管输天然气含水量/水露点的计算方法

Calculation method of water content/water dew point of natural gas

单纯依赖仪表监测管输天然气的水露点,无法直接获得天然气的含水量信息。基于SRK状态方程编制了天然气含水量/水露点的计算软件,将其应用于中亚输气管道投产初期气质含水量的计算,其结果与文献数据基本吻合,预测含水量的最大绝对偏差低于3mg/m3,预测水露点的最大绝对偏差低于0.5C。应用该计算软件确定了在投产初期双气源之一气质不达标的情况下,保证中亚输气管道进口气质达标的双气源合理掺混输量比范围为0.26～0.57。经现场应用验证,在此掺混输量比范围内输气,能够满足中亚输气管道气质运行安全,无液体析出。

It is impossible to access the information of natural gas water content directly only by the online natural gas water dew point measurement.A program is developed to calculate the water content and water dew point of natural gas based on SRK equation of state,and is successfully applied to predict the natural gas water content during the initial production period in Central Asian Natural Gas Pipeline.The simulated results are in good agreement with those presented in the literatures,with the maximum absolute deviation to predict water content of 3 mg/m3 and the maximum absolute deviation to predict water dew point of 0.5 oC.A reasonable range of flowrate ratio for the two gas sources is defined as 0.26 to 0.57 by using the program to guarantee the quality of mixed natural gas at the inlet of the Central Asian Natural Gas pipeline under the conditions of one of the unqualified gas sources during the initial running period of this pipeline.It is proved safe and no liquid condensed to transport the natural gas with the flowrate ratio of the two gas sources in this range by the field data.