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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