الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
For production of LNG , the refrigeration cycles require a significant amount of power for compression of the refrigerant and that is one of the most significant issues in a natural gas liquefaction facility. There are various Liquefication processes with different refrigeration loops. This study will focus on propane pre-cooling mixed refrigerant cycle as this process is the most preferred option in LNG plants. So, it is necessary to evaluate the performance and improve its energy efficiency by increasing the capacity and reducing the cost. The study provides two approaches of modification to reduce the compressor duty, the first approach is a minor structural modification in flash unit of mixed refrigerant and the second major approach investigates possibility of implementation the AP-X process, which designed by Air Products and Chemicals Incorporation by adding nitrogen expander sub-cooling cycle that gives an important feature of splitting the liquefaction required between refrigeration cycles. The simulation of the base case and modified cycles was conducted using Aspen HYSYS software version-11 by using the Peng-Robinson equation of state. The results of AP-X process for same condition and capacity of natural gas show a significant reduction in the total power consumption by about 10 MW, which represents 6% power saving of the total power consumption in the base case , due to reduction in propane and mixed refrigerant flow rate by 26.1% and 40.8% respectively. This study also provides an economic analysis after increasing the natural gas flow by 20% and it shows good plant profitability and short payback period less than one year.