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  • P-ISSN 1225-0163
  • E-ISSN 2288-8985

A study on quality assurance and evaluation of uncertainty for the analysis of natural gas

Analytical Science and Technology / Analytical Science and Technology, (P)1225-0163; (E)2288-8985
2006, v.19 no.6, pp.490-497





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Abstract

The sources of uncertainty in the analysis of liquified natural gas (LNG) process are evaluated. The uncertainty sources evaluated are the repeatability of measurement, non-linearity of GC, the uncertainty of standard gas used for calibration, difference of gas sampling and deviation after GC calibration and major revealed sources are the non-linearity of GC, the uncertainty of standard gas and the deviation after GC calibration. The determined values and uncertainties of methane and ethane as the major components are <TEX>$90.0%mol/mol{\pm}1.9%$</TEX> (relative and 95% level of confidence) and <TEX>$6.26%mol/mol{\pm}0.08$</TEX> (relative and 95% level of confidence), respectively. The contribution of uncertainty varies depending on the source of uncertainty and gas component. In the case of methane, non-linearity of GC, the uncertainty of standard gas and deviation after GC calibration contribute 0.28%, 0.25% and 0.24% of relative expanded uncertainty, respectively.

keywords
Analysis of LNG, quality assurance, measurement uncertainty, gas CRM, non-lineality, drift, sampling


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ISO, Natural Gas-Sampling guidelines , ISO 10715 ,

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ISO, Certification of reference materials-General and statistical principles, ISO Guide 35. ,

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