A role of hydrocarbon reaction for NOx formation and reduction in fuel-rich pulverized coal combustion

Taniguchi, Masayuki; Kamikawa, Yuki; Okazaki, Teruyuki; Yamamoto, Kenji; Orita, Hisayuki

doi:10.1016/j.combustflame.2010.04.009

Cited by 59 publications

(72 citation statements)

References 14 publications

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“…However, furnaces that burn low-quality coal with low volatile content are undesirable because low-NO x burners induce an increase in unburned carbon and lower furnace efficiency even if NO x emissions are reduced. A recent study by Hitachi Ltd. analyzed the relation between coal burnout and NO x emissions in a fuel-rich coal flame and found that unburned carbon linearly increases with a decrease in NO x emissions [3,4]. Consequently, maintaining high combustion efficiency in low-NO x burners, especially with frequent changes in coal quality, is important in the design and operation of pulverized coal furnaces.…”

Section: Introductionmentioning

confidence: 99%

Determining the optimum coal concentration in a general tangential-fired furnace with rich-lean burners: From a bench-scale to a pilot-scale study

Wang

Tan

Yan

et al. 2014

Applied Thermal Engineering

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Section: Introductionmentioning

confidence: 99%

Determining the optimum coal concentration in a general tangential-fired furnace with rich-lean burners: From a bench-scale to a pilot-scale study

Wang

Tan

Yan

et al. 2014

Applied Thermal Engineering

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“…In contrast, our previous paper shows the role of CO 2 was to advance CH 4 oxidation during fuel-rich O 2 /CO 2 combustion where the concentrations of reactants were high because R3 became insignificant under fuel-rich condition, and R1 produced an abundance of OH radicals that were more active than the H radicals in hydrocarbon reactions in the specific temperature range (12,13) . In addition to this, the total hydrocarbon in oxy-fuel coal combustion was lower than that in air combustion in some literature (1,2) . Therefore, further investigations are needed in hydrocarbon oxidation process under O 2 /CO 2 environments.…”

Section: Journal Of Thermal Science and Technologymentioning

confidence: 99%

“…typically coal, a large part of the fuel conversion occurs in the gas phase, and hydrocarbon oxidation plays an important role in combustion process (1)(2)(3)(4) . CH 4 is not only a natural gas component but also one of the major volatile matter released from coal.…”

Section: Journal Of Thermal Science and Technologymentioning

confidence: 99%

Experimental and Kinetic Studies of Chemical Role of CO2 in Hydrocarbon Oxidation during Fuel-Rich O2/CO2 Combustion

Watanabe

Kiatpanachart

Okazaki

2013

JTST

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Experimental and kinetic studies of the chemical role of CO 2 in hydrocarbon reactions were conducted in a fuel-rich CH 4 flat flame with air ratios varying from 0.60 to 0.74. Unburned hydrocarbons (CH 4 , C 2 H 2 , C 2 H 4 , and C 2 H 6 ) in O 2 /CO 2 combustion were found to be lower than those in air combustion. The differences in the CH 4 oxidation characteristics between the air and O 2 /CO 2 combustion were caused by the chemical role of CO 2 in the reaction R1 (CO 2 + H → CO + OH), R2 (CH 2 (S) + CO 2 → CH 2 O + CO), and higher third body efficiencies of CO 2 at an air ratio (= 0.62 where the concentrations of reactants were high. The role of CO 2 in R1, R2, and the higher third body efficiencies of CO 2 decreased the rate of CH 4 oxidation during the early stage of combustion, where O 2 was present. Even though R2 did not directly compete with the main chain branching reaction R3 (H + O 2 → H + OH) for H radicals, like R1 did, R2 changed the hydrocarbon reaction pathway, thereby decreasing the rate of R4 (CH 3 + HO 2 → CH 3 O + OH) which had negative sensitivity in CH 4 oxidation. However, we found that R1 and R2 advance CH 4 oxidation in the last stage of combustion where O 2 was mostly consumed. This is attributed to the fact that the reactions R1 and R2 were able to advance without the presence of O 2 , and that R1 produced OH radicals that were active in hydrocarbon oxidation in the specific temperature range and R2 enhanced hydrocarbon oxidation when the rate of R4 was insignificant. Although R1 was the dominant reaction to reduce unburned hydrocarbons in the O 2 /CO 2 combustion, the role of R2 was significant at  = 0.62. Meanwhile, when the air ratio was 0.74 where concentrations of reactants were relatively low, the chemical role of CO 2 is to only decrease the rate of CH 4 oxidation due to the presence of an excessive amount of O 2 .

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“…However, boiler design and development cannot be done efficiently if it is necessary to change the method of NO x reduction for each coal property. In a previous study, we proposed an index to estimate NO x reduction performance [5]. This index has hardly any influence from the burning conditions.…”

Section: Introductionmentioning

confidence: 99%

“…While studies on NO x reduction by char [16][17][18][19] have been made, the contribution for total NO x emission from the pulverized coal combustion was not clear. In previous studies, we proposed a NO x reaction model which focused on the gas phase reaction in the char combustion region [5,15]. A key reaction was reduction of NO x by hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

Application of the NOx Reaction Model for Development of Low-NOx Combustion Technology for Pulverized Coals by Using the Gas Phase Stoichiometric Ratio Index

Taniguchi¹,

Kamikawa²,

Shibata³

et al. 2011

Energies

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Abstract:We previously proposed the gas phase stoichiometric ratio (SRgas) as an index to evaluate NO x concentration in fuel-rich flames. The SRgas index was defined as the amount of fuel required for stoichiometric combustion/amount of gasified fuel, where the amount of gasified fuel was the amount of fuel which had been released to the gas phase by pyrolysis, oxidation and gasification reactions. In the present study we found that SRgas was a good index to consider the gas phase reaction mechanism in fuel-rich pulverized coal flames. When SRgas < 1.0, NO x concentration was strongly influenced by the SRgas value. NO x concentration was also calculated by using a reaction model. The model was verified for various coals, particle diameters, reaction times, and initial oxygen concentrations. The most important reactions were gas phase NO x reduction reactions by hydrocarbons. The hydrocarbon concentration was estimated based on SRgas. We also investigated the ratio as an index to develop a new low-NO x combustion technology for pulverized coals. We examined the relation between local SRgas distribution in the fuel-rich region in the low-NO x flame and NO x emissions at the furnace exit, by varying burner structures. The relationship between local SRgas value and local NO x concentration was also examined. When a low-NO x type burner was used, the value of SRgas in the flame was readily decreased. When the local SRgas value was the same, it was difficult to influence the local OPEN ACCESSEnergies 2011, 4 546 NO x concentration by changing the burner structure. For staged combustion, the most important item was to design the burner structure and arrangement so that SRgas could be lowered as much as possible just before mixing with staged air.

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A role of hydrocarbon reaction for NOx formation and reduction in fuel-rich pulverized coal combustion

Cited by 59 publications

References 14 publications

Determining the optimum coal concentration in a general tangential-fired furnace with rich-lean burners: From a bench-scale to a pilot-scale study

Determining the optimum coal concentration in a general tangential-fired furnace with rich-lean burners: From a bench-scale to a pilot-scale study

Experimental and Kinetic Studies of Chemical Role of CO<sub>2</sub> in Hydrocarbon Oxidation during Fuel-Rich O<sub>2</sub>/CO<sub>2</sub> Combustion

Application of the NOx Reaction Model for Development of Low-NOx Combustion Technology for Pulverized Coals by Using the Gas Phase Stoichiometric Ratio Index

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