Effect of oxygen supply method on the performance of a micro gas turbine-based triple combined cycle with oxy-combustion carbon capture

There is increasing interest in zero-carbon-emission power to prevent global warming. This study investigated an effective way to minimize the efficiency penalty and achieve near-zero carbon emission in a small-scale triple combined cycle. The power block of the cycle includes a solid oxide fuel cell, micro gas turbine, and organic Rankine cycle. The three oxy-combustion capture systems are a semi-closed cycle, a cycle using an ion transport membrane, and a cycle where the membrane is replaced with an air separation unit. A parametric analysis was performed to determine an optimal pressure ratio for each cycle. The performance characteristics of the three cycles and a cycle with conventional post-combustion capture were compared. It was found out that the cycle using an air separation unit is more efficient than the other two cycles and captures highly pure carbon dioxide. The efficiency penalty due to carbon capture is only 4.4%, resulting in 58% net efficiency. The most significant finding is that using the cryogenic air separation unit is more favorable than using the ion transport membrane to separate oxygen in a small triple combined cycle operating at low pressure, in contrast to one with high pressure.