發(fā)布時間：2018-06-27 22:17

  本文選題：天然氣液烴 + 氣液兩相流��； 參考：《西南石油大學》2014年博士論文

【摘要】：天然氣液烴(Natural Gas Liquids, NGL)的主要成分是乙烷、丙烷、丁烷、凝析油及其混合物,是重要石油化工原料與燃料,具有較高經(jīng)濟價值和廣闊應(yīng)用前景。凝析氣、頁巖氣和頁巖油中含有非常豐富的NGL成分,脫除NGL不僅可以降低其烴露點,還可以提高氣田的經(jīng)濟效益。管道是長距離、大量輸送NGL最為經(jīng)濟的方式之一。然而,沿線溫度、壓力的變化,可能會使NGL汽化,導致管道中出現(xiàn)氣液兩相流動。在氣液兩相流狀態(tài)下,氣液相的比例和組成、黏度、密度等基礎(chǔ)物性參數(shù)會不斷的發(fā)生變化,并反過來影響管道的水力、熱力參數(shù)分布規(guī)律。如果多條NGL管道相互連接,形成了復雜的NGL管網(wǎng),將會使流動參數(shù)的預測和分析變得更加困難。 針對上述問題,基于流體力學、熱力學和傳熱傳質(zhì)學理論,采用實驗、理論和數(shù)值模擬相結(jié)合的方法,研究了NGL的基礎(chǔ)物性參數(shù)變化規(guī)律、汽化規(guī)律、氣液兩相流動規(guī)律,探索了復雜NGL管網(wǎng)系統(tǒng)仿真技術(shù),開發(fā)了NGL氣液兩相流管網(wǎng)仿真軟件,為NGL管網(wǎng)的設(shè)計、運行和管理提供了理論和技術(shù)支撐。 具體的研究內(nèi)容和取得的主要成果如下： (1)結(jié)合NGL氣液兩相輸送管道中氣液兩相共存的特點,分析了SRK、PR、PRD、 PRSV2、PR-Twu、PRN、PRG、PPR78、VTPR共9種立方型狀態(tài)方程,對于天然氣露點及液烴密度預測的準確性；針對現(xiàn)有方法的局限性,提出了將基團貢獻法(用于二元交互作用系數(shù)計算)和體積平移法相結(jié)合的PR狀態(tài)方程改進新思路,建立了適用于NGL的VTPPR78狀態(tài)方程,并驗證了該方程的準確性。以此為基礎(chǔ),建立了NGL的泡點、露點、焓、熵、熱容等基礎(chǔ)物性參數(shù)計算模型。基于VTPRμ狀態(tài)方程,建立了NGL氣液兩相黏度計算模型�？紤]到化學位、逸度和表面張力之間的熱力學關(guān)系,建立了NGL表面張力計算模型。 (2)基于氣液兩相流動的Navie-Stokes方程、RPI沸騰模型、VOF(Volume of Fluid)模型和CFD技術(shù),開展了NGL汽化機理和氣泡動力學的研究,并建立了氣泡生成與發(fā)展過程的數(shù)值模擬模型；結(jié)合文獻提供的實驗數(shù)據(jù),驗證了數(shù)值模擬模型的可靠性�；趯嶒灁�(shù)據(jù)和數(shù)值模擬結(jié)果,研究了NGL氣泡的脫離直徑、起飛直徑、脫離頻率和活化核心密度等氣泡動力學特征參數(shù)理論計算模型。 (3)以一維不穩(wěn)定流動方程為基礎(chǔ),基于集中空穴假設(shè),建立了低含氣率NGL輸送管道數(shù)學模型,并采用特征線法和有限差分法對模型進行了求解；基于NGL氣泡起飛直徑、脫離頻率和活化核心密度,實現(xiàn)了對低含氣率NGL輸送管道中汽化速率的定量計算。 (4)以Navie-Stokes方程為基礎(chǔ),結(jié)合一維管道流動的特點,并針對NGL汽化過程中氣液兩相溫度不相等的情況,建立了非平衡熱力學狀態(tài)下的NGL管道氣液兩相雙流體模型。基于特征值理論,研究了NGL雙流體模型的數(shù)學特征,指出在管輸條件下：①當氣液兩相速度相等時,雙流體模型的類型為雙曲型；②當氣液兩相速度不相等時,雙流體模型的類型為拋物型；③當氣液兩相流退化為單相流動時,相應(yīng)的模型也退化為單相流動控制方程組,其類型為雙曲型。采用Barne方法進行流型判別；建立了氣泡流、分層流、段塞流和環(huán)狀流下的剪切應(yīng)力閉合關(guān)系式。針對模型的特點,研究了基于有限體積法的雙流體模型離散方法。 (5)考慮到NGL管網(wǎng)多元件、多節(jié)點的特點和物理結(jié)構(gòu)上的多樣性,采用節(jié)點一元件關(guān)聯(lián)矩陣法,實現(xiàn)了對任意管網(wǎng)物理結(jié)構(gòu)的數(shù)學描述。在此基礎(chǔ)上,結(jié)合管道元件,非管元件和節(jié)點的數(shù)學模型,建立了能夠適用于任意結(jié)構(gòu)管網(wǎng)的NGL氣液兩相流系統(tǒng)仿真模型。針對模型的高度非線性特點,研究了模型的線性化方法、以及基于LU分解法和阻尼Newton-Raphson法的模型求解方法。 (6)基于(1)～(5)的理論研究成果和西南石油大學“管網(wǎng)仿真系統(tǒng)PES”平臺,開發(fā)了具有完全自主知識產(chǎn)權(quán)、能夠適用于任意結(jié)構(gòu)形式管網(wǎng)的“液烴輸送管道仿真軟件NGLPES"軟件。