Feedforward on Feed Rate

While these figures show that both MVs need to change with feed rate this does not necessarily imply that feedforward control should be configured. It would be quite common for one variable to be under tray temperature control and the other ratioed to 

Dynamic compensation is likely to be necessary to ensure that the reflux and steam flows are adjusted at the right time. The method for tuning these deadtime/lead-lag algorithms is described in Chapter 6. Part of this procedure involves steptesting the DV, in this case feed rate, to obtain the dynamic response of the PV, in this case tray temperature. This can present a problem on some columns. 

In the same way that we showed that two composition controllers interact, so will feedforward control. While it is correct at steady state to maintain a constant ratio between MVs and feed rate it is likely to be the case that the two MVs should not be changed at the 

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