(304a) Process Intensification of the Production of Di-Methyl Carbonate (DMC) Using a New Synthesis and Design Process Intensification Methodology

Process
Intensification of the production of Di-Methyl Carbonate (DMC) using a New Synthesis
and Design Process Intensification Methodology

Deenesh
K. Babi¹, Johannes Holtbruegge², Philip Lutze²,
Andrzej Górak², John M. Woodley¹, Rafiqul Gani¹

dkbabi@kt.dtu.dk, johannes.holtbruegge@bci.tu-dortmund.de, philip.lutze@bci.tu-dortmund.de, andrzej.gorak@bci.tu-dortmund.de jw@kt.dtu.dk, rag@kt.dtu.dk

¹ Department of Chemical and
Biochemical Engineering, Technical University of Denmark (DTU), DK-2800 Kongens
Lyngby, Denmark

² Department of Chemical and
Biochemical Engineering, Technical University of Dortmund (TU
Dortmund), D-44227 Emil-Figge-Str. 70 Dortmund

Abstract

Process
Intensification (PI) is a means by which processes, whether new or existing,
can achieve a more efficient and sustainable chemical
process through the improvement of, for example, energy efficiency and waste
generation. PI can be defined as the improvement of a process at the phenomena
level which ultimately has an impact at the higher levels of a process, that is
the functional and unit operations (Unit-Ops) levels. More specifically PI is the
enhancement of the involved phenomena through the integration of Unit-Ops, functions
and phenomena. Except for reactive distillation and dividing wall columns, the
implementation of PI still faces hurdles [1]. For achieving PI via a systematic
approach different methodologies exist, of which two are mentioned here, the
task-based means-ends analysis developed by Sirrola [2] and the Unit-Ops based
synthesis and design method for achieving PI developed by Lutze et al. [1]. These
methods, which work at the Unit-Ops level, are limited to PI equipment already
in existence and are therefore able to generate new integrations/combinations
of intensified existing equipment but may not generate new/innovative PI
solutions.

The objective of this work is threefold: (1) the development
of a new/innovative systematic PI synthesis and design methodology, which
includes model based synthesis/design and experimental based validation; (2)
the development of a phenomena based synthesis and design method (PBS) which in
addition to the knowledge-based (KBS) and Unit-Ops based (UBS) methods (thereby
extending further, the application range) is one of the methodologies within
the new PI methodology; and (3) the application of the new PI methodology to a
case study - the production of di-methyl carbonate (DMC).

The new PI methodology has the following
characteristics: (a) flexible for a wide range of applications (b) finds
innovative (new) and predictive (existing) solutions and (c) model and
experimental based validation of intensified options. The new PI methodology
follows a systematic decomposition approach starting with a base case as a reference
point. In Step 1 a general problem definition is determined. In Step 2 system
information is collected based on thermodynamic data and the type of chemical/process
systems that are identified. Using this data, the process is analysed and in
Step 3, it is possible to use one or two or all of the PI methods. The three synthesis
and design methods considered are the KBS, the UBS and the PBS. The KBS and UBS
methods use knowledge stored in a knowledge-based tool on implemented PI
equipment used for overcoming certain limitations/bottlenecks (LB's), for
example, the use of reactive distillation for overcoming unfavourable
equilibrium in a reaction. The PBS methodology not only uses the knowledge of
the existing methodologies at the Unit-Ops level but also operates at a lower
level of aggregation (i.e phenomena level), where the apriori knowledge of
existing Unit-Ops is needed to some degree but also where new Unit-Ops, in
principle, can be designed. In Step 4 the feasible flowsheets obtained from
Step 3 are validated/ verified either through a model or experimental based analysis.
At the end of Step 4 the best PI process candidate and the other feasible
options are used to update the systems information. It should be noted that the
degree of complexity increase from the KBS to PBS while the possibility of
obtaining/generating novel PI equipment decreases from PBS to KBS.

A preliminary version for a phenomena-based
synthesis/design (PBS) methodology has been developed [3] and consists of a six
step workflow: Problem and objective function definition→
Process analysis using thermodynamic insights→
Identification of LB's of the process together with the
desirable and accompanying phenomena to overcome these LB's→
Phenomena building blocks are connected to form
simultaneous phenomena building blocks (SPBs) which are screened for the most
feasible connections using for example connectivity rules. The SPB's are then
connected to form operations which are then connected to form flowsheets just
as atoms are combined to form molecules→ Flowsheets are first screened using for example logical constraints
and performance metrics to obtain feasible PI options→ The
feasible flowsheets from are optimized with respect to
the objective function with the end result being the identification of the best
intensified process candidate. The emerging flowsheets consists of either novel
or existing PI equipment. Defined phenomena are for example mixing, two-phase
mixing, phase transition and phase separation. This preliminary version is now
extended and implemented within the general PI synthesis design methodology.

In this presentation the PI synthesis and design
methodology with focus on the PBS workflow will be highlighted together with
the details of its application to the production of DMC. DMC is an important
bulk chemical used as a solvent and fuel additive. It will be shown that the PBS
methodology systematically generates, besides other options, the current intensified
option proposed by the co-authors who have followed the UBS path of the combined
methodology and is as follows: a reactive distillation column→ membrane separation →distillation.

References:

[1] P. Lutze, A. Román-Martinez, J. M.
Woodley & R. Gani. A systematic synthesis and design methodology to achieve
process intensification in (bio) chemical processes. Comput. Chem. Eng. 2012
(36) 189? 207

[2] Jeffrey J.
Siirola. Strategic process synthesis: Advances in the hierarchical approach.
Comput. Chem. Eng. 1996, Supplement 2 (20) S1637-S1643

[3] P. Lutze, R. Gani & J. M. Woodley. Phenomena-based
Process Synthesis and Design to achieve Process Intensification. Comp. Aided
Chem. Eng. 2011 (29) 221?225