Characteristics of pulverized-coal combustion in the system of oxygen/recycled flue gas combustion

Kiga, Takashi; Takano, Shinichi; Kimura, Naokazu; Omata, K.; Okawa, Masafumi; Mori, Takenori; Kato, Mutsuo

doi:10.1016/s0196-8904(96)00258-0

Cited by 183 publications

(100 citation statements)

References 2 publications

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“…Slower mixing rates between fuel and oxygen in the case of oxyfuel combustion reduces the combustion rate. The figure also shows higher turbulent viscosity for the oxyfuel case towards the furnace exit, reflecting higher combustion rates in that region and leading to high temperature levels as indicated in The same overall trends are consistent with those of Kiga et al (1997), who investigated the ignition characteristics of oxyfuel combustion of pulverized coal in a CO 2 -rich atmosphere by measuring the flame propagation speed. It was found that the flame propagation speed in O 2 /CO 2 is lower than that in O 2 /N 2 environment, and this behavior was attributed to the higher heat capacity of CO 2 as compared to that of N 2 .…”

Section: Characteristics Of Oxyfuel and Air-fuel Combustion Processessupporting

confidence: 86%

“…It was found that the flame propagation speed in O 2 /CO 2 is lower than that in O 2 /N 2 environment, and this behavior was attributed to the higher heat capacity of CO 2 as compared to that of N 2 . The higher heat capacity has also been used to explain the delayed flame ignition in oxy-fuel combustion [Kimura 1995 andKiga et al 1997]. Flammability limits and flame speeds are affected by the substitution of CO 2 for N 2 and it was concluded that CO 2 has an inhibitory effect on flame propagation and stability.…”

Section: Characteristics Of Oxyfuel and Air-fuel Combustion Processesmentioning

confidence: 99%

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Characteristics of Oxyfuel and Air–Fuel Combustion in an Industrial Water Tube Boiler

Ben‐Mansour

Habib

Nemitallah

et al. 2014

Heat Transfer Engineering

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The characteristics of oxyfuel combustion are compared to those of air-fuel combustion in the furnace of a typical industrial water tube boiler. Two oxyfuel cases are considered. These correspond to 21% O 2 and 29% O 2 by volume. Validations for both oxyfuel combustion and air-fuel combustion indicate that the temperature levels are reduced in oxyfuel combustion. The results show that, as the percentage of recirculated CO 2 is increased, the temperature levels are greatly reduced. It is concluded that the flame propagation speed in O 2 /CO 2 environment is lower than that in O 2 /N 2 . It is found that the fuel and oxygen consumption rates are slower in oxyfuel combustion relative to air-fuel combustion. Heat transfer from the burnt gases to the water jacket along the different surfaces of the furnace is calculated. It is shown that the energy absorbed is much higher in the case of air-fuel combustion along all surfaces except for the end part of the furnace close to the furnace rear wall.

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Section: Characteristics Of Oxyfuel and Air-fuel Combustion Processessupporting

confidence: 86%

Section: Characteristics Of Oxyfuel and Air-fuel Combustion Processesmentioning

confidence: 99%

Characteristics of Oxyfuel and Air–Fuel Combustion in an Industrial Water Tube Boiler

Ben‐Mansour

Habib

Nemitallah

et al. 2014

Heat Transfer Engineering

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“…However, there have been contradictory observations on SO 2 emissions under oxy firing and air firing. Some researchers (Kiga et al 1997, Croiset et al 2001, Yamada 2007, D.M. Woycenko 1995, Hu et al 2000, Wall et al 2009) have indicated that SO 2 emissions under oxy firing decreased as compared to air firing.…”

Section: Subtask 34 -Oxy-coal Combustion In Circulating Fluidized Bedsmentioning

confidence: 99%

“…oxy-and air-fired conditions are inconsistent (Kiga et al 1997, Croiset and Thambimuthu 2001, Yamada 2007, D.M. Woycenko 1995, Hu et al 2000, Wall et al 2009).…”

