浅析LNG调峰气化设施的安全性

Safety Analysis of Peak Shaving LNG Vaporisation Facilities

由于LNG调峰气化设施的生产负荷以及LNG物性随季节或每日时段变化大,导致极端工况下浸没式燃烧气化器不能完全气化LNG,严重影响气化设施安全运行。以某调峰气化设施工厂为例,利用传热学理论,分别计算出某年冬季该厂浸没式燃烧气化器在设计工况和极端工况下的总传热系数。计算结果表明,极端工况下浸没式燃烧气化器不能为换热管内的LNG提供足够热量,少量LNG不能气化,引起管道低温脆裂,导致爆炸事故。为解决极端工况下浸没式燃烧气化器不能完全气化LNG的问题,在不过度增加浸没式燃烧气化器换热面积前提下,在调峰气化设施界区设置压力调节阀,分别计算出浸没式燃烧气化器在设计工况和实际工况下的总传热系数,保证浸没式燃烧气化器能够提供完全气化LNG的热量,确保操作压力低限值,提高调峰气化设施的安全性。调峰气化设施界区设置压力调节阀的方法可为类似气化设施设计提供借鉴。

Submerged type LNG vaporiser have difficulties meeting process duty in extreme operating conditions,caused by highly fluctuating demand of the peak-shaving duty and LNG physical properties fluctuation as change or daily change.As a result,not all LNG can be vaporized,and the low temperature liquid poses a threat to the safe operation of the facilities.In a case study of a LNG vaporization plant,the overall heat transfer coefficients of the submerged type vaporiser in both design and extreme operating conditions in one winter are calculated using heat transfer theory.The calculated results show that in extreme operating conditions,the submerged type vaporiser cannot meet the required heat transfer duty,leaving a small amount of LNG in the outlet piping,resulting in low temperature brittle failure of the piping,and gas explosion.To resolve the issue of insufficient heat transfer duty in extreme operating conditions,without any significant increase in heat transfer surface area,a pressure regulator was installed at the plant boundary,downstream of the vaporization facilities.The regulating valve maintains a constant set operating pressure of the vaporiser instead of the original design of floating on downstream pressure,which could become very low during high gas demand period.The optimum operating pressure of the vaporiser is determined via a calculation of the overall heat transfer coefficient in design and extreme operating conditions,making sure that the process duty of extreme operating conditions can be met at the set operating pressure and therefore enhance the safe operation of the facilities.The solution of installing a pressure regulating downstream of the vaporiser to ensure its constant operating pressure can be used as a reference for design of similar facilities.