Heterogeneous NO Reduction Research Articles

Experimental and DFT Analysis To Anchor the Role of SO2 in the Heterogeneous NO Reduction over a Char Surface: SOx-Mediated Oxygen Rearrangement

Experimental and DFT Analysis To Anchor the Role of SO₂ in the Heterogeneous NO Reduction over a Char Surface: SO_<i>x</i>-Mediated Oxygen Rearrangement

Density functional theory on the mechanism of NO reduction by hydroxyl groups during oxy-fuel combustion

To further clarify the influence mechanism of the hydroxyl group on NO heterogeneous reduction over char, this study demonstrates that the hydroxyl group affects the NO reduction over char through two different pathways based on density functional theory (DFT). For the first pathway, termed “Adsorption-only”, the hydroxyl group merely adsorbs onto the char surface as a surface functional group. Conversely, for the second pathway, termed “Modification”, the hydroxyl group engages in reactions with the char, inducing a redistribution of active sites on the char surface. Kinetics calculations reveal that the “Adsorption-only” pathway inhibits NO heterogeneous reduction over char, while the “Modification” pathway substantially enhances the reduction process. From the standpoint of the reaction pathway, the “Modification” mechanism shortens the reduction reaction pathway. Additionally, wave function analysis shows that this mechanism involves Coulomb attraction during bond formation and Coulomb repulsion during bond breaking, potentially lowering the energy barrier.

Theoretical and experimental insights into the effects of CO2 on the heterogeneous NO reduction over char surface: Gasification and CO2-mediated oxygen rearrangement

Nitrogen oxides are the major pollutants in solid fuel/waste combustion processes, which can be reduced by unburned or additive chars. The surface char–NO reaction is significantly influenced by CO2, whereas the impact mechanism is far from conclusive. Herein, fixed-bed experiments and computational methods were adopted to elucidate the role of CO2 on char–NO reaction. Experimentally, CO2 exhibited an inhibitive impact on NO reduction at 873 K but a promotive influence at 1023 K and 1173 K. According to the detection of outlet CO, characterization of char, and density function theory (DFT) calculations, CO and gasified char derived from char–CO2 gasification are both responsible for the promotive effect at 1173 K, which offers a clear image of the gasification mechanism conjectured in previous work. More importantly, a CO2-mediated oxygen rearrangement (CO2-MOR) mechanism has been found and confirmed for the first time, which can well explain the experimental results observed at 873 K and 1023 K. The adsorbed CO2 can intervene in the oxygen rearrangement on the char surface to alter the NO reduction behaviors. The present study offers a comprehensive insight into the roles of CO2 in the heterogeneous reduction of NO on char surface.

Unraveling the Role of Intrinsic Carbon Defects for the Heterogeneous Reduction of NO with NH3

ABSTRACT This study investigates the impact of intrinsic carbon defects on the reduction of nitrogen oxides (NOx) during coal combustion, with a focus on the synergistic effect of ammonia (NH3) and pulverized coal. Two representative computational models containing intrinsic carbon defects are described, and their influence on NH3 reduction of NO is studied. Stable species and transition states present in the pathways are calculated using B3LYP/6-31 G(d). Results indicate that exposed edge carbon atoms exhibit higher charge density distribution, affecting NH3 adsorption and NO reduction. The maximum energy barriers for both pathways do not exceed 45 kcal/mol, achievable in practical coal combustion systems. This paper also calculates the heterogeneous reduction process of a model without intrinsic carbon defects (Char model), with the aim of observing the specific effects of intrinsic carbon defects on the processes of migration of H/O atoms, migration and recombination of N atoms, and formation and desorption of N2 molecules. Furthermore, the analyses demonstrated an increase in the rate of heterogeneous reduction of NH3 and NO on defective carbon surfaces in comparison to the Char/NH/NO system, indicating that the intrinsic defects of the carbon have a contributory effect on the catalytic activity. With regard to the magnitude of the increase in reaction rate with increasing temperature, the presence of intrinsic defects in the carbon base serves to reinforce the role of temperature in the rate-determining step. Overall, this study provides insights into the role of intrinsic defects in carbon-based catalysis and offers implications for nitrogen oxide emission control strategies.

Effect of CO2 Gasification on Nitrogen Oxide Emission in Oxy-Fuel Combustion.

