(34a) Molecule Management:Crude Unit Diesel Recovery

Diesel recovery continues as an important driver in refinery crude unit economics. Overall refinery profits are best when the desired molecule is recovered as soon as possible. Conventional refinery units recover diesel from the atmospheric column. Less commonly, vacuum towers can recovery a diesel product. However, these are not the only options.

Other configurations may include:

• gas oil towers,
• vacuum preflash towers, and
• gas oil splitters.

In addition, recycles between towers and improved stripping of diesel from gas oil sidestrippers can improve diesel recovery.

This paper:

• reviews the basic options (atmospheric and vacuum towers) and
• compares the basic options to the less common configurations.

Results are shown for an example crude for both distillation and cloud point specifications.

The analysis focuses on combining both the fundamentals of fractionation with an understanding of equipment limits and performance. Fundamentals covered will include system pressure and relative volatility and liquid-to-vapor ratios in the different options.