(29a) Evaluation, Prediction, Management and Mitigation of Fouling in Heat Exchanger Networks for Improved Energy Efficiency

Energy efficiency and production in oil refineries are greatly affected by fouling, the progressive build-up of unwanted material on the heat exchanger surfaces. Fouling in crude pre-heat trains is a long-standing issue, estimated to cost over US$22 million per year to medium-small size (100,000 bbl/day) refineries [1]. Not only this is a very costly problem but it also leads to increased maintenance, health&safety risks and environmental impact of operations.

Traditional design methodologies neglect the dynamics of the fouling process and, as a result, heat exchangers are often performing poorly in the field. Moreover, even when good design and operating practices are followed and mitigation technologies are in place, very often fouling cannot be completely eliminated. As a result, it is necessary to carry out periodical cleaning and carefully plan maintenance to ensure minimum disruption to operations and maximum benefit not just from a thermal but also from a hydraulic point of view.

In this presentation, three industrial case studies are presented using Hexxcell Studio™, a novel thermo-hydraulic fouling analysis and prediction simulation software. The first case study illustrates how it is possible mitigate fouling by improving the design of individual heat exchangers and pre-heat train networks. The second shows how it is possible to capture the fouling behaviour from plant data, accurately monitor thermal and hydraulic performance of the network and quickly detecting abnormal events (e.g. carryover of inorganics from the desalter). Finally, the third case study illustrates the benefits of accurately assess the techno-economic trade-offs between mechanical and chemical cleaning options and devise optimal cleaning schedules that minimse the costs of fouling and its impact on operations.

[1] Coletti, F., Joshi, H. M., Macchietto, S., Hewitt,G. F. (2014). Introduction to Crude Oil Fouling. In: Coletti, F. and Hewitt, G.F. (Eds), Crude Oil Fouling, Deposit Characterization, Measurements, and Modeling. Gulf Professional Publishing (Elsevier). ISBN: 9780128012567.