7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Thermal Plasma Generation for Innovative Materials Processing
Takayuki Watanabe1
1Department of Chemical Engineering, Kyushu University, Japane-mail (speaker): watanabe@chem-eng.kyushu-u.ac.jp

Thermal plasmas are expected to be utilized for anumber of innovative industrial applications such as
decomposition of harmful materials, recovery of usefulmaterials from wastes, and synthesis of high-quality andhigh-performance nanoparticles. The advantages ofthermal plasmas including high enthalpy to enhancereaction kinetics, high chemical reactivity, and oxidation
or reduction atmospheres in accordance with required
chemical reactions are beneficial for innovativeprocessing.
The experimental and modeling efforts on thermal
plasma characteristics has been devoted to industrial
application. However, the thermal plasma characteristics
remain to be explored in spite of these efforts. The arc
fluctuation phenomena are one of the most considerable
issues, because it determines the processing performancein thermal plasmas. The objective of the talk is toinvestigate the physical and chemical phenomena inthermal plasma processing for industrial application.
A multiphase AC arc (MPA) as shown in Fig. 1 is oneof the most attractive thermal plasmas due to its
advantages such as large plasma volume with low gas
velocity, which are favorable for material processing [1,2].
Other advantages compared with other thermal plasmas
include high energy efficiency and low cost. The mostimportant phenomena to be explored are the arc stability,
the temporal and spatial characteristics of the arcdischarge.
Fluctuated temperature field of the MPA weresuccessfully visualized by a high-speed camera. Figure 2of the MPA temperature fluctuation with top and side viewis useful for industrial application. These temperature
distributions were measured from Ar I at 675 and 795 nm.
Water plasma system has been scaled up into a mobile
system in a vehicle with direct-current generator as shownin Fig. 3. This innovative in-vehicle plasma has great
advantage to reduce the risk and cost caused by thetransportation of harmful wastes [3]. Recent studies haverevealed the arc fluctuation and temperature field of thewater plasma by high-speed visualization. The
observation of arc fluctuation and the measurement of thearc temperature were conducted by employing the highspeed camera system. Water as plasma source wasintroduced from cathode nozzle to discharge area. The
copper or iron as anode material rotates to reduce anodeerosion.
A high-speed camera with an appropriate band-passfilter system was used to visualize the arc fluctuation andthe temperature field. The wavelengths of the filters were
656 nm and 486 nm for H α and Hβ, respectively. Highest
temperature was over than 15,000 K. These results
revealed that the arc temperature of in-vehicle waterplasma was sufficiently high to decompose any organicand inorganic compounds.

Fig. 1 Schematic image of multiphase AC arc.
generator.

Fig. 2 Temperature distributions measured (a) fromthe top and (b) from the side during one AC
cycle of 60Hz and 120 A.

Fig. 3 Plasma Truck with water plasma system.
References[1] T. Watanabe, et al., Plasma Chem. Plasma Process.
34, p.443 (2014)[2] M. Tanaka, et al., Jpn. J. Appl. Phys. 59, SHHC08(2020)[3] T. Watanabe, et al., J. Plasma Fusion Res., 95, 27(2019)