卸料初期罐压变化的计算

Calculation of the tank pressure change in the initial stage of LNG unloading

LNG开始卸料之前，首先要停止码头保冷循环，然后进行ESD1测试，之后开始预冷卸料臂。从停保冷循环到全速卸料大约需要3～4h，在此期间储罐压力变化较大。基于此，介绍了江苏LNG接收站的卸料流程以及非卸船期间码头保冷循环流程；计算了卸船管道和码头保冷循环管道与周围环境换热及预冷卸料臂所引起的罐压升高值，进入码头保冷循环的LNG所带的热量；分析了卸料初期储罐压力随时间的变化趋势；对比了罐压变化理论计算值偏离现场实际值的原因，提出了卸料过程的注意事项，以确保安全平稳生产。（图4，表3，参6）

The cold cycle need to be stopped firstly before LNG unloading, the ESDI test should be carry out next, and then cooling down the unloading arms. It may takes three or four hours from stopping the cold cycle to full speed unloading, the pressure of LNG tank changes a lot during this period. Base on that, this paper introduces the unloading process at Jiangsu LNG receiving terminal and the process of cold cycle during non-discharge period, and calculates the pressure change caused by heat exchange between LNG lines and surrounding atmosphere and LNG arms cooling down, and the quantity of heat generated while LNG get into the cooling cycle. The pressure change curve in the initial stage of LNG unloading is analyzed. Compares the deviation between theoretical calculation and practical value and introduces the matters needing attention when unloading LNG to ensure production safety. （4 Figures, 3 Tables, 6 References）.