THERMOECONOMIC ANALYSIS OF AN OIL SEPARATION PROCESS ON OFFSHORE PLATFORM

Petroleum is one of the major sources of energy in the world and its consumption is destined to increase in the next years. At the same time, the reduced availability of conventional reservoirs leads oil companies seeking for offshore reservoirs, with an increase of the environmental impact, costs and risks associated with oil exploration and exploitation. Oil platforms are complex systems where different processes occur and energy production is required. This work presents the analysis of a crude oil separation process and is divided into two parts. In the first part, a simplified model of a separation plant is described: the system is constituted of a pre-separator unit, an Electrostatic Oil Heater Treater (EOT) unit and one post-separator unit. Configuration and data are obtained from a real plant and simulated in Aspen Plus. In the second part, Exergy and Thermoeconomic analyses of each unit are performed. The two analyses take into account the irreversibility of the process and the economic costs. The exergy analysis shows that there is a great amount of heat discharged from the EOT to the environment, indicating that the process is far from being thermodynamically perfect, the Thermoeconomic analysis that the investment and O&M costs have a higher impact compared to exergy destruction. As a novelty within the paper, the whole set of thermoeconomic variables are here evaluated, i.e. unit thermoeconomic cost of resource and product, relative cost difference and exergoeconomic factor. Their study leads to a possible optimization of the units able to reduce fuel consumption, but results show however that the improved exergy efficiency remains under the 10% for the EOT and the 20% for the overall system, with a relatively small cost reduction. Nonetheless, the reduction of fuel in the optimized configuration can be relevant in terms of avoided CO2 emissions. Therefore, this work brings out the importance of exergy analysis as a tool that leads to several system improvements, even beyond the thermodynamic point of view. In this perspective, exergy-based analyses can support plants refinements and optimization both from the economic (i.e. reduction of costs) and the environmental perspective (i.e. reduction of emissions).