Nitrogen evolution, NOX formation and reduction in pressurized oxy coal combustion

Rahman, Zia ur; Wang, Xuebin; Zhang, Jiaye; Yang, Zhiwei; Dai, Gaofeng; Verma, Piyush; Mikulčić, Hrvoje; Vujanović, Milan; Tan, Houzhang; Axelbaum, Richard L.

doi:10.1016/j.rser.2021.112020

Cited by 47 publications

(6 citation statements)

References 172 publications

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“…The experiments range from highly fuel-rich (φ = 0.2) to fuel-lean conditions (φ = 2). Besides, the O 2 concentration was set to 5% to match the actual situation of boilers, except when studying the stoichiometric effect, which is consistent with the findings of Wang et al 3,18 And the inlet concentrations of NO and HCN were consistent with the research of Gimenez-Lopez et al 7 Table 2 lists the conditions of the performed simulations. An optimal temperature making NO emission lowest under different pressures was found (Figure 2c).…”

Section: Simulation Conditionssupporting

confidence: 61%

“…NO x in the flue gas is easily converted into nitrogen intermediates, mainly HCN, by reaction with char or hydrocarbon radicals 2 . HCN could not only be oxygenized to NO but also be able to react with the existing NO 3 . Therefore, the interaction of HCN with NO has an important effect on NO x final emissions, which could finally affect the appropriate design of the subsequent carbon process.…”

Section: Introductionmentioning

confidence: 99%

“…2 HCN could not only be oxygenized to NO but also be able to react with the existing NO. 3 Therefore, the interaction of HCN with NO has an important effect on NOx final emissions, which could finally affect the appropriate design of the subsequent carbon process.…”

Section: Introductionmentioning

confidence: 99%

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Interactions of HCN with NO in pressurized oxy‐combustion

Rahman

Wang

et al. 2022

Asia-Pacific J Chem Eng

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The process of recycling flue gas to the boiler of a pressurized oxy-combustion system could affect the final concentration of NOx, which is very important for an appropriate design of the carbon capture process. During the recycling process, HCN, as the main intermediate of the reburn reaction, may interact with NO significantly to determine the final NO emissions. The current study aims to assess the gas-phase interactions of HCN and NO in a CO 2 atmosphere, which is customary to pressurized oxy-combustion conditions. A kinetic modeling study of the oxidation of HCN in the presence of NO has been performed under POC conditions and in the 973-1473 K temperature range. The influences of the stoichiometry, pressure, H 2 O concentration, and NO inlet concentration are analyzed. The results show that the HCN-NO interaction reduces both HCN and NO and that the interaction increases as pressure increases when the temperature is above 1073 K, whereas the opposite is found in low-temperature regions. The effect of stoichiometric parameters also strongly depends on temperature but follows the opposite trend compared with the effect of pressure. These differences contribute to the suppressive effect on O 2 decomposition and the positive effect on H 2 O decomposition at elevated pressures. An optimal temperature for NO reduction is shifted to lower temperature with increasing pressure and H 2 O concentration. The analysis of the total fixed nitrogen (TFN) indicates that for an actual boiler (5% O 2 ), the temperature should be controlled at 1373, 1223, 1173, and 1173 K, respectively, as the pressure increases from 1 to 15 atm. Finally, a 21-species and 69-step reduced chemistry is developed and validated to accurately predict the interaction of HCN with NO at elevated pressures.

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Section: Simulation Conditionssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

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Interactions of HCN with NO in pressurized oxy‐combustion

Rahman

Wang

et al. 2022

Asia-Pacific J Chem Eng

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“…Pressurized oxy-fuel combustion is a new carbon capture technology. 104 By increasing the pressure from the standard to 0.5− 1.5 MPa, the system air leakage can be effectively suppressed because the in-combustor high pressure avoids atmospheric air leakage into the combustor. The water vapor enthalpy in flue gas can be fully recovered, reducing carbon capture costs.…”

Section: Synergistic Reduction Of Coal-relatedmentioning

confidence: 99%

MILD Combustion of Solid Fuels: Its Definition, Establishment, Characteristics, and Emissions

