Abstract: To reduce energy consumption in refineries, an exergy analysis model was established for an 8.0 Mt/a atmospheric and vacuum distillation unit. The model systematically studied the exergy efficiency and exergy losses of the main equipment and heat exchange network within the unit, identifying the energy utilization bottlenecks as the underutilization of high-temperature heat sources such as vacuum residue, atmospheric third-side cut, and atmospheric second-middle cycle oil. By calculating exergy losses and exergy efficiency, an energy-saving optimization retrofit plan was determined. Industrial results showed that after implementing the optimization plan for the atmospheric and vacuum distillation unit based on exergy analysis, the final temperature of the heat exchange network increased by 13℃. The unit could save 8.47 kt/a of fuel gas, reducing energy consumption by 1.15 kgOE/t（1 kgOE=41.8 MJ）. The project could save approximately 18.6 million yuan/a in fuel gas costs and reduce CO₂ emissions by about 18.8 kt/a, with an investment payback period of about 1.5 a.

Key words: atmospheric and vacuum distillation unit, Exergy analysis, heat exchange network, energy conservation and emission reduction