Oil and water don’t mix, but methane and H20 certainly do, which challenges producers to remove the greatest amount possible of the latter to deliver an acceptable commercial product, and maintain safety of their operations.
With the long distances natural gas often travels on its multi-stage journey from wellhead to local distribution networks, moisture measurement is performed multiple times en route : at production and gathering sites, along upstream pipelines, at custody transfer points, compressor stations, storage facilities and in the distribution markets. Given the commercial implications of making natural gas (or biogas) as ‘dry’ as possible, expectations for natural gas measuring instruments are constantly increasing. Operators want the highest levels of process and product quality, coupled with lowest possible maintenance and total cost of ownership.
Meeting such elevated expectations is keeping pressure on vendors for a new generation of TDLAS gas moisture analyzers, which Endress+Hauser is ushering in with the new J22 series. The J22 is the first in a series of advanced gas analyzers, powered by SpectraSensors technology, to be launched into the market.
While most moisture is removed during initial processing of the raw gas, some can be added back during downstream transmission via condensation along pipeline networks, and that is both a commercial and safety issue. Moisture measurement along trunk lines provides early detection of potentially hazardous hydrate buildup, leaks caused by corrosion or moisture buildup that could lead to a shut-in at a custody transfer point. A wetter product has a lower BTU value; Distribution companies have their acceptable delivery standards. For example, Enbridge says the water vapour content of gas in its system is typically 16-32 mg/m3.
Natural gas streams may also contain high levels of solid and liquid contaminants as well as corrosive gases in varying concentrations (glycol, methanol, compressor oil, sulfur compounds). This presents a challenge for some older moisture measurement technologies. The contaminants destroy some moisture sensors and cross-interference effects with the moisture readings must be avoided. With custody transfer in particular, false positives for any reason are very costly because the gas cannot be delivered if “wet.”
The traditional approach to moisture measurements uses a chilled mirror. A chilled mirror determines dew point on a carefully cooled mirror, it’s a slow and subjective measurement because many other components in gas streams can condense on the mirror. Additionally, a variety of electronic sensors have been used which rely on the adsorption of water onto a sensitive surface placed into the gas stream. In practice, sensors that are in contact with natural gas are adversely affected by gas components, causing errors, interference, and costly failures. Their readings are often unreliable.
TDLAS, or tunable diode laser absorption spectroscopy, is a gas measurement technology introduced to the natural gas industry by SpectraSensors over 20 years ago. It was a game changer then and still is unrivalled for accurate and consistent measurement. Since its inception, TDLAS has demonstrated its reliability in thousands of installations worldwide. TDLAS doesn’t require consumables or have contact with contaminants. There are no wet up or dry down hassles. The laser never comes in contact with the gas so it won’t become corroded like other sensors. TDLAS units suffer no impairment from glycol, methanol, amine, H2S, or moisture slugs in the gas stream. The rugged nature of TDLAS analyzers allows them to be used along pipelines. They require very little maintenance, and are immune to interference that plagues other methods. Their low-maintenance characteristic can be a huge time- and cost-saver for operators.
Endress+Hauser’s TDLAS analyzers require no calibration in the field; the calibration is stable for the life of the analyzer, yet validation of H2O concentration is simple to perform. The analyzers are equipped with validation gas connections to accept binary gas blends containing H2O.
Endress+Hauser’s TDLAS portfolio includes analyzers that can detect and measure more than one contaminant (two or three of H20, H2S, C02 or O2), however, moisture content is monitored more frequently along the supply chain.
The new J22’s advanced diagnostics and superior measurement algorithms differentiate it from all TDLAS analyzers that have proceeded it, assuring the highest analyzer availability yet. Its highly developed algorithms, plus the sophisticated diagnostics, monitoring, and verification concept of Endress+Hauser Heartbeat Technology, assure operators of fewer failures, lower operating costs and improved reliability, which translates into a sustainable competitive advantage.
The heart of the TDLAS measurement lies in the gas sample cell where the laser and signal detector are isolated from process contaminants, eliminating measurement errors. J22 analyzers have an accuracy of ±2 ppmv plus 2% of readings and a repeatability of ±1 ppmv or ±1% of reading (whichever is greater) and measuring ranges up to 0-6000 ppm (0-284 lb/mmscf) H2O
State-of-the-art gas mixing technology is used during factory calibration of J22s for measurement confirmation. This ensures superior measurement performance throughout the analyzer’s operations in the field.
The J22 analyzer platform offers versatile operating options using a standardized Endress+Hauser concept. It is tailored to meet gas quality specifications, prevent pipeline corrosion, stop hydrate formation, and minimize the risk of explosion to ensure human safety and asset integrity. The J22 uses proven virtually interference-proof metrology (with NIST traceable calibrations) to avoid shut-in, flaring, and interrupted gas delivery incidents.
The J22 can be integrated seamlessly into any plant asset management system, providing reliable information for optimizing gas or biogas production measurement processes.
J22 systems are available in multiple mounting configurations suitable for various locations:
• Panel mounted sample conditioning system for installation in shelters or in temperate locations
• Heated enclosure for use in outdoor settings or locations with harsh environmental conditions
• Filtration, with or without bypass to remove particulates or liquids in gas stream, assuring uninterrupted measurement
• Pressure regulation with or without pressure relief valve to ensure a steady gas flow into the analyzer for consistent and continuous measurement
• Rugged brackets for wall, rack, or pipe mount for effortless installation
The J22’s sampling system is built onto a compact panel with an option bypass, pressure relief and safety purge and can be packaged in a stainless steel enclosure for extra weather protection. This heated enclosure ensures reliable operations in even the harshest winter conditions. The J22 has all Class 1, Division 1 and Zone 1 certifications for locating in hazardous areas.
Many compressor stations the supply chain are fully automated. So operators want gas analyzers that need minimal maintenance or inspection.
The J22 TDLAS analyzer’s easy-to-replace components minimize downtime for the most efficient continuous analysis. Components are easily accessible and field-serviceable, allowing for quick replacements or upgrades. All replacement parts are accessible using simple hand tools. The simple-to-remove gas sample cells are designed to allow convenient cleaning and servicing.
The J22 functions equally well as a biogas/biomethane moisture analyzer, and it’s future proof. Endress+Hauser invested early in hydrogen blending stations to simulate customer streams for research and development, production calibration, and testing in hydrogen. The J22 is one of the first analyzers to benefit from this investment. It has a built-in capability for hydrogen-containing natural gas streams. Adapting the instrument for a hydrogen-containing stream is a simple field adjustment to the H2 concentration found in the user menu.
(Endress+Hauser)
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