Thermodynamic and economic assessment of an integrated carbon capture and liquefaction system for medium-scale CHP plants in cold climates

Fossil fuels remain the dominant source of global energy supply and a major contributor to CO2 emissions, highlighting the urgent need for effective mitigation strategies. In cold regions, high heating demand and the continued operation of fossil-fuel-based combined heat and power (CHP) plants make carbon capture technologies particularly important for achieving significant emission reductions. This study proposes and evaluates a thermodynamically integrated carbon capture and liquefaction system for medium-scale CHP plants, combining amine-based CO2 capture, ammonia–water absorption refrigeration, and recovery of CHP waste heat. A detailed thermodynamic and economic model was developed and calibrated using operational data from a real natural-gas-fired CHP plant, ensuring realistic system representation. The integrated configuration achieves a CO2 capture rate of 93% and produces high-purity liquid CO2 (>99%). The specific energy consumption for CO2 liquefaction is 0.53 kWh/ kgLCO2, while the overall exergy efficiency increases from 40% to 59%. Additionally, the integrated system generates an extra 136 kW of power during peak operating conditions and produces liquid CO2 at a rate of 2.3 m3/h. Economic analysis, based on representative North American energy and CO2 market conditions, indicates a payback period of 2.85 years and a net annual benefit of 8.42 MMUS$/year, with sensitivity analysis confirming the robustness of the results to key economic parameters. The findings demonstrate the technical feasibility and economic potential of integrating carbon capture and liquefaction into medium-scale CHP systems and highlight a scalable decarbonization pathway for district and institutional energy systems in cold climates.