Simulation And Optimization Of Mixed Refrigerant Cycle Plant

With the advantages of its high calorific value,easy transportion and low sulphur content,liquefied natural gas(LNG)has become an ideal clean energy source.Development of LNG is the key path to improve the overall energy efficiency.In the recent years,LNG has become an increasingly important new industry.With the strong support of national policy,the domestic LNG industry has made great progress,although still lags behind the advanced LNG technology of major developed countries.Construction of LNG plant is based on the principles of energy saving,emission reduction,etc.Among these factors,the optimization of liquefaction process is the key.This project mainly discusses different LNG processes.The ideal process is determined and optimized by using simulation software.All process equipment is calculated to obtain the best parameters and ensured to be domestically made.The main processes of LNG plant include:pre-treatment process and liquefaction process.The refrigeration is the core part of the liquefaction process.Mixed Refrigerant Cycle(MRC)is employed in this project to simplify the process and reduce the capital cost.There are several components involved in the pretreatment process:desulfurization,decarbonization,dehydration,heavy-hydrocarbon removal,mercury removal,denitrification,etc.Desulfurization and decarbonization are the most crucial steps in the pre-treatment process.Chemical absorption with methyl diethanol amine(MDEA)is the most widely used method.Skid-design of the equipment is also adopted even though the design cost rises.However,other costs involved during the transport,installation and debug steps significantly decrease.Thus,the overall LNG plant design for this project is:pre-treatment with MDEA;mixed refrigerant cycle for the liquefaction process;skid design for equipment of all steps.Hysys of AspenTech Inc.is used for all simulation and calculation parts.By simulating the compression,purification and liquefaction processes,one could yield the optimized parameters for LNG production.From material balance sheet,daily production average and other production related information can be determined.Calculation of equipment selection is conducted to provide a useful guide for optimized production process.