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CFB cyclones at high temperature:Operational results and design assessment

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Particuology 2008年第3期6卷 149-156页

作者： Raf Dewil jan baeyens Bart Caerts Department of Chemical Engineering Associated Faculty of Technology and Bio-sciencesCampus De NayerKatholieke Universiteit LeuvenJan De Nayerlaan 5B-2860 Sint-Katelijne-WaverBelgium Department of Chemical Engineering University of BirminghamEdgbastonBirmingham B15 2TTUnited Kingdom Department of Chemical Engineering Katholieke Universiteit LeuvenWillem De Croylaan 46B-3001 HeverleeBelgium

Pressure drop and cut size measurements are reported for a full scale cyclone operating within a 58 MWth CFB-combustor unit at 775 ℃. The paper reviews the vast number of equations to calculate the pressure drop and separation efficiency of cyclones, generally for operation at ambient temperature and at low Cs [〈0.5]. None of the literature correlations predicts the pressure drop with a fair accuracy within the range of experimental operating conditions. The cut size d50 can be estimated using direct empirical methods or using the Stokes number, Stk50. Both methods were used to compare measured and predicted values of d50. With the exception of Muschelknautz and Krambrock, none of the equations made accurate predictions. Finally, an alternative method to determine the friction factor of the pressure drop equation （Euler number, Eu） and of the cut size is proposed. The Eu number is determined from the geometry of common cyclones, and the derived value of Stk50 defines more accurate cut sizes. The remaining discrepancy of less than 5%, when compared with the measured values, is tentatively explained in terms of a reduced cyclone diameter due to the solids layer formed near its wall. Further measurements, mostly using positron emission particle tracking, elucidate the particle motion in the cyclone and both tracking results and the influence of the particle movement on Eu and Stk50 will be discussed in a follow-up paper.

关键词： Cyclone High loading High temperature Combustor

Investigation of operational parameters for an industrial CFB combustor of coal,biomass and sludge

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China Particuology 2007年第4期5卷 247-254页

作者： Manon Van de Velden jan baeyens Bill Dougan Alan McMurdo Department of Chemical Engineering University of Birmingham B15 2TT Birmingham United Kingdom UPM-Kymmene Caledonian Paper Ltd.AyrUnited Kingdom

The combustion of coal and/or biomass （sludge, wood waste, RDF, etc.） in a circulating fluidized bed has been a commercial topper for over 20 years, and references to principles and applications are numerous and widespread although few data are presented concerning the operation of large scale CFB-units. The authors studied the CFB-combustion at UPM-Kymmene （Ayr）, a major paper mill relying for its steam production upon the combustion of coal （80-85 %）, wood bark （5-10%） and wastewater treatment sludge （5-10%）. The maximum capacity of the CFB is 58 MWth. A complete diagnostic of the operation was made, and additional tests were performed to assess the operating mode. The plant schematics, relevant dimensions and process data are given. To assess the operation of the UPM-CFB, it is important to review essential design parameters and principles of CFB combustors, which will be discussed in detail to include required data, heat balance and flowrates, operating versus transport velocity, kinetics and conversion （including the possible effect of the Bouduard reaction if carbon is present）. Since the residence time in the riser and the cyclone efficiency determine the burnout of circulating fuel-particles, the UPM-CFB was subjected to a stimulus response technique using nickel oxide as tracer. Results illustrate the efficiency of the cyclone separation and the number of recycle loops for particles of a given size. Results will also be used to assess the cyclone operation and efficiency and to comment upon expected and measured carbon conversion.

关键词： Circulating fluidized bed Combustion Coal Biomass Operation Cyclone

A new design approach for the established flow region of vertical,dilute-phase pneumatic conveyors

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Particuology 2022年第7期20卷 10-20页

作者： John M.Wheeldon jan baeyens Shuo Li Yimin Deng European Powder and Process Technology Longfellow DriveKetteringUnited Kingdom KU Leuven Department of Chemical EngineeringProcess and Environmental Technology LabJ.De Nayerlaan 52860 Sint-Katelijne-WaverBelgium Beijing University of Chemical Technology Beijing Advanced Centre of Smart Matter Science and EngineeringBeijingChina

An analysis has been completed for a comprehensive set of vertical,dilute-phase pneumatic conveying pressure drop data from an investigation by *** data were collected in the established flow region for eight different materials conveyed in 0.05-,0.10-,0.20-m internal diameter,20-m tall steel *** velocities derived from the pressure drop data were used to develop an equation of motion that includes terms for pipe diameter,terminal velocity,coefficient of restitution,and particle *** best data fit was achieved using the actual gas density and the actual gas velocity adjusted for *** the terminal velocity for voidage,an approach recommended by many investigators,did not improve the fit for reasons identified by the present *** the equation of motion,particle velocities were predicted and used to calculate total pressure drops that are within±15%of the measured *** calculated values also produce the characteristic trough-shaped total pressure drop curves allowing the minimum pressure drop gas velocity to be determined without recourse to a separate correlation.A comparison with other studies using shorter risers indicates that data from these studies likely include acceleration effects.A separate study will investigate this observation further.

