A HISTORICAL REVIEW OF TURBOMACHINERY FOR LNG APPLICATIONS

摘要

Specialized turbomachinery designs are required for large scale refrigeration cycles in LNG applications, often pushing the envelope of the centrifugal compressor's flow rate and the horsepower rating of variable speed electric drive equipment. Over the last ten years, the refrigeration compressor drives (either gas turbine or electric motor) have evolved to meet the needs of larger LNG plants and advanced refrigeration cycles, accommodating increased variable speed ranges, integrated start-up equipment and harsh ambient condition ratings. The centrifugal compressor designs confront significantly higher flow coefficients and gas densities compared to pipeline and power generation applications, creating a challenging design to evenly distribute power per stage and control the Mach number limit, due to the higher molecular weight refrigerant. Although somewhat process dependent, the compression power can be supplied through steam turbine, gas turbine, fixed speed or variable speed electric motor. Both options can now be considered viable options up to 70 MW and driver selection must be evaluated in terms of the specific project needs and the LNG project location. Based on experience with the Apache Kitimat LNG project, this poster session investigation will compare tradeoffs associated with the driver selection and the LNG refrigeration cycle. The electrical power requirement, power conditioning, fuel consumption (hp per ton of LNG produced), machinery, start-up options and process conditions will be studied for the primary LNG cycles used in large LNG plants (greater than 500 MMSCFD per train). Recent engineering 'lessons learned' at Apache in reviewing LNG processes and machinery needs for the Kitimat LNG export facility will be highlighted as well.