Three-dimensional full-loop simulation of cold gas-solid flow in a pilot-scale dual fluidized bed system- a preliminary study

Frederik Zafiryadis, Anker Degn Jensen, Martin Høj, Yashasvi Laxminarayan, Elisabeth Akoh Hove, Morten Boberg Larsen, Hao Wu

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Abstract

Catalytic cracking of sugars in a circulating fluidized bed (CFB) system is a novel technology for producing intermediary oxygenate products that can be further converted to a variety of biobased chemicals. The technology has the potential to enable economically and environmental sustainable production of bio-based chemicals.The hydrodynamics of such a CFB system are very complex and play a critical role for successful operation of the plant. Hence, to support the design of the plant as well as the development and scaling-up of the technology, an in-depth understanding of the hydrodynamics in the system is needed. Three-dimensional computational particle fluid dynamics (CPFD)simulations are conducted based on the Eulerian-Lagrangian MP-PIC method to predict the hydrodynamic behavior of a cold flow-pilot scale CFB system at the Technical University of Denmark. The CFB system is of a dual fluidized bed (DFB) configuration, consisting of a reactor and a regenerator loop. Each loop is comprised of a riser, primary- and secondary cyclones, a bubbling bed, and a transfer line for connecting the two loops. A stripper section is located vertically below the regenerator bubbling bed to remove oxygen from the flow before re-entering the reactor riser. Detailed information on the hydrodynamic behavior of the system in terms of solids velocity, flux, residence time, as well as voidage and pressure distributions throughout the system are obtained and analyzed using a segregated modeling approach, decoupling the major parts of the system. The segregated method requires several subsystem simulations to be perfomed for achieving physical inflow conditions at the subsystem boundaries, improving modeling accuracy while reducing overall computational time and demands. Comparison of CPFD predictions with experimental data on the cold flow gas-solid pilotscale model is conducted in terms of pressure distributions throughout the entire system, demonstrating the ability of the segregated full-loop model to capture the behavioral trends of the DFB system. Further work includes modeling optimizations of each subsystem with respect to e.g. tuning of model parameters, drag modeling, grid- and sub-grid discretization. Further extensions of the model are to include a third (liquid) phase to simulate atomization and evaporation of the aqueous sugar solution required for ensuing introduction of chemical reactions to predict performance parameters (e.g conversion and yields) of the system in both pilot- and commercial scale.
Original languageEnglish
Publication date2019
Number of pages1
Publication statusPublished - 2019
EventBarracuda Virtual Reactor Users' Conference 2019 - Chicago, United States
Duration: 27 Jun 201928 Jun 2019

Conference

ConferenceBarracuda Virtual Reactor Users' Conference 2019
CountryUnited States
CityChicago
Period27/06/201928/06/2019

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