The control strategy illustrated in Figure. 14-2 can be developed starting with the loops “closest” to the process. Because virtually all controllers that operate final control elements manipulate flow in order to control another parameter, the application of flow controls should be considered first, followed by the management of volumes, and finally, the control of composition.
As was previously stated, most manipulated variables are flows, which in this application include:
• liquid flow to the next process,
• steam flow to the jet, and
• steam flow to the reboiler.
The cooling water flow to the condenser is an additional, manipulated variable that is ignored because the cooling water will be manually balanced. ...