(298c) Effective Homogenization of Stratified Liquids Using SIDE Entry Mixing

In many industrial applications, effective blending of fluids with different properties is very important. The ability to effectively blend fluids at lower power and torque inputs offers initial (capital) and longer term (power and maintenance) savings. Examining density stratified fluids in petroleum storage tanks is a unique subset of blending. The published literature on this topic is limited, and while newer contributions are available, the bulk of that data is forty to sixty years old.

Blending in oil storage tanks has been accomplished in several different ways historically. This includes the use of side entry mixers, angled or horizontal jet nozzles, and rotating jet nozzles. Although there is evidence that top entry mixers are more effective at blending in this application (Kehn 2011), because of the very large size and geometry of these vessels, conventional top entry mixers are rarely used.

There is strong evidence in the literature that angling a jet such that it is directed from near the base toward the liquid surface can significantly decrease blending and destratification times compared to a horizontal jet (Grenville, Tilton 2011). The use of side entry mixers in angled up orientation has been done for many years in tall tank applications like edible oil storage or in the food and beverage industry. Using a mixer angled up in oil storage has not been done in practice partly because the agitator has two separate duties in the system. In addition to blending, the mixer needs to be able to keep solids and water (basic sedimentation and water, BS&W) off the bottom of the tank.

To optimally meet the requirements of destratification in the upper portions of a vessel and off-bottom suspension at the vessel base the use of both technologies can be useful. Experimental and computational studies comparing blending in the angled and horizontal configuration were performed. This presentation will describe the findings of this study and highlight a new experimental method to examine blending in the presence of temperature based stratification.

Kehn, R. O., “Comparing top entry versus side entry agitator performance in low viscosity blending “, Can. J. Chem. Eng., 89: 1059–1067 (2011)

Grenville, R. K., J. N. Tilton, “Jet mixing in tall tanks: Comparison of methods for predicting blend times”, Chemical Engineering Research and Design, Volume 89, Issue 12, 2501 – 2506 (2011)