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Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Volumes per year:

various

Year 2006

DOI: 10.1615/IHTC13.p26

THERMAL OPTIMIZATION AND STABILITY OF A FIXED-BED CATALYTIC REACTOR − AN APPLICATION TO ETHYLENE OXIDE PRODUCTION

S. Ghaffari
Department of Chemical Engineering, University of Sydney, Sydney, Australia

O. Galan
Department of Chemical Engineering, University of Sydney, Sydney, Australia

V. Gomes
Department of Chemical Engineering, University of Sydney, Sydney, Australia

K. Ngian
Huntsman Corporation, NSW, Australia

J. Romagnoli
Department of Chemical Engineering, University of Sydney, Sydney, Australia

ABSTRACT

This work presents the first stage towards the optimal and stable operation of a full-scale fixed-bed catalytic reactor for the ethylene oxide (EO) production process. The chemical reactions involved in the synthesis of ethylene oxide are highly exothermic making the internal temperature control of this unit a challenging task. Moreover, temperature excursions at dangerous levels (i.e. hot-spot or runaway conditions) have been experienced due small variations in the reactor's operating conditions. Therefore, the thermal dynamic optimization of this process must be performed synergistically with a stability criterion as constraint. We tackled this study developing a one-dimensional heterogeneous model for the multi-tubular fixed-bed reactor where only external heat and mass transfer resistances are significant. Also, our model includes catalyst deactivation and the addition of an inhibitory chemical 1, 2-dichloroethene (DCE) that moderates the reaction rates, controlling the heat generation while the exothermic reactions take place. Thus, the thermal optimization of this specific reactive system involves the addition of DCE and the coolant (thermal oil) inlet temperature as decision variables. The dynamic model predictions were benchmarked against plant data, resulting in good correlation between them. A reactor runaway event was simulated when arbitrary selection of the operating conditions is implemented. Thus, the optimal profiles for inlet coolant temperature and inhibitor inlet concentration can be used to prevent reactor runaway and maximize product selectivity. The effects of simultaneous inter-intra particle mass and heat transport, catalyst geometry and other variables for this reactive system will be studied in future work.