Strategies for Hydrogen-Enriched Methane Flameless Combustion in a Quasi-Industrial Furnace

In this present work, simulations of 20 kW furnace were carried out with hydrogen-enriched methane mixtures, to identify optimal geometrical configurations and operating conditions to operate in flameless combustion regime. The objective of this work is to show the advantages of flameless combustion for hydrogen-enriched fuels and the limits of current typical industrial designs for these mixtures. The performances of a semi-industrial combustion chamber equipped with a self-recuperative flameless burner are evaluated with increasing H2 concentrations. For highly H2-enriched mixtures, typical burners employed for methane appear to be inadequate to reach flameless conditions. In particular, for a typical coaxial injector configuration, an equimolar mixture of hydrogen and methane represents the limit for hydrogen enrichment. To achieve flameless conditions, different injector geometries and configuration were tested. Fuel dilution with CO2 and H2O was also investigated. Dilution slows the mixing process, consequently helping the transition to flameless conditions. CO2, and H2O are typical products of hydrogen generation processes, therefore their use in fuel dilution is convenient for industrial applications. Dilution thus allows the use of greater hydrogen percentages in the mixture.