Maintain Peak HEN Performance Under Fouling Conditions Using New Approach for Optimum HX Cleaning Strategy

A new approach is presented for determining the optimum HX cleaning strategy in HEN subject to fouling, as is commonly found in oil refineries.

The strategy consists of the following key elements:

• Developing a high fidelity (hi-fi) simulation model for the HEN that includes individual heat exchangers on a tube-by-tube basis and pressure drop (vibration) constraints
• Validating the model against plant data – estimating phase and predictive phase
• Extracting HX fouling parameters, fitted to either a polynomial model or a modified Ebert-Panchal Model, as applicable
• Using the validated hi-fi simulation model to develop optimum HEN cleaning strategy with the goal of maximizing average heat recovery and minimizing utility costs and carbon emissions, within equipment and pressure-drop constraints

The final output from the analysis includes:

• A cleaning schedule for individual HX shells and the method to be used (chemical wash, mechanical cleaning – soft versus hard deposits)
• Estimated maintenance costs for HX cleaning
• Estimated impact on throughput, balancing production loss during HX cleaning against gain after cleaning
• Estimated reduction in utility costs
• Recommendations for mechanical modifications to individual HXs to improve overall HEN performance, such as changing number of tube passes, switching fluids between shell and tube side, adding tube inserts, helical baffles, twisted-tube bundles, etc.
• Recommendations for retrofit changes to the HEN configuration - matches, piping, bypasses, controls, etc.
• Recommendations for replacing existing HX (usually S&T) with more compact designs such as Plate, Spiral and Compabloc