Due to the cumulative effect of the recycled flue gas in oxy-fuel combustion, the reduction of NO has become the focus of research in which the role of CO2 gasification has a nonnegligible effect. In this article, the heterogeneous gasification mechanisms of CO2 on coal char during oxy-fuel combustion were studied by density functional theory and transition-state theory. The zigzag char model and char(N) model were selected to investigate the CO2 adsorption and gratification reactions at the molecular level. By comparison, the CO2 gasification reaction is preferred to occur on the zigzag char model with a reduction in the energy barrier and an increase in the reaction rate. When considering char nitrogen conversion, the gasification reaction is more prone to releasing NO first, leading to the contraction of the aromatic ring and the generation of CO at high temperatures. Therefore, the study further highlights the promoting role of CO2 gasification on the homogeneous and heterogeneous reduction of NO, which is mainly reflected in the reduction effect of CO. Moreover, it also accelerates the consumption of coal char and NO formation, which is favorable for the reduction reactions to a certain extent.

Novel ultra-low NOx coal combustion technologies based on local microenvironment targeted regulation. Part 1. Selective oxygenation

Developing a novel high-efficiency coal combustion technology with ultra-low NOx emission is urgently needed to sustain the good ecological environment. Here, the targeted regulation of local microenvironment around fuel-N, such as functional groups, radicals, molecular configurations, and reaction atmosphere, is realized by the selective oxidation. The molecular configurations, including pore networks and microcrystalline structure in coal, are well characterized through synchrotron radiation-induced SAXS (small angle X-ray scattering) and WAXS (wide angle X-ray scattering) simultaneously. Furthermore, by combining density functional theory (DFT) and experiments, the effects of the local microenvironment on the nitrogen transformation and NO evolution during the thermal conversion are focused on. The results indicate that for the PPA oxidation, the H radicals attack the adjacent carbon to pyrrole/pyridine nitrogen, promoting the conversion of fuel-N to HCN. On the other hand, for the H2O2 oxidation, disrupting the π bond electron cloud by the CO and C = O on the ortho carbon of pyrrole/pyridine dominates the NH3 generation. Additionally, the increased La (average graphene layer extent), a3 (average interlayer spacing), σ3 (standard deviation of interlayer spacing) and σ1 (standard deviation of the first-neighbor distribution) induce massive smaller pores, promoting the generation of abundant reaction defects inside the particles. Importantly, the intensified adsorption on abundant active sites lead to the decreased HCN and increased NH3 evolution, which is adverse for the interaction between homogeneous and heterogeneous NO reduction. Interestingly, the PAA selective oxidation can reduce NO emission by 31.72 % - 34.30 % during the air combustion, which is far better than the H2O2 oxidation. Overall, the attack of free radicals on nitrogen-containing heterocycles promotes the conversion of fuel-N to HCN, the adsorption of which on char surfaces can further enhance the heterogeneous reduction in a lean oxygen atmosphere. The work here provides a novel route for developing high-efficiency and low-NOx combustion technologies.

New insights into the heterogeneous reduction of NO on coal char based on molecular configuration evolution

No report reveals the relationship between coal char molecular configuration and NO heterogeneous reduction. Here, the molecular configuration of char, including pore structure and microcrystalline morphology, was well characterized through synchrotron radiation-based SAXS and WAXS. Furthermore, the universal relationship between molecular configuration and NO heterogeneous reduction was revealed. The adsorption configurations of NO on different defects were calculated through density functional theory (DFT). The results indicate that smaller pores are affected by both monolayer structure and layer stack characteristics, while larger pores are primarily dominated by the latter. The NO decline rate and final reduction efficiency of large higher-rank chars are driven by NO diffusion in larger pores. On the other hand, the active sites and flow patterns in smaller pores synergistically control the decline rate and reduction efficiency of small higher-rank chars. As for lower-rank chars, the diffusion in larger pores and the flow patterns in smaller pores affect the reduction efficiency and decreasing rate of NO, respectively. It is important to note that edge defects control the initial stage of NO reduction, while the single-vacancy and double-vacancy defects dominate the heterogeneous process in the final NO reduction stage. The findings can provide theoretical support for better predicting the NO heterogeneous behavior and thus promote the development of novel ultra-low NOx combustion technologies.

