Thermodynamic simulation and optimization of natural gas liquefaction cycle based on the common structure of organic rankine cycle

Abstract

In this paper, using Aspen HYSYS and two different structures of an organic Rankine cycle (ORC), thermodynamic and environmental improvements are made in the common process of a natural gas liquefaction process based on the PRICO method. According to the analyses, in the PRICO process, the total exergy efficiency, power consumption, and carbon dioxide (CO2) emission are 43.9%, 278.47 kWh/ton, and 0.17 kgCO2/kgLNG, respectively. Results showed that heat recovery by the ORC cycle results in decreasing the exergy loss, increasing the exergy efficiency, lowering the power consumption, and reduction in the CO2 emission. The total exergy efficiency of the PRICO process coupled with the modified ORC and ORC increases to 54.1% and 53.68%, respectively. Besides, the amount of consumed power is reduced to 225.42 kWh/ton and 227.26 kWh/ton, respectively. From the environmental aspect, it is demonstrated that the CO2 emission of the PRICO plus modified ORC process in comparison with PRICO and PRICO plus ORC is lower by 23.53% and 7.14%, respectively. Finally, comparing the results with previous papers revealed that the proposed scheme in this paper (PRICO plus modified ORC), regarding the energy and exergy efficiencies, has a better performance than technologies such as SMR, DMR, C3MR, and PRICO.