Importance of Initial Momentum Rate and Air-Fuel Premixing on Moderate or Intense Low Oxygen Dilution (MILD) Combustion in a Recuperative Furnace

Mi, Jianchun; Li, Pengfei; Dally, Bassam B.; Craig, Richard A.

doi:10.1021/ef900866v

Cited by 129 publications

(115 citation statements)

References 16 publications

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“…That is, all the temperature distributions suggest that the simulated combustion should be in the MILD mode no matter which model is employed and what chemical mechanism is considered. This is the case as shown experimentally in our previous work [26]. Hence, the above calculations based on the four models can simulate the MILD combustion, at least, qualitatively.…”

Section: Dif Ferent Turbulent Combustion Modelssupporting

confidence: 81%

“…When calculations are performed for D = 7.2 mm and Y + CO2 = 0 (no dilution), a case which was examined experimentally [26], the outcomes from using the four models are generally similar. Figure 3a and b show, respectively, the longitudinal temperature distribution on the centerline and the lateral one at z = 200 mm in the central yz-plane.…”

Section: Dif Ferent Turbulent Combustion Modelsmentioning

confidence: 96%

“…The present study simulates various premixed combustion cases at a laboratory-scale recuperative furnace, which has been used for previous studies [20,21,25,26]. Here only a brief description on the furnace is provided for the CFD domain establishment (Fig.…”

Section: Furnace Configuration and Fuelmentioning

confidence: 99%

“…The reason could be that preheating is not allowed for the operation of premixed combustion due to the tendency of self-ignition, while preheating combustion air to a temperature above self-ignition has been considered necessary for the establishment of MILD combustion (so termed HiTAC). However, our previous work [24][25][26][27][28] has found that, regardless of premixing air and fuel fully or partially, the MILD combustion can be established and maintained stably without air preheating as long as the initial jet momentum or Reynolds number is sufficiently high.…”

Section: Introductionmentioning

confidence: 99%

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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: Dif Ferent Turbulent Combustion Modelssupporting

confidence: 81%

Section: Dif Ferent Turbulent Combustion Modelsmentioning

confidence: 96%

Section: Furnace Configuration and Fuelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2011

Flow Turbulence Combust

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“…All the nozzles and exhausts were at the bottom of the furnace. This MILD combustion setup has produced data on various experiments, including fuel tests, flame tests, NO x tests, and heat exchanger tests (Christo and Dally, 2005;Colorado et al, 2009;Dally et al, 2002Dally et al, , 2004Dally et al, , 2010de Joannon et al 2009de Joannon et al , 2010Flamme, 2004;Li et al, 2011b;Lou et al, 2007;Maruta et al, 2000;Medwell et al, 2007Medwell et al, , 2008Mi et al, 2009;Mörtberg et al, 2006;Oryani et al, 2011;Park et al, 2004;Stankovic, 2006). MILD combustion technology is still not fully commercialized and well adopted in the furnace industry, thus it is very important to conduct substantial fundamental and applied research (Cavaliere et al, 2008;Danon, 2011;Li et al, 2011b;Parente et al, 2011aParente et al, , 2011b.…”

Section: Recent Trends In Mildmentioning

confidence: 99%

A review of MILD combustion and open furnace design consideration

Noor¹,

Wandel²,

Yusaf³

2012

Int J Automot Mech Eng

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Combustion is still very important to generate energy. Moderate or Intense Low-oxygen Dilution (MILD) combustion is one of the best new technologies for clean and efficient combustion. MILD combustion has been proven to be a promising combustion technology in industrial applications with decreased energy consumption due to the uniformity of its temperature distribution. It is clean compared to traditional combustion due to producing low NO x and CO emissions. This article provides a review and discussion of recent research and developments in MILD. The issue and applications are summarized, with some suggestions presented on the upgrading and application of MILD in the future. Currently MILD combustion has been successfully applied in closed furnaces. The preheating of supply air is no longer required since the recirculation inside the enclosed furnace already self-preheats the supply air and selfdilutes the oxygen in the combustion chamber. The possibility of using open furnace MILD combustion will be reviewed. The design consideration for open furnace with exhaust gas re-circulation (EGR) was discussed.

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Flameless combustion behaviour of preheated pulverized coal

Ouyang

Zhu

2017

Can J Chem Eng

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A method for stable flameless combustion of pulverized coal based on coal preheating was recently proposed. The method involves the initial heating of pulverized coal to a temperature above 800 °C. The heated coal is then transferred into a combustion chamber, where it is mixed with secondary air injected at a high velocity to achieve flameless combustion. The flameless combustion behaviour of the preheated pulverized coal was experimentally investigated in a lab‐scale test apparatus. The results showed that stable flameless combustion of bituminous coal and two different anthracite coals could be achieved. The temperature of the combustion chamber was also observed to be homogeneous. The peak temperature was below 1250 °C, while the average combustion temperature was about 1150 °C. The normalized root mean square temperature fluctuation over the combustion chamber is 7.0 %, 6.7 %, and 6.8 % for the three different coals. The colour of the entire combustion chamber was a faint yellow with no obvious flame front surface observed. Fuel preheating was found to be effective for improving the combustion efficiency, with values of 99.2 %, 98.3 %, and 97.9 % achieved for bituminous coal and two different anthracite coals, respectively. The experimental data further revealed that the NOX emissions for all the considered coals were very low compared to the corresponding cases of traditional combustion, with the values for the different coal types also significantly varying. The NOX emissions were determined to be 232, 187, and 165 mg/Nm3 (6 % O2) for bituminous coal and two different anthracite coals, respectively.

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Importance of Initial Momentum Rate and Air-Fuel Premixing on Moderate or Intense Low Oxygen Dilution (MILD) Combustion in a Recuperative Furnace

Cited by 129 publications

References 16 publications

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

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

A review of MILD combustion and open furnace design consideration

Flameless combustion behaviour of preheated pulverized coal

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