Research

Jump to: Review

17 pages, 8258 KiB

Open AccessArticle

Simulation of Multi-Phase Flow in Autoclaves Using a Coupled CFD-DPM Approach

by Bin Kou, Yanqing Hou, Weiqin Fu, Ni Yang, Junchang Liu and Gang Xie

Processes 2023, 11(3), 890; https://doi.org/10.3390/pr11030890 - 15 Mar 2023

Cited by 3 | Viewed by 1823

In this work, a numerical simulation study on the mixing characteristics of multiphase flow in an autoclave was carried out using CFD technology. The Eulerian–Eulerian model and discrete phase model (DPM) were employed to investigate the solid holdup, critical suspension speed, nonuniformity of [...] Read more.

In this work, a numerical simulation study on the mixing characteristics of multiphase flow in an autoclave was carried out using CFD technology. The Eulerian–Eulerian model and discrete phase model (DPM) were employed to investigate the solid holdup, critical suspension speed, nonuniformity of solid suspension, gas holdup distribution, bubble tracks, and residence time during stirring leaching in the autoclave. Experiments validate the accuracy of the numerical model, and the experimental values correspond well with the simulation results. The numerical simulation results show that the solid–liquid mixing is mainly affected by the axial flow, the best agitation speed is 400 rpm, and increasing the speed further cannot make the mixture more homogenous and buildup occurred above the autoclave. The calculated critical suspension speed is 406 rpm, which is slightly lower than that obtained from the empirical formula. The gas phase is mainly concentrated in the vortex area above the blade. When the gas phase is in a completely dispersed state (N = 300 rpm), the average residence time of the bubbles is 5.66 s. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

13 pages, 4596 KiB

Open AccessArticle

Determination of Viscosity, Density and Interfacial Tension of the Carbon Dioxide–Isopropanol, Argon–Isopropanol, Sulphur Hexafluoride–Isopropanol Binary Systems at 313.15 K and 333.15 K and at Elevated Pressures

by Dragana Borjan, Maja Gračnar, Željko Knez and Maša Knez Marevci

Processes 2022, 10(11), 2275; https://doi.org/10.3390/pr10112275 - 03 Nov 2022

Cited by 1 | Viewed by 1258

Abstract

Viscosity, density, and interfacial tension of three binary systems (carbon dioxide–isopropanol, argon–isopropanol, and sulphur hexafluoride–isopropanol) were measured at temperatures of 313.15 K and 333.15 K and at pressures up to 100 bar for carbon dioxide, and for argon and sulphur hexafluoride up to [...] Read more.

Viscosity, density, and interfacial tension of three binary systems (carbon dioxide–isopropanol, argon–isopropanol, and sulphur hexafluoride–isopropanol) were measured at temperatures of 313.15 K and 333.15 K and at pressures up to 100 bar for carbon dioxide, and for argon and sulphur hexafluoride up to 500 bar. A vibrating tube densimeter method has been used for density measurements and a variable-volume high-pressure optical view cell with some modifications for the other measurements. The results showed that pressure does not have a high impact on viscosity. Density is found to be a linear function of pressure and temperature and the densities of the investigated binary systems increase with pressure and decrease with temperature. Interfacial tension decreased with the elevated pressure at a constant temperature for all the investigated systems. Accurate prediction of thermodynamic and mass transfer data is fundamental in various engineering and industrial operations to design processes with a higher yield of targeted compounds. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

19 pages, 5613 KiB

Open AccessArticle

Characteristics of Gas–Solid Flow in an Intermittent Countercurrent Moving Bed

by Qingshuo Wan, Zhifeng Zhao, Ruojin Wang, Meng Tang, Dewu Wang, Shaofeng Zhang and Baisong Hu

Processes 2022, 10(10), 2116; https://doi.org/10.3390/pr10102116 - 18 Oct 2022

Viewed by 1087

Abstract

The calculation equations of pressure drop and solid flow rate are given in an intermittent countercurrent moving bed with multiple optimized structures. The flow fields are investigated by experimental methods under different conditions, e.g., ratio of position of the gas distributor to the [...] Read more.

The calculation equations of pressure drop and solid flow rate are given in an intermittent countercurrent moving bed with multiple optimized structures. The flow fields are investigated by experimental methods under different conditions, e.g., ratio of position of the gas distributor to the bed width (r_p = 0.5~1.5), gas superficial velocity (u_g = 0~0.1591 m/s), solid outlet diameter (D_o = 5~25 mm) and cone angle (α = 0~60°). It is found that when r_p ≥ 1.0, the flow field in the bed is little affected by r_p. Flow patterns are divided into three modes: continuous discharging, intermittent discharging (synchronous, asynchronous) and particle bridging. During continuous discharging, the calculation formula of the solid flow rate, which is closely related to D_o and gas–solid slip velocity v_slip, is established by referring to the modified De Jong and Beverloo formulas, and its error ≤ ±12.5%. The pressure drop of the total bed consists of the pressure drops of the granular bed and the solid outlets, which are affected by D_o, v_slip and α; it is built by referring to the Ergun formula, and its error ≤ ±17.0%. As the solid flow rate and pressure drop influence each other through v_slip, an iterative algorithm is proposed to enhance the computation accuracy. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

