Structure, chemical mechanism and properties of premixed flames in mixtures of carbon monoxide, nitrogen and oxygen with hydrogen and water vapour

1981 ◽  
Vol 303 (1476) ◽  
pp. 181-212 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Low Temperature ◽  
Water Vapour ◽  
Mole Fraction ◽  
Atmospheric Pressure ◽  
Burning Velocity ◽  
Chemical Mechanism ◽  
Reduced Pressure ◽  
Atom Concentration ◽  
Water Gas

Implicit solutions of the time-dependent flame equations have been used to calculate, for assumed reaction mechanisms, the expected structures and properties of a series of hydrogen-carbon monoxide-oxygen-nitrogen flames, some containing traces of added water vapour, at atmospheric and reduced pressures. Predicted burning velocities at atmospheric pressure have been compared with: ( a ) recent measurements, reported here, of the effect of addition of up to 10 % carbon monoxide on the burning velocity of a low temperature hydrogen-oxygennitrogen flame; ( b ) previous measurements by Scholte & Vaags (1959c) on dry hydrogen-carbon monoxide-air mixtures over the whole composition range on the fuel-rich side of stoichiometric; and ( c ) previously reported measurements by Jahn (1934), Badami & Egerton (1955), Scholte & Vaags (1959 b )and Wires et al . (1959) for moist carbon monoxide-air or carbon monoxide-oxygen mixtures, with or without traces of added hydrogen. Additionally, the following comparisons are made: ( d )The mole fraction profile for the decay of a trace of carbon dioxide added to the low temperature hydrogen-oxygen-nitrogen flame has been recalculated with the aid of the full reaction mechanism, for comparison with the previously reported measurements of Dixon-Lewis et al. (1965). ( e ) Computed structures of two hydrogen-carbon monoxide-oxygen-argon flames burning at reduced pressure have been compared with previous measurements by Fenimore & Jones (1959) and Vandooren et al . (1975). ( f ) The mole fraction ratio X co /X CO 2 in the burnt gas from a low temperature, fuel-rich hydrogen-carbon monoxide-oxygen-argon flame at atmospheric pressure was measured by using a mass spectrometer. The measured ratio agreed to within 1 % with that predicted by computation of the complete flame properties. Both the calculated and measured ratios were higher than would correspond with the establishment of the water gas equilibrium in the flame. The major part of the observed changes in burning velocity from those of hydrogen-air mixtures can be satisfactorily explained by the addition of the single reaction (xxi) , OH + CO ⇌ C O 2 + H , ( xxi ) to the mechanism already established for the hydrogen-oxygen-nitrogen flame system (Dixon-Lewis 1979). This applies particularly to fuel-lean flames and to fuel-rich mixtures not too far from stoichiometric. For fuel-rich flames further from stoichiometric, and particularly for the measurements in §(a), agreement between predicted and measured burning velocities is improved by adding to the mechanism a series of chain terminating steps involving the formation and subsequent reactions of the formyl radical. For reasonable values of its rate coefficient, reaction (xxii), O + CO + M ⇌ C O 2 + M , ( xxii ) never exerts more than a minor influence on the burning velocity. The major features of the structure of the flames are: ( a ) a preferential oxidation of hydrogen in the early stages of the reaction zones, leading to overshoot in the water concentration followed by a slow approach to the water gas equilibrium from the carbon monoxide-water side; and ( b ) marked enrichment of the oxygen atom concentration in the radical pool as the hydrogen content of the flames is decreased. In the flames containing only traces of hydrogen, the degree of enrichment is markedly influenced by reaction (xxii).

scholarly journals The flame spectra of carbon monoxide and water-gas. —Part I

1925 ◽  
Vol 109 (749) ◽  
pp. 176-186 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Nitrous Oxide ◽  
Continuous Spectrum ◽  
Systematic Investigation ◽  
Imperial College ◽  
Chemical Technology ◽  
Reduced Pressure ◽  
Research Fellow ◽  
The Subject ◽  
Water Gas

As part of my work as the Gas Light & Coke Company’s Research Fellow in the Department of Chemical Technology at the Imperial College of Science and Technology, South Kensington, I was asked to undertake a systematic investigation of the flame spectra of carbon monoxide, and of mixtures of carbon monoxide and hydrogen, under the joint supervision of Prof. W. A. Bone and Prof. A. Fowler, with a view to the elucidation, if possible, of certain aspects of the combustion of carbon monoxide which have been referred to in recent publications upon the subject. The present paper embodies the results of my experiments. The characteristic blue appearance of the highly radiative flame of carbon monoxide burning in air is, of course, well known; but on looking into the literature oi the subject, very little appears to have been published concerning the flame spectrum of carbon monoxide, which has not yet been adequately described. In 1901 Smithells recorded that the flame of carbon monoxide gives a continuous spectrum whether burning in air, oxygen or nitrous oxide, and that the same is also true when the combustion is inverted by burning oxygen in an atmosphere of carbon monoxide. He referred also to a previous observation of Burch’s that when the gas is burnt under reduced pressure, its spectrum becomes discontinuous, and that the maxima of light, though ill-defined, are in such positions as suggest that they are vestiges of oxy-carbon bands.

