(402c) Analyses on the Effect of Natural Gas's Supercooling Temperature on the Liquefaction Performance of Prico Process

Due to the advantages of cleanness, high calorific value and so on, LNG (liquefied natural gas) is becoming increasingly important in the energy structure with the changes of energy utilization situation and the development of technology. However, natural gas liquefaction processes are complicated with significant interactions of each component, making it difficult to obtain the optimal working condition. Meanwhile, in the mixed refrigerant liquefaction processes, compositions of the mixed refrigerant and other working parameters have predominant effects on the performance of compressor and the matching of hot/cold composite curves, which may result in large exergy losses of some components and low refrigeration efficiency if deviated from the optimum. Especially the natural gas subcooling degree varies in different literature, the optimization and determination of which needs further investigations.

Based on the simplified prico process, this paper focuses on the effects of the initial pressure and subcooling degree of the natural gas (the cooling temperature of liquefier) on the liquefaction performance such as the specific/unit liquefaction work and the specific/unit volumetric liquefaction capacity. The main contents are presented as follows.

(1)The mixed refrigerant composed of R600a, R290, R1150, R50 and R728 is applied.Pure methane is used to simulate natural gas. Aspen HYSYS was used to simulate the natural gas liquefaction process with an initial pressure range of 0.5 MPa ~ 5MPa.

(2) the effects of the initial pressure of natural gas and the cooling temperature of liquefier on the specific liquefaction work and specifc volumetric liquefaction capacity were analyzed . Results show that different initial pressure and cooling temperature of liquefier have significant effects on system performance.

(3) Through the comprehensive consideration of performance and cost optimization, the method for the determination of the natural gas subcooling degree of the prico process we proposed, which was of great significance to the subsequent experiment and application research.