Document Type

Working Paper

Date of this Version

4-2012

Abstract

This project recommends several possible processes which expand and improve upon an existing section of a natural gas liquefaction plant. The section in question involves the combustion of the effluent fuel from the liquefaction process to produce usable work that drives the overall process. The existing process involves a simple gas turbine, which utilizes a Brayton cycle to convert combustion heat to shaft work.

While the existing platform successfully provides power to the overall liquefaction process, the gaseous exhaust from this process leaves the system at elevated temperatures. The processes presented in this project seek to recover the heat that is lost through the exhaust and therefore, improve the thermodynamic efficiency of this system. Additionally, these processes more rigorously meet environmental standards concerning flue gas compositions and temperatures. Seven such processes are presented in this report. Each of these provides a net of 40MW, the required power to drive the liquefaction process, while performing at higher thermodynamic efficiencies than the simple gas turbine process.

Rigorous economic analyses were performed for each of the presented processes. One recovery system has a lower net present value (NPV) than that of the simple gas turbine, four have approximately equal NPVs, and two systems have significantly better NPVs than that of the simple gas turbine. The optimal system has an NPV of $22 million and an internal rate of return (IRR) of 28.2% versus the simple gas turbine with an NPV of $12.3 million and an IRR of 20.3%. Further analyses of the economic and pricing assumptions may be required before final project approval.

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Date Posted: 20 August 2012