Plastics as a reburning fuel: Pyrolysis at reburning temperatures and NO-reburning by simulated pyrolysis gas

Using waste plastics as a reburning fuel is promising for both reducing NOx emissions and managing plastic waste. To gain a better understanding of the chemistry involved in plastic reburning, pyrolysis products of different types of plastics at typical reburning temperatures (900–1200 °C) were investigated experimentally, and the reburning performance of simulated plastic pyrolysis gases was studied through experiments and chemical kinetic modeling. The plastics involved in the pyrolysis experiments included high-density polyethylene (HDPE), polypropylene (PP), polyamide 6 (PA6), and acrylonitrile–butadiene–styrene copolymer (ABS). HDPE exhibited the highest hydrocarbon gas yield (up to ∼ 70 wt% at 900 °C) while ABS had the lowest gas yield (<20 wt%) among the four plastics at the investigated temperatures. The hydrocarbon gas was composed mainly of methane, ethylene, and acetylene, with ethylene decreasing and acetylene increasing with temperatures rising from 900 to 1200 °C. Hydrogen cyanide was found to be the dominant gaseous nitrogen-containing compound for PA6 and ABS. Solid byproducts such as soot were generated at pyrolysis temperatures exceeding 1100 °C, leading to a reduction of the gas yield for all plastics. This indicates a potentially important contribution of heterogeneous NO reduction mechanisms during plastic reburning at high temperatures. Concerning the homogeneous NO reduction, reburning experiments using simulated plastic pyrolysis gases composed of methane, ethylene, and/or acetylene were carried out at 700–1200 °C in a flow reactor with an initial NO concentration of 1000 ppm and an excess air ratio λ of 0.7. Results for the simulated plastic pyrolysis gases showed NO reduction efficiencies ranging from 30 % to 46 % within the temperature range 950–1200 °C. The presence of acetylene in the simulated pyrolysis gas mixtures appears to facilitate NO reduction. A detailed chemical kinetic model applied to simulate the experiments gave a reasonable prediction of the NO reduction and revealed the important role of the ketenyl radical in removing NO.

Insight into the fate of nitrogen during char thermal conversion and the influence mechanism of potassium: A theoretical research

Nitrogen oxides (NOₓ) are primary pollutants produced during biomass combustion. During the devolatilization stage, char nitrogen (char(N)) is formed. In the subsequent char combustion stage, char(N) can decompose directly into NOx precursors or engage in heterogeneous reactions with O2 or NO to form NO and N2. Nonetheless, a comprehensive understanding of the reaction mechanisms and competitiveness of char(N) migration, especially the influence of the alkali metal potassium (K) present in biomass, remains incomplete. Building on the Zigzag char(N) models, the present study delves into the migration reactions of char(N), assessing their competitive dynamics through the integration of density functional theory, electronic structure analysis, and conventional transition state theory. Furthermore, it examines the impact of K on char(N) conversion. The competitiveness of the heterogeneous reactions follows the sequence: heterogeneous reduction of NO to N2 > heterogeneous oxidation of char(N) to NO > decomposition of char(N) to NOx precursors. Moreover, the formation of HCN is more favorable than NH₃ production. The successive conversion from char(N) to NO and then to N2 is the predominant migration route for char(N), with NO generation as the pivotal step. The less preferred char(N) migration route involves decomposition to NH3/HCN, followed by oxidation to NOx within the main combustion zone, which cannot be mitigated by char. K can accelerate NO generation and sustain the primacy of the heterogeneous NO reduction, consequently enhancing the oxidation-reduction process of char(N). As a result, K plays a constructive role in managing NOx emissions during the thermal conversion of char.

Enhanced NOx reduction through reburning of potassium chloride doped biomass at intermediate temperature in oxy-biomass combustion

The challenge of achieving low nitrogen oxide (NOx) emissions in carbon-negative oxy-biomass combustion remains significant. This study focuses on enhancing NOx reduction by doping washed biomass with varying ratios of potassium chloride (KCl) to determine the optimal quantity for maximum NOx reduction. Unlike the traditional high-temperature reburning method used in PC furnaces (above 1000 °C), this study explores reburning at intermediate temperatures (550–850 °C) to assess its feasibility in fluidized bed or grate fired furnaces. Flue gas analysis is performed using an FTIR gas analyzer (Gasmet DX-4000, Finland), while solid residue analysis utilizes SEM-EDS, XRD, XRF, and TGA techniques. Results demonstrate that the highest NO reduction efficiency, up to 80 %, is achieved at a stoichiometric ratio of 0.6, a temperature of 700 °C, and 1.5 % KCl doping in an oxygen-rich environment. These findings highlight the effectiveness of a small amount of KCl doping (1.5 %) in catalyzing heterogeneous NO reduction reactions for enhanced NO reduction. Furthermore, this same KCl doping quantity (1.5 %) effectively suppresses the formation of harmful substances such as HCN and N2O, thus improving the conversion of NO to N2. Overall, this study provides valuable insights for the development of NOx control methods in intermediate temperature oxy-biomass combustion systems.

