On a New MILP Model for the Planning of Heat-Exchanger Network Cleaning. Part III: Multiperiod Cleaning under Uncertainty with Financial Risk Management

This paper is a follow-up to a two-part paper on the scheduling of heat exchanger network cleaning. In the first part (Lavaja, J. H.; Bagajewicz, M. Ind. Eng. Chem. Res. 2004, 43, 3924-3938), a new mixed-integer linear model for the planning of heat-exchanger cleaning in chemical plants was presented, where the net present cost is minimized by carefully choosing the appropriate cleaning schedules. In the second part (Lavaja, J. H.; Bagajewicz, M. Ind. Eng. Chem. Res. 2005, 44, 80468056), throughput loss was added to the model, thus allowing the throughput to be reduced when convenient. Because of the high importance of financial risk in almost any industry and the presence of uncertainty in some of the parameters involved in the operation of heat exchanger networks, a stochastic version of the model was developed and applied to crude fractionation units. The model considers uncertainty not only in the future price of the natural gas expended in the furnace but also in the actual value of the fouling rates of the crudes and in the schedule of change of feedstock during the operation.