Barrierless HONO and HOS(O)2-NO2 Formation via NH3-Promoted Oxidation of SO2 by NO2

2021 ◽  
Author(s):  
Guoying Wang ◽  
Shangrong Ma ◽  
Xiuli Niu ◽  
Xuefu Chen ◽  
Fengshuo Liu ◽  
...  
Keyword(s):  
No2 Formation

Thermochemical Evaluation of Hydroxyl and Peroxyl Radical Precursors in the Formation of Tropospheric Ozone Reactions

2010 ◽  
Vol 3 ◽  
pp. 74-83
Author(s):  
G.O. Umosekhaimhe ◽  
S.E. Umukoro
Keyword(s):  
Particulate Matter ◽  
Tropospheric Ozone ◽  
Chemical Species ◽  
Basis Set ◽  
Enthalpies Of Formation ◽  
Ozone Formation ◽  
Complete Basis Set ◽  
Equilibrium Analyses ◽  
No2 Formation ◽  
Reaction Routes

The thermochemical properties of varieties of species needed to assess the most prominent pathways of tropospheric ozone transformation have been established. In the troposphere, ozone which is a secondary pollution produced by photochemical induced transformation, acts as an oxidizing agent to numerous atmospheric reactions leading to the formation of particulate matter. Based on the climate related problems resulting from the precursor of particulate matter, it is adequate to establish the feasible routes of ozone formation. In this study, the electronic structure methods which approximate the Schrödinger equation to compute Gibbs free energies and enthalpies of formation of the various chemical species participating in the reactions were used. These thermodynamic properties were determined using four computational model chemistry methods integrated in the Gaussian 03 (G03) chemistry package. Five known reaction pathways for the formation of NO2 (the O3 precursor specie), as well as the dominant ozone formation route from NO2 were examined and their energies determined. Of all the computational methods, the complete basis set (CBS-4M) method produced energies for all species of the five reaction routes. Out of the five routes, only the reactions involving radical species were favoured to completion over a temperature range of -100 and +100oC. The most relevant reaction route for the formation of NO2 and subsequently O3 is that involving the peroxyl acetyl nitrate (PAN) and hydroxyl radicals. Chemical equilibrium analyses of the reaction routes also indicated that reduction in temperature encourages NO2 formation while increase in temperature favours O3 production.

NO2 Formation and Mitigation in an Advanced Diesel Aftertreatment System

2018 ◽  
Author(s):  
Nathan Ottinger ◽  
Yuanzhou Xi ◽  
Niklas Schmidt ◽  
Z. Gerald Liu
Keyword(s):  
Aftertreatment System ◽  
No2 Formation

NO2 formation and its effect on the selective catalytic reduction of NO over Co/ZSM-5

1996 ◽  
Vol 38 (3-4) ◽  
pp. 271-278 ◽  
Author(s):  
A. Yu. Stakheev ◽  
C. W. Lee ◽  
S. J. Park ◽  
P. J. Chong
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Reduction Of No ◽  
No2 Formation

scholarly journals A kinetic evaluation on no2 formation in the post-flame region of pressurized oxy-combustion process

2020 ◽  
pp. 236-236
Author(s):  
Xuebin Wang ◽  
Gaofeng Dai ◽  
Gregory Yablonsk ◽  
Milan Vujanovic ◽  
Richard Axelbaum
Keyword(s):  
Power Plants ◽  
Combustion Process ◽  
Strong Acid ◽  
Dew Point ◽  
Kinetic Evaluation ◽  
Atmospheric Air ◽  
Energy Penalty ◽  
Flame Region ◽  
No2 Formation ◽  
Time Required