Experimental study on the catalytic effect of AAEMs on NO reduction during coal combustion in O2/CO2 atmosphere

During oxy-fuel combustion, the NO emission can be inhibited by the strongly reductive atmosphere caused by the high proportion of gasification reaction, which is a unique feature that differs from air combustion. The alkali and alkaline earth metals (AAEMs) contained in coal ash can catalyze gasification reactions, promoting the homogeneous reduction process of NO. Besides, AAEMs also suppress NO emission through catalyzing the NO heterogeneous reduction by char (CNO). Both catalytic effects of AAEMs have been studied at relatively low temperatures (below 1000 °C) in a simple atmosphere (pure CO2). However, the catalytic effect of AAEMs on NO reduction is still unclear during oxy-fuel combustion due to the more complex reaction atmosphere, higher reaction temperatures, and the presence of gasification reactions. In this work, the effect of different factors on the catalytic effect of AAEMs under O2/CO2 atmosphere is investigated. Results show that the order of the catalytic effect of AAEMs on NO reduction is Na > K > Ca > Mg, with the highest NO reduction efficiency of 30 % for Na. The catalytic effect of Na on NO reduction weakened as the temperature increases. When the temperature increased from 1373 K to 1573 K, the NO reduction efficiency (ηNO) of Na decreased from 30 % to 6 %. While the catalytic effect of Na on NO reduction strengthened as the oxygen concentration increases. When the O2 concentrations increased from 10 vol.% to 30 vol.%, the ηNO values of Na increased from 27 % to 35 %. The K-Na binary additive is more effective in reducing NO emissions than K and Na alone, with NO reduction efficiency as high as 46.8 % at a K/ Na is 1:2. Besides, the Raman test results reveal that K contributed to the conversion of amorphous carbon into a regular graphite crystal structure. Na disrupted the graphite structure resulting in more defective points appearing in the graphite lattice. These results are expected to provide a theoretical reference and new insights for the reduction of NO emission during oxy-fuel combustion.

The crucial role of oxygen in NO heterogeneous reduction with NH3 at high temperature

The high-temperature ammonia-injected technology is acknowledged as a promising denitrification method with great NOx reduction potential. In this work, char reduction experiments and density functional theory (DFT) calculations were conducted to investigate the heterogeneous reduction mechanism of NO by ammonia (NH3) synergism with char, focusing on the role of O2. Experimental results indicate that O2 has an inhibition effect on the NO reduction efficiency, whose detailed mechanisms can be inferred from a molecular perspective. Theoretical results reveal that both Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms exist in the NH3-injected denitrification reactions, presenting significant differences in N2, N2O, and H2O evolution. By comparison, the E-R mechanism governs the NH3–NO reactions, which reduces barriers by up to 14.5 %. The presence of O2 can lead to a significant increase in the energy barriers with a concomitant decrease in reaction rates within a certain temperature range, which however does not change the dominant mechanism governing the NH3 and NO interactions. Although some controversies are found in the kinetic analysis when the temperature increases, the results here shed light on the NO heterogeneous reduction mechanisms with NH3 at high temperature, which also guides the coal/NH3 co-firing investigations.

Mechanistic study on the effect of ammonia co-firing with pulverized coal on NO formation and reduction

In this study, the heterogeneous formation and reduction mechanisms of NO by ammonia (NH3) were determined to evaluate the performance of NH3 co-firing with coal in NO emissions by density functional theory and canonical variational transition-state theory. NO formation is initialized by the dissociative adsorption of O2 on the char, and the subsequent dehydrogenation reactions after NH3 adsorption are prioritized. NO reduction via char synergism with NH3 are also elucidated by the NNH dissociation or ONNH conversion. Thermodynamic and kinetic results indicate that introducing NH3 has the advantage of promoting heterogeneous NO reduction, which is characteristic of the synergistic effect afforded by the properties of char and reducing agent NH3. The reduction effect of NH3 on NO is more significant than its oxidation effect for NO formation at elevated temperatures, which provides theoretical evidence for the potential advantages of NH3 co-firing on NO emissions in coal-fired boilers.

