HETP charts

Strigle [94] proposed this term to better describe the performance of a packed column at or near the previously described loading point. Kister [93] evaluated the limited published data and proposed using the MOC at 95% of the flood point. The flood point can be estimated by Equation 9-20 or from the plots in References 90 and 93. The data are reported to be within 15-20% of the prediction [93]. See Figure 9-22 for the identification of MOC on the HETP vs. Cg chart For more accurate information... 

Figures 9-21G and 9-211 present the proprietary estimating capacity charts for the various sizes of the Intalox packing for a non-foaming system. The system base HETP of a packing is the flat HETP value produced by uniform distribution, see Figure 9-22.

Figure 13.45. Number of stages per meter (reciprocal of HETP), pressure loss per meter and pressure loss per theoretical stage in a 500 mm dia column filled with metal pall rings. Other charts in the original show the effects of packing height and column diameter, as well as similar data for Raschig rings (Billet, 1979). (a) Methanol/ethanol at 760Torr and total reflux in a column 500 mm dia. (b) Ethylbenzene/styrene at 100 Torr and total reflux in a column 500 mm dia.

For random packings there are many reports (3,56,98,136,140a, 162-167) of an increase in HETP with column diameter, fewer in which column diameter hed little effect on HETP (3,56,162,163), and an odd case in which increasing column diameter led to a decrease in HETP (56). Billet and Mackowiak s (3,62,166) scaleup chart for Pall rings implies that efficiency decreases as column diameter increases. 

Eckert (6) was first to tabulate HETP data in a format suitable for interpolation. Vital, Grossel, and Olsen (65) recommended such data over predictive methods, subject to availability of data for a system similar to that considered. The author concurs with this recommendation. In this chapter, Eckert s table is updated and largely expanded, and new tables and charts are edded for structured packings. 

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