Recent advances in low-gradient combustion modelling of hydrogen fuel blends

Buczyński, Rafał; Uryga-Bugajska, I.; Tokarski, Mieszko

doi:10.1016/j.fuel.2022.125265

Cited by 17 publications

(3 citation statements)

References 74 publications

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“…Moderate or intense low-oxygen dilution (MILD) combustion is another promising environmentally friendly technology, which can achieve ultralow NO x emissions in industrial furnaces. ,, MILD combustion is also called high-temperature air combustion (HiTAC), flameless oxidation (FLOX), colorless distributed combustion (CDC), and low-gradient combustion (LGC), whose obtainment requires reactants to be highly diluted and preheated by strong internal flue gas recirculation. As a result, in MILD combustion, flame fronts are invisible, temperature fields are uniform, and noises are low. ,− Motivated by their advantageous features, the combination of oxy-fuel and MILD combustion (i.e., oxy-MILD) technologies is a potential solution to control NO x emissions while achieving large-scale CO 2 capture in industrial furnaces.…”

Section: Introductionmentioning

confidence: 99%

Performance Improvement of Methane oxy-MILD Combustion with High Initial Oxygen Contents Using a Novel Non-premixed Oxygen/Recycled Flue Gas Jet Burner

Xu,

Tian,

Dou

et al. 2024

Energy Fuels

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Oxy-fuel moderate or intense low-oxygen dilution (oxy-MILD) combustion is a promising technology to control NO x emissions while achieving large-scale CO 2 capture in gas-fired industrial furnaces. However, oxy-MILD combustion still presents challenges at high initial oxygen levels, where less satisfactory thermal uniformity and even high NO x emissions may occur. To address these challenges, this paper reports a novel non-premixed oxygen/recycled flue gas (O 2 /RFG) jet burner, whose novelty lies in that O 2 and RFG are separately supplied (where RFG serves as a "barrier gas" between fuel and oxygen jets to delay their mixing before reaction) rather than premixed with each other conventionally. Meanwhile, an improved GRI-Mech 3.0 model is proposed to predict prompt-NO formation via the NCN pathway more accurately by adding the NCN, HNCN, and HNC reaction subsets. Using the improved GRI-Mech 3.0 model, the performances of the non-premixed O 2 /RFG jet burner and its difference from those of the premixed one during methane oxy-MILD combustion are evaluated at different oxygen concentrations of 25−35 vol % in a laboratory-scale furnace. In particular, NO formation and reduction via thermal, prompt, N 2 O-intermediate, NNH, and reburning pathways are revealed in addition to combustion and heat transfer characteristics. Results show that, compared to the premixed one, the non-premixed O 2 /RFG jet burner can sustain oxy-MILD combustion at a higher initial oxygen level, where better temperature/heat flux uniformity is obtained in a larger reaction zone. What's more, NO emissions can be reduced by 14.8− 64.9% if air leakage occurs, mainly due to less NO formation via N 2 + O → NO and N 2 O + H/O → NO in the thermal and N 2 Ointermediate pathways; also, the efficiency of NO reduction via HCCO/CH i=0−3 + NO reactions is enhanced by 2.3−8.6% when doping 100−800 ppm of NO in the oxidizer. In conclusion, the non-premixed O 2 /RFG jet burner is recommended to be used to help establish/sustain oxy-MILD combustion at high initial oxygen levels in industrial furnaces, where further NO emission reduction can be achieved while improving thermal uniformity.

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Section: Introductionmentioning

confidence: 99%

Performance Improvement of Methane oxy-MILD Combustion with High Initial Oxygen Contents Using a Novel Non-premixed Oxygen/Recycled Flue Gas Jet Burner

Xu,

Tian,

Dou

et al. 2024

Energy Fuels

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“…There are also works concerning improvements to the boiler control systems which are especially valuable during dynamic work [5,6,13,14]. Some other researchers, on the other hand, pay attention once again to the so-called Low-Gradient Combustion (LGC) also known as MILD (Moderate or Intense Low-oxygen Dilution), HiTAC (High-Temperature Air Combustion), Highly Preheated Air Combustion (HPAC), Colorless Distributed Combustion (CDC), FLOX (Flameless Oxidation), or FC (Flameless Combustion) [15][16][17][18][19][20]. This concept comes down to expanding the reaction zone to all the available volumes within the combustion chamber (a more uniformly distributed and diluted reactant) by means of enhanced flue gas recirculation, resulting in a uniform temperature profile with lowered peak temperatures by approximately several hundred Kelvins.…”

Section: Introductionmentioning

confidence: 99%

“…Low-gradient technology fits into the environmental objectives promoted by the EU and constitutes a clean, convenient, and promising way to use a wide range of fuels along with a waste disposal method. What is more, low-gradient combustion is seen as a very promising technology for efficient pure hydrogen (or hydrogen blends) combustion [15,22,23].…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer Analysis for Combustion under Low-Gradient Conditions in a Small-Scale Industrial Energy Systems

Tokarski,

Buczyński

2023

Energies

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The issue of maintaining low-gradient combustion in the conditions of high heat extraction has been investigated numerically in this work. The analyses include the application of a convective boundary condition at the wall (with estimated boiling heat transfer coefficient); analysis of the Internal Recirculation Device’s impact on combustion products and heat transfer under low-gradient conditions; and comparison of both traditional and low-gradient combustion modes. It was shown that the Internal Recirculation Device material and geometry has a significant impact on the nitrogen oxide (NOx) formation mechanism, as NO2 emission becomes predominant and can rise up to several hundreds ppm. What is more, along with decrease in thermal resistance of the IRD, CO emissions also increase rapidly, even achieving over 2000 ppm. Additionally, the convective heat transfer rate decreased by about 25% after switching from traditional to low-gradient combustion, whereas the radiative mechanism increased by ≈40% compared to traditional mode. It should also be mentioned that the low-gradient combustion applied in this work achieved approximately 10% higher efficiency than conventional combustion.

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Thermodynamic modelling and optimisation of a green hydrogen-blended syngas-fueled integrated PV-SOFC system

Saberi Mehr,

Ilkhani,

Sabernia

et al. 2024

Applied Thermal Engineering

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Recent advances in low-gradient combustion modelling of hydrogen fuel blends

Cited by 17 publications

References 74 publications

Performance Improvement of Methane oxy-MILD Combustion with High Initial Oxygen Contents Using a Novel Non-premixed Oxygen/Recycled Flue Gas Jet Burner

Performance Improvement of Methane oxy-MILD Combustion with High Initial Oxygen Contents Using a Novel Non-premixed Oxygen/Recycled Flue Gas Jet Burner

Heat Transfer Analysis for Combustion under Low-Gradient Conditions in a Small-Scale Industrial Energy Systems

Thermodynamic modelling and optimisation of a green hydrogen-blended syngas-fueled integrated PV-SOFC system

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