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Bechtel’s Impact Report

Thermo-Economic Analysis of Combined Cycle Based Liquefaction Plants

Authors: Cyrus Meher-Homji, Vinod Rajkumar, Himanshu Patel, David Messersmith, Jim Rockwell

The design of high-thermal-efficiency LNG liquefaction plants is of importance to minimize feed usage and to reduce CO2 emissions. High efficiency becomes important in gas constrained situations where savings in fuel auto consumption of the liquefaction facility can be converted into LNG production. The imposition of a CO2 taxes will further promote the need for higher energy efficiency.

This paper will examine heat integrated combined cycle approaches applied to the ConocoPhillips Optimized Cascade® Process and will address both industrial and aeroderivative gas turbines. Aeroderivative engines offer very attractive efficiencies where comprehensive steam systems are not viable or desired by the end customer. When steam systems are acceptable, a combined cycle type liquefaction facility can be attractive in increasing the efficiency of a simple cycle plant.

The paper will examine combined cycle/cogeneration configurations with respect to plant heat to power ratio. An evaluation of a range of technical options for heat recovery including the use of back pressure and condensing extraction steam turbines is first made. Finally, conceptual designs for four combined cycle configurations are examined from a thermodynamic perspective.

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