Moisture Measurement in Natural Gas is both essential and challenging. Many corrosive gases can interfere with the accuracy and effectiveness of the dew point measurement in a natural gas cryogenic gas plant, most especially Methanol, which can cause damage to the sensing element and render it inaccurate.
In a trial at a Cryogenic Plant in Colorado during inclement weather, the Phymetrix PPMa handheld analyzer was hooked up after the mole sieve dryer and after the methanol injection, just before the fractionating cryogenic separator. The PPMa was setup to log overnight, the moisture content of the gas in order to evaluate the capacity and column switching times of the mole sieve dryer.
Keeping the moisture content low has many benefits including a lessening need for thawing out the cryogenic separator to remove the accumulated ice. The ability of the PPMa to operate in a wide temperature range and its IP 65 Weatherproof housing allows it to be used even in the toughest environments such as the Colorado winter snowstorm that occurred during the overnight logging. The Phymetrix sensing technology's insensitivity to methanol is very unique and essential in the accuracy and reliability of this measurement.
Because of the measurements taken from the Gas Plant Computer System using the Phymetrix PPMa analyzer, the data determined that the mole sieve dryer to be undersized and the columns not switched often enough. The breakthrough of moisture which occurred about 6 or 7 hours into the cycle, added undesirable quantities of moisture. The test showed the engineers that they need to switch the columns more often and regenerate the mole sieve better by increasing regeneration cycle temperature and/or flow.
Most other analyzers experience interference from the methanol being injected into the gas stream, making the Phymetrix portable analyzer unique in its ability to measure in such rough environments with the highest accuracy.