天然气中水含量与水露点换算关系探讨

Conversion relationship between water content and water dew point in natural gas

目的采用实验加数学拟合的方法开发一种新型天然气中水含量与水露点的换算方法,以提高换算精度并降低误差。方法综合应用气体标准物质、便携式冷镜仪以及数学软件Matlab,采用三次样条插值技术建立了一种新型水含量与水露点换算方法。结果利用三次样条插值技术建立拟合曲面方法进行水露点换算,该方法的平均绝对误差(MAE)为1.16℃,均方根误差(RMSE)为2.28℃,满足合理可接受的最大偏差为2.8℃。将该方法与国内外主流的换算方法进行比较分析,3种方法的平均绝对偏差分别为0.46%(三次样条插值法)、0.69%(GB/T 22634-2008《天然气水含量与水露点之间的换算》)和0.84%(ASTM D1142-95(2021)《露点温度法测定气体燃烧水蒸气含量的标准试验方法》),并分析探究了3种方法在不同水含量和压力段的适用情况。结论通过与实验值的对比研究,当水的体积分数在0~200×10-6范围内时,三次样条插值法相比标准方法具有更好的换算精度,可有效降低水含量与水露点的换算误差。

Objective Experimental and mathematical fitting methods are used to develop a new approach for converting water content to dew point in natural gas to enhance conversion accuracy and reduce errors.Methods This paper adopts the combined application of gas standard substances,portable dew point mirrors,and Matlab mathematical software.Using cubic spline interpolation technique,it establishes a novel method for converting water content to water dew point.Results By utilizing surface fitting for the conversion of water dew point,this method achieves a Mean Absolute Error(MAE)of 1.16℃and a Root Mean Square Error(RMSE)of 2.28℃,meeting the reasonably acceptable maximum deviation of 2.8℃.By comparing this method with the domestic and international mainstream conversion methods,the average absolute deviation of the three methods are 0.46%(cubic spline interpolation),0.69%(GB/T 22634-2008 Conversion between water content and water dew point of natural gas),and 0.84%(ASTM D1142-95(2021)Standard test method for water vapor content of gaseous fuels by measurement of dew-point temperature),respectively,and the applicability of the three methods under different water content and pressure ranges is analyzed and explored.Conclusions Through comparative studies with experimental values,the cubic spline interpolation method shows better conversion accuracy for water volume fractions from 0 to 200×10-6 compared to standard methods,effectively reducing the conversion error between water content and water dew point.