Oscillatory Behavior

For the MTBE process also oscillatory behavior was reported in the literature. Potential sources for such an oscillatory behavior are either unwanted periodic forcing (e. g., by badly tuned controllers), fluid dynamic instabilities, or instabilities of the concentration dynamics.

Fluid dynamic instabilities were reported for the MTBE process by Sundmacher and Hoffmann [104]. The cycle times for fluid dynamic oscillations are typically in the order of minutes. They may occur in the reactive as well as in the non-reactive case.

In contrast to this, for concentration instabilities the cycle times are typically in the order of hours depending on the size of the column. Concentration instabilities for the MTBE system were reported by Schrans et al. [93] and by Hauan et al. [37]. Again, operating conditions were considered with the MTBE process close to chemical equilibrium. A more detailed analysis reveals, that the regions with oscillatory behavior in the space of the adjustable operating parameters are fairly small, again. This is in contrast to the ethylene glycol process considered above. Further, it is worth noting, that, as expected, no concentration oscillations were found for MTBE as well as TAME production in the kinetic regime of the chemical reaction [73, 74].

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