Circulating fluidized bed as a catalytic reactor: Experimental study

Abstract

In recent years, the circulating fluidized bed as a reactor has experienced increasing application in industry.

A review of multiscale CFD for gas–solid CFB modeling

“…One reason is the expectation that the heat/mass transfer rate is high in a CFB and therefore of minor effects to the overall reaction rate. For example, the reaction coefficient k r of ozone decomposition over FCC particles was reported of the order of magnitude of 10 s À1 , while that of the overall mass transfer coefficient k p a p was 10 5 s À1 (Ouyang et al, 1995;Dong et al, 2008a). That means, the overall performance is controlled by reaction rate and the mass transfer is negligible (Damköhler number Da ¼ k r =k p a p ( 1) in the case that the flow is regarded homogeneous.…”

“…Fig. 8 shows typical results through simulating an ozone decomposition experiment (Ouyang et al, 1995). It is demonstrated that the conventional approach without considering the structural effects gives poor results in that the relevant mass transfer rate and ozone decomposition rate are overestimated significantly (Fig.…”

A multiscale mass transfer model for gas–solid riser flows: Part 1 — Sub-grid model and simple tests

“…The overall conversion of O 3 inside the dense and the dilute phases is dominated by its intrinsic reaction rate, since k r ∼ (1.10) s −1 (Bi et al, 1992;Fryer et al, 1958;Ouyang et al, 1993Ouyang et al, , 1995Van Swaaij and Zuidenveg, 1972) while its mass transfer counterpart (k c p or k f p ) is of the order of magnitude of 10 5 s −1 . The meso-scale transfer is reserved for later comparison, thus the conversion rate of ozone in the dense and dilute phase can be written as follows:…”

“…The competition between mass transfer and reaction process makes the superficial reaction rate different from the intrinsic one (Levenspiel, 1999). To test the combined effects of mass transfer and reactions in a riser flow, we take the case of ozone decomposition performed by Ouyang et al (1995) (air-FCC particles, p = 1380 kg/m 3 , d p = 65 m, U g = 3.8.3.9 m/s, G s = 34.106 kg/m 2 s). The FCC catalyst particles used in that experiment fall into Geldart A in classification.…”

Experimental and theoretical investigation of mass transfer in a circulating fluidized bed

“…On the other hand, up to now, the mass transfer coefficient in CFBs are still mainly estimated on the basis of semi-empirical equations from experimental data-fitting in the literature (Breault., 2006). These mass transfer data in CFBs have been obtained by using ozone decomposition, naphthalene adsorption process, solid sublimation or liquid evaporation (Scala., 2007; Contents lists available at ScienceDirect Ouyang et al, 1995). These lead to mass transfer coefficient data published in the literature diverge significantly, reaching several orders of magnitude (Breault., 2006).…”