Investigation on optimal active layer thickness and pore size in dual-layer NH3-SCR monolith for low SO2 oxidation by numerical simulation

Qi, Xin; Hua, Zhesheng; Fu, Yujie; Yang, Yang; Liu, Shaojun; Song, Hao; Yu, Xinjie; Xiao, Lifeng; Zheng, Chenghang; Gao, Xiang

doi:10.1016/j.fuel.2020.118420

Cited by 17 publications

(7 citation statements)

References 33 publications

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“…Before the activity test, a two-stage calcination needed to be carried out to achieve quasi-Mn-BTC, which not only retained a porous structure and constructed hierarchical porous structure that can increase the active site density but also fabricated a more accessible oxygen defect (V O ) that can reduce the reaction energy barrier and promote molecular activation . What is more, the inorganic nodes were exposed as much as possible leading to dramatically enhanced catalytic performance in the LT reduction of NO with NH 3 . To ensure the accuracy of the test results and improve the repeatability of the experiment, the activated samples were pressed, crushed, and sieved (Figure S1, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

et al. 2023

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NO x emission is a major environmental issue, and selective catalytic reduction (SCR) is the most effective method for the conversion of NO x to harmless N2 and H2O. Manganese oxide has excellent low-temperature (LT) denitration (de-NO x ) activity, but poor SO2 tolerance hinders its application. Herein, we report an interesting SCR catalyst, quasi-metal–organic-framework (MOF) nanorod containing manganese (quasi-Mn-BTC) with abundant oxygen vacancies (Vo), unique hierarchical porous structure, and half-metallic property, which successfully overcome the disadvantage of poor SO2 tolerance of Mn-based catalysts. The NO x conversion over the Mn-BTC-335 °C only drops by 7% until SO2 is gradually increased to 200 ppm from 100 ppm for 36 h. Furthermore, the quasi-Mn-BTC presents excellent LT de-NO x performance with above 90% NO x conversion between 120 and 330 °C at a gas hourly space velocity of 36,000 h–1. Experimental and theoretical calculations confirm that the difficult electron transport between SO2 and active sites can prevent it from competing adsorption with NH3 and NO. Furthermore, the low degree of d–p hybridization and unstable p–p hybridization of SO2 on the active sites make it difficult for adsorption and oxidation; thus, the weak adsorption of SO2 can prevent it from sulfation on the active sites, ensuring Mn-BTC-335 °C excellent SO2 tolerance. Additionally, the half-metallicity property, the extraordinary d–sp hybridization, and the high degree of s–p hybridization cause strong bonding and the delocalization of electrons that promote the charge transfer and adsorbed ion diffusion for NH3 and NO adsorption, promoting the LT de-NO x performance. In situ diffuse reflectance infrared Fourier transform spectra and density functional theory calculation further reveal that the de-NO x reaction over Mn-BTC-335 °C follows both Eley–Rideal (E-R) and Langmuir–Hinshelwood (L-H) mechanisms. The “standard reaction” is more likely to occur in the E-R reaction, while the “fast reaction” is prone to occur in the L-H pathway, and HNNOH and NH3NO2 are the two key intermediates. This work provides a viable strategy for augmenting the LT de-NO x and SO2 tolerance of Mn-based catalysts, which may pave a new way in the application of MOFs in de-NO x , and the complete reaction mechanism provides a solid basis for future improvements of the LT NH3-SCR de-NO x reaction.

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Section: Resultsmentioning

confidence: 99%

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

et al. 2023

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“…It has been reported that the rate expression in the SCR reaction kinetic model of the overall catalyst [5,11] was described by the following equation: The SCR reaction kinetic model parameters shown in Table 2 are obtained through experiments [12]. The experiments carried out in a benchtop reactor used a commercial VOx/TiO 2 catalyst, and the reaction temperature was between 320~400°C.…”

Section: Governing Equationmentioning

confidence: 99%

“…Many scholars have also developed low-temperature SCR catalysts. Because of the complex composition of the coke oven flue gas and the weakness of the SCR catalyst [5], it has not been effectively applied and implemented in the flue gas system. For SNCR, the effective reaction temperature is 850~1175℃, and operating parameters restrict the NOx reduction efficiency.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of NO emission reduction in coke oven regenerator with synergistic SNCR/SCR process

Zhao

Feng

2021

E3S Web Conf.

