Electrostatic precipitator (ESP) has been used to improve the visibility index and clean the air in highway tunnels. Most of particles in the highway tunnels are composed of carbon. Decrease of the collection efficiency due to particle re-entrainment is important problem when ESP collects carbon particles that have low electric resistance. In this work, we discuss the exhausting process of re-entrained particles from ESP. The process was discussed by particle deposit condition on collecting electrodes. The results show that the collected particles on collecting electrodes migrate to downstream with jumping between grounded and positive collecting electrodes. The particle shapes change into sphere from pearl chain when particles have been jumped between collecting electrodes. Therefore, re-entrained particles deposit on middle of electrodes.

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ガス吸収とは，気相中の特定ガス成分を，固体や液体の吸収剤を用いて，分離，回収する方法である。火力発電所の

のような大きな装置から，麻酔時に用いる二酸化炭素吸収装置など比較的小さな装置まで開発されている。以下，ガス吸収の装置の基本構成，実際に用いられている装置の例，理論的な内容について簡単にまとめた。

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It is a worldwide problem to treat the diesel exhaust gas as clean as possible because the toxic emission damages not only a human health but also the global environment. In underground mine, it is also a serious problem because the space is limited and it is probably possible for workers to be exposed from the diesel exhaust gas.
Taiheiyo Coal Mining Co., Ltd (Taiheiyo Coal Mine) introduced the three types of diesel vehicles using the exhaust gas water type treatment system in the past. However there were many troubles such as supplying the water in a scrubber tank frequently, cleaning a scrubber tank anytime and keeping a floor in good condition. To solve these kinds of troubles, Taiheiyo Coal Mine developed new exhaust gas dry type treatment system consisted of the new oxidation catalyst, modified flame arrester, spark arrester and ceramics filter. As a result of exhaust gas analysis, the low content of toxic emission and temperature level in exhaust gas that could clear the government approval standard were achieved. Especially, CO and HC content were lower than limitation of the heavy diesel vehicle on surface in 2003.
Two types of diesel vehicles, one is 75kw LHD and the other is 45kW dump truck, have developed and operated since 1997 in underground. In this paper, new exhaust gas dry type treatment system and results of the exhaust gas analysis are described. Subsequently, efficiency of diesel vehicle compared with a conventional method is discussed.

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Non-thermal plasma produced by pulsed power discharge in atmospheric pressure gases has been used for high-efficiency treatment of exhaust gases. This paper describes the chemical reactions taking place in the discharges under different gas compositions. A 3-staged Blumlein line generator providing 44kV voltage pulse of 100ns duration was applied to the discharge reactors. A coaxial electrode system, 1-m in length with 83-mm outer and 1-mm inner electrode diameters, was used as a reactor. It was experimentally found that NO_x removal ratio becomes lower when NO_x gas includes either O₂ or H₂O, but NO_x removal ratio becomes higher when the gas includes both O₂ and H₂O. Therefore, adding both O₂ and H₂O species into exhaust gases is preferable.

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ナノ秒パルス放電は、オゾン生成やにおいて熱損失の少ない高効率な手法として注目されている。しかし、様々な応用展開をするうえで、その小型化が切望されており、本研究では、マイクロ秒パルス発生部及びナノ秒パルス圧縮部、ナノ秒パルス放電形成部よりなるナノ秒パルス放電システムのマイクロ秒パルス発生部に着目してその小型化を図った。今回、マイクロ秒パルス発生部を小型化するために、エネルギー蓄積密度が高い誘導性エネルギー蓄積方式を利用したパルス電源を製作し、そのナノ秒パルス放電システムへの適用性を評価した。

