Mitigation of crude oil refinery heat exchanger fouling through retrofits based on thermo-hydraulic fouling models

摘要

Crude oil fouling in refinery preheat exchangers is a chronic operating problem that compromises energy recovery in these systems.Progress is hindered by the lack of quantitative knowledge of the dynamic effects of foling on exchanger heat transfer and pressure drop.The ocncept of a thermal 'fouling threshold',first introduced by Ebert and Panchal,is revisited here alongside models of hydralic effects of fouling to provide a graphical tool,the modified tmeperature field plot,for assessing chronic chemical reaction fouling effects in refinery heat exchangers.Fouling data of varying quality,collected from pilot plant and refinery heat exchangers.Fouling data of varying quality,collected from pilot plant and one based on the Epstein deposition model.The model by Epstein showed the best agreement,primarily because it can accommodate fouling that is mass transfer as well as reaction controlled.The hydraulic analysis indicated that the simple slab approximation for fouling layers gave a resonably good mapping between heat transfer and pressure drop effects as long as roughness contributions are not significant.Where roughness effects (for tube blockage)are important,the relationship between thermal and hydraulic performance is not straightforward.A case study,based on the network described by Panchal and Huang-Fu,is used to illustrate the thermo-hydraulic effects of fouling and the application of the modified temperature field plot.