Numerical study of hydrogen effects on pressurized methane-oxy combustion in counter-flow diffusion flame

Hydrogen, a renewable energy source, is attracting interest because it does not emit the greenhouse gases and air pollutants generated by the use of fossil fuels. This study aims to analyze the effects of a hydrogen blend on pressurized oxy-fuel combustion (POFC) to support hydrogen infrastructure and reduce greenhouse gas emissions. A counter-flow diffusion flame model was used to analyze the characteristics of POFC. Purified and unpurified natural gas and hydrogen gas were used as fuels. Increased reactivity of the reactants and high flame stability can be simultaneously achieved through POFC. Pressure is a more important parameter for controlling the flame temperature dominantly than the hydrogen content and should be prioritized in the design of POFC systems. The third-body reaction is activated in pressurized methane-oxy combustion, promoting chemical reactions that contribute to the combustion process. In particular, it was confirmed that hydrogen blending inhibits the dehydrogenation of hydrocarbons and activates an exothermic reaction based on H radicals. As the hydrogen content increases to up to 30%, the adiabatic flame temperature and the increase in OH radicals enhance the NO-production rate when the fuel or oxidant contains some impurity (N-2). The nitrogen oxides produced by impurities have a higher rate of formation when present in the oxidant. Therefore, the NO-reduction method for the cofiring of unpurified methane and hydrogen in POFC should be considered.

Automated summary

This study analyzed the effects of a hydrogen blend on pressurized oxy-fuel combustion (POFC) and found that increased reactivity of reactants and high flame stability can be achieved through POFC. Pressure is a more important parameter for controlling flame temperature than hydrogen content and should be prioritized in POFC system design. Hydrogen blending inhibits the dehydrogenation of hydrocarbons and activates an exothermic reaction based on H radicals.