Gas Turbine Propulsion for LNG Transports

Abstract

GE aero-derivative gas turbines were first introduced into marine operations during the late 1960’s and early 1970’s. GE is now leveraging its many years of proven marine experience and offshore dual-fuel experience to offer dual-fuel gas turbines for LNG Carrier (LNGC) propulsion and electric power. With building of new larger LNGC’s now beginning, the industry is seriously considering a change to gas turbine based systems in order to capitalize on their many advantages. CoGES (combined gas turbine — steam generator electric) plants for LNGC’s consist of dual-fueled gas-turbine-generator (GTG) set(s) and auxiliaries, heatrecovery steam generator (HSRG), a steam-turbine-generator set, feed-water, steam and condensate systems. Leveraging cruise-ship reliability programs, the GTG instrumentation and control systems are single-point fault tolerant. Gas turbine power plants offer many additional advantages, including but not limited to: Use of boil-off gas as a cost-effective and environmentally friendly fuel (slow speed diesel ships require complex on-board reliquifaction of boil-off gas). When installed on deck, CoGES plants provide high power-volume density that translates into increased cargo revenue and deferred capital cost. Gas turbines ease of maintenance and quick changeout. Developed to meet the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC) and classification society standards for marine applications, GE’s 2 X LM2500 CoGES plant is a very simple and reliable solution. Dry-run capable HRSG’s are used in lieu of exhaust damper and by-pass systems. Outage of any one prime mover leaves the plant with nominally 50% power remaining. Common spares are inherent. Established as having an equivalent level of safety as traditional LNGC propulsion systems via FMECA type studies, the 2 x dual-fueled LM2500 CoGES plant has been “Approved in Principle” by Class for use on LNG Carriers. Alternatively, GE’s 1 X dual-fueled LM6000 or 1 X LM2500+/G4 CoGES plant addresses capital & operating cost pressures via reduced equipment costs and improved fuel economy. Redundancy and simplicity are achieved via a dry-run capable HRSG and an STG, combined with auxiliary diesel generator sets. Both the LM2500 family and LM6000 CoGES plants offer viable alternatives to traditional steam turbine and slow-speed-diesel propulsion. Gas-fuel, liquid-fuel, and bi-fuel operation provide flexibility and redundancy to ship owners who must safely and reliably deliver cargo at the lowest possible cost per MMBTU throughout a fleet life cycle.