Page 357 - Petroleum and Gas Field Processing

2. Guidelines on the order of sequence of separation (i.e., synthesis
of separation sequences).

13.3.2 Fundamentals of Distillation
For separation to take place, say by distillation, the selection of an
exploitable chemical or physical property difference is very important.
Factors influencing this are as follows:
1. The physical property itself
2. The magnitude of the property difference
3. The amount of material to be distilled
4. The relative properties of different species or components; purity
required
5. The chemical behavior of the material during distillation and its
corrosiveness
A measure of the ease of separation of one component A from
another B is known as the separation factor, SF, defined as

ðC =C Þ
A
B Top product
SF ¼
ðC A =C B Þ
Bottom product
where C is the concentration. A high value of SF means an easy
separation. A good example is the separation of salt from seawater by
‘‘evaporation.’’ Here, the value of SF is found, by intuition, to be infinity,
because we are separating water (volatile component) from salt (non-
volatile).
Consider a raw hydrocarbon stream to be fractionated, which may
contain the following hydrocarbons:

Selected Hydrocarbons with Corresponding
Boiling Point

Boiling point Fat
Component atmospheric pressure
Ethane 128
Propane 44
Isobutane 11
N-Butane 31
Pentanes Plus 82–250

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.