Maximum Nitric Oxide Reduction Research Articles

Nitric oxide emission reduction and thermal characteristics of fuel-pulsed oscillating combustion in an industrial burner system

An experimental study was conducted on the effects of non-oscillating and oscillating combustions on nitric oxide (NO)-emission reduction and heat-transfer enhancement in an industrial low-NOx burner for reheating furnaces. Natural gas was periodically supplied by an oscillating control valve equipped with a rotary-type disk generating an oscillating fuel flow inside the furnace. The furnace temperatures and gas-species concentrations were measured for non-oscillating and oscillating combustions with the oscillating-frequency and duty ratio in the ranges of 1–5 Hz and 10–40%, respectively. The flame sizes in oscillating combustion increased (decreased) under a fuel-rich (fuel-lean) combustion condition, corresponding to the oscillating fuel-flow rates. The NO-reduction efficiency of the oscillating combustion increased as the oscillating frequency (Hz) decreased and as the duty ratio (%) increased in contrast to the non-oscillating combustion. The maximum NO reduction was ∼32% under the 1 Hz/40% oscillating combustion. Although the peak temperature was lower in the oscillating combustion than in the non-oscillating combustion, the overall temperature distribution in the oscillating condition was higher than that in the non-oscillating combustion. Thus, the oscillating combustion improved the furnace-heating performance by ∼9.8%. Consequently, it effectively facilitated NO-emission reduction and heat-transfer enhancement simultaneously.

An experimental study on the effect of operating parameters and sodium additive on the NO xOUT Process

An experimental study on the nitric oxide (NO) reduction through the NO x OUT Process has been conducted on a drop tube furnace experimental system. At 1223 K, when stoichiometric ratio of urea to NO ( β) is fixed at 1.5 and 2, the maximum NO reduction efficiency of 70.19% and 78.89% could be achieved, respectively. The efficiency curve is presented as a reversed “V” as a function of temperature and the corresponding “temperature window” is 108 K and 154 K at β = 1.5 and 2. Also, these two β values are preferable to determine injected urea quantity. As oxygen concentration is increased from 1.5% to 4.5%, efficiency is continuously depressed from 68.35% to 55.37% at β = 1.5 and from 77.87% to 62.76% at β = 2. At the same time, residence time ( τ) should be guaranteed at least 0.61 s for thorough NO reduction. When 50 ppm of NaOH, 25 ppm of Na 2CO 3 or 50 ppm of CH 3COONa is injected as promoted additive, the maximum NO reduction efficiency is, respectively, heightened to 82.07%, 81.36% and 81.81% at β = 1.5 and these values are even higher than the ones which are achieved at β = 2 if no additive is injected. For both β = 1.5 and 2, efficiency improvement becomes slow when NaOH is increased to 20 ppm. Meanwhile, when NaOH is injected at β = 2, efficiency of above 90% could be achieved and this value is comparable to the one achieved in advanced reburning.

Nitric Oxide Reduction with Ethanol on Palladium Surfaces: A Molecular Beam Study

Nitric oxide (NO) reduction with ethanol has been carried out with molecular beam instruments in order to understand the influence of ethanol blended gasoline on NO reduction. Maximum NO reduction and nitrogen production was observed between 500 and 600 K. Oxidation products, CO, CO 2 , and H 2 0 were also observed. Beam switching experiments have been performed between fuel-rich and fuel-lean compositions to demonstrate that the NO reduction can be managed under net oxidizing conditions on Pd surfaces. Nitrogen production only occurs transiently on the relatively clean Pd surface in the oxygen-rich condition due to slow build up and blockage of the reaction by surface oxygen atoms. This shows the need to maintain relatively oxygen free surfaces to manage NO reduction under net-oxidizing conditions by beam oscillation between fuel-rich and fuel-lean compositions.

