B

FIG. 14-37 Aeration factor for pressure drop calculation. (a) Sieve trays. [Bolles and Fair, Encyclopedia of Chemical Processing and Design, vols. 16, 86. J. M. McKetta (ed.), Marcel Dekker, New York, 1982.] (b) Valve trays. (From G. F. Klein, Chem. Eng., May 3, 1982, p. 81; reprinted courtesy of Chemical Engineering.)

liquid heads and therefore weeping. Hole diameter has a complex effect on weeping, detailed by Lockett and Banik [Ind. Eng. Chem. Proc. Des. Dev. 25,561 (1986)].

Tests by Lockett and Banik (loc. cit.) show that weeping is often nonuniform, with some hydraulic conditions favoring weeping from the tray inlet and others from the tray outlet. Weeping from the tray inlet is particularly detrimental to tray efficiency because the weeping liquid bypasses two trays.

Weep Bate Prediction Lockett and Banik (loc. cit.) and Hsieh and McNulty (Chem. Eng. Progr., July 1993, p. 71) proposed correlations for predicting weep rates from sieve trays. Colwell and O'Bara (Paper presented at the AIChE Meeting, Houston, April 1989) rec ommended the Lockett and Banik correlation for low pressures (<1100 kPa or 165 psia), and the Hsieh and McNulty correlation for high pressures (>1100 kPa or 165 psia). They also corrected the Lock-ett and Banik correlation to improve its accuracy near the weep point.

The Lockett and Banik correlation (as corrected by Colwell and O'Bara) is

0 0

Post a comment