(293e) Designing Edible Oil Stripping Columns

Removal of impurities, consisting of free fatty acids and other valuable components as well as contaminants from edible oils occurs on largest industrial scale by hot steam stripping under deep vacuum conditions in columns equipped with structured packings. Due to a relatively large pressure drop (in the range of, or larger than the absolute pressure at the top of the column), operating conditions and consequently both hydraulic and mass transfer performance differ strongly at the top and the bottom of the bed. In order to arrive at an optimized design a tedious iterative procedure is required, reliability and accuracy of the predictive model for the pressure drop being the key to success in this respect.

A theoretically founded pressure drop expression (introduced at AIChE 2016 Spring Meeting) that accounts for peculiarities associated with the flow of a very low density gas that under laminar flow conditions ascends through the packed bed at a rather high effective velocity has served as the cornerstone for building of a simple predictive model, which enables a theoretically founded approach to conceptual (re)design of packed columns for edible oil stripping.

The model is arranged as a sequential algorithm with pressure drop estimation in inner loop and the bed height calculation procedure utilizing HTU-NTU approach in outer loop, which, implemented in Excel environment, eases performing numerous calculations required to evaluate properly the effect of design variables, such as operating pressure and temperature, packing size, and stripping hot steam flow rate, aiming at establishing the optimal bed height to diameter ratio for given application. Basic features of this model and peculiarities related to utilization of structured packings in deep vacuum applications will be illustrated and demonstrated using typical industrial cases.