Design for Partial Control

Once the most appropriate reactor system has been chosen, the next important design issue to consider is how to provide enough manipulated variables to ensure adequate partial control. The first step in this 

Economic Objectives. Yp Throughput Conversion Yield Selectivity Composition Molecular weight Viscosity 

Arbel et al. (1997) give a detailed account of this procedure applied to a fluidized catalytic cracker FCC). They show that unit control is possible when only one of the four dominant variables is under feedback control. The effectiveness of the partial control scheme is limited in satisfying the economic objectives when only one dominant variable is in closed-loop control. Superior reactor performance is achieved when all four dominant variables in the reactor are used. However, this requires manipulated variables that were not part of older FCC designs. The new manipulators have been added on modern units to make 

Similarly, the uncertainties around the rate controlling step for the slurry reactor may also be dealt with through overdesign of the control system. In that case it may be prudent to provide a couple of control loops that could control the addition of reactant gas through some high-pressure jet spargers or provide a variable speed agitator. 

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