DIVIDING-WALL COLUMN DISTILLATION

Dividing-wall column distillation (DWC) combines 2 thermally coupled distillations in a single column. The column is partly divided lengthwise into two, with the top and bottom sections of the two sections in common [1]. The first commercial scale implementation was in 1985 by BASF [2, 3]. Since then the number of commercial applications has grown strongly. The technology provider Montz reported over 90 installations in 2010 [4] and Sulzer Chemtech reported in 2012 that it had installed 36 DWC installations. [5]. Schultz already reported some DCW implementations by engineering firms other than Montz or Sulzer in 2002 [3]. The present total number of implementations is therefore well in excess of 130. The driving forces for using this technology are energy savings and investment cost savings [6]. The energy savings range typically from 10-30% [2]. The investment savings are typically 30% but in some cases can be 60% [3]. The basic design and control knowledge is available in the public domain [1, 7]. Detailed design for the construction is available from Montz [4] and Sulzer [5]. A nice overview is provided by Dejanović [7]. The scale-up method applied is model based. The model is validated in a mini plant or a pilot plant [2, 4]. The largest commercial scale DWC is operated by Sasol. It is 64.5 m high and has a diameter of 4 m [2].

By Jan Harmsen (Harmsen Consultancy BV)