Performance analysis of a modified Allam cycle combined with an improved LNG cold energy utilization method

Abstract

The Allam cycle is a promising power cycle that could achieve 100% carbon capture as well as high efficiency. In order to further enhance system operating performance, here we propose a modified Allam cycle with an improved liquified natural gas (LNG) cold energy utilization method. The flow rate fluctuation of LNG is suppressed by variable speed adjustment of the air compressor, and the cold energy of LNG is transferred to liquid oxygen, which could implement a stable cold energy supply. The whole process is modeled including air separation unit and LNG supply path. Furthermore, the system thermodynamic and economic performance is evaluated through parametric analysis, and the proposed system superiority is highlighted by comparing with conventional Allam-LNG cycle. The results indicate that the system could achieve 70.93% of net thermal efficiency, 65.17% of electrical efficiency, and $403.63 million of net present value, which performs 5.76% and 6.48% enhancement of efficiency and 11% improvement of economic revenue. Moreover, the system off-design operation is assessed; 87% to 100% of compressor speed adjustment range is determined that could cope with −13% to 9% of LNG flow rate fluctuation.