Decrease In NOx Research Articles

The experimental study of fly ash recirculation combustion characteristics on a circulating fluidized bed combustor

Fly ash recirculation combustion (FARC) technology is an effective way to improve the combustion performance due to the improvement of carbon burnout as well as the utilization of calcium oxide. In order to study the effect of FARC on operation and emission characteristics of CFB boilers, a series of experiments were carried out on a lab-scale CFB combustor by using two types of fly ash (desulfurization and non-desulfurization fly ashes). Results show that with FARC, the temperature distribution in the furnace becomes uniform. The difference between the two different types of fly ash is mainly reflected in the emissions of SO2 and NOX. Desulfurization fly ash would increase the NOX emission while decrease the SO2 emission, and the optimum desulfurization temperature is 880°C. On the contrary, non-desulfurization fly ash would increase SO2 emission while decrease NOX emission. FARC could effectively improve the combustion performance, as the recirculation rate increases from 0 to 0.3, the combustion efficiency increases by 2% for both two fly ashes and the CO emission decreases, but the particulate matter emission increases. For desulfurization fly ash, Ca/S molar ratio should be appropriately reduced for inhibiting the NOX emission when limestone was used for in situ desulfurization.

Abstract 169: Stable Nitric Oxide Metabolites Levels and Their Relation to the Metabolic Syndrome Components in Essential Hypertension

Objective: To investigate levels of the stable nitric oxide metabolites (NOx) in relation to components of the metabolic syndrome (MS) in essential hypertension (EH) Methods: We examined 124 untreated patients with EH (mean age 51.4 ± 6.5 years, mean hypertension duration 8,5±7,6 years) and 25 healthy volunteers with comparable age (47.2 ± 7.8 years, p>0,05). Plasma leptin levels were measured by radioimmunoassay, plasma NOx - by spectrophotometry. Results were processed with Statistica 6.0 software. Results: Visceral obesity had 64% of hypertensive patients, dyslipidemia - 80.6%, hyperglycemia - 41,6%, MS - 24%. In 32% the MS diagnosis was based on the presence of two additional criteria, in 68% - on three. NOx levels were significantly higher in hypertensives (43,18±21, μmol/l) than in controls (28.3 ± 9.6 μmol/l) ( p = 0.01). In patients with hyperglycemia NOx concentration was higher (46,5 ± 23,9 μmol/l) than in those without it (38,6±18, μmol/l)(p<0,05). NOx levels correlated with blood glucose levels (r=0,32, p<0,05). NOx concentration did not differ between hypertensives with or without dyslipidemia (43,2±22,2 and 42,05±21,1 μmol/l, accordingly p>0,05). Nonobese hypertensives had lower NOx concentration than obese hypertensives (38,8±17,9 and 48,5±24,7 μmol/l, p<0,05). NOx levels correlated with the presence (r=-0,44, p<0,05) and degree of obesity (r=-0,3, p<0,05). NOx levels were lower in patients with MS (31,6±11,3 and 47,05±20,7 μmol/l, p<0,05). NOx levels decreased with the increase of additional MS criterias: 37,99 ± 12,6 μmol/l in the presence of 2 and 28,3 ± 9,6 μmol/l in the presence of 3 criteria (p<0,05). NOx levels correlated with the amount MS components (r=-0,38, p<0,05). Hypertensives with high leptin levels had lower NOx concentration (29 ± 12,2 μmol/l), compared to hypertensives with normal leptin levels (34,7±10,5 μmol/l) (p<0,05). Conclusion: In essential hypertension NOx metabolism differs in relation to metabolic status. Hypertension per se and hyperglycemia increase NOx levels, whereas MS and its essential signsas visceral obesity and high plasma leptin level decrease NOx levels.

