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A novel dual-material probe for in situ measurement of particle charge densities in gas-solid fluidized beds

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Particuology 2015年第4期13卷 20-31页

作者： Chuan He Xiaotao T.Bi john r.grace Fluidization research Centre Department of Chemical and Biological EngineeringThe University of British Columbia

Particle charge density is vitally important for monitoring electrostatic charges and understanding particle charging behavior in fluidized beds. In this paper, a dual-material probe was tested in a gas-solid fluidized bed for measuring the charge density of fluidized particles. The experiments were conducted in a two-dimensional fluidized bed with both single bubble injection and freely bubbling, at various particle charge densities and superficial gas velocities. Uniformly sized glass beads were used to eliminate complicating factors at this early stage of probe development. Peak currents, extracted from dynamic signals, were decoupled to determine charge densities of bed particles, which were found to be qualitatively and quantitatively consistent with charge densities directly measured by Faraday cup from the freely bubbling fluidized bed. The current signals were also decoupled to estimate bubble rise velocities, which were found to be in reasonable agreement with those obtained directly by analyzing video images.

关键词： Electrostatics Particle charge density Dual-material collision probe Signal decoupling Fluidized bed Bubble rise velocity

Dynamic Force reduction and Heat Transfer Improvement for Horizontal Tubes in Large-Particle Gas-Fluidized Beds

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Journal of Thermal Science 2008年第1期17卷 77-83页

作者： Yusumi Nagahashi john r.grace Kok-Seng Lim Yutaka Asako Dept.Mech.Eng. Kochi National College of Technol.KochiJAPAN Professor Dept.Chem.Biological Eng. The University of British ColumbiaVancouverCANADA CSIrO Minerals VictoriaAUSTRALIA Dept.Mech.Eng. Tokyo Metropolitan UniversityTokyoJAPAN

The effects of tube bank configuration on forces and heat transfer were investigated for both two-dimensional and three-dimensional gas fluidized beds. Effective dynamic forces and heat transfer coefficients were measured for several tube bank configurations, and it was found that the average forces are smaller than for a single tube. The heat transfer coefficient can be increased by providing sufficient space for particles to descend around both sides of the tube bank. The results provide useful guidelines for optimizing the configuration of tube banks to achieve high heat transfer coefficients while reducing tube erosion due to dynamic forces.

关键词： fluidized beds forces heat transfer tube arrangement sofid circulation

Electrostatic beneficiation of fly ash in a free-falling system

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Particuology 2012年第2期10卷 154-160页

作者： Lifeng Zhang Jiangtian Hou Xiaotao T.Bi john r.grace Travis Janke Claudio Arato Fluidization research Centre Department of Chemical and Biological EngineeringUniversity of British ColumbiaVancouverCanada Sonoro Energy Ltd. VancouverCanada

A systematic study of fly ash electrostatic beneficiation in a free-falling separation system was carried out to provide fundamental understanding of the separation efficiency for the design of a suitable process for industrial applications. The parameters investigated included feeding position, electric field strength, particle size and moisture content. Particles larger than 105 μm presented the best separation efficiency among four different size fractions, whereas particles smaller than 44μm showed minimal separation. However, sonication treatments helped separation by liberating more carbon from ash particles, although particle sizes were reduced as well. Experiments also showed that exposure to moisture significantly altered charging behavior of fly ash and its subsequent separation due to more free mobile ion-induced charge exchanges. The optimal feeding position was found to be slightly on the side of the negative electrode, leading to a 30% reduction in loss-on-ignition （LOI） and a 45% recovery in a single pass. A simplified mechanical model based on trajectory analysis for charged particles in an electrical field was in reasonable agreement with experimental results.

