An investigation of the comparative performance of diverse humidity sensing techniques in natural gas

Determination of Water Content of Nitrogen Containing Hydrogen Sulfide by Karl Fischer Coulometric Titration

“…The first is a chilled mirror hygrometer (CMH), which is used to determine the dew point or frost point (FP) of natural gas, 3 and the second is water content analyzers or moisture analyzers, which include those based on Karl Fischer titration (KFT), capacitance-based sensors, quartz crystal microbalances (QCM), electrolytic-based sensors, and tunable diode laser absorption spectroscopy (TDLAS). [4][5][6][7][8][9][10] The frost point and water content can be converted to each other. 11 For CMH, the liquid of hydrocarbons formed at low temperature might interfere with the determination of the water dew point.…”

“…The lack of an accurate determination of the water content of natural gas leads to an inconsistency of results determined by analyzers based on different principles. 9,10 There remains an urgent need of an accurate determination of the water content of natural gas for online monitoring and calibration.…”

Tunable Diode Laser Absorption Spectroscopy Sensor for Calibration Free Humidity Measurements in Pure Methane and Low CO2 Natural Gas

“…Sensors such as chilled mirror, spectroscopic, polymeric, and metal oxide humidity hygrometers are typically used to quantify the water vapor content in natural gas. 1 However, the current practice for water vapor measurements is for the sensor to be calibrated in nitrogen or air as matrix gas at atmospheric pressure. 1 Nitrogen or air is quite a different gas matrix as compared to natural gas at ∼80 000 hPa pressure in natural gas transmission lines.…”

“…1 However, the current practice for water vapor measurements is for the sensor to be calibrated in nitrogen or air as matrix gas at atmospheric pressure. 1 Nitrogen or air is quite a different gas matrix as compared to natural gas at ∼80 000 hPa pressure in natural gas transmission lines. Therefore, the ideal condition for the quantification of the H 2 O content (typically less than 500 µmol/mol) would be to calibrate in natural gas and to perform the measurements at pipeline pressures.…”

“…However, changes in the water content from the pipeline gas to the sensor could be minimized by heated pressure regulators and connection lines to the sensor. 1 In addition, since gas is expanded during sampling and the water vapor dew point is dependent on the gas composition, pressure and temperature extrapolations would be needed during data analysis for sensors that measure the dew point. 1 A gas matrix dependent enhancement factor is needed in calculations to account for a pressure drop in sampling lines.…”