管道结蜡对停输再启动特性的影响研究

发布时间：2018-05-11 07:46

本文选题：结蜡 + 停输温降　；参考：《中国石油大学(华东)》2015年硕士论文

【摘要】：本文建立了埋地热油管道含有结蜡层时停输再启动过程的数学模型,并采用有限差分法、有限元法和双特征线法对数学模型进行求解,通过编写程序来模拟管道结蜡和停输再启动过程,并对程序的准确性进行了验证。以中洛线为例,详细分析了管道结蜡对停输温降、再启动压力以及安全停输时间的影响。管道结蜡使得正常运行时管内油温升高,但周围土壤温度场降低,停输阶段温降速率增大,不利于管道的顺利再启动。一定停输时间范围内,对比分析管道结蜡与管道无结蜡时的沿线油温分布发现二者存在虚拟交叉点。正常运行时的出站温度相同条件下,出站处至虚拟交叉点管段上管道结蜡时的沿线油温低于管道无结蜡时,虚拟交叉点至进站处管段上管道结蜡时的沿线油温高于管道无结蜡时。随着停输时间的延长,沿管道输送方向的不同位置依次出现虚拟交叉点;当停输时间超过管道进站处出现虚拟交叉点的时间后,整条管线上管道结蜡时的沿线油温均低于管道无结蜡时。随着结蜡厚度的增大,结蜡层对停输温降特性的影响愈发明显,虚拟交叉点逐渐靠近出站处。结蜡层的存在增大了再启动压力,一定程度上缩短了安全停输时间。文中还对比分析了管道采用实际结蜡厚度、全线取平均结蜡厚度、析蜡点后取平均结蜡厚度和不考虑结蜡四种处理方式对停输再启动特性的影响。含蜡原油管道在停输再启动过程中的壁面剪切应力对管壁结蜡层存在剪切作用,本文将这一过程抽象为结蜡层的脱落,以此来表征剪切作用的影响。模拟结果表明,随着再启动时间的延长,管壁结蜡层沿线依次发生脱落;停输时间越久,管壁结蜡层越不易脱落;流量越小,再启动对结蜡层的剪切作用越小;季节的不同对结蜡层剪切也有影响。
[Abstract]:In this paper, the mathematical model of stopping and restarting process of buried geothermal oil pipeline with wax deposit layer is established, and the mathematical model is solved by finite difference method, finite element method and double characteristic line method. The program is written to simulate the process of pipeline wax deposition and shutdown and restarting, and the veracity of the program is verified. Taking Zhongluo Line as an example, the effects of pipeline wax deposition on temperature drop, restart pressure and safe shutdown time are analyzed in detail. The wax deposit in the pipeline increases the oil temperature in the pipeline during normal operation, but the soil temperature field around the pipeline decreases and the temperature drop rate increases in the shutdown stage, which is not conducive to the smooth re-starting of the pipeline. In a certain stop time range, it is found that there is a virtual crossing point between pipeline wax deposit and pipeline oil temperature distribution when there is no wax deposit in pipeline. Under the same temperature of exit station during normal operation, the oil temperature along the pipeline at the exit station to the virtual crossing point is lower than that in the pipeline without wax deposit. The oil temperature along the pipeline from virtual intersection to entry station is higher than that without wax deposit. With the prolongation of the stop time, the virtual intersection appears in different positions along the pipeline transportation direction, and when the stop time exceeds the time when the pipeline enters the station where the virtual intersection occurs, The oil temperature of the whole pipeline is lower than that of the pipeline without wax deposit. With the increase of wax deposition thickness, the effect of wax deposition layer on the temperature drop is more and more obvious, and the virtual intersection point is closer to the exit station. The existence of wax deposit increases the restarting pressure and shortens the safe shutdown time to some extent. The effects of actual wax deposition thickness, average wax deposition thickness after wax precipitation and no consideration of wax deposition on the restarting characteristics of the pipeline are also compared and analyzed in this paper, which include the actual wax deposit thickness, the average wax deposit thickness in the whole line, the average wax deposit thickness after the wax precipitation point, and the failure to consider the wax deposit. The wall shear stress of waxy crude oil pipeline in the process of shutdown and restarting has shear effect on waxy layer of pipe wall. In this paper, the process is abstracted as the falling off of waxy layer to characterize the effect of shear action. The simulation results show that along the pipe wall waxy layer shedding occurs with the extension of restarting time, the longer the shutdown time, the less the pipe wall wax deposit layer is, and the smaller the flow rate is, the smaller the shear effect of restarting on the waxy layer is. Different seasons also affect the shear of waxy layer.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE832.2

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