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Coefficient of restitution for particles impacting on wet surfaces： An improved experimental approach

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Particuology 2016年第2期14卷 1-9页

作者： B. Cunger V. Salikov S. Heinrich S. Antonyuk V.S. Sutkar N.G. Deen J.A.M. Kuipers institute of solids process engineering and particle technology Hamburg University of Technology Denickestrasse 15 21073 Hamburg Germany particle process engineering Department of Mechanical and Process Engineering University ofKaiserslautern Cottlieb-Daimler-Strasse 67663 Kaiserslautern Germany Multiphase Reactors Group Department of Chemical Engineering and Chemistry Eindhoven University of Technology P.O. Box 513 5600 MB EindhovenThe Netherlands

The coefficient of restitution is widely used to characterize the energy dissipation rate in numerical simulations involving particle collisions. The challenge in measuring the coefficient of restitution is the strong scatter seen in experimental data that results from varying particle properties, i.e. shape and surface roughness, and from imperfections in the experimental technique. To minimize this scattering, a novel experimental setup was developed based on two synchronized high-speed cameras capturing the collision behaviour of a particle in three dimensions. To measure the wet restitution coefficient, which describes particle impact in the presence of a liquid layer in the contact region, additional accuracy can be achieved by measuring the liquid layer thickness by a high-precision optical confocal sensor. The coefficient of restitution was measured for glass particles with two different diameters, at different relative velocities and liquid layer thicknesses, with a focus on small collision velocities and thin liquid layers, using both the improved （three dimensional） and the conventional （two dimensional） approaches to quantify the improvement of the new method＇s accuracy.

关键词： particle impact Coefficient of restitution Liquid layer Improved experimental setup

Simulation-supported measurements in large circulating fluidized bed combustors

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Particuology 2009年第4期7卷 324-331页

作者： Joachim Werther Ernst-Ulrich Hartge Lars Ratschow Reiner Wischnewski institute of solids process engineering and particle technology Hamburg University of TechnologyD 21071 HamburgGermany Now with Pyry Energy GmbH HamburgGermany Now with Hydro Aluminium AS OsloNorway

The concept of simulation-supported measurement is suggested for the elucidation of processes occurring in the combustion chambers of large-scale circulating fluidized bed combustors where the desired information cannot be obtained by direct measurements. The concept is illustrated with the example of secondary air injection where the way the air is released, the penetration depth and the evenness of air distribution over the cross-sectional area of the combustion chamber are of interest. The measured information consists of lateral profiles of oxygen concentrations measured with gas sampling probes at two ports which were located 5 and 9 m, respectively, above the level of secondary air injection. The simulation is carried out on the basis of a 3D semi-empirical fluid-mechanical model of the circulating fluidized bed which is combined with models of gas and solids mixing, fuel distribution, devolatilization and combustion of char and volatiles. The combination of the simulation with the measurements yields a clear picture of the mechanism of secondary air injection, its penetration into the combustion chamber and its effect on the local combustion processes. The results confirm the usefulness of the concept of simulation-supported measurement for this application.

关键词： Fluidized bed Combustion Local measurements 3D modeling

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聚乙烯亚胺的抑膨促渗机理

Journal of Central South University 2024年第2期31卷 317-329页

作者：阳慧芳沙傲阳何正艳吴明瞿军吴晨捷徐志高池汝安 Key Laboratory of Resources Conversion and Pollution Control of the State Ethnic Affairs Commission College of Resources and Environmental ScienceSouth-Central Minzu UniversityWuhan 430074China Key Laboratory for Green Chemical process of Ministry of Education School of Resources&Safety EngineeringWuhan Institute of TechnologyWuhan 430073China

为解决风化壳淋积型稀土矿(WCE-DREO)原地浸出过程中出现的滑坡和浸出速度慢等问题,研究了聚乙烯亚胺(PEI)对蒙脱石(MMT)和风化壳淋积型稀土矿的抑膨性能及作用机理。随着聚乙烯亚胺浓度的增加,聚乙烯亚胺对蒙脱石和风化壳淋积型稀土矿... 详细信息

