Moisture Measurement for Hydrogen and Natural Gas Blending

Michell Instruments: supporting the roll-out of net zero technologies

If the UK is to meet its net zero target by 2050, dramatic changes need to take place in the way in which we produce and use energy, especially natural gas.   85 % of our homes and businesses are dependent on gas for heating.  In 2017, the average household produced around 2.7 tonnes of carbon emissions; to hit the 2050 target, this figure has to fall to just 138 kg, according to data from the Energy Systems Catapult. 

The challenge is to meet this goal as efficiently and cost-effectively as possible.  Clearly, renewables have an important role to play but so too does the transition from natural gas to a nationwide supply that will eventually be based on a combination of bio-methane and hydrogen. 

This process is already well-advanced.  A pilot project in a closed gas network at Keele University in Staffordshire is using a 20 % blend of hydrogen and natural gas, while a further hydrogen blending trial taking place at Winlaton, Gateshead is tapping into a public gas network.  Similar exercises are taking place in other countries around the world. 

The Energy Networks Association (ENA) now expects that the national gas grid will be ready for distribution companies to begin the widespread use of hydrogen injection into natural gas from 2023.  Over time, the objective is to introduce biomethane.  To this end, the ENA recently launched an ambitious Gas Goes Green initiative, bringing together the UK’s gas network companies to convert the nation’s 284,000 km of pipeline infrastructure to run on a blend of hydrogen and biomethane without affecting consumers’ heating, hot water or cooking equipment. 

The challenges to this transition are technical, commercial and political.  The ENA is calling for the UK government to be more ambitious in its target for low-carbon hydrogen generation, recommending that the goal of 5 GW is doubled by 2030.  Further issues include the ability to generate sufficient hydrogen sustainably to meet demand, while concerns exist over potential risks of hydrogen embrittlement in older iron and steel pipework, and the need to adapt pipeline pressures to compensate for the different levels of energy density between hydrogen and natural gas. 

Nonetheless, once these challenges have been overcome there is the potential that a 20 % hydrogen/natural gas blend will save, in the UK alone, around 6 million tonnes of carbon dioxide emissions every year – the equivalent of taking 2.5 million cars off the road. 

Trace moisture measurement in hydrogen/natural gas blends

In common with all natural-gas extraction, production and transmission applications, the process of blending and monitoring hydrogen and natural gas requires strict monitoring of a range of key criteria.  Of these, trace moisture measurement is one of the most crucial, to maintain gas quality, process system efficiency and safety, and to ensure compliance with both commercial and statutory obligations. 

Most of the gas distribution and transmission infrastructure has been developed to handle pure natural gas, with monitoring systems being designed accordingly.  Introducing a hydrogen blend often raises questions from plant, maintenance and control engineers about the continuing validity of process measurements using existing equipment, with concerns over the need for – and cost of –replacing sensors and analyzers with new dedicated units. 

The good news for customers using Michell Instruments’ moisture, water dew-point and hydrocarbon dew-point analyzers is that they are already designed for use in natural gas with a hydrogen blend of up to 20 %, without any modifications being required.  Similarly, all new analyzers will continue to comply with current and anticipated technical, commercial and regulatory requirements for hydrogen/natural gas blends. 

Our range of analyzers gives plant and production engineers a wide range of options, backed by an exceptional level of technical, applications and compliance knowledge and support.  The current product range has ATEX, IECEx, UKCA and NEC505 certifications for gas group IIC or IIB+H2, together with NEC500 Ex for gas group A or B, and includes the following instruments: 

QMA401/601 QCM Moisture Analyzer

The quartz crystal microbalance (QCM) principle is commonly used for moisture measurement in both natural gas and hydrogen. The oscillation frequency of the sensing piezoelectric quartz crystal varies in proportion to the mass of moisture vapor adsorbed by a hygroscopic coating on the surface of the crystal. This principle is independent of the background gas composition.

QMA401 analyzers provide trace moisture measurement in pure hydrogen supplied for automotive fuel cells. In oil refineries, QMA601 analyzers are used to monitor recycled gas within catalytic reforming processes. Typically, this gas contains 75 % volume hydrogen and 25 % mixed hydrocarbons.    

Promet IS/EExd Ceramic Metal-Oxide Moisture Analyzer

Moisture molecules within the flowing gas sample equilibrate into the porous hygroscopic dielectric of these capacitance/impedance ceramic metal-oxide moisture sensors. The sensors exhibit response to the partial pressure of water vapor, explicitly linked to water dew-point temperature, enabling calibration to that parameter and measurement of water dew point directly at process pressure condition. This principle is unaffected by background gas composition including the concentration of hydrogen. Michell Instruments’ ceramic metal-oxide moisture technologies meet the needs of diverse applications for gases and liquids across the manufacturing and process industries. Examples of hydrogen applications include metal annealing furnaces and generator cooling systems in electricity power stations.  

Condumax II Hydrocarbon Dew-point Analyzer

The Condumax II applies an adaptation of the fundamental chilled-/cooled-mirror dew-point measurement principle. The ‘Dark Spot’ optical technique detects formation of low-surface tension hydrocarbons condensing at the HC dew-point temperature. The Condumax II will accurately measure the hydrocarbon dew point of the overall gas composition inclusive of injected hydrogen. Injection of hydrogen into natural gas will proportionately dilute the concentrations of all hydrocarbons present, causing the hydrocarbon dew point to fall. Equation of state estimations predict that the change in hydrocarbon dew point will be relatively small – less than 1 ˚C reduction with 20mol % hydrogen injection – as shown in the table below.

CDP301 Condumax Dew-Point Tester

The direct chilled-/cooled-mirror dew-point method together with hi-definition camera imaging enables the CDP301 to measure actual hydrocarbon and water dew-point temperatures of the complete natural-gas composition, including any portion of hydrogen that is present.

Click here to learn more about our solutions for hydrocarbon dew point.

With over 40 years of experience in the development of innovative precision instruments, we are the experts in trace moisture measurements for all natural gas applications. If you would like to discuss your requirements, please contact our team today.

Sources:

Energy Systems Catapult

Energy Networks Association