Parameter Optimization And Effect Evaluation For The Mixed Refrigerant Natural Gas Liquified System

China's LNG technology is in the rapid development stage,but there is still a certain gap between China's LNG technology level and the developed countries.In the LNG process,the mixed refrigerant natural gas liquefaction process is widely used in LNG liquefaction plants because of its advantages of low energy consumption.Therefore,this paper designs a single cycle mixed refrigerant process for a small natural gas liquefaction unit and a double cycle mixed refrigerant process for a large natural gas liquefaction unit.Based on the steady simulation of liquefied natural gas(LNG)process,optimization analysis and Steady state simulation are carried out.First,the domestic and international research status of liquefied natural gas technology development and the simulation development of natural gas liquefaction process are discussed,the importance of studying mixed refrigerant refrigeration for liquefied natural gas is proposed,and the main mixed refrigerant liquefaction process is introduced.Secondly,the thermophysical properties of natural gas and mixed refrigerants are described,including basic thermodynamic parameters,phase equilibrium and enthalpy entropy calculation models.In this paper,the Peng-Robinson(PR)equation is selected as the phase equilibrium equation for calculating natural gas and mixed refrigerants,and on this basis,the HYSYS model of Single Mixed Refrigerant Cycle(SMR)and Dual Mixed Refrigerant Cycle(DMR)mixed refrigerant liquefaction processes were established to conduct steady-state simulation.Thirdly,based on the steady-state simulation of the natural gas liquefaction process,the optimization analysis was carried out.Taking the minimum specific power consumption of the process as the objective function,the optimizer in HYSYS was used to optimize the process parameters and the ratio of mixed refrigerant in the process.The system energy consumption is reduced by 18.38%,and the system energy consumption of the DMR process is reduced by 16.72%.On the basis of this optimization scheme,the pressure of natural gas is unchanged,the influence of factors such as natural gas composition and temperature on the application effect of the process is studied,and the change law of the application effect of the process is analyzed when the composition and temperature of the natural gas are simulated at a steady state,and the reason is analyzed;The loss of energy efficiency proposes a reasonable plan to reduce the loss of energy process equipment.The research results have reference value for adjusting parameters,optimizing parameters,increasing yield,and reducing energy consumption of LNG liquefaction plant that has been built or reconstructed;it also provides technical support and guidance for the design,parameter optimization and production of LNG liquefaction plant.