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Radiation and flame scale characteristics of ceiling jet are important key elements, which are related to the safety of hydrogen energy transport. In this study, the flame radiation characteristics caused by hydrogen-blended natural gas (mixed gas) pipeline leakage fire were investigated experimentally. The effects of heat release rate, hydrogen addition ratio, nozzle diameter and source-ceiling height are considered. The flame shape of the ceiling jet fire is modeled by a cylinder cone and a cylindrical model. The WSGGM model is applied to calculate the flame emissivity. The flame emissivity is quantized by the equivalent diameter and gas type. The flame emissivity, downward received radiative heat flux and radiative heat flux under ceiling increase with the increase of hydrogen addition ratio. The view factor is calculated by the solid flame model. Moreover, the calculated flame radiative heat flux is in a favorable agreement with experimental results. The research results may provide reference for risk assessment of hydrogen mixing. • Effect of H 2 on flame radiation of CH 4 jet fire is studied experimentally. • Fame shape of ceiling jet was modeled by the cylinder cone and a cylindrical model. • A mathematical model for the flame emissivity estimation is proposed. • A prediction model of the flame radiation the gas mixture is reported. [ABSTRACT FROM AUTHOR]

Ammonia-coal co-combustion is a feasible approach to reduce CO 2 emissions during thermal power generation, it is necessary to study NO formation mechanism in ammonia-coal co-firing to realize low-carbon and low-nitrogen combustion. The experimental results showed that temperature and ammonia ratio have a significant effect on the NO formation. Under the same ammonia blending amount, the NO production increased first and then decreased with temperature increasing. Theoretical calculations revealed that the formation of NH in NH 3 →NH→NO is one of the factors restricting ammonia combustion. NH oxidation on the char surface first occurred in the NH/coal/O 2 combustion system, and realized the conversion of N to NO, HNO and NO 2 through different reaction paths. Combined with the experimental and theoretical calculation results, it was concluded that the reduction of NO by ammonia/char is enhanced at high temperature (>1300 °C), which reduces the conversion of ammonia-N/coal-N to NO. • Temperature and ammonia blending ratio significantly influenced the NO emissions. • NO increased first and then decreased with temperature increasing at same ammonia mixing ratio. • Theoretical calculation results show that NH oxidation first in the co-firing system. • NH formation was one of the limiting factors of ammonia combustion speed. • Intermediate HNO played a key role in NO formation in NH 3 and coal co-firing. [ABSTRACT FROM AUTHOR]