As for feed natural gas with a nitrogen content of about 10%and a processing capacity of 150 000 m3·d-1,there are inevitably problems such as high energy consumption and serious risks at LNG storage tanks when it is liquefied through conventional process.Hence,three kinds of denitrification-liquefaction processes,including bottom heating rectification,top gas pressurization-condensation reflux,and top gas condensation reflux for demethanizer,are proposed to select an economical,efficient and adaptable one.HYSYS software and its related theories are adopted to simulate LNG quality,LNG output,energy consumption,methane content in exhaust gas and the adaptability to nitrogen content changes in feed gas for the three denitrification-liquefaction processes.It is found that the recovery rate of methane in the top gas pressurization-condensation reflux process is the highest,reaching 97.2%;its unit energy consumption is the lowest,being 12.81 W·m-3 raw gas;and its economic benefit is the best,increasing annual income by RMB 20.767 8 million.Therefore,this process is the most suitable for the studied denitrification and liquefaction of feed natural gas.This analysis method can be used as reference to select the denitrification and liquefaction process for similar scale natural gas with high nitrogen content.
natural gas liquefactionfeed gas with high nitrogen contentnitrogen removal processdemethanizercondensate reflux
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