Processes

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20 pages, 3054 KiB

Open AccessArticle

The Effect of Very Cohesive Ultra-Fine Particles in Mixtures on Compression, Consolidation, and Fluidization

by Abbas Kamranian Marnani, Andreas Bück, Sergiy Antonyuk, Berend van Wachem, Dominique Thévenin and Jürgen Tomas

Processes 2019, 7(7), 439; https://doi.org/10.3390/pr7070439 - 10 Jul 2019

Cited by 9 | Viewed by 3751

Abstract

This paper focuses on the effect of ultra-fine (

d

< 10 µm) powders in mixtures with fine (

d

< 100 µm) bulk material on compression processes and also evaluates the re-fluidization behavior of the compressed bed (history effect). Achieving this goal, [...] Read more.

This paper focuses on the effect of ultra-fine (

d

< 10 µm) powders in mixtures with fine (

d

< 100 µm) bulk material on compression processes and also evaluates the re-fluidization behavior of the compressed bed (history effect). Achieving this goal, different mixtures of fine and ultra-fine Ground-Carbonate-Calcium were compressed at three pressure levels. The results show that by increasing the applied pressure, the compressibility decreases due to change in compaction regime. Subsequently, for the higher pressure, the slope of packing density versus applied stress curves is noticeably different. However, this slope does not depend on the size distribution of mixtures, but on the type of material. Comparing fluidization and re-fluidization curves (bed pressure drop vs. gas velocity) shows an increase in the maximum bed pressure drop (

Δ P_{p e a k}

) for re-fluidization. By increasing the portion of ultra-fine particles in the binary mixture,

Δ P_{p e a k}

increases in a non-linear manner. Furthermore, the incipient fluidization point moves to a higher gas velocity. After compression, the peak of the bed pressure drop in the re-fluidization test happens at a lower gas velocity than in the initial fluidization test. Thus, the slope of the loading curve is much larger for re-fluidization. The opposite is observed for the unloading curves. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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16 pages, 5517 KiB

Open AccessArticle

Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed

by Min Wang, Yingya Wu, Xiaogang Shi, Xingying Lan, Chengxiu Wang and Jinsen Gao

Processes 2019, 7(5), 306; https://doi.org/10.3390/pr7050306 - 22 May 2019

Cited by 9 | Viewed by 3638

Abstract

With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application [...] Read more.

With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application of each method. All these simulations, using the Eulerian–Eulerian two-fluid model with the kinetic theory of granular theory, were conducted to simulate a pilot-scale CFB. The hydrodynamics, such as pressure balance, solids holdup distribution, solids velocity distribution, and instantaneous mass flow rates in the riser or CFB system, were investigated in different simulations. By comparing the results from different methods, it was found that riser-simplified simulation is not sufficient to obtain accurate hydrodynamics, especially in higher solids circulating rates. The riser-only simulation is able to make a reasonable prediction of time-averaged behaviors of gas–solids in most parts of riser but the entrance region. Further, the full-loop simulation can not only predict precise results, but also obtain comprehensive details and instantaneous information in the CFB system. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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26 pages, 5993 KiB

Open AccessFeature PaperArticle

Study of Industrial Naphtha Catalytic Reforming Reactions via Modelling and Simulation

by Aminu Zakari Yusuf, B. O. Aderemi, Raj Patel and Iqbal M. Mujtaba

Processes 2019, 7(4), 192; https://doi.org/10.3390/pr7040192 - 2 Apr 2019

Cited by 11 | Viewed by 11337

Abstract

Steady state and dynamic modelling and simulation of catalytic reforming unit of Kaduna Refining & Petrochemical Company, NNPC (Nigeria) was carried to find out the behaviour of the reactions under both steady and unsteady state conditions. The basic model together with kinetic and [...] Read more.

Steady state and dynamic modelling and simulation of catalytic reforming unit of Kaduna Refining & Petrochemical Company, NNPC (Nigeria) was carried to find out the behaviour of the reactions under both steady and unsteady state conditions. The basic model together with kinetic and thermodynamic parameters and properties were taken from the literature but is developed in gPROMs (an equation oriented modelling software) model building platform for the first time rather than in MATLAB or other modelling platform used by other researchers in the past. The simulation was performed using gPROMs and the predictions were validated against those available in the literature. The validated model was then used to monitor the behaviour of the temperature, concentrations of paraffins, naphthenes and aromatics with respect to both time and height of the reactor of the industrial refinery of Nigeria. Hydrogen yield, Research octane number (RON) and temperature profiles are also reported. The components behave similarly in terms of reactions in the reactors but the time to attain quasi-steady state is different. The results are in good agreement with the industrial plant data. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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17 pages, 4413 KiB