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According to the temperature gradient distribution characteristics of the regenerator of the coke oven, a method of synergistic the SNCR/SCR process inside the regenerator to achieve NO emission reduction was proposed in this work. Based on the verification of SNCR and SCR models, the NH3/NO concentration field and the spatial distribution characteristics of NO in the process of SNCR, SCR, and SNCR+SCR were studied. The conclusion shows that the synergistic SNCR and SCR processes had achieved NO reduction by 64.3% and 37.1%, respectively. However, the increase in reaction temperature caused by the change of injection position resulted in a 0.4% decrease in SNCR+SCR compared to SNCR. It was also found that temperature dramatically influences the SNCR process and the reductant injection position. Limited by the structure of the regenerator and the catalyst coating area, the SCR process exhibited a low NO reduction ability. The SNCR+SCR process should focus on improving the efficiency of the SCR process.

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“…However, there are many problems in these practical applications. Firstly, considering the vulnerability of SCR catalysts that are easily poisoned and non-renewable [18], enterprises face difficulties selecting the desulfurization and denitration sequence in the flue gas treatment system. Secondly, since the mainstream SCR catalyst has a working temperature window of 300~400 °C [19][20][21], installing a supplementary heating device is necessary to increase the flue gas temperature (180~230 °C).…”

Section: Introductionmentioning

confidence: 99%

Coupling selective catalytic reduction process inside a coke oven regenerator: The influence of mixing parameters on NO reduction

et al. 2022

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Many coking plants have adopted the process of preheating flue gas to apply medium and low-temperature SCR denitrification technology, which increases the NOx treatment cost, fuel consumption, and generates secondary pollutants. Based on the unique temperature distribution characteristics of the coke oven regenerator, this work proposes a method for synergizing SCR inside the regenerator to remove NOx. A three-dimensional numerical model of the synergy between heat storage and SCR reaction was constructed to study the influence of mixing parameters (atomization angle, injection velocity, nozzles number) on the NO reduction and NH3 distribution. The validity of the model was verified. The results showed that the uneven distribution of NH3 near the catalytic layer and the small SCR coating area limited the NO reduction efficiency. Increasing the number of nozzles was more beneficial than the injection velocity and atomization angle for improving the NH3 distribution uniformity and NO reduction efficiency, achieving a maximum NO reduction efficiency of 37.1% (reduced to 251.6 mg/m3). Further research found that the NO reduction capacity of the cooperative SCR model cannot exceed 36% without changing the thermal storage brick structure. When the inlet NO concentration is less than 235 mg/m3, the reaction model ensures that the outlet NO concentration meets the national emission standards.

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Investigation on optimal active layer thickness and pore size in dual-layer NH3-SCR monolith for low SO2 oxidation by numerical simulation

Cited by 17 publications

References 33 publications

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

Numerical simulation of NO emission reduction in coke oven regenerator with synergistic SNCR/SCR process

Coupling selective catalytic reduction process inside a coke oven regenerator: The influence of mixing parameters on NO reduction

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Investigation on optimal active layer thickness and pore size in dual-layer NH3-SCR monolith for low SO2 oxidation by numerical simulation

Cited by 17 publications

References 33 publications

Insight into the Origin of Excellent SO2 Tolerance and de-NOx Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

Insight into the Origin of Excellent SO2 Tolerance and de-NOx Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

Numerical simulation of NO emission reduction in coke oven regenerator with synergistic SNCR/SCR process

Coupling selective catalytic reduction process inside a coke oven regenerator: The influence of mixing parameters on NO reduction

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Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide