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Abstract The dual mixed refrigerant (DMR) cycle, which pre-cools natural gas with the mixed refrigerants and then liquefies the natural gas with another set of mixed refrigerants, is well known for having the highest efficiency among the liquefaction cycles. Its possible application to LNG FPSO is also extensively investigated. In this study, the optimal operating conditions, such as the equipment's flow rate, pressure, temperature, and refrigerant composition per flow of the DMR cycle, were determined in consideration of power efficiency. To determine the optimal operating conditions, a mathematical model was formulated based on the mathematical model of the single mixed refrigerant (SMR) cycle with additional consideration of tees, phase separators, and common headers. In the mathematical model, the 227 operating conditions were defined as unknowns and 196 equality constraints related to the thermodynamics for the equipment were formulated. Further, the 15 given variables related to the natural gas, compressor efficiency and seawater coolers were used. This mathematical model can be regarded as the optimization problem, in which the number of unknowns is larger than the total number of equality constraints and given variables. To obtain the optimal operating conditions, the minimization of the required power for the compressors at the cycle was defined as an objective function. Moreover, set as design variables were the 16 operating conditions, such as flow rate, pressure, temperature and composition of the main and precooling refrigerant, natural gas temperature after precooling, and flow rate ratio for the tee. In addition, the temperature conditions for the equipment’s operation were used as inequality constraints. The optimal operating conditions were then obtained by using a hybrid optimization method that consists of the genetic algorithm (GA) and sequential quadratic programming (SQP). The calculation results show that the required power at the obtained conditions was decreased by 34.5% compared with that of the relevant patent obtained in 2001, and 1.2% compared with the corresponding value from the past relevant study carried out in 2008.
Publication Date 2011-06-19

Kyu-Yeul Lee, Ju-Hwan Cha, Joon-Chae Lee, Myung-Il Roh, Ji-Hyun Hwang, "Determination of the Optimal Operating Condition of Dual Mixed Refrigerant Cycle at the Pre-FEED Stage of LNG FPSO Topside Liquefaction Process", Proceedings of ISOPE(International Society of Offshore and Polar Engineers) 2011, Maui, USA, pp. 151-158, 2011.06.19-24


List of Articles
번호 분류 제목 Publication Date
130 International Conference Sung-Min Lee, Myung-Il Roh, Ki-Su Kim, "Determination of Economical Ship Route Using Simultaneous Optimization Method", Proceedings of ACDDE 2016, Jeju, Korea, 2016.10.25-28 file 2016-10-27
129 International Conference Sung-Kyoon Kim, Sol Ha, Seun-Ho Ham, Myung-Il Roh, "Optimal Layout Method for Offshore Plant Topside Considering the Safey, Operability and Maintanability", Proceedings of IMDC 2015, Tokyo, Japan, 2015.5.11-14 file 2015-05-12
128 International Conference Sung-Jun Lee, Myung-Il Roh, Min-Jae Oh, Youngsoo Seok, Won-Jae Lee, June-Beom Lee, Hyun Soo Kim, "Image-based Object Detection and Tracking Method for Ship Navigation," Proceedings of ICCAS 2019, Rotterdam, Netherlands, pp. 89-92, 2019.09.24-26 file 2019-09-24
127 International Conference Sung-Jun Lee, Myung-Il Roh, Hye-Won Lee, Jisang Ha, Il-Guk Woo, "Image-based Ship Detection and Classification for Unmanned Surface Vehicle Using Real-Time Object Detection Neural Networks", Proceedings of ISOPE 2018, Sapporo, Japan, 2018.06.10-15 file 2018-06-13
126 International Conference Sun-Kyung Jung, Myung-Il Roh, Seung-Min Lee, Ki-Su Kim, "Optimal Arrangement Method for Naval Surface Ship Considering the Stability, Operability, and Survivability", Proceedings of ICCAS 2017, Singapore, Singapore, 2017.09.26-28 file 2017-09-26
125 International Conference Sol Ha, Seung-Ho Ham, Myung-Il Roh, "Dynamic Route Guidance for Evacuation, Escape and Rescue System at an Offshore Platform Considering Real-time Hazard Avoidance", Proceedings of the 28th Asian-Pacific TEAM 2014, Istanbul, Turkey file 2014-10-15
124 International Conference Sol Ha, Namkug Ku, Myung-Il Roh, Ju-Hwan Cha, "Reliability Analysis Method Using Dynamic Reliability Block Diagram Based on DEVS Formalism," Proceedings of the 13th International Conference on Systems Simulation(AsiaSim 2013), Singapore, pp. 219-230, 2013.11.06-08. file 2013-11-06
123 International Conference Sol Ha, Nam-Kug Ku, Myung-Il Roh, Xing Li, "Evacuation, Escape and Rescue EER Analysis of Offshore Plant Based on Human Behavior Model", Proceedings of OMAE 2014, San Francisco, USA, pp. 1-7, 2014.06.08-13 file 2014-06-10
122 International Conference Sol Ha, Nam-Kug Ku, Myung-Il Roh, Ki-Su Kim, Seung-Ho Ham, Xing Li, Jung-Woo Hong, Hye-Won Lee, "DEVS-based Scenario Manager of Multibody Dynamics Simulator for Shipbuilding Production Process (WIP)", Proceedings of Spring Simulation Multi-Conference 2014, Tampa, USA, pp. 358-363, 2014.04.13-16 file 2014-04-16
121 International Conference Sol Ha, Nam-Kug Ku, Myung-Il Roh, "Ontological Modeling and Process Simulation of LNG FPSO Liquefaction Cycle based on DEVS Formalism", Proceedings of ISOPE(International Society of Offshore and Polar Engineers) 2013, Alaska, USA, pp. 950-958, 2013.06.30-07.05 file 2013-06-30
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