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Nitrous oxide (N 2 0) is a trace gas contributing to stratospheric ozone depletion and global warming. Although a large quantity of information exists about N 2 0 emissions from various ecosystems, this study was initiated to demonstrate the features of N 2 0 emissions from sea-based waste disposal sites in Osaka City in relation to CH 4 emissions.Average N 2 0 emissions at an active landfill (S-Site) were several times higher than those at a closed landfill (N Site). Average CH 4 emissions were also much greater at the S-Site. Regarding the nature of N 2 0 emissions, remarkable emissions often were observed with aerobic waste layers at the N-Site, suggesting almost inversely related N 2 0 emissions with CH 4 production at the N-Site. However, at the S-Site a few exceptionally high N 2 0 emissions were noted in cases of high CH 4 emissions.

SUMMARYAn experimental study on performance of a disk MHD generator was carried out using a shock-tube driven facility. Effects of nozzle load resistance and stagnation gas pressure on the enthalpy extraction, the total pressure ratio, and the adiabatic efficiency were investigated for a disk MHD generator with a small area ratio. The enthalpy extraction and the adiabatic efficiency were found to be affected by the nozzle load resistance. The results suggest that the nozzle load resistance should be kept high for high performance of the disk MHD generator with small area ratio. Furthermore, an increase of stagnation pressure resulted in a slight increase of enthalpy extraction. However, the increase of stagnation pressure led to a remarkable increase of adiabatic efficiency. The increase of the adiabatic efficiency was due to an increase of the total pressure ratio. The effects of the electrical efficiency, the Mach number, and loss parameters for heat and friction on the total pressure ratio are discussed. The discussion suggests that the increase of total pressure ratio is due to a relative decrease of pressure loss due to wall friction. In addition, the highest adiabatic efficiency for cesium-seeded argon was achieved in the present experiment without the introduction of inlet swirl. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 3746, 2001

Adsorption using activated carbon is one of the most reliable techniques for preventing odor by substances such as H 2 S. Concurrent substances in effluent gas often reduce the removal capacity of activated carbon for H 2 S. As a means of restoring capacity under such conditions, ozone injection into an activated carbon column was examined. When activated carbon was saturated with substances such as toluene, ethanol, n-butanol, or iso-butanol, its capacity to remove H 2 S decreased in proportion to the amount of the saturating substance. Under such conditions, ozone injection greatly increased capacity. Toluene, which is not easily decomposed by ozone, was displaced by ozone and by oxidized products of H 2 S. Ethanol, which is adsorbed in small amounts by activated carbon and easily decomposed by ozone, was removed by ozone injection. Butanols, which are also decomposed by ozone and adsorbed in large quantities by activated carbon, showed intermediate behavior between that of toluene and ethanol.