Multi-aspect evaluation of integrated ethane liquefaction processes: economic, energy, and thermodynamic analysis for transport applications

Ethane liquefaction processes vary widely in energy consumption, capital investment, and technical complexity, especially in low-capacity production. The refrigeration cycles, equipment arrangement, and liquefaction facilities are important factors influencing the efficiency and performance of the technology. In this study, a case study is performed to evaluate several ethane liquefaction processes and to control the related energy consumption levels while reducing capital investment. To this end, six methods and technologies are proposed to produce liquefied ethane as case studies. Evaluation of the technical conditions, thermodynamic analysis, and cost estimation was done using Aspen HYSYS, Refprop, and Aspen Capital Cost Estimator software, respectively. Based on the results of the case studies, it can be concluded that Cases 4 and 6 are more desirable than the others due to lower capital costs and reduced energy and operating costs. In Case 4, it should be noted that cooling and liquefaction down to −34 °C are achieved at pressures above 9.5 bar. The results indicate that the estimated Total Annualized Cost (TAC) for Cases 1 to 6 are 4,375,639; 4,403,845; 4,738,296; 4,629,148; 3,467,939; and 4,124,547 USD, respectively. Consequently, among the available cases, Case 6 is the best option for the liquefaction process due to its lower cost (126 USD/T). This case operates with a propane refrigeration cycle and three main cold boxes to execute the liquefaction process.