The Numerical Simulation Of Natural Gas Liquefaction Process With Nitrogen-methane Expander

Natural gas is one of the main energy in the 21 st century,which consumption is increasingly.Liquefied natural gas has obvious advantages in storage and transportation,and has been developed into a new industry.The natural gas liquefaction technology in abroad is relatively mature;nevertheless,considering the research status and industry of domestic demand,it is necessary to carry out further research and discussion on the technology of liquefied natural gas.Based on thermodynamics,this paper gives the optimization and simulation process of nitrogen-methane expander cycle.In this paper,the nitrogen-methane expansion of natural gas liquefaction process are chosen as the research object,and the small and medium-sized natural gas liquefaction process and device research progress is discussed both at home and abroad.The simulation basis of natural gas and gas source conditions,which is determined by the survey of natural gas composition and pressure in Changqing oil field,Shaanxi province.According to the physical properties and the analysis of the thermal properties of natural gas,the P-R equation and the LKP equation are selected to calculate the phase equilibrium of natural gas liquefaction process and the enthalpy and entropy of each node in the process of natural gas liquefaction respectively.HYSYS software is used to simulate the whole process,and the calculation module of the main equipment in HYSYS software is introduced in detail.From thermodynamic point of view,the effects of nitrogen-methane expansion of liquefaction process performance in the main process parameters(e.g.gas pressure,gas temperature,gas composition,LNG storage pressure,refrigerant high pressure,low pressure refrigerant pressure,refrigerant in the methane content,refrigerant expansion temperature before)are analyzed.On the basis of the objective function of consumption,the process parameters are optimized,thereby the liquefaction rate is increased and the specific power consumption is reduced.The characteristics of three kinds of natural gas liquefaction processes are compared and analyzed.Furthermore,the natural gas liquefaction process were determined by calculating the exergy analysis.The compressor flow is analyzed by energy consumption of the equipment,and some effective measures,which take the consideration of the reasons of exergy loss,are put forwardto reduce exergy loss.The research results of this paper have certain theoretical guiding significance and practical value for the further study of the liquefaction process of nitrogen methane expanded natural gas.