含蜡热油管道系统工作特性研究

发布时间：2018-05-25 06:55

  本文选题：含蜡原油 + 管道和泵站　； 参考：《西南石油大学》2015年硕士论文

【摘要】：我国生产的大部分原油为含蜡原油,且管输含蜡原油的工艺多采用加热输送。在含蜡原油加热输送的过程中,管壁结蜡会给管道输送带来很大的安全隐患,同时也会造成很大的能量(热能和压能)损耗。因此,研究站间结蜡规律,弄清蜡沉积对于管道和泵站系统工作特性的影响,建立模型预测管道中蜡沉积分布情况,对于提高管道系统的输送效率,确保原油的安全输送和制定合理的清管方案有着重要的实际意义。为此,本文以含蜡热油管道系统为研究对象,展开了以下主要研究内容。 在站间含蜡热油管道实际运行过程中,原油物性及摩阻特性会随沿线油温的降低而不断变化,结蜡段管道的有效流通面积和传热系数将随着蜡层厚度的增加而不断减小,综合以上因素,同时计入沿程摩擦热的影响,对压降反算蜡层厚度的水力学平均蜡层厚度算法进行了改进,并利用MATLAB7.0编制了相应的计算程序。 通过OLGA建立了站间等距的水平输油管道系统模型,各站间在相同的外界条件和输送同样油品的情况下,依次对不同的泵站升压方式：定速单泵、定速双泵串联和变速单泵进行了站间管道蜡沉积过程的模拟。根据模拟结果,分析了站间管道蜡沉积对不同型号离心泵的工作特性影响,研究了站间管道蜡沉积的分布规律和泵型选择对站间蜡沉积分布的影响。 根据大庆原油随温度变化的物性数据,采用最小二乘法回归求得物性公式中的常数项。根据铁岭至鞍山沿线在四季输油中的运行参数,应用本文结蜡段平均蜡层厚度模型计算了不同季节、不同运行时间段下的蜡层厚度,并结合OLGA模拟结果与大庆原油蜡沉积速率预测模型,对铁岭站与沈阳站站间管线的蜡沉积规律及其蜡沉积对管道系统工作特性的影响作了分析。 通过以上的分析与研究,得出以下结论：析蜡高峰点以后的管壁处剪切应力、原油黏度以及径向温度梯度是影响蜡沉积速率的主要因素,其中径向温度梯度是首要影响因素,而当地温升高时,径向温度梯度对于蜡沉积速率的影响有所减弱,且地温升高越多,减弱幅度越大；站间沿线结蜡分布情况与泵站所选泵型直接相关,对于含蜡热油长输管道,泵站在选择用泵时,更应选择扬程与流量特性曲线较陡降的泵；大庆原油站间析蜡高峰区的温度区间为40℃左右,此温度区间正好处于站间II区(析蜡点与反常点之间)内,一年四季中,若1I区长度越长,则站间管道结蜡情况越严重。另外,结蜡高峰区内的蜡沉积速率相差不大,因此,站间高峰区越长,蜡沉积分布将越近视为“阶梯型”。
[Abstract]:Most of the crude oil produced in China is waxy crude oil, and the process of pipe transportation of waxy crude oil is mostly heated. In the process of heating and transporting waxy crude oil, wax deposit on pipe wall will bring great hidden trouble to pipeline transportation, and also cause great loss of energy (heat energy and pressure energy) at the same time. Therefore, the law of wax deposition between stations, the influence of wax deposition on the working characteristics of pipeline and pumping station system, and the establishment of model to predict the distribution of wax deposition in pipeline system can improve the transportation efficiency of pipeline system. It is of great practical significance to ensure the safe transportation of crude oil and to formulate a reasonable pipe-clearing scheme. Therefore, this paper takes the waxy hot oil pipeline system as the research object, and carries out the following main research contents. During the actual operation of the waxy hot oil pipeline between stations, the physical properties and friction characteristics of crude oil will change with the decrease of oil temperature along the line, and the effective circulation area and heat transfer coefficient of the pipeline will decrease with the increase of wax thickness. Based on the above factors and taking into account the influence of the heat of friction along the path, the average thickness of wax layer in hydraulics with pressure drop is improved, and the corresponding calculation program is compiled by MATLAB7.0. The model of horizontal oil pipeline system with equal distance between stations is established by OLGA. Under the same external conditions and the same oil products, the pressure of different pumping stations is increased in turn: constant speed single pump, The process of wax deposition in pipeline between stations was simulated by two constant speed pumps in series and one pump with variable speed. Based on the simulation results, the effects of pipeline wax deposition on the working characteristics of different types of centrifugal pumps are analyzed, and the distribution law of wax deposition between stations and the influence of pump type selection on the distribution of wax deposition between stations are studied. According to the physical property data of Daqing crude oil varying with temperature, the constant term in the physical property formula is obtained by least square regression. According to the operating parameters of Tieling to Anshan in the four seasons oil transportation, the wax layer thickness of different seasons and different operating periods is calculated by using the average wax layer thickness model of the wax deposit section in this paper. Combined with OLGA simulation results and Daqing crude oil wax deposition rate prediction model, the wax deposition law of pipeline between Tieling station and Shenyang station and the influence of wax deposition on the working characteristics of pipeline system are analyzed. Through the above analysis and research, the following conclusions are drawn: the shear stress at the pipe wall after the peak point of wax evolution, the viscosity of crude oil and the radial temperature gradient are the main factors affecting the wax deposition rate, among which the radial temperature gradient is the primary factor. When the ground temperature rises, the influence of radial temperature gradient on wax deposition rate is weakened, and the more the ground temperature rises, the greater the weakening amplitude is, and the distribution of wax deposition along the interstation is directly related to the pump type selected by the pump station, and for the waxy hot oil long distance transportation pipeline, the distribution of wax deposition along the interstation is directly related to the pump type selected by the pump station. When the pump is selected for pump use, the pump with steep drop of lift and flow characteristic curve should be selected, and the temperature range of wax precipitation peak area between Daqing crude oil stations is about 40 鈩，

本文编号：1932513