Chemical Engineering Science: X最新文献

{"title":"Numerical modeling of collision of adhesive units: Stability and mechanical properties during handling","authors":"Sohan Sarangi ,&nbsp;Kyrre Thalberg ,&nbsp;Göran Frenning","doi":"10.1016/j.cesx.2019.100051","DOIUrl":"10.1016/j.cesx.2019.100051","url":null,"abstract":"<div><p>Binary interaction between adhesive units formed from monodisperse spherical fines and carrier particles was studied with the discrete element method (DEM) in order to better understand phenomena such as lumping, bridging and flowability of adhesive units and mixtures. Three different surface coverage ratios (SCRs) representing different number of fines on the carrier, five different surface energies of interaction between fines and carrier, fifteen different relative velocities ranging from 0.04 m/s to 1.7 m/s were studied, with three replicates for each scenario. A total of over 700 independent simulations were conducted and stability ratios (retention, transfer and loss) and mechanical properties (coefficient of restitution) were determined. The critical velocity for the units, below which they tended to aggregate, was extracted. The units with high SCR and high surface energy were most stable and most cohesive. With increasing SCR, the fines tended to act as a damping pad, thus increasing the critical velocity. The adhesive units were found to be dynamic in nature and to undergo constant exchanges of particles. A detailed map of this behaviour was determined. The obtained findings constitute a first step towards the creation of multiscale DEM models for the mechanics of adhesive mixtures and provide insights into flowability and integrity of the mixtures.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"6 ","pages":"Article 100051"},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"105300131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scaling method of CFD-DEM simulations for gas-solid flows in risers","authors":"L. Mu ,&nbsp;K.A. Buist ,&nbsp;J.A.M. Kuipers ,&nbsp;N.G. Deen","doi":"10.1016/j.cesx.2019.100054","DOIUrl":"10.1016/j.cesx.2019.100054","url":null,"abstract":"<div><p>In this paper a scaling method is proposed for scaling down the prohibitively large number of particles in CFD-DEM simulations for modeling large systems such as circulating fluidized beds. Both the gas and the particle properties are scaled in this method, and a detailed comparison among alternative mapping strategies is performed by scaling both the computational grid size and the riser depth. A series of CFD-DEM simulations has been performed for a pseudo-2D CFB riser to enable a detailed comparison with experimental data. By applying the scaling method, the hydrodynamic flow behavior could be well predicted and cluster characteristics, such as cluster velocity and cluster holdups agreed well with the experimental data. For a full validation of the scaling method, four mapping conditions with different ratios of the grid size and particle volume and of modified ratio of riser depth to particle size were analyzed. The results show that in addition to hydrodynamic scaling of the particle and fluid properties, scaling of the dimensions for the interphase mapping is also necessary.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"6 ","pages":"Article 100054"},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100054","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41493435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel approach to MP-PIC: Continuum particle model for dense particle flows in fluidized beds","authors":"Vikrant Verma,&nbsp;Johan T. Padding","doi":"10.1016/j.cesx.2019.100053","DOIUrl":"https://doi.org/10.1016/j.cesx.2019.100053","url":null,"abstract":"<div><p>A novel approach to Multiphase-Particle-in-Cell (MP-PIC), called Continuum Particle Model (CPM), is developed for dense gas-particle flows. CPM has high computational speed, comparable to that of MP-PIC, but a robustness and accuracy closer to that of a Discrete Element Model (DEM). The gas phase is treated as a continuum phase and particles are tracked discretely, but particle collisions are modelled by considering the divergence of the continuum particle stress tensor. Details on efficient solution to the model are presented. For comparison, a parametric study is performed for quasi-2D fluidized beds. Comparison of CFD-CPM is made with MP-PIC and CFD-DEM. The particle stress models by Harris and Crighton, and by Srivastava and Sundaresan are tested in our CFD-CPM. Results from CFD-CPM based on the Srivastava and Sundaresan particle stress model show good agreement with CFD-DEM results. We validate our model by comparison with experimental benchmark results from Gopalan et. al. (2016).