The global use of natural gas is growing quickly. This is primarily attributed toits favorable characteristics and to the environmental advantages it enjoys over otherfossil fuels such as oil and coal. One of the key challenges in supplying natural gas is theform (phase) at which it should be delivered. Natural gas may be supplied to theconsumers as a compressed gas through pipelines. Another common form is to becompressed, refrigerated and supplied as a liquid known as liquefied natural gas (LNG).When there is a considerable distance involved in transporting natural gas, LNG isbecoming the preferred method of supply because of technical, economic, and politicalreasons. Thus, LNG is expected to play a major role in meeting the global energydemands.This work addresses the simulation and optimization of an LNG plant. First, theprocess flowsheet is constructed based on a common process configuration. Then, thekey units are simulated using ASPEN Plus to determine the characteristics of the variouspieces of equipment and streams in the plant. Next, process integration techniques areused to optimize the process. Particular emphasis is given to energy objectives through three activities. First, the synthesis and retrofitting of a heat-exchange network areconsidered to reduce heating and cooling utilities. Second, the turbo-expander system isanalyzed to reduce the refrigeration consumption in the process. Third, the processcogeneration 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 LNGfacilities is solved to examine the benefits of simulation and integration of the process.The technical, economic, and environmental impact of the process modifications are alsodiscussed.
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