Maximum NO Concentration Research Articles

Experimental and numerical analysis of ammonia/hydrogen combustion under artificial exhaust gas recirculation

This paper investigates the potential of exhaust gas recirculation in hydrogen/ammonia mixtures. The effects of artificial exhaust gas recirculation were evaluated on flame morphology and unstretched laminar burning velocities experimentally, while the flame stability and NO emissions were simulated using previous kinetic models. The experiments and numerical simulations were performed for various equivalence ratios, initial temperatures, pressures, exhaust gas recirculation rates, and compositions. Results show that recirculation of exhaust gases can enhance flame stability by diminishing the hydrodynamic instabilities while negatively affecting the flame laminar burning velocities. This negative impact, which is more sensible at non-stoichiometric conditions, reduces the flame speed between 19% and 58% based on the flue gas content of the combustible mixture. Despite this reduction, recirculating the exhaust gases can considerably reduce the high NO emissions of hydrogen/ammonia/air mixtures. Indeed, adding flue gases can decrease the maximum NO concentrations up to 45% at near stoichiometric conditions. The effects are even more significant in fuel-rich mode, diminishing the NO emissions up to 84% at an equivalence ratio of 1.3. Finally, these evaluations support the idea of exhaust gas recirculation application for using hydrogen/ammonia blends as a clean fuel while considering the expenses of burning rate reduction.

Assessment of a hydrogen-fueled swirling trapped-vortex combustor using large-eddy simulation

In recent years, the study of hydrogen combustion has gained significant interest due to its exceptional lean blow-out (LBO) performance, high efficiencies, and almost negligible greenhouse gas emissions. The present study combines the advantages of hydrogen combustion with the beneficial characteristics of trapped-vortex combustion (TVC) and swirling flows. Large-eddy simulation (LES) is conducted to evaluate the performance of a swirling trapped-vortex combustor. LES sub-gird terms are described using k-equation subgrid model, while, turbulence-combustion interaction is modelled employing the PaSR (Partially Stirred Reactor) closure with a detailed 23-step chemical reaction mechanism for hydrogen/air. A radial vane swirler is incorporated to supply an annular mainstream and generate a wake region in front of the cavity leading edge to enhance cavity flow entrainment. To evaluate the performance of a hydrogen-fueled TVC under non-swirl and swirling conditions with varying swirl numbers (0.1–0.6), several flow and combustion characteristics are analyzed. These includes temperature distribution, vortical structure, combustion efficiency, NO emission, and flame shape. The results show that a large recirculation zone dominates the cavity for the all swirl numbers resulting in a strong fuel–air mixing and high combustion efficiency. It is demonstrated that the swirling motion effectively mitigates the negative impacts of pressure fluctuations arising from the interaction of combustion with cavity oscillations. A stable flame is observed inside the cavity and in the shear layer at the cavity lip in all cases, merging to form a distinctive C-shaped flame. Increasing the swirl number causes the second part of the flame to move to the wake region before the leading edge, enhancing combustion stability and efficiency. Combustion efficiency exceeds 98.5% for all cases, reaching 99.8% for a swirl number of 0.6. The temperature distribution is nearly uniform inside the cavity, with an improved distribution at the TVC’s outlet for higher swirl numbers. Under non-swirling conditions, the corrected NO concentration is below 5 ppm. Increasing the swirl number escalates the outlet NO emission, nevertheless, a maximum NO concentration of 19 ppm is observed for the swirling cases. Comparing these findings with existing data suggests that the swirling TVC offers advantages over other hydrogen-fired TVC’s.

State of gaseous air pollutants and resulting health effects in Karachi, Pakistan.

