An operating economics-driven perspective on monitoring and maintenance in multiple operating regimes: Application to monitor fouling in heat exchangers

Process monitoring is required to ensure consistent product quality and safe operation. Equipment degradation leads to changes in the process model causing plant-model mismatch, e.g., fouling in heat exchangers. This is particularly important for slow drifting industrial processes, where monitoring just the process variables is insufficient, as controllers continuously seek to track key process variables to ensure that they adhere to strict design conditions, despite increased operating costs to compensate for the model degradation. An objective of this work is to develop a straightforward operating economics-driven monitoring algorithm to track process drifts and equipment degradation in multiple operating regimes by monitoring deviations in model parameters along with the states. A 2014 estimate put the economic cost of fouling in heat exchangers for US industries at $14 billion per year. To mitigate this expenditure, and highlight the importance of this work, illustrative examples involving both simulated synthetic data and experimental data from a double-pipe heat exchanger are used. Traditional state estimation methods are integrated with cost contours based on operating economics to accurately track equipment degradation by monitoring deviations in model parameters, even when drastic changes in input conditions are present. Tracking process drifts and equipment degradation while evaluating the economic impact helps determine the urgency of cleaning and maintenance that is required.