Strategies for the Operation and Control of Heat Exchanger Networks

The continued high cost of energy has mandated that the Chemical Process Industries reduce operational and capital costs through process heat integration. However, the heat integration of process streams can lead to process structures that are difficult to operate and control. This paper addresses the control of heat exchanger networks and it shows the importance of dynamic simulations in the synthesis of workable control structures. Steady-state simulations were used to delineate the trade-off between flexibility and capital costs of networks. Dynamic simulations were used to assess the placement of the by-pass on the process-to-process heat exchangers. Steady-state simulations showed that the use of stream splitting should be avoided as a control scheme. For control purposes the methodology of Glemmstad and Gundersen’s (1998) was modified and improved upon in order to determine the degrees of freedom of a heat exchanger network. Heuristic rules were proposed to identify the best control strategy for a heat exchanger network.