(324f) Practical Application of Column Profile Maps: Distributed Feed Crude Distillation Column

Distillation
columns with multiple feeds are often used in the process industry for the
separation of multicomponent mixtures, though the energy-saving potential for
different column variations like reflux reduction and stage reduction have not been
fully addressed for complex columns (Bandyopadhyay et al., 2004). This paper
will be founded on the premise that there are economic benefits in having feeds
entering the column at different locations.

The
CPM method, a novel graphical distillation design technique developed by Tapp
et al. (2004), has already been established to be effective in distillation
systems analysis and can be generalised for any number of components. This
paper proposes the use of distributed feed on an Atmospheric Crude Distillation
column (ACD) for a crude oil refinery with the aid of CPMs and a software
simulation package (ASPEN®). Separation is not perfect in the commercial ACD, and
that makes it an ideal candidate for distributed feed because of the non-sharp
split product specifications (Holland, 2005). Since plotting CPM profiles for a
system with more than 4 components makes it very hard to get a clear picture of
the compositional profile plots, this issue can be circumvented by taking a
representative three component mixture that fairly mimics the real
multicomponent system. For the purposes of this study a constant volatility
n-butane/n-decane/n-hexadecane mixture was chosen on the basis that a
paraffinic crude oil would be processed. The CPM method would then be used to
analyse the distributed feed scheme and the results can be generalised for the crude
oil system by using the CPM results to initialise the ASPEN® simulation.

At
the end of the study, the paper would have further validated the authenticity
of the CPM method by having applied it on a well-established process thus
proving that it has real practical applications rather than just scientific. Finally
the question of whether the alternative distributed feed configuration proposed
is worthy will be answered by looking at the  approximate potential savings in capital,
energy as well as operating costs.

  References

Bandyopadhyay,
S., Mishra, M. & Shenoy, U.V., 2004. Energy-Based Targets for Multiple-Feed
Distillation Columns. AIChE, 50(8), pp.1837-53.

Holland, S.T., 2005. Column Profile
Maps: A Tool for the Design and Analysis of Complex Distillation Systems.
Thesis. Johannesburg: COMPS University of the Witwatersrand.

Tapp, M., Holland, S.T., Hildebrandt, D.
& Glasser, D., 2004. Column Profile Maps. 1. Derivation and Interpretation.
Ind Eng Chem Res, 43, pp.364-74.