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flue’s clues

This is supported by previous studies³ FIGURE 3 - CARBON DIOXIDE READINGS AGAINST GAS QUALITY
into the effects of fuel composition on
flue gas concentrations.
To support the data analysis of the
measured flue gas concentrations
against gas quality, a first-principle
combustion model was developed
which allowed flue gas compositions to
be predicted based on a specified fuel
composition and air/fuel ratio. This
model allowed a prediction of the
effects of hydrogen blending on flue gas
analysis to be undertaken, for
comparison with measured values. An
expected relationship was derived of
the flue gas compositions from the
boilers. This was carried out by first
calibrating the model using the excess
oxygen measurements recorded, which
allowed the commissioning air/fuel
ratio of the boilers to be found. The
results of this calibration exercise are
shown in Figure 2. the fuel’s Wobbe. This observation is hydrogen. This is a critical evidence
Following this calibration, real-world meaningful, as it supports the current base in unlocking the deployment of
natural gas compositions were used to process used by Gas Safe operatives of hydrogen blends across the UK gas
derive the full range of expected flue using the CO/CO₂ ratio to determine network as it does not necessitate a
gas compositions based on the safe combustion quality (alongside the wholesale change to current flue gas
maximum allowable Wobbe range absolute measurements). Given that the analysers utilised by Gas Safe
within the UK of 47.2-51.4MJ/m³. ratio is almost independent of fuel engineers, nor does it imply any
The flue gas data (O₂, CO₂, CO and quality, it allows a determination of upskilling or procedural changes are
CO/CO₂ ratio) was compared against the combustion quality to be undertaken required. In short, current Gas Safe
boilers operating with natural gas and without the need to take account (and competencies and standards to manage
the boilers operating with a hydrogen therefore measure) the fuel composition combustion should be adequate to
blend. The analysis showed that there being supplied to the appliance at the manage a blend of hydrogen.
was a non-material effect due to the time of measurement. This research was peer reviewed by
presence of a hydrogen blend, namely HSL, Worcester Bosch, Baxi, Ideal,
how a hydrogen blend affects the It was found that, both carbon Vaillant, Crowcon and Kane, as well as
Wobbe of the gas. In other words, two being more widely peer reviewed by
natural gases of equal Wobbe number, dioxide and carbon monoxide members of the Heating and Hotwater
one containing a hydrogen blend and concentrations reduce with Industry Council (HHIC) and is
the other containing no hydrogen, reducing Wobbe numbers. currently under peer review with IGEM
resulted in near identical flue gas Therefore, the addition of members. Following this rigorous peer
compositions. This result was found to review process, the research was
be true for both types of flue gas hydrogen within natural gas written into an HHIC-authored Gas Safe
detectors (indirect and direct CO₂ supplies reduces both of these technical bulletin (TB), TB 157, which
measurement). An example of the concentrations was published in May 2020. The full
results obtained are shown in Figure 3. research paper is available upon
It was found that, both carbon request from IGEM, reference:
dioxide and carbon monoxide The results of the research show that, Communication 1837.
concentrations reduce with reducing if a hydrogen blend remains within the
Wobbe numbers. Therefore, the regulatory Wobbe limits of natural gas, HyDeploy is a pioneering hydrogen
addition of hydrogen within natural gas there will be no material change to the energy project designed to help reduce UK
supplies reduces both of these expected range of flue gas compositions CO emissions and reach the government’s
2
concentrations. However, the that would result from appliances across net zero target for 2050. For more
magnitude of reduction was within the the UK. Therefore, current flue gas information, visit www.hydeploy.co.uk
general range of carbon dioxide and analysers used by Gas Safe engineers, as
carbon monoxide concentrations that well as current combustion criteria used
UK appliances are expected to produce to assess safe performance, should not References
when supplied with GSMR-compliant need to change to accommodate a 1. Dutton, B.C, 1978. Interchangeability Prediction –
natural gas. The CO/CO₂ ratio blend of hydrogen within natural gas the Framework for a New Approach, Journal of the
Institute of Fuel, 225-229.
measurements were found to be fairly supplies up to 20vol%. 2. GSMR, 1996. UK Gas Safety (Management)
independent of Wobbe number, this is The consequences of this research Regulations, 1996, UK Statutory Instruments 1996,
because both of the individual readings demonstrate the suitability of current No. 551.
have the same directional trend with a equipment and procedures to safely 3. Brown, M., McKay, G. and Williams, T., 2004.
Assessment of the impact of gas quality on the
fuel’s Wobbe, therefore the ratio of the manage current appliances following performance of domestic appliances (a pilot study),
two numbers is almost independent of the introduction of a 20vol% blend of Advantica.

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