天然气管道干空气干燥技术模拟

SIMULATION RESEARCHES ON THE DRIED-AIR DRYING TECHNOLOGY OF NATURAL GAS PIPELINE

商品天然气输送中,输气管道入口处天然气中的水汽含量被控制到能使天然气在最高输送压力下的露点温度低于它在输送中可能达到的最低温度。但输气管道投产前存在于管道内壁和管道低洼处的液态水对天然气有增湿作用,导致天然气露点在输气管道投产初期不能满足管输要求。为此,投产前需要对天然气管道进行干燥处理。干空气干燥天然气管道是一个复杂的传热、传质过程。基于质量守恒定律、相平衡原理和费克定律,提出干燥过程以及随后封闭过程的机理模型。运用隐式差分法求干燥模型的数值解和分离变量法求封闭过程的解析解。在此基础上编制了反映干空气流动过程中的吸水和液态水平衡蒸发过程的应用程序。利用西气东输管线的干燥实例验证了模型的正确性,并提出了建议。

During the transmission of commercial natural gas.the water content at the inlet of the gas transmission pipeline should be controlled within a value under which the natural gas's dew point temperature under the maximum transmission pressure is lower than its probable lowest temperature during the transmission.However,the liquid water exists on the inner wall and the pipeline sinkage before the line comes on stream will have a humidification function to the natural gas,because of which the dew point temperature of natural gas can not meet the requirement of gas transmission at the early stage of the pipeline commissioning.Thus,the natural gas pipeline is needed to be dried before it goes on stream.Drying the natural gas pipeline with dry air is a complex heat transmission and mass transferring course.The paper put forth the mechanism model of the drying and the subsequent sealing process on the basis of the law of conservation of mass,the phase equilibrium principle and the Kicks Law.It explored the drying models numerical solution with implicit difference method and explored the sealing process's analytical solution with the separation of variables method.The application program which can reflect the water absorption and liquid water equilibrium vaporization course during the flow of the dry air was developed upon the abovementioned procedures.The accuracy of the model was verified by the drying case of the West-to-East Natural Gas Transmission Pipeline Project and several suggestions were proposed.