scholarly journals Water activation and carbon monoxide coverage effects on maximum rates for low temperature water-gas shift catalysis

2017 ◽  
Vol 347 ◽  
pp. 197-204 ◽  
Author(s):  
W. Damion Williams ◽  
Jeffrey P. Greeley ◽  
W. Nicholas Delgass ◽  
Fabio H. Ribeiro
Keyword(s):  
Carbon Monoxide ◽  
Low Temperature ◽  
Water Gas Shift ◽  
Water Activation ◽  
Coverage Effects ◽  
Water Gas ◽  
Temperature Water

Effect of Minerals in Coal on the Product Yield of Coal Pyrolysis and Phenols in the Low-Temperature Tar

2012 ◽  
Vol 512-515 ◽  
pp. 1129-1136 ◽  
Author(s):  
Fan Hu Zeng ◽  
De Min He ◽  
Jun Guan ◽  
Qiu Min Zhang
Keyword(s):  
Carbon Monoxide ◽  
Low Temperature ◽  
Brown Coal ◽  
Atmospheric Pressure ◽  
Fixed Bed ◽  
Product Yield ◽  
Fixed Bed Reactor ◽  
Coal Pyrolysis ◽  
Catalytic Role

Wulagai brown coal and Wulagai acid washed brown coal were used to investigate the effect of minerals in coal on the reactivity of coal pyrolysis. The experiments were carried out at atmospheric pressure in a fixed bed reactor. The results showed that minerals in brown coal affected the product yield of coal pyrolysis and phenols in the low-temperature tar. The minerals in coal played a catalytic role on the generation of carbon monoxide and ethylene, and the decomposition of tar. At the same time, they may suppress the decomposition of intermediates or the producing of final phenols during coal pyrolysis.

Flame structure and flame reaction kinetics. VI. Structure, mechanism and properties of rich hydrogen+nitrogen+oxygen flames

1972 ◽  
Vol 330 (1581) ◽  
pp. 199-218 ◽  
Keyword(s):  
Composition Range ◽  
Burning Velocity ◽  
Flame Structure ◽  
Chemical Mechanism ◽  
Oh Radical ◽  
Atom Concentration ◽  
Numerical Experimentation ◽  
Chain Breaking ◽  
Satisfactory Prediction ◽  
Unambiguous Assignment

Burning velocities of a number of slow-burning, fuel-rich hydrogen + nitrogen + oxygen flames have been measured and compared with values computed on the basis of the chemical mechanism proposed by Dixon-Lewis (1970 a ). This mechanism is shown to be incomplete, and in order to obtain agreement between theory and experiment over the composition range studied, it is necessary to invoke some further chain breaking steps involving hydroxyl radicals and oxygen atoms. The steps which have been considered lead to the extended mechanism OH + H 2 ⇌ H 2 O + H, (i) H + O 2 = OH + O, (ii) O + H 2 ⇌ OH + H, (iii) H + O 2 + M = HO 2 + M, (iv) H + HO 2 = OH + OH, (vii) H + HO 2 = O + H 2 O, (vii a ) H + HO 2 = H 2 + O 2 , (xii) OH + HO 2 = H 2 O + O 2 , (xiii) O = HO 2 = OH +O 2 , (xiv) H + H + M = H 2 + M, (xv) H + OH + M = H 2 O + M, (xvi) H + O + M = OH + M, (xvii) With the use of steady-state approximations for the small concentrations of OH and O present in the flames, the important new parameters in the analysis are k 16 , k 17 , and the ratios k 7 / k 12 , k 7a / k 12 , k 13 / k 12 and k 14 / k 12 . Although the number of these precludes an unambiguous assignment of values to them, numerical experimentation on reasonable assumed values of k 15 , k 16 and k 17 has led to the conclusions that: ( a ) The ratio ( k 7 + k 7a )/ k 12 lies in the range 6.5 ± 1.0, assumed independent of temperature in the flame reaction zone. ( b ) The ratio k 7 / k 7a is unlikely to be much greater than 0.1, and it may be much less than this. ( c ) Assuming k 7a = k 14 = 0, a maximum possible value of k 137 / k 12 = 5.5 may be deduced from the dependence of burning velocity on composition. A further important feature shown by the computation is that for the imposed condition of satisfactory prediction of measured burning velocities, the hydrogen-atom concentration profiles in specific flames are not appreciably affected by the particular combination selected from the six adjustable parameters given above. In this context the more important parameters, apart from k 15 (Dixon-Lewis 1970 a ), are shown to be the ratios 2 k 2 / k 4 . Also in connexion with the atom and radical concentrations, a comparison of measured profiles of the relative intensity of chemiluminescence when traces of sodium salts are added to three of the flames studied, with profiles derived from the computed H and OH radical concentrations, leads to the conclusion that reaction (xix) is some 25 times faster than reaction (xviii) H + H + Na = H 2 + Na*, (xviii) H + OH + Na = H 2 O + Na*. (xix) Lastly, the satisfactory prediction of the burning velocity of a much faster and hotter flame than those concerned in the bulk of the investigation provides further very powerful support for the reaction mechanism involving participation of hydroperoxyl. Effects of thermal diffusion in this and the other flames are discussed.