关键词： Dilute-phase Vertical Pneumatic conveying Design equations Pressure drops

Environmental and economic assessment of vegetable oil production using membrane separation and vapor recompression

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Frontiers of Chemical Science and Engineering 2017年第2期11卷 166-176页

作者： Weibin Kong Qi Miao Peiyong Qin jan baeyens Tianwei Tan Beijing Key Lab of Bioprocess College of Life Science and Technology Beijing University of Chemical Technology Beijing 100029 China School of Engineering University of Warwick Coventry CV4 7AL UK

Solvent extraction of crude oil from oilseeds is widely applied for its high production capacity and low cost. In this process, solvent recovery and tail gas treatment are usually performed by adsorption, paraffin scrubbing, or even cryogenics （at low tail gas flow rates）. Membrane separation, which has a lower energy consumption than these techniques, spans a broad range of admissible concentrations and flow rates, and is moreover easily combined with other techniques. Vapor recompression has potentials to reduce the heat loss in association with distillation and evaporation. In this study, we proved the possibility of combining membrane separation and vapor recompression to improve the conventional vegetable oil production, by both experiments and process simulation. Nearly 73% of energy can be saved in the process of vegetable oil extraction by the novel processing approach. By further environmental assessment, several impact categories show that the optimized process is environmentally sustainable.

关键词： vegetable oil solvent-extraction membrane separation vapor recompression environmental and economic assessment

The use of ultrasound probes to monitor multi-phase behavior in opaque systems

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Particuology 2019年第4期17卷 91-97页

作者： Weibin Kong Shuo Li Hui Ke Huili Zhang jan baeyens College of Life Science and Technology Beijing University of Chemical Technology Beijing 100029 China College of Chemical Engineering Beijing University of Chemical Technology Beijing 100029 China European Powder and Process Technology 3120 Tremelo Belgium Beijing Advanced Innovation Centre for Smart Matter Science and Engineering Beijing University of Chemical Technology Beijing 100029 China

The detection of phenomena occurring inside multiphase opaque reactors is difficult. The present work investigated the novel application of a non-intrusive ultrasound monitoring technique to the complex case of gas-solid fluidized beds. Comparisons of data obtained from video-imaging and theoretical calculations with the ultrasound signal data demonstrate that the ultrasound system is a reliable means of characterizing essential bubble properties by measuring the point bubble frequency, when applying a special protocol during signal treatment. Additional uses in different multiphase systems are further described.

关键词： Ultrasound monitoring Non-intrusive Multiphase system Opaque

Solids flow diagram of a CFB riser using Geldart B-type powders

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Particuology 2012年第1期10卷 51-61页

作者： Shiva Mahmoudi Chian Wen Chan Anke Brems Jonathan Seville jan baeyens University of Warwick School of Engineering Katholieke Universiteit Leuven Department of Chemical Engineering University of Surrey Faculty of Engineering and Physical Sciences

Riser operating modes are vital to designing a circulating fluidized bed （CFB） reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids＇ residence times and mixing behaviors, which define the reactions＇ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking （PEPT） in a riser of B-type bed material to determine the different operating modes by measuring （i） particle velocities and residence time distribution, （ii） population densities of these particles in the cross-sectional area of the riser, and （iii） solids flow pattern at the bottom of the riser, Data treatment defines four distinct solids hold-up regimes in the riser and proposes a ＂phase diagram＂ depicting the existence of the different operating modes （dilute, dense, core-annulus and combined） as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics.

关键词： Phase diagramDilute riser flowTurbulent fluidized bottom bedCore-annulus flowDense riser up-flow

PEPT study of particle motion for different riser exit geometries

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Particuology 2010年第6期8卷 623-630页

作者： Chian Wen Chan Anke Brems Shiva Mahmoudi jan baeyens Jonathan Seville David Parker Thomas Leadbeater Joseph Gargiuli University of Warwick School of EngineeringCoventryCV4 7 ALUK Katholieke Universiteit Leuven Department of Chemical Engineeringde Croylaan463001LeuvenBelgium University of Birmingham School of Physics and AstronomyBirminghamB22 T15UK

Laboratory and industrial risers are equipped with exits of many different layouts, and numerous publications discuss the influence of riser exit geometry on local and overall solids hydrodynamics in the riser. The present paper reviews literature findings--mostly based upon indirect experimental techniques and often somewhat contradictory, Direct measurement of particle velocity and particle occupancy near and in the riser exit provide a better indication of the effect of riser exit geometry. Positron Emission Particle Tracking （PEPT） was used in this work for the first time to investigate the exit region of the riser, An abrupt or sharp exit causes particles to be knocked out of the gas flow, so forming a recirculation or reflux region in the upper part of the riser. This is much less pronounced with a curved or gradual exit.

