T

Distillation Tray Spray Regime
(c)

Figure 6.26 {Continued) Tray action closeups in various flow regimes, (c) spray. Note the existence of gas jets at tray orifices (orifice positions are marked). Dotted horizontal lines indicate positions of minimum and maximum in the vertical dispersion sensitivity profiles (such as the spray profile shown in Fig. 6.286). id) Inclined gas bubbling under influence of a horizontal liquid flow, typical of the emulsion regime, [part c from W, V. Pinczewski and C. J D. Fell, Trans. Inst. Chem. Engrs. (London), 52, p. 294, 1974; part d from F. J. Zuiderweg, P. A. M. Hofhuis, and J. Kuzniar, Chem. Eng. Res. Des., 62, p. 39, 1984. Parts c and d reprinted courtesy of the Institution of Chemical Engineers, UK.)

Figure 6.26 {Continued) Tray action closeups in various flow regimes, (c) spray. Note the existence of gas jets at tray orifices (orifice positions are marked). Dotted horizontal lines indicate positions of minimum and maximum in the vertical dispersion sensitivity profiles (such as the spray profile shown in Fig. 6.286). id) Inclined gas bubbling under influence of a horizontal liquid flow, typical of the emulsion regime, [part c from W, V. Pinczewski and C. J D. Fell, Trans. Inst. Chem. Engrs. (London), 52, p. 294, 1974; part d from F. J. Zuiderweg, P. A. M. Hofhuis, and J. Kuzniar, Chem. Eng. Res. Des., 62, p. 39, 1984. Parts c and d reprinted courtesy of the Institution of Chemical Engineers, UK.)

Figure 6.27 Tray action in the froth, spray, and emulsion regimes. Horizontal bars indicate height above tray floor in inches, (a) Froth regime; (fc) Spray regime. [All paru courtesy of Fractionation Research Inc. (FRI).}

Figure 6.27 Tray action in the froth, spray, and emulsion regimes. Horizontal bars indicate height above tray floor in inches, (a) Froth regime; (fc) Spray regime. [All paru courtesy of Fractionation Research Inc. (FRI).}

Froth Regime

FigurĀ» 6.27 (Continued) Tray action in the froth, spray, and emulsion regimes. Horizontal bars indicate height above tray floor in inches, (c) Emulsion regime. Wall on right is aowncomer from tray above. [Alt parts courtesy of Fractionation Research Inc. (FRI).]

FigurĀ» 6.27 (Continued) Tray action in the froth, spray, and emulsion regimes. Horizontal bars indicate height above tray floor in inches, (c) Emulsion regime. Wall on right is aowncomer from tray above. [Alt parts courtesy of Fractionation Research Inc. (FRI).]

in the emulsion regime below) vapor is distributed as bubbles in continuous liquid, in the spray regime the phases are reversed. In this regime, vapor is the continuous phase, while the liquid, which is present in the form of drops of various sizes, is the dispersed phase. The dispersion has the appearance of a highly turbulent cloud of liquid droplets. A jet is formed at each perforation, which atomizes liquid in its path. A small pool of liquid or froth exists near the tray floor, through which the gas passes as high-velocity jets. As the gas passes through, it draws up liquid into ligaments and tears them up into drops (Fig. 6.28a). The bulk of the liquid is present as drops that reside at high elevations above the tray (Fig. 6.286) and follow free trajectories (Fig. 6.28c). Some may be entrained to the tray above, while others may fall back into the liquid pool, and the process repeats itself.

The spray regime frequently occurs in industrial practice, particularly where vapor velocities are high and liquid loads are low (e.g., vacuum). The classical hydraulic model (Sec. 6.2.1; Fig. 6.5) provides a poor approximation for the spray regime.

Emulsion (Figs. 6.25 e, 6.26d, and 6.27c). At high liquid loads and relatively low vapor loads, the shearing action of the high-velocity liquid bends the vapor bubbles and jets leaving the orifices, and "tears off"

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