Improvement on Hybrid SNCR-SCR Process for NO Control: a Bench Scale Experiment

The reducing agent [ammonia (NH3)] injection procedure was improved for the hybrid process of selective non-catalytic reduction followed by selective catalytic reduction (hybrid SNCR-SCR) to remove nitric oxide (NO) through a bench-scale experiment. Instead of injecting all of the NH3 from the SNCR inlet, part of it was injected from the SNCR inlet and part from the SCR inlet, to react with NO in the flue gas. The experiment resulted in the significant reduction of NO. The effects of the operational conditions such as the SNCR reaction temperature, the SCR reaction temperature, and the initial concentration ratio of NH3 to NO were also investigated. Under the initial NO concentration of 300 ppm (dry, 6%O2), the space velocities of SNCR 5100-6300 hr-1 , the space velocities of SCR 7100-10000 hr-1 , and with the initial concentration ratios of NH3 to NO 1.0-1.5, the best operational temperatures were discovered to be SNCR reaction of 850°C and SCR reaction of 350°C for the improved hybrid SNCR-SCR process. In addition, a correlation equation has been developed of the maximum NO reduction under the above bestoperational temperatures for the hybrid SNCR-SCR process, and closely fits with the experiment results.

Experimental and kinetic modeling study of the reduction of NO by hydrocarbons and interactions with SO 2 in a JSR at 1 atm ☆

The reduction of nitric oxide (NO) by a mixture of methane, ethylene and acetylene with and without addition of SO 2 has been studied in a fused silica jet-stirred reactor operating at 1 atm in simulated conditions of the reburning zone. The temperatures were ranging from 800 to 1400 K. In these experiments, the initial mole fractions of NO and SO 2 were 0 or 1000 ppm, that of methane, ethylene and acetylene were, respectively, 2400, 1200 and 600 ppm. The equivalence ratio has been varied from 0.5 to 2.5. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO reduction occurs slightly above stoichiometric conditions. The addition of SO 2 inhibited the process of reduction of NO under the present conditions. The present results generally follow those obtained in previous studies involving simple hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (1006 reversible reactions and 145 species). An overall reasonable agreement between the present data and the modeling was obtained. Also, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethane, ethylene, a natural gas blend (methane–ethane 10:1). The kinetic modeling indicates that the reduction of NO proceeds via the following sequence of reactions: HCCO+NO=HCNO+CO; HCCO+NO=HCN+CO 2; HCN+O=NCO+H; HCN+O=NH+CO; HCN+H=CN+H 2; HCNO+H=HCN+OH; CN+O 2=NCO+O; NCO+H=NH+CO; NCO+NO=N 2O+CO; NCO+NO=CO 2+N 2; NH+NO=N 2O+H; NH+NO=N 2+OH. The inhibition of this process by SO 2 is explained by the sequence of reactions H+SO 2+M=HOSO+M and HOSO+H=SO 2+H 2 that acts as a termination process: H+H+M=H 2+M.

Reduction of NO by n-Butane in a JSR: Experiments and Kinetic Modeling

A study of the reduction of nitric oxide (NO) by n-butane, in simulated conditions of a reburning zone, has been undertaken in a fused silica jet-stirred reactor operating at 1 atm. The temperatures ranged from 1100 to 1450 K, the initial mole fraction of NO was 1000 ppm, and that of n-butane was 2000−2200 ppm. The equivalence ratio (φ = [fuel%/O2%]/[fuel%/O2%]at φ=1) was varied from 0.68 to 2. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO reduction occurs, slightly above stoichiometric conditions. Generally, the present results follow those obtained in previous studies involving simple hydrocarbons or natural gas as reburn-fuel. The oxidation of n-butane was also studied without NO in the same conditions of temperature, pressure, and residence time. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (892 reversible reactions and 113 species). An overall reasonabl...

00/00994 Prediction of NOx control by basic and advanced gas reburning using the Two-Stage Lagrangian model

The reduction of nitric oxide (NO) by acetylene in simulated conditions of the reburning zone has been undertaken in a fused silica jet-stirred reactor operating at 1 atm, at temperatures ranging from 1050 to 1300 K. In the present experiment, the initial mole fraction of NO was 1000 ppm, and that of acetylene was 4400 ppm. The equivalence ratio has been varied from 0.75 to 2. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO reduction occurs slightly above stoichiometric conditions. Thus, operating in optimal NO-reburning conditions is possible for particular combinations of equivalence ratio and temperature. The present results generally follow those obtained with previous studies involving simple hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiment was performed using an updated and improved kinetic scheme (877 reversible reactions and 122 species). An overall reasonable agreement between the present data and the modeling was obtained although improvements of the model are still necessary. Also, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethane, ethylene, a natural gas blend (methane–ethane 10:1) and HCN, and the low temperature interactions between NO and simple alkanes. According to this study, the main route to NO-reduction by acetylene involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: C2H2+O→HCCO, CH; HCCO+NO→HCNO+CO and HCN+CO2; CH+NO→HCN; HCNO+H→HCN+OH; HCN+O→NCO→NH; NH+H→N; N+NO→N2; NH+NO→N2O followed by N2O+H→N2.