关键词： CFB Riser Exit geometries Positron Emission Particle Tracking

Gasification of plastic waste as waste-to-energy or waste-to-syngas recovery route

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Natural Science 2013年第6期5卷 695-704页

作者： Anke Brems Raf Dewil jan baeyens Rui Zhang College of Life Science and Technology The Key Laboratory of Bioprocess of Beijing Beijing University of Chemical Technology Beijing China Department of Chemical Engineering Chemical and Biochemical Process Technology and Control Section Katholieke Universiteit Leuven Heverlee Belgium

The disposal of plastic solid waste (PSW) has become a major worldwide environmental problem. New sustainable processes have emerged, i.e. either advanced mechanical recycling of PSW as virgin or second grade plastic feedstock, or thermal treatments to recycle the waste as virgin monomer, as synthetic fuel gas, or as heat source (incineration with energy recovery). These processes avoid land filling, where the non-biodegradable plastics remain a lasting environmental burden. Within the thermal treatments, gasification and pyrolysis gain increased interest. Gasification has been widely studied and applied for biomass and coal, with results reported and published in literature. The application to the treatment of PSW is less documented. Gasification is commonly operated at high temperatures (> 600℃ to 800℃) in an air-lean environment (or oxygen-deficient in some applications): the air factor is generally between 20% and 40% of the amount of air needed for the combustion of the PSW. Gasification produces mostly a gas phase and a solid residue (char and ashes). The use of air introduces N2 in the product gases, thus considerably reducing the calorific value of the syngas, because of the dilution. The paper will review the existing literature data on PSW gasification, both as the result of laboratory and pilot-scale research. Processes developed in the past will be illustrated. Recently, the use of a sequential gasification and combustion system (at very high temperatures) has been applied to various plastic-containing wastes, with atmospheric emissions shown to be invariably below the legal limits. Operating results and conditions will be reviewed in the paper, and completed with recent own lab-scale experimental results. These results demonstrate that gasification of PSW can be considered as a first order reaction, with values of the activation energy in the order of 187 to 289 kJ/mol as a function of the PSW nature.

关键词： Plastic Waste Re-Use Gasification Syngas Char Sustainability Reaction Rate

Energy-Efficient Production of Cassava-Based Bio-Ethanol

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Advances in Bioscience and Biotechnology 2014年第12期5卷 925-939页

作者： Qian Kang Lise Appels jan baeyens Raf Dewil Tianwei Tan Process and Environmental Technology Laboratory Department of Chemical Engineering Sint-Katelijne-Waver Belgium Beijing Key Laboratory of Bioprocess College of Life Science and Technology Beijing University of Chemical Technology Beijing China

Fuel ethanol is an important renewable and sustainable fuel, produced in China by fermentation of mostly corn, wheat and cassava feedstock. Fermentation produces an ethanol-lean broth (10 to 12 vol%). Ethanol is recovered by distillation, followed by a molecular sieve drying beyond the azeo-tropic point. The distillation and molecular sieve operations consume most of the total energy used, with the steam consumption currently being ~1.8 kg/kg ethanol, including 0.5 kg/kg ethanol in the final molecular sieve stage during regeneration. The objectives of the paper are fourfold: 1) firstly to study the distillation process of a large-scale cassava-based fuel ethanol production (200,000 tons per year), by field measurements and by using an Aspen Plus V8.2 simulation, with and without energy integration of condensers and reboilers, resulting in a distillation steam consumption of ~1.3 kg/kg ethanol;2) secondly, to examine the effects of using Very High Gravity (VHG) fer-mentation of cassava meal mash. By using VHG fermentation, the ethanol concentration in the fermenter broth is significantly increased, to about 19 vol% (15.4 wt%). The steam consumption is then reduced to ~0.94 kg/kg, representing a considerable saving in comparison with the current operation. Applying VHG fermentation needs minor additional investment, rapidly recovered through the energy savings and the smaller size of equipment;3) thirdly, to assess the application of a hybrid operation, where pervaporation will be used to selectively and continuously remove ethanol from the fermenter broth, thus slightly increasing the fermentation yield by reducing the risk of ethanol inhibition, whilst producing an ehtanol-rich permeate (about 30 wt%);and finally 4) to demonstrate that the production cost of cassava-based ethanol can substantially be reduced by applying the proposed improvements.

关键词： Bio-Ethanol Hybrid Process VHG Membranes Energy Optimization Simulation