</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"6 ","pages":"Article 100053"},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100053","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91669462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Production of ethanol fuel via syngas fermentation: Optimization of economic performance and energy efficiency","authors":"Elisa M. de Medeiros ,&nbsp;Henk Noorman ,&nbsp;Rubens Maciel Filho ,&nbsp;John A. Posada","doi":"10.1016/j.cesx.2020.100056","DOIUrl":"10.1016/j.cesx.2020.100056","url":null,"abstract":"<div><p>In this work, a model was developed to predict the performance of a bubble column reactor for syngas fermentation and the subsequent recovery of anhydrous ethanol. The model was embedded in an optimization framework which employs surrogate models (artificial neural networks) and multi-objective genetic algorithm to optimize different process conditions and design variables with objectives related to investment, minimum selling price, energy efficiency and bioreactor productivity. The results indicate the optimal trade-offs between these objectives while providing a range of solutions such that, if desired, a single solution can be picked, depending on the priority conferred to different process targets. The Pareto-optimal values of the decision variables were discussed for different case studies with and without the recovery unit. It was shown that enhancing the gas-liquid mass transfer coefficient is a key strategy toward sustainability improvement.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"5 ","pages":"Article 100056"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2020.100056","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"94893669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Direct numerical simulation of mass transfer and mixing in complex two-phase systems using a coupled volume of fluid and immersed boundary method","authors":"L. Yang ,&nbsp;E.A.J.F. Peters ,&nbsp;L. Fries ,&nbsp;Y.M. Harshe ,&nbsp;J.A.M. Kuipers ,&nbsp;M.W. Baltussen","doi":"10.1016/j.cesx.2020.100059","DOIUrl":"10.1016/j.cesx.2020.100059","url":null,"abstract":"<div><p>In this paper, a hybrid computational technique for the Direct Numerical Simulation of hydrodynamics and (convective) mixing in complex two-phase systems is presented. The hybrid Immersed Boundary and Volume of Fluid method is based upon a single-fluid approach in combination with Henry’s law for the concentration jump. The convective species fluxes are evaluated using PLIC-based geometrical advection, which is consistent with the advection of the local fluid volume fractions. Complex geometries can be accounted for and are treated with the Immersed Boundary method. Following the verification for single phase and two-phase systems, the model was used to investigate the influence of the container geometry on the mixing of a tracer due to tilting of the container. For both cylindrical and rectangular containers, an increasing tilting angle enhances the convective motion and consequently the mixing efficiency. The cylindrical geometry was found to possess a better mixing efficiency than the rectangular geometry.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"5 ","pages":"Article 100059"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2020.100059","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"97238055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamics of narrow-tube fixed bed reactors filled with Raschig rings","authors":"E.M. Moghaddam,&nbsp;E.A. Foumeny,&nbsp;A.I. Stankiewicz,&nbsp;J.T. Padding","doi":"10.1016/j.cesx.2020.100057","DOIUrl":"10.1016/j.cesx.2020.100057","url":null,"abstract":"<div><p>The local flow structure and pressure drop in random packings of Raschig rings are analyzed using sequential Rigid Body Dynamics (RBD) method and Computational Fluid Dynamics (CFD) simulation. Tube-to-pellet diameter ratios, N, between 3 and 6 are investigated for laminar, transitional and turbulent flow regimes (5 ≤ Re_p ≤ 3,000). The computed pressure drops are in good agreement with the empirical correlation of <span>Nemec and Levec (2005)</span>, while the Ergun equation exhibited high deviations of more than 60%, even when it is modified to explicitly account for non-sphericity of pellets. This deviation is ascribed to additional sources for eddy formation offered by Rashig rings, compared to spheres and cylinders, which cannot be counterbalanced by the usage of a higher specific surface area. The 3D results of flow structure demonstrate a large influence of packing topology on the velocity distribution: rings oriented parallel to the flow accelerate the local velocity through their axial holes, while rings oriented perpendicular to the flow