(49g) An Axial Flow Hermetic Turbine for Flashing LNG Applications

Two-phase axial flow turbines have been developed and commercialized for flashing liquid applications.  Over 75 of these turbines have been applied to replace the Joule Thomson valves in large centrifugal chillers. Some have operated for 15 years. These turbines have increased the efficiency of the chiller system by 7-8% by generating power for the compressor from the pressure energy previously wasted in the valves.

Other two-phase axial flow turbines have been applied to generate power from flashing hydrocarbon mixtures, from steam and brine flows and from flashing liquid nitrogen.

An engineering design study of a flashing axial flow turbine, for the high pressure letdown in the ConocoPhillips Optimized Cascade® LNG Process, was conducted in conjunction with ConocoPhillips Corporation. The machine designed was a hermetic turbine-generator. The generator is immersed in the LNG. Proven design practice of commercial LNG submerged pumps was used.     

The lightweight impulse rotor generates 2 megawatts for the process conditions analyzed.  The LNG output was increased by 2.1%, 159,000 tons per year for the case studied.

The performance and design of the flashing LNG turbine designed is presented. The performance and reliability of two-phase axial turbines is also discussed and documented in the paper. Recent results from testing an axial flow hermetic turbine for flashing liquid nitrogen are presented. That turbine was tested with two-phase flow at the inlet. The operation was stable and predictable.

Nearly 100 axial flow two-phase turbines comprising 30 years of experience are referenced. Some have been applied to much more severe conditions of temperature, pressure and corrosion than the LNG applications. Key examples of the technology are discussed.