Ternary BTX System

STEADY-STATE CALCULATIONS FOR CONTROL STRUCTURE SELECTION 

The SVD results are similar to the sensitivity results. They indicate that Stage 21 can be controlled by reflux and Stage 23 by heat input. The singular values of the steady-state gain matrix are Ti =9.14 and T2 = 0.518, which gives a condition number CN = (Ti/(T2 = 17.6. This indicates that the two temperatures are not nearly as independent as in the propane/isobutane system, so a dual-temperature control scheme may not be as 

For changes in the benzene/toluene ratio in the feed, the results show that the temperature on Stage 27 does not change for constant product impurities. So if this is the type of feed composition disturbance expected, controlling Stage 27 should provide effective control. 

However, for the change in the xylene concentration of the feed. Stage 27 changes almost 3 K. 

The justification for choosing constant reflux as opposed to constant reflux ratio is given in the middle three rows of Table 6.2. The required changes in reflux flow rate are 

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