非卸船工况下LNG接收站BOG产生量的计算

在LNG接收站运行过程中,准确计算BOG产生量是保证安全生产的重要工作之一。基于BOG产生量常用的计算方法,总结了非卸船工况下BOG产生量的关键因素,主要包括储罐吸热、保冷管道吸热、泵运行产热,同时增加了再冷凝器冷凝BOG随保冷循环LNG重新回流到储罐这一不可忽略的因素,并分析了罐压变化对BOG产生量的影响。通过对罐压不变、罐压逐渐上升、罐压逐渐下降3种工况下的BOG产生量与处理量进行计算,结果表明:在3种不同工况下,利用储罐吸热量、保冷管道吸热量、泵热量回流量、再冷凝器冷凝BOG回流储罐流量计算BOG产生量具有较高的准确性和可行性;BOG产生量与处理量计算结果的偏差均小于5%,但若忽略冷凝BOG回流储罐、罐压变化的影响,则二者偏差可分别达到50%、23%。在LNG接收站生产运行中,建议重视罐压变化对BOG产生量的影响,并对再冷凝器冷凝BOG回流储罐的流量加以控制。

Calculation of BOG production in LNG receiving terminal under nonunloading condition

Accurate calculation of BOG production is an essential task for safe production during the operation of LNG receiving terminal.Based on the commonly used calculation methods for BOG production,the key factors that affect BOG production under non-unloading conditions were summarized,mainly including the tank heat absorption,the cold insulation pipeline heat absorption and the heat generation by pump running.The non-negligible factor that the BOG is condensed by recondenser and flows back to the tank together with cold insulation circulating LNG was additionally taken into account,and the influence of tank pressure change on BOG production was analyzed.The BOG production and handling capacity under the three conditions of constant tank pressure,gradually rising tank pressure and gradually dropping tank pressure were calculated respectively.The results show that,under the three different conditions,the BOG production calculated with the tank heat absorption,the cold insulation pipeline heat absorption,the pump heat reflux and the BOG which is condensed by recondenser and flows back to the tank performs well in accuracy and feasibility.The calculation results of both BOG production and handling capacity deviates within 5%,whereas if the influence of the condensed BOG flows back to the tank and the pressure change are ignored,the deviations of the two may be up to 50% and 23% respectively.During the production and operation of LNG receiving terminal,attention should be given to the influence of tank pressure change on BOG production,and the condensed BOG flow back to the tank should be appropriately controlled.