Integrated column design for coke oven gas purification: Energy–economic–safety trade-offs in NH₃/H₂S removal

The reutilization of coke oven gas (COG), a byproduct of steel manufacturing, is increasingly emphasized as a strategy to improve energy efficiency and reduce emissions. However, raw COG contains hydrogen sulfide (H₂S) and ammonia (NH₃) impurities, which can lead to equipment corrosion, catalyst deactivation, and environmental pollution, thereby limiting its direct reuse. Limited research has quantitatively compared the performance of conventional amine-based purification systems with emerging integrated-column configurations for simultaneous removal of H₂S and NH₃. In this study, two COG purification configurations were modeled using Aspen Plus and systematically compared from 2ES (Energy, Economic, and Safety) perspectives. Case 1 represents a conventional absorption-regeneration process employing a methyldiethanolamine (MDEA)-based amine solvent, whereas Case 2 integrates the H₂S and NH₃ scrubbers into a single column. Both cases were modeled under identical inlet conditions to achieve a 95% H₂S removal efficiency. The comparative analysis reveals a clear trade-off between energy efficiency and safety. While the economic performance of the two cases was nearly identical, with only ∼1% difference in gas processing cost (GPC), Case 2 exhibited an energy-saving potential of about 65% compared to Case 1. However, under a large accidental release scenario, Case 2 indicated a leakage rate about 3.6 times higher, leading to a hazard radius approximately 1.7 times larger than that of Case 1. These findings highlight that the MDEA-based absorption process is more favorable from a safety perspective, whereas the integrated NH₃/H₂S column process offers a substantial advantage in energy efficiency.