Modeling, thermodynamic and techno-economic analysis of coke production process with waste heat recovery

Coke production is high energy consuming and accounts for around 10% of the energy demand in the iron and steel industry. A large amount of the thermal energy in the coke production process is lost from the discharge of flue gas and quenching of incandescent coke and raw coke oven gas (COG). This paper conducts a detailed plant-wide modeling of coke production process combined with waste heat recovery (WHR). The model is compared with the actual plant and literature data. Three cases of coke production process based on the quenching mode and waste heat recovery are researched through thermodynamic, techno-economic and CO2 emissions analysis. Case CWQ represents the process with coke wet quenching (CWQ), Case CDQ represents the process with coke dry quenching (CDQ), and Case WHR represents the process with WHR. For a typical coking plant, CWQ wastes most of the thermal energy, CDQ can offer 22.98 MWe of electricity, while WHR can provide 32.12 MWe of electricity and 8.44 MWth of low pressure (LP) steam. The energy efficiency of Case CWQ, CDQ and WHR is 88.26%, 89.30% and 90.13%, respectively. The total exergy efficiency is 86.54%, 87.61% and 88.08%, and the physical exergy efficiency is 1.28%, 11.00% and 15.69%, respectively. The exergy inefficiencies of the subsystem are quantified. The economic performance and CO2 emissions of the three cases are also discussed.