Effect of Liquid Rate

The coefficients are usually corrected to a hydroxide conversion of 25 percent at 24°C. For other conversions. Fig. 14-15 may be used. Reported values of Kog< for representative random packings are given in Table 14-8. The effect of liquid rate on the coefficient is shown in Figs. 14-70 and 14-71. 

Figure 9-17 plots flood capacity versus flow parameter. The FP values of 0.4-0.7 are estimated by Kister, el al. [136] in absence of data. The plots show that for low and moderate pressures the flood capacity factor versus FP correlates the effects of liquid rate and pressure on the optimized tray capacity [136]. At higher pressures an additional effect of pressure on capacity shows a decline of optimized tray capacity. 

Figure 11.62. Effect of liquid rate on the degree of wetting of packing1 80)...

Figure 12.8. Effect of liquid rate on height of transfer unit Hol- Comparison of the results of Sherwood and...

York, 1992). Figure 14-29 demonstrates the effect of liquid rate and fractional hole area on CSB. As liquid load increases, CSB first increases, then peaks, and finally declines. Some interpret the peak as the transition from the froth to spray regime [Porter and Jenkins, I. Chem. E. Symp. Ser. 56, Summary Paper, London (1979)]. CSB increases slightly with fractional hole area at lower liquid rates, but there is little effect of fractional hole area on CSB at high liquid rates. CSB,slightly increases as hole diameter is reduced. 

FIG. 14-75 Effect of liquid rate on ultimate capacity at higher liquid rates. (From Stupin, W. J., and H. Z. Kister, Trans. IChemE, vol. 81, Part A, p. 136, January 2003. Reprinted courtesy of IChemE.)... 

Figure 6.9 Factors affecting the flood capacity factor. FRI sieve tray test data, DT 4 ft, S = 24 in, hw = 2 in, dH = 0,5 in, straight downcomers, AJAT = 0.13. (a) Effect of liquid rate, Af = 0,08, (i>) Effect of fractional hole area. Cydohexane-Af-heptane, 24 psia.

Effect of liquid rate. At low liquid rates, entrainment diminishes with higher liquid loads, while at high liquid rates entrainment increases with liquid loads (22,24,26,33,40,53-55 Fig. 6,15), When most of the dispersion is in the form of a spray, entrainment diminishes with higher liquid loads (22,24,27). The point at which the trend reverses, and entrainment begins to increase with liquid rate, has been interpreted either as the point where the dispersion changes from partially developed spray to froth (40,53), or where the dispersion changes from the spray to froth regime (22-24,45,55). 

Hgura 9.4 Fraction of flow in the wall region of a packed column, (a) Effect of liquid rate and packing size, (20-in-ID column, water study. Data from p j Ph n thesis. University of Delft, The Netherlands, 1983). 

Figure 12 shows the effect of liquid rate on foam... 

Liquid rate decreases (Note This is the reverse of the effect of liquid rate on the weeping tendency. The effect of liquid rate on weeping and dumping is depicted in Fig. 6.6.)... 

In a gas-film-controlled system, the effect of liquid rate on the overall Koa value is essentially the same as for a liquid-film-controlled system, such as that shown in Table 5-6. In addition, in such a system the gas rate has a significant effect on the overall mass transfer coefficient. Similarly, Figures 5-4, 5-5, and 5-6 allow a rapid determination of the packed depth required for fume scrubbers in gas-film-controlled systems. In these plots, the overall K a value has been corrected for the effect of the gas flow rate. Because the K a value increases with an increasing gas flow rate, the solute removal efficiency drops only slightly for a fixed packed depth as the gas rate is increased in such a system. 

Tepe and Dodge found Kca to be essentially independent of gas rate, a condition which would normally indicate that the liquid film was controlling absorption. However, the exponent relating the effect of liquid rate is not as high as would be expected in a simple liquid-film-controlled absorption. As shown in the figure, the absorption coefficient increases with increased sodium hydroxide concentrations up to about 2 N and then decreases. The decrease is presumably due to the higher viscosity of more concentrated solutions—a phenomenon also observed for alkanolanune solutions. 

---