小型LNG站便携式取样技术研究

A portable sampling technology for small LNG stations

关键词:  小型LNG站  液化天然气  取样  便携  质量检测 

Key words:  small LNG stations  liquefied natural gas  sampling  portability  quality inspection

摘要:

目的 为了解决小型液化天然气(LNG)站缺乏有效质检取样技术,现有便携式LNG取样技术缺少取样应用实践,可靠性需要进一步验证的问题,提供一种新型便携式LNG取样装置和技术,以及取样可靠性验证方法。方法 基于LNG相图控制理论基础,通过理论计算设计取样装置真空保冷探头和气化器,研制了基于真空保冷技术的便携式LNG取样装置,保障在取样过程中LNG以过冷态进入气化器并完全气化,确保LNG样品的代表性,并研制了基于LNG循环保冷技术的便携式LNG取样装置,通过对比两种取样装置所取样品的组成分析结果,进行了便携式LNG取样技术可靠性研究。结果 在LNG加气站和LNG工厂的示范应用实践结果表明,采用便携式LNG取样装置11次连续取样获得的样品几乎一致,连续取2次LNG液体样品后组成分析的结果满足GB/T 13610-2020 《天然气的组成分析 气相色谱法》的再现性要求,且通过两种取样方法获得的样品的组成分析结果相吻合,表明便携式LNG取样技术可靠。结论 该便携式LNG取样装置和技术取样效果达到了预期,满足了小型LNG场站LNG质量检测取样需求。 

Abstract:

Objective In order to the solve the problems that there is a lack of effective quality inspection sampling technology for small liquefied natural gas (LNG) stations, the existing portable LNG sampling technology lacks practical sampling applications, and the reliability needs further verification, a new type of portable LNG sampling device and technology, as well as a sampling reliability verification method are provided. Methods This study builds upon the theoretical framework of LNG phase diagram control. Through theoretical calculations, we have devised a portable LNG sampling apparatus featuring a vacuum-cooled probe and a vaporizer. This ensures that LNG remains in a supercooled state during the sampling process, subsequently undergoing complete vaporization upon entry into the vaporizer. Consequently, the representativeness of the LNG samples is guaranteed. Additionally, we have developed a point sampling device to facilitate comparative analyses with the portable LNG sampling method. By comparing the compositional analysis results of samples obtained from both methods, we have conducted a comprehensive study to verify the representativeness and reliability of the portable LNG sampling technique. Results Demonstration applications have been successfully carried out at LNG refueling stations and LNG plants. The outcomes of these practical tests have demonstrated remarkable consistency among the samples obtained through the use of the portable LNG sampling apparatus across eleven consecutive sampling attempts. The composition analysis results of the LNG liquid samples, obtained through two consecutive sampling attempts, have satisfied the reproducibility requirements outlined in GB/T 13610-2020 Analysis of natural gas composition-Gas chromatography. Furthermore, these results have aligned with the composition analysis findings of the samples obtained through the point sampling method. This indicates that the sampling process is genuinely representative. Conclusion The portable LNG sampling device and technique have achieved the expected sampling effect, and fulfilled the sampling requisites for quality inspection at small LNG stations.