DFT Study of the Catalytic Mechanisms of NO Heterogeneous Reduction: The Effect of the Gasification Reaction

ABSTRACT The NO heterogeneous reduction mechanisms on both Ca-char and gasified Ca-char by b3lyp/6–311+g (d, p) group are systematically investigated to clarify the role of the catalyst. All the computed reaction paths can proceed smoothly after the first step occurs, and they are exothermic during the reaction process, which means this reaction is supported by thermodynamics and kinetics. The results indicated that Ca can promote NO heterogeneous reduction by increasing the adsorption energy and reducing the energy barrier of gas products (nitrous oxide N2O, nitrogen N2, CO and CO2) emission. Furthermore, the computed results also indicated that the model is a significant element affecting NO reduction. Compared with Ca-char model, gasified Ca-char model has higher potential energy surface and tends to remain O atoms. The computed reaction path on the surface of gasified Ca-char is a supplement to previous studies, which gives insight to the catalytic mechanisms of NO heterogeneous reduction in the presence of gasification.

A pilot-scale test facility of 500 kWth for industrial CFB boilers on low nitrogen combustion-discussion of design, experiment, and economic analysis

The design and construction of a pilot-scale test facility of 500 kWth for a novel CFB boiler with three separate sub-furnaces and two steps for material circulation are introduced in detail. A thorough test was conducted with the facility to verify the applicability of fuel staging on NOx abatement in the novel CFB. The varied trends of temperature distribution and NOx emissions during fuel staging are presented in the study. It was observed that fuel staging can effectively and immediately reduce the initial emission concentration of NOx in the flue gas. Under the tested conditions, the NOx removal efficiency can reach up to 40% at a fuel-staged proportion of 5%. The initial NOx emission concentration can be controlled to below 80 mg/m3, even. The main reason for the NOx reduction is the heterogeneous reduction of NO on the surface of coal char formed after the devolatilization of staged fuel. In addition, economic analysis was made by comparing fuel staging and SNCR. The estimated operating costs showed that fuel staging can be applied as an alternative technology for SNCR when the initial concentration of NOx in the flue gas ranges from 300 to 360 mg/m3.

Catalytic mechanism of bi-alkali-metal-doped char in heterogeneous reduction of NO: A density functional theory study

Bi-alkali-metal doping in char can significantly increase the heterogeneous reduction rate of NO. In this study, the effect of Na and K doping on heterogeneous reduction of NO by a char model with zigzag edge was systematically investigated by density functional theory. It was found with reduced density gradient and Mayer bond order analyses that alkali metals promoted the dissociation of the N–C and combination of N–Na or O–K. Moreover, bi-alkali-metal doping changed charge characteristics of the char, and promoted N–N formation and N–O breaking to shorten the reaction path. The simulation paths indicated that Na/K co-doping could reduce the energy barrier from 52 to 117 kJ/mol to less than 10 kJ/mol in the second and third steps of heterogeneous reduction. Both the mono- and bi-metals promoted reduction of NO on char. The kinetic calculation illustrated that the maximum fitted reaction activation energy is 179 kJ/mol for NO heterogeneous reduction at the edge of Na/K-doped char, whereas those for Na- and K-doped chars are 210 and 200 kJ/mol, respectively. This work provided a new and deep insight into the microscopic mechanism of NO-char reaction catalyzed by composite metal.

Study on the influence mechanism of mineral Ca on NO reduction in the high temperature oxygen-lean zone of ammonia-coal co-combustion

Ammonia-coal co-combustion can effectively reduce CO2 emissions in power plant. However, ammonia, as an N source, will increase NOx foamation path when it is co-fired with coal. It is very necessary to explore the NO reduction mechanism in ammonia-coal co-combustion to realize low-nitrogen emissions. In this study, the mechanism of NO reduction in the high temperature oxygen-lean zone of ammonia-coal co-combustion is explored through experiment and quantum chemical theory calculation, and the influence mechanism of Calcium, an important mineral in coal, on the reduction of NO by NH3 and char is further explored. The experimental results show that mineral Ca in char inhibits NO reduction by char and ammonia. Under the same temperature and NSR, the efficiency of NO heterogeneous reduction by char impregnated with Ca is lower than that by demineralized char. Theoretical calculation results have shown that amino/char in the high-temperature lean-oxygen area can reduce NO to N2 through the formation of important transition intermediates such as NNH and N2O, and the participation of Ca inhibits the reduction of NO by NH3 and char. Ca enhances the binding energy between the NNH group and the char surface, so that under the participation of top-Ca, the energy barrier of the rate-determining step is 197.92 kJ/mol higher than that of the NH/char/NO system. The participation of face-centered Ca has a stronger inhibitory effect on NH/char/NO system than that of top-Ca. The kinetic results show that the reduction rate of NO by NH on the char surface in the presence of Ca is lower than that in the absence of Ca.