为解决风化壳淋积型稀土矿(WCE-DREO)原地浸出过程中出现的滑坡和浸出速度慢等问题,研究了聚乙烯亚胺(PEI)对蒙脱石(MMT)和风化壳淋积型稀土矿的抑膨性能及作用机理。随着聚乙烯亚胺浓度的增加,聚乙烯亚胺对蒙脱石和风化壳淋积型稀土矿的抑膨效果逐渐增强。由0.4%聚乙烯亚胺和2%硫酸铵组成的复合浸出剂与单独使用2%硫酸铵相比,稀土的浸出效率从93.94%提高到95.24%,浸出时间缩短了约33%。聚乙烯亚胺可通过水解产生大量-NH_(3)^(+),从而中和黏土矿物夹层和表面的负电荷,减少静电排斥,削弱黏土矿物的水化和膨胀。PEI可在黏土颗粒上形成一层聚合物膜,改变颗粒表面的亲水性,减少水的侵入。小颗粒在长链PEI的包裹和桥联作用下发生团聚,从而增大了颗粒尺寸,有利于浸出剂的渗入。PEI骨架还能嵌入黏土夹层并挤出夹层水,从而抑制黏土矿物的膨胀。

关键词：聚乙烯亚胺蒙脱石风化壳淋积型稀土矿抑膨促渗

particle formulation of hydroalcoholic rosemary (Rosmarinus officinalis L.) extracts using a spouted bed

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Particuology 2020年第4期18卷 26-34页

作者： D.Peshev E.Eichner M.Goslinska S.Pietsch Y.Trambabova T.Terzieva N.Georgieva S.Heinrich Department of Chemical engineering University of Chemical Technology and Metallurgy1576 SofiaBulgaria institute of solids process engineering and particle technology Hamburg University of Technology21073 HamburgGermany Department of Biotechnology University of Chemical Technology and Metallurgy1576 SofiaBulgaria

In this study,spouted bed technology was applied to the protection and functionalization of polyphenolic rosemary ***,solid-liquid extraction was performed at 25℃with *** ethanol-water ratio was chosen to obtain high phenolic acid and diterpene concentrations in the *** selected solvent composition gave liquid extracts that could be directly added to a coating mixture for feeding into a spouted bed ***,no preliminary solvent exchange or evaporation of the extraction solvent to dryness was *** grade Paselli MD 6 maltodextrin and HiCap 100 modified starch were used as inert core and shell materials in the spouted bed encapsulation process under mild operating *** antioxidant activity of the fresh extract was retained during processing,which indicated that the active constituents were preserved and quantitatively transferred into the encapsulated formulations,which were readily soluble in *** obtained powders were composed of nearly spherical *** compositions,water solubilities,and particle morphologies make them a strong candidate for food and beverage applications as natural antioxidants,preservatives,or functional ingredients.

关键词： particle Polyphenolic rosemary extract Encapsulation Spouted bed Bioactive Antioxidant

A modified back analysis method for deep excavation with multi-objective optimization procedure

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Journal of Rock Mechanics and Geotechnical engineering 2024年第4期16卷 1373-1387页

作者： Chenyang Zhao Le Chen Pengpeng Ni Wenjun Xia Bin Wang State Key Laboratory of Geomechanics and Geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Guangdong Research Center for Underground Space Exploitation technology School of Civil EngineeringSun Yat-sen UniversityGuangzhou510275China Southern Marine Science and engineering Guangdong Laboratory (Zhuhai) Zhuhai519000China Jiangsu Provincial Transportation engineering Construction Bureau Nanjing210004China

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction *** paper proposes a modified back analysis method with multi-objective optimization procedure,which enables a real-time prediction of horizontal displacement of retaining pile during *** opposed to the traditional stage-by-stage back analysis,time series monitoring data till the current excavation stage are utilized to form a multi-objective ***,the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter *** optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction *** achieve efficient parameter optimization and real-time prediction of system behavior,the back propagation neural network (BPNN) is established to substitute the finite element model,which is further implemented together with MOPSO for automatic *** proposed approach is applied in the Taihu tunnel excavation project,where the effectiveness of the method is demonstrated via the comparisons with the site monitoring *** method is reliable with a prediction accuracy of more than 90%.Moreover,different optimization algorithms,including non-dominated sorting genetic algorithm (NSGA-II),Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO,are compared,and their influences on the prediction accuracy at different excavation stages are *** results show that MOPSO has the best performance for high dimensional optimization task.

关键词： Multi-objective optimization Back analysis Surrogate model Multi-objective particle swarm optimization(MOPSO) Deep excavation

Influence of liquid layers on energy absorption during particle impact

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Particuology 2009年第4期7卷 245-259页

作者： Sergiy Antonyuk Stefan Heinrich Niels Deen Hans Kuipers Hamburg University of technology Institute of Solids Process Engineering and Particle Technology Denickestr. 15 21071 Hamburg Germany University of Twente Fundamentals of Chemical Reaction Engineering Faculty of Science and Technology PO Box 217 Enschede 7500 AE The Netherlands

The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic-plastic γ- Al2O3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity （1-300 mPa s）, In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained, A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.