Karachi, Pakistan, is a priority site for air pollution research due to high emissions of air pollutants from vehicular traffic, industrial activities, and biomass burning, as well as rapid growth in population. The objectives of this study were to investigate the levels of gaseous pollutants (NO, NO2, O3, HNO3, and SO2) in Karachi, to determine temporal and seasonal variations, to compare Karachi's air quality with other urban centers, to identify relationships with meteorological conditions, to identify source characterization, and to perform a backward-in-time trajectory analysis and a health impact assessment. Daily samples of gaseous pollutants were collected for six consecutive weeks in each of the four seasons for a year. Daily maximum concentrations of NO (90 parts per billion by volume (ppbv)), NO2 (28.1 ppbv), O3 (57.8 ppbv), and SO2 (331 ppbv) were recorded in fall, while HNO3 (9129 parts per trillion by volume (pptv)) was recorded in spring. Seasonal average concentrations were high in winter for NO (9.47 ± 7.82 ppbv), NO2 (4.84 ± 3.35 ppbv), and O3 (8.92 ± 7.65 ppbv), while HNO3 (629 ± 1316 pptv) and SO2 (20.2 ± 39.4 ppbv) were high in spring and fall, respectively. The observed SO2 seasonal average concentration in fall (20.2 ± 39.4) was 5 times higher than that in summer (3.97 ± 2.77) with the fall 24-h average (120 ppbv) exceeding the WHO daily guideline (7.64 ppbv) by a factor of about 15.7. A health impact assessment estimated an increase of 1200 and 569 deaths due to short-term exposure to SO2 in fall and spring, respectively. Chronic daily intake estimated risk per 1000 was 0.99, 0.47, 0.45, and 0.26 for SO2 in fall, NO in winter, O3 in winter, and NO2 in spring, respectively. This study confirms the effect of poor urban air quality on public health and demonstrated the influence of photochemical reactions as well as unfavorable meteorological conditions on the formation of secondary pollutants.

Behavior of nitrogen oxides in a lab-scale coal ammonia co-firing system

The objective of this study was to determine the ideal coal–ammonia (NH3) co-firing conditions to achieve carbon neutrality and suppress NOx formation. This paper describes the characteristics of NOx formation in NH3–coal co-firing experiments. NH3 co-firing experiments were performed under intensive and air-staged combustion conditions using a 5 kW fluidized bed reactor. Air-staged combustion and divided fuel-injection were effective in suppressing NOx formation during NH3 co-firing combustion. The minimum and maximum NO concentration observed during intensive and air-staged combustion was 70 ppm and 700 ppm, respectively. In addition, some NH3 slips were observed under an NH3 co-firing ratio of 20% or more; however, the reduction effect of NO was observed. The NO concentration increased to approximately 500 ppm under pure NH3 combustion. The simultaneous injection of fuel and oxygen under fuel-rich conditions generated NO and N2O. It increased rapidly under incomplete combustion conditions and increased in proportion to the concentrations of HCN and CO. NH3 co-firing was accompanied by the suppression of NO formation and reduction of N2O and CO2 if injected in consideration of the temperature and oxygen concentration.

Chemical structure of premixed ammonia/hydrogen flames at elevated pressures

Because it is a carbon free fuel with high volumetric and gravimetric hydrogen density, ammonia is considered to be a promising hydrogen carrier molecule; its combustion chemistry, consisting of ammonia and ammonia/hydrogen blends, are of great importance in engine and gas turbine systems. This paper presents experimental data and kinetic modeling of the structure of NH3/H2/O2/Ar premixed flames at elevated pressures. Equivalence ratios were maintained at 0.8, 1.0 and 1.2, and the NH3/H2 ratio was 1:1 (molar ratio). Experiments were performed at pressures of 4 and 6 atm. Eight recently published chemical-kinetic mechanisms of ammonia combustion and oxidation were applied to numerically simulate flame structure. Experimental and numerical data showed that the main nitrogen containing compounds in the post flame zone were N2 and NO, while the concentrations of N2O and NO2 were negligible. In terms of NO emissions reduction, it was revealed that rich conditions were more effective. At the same time, pressure increases resulted in decreasing NO concentration in the post flame zone, as well as lower maximum concentration of NO and N2O. Numerical analysis showed that N2O and NO2 were formed mainly from NO. To improve the agreement between experimental and numerical data, rate kinetic parameters of these reactions should be refined.

