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A reduced model for particle calcination for use in DEM/CFD simulations

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Particuology 2024年第10期93卷 316-327页

作者： Lucas Mieg Torben Bergold Enric Illana Mahiques Viktor Scherer Martin Mönnigmann Automatic Control and System Theory Ruhr University BochumGermany Energy Plant Technology Ruhr University BochumGermany

We treat the accurate simulation of the calcination reaction in particles,where the particles are large and,thus,the inner-particle processes must be *** these processes need to be described with coupled partial differential equations(PDEs)that must be solved numerically,the computation times for a single particle are too high for use in simulations that involve many *** of this type arise when the Discrete Element Method(DEM)is combined with Computational Fluid Dynamics(CFD)to investigate industrial systems such as quicklime production in lime shaft *** show that,based on proper orthogonal decomposition and Galerkin projection,reduced models can be derived for single particles that provide the same spatial and temporal resolution as the original PDE models at a considerably reduced computational *** the finite volume particle models with the reduced models results in an overall reduction of the reactor simulation time by about 40%for the sample system treated here.

关键词： Calcination Reactive bulk Model reduction Discrete element method Galerkin projection

INFLUENCE OF PHASE RATIO ON PACKING EFFICIENCY IN COLUMNS FOR MASS TRANSFER PROCESSES

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Chinese Journal of Chemical Engineering 1997年第2期5卷 25-34页

作者： Reinhard Billet Michael Schultes Institute of Thermo-and Fluid-dynamics Ruhr-University BochumInstitute of Thermo-and Fluid-dynamicsRuhr-University Bochum D-44780 BochumGermanyD-44780 BochumGermany

The phase ratio has been found to affect the packing efficiency in packed *** ac-count for the effect,a model is set up to correlate the height of a mass transfer unit with the phaseratio with reasonable *** also is a correlation that allows to predict the efficiency inquestion at any given liquid-gas ratio using the knowledge of other efficiency values at other liquid-gas ratios.

关键词： phase ratio height of a transfer unit packings

Numerical simulation of three dimensional concrete printing based on a unified fluid and solid mechanics formulation

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Frontiers of Structural and Civil Engineering 2024年第4期18卷 491-515页

作者： Janis REINOLD Koussay DAADOUCH Günther MESCHKE Institute for Structural Mechanics Ruhr University BochumBochum 44801Germany

Deformation control constitutes one of the main technological challenges in three dimensional(3D)concrete printing,and it presents a challenge that must be addressed to achieve a precise and reliable construction ***-based information of the expected deformations and stresses is required to optimize the construction process in association with the specific properties of the concrete *** this work,a novel thermodynamically consistent finite strain constitutive model for fresh and early-age 3D-printable concrete is *** model is then used to simulate the 3D concrete printing process to assess layer shapes,deformations,forces acting on substrate layers and prognoses of possible structural collapse during the layer-by-layer *** constitutive formulation is based on a multiplicative split of the deformation gradient into elastic,aging and viscoplastic parts,in combination with a hyperelastic potential and considering evolving material properties to account for structural buildup or *** advantage of this model is the stress-update-scheme,which is similar to that of small strain plasticity and therefore enables an efficient integration with existing material *** constitutive model uses the particle finite element method,which serves as the simulation framework,allowing for modeling of the evolving free surfaces during the extrusion *** analyses of three printed layers are used to create deformation plots,which can then be used to control the deformations during 3D concrete *** study offers further investigations,on the structural level,focusing on the potential structural collapse of a 3D printed concrete *** capability of the proposed model to simulate 3D concrete printing processes across the scales—from a few printed layers to the scale of the whole printed structure—in a unified fashion with one constitutive formulation,is demonstrated.

关键词： particle finite element method 3D concrete printing multiplicative split additive manufacturing elastoviscoplasticity

A holistic approach for the investigation of lining response to mechanized tunneling induced construction loadings

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Underground Space 2018年第1期3卷 45-60页

作者： Vojtech Ernst Gall Ahmed Marwan Mario Smarslik Markus Obel Peter Mark Gunther Meschke Inustitute for Structural Mechanics Ruhr University BochumBochunGermany Institute of Concrete Structures Ruhr University BochumBochumGermany

