(34d) Modified Shed Decks Tackle Crude Tower Fouling Problems

Shed decks are simple, uncomplicated; and as Fair noted in several of his studies, the number of geometric design variables are few. These trays have high capacity/fouling resistance; yet, low efficiency. But should engineers think of sheds in a different way?

While Distillation practitioners seek improvements to the cross-flow or counter-flow tray designs, they rarely evaluate technology that simplifies the designs. The same practitioners consider sheds a necessary efficiency downgrade to gain fouling resistance. However, is this a fair evaluation for shed decks? A counter-flow tray revamp of a cross-flow trayed tower is rarely a one-for-one basis; so why do we apply the same limits to a potential shed deck revamp of a cross-flow tray. The authors propose to deviate from the traditional evaluation protocol and to consider a non-one-for-one scenario when revamping a conventional tray with a shed deck in a fouling system.

The authors will share a case study of several recent applications where shed decks replaced sieve trays on a non-one-for-one basis without a loss in operating efficiency. In each application, the shed deck conversion was preceded by multiple revamp iterations with designs intended to improve anti-fouling characteristics. The previous revamps not only provided limited success in improving run-length, but also provided lower hydraulic capacity than the final shed deck revamp.