Numerical assessment of NOx evolution in ammonia oxidation and its control by reburning in pressurized oxy-combustion

Rahman, Zia ur; Wang, Xuebin; Mikulčić, Hrvoje; Zhou, Shangkun; Zhang, Jiaye; Vujanović, Milan; Tan, Houzhang

doi:10.1016/j.joei.2021.11.002

Cited by 20 publications

(3 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Besides, it allows quick identification of dominant reaction pathways 21,22 . The normalized or relative contributions to production and destruction are calculated based on the maximum contribution absolute rates for certain species and are defined as “relative ROP”

{\overset{true¯}{C}}_{i, j}

{\overset{true¯}{C}}_{i, j} goodbreak= \frac{C_{i, j}}{\max_{j = 1}^{J} ((), |C_{i, j}|)}

where C i,j is the contribution rate of reaction j to specie i and J is the total reaction number 23 …”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Interactions of HCN with NO in pressurized oxy‐combustion

Rahman

Wang

et al. 2022

Asia-Pacific J Chem Eng

Self Cite

View full text Add to dashboard Cite

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.

show abstract

{\overset{true¯}{C}}_{i, j}

{\overset{true¯}{C}}_{i, j} goodbreak= \frac{C_{i, j}}{\max_{j = 1}^{J} ((), |C_{i, j}|)}

where C i,j is the contribution rate of reaction j to specie i and J is the total reaction number 23 …”

Section: Methodsmentioning

confidence: 99%

“…where C i,j is the contribution rate of reaction j to specie i and J is the total reaction number. 23…”

Section: Rate-of-production (Rop) and Sensitivity Analysesmentioning

confidence: 99%

Interactions of HCN with NO in pressurized oxy‐combustion

Rahman

Wang

et al. 2022

Asia-Pacific J Chem Eng

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hydrogen-enriched flames in low-NOx combustion have been widely studied for NOx concentration (Liu et al, 2022;Rahman et al, 2022). It should be mentioned that besides thermal NOx, the hydrogen addition also promotes the generation of the NNH route (Purohit et al, 2021) and the fact that the NNH route dominating the NOx formation has been reported recently.…”

Section: Effects Of Hydrogen Addition On No X Formation In a Nonpremi...mentioning

confidence: 99%

Effects of hydrogen addition on NOx formation in a non-premixed methane low-NOx combustor

CHENG,

ZHU,

DENG

2024

Mechanical Engineering Journal

View full text Add to dashboard Cite

Hydrogen is a promising carbon-free fuel, but nitric oxides (NO x ) emissions are significantly increased with higher temperature in hydrogen combustion. Internal flue gas recirculation (IFGR) is one of the most effective NO x reduction techniques in boilers. Previous research has widely reported NO x generation with hydrogen enrichments from a chemical kinetic perspective, however, the NO x formation principles in non-premixed methane/air combustion using IFGR with hydrogen addition are still unclear. This work aims to investigate the effects of hydrogen addition on NO x formation in a non-premixed methane low-NO x combustor using IFGR. The Reynolds-averaged Navier-Stokes (RANS) simulations were conducted on a 5 kW non-premixed combustor with IFGR rate of 17.7%, which generated 11.3 mg/m 3 of total NO x generation in methane combustion. A series of three-dimensional computational fluid dynamics (CFD) simulations with detailed mechanisms was tested on four hydrogen power fractions. The reaction intensities of the main NO x formation pathways were analyzed on reaction rates. The results show that 70% hydrogen power fractions lead to significantly greater NO x concentration to 677.8 mg/m 3 , as high as 60 times of the original concentration. With no additional techniques, the original methane low-NO x combustor is only allowed for hydrogen addition of less than 20% power fraction. The NNH route becomes the second dominant pathway in hydrogen-added flames. Influenced by the growing hydrogen contents, the generation of the NNH route is largely generated from 2 mg/m 3 to 65 mg/m 3 . This work connects the hydrogen addition and the NO x formation pathways in non-premixed methane combustion, and highlights the importance of eliminating thermal NO x and the NNH route to achieve low-NO x combustion rather than sole NO x suppression method, which can provide a reference for designing low-NO x techniques.

show abstract