Wet-type Reactor Research Articles

Toward Ideal VOCs and Nanoparticle Emission Control Technology Using a Wet-Type Catalysis Nonthermal Plasma Reactor

Several exhaust gas regulations are being implemented to prevent the hazardous emissions of volatile organic compounds (VOCs) and particulate matter (PM) from paint and print factories. The VOCs generate photochemical oxidants and suspended PM, such as PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> , which has become a global environmental problem. We evaluate the catalytic nonthermal plasma (NTP) technique for controlling the emission of VOCs. The article proposes a wet-type catalysis plasma reactor to extend the treatment of water-soluble VOCs. Initial evaluation of the proposed technique involves simultaneous removal of nanoparticles along with individual VOCs, toluene, acetaldehyde, acetic acid, and ammonia, at a relatively high gas flow rate of 10 L/min. Further, pellets of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</i> -alumina and TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> spheres are employed in the NTP reactors for assessing their catalytic performance. We install an MnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> catalytic reactor downstream of the plasma reactor for ozone removal. Simultaneous treatment of typical VOCs and nanoparticles using dry and wet-type catalytic NTP reactors shows that the wet-type reactor has superior average particle collection efficiency of 100%. However, the dry-type NTP with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</i> -alumina shows a higher toluene removal efficiency of 91% compared to 73% in the wet type. Further, the respective removal efficiencies for acetaldehyde, acetic acid, and ammonia are 100%, 100%, and 95%. Notably, the toluene removal efficiency drops to 65% with the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> catalyst.

Evaluation of a Catalyst Packed-bed Nonthermal Plasma Reactor for VOC and PM Removal

Volatile organic compounds (VOCs) and particulate matter (PM) emitted from factories in the painting and printing industries, and various exhaust gas regulations have been implemented. VOCs are the cause of photochemical oxidants and suspended PM such as PM2.5, which has become a global environmental problem. As one of the solution technologies, catalysis nonthermal plasma (NTP) techniques have been studied as VOCs control methods. In this study, in order to extend the application to the treatment of water-soluble VOCs, a wet-type catalysis plasma reactor is proposed. As an initial step to evaluate proposed technique, the simultaneous removal of nanoparticles and toluene or typical VOCs, are performed at relatively high gas flow rates of 10 L/min. As catalyst pellets, α-alumina spheres are filled in the NTP reactor, and a MnO2 catalytic reactor is installed after the plasma reactor for ozone removal. Simultaneous removal of toluene and nanoparticles using dry and wet-type catalytic NTP reactors showed that the results used the wet-type reactor were superior in particle collection efficiency of 99%. As for the toluene removal efficiency, the dry-type was 91% and the wet-type was 73%, with the dry-type showing better results. However, the proposed wet-type catalysis NTP reactor could efficiently treat water-soluble VOCs, such as acetaldehyde and acetic acid.

304 プラズマ・ケミカル複合技術を用いたガラス溶解炉向け湿式排ガス処理パイロットスケール実験(大気環境保全・改善技術(2))

The plasma and chemical hybrid process (PCHP) is an innovative technology for simultaneous removal of NO_x (NO and NO_2) and SO_x (SO_2 and SO_3). PCHP is demonstrated for an exhaust gas in glass melting furnaces. NO which compose 90% of the NO_x contained in the exhaust gas is oxidized effectively by injecting ozone with the cooling soft water and compressed air using the three-fluid spray nozzle. SO_2 is desulfurized to Na_2SO_3 at the wet-type reactor by absorbing solution of NaOH. Furthermore, oxidized NO_2 is removed to N_2 by Na_2SO_3. As a result, performance of pilot-scale test is maintained stable during 140 min. When the ozone of 1.4 kg/h is injected to exhaust gas which is 6,700 m^3N/h at 150℃, NO_x concentration is reduced to 222 ppm from 301 ppm in average with removal efficiency of 34% (NO is 38%) in maximum. Furthermore, SO_2 concentration decreased to more than 98%. The PCHP that can be applied effectively to wet-type exhaust gas treatment system of glass melting furnace is demonstrated.

Application of a non-thermal surface plasma discharge in wet condition for gas exhaust treatment: NOx removal

This paper deals with the NOx removal with the help of a non-thermal surface plasma discharge in wet conditions. The gas treatment device consisting of a surface discharge and a wet-type reactor, was characterized through FTIR and electrical measurements. The ability of the proposed system for the cleaning of gas exhaust was studied. NOx as gaseous pollutant was decomposed effectively. To improve the chemical conversion, a coil was inserted in the electric circuit then a catalyst was placed in the plasma area. Results showed an improvement of NOx removal by an increase in radical species produced and synergistic effect, respectively. ► Non-thermal surface plasma discharge in wet conditions for gas exhaust treatment is investigated. ► Several parameters are tested such as voltage-frequency, coil and catalyst. ► The removal of NOx is higher with the variation of waveform frequency rather than the applied voltage. ► Inductance enhances the NOx remediation efficiency and reduces the power consumed in the case of the voltage variation. ► γ-Al 2 O 3 enables a synergetic effect with plasma discharge mainly on the NO 2 oxidation.

The Role of H2O in Nitric Oxide Removal by Wet-Type Corona Discharge Plasma Reactor

We have applied the dc corona discharge process to the removal of NO from a simulated flue gas. The effect of H2O on the oxidation of NO to NO2 was investigated. The experimental results show the removal rate of NO is improved in wet-type reactor than that of dry-type reactor. NO is mostly oxidized into NO2 by the reaction with O and O3 and NO2 is changed into HNO3 by the reaction with OH, which is generated from H2O.

Pulsed-plasma treatment of polluted gas using wet-/low-temperature corona reactors

Application of pulsed plasma for gas cleaning is gaining prominence in recent years, mainly from the energy consideration point of view. Normally, the gas treatment is carried out at or above room temperature by the conventional dry-type corona reactor. However, this treatment is still inadequate for the removal of certain stable gases present in the exhaust/flue gas mixture. The authors report here some interesting results of the treatment of such stable gases like N/sub 2/O with pulsed plasma at subambient temperature. Also reported in this paper are improvements in DeNO/DeNO/sub x/ efficiency using unconventional wet-type reactors, designed and fabricated by us, and operating at different subambient temperatures, DeNO/DeNO/sub x/ by the pulsed-plasma process is mainly due to oxidation, but reduction takes place at the same time. When the wet-type reactor was used, the NO/sub 2/ product was absorbed by water film and higher DeNO/sub x/ efficiency could be achieved. Apart from laboratory tests on simulated gas mixtures, field tests were also carried out on the exhaust gas of an 8-kW diesel engine. A comparative analysis of the various tests are presented, together with a note on the energy consideration.