Evaluation of production processes for LNG in arctic climate
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Most of nowadays base load LNG plants are localized in the area around equator, with stable warm air and cooling water temperature. For new LNG developments in arctic areas there are several features that differ them from plants operating further south. In this work a ConocoPhillips Optimized Cascade LNG process model has been established in HYSYS® and evaluated. The evaluation focus on the driver configuration and cooling method used in order to optimize process efficiency and capacity of the plant for operation in cold climate. Simulations with air cooling and water cooling have been done. Each cooling method has been evaluated for an aero derivative gas turbine compressor driver, an industrial heavy duty gas turbine compressor driver, and an electric compressor driver configuration. Yearly temperature statistics from Kola has been used. The air cooled simulations have a design temperature of 20°C and the water cooled simulations have a design temperature of 4°C seawater temperature and an air temperature of 5°C. The air cooled cases are not close to design operation the entire year. The aero derivative driver configuration will have problems operating at high air temperatures and a higher design temperature is needed. The heavy duty gas turbine driver configurations have limitation in speed variation and this leads to low process efficiency at low temperatures. The electrical driver configuration will not have problems operating. The results show that air cooling is not the desired cooling method because of lower production variation and lower process efficiency. The water cooled cases are close to design conditions the entire year; hence it has the highest flexibility when it comes to production variation and highest process efficiency. The aero derivative driver configuration varies most throughout the year with lowest production in the summer. The heavy duty gas turbine driver configuration has a lower variation in production. The power delivered to the electrical motors will not be affected by air temperature which lead to high process efficiency and stable production plateau throughout the year.