Heat integration and exergy analysis for a supercritical high-ash coal-fired power plant integrated with a post-combustion carbon capture process

摘要

The International Energy Agency (IEA) has recommended eliminating at least 80% of the CO_2 emission from the power sector by 2050 as a response to climate change. Meeting this target is expected to be challenging since a lion's share of the power generation is based upon coal combustion. A cost effective strategy to decarbonise the power sector would require carbon capture and storage, largely through a post-combustion capture (PCC). In this study, a model of the supercritical coal-fired power plant (CFPP) fed with a high-ash coal was developed and validated, a validated model of a PCC pilot plant using monoethanolamine (MEA) solvent is scaled-up to meet the CFPP capacity, a CO_2 compression unit model was developed to fully assess the energy penalty, and the three models were integrated for a 90% capture level. This required determination of the PCC steam requirement and identification of the optimal condensate return location. The performance of the integrated models was compared with the reference CFPP model (with a net efficiency of 39.1%), and the energy penalty was estimated to cause a 25% fall in the CFPP power output. Then, energy saving opportunities were investigated through the heat exchanger network (HEN) analysis. Several HEN designs were analysed, revealing that heat can be recovered from the flue gas leaving the CFPP, and used to heat up boiler feedwater to enhance the plant efficiency. Such a configuration resulted in reduction of energy penalty by 4.15%, improving the performance of the integrated plant. Finally, it is inferred from the exergy analysis that further energy savings can be achieved by reducing the exergy destruction in the PCC.