基于有限元法的含蜡原油管道停输过程温降数值模拟

Numerical Simulation on Temperature Drop in Shutdown Process of Waxy Crude Oil Pipeline Based on the Finite Element Method

含蜡原油在管输过程中不可避免地会发生停输情况,随着管内原油温度降低至凝点以下,会出现凝油层导致凝管现象,严重影响管道安全经济运行,因此有必要研究含蜡原油管道停输过程的温降问题。在原油管道正常运行工况的基础上,考虑蜡沉积现象,建立了含蜡原油管道停输传热模型。采用温度场三角形单元格划分→离散→合成有限元这一有限元法求解思路对模型进行数值求解,讨论了在不同停输时间管道温降的变化规律。通过对管道温度场计算结果进行分析可知,管道对周围环境温度场的影响随着离管道距离的增大而逐渐减小;在不受热影响的外部区域,温度场等温线近似为一组波动的平行线。该研究成果提供了一种简单易行、准确可靠的温降模拟计算模型,为蜡质原油停输后再启动过程的方案制定提供了关键数据的采集方法。

Shutdown condition will inevitably occur during pipeline transportation of waxy crude oil. As the tem - perature of crude oil in pipeline drops below freezing point, oil condensation layer will occur and lead to pipeline condensation,which seriously affects the safe and economic operation of pipeline. It is necessary to study the temperature drop during the shutdown process of waxy crude oil pipeline. Based on the normal operation conditions of crude oil pipeline and with wax deposition phenomenon taken into consideration, a heat transfer model for the shutdown of waxy crude oil pipeline is established. The model is numerically solved by the finite element method of dividing the temperature field into triangular cells→ dispersing→ synthesizing the finite element,and the change law of pipeline temperature drop under different shutdown time is discussed. Through the calculation result analysis of pipeline temperature field,it is found that the influence of pipeline on the environmental field around decreases gradually as the distance increases. In the region without heat influence, the isotherms of temperature field are almost a set of fluctuating parallel lines. The study results provide a simple,accurate and reliable simulation calculation model for temperature drop and key data acquisition method for the formulation of restart process plan of waxy crude oil after shutdown.