Design methods for segmental tunnel linings used in mechanized tunnel constructions typically employ numerical bedded beam mod-els and/or classical analytical solutions for the determination of structural forces(*** and shear and axial forces)and simple load spreading assumptions for the design of the reinforcement in joint *** effcient such methods may be,many physical details are often overlooked and/or oversimpliﬁed in the process of reducing the actual structure to a structural beam model,***-lytically derived loadings are employed,the grouting and ground reactions are reduced to a spring bedding,and the conﬁnement due to grouting at the longitudinal joint is largely not considered in reinforcement *** a design process is not able to account for,or predict,the susceptibility of tunnel linings to often observed damages that,although they may not be structurally relevant,lead to ser-viceability or durability issues,such as crack development or chipping at the segment *** methods,such as the Finite Element Method,provide an opportunity to model the segmental tunnel lining and its response to the entire TBM construction process and to explicitly model the crack development within individual segments using modern methods to model the discontinuities in *** this contribution,a holistic modeling procedure for the representation of the tunnel lining within the tunneling process is pro-posed and compared to traditional lining models.A 3D process oriented Finite Element model is used to calculate the predicted forces on the tunnel lining and the obtained results are compared with those generated by traditional ***,the predicted defor-mations are then transferred to a detailed segment model in which the nonlinear response of the segment at the longitudinal joint is mod-eled using an interface element based approach to simulate concrete cracking.

关键词： Mechanized tunneling Segmental tunnel linings Finite element method

Shape-changing particles for locally resolved particle geometry in DEM simulations

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Particuology 2024年第6期89卷 185-190页

作者： Enric Illana Klidi Qyteti Maik Scharnowski Maximilian Brömmer Siegmar Wirtz Viktor Scherer Institute of Energy Plant Technology Ruhr-University BochumBochumGermany

Taking into account the complex shape of particles in discrete element method (DEM) simulations of large-scale granular systems is computationally demanding due to the time-consuming contact detection algorithms for polyhedral particles. In this short communication, a novel approach that locally resolves the particle shapes where needed and uses a simplified representation elsewhere, to accelerate simulations without compromising accuracy, is presented. For this purpose, a method employing a smooth transition of the particle shape representation from analytical spheres to shape-resolving polyhedra is introduced in DEM. The feasibility and correct implementation of this approach are demonstrated through simulations of hopper discharge involving spherical and dodecahedral particles from a flat bottom silo or shaft kiln. The model capabilities, in terms of accuracy as well as reduction in computational effort, are quantified for a moving bed with continuous outflow.

关键词： Polyhedron Size change Shape change Locally resolved DEM

Nickel nanoparticles supported on nitrogen-doped carbon nanotubes are a highly active,selective and stable CO_(2) methanation catalyst

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Journal of Energy Chemistry 2021年第3期30卷 323-331页

作者： Julian Godde Mariia Merko Wei Xia Martin Muhler Laboratory of Industrial Chemistry Ruhr University BochumD-44780 BochumGermany

CO_(2) methanation using nickel-based catalysts has attracted large interest as a promising power-to-gas *** nanoparticles supported on nitrogen-doped CNTs with Ni loadings in the range from 10 wt% to 50 wt% were synthesized by impregnation,calcination and reduction and characterized by elemental analysis,X-ray powder diffraction,H_(2) temperature-programmed reduction,CO pulse chemisorption and transmission electron *** Ni/NCNT catalysts were highly active in CO_(2) methanation at atmospheric pressure,reaching over 50% CO_(2) conversion and over 95% CH_(4) selectivity at 340℃ and a GHSV of50,000 mL g^(-1) h^(-1) under kinetically controlled *** small Ni particle sizes below 10 nm despite the high Ni loading is ascribed to the efficient anchoring on the N-doped *** optimum loading of 30 wt%-40 wt% Ni was found to result in the highest Ni surface area,the highest degree of conversion and the highest selectivity to methane.A constant TOF of 0.3 s^(-1) was obtained indicating similar catalytic properties of the Ni nanoparticles in the range from 10 wt%to 50 wt% Ni ***-term experiments showed that the Ni/NCNT catalyst with 30 wt% Ni was highly stable for 100 h time on stream.

