Research Of Bog Treatment Process In LNG Receiving Terminal

The gas transmission capacity of LNG receiving terminal has a characteristic of fluctuating with season,however the generation rate of Boil-off Gas(BOG)is different in normal cases and unloading cases.The BOG treatment process changes from different LNG throughputs in receiving terminal.BOG treatment process system is the most importment unit of LNG receiving terminal,it is of great significance to select the appropriate BOG treatment process for the safe operation of the receiving terminal and the effective utilization of BOG.Based on the analysis of the factors which affect the BOG generation rate,the capacity of BOG is simulated under kinds of cases,and obtain the BOG yield in different transmission of LNG.With the help of HYSYS software,the treatment process of recondensation is built,the minimum flow rate of LNG of receiving terminal is clarified,and analyze the influence of different operating cases and process parameters on the liquid gas ratio of recondensation process,the transmission of LNG has a great influence on the recondensation process and the compressor outlet pressure has the greatest influence on the performance of the recondensation process.Based on the shortage of the recondensation process,and the direct compression process and BOG reliquefaction process are studied,analyze the influence of refrigerant component on the power consumption of reliquefaction system,and the proportion of refrigerant components was determined,which made the reliquefaction process more energy efficient.Finally,combining the characteristics of gas transmission of current LNG receiving terminal with the premise of the minimum energy consumption of the system,the optimal BOG treatment method for the receiving terminal under the condition of normal gas transmission,gas transmission valley period and zero output period is proposed.The process of recondensing treatment or direct compression is selected for normal condition.During gas transmission valley period,the recondensation process is selected,but the outlet pressure of the compressor needs to be improved to reduce the amount of LNG needed for condensation.Under the condition of zero output,the BOG in the station is directly transported to the natural gas pipeline,which means that the direct compression is adopted,it could save more energy consumption and benefit to environment.