Entrainment sieve tray, correction

Figure 8-121. Sieve tray entrainment correction. Used by permission, Hunt, C. D A., Hanson, D. N., and Wilke, C. R., The American Institute of Chemical Engineers, Chemical Engineers Journal, V. 1 (1955), p. 441, all rights reserved.

Problem 12.6 deals with the dimensioning of a large ethylbenzene/styrene tray-type fractionator. The overall column efficiency for the sieve trays is to be estimated, based on the same conditions given for Problem 12.6. Two methods will be used (a) the O Connell (Figure 12.60) approximate method and (b) the Chan/Fair more basic method [Equation (12.84)], corrected for entrainment and liquid crossflow effects. 

Methods for estimating the Murphree tray efficiency corrected for entrainment MGE sieve trays are discussed in detail in Chap, 6. For a given absorber or stripper, these permit estimation of the tray efficiency as a function of fluid compositions and temperature as they vary from one end of the tower to the other. Usually it is sufficient to make such computations at only three or four locations and then proceed as in Fig. 8.16, The broken line is drawn between equilibrium curve and operating line at a fractional vertical distance from the operating line equal to the prevailing Murphree gas efficiency. Thus the value of MCE bottom tray is the ratio of the lengths of lines, AB/AC. Since the... 

The Smith et al. correlation (20, Fig. 6.11). This is another early entrainment flooding prediction method that has sometimes been recommended (11). Compared to Fair s correlation, the Smith et al. correlation is claimed (20) to be less conservative. It was derived from a small base of field data for sieve, valve, and bubble-cap trays. Similar to Fair s correlation, Smith s correlation uses CSB versus a flow parameter plot, but here the dependence of CSB on the flow parameter is weaker, and there is no surface tension correction factor. CSB and flood 316 both based on the net area AN, and are evaluated from Fig. 6.11 and Eq. (6,9), respectively. The height over the weir, how, is obtained from Eq, (6.49). 

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