Scaling of NOx emissions from a laboratory-scale mild combustion furnace

Szego, G.; Dally, Bassam B.; Nathan, Graham J.

doi:10.1016/j.combustflame.2008.02.001

Cited by 148 publications

(88 citation statements)

References 39 publications

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“…The effect of initial fuel or air dilution on non-premixed MILD combustion has been investigated by previous experiments [20][21][22]. Szegö et al [20,21] found that fuel dilution increases fuel jet momentum and causes the reaction to switch from conventional flame mode to MILD mode.…”

Section: Introductionmentioning

confidence: 98%

Influence of Inlet Dilution of Reactants on Premixed Combustion in a Recuperative Furnace

2011

Flow Turbulence Combust

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This paper presents a numerical study by RANS modeling that investigates the effect of external dilution on the premixed combustion occurring in a recuperative furnace. Calculations are performed using the detailed GRI-Mech 3.0 mechanism to ensure the accuracy of the modeling. Results of the in-furnace flow, temperature, and concentrations of OH, O 2 , CO 2 and NO x are provided. It is found that the external dilution with the inert gas CO 2 plays a significant role in establishing the premixed MILD (Moderate or Intense Low-oxygen Dilution) combustion. Externally diluting the reactant mixture not only reduces the initial concentration of O 2 but also ensures a stronger internal dilution by recirculation of more hot combustion products. Importantly, the latter effect is more significant for achieving the MILD regime. There is a critical mass fraction of the diluent CO 2 present, below which MILD combustion cannot occur. While the traditional premixed flame produces much more NO x than the MILD combustion, the emission of NO x appears to result most from the thermal-NO route and least from the N 2 O route no matter which mode occurs. Moreover, the present simulation demonstrates that the MILD mode occurs over a wider range of initial reactant conditions for premixed combustion than for diffusion combustion.

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Section: Introductionmentioning

confidence: 98%

Influence of Inlet Dilution of Reactants on Premixed Combustion in a Recuperative Furnace

2011

Flow Turbulence Combust

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“…Therefore, the flame formed in this case is inferred to be conventional spray flame with high temperature reaction layers. From above discussion, we inferred that Zel'dovich mechanism is dominant for NOx formation at a condition of X O2 = 21 % and T O = 1023 K. Szegö et al (2008) reported that contribution of prompt mechanism for NOx formation is remarkable in MILD combustion. Since the flame formed at X O2 = 12 % and T O = 623 K exhibits features similar to MILD combustion, the prompt mechanism is possibly dominant for NOx formation in this case.…”

Section: Nox Emissions From the Furnace At A Nozzle Distance Of 30 MMmentioning

confidence: 99%

“…Mixing with the recirculated burned gas dilutes both the fuel gas and the oxidizing gas while simultaneously raising the temperatures of the diluted gases, thus achieving a uniform temperature distribution throughout the furnace and allowing a low flame temperature. This process reduces NOx emissions through the Zel'dovich mechanism (Szegö et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Effect of the distance between fuel and oxidizer nozzles on NOx emissions from spray combustion furnaces incorporating high-temperature preheated oxidizers

Nada

Shibata

Imaoka

et al. 2015

JTST

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The objective of the present study was to investigate the effect of the distance between fuel and oxidizer nozzles on NOx emissions from a laboratory-scale spray combustion furnace simulating an industrial high-temperature air combustion (HiTAC) furnace. The furnace employed in these trials was fueled with commercially obtainable kerosene in combination with highly preheated oxidizer gases. The oxidizer was pre-diluted by the addition of nitrogen in order to produce dilution levels equivalent to those in industrial HiTAC furnaces. The resulting NOx measurements indicate a trend opposite to that reported by previous studies, such that increasing the distance between the nozzles increases the NOx emissions, and a theory is advanced to explain this unusual observation. In a furnace within which the nozzle distance in the burner is small, the properties of the oxidizer supplied from the nozzle located near the spray nozzle greatly affect NOx emissions. The use of an oxidizer with a much lower preheat temperature and a lower O 2 concentration induces flame lifting further downstream, which significantly reduces NOx emissions through the formation of an invisible flame exhibiting a uniform temperature distribution throughout the furnace. In contrast, in a furnace in which the burner has a large nozzle distance, a highly luminous flame is anchored near the spray nozzle exit due to ignition of fuel vapor by high-temperature burned gases recirculated to the lower section of the furnace. This flame represents a zone with high combustion intensity and generates significant NOx emissions. In such cases, the influence of the oxidizer properties is moderated due to the widely separated nozzle locations.

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“…To achieve stable combustion at the low oxygen levels associated with the very high recirculation rates of MILD combustion it is necessary for the initial temperature to exceed the auto-ignition temperature (Katsuki & Hasegawa, 1998). The method of achieving recirculation can be internal or external with regard to the combustor (Szegö et al, 2007). The recirculation, typically achieved with high velocity nozzles (Cavaliere & De Joannon, 2004), and the resultant reduction in oxygen concentration, lead to MILD combustion flames being associated with low Damköhler numbers (Katsuki & Hasegawa, 1998).…”

Section: Characteristics Of Mild Combustionmentioning

confidence: 99%