Peng

Wang

et al. 2023

Energy Fuels

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Moderate or intense low-oxygen dilution (MILD) combustion has the advantages of high thermal efficiency and ultralow NO x emissions. This technology has attracted extensive attention from the combustion community since 1990 or so. The early development of MILD combustion technologies required highly preheating the combustion air externally, thus limiting the range of its industrial applications, especially for burning solid fuels. Later, this technical limitation was gradually overcome, particularly becoming possible to burn solid fuels without preheating under MILD conditions. Significant progress has since been made in solid-fuel MILD combustion. Some examples include the development of solid-fuel MILD burners utilizing low-volatile residual char and high-volatile biomass, low emissions of pollutants such as NO x and fine particles, MILD oxy-fuel combustion, and pilot-scale demonstrations and industrial applications. Solid fuels adopted for MILD combustion comprise coal, residual char, biomass, and sludge. This paper reviews the research progress achieved so far for solid-fuel MILD combustion. The definition of solid-fuel MILD combustion is first introduced. Then, the establishment approach is discussed. The combustion features and NO x emission mechanisms are investigated in detail. The advantages of MILD oxy-fuel combustion are also presented. The future development of solid-fuel MILD combustion is proposed finally. This review covers the fundamentals and applications of MILD combustion of solid fuels.

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“…The nitrogen present in the coal structures is mainly found in the form of organic aromatic heterocycles. Among them, pyrrole with a nitrogenous five-membered ring and pyridine with a nitrogenous six-membered ring exhibit the simplest structures and are commonly used as model compounds for studying the structures of nitrogen-containing molecules. , However, pyrrole and pyridine do not exist independently in coal bodies and are often combined with aromatic rings to form carbazole, indole, and quinoline structures. − Therefore, in this paper, pyrrole, pyridine, indole, quinoline, and carbazole were examined to reveal the effects of nitrogen-containing molecular structures on CSC. The optimized model structure is shown in Figure .…”

Section: Calculation Details and Experimental Sectionmentioning

confidence: 99%

Reaction Mechanism of Nitrogen-Containing Heterocyclic Compounds Affecting Coal Spontaneous Combustion

Zhang,

Xi,

Gong

et al. 2023

ACS Omega

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To uncover the reaction mechanism of nitrogencontaining heterocyclic compounds affecting coal self-heating, quantum chemical calculations and X-ray photoelectron spectroscopy (XPS) experiments were applied to elucidate the reaction pathways and thermodynamic characteristics of pyrrole, pyridine, indole, quinoline, and carbazole. Results show that in pyrrole, pyridine, indole, quinoline, and carbazole, the reaction with O 2 captures the H atom and leads to the formation of •OOH and pyrrolyl, pyridinyl, indolyl, quinolinyl, and carbazolyl radicals, respectively. The activation energies are 118.15, 86.642, 34.132, 21.004, and 47.259 kJ/mol, respectively. ROO• formed by spontaneous adsorption of O 2 by nitrogen-containing radicals undergoes self-reaction, and the O−O bond is broken and dehydrogenated to generate •OH. Subsequently, at room temperature, •OH reacts with pyrrole, pyridine, indole, quinoline, and carbazole, resulting in the formation of H 2 O and pyrrolyl, pyridinyl, indolyl, quinolinyl, and carbazolyl radicals, respectively, thereby forming a cyclic chain reaction. The XPS analysis yielded the following findings: (i) when the temperature rises to 70 °C, the N-5 and N-6 content decrease, which is attributed to the activation energy; (ii) when the temperature reaches 200 °C, the N-5 content decreases, which can be attributed to the activation energy required for the oxidation of pyrrole (118.5 kJ/mol).

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Nitrogen evolution, NOX formation and reduction in pressurized oxy coal combustion

Cited by 47 publications

References 172 publications

Interactions of HCN with NO in pressurized oxy‐combustion

Interactions of HCN with NO in pressurized oxy‐combustion

MILD Combustion of Solid Fuels: Its Definition, Establishment, Characteristics, and Emissions

Reaction Mechanism of Nitrogen-Containing Heterocyclic Compounds Affecting Coal Spontaneous Combustion

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