Optimization And Energy Analysis In The Simulation Process For Natural Gas Liquefaction

In recent years, growing louder environmental governance has forced to accelerate the development in the direction of clean energy under the pressure of controlling haze and reducing pollution. With the vigorous development and utilization of low-carbon resources, energy consumption structure has been further optimized in China. The proportion of coal in primary energy consumption structure drops while the one of the consumption of the high quality, clean and efficient natural gas increases, and the consumption was increasing trend. The current situation and development trend of natural gas liquefaction technology is described respectively. The advantages and disadvantages of several kinds of natural gas liquefaction process are briefly introduced. It is obvious that the new and efficient natural gas liquefaction processes of mixed refrigerant cycle with a propane pre-cooled system widely used in the current at home and abroad is preferentially selected as the simulation process in this paper through the technical and economic comparison. To meet the requirements of accuracy, the PR equation and the LKP one are selected to calculate the equilibrium properties of refrigerants and other thermal physical properties such as enthalpy entropy and so on according to the thermal properties of the natural gas and mixed refrigerants. The comparative results both the results calculated by the simulation software of ASPEN HYSYS and the known experimental data deserved from Shanghai Jiaotong University are available within the error range, which indicates the selected thermodynamic equations are suitable in the simulation process. Every device in the process is simulated by the modular thought. The simulation process is established by ASPEN HYSYS software, of which the modules of compressors, condensers, throttle valves, multi-stream heat exchangers, throttle and mixer are made in detail to parameter settings. In steady-state process conditions, the effect is simulated of the components, high and low pressure of mixed refrigerants, the pressure and temperature of feed gas and propane pre-cooling temperature on the process respectively, for the reasonable proportion of refrigerant and the scientific process parameters. The best ratio of mixed refrigerant is that methane is 0.436(mole fraction, similarly hereinafter), and ethane, propane and nitrogen is 0.393, 0.099 and 0.072 respectively. The key equipment in the process is analyzed and further optimized by exergy based on the above, in order to achieve the purpose of saving energy, reducing consumption, and improving the device efficiency. The minimum unit power consumption of the optimized process compressor is 7.692 k W?h/kmol, which less 4.0585 k W ? h / kmol than the one of the non-optimized process compressor, which is 11.75 k W ? h / kmol. The simulation results have a strong theoretical and practical significance, and reliable reference for optimizing the actual natural gas liquefaction process.