A non-threshold model to estimate carcinogenic risk of nitrate-nitrite in drinking water

Understanding nitrate–nitrite ( NO 3 − − NO 2 − ) levels in drinking water and the associated non-carcinogenic and carcinogenic health risks are essential to protect public health. The non-carcinogenic risk assessment of NO 3 − – NO 2 − in drinking water has been well documented, however, there remains a knowledge gap in understanding and quantification of the carcinogenic risk of NO 3 − – NO 2 − . This study develops a non-threshold–based model for estimation of carcinogenic risk of NO 3 − – NO 2 − ingested through drinking water for a densely populated urban area with a case study of Tehran's potable water (TPW). In this regard, 200 tap water samples from different parts of the city were taken in wet (May 2018) and dry (October 2018) periods to determine NO 3 − – NO 2 − concentration in the TPW and the associated health risks across different groups of end-users. Sampling results reveal higher concentrations of NO 3 − – NO 2 − during the dry period, which can be associated to the significant contribution of nitrogen–rich groundwater in supplying the city's water demands during the dry period. Findings suggest concerns associated with the non-carcinogenic risk of NO 3 − – NO 2 − in the TPW, especially for children. More than 55% of the samples taken during the dry period show a positive carcinogenic risk for all groups of end-users (68% for men, 72% for women, and 56% for children) whilst just 8% of the samples are deemed unsafe with regards to the permissible NO 3 − level in drinking water, i.e. 50 mg/L. Approximately, 45% of the samples taken during the wet period show a positive carcinogenic risk for adults whilst the maximum concentration of NO 3 − was about 23 mg/L, i.e. two times less than the permissible level in drinking water. The findings emphasize on the necessity of reducing the permissible level of NO 3 − in drinking water, set out by the existing water quality standards , to safeguard public health against the carcinogenic risks. The model developed within this study recommends the urgent need for reduction of NO 3 − level in Tehran's water resources to protect public health of over 13 M population who incessantly use the TPW. • A model is developed to estimate carcinogenic risk of NO 3 − in drinking water. • Non-carcinogenic risk of NO 3 − – NO 2 − was observed in Tehran's drinking water. • Majority of samples taken in dry period show a positive carcinogenic risk of NO 3 − • The permissible level of NO 3 − does not safeguard human health vs carcinogenic risks.

Effect of bluff body addition in fuel-rich stream on reaction behaviours of large-proportion semicoke rich/lean blended combustion

Fuel-rich/lean combustion is considered as a novel combustion technology due to its enhanced ignition performance and low NOx emissions. To further improve the poor performance of large-proportion semicoke and bituminous coal blended combustion and reduce NOx emissions, under a bias concentration ratio (BCR) of 2:1, an addition of bluff bodies at the fuel-rich side is proposed to numerically and experimentally investigate the turbulence-chemistry interaction behaviours of the fuel-rich/lean combustion regime in a 0.3 kW pilot-scale bias combustion furnace for various bluff body blockage ratios (BR = 0%, 11% and 21%). The results show that, increasing the blockage ratio evidently shortens the ignition delay time and burnout time of bituminous coal and semicoke, and the promotive effect of triangular bluff-body (BR = 21%) is greater. The turbulent Damköhler number Dat maximums decrease from 194 to 113 with increasing BR, denoting the regime is traditional combustion mode controlled by mixing. On the fuel-rich side, a local homogeneous MILD combustion zone (Dat <10) extends with increasing BR. For the heterogeneous combustion, the char-O2 reaction determined by diffusion/kinetics and the char gasification reaction controlled by kinetics both show a kinetically controlled trend with increasing BR. Moreover, with increasing BR, a decreasing in the NO concentration in the main reaction zone can be attributed to an enhanced recirculation rate Kv. There is a strong correlation between the maximum NO and the local homogeneous/heterogeneous Damkhöler number on the fuel-rich/lean side in the plane of maximum Kv. Increasing BR can evidently decrease the maximum NO concentration on the fuel-rich side due to the enhanced local MILD combustion regime, and thus reducing NOx exit emissions. Considering temperature, ignition, burnout, turbulence-chemistry interactions and NOx emissions, a triangular-shaped bluff body on the fuel-rich side (BR = 21%) is recommended rather than a cubic bluff body in the fuel-rich/lean co-combustion of semicoke.