Section: Sulfur Release In Oxy-fuel Combustion and Air-combustion Obmentioning

confidence: 99%

Oxy-coal Combustion Studies

Wendt

Eddings

Lighty

et al. 2012

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The objective of this project is to move toward the development of a predictive capability with quantified uncertainty bounds for pilot-scale, single-burner, oxy-coal operation. This validation research brings together multi-scale experimental measurements and computer simulations. The combination of simulation development and validation experiments is designed to lead to predictive tools for the performance of existing air fired pulverized coal boilers that have been retrofitted to various oxy-firing configurations. In addition, this report also describes novel research results related to oxy-combustion in circulating fluidized beds. For pulverized coal combustion configurations, particular attention is focused on the effect of oxy-firing on ignition and coal-flame stability, and on the subsequent partitioning mechanisms of the ash aerosol. To these ends, the project has focused on the following:• The development of reliable Large Eddy Simulations (LES) of oxy-coal flames using the Direct Quadrature Method of Moments (DQMOM) (Subtask 3.1). The simulations were validated for both non-reacting particle-laden jets and oxy-coal flames.• The modifications of an existing oxy-coal combustor to allow operation with high levels of input oxygen to enable in-situ laser diagnostic measurements as well as the development of strategies for directed oxygen injection (Subtask 3.2). Flame stability was quantified for various burner configurations. One configuration that was explored was to inject all the oxygen as a pure gas within an annular oxygen lance, with burner aerodynamics controlling the subsequent mixing.• The development of Particle Image Velocimetry (PIV) for identification of velocity fields in turbulent oxy-coal flames in order to provide high-fidelity data for the validation of oxy-coal simulation models (Subtask 3.3). Initial efforts utilized a laboratory diffusion flame, first using gas-fuel and later a pulverized-coal flame to ensure the methodology was properly implemented and that all necessary data and image-processing techniques were fully developed. Success at this stage of development led to application of the diagnostics in a large-scale oxy-fuel combustor (OFC).• The impact of oxy-coal-fired vs. air-fired environments on SO x (SO 2 , SO 3 ) emissions during coal combustion in a pilot-scale circulating fluidized-bed (CFB) (Subtask 3.4). Profiles of species concentration and temperature were obtained for both conditions, and profiles of temperature over a wide range of O 2 concentration were studied for oxy-firing conditions. The effect of limestone addition on SO 2 and SO 3 emissions were also examined for both air-and oxy-firing conditions.• The investigation of O 2 /CO 2 and O 2 /N 2 environments on SO 2 emissions during coal combustion in a bench-scale single-particle fluidized-bed reactor (Subtask 3.5). Moreover, the sulfation mechanisms of limestone in O 2 /CO 2 and O 2 /N 2 environments were studied, and a generalized gassolid and diffusion-reaction single-particle model was developed to s...

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“…The reduction of NO x due to recycled flue gas is a known benefit of oxy-fuel combustion (Kiga et al, 1997;Chui et al, 2004;Buhre et al, 2005;Ahn et al, 2009). Part of the NO in the flue gas is reduced by precursors, such as HCN and NH 3 , and carbonaceous reducing radicals in fuel-rich regions (Buhre et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Effect of dilution of fuel in CO2 on the conversion of NH3 to NO x during oxy-fuel combustion

Qiu

Yang

You

et al. 2015

J. Zhejiang Univ. Sci. A

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Abstract:The indirect chemical effects of fuel dilution by CO 2 on NO formation were investigated numerically in this paper. CH 4 doped with NH 3 was used as fuel, while CO 2 and O 2 were mixed as oxidant. The dilution effect of CO 2 was then investigated through adding extra CO 2 to the reaction system. An isothermal plug flow reactor was used. An unbranched chain reaction mechanism is proposed to illustrate the chemical effects of CO 2 on the H/O/OH radical pool and NO x . Due to the reaction between CO 2 and H, extra NO will be formed in fuel-rich conditions, while NO will be inhibited in fuel-lean conditions and high CO 2 dilution conditions. The reaction affected the radical pools of OH, H, and O of the branched chain reaction, and then the formation and reduction of NO. The pool of H had the greatest effect on NO reduction. The results suggest that the indirect chemical effects on NO formation differ between diluted fuel oxy-fuel combustion conditions and normal oxy-fuel conditions.

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Characteristics of pulverized-coal combustion in the system of oxygen/recycled flue gas combustion

Cited by 183 publications

References 2 publications

Characteristics of Oxyfuel and Air–Fuel Combustion in an Industrial Water Tube Boiler

Characteristics of Oxyfuel and Air–Fuel Combustion in an Industrial Water Tube Boiler

Oxy-coal Combustion Studies

Effect of dilution of fuel in CO2 on the conversion of NH3 to NO x during oxy-fuel combustion

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