ONLINE OPTIMIZATION AND CHOICE OF OPTIMIZATION VARIABLES FOR CONTROL OF HEAT-EXCHANGER NETWORKS

The paper discusses optimal operation of a general heat exchanger netw ork with given structure, heat exchanger areas and stream data includi ng predefined disturbances. A method that combines the use of steady s tate optimization and decentralized feedback control is proposed. A ge neral steady state model is developed, which is easily adapted to any heat exchanger network. Using this model periodically for optimization , the operating conditions that minimize utility cost are found. Setpo ints are constant from one optimization to the next, and special atten tion is paid to the selection of measurements such that the utility co st is minimized in the presence of disturbances and model errors. In a ddition to heat exchanger networks, the proposed method may also be ap plied to other processes where the optimum lies at the intersection of constraints.