The effect of Na/K on the NO adsorption behavior and heterogeneous reduction of internal nitrogen-containing char: A DFT study

Sodium and potassium in high alkali coal have an effect on the heterogeneous reduction of NO with char. The microscopic mechanisms of the effect of Na and K on the adsorption behavior and heterogeneous reduction roads of NO on the surface of internal nitrogen-containing char were investigated at the GGA-PBE level using DFT. The adsorption energy of NO on the surface of nitrogen-containing char doped with Na and K was calculated using zigzag, armchair and saturated structures, and the reaction path of Z-N-2 with NO was also calculated. The results showed that the adsorption effects of the three types of nitrogen-containing char on NO ranked from strong to weak were: Z-N > A-N > G-N. The addition of Na and K both promoted the adsorption of NO with char structure. The highest energy barrier for the reaction of the Z-N-2 structure with NO was 232.80 kJ/mol, which decreased to 180.52 kJ/mol when Na doped and 176.04 kJ/mol when K doped. The exotherm of the reaction increases from 378.59 to 1245.26 kJ/mol, it appears that the addition of sodium and potassium facilitates the reaction. The study will provide a theoretical pavement for the continued study of the heterogeneous reduction process, which is of great significance for the clean use of high alkali coals.

A theoretical insight into the mechanism of NO heterogeneous reduction on char surface: The catalytic effect of potassium

In this paper, the catalytic effect of K on the NO heterogeneous reduction over char surface was investigated using the quantum chemistry calculation. The adsorption performance and the detailed reaction pathways were obtained via density function theory before and after potassium decorating. Additionally, the mayer bond order, thermodynamic and kinetic analysis were studied to further clarify the effect of K on the NO-char reaction. The calculation results showed that K can promote the adsorption of NO molecules on char surface. It was found that the reaction energy barriers were reduced with the decoration of K, indicating that K can promote the chemical reaction. Four reaction pathways were obtained based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms, and the order of reaction activity was as follows: L-H@K > L-H > E-R@K > E-R. Moreover, thermodynamic analysis showed that the reaction equilibrium constants increased with the addition of K, suggesting that the reaction was more complete and irreversible. From kinetic analysis, the reaction rate constants increased with temperature, and the rate of reactions were more faster in the presence of K, which indicated that K can accelerate the NO heterogeneous reduction. Based on the thermodynamic and kinetic performances, it is concluded that K has a significant promotion on the NO heterogeneous reduction by char. The theoretical results systematically reveal the catalytic mechanism of K on the NO reduction by char, which can make contributions to the clean and efficient utilization of the potassium-containing fuels.

Microscopic mechanism for the effect of potassium on heterogeneous NO–char(N) interaction: A theoretical account

Reburning is an effective way for the clean and efficient utilization of biomass with low nitrogen oxides (NOx) emission. During the reburning process, the heterogeneous reaction between NOx and char nitrogen (char(N)) obviously affects the removal efficiency of NOx, and the abundant K species in biomass can inevitably affect the NOx–char(N) reaction. In the present study, char(N) models of Zigzag(N) and Armchair(N) configurations were adopted, abbreviated as ZN and AN. The effects of K on heterogeneous NO–char(N) reactions were investigated by density functional theory (DFT) and wave function analysis, and the rate constants for all reaction rate-determining steps in the temperature range from 800 to 1800 K were calculated by conventional transition state theory. The results show that NO can react with ZN and AN to generate N2 easily. The presence of K changes the reaction path of NO–char(N) by facilitating the heterogeneous reduction of NO and inhibiting the migration of char(N). According to kinetics calculation, K can inhibit the occurrence of NO–ZN in the low temperature while it inhibits NO–AN along all the investigated temperatures. The heterogeneous migration mechanism of nitrogen can provide theoretical guidance for NOx emission control during biomass reburning.