关键词： Fly ashElectrostatic separationLoss-on-ignitionBi-polar chargingVibratory feeder

the future of PArTICUOLOGY

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China Particuology 2003年第1期1卷 2-6页

作者： Arthur M. Squires Kui Wang john F.Davidson Qingru Chen john r.grace Kefa Cen Terry A.ring Guilin Yang George E. Klinzing Member U. S. National Academy of Engineering Fellow American Academy of Arts & Sciences University Distinguished Professor (emeritus) Virginia Polytechnic Institute & State University Member Chinese Academy of Sciences Department of Chemical Biology School of Pharmaceutical Sciences Peking University Shell Professor of Chemical Engineering Cambridage University Member Chinese Academy of Engineering China University of Mining and Technology Professor of Chemical Engineering University of British Columbia Member Chinese Academy of Engineering College of Mechanical & Energy Engineering Zhejiang University Professor and Chairman of Chem.& Fuels Eng.Professor of Maer.Sci.& Eng.University of Utah Professor CAS Institute of Coal Chemistry W.K. Whiteford Professor & Vice Provost for res.University of Pittsburgh

I congratulate the Chinese Society of Particuology(and especially my friend Professor Mooson Kwauk,the Society’s distinguished President Emeritus) forits initiative in launching a new journal devoted to studiesof par... 详细信息

关键词： of in or is as PA In the future of PArTICUOLOGY that

Effects of the plenum chamber volume and distributor geometry on fluidized bed hydrodynamics

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Particuology 2010年第1期8卷 2-12页

作者： Kiarash Vakhshouri john r. grace Department of Chemical and Biological Engineering University of British Columbia

Most hydrodynamic fluidized bed models, including CFD codes, neglect any effects of the plenum chamber volume. Experiments were performed in a 0.13 m ID fluidization column to determine plenum chamber volume effects on fluidized bed hydrodynamics for FCC and glass particles. Two low-pressure-drop distributors were used, one with a single orifice, and the other with 33 orifices and the same total open area as the single orifice. The results show two peaks in the frequency spectra for the single-orifice distributor, one representing bubble eruption at the bed surface and the other of higher frequency corresponding to the bubbling frequency at the distributor. The latter decreased slightly with increasing plenum volume and with increasing bed depth. For the multi-orifice distributor, broad frequency spectra from pressure measurements became narrower and moved towards higher frequency with decreasing plenum volume.

关键词： Fluidization Bubble Distributor Plenum chamber Hydrodynamics Pressure drop

Complementarity of CFD,experimentation and reactor models for solving challenging fluidization problems

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Particuology 2010年第6期8卷 498-500页

作者： john r. grace Tingwen Li Department of Chemical and Biological Engineering University of British Columbia Vancouver V6T 1Z3 Canada National Energy Technology Laboratory 3610 Collins Ferry Rd Morgantown WV26507 USA

Experimentalists, numerical modellers and reactor modellers need to work together, not only just for validation of numerical codes, but also to shed fundamental light on each other＇s problems and underlying assumptions. Several examples are given, Experimental gas axial dispersion data provide a means of choosing the most appropriate boundary condition （no slip, partial slip or full slip） for particles at the wall of fluidized beds. CFD simulations help to identify how close ＂two-dimensional＂ experimental columns are to being truly two-dimensional and to representing three-dimensional columns. CFD also can be used to provide a more rational means of establishing assumptions needed in the modelling of two-phase fluidized bed reactors, for example how to deal with cases where there is a change in molar flow （and hence volumetric flow） as a result of chemical reactions.

