In the context of achieving the “dual-carbon” goals in the new era, coal-fired cogeneration systems are required to be highly efficient, flexible, and low in pollution and carbon emissions.

To tackle these challenges, this study proposes a novel system that integrates a supercritical CO₂ cycle with split-flow heating and low-temperature regeneration (SR-SCO₂-CHP), an ultra-low emission (ULE) flue gas control module, and a vacuum temperature swing adsorption (VTSA) carbon capture module (denoted as the SR-SCO₂-CHP-ULE-VTSA system). A system using monoethanolamine (MEA) for carbon capture (SR-SCO₂-CHP-ULE-MEA) serves as the benchmark for comparison. A comparative exergy analysis is conducted.

The results demonstrate that the proposed system achieves superior exergy efficiency across all electrical loads, because the exergy loss of the VTSA carbon capture submodule is less than one-third of that of the MEA. The exergy losses of MEA mainly occur in the absorption tower and desorption tower, which account for 80% of the total exergy losses of the carbon capture submodule. However, the exergy losses of VTSA adsorption & desorption tower and the pressure machine are relatively large, accounting for more than 60% of the total exergy losses of the carbon capture submodule. At full load, its exergy efficiency reaches 39.84%, significantly outperforming the benchmark system’s 35.16%. Furthermore, the proposed system enables effective thermo-electric decoupling through adjustments in the heat split ratio (x₁) and the split ratio of CO₂ turbine driving vacuum pump (x₂). The exergy efficiency of the system decreases as the split ratio x₁ and x₂ increase under any electrical load, and the optimal split ratios of x₁ and x₂ increase as the electrical load decreases. At 100% electrical load, the optimal values for x₁ and x₂ are 0.52 and 0.14, respectively. The carbon reduction capability of the proposed system is also remarkable. Across the electrical load range from 100% to 30%, the carbon reduction increases from 11.9 g/(kW·h) to as high as 85.3 g/(kW·h), demonstrating a significant advantage over the benchmark system.

This work confirms the SR-SCO₂-CHP-ULE-VTSA system as a promising solution for highly efficient and low-carbon coal-fired cogeneration. It should be noted that in terms of economic performance, the initial investment of the carbon capture module of the SR-SCO₂-CHP-ULE-VTSA system is closely related to the performance of the adsorbent material, and further optimization of the adsorbent is required to reduce equipment size and cost. Additionally, in terms of operation, its carbon capture module has a complex structure and high requirements for multi-tower operation switching, so its technical maturity needs to be further improved to promote its industrial application.