Experimental Research on Utilization of Steel Rolling Sludge in Sintering Process

Abstract A quantity of steel rolling sludge (SRS) produced in the rolling mill is harm to the environment and difficult to dispose. This article is devoted to study on utilization of SRS in sintering process. A sinter pot system with capacity of 75 kg was established. The sintering time, the flue gas temperature, the sintering temperature and the suction pressure in sintering process were measured. Besides the sinter quality, air pollutants discharged from the sintering process with the mass fraction of SRS ranging from 0 to 3% was investigated. The results showed that the CO2 concentration is corresponding to the sintering process, the SO2 concentration has a self-sustaining characteristic and the NOX concentration maintains stability. Increase in mass fraction of SRS leads to the decrease of sintering temperature, particle size, tumbler index and basicity of the sinter. Besides, the sintering time and the average concentration of NOX decrease first and then increase, while the suction pressure appears an opposite trend with increasing mass fraction of SRS. Moreover, the average concentration of CO2 and SO2 both decrease with increasing mass fraction of SRS, and the fuel consumption per sinter produced is the least when the mass fraction of SRS is 2%. Therefore, when the mass fraction of SRS was 2%, the sintering process had the best performance in consideration of sinter quality, emission of air pollutants and behaviors in sintering process.

Catalytic combustion of brown coal particulates over ceramometal honeycomb catalyst

Catalytic combustion of brown coal particulates over CuO/Al 2 O 3 /FeAlO/ FeAl honeycomb ceramometal catalyst in the fluidized bed regime with the sand as a heat transfer material has been studied during 100 hours at 973-1023 K. The catalyst before and after tests has been analyzed. The coal conversion in the presence of cermet catalyst was found to be in the range of 97.8-98.5% while without catalyst it was lower (91.2-94.6%). A substantial decrease of CO, NOx and SO 2 emissions in catalytic combustion was also demonstrated.

Development of a Nitrogen-enrichment/Humidification Membrane System for NOx Emission Reduction in a Marine Diesel Engine

Since the IMO Tier III standards are scheduled to come into effect at the beginning of 2016, the development of NOx reduction technologies is critical for marine diesel engines. The authors are developing an NHM (Nitrogen-enrichment / Humidification Membrane) system as a method to reduce NOx emissions. The NHM system is composed of polymeric gas separation membranes. Oxygen and water molecules can permeate the membranes faster than nitrogen molecules, so the system can feed SOx free, clean nitrogen-enriched and humidified intake air into an engine. The NHM system was connected to a four-stroke high-speed engine having a rated power of 103 kW and a rated speed of 2400 rpm. NOx concentration in the exhaust gas was measured under loads of 75%, 50%, and 25%. The results show a remarkable decrease in NOx to a value less than 1.9 g/kWh which represents an 80% reduction compared to normal operating conditions.

Simulation and Optimization of Absorption Column of the Dual-Pressure Nitric Acid Production Process

Simulation of the absorption column was studied. A new mathematic model was developed and tested against the actual operation data. From this, the accuracy of the model was proved. The pressure, temperature and gas composition on absorption effect was discussed. And from the point of the practical production, more optimized operating conditions of the nitric acid absorption tower were showed. It makes the dilute acid concentration increase by 3 percent and the exhaust emission of NOx decrease by 45ppm.

The Effect of the Thickness of the Sensitive Layer on the Performance of the Accumulating NOx Sensor

A novel and promising method to measure low levels of NOx utilizes the accumulating sensor principle. During an integration cycle, incoming NOx molecules are stored in a sensitive layer based on an automotive lean NOx trap (LNT) material that changes its electrical resistivity proportional to the amount of stored NOx, making the sensor suitable for long-term detection of low levels of NOx. In this study, the influence of the thickness of the sensitive layer, prepared by multiple screen-printing, is investigated. All samples show good accumulating sensing properties for both NO and NO2. In accordance to a simplified model, the base resistance of the sensitive layer and the sensitivity to NOx decrease with increasing thickness. Contrarily, the sensor response time increases. The linear measurement range of all samples ends at a sensor response of about 30% resulting in an increase of the linearly detectable amount with the thickness. Hence, the variation of the thickness of the sensitive layer is a powerful tool to adapt the linear measurement range (proportional to the thickness) as well as the sensitivity (proportional to the inverse thickness) to the application requirements. Calculations combining the sensor model with the measurement results indicate that for operation in the linear range, about 3% of the LNT material is converted to nitrate.

