| Natural gas is a high quality and efficient green energy source.The moisture in natural gas can cause ice blocking and cause serious safety problems.The water dew point meter and the moisture meter of various different principles have inconsistent results of measuring the moisture of natural gas,causing troubles for the quality control of natural gas moisture.Therefore,the natural gas industry urgently needs a moisture measurement method with accurate measurement results and resistance to complex components of natural gas.It is used for on-line calibration of water dewpoint and moisture meters.The Karl Fischer Coulometry is a direct method of moisture measurement.It generates iodine molecules through electrolysis to participate in the Karl Fischer reaction.Then,according to Faraday’s Law,the total iodine is calculated by electricity,so that the moisture content can be obtained.Karl Fischer Coulometry can measure the moisture in natural gas more accurately.The Coulometry method is generally considered to be an absolute method of moisture measurement and does not require correction.The main problem with Coulometry’s application to natural gas is the interference of reducing substances such as hydrogen sulfide and mercaptans in natural gas.First of all,by building a moisture test platform,the humidity generated by the humidity generator is divided into two,which are respectively provided to the standard chilled mirror dew point meter and the Karl Fischer Coulometry for comparison.By comprehensive analysis of all parameters that may affect the experimental results when measuring the moisture content of the gas by Karl Fischer Coulometry,to determine the effect of different experimental conditions on the reaction.Then,under the optimized experimental conditions,the calibration formula of the Karl Fischer Coulometry is obtained.After calibration,the extended uncertainty of the Karl Fischer moisture analyzer in the moisture measurement range of 14.84 mg/kg to 907.50 mg/kg was 1.40%to 10.34%.The traceability of the Coulometry water amount value is achieved.Finally,through the addition of hydrogen sulfide to moisture,a special Karl Fischer reagent without sulfur dioxide is used to study the interference of different concentrations of hydrogen sulfide on the Coulometric moisture analyzer;by comparing with the national standard method and the Non-SO2 deduction method,three-dimensional fitting method is used to deduct the interference of hydrogen sulfide and obtains a fitting function with a fitting degree of 0.9999.The average value of the simulated water recovery was in the range of 94%to 145%,and the dew point indication error was in the range of-0.43℃ to 2.88℃.The overall fitting accuracy is high and the interference of hydrogen sulfide in natural gas is effectively deducted,which provides a reference for the Coulometxy to become the standard device for on-line measurement of natural gas moisture. |
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