Exergy Analysis as a Thermodynamic Tool for Gaining New Insights into Chemical Processes

Exergy Analysis as a Thermodynamic Tool for Gaining New Insights into Chemical Processes: Demonstrated on the SNC Pernis Isopropylalcohol Process

Blokker, W.R.
Molenaar, P.

de Swaan Arons, J. (mentor)
van der Kooi, H.J. (mentor)
Mooiweer, A.L. (mentor)
Iwema, K.A. (mentor)
Schoonakker, M.C. (mentor)
van Diepen, P.B.J. (mentor)
Donkers-Dijken, M.R.G. (mentor)
Scholes, G. (mentor)

Applied Sciences

Chemical Engineering and Materials Science

1998-02-19

This thesis demonstrates how exergy analysis can be used to gain new insights into chemical processes. Exergy analysis has been applied to the SNC Pernis Isopropylalcohol process in order to introduce the concepts of exergy and exergy analysis together with its applications to Shell personnel and to show the strength and the usefulness of an exergy analysis in the chemical industry. These objectives have been met by using exergy analysis as a tool for identifying the weaknesses of the SNC Pernis Isopropylalcohol process (COF/3) with regard to exergy utilization by locating and quantifying the main exergy losses, by interpreting and understanding the reasons and causes of excessive exergy losses and by introducing and investigating possible solutions to reduce those losses and to conserve exergy as long as possible. Exergy analysis has proved to be an invaluable thermodynamic, diagnostic tool for process analysis. Exergy analysis provides clear insights into a chemical process and should therefore preferably be used in the design phase of new process designs. The strength of exergy analysis lies in the fact that it is able to direct research and new thinking in order to develop new processes based on minimal exergy consumption and that it covers all aspects relating to process. Analysis of the exergy utilization of the IPA-cbm/IPA section of the COF/3 plant shows that the main exergy losses arise as a result of the original process design: the choice of a reaction route with low conversion to isopropylalcohol and the maintenance of a large water recycle in the separation sections. Potential improvements include, the choice of a reaction route based on the partial oxidation of propane; to reduce the size of the water recycle, a unique combination of a membrane and a heat-pump is proposed. As far as is known such a combination has never been applied on an industrial scale; the use of membranes as an end-of-pipe solution to break the water/IPA azeotrope; the installation of a hot water plant possibly in combination with a heat transformer and the installation of heat pumps. The analysis of the DMK/MIBK section of the COF/3 plant shows that, from an exergetic point of view, the use of DMK originating from the cumene oxidation process is unfavourable compared to the DMK produced in the COF/3. Also a capacity enlargement of the after reactor rather than the direct route reactor should be preferred for the production of MIBK. Finally the replacement of the current heat integration to drive the reboiler of the finished DMK column has been investigated. The essential conclusion of this graduation project is that exergy analysis provides a more fundamental approach to the analysis of chemical processes.

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Student theses

student report

(c) 1998 W.R. Blokker, P. Molenaar