(507b) A Framework for Process Synthesis Integrated With Sustainability and Process Intensification

A Framework for Process
Synthesis integrated with Sustainability and Process Intensification

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

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

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

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

The objective of
process synthesis is to find the best flowsheet, among numerous alternatives for
converting specific raw materials to specific desired products subject to
predefined performance criteria. The unit operations concept is the one most
used for process synthesis because it allows to associate the operational tasks
with the processing route to be followed. This concept has been sufficient
until now, however, due to increasing demands on the chemical industry, such as
the design of sustainable/new processes, an extension of the current concepts by
considering lower levels of aggregation than the unit operations level as well
as sustainability is necessary. That is, when applying the unit operations
concept one automatically connects the unit operations with their function and
therefore this mode of thinking restricts the solution space to the limited
number of ?'well defined'' unit operations [1]. However, by incorporating a
sustainability analysis within process synthesis bottlenecks can be identified and
ordered in terms of those having the highest impact for improvement of the
process with respect to the environment. But within the solution space,
intensified and integrated unit operations must also be included in order to
achieve a targeted improvement. Therefore, by incorporating different levels of
aggregation at the flowsheet, the unit operations, the task and the phenomena
levels, the opportunity to innovate is provided.

Different
methods have been developed which perform process synthesis incorporating
process intensification at the different levels [2, 3]. This work focuses on the
inclusion of a sustainability analysis as a means by which process bottlenecks
can be identified and the inclusion of the phenomena level [4] as a lower level
of aggregation in process synthesis. It should be noted that the degree of
complexity as well as the search space increases as one operates at the lower
levels of aggregation. For example, the considered process phenomena need to be
combined to perform the identified tasks and these combinations are then
translated into unit operations, which define the final process flowsheet. Therefore,
operating at the phenomena level allows one to include known as well as new intensified
unit operations as part of process synthesis.

The computer-aided
framework for process synthesis has been developed and it consists of 10
hierarchical steps exclusive of the intensification method. Steps 1-6 consist
of the problem and objective function definition, the investigation of whether
a base-case design exist or not. If no, flowsheet alternatives are generated
and screened using the means-ends analysis [2] and thermodynamic insights [5].
If yes, then this design is considered as a reference for further improvement/intensification.
Steps 7-8 consist of performing a sustainability analysis using data obtained
from rigorous simulation of the base case design, to identify process
bottlenecks. Having this information the phenomena-based synthesis (PBS) intensification
sub-method is entered. Steps 9-10 consist of equipment sizing and economic
evaluation followed by a further environmental and sustainability analysis for comparison
to the base case design.

The PBS
sub-method consists of 7 hierarchical steps. Steps 1-2 consists of metric
definition and translation which provide the system constraints related to
structural, logical and operational and process analysis where the system is
decomposed from the flowsheet level to the phenomena level. The thermodynamic
properties of the system [4] are also investigated in order to identify further
process bottlenecks. Steps 3-4 consists of identifying tasks and phenomena for
overcoming the process bottlenecks based on the thermodynamic insights gained
from the process analysis. The means-ends analysis together with the identified
phenomena which are connected, are used for generating the flowsheet
alternatives based on tasks and phenomena. These connected phenomena referred
to as operations are then translated to unit operations which fulfil process
requirements, whether traditional, existing or innovative PI equipment. In
translating the connected phenomena to unit operations a concept known as
S-Files, similar to SMILES for representing molecular information, is used in
order to store and easily retrieve from a knowledge-base the unit operations that
built the flowsheet. In case a unit operation cannot be found from a set of
connected phenomena then a design is proposed for a new unit operation. Steps
5-7 consist of stepwise screening the alternatives with respect to the
constraints set previously in Step 2 and optimizing for identifying the most
promising flowsheet.

In the proposed presentation
the computer-aided framework will be presented along with the tools and data
needed for its application, which will be highlighted through two case studies:
the production of methyl-acetate for verification of the framework and the
production of di-methyl-carbonate as an industrial example.

References

[1] H. Freund,
K. Sundmacher. Ullmann's Encyclopedia of Industrial Chemistry, Process
Intensification, 2. Fundamentals and Molecular Level. Wiley-VCH Verlag GmbH
& Co. KGaA, 2000

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

[3] 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

[4] P. Lutze, D. K. Babi, J. M.
Woodley, and R. Gani. Phenomena Based Methodology for Process
Synthesis Incorporating Process Intensification. Ind. Eng. Chem. Res. 2013 Special
Issue PSE-2012

[5] C. Jaksland, R. Gani, K. M. Lien. Separation
process design and synthesis based on thermodynamic insights. Chem Eng
Sci, 1995 (50) 511-530