Zero-Emission Combined Power Cycle Using LNG Cold

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A potential zero emission combined power generation plant fired by liquefied natural gas (LNG) has been investigated. A mixture of carbon dioxide(CO2)-steam is used as the working fluid of a gas turbine cycle, which replaces the normal combustion-in-air products and air, notably as the thermal ballast for the control of flame temperature. Oxygen (O2) is used as the fuel oxidant and is obtained from an air separation unit (ASU). The excess CO2 due to combustion is extracted by a simple flow separator and liquefied ready to be reused and/or sequestered. We proposed several types of cycles and compared with each other by analyzing them thermodynamically with the aid of ASPEN-PLUS software. The plant configuration and thermodynamics of the cycle are discussed first and then the optimised overall efficiency of the plant is calculated with a comparison of 100 % and 120 % stoichiometric combustion. The overall net efficiency, optimised to pressure and temperature levels complying with the material and cooling techniques currently available, is around 56 % (LHV basis), including the energy penalty of the ASU and the CO2 separation.