Efficiency Assessment of Crude Oil Distillation Systems

Abstract

The assessment of energy and exergy efficiencies is conducted on a crude oil distillation system for three different cases. Each case defines efficiency in a unique way with different inputs and outputs. First case treats the heat transfer rate as useful output and the heat gained from the heaters as input. For the second case, we consider the heat provided by the heaters as input and the heat transfer rate in the distillation system as output. The third case treats the heat provided by the heaters as input and heat transfer rate along with the heat of exhaust gases as useful output. The system efficiencies are studied parametrically by changing the amount of heat transfer rate and the ambient temperatures. The results show that case 1 has the baseline energy and exergy efficiencies at 53 % and 25.3 % respectively. Case 2 has the efficiencies at 40 % for energy and 23.3 % for exergy efficiency. Case 3 efficiencies are at 72 % for energy while exergy efficiency is at 65 %. Case 1 has the highest efficiencies, followed by case 3 then the least efficient is case 2. Utilizing the unused energy, as a useful input to some other system, improves the overall efficiency of the plant and saves operating cost while making the system more environmentally friendly.

Nomenclature

ADU:

Atmospheric distillation unit

$\dot{\mathrm{E}}$ :

Energy rate, W

$\dot{\mathrm{E}}\mathrm{x}$ :

Exergy rate, W

$\dot{\mathrm{I}}$ :

Exergy destruction rate

PA:

Pump-around circuit

$\dot{\mathrm{Q}}{\operatorname{}}_{\mathrm{CV}}$ :

Heat rate consumed in the distillation system, W

T:

Temperature, K

T₀ :

Ambient temperature, K

VDU:

Vacuum distillation unit

η:

Energy efficiency

Ψ:

Exergy efficiency

1–17:

States

C:

Case for efficiencies

H:

Heater