Pressurized oxy-combustion is a promising technology that can significantly reduce the energy penalty associated with first generation oxy-combustion for CO2 capture in coal-fired power plants. However, higher pressure enhances the production of strong acid gases, including NO2 and SO3, aggravating the corrosion threat during flue gas recirculation. In the flame region, high temperature NOx exists mainly as NO, while conversion from NO to NO2 happened in post-flame region. In this study, the conversion of NO ? NO2 has been kinetically evaluated under representative post-flame conditions of pressurized oxy-combustion after validating the mechanism (80 species and 464 reactions), which includes nitrogen and sulfur chemistry based on GRI-Mech 3.0. The effects of residence time, temperature, pressure, major species (O2/H2O), and minor or trace species (CO/SOx) on NO2 formation are studied. The calculation results show that when pressure is increased from 1 to 15 bar, NO2 is increased from 1 to 60 ppm, and the acid dew point increases by over 80?C. Higher pressure and temperature greatly reduce the time required to reach equilibrium, e.g., at 15 bar and 1300?C, equilibrium is reached in 1 millisecond and the NO2/NO is about 0.8%. The formation and destruction of NO2 is generally through the reversible reactions: NO+O+M=NO2+M, HO2+NO=NO2+OH, and NO+O2=NO2+O. With increasing pressure and decreasing temperature, O plays a much more important role than HO2 in the oxidation of NO. A higher water vapor content accelerates NO2 formation in all cases by providing more O and HO2 radicals. The addition of CO or SO2 also promotes the formation of NO2. Finally, NO2 formation in a Pressurized oxy-combustion furnace is compared with that in a practical atmospheric air-combustion furnace and the comparison show that NO2 formation in a Pressurized oxy-combustion furnace can be over 10 times that of an atmospheric air-combustion furnace.

The role of sulfate and its corresponding S(IV)+NO2 formation pathway during the evolution of haze in Beijing

2019 ◽  
Vol 687 ◽  
pp. 741-751 ◽  
Author(s):  
Fange Yue ◽  
Zhouqing Xie ◽  
Pengfei Zhang ◽  
Shaojie Song ◽  
Pengzhen He ◽  
...  
Keyword(s):  
Formation Pathway ◽  
No2 Formation

A Literature Review of NOx Formation Kinetics and a Prediction Method for Lean-Burn, Two-Stroke Natural Gas Engines

2019 ◽  
Author(s):  
Taylor F. Linker ◽  
Mark Patterson ◽  
Greg Beshouri ◽  
Abdullah U. Bajwa ◽  
Timothy J. Jacobs
Keyword(s):  
Natural Gas ◽  
Chemical Properties ◽  
Prediction Method ◽  
Operating Conditions ◽  
Combustion Mechanism ◽  
Nox Emissions ◽  
Lean Burn ◽  
Nox Formation ◽  
Gas Combustion ◽  
No2 Formation

Abstract The increased production of natural gas harvested from unconventional sources, such as shale, has led to fluctuations in the species composition of natural gas moving through pipelines. These variations alter the chemical properties of the bulk gas mixture and, consequently, affect the operation of pipeline compressor engines which use the gas as fuel. Among several possible ramifications of these variations is that of unacceptably high engine-out NOx emissions. Therefore, engine controller enhancements which can account for fuel variability are necessary for maintaining emissions compliance. Having the means to predict NOx emissions from a field engine can inform the development of such control schemes. There are several types of compressor engines; however, this study considers a large bore, lean-burn, two-stroke, integral compressor engine. This class of engine has unique operating conditions which make the formation of engine-out NOx different from typical automotive spark-ignited engines. For this reason, automotive-based methods for predicting NOx emissions are not sufficiently accurate. In this study, an investigation is performed on the possible NO and NO2 formation pathways which could be contributing to exhaust emissions. Additionally, a modeling method is proposed to predict engine-out NOx emissions using a 0-D/1-D model of a Cooper-Bessemer GMWH-10C compressor engine. Predictions are achieved with GRI-Mech3.0, a natural gas combustion mechanism, which allows for simulated formation of NOx species. The implemented technique is tuned using experimental data from a field engine to better predict emissions over a range of engine operating conditions. Tuning the model led to acceptable agreement across operating points varying in both load and trapped equivalence ratio.

An Experimental Investigation of the Conversion of NO to NO2 at High Pressure

1995 ◽  
Author(s):  
James W. Hunderup ◽  
Richard J. Roby
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Computer Modeling ◽  
Flow Reactor ◽  
Injection Point ◽  
No Conversion ◽  
Temperature Window ◽  
High Concentrations ◽  
No2 Formation ◽  
Stack Emissions

Unexpectedly high concentrations of NO2 have been noted in stack emissions from industrial combustors. NO2 formation has been reported to occur through the so called “HO2 mechanism” in which NO combines with HO2 to produce NO2 and OH. In this study, the formation of NO2 was investigated at super-atmospheric pressures through experiments and computer modeling. Computer modeling utilized the CHEMKIN chemical kinetics program and a subset of a previously published C-H-O-N system mechanism. Experimental work was conducted using a high pressure flow reactor designed and built in the course of the study. The effects of pressure, temperature, and the presence of a NO2 promoting hydrocarbon, methane, were investigated. It was discovered that as pressure increased from 1 atm. to 8.5 atm., the rate and amount of NO converted to NO2 also increased. The results also show a temperature “window” between approximately 800 K and 1000 K in which NO to NO2 conversion readily occurred. The presence of methane was seen to enhance NO conversion to NO2, and a ratio of [CH4]/[NO] was found to be a useful parameter in predicting NO2 formation. Significant NO conversion to NO2 was noted for [CH4]/[NO]>1 at the hydrocarbon injection point. Experimental results validated those trends obtained from modeling with a modified C-H-O-N mechanism.

