(376bp) Effect of Rotating Elements on HETP of a Horizontal Distillation Column

Authors: 
Shimada, Y., Tokushima University
Sotowa, K. I., Tokushima University
Uno, Y., Tokushima University
Horikawa, T., Tokushima University
Alcantara-Avila, J. R., Kyoto University
Small scale continuous separation technology needs to be developed to realize continuous pharmaceutical production systems. There are several studies on the development of small scale unit operations such as extraction, crystallization and absorption. However, the number of reports on the small scale distillation is limited. Thus, this study aims at development of a new compact distillation apparatus which can be operated in a continuous mode. To realize small scale continuous distillation apparatus, it is essential to intensify the mass transfer rate between vapor and liquid phases in the column. Usually this has been achieved by improving packing materials and trays. Recently Katayama et al. [1] proposed a distillation apparatus that incorporates rotating elements at the center of a horizontal column to promote mass transfer. By the motion of the rotating elements, a thin liquid film is formed and mass transfer between vapor and liquid is expected to be promoted.
In this study, a horizontal type distillation apparatus equipped with rotating elements was constructed and the separation performance was evaluated by performing a total reflux distillation experiment. A horizontal column with an inner diameter of 3.0 cm and a length of 40 cm was used. Distillation experiments were carried out under total reflux conditions using cyclohexane / n-heptane system. Several different types of rotating elements were tested in the study, since the performance of the column is expected to be dependent on the shape of them. For fabrication of some rotating elements, a 3D printer was used.
Experiments were conducted to investigate the effect of rotating elements on the HETP and pressure drop. It was confirmed that HETP decreases greatly by increasing the rotation speed, and it reduced to 4 cm when the speed was 1000 rpm. However, pressure drop increased with increasing the rotation speed.
HETP and The magnitude of pressure drop depended on the shape of the rotating elements. Further optimization of the rotating element would lead to an improvement in both of them.

[1] H.Katayama et al., Journal of Chemical Engineering of Japan, 33, (5), pp. 689-695, 2000