15 pages, 770 KiB

Open AccessArticle

Accurate Effective Diffusivities in Multicomponent Systems

by William Q. Rios, Bruno Antunes, Alírio E. Rodrigues, Inês Portugal and Carlos M. Silva

Processes 2022, 10(10), 2042; https://doi.org/10.3390/pr10102042 - 09 Oct 2022

Cited by 2 | Viewed by 1731

Abstract

Mass transfer is an omnipresent phenomenon in the chemical and related industries for which effective diffusivities (

D_{i, eff}

) constitute a useful and simple mathematical tool, especially when dealing with multicomponent mixtures. Although several models have been published for [...] Read more.

Mass transfer is an omnipresent phenomenon in the chemical and related industries for which effective diffusivities (

D_{i, eff}

) constitute a useful and simple mathematical tool, especially when dealing with multicomponent mixtures. Although several models have been published for

D_{i, eff}

they generally involve simplifying assumptions that severely restrict their use. The current work presents the derivation of accurate analytical equations for

D_{i, eff}

, which take into account the nonideal behavior of multicomponent mixtures. Additionally, it is demonstrated that for an ideal mixture the new model reduces to the well-known equations of Bird et al., which are the exact analytical solution for ideal systems. The procedure for

D_{i, eff}

estimation is described in detail and exemplified with two chemical reactions: the liquid phase ethyl acetate synthesis and the high pressure gas phase methanol synthesis. Relative to the Bird et al. ideal equations the effective diffusivities calculated with the new model show differences up to 38% for ethyl acetate synthesis when using UNIFAC model to evaluate activity coefficients. For methanol synthesis, deviations from −23% to 22% are found using PC-SAFT equation of state (EoS) and from −49% to 24% when applying the Peng–Robinson EoS to estimate fugacity coefficients. Comparisons are also performed with the models by Wilke, Burghardt and Krupiczka, Kubota et al., and Kato et al. The worst results are achieved by the Wilke and Kubota et al. equations for the liquid phase and gas phase reactions, respectively. Furthermore, it is shown that substantial errors in effective diffusivity calculations may occur when deviations from the ideal behavior are unaccounted for. This can be avoided by adopting the new rigorous approach here presented. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

17 pages, 6446 KiB

Open AccessArticle

The Hydrodynamics of a Rod-Shaped Squirmer near a Wall

by Hao Ye, Jianzhong Lin and Zhenyu Ouyang

Processes 2022, 10(9), 1841; https://doi.org/10.3390/pr10091841 - 13 Sep 2022

Cited by 1 | Viewed by 1210

Abstract

The hydrodynamic characteristics of a rod-shaped squirmer swimming near a wall were studied numerically using the immersed boundary-lattice Boltzmann method in the swimming Reynolds number range of 0.1 ≤ Re_s ≤ 2.0, where the number of assembled squirmers was 2 ≤ i [...] Read more.

The hydrodynamic characteristics of a rod-shaped squirmer swimming near a wall were studied numerically using the immersed boundary-lattice Boltzmann method in the swimming Reynolds number range of 0.1 ≤ Re_s ≤ 2.0, where the number of assembled squirmers was 2 ≤ i ≤ 4 and the distance between two adjacent assembled squirmers was 0.75 d ≤ s ≤ 1.5 d (d is the diameter of a single squirmer). The effect of Re_s, i and s on the swimming mode of the squirmer was explored. The results showed that there are four swimming modes after the first collision between the rod-shaped squirmer and the wall. There are also four swimming modes when Re_s changes from 0.1 to 2.0. Puller, pusher and neutral squirmers showed different swimming modes when i changed, and the effect degree of the flow at the previous moment on the squirmer’s motion was different for different values of i. The change in s only affected the trajectory of the squirmer without changing its motion mode. Puller, pusher and neutral squirmers showed different swimming modes and velocity changes when s changed. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

18 pages, 10381 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Scale-Up Strategies of Jet Loop Reactors for the Intensification of Mass Transfer Limited Reactions

by Marc Maly, Steffen Schaper, Rafael Kuwertz, Marko Hoffmann, Joachim Heck and Michael Schlüter

Processes 2022, 10(8), 1531; https://doi.org/10.3390/pr10081531 - 04 Aug 2022

Cited by 3 | Viewed by 3508

Abstract

For the purpose of the intensification of an industrial-scale gas-liquid process, the implementation in an alternative reactor concept is investigated at Hamburg University of Technology (TUHH) in cooperation with Ehrfeld Mikrotechnik GmbH. Existing process operation data from a bubble column hint at a [...] Read more.

