摘要
Abstract
Large-scale tanks in LNG terminals should be cooled gradually down to-162 ℃ before they are put into service.Before the cooling operation,tanks are full of nitrogen.In the process of cooling,therefore,a large amount of boil-off gas (BOG) with high nitrogen content is generated,but it can only be discharged directly to the flare because the technological system of an LNG terminal is incapable of recycling it.Besides,the BOG flow rates in the middle and late stages of LNG tank cooling are extremely high,being beyond the recycling capacity of the terminal,so a large amount of BOG is discharged to the flare.As a result,a large amount of waste is generated.To solve this problem,the Zhuhai LNG Terminal investigated the cooling modes of in-service LNG tanks in China and studied their precooling processes and innovatively proposed a down-discharge nitrogen replacement method before tank cooling and a "BOG+LNG" tank cooling technology.As a result,nitrogen content of BOG in the cooling process of LNG tanks is decreased and cold energy utilization efficiency of LNG terminals is improved.Meanwhile,BOG generated in the process of LNG tank cooling is decreased to well match the BOG recycling capacity of LNG terminals.On-site experimental results indicated that by virtue of down-discharge nitrogen replacement,the nitrogen inside the tank is replaced to a qualified level.With the "BOG+LNG" tank cooling technology,BOG generated in the process of LNG tank cooling is reduced effectively,without exceeding the recycling capacity of the terminal.Thus,BOG zero emission is realized in the process of LNG tank cooling.This method can provide a reference for operation and production of LNG tanks.关键词
LNG接收站/储罐/投产试车/氮气置换/预冷/BOG/零排放/仿真/置换Key words
LNG terminal/Tank/Nitrogen replacement/Precooling/Boil-off gas (BOG)/Zero emission/Simulation/Replacement
