GPDC

Figures 9-21B and -21C are the earliest generalized pressure drop correlations (GPDC) proposed and have been used for many industrial plant design. Progressively, Figures 9-21E-H are more recent correlations. These charts will be discussed in a later section.

Figure 9-21F is the most current updated version of the GPDC as presented by Strigle [139] to facilitate interpolation of the ordinate and pressure drop curves on the chart. The flooding and loading regions are not identified. For this chart ... 

Note differences in some symbol units for variotis GPDC charts. 

Figure 9-21E. Latest version, generalized pressure drop correlation (GPDC). Used by permission of Norton Chemical Process Products Coro (rev. 1985).

Nutter uses their owti proprietary computer program and not the conventional GPDC Chart shown in Figures 9-21B-E. Values shown developed by Kister [90] from data supplied by Nutter Engineering Co., a Harsco Corp. 

Pressure drop data for several styles and arrangements of drip point grid tile are given in Figures 9-25A-9-25E. These are not included in the general GPDC correlations for random packings. 

Vacuum distillation varies with the system tmd particularly with the absolute pressure required at the bottom of the column normally select low pressure drop in the range of 0.1 to 0.2 in. water/ft of packing. For in vacuum service of 75 mm Hg and lower, the pressure drop obtained from the GPDC,... 

For high pressure distillation of light hydrocarbons, industrial performance indicates that the pressure drop actually obtained is about two times that predicted by the use of the GPDC charts. Figure 9-21F and 9-21G (for Norton s IMTP packing only). When the vapor density is at least 6% of the liquid density, the actual pressure drop is expressed [82] ... 

Strigle [82] and Kister [93] point out the importance of evaluating data where available to reduce the need for interpolating the GPDC charts. The question of reasonably accurate ( 10 to 15%) flooding pressure drop data has been studied by Kister [93], and the results suggest that the establishment of flooding pressure drop curves... 

Leva, M. (1995) Chem. Engr. London No. 592 (July 27) 24. Revised GPDC applied. 

The GPDC charts in Figs. 14-55 and 14-56 do not contain specific flood curves. Both Strigle and Kister and Gill recommend calculating the flood point from the flood pressure drop, given by the Kister and Gill equation... 

FIG. 14-56 The Kister and Gill GPDC (SP) chart for structured packings only. Abscissa and ordinate same as in Fig. 14-55. (From Kister, H. and D. R Gill, IChemE Symp. Ser. 128, p A109,1992. Reprinted courtesy of IChemE.)... 

Pressure Drop The GPDC discussed above (Figs. 14-55 and 14-56) and the Kister and Gill interpolation charts provide popular methods for calculating packing pressure drops. An alternative popular method that is particularly suitable for lower liquid loads was presented by Robbins (below). 

The last popular version of the GPDC chart that contained a flood-point curve was the Eckert correlation (53,72). This version (Fig. 8.17)... 

Figure B.17 The Eckert 1970 version of the GPDC correlation. (From J. S. Eckert, Ckem. Eng. Progr., 66(3), March 1970, p. 39. Reproduced courtesy of the American Institute of Chemical Engineers.)...

The GPDC chart abcissa is the flow parameter [Eq. (8.21)], the ratio of liqnid kinetic energy to vapor kinetic energy. This parametm... 

Kister and Gill compared flood-point predictions from Eq. (8.1) to their massive data banks for second and third-generation random packings (60) and for structured packing (60a). Pressure drops were calculated using the Kister and Gill GPDC interpolation charts (Sec. 8.2.9). They showed that Eq. (8.1) predicted all the flood points in their data bank to within 15 percent and most to within 10 percent. 

Flood prediction by interpolation. GPDC interpolation plote are used to interpolate actual flood data. Data interpolation gives accurate flood-point prediction, but can only be used where sufficient flood point data are available. 

Chapter 10 presents a compendium of GPDC data interpolation charts for flood, MOC, and pressure drop prediction, both for random and structured packings. When flood data are absent, pressure drop data can be used for approximating the flood point using Eq. (8.1). 

Rgure B.1S GPDC interpolation plots for structured packings flood points, i.o) The Fair and Bravo plot for Sulzer BX and Mellapek 250Y. (Part a. from J. R, Fair and J. L, Bravo, I, Citem, E, Symp. Ser, No. 104, p. A183,... 

Figure B.1B (Continued) GPDC interpolation plots for structured packings flood points, (b) The Billet plot for several structured packings (cj the Spiegel and Meier plot for Mellapak , (Part b from R, Billet, Packed Column Analysis and Design, Ruhr University, Bochum, 1989, reprinted courtesy of Ruhr University part e, from L. Spiegel and W. Meier, 1. Chem. E. Syrtip. Ser. 104, p. A203, 1987 reprinted courtesy of the Institution of Chemical Engineers (UK).)...

Figure 8.1 B (Continued) GPDC interpolation plots for structured packings flood points. (d) The Dolan, Hausch and Petschauer plot for Intelox 2T Structured Packing. (Port d. from G,W. Hausch, P. Quvtson, and K. Seeger, Structured Packing Revamp of a 305 Psig Depropanizer, paper presented at the AJChE Annual meeting, Los Angeles, California, November 1991 reprinted courtesy of the Norton Company,)...

Both agreement (75,86) and disagreement (87,88) between measured pressure drops and those predicted by the Eckert GPDC have... 

Figure 8.19 The latest version of the GPDC pressure drop correlation, (a) The latest log-log version of Eckert s correlation, as presented by Strigle (15). (Part a from Ralph F. Strigle, Jr Random Packings and Packed Towers. Copyright 1987 by Gulf Publishing Company, Houston, Texas. Used with permission. All rights reserved.)...

For nonaqueous systems, the Eckert correlation is also optimistic for flow parameters lower than 0.03, which are typical of vacuum distillation and/or low liquid rates. Robbins (89) shows that the GPDC correlation use of liquid density and liquid viscosity is invalid at low flow parameters, where liquid properties should have little effect on pressure drop. It is worth noting that according to Robbins, this prediction difficulty is not unique to the Eckert correlation, but will be encountered whenever a correlation predicts a pressure drop dependence on liquid properties at low liquid rates. 

Figure 8.19 (Contin usd) The latest version of the GPDC pressure drop correlation, (rf) Superimposing experimental pressure drop data for a given pecking generates a GPDC interpolation chart for this packing.

---