Dimension and Flow Characteristics of Highly Viscous Liquid Filaments in a High-Speed Disperser

Experimental Studies and Modeling of Devolatilization of Highly Viscous Solution in High-Speed Disperser

“…After entering the high-speed disperser, the acetone-syrup solution is dispersed into a large amount of liquid filaments in the order of millimeter/sub-millimeter by the high-speed rotating rotor, and a mass of bubbles come into being in the liquid filaments at sufficiently high superheat degree. First of all, as mentioned in our previous work (Gao et al, 2016), higher rotational speeds can generate thinner liquid filaments, thereby facilitating the movement of bubbles from the interior of the liquid filaments to the gas-liquid interface and the removal of acetone by bubble collapse. Furthermore, the higher shear stress and turbulence caused by a higher rotational speed can further facilitate the nucleation of bubbles (Wong and Park, 2012), and then promote foam devolatilization.…”

“…Finally, in spite of its modest contribution to acetone removal, diffusion devolatilization often coexists with foam devolatilization; thus, the mass transfer resistance for acetone removal by diffusion through the gas-liquid interface can be reduced by the thinner liquid filaments. However, with the increase of rotational speed, the mean residence time of liquid filaments in the cavity zone decreases (Gao et al, 2016). With the decrease in residence time of liquid filaments in the cavity zone, there is insufficient time for the mass transfer, so the increase of acetone removal rate slows down with further increases of rotational speed.…”

“…(4)-(6) in our previous work (Gao et al, 2016). Also, an expression for the liquid filament diameter d as a function of the angular velocity ω 0 of the rotor and the polar radius r in the cavity zone was proposed in our previous work (Gao et al, 2016).…”

“…The acetone inside the liquid filaments passes through the mass transfer interface between the solution and continuous gas phase, and then is stripped by means of vacuum. The highly viscous acetone-syrup solution can be split into large amounts of arc-shaped liquid filaments by the high-speed rotating rotor, and in the continuous operation, the liquid filaments move forward along the direction of their extension (Gao et al, 2016), so it is reasonable to consider that no backmixing of materials exists in a single liquid filament. Meanwhile, without regard to the interaction between liquid filaments in the cavity zone, it can be assumed that the acetone concentration distributions along all the liquid filaments are consistent with one another.…”

“…The devolatilization experiments were conducted to study the effects of absolute pressure, rotor rotational speed, initial acetone concentration, and inlet flow rate on the removal rate of acetone from the highly viscous acetone-syrup solution. Moreover, based on our previous work (Gao et al, 2016) on the dimension and flow characteristics of highly viscous liquid filaments dispersed by the same rotor in a high-speed disperser, a semi-empirical model of devolatilization was put forward to describe the diffusion devolatilization process under the experimental absolute pressure, so as to understand the diffusion devolatilization mechanism in depth and provide a theoretical foundation for the application and optimization of this high-speed disperser.…”