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.