The potential benefits of feed distribution when applied to atmospheric crude distillation units
Distributed feed was applied on an Atmospheric Crude Distillation Unit (ACDU) to establish the energy and capital expenditure saving potential of the distributed feed policy, with the aid of (Column Profile Maps) CPMs and Aspen Plus as analysis tools. As shown by Holland (2005), the advantages of using distributed feed over single feed are seen in separations with non-sharp split product specifications, thus making ACDU an ideal candidate for feed distribution. For multicomponent mixtures with more than 3 components, compositional plot visualisation is more difficult, thus most graphical methods fail and as a result a representative three component constant volatility mixture of pentane, heptane and hexane was selected on the assumption that it would fairly mimic the paraffinic synthetic crude oil behaviour. After analysis of the three component distributed feed schemes, the ideas were then extended to a synthetic crude oil system in Aspen Plus. The results showed that there was potential to reduce equipment size, such as the condenser and furnace, plus there is a real opportunity to possibly do away with at least one or two pump-around circuits. Energy savings of above 30% were realized.