Design of a Dividing-Wall Column
Considering its Multiple Steady State
A dividing-wall column (DWC) may have more than one solution of liquid and
vapor split ratio for the same feed and product streams under a fixed number of
stages and reflux ratio, so the multiple steady states (MSS) of a DWC in the design
stage should be considered. An improved design method of a DWC is proposed
by studying its MSS characteristics. Additional steps are inserted after optimiza-
tion to check if MSS exist for the obtained optimal solution of vapor and liquid
split ratio, and further to select the best candidate. Finally, two cases of three-
product DWCs are described to verify this method. The results indicate that mul-
tiple solutions exist for these cases, which confirm the necessity of this method
and provide an important guidance for the flowing design of a DWC.
Keywords: Dividing-wall column, Liquid split ratio, Multiple steady states, Vapor split ratio
Received: April 04, 2017; revised: September 08, 2017; accepted: November 23, 2017
Distillation, as one of the most common methods in the chemi-
cal industry, accounts for a large percent of energy consumed
in industrial processes. To reduce energy costs, numerous strat-
egies are applied, of which the thermally coupled distillation
column appears to be a good alternative. It applies to perform
separations of three or more components and only needs one
condenser and one reboiler for two columns which are con-
nected by two pairs of coupled liquid and vapor streams, as
illustrated in Fig. 1.
This column was first introduced in by Petlyuk et al. in 1965
, so it is usually called the Petlyuk column. Compared with
the conventional two-column-in-series configuration, the
Petlyuk column boosts significantly the economical profit due
to reduced capital cost, and avoids the remixing phenomenon,
thus contributing to its thermal efficiency. However, it is diffi-
cult to develop a systematic mature design method for the
Petlyuk column and to deal with the problem of pressure bal-
ance between the prefractionator and the main column, leading
to only few industrial applications of this column.
The dividing-wall column (DWC) has been developed from
thermally coupled distillation and widely employed in chemical
industry [2–6]. As shown in Fig. 2, the DWC, thermodynami-
cally equivalent to the fully thermally coupled distillation col-
umn, integrates two columns into one shell and divides the
middle section into two parts by inserting a vertical wall. The
left-side section of the dividing wall is similar to the prefractio-
Chem. Eng. Technol. 2018, 41, No. 3, 517–523 ª 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com
Erwei Song, Dr. Erqiang Wang
University of Chinese Academy of Sciences, School of Chemistry and
Chemical Engineering, No. 19 Yu Quan Road, 100049 Beijing, China.
Figure 1. Scheme of the Petlyuk column.
Figure 2. Scheme of the dividing-wall column.