**5. Conclusions**

ethyl-hexanal input is considered along with the process parameter variations. Good

**Figure 22.** Output temperature evolution—robust controller: nominal vs. uncertain considering a reference step varia-

Another performance that needs to be evaluated is the ability to counter act the catalyst

By analysing all the results obtained in the previous it can be concluded that even considering the catalyst deactivation steady-state errors of 0.006% and 0.18% are achieved for the output temperature and 2 ethyl-hexanol concentration, which are clearly within acceptable limits making the robust control strategy the most suitable for 2 ethyl-hexanal hydrogenation

tion of the 2 ethyl-hexanal input

deactivation (**Figure 23**).

**Figure 23.** Catalyst deactivation: robust controller.

process control.

performances are reached even in the case of the uncertain plants (**Figure 22**).

The developed model of the hydrogenation process, presented in this chapter, is able to represent the dynamic behaviour of the reactor during operation. Real plant data was used for mathematical model validation. From the dynamic point of view, the system behaves as an element with a large time constant and a large time delay. Hydrogenation multiphase catalytic reactors have complex behaviour and from this point of view, the use of advanced control strategies together with online optimization techniques appears to be a suitable procedure to deal with the problem of operating at high level of performance and safety.

A possibility to describe the processes which occur inside the reactor by a linear nominal transfer matrix and uncertainty description is detailed. A practical method for obtaining the uncertainty description is also presented. Three control strategies are proposed, developed, implemented and tested.

Finally, a comparison between the advantages and disadvantages of the proposed control solutions is performed.
