【作者】 陈五花；

【导师】 赵宗昌；

【作者基本信息】 大连理工大学 ， 化学工程， 2006， 硕士

【摘要】 含有蜡(长链烷烃化合物的混合物)的原油体系,当温度降低到一定值时,原先溶于原油中的蜡逐渐饱和析出。当温度进一步降低,析出的蜡晶增多,它们之间聚结成大的晶体进而连接成三维空间网络结构,造成输送管道的阻塞,影响原油的输送和生产。因此,预测给定条件下原油体系的析蜡点和析蜡量,对油气生产过程中有效防止石蜡沉积有非常重要的意义。 本论文进行的原油体系石蜡沉积研究,分为石蜡沉积的实验研究和热力学模型研究两个方面,主要有如下内容: 1.建立了差示扫描量热法(DSC)测石蜡沉积条件的实验方法,该方法可以同时测定析蜡点和析蜡量,而且分析速度快,试样用量少,实验重复性好,具有工业推广和应用价值。 2.用DSC法测定了模拟原油体系在不同冷却速率下的沉积变化规律,确定了最佳冷却速率,测定了模拟油体系的析蜡点及其在不同的温度下的石蜡沉积量。通过以上实验研究获得了一套完善的石蜡沉积实验数据。 3.用气相色谱法测定了模拟油体系中石蜡的组成,作为模型研究的输入数据。 4.本文从正规溶液理论角度,结合固-液相平衡热力学,建立了石蜡沉积的正规溶液理论热力学模型。 本文建立了一个改进的用于计算石蜡沉积的热力学固-液相平衡模型。该模型认为原油温度低于析蜡点温度时,正构烷烃以旋转相、三斜晶、单斜晶和正交晶四种形式存在,随着温度的进一步降低,它们都以正交晶的形式稳定存在,其间不同碳原子数的正构烷烃经历了不同晶形到正交晶的转换,因此模型考虑了固-固转换。拟组分的热力学参数采用经验关系式来计算,其中对于正构烷烃的固-固转换焓、固固转换温度、熔解焓以及溶解温度,基于文献资料建立了新的关系式。 运用上述模型与文献中Leelavanichkul模型对文献中的三个原油体系以及本文实验体系进行了模拟计算并与实验结果进行了比较,发现不管是复杂的原油体系还是简单的模拟原油,对于不同温度下的石蜡沉积量本文新建立的模型其模拟结果要远远优于Leelavanichkul模型。对于石蜡沉积点,本文模型的模拟结果要稍大于实验值。更多还原

【Abstract】 For the crude oils which contain wax (mixture of long chain alkanes), when the temperature of crude oil drops, the solubility of the heavy hydrocarbons would be sufficiently reduce and they will precipitate in the form of wax. With the more decrease of temperature, the amount of wax precipitated increase and they assemble into large crystal and finally the three-dimensional network structure is constructed. The plug of pipeline caused by wax precipitation has important influence on the production and transportation of crude oils. A model that can predict the conditions under which solids will precipitate and the amount of solids formed under different conditions can be used as a fundamental tool to prevent the solid precipitation.The research work on the wax precipitation principally involves:1. The DSC method for determination of wax precipitation condition has been established. The wax appearance temperature and the amount of wax precipitated under different temperature can be obtained at the same time by DSC method. The method is quickly and reliable and can be done in industry.2. Detail experiments have been conducted to study the best wax precipitation condition under different cooling rate. The wax appearance temperature and the amount of wax precipitated under different temperatures are obtained using DSC method.3. The composition of wax is obtained by gas chromatography, the characterization data are used for the model input data.4. Regular solution thermodynamic theories: a modified thermodynamic solid-liquid equilibrium model which is used to calculate wax precipitation in crude oils has been established in resent work. The researches indicate that when temperature of crude oil lower WAT, the solid paraffin exist in forms of hexagonal 、 orthorhombic、 triclinic and monoclinic phases, with the decrease of temperature, all of the solid alkane become steady orthorhombic phase, so the solid-solid transition is considered in the model. The properties of the pseudo-components are determined by using empirical correlations. New correlations for solid-solid transition enthalpy、 solid-solid transition temperature、 fusion enthalpy and fusion temperature are also established in this work based on the data from literatures.The calculation results for three crude oil systems from literature and the model crude oil system studied in this research by the modified thermodynamic model present in this work and the regular solution model proposed by Leelavanichkul are compared with theexperimental ones, it can be seen that not only for complicated crude oil systems but also for simple model system, the modified thermodynamic model is much better than the regular solution model proposed by Leelavanichkul for calculating the amount of wax precipitation under different temperatures. For the wax precipitation temperature, the calculation results by the model present in this work are little higher than the experiment ones.更多还原