Bypass Design for Control and Optimization of Heat Exchanger Networks

Disturbance propagation during a HEN operation may make the control difficult if the HEN is improperly design. Utility flow rates and bypasses are widely used for effective control of process stream target temperatures, but the number of utility units is usually much less than the number of process streams in the network. This paper addresses the optimal bypass design in heat exchanger networks. It consists in a model-based iterative procedure considering a worst-case disturbance rejection with minimum economic penalty. The methodology is demonstrated using a case study with 3 different structures, making possible a comparison between different options on a quantitative basis, taking into account the optimal operation attainable with minimum total annual cost.