Study on NO and N<sub>2</sub>O Formation and Destruction Mechanisms in a Laboratory-Scale Fluidized Bed

Loeffler, G.; Wartha, Christian; Winter, Franz; Hofbauer, Hermann

doi:10.1021/ef010228n

Cited by 24 publications

(9 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…31 Several researchers have identified HCN as the main product arising during coal devolatilization. 4,31,34,35 However, it is possible that during the process, the NH 3 can result from the HCN hydrogenation 31,32,[36][37][38] or direct hydrogenation of coal/char-N. 39 Both NH 3 and HCN could be the origin of NO; while at the temperatures typical of AFBCC the NH 3 seems to yield mostly NO, 18,26,37,[40][41][42][43][44][45][46][47][48] the NO originated from HCN is temperature dependent and has been discussed in the context of a NO/N 2 O tradeoff, the NO formation prevailing at the higher temperatures. 4,18,34,[49][50][51][52][53][54] The intermediate species that are crucial in the NH 3 and HCN oxidation appear to be NH for the first and NCO for the second.…”

Section: No Chemistry In Combustionmentioning

confidence: 99%

“…Both NH 3 and HCN could be the origin of NO; while at the temperatures typical of AFBCC the NH 3 seems to yield mostly NO, ,,,− the NO originated from HCN is temperature dependent and has been discussed in the context of a NO/N 2 O tradeoff, the NO formation prevailing at the higher temperatures. ,,,− The intermediate species that are crucial in the NH 3 and HCN oxidation appear to be NH for the first and NCO for the second.…”

Section: No Chemistry In Combustionmentioning

confidence: 99%

See 1 more Smart Citation

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

2004

View full text Add to dashboard Cite

Atmospheric bubbling fluidized bed coal combustion of a bituminous coal and anthracite with particle diameters in the range 500-4000 µm was investigated in a pilot-plant facility. The experiments were conducted at steady-state conditions using three excess air levels (10, 25, and 50%) and bed temperatures in the 750-900°C range. Combustion air was staged, with primary air accounting for 100, 80, and 60% of total combustion air. For both types of coal, high NO concentrations were found inside the bed. In general, the NO concentration decreased monotonically along the freeboard and toward the exit flue; however, during combustion with high air staging and low to moderate excess air, a significant additional NO formation occurred near the secondary air injection point. The results show that the bed temperature increase does not affect the NO flue gas concentration significantly. There is a positive correlation between excess air and the NO flue gas concentration. The air staging operation is very effective in lowering the NO flue gas, but there is a limit for the first stage stoichiometry below which the NO flue gas starts rising again. This effect could be related with the coal rank.

show abstract

Section: No Chemistry In Combustionmentioning

confidence: 99%

Section: No Chemistry In Combustionmentioning

confidence: 99%

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

2004

View full text Add to dashboard Cite

show abstract

“…In the study by Pels et al it was observed that during the volatile combustion, intermediate NCO, which originates from HCN, reacts to NO at higher temperatures, whereas lower temperatures favored N 2 O formation. Loeffler et al also observed that above 800 °C, the conversion to NO increases if the radical level in the combustor is high. However, the effect in lower temperatures was opposite, which was explained by reaction . …”

Section: Results and Discussionmentioning

confidence: 96%

Fuel Staging and Air Staging To Reduce Nitrogen Emission in the CFB Combustion of Bark and Coal

Saastamoinen

Leino

2019

Energy Fuels

View full text Add to dashboard Cite

Nitrogen oxide (NO) and nitrous oxide (N 2 O) formation in the circulating fluidized bed (CFB) combustion can be controlled by air staging and fuel staging. An extensive test campaign was carried out with a pilot-scale CFB test rig to observe the possibilities of the methods in the spruce bark and bituminous coal combustion as well as in co-combustion. Fuel staging with liquid petroleum gas (LPG) was done alternately from three locations with three intensities. Air staging was studied alone and during the fuel staging experiment. The experimental trends for NO and N 2 O emission formation during fuel staging and air staging are presented in this study. It was observed that air staging and fuel staging can have opposing effects on nitrogen oxide emission formation, and thus, when used together, a clear understanding of the fuel behavior and conditions, as well as NO x chemistry in the combustor, is needed. Under the tested conditions, it was observed that if air staging is effective, then fuel staging does not bring further benefits in the NO reduction. Instead, the LPG feed can increase the emission in the lack of oxygen. However, if it is not possible to carry out air staging, then fuel staging can be used in generating oxygen-lean reducing zones for NO. The N 2 O concentration was also further reduced with LPG in the tests with effective air staging.