Combustion characteristic study with a flue gas internal and external double recirculation burner

A new low NOx burner for gas boiler is designed. A hollow tube is embedded in the burner axial center line, which is combined with the flared flame stabilizer to draw back the internal flue gas from inside the boiler, and a flue gas recirculation tube is installed outside the boiler to draw back the flue gas from the end of the boiler. The effectiveness of the burner is evaluated by industry experiments and extensive computational fluid dynamics (CFD) simulations. The research results show that the excess air ratio and external flue gas recirculation (e-FGR) rate significantly alter the temperature distribution and NOx emission of the boiler. The temperature and NOx emission do not vary monotonically with the excess air ratios, but decrease monotonically with the e-FGR rates. To achieve the low NO emission, the optimum excess air coefficient α should be 1.15 due to the better temperature uniformity, and the value of e-FGR rate should be in the range of 28%–40%. In addition, the maximum concentration of NO does not appear on the flame surface, but in the downstream region of the flame.

The role of hydroxylamine in promoting conversion from complete nitrification to partial nitrification: NO toxicity inhibition and its characteristics

This study investigated a strategy for hydroxylamine (NH2OH) addition for promoting the conversion of complete nitrification to partial nitrification in a sequencing batch reactor (SBR). The results showed that continuous dosing of 5 mg-N/L NH2OH into a complete nitrification reactor for 16 days led to an increase in the nitrite accumulation ratio (NAR) from 0.22% to 95.08% and a significant enhancement in the accumulation of NO and N2O in the liquid. The maximum concentration of NO in each cycle rose with the increase of NAR during NH2OH addition. With the stopping of NH2OH addition, the partial nitrification disappeared progressively in 21 days. The analysis for microbial community showed that Nitrospira was the main NOB and its relative abundance decreased with NH2OH addition and recovered after the cessation of NH2OH addition. Accordingly, NH2OH has a significant and reversible inhibition on Nitrospira and its essence might be related to NO toxicity.

Effects of OH concentration and temperature on NO emission characteristics of turbulent non-premixed CH4/NH3/air flames in a two-stage gas turbine like combustor at high pressure

This study examined the effects of OH concentration and temperature on the NO emission characteristics of turbulent, non-premixed methane (CH4)/ammonia (NH3)/air swirl flames in two-stage combustors at high pressure. Emission data were obtained using large-eddy simulations with a finite-rate chemistry method from model flames based on the energy fraction of NH3 (ENH3) in CH4/NH3 mixtures. Although NO emissions at the combustor exit were found to be significantly higher than those generated by CH4/air and NH3/air flames under both lean and stoichiometric primary zone conditions, these emissions could be lowered to approximately 300 ppm by employing far-rich equivalence ratios (ϕ) of 1.3 to 1.4 in the primary zone. This effect was possibly due to the lower OH concentrations under far-rich conditions. An analysis of local flame characteristics using a newly developed mixture fraction equation for CH4/NH3/air flames indicated that the local temperature and NO and OH concentration distributions with local ϕ were qualitatively similar to those in NH3/air flames. That is, the maximum local NO and OH concentrations appeared at local ϕ of 0.9, although the maximum temperature was observed at local ϕ of 1.0. Both the temperature and OH concentration were found to gradually decrease with the partial replacement of CH4 with NH3. Consequently, NO emissions from CH4/NH3 flames were maximized at ENH3 in the range of 20% to 30%, after which the emissions decreased. Above 2100 K, the NO emissions from CH4/NH3 flames increased exponentially with temperature, which was not observed in NH3/air flames because of the lower flame temperatures in the latter. But, the maximum NO concentration in CH4/NH3 flames was occurred at a temperature slightly below the maximum temperature, just as in NH3/air flames. The apparent exponential increase in NO emissions from CH4/NH3 flames is attributed to a similar trend in the OH concentration at high temperatures.

