45 / 100
August
2019
43
HYDROCARBON
ENGINEERING
T
his is the second part of a two part article in
which the unbalanced heat method (UHM) is
discussed in detail. The first part, which featured
in the April 2019 issue of
Hydrocarbon
Engineering
, highlighted the essentials of the UHM for
estimation of fractionating tower relief load with emphasis
on the simplicity and applicability of the method.
1
In this
second part, the applicability of UHM is illustrated through
two case studies. Detailed calculations are also presented.
Case studies
The first of the following case studies illustrates the
possible growth in total power failure relief scenario load
from the FEED to the detailed engineering phase of a
project based on the considerations highlighted above.
The second describes how UHM can be applied to
analyse a total power failure scenario for a heat-pumped
P-P splitter tower.
Case study 1: depropaniser column
In a depropaniser, the heavier C4+ components are
separated from the propane feed (Figure 1). The column
is equipped with a thermosiphon reboiler and an
air-cooled condenser (induced draft-type equipped with
louvres). The heating medium for the reboiler is
low-pressure (LP) steam at 350 kPag. The overhead
product is propane while the bottoms product is the
C4+ stream. The tower top PSV is set at 2400 kPag. The
normal reboiler and condenser duties are 23.5 MW and
28.81 MW, respectively.
In the final instalment of this two part article,
David A.G. Suares,
Fluor Daniel India Pvt. Ltd, India,
outlines the applicability of
the unbalanced heat method through two case studies.