Low-energy-penalty principles of CO₂ capture in polygeneration systems

Polygeneration is identified as an effective way to overcome the challenges of energy efficient utilization and CO₂ emission reduction. This paper analyzes the energy saving mechanism and carbon reduction laws of decarbonized polygeneration systems, and discusses the compatibility of CO₂ capture for different integral schemes. Based on the novel method of chemical exergy balance, two typical methanol-power polygeneration systems with CO₂ recovery are analyzed in detail, and integral factors that indicate the level of energy cascade utilization and the compatibility with CO₂ capture are proposed. Both polygeneration systems show large performance improvements compared to the single production systems, but the advantages of scheme (b), removing the composition adjustment and capturing CO₂ from unrecycled gas after synthesis, are more prominent. This scheme has an excellent compatibility with CO₂ recovery, and it shows a fairly optimal performance in the full working field. Further, according to the analysis of the integral factors, a higher CO₂ recovery ratio is recommended for scheme (b), while a lower one is recommended when scheme (a) is employed.