INNOVATION January-February 2013

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Norway’s 4.2 million ton per annum single train Snøhvit LNG project, the first to adopt electrical drives, is a good example of a successful implementation. Careful due diligence culminated in the selection of five LM6000 gas turbine generators, each site rated at 46 MW with an electrical efficiency of 41%. To address redundancy, a 50 MW power supply from the Norwegian grid was installed, thereby allowing one turbine to be out of service without impacting LNG production. Waste heat recovery to meet the process heat and winterization loads yielded a 70% thermal efficiency. The claimed 6% fuel consumption has been independently verified by CDS. Conclusion BC is endowed with huge gas reserves. With low demand in Canada, and the US becoming not only self-sufficient but an LNG exporter, our gas is essentially stranded. Big investments already made in upstream assets and a race by major players to share LNG export opportunities in BC herald the dawn of a major economic boom for our province, expected to last at least 50 years. BC engineers and geoscientists will no doubt meet the many challenges specific to our province and climate. Sustaining high production from shale gas formations and managing its costs and environmental impact is one of these challenges, and a broad range of services will be needed in Northern BC, including the expansion of air transportation. Our care for the environment makes it easier for us to embrace cleaner designs and technologies. It is no accident that the first BC LNG export project to complete front-end engineering design is also the most efficient in the world. High tech in nature and capital intensive, the development of an LNG industry presents unique opportunities to expand significantly BC’s technology base. It will also create significant demand for electrical power with the potential of benefiting green power suppliers. v

load of the plant made up of air coolers, boil-off compressor, LNG loading pumps, starter/helper for refrigeration compressors, lighting, controls, trace heating, miscellaneous pumps and com- pressors, etc. • Flaring during plant shutdown • Flaring during plant start up • Flaring due to unloading a compres- sor prior to start up • Continuous purging of flare headers with boil-off gas • Activation of pressure relief valves and fugitive emissions • Process heaters • CO 2 extracted from feed gas • Testing of stand-by generators, etc. Faced with stricter air emissions and limited options for mitigation, the LNG industry is currently considering electrical drives for projects in different parts of the world including Australia, Iran, Angola, Norway and Nigeria. During preliminary front-end engineering design, CDS Research performed the evaluation and selection of electrical drives for the front runner of the LNG export prospects from BC: Kitimat LNG. Configured for a power supply from BC Hydro grid, the Kitimat LNG project is currently known to be the most efficient in the world. This is, however, an exception as there are very few locations in the world with a grid

supply that have the capacity and reliability needed by an LNG plant. There are fundamental differences between a gas turbine drive and an electrical drive for a compressor. An electrical drive has the following advantages: 95% motor efficiency; 47% efficiency of industrial power generation in open cycle, 55% in combined cycle; high efficiency available over a wide speed range; faster control response; a compressor may be started under load thereby alleviating flaring; lower fuel consumption; lower carbon tax burden; and higher availability resulting in increased LNG production. The disadvantage of an electrical drive with onsite power generation is higher capital cost. Electric motors in the 45 to 70 MW rating require an electrical drive to limit the current drawn during start-up and adjustment of the compressor speed. Only the load commutation inverter (LCI) type of drive is considered proven for this rating. The LCI has, however, a poor harmonic signature which requires a harmonic filter. The drive and filter come in two separate modules, each the size of a 40 ft container. Adopting electrical drives and an appropriate power supply system is anything but straightforward. Numerous factors need to be taken into account including the site ambient conditions. For one, availability is a major consideration. On a 500 MW combined cycle power generation plant using two gas turbines, the loss of one turbine would shut down one liquefaction train.

Dr. Zoher Meratla, P.Eng., is principal of CDS Research Ltd., a specialty engineering company focusing on LNG projects worldwide.

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