scholarly journals Laminar Burning Velocity and Flammability Characteristics of Biogas in Spark Ignited Premix Combustion at Reduced Pressure

2013 ◽  
Vol 376 ◽  
pp. 79-85 ◽  
Author(s):  
Willyanto Anggono ◽  
I.N.G. Wardana ◽  
M. Lawes ◽  
K.J. Hughes ◽  
Slamet Wahyudi ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Pressure ◽  
Burning Velocity ◽  
Initial Pressure ◽  
Dilution Effect ◽  
Laminar Burning Velocity ◽  
Fundamental Study ◽  
Reduced Pressure ◽  
Premix Combustion ◽  
Flammability Characteristics

Biogas as a “Powergas” is an alternative fuel produced in digestion facilities, that is sustainable and renewable. Based on chemical analysis, the composition of the biogas produced in East Java is 66.4% methane, 30.6% carbon dioxide and 3% nitrogen. Methane is a flammable gas, whereas, nitrogen and carbon dioxide are inhibitors. Given it has a different composition to traditional fuels, a fundamental study of biogas flame propagation characteristics is desirable to quantify this important fuel property. Spherically expanding flames propagating at constant pressure are employed to measure the laminar burning velocity and flammability characteristics as mixture function of the mixture composition. These important parameters were measured using a photographic technique in a high pressure fan-stirred bomb. The characteristics of biogas-air flames were initially studied at reduced pressure and at various equivalence ratios from the lower flammable limit to the upper flammable limit. The results were compared with those from biogas-air flames at atmospheric pressure. Based on this experimental investigation, the laminar burning velocities of biogas-air mixtures at reduced pressure were 0.218 m/s for ϕ=0.75, 0.246 m/s for ϕ=0.80 and 0.269 m/s for ϕ=0.85 respectively and only for these biogas mixtures propagated at reduced pressure. At the same equivalence ratio (ϕ), the laminar burning velocities of the biogas-air mixtures at reduced pressure are higher than those at atmospheric pressure. The flammable region of biogas became narrower by reducing initial pressure. The dilution effect is stronger at reduced pressure. Therefore, the flammable composition mixture areas of biogas-air mixtures are more limited at reduced pressure than those at atmospheric pressure.

Effect of the ionizing radiation on the catalytic activity of the BASF K-3-10 catalyst in the low-temperature conversion of carbon monoxide by water vapour. Catalytic activity of the pre-irradiated catalyst

1986 ◽  
Vol 51 (2) ◽  
pp. 279-287 ◽  
Author(s):  
Alois Motl
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Low Temperature ◽  
Ionizing Radiation ◽  
Water Vapour ◽  
Effective Activation Energy ◽  
Absorbed Dose ◽  
Beta Radiation ◽  
Fast Neutrons ◽  
Different Types

The catalytic activity of the BASF K-3-10 catalyst with regard to the low-temperature conversion of carbon monoxide by water vapour and its changes after irradiation of the contact area by gamma or beta radiation or by fast neutrons has been investigated. The irradiated samples exhibit a moderately or even substantially higher catalytic activity in comparison with the non-irradiated catalyst, the change being dependent on the absorbed dose; moreover, the effective activation energy of the reaction increases, too. Important differences in the action of different types of the ionizing radiation used have been observed and their probable explanation is offered. In course of these experiments the catalysts were analyzed and the specific surface of the catalyst was measured at various stages of their history. It has been found that at all stages the specific surfaces of the irradiated catalyst are equal to the respective specific surfaces of the non-irradiated contacts.

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