Simulation and integration of liquefied natural gas (lng) processes
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The global use of natural gas is growing quickly. This is primarily attributed to its favorable characteristics and to the environmental advantages it enjoys over other fossil fuels such as oil and coal. One of the key challenges in supplying natural gas is the form (phase) at which it should be delivered. Natural gas may be supplied to the consumers as a compressed gas through pipelines. Another common form is to be compressed, refrigerated and supplied as a liquid known as liquefied natural gas (LNG). When there is a considerable distance involved in transporting natural gas, LNG is becoming the preferred method of supply because of technical, economic, and political reasons. Thus, LNG is expected to play a major role in meeting the global energy demands. This work addresses the simulation and optimization of an LNG plant. First, the process flowsheet is constructed based on a common process configuration. Then, the key units are simulated using ASPEN Plus to determine the characteristics of the various pieces of equipment and streams in the plant. Next, process integration techniques are used to optimize the process. Particular emphasis is given to energy objectives through three activities. First, the synthesis and retrofitting of a heat-exchange network are considered to reduce heating and cooling utilities. Second, the turbo-expander system is analyzed to reduce the refrigeration consumption in the process. Third, the process cogeneration is introduced to optimize the combined heat and power of the plant. These activities are carried out using a combination of graphical, computeraided, and mathematical programming techniques. A case study on typical LNG facilities is solved to examine the benefits of simulation and integration of the process. The technical, economic, and environmental impact of the process modifications are also discussed.
Al-Sobhi, Saad Ali (2007). Simulation and integration of liquefied natural gas (lng) processes. Master's thesis, Texas A&M University. Available electronically from