天然气及类似气体产品标准水露点指标解读

Indicator interpretation on product standard of natural gas and similar gas for water dew point

水露点是天然气及类似气体产品的一项重要质量指标,正确理解不同产品标准对水露点的技术要求,对天然气及类似气体加工、输送条件的选择和控制具有重要意义。对比分析了GB 17820-2018《天然气》、GB 18047-2017《车用压缩天然气》和GB/T 37124-2018《进入天然气长输管道的气体质量要求》等对水露点的指标要求,详细解读了各标准对判定水露点超标的工况条件,并通过实例分析了当工况条件发生变化时,测定和评判水露点结果时的关注要点。结果表明:天然气及类似气体的水露点有定性和定量两类指标,定性指标要求在交接点的压力和温度条件下应不存在液态水;定量指标采用“在一定压力下,水露点应比输送条件下最低环境温度低5℃”的要求。在此情况下,标准的使用者正确理解“一定压力”和“最低环境温度”是有效判断水露点是否超标的关键。而车用压缩天然气以环境温度-13℃为界点,分两种情况规定水露点或水含量,其指标具体明确,具有较好的操作性。提出了GB 18047-2017和GB/T 37124-2018规定水露点指标的局限性,为今后修订相关国家标准提出了建议。其结论对从事天然气分析测试及质量管理的人员正确理解和使用标准具有实际意义,也为天然气脱水处理装置和输气管道的安全平稳运行提供了技术参考。

Water dew point is an important technical index of natural gas and similar gas,which is of great significance to the selection and control of natural gas and similar gas processing and transportation conditions with a correct understanding of the water dew point requirements of different product standards.The paper compares and analyzes the water dew point index requirements of GB 17820 Natural Gas,GB 18047 Compressed Natural Gas as Vehicle Fuel and GB/T 37124 Quality Requirement for Gases Eetering Long-distance Transportation Gas Pipeline,detailed interpretation of the criteria for determining whether the water dew point measurement results meeting the requirements of the technical provisions.At the same time,the attention point of measuring and judging water dew point results is analyzed in the form of example.The results show that the water dew point index of natural gas and similar gas can be divided into qualitative and quantitative indexes,and the qualitative index emphasizes that there should be no liquid water under the condition of pressure and temperature at the handover point,no need to detect the water content.At a certain pressure,the water dew point should be 5℃lower than the minimum ambient temperature under the conveying condition.At this time,the standard users correctly understand"certain pressure"and"minimum ambient temperature"is the key to effectively judge whether the water dew point exceeding the limit value of standard.The ambient temperature-13℃is as the boundary point for vehicle compressed natural gas,and the water dew point or water content is specified in two cases,its indexes are specific and clear with good operability.This paper puts forward the limitation of water dew point index stipulated by GB 18047-2017 and GB/T 37124-2018 standards,and gives some suggestions for revising relevant national standards in the future.The conclusion has reference value for the personnel engaged in natural gas analysis and testing and quality management to understand and use the standard correctly.It is also of practical significance for the safe and smooth operation of natural gas dehydration treatment plant and gas pipeline.