For the purpose of the intensification of an industrial-scale gas-liquid process, the implementation in an alternative reactor concept is investigated at Hamburg University of Technology (TUHH) in cooperation with Ehrfeld Mikrotechnik GmbH. Existing process operation data from a bubble column hint at a mass transfer limitation of the gas-liquid reaction. In the project, a jet loop reactor (JLR) is chosen to increase the specific interfacial area between gas and liquid, and thus increase mass transfer, while keeping the reactor system mechanically simple and low-maintenance. For the investigation, a laboratory scale reactor has been designed on the basis of an existing industrial scale process and scaled according to a pilot scale reactor available at TUHH. For scaling, geometric similarity is desired, while specific energy dissipation rate and volumetric gas input are kept constant for the chosen scale-up strategy. Between the two different scales, the reactors are successfully characterised in a water-air system with regards to the important mass transfer, among other parameters. A pressure- and chemical-resistant twin of the laboratory-scale reactor is provided to the project partner for trials under real process conditions with the original material system. The presented work shows that the JLR concept can be transferred sufficiently well between different scales when suitable parameters are chosen, and offers a wide operating window. The investigations aim to provide a basis for a future scale-up of the chemical process in the JLR system to the industrial scale. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

13 pages, 3507 KiB

Open AccessArticle

Phase Equilibrium of the Quaternary System LiBr-Li₂SO₄-KBr-K₂SO₄-H₂O at 308.15 K

by Bin Li, Xinjun Jing and Junsheng Yuan

Processes 2022, 10(5), 823; https://doi.org/10.3390/pr10050823 - 21 Apr 2022

Cited by 1 | Viewed by 1409

Abstract

The phase equilibria of the reciprocal quaternary system LiBr-Li₂SO₄-KBr-K₂SO₄-H₂O and its ternary sub-systems LiBr-Li₂SO₄-H₂O and KBr-K₂SO₄-H₂O at 308.15 K were studied [...] Read more.

The phase equilibria of the reciprocal quaternary system LiBr-Li₂SO₄-KBr-K₂SO₄-H₂O and its ternary sub-systems LiBr-Li₂SO₄-H₂O and KBr-K₂SO₄-H₂O at 308.15 K were studied using the isothermal dissolution equilibrium method. Then, the solubility data of the equilibrium solutions were collected, and the phase diagrams were plotted. The phase diagrams of the ternary sub-systems at 308.15 K were compared with those at other temperatures. This study found that the phase diagram of the LiBr-Li₂SO₄-H₂O system at 308.15 K consisted of an invariant point, two solid-phase crystallization regions of Li₂SO₄·H₂O and LiBr·2H₂O, and their corresponding solubility curves. The system generated two hydrated salts, which belonged to the hydrate type I phase diagram. The phase diagram of the KBr-K₂SO₄-H₂O system at 308.15 K consisted of an invariant point, two univariant solubility curves, and two solid-phase crystallization regions of KBr and K₂SO₄, and no solid solution and double salts were formed. Thus, it belonged to a simple co-saturation type phase diagram. In the LiBr-Li₂SO₄-KBr-K₂SO₄-H₂O system, K₂SO₄·Li₂SO₄ double salt formed at 308.15 K, and the phase diagram consisted of three invariant points, five crystallization regions, and seven univariant solubility curves. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

Review

Jump to: Research

14 pages, 1489 KiB

Open AccessFeature PaperReview

Unified Approach for Prediction of the Volumetric Mass Transfer Coefficients in a Homogeneous and Heterogeneous Bubble Column Based on the Non-Corrected Penetration Theory: Case Studies

by Stoyan Nedeltchev

Processes 2022, 10(9), 1828; https://doi.org/10.3390/pr10091828 - 10 Sep 2022

Cited by 2 | Viewed by 1403

Abstract

A critical review on the improvement of penetration theory is presented in this work. The volumetric liquid-phase mass transfer coefficients k_La in seven different liquids (1-butanol, 2-propanol, anilin, decalin, nitrobenzene, tetralin, and ethylene glycol) aerated with air in a small bubble [...] Read more.

A critical review on the improvement of penetration theory is presented in this work. The volumetric liquid-phase mass transfer coefficients k_La in seven different liquids (1-butanol, 2-propanol, anilin, decalin, nitrobenzene, tetralin, and ethylene glycol) aerated with air in a small bubble column (BC) (inner diameter: 0.095 m) were measured at ambient conditions and further analyzed. It was found that the k_La values can be predicted satisfactorily on the basis of the classical Higbie’s penetration model. The gas–liquid contact time was defined as the ratio of the Sauter-mean bubble diameter to bubble rise velocity. Moreover, the experimental k_La values were well predicted, not only in the homogeneous regime, but also in the transition and heterogeneous regimes. This is a new finding, since to date, it was considered that the penetration theory needs a correction factor for a successful application to any liquid, even in the homogeneous regime. The predictions of the mass transfer coefficients k_La in the above-mentioned seven liquids imply that the mean bubble diameters are always ellipsoidal or spherical, which is the key condition for the applicability (without a correction) of penetration theory. In the presented (in this work) model-based k_La predictions, the Sauter-mean bubble diameters were estimated by means of the reliable correlation of Wilkinson et al., which always predicts a gradually decreasing bubble size at higher gas velocities. Full article

(This article belongs to the Special Issue Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Multiphase Mass Transfer and Phase Equilibrium in Chemical Processes

Share This Special Issue

Special Issue Editors

Special Issue Information

Published Papers (8 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI