ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Comparative evaluation of critical operating conditions for a tubular catalytic reactor using thermal sensitivity and loss-of-stability criteria

Gheorghe Maria and Dragoş-Nicolae Ştefan

Department of Chemical Engineering, University Politehnica of Bucharest, P.O. 35-107, Bucharest, Romania

E-mail: gmaria99m@hotmail.com

Received: 26 October 2009  Revised: 2 February 2010  Accepted: 5 February 2010

Abstract: Optimal operation of a chemical reactor according to various performance criteria often drives the system towards critical boundaries. Thus, precise evaluation of runaway limits in the parametric space becomes a crucial problem not only for the reactor’s safe operation, but also for over-designing the system. However, obtaining an accurate estimate for operating limits is a difficult task due to the limited validity of kinetic models describing complex processes, as well as the inherent fluctuations of the system’s properties (catalyst, raw-material quality). This paper presents a comparison of several effective methods of deriving critical conditions for the case of a tubular fixed-bed catalytic reactor used for aniline production in the vapour phase. Even though the methods being compared are related to one another, the generalised sensitivity criterion of Morbidelli-Varma (MV) seems to be more robust, not depending on a particular parameter being perturbed, when compared to the criteria that detect an incipient loss of system stability in the critical region (i.e., div-methods based on the system’s Jacobian and Green’s function matrix analysis). Combined application of div- and MV criteria allows for an accurate evaluation of the distance from the reactor’s nominal conditions to the safety limits.

Keywords: runaway boundaries - tubular reactor - aniline - sensitivity - stability

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-010-0035-5

Chemical Papers 64 (4) 450–460 (2010)