The fresh C5 stream containing the reactive isoamylenes and the chemically inert other C5 components is fed into the reactor on flow control. The methanol fed to the prereactor is ratioed to the fresh feed flowrate. The exit temperature of the reactor is controlled using a temperature/temperature cascade structure. The reactor effluent temperature controller changes the setpoint of the circulating cooling water temperature controller, which manipulates the cooling water makeup valve (see Fig. 14.7).

In the Aspen Dynamics simulation, a valve must be installed between the reactor and the column. In reality, no valve is necessary if the reactor pressure can be the same as the

Figure 14.7 Control structure for prereactor and C1.

MeOH flow controlled

Figure 14.8 Control structure for C2 and C3.

column pressure. If it were necessary to keep the reactor pressure higher than the column pressure, a valve would be required. However, the valve in the C5 fresh feedline would have to be removed so that the first law of plumbing is not violated ("Never put two valves in series in a liquid-filled line."). The flowrate of the C5 fresh feed would have to be manipulated by using a variable speed pump instead of a valve.

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