Predicting the Pressure Drop of Corrugated Sheet Structured Packings in Deep Vacuum Applications

Žarko Olujić

doi:10.15255/cabeq.2018.1574

Abstract

Advanced corrugated sheet structured packings are considered a natural choice for<br /> deep vacuum distillation. In many of these applications that occur at absolute pressures<br /> below 0.01 bar at the top of the column, the low density gas/vapor driven by pressure<br /> ascends through an irrigated packed bed under laminar flow conditions. This implies that the packing geometry features aiming to reduce the form drag of advanced packing may not be as effective, if at all, as experienced in common applications where turbulent flow prevails. To consider this appropriately, a theoretically founded expression for laminar flow friction factor has been incorporated into Delft model (DM). With this extension, the predicted pressure drop within laminar flow region approaches closely that estimated using well-established empirical model available in software package SULCOL. In absence of adequate experimental evidence, extended DM was validated using newest data obtained at FRI with an advanced wire gauze structured packing in total reflux experiments carried out with paraxylene/orthoxylene system at 0.02 and 0.1 bar top pressure in a column with internal diameter of 1.22 m.

Highlights

In a paper presented at AIChE Spring Meeting held in 2013 in San Antonio, TX, USA, Duss[1] has indicated a number of industrially important deep vacuum applications of structured packing with gas or vapor phase ascending under laminar flow conditions
F i g . 7 – Specific pressure drop as estimated by extended Delft model (DM) (DM-new) for four structured packings considered in present study in conjunction with given hypothetical base case
If we consider the spread of four curves, the width of the band within turbulent flow region, reflecting the corrugation inclination angle effect, is considerably larger according to DM than SULCOL

Summary

Introduction

In a paper presented at AIChE Spring Meeting held in 2013 in San Antonio, TX, USA, Duss[1] has indicated a number of industrially important deep vacuum applications of structured packing with gas or vapor phase ascending under laminar flow conditions. 1 – Drag coefficient as a function of gas or vapor Reynolds number for four representative different types and sizes of Sulzer corrugated sheet structured packings in conjunction with hypothetical operating conditions base case, with fixed values of vapor load, liquid load, vapor viscosity, and liquid properties (see Table 1), considered in this study[1,11] curves exhibit similar trend, and tend to flatten with increasing Reynolds number, indicating a gradual transition from laminar to turbulent flow, but differ in absolute values to the extent depending on distinctive macro geometric features, i.e., corrugation inclination angle and hydraulic diameter.

Results

Conclusion