DV L

a beneficial effect on the net reaction rate that might result in an effective decrease in the liquid leaving a reactive stage. If this effect is substantial enough, it will result in a change (dB\

of sign of — and, therefore, satisfy condition (8.6) and result in an output multiplicity.

V dLJ y

Figure 8.5 shows a section of the bifurcation diagram for constant reflux rate in the 17 stage MTBE column described in Table 8.2. Multiple steady states exist for boilup rates of 80-82 kmol/hr if the simulation model includes the energy balance for each theoretical stage but only one steady state if the results are obtained with a CMO model. The offset between the two curves is also a result of the exclusion of energy balances as the heat of reaction is not considered in the CMO case. The cause of the observed multiplicity can be seen in Figure 8.6 which shows the influence of the energy balance on the relationship between the boilup rate and the distillate rate for the same section of the bifurcation diagram. Condition (8.7) is satisfied at boilup rates of 80-82 kmol/hr with the energy balance model while always greater than zero with the CMO model.

Figure 8.5 - Multiple Steady States Caused bv the Energy Balance

Boilup (mol/min)

Figure 8.6 - Effect of Molar Boilup on the Distillate Product Rate

Boilup (mol/min)

Figure 8.6 - Effect of Molar Boilup on the Distillate Product Rate

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