NGLPES模擬的塔里木液化氣管道的流量與實測值之間的平均絕對偏差為0.0845t/h,相對偏差為0.956%,溫度的平均絕對偏差為1.29℃。仍基于塔里木液化氣管道的基本參數(shù),在動態(tài)工況下,NGLPES模擬的壓力值與OLGA軟件模擬值之間的平均絕對偏差為58.5kPa,持液率的平均絕對偏差為0.03。通過仿真實例,進一步驗證了NGLPES對于復雜枝狀、環(huán)狀氣液兩相流管網(wǎng)仿真的適應(yīng)性。 NGLPES已經(jīng)獲得了國家軟件著作權(quán),著作權(quán)登記號2014SR043986,并在中石油塔里木油田分公司油氣運銷部得到了實際應(yīng)用。
[Abstract]:The main components of natural gas and liquid hydrocarbons (Natural Gas Liquids, NGL) are ethane, propane, butane, condensate, condensate oil and their mixtures. It is an important petrochemical raw material and fuel. It has high economic value and wide application prospect. Condensate gas, shale gas and shale oil contain very rich and rich NGL components. Removing NGL can not only reduce the dew point of hydrocarbon, but also can reduce its hydrocarbon dew point. In order to improve the economic benefit of the gas field, the pipeline is one of the most economical ways to transport NGL in a long distance. However, the change of temperature and pressure along the line may cause NGL vaporization and lead to gas-liquid two-phase flow in the pipeline. In the state of gas-liquid two-phase flow, the basic physical parameters, such as the proportion of gas-liquid phase, formation, viscosity, density and other basic physical parameters will continue to occur. Change and in turn affect the hydraulic and thermodynamic parameters distribution of the pipeline. If multiple NGL pipes are connected to each other, a complex NGL pipe network will be formed, which will make the prediction and analysis of the flow parameters more difficult.
In view of the above problems, based on the theory of fluid mechanics, thermodynamics and heat and mass transfer, the change law of the basic physical parameters of NGL, the law of vaporization and the law of gas-liquid two phase flow are studied by the method of experiment, theory and numerical simulation. The simulation technology of complex NGL pipe network system is explored, and the simulation software of NGL gas and liquid two phase flow network is developed. It provides theoretical and technical support for the design, operation and management of NGL pipe network.
