Investigation of the Bottoming Cycle for High Efficiency Combined Cycle Gas Turbine System With Supercritical Carbon Dioxide Power Cycle

Abstract

The supercritical CO2 (S-CO2) power cycle has been receiving attention as one of the future power cycle technology because of its compact configuration and high thermal efficiency at relatively low turbine inlet temperature ranges (450∼750°C). Thus, this low turbine inlet temperature can be suitable for the bottoming cycle of a combined cycle gas turbine because its exhaust temperature range is approximately 500∼600°C. The natural gas combined cycle power plant utilizes mainly steam Rankine cycle as a bottoming cycle to recover waste heat from a gas turbine. To improve the current situation with the S-CO2 power cycle technology, the research team collected various S-CO2 cycle layouts and compared each performance. Finally, seven cycle layouts were selected as a bottoming power system. In terms of the net work, each cycle was evaluated while the mass flow rate, the split flow rate and the minimum pressure were changed. The existing well-known S-CO2 cycle layouts are unsuitable for the purpose of a waste heat recovery system because it is specialized for a nuclear application. Therefore, the concept to combine two S-CO2 cycles was suggested in this paper. Also the complex single S-CO2 cycles are included in the study to explore its potential. As a result, the net work of the concept to combine two S-CO2 cycles was lower than that of the performance of the reference steam cycle. On the other hand, the cascade S-CO2 Brayton cycle 3 which is one of the complex single cycles was the only cycle to be superior to the reference steam cycle. This result shows the possibility of the S-CO2 bottoming cycle if component technologies become mature enough to realize the assumptions in this paper.

On the Conceptual Design of Novel Supercritical CO2 Power Cycles for Waste Heat Recovery

“…They found that the partial heating cycle improves by 23.3% to 26.2% the power output generated by the traditional layouts and even marginally improves by 2.6% the power generated by the single flow split with a dual expansion cycle. The power output of the latter was found to be equal to 83% to 86% of that achievable by the dual flow split with a dual expansion cycle, which is consistent with Cho et al [23]. On the other hand, the new concepts devised by the authors could not exceed the power output achieved by the partial heating cycle, which was finally considered the most promising option for a megawatt scale due to the simpler layout, smaller number of components, and simpler operational scheme.…”

“…These first promising results paved the way for further studies aimed at comparing the performance of the novel s-CO 2 power cycles against that attainable by single or cascaded layouts of traditional s-CO 2 cycles or multi-pressure steam cycles. In this context, one of the earliest and most comprehensive Energies 2020, 13, 370 5 of 31 study is by Cho et al [23], who compared the performance of the novel s-CO 2 power cycles proposed by Kimzey [18] against that attainable by cascaded systems composed of the sequence of recompression or pre-compression and partial heating cycles. In the WHR from a gas turbine having an exhaust temperature of 580 • C, the authors found that the dual flow split with a dual expansion cycle improves by 6.6% to 8.5% the power generated by the cascaded s-CO 2 systems, and even improves by 3.6% the power output of a triple pressure with a reheat steam cycle.…”

Development of a novel dual heated cascade supercritical carbon dioxide cycle and performance comparison with existing two configurations for waste heat recovery

“…Thereafter, performances of these three cycles were compared with those of combined systems and a partial heating cycle. 29 The results showed that the cycle with dual splitting is the best in terms of the exhaust heat utilization and cycle efficiency. With the purpose to compare different S-CO 2 cycles comprehensively, Kim et al 30 analyzed performances of these cycles in recovering the waste heat.…”

“…To reduce the compressor work of original cycle, the intercooling technology is employed, thus developing a dual heated cascade S-CO 2 cycle with an intercooler, 29,30 as presented in Figures 3 and 4. For simplicity, this configuration is shortly called "intercooling cycle".…”

The potential of gas switching chemical looping technology to eliminate the energy penalty of CO2 capture

“…The CO2 cooler does not operate in the two phase region as in a steam condenser, resulting in a wider temperature gap in this the heat rejection unit and consequently a higher exergy destruction in this section. An outline of the s-CO2 cycle evaluated is provided in Figure 82, with modelling assumptions taken from [110].…”