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近年、やオゾン生成に用いられているストリーマ放電では，一般的に対象ガス流場中で放電を高繰り返しで行うため，放電による気体加熱や生成物の影響は無視できないと考えられる．本研究では，大気圧下の乾燥空気ガス流場で正・負極性のインパルスストリーマをそれぞれ100から7,000 pulse/sec. (pps)の頻度で繰り返し発生させ，各繰り返し頻度における電極間の気体温度や放電生成物であるオゾン・NOx濃度を計測し，それらの変化が放電に及ぼす影響を調査した．その結果，極性によらず、繰り返し頻度の増加に伴う気体温度の上昇及び放電体積の縮小が確認された。また、気体加熱によってオゾン発生量が低下し、NOx発生量は増加した。

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The discharge using pulse power with a short pulse width can produce a lot of electrons with high energy. This method has a possibility to remove poisonous gases with low energy consumption. In this paper, the inductive energy storage pulsed power generator, which can generate narrow and high voltage pulses (FWHM less than 100ns, output voltage of about 100kV), is used to remove NO_x gas. It is found from spectrum measurement that this generator can produce high energy electrons, more than 10eV, in the discharge region at atmospherics pressure. The mixed gases of NO and N₂ are used as a trial gas. The NO removal ratio of about 95% is achieved without producing NO₂. These chemical phenomena are approximately explained by solving rate equations.

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Removal of NO_x has been successfully demonstrated using an intense, pulsed relativistic electron beam (IREB). The elongate gas chamber (1.8 m long) is filled up with dry-N₂-balanced or dry-N₂/O₂-balanced NO gas mixture with the pressure of 120 kPa, and is irradiated by the IREB. The kinetic energy, current and pulse width of the IREB are ∼2 MeV, ∼2.2 kA and ∼90 ns (full width at half maximum), respectively. With the initial NO concentration of 100 ppm in N₂-balanced NO gas mixture, ∼96 % of NO_x is removed by firing 10 shots of the IREB. We have obtained the energy efficiency of NO_x removal of ∼220 nmol/J in N₂-balanced NO gas mixture with the initial NO concentration of 880 ppm. The energy efficiency of NO_x removal increases with increasing the initial NO concentration. In N₂/O₂-balanced NO gas mixture, NO_x is removed if the initial NO concentration is less than 200 ppm. However, the NO₂ is also generated by the irradiation of the IREB. The theoretical calculation on the half-life time of NO shows that the NO₂ is generated by the oxidation of NO by O or O₃.

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セリア_-_ジルコニア固溶体（CeZrO4）は、酸素の吸蔵および放出能が大きいために、自動車排ガス浄化触媒の助触媒材として用いられており、効率を増大させることが明らかにされている。しかしながら、この固溶体の結晶構造の温度依存性に関する正確な構造解析は行われていない。そこで本研究では、セリア_-_ジルコニア固溶体の高温中性子回折測定を行い、リートベルト解析を行うことにより、結晶構造を研究することを目的とした。つまり、粉末中性子回折装置（ＨＥＲＭＥＳ）を用い室温から１５５０℃の温度範囲において空気中で測定を行い、プログラムＲＩＥＴＡＮ_-_２０００を用いてリートベルト解析を行い、結晶構造の精密化を行った。

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CeZrO₄固溶体は、酸素の吸蔵および放出能が大きいために、自動車排ガス浄化触媒の助触媒材として用いられており、効率を増大させることが明らかにされている。しかしながら、この固溶体の結晶構造の温度依存性に関する正確な構造解析は行われていない。そこで本研究では、CeZrO4固溶体の高温中性子回折測定を行い、リートベルト解析を行うことにより、結晶構造を研究することを目的とした。つまり、粉末中性子回折装置（ＨＥＲＭＥＳ）を用い室温から１５５０℃の温度範囲において空気中で測定を行い、プログラムＲＩＥＴＡＮ_-_２０００を用いてリートベルト解析を行い、結晶構造の精密化を行った。

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The catalytic conversion of automotive exhaust gas into less harmful substances become an important problem from the view point of the cleansing of the air pollutants. However, the cleaning of the automotive exhaust gas, especially conversion of nitrogen oxides into harmless gases, is very difficult.
In this paper, the conversion catalysts of automotive exhaust gas and its catalytic action have been explained.

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