Energy Efficiency Analysis of Carbon Capture Systems Using Chemical Absorption Based on the Second Law of Thermodynamics

  Objective  This study aims to investigate the actual energy efficiency of coal-fired flue gas chemical absorption-based carbon capture systems, providing a scientific basis for the optimization and promotion of this technology.

  Method  Initially, the energy consumption status of typical chemical absorption-based carbon capture systems worldwide was reviewed to establish the energy consumption levels of existing technologies. Subsequently, based on actual engineering cases, a heat balance analysis of the chemical absorption-based carbon capture system was conducted, and the system's heat and electricity consumption were measured and calculated. On this foundation, an equivalent total energy consumption calculation method was proposed to comprehensively evaluate the system's overall energy consumption. The concept of "Second Law of Thermodynamics efficiency" was introduced as a thermo-economic evaluation method to analyze the system's energy efficiency. Furthermore, by taking the steam thermal consumption - one of the critical energy-consuming links in the system - as an example, an exergy loss analysis was performed to identify critical nodes of energy utilization.

  Result  The results indicate that the target carbon capture system has an equivalent total electricity consumption of 397.8 kWh/t CO₂, an equivalent total heat consumption of 33.4 GJ/t CO₂, a Second Law of Thermodynamics efficiency of 28.1%, and a steam exergy loss rate of 18.81%. Compared with existing chemical absorption-based carbon capture technologies, the system demonstrates superior performance in energy consumption control and energy utilization efficiency, although further optimization potential remains.

  Conclusion  It is recommended to conduct further research on absorbents and optimize the process technology for the carbon capture system to enhance the system's Second Law of Thermodynamics efficiency. Exploring more economical heat source alternatives or utilizing heat pump technology to recover low-grade heat from steam condensate for energy recycling could reduce the consumption of high-grade energy and improve the system's overall economic viability.