Sensitivity analysis of peak-shaving natural gas liquefaction cycles to environmental and operational parameters

Existence of huge reserves of natural gas in the country and also the extent of its distribution lines has caused the use of natural gas as the main energy carrier. Seasonal fluctuations in gas consumption in domestic sector and giving priority to this sector has led that the gas supply to other sectors such as thermal power plants is faced with many problems in the cold season. One way to deal with this issue (shortage of natural gas) is the liquefaction and storage of surplus natural gas in the summer, using peak-shaving gas liquefaction plants. In this study, SMR and N2-expander processes have been evaluated. Changing in operational and environmental parameters (such as changes in flow rate, pressure, temperature and composition of the feed gas and working fluid of the cycle) are the main problems that peak-shaving plants will be permanently encountered with them, thus low sensitivity to changing conditions is the one of the important criteria in the selection of suitable process for peak-shaving. In this study, the sensitivity of liquefaction processes has been investigated using normalized sensitivity analysis. The results indicate that SMR process, despite lower power consumption is more sensitive to changes of the environmental and operational parameters and even, in some cases, the applied perturbation in the probable error range of measurement devices (such as 20 kPa uncertainty or fluctuation in compressor suction pressure), causes malfunction of the liquefaction process (wet entering the compressor).