*4.2. Effect of Liquid Flow Rate*

Figure 6 presents the effect of the liquid flow rate on *K*G*a* in the RZB. It can be seen that *K*G*a* in NaOH solution obviously increased, with a rise in the liquid flow rate from 25 to 40 L/h.

With a rising liquid flow rate, more fine droplets from the rotating baffles are produced. The falling velocity of the filmy liquid on the static baffles also increases in terms of the expression of *u*g,*<sup>i</sup>* in Table 2, causing an increasing area of the flying liquid sheet between the static and rotating baffles according to Equation (12). These factors enhance the liquid holdup in the RZB, thereby causing a rising gas–liquid contact area based on Equation (8). Meanwhile, with the increase of the liquid flow rate, the circumferential distribution of droplets in zone I is improved [10], and more droplets continually impinge on the filmy liquid on the lower section of the static baffles, leading to an enhancement of liquid turbulence and a higher surface renewal rate of liquid film in the turbulent filmy liquid in zone II, as suggested by Equation (40), which are conducive to the liquid-side mass transfer. Therefore, a higher liquid flow rate brought about a larger *K*G*a* in this study because *a* and *k*<sup>L</sup> contributed notably to *K*G*a* for CO2 absorption into NaOH solution.

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**Figure 6.** Effect of liquid flow rate on *K*G*a* in the RZB (*G* = 1000 L/h, *T* = 298.15 K, *T*gas = 298.15 K, *y*CO2-in = 4%, *C*NaOH = 0.15 kmol/m3).