Reduction of the Pollutant Emissions from a Diesel Engine by the Application of Dimethyl Ether (DME) and the Control of the Intake Oxygen Flow Rate

The aim of this study was to investigate the effects of varying the global equivalence ratio and intake oxygen flow-rate on the combustion and exhaust emission characteristics of dimethyl ether (DME)-fueled combustion engine. This study dealt with the reduction characteristics of HC and CO emissions, as well as a simultaneous decrease of NOx and soot in a DME-fueled single-cylinder combustion engine. Our findings demonstrate that increasing the global equivalence ratio while holding the intake oxygen flow-rate constant caused the premixed combustion duration (CA10-CA50) to increase. Additionally, it was observed that decreasing the intake oxygen flow-rate while holding the injection quantity constant shortens the duration of CA10-CA50. In this investigation, simultaneous reduction of soot and indicated specific (IS)-NOx emissions from a diesel engine can be achieved by fueling with DME and setting a high EGR rate (low intake oxygen flow-rate). Further, applying high equivalence ratio together with a high EGR rate resulted in a near zero level of soot and IS-NOx emissions in DME combustion. In addition, DME combustion yielded lower IS-CO and IS-HC emissions than diesel combustion, even with a low intake oxygen flow-rate.

Airborne and ground‐based observations of a weekend effect in ozone, precursors, and oxidation products in the California South Coast Air Basin

Airborne and ground‐based measurements during the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May/June 2010 show a weekend effect in ozone in the South Coast Air Basin (SoCAB) consistent with previous observations. The well‐known and much‐studied weekend ozone effect has been attributed to weekend reductions in nitrogen oxide (NOx = NO + NO2) emissions, which affect ozone levels via two processes: (1) reduced ozone loss by titration and (2) enhanced photochemical production of ozone due to an increased ratio of non‐methane volatile organic compounds (VOCs) to NOx. In accord with previous assessments, the 2010 airborne and ground‐based data show an average decrease in NOx of 46 ± 11% and 34 ± 4%, respectively, and an average increase in VOC/NOxratio of 48 ± 8% and 43 ± 22%, respectively, on weekends. This work extends current understanding of the weekend ozone effect in the SoCAB by identifying its major causes and quantifying their relative importance from the available CalNex data. Increased weekend production of a VOC‐NOxoxidation product, peroxyacetyl nitrate, compared to a radical termination product, nitric acid, indicates a significant contribution from increased photochemical production on weekends. Weekday‐to‐weekend differences in the products of NOx oxidation show 45 ± 13% and 42 ± 12% more extensive photochemical processing and, when compared with odd oxygen (Ox = O3 + NO2), 51 ± 14% and 22 ± 17% greater ozone production efficiency on weekends in the airborne and ground‐based data, respectively, indicating that both contribute to higher weekend ozone levels in the SoCAB.

Experimental Investigation of the Effect of Using Ethanol-Blended Diesel Fuels on Engine Performance and Exhaust Emissions

In this experimental work, the variations of cylinder pressure and exhaust emissions using ethanol–diesel fuel mixtures with different blends and compression ratios in a diesel engine are reported. Experiments are carried out using an ASTM-CFR monocylinder test engine, operated at constant engine speed and without loading. Comparison of the results with standard Eurodiesel fuel combustion experiments indicate that NOx, soot, and CO emissions decrease, whereas CO2 emissions increase with increaseed ethanol concentration. An increase in the compression ratio results in a decrease in NOx and CO2 emissions and an increase in CO and soot emissions.

Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume

Abstract. Observations of NOx in the Sacramento, CA region show that mixing ratios decreased by 30 % between 2001 and 2008. Here we use an observation-based method to quantify net ozone (O3) production rates in the outflow from the Sacramento metropolitan region and examine the O3 decrease resulting from reductions in NOx emissions. This observational method does not rely on assumptions about detailed chemistry of ozone production, rather it is an independent means to verify and test these assumptions. We use an instantaneous steady-state model as well as a detailed 1-D plume model to aid in interpretation of the ozone production inferred from observations. In agreement with the models, the observations show that early in the plume, the NOx dependence for Ox (Ox = O3 + NO2) production is strongly coupled with temperature, suggesting that temperature-dependent biogenic VOC emissions and other temperature-related effects can drive Ox production between NOx-limited and NOx-suppressed regimes. As a result, NOx reductions were found to be most effective at higher temperatures over the 7 year period. We show that violations of the California 1-h O3 standard (90 ppb) in the region have been decreasing linearly with decreases in NOx (at a given temperature) and predict that reductions of NOx concentrations (and presumably emissions) by an additional 30 % (relative to 2007 levels) will eliminate violations of the state 1 h standard in the region. If current trends continue, a 30 % decrease in NOx is expected by 2012, and an end to violations of the 1 h standard in the Sacramento region appears to be imminent.

217 外部混合式3流体噴射弁を用いたNOx・PMの低減(GS-7燃焼(2))

217 外部混合式3流体噴射弁を用いたNOx・PMの低減(GS-7燃焼(2))

Role of mouse cerebellar nicotinic acetylcholine receptor (nAChR) α4β2- and α7 subtypes in the behavioral cross-tolerance between nicotine and ethanol-induced ataxia

We have demonstrated that nicotine attenuated ethanol-induced ataxia via nicotinic-acetylcholine-receptor (nAChR) subtypes α4β2 and α7. In the present study, ethanol (2g/kg; i.p.)-induced ataxia was assessed by Rotorod performance following repeated intracerebellar infusion of α4β2- and α7-selective agonists. Localization of α4β2 and α7 nAChRs was confirmed immunohistochemically. Cerebellar NOx (nitrite+nitrate) was determined flurometrically. Repeated intracerebellar microinfusion of the α4β2-selective agonist, RJR-2403 (for 1, 2, 3, 5 or 7 days) or the α7-selective agonist, PNU-282987 (1, 2, 3 or 5 days), dose-dependently attenuated ethanol-induced ataxia. These results suggest the development of cross-tolerance between ethanol-induced ataxia and α4β2 and α7 nAChR agonists. With RJR-2403, the cross-tolerance was maximal after a 5-day treatment and lasted 48h. Cross-tolerance was maximal after a 1-day treatment with PNU-282987 and lasted 72h. Pretreatment with α4β2- and α7-selective antagonists, dihydro-β-erythroidine and methyllycaconitine, respectively, prevented the development of cross-tolerance confirming α4β2 and α7 involvement. Repeated agonist infusions elevated cerebellar NOx 16h after the last treatment while acute ethanol exposure decreased it. Pretreatment with repeated RJR-2403 or PNU-282987 reversed ethanol-induced decrease in NOx. The NOx data suggests the involvement of the nitric oxide (NO)–cGMP signaling pathway in the cross-tolerance that develops between α4β2- and α7-selective agonists and ethanol ataxia. Both α4β2 and α7 subtypes exhibited high immunoreactivity in Purkinje but sparse expression in molecular and granular cell layers. Our results support a role for α4β2 and α7 nAChR subtypes in the development of cross-tolerance between nicotine and ethanol with the NO signaling pathway as a potential mechanism.

Modeling the regional impact of ship emissions on NO<sub>x</sub> and ozone levels over the Eastern Atlantic and Western Europe using ship plume parameterization

