对于含氮气约为10%、处理量为150 000 m³/d的原料气,当采用常规工艺液化时,不可避免地存在能耗高与LNG储罐安全隐患大等问题。为此,提出脱甲烷塔的塔底加热精馏、塔顶气增压冷凝回流和塔顶气冷凝回流3种脱氮-液化工艺,旨在比选出经济高效、适应性强的脱氮-液化工艺。采用HYSYS软件模拟分析3种脱氮-液化工艺的LNG质量、产量、能耗、排放尾气甲烷含量以及原料气含氮量变化对其适应性,结果发现,塔顶气增压冷凝回流脱氮-液化工艺的甲烷收率最高,达到97.2%;单位能耗最低,达12.81 W/m³原料气;经济效益最好,年收入增加2 076.78万元。因此,该工艺最适合研究原料气的脱氮液化,其分析方法可供类似规模的高含氮天然气脱氮液化工艺比选参考。

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.

俞徐林(1982-),男,本科,高级工程师,研究方向为油气储运和新能源,通讯联系人,yuxulin.osec@sinopec.com。