Uncertainty quantification of fuel variability effects on high hydrogen content syngas combustion

Fuel variability effects on high hydrogen content syngas combustion physicochemical properties and NOx emission characteristics are investigated invoking polynomial chaos expansion based uncertainty quantification. The focus is put on providing an in-depth understanding of fuel variability effect under very lean conditions, i.e., near lean blowout limit. It is found that leaner combustion of syngas leads to higher flame speed fluctuation. Under 1.5% small fluctuations in species concentration of syngas fuels, a maximum of 5% fluctuation of flame speed is observed at equivalence ratio of 0.45 for H60CO30 (60%H2 + 30%CO), while the lowest fluctuation is observed near equivalence ratio of 0.8 for the cases considered. Meanwhile, maximum NO concentration fluctuation of 8.3% and NO2 concentration fluctuation of 6.5% are observed at very lean conditions. Uncertainty analyses show that on one hand, hydrogen always has the highest contribution to flame speed variation followed by carbon monoxide, carbon dioxide, and methane. On the other hand, carbon monoxide is found to have the highest contribution to variation of flame temperature, followed by hydrogen, carbon dioxide, and methane. The quantified sensitivity information reported in present study can be used to guide targeted uncertainty reduction from syngas upstream gasification process.

Afterglow dielectric-barrier discharge air plasma (ADDAP) for the inactivation of Escherichia coli O157:H7

The afterglow of an atmospheric pressure plasma can conveniently be used for large scale decontamination operations. In the present study, an afterglow dielectric-barrier discharge air plasma (ADDAP) was used to inactivate Escherichia coli O157:H7, which was used as a model microorganism for studying the inactivation effect of the plasma. ADDAP was generated at different input currents in the range of 0.4–0.8 A. At all tested plasma exposure times, temperatures inside sample treatment chamber remained less than 30 °C. Regarding chemical composition of ADDAP in the treatment chamber, NOx species (NO and NO2) were predominantly observed. The levels of the NOx species increased as the current intensity increases and the maximum NO and NO2 concentrations noted were 6 and 4 ppm, respectively, but that of CO was less than 1 ppm level at 0.8 A. Upon treatment using ADDAP generated at 0.4–0.8 A for 180 min, glass-bound E. coli O157:H7 counts were reduced in the range of 1.24–2.71 log CFU/mL. The inactivation patterns exhibited better fit to the Weibull tail model. The comparison of delta values indicated that superior inactivation effects were observed as current intensity increases.

On Low-Emission Annular Combustor Based on Designing of Liner Air Admission Holes

Numerical experiments was carried out to predict the total temperature characteristics and formation of nitrogen oxide emissions and pattern factor in an annular combustor liner based on geometrical parameters and location and rows of different air admission holes, for 6 various cases, using computational fluid dynamics (CFD) .The simulation has been performed using ANSYS CFX including finite rate chemistry and eddy dissipation model, for simulation of liquid kerosene (Jet A) – air combustion after fuel droplet evaporation. The spray modeling was performed, including Rosin-Rammler droplet distribution. Thermal and prompt nitrogen oxide (NO x ) formation was performed to predicting NO x emission characteristics with a k -e model of turbulent. In this investigation the 3D CAD model of the realistic annular combustion chamber is presented for the simulation with double radial air swirler for the better mixing fuel with air. Beside this the characteristic and the flame structure is presented including the contour plots of total temperature and NO concentration at the outlet of the combustor liner and in cross section plane along the X axis from the injector center of the combustor including the chart of the velocity and NO, CO, CO 2 , O 2 and the total temperature along the liner from the injector center. For the combustion of kerosene with air 2 step kinetic schemes are presented in this study. The results show that the best result with the low concentration of NO is the case 5 but with a high percentage of pressure drop and the case 3 have the maximum concentration of NO with the low percentage of pressure drop.

