Analysis and preliminary design of a possible CO2 compression system for decarbonized coal-fired power plants

Carbon capture, utilization, and storage (CCUS) is a key technology for decarbonizing existing or newly designed fossil fuel power plants, which in the short to medium term remains essential to offset the variability of nonprogrammable renewable sources in power generation. In this paper, the authors focus on the CO2 compression phase of CCUS systems, integrated with power plants, and propose, according to the technical literature, a plant layout aimed at minimizing energy consumption; then, they carry out the preliminary design of all compressors, identifying compact and efficient configurations. The case study concerns an advanced ultra-supercritical steam plant (RDK8 Rheinhafen-Dampfkraftwerk in Karlsruhe, Germany) with a nominal net thermal efficiency of 47.5% and an electrical output of 919 MW. The main results obtained can be summarized as follows. The overall compression in the IGC configuration requires only six stages and each compressor is single-stage, while in the inline configuration, ten stages are needed; the diameters in the IGC solution, also due to a higher rotational speed, are smaller, despite the in-line solution being multistage. An interesting further investigation could be related to modifications of the plant scheme, especially to test whether CO2 liquefaction at an intermediate stage of compression could result in reductions in energy consumption, as well as even more compact design solutions.