Proposal and Analysis of a Novel Zero CO2 Emission Cycle With Liquid Natural Gas Cryogenic Exergy Utilization

Abstract

A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO2 and other emissions and a high efficiency. Natural gas is fired in highly enriched oxygen and recycled CO2 flue gas. The plant operates in a quasi-combined cycle mode with a supercritical CO2 Rankine type cycle and a CO2 Brayton cycle, interconnected by the heat transfer process in the recuperation system. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO2 ready for disposal can be withdrawn from the cycle without consuming additional power. Good use of the coldness exergy and internal exergy recovery produced a net energy and exergy efficiencies of a base-case cycle over 65% and 50%, respectively, which can be increased up to 68% and 54% when reheat is used. Cycle variants incorporating reheat, intercooling, and reheat+intercooling, as well as no use of LNG coldness, are also defined and analyzed for comparison. The approximate heat transfer area needed for the different cycle variants is also computed. Besides electricity and condensed CO2, the byproducts of the plant are H2O, liquid N2 and Ar.