provide additional space for vortex formation. The flow fields are substantially different from that found in packings of spheres and cylinders, both in terms of volume of backflow regions and velocity hotspots. This implies a higher order of local flow inhomogeneity in azimuthal and axial directions compared to spherical and cylindrical packings. Furthermore, it is found that azimuthal averaging of the 3D velocity field over the bed volume, which has been used to improve classical plug-flow pseudo-homogenous models to account for the role of tortuous velocity fields, cannot reflect the appearance of vortex regions and thereby leads to underestimation of the local axial velocity values by over 500% of the inlet velocity.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"5 ","pages":"Article 100057"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2020.100057","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"98713082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel approach to MP-PIC: Continuum particle model for dense particle flows in fluidized beds","authors":"V. Verma, Jt Johan Padding","doi":"10.1016/j.ces.2019.115408","DOIUrl":"https://doi.org/10.1016/j.ces.2019.115408","url":null,"abstract":"","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ces.2019.115408","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46997690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Representative resolution analysis for X-ray CT: A Solid oxide fuel cell case study","authors":"T.M.M. Heenan,&nbsp;C. Tan,&nbsp;R. Jervis,&nbsp;X. Lu,&nbsp;D.J.L. Brett,&nbsp;P.R. Shearing","doi":"10.1016/j.cesx.2019.100043","DOIUrl":"10.1016/j.cesx.2019.100043","url":null,"abstract":"<div><p>A requirement to reduce dependency on high-carbon fuels has resulted in the rapid advancement of electrochemical devices. Considerable research has been applied to improve device performance and lifetime in order to compete with incumbent technologies. Of the portfolio of electrochemical conversion technologies, solid oxide fuel cells (SOFC) offer high fuel versatility and fast reaction kinetics without the requirement of expensive catalysts. However, degradation due to high temperature operation limits cell performance and lifetime, impeding widespread commercialisation. Due to the inherent link between microstructure and electrochemical performance, many three-dimensional (3D) characterisation techniques have been employed in the pursuit of the mitigation of degradation through rational electrode design. Instruments such as lab-based X-ray microscopes are now capable of imaging across multiple length scales, where the highest resolutions (i.e. smallest voxel lengths) are comparable to specialist synchrotron facilities. A widely used metric to describe electrode microstructure is the triple-phase boundary (TPB); the location where reactions occur within the SOFC electrode. The total TPB length is a vital metric in assessing the quality of an SOFC material, and thus many efforts have been made to determine accurate values. In order to map the TPB locations in 3D, the three constituent phases: metal, ceramic, and pore, need to be distinguished and segmented, requiring high resolutions. Although TPB values have been reported and compared extensively in the literature, the influence of the microscopic roughness is yet to be investigated. Using X-ray computed tomography (CT), here, for the first time, the effect of resolution is inspected for several key microstructural parameters. Moreover, the study is extended through the use of multiple instruments for a variety of sample structures. This work introduces the importance of the fractal properties of structures characterised using X-ray CT, which we expect to be influential across a broad range of materials. The choice of resolution when characterising a structure is important and determined by a variety of factors: instrument, feature size, image quality, etc., and should ultimately be chosen in order to efficaciously expose the features under investigation, in addition to this, metrics extracted should only be directly compared at the same resolution and, if possible, should be inspected for fractal properties via a representative resolution analysis. These conclusions are not restricted to SOFCs but should be applied to all fields of microstructural analysis.