(166c) Crude Unit Fouling:Consequences and Costs

Heat exchanger fouling adds considerable cost to both crude unit construction and operation. Higher fouling shifts optimum heat recovery investment to higher capital and lower energy recovery.

Previous work [1] based on a literature identified reasonable fouling factors for commercial units. These factors are at last three times higher than the commonly used TEMA (Tubular Exchanger Manufacturer Association) values. For highly fouling crudes, the fouling factors may reach eight times TEMA values. Operating data from four crude units supported the use of fouling factors at three times TEMA values.

Fouling rates may vary dramatically from unit to unit and from exchanger to exchanger within the same unit. The previous work focused on using unit-average fouling rates.

This paper includes

• additional comparisons with operating data,
• a Monte Carlo analysis comparing using average fouling rates versus a distribution of fouling rates,
• an analysis identifying specific preheat configurations that have higher risk of operating problems with fouling, and
• estimates of energy efficiency and capacity costs of fouling in crude units.

[1] A. W. Sloley, “Crude Unit Fouling: What’s Normal? Why’s it Important?,” presented at the AIChE Southwest Process Technology Conference, Galveston, TX, 2018.