Dispersion Modeling of Nitrogen Dioxide in Ambient Air of Ahvaz City

Background: Air emission modeling is used to study how pollutants are spread in the environment and to forecast their emissions rate in different climatic conditions in the study area. Today, air pollution threatens human public health and the environment, and Ahvaz is considered one of the main centers of air pollution in Iran. Objectives: This aim of this study was to evaluate the nitrogen dioxide distribution in Ahvaz by using the software program Screen 3. Materials and Methods: This analytical study was conducted in 2013 in Ahvaz. Data collections were performed by the Ahvaz Department of Environment. After processing the data received (averaging instruction set, coding), the file was converted to an input file for the software program Screen 3. In the next phase, study of the distribution and release of nitrogen dioxide during the year 2013 was modeled using the Screen 3 software. Results: Based on the results of this study, the highest and the lowest nitrogen dioxide concentration were in the Bureau of Meteorology and Head office of ADoE stations, respectively. The maximum concentration of NO 2 , at a height of 45 m, was 20 μg/m 3 .According to the findings of the modeling, examination of the combustion process was observed, and this was caused by the amount of nitrogen dioxide emitted by flue outlets, which was affected by temperature and pressure, fuel flow rates and inlet air temperature. Also, results showed that in most cases emission of air pollutants was towards the southwest. Conclusions: Results of this study showed that the Screen3 software is one of the popular models for estimating the distribution of air pollutants. Nitrogen dioxide emissions are highly regulated in most industrialized regions. Decreased emissions from fuel combustion, the use of scrubbers and filters that absorb pollution can be very useful for reduction and control of nitrogen dioxide emissions.

Combustion and NO Emission Characteristics of Liquefied Petroleum Gas/Dimethyl Ether Blended Fuel in Counterflow Non-Premixed Flame

Combustion and NO emission characteristics of a fuel blend comprising liquefied petroleum gas (LPG) and dimethyl ether (DME) were investigated using counterflow diffusion flames. Visible light photos, Schlieren photos, OH planar laser-induced fluorescence (PLIF) images, and maximum NO emissions were examined. The temperature, fuel-consumption rate, species mole fraction, species-production rate, and emission index of NO (EINO) were examined by numerical simulation. The experimental and numerical results showed that DME has a wider reaction zone, higher peak temperature, and greater reaction rate than butane. Although the overall LPG/DME mixture characteristics ranged between those of butane and DME, they were closer to those of butane. When the LPG contained propane, the mixture characteristics closely resembled those of DME because of their similar physical and chemical characteristics. The maximum NO concentrations decreased when the DME concentration increased. Owing to the higher fuel-consumption rate of DME, the EINO decreased almost linearly with the increase in the DME content.

Evaluation of Relationship Between Air Pollutant Concentration and Meteorological Elements in Winter Months

Abstract The paper presents the evaluation of the relation between meteorological elements and air pollutants’ concentrations. The analysis includes daily concentrations of pollutants and variation of meteorological elements such as wind speed, air temperature and relative humidity, precipitation and total radiation at four monitoring stations located in the province of Lower Silesia in individual months of the winter half-year (November–April, according to hydrological year classification) of 2005–2009. Data on air quality and meteorological elements came from the results of research conducted in the automatic net of air pollution monitoring conducted in the range of the State Environment Monitoring. The effect of meteorological elements on analysed pollutant concentration was determined using the correlation and regression analysis at significance level α &lt; 0.05. The occurrence of maximum concentration of NO, NO2, NOX, SO2 and PM10 occurred in the coldest months during winter season (January, February and December) confirmed the strong influence of “low emission” on air quality. Among the meteorological factors assessed wind speed was most often selected component in step wise regression procedure, then air temperature, less air relative humidity and solar radiation. In the case of a larger number of variables describing the pollution in the atmosphere, in all analyzed winter seasons the most common set of meteorological elements were wind speed and air temperature.