Abstract. In general, regional and global chemistry transport models apply instantaneous mixing of emissions into the model's finest resolved scale. In case of a concentrated source, this could result in erroneous calculation of the evolution of both primary and secondary chemical species. Several studies discussed this issue in connection with emissions from ships and aircraft. In this study, we present an approach to deal with the non-linear effects during dispersion of NOx emissions from ships. It represents an adaptation of the original approach developed for aircraft NOx emissions, which uses an exhaust tracer to trace the amount of the emitted species in the plume and applies an effective reaction rate for the ozone production/destruction during the plume's dilution into the background air. In accordance with previous studies examining the impact of international shipping on the composition of the troposphere, we found that the contribution of ship induced surface NOx to the total reaches 90% over remote ocean and makes 10–30% near coastal regions. Due to ship emissions, surface ozone increases by up to 4–6 ppbv making 10% contribution to the surface ozone budget. When applying the ship plume parameterization, we show that the large scale NOx decreases and the ship NOx contribution is reduced by up to 20–25%. A similar decrease was found in the case of O3. The plume parameterization suppressed the ship induced ozone production by 15–30% over large areas of the studied region. To evaluate the presented parameterization, nitrogen monoxide measurements over the English Channel were compared with modeled values and it was found that after activating the parameterization the model accuracy increases.

Revamping of treatment furnaces with Tenova FlexyTech®TLX burners

Tenova started a research program in 2002 for strongly lowering NOx emissions. After the excellent results achieved in the reheating furnaces, the Tenova FlexyTech® burner family was enlarged with the TLX burner whose first application was in the furnace for austenitizing treatment of seamless tubes at TenarisDalmine (2006). The main goals of the revamping were strongly decreasing NOx emissions and increasing the productivity. The results after one year of operation are presented.

Plasma-Chemical Hybrid NOx Reduction System for Commercial Cogeneration Boiler -Recent Status Report-

Operation tests of the smoke-tube boiler emission NOx treatment plant which consists of a plasma ozonizer using a pressure swing adsorption (PSA) oxygen generator and silent discharge for indirect NO oxidation and a Na2SO3 chemical scrubber are carried out for cogeneration boilers which uses a city gas and heavy oil as a fuel based on our proposed plasma-chemical hybrid NOx reduction principle. It is clear that amount of NO removed is almost same as the amount of corresponding O3 concentration to oxidize NO regardless of fuels and flow rates of flue gas. After the relation between oxidation-reduction potential (ORP) and the NOx removal efficiency is obtained, continuous operation tests of this plant are performed. For gas firing boiler emission, the NO complete removal and the decrease in NOx from 32 ppm to 3 ppm are achieved for 300 min by keeping -30 mV of ORP. For the treatment of heavy oil boiler emission, the decrease in NOx from 90 ppm to less than 25 ppm is maintained for 250 min. It is demonstrated that the high NOx removal performance can be maintained for a long time by keeping the optimum value of ORP.

Exercise Training, NADPH Oxidase p22phox Gene Polymorphisms, and Hypertension

Oxidative stress that is mediated through NADPH oxidase activity plays a role in the pathology of hypertension, and aerobic exercise training reduces NADPH oxidase activity. The involvement of genetic variation in the p22phox (CYBA) subunit genes in individual oxidative stress responses to aerobic exercise training has yet to be examined in Pre and Stage 1 hypertensives. Ninety-four sedentary Pre and Stage 1 hypertensive adults underwent 6 months of aerobic exercise training at a level of 70% VO2max to determine whether the CYBA polymorphisms, C242T and A640G, were associated with changes in urinary 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), urinary nitric oxide metabolites (NOx), and plasma total antioxidant capacity (TAC). Demographic and subject characteristics were similar among genotype groups for both polymorphisms. At baseline, a significant (P = 0.03) difference among the C2424T genotype groups in 8-iso-PGF2alpha levels was detected, with the TT homozygotes having the lowest levels and the CC homozygotes having the highest levels. However, no differences were found at baseline between the A640G genotype groups. After 6 months of aerobic exercise training, there was a significant increase in VO2max (P < 0.0001) in the entire study population. In addition, there were significant increases in both urinary 8-iso-PGF2alpha (P = 0.002) and plasma TAC (P=0.03) levels and a significant decrease in endogenous urinary NOx (P < 0.0001). Overall, aerobic exercise training elicited no significant differences among genotype groups in either CYBA variant for any of the oxidative stress variables. We found that compared with CYBA polymorphisms C242T and A640G, it was aerobic exercise training that had the greatest influence on the selected biomarkers; furthermore, our results suggest that the C242T CYBA variant influences baseline levels of urinary 8-iso-PGF2alpha but not the aerobic exercise-induced responses.

