Methane concentration effects

Hjertager, B. H., K. Fuhre, and M. Bjorkhaug. 1988a. Concentration effects on flame acceleration by obstacles in large-scale methane-air and propane-air explosions. Comb. Sci. Tech., 62 239-256. 

Effects of Cold Gas Recycle and Approach to Equilibrium. Product gases resulting from various CGR ratios were analyzed (Table XI). For the experiments tabulated, a decrease in the cold recycle ratio resulted consistently in increases in the product gas concentrations of water vapor, hydrogen, and carbon dioxide and a decrease in methane concentration. These trends may be noted in experiment HGR-12 as the CGR ratio decreased from 8.7 1 to 1.2 1, in experiment HGR-13 as it increased from 1.0 1 to 9.1 1, and in experiment HGR-14 as it decreased from 3.0 1 to 1.0 1. These trends indicate that the water-gas shift reaction (CO + H20 —> C02 + H2) was sustained to some degree. Except for the 462-hr period in experiment HGR-14, the apparent mass action constants for the water-gas shift reaction (based on the product gas compositions in Table XI) remained fairly constant at 0.57-1.6. These values are much lower than the value of 11.7 for equilibrium conversion at 400°C. In... 

Such a complicated interactivity of processes can both directly and indirectly affect formation of the atmospheric greenhouse effect. Derwent et al. (2001) described a global 3-D Lagrangian chemistry transport model (STOCHEM) which reproduces chemical processes including MGC transport and can be used to reproduce interrelated fields of TO and methane concentration (Johnson et al., 2002) under conditions of emission to the atmosphere of short-lived TO precursors such as CH4, CO, NOx, and hydrogen. At the same time, the radiative forcing (RF) of NOx emissions depends on the location of emissions near the surface or in the upper troposphere, in the Northern or Southern Hemisphere. For each short-lived MGC/... 

The study of the aqueous H202 concentration effect on the course of the reaction shows almost full methane conversion with high hydrogen yield (74%) and a carbon dioxide concentration decrease to 0.4% in the presence of 15% hydrogen peroxide at 880 °C [130], Experimental results from temperature influence on methane oxidation to hydrogen-containing gas are presented in Figure 4.18. It is obvious that besides total methane conversion,... 

Catledge, S., and Vohra, Y., Effect of nitrogen addition on the microstructure and mechanical properties of diamond films grown using high-methane concentrations. /. App. Phys. 86 (1), 698-700 (1999). 

There is growing evidence that the composition of the troposphere is changing. For example, analysis of historical ozone records has indicated that tropospheric ozone levels in both hemispheres have increased by a factor of 3-A over the last century. Methane concentrations have effectively doubled over the past 150 years and N2O levels have risen by 15% since pre-industrial times.Measurements of halocarbons have shown that this group of chemically and radiatively important gases to be increasing in concentration until relatively recently. 

Gilbert B. and Frenzel P. (1995) Methanotrophic bacteria in the rhizosphere of rice microcosms and their effect on porewater methane concentration and methane emission. Biol. Fertility... 

King G. M. and Schnell S. (1994b) Effect of increasing atmospheric methane concentration on ammonium inhibition of soil methane consumption. Nature 370, 282-284. 

Schulz S. and Conrad R. (1995) Effect of algal deposition on acetate and methane concentrations in the profundal sediment of a deep lake (Lake Constance). FEMS Microbiol. Ecol. 16, 251-259. 

Recent measurements (1980) Indicate that the atmospheric methane is about -47.0 0.3 /oo (48). The average isotopic fractionation associated with the sink process is -2.5 1.5°/oo, and there is a +0.3°/oo Isotope effect resulting from the nonsteady state increasing methane concentrations (48). This implies that the average for all sources is about... 

On the other hand this view is well supported by the experimental evidence of the processes themselves. In all of the work only low conversions to formaldehyde have been obtained. Thus Tropsch and Roelen --studied the effect of composition of the gas mixtuve, diameter of reaction tube, temperature, and time of contact. Their best results were obtained with 4.0 mm. reaction tubes, a time of contact of about 1/1000 second, a temperature of 1000° C., and a methane concentration of 16 per cent. Under these conditions the yield was 1.2 per cent of the theoretical. At lower temperatures the conversion of methane to formaldehyde was higher but the formaldehyde in the reaction mixture extremely low, and as the temperature was raised, although the conversion of methane to formaldehyde decreased, the absolute quantity of formaldehyde produced became greater. 

The effect of paraffin carbon number on the equilibrium methane concentration is shown for three feed steam-carbon ratios in Figure 6. These results indicate that a higher methane-content gas can be produced from low molecular weight paraffins than from high molecular weight paraffins. 

The effect of reactor pressure was mainly to shift the methane concentration in the gas. However, the heat content of the gas generated (net gas yield/lb maf wood x heating value of gas) was, if anything, increased by lowering the reactor pressure. 

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