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Gas–Liquid Reactors
Published in Salmi Tapio, Mikkola Jyri-Pekka, Wärnå Johan, Chemical Reaction Engineering and Reactor Technology, 2019
Salmi Tapio, Mikkola Jyri-Pekka, Wärnå Johan
A variety of different types of gas–liquid reactors exist. The choice of the reactor type is sometimes obvious and sometimes very difficult. A summary of the selection criteria is listed in Table 7.2. For slow reactions, a bubble column is preferred; for fast reactions, a column, a scrubber, or a spray tower should be used. For absorption processes in which a high conversion of the gaseous reactant is the main goal, the self-evident reactor type is a packed bed or a plate column.
TiO2 nanofluid for oxygen mass transfer intensification in pulsed plate column
Published in Chemical Engineering Communications, 2021
Amruta S. Shet, Vidya Shetty K
Figure 5(a)–(c) also show the effect of frequency as a function of Φ on kLa at various amplitudes of pulsation of 3.2, 4.7, and 6.3 cm. kLa increases with the increase in frequency from 0.25 to 1 s−1. Maximum values of kLa were obtained at the highest frequency of 1 s−1 with all nanoparticle loadings and amplitudes of pulsation. The increase in frequency results in a greater velocity of reciprocating motion of nanofluids and intensifies the movement of the nanoparticles within the nanofluid. It leads to the collision of nanoparticles with gas bubbles. This breaks and deforms the gas bubbles dispersed in nanofluids (Haghtalab et al. 2015). As a result of the increased frequency of pulsation, the gas bubbles are disintegrated into smaller bubbles (Kim et al. 2008). Smaller bubbles provide a larger interfacial area for mass transfer and thus lead to enhancement of kLa. The turbulence-induced by increasing the frequency is very high and thus the aggregation potential of nanoparticles reduces (Pashaei et al. 2018), resulting in enhanced bubble dispersion (Stamenković et al. 2005) and increase in the bubble residence time (Lounes and Thibault 1994; Gomaa and Al Taweel 2005; Shetty and Srinikethan 2010) in the column, which further leads to increase in kLa. The surface available for mass transfer is periodically renewed and the thickness of the liquid film around the gas bubble is reduced due to the pulsation (Kodialbail and Srinikethan 2011). The resistance offered to mass transfer is reduced due to the pulsation, which enhances the kLa in PPC (Shetty and Srinikethan 2010). It is observed that at the amplitude of 6.3 cm, around 64% increase in kLa could be achieved with 0.016% loading of TiO2 in the nanofluid, by increasing the frequency by four-folds. The use of nanofluid of 0.016% loading could yield higher kLa at a frequency of 0.25 s−1, as compared to that which was achieved at 1 s−1 in the absence of nanoparticles. The kLa value obtained with the nanofluid at a frequency of 0.25 s−1 is above 21% higher than that obtained with the base fluid (absence of nanoparticles), at the frequency of 1 s−1. It shows that the required frequency can be reduced by one quarter, by use of nanofluid. Thus, enhanced oxygen mass transfer characteristics can be achieved with nanofluids in the pulsed plate column with the tremendous saving of energy. A maximum of 99.9% enhancement in kLa with reference to the base fluid can be achieved in the presence of nanofluid containing 0.016% TiO2 in PPC operated at f = 1 s−1 and A = 6.3 cm.