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"4 ","pages":"Article 100043"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46805175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of oil-water flow in concentric and fully eccentric annuli pipes","authors":"Roberto Ibarra,&nbsp;Jan Nossen","doi":"10.1016/j.cesx.2019.100042","DOIUrl":"10.1016/j.cesx.2019.100042","url":null,"abstract":"<div><p>Experimental investigations are performed on co-current flow of oil (Exxsol D60) and water in concentric and fully eccentric annuli with the inner pipe located at bottom of the outer pipe. The annulus outer and inner pipe have an inside diameter of 99 mm and outside diameter of 50 mm, respectively. This yields a diameter ratio of <em>K</em> = 0.505. The flow conditions studied span mixture velocities and input water cuts in the range 0.50–1.75 m/s and 10–90%, respectively, at pipe inclinations of 0° and 4° upward. Flow regimes have been identified and maps constructed using instantaneous images of the flow from high-speed cameras (shadowgraph) and X-ray chordal holdup measurements along the vertical projection. Flow regimes in the concentric annulus exhibit a higher level of mixing than that observed in the fully eccentric configuration. The transition to dispersed flow occurs at lower mixture velocities in the concentric annulus. Measurements from broad-beam gamma densitometers reveal that the mean water holdup is higher in the fully eccentric annulus for a given mixture velocity and input water cut. The higher water accumulation in this annulus configuration can be attributed to a low velocity region in the narrow gap at the annulus pipe bottom. The frictional pressure gradient in the concentric annulus is higher as compared with the fully eccentric configuration. Peaks in the pressure gradient profile, for a constant mixture velocity, are observed at high water cuts (<em>i.e.</em> WC ≥ 50%) at the transition between dual continuous and dispersed flows. Pressure gradient data are compared with predictions using the homogeneous and two-fluid model. In general, the homogeneous model using a modified Brinkman (Brinkman, 1952)/Roscoe (Roscoe, 1952) dispersion viscosity model shows the best agreement with data in both concentric and fully eccentric annuli.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"4 ","pages":"Article 100042"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100042","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45742857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nuclei size distribution modelling in wet granulation","authors":"Stefan Bellinghausen ,&nbsp;Emmanuela Gavi ,&nbsp;Laura Jerke ,&nbsp;Pranay K. Ghosh ,&nbsp;Agba D. Salman ,&nbsp;James D. Litster","doi":"10.1016/j.cesx.2019.100038","DOIUrl":"10.1016/j.cesx.2019.100038","url":null,"abstract":"<div><p>Nucleation is an important wet granulation rate process that sometimes has a profound effect on granule attributes and which needs to be captured in process modelling studies. However, existing models fail to predict nuclei size distribution of a range of spray conditions typically used in industry. In this paper, the dimensionless nucleation number <span><math><mrow><msub><mrow><mi>Ψ</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span> is used to develop two new nuclei size distribution models, one empirical and one semi-mechanistic. The empirical model assumes a log-normal distribution (LND), and the semi-mechanistic model is based on a approach proposed by Hapgood et al. (2009), which applies the Poisson distribution (PD) function. Modelling parameters are estimated using Monte Carlo simulations (MCS) data. From the models, the nuclei size distribution can be easily determined using analytical equations, which simplifies the inclusion in a population balance modelling (PBM) framework. The results of both models are assessed using MCS data as well as experimental data from literature. The empirical LND model is able to capture the MCS results accurately, and the predictions agree reasonably well with the experimental results over a wide range of dimensionless nucleation number (<span><math><mrow><mn>0</mn><mo>&lt;</mo><msub><mrow><mi>Ψ</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>&lt;</mo><mn>3</mn></mrow></math></span>). The predictions of the semi-mechanistic modified Poisson distribution (MPD) model do not agree qualitatively with the MCS or experimental results. A sensitivity analysis shows that the MCS modelling assumptions need to capture the spatial drop distribution in the spray accurately, while the drop size distribution can be assumed to be uniform. Overall, we recommend that the LND model with the parameter values estimated be used in PBM frameworks to determine nuclei size distribution for a wide range of experimental conditions in mixers and fluidised granulators.</p></div>","PeriodicalId":37148,"journal":{"name":"Chemical Engineering Science: X","volume":"4 ","pages":"Article 100038"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cesx.2019.100038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43807344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}