Multiobjective Optimization and Retrofit of Energy Utilization System in a Refinery Based on CO₂ Emission Control

For energy utilization system in a refinery, strategies combining retrofit of heat exchanger network and fuel switching were proposed to reduce CO2 emission in the refinery. A multiobjective optimization model that is subject to a tradeoff between the total annual costs for retrofit and total annual CO2 emission was developed. In the proposed method, influences of economy for retrofit and its extra CO2 emission were taken into consideration. The Pareto front was obtained through ε constraint method. The procedure and effects of the proposed approach were exemplified through a heat exchanger network in a wax oil hydrotreating unit. The Pareto front representing the tradeoff between total annual costs for retrofit and total annual CO2 emission was obtained, and the optimal retrofit schemes under different annual CO2 emissions were obtained accordingly. The proposed method provides theoretical fundamentals of a multiobjective optimization for CO2 emission reduction in refineries.