Characterization of the pneumatic behavior of a novel spouted bed apparatus with two adjustable gas inlets

Abstract

-Recently the importance of spouted bed technology has significantly increased in the context of drying processes as well as granulation, agglomeration or coating processes. Particulate systems concerning very fine or non spherical particles that are difficult to fluidize, often cannot be treated in conventional fluidized beds. In contrast to those fluidized beds, the spouted bed technology with its specific flow structure offers the opportunity of stable fluidization under controlled conditions. Within this work the fluid dynamics of a novel spouted bed with two adjustable gas inlets is investigated. By analysis of gas fluctuation spectra by means of a fast Fourier transformation algorithm, different operation regimes are identified and depicted graphically. Furthermore, continuum CFD-modeling of the granular solid phase motion by means of an Euler/Euler approach and comparisons with experimental obtained velocity vector fields by means of particle image velocimetry (PIV) measurements will be presented in this work.

CFD modeling of a prismatic spouted bed with two adjustable gas inlets

“…Recapitulating it can be stated, that after application of a variety of drag models in this work and in Gryczka et al (2008), the search for an appropriate drag model alone is not sufficient to fit the simulation results to the experimental findings. As claimed by Goldschmidt et al (2001), other contributions like the particle rotation (which is neglected in the continuum model) or a frictional stress model (Patil et al, 2004) should be focus of further development work of continuum models to achieve a better agreement with experimental results.…”

“…To improve the results presented previously (Gryczka et al, 2008), the drag model of Clift et al (1978) was used to achieve a better agreement with experiments. Experimental and predicted time-dependent distributions of the granular solid phase in the apparatus as well as gas phase pressure fluctuations over the entire bed were analyzed and compared.…”

“…Compared to the simulations with the Schiller and Naumann (1935) drag model in Gryczka et al (2008), a higher bed expansion was calculated. However, compared to the experiment, the bed expansion is still slightly underpredicted.…”

“…However, due to the good fit of the Clift et al (1978) drag curve with the standard drag curve (see Figure 2), it is expected that a better agreement with experimental findings can be achieved by application of that drag model. Particularly, a higher bed expansion compared to the Schiller and Naumann (1935) drag model would improve the simulation results considerably presented previously (Gryczka et al, 2008). Another aspect that can be extracted from Figure 3 is the difference between the values of the gas-solid momentum exchange coefficient calculated with the Ergun (1952) equation and the Wen and Yu (1966) equation that are both applied in the Gidaspow et al (1992) drag model.…”

“…Recently Gryczka et al (2008) carried out CFD-continuum simulations of the hydrodynamic behaviour of this novel spouted bed testing the drag models of Schiller and Naumann (1935), Wen and Yu (1966), Syamlal and O'Brien (1989), Gidaspow et al (1992), Koch and Hill (2001), van der Hoef et al (2005), and Beetstra et al (2007) to simulate realistic flow structures. Here, the Gidaspow et al (1992) drag model over-predicted the bed expansion considerably and the gas phase pressure fluctuations did not reflect the hydrodynamic behaviour of the realistic spouting process.…”