Modelling NO-NO2 Conversion in Counter-Flow Diffusion Flames

2003 ◽  
Author(s):  
A. G. Kyne ◽  
M. Pourkashanian ◽  
C. W. Wilson ◽  
A. Williams
Keyword(s):  
Diffusion Flame ◽  
Diffusion Flames ◽  
Common Knowledge ◽  
Aircraft Engine ◽  
Combustion Products ◽  
Counter Flow ◽  
Kinetic Rates ◽  
Gas Turbine Exhaust ◽  
No2 Formation ◽  
Combustion Processes

As emission regulations become more stringent there is increasing interest in the formation of NO2 in combustion products where it is in higher concentration than if slowly formed from NO in the atmosphere. It is common knowledge that NO2 is significantly more toxic than NO. The chemistry of NO2 formation in combustion processes is simple in comparison to that of NO. Indeed, all NO2 is formed from oxidation of NO mainly by reaction with HO2 radicals with its conversion back to NO resulting from reactions involving O and H atoms. Since consumption and formation of NO2 always occur simultaneously, although with unbalanced kinetic rates leading to local super-equilibrium concentrations, parameters such as temperature, velocity and species concentrations fields can drastically affect the degree of conversion of NO to NO2 in combustion applications. It is not well known what these conditions are and in certain circumstances, such as aircraft engine reheat systems, the emission of NO2 is clearly visible under the form of brown fumes. A comprehensive numerical simulation was undertaken to investigate the NO-NO2 relationship in a counter-flow diffusion flame. The CHEMKIN II suite of software (Kee et al., 1989) in conjunction with the opposed diffusion flame code OPPDIF (Lutz et al, 1997) was run using the Gas Research Institute’s (GRI’s) methane reaction mechanism v.3.0. A number of different strain rates using boundary conditions typical in a gas turbine exhaust were investigated. A rate of production and sensitivity analysis was made in determining which reactions were important in the NO-NO2 conversion process.

scholarly journals Experimental Study on NOx Reduction in Oxy-fuel Combustion Using Synthetic Coals with Pyridinic or Pyrrolic Nitrogen

2018 ◽  
Vol 8 (12) ◽  
pp. 2499 ◽  
Author(s):  
Chang’an Wang ◽  
Pengqian Wang ◽  
Lin Zhao ◽  
Yongbo Du ◽  
Defu Che
Keyword(s):  
Oxygen Content ◽  
Power Plants ◽  
Large Scale ◽  
Nox Reduction ◽  
Fuel Combustion ◽  
Combustion Technology ◽  
Carbon Dioxide Co2 ◽  
No2 Formation ◽  
The Impact ◽  
Pyridinic Nitrogen

Oxy-fuel combustion technology can capture carbon dioxide (CO2) in the large-scale and greatly lower nitrogen oxides (NOx) emission in coal-fired power plants. However, the influence of inherent minerals on NOx reduction still remains unclear and the impact of oxy-fuel combustion on the transformation of different nitrogen functional groups has yet to be fully understood. The present work aims to obtain a further understanding of the NOx reduction during oxy-fuel combustion using synthetic coals with pyrrolic or pyridinic nitrogen. Compared to pyridinic nitrogen, more of the pyrrolic nitrogen in synthetic coal was converted to NOx. The conversion ratio of nitric oxide (NO) first increased significantly with the rising oxygen content and then trended to an asymptotically constant as the oxygen (O2) content varied between 10–50%. The nitrogen dioxide (NO2) formation was roughly proportional to the oxygen content. The NO2 conversion was increased with particle size but the case of NO showed a non-monotonic variation. The catalytic effects of sodium carbonate (Na2CO3), calcium carbonate (CaCO3), and ferric oxide (Fe2O3) on the transformation of pyridinic nitrogen to NO were independent of the combustion atmosphere, while the alteration from air to the oxy-fuel combustion led to a change of mineral catalytic effect on the oxidation of pyrrolic nitrogen within the coal matrix.

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