Experimental performance and techno-economic assessment of an ionic liquid-based scrubber for maritime SO₂ capture

Sulfur dioxide (SO₂) emissions from maritime exhaust pose environmental and regulatory challenges. This study evaluates a scrubber system using 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) for SO₂ capture in shipping. Experimental results show high absorption capacity (512 mmol SO₂/mol IL at 50°C) and over 95 % SO₂ capture efficiency across multiple cycles. The system utilizes water as a solvent for ionic liquid regeneration, demonstrating effective and practical desorption performance at a low water-to-IL mole ratio (3:1), ensures efficient desorption with minimal water and energy use. Techno-economic comparisons against seawater, NaOH, and Wellman–Lord scrubbers reveal the [BMIM][Cl] system as the most cost-effective, with annual savings up to USD 5.26 million over VLSFO use and up to USD 558,000 over NaOH systems. Energy use is low (31.5 kW), with thermal demand fully offset by waste heat. Space requirements (27 m³) are far lower than those of NaOH (200 m³) and Wellman–Lord systems (118 m³). Environmental assessment confirms lower greenhouse gas emissions than NaOH but higher than Wellman-Lord process. Potential long-term stability concerns, detailed study on viscosity, and oxygen exposure effects are noted for future investigation. Overall, the [BMIM][Cl] scrubber emerges as a compact, energy-efficient, and cost-effective alternative for SO₂ compliance in shipping.