Experimental investigation into pulverized-coal combustion performance and NO formation using sub-stoichiometric ratios

The influence of using sub-stoichiometric ratios on pulverized-coal combustion and NO formation and reduction in a pulverized-coal combustion test system with a swirl burner was investigated. Local gas components, gas temperature, the char burnout rate, and carbon and nitrogen release rates were measured at different positions in the test facility. A method for determining the fuel-rich zone boundary within the swirl pulverized-coal flame is proposed, and a new parameter, for scaling the degree of released fuel-N conversion to NO is defined. The maximum NO concentration was at the boundary between the primary-air and secondary-air jets along the cross-sections near the burner, at different stoichiometric ratios. The overall NO emission concentration decreased from 661.89 mg/N m3 (at 6% O2) to 169.99 mg/N m3 (also at 6% O2) when the stoichiometric ratio decreased from 1.0 to 0.7. The conversion of released fuel-N to NO dominated the overall NO emissions at sub-stoichiometric ratios. Decreasing the stoichiometric ratio did not significantly affect the ignition performance of the burner, but the position of the flame center moved downstream and the slagging tendency increased.

Mechanistic Study on Adsorption and Oxidation of NO over Activated Carbon

Themechanism of NO adsorption and oxidation over activated carbon at lowtemperature has been studied by NO adsorption and oxidation, NO2adsorption and Fourier transform infrared spectroscopy. The results show thatwhen oxygen is present, activated carbon catalyses NO oxidation into NO2and a stable NO conversion rate is achieved. NO is adsorbed in the form of (NO)2due to the confinement effects of the activated carbon micropore. (NO)2is oxidized into NO2 by oxygen. The disproportionation of NO2gives NO and NO3, that causes the peak of the maximum NOconcentration. When the active sites are saturated by NO3, NO2adsorption and disproportionation gradually diminish, that results in NO2breakthrough and increases the concentration of NO2 to thestationary one. At the same time, the concentration of NO gradually decreasesto the stationary one after the maximum.

NO concentrations in laminar premixed CH4/O2/N2 flames with varying equivalence ratio

Number density and concentration of nitric oxide have been investigated in laminar premixed CH4/O2/N2 flames using laser-induced fluorescence technique. Emphasis was placed on quantitative measurements, which were taken in flames at various equivalence ratios ranging from 0.9 ∼ 3.0. The flow rate was fixed at 2 SLPM. The NO A-X (0,0) vibrational band around 226 nm was excited using a XeCl excimer-pumped dye laser. By selecting an appropriate NO transition, the interferences from elastic scattering and O2 fluorescence were minimized. Results show that the maximum NO concentration increased at the range of equivalence ratio from ϕ = 0.9 to 1.6, decreased from ϕ = 1.6 to 2.0 and slowly increased with increasing equivalence ratio above ϕ = 2.0. Also, the maximum NO concentration was at around the reaction zone.

Influence of Sugarcane Bagasse-derived Biochar Application on Nitrate Leaching in Calcaric Dark Red Soil

Application of biochar has been suggested to improve water- and fertilizer-retaining capacity of agricultural soil. The objective of this study was to evaluate the effects of bagasse charcoal (sugarcane [ L.] bagasse-derived biochar) on nitrate (NO) leaching from Shimajiri Maji soil, which has low water- and fertilizer-retaining capacity. The nitrate adsorption properties of bagasse charcoal formed at five pyrolysis temperatures (400-800° C) were investigated to select the most suitable bagasse charcoal for NO adsorption. Nitrate was able to adsorb onto the bagasse charcoal formed at pyrolysis temperatures of 700 to 800° C. Nitrate adsorption by bagasse charcoal (formed at 800° C) that passed through a 2-mm sieve was in a state of nonequilibrium even at 20 h after the addition of 20 mg N L KNO solution. Measurements suggested that the saturated and unsaturated hydraulic conductivity of bagasse charcoal (800° C)-amended soils are affected by changes in soil tortuosity and porosity and the presence of meso- and micropores in the bagasse charcoal, which did not contribute to soil water transfer. In NO leaching studies using bagasse charcoal (800° C)-amended soils with different charcoal contents (0-10% [w/w]), the maximum concentration of NO in effluents from bagasse charcoal-amended soil columns was approximately 5% less than that from a nonamended soil column because of NO adsorption by bagasse charcoal (800° C). We conclude that application of bagasse charcoal (800°C) to the soil will increase the residence time of NO in the root zone of crops and provide greater opportunity for crops to absorb NO.