Time min

Figure 7.1- Open Loop Response to a Step Increase in the Feed Rate

7.4.1.2 Step Change in Feed Composition

Figure 7.2 shows the transient response of the same column after the feed composition was adjusted to increase the ratio of ethanol to isobutene by 2%. The total molar feed rate was fixed as were the pressure, reboiler duty and reflux rate. The responses were essentially first order under this scenario and the permanent responses became fully evident after about 40 minutes. The isobutene conversion increased slightly by the additional driving force for the reaction but ether purity decreased as the ethanol content of the bottoms product increased without additional heat input. The bottoms temperature followed the composition changes as phase equilibrium was maintained.

100%

158 157 156

30 60 90 120

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