Experimental Studies On An Auto-cascade Natural Gas Liquefier Using A Distillation Device And Mixed Refrigerants

Small-scale natural gas liquefiers can reclaim the low-pressure small natural gas reserves, which are widely scattered throughout China, to alleviate the increasing energy crisis. On the basis of the review of the literatures on the small-scale natural gas liquefiers in at home and abroad and their application characteristics, a small-scale mixed refrigerant auto-cascade natural gas liquefier is proposed in the thesis and theoretical and experimental research is conducted on the performance of the system.As the following, the major contents and key points are:(1) The influence of the key parameters such as the composition of mixed refrigerant, natural gas pressure and operation pressure on the performance of the system is obtained by the thermodynamic analysis based on the minimum specific liquefaction work of the auto-cascade natural gas liquefier using a liquid-gas separator.(2) The mixed refrigerant auto-cascade natural gas liquefier using a distillation column is designed, built and adjusted successfully, which is equipped with a composition-variable module and process selection module to improve its performance.(3) The liquefaction experiments are conducted for the pure methane at the pressures of0.3MPa,0.35MPa,0.4MPa,0.45MPa and0.5MPa using the mixed refrigerants composed by N2, CH4, C2H4, C3H8and iC+H10. The influence of important parameters on the system performance is basically matched in theory and experiment. The system performance could be improved by the increase of middle-boiling point components, the decrease of the lowest-boiling and highest-boiling point components, the increase of natural gas pressure, and the decrease of suction pressure.(4) The specific liquefaction work of2.959kWh/kg was obtained with the natural gas pressure of0.514MPa in experiment, which provides the foundation for the further research...