Effect of flue gas condensing waste heat recovery and its pressure drop on energy saving and carbon reduction for refinery heating furnace

The refinery heating furnace has high energy consuming and high carbon emission, and the flue gas condensing waste heat recovery can achieve prominent results in saving energy and reducing emissions of petrochemical industry. Based on adding a flue gas condensing heat exchanger (FGCHE) at the rail of heating furnace, this paper investigates the effects of flue gas waste heat recovery and pressure drop on the energy saving and carbon reduction through theoretical and on-site testing methods. Flue gas heat recovery and pressure-drop characteristics of the FGCHE are analyzed to achieve maximum energy saving and emissions reduction under the normal operating conditions of heating furnace. Meanwhile, the effects of flue gas temperature and pressure drop on the energy saving and carbon reduction are derived under different combustion air temperature, humidity and excess air coefficient after fuel gas complete combustion. The results show that when the flue gas temperature is reduced from 180 °C to 20–40 °C, the energy saving efficiency, utilization ratio of flue gas waste heat, condensate recovery efficiency and carbon emission reduction ratio reach 12.5–16.9%, 74.4–98.1%, 58∼89.3% and 13.7–18.3%, respectively. Reducing the flue gas pressure drop can significantly improve the flue gas waste heat utilization ratio and carbon reduction.