Simulation And Optimization Of Purification & Liquefaction Process For Small-Scale Natural Gas Plant

Energy and the environment are two critical issues for the world’s sustainable development. Currently, our country’s energy structure is heavily dependent on conventional fossil fuels, and thus always faces many challenges including high price of the raw materials and greenhouse gas emissions. To further promote the utilization of diverse, lower-carbon and independent primary energy sources, considerable efforts have been taken to exploit scattered and remote energy resources, such as natural gas. This work focuses on the simulation and optimization of purification and liquefaction for small-scale natural gas plant.This article first introduces the research progress of natural gas purification and liquefaction process, focusing on the alcohol amine desulfurization, decarbonization purification process and glycol dehydration process, to present the main working application characteristics, in which liquefaction processes were described and analyzed. And this work focus on the single mixed refrigerant liquefaction process.For purification process, steady-state model has been designed for three typical acid gas removal processes, MEA、DEA and MDEA process, using Aspen HYSYS. And then this article presents a respective systematical analysis of the purity levels, energy consumption and so on. According to the result, the most favorable process is DEA process. Simultaneously, this article develops a steady-state model for the typical Dehydration process-TEG process. Finally, due to the integrated relationship between these two processes, corresponding optimization is conducted using Analytic Hierarchy Process (AHP).For liquefaction process, the selection of the refrigerant and operating variables of the novel double mixed refrigerant process are analyzed. Based on the phase diagram, the effect of mixed refrigerant composition on the process energy consumption is analyzed and mixed refrigerant has been selected. Then a steady-state model of improved mixed refrigerant liquefaction process has been developed using the HYSYS. Then Genetic algorithm in the software of MATLAB is selected as the optimization method for the process to minimize energy consumption. Furthermore, the effect of operating variables on energy consumption and minimum temperature difference approach of LNG exchangers are analyzed. Finally, a better direction of this process is proposed combined with Thermodynamic Analysis.