Open AccessFeature PaperArticle

A Novel Multiphase Methodology Simulating Three Phase Flows in a Steel Ladle

by Marco A. Ramírez-Argáez, Abhishek Dutta, A. Amaro-Villeda, C. González-Rivera and A. N. Conejo

Processes 2019, 7(3), 175; https://doi.org/10.3390/pr7030175 - 26 Mar 2019

Cited by 10 | Viewed by 3860

Abstract

Mixing phenomena in metallurgical steel ladles by bottom gas injection involves three phases namely, liquid molten steel, liquid slag and gaseous argon. In order to numerically solve this three-phase fluid flow system, a new approach is proposed which considers the physical nature of [...] Read more.

Mixing phenomena in metallurgical steel ladles by bottom gas injection involves three phases namely, liquid molten steel, liquid slag and gaseous argon. In order to numerically solve this three-phase fluid flow system, a new approach is proposed which considers the physical nature of the gas being a dispersed phase in the liquid, while the two liquids namely, molten steel and slag are continuous phases initially separated by a sharp interface. The model was developed with the combination of two algorithms namely, IPSA (inter phase slip algorithm) where the gas bubbles are given a Eulerian approach since are considered as an interpenetrating phase in the two liquids and VOF (volume of fluid) in which the liquid is divided into two separate liquids but depending on the physical properties of each liquid they are assigned a mass fraction of each liquid. This implies that both the liquid phases (steel and slag) and the gas phase (argon) were solved for the mass balance. The Navier–Stokes conservation equations and the gas-phase turbulence in the liquid phases were solved in combination with the standard k-ε turbulence model. The mathematical model was successfully validated against flow patterns obtained experimentally using particle image velocimetry (PIV) and by the calculation of the area of the slag eye formed in a 1/17th water–oil physical model. The model was applied to an industrial ladle to describe in detail the turbulent flow structure of the multiphase system. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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20 pages, 1993 KiB

Open AccessArticle

Multiphase Open Phase Processes Differential Equations

by Nikolay A. Charykov, Marina V. Charykova, Konstantin N. Semenov, Victor A. Keskinov, Alexey V. Kurilenko, Zhassulan K. Shaimardanov and Botagoz K. Shaimardanova

Processes 2019, 7(3), 148; https://doi.org/10.3390/pr7030148 - 8 Mar 2019

Cited by 8 | Viewed by 3700

Abstract

The thermodynamic approach for the description of multiphase open phase processes is developed based on van der Waals equation in the metrics of Gibbs and incomplete Gibbs potentials. Examples of thermodynamic modeling of the multiphase and multicomponent A³B⁵ systems (In-Ga-As-Sb [...] Read more.

The thermodynamic approach for the description of multiphase open phase processes is developed based on van der Waals equation in the metrics of Gibbs and incomplete Gibbs potentials. Examples of thermodynamic modeling of the multiphase and multicomponent A³B⁵ systems (In-Ga-As-Sb and In-P-As-Sb) and Na⁺, K⁺, Mg²⁺, Ca²⁺//Cl⁻, SO₄²⁻-H₂O water–salt system are presented. Topological isomorphism of different type phase diagrams is demonstrated. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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24 pages, 5482 KiB

Open AccessArticle

Computational Fluid Dynamics (CFD) Simulations and Experimental Measurements in an Inductively-Coupled Plasma Generator Operating at Atmospheric Pressure: Performance Analysis and Parametric Study

by Sangeeta B. Punjabi, Dilip N. Barve, Narendra K. Joshi, Asoka K. Das, Dushyant C. Kothari, Arijit A. Ganguli, Sunil N. Sahasrabhude and Jyeshtharaj B. Joshi

Processes 2019, 7(3), 133; https://doi.org/10.3390/pr7030133 - 4 Mar 2019

Cited by 4 | Viewed by 4292

Abstract

In this article, electrical characteristics of a high-power inductively-coupled plasma (ICP) torch operating at 3 MHz are determined by direct measurement of radio-frequency (RF) current and voltage together with energy balance in the system. The variation of impedance with two parameters, namely the [...] Read more.

