Model-based monitoring of thermal-hydraulic performance of refinery heat exchangers undergoing fouling

Abstract

Monitoring of fouling is key to assess the performance of refinery heat exchangers, estimate resulting economic costs, and assist in planning of mitigation and cleaning. Such monitoring typically addresses just thermal performance, while hydraulic limitations are often also important. A dynamic thermo-hydraulic plot (TH-λ) for simultaneous monitoring the thermal and hydraulic performance of heat exchangers was recently presented. The features and benefits of the plot were illustrated for fixed inlet conditions. In this work, a model-based monitoring solution is presented which enables the application of the TH-λ plot with time-varying inputs. The TH-λ concept is integrated with a software framework that describes a shell-and-tube heat exchanger using a high-fidelity dynamic, distributed system model undergoing fouling. A method is presented to decouple the variations in exchanger performance due to changes in inlet conditions from those due to changes in fouling rates and/or deposit properties. The method and its benefits are illustrated with a case study using typical refinery data.