Energy and exergy analysis of a pre-distillation unit. A case study

Abstract

Energy and exergy balances were evaluated for the pre-distillation unit (Un-0100) of an aromatics plant from a Portuguese refinery. The main objective of the study was to find out the relevant thermal energy losses in order to implement energy recovery procedures, without questioning the operating processes of the plant. In its overall analysis, the Un-100 obtained an energy efficiency of 13.4% and an exergy efficiency of 2.3%. The equipment that has higher energy losses in this unit is the air coolers, representing 59.9% of the energy losses, i.e., most of the energy lost in this unit is due to the cooling process. The irreversibility observed in these equipment groups was 11.2%. Moreover, the furnace represents 15.6% of energy losses, but this component stands out in the irreversibility analysis, with 56.3% of the total. Based on these values, it can be said that this equipment presents a high potential of improvement of its energy and exergy performance. These results, concern a small part of a more general case study about the performance of the aromatics plant, and clearly show the need to establish complementary energy and exergy balances in order to increase the energetic performance of the unit.