Experimental and kinetic modeling of the reduction of NO by isobutane in a Jsr at 1 atm

A kinetic study of the reduction of nitric oxide (NO) by isobutane in simulated conditions of the reburning zone was carried out in a fused silica jet-stirred reactor operating at 1 atm, at temperatures ranging from 1100 to 1450 K. In this new series of experiments, the initial mole fraction of NO was 1000 ppm, that of isobutane was 2200 ppm, and the equivalence ratio was varied from 0.75 to 2. It was demonstrated that for a given temperature, the reduction of NO is favored when the temperature is increased and a maximum NO reduction occurs slightly above stoichiometric conditions. The present results generally follow those reported in previous studies of the reduction of NO by C1 to C3 hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (979 reversible reactions and 130 species). An overall reasonable agreement between the present data and the modeling was obtained. Furthermore, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethylene, ethane, acetylene, a natural gas blend (methane-ethane 10:1), propene, and HCN. According to this study, the main route to NO reduction by isobutane involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: iC4H10 → C3H6 → C2H4 → C2H3 → C2H2 → HCCO; HCCO + NO → HCNO + CO and HCN + CO2; HCNO + H → HCN → NCO → NH; NH + NO → N2 and NH + H → followed by N + NO → N2; NH + NO → N2O followed by N2O + H → N2. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 365–377, 2000

NO-Reduction by Ethane in a JSR at Atmospheric Pressure: Experimental and Kinetic Modeling

Abstract The reduction of nitric oxide (NO) by ethane in simulated reburning conditions has been studied in a fused silica jet-stirred reactor operating at 1 atm, in the temperature range 900-1400 K, in diluted conditions. In the present experiments, the initial mole fraction of NO was 1000 ppm, that of ethane was 4400 ppm. The equivalence ratio has been varied from 0.75 to 2. It was demonstrated that the reduction of NO varies as the temperature and that, for a given temperature, a maximum NO reduction occurs slightly above stoichiometric conditions. Then, optimal NO-reburning conditions can be achieved for particular combinations of equivalence ratio and temperature. The present results generally show the same trends as observed in previous studies using simple hydrocarbons or natural gas (NG) as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using an updated and improved kinetic scheme (877 reversible reactions and 122 species). An overall reasonable agreemen...

The kinetics of C 1 to C 4 hydrocarbons/no interactions in relation with reburning

A study of the reduction of nitric oxide (NO) by C 1 to C 4 hydrocarbons, in simulated conditions of the reburning zone, was undertaken in a fused-silica jet-stirred reactor (JSR) operating at 1 atm. The temperatures ranged from 1000 to 1450 K: the initial mole fractions of NO were 750–1000 ppm, and the initial mole fraction of reburn fuel corresponded to 8800 ppm of carbon. The equivalence ratio varied from 0.7 to 2.5. It was demonstrated that the reduction of NO increases as the temperature rises, and that for a given temperature, a maximum NO reduction occurs, slightly above stoichiometric conditions. Generally, the present results follow those obtained in previous studies involving simple hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiments was performed using a single updated and improved kinetic scheme (892 reversible reactions and 113 species). An overall reasonable agreement between the experimental data and the modeling was obtained. Furthermore, the proposed kinetic mechanism was successfully used to model the JSR heat oxidation of the fuels considered here. HCN oxidation in a JSR, C 1 to C 2 flames, and NO reduction by CH 4 in a JSR at 1580–1800 K. According to this study, NO reduction by the hydrocarbons mainly proceeds via reaction with the ketenyl radical: fuel →C 2 H 2 →HCCO, CH; HCCO+NO→HCNO+CO and HCN+CO 2 ; CH 2 +NO →HCN; HCNO+H→HCN+OH; HCN+O→NCO→NH; NH+H→N; N+NO→N 2 ; NH+NO→N 2 O followed by N 2 O+H→N 2 .

