Measurement and Testing
Proven, precise and reliable trace moisture measurement for hydrogen and natural gas applications
Sep 20 2022
At the upcoming H2 Expo in Bremen, BARTEC will be showing off their hugely popular HYGROPHIL F 5673 process trace moisture analyser. The conversion of electric power from renewable sources to hydrogen is significant technology to decarbonisation and seasonal energy storage. Precise and dependable moisture measurements are crucial for plants to comply to contracted limits and ensure safety at the plant.
Polymer Electrolyte Water Electrolysis (PEM) or Alkaline Water Electrolysis are widely accepted principles for decomposing water to hydrogen and oxygen by use of electric current. The conversion of electric power to hydrogen makes is storable and possible to transport via the existing gas pipeline grid, where it can be re-electrified or used as fuel for vehicles or other industrial processes.
At the gas pressure regulating and metering station, the hydrogen is analysed for traces of oxygen and nitrogen, flow rate and heating value. The analysis of trace humidity is of particular importance when additional gas compression is needed to feed the gas to the natural gas pipeline grid. Contracted feed-in limits (e.g. 50 mg/m³ moisture) are important to prevent condensation in pipeline which leads to operational problems (corrosion and erosion) and safety risk (water slugs and even blockage by hydrate formation).
The BARTEC HYGROPHIL F 5673’s trace moisture sensors are trimmed to be extra robust; even water slugs will not damage the sensor. The reliability of the sensor’s calibration can be tested by an independent and accredited laboratory on request.
Most hydrogen plants are small and unmanned, or even located offshore, so regularly changing sensors or extensive maintenance is impractical for keeping operational costs as low as possible. When it comes to the annual check, the installation of the sensor with the sensor retraction armature makes maintenance quick and easy while avoiding costly and time-consuming process interruption.
The HYGROPHIL F 5673 was designed specifically for the natural gas industry. At the heart of the moisture sensor is an optical thin film element made of silicon dioxide and zirconium dioxide. The microporous stack of alternating high and low refracting optical layers forms a Fabry-Pérot Interferometer with a distinctive and reliably detectable reflection minimum in the spectral range around 820 nm.
Selective to water, molecules can diffuse into the porous Fabry-Pérot element, which then performs a shift of the reflection minimum in proportion to the actual water vapour pressure. The spectral shift is detected and evaluated with a compact high-resolution polychromator, which is found in the evaluation unit along with the light emitting diode. The interconnecting fibre optic cable can be up to 800 m long to allow the detection of an optical minimum instead of an intensity change.
The evaluation unit processes and calculates the current dew point temperature and other parameters such as water vapour pressure, parts per million, mg/m³. It also provides dew point temperature data at current line pressure as well as to other operator-defined reference pressures. Users have the option of making the calculation from dew point temperature to mg/m³ in conformity to DIN EN ISO 18453, which takes into account the entered gas composition. Several analogue outputs, MODBUS, PROFIBUS RTU and via TCP/IP as well as relay contacts are included as standard for interconnection to the control system.
Thousands of HYGROPHIL F 5673 operators across the globe can testify to its reliability and accuracy of this instrument; it provides trouble-free long-term operation, even offshore. Cleaning and maintaining the sensors is quick and easy. BARTEC also offer flexible, on-line solutions with customised sample conditioning systems and it is possible to carry out in-line installation with sensor retraction armature which is both fast response and emission-free. The HYGROPHIL F 5673 is certified for use in hazardous locations (ATEX, IECEx, CSA, TR CU).
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