原油差温顺序输送最大安全停输时间

Maximum safe shutdown time of differential temperature batch transportation of crude oil

原油差温顺序输送管道最大安全停输时间的确定是目前原油顺序输送技术领域重要而又尚无公认可行方法的技术难点。为此,基于数值模拟结果,从"再启动难易程度"的角度对停输安全性进行分析。通过一系列理论分析,导出了既能满足生产需求又简便易行的原油差温顺序输送管道最大安全停输时间的确定方法:对于不存在停输危险性的停输时机,理论上最大安全停输时间为无穷大;对于存在停输危险性的停输时机,通过数值模拟分析,先找到刚好使无量纲排空时间趋于无穷大的停输时间,再进一步在该停输时间附近找到满足判定条件"只要再启动过程出现进站流量随时间减小的现象都不安全"的停输时间,即最大安全停输时间。该方法同时适用于普通含蜡原油管道。

It is a great challenge to determine maximum safe shutdown time of differential temperature batch transportation of crude oil pipeline, for which there is no accepted feasible method. In this paper, based on the results of numerical simulation, the safety of shutdown is analyzed in view of ＂restart difficulty＂. Finally, a simple and easy determination method is derived, which can meet the demands of pipeline running, through a series of theoretical analysis. Theoretically, maximum safe shutdown time is infinite for shutdown time without risks. In contrast, for shutdown time with risks, the shutdown time at which the dimensionless emptying time just goes to infinity is found, and then another shutdown time, which satisfies the criteria, i.e. it is not safe as long as input flow decreases with time in restart procedure, is found near the one determined above. The later is the maximum safe shutdown time. This method is also applicable to ordinary waxy crude oil pipeline.