Sharp Split Constraints

FIGURE 7.45 Difference point behavior for the sharp split Kaibel column. 

We also know from the geometric arguments above that X = X51 (for sharp sphts only), making Equation 7.32 reduce to 

Similarly, the material balance across the second side-draw stage with Xas = s2 (for sharp splits only) results in 

Equation 7.35 holds for all elements of x i and X52. Since Xsi Xs2 for certain elements (due to the product specification that have been set), the only possible solution for Equation 7.35 is 

FIGURE 7.46 Typical operating line for the Kaibel column operating at sharp spht condition. 

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One important issue that still needs attention is the objective function. It is intuitively obvious that if a separation cost is not associated with it, we will usually end up getting near-complete separations of products, and hence complete conversions to the extent possible within stoichiometric constraints. Thus the AR in concentration space can easily be the entire stoichiometric space. Unfortunately, it is difficult to get an accurate representation for the separation cost, e.specially when sharp splits are not enforced. Here, we present a simple cost model by assuming that the variable cost of separation is determined by two factors, namely, the difficulty of separation and the mass flow rate through the separator. 

Figure 25 presents the homopolymer data in a scaled form. The splitting into Q-dependent plateau levels is much more pronounced than for PI, a phenomenon resulting from a faster relaxation rate and somewhat stronger constraints. Again, the Ronca model represents an excellent description of the experimental data reproducing the line shape, i.e. the relatively sharp crossover and the... 

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