Advances in Systematic Creativity by Leonid Chechurin & Mikael Collan

Author:Leonid Chechurin & Mikael Collan
Language: eng
Format: epub
ISBN: 9783319780757
Publisher: Springer International Publishing

Fig. 3Control space analysis when disturbance variables are taken into account. MV1 is the water addition rate (around the nominal value of 90 L/h), MV2 is the air addition rate (around the nominal value of 300 L/h)

How can the process design be altered in order to meet the controllability requirements? There are several alternatives to change the process requirements. The first option is to allow more variation in the design space (range of CVs). However, this option is often the last choice or compromise, as the intensification targets cannot be fully achieved. The second option is to expand the ranges of the MVs. It should be noted that there might be physical limitations to the manipulated variables, which eventually determine the allowable range. For example, in Fig. 3, it can be seen that the range of MV1 should be expanded by setting the lower limit to −280 with respect to the nominal value. However, Table 2 depicts that the nominal value is 90 and the current minimum value is zero. Evidently, a negative water addition rate (L/h) cannot be established and the expansion of MV1 range is not possible in this case. The third option is to control the upstream disturbances by some other means, hence reducing their effect in the inspected sub-process. This approach requires availability and expertise of plant-wide interactions, and may be beyond the process concept evaluation. The fourth option is to discard the proposed set of variables and try a different set of MVs (and possibly CVs). If none of these lead to a controllable process, the process concept studied cannot be seen as feasible from the process operation point of view.

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