show abstract

“…Detailed Chemical Reaction Mechanism. The detailed homogeneous reaction mechanism is taken from Löffler, which has been proven well describing NO x and N 2 O emissions within a wide range of conditions. − This reaction mechanism is able to simulate CH 4 combustion as well as all discussed paths of NO x formation. It is based on the mechanism of Bowman et al with the H/N/O reactions replaced by the mechanism of Glarborg and co-workers , as supposed by Wargadalam et al Moreover, the kinetics of the N 2 O destruction reactions was adapted as recommended by Löffler et al, and to account for the NO x -sensitized CH 4 oxidation, the changes proposed by Löffler et al were included.…”

Section: Methodsmentioning

confidence: 99%

NO_x Formation in Natural Gas CombustionEvaluation of Simplified Reaction Schemes for CFD Calculations

Löffler

Sieber

Harasek

et al. 2005

Ind. Eng. Chem. Res.

Self Cite

View full text Add to dashboard Cite

There is a demand for further reducing NO x emissions from natural gas burners in heat and power production. For this issue, computational fluid dynamics (CFD) is a powerful tool, gaining in importance. However, because of computational efforts, there is the necessity for simplified models in order to simulate the combustion reactions and the NO x formation, respectively. In this work, different simplified models for the NO x formation, i.e., thermal NO and prompt NO formation, are validated against the predictions of a detailed chemical kinetic mechanism. NO x formation from CH 4 combustion becomes relevant above ∼1200 °C. For temperatures >1600 °C, thermal NO formation is dominant. At lower temperatures, the N 2 O/NO and NNH routes have a significant contribution. For the conditions investigated, prompt NO formation is not relevant except for fuel-rich combustion. The simplified models capture thermal NO formation quite well. The superequilibrium radical concentration in the flame zone can be modeled by the "partial equilibrium approach" for the O radical, assuming its concentration in the relevant temperature range is ∼30% higher than that for the equilibrium approach. However, this model overestimates NO formation under postflame conditions. For the prompt NO model, CH 4 and O 2 concentrations are necessary. These are obtained from the combustion model, which can be a local thermodynamic equilibrium (mixing rate limiting), a global reaction (reaction and/or mixing rate limiting), or a simplified reaction mechanism (flamelet model 1 ). The prompt NO model based on these combustion calculations is able to reasonably capture the NO emissions predicted by the detailed mechanism. However, the performance of the prompt NO model is rather dependent on the combustion model. Thus, this one must be chosen carefully. Critically, it has to be stated that, although the simplified prompt NO model captures the observed trends acceptably, it lacks a physical basis. It assumes the prompt NO formation to be proportional to the fuel concentration. The detailed reaction mechanism shows that the NO formation is more strongly related to the fuel oxidation rate, i.e., the radical concentration. Moreover, the detailed mechanism shows that prompt NO formation is of secondary relevance. Low-temperature NO formation is more related to the N 2 O/NO and the NNH routes.

show abstract

Study on NO and N₂O Formation and Destruction Mechanisms in a Laboratory-Scale Fluidized Bed

Cited by 24 publications

References 26 publications

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

Fuel Staging and Air Staging To Reduce Nitrogen Emission in the CFB Combustion of Bark and Coal

NO_x Formation in Natural Gas CombustionEvaluation of Simplified Reaction Schemes for CFD Calculations

Contact Info

Product

Resources

About

Study on NO and N2O Formation and Destruction Mechanisms in a Laboratory-Scale Fluidized Bed

Cited by 24 publications

References 26 publications

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

Axial Concentration Profiles and NO Flue Gas in a Pilot-Scale Bubbling Fluidized Bed Coal Combustor

Fuel Staging and Air Staging To Reduce Nitrogen Emission in the CFB Combustion of Bark and Coal

NOx Formation in Natural Gas CombustionEvaluation of Simplified Reaction Schemes for CFD Calculations

Contact Info

Product

Resources

About

Study on NO and N₂O Formation and Destruction Mechanisms in a Laboratory-Scale Fluidized Bed

NO_x Formation in Natural Gas CombustionEvaluation of Simplified Reaction Schemes for CFD Calculations