Nitric Oxide Metabolites, Leukocyte Activation Markers and Oxidative Status in Dialyzed Subjects

Aims: Our purpose was to evaluate, in a group of 42 end-stage renal disease patients who regularly undergo hemodialysis, some indexes of leukocyte activation, nitric oxide metabolites (NOx) and other parameters that reflect the oxidative stress before and after a standard hemodialysis session. Methods: Elastase and myeloperoxidase (MPO) were determined by means of ELISA. The NO production was evaluated by a micromethod which measures the concentration of NOx. The oxidation of polyunsaturated fatty acids was evaluated in plasma by detection of thiobarbituric acid-reactive substances (TBARS). Total antioxidant status (TAS) was obtained using spectrophotometry. Results: At baseline, we observed an increase of elastase, NOx, TBARS and TAS, without any variation of MPO. After the dialysis session, we found an increase in elastase and MPO, a decrease in NOx and TAS and no variation in TBARS. No modification occurred after subdividing the patients in two subgroups. Conclusions: Our data confirm the involvement of leukocytes and oxidative stress in hemodialysis patients.

Performance and emissions of motorcycle engines using water-fuel emulsions

This article studied water?gasoline emulsions for reducing the NOx emissions of a motorcycle engine. Emulsified gasoline fuels of 0, 5, 10 and 15% water by volume were used in a four-stroke, 125 cc, port injection, spark-ignition engine. Both full throttle speed ranging from 2,000 to 7,000 rpm and low load were tested. The engine torque, fuel consumption, exhaust emissions and combustion characteristics were investigated. The experimental results show that the engine torque and fuel consumption are improved for 5 and 10% water emulsions. However, at 15%, the engine torque and fuel consumption deteriorate and the exhaust temperature is increased owing to slow burn rate. The exhaust emissions of NOx and CO decrease as the water percentage in the emulsion increases. A higher oxygen concentration in exhaust gas of emulsified fuel was found, which results in lower CO emission. The HC emission is increased with increasing water content, which might be caused by the thicker quench layer of emulsified fuel combustion. An appropriate concentration of water in the emulsified gasoline fuel for a 125 cc motorcycle engine is found to be 10%.

Study of Fuel Temperature Effects on Fuel Injection, Combustion, and Emissions of Direct-Injection Diesel Engines

The influence of inlet liquid fuel temperature on direct-injection diesel engines can be noticeable and significant. The work in this paper investigates the effects of inlet fuel temperature on fuel-injection in-cylinder combustion, and output performance and emissions of medium-speed diesel engines. An enhanced understanding and simplified modeling of the variations in the main fuel-injection parameters affected by inlet fuel temperature are developed. The study indicates that the main injection parameters affected include the injection timing at the injector end relative to the injection-pump actuation timing, the fuel-injection rate, the fuel-injection duration, and the injection spray atomization. The primary fuel temperature effects on the injection parameters are from the fuel bulk modulus of elasticity and the density with the fuel viscosity less significant as the injector-nozzle flow is usually in a turbulent region. The developed models are able to predict the changes in the injection parameters versus the inlet fuel temperature. As the inlet fuel temperature increases, the nozzle fuel-injection-start timing is predicted to be relatively retarded, the injection rate is reduced, and the needle-lift duration is prolonged from the baseline. The variation trends of the engine outputs and emissions versus fuel temperature are analyzed by considering its consequent effect on in-cylinder combustion processes. It is predicted that raising fuel temperature would result in an increase in each of CO, HC, PM, and smoke emissions, and in a decrease in NOx, and may adversely affect the fuel efficiency for a general type of diesel engine at a full-load condition. The experimental results of the outputs and emissions from testing a medium-speed four-stroke diesel engine agreed with the trends analytically predicted. The understanding and models can be applied to compression-ignition direct-injection liquid fuel engines in general.