Chemical Engineering and Processing: Process Intensification
Process synthesis for reactive separations
Introduction
The integration of chemical reaction and physical separation in one single unit often leads to a significant reduction in investment and operating costs. The economic benefit may be caused by a reduction of raw material use, diminution of recycle streams by higher rates of conversion, improvements in selectivity and/or energy integration.
Due to this potential economic benefit there is a need to evaluate integrated reactive separations at a very early stage of the development of chemical processes. Unfortunately, a systematic evaluation of reactive separation units during process synthesis has not been established as common procedure.
Although knowledge has been generated and published about the synthesis of dedicated reactive separations like reactive distillation a general approach to the synthesis problem has not been addressed so far [1], [2].
One major reason might be that due to the combination of two or more physical and chemical phenomena the degrees of freedom to obtain a feasible and economic operating point of the process unit are limited. Besides the traditional considerations of process selection this requires an additional evaluation whether the chemical and physical needs allow the use of a reactive separation. Due to this increased complexity most of the research work published refers to single integrated reaction and separation units (IRS units). Moreover, authors rather focus on the design of stand-alone IRS units than on the whole process in which these reactive separations are used. However, in order to evaluate the real benefit of an IRS unit the whole process including all additional process steps (e.g. additional separations) has to be designed and economically assessed.
The aim of this paper is to present on the one hand a strategy to integrate the evaluation of IRS units in a process synthesis environment. On the other hand it introduces a general process synthesis procedure which is independent from specific separation effects applied in the unit.
Section snippets
Stand-alone synthesis and design of IRS units
In order to rate the potential advantage of using a reactive separation in a chemical process two steps have to be performed. At first the chemical reaction system has to be analyzed whether an IRS unit may improve the performance of the reaction unit only. Then the designer has to check whether the use of such a unit enhances the whole chemical process. This section deals with the process synthesis of reactive separations disregarding any effect on the other down- or upstream-process steps.
Synthesis of IRS units in the framework of conceptual design of total flowsheets
Regarding the overall performance of a chemical process the introduction of an IRS unit might contribute to the economics by addressing different effects:
- •
Chemical reaction aspects
- •
Separation aspects
- •
Energy integration aspects
Improving the chemical reaction by increasing the conversion rate and/or the selectivity affects all up-stream and down-stream units. On the one hand the throughput might be lowered while producing the same amount of desired products in the plant. On the other hand the
Conclusion
The process synthesis procedure presented does not guarantee to find the one single optimal flowsheet operated at the optimal conditions. But its pragmatism leads to feasible and economic flowsheet options in a limited amount of time. It allows the designer to evaluate the performance of IRS units in a very early step of process development when often only qualitative information about the chemical and physical behavior of the chemical components are available. The method presented might
Acknowledgements
The authors like to thank the Deutsche Forschungsgemeinschaft for the financial support of the research work reported here.
References (18)
- et al.
Industrial application of multi-functional, multi-phase reactors
Chem. Eng. Sci.
(1999) - et al.
A continuous chromatographic reactor; SMBR
Chem. Eng. Sci.
(1996) - et al.
Reactive distillation by design
Trans. J. Chem.
(1992) - et al.
High-purity methyl-acetate via reactive distillation
Chem. Eng. Prog.
(1990) - et al.
Entwicklung membranunterstiltzter Reaktionsprozcssc
Chem. Ing. Tech.
(1996) Phase equilibrium chemical engineering
(1985)Chemical reaction engineering
(1999)- B. Fried, Regelbasierte Auswahl grundlegender Reaktortypen mittels wissensbasierter Programmierung, Dissertation...
- U. Westhaus, Beitrag Auswahl chemischer Reakoren mittels heuristischer-nurnerischer Dissertation Universitat Dortmund,...
Cited by (86)
Methanol compared to other fuels for on-board hydrogen production in thermally balanced membrane reactors with internal recycle
2024, Chemical Engineering and Processing - Process IntensificationEconomic comparison of reactive distillation (RD) to a benchmark conventional flowsheet: Regions of RD applicability and trends in column design
2023, Chemical Engineering Research and DesignOperating windows for early evaluation of the applicability of advanced reactive distillation technologies
2023, Chemical Engineering Research and DesignCitation Excerpt :Although engineers’ knowledge can significantly reduce the effort of gathering information to support decision-making, Steimel et al. (2014) showed that the use of operating windows facilitates the collaborative collection of information. The overlap between the reaction, separation and apparatus operating windows determines the feasibility of a flowsheet (Schembecker and Tlatlik, 2003; Kiss, 2019). Tylko et al. (2006) provide a graphical description of the level of integration of functionalities based on the overlap of the reaction and separation windows (Figure S1, Supplementary Information).
Demonstration of applied linear model predictive control for an enzymatic reactive dividing wall column
2022, Chemical Engineering Research and DesignAsymmetric 5-sulfosalicylic acid-PVA catalytic pervaporation membranes for the process intensification in the synthesis of ethyl acetate
2022, Separation and Purification TechnologyEvaluation of process integration for the intensification of a biotechnological process
2021, Chemical Engineering and Processing - Process Intensification