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Chaging gas quality and security

2013-04-16

A symposium recalls that new gas quality and security go hand in hand

Hans de Laat showing a gas experimental setup in Appeldoorn on 11 April 2013 (Photo: KIWA/Harald Ophoff) Hans de Laat showing a gas experimental setup in Appeldoorn on 11 April 2013 (Photo: KIWA/Harald Ophoff)

Requirements for a safe and reliable gas infrastructure will most likely change with the upcoming of new gas quality. Technical committees will have to adjust standards, norms and specifications that maintain the integrity of the gas infrastructure. Several researchers at Kiwa Technology address this concern. They have presented their preliminary results at a symposium in Apeldoorn on 11 April. Distribution system operators, infrastructure suppliers and appliance manufacturers will find them engaging.

Researchers have contributed to increase the reliability of current measurement methods, said Eric Polman, a senior consultant at Kiwa Technology. They have chosen to focus on siloxanes, a trace component found in biogas, which can pose security risks when burned. Distribution system operators rely on measurement methods to ensure the security of the gas infrastructure. They have to measure accurately siloxane concentration.

They cannot rely on current measurement methods, argued Mr Polman. Sampling the gas, using specific materials, referring to another gas and several other details can make a measurement inaccurate. Mr Polman’s work taps on fresh understanding of siloxane behavior in combustion. Thus far, scientists have identified nine types of siloxanes, types D4 and D5 being the most common of them. Biogas produced from landfills, sewage treatment and garbage fermentation usually contains high concentrations of siloxanes.

How does the density of new gas affect their detectability in case of leakage?” asked Kees Pulles from Kiwa Technology. Pipes, valves and fittings, which deteriorates under the effect of gas components, can leak and and let gas spreading in the ground. When gas distribution operators detect these leaks, they have to repair the faulty component in an impaired time frame, depending on the gravity of the situation. The problem of the detectability arises with the fact that new gases have a different density than natural gas.

Mr Pulles installed an experimental set up, made of eight measuring tubes, in the underground at Kiwa Technology research facilities in Apeldoorn. He let natural gas and biogas diffusing into the ground through controlled leakages and measure their relative concentration over time. Mr Pulles’s preliminary conclusions indicate that gas density has a significant effect on concentration.

Effects on infrastructure and appliances

It is not fully clear what effects new gases will have on materials. The Netherlands has deployed an infrastructure to transmit G-gas quality. “How will new gases affect the infrastructure?” asked René Hermkens, a project manager at Kiwa Technology. Mr Hermkens tested in laboratory the effects of gas at various concentrations on a broad range of infrastructure materials at given periods of exposition.

Mr Hermkens also investigates the quality of the materials that have been exposed to the tests. Plastic PVC is placed under stress and deformation, while steel is exposed to uniform and localized corrosion. Can these materials withstand new gases? What is the maximum concentration of gas components for these materials? Answers to these questions can have a significant impact on gas distribution operators’s maintenance routines, security measure and asset management practices.

"What effects will new gases have on end-user equipment?" asked Hans de Laat, a product manager at Kiwa Technology. Indeed, manufacturers have produced household and industrial appliances that perform with the G-gas, which has a low caloric value. New gases have a broader range of calorific value. They generate various levels of emission of carbon dioxide, non-nitrogen oxide, methane, etc. when they burn. Mr De Laat has, therefore, tested appliances certified for G-gas with various gas qualities, such as to determine if they can still perform well.

Devices are rugged but remain robust, because manufacturers have designed the equipment with a high safety margin, according to the first results. On the other hand, devices functioning with new gas quality may lead to more rejection of components, which, in turn, may affect the security margin of the devices.  Results of this study will help out distribution system operators to figure out which gas can be injected into the grid without creating adverse effects on users’ equipment.

By Jean-François Auger