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

Abstract

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.

A Comprehensive Review on the Prospects of Using Hydrogen–Methane Blends: Challenges and Opportunities

“…The possibility of using methane-hydrogen mixtures for operation under low-temperature regimes of the flameless combustion, which makes it possible to significantly reduce NOx emissions, was studied in [66]. To optimize the design of a semi-industrial combustion chamber with an increase in the concentration of H 2 , the operation of a recuperative flameless burner with a power of 20 kW on methane-hydrogen mixtures was simulated.…”

MILD Combustion and Biofuels: A Minireview

“…This is the most common solution in actual devices, not relying on regenerative systems. The two main strategies followed in the design of MILD combustion chambers with internal recirculation are summarized in the two sketches and related pictures reported in Figure b and c. Figure b represents the typical configuration where a reverse flow is generated by means of the fluid-dynamic flow field which is established due to a very high inlet air jet velocity and appropriate aspect ratio of the combustion chamber. − Very often, the configuration of this typology has the gas exit section on the same side of fuel and air inlet. , …”

“…Despite the lower maximum temperature and higher residence times than the ones of conventional combustion processes, the effectiveness of MILD combustion in a wide range of power and power density is guaranteed, as discussed in reviews 14,27,59 and archival papers 8,34,43,60 as well as in the outcomes of international research projects funded by international entities. 61 This is also confirmed by its utilization in gas turbine (e.g., sequential combustion) 59 or reheating furnaces 32 as a small set of examples.…”

"Flow variation and fuel savings when using Hydrogen- Methane mixture as combustible in wall-mounted boilers’ operation"

“…The investigations that have been done thus far are largely theoretical, and the experimental component is necessary to validate the findings. Articles like [5][6][7][8][9][10][11][12][13][14][15] are valuable in the field, but they generally present numerical modeling or process simulations in specialized software, and in the situation where the data are obtained after conducting experiments, the effects of using the methane-hydrogen mixture on the operation of wall-mounted condensing boilers are not highlighted. Among the most challenging studies involved testing a variety of combustion devices to see how a hydrogen-natural gas mixture affected performance and emissions.…”