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--颗粒学报PARTICUOLOGY

Kraft, S., Kirnbauer, F., & Hofbauer, H. (2018). Influence of drag laws on pressure and bed material recirculation rate in a cold flow model of an 8MW dual fluidized bed system by means of CPFD. Particuology, 36, 70-81. https://doi.org/10.1016/j.partic.2017.04.009

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

Stephan Kraft ^{a b *}, Friedrich Kirnbauer ^a, Hermann Hofbauer ^b

a Bioenergy 2020+ GmbH, Wiener Strasse 49, A-7540 Güssing, Austria
b TU Wien, Institute of Chemical Engineering, Getreidemarkt 9/166, Vienna, Austria

10.1016/j.partic.2017.04.009

Volume 36, February 2018, Pages 70-81

Received 10 October 2016, Revised 28 March 2017, Accepted 6 April 2017, Available online 24 August 2017, Version of Record 22 December 2017.

E-mail: stephan.kraft@bioenergy2020.eu

Highlights

• A cold flow model of an industrial-sized dual fluidized bed system was simulated.

• Pressure drops, pressure profiles and bed material recirculation rates were measured.

• Four drag laws were used and the measured values are compared to the simulation.

• Pressure profiles and pressure drops were best predicted by the EMMS drag law.

• The bed-material recirculation rate was best predicted by the Ganser drag law.

Abstract

A cold flow model of an 8 MW dual fluidized bed (DFB) system is simulated using the commercial computational 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 hydrodynamics 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 hydrodynamics 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 distribution 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 of a DFB system with CPFD.

Graphical abstract

Keywords

Cold flow modeling; Fluidization; Computational particle fluid dynamics (CPFD) simulation; Dual fluidized bed; Computational fluid dynamics

文章导读