Theoretical And Experimental Studies On An Auto-cascade Natural Gas Liquefier Using A Rectifying Column

As the demands of clean energy is increasing gradually and the technology of shale gas extraction is maturing, gas industry will develop rapidly in the future. Small-scale natural gas field with low-pressure small natural gas reservers are widely scattered throughout China and natural gas pipe network can only cover a small part of China, which demand for the development of the small-scale natural gas liquefaction systems. A small scale autocascade natural gas liquefier operating mixed refrigerant is studied in this thesis by simulations and experiment. The major contents of the thesis are as follows:(1) An VB program using the modified PT equation was developed to calculate the vapor-liquid equilibrium and other thermodynamic properties of the mixed refrigerant.(2) The mixed refrigerant is composed by R600a,R290,R1150,R50,R728and the natural gas is composed by pure methane in the research. The influence of the critical parameters such as the operation pressure, natural gas pressure, throttle valve opening, composition and charge of the mixed refrigerant on the performance and operational reliability of the system is obtained by Theoretical and experimental studies. The results of experiment are basically consistent with those of the theory.(3) The system is optimized by adjusting composition and charge of mixed refrigerant and opening of the throttle valve to obtain the minimum liquefaction work per kilogram of the liquefied pure methane. As a result, the liquefaction work per kilogram of the liquefied pure methane at4.49kW·h/kg,1.98kW·h/kg,1.61kW·h/kg,1.29kW-h/kg with pure methane pressure at0.1MPa,0.3MPa,0.5MPa,0.7MPa are obtained, and it takes only3hours for the starting process.which follows the advanced levels in the world.