Life-Cycle Carbon Footprint Assessment of the MDEA-Based Gas Separation and Purification in SRU Tail Gas Treatment and Feasible Decarbonization Pathway

Accurately quantifying and reducing the carbon footprint of the sulfur recovery unit (SRU) tail gas treatment process is crucial for pollution and carbon reduction in the chemical industry. This study employed Aspen Plus to simulate the N-methyldiethanolamine (MDEA)-based SRU tail gas treatment process at a sulfur production plant in Shandong, China. A carbon footprint of a product (CFP) method based on life cycle assessment was used to calculate the cradle-to-gate carbon footprint of the SRU tail gas treatment process. The results demonstrate that the carbon footprint of treating 1 Nm3 pretreated SRU tail gas (CFPTG) is 0.495 kgCO2e/Nm3, with gas treatment and steam contributing 99.9% and 98.8%, respectively. The data quality indicator—Monte Carlo simulation uncertainty analysis indicates that the relative standard deviation of CFPTG is 7.4%. Furthermore, 16 emission mitigation pathways were established, focusing on energy supply. Biomass boilers reduce CFPTG by 92.6%, whereas electric boilers increase it by 45.2% under the current power mix. Electricity substitution alone reduces emissions by only 0.1–0.4%, while boiler electrification coupled with low-carbon electricity achieves 85.1–96.5% reduction. This study quantifies the life cycle carbon footprints of the MDEA-based SRU tail gas treatment process, providing a scientific basis for low-carbon transformation in tail gas treatment.