(449j) Study on the Distillation Sequence with Dividing Wall Column

Study on the Distillation Sequence with Dividing Wall Column

Zengzhi Du^a,
Jianhong Wang^a, Chi Zhai^a, Yunlu Zhang^a, Zhexi
Zhu^a, Wei Sun^a*,

^a China Beijing Key Lab of Membrane Science and
Technology, College of Chemical Engineering, Beijing University of Chemical
Technology, 100029 Beijing, China

Abstract

As an important separation
unit, distillation column is widely applied in petrochemical and other process
industry. It is reported that there are over 40,000 distillation columns all
over the world¹. Despite its flexibility and widespread use, one
important concern is its considerable energy consumption, as distillation can account
for more than 50% of plant operating cost. Therefore a large number of researchers
have been concentrated on energy-efficient distillations. For the separation of
multi-component mixtures, distillation sequence is required in industry. Dividing
wall column (DWC), as a thermally coupled distillation column, has been
proposed and applied in distillation sequence². It is an atypical
distillation column with an internal, vertical partition wall, which
effectively accommodates two conventional distillation columns into one shell, for
separating a multi-component feed mixture into pure products. For three
components separation process, there are two columns, two condensers and two
reboilers in conventional distillation sequence, while only one DWC with a
condenser and a reboiler can be achieved. Compared with conventional distillation
column, about 30% energy and equipment investment cost can be saved by DWC³.
Until now, it is reported that the number of applications of DWCs have exceeded
100⁴.

Distillation
sequence has been well studied based on simple column series, by which an
overall optimization at both process and equipment levels can be achieved. A
distillation sequence with DWC will give more number of feasible sequences,
which will increase computation load significantly. DWC may not be the best
choice for all three component mixture separations in terms of its physical
properties and feed composition. It will be more efficient to eliminate
distillation sequences with unnecessary DWC.

In this paper, the
influence of mixture and its component compositions on the operation of DWC is
systematically investigated based on the simulation implemented by gPROMS on
different mixture systems. The unnecessary DWC can be eliminated from
distillation sequences. Then, the optimal distillation sequence with DWC can be
efficiently identified.

Key Words: Dividing wall column; Distillation sequence;
Simulation

Reference:

1. Kiss, A. A., Design, Control
and Economics of Distillation. In Advanced Distillation Technologies, John
Wiley & Sons, Ltd: 2013, 37-65.

2. Wright, RO., Fractionation apparatus, United States
patent, US 2471134, 1949.

3. Triantafyllou, C., Smith, R.,
The design and optimisation of fully thermally coupled distillation columns:
Process design, Chemical Engineering Research & Design, 1992, 70, 118-132.

4. Asprion,
N.; Kaibel, G., Dividing wall columns: Fundamentals and recent advances. Chemical
Engineering and Processing: Process Intensification, 2010, 49 (2), 139-146.