The specific research contents and main achievements are as follows:
(1) combining the characteristics of gas-liquid two phase coexistence in NGL gas and liquid two phase transport pipeline, the 9 cubic equation of state, which are 9 kinds of cubic equation of state, for natural gas dew point and liquid hydrocarbon density, are analyzed for SRK, PR, PRD, PRSV2, PR-Twu, PRN, PRG, PPR78 and VTPR, and the group contribution method (used for the interaction coefficient meter of two yuan) is put forward in view of the local limit of the existing methods. A new idea to improve the PR equation of state combined with the volume translation method is proposed. The VTPPR78 equation of state suitable for NGL is established and the accuracy of the equation is verified. Based on this, a calculation model for the basic physical parameters of NGL is established, such as the bubble point, dew point, enthalpy, entropy, heat capacity and so on. Based on the VTPR Mu state equation, the calculation model of NGL gas and liquid two phase viscosity is established. Taking into account the thermodynamic relationship between degree of change, fugacity and surface tension, a NGL surface tension calculation model is established.
(2) based on the Navie-Stokes equation of gas-liquid two-phase flow, RPI boiling model, VOF (Volume of Fluid) model and CFD technology, the study of NGL vaporization mechanism and bubble dynamics is carried out, and the numerical simulation model of bubble generation and development process is established, and the reliability of the numerical simulation model is verified based on the experimental data provided by the literature. The experimental data and numerical simulation results are used to study the theoretical calculation model of the bubble dynamics, such as the diameter of the NGL bubble, the take-off diameter, the separation frequency and the density of the activation core.
(3) based on the one-dimensional unsteady flow equation and based on the centralized cavitation hypothesis, a mathematical model of the low gas bearing rate NGL pipeline is established. The model is solved by the characteristic line method and the finite difference method. Based on the NGL bubble take-off diameter, the vaporization rate of the low gas bearing rate NGL pipeline is realized by the separation of the frequency and the density of the activation core. The quantitative calculation.
(4) based on the Navie-Stokes equation, combined with the characteristics of one dimensional pipe flow, and aiming at the unequal gas and liquid two phase temperature in the NGL vaporization process, a two-phase two-phase fluid model of the NGL pipeline under the state of non equilibrium thermodynamics is established. Based on the eigenvalue theory, the mathematical characteristics of the NGL double fluid model are studied, and it is pointed out under the tube transport condition. When the velocity of gas-liquid two phases is equal, the type of two fluid model is hyperbolic type. When the velocity of gas-liquid two phases is not equal, the type of the two fluid model is parabolic. When the gas-liquid two phase flow is degraded into single phase flow, the corresponding model is also degenerated into a single phase flow control equation group, and its type is hyperbolic type. The Barne method is used. The flow pattern discrimination is used to establish the relationship between the bubble flow, the stratified flow, the slug flow and the shear stress closure under the annular flow. In view of the characteristics of the model, a two fluid model discrete method based on the finite volume method is studied.
(5) considering the characteristics of multi element and multi node in NGL pipe network and the diversity of physical structure, the mathematical description of physical structure of any pipe network is realized by using the node one element correlation matrix method. On this basis, the NGL gas liquid two, which can be applied to any structure pipe network, is established in combination with the mathematical model of pipe element, non tube element and node. In view of the highly nonlinear characteristics of the model, the linearization method of the model and the method of solving the model based on the LU decomposition method and the damping Newton-Raphson method are studied.
(6) based on the theoretical research results of (1) ~ (5) and the "PES" platform of the "network simulation system" of the Southwest Petroleum University, the average between the flow rate and the measured value of the Tarim liquefied gas pipeline, which has a complete independent intellectual property right and can be applied to a "liquid hydrocarbon conveying pipeline simulation software NGLPES", which can be applied to any structure pipe network, is developed. The absolute deviation is 0.0845t/h, the relative deviation is 0.956%, the average absolute deviation of the temperature is 1.29 C. It is still based on the basic parameters of the Tarim liquefied gas pipeline. Under the dynamic condition, the mean absolute deviation between the pressure value of the NGLPES simulation and the simulated value of the OLGA software is 58.5kPa, and the mean absolute deviation of the liquid holdup rate is 0.03. through the simulation example. One step verifies the adaptability of NGLPES to the simulation of complex branch and annular gas liquid two phase flow network.
NGLPES has obtained the national software copyright, the copyright registration number 2014SR043986, and has been applied in the oil and gas marketing department of PetroChina Tarim Oilfield Branch.
【學位授予單位】：西南石油大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TE832

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