In this article, electrical characteristics of a high-power inductively-coupled plasma (ICP) torch operating at 3 MHz are determined by direct measurement of radio-frequency (RF) current and voltage together with energy balance in the system. The variation of impedance with two parameters, namely the input power and the sheath gas flow rate for a 50 kW ICP is studied. The ICP torch system is operated at near atmospheric pressure with argon as plasma gas. It is observed that the plasma resistance increases with an increase in the RF-power. Further, the torch inductance decreases with an increase in the RF-power. In addition, plasma resistance and torch inductance decrease with an increase in the sheath gas flow rate. The oscillator efficiency of the ICP system ranges from 40% to 80% with the variation of the Direct current (DC) powers. ICP has also been numerically simulated using Computational Fluid Dynamics (CFD) to predict the impedance profile. A good agreement was found between the CFD predictions and the impedance experimental data published in the literature. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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28 pages, 10255 KiB

Open AccessArticle

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

by Abbas Kamranian Marnani, Andreas Bück, Sergiy Antonyuk, Berend van Wachem, Dominique Thévenin and Jürgen Tomas

Processes 2019, 7(1), 35; https://doi.org/10.3390/pr7010035 - 11 Jan 2019

Cited by 11 | Viewed by 6989

Abstract

The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of [...] Read more.

The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of the fine particles in some processes which totally changes the size distribution and also fluidization behaviour. The materials used in this study are both ground calcium carbonate (GCC); fine is CALCIT MVT 100 (Geldart’s group A) and ultra-fine is CALCIT MX 10 (group C). The experimental results for different binary mixtures of these materials (ultra-fines have 30%, 50%, or 68% of the total mixture weight) show that the physical properties of the mixtures are close to those of pure ultra-fine powders. Using mean values of the bed pressure drop calculated from several independent repetitions, the fluidization behaviour of different mixtures are compared and discussed. The fluidization behaviour of the mixtures is non-reproducible and includes cracking, channelling and agglomeration (like for pure ultra-fine powders). Increasing the portion of ultra-fine materials in the mixture causes a delay in starting partial fluidization, an increase in the bed pressure drop as well as a delay in reaching the peak point. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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12 pages, 4064 KiB

Open AccessArticle

Effect of Particle Size on Carbon Nanotube Aggregates Behavior in Dilute Phase of a Fluidized Bed

by Sung Won Kim

Processes 2018, 6(8), 121; https://doi.org/10.3390/pr6080121 - 8 Aug 2018

Cited by 15 | Viewed by 4843

Abstract

Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (d_p = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles [...] Read more.

Fluidized bed reactors have been increasingly applied for mass production of Carbon Nanotube (CNT) using catalytic chemical vapor deposition technology. Effect of particle size (d_p = 131 μm and 220 μm) on fluidization characteristics and aggregation behavior of the CNT particles have been determined in a fluidized bed for its design and scale-up. The CNT aggregation properties such as size and shape were measured in the dilute phase of a fluidized bed (0.15 m-ID × 2.6 m high) by the laser sheet technique for the visualization. Two CNT particle beds showed different tendency in variations of the aggregates factors with gas velocity due to differences in factors contributing to the aggregate formation. The CNT particles with a larger mean size presented as relatively larger in the aggregate size than the smaller CNT particles at given gas velocities. The aggregates from the large CNT particles showed a sharp increase in the aspect ratio and rapid decrease in the roundness and the solidity with gas velocity. A possible mechanism of aggregates formation was proposed based on the variations of aggregates properties with gas velocity. The obtained Heywood diameters of aggregates have been firstly correlated with the experimental parameter. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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8 pages, 4470 KiB

Open AccessCommunication

A New Concept of Stirred Multiphase Reactor Using a Stationary Catalytic Foam

by Nassima Benamara, Didier Assoua, Louis Jaffeux, Laurent Vanoye, Florica Simescu-Lazar, Marie-Line Zanota, Frédéric Bornette, Valérie Meille and Isabelle Pitault

Processes 2018, 6(8), 117; https://doi.org/10.3390/pr6080117 - 7 Aug 2018

Cited by 4 | Viewed by 4333

Abstract

Developing new stirred gas–liquid–solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas–liquid (GL) and liquid–solid (LS) mass transfer rates [...] Read more.

Developing new stirred gas–liquid–solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas–liquid (GL) and liquid–solid (LS) mass transfer rates in this reactor were compared to a stirred reactor with basket filled with beads. Batch absorption of hydrogen and measurement of

α

-methylstyrene hydrogenation rate on

P d / A l_{2} O_{3}

catalyst were used to evaluate

k_{G L} a_{G L}

coefficients and

k_{L S}

coefficients, respectively. With similar LS transfer rates to the basket-reactor and much higher GL transfer rates, the new reactor reveals a very promising tool for intrinsic kinetics investigations. Full article

(This article belongs to the Special Issue Multiphase Reaction Engineering, Reactors and Processes )

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