Oxygen enrichment experiments

Fig. 8. The relationship between annual total system net production during the day and consumption during the dark in the MERL mesocosms during two years in which they were receiving different levels of inorganic nutrient (N, P, Si) input. Estimates are based on dawn-dusk changes in dissolved oxygen and have been corrected for air-sea gas exchange. The solid line represents a P/R ratio of 1 with no net organic accumulation in, or export from, the tanks. The broken line represents a net accumulation and/or export of 100 g C m-2 y-1 assuming a PQ of 1. Data from C. Oviatt. A description of the mesocosms and the enrichment experiment is given in Nixon et al. (198 ).

There were several important results from those experiments. The first is that the NOx emissions for low-level oxygen enrichment were nearly an order of magnitude higher than for high-level enrichment. The second is that the experimental NOx trends were the same as those predicted by theory. However, the experimental measurements were about an order of magnitude lower than the theoretical predictions. This is due to the fact that actual flames are not adiabatic processes, since a large amount of heat is radiated from the flames. The actual flame temperature is usually much lower than the adiabatic equilibrium flame temperature. 

After successful experience with oxygen enrichment of wall-mounted conventional air/fuel burners, several smelters have successfully tried roof-mounted... 

Hase, E. A., Experiments with oxygen-enriched blast at the ASARCO East Helena lead smelter, paper presented at First Operating Metallurgy Conference and Symposium, Pittsburgh,... 

In addition to oxide film or scale formation at elevated temperatures, titanium alloys can also experience oxygen enrichment of metal surfaces beneath the oxide scale. These hard, brittle metal surface layers, known as "alpha case," result from diffusion of oxygen or nitrogen interstitials, or both, into the metal. This time/temperature-dependent phenomenon becomes significant above 540-590°C depending on alloy type, and severely reduces metal formability, ductility, and fatigue life, particularly as metal section thickness is reduced. Typical examples of an alpha case in o/p and P titanium alloys are shown in Fig. 11. 

Oxygen exchange experiments were performed between single crystals of sanidine feldspar and oxygen gas enriched in 1°0, at 869 to 1053C, under a total pressure of latm. The O isotope diffusion profiles in a direction perpendicular to (001) were determined using an ion microprobe. The experimental data obeyed the Arrhenius relationship ... 

Experience with oxygen enrichment of blast air is illustrated in Figure 5.6 (Fern and Jones, 1980), which shows that furnace capacity is increased by five times the oxygen percentage increase. A two per cent enrichment from 21 per cent to 23 per cent will raise furnace lead production by ten per cent. Blast furnace production is thus directly proportional to the oxygen flow rate given a constant tuyere volume and other furnace parameters. 

In an extension of the work described m the preceding section Bender showed that basic ester hydrolysis was not concerted and like acid hydrolysis took place by way of a tetrahedral intermediate The nature of the experiment was the same and the results were similar to those observed m the acid catalyzed reaction Ethyl benzoate enriched m 0 at the carbonyl oxygen was subjected to hydrolysis m base and samples were isolated before saponification was complete The recovered ethyl benzoate was found to have lost a por tion of Its isotopic label consistent with the formation of a tetrahedral intermediate... 

The saponification of °0-labeled ethyl propanoate was described in Section 20.11 as one of the significant experiments that demonstrated acyl-oxygen cleavage in ester hydrolysis. The 0-labeled ethyl propanoate used in this experiment was prepared from 0-labeled ethyl alcohol, which in turn was obtained from acetaldehyde and 0-enriched water. Write a series of equations... 

Release of from preoxidised 4% RhO /CeOj at temperatures > 473 K into a low pressure of Oxygen-18 enriched Oj was reported previously on the basis of measurements made with the recirculatory reactor system [8]. An analagous experiment in the present study, featuring a low pressure of Nj O in contact with preoxidised 4% RhO /CeOj while temperature was raised 300-500 K, likewise showed a small release of (together with Nj). However, Oj release was not observed when that sample was mildly prereduced nor when CeO was similarly tested. Preoxidised rhodia dispersed upon Ceria is thus seen to enhance the ease of release of O, at temperatures < 550 K. 

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