| Natural gas produced overseas is liquefied to reduce its volume by a factor of 600 so that it can be transported economically by ship. Once the Liquefied Natural Gas (LNG) ship arrives in the U.S., it docks at an LNG import terminal to deliver its contents. The LNG is stored in liquefied form until needed; then it is revaporized and sent to a natural gas pipeline for distribution throughout the U.S.; For the LNG import terminal simulation, Aspen Plus version 12.1 has been used to develop the steady state model for the process engineering design, and then the Aspen Dynamics 12.1 model has been developed for subsequent transient studies. At optimum reliquefication pressure of 5 bars, a boil off gas liquefaction system can save 60% of the electric power compared to a conventional system. During rollover conditions, 47699.34 m3 of vapor is produced instantaneously, whereas during normal operation the vapor generation is approximately 3908 m3/hr. The study developed LNG terminal emergency shut down procedures using cause and effect matrix. LNG storage tank pressure regulation using advanced process control can optimize the vapor handling and minimize the downstream fluctuations. The work analyzed LNG release from various breached locations along with spill calculation from a non-pressurized tank with a single hole, and behavior of the pressure safety valve, which is the last line of defense in the event of process upset. |
