Abstract: Heat integration across different units is an effective method to improve energy utilization in chemical plants. In order to precisely obtain the energy-saving potential across the units and improve the fluctuation resistance of the retrofitting schemes, a retrofitting method based on actual cold and heat composite curves is developed. Based on the industrial data of benzene production and C₈ units from a petrochemical company, the heat exchanger networks of the two units are simulated in Aspen HYSYS, and pinch analysis is carried out with Aspen Energy Analyzer. Considering the unsatisfactory heat transfer of the original benzene production unit and safety constraints, new retrofitting schemes for the heat exchanger network of benzene production unit are proposed to reduce the steam consumption. The heat exchanger network of the C₈ unit is not retrofitted due to the limited space in energy-saving and irrational heat transfer distribution in different heat exchangers. The energy-saving potential of heat integration between the two units is analyzed by constructing the actual cold and hot composite curves. The advantage of using the actual cold and hot composite curves to guide the heat integration across the two units is that it uses the actual residual energy, which is more practical than the theoretical situation such as the total composite curve. In addition, limitations and complexity of implementation are also considered to make the retrofitting schemes. The results show that the scheme with more energy saving raises the investment cost, has a slightly longer payback period, but has more long-term economic benefits.