L. T. POPOOLA ET AL. 479
Figure 3. Flow chart optimization algorithm of crude oil
distillation column for unlimited market and feed stock.
and thus, its maximum concentration is calculated by
using Equation (4). However, the heavy key (petrol) in
the bottom becomes its limiting constraint whose con-
centration must not be less than that of the sales specifi-
cation (Equation (5)). To get the value of
D
HK o to be
used in Equation (4), the column is assumed to approach
an operating constraint of flooding above the feed tray.
The loading equation for this constraint is stated as Equa-
tion (6). As the value of
Do gotten from Equation
(1) is reduced from optimum, the values of Li/F and B/F
HK
change. Thus, the value of
Do
HK that satisfies Equa-
tion (6) is obtained to solve for
max
B
LK in Equation
(4) while other variables are stated. When unlimited
market and feed stock exist with known product prices,
the optimum separation [i.e.
Do
HK and
Bo
LK ] is
determined using Equations (1) and (4) but with the lim-
iting purity constraints stated in Equations (7) and (8).
The maximum feed flow rate that gives maximum profit
rate is determined using Equation (9) in which the tem-
perature of the overhead vapour (To) is a function of the
column pressure. If the feed loading is assumed to be
limited by the reboiler capacity instead of the column
pressure, the feed flow controller set point that gives the
maximum reboiler heat input rate is evaluated using
Equation (10). The proposed optimization models can be
used to simulate an existing crude oil distillation column
of a refinery.
4. Conclusion and Recommendation
The optimization of crude oil distillation column in the
context of feed stock and market condition can be
achieved using the stated models. The products prices
from the crude oil distillation column must be known and
the consumers’ products specification were put into con-
sideration using the products limiting purity constraints.
Also, the effect of operating cost on the products worth
was considered by assuming that the change in operating
cost equals the change in product worth. Nevertheless,
the proposed optimization modelling equations are ap-
plicable for both the conditions of limited and unlimited
feed stock and market situations for known product
prices. The situation in which either the top products or
bottom products being valuable than each other for the
condition of limited feed stock and market condition had
been examined. However, it is recommended that the
point of introducing the feed into the column be known
to validate the assumption of flooding above the feed tray.
Finally, the proposed models should be tested on an ex-
isting crude oil distillation column of a refinery for future
research in order to validate the applicability.
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