Investigating the Natural Gas Transmission in Supercritical Condition

Pipeline is one of the main methods of natural gas transmission. This method has some limitations such as inflexibility, limited gas transmission capacity, and high costs of installing and maintaining the equipment. To overcome some of these limitations, dense phase gas transmission (supercritical fluid) has recently been proposed. Among the benefits of supercritical natural gas transmission, increased density, decreased viscosity, less compressor stations, smaller pipe diameter, reduced pressure drop, lower maintenance costs, as well as the lack of two-phase fluid formation should be mentioned. To change the gas from usual condition to a dense phase, the gas pressure should be more than the cricondenbar point and the gas temperature should be between the critical temperature and the cricondentherm point in the phase diagram. In this paper, after expressing the theory and equations of gas transfer, the results of two case studies on natural gas transmission in supercritical conditions are presented. These studies showed that the compression and cooling energy in the supercritical gas transmission were 70% and 50% lower than the two-phase gas transmission mode, respectively. The extractable amount of liquefied gas in the supercritical condition was 74% higher than the two-phase state. Also, the amount of energy of the compressors in the dense phase state was 51% and 63% lower than the medium and low-pressure gas transmissions states, respectively.