Characteristics of water thermal plasma for biomass utilization system

The purpose of the present work is to visualize the temperature fluctuation of water thermal plasma for biomass gasification. Another purpose is to investigate D-glucose decomposition mechanism in water thermal plasma because D-glucose is one of the main components in general biomass products. Arc temperature distributions of water thermal plasma with and without D-glucose injection were successfully visualized by high-speed camera. Two synchronized arc images in different wavelengths of Hα and Hβ were observed owing to appropriate optical band-pass filters with negligible other emissions from the arc. The arc temperature was measured based on Boltzmann-plot method. Measured arc temperature without D-glucose was 9000 K, and that with D-glucose was 7500 K. These temperatures were sufficiently high to decompose D-glucose completely. Furthermore, frequency analysis of arc fluctuation revealed that the time period of arc fluctuation was sufficiently shorter than that of the time constant of D-glucose decomposition. These results implied that the influence of arc fluctuation on D-glucose decomposition was negligible. In addition, the decomposition mechanism of D-glucose was discussed on the basis of the analyses of the products in vapor, liquid, and solid phases. They were converted from D-glucose through the water thermal plasma. Decomposition rate of D-glucose reached 99%. Gaseous product contains more than 86% of syngas, H₂ and CO. This ratio is much higher than that in conventional gasification device. From these characteristics, water plasma system is suitable device for biomass utilization.