Taisuke Nose

The Effect of Spraying of Water Droplets and Location of Water Droplets on the Water Treatment by Pulsed Discharge in Air

In this paper, some characteristics of a method for decomposing organic compounds by spraying a water solution of organic compounds as droplets into pulsed streamer discharges in air are presented. For the characteristics, the effect of spraying the water droplets compared with water film flowing in a chamber wall, and locations of water droplets into the discharge area on water treatment by the pulsed discharge in air was investigated. In the experiments, a coaxial electrode was used. A solution of organic dye, indigo carmine, was used for a sample. Experimental methods of the effect of spraying the water droplets were to sample each solution gotten through the discharge area as water droplets and water film. Experimental methods of the effect of locations of the water droplets were to spray the water droplets near the wire electrode or the cylindrical electrode. The time spent for decolorizing the water droplets, including indigo carmine, was 0.57 times shorter than that flowing along the inner wall of a reactor into the discharge. This result shows that spraying as water droplets into the discharge in air is effective for faster treatment of water. The time spent for decolorizing the water droplets, including indigo carmine, at the location near the cylindrical electrode of the reactor was 1.5 times faster than that at the location near the wire electrode of the reactor. This result shows that the location near the cylindrical electrode of the reactor has many radicals that are effective for degradation of organic compounds.

Decomposition of Sodium Acetate by Pulsed Discharge in Water Droplet Spray

The characteristics and the effects of oxygen on the decomposition of sodium acetate have been investigated by pulsed discharge in water droplet spray in O₂ and N₂ used as carrier gases in the reactor. Two experimental conditions of gas mixing ratios of O₂/N₂ = 10/90 and O₂/N₂ = 50/50 were performed to evaluate the effect of oxygen. In both conditions, acetate was decomposed by pulsed discharge in water droplet spray, and formate and the other products were detected as intermediate products. Formate was gradually decomposed with increased treatment time. Acetate decomposition rates after 10 h treatment in the gas mixing ratios of O₂/N₂ = 10/90 and O₂/N₂ = 50/50 were 39% and 80%, respectively, and TOC decomposition rates were 48% and 78%, respectively. It was found that it is possible to decompose sodium acetate. These results indicate that organic compounds which have a carbon-carbon single bond can be completely decomposed by this technology. Decomposition efficiencies in the gas mixing ratios of O₂/N₂ = 10/90 and O₂/N₂ = 50/50 were 43 μg/kJ and 97 μg/kJ, respectively. Decomposition efficiency in the gas mixing ratio of O₂/N₂ = 50/50 is about 2.2 times higher than that of the gas mixing ratio of O₂/N₂ = 10/90 . These obtained results show that oxygen plays important roles in enhancing the decomposition of organic compounds.

Effect of Iron Addition on the Decomposition of Dye by Pulsed Discharge in Air With Water Droplets Spray

The effect of iron addition in the treated solution on the decomposition of indigo carmine is reported. The effect of iron addition was evaluated for various Fe²⁺ concentrations ranging from 0 to 118 μmol/L (μM). The decolorization rate and efficiency with Fe²⁺ addition were higher than those without Fe²⁺ and increased with the rise in Fe²⁺ concentrations. The optimal Fe²⁺ concentrations for decolorization rate and efficiency were 95 and 83 μM, respectively. The pH effect was evaluated in the range of 2.3-11.3 values for the initial solution containing 71 μM Fe²⁺. The decolorization rate was approximately constant for pH ranging from 4.7 to 8.0. The increases in decolorization rate and efficiency with Fe²⁺ are attributed to a significant increase in hydroxyl radicals quantity, which is generated by Fentons reaction of iron and hydrogen peroxide.

Investigation of optimum pulse width of appled voltage for water treatment by pulsed streamer discharge in air spraying water droplets

We have studied the water treatment method of spraying the droplets of waste water into a pulse discharge space. In this method, we have been developing the pulse generator which realizes higher treatment efficiency. For that, the investigation of an optimum applied voltage from the pulse generator for the treatment is needed. In this paper, investigation of an optimum pulse width has been carried out by applying the voltage of different pulse widths. As sample water for the investigation, indigo carmine solution was used. The pulse widths of applied voltage was 40, 60 and 80 ns, and Those rIse time was 12, 19 and 32 ns, respectively. By the water treatment of the pulse width of 40 ns, indigo carmine was decomposed at lower energy than that of the other pulse width. From the result, generating of active species is considered to increase in early time of the discharge and to decrease with development of the discharge. Therefore it is expected that shorter pulse width realize higher treatment efficiency.

Initial Concentration Dependence of Dimethyl Sulfoxide Oxidation by Pulsed Discharge Plasma in Air with Water Droplets Spray

Abstract Initial concentration dependence of dimethyl sulfoxide (DMSO) oxidation has been investigated by pulsed discharge plasma in air with water droplets spray for the first time. Dimethyl sulfone (DMSO2) was produced by the oxidation of DMSO, and the concentration of DMSO2 linearly increased with an increase in the treatment time. The conversion rate of DMSO in the initial concentration of 443 mg/L was 51% after 10-h treatment. The experimental yield of DMSO2 was approximately 70% of the theoretical yield of DMSO2. These results indicated that mineralization of DMSO is possible by further treatment and that other oxidized intermediate compounds besides DMSO2 were produced by the oxidation of DMSO. The kinetics and efficiency of DMSO conversion to DMSO2 were investigated under different initial concentrations of DMSO. The DMSO conversion rate and efficiency increased with the rise in the initial DMSO concentrations. It was found that DMSO was efficiently oxidized at a higher initial concentration of DMSO.

Investigation of a pulse circuit design and pulse condition for the high energy efficiency on water treatment using pulsed power discharge in a water droplet spray

One of industrial applications by pulsed power technologies is water treatment using pulsed streamer discharge. The pulsed streamer discharge can generate ozone, chemical active species, ultraviolet rays and shockwaves. All of these can be utilized to decompose the organic compounds in water. In the water treatment by discharge, energy efficiency for the treatment is very important factor at commercial viability. Therefore, we have been studying the decomposition of organic compounds in water using the pulsed streamer discharge in air with water droplet s for a high energy efficiency water treatment method. In this study, we have investigated a pulse circuit design and pulse conditions in which the energy is transferred effectively from the power supply to the discharge. The experimental set up consist of a pulsed power generator and a discharge reactor. A pulsed high voltage is generated by the pulsed power generator. The pulsed power generator is consist of high voltage FET switches, resistors and capacitors. In this pulsed power generator, the output energy from the capacitors is limited by a switching time of the high voltage FET switch. The discharge reactor has a coaxial electrode that consists of a stainless steel wire of 0.28mm diameter for applying pulsed voltage and a cylindrical stainless steel mesh of 38mm inner diameter for a ground electrode. The electrode length of the streamer discharge area is 300mm. In an experiment, an optimum pulse width for high energy efficiency was investigated.