Experimental and kinetic modeling of nitric oxide reduction by acetylene in an atmospheric pressure jet-stirred reactor

The reduction of nitric oxide (NO) by acetylene in simulated conditions of the reburning zone has been undertaken in a fused silica jet-stirred reactor operating at 1 atm, at temperatures ranging from 1050 to 1300 K. In the present experiment, the initial mole fraction of NO was 1000 ppm, and that of acetylene was 4400 ppm. The equivalence ratio has been varied from 0.75 to 2. It was demonstrated that the reduction of NO varies as the temperature and that for a given temperature, a maximum NO reduction occurs slightly above stoichiometric conditions. Thus, operating in optimal NO-reburning conditions is possible for particular combinations of equivalence ratio and temperature. The present results generally follow those obtained with previous studies involving simple hydrocarbons or natural gas as reburn fuel. A detailed chemical kinetic modeling of the present experiment was performed using an updated and improved kinetic scheme (877 reversible reactions and 122 species). An overall reasonable agreement between the present data and the modeling was obtained although improvements of the model are still necessary. Also, the proposed kinetic mechanism can be successfully used to model the reduction of NO by ethane, ethylene, a natural gas blend (methane–ethane 10:1) and HCN, and the low temperature interactions between NO and simple alkanes. According to this study, the main route to NO-reduction by acetylene involves ketenyl radical. The model indicates that the reduction of NO proceeds through the reaction path: C 2H 2+O→HCCO, CH; HCCO+NO→HCNO+CO and HCN+CO 2; CH+NO→HCN; HCNO+H→HCN+OH; HCN+O→NCO→NH; NH+H→N; N+NO→N 2; NH+NO→N 2O followed by N 2O+H→N 2.

The selective catalytic reduction of nitric oxide by propylene over Pt/SiO 2

Kinetic and in situ infrared measurements were utilized in the investigation of the selective catalytic reduction (SCR) of nitric oxide (NO) by propylene (C 3H 6) over a Pt/SiO 2 catalyst. The results of these studies indicate the presence of two kinetically distinct regions at temperatures above and below the temperature of maximum NO reduction. They further suggest that the activation of the hydrocarbon by molecular oxygen is the kinetically significant step in the low temperature region. Similar results were previously obtained with a Pt/Al 2O 3 catalyst, suggesting that the mechanism of the reaction is the same in both cases. The in situ infrared spectra of these two catalysts indicate the presence of surface isocyanate and cyanide groups in both cases, suggesting that one or both of these species may be involved in the reaction.

Kinetic Investigation of the Selective Catalytic Reduction of Nitric Oxide by Propylene over Pt/Al2O3

A kinetic investigation of the selective catalytic reduction (SCR) of nitric oxide (NO) by propylene (C{sub 3}H{sub 6}) was conducted over a 0.8 wt% Pt/Al{sub 2}O{sub 3} catalyst in the temperature range of 200--500 C. The results indicate the presence of two kinetically distinct regions at temperatures above and below the temperature of maximum NO reduction. The activation of the C{sub 3}H{sub 6} is kinetically significant in the low-temperature region. Nitrogen selectivities are significantly different in the two regions and are primarily affected by the amount of C{sub 3}H{sub 6} available for the NO--C{sub 3}H{sub 6} reaction.

Reduction of Nitrogen Oxides in Engine Exhaust Gases by the Addition of Cyanuric Acid

Nitric oxide concentrations in a portion of the exhaust of a diesel engine operated with equivalence ratios between 0.25 and 0.75 were reduced by up to 98 percent by the addition of cyanuric acid. The cyanuric acid was combined with the exhaust gas in an electrically heated quartz flow reactor. The effects of the key process parameters (temperature, exhaust gas composition and residence time, and the overall engine equivalence ratio) on NO reduction by cyanuric acid were investigated. Nitric oxide reduction was evident at flow reactor temperatures above 700 K. The maximum nitric oxide reduction varied from 80 percent for a reactor temperature of 1180 K and an engine equivalence ratio of 0.25 to 98 percent for a temperature of 1120 K and an equivalence ratio of 0.75. The temperature range over which 60 percent or greater nitric oxide reduction was obtained was 1100 to 1340 K. Increasing the exhaust gas carbon monoxide concentration lowered the required reactor temperature and increased the temperature range for significant nitric oxide reduction. Increasing the exhaust gas nitric oxide concentration lowered the ratio of cyanuric acid to nitric oxide required for maximum nitric oxide reduction.