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In 2020, energy-related CO2 emissions reached 31.5 Gt, leading to an unprecedented atmospheric CO2 level of 412.5 ppm. Hydrogen blending in natural gas (NG) is a solution for maximizing clean energy utilization and enabling long-distance H2 transport through pipelines. However, insufficient comprehension concerning the combustion characteristics of NG, specifically when blended with a high proportion of hydrogen up to 80%, particularly with minority species, persists. Utilizing the heat flux method at room temperature and 1 atm, this experiment investigated the laminar burning velocities of CH4/NG/H2/air/He flames incorporating minority species, specifically C2H6 and C3H8, within NG. The results point out the regularity of SL enhancement, reaching its maximum at an equivalence ratio of 1.4. Furthermore, the propensity for the enhancement of laminar burning velocity aligned with the observed thermoacoustic oscillation instability during fuel-rich regimes. The experimental findings were contrasted with kinetic simulations, utilizing the GRI 3.0 and San Diego mechanisms to facilitate analysis. The inclusion of H2 augments the chemical reactions within the preheating zone, while the thermal effect from temperature is negligible. Both experimental and simulated results revealed that CH4 and NG with a large proportion of H2 had no difference, no matter whether from a laminar burning velocity or a kinetic analysis aspect. [ABSTRACT FROM AUTHOR]

Utilizing ammonia as a co-firing fuel to replace amounts of fossil fuel seems a feasible solution to reduce carbon emissions in existing pulverized coal-fired power plants. However, there are some problems needed to be considered when treating ammonia as a fuel, such as low flame stability, low combustion efficiency, and high NO x emission. In this study, the co-firing characteristics of ammonia with pulverized coal are studied in a drop tube furnace with staged combustion strategy. Results showed that staged combustion would play a key role in reducing NO x emissions by reducing the production of char-NO x and fuel(NH 3)-NO x simultaneously. Furthermore, the effects of different ammonia co-firing methods on the flue gas properties and unburned carbon contents were compared to achieve both efficient combustion and low NO x emission. It was found that when ammonia was injected into 300 mm downstream under the condition of 20% co-firing, lower NO x emission and unburnt carbon content than those of pure coal combustion can be achieved. This is probably caused by a combined effect of a high local equivalence ratio of NH 3 /air and the prominent denitration effect of NH 3 in the vicinity of the NH 3 downstream injection location. In addition, NO x emissions can be kept at approximately the same level as coal combustion when the co-firing ratio is below 30%. And the influence of reaction temperature on NO x emissions is closely associated with the denitration efficiency of the NH 3. Almost no ammonia slip has been detected for any injection methods and co-firing ratio in the studied conditions. Thus, it can be confirmed that ammonia can be used as an alternative fuel to realize CO 2 reduction without extensive retrofitting works. And the NO x emission can be reduced by producing a locally NH 3 flame zone with a high equivalence ratio as well as ensuring adequate residence time. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a comparative life cycle assessment of two types of H2 carriers, methanol and ammonia, using GaBi 10 software. Two types of H2 carriers that is, methanol and ammonia are compared from coal, natural gas and renewables, respectively. The full supply chain is considered in the carbon footprint evaluation, which contains production, storage, transportation, and utilization phase. The energy analysis results show that H2 carrier produced from natural gas has higher energy efficiency than that from renewables, which can be attributed to the high energy consumption during H2 generation in the latter. Carbon footprint evaluation indicates that solar PV‐based ammonia production route has the lowest GWP in all scenarios, with a value of 43.9 g of CO2‐Equation MJ−1 of ammonia. In addition, electricity has been found as the key factor affecting GHG emissions in the routes of fuels produced from renewable H2 through sensitivity analysis. By optimizing electricity generation and expanding the carbon capture scale of power plant, the GHG emissions level of CCU‐based methanol production route and solar PV‐based ammonia production route can be further reduced. [ABSTRACT FROM AUTHOR]