Effects of fouling on performance of retrofitted heat exchanger networks: A thermo-hydraulic based analysis

In refineries, fouling in crude pre-heat trains (PHTs) causes several thermal-hydraulic inefficiencies which lead to increased operating costs (from reduction in throughput and extra fuel burnt at the furnace), carbon emissions, and maintenance issues. The energy recovery performance of PHT can be severely affected over time. Such time varying effects are normally not considered in the design or retrofit of heat exchangers networks. In this paper, an existing PHT network is simulated including its fouling behaviour of over ca. two years. For this purpose, a dynamic, distributed mathematical model for shell-and-tube heat exchangers undergoing crude oil fouling (developed and validated against refinery data in previous work) is used. Three retrofit options aimed at maximizing overall heat recovery are proposed. Simulation results show that networks designs that maximize energy recovery in clean conditions (following traditional pinch rules) may not be best when fouling occurs and that a proper retrofit design must include consideration of time varying fouling effects.

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