Proposal and Thermodynamic Characteristics Evaluation of a New Combined Power Generation System under CO₂ Emission Constraints

It has been becoming important to realize CO₂-capturing power generation systems (PGS) for drastically decreasing the amount of CO₂ emissions into the atmosphere. Hence it is considered that a newly constructed PGS should be better to have a CO₂-capturing capability. This paper proposes a new combined PGS under CO₂ emission constraints. In the proposed system, exhaust gas of a high-temperature gas turbine is used to produce high, medium, and low steam, and used as main working fluid of a kind of gas turbine based on oxy-fuel combustion method. A conventional high-efficient combined cycle PGS (CCPS) is adopted as a reference PGS in the paper. The proposed system can generate 2.05 times greater net electric power compared to the CCPS, with a thermal efficiency of 54.9%, even if additional power of O₂ production and captured CO₂ liquefaction is taken into account. That is, compared to the CCPS, the degradation of the thermal efficiency of the proposed CO₂-capturing PGS based on the oxy-fuel combustion method is estimated to be 1.28%, from 56.2% of the CCPS. CO₂ emission per 1 ㎿h of electricity has been calculated to be 0.171 t-CO₂, compared to 0.351 t-CO₂ of the CCPS, 51.3% smaller.