Kalina cycles for waste heat exploitation in carbon capture: Multi-objective comparison, technoeconomic and sustainability assessment with novel working fluids

Solvent-based carbon capture (CC) is receiving increased attention for short-term industrial implementation, but exhibits high energetic requirements in solvent regeneration. The exploitation of waste heat from the flue gas of the emitting plant may reduce the associated costs. The Kalina cycle (KC) constitutes a promising option for heat-to-power conversion from low-grade sources. This work explores the performance of 37 working fluid mixtures for KCs, with 33 being novel options. KC design is performed for each mixture considering thermodynamic, phase stability, technoeconomic, safety, health, and environmental performance criteria. The multi-criteria performance assessment of the mixtures reveals five optimal pairs (Acetaldehyde with 1-Ethyl-3-methylimidazolium ethyl sulphate, or Dimethylformamide, or Ethyl Vanillin, or Dodecanal and Acetone with 1 Ethyl-3-methylimidazolium ethyl sulphate) that well-exceed the performance of the widely used NH 3 -H 2 O. A detailed technoeconomic analysis shows that all five pairs exhibit lower cost per ton of CO 2 captured than the conventional approach of directly disposing of the flue gas thermal load via a Direct Contact Cooler (DCC). The economically optimum pair of Acetaldehyde- Ethyl Vanillin exhibits up to 14.5% and 39.6% lower cost per ton CO 2 than a DCC and a Vapor Compression Heat Pump. Acetaldehyde and Ethyl Vanillin also exhibit good safety and environmental performance, with a lower but competitive score in the health index. Insights are provided on important issues like fluid thermal stability, corrosion and risks of use. • Evaluation of 37 mixtures for heat-to-power conversion with Kalina cycle • Techno-economic assessment for use in carbon capture plants • Conventional NH 3 /H 2 O outperformed by acetaldehyde-based mixtures • Comparison with direct contact cooler (DCC) and vapor compression heat pump (VCHP) • Acetaldehyde- Ethyl Vanillin exhibits up to 39.6% lower cost/tCO 2