关键词： CO_(2)methanation Nickel nanoparticles Carbon nanotubes Nitrogen doping

INFLUENCE OF INITIAL LIQUID DISTRIBUTION ON MASS TRANSFER IN PACKED BEDS

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Chinese Journal of Chemical Engineering 1994年第2期2卷 39-53页

作者： Reinhard Billet Department of Process and Environmental Engineering Ruhr University Bochum 44780 Bochum Germany

Experience from experimental studies shows that the efficiency of a column packing depends considerably on liquid flow management at the top of the column. Therefore, attention must be drawn to the need for a proper liquid distribution design in order to obtain good operation of the packed bed.The choice of the liquid distribution system depends on the geometry of the selected packings and on the operating conditions. One of the main parameters which determines the operation of the distribution and its influence on bed efficiency is the number of liquid feeders. Extensive systematic investigations were carried out under absorption, desorption and rectification conditions in beds of different dumped and regular packings, applying distributors with varying numbers of liquid outlets.The evaluations and modelling of the experimental results led to the determination of the proper number of feeder points, which mainly depends on the packing geometry represented by its open area and void fraction. The main results are shown in the form of diagrams and equations.

关键词： liquid distribution packed bed

Operando electrochemical SERS monitors nanoparticle reactions by capping agent fingerprints

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Nano Research 2022年第5期15卷 4517-4524页

作者： Kevin Wonner Steffen Murke Serena RAlfarano Pouya Hosseini Martina Havenith Kristina Tschulik Chair of Analytical Chemistry Ⅱ Faculty of Chemistry and BiochemistryRuhr University BochumBochum 44801Germany Chair of Physical Chemistry Ⅱ Faculty of Chemistry and BiochemistryRuhr University BochumBochum 44801Germany

Nanomaterials are frequently employed in daily life goods,including health,textile,and food industry.A comprehensive picture is lacking on the role of the capping agents,added ligand molecules,in case of nanoparticle reactions and degradation in aqueous solutions,like surface waters or ***,we aim to elucidate the capping agent influence on nanoparticle reactivity probing two commonly employed capping agents citrate and polyvinylpyrrolidone(PVP).Their influence on silver nanoparticle(AgNP)transformation is studied,which is particularly important due to its application as an antimicrobial *** induce oxidation and reduction processes of AgNPs in halide solutions and we monitor the associated transformations of particles and capping agents by spectro-electrochemical surface-enhanced Raman spectroscopy(SERS).Raman bands of the capping agents are used here to track chemical changes of the nanoparticles under operando *** sparingly soluble and non-plasmon active silver salts(AgBr and AgCl)are formed under potential *** addition,we spectroscopically observe plasmon-mediated structural changes of citrate to cis-or trans-aconitate,while PVP is *** different behavior of the capping agents implies a change in the physical properties on the surface of AgNPs,in particular with respect to the surface ***,we showcase that reactions of the capping agents induced by different external stimuli,such as applied bias or laser irradiation,can be *** results demonstrate how SERS of capping agents can be exploited to operando track nanoparticle conversions in liquid *** approach is envisaged to provide a more comprehensive understanding of nanoparticle fates in complex liquid environments and varied redox conditions.

关键词： capping agent electrochemical surface-enhanced Raman spectroscopy silver nanoparticle nanoparticle reaction

Experimental investigation of radiative heat propagation in a simplified generic packed bed

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Particuology 2024年第5期88卷 149-160页

作者： Matthias Tyslik Lukas Pörtner Siegmar Wirtz Martin Schiemann Institute of Energy Plant Technology Ruhr-University Bochum44780 BochumGermany

A novel test rig for the investigation of radiative heat transfer in packed beds has been developed and is introduced with representative experimental *** individual components and the calibration are *** generic packed bed is realized in a simplified way by an arrangement of parallel rods,which represent particles in *** this arrangement,electrically heated rods provide the radiation propagating through the rod array to heat the passive counterparts.A sophisticated temperature-control scheme with a large number of thermocouples and infrared-imaging provides in-depth information about heat transfer in the *** radiation intensities are determined with a Fourier-transform infrared spectroscopy,which has been modified and validated for this specific *** order to compare the influence of different surface properties of particles on the heat propagation and surface reflections,rod samples made of stainless steel and magnesium oxide are *** influence of material properties becomes clearly visible by comparing the high radiation intensities resulting from a stainless steel rod array to the same geometry built from magnesium oxide *** addition,the influence of the surface properties is particularly evident in the infrared images since the reflections are significantly higher for the stainless steel samples than for the magnesium oxide *** experimental results in the current work demonstrate the ability of the test rig to provide data with a well-defined accuracy as a validation base for numerical radiation simulations in packed beds.

关键词： Thermal radiation Spectral reflections Fourier-transform infrared spectroscopy