Complex Configurations of Partial Cooling With Recompression Brayton Cycles Using s-CO2 Mixtures

Abstract

This work evaluates the impact of using supercritical carbon dioxide mixtures (s-CO2/COS, s CO2/H2S, sCO2/NH3, and s-CO2/SO2) as a working fluid carried out Brayton s-CO2 power cycles. Some complex configurations were studied: partial cooling with recompression without reheating (PCRC), partial cooling with recompression and reheating (PCRC RH), partial cooling with recompression and two reheatings (PCRC 2RH), and partial cooling with recompression and three reheatings (PCRC 3RH). The design parameters evaluated are the solar plant performance at the design point, the pinch point in the heat recuperators, and total conductance (UAtotal) with values between 5 – 20 [MW/K]. This analysis is complemented by studying the effects of the compressor inlet temperature (CIT) variation in each configuration. Interesting results are obtained from this work; the mixtures containing COS and H2S provide better efficiency from a CIT = 55 °C compared to the pure s-CO2 fluid in PCRC configuration. While in the PCRC-RH and PCRC-2RH configurations, this occurs at a compressor inlet temperature higher than 57 °C. Finally, in the PCRC-3RH configuration, the efficiency is only slightly better when the CIT is 60 °C.