Design of Crude Fractionation Units with Preflashing or Prefractionation:  Energy Targeting

This paper uses a previously developed systematic procedure to obtain design targets for heat integration in conventional crude fractionation units that use prefractionation columns or preflash drums. It is shown that, under the same high product yield conditions, prefractionation or preflashing followed by a conventional unit are not as energy efficient as straight conventional crude units. This is in great part due to the loss of the carrier effect that light components have in separating heavy gas-oil fractions in the flash zone. Such a carrier effect is discussed. In addition, if one accepts the yield of atmospheric gas oil to be smaller, then these prefractionation/preflash options consume less energy.