大型油罐主动安全防护系统设计及应用

Design and application of an active protection system used for large oil tanks

外浮顶油罐的一二次密封空间属于相对密闭的环形油气聚集空间,在油罐罐壁挂油、收发油作业中随着浮盘的升降会产生大量可燃气体,遇雷击、静电产生的火花可能引发燃烧甚至爆炸事故。针对大型外浮顶油罐的结构特点,采用实时气体分析系统与主动惰化保护系统相结合的闭环控制方式,设计了大型油罐主动安全防护系统,主要由控制系统、监测系统、供氮系统、管网系统及其他配套系统组成。其防护技术原理:在浮顶油罐的一二次密封区域内安装一套可燃气体泄漏探测及保护系统,当可燃气体浓度超过爆炸下限值时,系统主动向密闭区域内注入惰性气体,置换出可燃气体,有效降低密闭区域内可燃气体浓度,阻止火灾或爆炸发生。通过在长庆某输油站3年多的应用结果表明,该系统稳定可靠,安全防护效果显著。

The primary and secondary seal spaces in external floating roof oil tanks are annular oil and gas accumulation spaces which are relatively closed. In the process of oil hanging on the tank wall and oil loading and unloading, a large amount of combustible gas can be generated as the floating roof goes up and down. And the gas may be burnt and even exploded by spark which is resulted from lightning or static electricity. In view of the structural characteristics of large external floating roof tanks, an active safety protection system suitable for large oil tanks was designed by using the closed loop control mode which combines the real-time gas analysis system with the active inerting protection system. This system is mainly composed of control system, monitoring system, nitrogen supply system, pipeline network system and other support systems. And its protection principle is as follows. A set of combustible gas leakage detection and protection system is installed in primary and secondary seal zones of floating roof tanks. When the concentration of combustible gas is above the lower explosive limit, the system will inject inert gas actively into the seal zone to replace the combustible gas. And consequently, the concentration of combustible gas in the seal zone is reduced effectively, and fire or explosion can be avoided. This system is applied in Changqing Oilfield for over three years and its application result is remarkable. It is indicated that this system is stable and reliable.