关键词： Fluidization Mixing Computational Fluid dynamics Wall slip reactor modelling Volume change

Hydrodynamics and solids mixing in fluidized beds with inclined-hole distributors

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Particuology 2019年第2期17卷 19-28页

作者： Alhussain Bakhurji Xiaotao Bi john r. grace Fluidization research Centre Department of Chemical and Biological Engineering University of British Columbia Vancouver V6TJZ3 Canada

Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diameter 154p.m) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed expansion, and minimum fluidization velocity. Solids residence time distributions were determined using phosphoresce nt tracer particles (mea n diameter 76 pm), activated by ultraviolet light. The bed pressure drop was higher with the inclined-hole distributors and increased with static bed height. In a shallow bed, the inclined-hole distributors gave less expansion;however, in deep beds, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity varied with static bed height for the inclined-hole distributors and was higher for steeper angles. The turnover time estimated using bubbling-bed equations matched the experimental results well for vertical mixing. Probes and ports at the walls of the fluidization column reduced the dense-phase downward velocity by up to 40%. The tangential particle velocity was highest for the 30 -hole distributor and decreased with increasing orifice angle. Tangential mixing was described by a dispersion model;the dispersion coefficient for the inclined-hole distributors was approximately twice that for the 90 -hole distributor in a shallow bed.

关键词： Swirling fluidized bed Fluidization Solids mixing Inclined-hole distributor

Biomass torrefaction in a slot-rectangular spouted bed reactor

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Particuology 2019年第1期17卷 154-162页

作者： Ziliang Wang C. Jim Lim john r. grace Department of Chemical and Biological Engineering. University of British Columbia Vancouver. Canada

Sawdust was subjected to torrefaction in a "semi-batch" slot-rectangular spouted bed (SrSB) reactor at temperatures from 240 to 330℃ and biomass feed rates from 220 to 710g/*** spouting of the sawdust was achieved in the slot-rectangular spouted bed,although the pressure drop across the reactor was observed to *** to the biomass feed rate,the temperature had a greater effect on the biomass weight loss and energy *** in temperature were found to promote weight loss of the sawdust while decreasing the energy *** main solid product was the torrefied sawdust,which remained in the SrSB reactor and was captured by a *** ratio of the torrefied biomass removed by the cyclone to the total torrefied biomass increased along with both the feed rate and *** undergoing torrefaction,6.7%-39.2% of the original sawdust mass was lost while 67.4%-98.7% of its energy was *** torrefied sawdust had a higher carbon content but less oxygen,hydrogen and volatiles,along with a greater higher heating value and increased density compared to the raw *** size of the sawdust particles also decreased markedly during the torrefaction process.

关键词： Torrefaction Slot-rectangular spouted bed reactor Temperature Biomass feed rate Torrefied sawdust property

Tribo-charging of binary mixtures composed of coarse and fine particles in gas-solid pipe flow

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Particuology 2019年第2期17卷 101-109页

作者： Haifeng Wang Farzam Fotovat Xiaotao T. Bi john r. grace Department of Chemical Engineering China University of Mining and Technology. Xuzliou 221166 China Department of Chemical and Petroleum Engineering Sharif University of Technology Azadi Avenue P.O. Box 11365-9465 Tehran Iran Fluidization research Centre Department of Chemical and Biological Engineering University of British Columbia. Vancouver V6T 1Z3 Canada

Experiments were conducted to investigate the effect of adding fines on the tribo-charging of coarse glass beads. Four types of fines, i.e., copper, stainless steel, uncoated and silver-coated fine glass beads, mixed w让h 240-830 μm glass beads were conveyed by air through a stainless-steel spiral pipe acting as a tribo-charger. regardless of the type or electrical conductivity of the fine particles tested, adding small amounts of fines (up to 10wt%) to coarse glass beads resulted in a sharp increase in the mass and surface charge densities of the particles. In gen eral, the profiles of the mass and surface charge den sides of the fine-coarse particle mixtures as a function of the mixture composition were determined by the relative magnitude of contact potential differences and the total surface areas of all the comp on ents. The domi nant particle tri bo-electrification mecha nism switched from coarse particle-wall con tacts to fine particle-wall contacts when the fines weight percentage in the mixture exceeded 10%. A model was developed to predict the mass charge density of bi nary mixtures as a function of the mixture composition.

关键词： Tribo-charging Electrostatics Fine particles Binary mixture Gas-solid flow