In experimental studies, major newly developed visualization systems and related real refrigeration systems are summarized and discussed. As more and more studies proposed application systems, several representative refrigeration systems are also introduced and compared in this paper, which may give useful indications for future innovations. Future research focuses are also proposed in this review study while this field is still young (but promising), both for scientific research and real system designs. It is hoped that this brief review can contribute to the development of novel refrigeration systems and the development of cryogenic science and engineering.
18 citations
TL;DR: This work presents a numerical workflow to generate a virtual packed bed made of non-spherical polydisperse particles, and subsequently predict its permeability, and opens the door to numerical estimation of bed tortuosity, dispersion coefficients, volumetric heat exchange coefficients, and much more, using the particle size distribution as unique input data.
12 citations
Cites background from "Hydrodynamics and heat transfer of ..."
...Most of the time, these beds are made of particles poured into a container which is then crossed by a reacting flow [1, 2, 3, 4]....
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References
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Book•
27 Oct 2012
TL;DR: In this article, the origin of Bubbles is discussed, and the theory of Granular Mixtures is presented, along with the application of Kinetic Theory in the field of Continuum Problems.
Abstract: (Chapter Headings): Transport Equations. One-Dimensional Steady Gas Solid Flow. Drift Flux. Critical Granular Flow. The Fluidized State. On the Origin of Bubbles. Inviscid Multiphase Flows: Bubbling Beds. Viscous Flow and Circulating Fluidized Beds. Kinetic Theory Approach. Applications of Kinetic Theory. Kinetic Theory of Granular Mixtures. Sedimentation and Consolidation. Appendices: Formulation of Continuum Problems: Introduction. Appendices: The Method of Characteristics: Introduction. Chapter References. Index.
2,421 citations
"Hydrodynamics and heat transfer of ..." refers background or methods in this paper
...where Cd is the drag coefficient of particles given by Gidaspow [30]:...
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...The governing equations used for the work consist of the following continuity and momentum conservation equations [30]....
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10 Mar 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the Birmingham positron camera was used for tracking positron-emitting particles within engineering structures, using particles typically 4 MBq (100 μCi) 18 F or 22 Na.
Abstract: The use of the Birmingham positron camera for tracking positron-emitting particles within engineering structures has been investigated, using particles containing typically 4 MBq (100 μCi) 18 F or 22 Na. An algorithm for discarding γ-ray trajectories corrupted by scattering, etc., and using the remaining trajectories to compute the particle's location in three dimensions has been developed, and its performance explained. A slowly moving particle can be located to within 1 mm several times per second, while a particle moving at 1 ms −1 can be located to within 5 mm 50 times per second, through a considerable thickness of surrounding material. An example of results obtained from tracking a particle in a rotating drum of powder illustrates the potential value of the technique.
342 citations
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TL;DR: In this article, the equilibria and kinetics of high temperature CO 2 adsorption on hydrotalcite adsorbent have been studied using semi-technical and bench-scale elution apparatus.
323 citations
TL;DR: In this article, a new radial bed porosity model was proposed and experimental data and a radial bed voidage model was presented, which is used to predict the radial bed's voidage and average bed's porosity.
Abstract: Randomly packed beds of equal spheres exhibit damped oscillatory voidage variation in the near wall region. Models reported in literature were found to be lacking in their ability to relate this variation to average bed porosity. The changing mean of the voidage oscillations and deviations from sinusoidal behavior were not described well either. Experimental data and a new radial bed porosity model are presented. Improved radial bed voidage and average bed voidage predictions were demonstrated. It has further been shown that multiple stable packing configurations exist within the same packing mode, which complicates modeling at a small column to particle diameter ratio.
321 citations
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