(99b) Identifying the Causes of Acute Fouling in Refinery Preheat Trains

Fouling deposition on heat transfer surfaces is a costly, long-standing problem particularly severe in pre-heat trains of crude distillation units [1]. Experimental analysis of fouling deposits collected upon dismantling such heat exchangers shows that both organic and inorganic species are typically present. These vary in proportion depending on the crude slates processed, refinery operating conditions, heat exchanger metallurgy and dominant fouling mechanisms. It has also been shown that the heat transfer given by fouling depends on the amount of the inorganic and organic phases, their structural arrangement and stratification or layering.

This paper presents a novel advanced mathematical model, implemented in Hexxcell Studio™, capable of describing the fouling deposit layer as a multi-component structure [2, 3, 4]. It is then shown how this approach allows to detect the fouling layer composition using plant data (i.e. temperature, flowrates and pressures). The improved capabilities in monitoring, troubleshooting and prediction that can be achieved with this approach are also demonstrated.

References

[1] Coletti, F. and Hewitt, G.F. (2014). Crude Oil Fouling, Deposit Characterization, Measurements, and Modeling. Gulf Professional Publishing. ISBN: 9780128012567

[2] Coletti, F. and S. Macchietto (2011). A dynamic, distributed model of shell–and–tube heat exchangers undergoing crude oil fouling. Ind. Eng. Chem. Res. 50 (8): 4515–4533.

[3] Diaz-Bejarano E, Coletti F, Macchietto S, (2016). A New Dynamic Model of Crude Oil Fouling Deposits and Its Application to the Simulation of Fouling-Cleaning Cycles, AIChE J., 62(1):90-107.

[4] Diaz-Bejarano E., F. Coletti, S. Macchietto (2016). Impact of complex layering structures of organic and inorganic foulants on the thermo-hydraulic performance of a single heat exchanger tube – a simulation study. Ind. Eng. Chem. Res. 55 (40), pp 10718–10734.