On the use of hydrogen in oxy-fuel glass melting furnaces: An extensive numerical study of the fuel switching effects based on coupled CFD simulations

Abstract

The present study examined the potential of utilizing hydrogen as a fuel in an industrial cross-fired oxy-fuel glass melting furnace with a total energy input of 3.9 MW. To this end, comprehensive three-dimensional CFD simulations were performed in Ansys Fluent, employing a coupled numerical model from preceding works. A two-step validation process was presented, comprising the validation of both the numerical furnace setup and the modeling of industrial oxy-fuel combustion setups using hydrogen as a fuel gas. Assuming an equal thermal energy input for both combustion conditions, the fuel/oxidizer ratios of velocity and momentum of the six PrimeFire burners were found to be significantly affected. Consequently, the low-momentum flames with natural gas transformed into jet-type flames with a straighter trajectory when transitioning to hydrogen. This change led to an enhanced turbulent mixing and a reduction of flame lengths by over 25%, while the average flame temperature increased by up to 82 K due to the accelerated reaction kinetics. In addition, the elevated flame momentum in the cross-fired burner configuration resulted in a localized rise in maximum side wall temperatures by more than 20 K. With the exception of these local effects, the global temperature distribution and heat transfer mechanisms were not significantly impacted. This indicated a comparable melting process and furnace efficiency, while still allowing for a reduction of total CO2 emissions by 77.5%. Future research should concentrate on both the impact on glass quality and the evaluation of potential alternative burner configurations for hydrogen-fired oxy-fuel glass melting furnaces.