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Influence of drag laws on pressure and bed material recirculation rate in a cold flow model of an 8 MW dual fluidized bed system by means of CPFD

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Particuology 2018年第1期16卷 70-81页

作者： Stephan Kraft Friedrich Kirnbauer Hermann Hofbauer Bioenergy 2020+ GmbH Wiener Strasse 49 A- 7540 Gussing Austria TU Wien Institute of Chemical Engineering Getreidemarkt 9/166 Vienna Austria

A cold flow model of an 8 MW dual fluidized bed （DFB） system is simulated using the commercial compu- tational particle fluid dynamics （CPFD） software package Barracuda. The DFB system comprises a bubbling bed connected to a fast fluidized bed with the bed material circulating between them. As the hydrodynam- ics in hot DFB plants are complex because of high temperatures and many chemical reaction processes, cold flow models are used. Performing numerical simulations of cold flows enables a focus on the hydro- dynamics as the chemistry and heat and mass transfer processes can be put aside. The drag law has a major influence on the hydrodynamics, and therefore its influence on pressure, particle distribution, and bed material recirculation rate is calculated using Barracuda and its results are compared with experimental results. The drag laws used were energy-minimization multiscale （EMMS）, Ganser, Turton-Levenspiel, and a combination of Wen-Yu]Ergun. Eleven operating points were chosen for that study and each was calculated with the aforementioned drag laws. The EMMS drag law best predicted the pressure and dis- tribution of the bed material in the different parts of the DFB system. For predicting the bed material recirculation rate, the Ganser drag law showed the best results. However, the drag laws often were not able to predict the experimentally found trends of the bed material recirculation rate. Indeed, the drag law significantly influences the hydrodynamic outcomes in a DFB system and must be chosen carefully to obtain meaningful simulation results. More research may enable recommendations as to which drag law is useful in simulations ofa DFB system with CPFD.

关键词： Cold flow modeling Fluidization Computational particle fluid dynamics(CPFD) simulation dual fluidized bed Computational fluid dynamics

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Effect of fluidizing velocity on gas bypass and solid fraction in a dual fluidized bed gasifier and a cold model

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Particuology 2015年第1期13卷 58-65页

作者： Mook Tzeng Lim Woei-Lean Saw Shusheng Pang Department of Chemical and Process Engineering University of Canterbury Centre for Energy Technology School of Chemical EngineeringUniversity of Adelaide

dual fluidized bed gasifiers （DFBG） are effective in producing nitrogen-free syngas from biomass. How- ever, to improve the gasifier performance, pressure drops and solid fractions within the DFBG system need to be controlled. In this study, the effects of varying the fluidizing velocity in the fast fluidized bed （FFB） on the pressure drops and the solid fractions in the system were investigated in a 100 kW DFBG and in a dual fluidized bed cold model （DFCM）. Based on the experimental results, empirical correlations were developed to predict the height-averaged solid fraction in the bottom section of the FFB. Accuracy and advantages of the correlations were analyzed. The correlation is useful for design and modeling of the DFBG systems where the height-averaged solid fraction is required to be determined.

关键词： Cold model Hydrodynamics Steam gasification dual fluidized bed

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Analysis of the overall pressure balance loop for a methanol-to-olefins dual fluidized bed reactor-regenerator

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Particuology 2023年第11期82卷 13-24页

作者： Bijan Hejazi Neda Shabany Chemical Engineering Department Faculty of EngineeringFerdowsi University of MashhadMashhad***Iran Petrochemical Research and Technology Co. TehranIran

Development of a comprehensive reactor model is of paramount importance for design and scale-up of methanol-to-olefins (MTO) process in a dual fluidized bed reactor (DFB). These models must integrate suitable reaction kinetic expressions with hydrodynamic models properly descriptive of gas-solid contact in fluidized bed reactors. In this modeling study, our previously developed kinetic models of MTO fluidized bed reactor and regenerator are coupled with overall mass, energy and pressure balances to ensure smooth circulation of catalyst particles between the two fluidized beds. This integrated model was then applied to determine geometric dimensions of a demo-scale MTO DFB configuration and to obtain the mass distribution of catalyst particles throughout the entire system including the pipes connecting the two reactors. Our model is capable of being integrated into simulation software such as Aspen Plus for plant-wide optimization and scale-up studies.

关键词： Pressure balance loop Methanol-to-olefins dual fluidized bed SAPO-34 catalyst

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Study of biomass gasification in an industrial-scale dual circulating fluidized bed(DCFB)using the Eulerian-Lagrangian method

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Particuology 2023年第12期83卷 156-168页

作者： Jiahui Yu Shuai Wang Kun Luo Debo Li Jianren Fan State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou310027China Shanghai Institute for Advanced Study of Zhejiang University Shanghai200120China Guangdong Diankeyuan Energy Technology Co. Ltd.Guangzhou510080China

dual circulating fluidized bed(DCFB)has emerged as an efficient reactor for biomass gasification due to its unique feature of high gas-solid contact efficiency and separated reactions in two reactors,yet the understanding of complex in-furnace phenomena is still *** this study,biomass gasification in an industrial-scale DCFB system was numerically studied using a multiphase particle-in-cell(MP-PIC)method featuring thermochemical sub-models(e.g.,heat transfer,heterogeneous reactions,and homogeneous reactions)under the Eulerian-Lagrangian *** model validation,the hydrodynamics and thermochemical characteristics(i.e.,pressure,temperature,and species)in the DCFB are comprehensively *** results show that size-/density-induced segregation makes solid fuels concentrate on the bed *** momentum exchange leads to the continuous decrease of the gas pressure *** the gasifier and combustor,the lower heating value(LHV)of the gas products is 5.56 MJ/Nm^(3)and 0.2 MJ/Nm^(3)and the combustible gas concentration(CGC)is 65.5%and 1.86%,*** temperature in the combustor is about 100 K higher than that in the gasifier.A higher solid concentration results in a smaller value of particle heat transfer coefficient(HTC).The HTCs range from 50 to 150 W/(m^(2) K)for a solid concentration larger than 0.3 in the combustor while the HTCs range from 100 to 200 W/(m^(2 )K)in the *** Reynolds number of biomass particles is two orders of magnitude larger than that of the sand *** numerical results shed light on the reactor design and process optimization of biomass gasification in DCFBs.

关键词： dual fluidized bed Biomass gasification Numerical simulation MP-PIC Heat transfer coefficient

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