关键词： Granule impact Restitution coefficient Energy dissipation Liquid layer Liquid bridge

Simulation of spray coating in a spouted bed using recurrence CFD

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Particuology 2019年第1期17卷 92-103页

作者： Paul Kieckhefena Thomas Lichtenegger Swantje Pietsch Stefan Pirker Stefan Heinrich institute of solids process engineering and particle technology Hamburg University of Technology. HamburgGermany Department for Particulate Flow Modelling. Johannes Kepler University LinzAustria Linz institute of technology (LIT) Johannes Kepler UniversityLinzAustria

Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-scale apparatuses with many particles and time scales ranging from minutes to hours remains a challenge. The recently developed recurrence CFD (rCFD) method seeks to overcome these issues in pseudo-periodic processes by extrapolating globally recurring patterns in a physically meaningful way and describing the transport and interaction of passive scalars using Lagrangian tracers. Spouted beds represent an interesting target because of the associated variety of flow regimes. They can be effectively described by CFD–DEM on the time scale of tens of seconds, whereas industrially relevant processes typically take hours. In this contribution, we established the validity of applying the Lagrangian rCFD method to spouted beds by demonstrating the accurate reproduction of the particle residence time distribution in a fictitious spray zone. The deposition of spray droplets onto tracer particles was simulated for 1 h, and the particle surface coverage distribution was estimated using a statistical approach for both an unstabilized prismatic spouted bed and one stabilized by draft plates.

关键词： CFD–DEM Recurrence CFD Spray coating Time-scale decoupling Spouted bed Draft plate

Bauxite washing for the removal of clay

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International Journal of Minerals,Metallurgy and Materials 2014年第11期21卷 1045-1051页

作者： Ishaq Ahmad Ernst-Ulrich Hartge Joachim Werther Reiner Wischnewski Department of Mining engineering University of Engineering and TechnologyPeshawar-25120 Pakistan institute of solids process engineering and particle technology Hamburg University of Technology (TUHH)Denickestrasse 1521073 Hamburg Germany Norsk Hydro Aluminum ASA Skφyen Oslo Norway

Clay impurities associated with bauxite negatively affect the Bayer process for alumina production. These impurities should be removed as far as possible by a beneficiation technique before the ore is used as feed for the Bayer process. In this current investigation, bauxite washing was conducted in the laboratory. Bauxite washing is a physical process that causes the disintegration and deagglomeration of the clay matrix, and bauxite is liberated from the clay（mainly rich in silica）. Subsequently, separation occurs with the assistance of wet screening at a predetermined cut size. Three techniques were investigated in the laboratory： drum washing, water-jet washing, and ultrasonic washing. Various operating parameters were investigated for drum washing and water-jet washing, including materials retention time, drum rotation speed, solid concentration, water-jet spray duration, pressure, and height. We concluded that the retention time of bauxite inside the drum at a solid concentration of 55wt% and a drum rotation speed of 31 r/min is the dominant parameter for the removal of clay from the bauxite surface.

关键词： beneficiation bauxite washing clay Bayer process

Machine Learning for heat radiation modeling of bi-and polydisperse particle systems including walls

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Particuology 2023年第3期74卷 119-140页

作者： Josef Tausendschön Gero Stöckl Stefan Radl institute of process and particle engineering Graz University of TechnologyInffeldgasse 13/III8010GrazAustria

We investigated the ability of four popular Machine Learning methods i.e.,Deep Neural Networks(DNNs),Random Forest-based regressors(RFRs),Extreme Gradient Boosting-based regressors(XGBs),and stacked ensembles of DNNs,to model the radiative heat transfer based on view factors in bi-and polydisperse particle beds including *** training and analyzing the predictive capability of each method,an adjustment of markers used in monodisperse systems,as well as an evaluation of new markers was *** the basis of our dataset that considers a wide range of particle radii ratios,system sizes,particle volume fractions,as well as different particle-species volume fractions,we found that(i)the addition of particle size information allows the transition from monodisperse to bi-and polydisperse beds,and(ii)the addition of particle volume fraction information as the fourth marker leads to very accurate *** terms of the overall performance,DNNs and RFRs should be preferred compared to the other two *** particle-particle view factors,DNN and RFR are on par,while for particle-wall the RFR is *** demonstrate that DNNs and RFRs can be built to meet or even exceed the prediction quality standards achieved in a monodisperse system.

关键词： Discrete element method(DEM) Heat radiation modeling Machine learning View factors Wall radiation Polydisperse particles